Keshu Xu

Fabrication of Surface-Stabilized Ferroelectric Liquid Crystal Display with Stripe-Shaped Domain Structure

The new dopant we developed is silicon naphthalocyanie, abbreviated as SiNc. It exhibits a good solubility in the polyamic acid solution and meltability with the thus imidized polymer films shown in Fig. 1. The doping concentration ofSiNc in the polyamic acid solution ranges from 0.1% to 0.3% in weight. The solution was spun onto the indium-tin-oxide (ITO) substrates at 4,000 rpm rate and then baked at 200 � C for 1 hr for the imidization to get the SiNc doped polyimide (PI) films. The resulting PI films were rubbed unidirectionally under a velvet-covered cylinder. Empty LC cells were fabricated with the substrate rubbing directions parallel to each other. The cell gap was controlled at 1.5–1.8 mm with the photolithographic polymer spacers. The FLC material CS-1024 (Chisso Co., Japan) was injected into the empty LC cell by capillary flow at a temperature above the LC clearing point and then cooled down to the room temperature slowly. The CS-1024 FLC mixture has the following phase transition sequence: Crystal (� 12 � C) ! SmC � (62 � C) ! SmA (82 � C) ! N � (90 � C) ! Isotropic. An anti-parallel cell was assembled for the pretilt angle measurement in the nematic phase. A cell with 27 mm gap was filled with nematic liquid crystal mixture ZLI-3417-006 (Merck, Germany) under vacuum. The crystal rotation method which has precision up to 0.01 � (DMS-501, Germany) was used for measuring the pretilt angle. The microscopic textures ofthe SSFLC cells were observed using a polarizing microscope. The EO properties ofthe SSFLC cells were measured between the crossed polarizers using a He–Ne laser (� ¼ 632:8 nm). The light transmittance was detected by a photomultiplier and recor

AFM investigation of polymer LB films on the alignment of ferroelectric liquid crystal

Abstract A kind of newly synthesized polyimide (PI) LB films were fabricated to align ferroelectric liquid crystal (FLC). The topologies of PI LB films treated by different imidization processes were investigated by atomic force microscopy (AFM). It is found that the imidization temperature influences the crystalline structure of the LB films and high-temperature imidized LB films can provide the energy barrier for the realization of excellent bistability, while the ultra-thinness of LB films is helpful for the quick response of the FLC cell.

Liquid crystal alignment controlled by LB films

Abstract Copper phthalocyanine doped polymethacrylate Langmuir-Blodgett films were transferred to align a nematic liquid crystal 5CB. It is found that the pre-tilt angle of the liquid crystal can be controlled with the variation of the doped copper phthalocyanine molecular ratio and is correlated with the dichroic ratio of the aligning layer. The polarity of the aligning layer is regarded as the most likely underlying factor that causes the different LC alignment configurations.

Electro-optic characteristics of surface-stabilized ferroelectric liquid crystal devices with the stripe-shaped domain structure

The stripe-shaped domain (SSD) structure has been obtained in the initial ferroelectric liquid crystal (FLC) alignment after the doping of a naphthalocyanine compound into rubbed polyimide films. Pre-tilt angles on the aligning films have been measured. The memory capability of aligned SSFLC cells has been enhanced nearly to completion, and contrast ratios reached 86:1 with the appearance of the SSD structure. Thus fabricated, 64 64 electrically controlled FLC spatial light modulator has better electro-optic characteristics and stability than a non-doped device.

Fabrication of ferroelectric liquid crystal devices

Electrically-controlled 64 X 64 ferroelectric liquid crystal spatial light modulators (FLC-SLMs) were fabricated with a quick response, high contrast ratio and good bistability at the resolution of 10 lmm. The special polymer films aligned SLMs have a quite long operation life. A 1.6 inch 64 X 80 FLC device for the display aim was fabricated, which e-o properties have been improved by the modification of the aligning layers and a large area FLC alignment with uniformity can be obtained. A FLC light shutter at the aperture of 30 mm X 30 mm was also fabricated and used as a phase-sensitive image system for the investigation of fluorescence lifetime.

The Characteristics of SSFLC Cells with Stripe-Shaped Domain Structure

Abstract The stripe-shaped domain (SSD) structure has been obtained in the initial ferroelectric liquid crystal (FLC) alignment by doping phthalocyanine compound into the rubbed polyimide films. Atomic force microscopy (AFM) was used to investigate the aligning films and the corresponding aligning ability was evaluated through the pre-tilt angle measurement. The memory capability and the contrast ratio of the aligned SSFLC cells have been enhanced and improved with the appearance of the SSD structure. In addition, the stability of 64 × 80 electrically controlled FLC spatial light modulator has been improved, too. The possible formation mechanism of the SSD structure was also discussed.

Liquid Crystal Alignment on Polymer Films

The rubbed polyimide (PI) and PI LB films were fabricated and treated to align the nematic liquid crystal (LC) 5CB. The rubbed polyimide (PI) films aligned LC cell shows a higher LC pretilt angle t...

Liquid crystal alignment using naphthalocyanine Langmuir-Blodgett films

Abstract Both odd and even numbers of layer of silicon naphthalocyanine Langmuir-Blodgett films can align nematic liquid crystal molecules perpendicular to the substrates. An atomic force microscope (AFM) was used to observe the morphology of the Langmuir-Blodgett monolayer. The alignment mechanism seems mainly connected with Van der Waals forces and the molecular scale “grooves”.

Alignment of Surface Stabilized Ferroelectric Liquid Crystal Cell on Obliquely Evaporated Silicon Monoxide Film

Abstract An alignment method for obtaining uniform surface stabilized ferroelectric liquid crystal (SSFLC) cell is presented. The uniform alignment is realized by ultrathin ( 1000A) both evaporated at 80°C and the SiO film evaporated at 60° on the FLC are described. The layer direction of FLC cell with ultrathin SiO film at 80° is perpendicular to that with thick film at the same deposition angle. The advantage of the ultrathin film is that the SSFLC cell aligned by it can be easily treated to perform perfect bistability, excellent contrast and fast switching speed. An possible orientation mechanism on surface of oblique evaporation film is discussed.

Characteristics of phthalocyanine-LB-film-aligned LC cells

A series of phthalocyanine complex Langmuir-Blodgett films were fabricated to align nematic liquid crystals. The antiparallel type, twisted nematic type and hybrid-alignment nematic type cells were realized and their corresponding electro-optic characteristics were investigated adopting the He-Ne laser as the light source.