The 'Paintable LCD' approach allows the preparation of an LCD on a single substrate by the sequential coating and curing of a stack of tailored organic layers. This revolutionary new technology for the manufacturing of liquid crystal displays (LCDs) provides freedom in display design as well as in production methodology. In fact, displays can be prepared on any substrate. The key process that enables layer stacking on top of the liquid crystal (LC) layer is called photo-enforced stratification (PES). It comprises a two-step photopolymerisation-induced phase-separation of an LC blend and a polymer precursor. In these polymerization steps, the single thin layer (a homogeneous mixture of an LC blend and a polymer precursor) very accurately phase-separates in a hard polymer top coat and a pure LC layer underneath. Directionality with respect to the phase-separation can be achieved by using the absorption of one of the compounds in the mixture which provides a UV intensity gradient over the layer thickness. As a result, the photopolymerisation predominantly takes place where the UV intensity is the highest i.e. near the film surface that is directed towards the UV source. Also other optical layers, like polarisers or retarders, can be deposited by simple coating techniques, so that the complete display can be made using one, very simple and versatile, technology.

The Vertically Aligned (VA) technology is one of the newer modes of operation among TFT displays. For VA displays, the liquid crystal is aligned homeotropically and possess a negative dielectric anisotropy (De<0) in order to switch perpendicular to an applied electric field. A new generation of nematic LC materials has been developed which reduces rotational viscosity (g1) but keeps other important parameters unchanged. The switching time parameter, g1/Dn2, is compared with those of previous reference mixtures possessing a range of optical anisotropies. The results show that the new mixtures give a consistent reduction in g1/Dn2 for a wide spread of Dn. Reduction in threshold voltage (V0) is an important goal for the majority of applications and can be achieved by increasing the absolute magnitude of (formula available in paper). However this in turn increases rotational viscosity (g1). The new mixtures overcome this drawback and significantly decrease the values of g1/Dn2 over a wide range of V0. A requirement for TV displays is increased brightness. The result is an increased operating temperature and therefore, higher clearing temperatures of the LC mixtures are demanded, but they lead to higher g1. The new LC components were successful in reducing g1/Dn2 in comparison with the previous standards for a range of clearing points.

For mobile devices, permanent image displays are very attractive. We present one: the Binem® display which is close to appear on the market. A first demonstrator was shown at SID’ 97. An important research and development work has been made in the Paris-Sud University and in Nemoptic to increase the temperature domain and define industrial processes to realise mean size displays. The Binem uses two equal lower energy states of a chiral nematic liquid crystal. The molecules are oriented almost parallel to the cell plates by monostable surface treatments. One state (U) is uniform, the other (T), is twisted by 180°.To switch, a high field pulse orients the molecules on one of the plate perpendicular to it: the anchoring is broken. After the pulse, this state is unstable, the molecules on the plate will relax to the anchoring orientation. If they fall in one direction the U state builds, if they fall in the opposite direction the T state is realized. The fall time of the pulse and the pretilts on the two plates control this process. We explain the mechanism of switching by surface anchoring breaking and the obtained display performances.

Holographic polymer-dispersed liquid crystal (HPDLC) gratings have been employed in various display applications. Two prototypes that have been developed are switchable lenses in wearable displays and electronic filter wheels in video projectors. Acrylate-based HPDLCs have been utilized for the most part. These have many desirable properties, including fast switching speeds, but have contributed to stability problems, including long-term diffraction notch blue shift (shrinkage) and voltage creep due to post-polymerization effects. Thiol-ene based HPDLCs have been investigated and show potential for overcoming these shortcomings. We present a comparison of acrylate and thiol-ene HPDLCs and discuss the implications for long-term stability in display applications.

We describe a detailed study of the bend nematic structure stabilized by the polymer network. The formation of phase-separated polymer network in a bend nematic structure is affected by various factors, such as the polymer network morphology, polymer concentration, applied electric field, UV exposure time, and UV intensity. SEM images of the polymer network morphology show a templating effect, where highly ordered nanofibers mimic the bend state of the liquid crystal. At low monomer concentration and low curing voltage, liquid crystal can be oriented into the twist or splay state. High monomer concentration conveys excessive strength of the polymer network on liquid crystal and shows poor electro-optical properties of liquid crystal. With the current nematic host, the best condition of our experiments is 3% monomer concentration and 5V curing voltage. The resulted liquid crystal-polymer composite shows fairly fast optical response to the applied field.

The novel approach to the thresholdless hysteresis free switching is described. The key parameters for this mode are capacitance of the alignment/insulating layers and conductivity of the FLCs. The influence of the chemical structure of FLC on the performance of the V-shape mode is discussed. Utilizing this new approach, we constructed a cell with an inversion frequency around 1 kHz and the saturation voltage less than 4V.

We synthesized two side chain polymethacrylate derivatives polymers 1 and 2 side chain polymer 3 and 4 and main chain polyimide polymer 5 derivatives containing a chalconyl moiety to investigate the extent of photoreaction and photoalignment behavior of liquid crystalline (LC) molecules. A smectic A phase was exhibited for the polymethacrylate derivatives, while polyimide derivatives did not show any mesophases. Only a glass transition was observed for the polyimides. The LC phase of polymethacrylate derivatives showed a good value of the extent of photoreaction, while the extent of photoreaction for polyimides above glass transition temperature was also larger than that below glass transition temperature. Mixtures of low molar mass liquid crystal (MBBA or 5CB) and dichroic dye were filled in the LC cell fabricated from the polymer. In the case of the LC cells fabricated from polymer 1 film irradiated with linearly polarized UV (LPUV) light in the LC phase, the dichroic ratio (DR) values were positive showing parallel orientation of the LC molecule to the electric vector of the incident LPUV light. The DR values were also positive for the LC cells fabricated from the polymers 3 and 4 film irradiated with LPUV light, while the negative DR values were obtained for the polymer 5 film.

Novel scattering-type displays using antiferroelectric smectic phases of liquid crystals of bent-shape molecules are reviewed and discussed. There can be two distinct states racemic and chiral that work in opposite ways. The racemic structure is scattering in the OFF state and is optically clear under sufficiently large (E~4-6V/m) electric fields. The chiral structure is transparent at zero fields and scattering in the field ON state. These two structures may be reversibly interchanged implying their use in devices that consume energy only during switching from one stable state to the other. After summarizing the previous results on the film thickness, driving voltage and temperature dependences of the light shutters, new results will be presented on a banana smectic material, which has an optically isotropic transparent antiferroelectric OFF state. We show that the optically isotropic and transparent OFF state can be reversibly switched to birefringent and scattering ferroelectric states in less than hundred microseconds.

The process of phase separation leads to several well known display technologies such as Polymer Dispersed liquid crystals and Polymer Stabilized cholesteric and ferroelectric devices. Several new limits of the general phenomena of phase separation have been discovered in recent years. In one of the limits, a very simple and powerful process known as the phase separated composite structures method permits the construction of conventional devices; such as, TN, STN, and FLC devices with great ease and with flexible substrates. It has also been employed in the fabrication of one- and two-dimensional optical gratings and fly's eye lenses (micro-lens array) with electrically controllable focal length. In the second limit, one obtains microscopic polymer columns perpendicular to the substrates. These structures have been used to fabricate large area homeotropic nematic devices having very high-contrast.

Defect free polymer-stabilized (PS-)V-mode FLCDs and intrinsic half (H-)V-mode FLCDs have been fabricated; they exhibit high contrast ratio over 700:1 and high reliability for a temperature cycling test by using specially developed polyimide alignment materials, RN-1411 series, from Nissan Chem. Ind., and also by adopting special alignment technique such as appropriate rubbing technique, photoalignment, and ion beam irradiation techniques and also particularly developed polymer-stabilization technique. These FLCDs are shown to be useful for implementing a field sequential type full color (FS-FC) LCDs due to their fast response with the response time of τ = 100μs ~ 500μs that is 10 to 100 times faster that those of LCDs using NLCs. We have developed several prototype models of FS-FC LCDs having VGA specifications that exhibit good performance for displaying fast moving video rate images with wide color gamut.

Optical performance of the LCD is strongly affected by optical films such as polarizers and retardation films. The characteristics of polarizers, which determine the contrast ratio and the hue balance of the LCD, need to be improved, in particular, to meet the current requirements on high-performance LCDs. Most polarizers for LCDs are made from polyvinyl-alcohol (PVA) films and iodine compounds by the wet dyeing method. Polarizers with high polarization efficiency and transmittance can be obtained by optimizing the dyeing and stretching conditions. In transmissive LCDs, blue decolorization in black images need to be improved by controlling the chemical species of PVA-iodine complexes. The authors analyzed the dichroic ratios of chemical species by separating each absorption peak, and presented a guide for the neutralization of the hue balance of polarizers. The characteristics of reflective LCDs, on the other hand, are largely dependent on the optical design of circular polarizers and quarter-wave plates, which constitute the circular polarizers. The important design elements of reflective LCDs include wavelength dispersion and viewing angle characteristics. The authors have contributed to the improvement of the performance of reflective LCDs by enhancing the characteristics of polymer films using stretching and optical lamination technologies

The major factor of the power consumption of the driving LSIs for TFT-LCDs is AC power consumption stemming from charging and discharging data lines that have quite large parasitic capacitance. Since the AC power consumption is linearly proportional to the supply voltage of the driver circuits, the number of data lines and its parasitic capacitance, voltage swing and operating frequency. In this paper, therefore, we review the low power driving methods with four categories. The VCOM alternation method can reduce both the supply voltage and voltage swing. And there were several panel structure and driving methods for reducing the number of data lines in the TFT-LCD panel. Both multi-field driving method and a recent trend of embedded memory in pixel are focused on reducing the operating frequency. Finally, there are several researches to reduce the voltage swing with using energy recovery such as charge sharing method that is very simple and its maximum power saving efficiency is 50% and triple charge sharing method, stepwise source driving method and L2C energy recovery circuits whose power saving efficiency are up to 66.6%, 78% and 78.8%, respectively.

In this paper, we present several different types of liquid-crystal WDM signal processors includign broadband optical switches, voltage-controlled variable optical attenuators and optical harmonic equalizers.

Liquid Crystals (LCs) prove to be the basic material for various applications in Electronic Imaging and Displays as well as Optoelectronics. We will consider the following LC devices for fiber optical applications. 1) Fast reliable low power optical switches. At present LC switches show certain advantages in comparison with microelectromechancial (MEM) systems, commonly used for the same purpose, such as (i) fast switching time; (ii) low controlling voltages and power consumption; (iii) higher reliability and working time. We shall demonstate the new possible configurations of the fast LC shutters for fiber-optical system, based on (i) STN-LCD cell and (ii) fast deformed-helix ferroelectric liquid crystal mode. 2. Passive elements of fiber optical communication system, such as optical filters, attenuators, equalizers, polarization rotation, voltage controllable diffraction and fast switching of LC refractive index. The software for optimization of the LC modulation characteristics is demonstrated. 3. Passive fiber optical elements based on Photonic Crystals (PCs) and Liquid Crystals (LCs). Photonic crystals are known to provide wavelength-dependent filters, beam splitters, mirror components. Filling of the interstices of the photonic crystal with the photo-aligned LC material and subjecting the LC to a varying electric field can provide a tunable photonic crystal element. A method for the formation of controllable PC/LC structures, based on multiple-redrawing technique, applied for different types of glass filled with photo-aligned LC is discussed.

At present, we have studied and developed a liquid crystal device applied to the optical device. A liquid crystal device is useful for the transformation of polarization and phase of the light. This device is excellent in the miniaturization of the device and static because it is not necessary to use a mechancial movement and can control the light electrically. Moreover, their devices are trustworthy as optical devices and there make practicable as the wave front control devices applied for DVD optical pick up systems. This time, we report a beam deflector using liquid crystal devies we have developed.

A new spatial light modulator system based on a high-resolution LCOS micro-display is presented. The parameters like pixel size and number as well as the fill factor and especially the phase modulation properties open up many application in coherent optical applications. The light efficiency of this system can compete with other static optical solutions. A major application field diffractive optics will be illustrated and performance and perspectives of this system will be discussed. Investigations were done mostly on the addressing of the 2.3 Mega pixel device. The effect of ghost images and cross talk due to the addressing scheme will be discussed concerning the influence of the optical performance. General optical measurements like complex modulation is presented, particularly focused on the phase modulation properties. Furthermore, possibilities of adapting the modulation by the use of "Gamma-correction" curves are shown. Various experiments which illustrate different application fields the modulator system are presented.

We exploit the use of azobenzene-containing polymer networks in ferroelectric liquid crystals (FLCs). One possible utility of the polymer in such a system is to induce and stabilize a bulk alignment of the FLC host, without surface orientation layers, through the photo-orientation of the azobenzene groups on the network under lineally polarized irradiation. Three azobenzene monomers, inclduign an achiral diacrylate, a chiral dimethacrylate and an achiral divinyl ether, were synthesized and investigated with two commercial FLC mixtures; polymerization was carried out thermally and photochemically. The photo-induced alignment of FLC was observed with two of these azobenzene polymers. Different phase separation behaviors and resulting morphologies were observed.

Light scattering electrooptical switching has been achieved for liquid crystal physical gels consisting of a room temperature nematic liquid crystal and a hydrogen-bonded gelator. The use of the nematic liquid crystal exhibiting higher isotropization temperature and the gelator with four hydrogen-bonded moieties leads to the formation of thermally more stable liquid crystal gels. The liquid crystal gels show significant electrooptical properties for light scattering display materials. We have examined the effects of the concentration of the gelator and the cell thickness on the electrooptical behavior.

We show an electro optic linear polarizer for the visible spectrum region. The device is made of a Cyberdisplay^TM liquid crystal display (LCD) manufactured by Kopin Co. and a linear polarizer. The device can rotate from 0 to 70 degrees the linear polarization state of a beam. To control the polarization rotation, we displayed gray levels from 0 to 255 in a PC connected to the LCD. We present the complete characterization of our device and experimental results.

Columnar liquid crystals are useful for the construction of organic light emitting diodes (OLED) due to their high charge carrier mobility and their ability of developing defect-free superstructures. We investigated the electroluminescent properties of various mesogenic derivatives of triphenylene, pyrene, perylene, benzoperylene and hexa-peri-hexabenzocoronene (HBC) which combine good charge carrying properties and luminescence. The wavelengths of maximum electroluminescence range from about 400 nm to 720 nm, depending on the core and the substitution of the molecules. Nearly white emission can be obtained in samples containing two or more emitting layers. The perylene core is so efficient that even a single organic layer between an ITO anode and an aluminum cathode can give luminance values up to 100 cd/m². In addition to the electroluminescence, we present results on the photovoltaics in hetero junction structures of the compounds. Samples with two organic layers made of a HBC- and a perylene derivative show an open circuit voltage V_oc of about 0.8 V, a short circuit current I_sc of a few μA/cm², and a filling factor FF of about 31 %.

We developed an LCD module that uses a color conversion circuit to improve imperfect color reproduction in the LCD panel. Our module implements a color conversion circuit that uses a matrix calculation we developed. This color conversion circuit supports motion picture display and real-time processing, enabling desired color conversion characteristics and facilitating use of 2 modes of color conversion characteristics by selection sRGB mode and consumer-TV-like color mode consumer-TV-like color mode. The international sRGB standard is the default RGB color space for multimedia, in which 'reference image display system characteristics' are specified, i.e., a display device must have characteristics close to sRGB characteristics to properly display color image data conforming to sRGB. This is why the sRGB specification for liquid crystal displays has been defined. Our TFT-LCD module achieves less than one tenth the color difference for the sRGB specification. Devices with low color reproducibility are improved using a color conversion circuit to increase apparent color depth, but conventional approaches to this have such adverse effects as color saturation in high-chroma areas and emphasized color noise in dark areas. Our module achieves consumer-TV-like color by implementing a new color conversion circuit that includes a gamut compression function to solve such problems.

Sixty-four color LCD panels were employed to implement a natural 3D display. Sixty-four images displayed on the LCD panels are projected in the different horizontal directions by using modified 2D aligned telecentric optical systems. Because the projection angle pitch in the horizontal direction is as small as 0.33 degree, observers’ eyes can focus on the 3D images. Because the projection systems are telecentric, images are defocused little so that clear 3D images are generated in the 3D space. The horizontal viewing angle is 21.2 degrees, and the 3D screen size is 192 mm X 151 mm (9.6 inch.) The 3D objects can be displayed in the range of ~ 400 mm both in front of and behind the 3D screen. The prototype 3D display has following features: a) no need of wearing 3D glasses, b) simultaneous observation by multiple persons, c) no restriction on observing position, d) compatible with human 3D perception, e) providing high presence, and f) offering photorealistic and moving 3D images. The human accommodation responses to the prototype 3D display are very similar to those obtained for real 3D objects.

The idea of using liquid crystal devices as an adaptive optics component has been proposed by several authors. In recent years a vigorous research effort has been carried out, and it is still flourishing, in several countries. Mainly the research and experimental work has been concentrated in the USA, U.K. and Russia. There are several reasons why liquid crystals may represent a valid alternative to the traditional deformable mirror technology that has been used for the past two decades or so. The main attractiveness of LC resides in the cost. Current deformable mirror technology has a range of price going from $2K to $15K per channel. LC technology promises to be at least a couple of orders of magnitude cheaper. Other reasons are connected with reliability, low power consumption and with a huge technological momentum based on a wide variety of industrial applications. In this paper we present some preliminary characterizations of a new, large format device. Such devices have the potential for extremely high-resolution wave-front control due to the over 10,000 corrective elements. The characterization of the device, so far, consists of measurements of the overall optical quality and of the phase control relationship

Programmable diffractive optics utilizing a high-resolution liquid-crystal phase modulator is demonstrated as a versatile technique for wide-dynamic-range, two-dimensional wavefront control. A high-resolution phase modulator system introduces modulo-2π phase modulation and operates with 307,200 independently addressable elements, 100% fill factor and total optical efficiencies of up to 93%. Demonstrations include beam steering, large aberration compensation, and near-diffraction-limited imaging and beam directing in a telescope system with large defocus and off-axis aberrations.