Uniform Cell Gap Research Articles

16.3: Flexible Liquid Crystal Displays with Fine‐Width Polymer Walls and Self‐Assembled Monolayer Alignment

Flexible liquid crystal displays (LCDs) are regarded as one of the most promising candidates to achieve flexible displays. In this paper, we proposed a novel technique to fabricate flexible LCDs combining polymer walls (PWs) and self‐assembled‐monolayer(SAM). The PWs with fine morphology and line‐width (about 20 µm) were fabricated to keep uniform cell gap and provided a larger aperture opening ratio for flexible LCDs. Alignment by alkyl trichlorosilane(TS) SAM was achieved at room temperature. In this way, general flexible substrates could be used for flexible LCDs. This work is promising for the manufacture of flexible LCDs.

Gradient pretilt angle alignment materials with different photosensitivity for tunable polarization‐independent self‐aligned liquid crystal lens

AbstractAlignment of benzaldehyde materials with different photosensitivity thresholds, capable of changing the pretilt angles of nematic liquid crystal (LC) from 90° to 0° in a controlled manner under UV‐B exposure, has been developed. Inhomogeneous exposure of uniform rubbed alignment layers allows the formation of a refractive index gradient inside the LC cell. The concept of tunable polarization‐independent self‐aligned LC lens based on gradient pretilt angle alignment materials with different photosensitivity is demonstrated. Self‐alignment of two polarization‐dependent sub‐lens is achieved due to a single exposure act of two alignment layers, which are located on the same piece of glass on both sides, forming one common optical axis for a polarization‐independent LC lens. The sub‐lens cells have uniform cell gap and are independently controlled using low‐voltage driving. Devices based on gradient benzaldehyde alignment materials can be used in many modern optical and photonic devices.

GRADIENT ALIGNMENT MATERIALS WITH DIFFERENT PHOTOSENSITIVITY FOR TUNABLE POLARIZATION-INDEPENDENT LIQUID CRYSTAL LENS

The development of electrically tunable liquid crystal (LC) lenses is perspective and promising for a wide range of applications, for example, for imaging system, pico projectors, optical zoom systems, ophthalmology applications and other. Of particular note is the development of polarization-independent LC lenses, as eliminates polarizers from application devices that reduce the efficiency of light transmission through optical systems. Alignment benzaldehyde photosensitive materials, capable of changing the pretilt angles of nematic LC from 90 to 0 ºС in a controlled manner under UV exposure are developed. The anisotropy of the benzaldehyde alignment layers is generated by a two-stage treatment consisting of uniform rubbing with a cloth and subsequent non-polarized UV exposure. Inhomogeneous UV exposure of uniformly rubbed alignment layers allows formation of refractive index gradient inside the LC cell. The concept of tunable polarization-independent self-aligned LC lens based on gradient pretilt angle alignment materials with different photosensitivity is demonstrated. Self-alignment of two polarization-dependent sub-lens is achieved due to a single UV exposure act of two alignment layers, which are located on the same piece of glass on both sides, forming one common optical axis for a polarization-independent LC lens. The independence of the polarization of LC lenses is achieved by setting the azimuthal rubbing direction of the alignment layers of two polarizationdependent LC lenses perpendicular to each other. The sub-lens cells have uniform cell gap and are independently controlled using low-voltage driving. Devices based on gradient benzaldehyde alignment materials can be used in many modern optical and photonic devices.

Microfabrication of a spherically curved liquid crystal display enabling the integration in a smart contact lens

A spherically curved liquid crystal display based on a guest-host liquid crystal configuration is fabricated. An asymmetric display design is introduced: two flexible display substrates with varying surface area are used, allowing for compact integration of powering and driving electronics. A matrix of spacer structures composed of photosensitive adhesive and defined by photolithography, simultaneously provides the uniform cell gap while acting as glue between both display substrates. Using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as transparent, conductive electrode layer and obliquely evaporated SiO2 as alignment layer, a functional single-pixel display was fabricated. The display can be embedded in a smart contact lens, thereby enabling applications within the emerging biomedical field. An artificial iris, for example, could be designed to help people suffering from iris deficiencies that involve hypersensitivity to light.

Tunable Liquid Crystal Lens Based on Pretilt Angle Gradient Alignment

ABSTRACTThe new method of LC lenses fabrication based on innovative alignment material for pretilt angle gradient generation is developed. The alignment layer provides LC lens pretilt angle gradient via two-step treatment: uniform rubbing and gradient nonpolarized UV exposure. LC lens has uniform cell-gap, 2–10 V tunable voltage range. The fabrication method is scalable for lens arrays for two-dimensional/three-dimensional autostereoscopic and light-field displays.

Ultrathin Reflective Flexible Liquid Crystal Display Film

In this investigation, we present a thin reflective liquid crystal film with a mixed-mode twisted nematic mode. A low-temperature alignment process is used to obtain good orientation of the liquid crystal molecules. A microcell process is utilized to maintain a uniform cell gap of the flexible display under various bending conditions. To simplify the structure of a flexible mixed-mode twisted nematic liquid crystal display film, a layer of Zeonor optical plastic material is used in place of conventional plastic substrates; this material exhibits quarter wave retardation. The ultrathin device exhibits good cell gap uniformity, a high reflectivity of 35%, and a short response time of 6.67 ms.

Wide Viewing Liquid Crystal Displays with Bi-level Surface Microstructures Fabricated by an Imprinting Method

We report on a wide viewing liquid crystal display with bi-level microstructures fabricated at ambient temperature through an imprinting process which is simple and versatile. Hemispherical microstructures and rectangular microstructures, made of a photopolymer through a single-step imprinting process, produce multi-domains of the liquid crystal (LC) for enhancing the viewing property and provide spacers for maintaining the uniform cell gap, respectively. Our LC cell with embossed bi-level microstructures shows symmetric viewing properties in a wide range of polar angles, contrast ratio of 100:1, and the response time of 34 ms.

Etchingless fabrication of bi‐level microstructures for liquid crystal displays on plastic substrates

In this study, the selective‐wettability‐inscription (SWI) technique for the wet‐etchingless fabrication of surface microstructures applicable to wide‐viewing liquid crystal displays (LCDs) on plastic substrates was demonstrated. On the basis of the selective wetting of the photopolymer, the bi‐level microstructures were spontaneously formed to serve as spacers for maintaining uniform cell gap and protrusions for the generation of multi‐domains. The LC cell that has bi‐level microstructures shows good extinction in the field‐off state and a wide‐viewing property in the field‐on state. The SWI technique would be useful for the fabrication of flexible displays on plastic substrates.

44.3: A Liquid Crystal Lens with Non‐uniform Anchoring Energy

AbstractThe study of a tunable liquid crystal lens having a uniform cell gap, uniform applied voltage and non‐uniform anchoring energy was done. Optimal parameters of such a lens were found and discussed. We demonstrated that producing a desired director gradient profile with non‐uniform spatial distribution of the anchoring energy is a good alternative for other known methods applied for liquid crystal lenses.

P‐121: Direct Formation of Polymer Walls by Wettability Patterning for Flexible Liquid Crystal Displays

AbstractWe report on a flexible liquid crystal display (LCD) fabricated using self‐aligned microstructures of the photopolymer/spacer composite material through a wettability patterning process. The microstructures confined on the patterned alignment layer provide spacers for the uniform cell gap as well as the mechanical stability. No structural change of the substrates was observed during the fabrication process. Our flexible LCD provides good flexibility, durability, and excellent electro‐optic performances. This method can be applicable to the fabrication of large plastic LCDs using a roll‐to‐roll process.

Preparation of Composite Adhesive Spacer Particles for Flexible LCD Application

Adhesive spacer particles were fabricated to ensure the uniform cell gap between the plastic substrates for application in flexible liquid crystal display (LCD). Surface modification of rigid silica particles was performed to render adhesive polymer layer on the surface of the silica particles while maintaining the rigid properties. Methyl methacrylate (MMA) and styrene were graft-polymerized onto silica surface by UV irradiation and characterization experiments confirmed the formation of covalent bond between polymer and silica particle. FE-SEM image analysis indicated substantial increase in mean diameter of the particles after UV-induced grafting of the monomers. T-peel test value of 2.7 N/cm for PMMA film/Polyimide-PES substrate system also confirmed the applicability of these composites in flexible LCD.

Alignment layerless flexible liquid crystal display fabricated by an imprinting technique at ambient temperature

The authors report on an alignment layerless (AL) flexible liquid crystal (LC) display fabricated at ambient temperature through an imprinting process. One-dimensional microgrooves and two-dimensional arrays of microstructures embossed on plastic substrates provide the spontaneous alignment of the LC molecules and spacers for the uniform cell gap in a flexible LC display, respectively. It is found that the azimuthal anchoring energy, generated from the microgrooves, is on the order of 10−5J∕m2 which is strong enough to uniformly align the LC over large area. Our AL flexible LC display shows symmetric viewing characteristics and stable electro-optic properties under a bent environment.

대 면적 LCD에서 Patterned Spacer Color Filter 사용 시 발생하는 중력무라 분석

In recent, it is said that the trend of LCD is direction to pursue high qualities like as high transmittance, high contrast ratio, wide viewing angle, fast response time, and so on. Especially, it is known that these qualities are essential to large size LCD like as LCD TV and we can realize them through to uniform cell gap and deep black state. Until now, the ball spacer has been used to control of uniform cell gap. However, the existence of ball spacer inside the cell causes the deformation of the liquid crystal molecules and damage to alignment layer. Such a deformation of the liquid crystal causes light-leakage in the dark state, which lowers contrast ratio of the display. Nowadays, this problem has been solved by using Patterned Spacer on Color Filter. but Side Effect just as gravity mura has been induced. In this paper, we studied the mechanism on gravity mura in case of using patterned spacer on color filter.

Flexible Display i Low Temperature Processes for Plastic LCDs

Flexible displays such as plastic-based liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDDs) have been researched and developed at KETI since 1997. The plastic film substrate is very weak to heat and pressure compared to glass substrate, that its fabrication process is limited to 110 and low pressure. The ITO films were deposited on the bare plastic film substrate by rf-magnetron sputtering. Moreover, in order to maintain uniform cell gap and pressure on the plastic film substrate, we utilized newly-invented jig and fabrication process. Electro-optical characteristics were better than or equivalent to those of typical glass LCDs though it is thinner, lighter-weight, and more robust than glass LCDs.

56.4: Post Spacer Technology for TFT/LCD

AbstractIBM has developed and already has started production of high screen quality and reliable TFT/LCD panels for vibration stress by Post Spacer(PS) technology. PS now is mandatory for 1) high contrast panel because of no degradation by light leakage which ball spacer has, 2) High quality IPS panel because of uniform cell GAP, 3) thin glass(0.5mm) panel because of wide margin for vibration stress.

33.2: Development of 2‐in. Plastic‐Film STN‐LCD with Uniform Cell Gap

AbstractSTN LCDs on plastic film substrates for mobile communication devices have been researched and developed at KETI in KOREA. The plastic film substrate is so weak to heat and pressure that its fabrication process is limited to 110°C. The ITO electrode layer was deposited on the bare plastic film substrate by rf‐magnetron sputtering. And in order to maintain uniform cell gap and press on the plastic film substrate without deformation of substrate surface, we utilized newly invented jig and fabrication process. Electro‐optical characteristics are better than or equivalent to those of typical glass LCDs though it is thinner, lighter‐weight, and more robust than glass LCD.