Transport Properties of Ions in Ferroelectric Liquid Crystal Cells

Chieu, T. C.; Yang, K. H.

doi:10.1143/jjap.28.2240

Cited by 46 publications

(19 citation statements)

References 11 publications

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“…The space charge in the liquid crystal sample cannot be freely discharged, and piles up in the interface layer between the liquid crystal and the surface molecular alignment layer in the case where the surface alignment layer is thick. This space charge accumulation mode has been studied by polarization switching current measurements, [7][8][9] electro-optic measurements, 10,11) and more recently by dielectric measurements. 2,3) In this work we studied the space charge accumulation using a dielectric measurement of dielectric strength and relaxation frequency ω r as a function of temperature and the temperature dependence of the X-mode relaxation.…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Low Frequency Dielectric Constants in Surface-Stabilized Ferroelectric Liquid Crystal

Wang¹,

Kim²

2000

Jpn. J. Appl. Phys.

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We have studied the temperature dependence of two low-frequency dielectric relaxation modes in a surface-stabilized ferroelectric liquid crystal (SSFLC): space charge accumulation and X modes. From investigation of Cole-Cole plots the temperature dependence of dielectric strength and relaxation frequency ω r for the two low-frequency modes was obtained. The relaxation frequency follows the Arrhenius relation in the respective asymptotic regions far from the phase transition temperatures. From the Arrhenius plots the activation energies for the space charge accumulation mode and the X-mode were obtained as 0.42 eV and 0.13 eV, respectively. Temperature dependence of rotational viscosity in the smectic C * (SmC * ) phase conformed with the temperature dependence of the X-mode parameters in the effective Debye relaxation regime, which implicates a common origin of azimuthal molecular rotation for both the Goldstone mode and the X-mode. However, the X-mode is irrelevant to the symmetry breaking phase transition and continues to be observed at all temperatures far from the phase transition.

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Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Low Frequency Dielectric Constants in Surface-Stabilized Ferroelectric Liquid Crystal

Wang¹,

Kim²

2000

Jpn. J. Appl. Phys.

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“…Most neutral impurities are ionized above the critical temperatures. 9,10 Hence, the concentration of ions in the LC layer increases with increasing temperature. For the evaluation of the temperature dependence, homogeneously aligned LC cells with 5.0-µm gaps were prepared with ZLI-1132 liquid crystal (Merck Corp.) and AL-1051 alignment layer material (JSR Corp.).…”

Section: Adsorption and Desorption Of Ions Under The Application Of Amentioning

confidence: 99%

“…7,8 It is generally known that the degree of ionization changes with a shift in temperature. 9,10 In most cases, the concentration of the ion increases with increasing temperature. The fact indicates that V rDC also changes with shifting temperature.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of residual DC voltage and its evaluation parameter related to liquid‐crystal and alignment‐layer materials

Mizusaki¹,

Miyashita²,

Uchida³

et al. 2008

J Soc Info Display

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Abstract— The temperature dependence of residual DC voltage was studied based on the adsorption and desorption of ions in the liquid‐crystal (LC) layer to and from the interface between the LC and alignment layers during the application of an external DC offset voltage. The relaxation process of the adsorbed ions during the open‐circuit state was also studied after applying the DC offset voltage. Those processes were found to follow the Arrhenius rule, and a new evaluation parameter related to the temperature is proposed for the design of the LC and alignment‐layer materials.

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“…It is based on the model presented by Chieu and Yang [19]. As was also pointed out by Zou [20], some improvements had to be made.…”

Section: The Modelmentioning

confidence: 99%

<title>Ionic effects in LCDs</title>

et al. 1993

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In this paper we give an overview of the effects of ionic impurities present in LCD's. First we discuss the case of Active Matrix addressed nematic LCD's (AMLCD) as these are at this moment the most interesting candidates for high preformance flat display panels with multi-colour possibilities. As a second type we consider the Surface Stabilized Ferroelectric LCD's (SSFLCD).1 Active Matrix Twisted Nematic LCD's Liquid crystal displays have been used for many years as cheap, low performance small displays in watches, video games etc. Recently however, also high information content displays became feasible using LCD's. The STN effect already allowed for reasonable performance displays and now the Active Matrix LCD's can combine high resolution with multi colour possibilities.Thanks to intensive research efforts made by the LC-producers, extremely pure LC-mixtures are now available. Intrinsic resistivities of more than 1O'31crn are reached [1]. After processing and operating the LCD however, resistivity values can drop over an order of magnitude or more [2] [3]. A possible explanation for this phenomenon is the introduction of impurities during processing or operating. These impurities, but also the LC-material itself, can ionize partly.Two important parameters of an LCD are the switching speed (possibility to obtain video speed) and the number of grey levels (and thus the number of colours) that can be created. We will explain how the presence of ionic impurities deteriorates the performance of an AMLCD in both respects. Holding Ratio of the AMLCDIn each pixel of an AMLCD, a thin film transistor (TFT) is included as a switching element ( fig. 1)[4] [5]. During one line time the driving voltage is switched on the pixel. During the remaining frame time the TFT is in cut-off and the charge should be retained on the pixel capacitor in order to obtain a controllable r.m.s.-voltage over the pixel. However, when the voltage waveform over a pixel in an AMLCD is actually measured, a voltage drop is noticed ( fig. 2).Because of the dielectric anisotropy e of liquid crystals, the slow reorientation of nematic LC molecules causes a change of the pixel capacitance during the frame time. Since in active matrix addressing the charge on the pixel O-8194-1073-X/93/$6.OO SPIE Vol. 1845 Liquid and Solid State Crystals (1992)! 391 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/03/2015 Terms of Use: http://spiedl.org/terms

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Transport Properties of Ions in Ferroelectric Liquid Crystal Cells

Cited by 46 publications

References 11 publications

Temperature Dependence of Low Frequency Dielectric Constants in Surface-Stabilized Ferroelectric Liquid Crystal

Temperature Dependence of Low Frequency Dielectric Constants in Surface-Stabilized Ferroelectric Liquid Crystal

Temperature dependence of residual DC voltage and its evaluation parameter related to liquid‐crystal and alignment‐layer materials

<title>Ionic effects in LCDs</title>

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