Alignment of nematic liquid crystals on ruled grating surfaces

Nakamura, Minoru; Ura, Mitsuru

doi:10.1063/1.328478

Cited by 67 publications

(16 citation statements)

References 22 publications

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“…Generally, the LC cell made from rubbed PI and PS film has been known to parallel and perpendicular LC alignment with respect to the rubbing direction, respectively. Among the many mechanisms proposed by other research groups, physico-chemical interaction [6,11,12] and microgroove effect [13][14][15][16] mechanisms have been mainly considered as a mechanism of LC alignment. In particular, not only interaction between LC molecules and micro and/or nanogroove but physico-chemical interaction between LC molecules and oriented chemical groups in main and side chain have been important role in LC alignment behavior [17].…”

Section: Introductionmentioning

confidence: 99%

Liquid Crystal Alignment Behaviors of Polystyrene Derivatives Containing Coumarin Moieties

Kang

Hong

Kang

2014

Molecular Crystals and Liquid Crystals

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We synthesized a series of polystyrene derivatives containing coumarin side groups, poly (7-(4-vinylbenzyloxy)coumarin) (P7COU#) and poly (7-(4-vinylbenzyloxy)4-phenylcoumarin) (P7COU4P#), where # is the molar content of 7-hydroxycoumarin and 7-hydroxy-4-phenyl coumarin, respectively, using polymer analogous reaction, in order to study the effect of the 7-hydroxycoumarin and 7-hydroxy-4-phenyl coumarin side groups on the liquid crystal (LC) alignment properties. The LC alignment behavior of these two series was investigated by photoalignment or rubbing alignment. The LC cells made from photoirradiated P7COU# and P7COU4P# films showed homogeneous planar LC alignment. We found that LC aligning ability of the LC cells made from rubbed P7COU# and P7COU4P# films were affected by the structure and molar content of coumarin side groups. For example, anchoring energy of the LC cell fabricated with rubbed P7COU82 (7 × 10 −5 J/m 2 ) and P7COU4P81 (7 × 10 −7 J/m 2 ) film was increased drastically and slightly compared to polystyrene (10 −7 −10 −8 J/m 2 ), respectively. Particularly, anchoring energy of the LC cell made from rubbed P7COU# having more than 51 mol % of the 7-hydroxycoumarin as a side groups is comparable to that of the conventional polyimide in the LCD industry.

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Section: Introductionmentioning

confidence: 99%

Liquid Crystal Alignment Behaviors of Polystyrene Derivatives Containing Coumarin Moieties

Kang

Hong

Kang

2014

Molecular Crystals and Liquid Crystals

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“…Several molecular alignment techniques have been developed such as the grating method [1], the photo alignment method [2], and the rubbing method [3][4][5][6], and some of them have been adopted for commercial LCD production. Among these methods, the rubbing method is still popular because of its simple process.…”

Section: Introductionmentioning

confidence: 99%

A study on the relationship between rubbing scratches on an alignment film and rubbing cloths using a high-speed camera

Inoue

Kuramoto

Kimura

et al. 2011

Journal of Information Display

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“…A variety of factors has been proposed to explain the surface anchoring and alignment of LC molecules: (i) microgrooves in connection with anisotropic LC orientational elasticity via steric interactions, [77][78][79][80][81][82][83][84][85][86] (ii) polymer molecules from the velvet fabric deposited and oriented on the alignment layer surface during the rubbing process, 67,87,88 (iii) anisotropically oriented polymer chains, 74,75,[88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105] (iv) a near-surface order parameter different from that of bulk LC molecules, 105,106 (v) surface electric fields, 107 and (vi) coupling of the bending mode of the LC director with surface electric fields. 108 Of the mechanisms proposed so far, the anisotropic polymer chain orientation mechanism 74,75,[88][89][90][91][92][93][94]…”

Section: Introductionmentioning

confidence: 99%

The alignment of liquid crystals on the film surfaces of soluble aromatic polyimides bearingt-butylphenyl and trimethylsilylphenyl side groups

et al. 2009

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With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride (BTPD), and 2,2'-bis(4''-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyimides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from 0.45×10 -4 -1.37×10 -4 J/m 2 and from 0.86×10 -5 -4.26×10 -5 J/m 2 , respectively, depending on the polyimides. The pretilt angles of the LCs were in the range 0.10-0.62 o .In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

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Alignment of nematic liquid crystals on ruled grating surfaces

Cited by 67 publications

References 22 publications

Liquid Crystal Alignment Behaviors of Polystyrene Derivatives Containing Coumarin Moieties

Liquid Crystal Alignment Behaviors of Polystyrene Derivatives Containing Coumarin Moieties

A study on the relationship between rubbing scratches on an alignment film and rubbing cloths using a high-speed camera

The alignment of liquid crystals on the film surfaces of soluble aromatic polyimides bearingt-butylphenyl and trimethylsilylphenyl side groups

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