Der Fernseher in der Westentasche: Flüssigkristall‐ Materialentwicklung für das neue Jahrtausend

Abstract

Neue Flüssigkristalle mit sehr niedriger Viskosität, gutem Mesophasenverhalten und hoher Zuverlässigkeit ermöglichen den Durchbruch vom flachen Computermonitor zum großformatigen LCD‐Fernseher. Fluor spielt hierbei eine entscheidende Rolle, nicht nur, weil es Polarität in organischen Molekülen induziert, sondern auch wegen seiner niedrigen Polarisierbarkeit und seiner schwach ausgeprägten Tendenz zur Ionensolvatation. Zusätzlich sind in fluorierten Flüssigkristallen subtile stereoelektronische Effekte am Werk und ermöglichen eine Feinabstimmung der gewünschten Eigenschaften. Dafür ist eine aufwendige Chemie erforderlich, wie sie sich normalerweise in der Spezialchemie allein schon aus Kostengründen verbietet. Der Markt für Fernseh‐Displays tritt heute in eine Phase der Sättigung ein. Bedingt durch die weite Verbreitung des Internets gibt es jedoch einen neuen Trend zu mobilen Geräten. Tablet‐PCs und Smartphones benötigen berührungsempfindliche Bildschirme und niedrigen Stromverbrauch. Neue LC‐Modi mit hocheffizienten Flüssigkristallen und zusätzlichen Komponenten, z. B. polymerisierbaren Materialien, werden in solchen Produkten verwendet.

Functional Liquid Crystals towards the Next Generation of Materials

“…[86] Electric-field stimuli have been am ajor driving force to align liquid crystals.F lat-panel display devices have been realized by preparing low viscous and polar nematic molecules. [2] Fort he alignment of nanostructured liquid crystals, ferroelectric liquid crystals exhibiting chiral smectic Cphases were intensively studied. [87] Columnar liquid crystals can also be oriented under electric fields.…”

“…Anematic phase is the simplest LC phase and it has long history of study and application. [1,2,26] However,new nematic structures and materials and their functionalization, and alignment methods for nematic phases have also received much attentions.These new aspects of nematic liquid crystals may open an ew field of materials science. [74,[161][162][163][164][165][166] Liquid crystal dimers,i nw hich two mesogenic moieties are connected by an aliphatic flexible spacer, were initially synthesized as am odel of main-chain LC polymers.…”

“…[169] Orientational switching of nematic liquid crystals under an electric field has been utilized for the manufacture of flat panel displays. [2] Generally,the electrooptical response of LC phases has been one of the most useful properties for applications.B lue phases,w hich have double chiral nematic structures,w ere reported to exhibit fast responses,o ptically isotropic nature,a nd no requirement for rubbing process for applications of displays. [162,170,171] Blue-phase materials are also studied for use in optical lasers.…”

“…Liquid crystals are basically molecular materials that combine molecular order and mobility. [1][2][3][4][5][6][7] They can be recognized as ac lass of functional materials that have great potential to be used in fields of information, energy,environment, separation, and healthcare.Since the discovery of liquid crystals in 1888 by Reinitzer, [8] liquid crystals have been studied for about 130 years in multiple disciplines,s uch as chemistry,p hysics,b iophysics,a nd engineering,l eading to progress in basic science and technologies.…”

“…In contrast to nanostructured liquid crystals,n ematic liquid crystals which form the simplest LC structures have been applied to flat-panel displays as ar esult of their three important characteristics,f luidity (low viscosity), responsive-ness to electric fields,and easy formation of mono-domains. [2] This successful application of nematic liquid crystals results from the cooperation and accumulation of studies by many scientists and engineers in avariety of fields related to liquid crystals.F urthermore,h igh mechanical strength fibers and plastics [24] and optical compensation films [25] have also been developed by fixing the molecular oriented structures formed by nematic or nematic columnar liquid crystals.Inaddition to these conventional liquid crystals,new designs for functional nematic liquid crystals have emerged recently. [26] In this Review,w ed escribe topics on recent progress in LC materials in view of the design of molecular structures and the relationships between molecular self-assembled structures and functions.I np articular, we focus on the design of new self-assembled structures for LC materials for potential applications as unique nanostructured materials.…”