Temporal electrical response of chiral smectic liquid crystal displays with V/W-shaped electrooptical characteristic

Sánchez‐Pena, José Manuel; Pérez, Isabel; Urruchi, V.; Torres, Juan Carlos; Otón, J. M.

doi:10.2478/s11772-007-0032-6

Cited by 3 publications

(3 citation statements)

References 12 publications

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“…reorientation of LC molecules and MWCNTs) and other physical phenomena. Several EECs have been proposed to describe the electrical behavior of LC devices [23][24][25]. A simple EEC has been recently demonstrated [9] to justify the behavior of MWCNT/ LC composites at intermediate frequencies; yet when the Impedance spectroscopy customarily employs sufficiently small voltage signals (100 mV rms ) for the system response to be linear.…”

Section: Characterization Method: Driving Waveform Electric Equivalenmentioning

confidence: 99%

“…Although EECs of different types and configurations of LC cells have been reported [23][24][25], a description of the electrical behavior of CNT-doped LC cells in a wide range of frequencies and voltages has not been performed yet. Once the cell behavior has been mirrored to elementary electrical components (resistors, capacitors, coils, etc), every one standing for a physical effect, the contribution of each cell component-LC, CNTs, external circuitry-to the electrical parameters may be established.…”

Section: Introductionmentioning

confidence: 99%

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The peculiar electrical response of liquid crystal-carbon nanotube systems as seen by impedance spectroscopy

García-García¹,

Vergaz²,

Algorri³

et al. 2015

J. Phys. D: Appl. Phys.

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Conductive nanoparticles, especially elongated ones such as carbon nanotubes, dramatically modify the electrical behavior of liquid crystal cells. These nanoparticles are known to reorient with liquid crystals in electric fields, causing significant variations of conductivity at minute concentrations of tens or hundreds ppm. The above notwithstanding, impedance spectroscopy of doped cells in the frequency range customarily employed by liquid crystal devices, 100 Hz-10kHz, shows a relatively simple resistor/capacitor response where the components of the cell can be univocally assigned to single components of the electrical equivalent circuit. However, widening the frequency range up to 1 MHz or beyond reveals a complex behavior that cannot be explained with the same simple EEC. Moreover, the system impedance varies with the application of electric fields, their effect remaining after removing the field. Carbon nanotubes are reoriented together with liquid crystal reorientation when applying voltage, but barely reoriented back upon liquid crystal relaxation once the voltage is removed. Results demonstrate a remarkable variation in the impedance of the dielectric blend formed by liquid crystal and carbon nanotubes, the irreversible orientation of the carbon nanotubes and possible permanent contacts between electrodes.

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Section: Characterization Method: Driving Waveform Electric Equivalenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The peculiar electrical response of liquid crystal-carbon nanotube systems as seen by impedance spectroscopy

García-García¹,

Vergaz²,

Algorri³

et al. 2015

J. Phys. D: Appl. Phys.

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show abstract

“…An experimental protocol, designed and checked in previous works, 8,9 has been implemented to derive the values of components in the EEC of AFLC devices. As a result of this work, a modified EEC from the previous one displayed in Fig.…”

Section: Introductionmentioning

confidence: 99%

Electrical modeling of tristate antiferroelectric liquid crystal devices

Zafra

2011

Opt. Eng

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Abstract.A new electrical equivalent circuit (EEC) has been proposed to model antiferroelectric liquid crystal devices. This circuit includes a constant phase element to take into account the ferroelectric part of the dielectric response in these devices. Electrical characterization of samples has been carried out using a specific experimental protocol based on impedance spectroscopy. The parameters of waveforms used in impedance measurements have been optimized. The procedure to obtain the components of the EEC has also been explained. Finally, the EEC has been validated by comparing experimental and simulated impedance results. A reasonable agreement between both of them has been obtained in a wide frequency range for all selection voltages. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Reorientation effect and electrical current in a weakly anchored nematic cell

et al. 2009

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A nematic cell subjected to a large electric field undergoes a molecular reorientation that affects the electrical current flowing through it. To analytically establish the dependence of the current on the applied voltage, the cell is considered as parallel of resistance, R(t) , and capacitance, C(t) , that are connected with the nematic director profile. This profile is determined in the quasistatic regime in which the nematic orientation follows the time variation in the external field normal to the cell plates without delay. The analysis performed for a weakly anchored cell shows that the current presents a peak when the applied voltage overcomes the threshold voltage for the transition of Fréedericksz at a critical time t* as in the case of strong anchoring. For large voltages, R(t)-->R|| and C(t)-->C||, where parallel refers to the nematic director. We show that, for large enough time t>>t*, it is possible to connect the measured current with the extrapolation length characterizing the sample by means of simple analytical expressions. This connection can be used to experimentally estimate the anchoring energy by means of current measurements.

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Temporal electrical response of chiral smectic liquid crystal displays with V/W-shaped electrooptical characteristic

Cited by 3 publications

References 12 publications

The peculiar electrical response of liquid crystal-carbon nanotube systems as seen by impedance spectroscopy

The peculiar electrical response of liquid crystal-carbon nanotube systems as seen by impedance spectroscopy

Electrical modeling of tristate antiferroelectric liquid crystal devices

Reorientation effect and electrical current in a weakly anchored nematic cell

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