Long-term Ion Transport in Nematic Liquid Crystal Displays

Vleeschouwer, Herbert De; Asselt, Alwin Verschueren; Alexander, Els; Vermael, Stefaan; Neyts, Kristiaan; Pauwels, Herman

doi:10.1143/jjap.40.3272

Cited by 55 publications

(22 citation statements)

References 13 publications

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“…The most important are ionic dissociations of the residual impurities [2,29], ionic contamination during the manufacturing process (the alignment layers, the glue, and the filling process are the sources of the contaminations) [19,30], charge injection, charge transfer and electrochemical reactions in the electrodes and/or in the bulk of the liquid crystal cell [2,[31][32][33][34][35], and aging (chemical decomposition and self -dissociation of liquid crystals) [2,11]. The simultaneous presence of more than one of the processes mentioned above is a very common thing and should be considered by experimentalists [2,36,37].…”

Section: Ions In Liquid Crystalsmentioning

confidence: 99%

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

2015

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Abstract:The presence of ions in liquid crystals is one of the grand challenges that hinder the application of liquid crystals in various devices, which include advanced 3-D and flexible displays, tunable lenses, etc. Not only do they compromise the overall performance of liquid crystal devices, ions are also responsible for slow response, image sticking, and image flickering, as well as many other negative effects. Even highly purified liquid crystal materials can get contaminated during the manufacturing process. Moreover, liquid crystals can degrade over time and generate ions. All of these factors raise the bar for their quality control, and increase the manufacturing cost of liquid crystal products. A decade of dedicated research has paved the way to the solution of the issues mentioned above through merging liquid crystals and nanotechnology. Nano-objects (guests) that are embedded in the liquid crystals (hosts) can trap ions, which decreases the ion concentration and electrical conductivity, and improves the electro-optical response of the host. In this paper, we (i) review recently published works reporting the effects of nanoscale dopants on the electrical properties of liquid crystals; and (ii) identify the most promising inorganic and organic nanomaterials suitable to capture ions in liquid crystals.

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Section: Ions In Liquid Crystalsmentioning

confidence: 99%

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

2015

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“…The recombi− nation constant a was equal to 4.93´10 -18 . This value was calculated using the formula [23] , which is characteristic to well−purified and contaminated liquid crys− talline material, respectively. Quasi−blocking electrodes were assumed, reflecting the fact that they are normally cov− ered with insulating aligning films.…”

Section: Geometry and Parametersmentioning

confidence: 99%

Threshold voltages and optical retardation of deformed flexoelectric nematic layers with asymmetric surface anchoring

Derfel

Buczkowska

2013

Opto-Electronics Review

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Deformations of homeotropically aligned flexoelectric nematic layers induced by dc electric fields were simulated numerically. Two different anchoring strengths on the limiting surfaces were assumed. Nematic material was characterised by negative dielectric anisotropy. Both signs of the sum of flexoelectric coefficients were taken into account. The electric properties of the layer were described in terms of a weak electrolyte model. Mobility of cations was assumed to be one order of magnitude lower than that of anions. Quasi-blocking electrode contacts were assumed. The threshold voltages for deformations were determined by means of calculations of the phase difference Φ between ordinary and extraordinary light rays passing through a layer placed between crossed polarisers. The threshold values depended on the polarity of the bias voltage U. When the threshold value was exceeded, the phase difference increased with the voltage. Two different Φ(U/Uthreshold) dependencies for the two polarities of the voltage were found for each layer if the nematic possessed the flexoelectric properties. The possibility of using this effect to detect the flexoelectricity in the nematic was explored by simulated experiments. The effectiveness of the proposed method is discussed.

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“…The ion concen− trations were determined by the generation constant b 0 and the recombination constant a [6,12]. The value of b 0 was varied from 10 18 to 10 22 m -3 s -1 in order to control the ion concentration whereas a resulted from the parameters of the nematic, and it was equal to 4.93´10 18 m 3 s -1 for De = -2 and 3.85´10 18 m 3 s -1 for De = 2 [12]. The low, moderate, and high values of the average ion concentrations N 0 were taken into account.…”

Section: Geometry and Parameters Of The Systemmentioning

confidence: 99%

Analysis of deformations of flexoelectric homeotropic liquid crystal layers with various anchoring strengths

Buczkowska

Derfel

2011

Opto-Electronics Review

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Deformations of homeotropic layers of nematic liquid crystal possessing flexoelectric properties and subjected to external dc voltage were studied numerically. The influence of the anchoring strengthWwas investigated. The calculations were performed for two types of layers, one with positive dielectric anisotropy and positive sum of flexoelectric coefficients and the other with opposite signs of these parameters. Strongly blocking electrodes were assumed. The threshold voltages for deformations were computed for several anchoring strength values and for low, moderate, and high ion contents. The director distributions were also determined. They were influenced by joined effects of anchoring strength and space charge of ions. For increasing ion contents and increasing anchoring strength, remarkable change of deformation character was noticed. In the case of negative dielectric and flexoelectric parameters, the threshold was nearly proportional to W for low anchoring strength and saturated at some high value of W. In the case of positive dielectric and flexoelectric parameters, the threshold voltage increased strongly with W. In the range of enhanced ion concentrations, the deformation arose in two voltage ranges. The increasing anchoring strength damped the deformations in the whole layer, however, this effect was minor at high ion content.

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Long-term Ion Transport in Nematic Liquid Crystal Displays

Cited by 55 publications

References 13 publications

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

Threshold voltages and optical retardation of deformed flexoelectric nematic layers with asymmetric surface anchoring

Analysis of deformations of flexoelectric homeotropic liquid crystal layers with various anchoring strengths

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