Polymer dispersed liquid crystals have received much attention recently due to their potential applications in projection and direct view displays. In this paper, the effect of curing conditions, i.e., UV lamp power, exposure time and curing temperature, on the electro-optic properties of PDLC films are reported for both direct view and projection applications. The variation of electro-optic properties with variation of film thickness for different liquid crystal mixtures is also reported. The results presented indicate that an optimum curing temperature and lamp power exist at which an optimum contrast can be achieved for a given film thickness.

A novel series of siloxane containing low molar mass liquid crystals have been synthesized and characterized by DSC, optical microscopy and electro-optic properties. The compounds described all exhibited room temperature bistable chiral smectic C phases. In this paper we concentrate on the electro-optic properties of both low (approximately 20 nC cm^-2) and high (approximately 150 nC. cm^-2) spontaneous polarization homologues. Data is also presented on tilt angles, response times and rotational viscosities for these compounds. All of the materials gave wide temperature range (> 50 degree(s)C) ferroelectric phases with tilt angles, varying between 28 degree(s) and 36 degree(s), that were independent of temperature. Response times of the order of microseconds, or longer, were observed. Dichroic dye guest-host mixtures were prepared and their unusual electro-optic properties leading to high contrast ratios also are described. The implications for both birefringence and dichroism based devices are considered.

We have studied the pyroelectric behavior of both low molecular weight and polymeric ferroelectric liquid crystals. The alignment and electric quality of the pyroelectric LC samples is found to strongly influence the measured pyrosignal. The pyroelectric current is recorded as a function of temperature, and by a calibration procedure absolute values of the pyroelectric coefficient can be obtained. For a well-aligned siloxane copolymer FLC with high spontaneous polarization, a maximum value of about 13 nC/cm².K for the pyroelectric coefficient was evaluated, comparable to values found for low-molar mass compounds.

Chiral smectic A (Sm A) liquid crystals are of increasing interest because of their potential for fast analog electro-optic modulation. Chiral smectic A liquid crystals, when viewed between crossed polarizers, exhibit distinctive periodic stripe domains due to a voltage dependent deformation (kink) of the bookshelf geometry. These stripe domains reduce the contrast ratio of electro-optic devices employing these materials. This paper describes a novel optical technique to probe spatial variations in the optical properties of liquid crystals with micron resolution. The effect of the stripe formation on the electro-optic properties of a electroclinic Sm A liquid crystal, denoted as KN125, is investigated. The electric field induced stripe domains were experimentally characterized by measuring the transmission of KN125, interposed between crossed polarizers. A sharply focused visible cw laser beam was translated across the sample with one-micron resolution. A quasi periodic modulation of the transmission due to stripe deformation of the bookshelf geometry was observed. measurements performed within a single stripe and between adjacent stripes permitted an independent determination of the true optical tilt angle and the kink angle. The electric field dependence of the optical tilt angle for the KN125 liquid crystal is reported.

Measurement of the fuel aerosol droplet diameter is very important in the course of construction of new types of sprayers (burners, carburettors, injectors) and diagnostic processes as well. Diffraction method is one of the most useful measuring procedures in this case. The droplet size of monodispersion medium is easy to recognize (Airy rings). Analysis of the diffraction pattern of polydispersion medium is considerably more difficult. After recording the diffraction pattern I(r) of an aerosol stream one of the numerical procedures is used. The registration process and data processing are usually separated. The final result of the investigation -- average droplet diameter D_(rho ) of distribution (rho) (D) -- is obtained after some time. The most useful procedure in the diagnostic is real-time measuring. The diffraction light intensity curve I(r) depends on the type of droplet diameter statistical distribution (rho) (D) and relative standard deviation d equals (sigma) /D_(rho ) as well. Precise analysis in nondimensional units [z equals (pi) Dr/(lambda) f and I_w(z) equals I(z)/I_max] shows the point [z₀ equals 1.47, I_w(Z₀) equals 0.57] which may be used to display average droplet diameter D_(rho ). The position of point [z₀, I(z₀)] is independent of relative standard deviation d and the type of distribution function (rho) (D) as well. After finding the value of radius-vector r_0.57 that I(r_0.57) equals 0.57 it is possible to evaluate average droplet diameter from relation D_(rho ) equals (0.47 (lambda) f)/r_0.57. After using an image converter with a rectangular optical response OR(I), the Airy picture I(r) becomes a ring. The radius of that ring depends on threshold light intensity I_p of characteristic OR(I). If I_p equals 0.57I_max, the radius of the converted Airy picture will be r equals r_0.57. After introducing non-linear scale D equals f(r_0.57) the image converter becomes an analogue measuring instrument. This idea has been tested with TV and CCD cameras. Making use of threshold effects of liquid crystal displays it is possible to reduce the volume of the measuring stand and its price as well.

Liquid crystal spatial light modulators (LC SLM) are being applied as input devices in optical data processing systems, optical filters in optical coherent correlators and projection display devices. The methods of self-filtration of image in image and/or Fourier planes, including spectral, nonlinear, and other types of image filtration, are reported here. The methods are established both on high spatial resolution and nonlinearity of optical response to the input optical signal of LC SLM. A few optical schemes for input image self-filtration were experimentally realized with spatial light modulators based on monocrystalline semiconductors (GaAs, BSO, CdZnSeS), combining sensitivity, spatial resolution, and highly nonlinear modulation curve corresponding to most of the electro-optical effects used in LC SLM.

Polymer modified materials have been shown to be useful in controlling the operational voltages and speed in TN devices; and the operational voltages and the suppression of the `stripe' deformation in STN cells.

Liquid crystal displays (LCDs) have become, in the last decade, the most significant and fastest growing category of advanced display technology. The operability of LCDs is essentially determined by the liquid crystal material properties. Since the material parameters of liquid crystals are the result of their molecular properties amplified by their long range molecular interactions, the proper application design of liquid crystalline molecules is crucial. This paper contains a review in the molecular design of nematic liquid crystals for active matrix displays (AMLCDs), thin-film-transistor polymer dispersed liquid crystal displays (TFT-PDLCD) and supertwisted-nematic liquid crystal displays (STN-LCDs). The relationship between the physico-chemical properties of the nematic liquid crystalline phase and the structural features of their mesogenic molecules experimentally obtained are discussed in terms of existent theories.

Use of liquid crystal display technology for ocular prosthesis was recently proposed. Liquid crystal light valves are used for the purpose of light modulation to control pupil size proportional to incident light intensity. In the current study two different types of liquid crystal technology are tested for use in a prosthetic eye. The first type is the conventional twisted nematic (TN) cell. The second type of technology is a color dispersion system consisting of liquid crystal droplets in a polymer binder. Because of the principle of operation of the prosthetic device, in the off state the display should block light and appear black. This is easily achieved with TN cells. For the dispersed technology, a colored dispersed system using a black dichroic dye is used so that the display is black in the off state. The response of the two types of technology are measured and compared for ocular prosthesis. Factors such as photostability, battery life, alternate modes of operation, and the use of other types of liquid crystal display technology are also discussed.

The relationship between waveguide properties and their morphological regularity is investigated for the LB films prepared by two preparation methods. The optical propagation loss of the LB film prepared by the multi-step creep method was 2.5 dB(DOT)cm^-1, whereas that of the LB film prepared by the continuous compression method was 8.4 dB (DOT)cm^-1. The lower propagation loss of the LB film prepared by the multi-step creep method results from a remarkable reduction of the surface light scattering due to the flat surface morphology of the LB film.

We report a novel scheme of making programmable binary optical elements using the cathode- ray tube coupled liquid crystal light valve (CRT-LCLV) spatial light modulator (SLM). The CRT-LCLV is a kind of electronically addressed SLM. The programmable code can be directly input onto the CRT-LCLV SLM using a microcomputer. The programmable Fresnel lens is as an example of the programmable binary optical elements. The Fresnel lens function is written onto each pixel of the CRT-LCLV spatial light modulator. Experimental results of making programmable binary optical elements using CRT-LCLV spatial light modulator are presented.

We describe opto-electronic LC spatial light modulators which allow the generation of alterable diffraction gratings down to 1 micrometers period. Optically defined binary and blazed phase gratings are used in which the diffraction is altered by a parallel aligned nematic LC phase modulation layer. This enables the creation of arbitrary fine-pitch gratings. Different types of modulators have been theoretically and experimentally investigated. The theoretical results show that in the case of small grating structures the exact wave theory has to be applied to calculate the diffraction properties. Then the grating modulation becomes dependent on the light polarization and the grating period. Modulators with gratings of 1 to 10 micrometers period have been fabricated. The modulator structure, the LC phase modulation layer, the problems of combining LCs with fine-pitch gratings, and the modulator properties are discussed. Good diffraction efficiencies and extinction ratios for the diffraction orders of the modulators for monochromatic light have been obtained as well as short switching times.

A review of LC alignment properties on UV-cured photoanisotropic films is given. Special attention is attracted to photopolymers (like PVC), as aligning agents. Such aspects as orientation quality, tilt angle, etc. are taken into account. The new aligning methods seem to be very attractive in LCD technology as they allow the user to avoid electrostatic charges and impurities, which usually exist in conventional rubbing techniques. Such applications of photoanisotropic aligning methods as the improvement of viewing angles of TN LCDs or the restoration of bistability in FLCs are discussed.

The reorientational steepness of nematic liquid crystalline molecules is strongly dependent on the elastic constants of the liquid crystalline director. The steepness increases with decreasing the ratio of elastic constants of the bend mode to the splay one, K₃/K₁ when the homogeneous or twisted alignment of nematics is transformed to the homeotropic one. It has been suggested that the elastic constants are affected by the geometrical shape of a liquid crystalline molecule and a short-range ordering for the alignment of liquid crystalline molecules. The composite systems films being composed of side-chain type liquid crystalline polymer (PS6EC) and low molecular weight nematic liquid crystal (E7) were prepared by a solvent cast method. The phase transition behaviors and the aggregation state of the composite system were investigated on the basis of the DSC, polarizing optical microscopy and x-ray diffraction studies. The magnitude of K₃/K₁ and the reorientational steepness were evaluated by an electric capacitance measurement of the homogeneous cell. It became apparent from x-ray diffraction studies that the smectic-like short-range ordering among mesogenic molecules increases with increasing the fraction of PS6EC even in a nematic state of the composite system. The magnitude of K₃/K₁ was anomalously small, nearly zero, in an intermediate region between the smectic and the nematic phases for the (PS6EC/E7) composite system. At that region, furthermore, a discontinuous jump in the reorientation of liquid crystalline molecules, i.e., sharp steepness in an electro-optical switching, was successfully achieved.

Review of our results of the steadies of the distribution of the director of a nematic liquid crystal in a cell with photosensitive aligning layers is presented. It is shown that a doubly degenerate easy orientation axis is induced on the nematic-orientant interface. It was also found that the degeneracy of the easy axis orientation could be removed by NLC molecules flow during LC cell filling and an oblique liquid crystal orientation is realized. The theoretical and experimental investigations of the reorientation of the director toward the light-induced easy axis caused by light-induced adsorption of dye molecules are presented. Threshold and nonthreshold effects are considered.

The influence of dipole phototransformed molecules on the orientational instability threshold of homeotropic and planar NLC exposed to spatially modulated light is studied. The orientational spatial distribution of the director is calculated, in linear approximation, at the non threshold director reorientation. It is shown that the orientational instability threshold may significantly decrease (increase) and the optical nonlinearity constant may increase (decrease) by orders of magnitude as phototransformed molecules with typical value of permanent electric dipole appear in the nematics.

In this paper we consider nematic liquid crystal (NLC) confined to a cylindrical cavity under the anchoring conditions of various type. The influence of the saddle-splay and splay-bend terms (the K₂₄-term and the K₁₃-term) on the axial director configuration stability is investigated. By using the Fourier expansion of director fluctuations over azimuth angle our analytical method of attack enables the stability conditions to be found in terms of the stability to each fluctuation mode. Two ways to stabilize the structure are explored: the stabilization by magnetic field and by the action of the boundary conditions. We get the restrictions imposed on the constant values to make the stabilization possible. The dependence of the resultant stability threshold on the surfacelike elastic constant values is calculated. We discuss in detail experimentally detectable effects due to the presence of the K₁₃-term. It is shown that the escaped-radial director structure exhibits some special features induced by the K₁₃-term.

Thin film luminescent layers have applications in electroluminescent devices and potential application to other displays with high brightness and high resolution requirements. Displays such as field emission devices where high current densities, high electric fields, and small dimensional tolerances are present require phosphors which have high maintenance qualities and good adherence to the face plate. To increase the luminance of EL displays high quality phosphor layers are necessary. In this study, we report the growth kinetics studies of ZnS and the properties of high quality ZnS layers grown by metalorganic molecular beam epitaxial deposition for display applications. The layers' structural and optical properties have been characterized by x-ray diffraction, electron and optical microscopy, and photoluminescence spectroscopy. These measurements were made as a function of the growth and process conditions such as growth temperature, flux ratios, different sulfur precursors, etc. PL spectra exhibited free- and bound-exciton transitions indicative of high quality ZnS material.

One of the key factors that will determine the future success of field emission devices (FEDs) as a competitive technology in the flat panel display market is obtaining a red, green, blue (RGB) phosphor set that will satisfy a strict set of criteria. These criteria are imposed by at least three different sets of demands: (1) The RGB set must be capable of reproducing a color gamut close to the NTSC standard. (2) The chemical and physical properties of the phosphor set must be compatible with the cathode environment of the device. (3) The set must be efficient enough to equal or outperform competing flat panel technologies in terms of power consumption. In this paper a series of commercial and experimental phosphors is examined to assess their potential as candidates to satisfy some of the above demands. Over the last twenty years considerable effort has been expended in developing the high voltage (20 kV - 30 kV) phosphors used in television, special purpose CRTs and x-ray imaging. In spite of this, however, there is a relative paucity of information available on performance in the range 300 V - 1000 V. We present experimental results of luminous efficiencies of a range of phosphors as a function of excitation voltage and low voltage saturation results of some phosphors under FED working conditions to discuss the potential of these phosphors in field emission device environments.

Ion implantation can introduce color centers into thin film phosphors for electroluminescent (EL) and cathodoluminescent (CL) displays. Color pixel patterns are defined through a simple shadow mask that is translated across the thin film phosphor host. Thin film samples of the traditional EL and CL hosts ZnS and Zn₂SiO₄ and thin film CaGa₂S₄ were prepared on conducting glass substrates. The samples were implanted with various doses of Cu, Mn, Tb, Sm, Ce, and Eu ions; effects of cation-anion stoichiometry were studied through co-implantation of S, O, F, and Al in combination with the activator ion. Post implant anneals were used to redistribute the implanted ions and remove any residual damage. We have demonstrated four-color EL emission (RGBY) in a single thin film panel by implanting Sm, Mn, Tb, and Tm into ZnS. The Mn yellow brightness equaled that of co-evaporated films. CaGa₂S₄ implanted with Ce showed blue emission of about 1 fL 60 Hz. For thin film CL phosphor studies, we implanted Cu and Al at different relative doses in ZnS, followed by annealing. CL measurements at 1500 eV showed that emission changed from blue (470 nm) to green (520 nm), depending on the implanted Cu/Al ratio. Bright green CL (531 nm) was achieved by implanting Mn in Zn₂SiO₄ followed by a relatively high temperature anneal, to form the standard P-1 phosphor as a thin film.

The technique of dry etching as applied to the patterning of thin films is described, and compared to wet etching in terms of the etch precision and in terms of the usage and disposal of etch chemicals. The etch requirements of three representative display technologies (AMLCD, FED and EL) are outlined, and the range of plasma etch processes which are applicable to these requirements is described.

A new type of high definition large area photolithography system, based on scanning projection lithography, has been developed and successfully implemented as a tool for flat panel display manufacturing. The machines built on this principle have a resolution of better than 4 micrometers and can expose areas of 500 mm X 600 mm (20' X 24'). Comparison of the complexities of the ways and means to obtain these specifications leads to the conclusion that this equipment is highly cost effective. To support this claim, results of a cost of ownership model are presented.

Inspection and repair offer higher yields and lower costs for AMLCDs, plasma displays and field emission displays, especially as display size increases. For repair to contribute, it must be fast and fully reliable. Building on L1 technology, a second generation L2 laser repair tool utilizes laser cutting and laser deposition technologies to repair electrical open and short defects on the active plates and on the passive color filter plates. This paper details engineering modifications which significantly reduce the time to repair a panel while maintaining repair reliability. Moreover, the L2 can receive up to 800 X 800 mm substrates of varied thickness.

Planar has developed the first manufacturable, full color, high contrast, 320.256 line thin film electroluminescent (TFEL) display; the FC-2. Three primary tasks in developing the FC-2 were (1) blue phosphor improvement, (2) unique panel structure development for enhanced optical properties, and (3) application of high density interconnects. We review progress in the development of the cerium doped, alkaline earth thiogallate compounds for blue emission. ZnS:Mn is filtered for red emission and ZnS:Tb is used for green. The panel structure reported optimizes key performance parameters by enhancing the fill factor, frequency of operation, and power efficiency. It uses a `dual substrate' approach, placing the blue phosphor on one substrate and the red/green on the other. We describe panel fabrication processes and assembly techniques utilized. We also describe the electronic driver and addressing schemes used to maximize the brightness. The high interconnect density in this 5' diagonal display demands an improved driver interconnect scheme. Planar has developed a chip on glass (COG) process with the driver chips bonded directly to the glass substrate and wire bonded to the rows, columns, and control electronics. This approach is compared to conventional tape carrier package (TCP) and flex interconnects. Mechanical, optical and electrical panel performance specifications are reported together with some exiting areas of future development.

With the advent of portable electronics and HDTV, there has been much activity in the development of flat panel displays. Flat panel displays are a key component and product differentiator for a variety of electronic products including portables, instrumentation, computers, and entertainment. They are frequently the most visible, costly, and difficult to obtain product component. Currently, the high performance flat panel display industry is dominated by Japanese manufacturers of active matrix liquid crystal displays (AM-LCD). In AM-LCDs, a thin-film transistor is fabricated underneath each pixel to control it more efficiently. The performance is thus improved, but at the expense of an increase in display complexity. Micron-size lithography and alignment capabilities similar to those used for integrated circuits are needed over large display areas. As a consequence AM-LCD manufacturing requires a large capital investment for the VLSI-type equipment that is needed and yields have been increasing only at a slow pace, thus keeping the display costs high. In addition, LCDs are a non-emissive display technology requiring a backlight. This entails an inefficient power use and brightness limitations. Only a small percentage of the emitted light actually makes it through the LCD. Due to these problems, even the most aggressive forecasts do not project AM-LCDs larger than about 18".

The development of an integrated digitizing and display surface, which utilizes touch entry and flat panel display (FPD) technology, is a significant hardware advance in the field of geographic information systems (GIS). Inherent qualities of the FPD, notably the ac gas plasma display, makes such a marriage inevitable. Large diagonal sizes, high resolution color, screen flatness, and monitor thickness are desirable features of an integrated digitizing and display surface. Recently, the GIS literature has addressed a need for such an innovation. The development of graphics displays based on sophisticated technologies include `photorealistic' (or high definition) imaging at resolutions of 2048 X 2048 or greater, palates of 16.7 million colors, formats greater than 30 inches diagonal, and integrated touch entry. In this paper, there is an evaluation of FPDs and data input technologies in the development of such a product.

The high resolution CRT displays used for computer monitor and high performance TV often produce a pattern of bright and dark stripes on the screen called a moire pattern. The elimination of the moire is an important consideration in the CRT design. The objective of this study is to provide a practical method for estimating and evaluating a moire pattern considering the visibility by the human vision. On the basis of the mathematical model of a moire generation, precise value of the period and the intensity of a moire are calculated from the actual data of the electron beam profile and the transmittance distribution of apertures of the shadow mask. The visibility of the moire is evaluated by plotting the calculation results on the contrast-period plane, which consists of visible and invisible moire pattern regions based on experimental results of the psychological tests. Not only fundamental design parameters such as a shadow mask pitch and a scanning line pitch but also details of an electron beam profile such as a distortion or an asymmetry can be examined. In addition to the analysis, the image simulation of a moire using the image memory is also available.

Emissive flat panel display systems operating in full color demand higher performance at low voltages (ca. 50 - 1000 V) from cathodoluminescent (CL) phosphors than cathode ray tubes require. Hydrothermal synthesis has been suggested as a route to phosphors with improved efficiencies, lower voltage thresholds, and increased saturation power. This hypothesis was tested in europium-doped yttrium orthovanadate (YVO₄:Eu), an efficient, red emitting CL phosphor. The CL efficiency of YVO₄:Eu crystallized from aqueous solution at 200 degree(s)C is relatively low until it is annealed. The distribution of particle sizes in the low- temperature phosphor is similar to that in material made via a solid-state route, but crystallites remain much smaller (ca. 400 angstrom) until they are annealed. These observations, along with the anomalously strong dependence of CL intensity on europium concentration, support a model in which efficiency principally depends on crystallite size. CL efficiency of both solid state and hydrothermal YVO₄:Eu increases with voltage at constant power. Surface-bound electrons are likely the dominant influence on efficiency at voltages near threshold. Saturation power is independent of synthetic route. It is apparent that the CL properties of hydrothermally synthesized YVO₄:Eu are essentially the same as those of YVO₄:Eu produced via conventional, high-temperature routes.

Ferroelectric smectic C* liquid crystals have been shown to exhibit high speed, electro-optic switching when incorporated into the surface stabilized ferroelectric liquid crystal (SSFLC) light valve. Certain applications utilizing IR modulation, waveguide, and phase modulation, and certain fiber-optic devices, can benefit from materials with a birefringence higher than that typically seen in FLC materials ((Delta) n approximately equals 0.15). A new class of compounds, the tolane cinnamates, was developed to help meet this need. These compounds combine a cinnamate moiety with the well known high birefringence tolane core, resulting in two improvements: first, the birefringence increases from 0.24 to 0.29; and second, the tolane cinnamate system is significantly more stable to UV light than the parent tolane system. The new materials show smectic C as well as nematic phases and demonstrate good compatibility with both nematic and FLC hosts.

Two novel series of siloxane containing low molar mass liquid crystals have been synthesized and characterized by DSC, optical microscopy and x-ray scattering. The compounds have been shown to exhibit nematic, smectic A, and chiral smectic C phases. In this paper we concentrate on the unusual electro-optic threshold voltage and response time behavior of these materials in the S_A phase. Pleochroic and fluorescent dyes have been incorporated into mixtures and data is presented on the electro-optic properties of such guest-host materials.