Nematische Flüssigkristalle für Aktiv-Matrix-Displays: Design und Synthese

Kirsch, Peer; Bremer, Matthias

doi:10.1002/1521-3757(20001201)112:23<4384::aid-ange4384>3.0.co;2-s

Cited by 95 publications

(29 citation statements)

References 102 publications

(32 reference statements)

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“…In contrast, the vertically aligned (VA) mode LCD's [1][2][3][4][5], based on liquid crystal materials with negative dielectric anisotropy, offers a superior picture quality with wide viewing angle [6,7], high contrast [8] and video-compatible switching times [9,10]. Liquid crystalline materials suitable for VA mode LCD's are mainly focused on dielectrically negative fluorinated liquid crystals comprising of 1,2-difluorobenzene building block [11] which combine the necessary polarity with chemical stability and low polarizability [12,13] suitable for their application in VA mode LCD's. Difluorinated alkoxy compounds are suitable for preparation of VA mixtures because of their large negative dielectric anisotropy and low optical birefringence.…”

Section: Introductionmentioning

confidence: 99%

Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements

Basak¹,

Dasgupta²,

Das³

et al. 2011

Acta Phys. Pol. A

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Two tri-component mixtures as base mixtures for vertically aligned mode LCD's were prepared. The eutectic compositions were theoretically estimated and experimentally verified from differential scanning calorimetry studies. A room temperature nematic mixture with fairly broad operating range emerged from each of the tri-component mixtures. The optical birefringence of these mixtures at the eutectic composition was measured as a function of temperature. X-ray diffraction measurements were done on these mixtures to obtain the orientational order parameters as a function of temperature. The order parameter values were also determined from birefringence measurements and the results were compared with mean field theory. Structural parameters like intermolecular distance and apparent molecular length have also been determined.

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Section: Introductionmentioning

confidence: 99%

Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements

Basak¹,

Dasgupta²,

Das³

et al. 2011

Acta Phys. Pol. A

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“…In continuation of our earlier work on two tricomponent mixtures (ABC and ABD) as base mixtures for vertically aligned (VA) mode LCD's [13], where we had reported the orientational order parameters from optical birefringence and X-ray diraction measurements [4], in this paper, we report the results of the dielectric permittivity, bend elastic constant and rotational viscosity measurements on these mixtures at the eutectic composition throughout their entire mesomorphic range. Vertically aligned mode applications require liquid crystalline materials with negative dielectric anisotropy [5,6]. Such features are realized with liquid crystals having lateral polar substituents which induce a dipole moment perpendicular to the long axes of the molecule [7].…”

Section: Introductionmentioning

confidence: 99%

Dielectric Permittivity and Viscoelastic Measurements οf Two Tricomponent Mixtures Consisting οf Laterally Fluorinated Terphenyl Derivatives

Basak¹,

Dasgupta²,

Das³

et al. 2013

Acta Phys. Pol. A

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Two tricomponent room temperature nematic eutectic mixtures ABC and ABD with laterally uorinated constituents A and B were prepared as base mixtures for vertically aligned mode LCD's. The physical properties of these mixtures viz. birefringence, dielectric anisotropy, bend elastic constant, relaxation time and rotational viscosities were determined in order to compare with the optimum values required to achieve the target specications of VA mode materials. The dielectric anisotropy, ∆ε, and optical birefringence, ∆n, of these mixtures were found to be in the range of (1.3 to 1.4) and (0.13 and 0.14), respectively, at around 20• C. The gure of merit for the ABD mixture has been found to be higher than that of ABC mixture throughout the entire temperature range. The pretilt angle eect in the physical parameters has also been studied. At T = 20• C, the response time decreases to 25% and 35% for mixture ABC for 2• and 5• pretilt respectively in comparison to zero pretilt. On the other hand, at the same temperature for the ABD mixture these values are reduced by 16% and 35%, respectively.

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“…Reinitzer's discovery in 1888 [1] that cholesteryl benzoate (1) forms at elevated temperatures an up to then unknown state of matter -a liquid crystalline mesophase -triggered a development culminating in the last few years in the ubiquitous presence of liquid crystal displays (LCD) in our daily lives [2,3]. The mesophase formed by cholesteryl benzoate was later classified as ''chiral nematic'' or simply ''cholesteric'' (Scheme 1) [4].…”

Section: Introductionmentioning

confidence: 99%

“…If not carefully controlled, this may result in unpredictable changes of the pitch of the cholesteric phase during the mixture and LCD panel production process. Therefore, there is a need for chiral dopants which are easily accessible, chemically more robust and fully compatible with any type of active matrix LCD technology [2]. Additional favourable features may be improved solubility and the ease of adaptation of the electrooptical properties of the chiral dopant to different types of nematic liquid crystal preparations.…”

Section: Introductionmentioning

confidence: 99%