Search results for "liquid crystal"

The problem of spatial homogeneity in an LCoS projector

2019

Abstract Video projectors allow interesting applications in vision sciences since they provide a large projection area. We have colorimetrically characterized a LCoS projector using a mathematical model requiring additivity and constancy of the primaries -a sigmoid function in our case. Significant differences in chromaticity in the CIELAB space, but not in lightness, were found between the center and the corners of the screen. The lack of spatial homogeneity led us to estimate the parameters of the model as a function of spatial position, using different strategies. The best result was obtained by interpolating the values of the parameters of the model determined from experimental measurem…

Photoreactive Liquid Crystals in the Series of Dendritic and Cyclic Stilbenoid Compounds

2000

The dendrimers 1 and 2 and the areno-condensed annulenes 3 and 4 represent new mesogens for the generation of discotic mesophases. The stilbenoid building blocks of these compounds provide the molecular basis for interesting photochemical and photophysical effects like dimerisation, oligomerisation or the formation of charge carriers.

A new synthetic route to tribenzo[a,e,i][12]annulenes

2000

Abstract The tribenzo[a,e,i][12]annulene 10 and the corresponding twofold annulene 14 were prepared on synthetic routes which first led from suitably functionalised starting compounds (2, 11) to the 1,2-distyryl- and 1,2,3,4-tetrastyrylbenzene derivatives 9 and 13 with two and four formyl groups, respectively. The cyclisation to 10 and 14 was achieved by applying the McMurry reaction. The extended ring system of compound 14 represents a discotic mesogen. The generation of liquid crystals was obtained with eight hexyloxy chains on the periphery.

ChemInform Abstract: A New Synthetic Route to Tribenzo[a,e,i][12]annulenes.

2010

Abstract The tribenzo[a,e,i][12]annulene 10 and the corresponding twofold annulene 14 were prepared on synthetic routes which first led from suitably functionalised starting compounds (2, 11) to the 1,2-distyryl- and 1,2,3,4-tetrastyrylbenzene derivatives 9 and 13 with two and four formyl groups, respectively. The cyclisation to 10 and 14 was achieved by applying the McMurry reaction. The extended ring system of compound 14 represents a discotic mesogen. The generation of liquid crystals was obtained with eight hexyloxy chains on the periphery.

Fluorinated azole-azine systems as new Liquid-crystalline Ionic Liquids

2015

Dysprosium-Based Ionic Liquid Crystals: Thermal, Structural, Photo- and Magnetophysical Properties

2009

[C12mim]3[DyBr6] (C12mim = 1-dodecyl-3-methylimidazolium) represents a new material with interesting luminescent behavior as well as mesomorphic and magnetic properties. The compound was found to show thermotropic liquid crystalline behavior and forms smectic mesophases which were investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry. The emission color of [C12mim]3[DyBr6] can be tuned from white to orange-yellow by the choice of the excitation wavelength. Sample excitation with λex = 366 nm leads to the blue-whitish luminescence from the imidazolium cation itself. With λex = 254 nm the common Dy(III) emission is observed which mainly arises from the …

Iris-Like Tunable Aperture Employing Liquid-Crystal Elastomers

2014

A liquid-crystal elastomer (LCE) iris inspired by the human eye is demonstrated. With integrated polyimide-based platinum heaters, the LCE material is thermally actuated. The radial contraction direction, similar to a mammalian iris, is imprinted to the LCE by a custom-designed magnetic field. Actuation of the device is reproducible over multiple cycles and controllable at intermediate contraction states.

Shape-persistent V-shaped mesogens—formation of nematic phases with biaxial order

2006

A homologous series of shape-persistent V-shaped molecules has been designed to form the biaxial nematic phase. Phenyleneethynylene moieties are attached to a bent fluorenone unit to create an apex angle of about 90°, which is determined from the single crystal structure. Two mesogens, one symmetric and another unsymmetric, have been synthesized by attaching a cyano group to one or both of the peripheral phenyl units, respectively. These groups introduce local dipoles essential for the formation of the nematic phases. The tendency to form a crystalline phase is reduced by laterally substituted hexyloxy chains which allow the nematic phase to be supercooled to a glassy state. Two of the thre…

Programmable color tuning of a multiline laser by means of a twisted nematic liquid crystal display.

2012

An optical system useful to tune in a controlled way the color of a triline argon krypton (Ar–Kr) laser by means of a twisted nematic liquid crystal display (TNLCD) is presented. The optical setup employs a 4f system and two blazed gratings to first separate and then recombine the spectrum of the light beam. The TNLCD is included in the intermediate focal plane operating in the amplitude modulation mode to control the relative transmission of each spectral line. The resulting color is accurately predicted by using a previously developed physical model of the spectral and voltage dependence of the TNLCD birefringence. By simply changing the gray level image addressed to the display, the Ar–K…

Using birefringence colors to evaluate a tunable liquid-crystal q-plate

2019

Q-plates are geometrical phase elements that enable the realization of vector beams in simple and compact optical setups. In this work, we consider a tunable liquid-crystal commercial q-plate operative in the visible and near-IR range and study its spectral and color birefringence properties under broadband illumination. We first characterize the spectral retardance function of the device in a wide range from 400 to 1600 nm and determine how it changes upon applied voltage. Then we evaluate the color transmission characteristics when inserting the q-plate between crossed and parallel linear polarizers. These color properties agree with the trajectory in the CIExy chromaticity diagram as the…