Search

We propose a linearly polarized organic light emitting diode with patterned orthogonal polarizations for enhancement of brightness in 3-dimensional (3D) display. The orthogonally polarized emissions are converted to the orthogonally circular polarizations for the stereoscopic 3D display via a quarter-wave plate.

In this paper, we proposed the photo-alignment method with the strong surface anchoring energy by applying the two band UV exposure method on the photosensitive PI layer embedded with reactive mesogens (RMs) for achieving the fast response time properties of the in-plane switching (IPS) LC mode. We first enhanced the interconnection between a RM polymer and a photo-alignment layer through high band ultra-violet (UV) exposure on the long pass UV filter over 340 nm and then established the alignment of LCs through low band linear polarized UV exposure at 254 nm after eliminating the UV filter. As results, we measured the surface anchoring energy and response time of the proposed photo-alignment method and also confirmed that the optical response time was reduced by approximately 22.3 % compared to that of the IPS-LC cell of pure photo-alignment layer.

We propose a vertical alignment (VA) liquid crystal (LC) mode with square-cross-pattern, so called SXVA mode, for high transmittance characteristics. A common electrode has cross shaped slits with wings along with polarizer direction, which make a lattice structure. The slits make a diagonal direction of electric field and uniform alignments of LC molecules for high transmittance characteristics in SXVA mode.

We propose a polymer-stabilized blue phase liquid crystal (PS-BPLC) device with low operation voltage in fringe-field switching (FFS) electrodes. The in-plane field between the silt electrodes improve the transmittance due to the enhancement of the horizontal field. High transmittance in our PS-BPLC was obtained under low operation voltage.

In this paper, we fabricated the inverse four domain twisted nematic liquid crystal cell using stacked vertical alignment layer on planar alignment layer for strong azimuthal anchoring energy. That makes possible twist structures under applied voltage without chiral-dopant, as a result, high transmittance and wide viewing angle could be revealed.

We demonstrated an axially symmetric multi-domain liquid crystal (LC) structure formed by soft-lithographically patterned LC alignment layers. In our structure, homeotropic LC alignment layers are periodically patterned on a unidirectionally rubbed homogeneous LC alignment layer. The field-induced LC reorientation on the non-rubbed patterned surfaces is determined by the easy axis of the pattern boundaries, producing axially symmetric multi-domains or a mono-domain LC structures.

We proposed the wide-viewing-angle liquid crystal display (WVALCD) of the patterned vertical alignment (PVA) mode by adopting differential geometry of the electrode pattern. Due to the patterned electrode structure, we can obtain 8-domain LC alignment in a simple fabrication process while the conventional PVA mode has only 4-domain structure. This multi-patterned electrode technique enlarges the viewing angle of LCD about 12% compared to the conventional PVA mode.

We proposed a lamination process of a polymer film with a photo-curable polymer for fabricating flexible liquid crystal (LC) displays on single substrate. In our structure, a cover film layer was tightly attached to the polymer wall structure of a bottom plastic substrate after lamination, and LCs were uniformly aligned by grooves formed on the laminated cover film. 1. Introduction Flexible displays have attracted much attention due to their good portability such as light weight, thin packing, and flexibility. Among currently available competing technologies, flexible liquid crystal displays (LCDs) are considered to be the most promising ones, in that they have well-established techniques guaranteeing superior visibility with low power consumption. The serious obstacles to successful commercialization of flexible LCDs have been highly nonuniform electro-optic (EO) properties under external mechanical distortions on the plastic substrates, which originated from LC distortion or cell gap variation [1, 3, 4, 5]. Our recent results showed that such problems could be effectively solved by using pixel-isolated liquid crystal (PILC) mode [4, 5], where the stabilization of LC modes and the cell gap uniformity were provided by polymer wall structures. However, previous works required cumbersome anisotropic phase separation from LC/polymer mixtures to make polymer wall structures or to attach the polymer wall structures on one plastic substrate to the other plastic substrate [4, 6, 7]. Therefore, several efforts have been devoted to the development of a simple fabrication process for stable flexible LCDs. Among them, fabrication methods of flexible LCDs on single plastic substrate are regarded to be very suitable ones in applying cost-effective roll-to-roll process [8-10]. In this work, we demonstrate that the PILC mode can be simply obtained by laminating functional cover film, where the top cover film is tightly attached to the polymer wall structures of the bottom plastic film via photo-polymerization and the LCs are well-aligned by the patterned groove structure on the cover films. The proposed lamination method can be achieved by laminating a photo-curable polymer film layer from surface modified elastomeric buffer layers. With the method, it is expected that stable flexible LCDs can be simply fabricated via a cost-effective roll-to-roll mass production.

We propose the stabilization technique for the memory state of bistable liquid crystal (LC) mode in the pixel-isolated LC (PILC) structure. To obtain the enhanced retention time of memory state, we apply the multi-rubbing method to create the partial 90° twisted domains in each sub-pixel as the seeds of stabilizing the π-twist states. The PILC structure provides the uniform and stable cell gap against various external deformations. The suggested structure can be very useful for portable flexible display applications with high quality device performance such as low power consumptions and good mechanical reliability.

a novel technique to maintain a constant cell gap of the flexible LCD under various external distortions. The two flexible substrates were assembled tightly by the UV curable polymer placed on top of rigid pillar spacer array. In this technique, we designed the columnar micro-structure to lead the self-collected construct of adhesive polymer which promotes the good adhesion and high mechanical stability against the external deformations.

We proposed a high sensitive electro-optic modulator based on a polymer-dispersed cholesteric liquid crystal (PDCLC) for the TFT array inspector. Since the PDCLC is operated in a reflective mode, the PDCLC-based inspection system is very simple since a dielectric mirror, which is generally used in a conventional TFT array inspector, is not required. 1. Introduction Thin-film-transistor (TFT) liquid crystal displays (LCDs) have the advantages of picture quality such as contrast, response, and brightness. To reduce costs for the widespread use of TFT-LCDs, the yield and throughput of the fabrication process of TFT arrays must be improved. In order to increase yield and reduce costs, it is necessary to test TFT arrays and detect defects during the manufacturing process. A manufacturing the TFT-LCD with no pixel defects is one of the important issues in the TFT-LCD manufacturing industry. Therefore, the importance of the efficiency enhancement on LCD production process has been increasing and the ALDI (Automated LCD Defect Inspection) system is demanded for this efficiency enhancement. There are several established methods for various inspections [1-7]. In general, the inspector shows a common electrode configuration in a single substrate and the TFT array is acted as the other pixel electrode for inspection. Most of them are noncontact methods that use a two-dimensional electro-optic (EO) modulator and detect the surface potential of the TFT array induced by phase modulation [5, 6]. The positional resolution of the modulator is required to level of several tens of micrometers. However, the fringe electric field from the edges on the pixel electrode has influence on liquid crystal configurations even at the neighboring pixel regions. Thus, the EO variation penetrates into the neighboring pixels. The variation is increased with increasing the applied voltage and thus it gives rise to degrading the detection sensitivity of the inspector. With increasing resolution TFT-LCD, it is hard to detect a fine pitch pixel of TFT-LCDs by using the modulator based on polymer-dispersed liquid crystal (PDLC) [6]. In this research, we propose a novel high sensitive EO modulator based on the polymer-dispersed cholesteric liquid crystal (PDCLC) for TFT array inspector. The non-contact inspecting system for the novel light modulator based on PDLC is shown in Fig. 1. A conventional PDLC-based modulator has to require dielectric mirror. Conversely, the proposed modulator based on PDCLC is operated in the reflected mode. Therefore, the proposed modulator has the advantages of simple structure without the dielectric mirror instead of conventional modulators.

We fabricated 4.3-inch WVGA fringe-field switching mode with fast response time using reactive mesogen (RM) mixed in planar alignment layer. The RM-mixed alignment layer gave rise to improvement of the response time by an enhancement of azimuthal anchoring energy. In addition, due to low pretilt angle of the RM-mixed alignment layer, no gray inversion was observed. Author Keywords Reactive mesogen; Azimuthal anchoring energy; Fringe field switching; Response time

We fabricated an inverse four domain twisted nematic (IFDTN) mode using a stacked photo-alignment layer enhancing the azimuthal anchoring energy. The strong anchoring energy generates the stable 4D twist structures under an applying voltage. High transmittance and contrast device is achieved without complex rubbing processes.

We demonstrate a transparent display using a chiral hybrid in-plane-switching (CH-IPS) mode with high transmittance. To obtain the stable alignment in the CHIPS mode, the vertical alignment layer mixed with reactive mesogen was used. High transparency and excellent dark state for the transparent display applications were achieved.

proposed the fabrication technique of Fresnel lenses in a binary type by using electrohydrodynamic instability (EHDI) of the optically anisotropic layer. It was found that the Fresnel lens has a high-efficiency performance with fast, simple and reliable fabrication for producing Fresnel lens.

We report an enhancement of memory characteristics in a bistable chiral splay nematic (BCSN) display mode with reactive mesogens (RMs). The polymerized RMs give rise to hindrance to relaxation in a memory mode and thus a memory retention time is significantly improved in the BCSN mode.

We proposed a method to control pre-tilt angle of liquid crystals by coating vertical alignment reactive mesogen(RM) material on the planar alignment layer. The pre-tilt angle can be precisely and simply controlled in full range (0° ~ 90°). We also easily obtained a patterned alignment layer using this method.

We propose a novel method for a stable four-domain twisted nematic (4DTN) structure by injecting nematic liquid crystal in an isotropic phase under an applied electric field. In this method, no high pre-tilt angle is required to stabilize the 4DTN structure and thus the high transmittance and fast response are obtained.

We proposed a stable four domain TN structure with high pre-tilt angle. A stacked alignment layer produced high pre-tilt angle and stabilized the four TN domains at even zero or low voltage regime. In our structure, the excellent viewing characteristics were obtained.

We propose a patternless vertical alignment (VA) mode with infinite domains for mobile displays. Memorizing switching directions of the liquid crystals by a polymerized reactive mesogen on surfaces produced infinite domains and fast response. Also, the transmittance of our patternless VA cell was enhanced by using circular polarizers.

a multi-color cholesteric liquid crystal (CLC) film in a single-layered configuration with reactive mesogen (RM). The cholesteric pitches are controlled by temperature and memorized by photo-polymerization of the RM. Using the multi-pitch stabilization in a single layer, multicolor CLC display was obtained without any additional components.

a patterning method of liquid crystalline polymer by using electrohydrodynamics. Using this method, the patterned retarder films, applicable to 3-dimensional displays and transflective liquid crystal displays, were simply fabricated without complicated processes.

We propose twisted nematic (TN) mode liquid crystal device with high contrast ratio (CR) using a new microlens array (MLA) configuration composed of switching unit, focusing unit, and circular black matrix layer (BML). Consequently, CR of TN mode is improved dramatically.

We 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.

We developed novel substrate adhesion technique using thermosetting resin to apply roll-to-roll process to manufacturing of LCDs. We can use one-drop-filling (ODF) process without any distortion of LC alignment using the mixture of thermosetting resin and tetrahydrofuran(THF). This technique can be used to roll-to-roll process for flexible LCDs.

We proposed azimuthally continuous nematic domain (ACD) mode characterized by a cone-like- field of patterned electrode with a circular slit. Such an electrode structure avoids the domain defect induced in a turn of chevron type electrode of patterned vertical aligned nematic (PVA) mode. Consequently, this ACD mode has wider viewing and higher transmittance with maintaining the merits of PVA mode. Therefore, we expect that this proposed mode will be applied to various liquid crystal displays.

We propose a new liquid crystal display (LCD) mode, named as chiral hybrid in-plane switching (CHI) mode, which has high brightness and contrast ratio by using a twist effect applied to a conventional hybrid mode on the interdigitated electrode. The mode is optimized to normally white mode without any loss of transmittance on the electrode. The mode has also excellent darkness under field on because LCs are well aligned parallel to the optics axis of polarizer due to lower bulk elastic strength.

We have investigated a reflective type of nematic liquid crystal display (LCD) using 180˚ twisted state configuration in the � cell which comprises one polarizer and one optical retardation film. This reflective mode has lower driving voltage as well as sufficient gray. Consequently, proposed reflective LC mode could be suitable for low power consumption with excellent optical image by various gray levels..

We propose optical configuration for wide-band characteristics in transflective liquid crystal display with a single cell gap at patterned vertically aligned mode. Difference of the optical path between transmissive and reflective parts is compensated by designing the electrode structure and adopting two retardation films which show wide band characteristics calculated from mirror imaging method.

We proposed a simple method for patterning alignment layers to produce multi-domain liquid crystal (LC) alignment. By micro-contact printing method, we produced multi-directional easy axis on the alignment layer using conventional LC alignment materials. Our printing method would be a very useful tool for designing a LC mode in wide-viewing LCDs or transflective LCDs.

We proposed a pixel-isolated liquid crystal (PILC) mode for enhancing mechanical stability of flexible display applications. Since the LC molecules in this mode are isolated in pixels by patterned or phase-separated microstructures, the LC alignment is stable against external pressure. Moreover, the cell gap of our structure is uniformly preserved against bending deformation of the plastic substrates since two substrates are tightly attached each other by the solidified polymer layer produced by photo-induced anisotropic phase separation. For flexible display applications, we have tested the mechanical stability of electro-optic properties in PILC structures with plastic substrates. 1. Introduction In recent years, roll-up displays have drawn considerable attention for next-generation information displays because of their excellent portability such as light weight, thin packaging, and flexibility. Among several available technologies, it is expected that a liquid crystal display (LCD) using plastic film substrates is the most promising device because of its superior visibility with low power consumption over other displays such as organic light-emitting device or electrophoretic displays. However, there are still critical problems regarding the fabrication of commercially available plastic LCDs with current technologies based on the glass substrates. One of those problems is the instability of LC structures due to hydrodynamic properties of LCs at bending and another is the separation of two plastic substrates due to the flexibility of film substrates. Such problems do not exist in conventional glass-substrate-based LCDs since glass substrates can sustain a stable LC alignment condition against external bending or pressure. To solve these problems, several types of polymer wall and/or network as supporting structures have been proposed and demonstrated [1]-[7]. These structures were fabricated using an anisotropic phase separation method from polymer and LC composite systems by applying a patterned electric field or spatially modulated UV intensity. However, these methods require high electric field to initiate the anisotropic phase separation or remain residual polymers in unexposed regions that reduce optical properties and increase the operating voltage of the devices.

We developed a new device structure using anisotropic phase separation from liquid crystal (LC) and polymer composite materials using UV intensity variation and polymer wetting properties. In the device, the LC molecules are isolated in pixels where LCs are surrounded by the inter-pixel vertical polymer walls and the horizontal polymer films on the upper substrate. These devices show very good mechanical stability against external pressure. The electro-optic characteristics and the mechanical stability of the devices are discussed in view of the flexible display applications.

We have fabricated dual-domain twisted structure by imprinting of LC alignment on polymer layers during polymerizing induced phase separation in polymer and liquid crystal (LC) composite systems. By application of electric field during UV exposure, the photopolymerized polymer chains are formed along the long molecular axis of LC aligned by the field. The aligned polymer chains align LC molecules after removing the field. Using this method, we successfully fabricated dual-domain twisted nematic structures.

Polyimide containing the chalcone moiety is expected to show the high photodimerization rate and stable alignment characteristics. We introduced the chalcone moiety as a side chain into the polyimide backbone to apply to the photo-alignment layer. The photochemical reaction with the tilted incident light produced out-of -the plane orientation of chalcone side chain. The orientation effects align the LC in LCD, which possesses the various pretilt angles depending on the length of side chains.

A new type of LCD has been developed using recently developed phase separated composite film method with a single glass substrate. The resultant structures are made of adjacent parallel layers of liquid crystal and polymer. The LC layer is confined between the solidified polymer layer and glass substrate. The electro-optical properties of the display have been investigated. This technique has the potential to realize a lightweight display for hand-held portable electronic products.

Polyimide alignment layers have been prepared using “in-situ” exposure to linearly polarized UV LPUV light during imidization. Liquid crystal alignment on these layers exhibits higher anchoring strength and thermal stability than the “conventional” UV method that employs LPUV exposure after imidization. The in-situ method requires fewer steps and shorter processing time compared to the conventional method.

Very flexible nematic LCDS have been built with plastic substrates using phase separated composite organic method. A study of electro-optical properties of these displays shows a low voltage operation, high contrast, and a high degree of mechanical flexibility.