Low threshold voltage asymmetric antiferroelectric liquid crystal cells

Abstract

Asymmetric antiferroelectric liquid crystal displays (AAFLCD) are attractive since they show a very well defined off state and fast switching time. Moreover, they can be driven by a simple biasless DC compensated waveform. The electrooptical response of an AAFLCD allows for new addressing modes, including quasi-static intermediate greyscales maintained without applying a field and passively addressed multiplexed high-frequency displays and spatial light modulators. A new kind of asymmetric cells have been obtained by using fluorinated block copolymer (FBC) alignment, which enhances surface segregation and provides a low energy surface. In this work we combine FBC alignment with antiferroelectric liquid crystal mixtures containing strongly electronegative fluorinated components. Threshold voltages for the antiferroelectric-ferroelectric phase transition as low as 3 volts are observed. We report the time evolution of the shift of the electro-optical response.

Mesophase structure of low‐wetting liquid crystalline polyacrylates with new perfluoroalkyl benzoate side groups

“…The nonpolar and ordered nature of perfluoroalkyl liquid crystalline surfaces makes them potentially useful in a wide range of technological applications of inert, nonwetting films from photonics and optoelectronics to medicine and biology. We are interested in thin films for alignment layers of ferroelectric/antiferroelectric liquid crystals in electrooptical devices64 and for nonbiocidal, nontoxic coatings with antibiofouling performance in the marine and freshwater environments 65…”

PEDOT as an alignment layer and electrode in AFLC devices

“…In order to improve the contrast of LCs displays, we have previously studied the use of dissimilar alignment conditioning the two aligning surfaces [2]. We used, as a reference, one substrate coated with rubbed Nylon 6 and the other coated with polyimide, un−rubbed Nylon 6, angular evaporated SiO X or fluorinated co−block polymers [3]. These configurations all improved the alignment of the AFLCs and produced an important reduction of the inherent AFLC pretransitional effect, increasing substantially the contrast.…”

Liquid crystal photonic devices based on conductive polymers = Dispositivos fotónicos de cristal líquido basados en polímeros conductores

“…In order to improve the contrast of LCs displays, we have previously studied the use of dissimilar alignment conditioning the two aligning surfaces [60]. We used, as a reference, one substrate coated with rubbed Nylon 6 and the other coated with polyimide, un−rubbed Nylon 6, angular evaporated SiO X or fluorinated co−block polymers [61]. These configurations all improved the alignment of the AFLCs and produced an important reduction of the inherent AFLC pretransitional effect, increasing substantially the contrast.…”

“…An alternative alignment conditioning generating asymmetric AFLC response with large hysteresis shift has been used. It consists of replacing the thermally evaporated inorganic oxide by a spin coated fluorinated block copolymer (FBCP) [61]. Fluorinated polymers exhibit very low values of surface tension (γ s < 15-20 mN/m) [93]- [95] and might be exploited for new alignment layers of liquid crystals cells with slippery surfaces.…”

“…The reference electrode is always coated with rubbed Nylon 6 and the other electrode is coated with polyimide, un-rubbed Nylon 6, angular evaporated SiO X or fluorinated co-block polymers [61]. These configurations all improved the alignment of the AFLCs and produced an important reduction of the inherent AFLC pretransitional effect.…”