Vertical Alignment Layer Research Articles

Fast vertical alignment mode with continuous multi-domains for a liquid crystal display

We proposed a fast liquid crystal display (LCD) in a vertical alignment (VA) mode with continuous multi-domains for wide-viewing characteristics. The fast VA LCD was fabricated by the mixed vertical alignment layer with UV curable reactive mesogen (RM) polymer memorizing the switching directions of the LC molecules. The wide-viewing and fast response characteristics were obtained by axially symmetric switching directions and the memorization of them without any specific electrode patterns or surface structures.

The correlation between electron density and anchoring strength in the inorganic vertical alignment layer

The relationship between the liquid crystal (LC) alignment and the density of the silicon oxide alignment layer was studied by theoretical and experimental approaches. The thin films were deposited by various methods and conditions, and then their densities were analyzed by x-ray reflectivity measurement. The alignment of LC was highly dependent on their densities, which we found to be closely related to the number of interacting dipoles. Ultimately, a-SiOx thin film with lower density gives rise to the uniform vertical alignment of liquid crystal.

45.1 Fabrication of Fast Switchable Patterned Vertical Alignment Mode Using Modified Surface with Reactive Mesogen

AbstractWe proposed a new fast switchable patterned vertical alignment (PVA) mode using UV curable reactive mesogen (RM) which was mixed with vertical alignment layer. In this mixed alignment layer, the pretilt angle was controlled according to an applied voltage during UV exposure for curing the RM. As a result, the response time was dramatically improved at the whole grey levels by controlling the pretilt angle in conventional PVA mode.

Preparation of vertical alignment layers by blending polyimide precursors with and without side chains

A series of polyimides (PIs) were prepared from the precursors, blends of a poly(amic acid) and a side-chain poly(amic acid), based on a diamine 4′-(tert-butyldimethylsiloxy)biphenyl-4-yl 3,5-diaminobenzoate (DPA). The blended polyimide (bl-PI) films were relatively tough. The surface properties of the bl-PI films were characterised by surface energy measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR-IR). The results showed that the non-polar side chains were highly enriched on the surface and 90° pretilt angles of liquid crystal molecules were generated regardless of side chain content. For comparison, the copolyimides (co-PI) with different DPA contents were synthesised. It was found that the enrichment of the side chain on the surface increased with increasing DPA content and the pretilt angles of liquid crystal molecules rose from 3° to above 20° when DPA content increased from 10% to 30%. For the polyimides based on a diamine without a non-polar end group, 4′-biphenyl-4-yl 3,5-diaminobenzoate (DABBE), both bl-PIs and co-PIs could only generate the same low pretilt angles. In conclusion, by blending poly(amic acids) based on DPA, tough vertical alignment layers could be prepared.

Control of liquid crystal pretilt angle by anchoring competition of the stacked alignment layers

We proposed a method to control the pretilt angle of liquid crystals by stacking of a vertical alignment layer on a planar alignment layer. The pretilt angle can be controlled over the full range (0°–90°) depending on the thickness of the vertical alignment layer. We also proposed a numerical model to describe the physical mechanism based on the anchoring competition between liquid crystal, planar, and vertical polyimide alignment layers.

Preparation and characterization of a novel polyimide liquid crystal vertical alignment layer

A series of diamines with a side chain containing rigid biphenyl unit and nonpolar alkoxy side end group [4-alkoxy-biphenol-3′,5′-diaminobenzoate] (Cm-BBDA, m = 4, 6, 12) were synthesized and their chemical structures were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and nuclear magetic resonance spectroscopy ( 1H NMR). Then three polyimides (PIs) were prepared by copolymerization of pyromellitic dianhydride (PMDA), 4,4′-methylenedianiline (MDA) and Cm-BBDA in N-methyl-2-pyrrolodone (NMP), and chemical structures of all PIs were confirmed by FT-IR. Structural identification of all poly(amic acid)s (PAA) was performed by 1H NMR. Liquid crystal (LC) cells were fabricated using these PIs as the alignment layer for characterization of the alignment properties of LCs. It was found that the planar alignment was obtained when PI with side chain containing alkoxy side end group of 4 carbon atoms was employed and the vertical alignment was observed when alkoxy side end groups of 6 or 12 carbon atoms were included. A uniform vertical alignment was validated by polarizing microscopy. It was testified that LC vertical alignment possessed high thermal stability.

High-Precision Measurement of the Polar Anchoring Strength of Several Vertical Alignment Layer Materials by Psi Delta Hybrid Aligned Liquid Crystal Cell Method

With the increasing popularity of vertically aligned mode liquid crystal displays (VA-mode LCDs), the evaluation of the surface polar anchoring strength of the vertical alignment layer has become increasingly important. The surface polar anchoring strength is believed to be one of the most crucial elements that influence the response property of VA-mode LCDs. Therefore, a quantitative evaluation of the relationship between the anchoring strength and the response property of a VA-mode LC cell is a key issue. In this paper, we discuss the relationship between the polar anchoring strength and the response speed of a VA-mode LC cell referring to the results of an evaluation by the psi delta hybrid aligned liquid crystal cell method.

Dynamic Characteristics of Vertically Aligned Liquid Crystal Device Using a Polymer Wall Associated with the Boundary Condition of Alignment Layer

Voltage-dependent liquid crystal (LC) reorientation was analyzed in a vertically aligned nematic liquid crystal display with a polymer wall (called a locked-super homeotropic (LSH) device) through the LC textures. The LC textures generated have a singularity of S = + 1, however, they were strongly dependent on the order of fabrication between the polymer wall and the vertical alignment layer, generating either pure radial or twisted radial orientation of the mid-director. In this article, we investigate how the boundary condition of the alignment layer on a wall surface affects the dynamics of LCs in the LSH mode.

Application of nanoparticle-induced vertical alignment in hybrid-aligned nematic liquid crystal cell

The spontaneous vertical alignment of the mixtures consisting of nematic liquid crystals (LCs) and nanoparticles and its application to hybrid-aligned nematic (HAN) modes were investigated. The LC directors were aligned perpendicular to the nontreated indium-tin-oxide surface by adding the nanoparticles. Therefore, we fabricated a nanoparticle-filled HAN LC cell without using the vertical alignment layer. The electro-optical properties of nanoparticle-filled HAN cells are very similar to those of conventional HAN cells containing vertical alignment layers. The method of nanoparticle-induced vertical alignment is suitable for fabricating a flexible display due to the reduction of high temperature process of alignment layers.

VA-mode LCDの高速化のための高精度極角アンカリング強度測定

VA-mode LCDの高速化のための高精度極角アンカリング強度測定

Two-Domain Hybrid-Aligned Nematic Cell Fabricated by Ion Beam Treatment of Vertical Alignment Layer

Organic materials for vertical alignment can be used to align liquid crystals horizontally by irradiating an ion beam on the surface under appropriate conditions. Using this technique, we can achieve easily a multidomain alignment for a hybrid-aligned nematic (HAN) cell. We found that a two-domain HAN cell obtained by ion beam exposure shows excellent electro-optical characteristics. The use of the same alignment material in a HAN cell could reduce the cost of production and generation of DC offset voltage.

39.2: SXRD (Silicon X-tal Reflective Display); A New Display Device for Projection Displays

A new display device, SXRD, has been developed for projection displays. SXRD consists of vertical aligned nematic (VAN) liquid crystal and inorganic alignment layers with narrow cell thickness less than 2 μm on uniquely-designed Silicon backplane, featuring high resolution more than Full HD, high contrast ratio of 4000:1 and rapid response less than 5 msec. The SXRD devices developed deliver Full HD (1920H × 1080V) in 0.78-inch diagonal panel and 8.85M resolution (4096H × 2160V) in 1.55-inch diagonal panel. Products using SXRD will appear into the market for rear projection TVs, front projectors and Digital Cinema Projectors.

LP‐8: Late News Poster: Ion Beam Sputter Deposition Process of Inorganic Vertical Alignment Layers

AbstractThe research results of silicon dioxide thin films alignment properties is presented. The films was deposited by oblique ion beam sputtering on glass substrate. Films thickness and angle condensation influences on the value of pretilt angle of liquid crystal vertical alignment mode is shown. Role of the surface morphology of alignment layers is discussed. The highly uniform vertical alignment layers can be produced using ion beam coating on the substrates with dimensions 300 × 400mm and more.