Strengthening of liquid crystal photoalignment on azo dye films: passivation by reactive mesogens

Tseng, Man Chun; Yaroshchuk, O.; Bidna, Tetyana; Srivastava, Abhishek Kumar; Chigrinov, Vladimir G.; Kwok, Hoi Sing

doi:10.1039/c6ra05298c

Cited by 40 publications

(22 citation statements)

References 28 publications

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“…The reader is referred to seminal works in the development and demonstration of using photoalignment to control the self-assembly of liquid crystalline materials for progress in optics. [59][60][61][62][63][64][65][66][67] These 4G static diffractive elements are usually created by first applying a photoalignment layer to a substrate by spin-coating or through other thin film coating processes, such as ink-jet printing. There are various approaches to patterning the photoalignment material.…”

Section: Fabricationmentioning

confidence: 99%

Advances in Transparent Planar Optics: Enabling Large Aperture, Ultrathin Lenses

Tabiryan

Roberts

Liao

et al. 2021

Advanced Optical Materials

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Unlike electronics, optics do not follow Moore's law. This statement, expressed by Microsoft's Bernard Kress, refers to the hard challenges to solve in augmented reality hardware. While light sources have undergone numerous revolutions from candles to light emitting diodes, the evolution in transparent optics has been much slower. For transparent materials, variation of the shape, bulk refractive index, and/or its distribution leads to control of the transmitted beam in an optical system. An alternative, the control of the optical axis orientation in an anisotropic material in transparent micrometer‐thin films on a variety of substrates, is explored here. In contrast to metamaterials, these diffractive waveplates have a continuous structure allowing multilayer/multifunctional planar optical systems with close to 100% efficiency across broad bands of wavelengths (ultraviolet to infrared) with customizable spectra. The low‐cost and fast fabrication technology of this fourth generation of optics is scalable to very large aperture sizes. In addition to wearable adaptive optics, the technology enables thin and compact non‐mechanical fast beam steering systems for light detection and ultralight space telescopes. This review will first serve as an introduction to these unique transparent, planar optical films, and then recent advances enabled by specific optical designs will be presented.

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Section: Fabricationmentioning

confidence: 99%

Advances in Transparent Planar Optics: Enabling Large Aperture, Ultrathin Lenses

Tabiryan

Roberts

Liao

et al. 2021

Advanced Optical Materials

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show abstract

“…Second, make a multiple‐layer stack and arrange the high‐energy emitters on the top of the low‐energy emitters, which is a process flow illustrated in Figure f. It has been observed that the LCP layer coated on the top of the previously deposited photoalignment layer offers similar anchoring and alignment conditions that transfer all the local microscopic information to the subsequent LCP layers coated on the top of it, without any screening in the anchoring energy up to 2–3 layers . Usually, alignment anchoring screening can be only observed after three stacked layers of LCP.…”

Section: Lcd Components With Their Optical Efficiencies and Brightnesmentioning

confidence: 99%

Photoaligned Nanorod Enhancement Films with Polarized Emission for Liquid‐Crystal‐Display Applications

et al. 2017

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Semiconductor nanorods (NR) emit polarized light, which is expected to bring manifold benefits, in terms of brightness and color enhancement, for modern liquid-crystal displays (LCD). In this regard, photoaligned nanorod enhancement films (NREF) for color and polarization conversion for LCD backlights are introduced here. The photoinduced anchoring forces, by the photoalignment layer, stimulate well-ordered self-assembly of NR in the thin polymer films. Green and red emitting NR with a quantum yield of ≈80% are aligned unidirectionally and in-plane, showing a polarization ratio of >7:1 and a degree of polarization of >0.81. The photoalignment technique facilitates the fabrication of mixed and multiple stacked NREF for LCDs, which improves the color gamut and polarization efficiency, and is thus expected to increase the optical efficiency of conventional LCDs by ≈60%.

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“…The moving of mobile ions driven by electric forces towards alignment layers results in their accumulation on alignment layers, which finally generates residual direct current (DC) voltage (V rdc ) inside LC cells and adversely affects LC' switching [1][2][3][4][5][6]. During the last several decades, a series of researches focused on distinguishing, detecting mobiles ions, and revealing the influences of mobile ions shifting on LC switching were conducted, and nowadays a lot of explorations are carried out to reduce mobile ions' adverse functions on LC [7][8][9][10][11][12] A lot of attempts have been adopted to prevent the influences of mobile ions on LC electro-optical performances, such as designing special LC molecules, purifying LC, doping LC [13,14], replacing the polyimide (PI) alignment layers with conductive materials [15][16][17][18], and photo-aligning LC [19][20][21], etc. Compared with other methods, doping is much easier; however, doping LC with nano-materials brings new issues, for instance, the doped nano-materials are too poor to be dispersed, and the aggregation of these nano-materials makes LC insensitively respond to external voltage.…”

Section: Introductionmentioning

confidence: 99%

Decreasing the Residual DC Voltage by Neutralizing the Charged Mobile Ions in Liquid Crystals

et al. 2019

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The decrease of the residual direct current (DC) voltage (Vrdc) of the anti-parallel liquid crystal (LC) cell using silver (Ag)-doped Polyimide (Ag-d-PI) alignment layers is presented in this manuscript. A series of Ag/PI composite thin layers are prepared by spurting or doping PI thin layers with Ag nano-particles, and Ag/PI composite thin layers are highly transparent and resistive. LC are homogeneously aligned between 2.0 mg/ml Ag-d-PI alignment layers, and the Vrdc of the cell that assembled with Ag-d-PI alignment layers decreases about 82%. The decrease of Vrdc is attributed to the trapping and neutralizing of mobile ions by Ag nano-particles. Regardless of the effect of Ag nano-particles on the conductivity of Ag-d-PI alignment layers, the voltage holding ratio (VHR) of the cells is maintained surprisingly. The experiment results reveal a simple design for a low Vrdc LC cell.

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Strengthening of liquid crystal photoalignment on azo dye films: passivation by reactive mesogens

Abstract: Passivation of photoalignment films by continuous layers of reactive mesogen provides stable liquid crystal alignment and electro-optic performance equivalent to that of rubbed polyimide films.

Cited by 40 publications

References 28 publications

Advances in Transparent Planar Optics: Enabling Large Aperture, Ultrathin Lenses

Advances in Transparent Planar Optics: Enabling Large Aperture, Ultrathin Lenses

Photoaligned Nanorod Enhancement Films with Polarized Emission for Liquid‐Crystal‐Display Applications

Decreasing the Residual DC Voltage by Neutralizing the Charged Mobile Ions in Liquid Crystals

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