Influence of the flow on the anchoring of nematic liquid crystals on a Langmuir-Blodgett monolayer studied by optical second-harmonic generation

The influence of capillary flow on the alignment of the nematic liquid crystal MBBA on fatty acid Langmuir-Blodgett monolayers was studied by optical second-harmonic generation. The surface dipole sensitivity of the technique allows probing the orientation of the first liquid crystal monolayer in the presence of the liquid crystal bulk. It was found that capillary flow causes the first monolayer of liquid crystal molecules in contact with the fatty acid monolayer to be oriented in the flow direction with a large pretilt (78 degrees), resulting in a quasi-planar alignment with splay-bend deformation of the nematic director in the bulk. itself is affected by the flow. The quasi-planar flow-induced alignment was found to be metastable. Once the flow ceases, circular domains of homeotropic orientation nucleate in the sample and expand until the whole sample becomes homeotropic. This relaxation process from flow-induced quasi-planar to surface-induced homeotropic alignment was also monitored by SHG. It was found that in the homeotropic state the first nematic layer presents a pretilt of 38 degrees almost isotropically distributed in the plane of the cell, with a slight preference for the direction of the previous flow.Comment: LaTeX2e article, 11 figures, 17 EPS files, submitte

Fountain fringe field switching (FFFS) for wide viewing angle LCDs

To reduce or completely remove the viewing angle dependence of liquid crystal (LC) displays and devices, we have recently introduced a new electrode structure for LC displays. This electrode structure has openings (holes) in the pixel electrode (PixE) for generating fringe electric field with azimuthal degenerated distribution of the field lines around each hole, resembling a fountain. Such a field is promoting azimuthally degenerated switching of the LC molecules and thus generation of images with 360◦ viewing angle constant contrast when a pair of crossed circular polarisers are used. A theoretical model of the fountain fringe field, generated around a single circular hole and plurality of such holes in the PixE, is presented

Flexoelectric Polarization in a Nematic Liquid Crystal Enhanced by Dopants with Different Molecular Shape Polarities

Funding Information: We would like to acknowledge the great support which we received from Prof. I. Muševič, JSI, Ljubljana, Slovenia, Dr M. Klasen-Memmer, Merck, Germany, Dr Santanu Kumar Pal and Dr Golam Mohiuddin, Indian Institute of Science Education and Research (IISER) Mohali, India, and Prof. P. Kula and K. Garbat, MUT, Warsaw, Poland. This work has been partially supported by SeeReal Technologies and MUT Research Grants 13-843/WAT/2022.Peer reviewedPublisher PD

Sensitive methods for estimating the anchoring strength of nematic liquid crystals on Langmuir-Blodgett monolayers of fatty acids

The anchoring of the nematic liquid crystal N-(p-methoxybenzylidene)-p-butylaniline (MBBA) on Langmuir-Blodgett monolayers of fatty acids (COOHC$_{n}$H$_{2n+1}$) was studied as a function of the length of the fatty acid alkyl chains, $n$ ($n = 15, 17, 19, 21$). The monolayers were deposited onto ITO-coated glass plates which were used to assemble sandwich cells of various thickness that were filled with MBBA in the nematic phase. The mechanism of relaxation from the flow-induced quasi-planar to the surface-induced homeotropic alignment was studied for the four decreases linearly with increasing the length of the alkyl chains $n$ which suggests that the Langmuir-Blodgett film plays a role in the phenomenon. This fact was confirmed by a sensitive estimation of the anchoring strength of MBBA on the fatty acid monolayers after anchoring breaking which takes place at the transition between two electric-field--induced turbulent states, denoted as DSM1 and DSM2. It was found that the threshold electric field for the anchoring breaking, which can be considered as a measure of the anchoring strength, also decreases linearly as $n$ increases. Both methods thus possess a high sensitivity in resolving small differences in anchoring strength. In cells coated with mixed Langmuir-Blodgett monolayers of two fatty acids ($n=15$ and $n=17$) a maximum of the relaxation speed was observed when the two acids were present in equal amount. This observation homeotropic cells by changing the ratio between the components of the surfactant film.Comment: LaTeX article, 20 pages, 15 figures, 17 EPS files. 1 figure added, references moved. Submitted to Phys. Rev.

A liquid crystal device and a method for manufacturing thereof

The invention relates to a liq. crystal device comprising a liq. crystal bulk layer and a dynamic surface-director alignment layer, wherein the liq. crystal bulk layer comprises a liq. cryst. material possessing a phase sequence consisting of isotropic phase, nematic phase and optionally cryst. phase (s), and the surface-director alignment layer comprises a chiral smectic liq. cryst. polysiloxane. The invention also relates to a method for its manufg. [on SciFinder (R)]74 FIELD Section Title:Radiation Chemistry, Photochemistry, and Photographic and Other Reprographic ProcessesField url:Ae, ag, al, am, at, au, az, ba, bb, bg, br, bw, by, bz, ca, ch, cn, co, cr, cu, cz, de, dk, dm, dz, ec, ee, eg, es, fi, gb, gd, ge, gh, gm, hr, hu, id, il, in, is, jp, ke, kg, km, kp, kr, kz, lc, lk, lr, ls, lt, lu, lv, ma, md, mg, mk, mn, mw, mx, mz, na, ng, ni, no, nz, om, pg, ph, pl, pt, ro, ru, sc, sd, se, sg, sk, sl, sm, sy, tj, tm, tn, tr, tt, tz, ua, ug, us, uz, vc, vn, yu, za, zm, zw.At, be, ch, cy, de, dk, es, fi, fr, gb, gr, ie, is, it, lu, mc, nl, pt, se, tr, bf, bj, cf, cg, ci, cm, ga, ml, mr, ne, sn, td, tg.G02f001-1347.G02f001-1337; g02f001-141; c09k019-40.Application: WO20050608.2005-ep6145Ep2004-1359220040609 FIELD Citations:Demus, D; WO 0003288 A 2000|Galli, G; MOLECULAR CRYSTALS AND LIQUID CRYSTALS 2001, 360, 147|Komitov, L; WO 03081326 A 2003|Komitov, L; JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY SOC, 11, 437|Merck Patent Gmbh; WO 8909203 A 198

Fast Switching Liquid Crystal Display Modes

We present two LCD modes enabling short rise and fall switching time, being in the microsecond range in most of the modes. Polymeric network, created in the liquid crystal bulk, as well as in the presence of flexoelectric polarization are among those employed for achieving of fast switching modes in LCDs. Proper assembling and electronic driving of two parallel liquid crystal cells, arranged in a double cell configuration, is another approach enabling a fast switching mode between bright and dark state of the device. We discuss these modes in terms of device performance and their suitability for application in LCDs

Polymers for use as alignment layers in liquid crystal devices

The invention relates to a polymer for use as a surface-director alignment layer in a liq. crystal device, said polymer comprising a polymeric backbone and side-chains attached thereto, wherein the polymeric backbone lacks directly coupled ring structures, and each side-chain of at least some of the side-chains comprises >=2 unsubstituted and/or substituted phenyls coupled via a coupling selected from a carbon-carbon single bond, a carbon-carbon double bond contg. unit (CH:CH), a carbon-carbon triple bond contg. unit (C.tplbond.C), a methylene eter unit (CH2O) , an ethylene eter unit (CH2CH2O), an ester unit (COO) and an azo unit (N:N), exhibits a permanent and/or induced dipole moment that in ordered phase provides dielec. anisotropy, and is attached to the polymeric backbone via at least two spacing atoms. Thus, 4\u27-(11,11-diethoxyundecyloxy)biphenyl-4-carbonitrile 0.70, octanal 0.081, and polyvinyl alc. 0.198 g were reacted in DMF at 55 Deg for 24 h to give a side-chain liq. crystal polymer, which was fabricated into a liq. crystal device as alignment layer. [on SciFinder (R)

A liquid crystal device and a method for manufacturing thereof

The invention relates to a liq. crystal device comprising a liq. crystal bulk layer and a dynamic surface-director alignment layer, wherein the liq. crystal bulk layer comprises a liq. cryst. material possessing a phase sequence consisting of isotropic phase, nematic phase and optionally cryst. phase (s), and the surface-director alignment layer comprises a chiral smectic liq. cryst. polysiloxane. The invention also relates to a method for its manufg. [on SciFinder (R)]74 FIELD Section Title:Radiation Chemistry, Photochemistry, and Photographic and Other Reprographic ProcessesField url:Ae, ag, al, am, at, au, az, ba, bb, bg, br, bw, by, bz, ca, ch, cn, co, cr, cu, cz, de, dk, dm, dz, ec, ee, eg, es, fi, gb, gd, ge, gh, gm, hr, hu, id, il, in, is, jp, ke, kg, km, kp, kr, kz, lc, lk, lr, ls, lt, lu, lv, ma, md, mg, mk, mn, mw, mx, mz, na, ng, ni, no, nz, om, pg, ph, pl, pt, ro, ru, sc, sd, se, sg, sk, sl, sm, sy, tj, tm, tn, tr, tt, tz, ua, ug, us, uz, vc, vn, yu, za, zm, zw.At, be, ch, cy, de, dk, es, fi, fr, gb, gr, ie, is, it, lu, mc, nl, pt, se, tr, bf, bj, cf, cg, ci, cm, ga, ml, mr, ne, sn, td, tg.G02f001-1347.G02f001-1337; g02f001-141; c09k019-40.Application: WO20050608.2005-ep6145Ep2004-1359220040609 FIELD Citations:Demus, D; WO 0003288 A 2000|Galli, G; MOLECULAR CRYSTALS AND LIQUID CRYSTALS 2001, 360, 147|Komitov, L; WO 03081326 A 2003|Komitov, L; JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY SOC, 11, 437|Merck Patent Gmbh; WO 8909203 A 198

Fast Liquid Crystal Light Shutter

By proper assembling and electronic driving of two parallel single nematic liquid crystal cells with planar and vertical alignment of the liquid crystal molecules, respectively, arranged in a double cell, fast switching between bright and dark states, back and forth, is achieved. The switching rise and fall time of the device corresponds to the switching rise time of the cells from the relaxed to the switched state. The simultaneous transition of the cells from the switched to the relaxed state, however, remains optically hidden from the observer due to the optical compensation effect during this transition