杉村 明彦

Time-resolved NMR spectroscopy is a powerful method to investigate field-induced rotation of the director in a nematic liquid crystal. The method requires that the director does not rotate significantly during the acquisition of the free induction decay and hence the NMR spectrum. We have extended the method to systems where this is not the case and the observed NMR spectra are now found to contain novel oscillatory features. To understand these oscillations, we have developed a model combining both director and spin dynamics. In addition to increasing the information content of the time-resolved NMR spectra, it also proves possible to determine the field-induced relaxation time from a single spectrum.

Deuterium NMR spectroscopy is widely employed to investigate the static and dynamic director alignment for low molar mass nematics contained in a thin sand-wich cell. When the director is not uniformly aligned the appearance of the deu-terium NMR spectra, recorded in the measurements, reflects the form of the director distribution. This occurs because the observed spectrum is a weighted sum of the spectra from all director orientations in the sample. In order to obtain the form of the director distribution function by simulating the spectra it is necessary to know how the spectral lineshape varys with the director orientation. As well as being of practical relevance, when the director distributes thermally with the average director orientation in multi domains, this contribution to the lineshape is of funda-mental interest for nematic behaviour.

Surface relief gratings on organic polysilane thin films are fabricated by holographic exposure of ultra-violet light, and Au gratings are subsequently prepared on polysilane gratings by vapor deposition of Au. The anchoring energies of 4-pentyl-4’-cyanobiphenyl (5CB) nematic liquid crystal on the fabricated gratings are determined with a saturation voltage method. The anchoring energies of Au gratings are weaker than those of organic polysilane gratings because of suppression of π?π interaction between the liquid crystal and the alignment layer. The polar anchoring energies of Au gratings are also weaker than those reported in literature.

Deuterium NMR spectroscopy is widely employed to investigate the<br /> static and dynamic director alignment for low molar mass nematics <br /> contained<br /> in a thin sandwich cell. When the director is not uniformly aligned the<br /> appearance of the deuterium NMR spectra, recorded in the measurements,<br /> reflect the form of the director distribution. This occurs because the<br /> observed spectrum is a weighted sum of the spectra from all director<br /> orientations in the sample. In order to obtain the form of the director<br /> distribution function by simulating the spectra it is necessary to know <br /> how<br /> the spectral linewidths vary with the director orientation. As well as<br /> being of practical relevance, the angular dependence of the linewidths is<br /> of fundamental interest for nematic behaviour because it is related to<br /> factors such as molecular rotation, director fluctuations and <br /> orientational<br /> order. Here we explore ways to vary the director orientation, as a<br /> monodomain, using an electric field and employ this to measure the angular<br /> dependence of the NMR linewidths for the nematic phase of<br /> 4-α,α-d2-pentyl-4′-cyanobiphenyl as a function of temperature.

Film thickness dependences of the unified surface anchoring strengths from the splay deformation for nematic cells were discussed. Thin <br /> nematic parallel (d =2–50 μm) and wedge (d = 0.3–5 μm) cells with the same solid surface were prepared to evaluate the surface anchoring <br /> strength. The surface anchoring strengths from the splay deformations for two kinds of liquid crystals were measured by using the saturation <br /> method. The nematogens used were 4-pentyl-4′-cyanobiphenyl and mixture compound ZLI-4792 (Merck Japan Co., Ltd.) with positive dielectric <br /> anisotropy. Film thickness dependence of the surface anchoring strength was elucidated on the basis of the conventional ionic surface polarization. <br /> It was also discussed that a surface anchoring strength from the splay deformation is to be an intrinsic value defined at an interfacial region and not <br /> a value changing with the film thickness.

液晶表示デバイスの高密度表示に向けて新規な機能性を有する液晶ダイレクタ配向手法の確立が求められている。本論文では、新たに開発したフッ素系ポリマ材料（perfluoropolyether (PFPE)）のダイレクタ配向性について報告した。PFPE-Langmuir-Blodgett膜を作成し、同膜上でシアノビフェニール系液晶のアンカリングエネルギを測定し、その値が、10-5 J/m2であることを明らかにした。この強度は、従来の材料で報告されている中で最も弱い強度である。この結果より、PFPE-Langmuir-Blodgett膜が、多値光安定化液晶素子に最適であることを示した。

人々の生活をより豊かにすることの出来る安心で身近な質の高いエレクトロニクス技術に関心が集まっている。そのためには、ソフトで軽量な有機材料をエレクトロニクス機器の中で自在に活用することが是非とも必要になる。特に有機分子の持つ幾何学的な特徴・機能を活かすことにより、新しいエレクトロニクスの分野が開かれると考えられる。そこで、本解説記事では、有機分子・材料の幾何学的断面に注目し、分子システム、有機プロセス、界面現象制御、デバイス物理という4つの切り口から最近のエレクトロニクス研究の流れと克服すべき課題について概説した。

有機デバイスに関連した研究が活発である。学会での関連分野の研究発表件数の増大は、このことを物語っている。しかし、研究対象とするＦＥＴ，ＥＬなどのデバイスの中で、有機材料本来の機能が活かしきれていないのが実状である。柔軟さなど有機材料独特の機能を使い切るためには、有機分子の幾何学的形状、界面のトポロジー、分子集合体のパターン、分子・分子集合体の動的な挙動など、有機材料の特徴を総合的にとらえ、その扱いを可能にするデバイス物理・工学手法が必要である。「界面幾何工学」という視点からの研究はその糸口となる。そこで本稿では、「界面幾何工学」という視点から、最近の有機エレクトロニクス関連の研究を概観し、その将来展望について述べる。

It is important, both for basic science and device<br /> applications, to investigate the static and dynamic director distribution in a thin nematic liquid crystal (NLC) slab confined between two transparent electrodes. Optical and electrical measurement methods are generally used to determine the director distribution as a function of an electric field. It is to be expected that deuterium NMR spectroscopy combined with simultaneous in situ observation of the light transmittance should give us a good understanding of the director distribution for a thin NLC slab because the former is the sum of the spectra for each position in the slab and the latter by the optical anisotropy averaged over the slab. This combined method is used to investigate the director distribution in a thin<br /> NLC slab of 4-pentyl-40-cyanobiphenyl subject to competing constraints.

本論文は、平成17年9月にノビシビルスク工科大学（ロシア）で<br /> 行った講演発表をまとめ、ロシアの科学論文誌へ寄稿したものである。論文内容は、著者が近年進めている、重水素化核磁気共鳴法を用いた液晶ダイレクタの静的・動的挙動研究の成果概要を述べるとともに、同研究分野での問題点と、それらの解決に向けた理論的・実験的な方向を示した。

本論文では、外部電場重複印加による重水素化核磁気共鳴法を用<br /> いたネマチック液晶ダイレクタの動的挙動実験により得られる液晶の物理定数の解析法を新たに提案した。この解析法と核磁気共鳴実験の組み合わせにより、液晶の帯磁率異方性、誘電率異方性、測定系における電場と磁場のなす角度を正確に決定できることを示した。

本論文では、8CB液晶の層構造を有するスメクチックA相でのダイレクタ動的挙動を電界重複印加による重水素化核磁気共鳴法により調べた。磁場と電場が直交する系では、ダイレクタ動的挙動が縮退し、その緩和過程を理解することは困難である。ここでは、磁場と電場のなす角を90度以下に設定することにより、層構造を有する液晶相においても、ダイレクタ回転の緩和過程を明確にできることを示した。

アンカリング強度の周期変化を有する基板を用いたホモジニアス液晶セルは、電場印加により異常な光漏洩現象が発生することを既に報告している。本論文では、この光漏洩現象の発生機構が、一般化表面アンカリング理論と連続体理論に基づき、周期的なアンカリング強度変化 により誘起される表面ダイレクタ歪みに 起因することを明らかにした。さらに、 光配向膜を用いて一次元アンカリング強度周期変化セルにより理論解析結果を実験的に確認した。

Studies of the field-induced alignment of the nematic <br /> director for low molar mass materials using vibrational spectroscopy have revealed some fascinatingly unexpected results. Several studies have found that the relaxation time for the director alignment is dependent on the group in the molecule used to monitor the director orientation. Seemingly this undermines the basic concept of the Leslie-Ericksen hydrodynamic theory of nematics. Here we report <br /> complementary studies using deuterium NMR spectroscopy of <br /> perdeuteriated 4-pentyl-4￠-cyanobiphenyl where the director is aligned by a magnetic or an electric field. This particular technique was chosen because the spectral peaks associated with each rigid group in the molecule <br /> are clearly resolved and of comparable intensity. We have investigated the director alignment using different temperatures, electric field strengths and angles between the magnetic and electric fields, each of which influences the director relaxation time. For all of the experiments we find that the relaxation times are independent of the group used to determine the director orientation during the alignment process.

Macroscopically, the surface-induced director orientation has an influence on that in the bulk．It is important for basic science and device applications to investigate the director distribution in a thin nematic slab experimentally and theoretically．In this study the director deformation in nematic slabs with different surface anchoring conditions has been investigated using a deuterium nuclear magnetic resonance spectroscopy method．A series of NMR spectra has been acquired as a function of the applied electric field normal to the magnetic field, which can also be used to provide an estimate of the director deformation．This experimental techniques help to give us a better understanding of the surface-induced static director distribution．

Deuterium NMR spectroscopy has been used to investigate the director dynamics in the nematic liquid crystal, 4-pentyl-4&#039;-cyanobiphenyl, confined between two glass plates and subject to the magnetic and pulsed electric fields. A series of deuterium NMR spectra, obtained using a quadrupolar echo sequence, was acquired as a function of the applied electric field and time. When the electric field, whose intensity is controlled so that the director makes an angle with the magnetic field is applied to the nematic film, the director moves from being parallel to the magnetic field to being <br /> at an angle with respect to the magnetic field because of a <br /> positive and for 5CB. After the electric field is switched off, the <br /> director relaxes back to being parallel to the magnetic field. Deuterium NMR spectra were recorded during the turn-on and the turn-off realignment processes as a function of time. The realignment pathway of the director <br /> was monitored by measuring i, the deuterium quadrupolar splittings. We <br /> have studied the time dependence of the director orientations for the turn-on and turn-off processes. The deuterium NMR spectra corresponding to the

Deuterium NMR spectroscopy has been used to investigate the director dynamics in the nematic liquid crystal, 4-pentyl-4&#039;-cyanobiphenyl, confined between two glass plates and subject to orthogonal magnetic and pulsed electric fields. When the pulsed electric field, whose intensity is strong enough to make the director align normal to the magnetic field, is applied to the nematic film, the director moves from being parallel to the magnetic field to being parallel to the electric field. After the pulsed electric field is switched off, the director relaxes back to being parallel to the magnetic field. Deuterium NMR spectra were recorded during the turn-off realignment process as a function of time. With this experimental geometry the director alignment is not unique as it can rotate equally probably clockwise or counterclockwise in this realignment process. That is, the realignment pathway for the director is degenerate, which establishes a director flow pattern. We have studied the time dependence of the director orientation and distribution for the turn-off process. The deuterium NMR spectra corresponding to the director dynamics in the realignment pathways were predicted

先に報告した一般化表面アンカリングエネルギモデルより飽和閾値法が導かれる。本手法を用いて、種々の配向膜に対するシアノ系液晶およびフッソ系液晶の表面アンカリングエネルギを測定した。表面アンカリングエネルギ増加に対するチルト角の変化は、シアノ系およびフッソ系液晶では逆の傾向を示す。配向膜材料については、膜表面での電子密度と同等以上に、配向膜分子側鎖による液晶分子挙動の阻害が表面アンカリングエネルギに影響を与える。

The director distribution in a thin nematic liquid crystal (NLC), 4-pentyl-d2-4&#039;-cyanobiphenyl (5CB-d2) deuteriated in the a-position of the pentyl chain, confined between two glass plates, with untreated and treated anchoring conditions, has been investigated using a deuterium nuclear magnetic resonance (NMR).<br /> The NMR spectra have been measured as a function of the applied electric field.In the absence of surface forces it is found that the director aligns parallel to the magnetic field at relatively low values of the electric <br /> field as the dielectric anisotropy is positive for 5CB. Then as the electric field is increased the director remains parallel to the magnetic field until some critical value of the electric field, at which point the director is aligned parallel to the electric field and <br /> hence perpendicular to the magnetic field, since the diamagnetic anisotropy is positive for 5CB. In the presence of surface forces with increasing electric field the quadrupolar splitting decreases, passes through zero and then increases again to a value which is essentially half of that at zero electric field. That is, the director orientation changes more or

Deuterium nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the electric field-induced alignment of the director of the smectic A phase of the liquid crystal, 4-α,α-d2-octyl-4&#039;-cyanobiphenyl (8CB-d2), at 303.3K. The electric field is arranged to be orthogonal to the magnetic field.<br /> The alignment process has been investigated at different electric field strengths and the rate of director alignment was monitored by recording the deuterium NMR spectra as a function of time after the electric field was switched on.The results reveal a complex pattern of electric field-induced director alignment. At high electric field strengths a rapid process is observed in which the director switches from an orientation parallel to the magnetic field to one in which it is parallel to the electric field. An induction period is also observed in which no apparent change in director orientation occurs. This induction period becomes longer (hours in magnitude) as the electric field strength is lowered. <br /> Other, intermediate, director orientations are observed as the electric field strength is lowered further. The role of defects is invoked in trying to interpret some of

The director distribution in thin nematic slabs with allel <br /> structure have been calculated as a function the applied electric field. They are different from the cells with the anti-parallel structure, in that three solutions exist in a specified voltage range which predict a transition of the director deformation from splay to bend onfigurations in the parallel structure.This splay-bend transition has been confirmed experimentally by a capacitance-voltage (C-V)hysteresis method. The C-V characteristics showed a esis around the deformation transition and this magnitude corresponded to the facility of the splay-bend transition:<br /> a comparison of these hysteresis characteristics for different materials enables us to evaluate the splay-bend transition speed easily.

Deuterium nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the field-induced director dynamics in a nematic liquid crystal,4-pentyl-d2-4&#039;-cyanobiphenyl (5CB-d2) deuteriated in the a-position of the pentyl chain, confined between two glass plates. The NMR spectra have been measured as a function of time after turning an electric field on and off.It is demonstrated that the field-induced director dynamics in the nematic liquid crystal cells can be successfully<br /> time-resolved. In addition, it is found that the doublet <br /> NMR spectra become powder-like during the turn-on and turn-off processes. It is shown that the rotational viscosity and the diamagnetic anisotropy of 5CB-d2 can be determined <br /> from the time-resolved NMR spectra by assuming uniform alignment of the director.

Transient diffraction phenomena induced by external applied electric field to nematic liquid crystal cells have been investigated. Far-field ring diffraction pattern is observed and is caused by a quasiperiodic herringbone pattern. It is found that the electric-field and the temperature dependences of the diffraction transients have <br /> correlation with those of current transients due to the conduction of impurity ions. It is concluded that the transient diffraction is attributable to the ion conduction via the formation of the herringbone texture.

The unified surface anchoring energy was investigated for <br /> nematic slabs of various cyano- and fluorinated liquid crystals on a polyimide alignment layer. The surface anchoring strength was found to vary over the range 10^-4 to 10^-3 J/m^2 dependent on the liquid crystal structure. It was also found that the values of surface anchoring strength change with respect to the tilt angle in opposite <br /> directions for the cyano- and fluorinated liquid crystals.