A Theory of the Cholesteric Mesophase

Keating, P. N.

doi:10.1080/15421406908084912

Cited by 111 publications

(31 citation statements)

References 2 publications

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“…When the temperature rises, the reflection wavelength of the cell will become shorter due to the thermodynamic vibrations effect on the original SH structure. The increased thermal vibration strength results in increased twisting power variation between the neighboring molecular structures, and the helical pitch length of the N*LC cell will be reduced [5,52]. Such a thermal vibration effect also decreases the light intensity of the Bragg reflection, which is attributed to the fact that the director of the helical axis is disturbed (i.e., it is no longer perpendicular to the substrate surface), leading to the light scattering.…”

Section: Resultsmentioning

confidence: 99%

“…The self-assembled helical pitch length is a critical factor which significantly affects the optoelectronic cell properties of the cell. Various approaches for tuning the helical pitch length of N*LCs have been proposed such as mixing different chiral concentrations [2][3][4], changing the operating temperature [5], using photo-tunable chiral dopants [6], and applying external electric fields [7]. The current trend in the fabricated helical pitch length of N*LC cells is to shorten it so as to reduce the light leakage (i.e., reduce the transmitted light) in the dark state when the cell is placed between the crossed polarizers [8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Lin¹,

Chen²,

Lin³

et al. 2014

Opt. Mater. Express

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The electro-optical properties of the chiral nematic liquid crystal cell, driven by in-plane switching and non-uniform vertical electric fields, are investigated. The Bragg reflection, threshold voltage, and helical configuration are significantly related with the chiral dopant concentration. Through the driving-mode switching, two bistable helical structures without holding voltages are developed. The behavior of voltage-and temperaturedependent light reflection associated with the helical structure transition is also revealed. A fast bistable switching response (~5 ms) is successfully achieved by the three-terminal-electrode architecture. Further, the proposed cell shows a display time of over 6 hr in the unplugged power state.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Lin¹,

Chen²,

Lin³

et al. 2014

Opt. Mater. Express

View full text Add to dashboard Cite

show abstract

“…The molecules perform torsional vibrations in an anharmonic potential due to chirality. For increasing temperature the angle of these vibrations becomes larger, thus the pitch of the helix becomes shorter [27]. In reality, intermolecular interactions cause the anharmonic potential and thus the temperature dependence of the pitch.…”

Section: Propertiesmentioning

confidence: 99%

Chiral Liquid Crystals: Structures, Phases, Effects

2014

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The introduction of chirality, i.e., the lack of mirror symmetry, has a profound effect on liquid crystals, not only on the molecular scale but also on the supermolecular scale and phase. I review these effects, which are related to the formation of supermolecular helicity, the occurrence of novel thermodynamic phases, as well as electro-optic effects which can only be observed in chiral liquid crystalline materials. In particular, I will discuss the formation of helical superstructures in cholesteric, Twist Grain Boundary and ferroelectric phases. As examples for the occurrence of novel phases the Blue Phases and Twist Grain Boundary phases are introduced. Chirality related effects are demonstrated through the occurrence of ferroelectricity in both thermotropic as well as lyotropic liquid crystals. Lack of mirror symmetry is also discussed briefly for some biopolymers such as cellulose and DNA, together with its influence on liquid crystalline behavior.

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“…The reflected color of CLCs can be changed by the pitch variation by the external factors. For the application to the electronic paper display, various technologies to diversify the reflected color of CLCs have been investigated such as varying the temperature of the cholesteric LC phase [4], adding different amounts of the chiral compounds [5], using phototunable chiral compounds [6], and applying an 978-1-4673-2204-1/12/$31.00 ©2012 IEEE 624 external field [3]. Recently, the technology of controlling the pitch by the chiral dopant solubility depending on the temperature is reported.…”

Section: Introductionmentioning

confidence: 99%

Tunable colors of chiral liquid crystal displays

Youn

Bae

Hwang

et al. 2012

2012 3rd IEEE International Conference on Network Infrastructure and Digital Content

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We report a method of the color variation in the reflective CLC displays depending on thermodynamically and the electric field switching. The reflective wavelength can be thermodynamically switched to reflect green from a cell initially reflecting a red color. Afterwards, the reflective wavelength can be electrically switched to reflect blue color. It is found that continuous decrease of the pitch is mainly originated from the dopant solubility below the critical temperature and stepwise decrease of the pitch is dominantly affected by the thermodynamic property above the critical temperature. The blue color change is a result of the compression to the helical pitches in planar layers in response to the applied voltage.

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A Theory of the Cholesteric Mesophase

Cited by 111 publications

References 2 publications

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Effects of chiral dopant on electro-optical properties of nematic liquid crystal cells under in-plane switching and non-uniform vertical electric fields

Chiral Liquid Crystals: Structures, Phases, Effects

Tunable colors of chiral liquid crystal displays

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