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The motion of single- and two-cavitation bubbles generated by laser beams directly beneath a free surface is studied experimentally, using high-speed photography, and theoretically using the highly accurate boundary integral method. Favorable comparisons of bubble shape history and centroid motion are observed while the numerical calculations provide information on the pressure field surrounding the bubbles. A range of responses, including the null impulse state, is obtained for the two bubbles depending on the bubble size ratio and the interbubble and bubble-free surface distances, although in all cases reported in this article, the bubble nearest the free surface yields a high-speed liquid jet directed away from the free surface. It is also found that when the free-surface–bubble interaction is strong, a fast free-surface spike is formed for both the single- and two-bubble cases.

The xerographic technique was used to investigate the photogeneration of charge carriers in a methyl-substituted ladder-poly(para-phenylene) (LPPP). The quantum efficiency of charge carrier generation was calculated from photoinduced-discharge curves (PIDCs) and found to be independent of the excitation wavelength and temperature. This is in contrast to the 3D Onsager theory which predicts a wavelength and temperature dependent photogeneration of free charge carriers. LPPP shows a high overall quantum efficiency up to 25%, a very low residual potential and a small dark decay. Thus, LPPP provides a promising way to build a single component one-layer photoreceptor sensitive to blue light.

A number of technologies, including electrophotographic printing, require an understanding of particle–surface adhesion forces. At Xerox, we have developed and applied new techniques in order to understand the dependence of particle adhesion on physical properties, such as particle charge, shape and surface roughness. Atomic force microscopy and computer modeling were used to investigate the effects of surface roughness, external additives and applied electric fields on the adhesion of single particles. Centrifugal detachment was used to measure the adhesion force distribution of several hundred particles simultaneously and to determine its sensitivity to particle charge and size. Electric field detachment has enabled rapid characterizations of the adhesion of particle layers, providing insight into the roles of particle–surface contact area and nonuniform particle charging on the adhesion of ensembles of particles. The addition of digital photography to the detachment techniques has allowed in-situ visualization of particle detachment, enabling us to probe interparticle effects on adhesion.

Photogeneration of charge carriers in a methyl-substituted ladder-poly(para-phenylene) (LPPP) has been investigated by xerographic experiments. The quantum efficiency of charge carrier generation was calculated by evaluating the photoinduced discharge curves (PIDCs) and found to be independent of both excitation wavelength and temperature. The results can be described by a modified Braun theory with a simple exponential distribution of radii of thermalized electrons. LPPP shows a very high primary quantum efficiency of 80%, a low residual potential, and a small dark decay. Thus, LPPP represents a promising material to build single component single-layer photoreceptors.

The mechanism of incorporation of metallic antimony in amorphous and glassy samples of the Sb x Se1−x (0 ≤ x ≤ 0.10) system is studied by measuring the xerographic discharge characteristic, drift mobility and optical absorption. It is observed that the addition of antimony increases the DC conductivity, decreases the electron mobility, changes the xerographic parameters and decreases the optical gap of the system. The Compositional dependence of the electronic properties are related to the defect states produced due to incorporation of Sb atoms in glassy selenium matrix.

Due to its superior photosensitivity in the visible wavelength region, amorphous selenium-based material is widely used as the basic photoreceptor material in xerography. The optoelectronic properties of the samples were measured and calculated with photoinduced discharge curve (PIDC) by using Electrostatic Paper Analyzer, and the initial surface potential (V so), dark decay time (t d), photosensitivity (E 1/2) and residual potential (V r) could be obtained. It is found that the contrast voltage which affects directly the resolution of image can be improved by the blocking layer between the bulk (such as a-Se, a-As2Se3) and substrate (Al). Furthermore, the relations between thickness and optoelectronic properties of photoreceptor could be identified, and compared with different blocking layers and isothermal annealing effect for the photoreceptors.

Xerographic printing of a number of common fabrics was investigated. The role of the polymeric binder used for the formulation of the commercially available and custom-made toners was investigated. Fabric performance tests (crockfastness), friction tests, and morphological investigations using scanning electron microscopy were performed. The intricate relations of toner and fabric properties with the results of an important overall industrial performance test for fabrics (crockfastness) are discussed. Both cohesive and adhesive toner failure can be important. Improved toner performance was achieved with a thermoset polymer as the toner binder. However, curing times for the thermoset polymer used are not sufficiently short for high-speed industrial printing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2425–2434, 2000

Computer simulation is used to study the effect of iodide impurity on silver cluster formation on AgBr microcrystals. The simulation is based on a nucleation-and-growth model of silver cluster formation in competition with recombination of electrons and holes. The efficiency of silver cluster formation is calculated as a function of microcrystal size and shown to increase with size for the impurity-free control, contrary to experimental data. This behavior is due to a partitioning of the hole between free and trapped states which favors the free side as size increases. As a result, recombination decreases and efficiency increases at large microcrystal size. Iodide impurity decreases efficiency relatively more at larger sizes because it introduces an internal recombination pathway not present in the control simulation. Because of their larger volume-to-surface-area ratios, the larger microcrystals are affected more by this additional recombination pathway than smaller microcrystals.

Our aim is to improve the charge-generation efficiency of organic-photoreceptor materials used in xerography and for laser printers by mixing the material with buckminsterfullerene C60. The improvement is based on an electron transfer from the excited excitonic state of the photoreceptor molecule to the C60 thus reducing the recombination probability. Typical materials studied are various metal-phthalocyanines (M-Pc, with M=TiO, VO, Ni, Fe, Cu) and metal-free H2-Pc. Using techniques like X-ray absorption near edge spectroscopy (XANES) and photoelectron spectroscopy with ultraviolet radiation (UPS) we demonstrate that the electron transfer is energetically possible and no ground state electron transfer occurs. The observation of fluorescence quenching upon doping with C60 validates the electron transfer-model.

Electroluminescence (EL) from organic materials was first observed in the early 1960s, during what might be considered a “golden age” of the physical chemistry of organic materials: the foundations of our current knowledge of electronic excitations, energy transport, and photochemistry were all laid in that era.1,2 The potential of these materials for commercial application was quickly recognized, and a great deal of work has been expended over the years in attempts to develop such products as solar cells, photochromic or holographic memories, nonlinear optical devices, displays, and transistors. Until recently, however, the only significant success story was in xerography: essentially all photocopiers today use organic photoconductors.3 Today a second contender has finally entered the arena: Pioneer Electronics now markets a 64 × 256 pixel organic EL (OEL) monochrome display for automobiles. Although they are first to market with a product, other companies are in close contention: Philips and Uniax have both built production facilities and are prepared to supply prototype samples of OEL displays, and the list of companies and universities with RD hence, external quantum efficiency, which is the quantity of practical interest, is much lower than internal quantum efficiency). By using two organic layers, having an interface with energy level offsets, the majority charge carriers can be slowed and prevented from flowing through the device without recombination, thus increasing quantum efficiency at the expense of higher bias. The appearance of organic electroluminescence as a practical display technology traces its origins to Tang and VanSlyke,4 who introduced the double-layer concept in 1987: this was the first publication that combined modern thin film deposition techniques with suitable materials and structure to give a moderately low bias voltage, attractive efficiency, and encouraging lifetimes. Their devices were made by subliming molecules of a triarylamine as hole transporter, followed by aluminatotris(8hydroxyquinolate) (Alq3) for electron injection and emission, and a magnesium-silver alloy cathode. In 1991 Burroughes et al.,5 at Cambridge University, reported a similar single-layer device made with a polymeric meJames R. Sheats received his B.S. in chemistry from Colorado State University in 1974, and his Ph.D. in physical chemistry in 1978 at Stanford University (under H. M. McConnell), with a thesis on molecular motion in lipid membranes. After postdoctoral work in nonlinear chemical dynamics at the Massachusetts Institute of Technology and Stanford, he joined HP Laboratories in 1982 where he has contributed to a wide range of applications of chemistry in electronics, including photolithography, high-temperature superconductors, and organic electroluminescence, described in 40 journal articles and several patents. While remaining active in the development of organic materials for electronics, he currently manages a program to analyze and develop technology opportunities motivated by environmental sustainability.

The xerographic property has been studied in the double-layered photoreceptor device where azo/TiOPc composite is used as the charge-generation material (CGM) and p -diethylaminobenzaldehyde-α-naphthalenylphenylhydrazone (DENPH) or p -dimethylaminobenzaldehyde diphenylhydrazone (DMDPH) is used as the charge-transportation material (CTM) under the exposure of various spectral regions. The results show that the azo/TiOPc composites exhibit high photosensitivity not only in the visible and near-infrared regions, but also in the entire spectral ranges, indicating the co-enhancement effect. The UV–VIS spectra suggest that the absorption spectra of the azo/TiOPc composites are broadened. The composite mechanism is investigated through X-ray diffraction and ESR.

The xerographic properties of dual-layer photoreceptors having different molecular structure, are described with respect to their photosensitivities. A correlation between the absorption wavelength and the photosensitivity was found. A study on device optimization of 3,4,9,10-perylenetetracarboxylic diimides was carried out. The dual-layer photoreceptor device exhibited low dark decay and flat spectral response from 450–750 nm. The spectral sensitivity of the dual-layer photoreceptor extends to the near-IR region.

Textile printing systems are needed that will meet the requirements of time-driven, demand activated manufacturing. Xerography has the potential of meeting these requirements, but textile specific xerographic toners must be developed to gain acceptance of this technology by the textile industry. One thermoplastic and three thermoset-based toners were evaluated for xerographic printing on fabrics (cotton, silk, Dacron, nylon). The toners were successfully applied to the fabric using xerography, however, toner transfer efficiencies to fabrics were low. The textile print properties were compared with commercial rotary screen and hand screen printed fabrics. Color fastness to crocking (rubbing) varied with type of toner and fabric characteristics such as fiber type and fabric weight. Crosslinking of thermoset toners resulted in crockfastness that was superior to conventional screen print. Surface morphological studies were used to characterize the failure mechanisms occurring during the crocking tests. Wet and dry friction properties of the printed fabrics were studied in an effort to explain the crocking results. Fabric flexibility, a key component of fabric hand, depended significantly on fabric weight. The toner type significantly affected flexibility for the lighter weight fabric, but had little effect for the heavier weight fabric.

Based on the light extinction of total internal reflection by triangular prisms, very sensitive detection of the shock front and fast moving free surface has been demonstrated for 1 GPa shock waves in polymers. This is the first experimental verification of the feasibility of the inclined-prism technique for the relatively low shock stress region, which was originally proposed and used by Eden and Wright for obtaining the high-explosive generated shock Hugoniot of several condensed materials. The present method has the advantage that it only requires closing the gap between the free surface of the target and the reflected surface of the prisms. The feasibility and the limitation of the method have been discussed both theoretically and experimentally. A typical streak photograph for a PMMA specimen is shown to compare with the published data. It is seen that the present method is very sensitive for shock arrival detection even in the 1 GPa shock stress region.

Single photogeneration layers of a phthalocyanine pigment dispersed in a polyvinyl butyral binder, and double layers consisting of the photogeneration layer coated with hole transport layers of TPTA, DEH and BD molecularly dispersed in polycarbonate were exposed to single-shot light excitation. The charge collected was measured as a function of temperature, electric field, exposure intensity and duration. The resulting mean transport level of TPTA was found to be 0.17 eV, and that of DEH 0.11 eV, below the valence band of the pigment, but that of BD was found to be 0.09 eV above it. The injection efficiencies were independent of field and amounted to for TPTA and 0.02 for DEH, at room temperature, but that for BD was 0.1 independently of temperature. Models for the injection efficiencies in these cases are also discussed in this work for the first time.

Multilayer amorphous selenium-based photoreceptors were prepared by thermal evaporation in a vacuum at . Amorphous multilayers of Se/CdSe, as well as a combination of a thin film and multilayers were used as photogeneration layers. `Pure' Se or were the transport layers. The xerographic properties of the photoreceptors were studied and some peculiarities of the charge transport in different designed photoreceptors are discussed. Xerographic photosensitivity at illumination with different wevelengths was determined and a comparison with the sensitivity of conventional photoreceptors is made. All photoreceptors are photosensitive in the whole visible region. The photoreceptors including are also sensitive in the near-infrared region. The xerographic properties of the studied photoreceptors remained unaltered in air at room temperature for more than 12 months.

We examined both photoconductive and electro-optical properties of the monolithic photorefractive polymer. The photoconductive sensitivity of 1.2 × 10−12(S cm−1)/(W cm−2) was obtained under a field strength of 5 × 105V/cm and a wavelength of 534nm. The EO signals linearly increased with the poling electric field.

Ballistic Aerosol Marking (BAM) is a radically new printing concept that combines the simplicity of a direct marking technique such as inkjet printing with the quality and color range/stability of Xerography. This is achieved by using high-speed gas jets as the transport fluid and Xerographic toner particles as the marking material. In this paper we will provide an introduction into this novel concept, discuss design considerations from Computational Fluid Dynamics (CFD) and electrostatics simulations, and show some proof-of-concept results from single channel experiments.

Electro-optic devices such as fast (>20 GHz) modulators are one application of ferroelectric-oxide thin-film waveguides. A compact, blue laser source of a few milliwatts power capable of lasting thousands of hours is of great interest as applied to optical data storage and xerography. Ferroelectric-oxide thin films offer several potential advantages over bulk materials for optical waveguides, though no electroceramic thin-film devices have replaced bulk devices yet. Bulk waveguides are defined by ion exchange, which produces only a small index difference. Thin films therefore permit higher intensity per unit power in the guide, and hence larger nonlinear effects and shorter interaction lengths.

The optimum x-ray spectra for acquisition of digital mammographic images using an amorphous selenium (a-Se) photoconductor are investigated. The recorded images consist of latent charge distributions on the surface of an a-Se plate, which are then read out using two methods, laser discharge, or flat panel recharge. The investigation is based on a model of the breast previously developed for a phosphor-based digital readout system, and has been extended to include the effects specific to the use of photoconductors. The effects of plate thickness, x-ray scatter, readout noise, dose, and the kind of breast tissue on the nature of the optimum spectrum are explored for the two readout methods. The results indicate that use of a kilovoltage setting in the current mammographic range, and a molybdenum target spectrum is appropriate for digital readout of a-Se detectors. This conclusion contrasts with the appreciably higher kilovoltages traditionally used with the xerographic (toner) readout of latent charge images on a-Se.

A study has been made of the xerographic properties of amorphous selenium doped with chlorine at concentrations below 100 parts per million (ppm) by weight. The sample consisted, in each case, of an aluminum plate with a thin deposited rf sputtered aluminum oxide film, on which a 50 μm layer of amorphous selenium was deposited by evaporation, at a substrate temperature of 50 °C. It was found that the chlorine decreased the acceptance voltage following corona charging, increased the dark decay rate, and decreased the residual voltage after illumination discharge. The changes were such as to be beneficial xerographically for small additions of chlorine to the selenium in the ppm range. Analysis of the time derivative of the dark decay voltage indicated that depletion discharge was the dominant process in the decrease of dark decay voltage with time and a modified relation was introduced to describe the increase of bulk space‐charge density with time, arising from thermal excitation of holes from deep discrete centers in the photoreceptor. This analysis indicated a decrease of the release time of the holes with increase of chlorine content, whereas an observed decrease of single cycle and cycled‐up residual voltages with increased chlorine indicated an increase of hole capture time from their relevant trapping centers.

The spectral selective thermography with infrared filters can be used to determine or to distinguish materials such as contaminations on a metallic component. With additional visual information, the indications by the IR signal can be selectively accentuated or suppressed for easier evaluation of passive and active thermography measurements. For flash thermography the detected IR signal between 3.4 and 5.1 μm is analyzed with regard to the spectral material information. The presented hybrid camera uses beam overlapping to obtain combined images of both in the infrared and the visual range.

In the 1930s, Chester Floyd Carlson invented Electrophotographic Printing, which was later named xerography. Xerography has played an eminent role in the evolution of the Information Age. This invention has revolutionized the way information is processed and disseminated. It provides a cheap, simple, and reliable way of reproducing and creating documents. The development of xerography has led to new technologies that might eventually eradicate traditional offset printing machines. A crucial part of this technology is the photoreceptor, which optically captures information. Accurate photoreceptor performance requires the properties of photoelectronic, electrostatic, mechanical, and fabrication materials, which are amorphous. This chapter presents an overview of the xerographic process, its basic steps, and the relevant physical phenomena involved in the formation of latent imagery. Emphasis is placed on the electronic properties of amorphous selenium. This chapter also draws attention to the history and market of xerography and discusses alternative powder marketing technologies. It provides the physics within each step of the xerographic process.

The location and bonding of atoms and molecules on surfaces is of great interest to surface chemists and to those interested in the application of surfaces through exploitation of their unique properties. These properties include chemical properties that give rise to selective adsorption and heterogeneous catalysis; mechanical properties that control adhesion, fric­ tion, slide, or fracture; electrical properties utilized in microelectronic circuitry and xerography; magnetic properties used in information storage on tape or disk drives; and optical properties that give rise to nonlinear effects such as second harmonic and sum frequency generation. During the past 25 years, over 50 new techniques have been developed that permit the investigation of surfaces on the molecular level (l). The ability to study surfaces with increased time and spatial resolution (and energy resolution, when applicable) controls the development of many surface technologies. The contributions of science push and surface technology pull have resulted in an exponential growth in the field of surface science and pro­ pelled it among the frontier fields of physical chemistry. Several new surface science techniques permit quantitative deter

We have used an atomic force microscope to measure the adhesion of surface-modified toner particles to various surfaces of relevance to xerography. We will present adhesion data on several toner and toner surface additive surface modification techniques and use supporting machine performance data to discuss the advantages and disadvantages of the techniques.

In this work xerographic spectroscopy is extended for an arbitrary trap distribution for both ballistic and diffusive trapping. We have investigated the dynamic equilibrium at saturation and the effect of experimental parameters on the occupation function. The relationships derived allow us to determine precisely which gap states are being mapped in a specific experiment. It is shown, that at saturation during cycled-up measurements, a quasi-Fermi level, E f ∗ , can be defined which separates filled and empty states. A linear relationship between the cycling frequency and the saturated residual potential Vrs corresponds to traps well below E f ∗ , where the Boltzmann distribution applies. At higher frequencies Vrs is no longer dependent on cycling and E f ∗ moves below all traps resulting in full trap occupation. These results form the basis of a novel experiment -similar to xerographic cycling-, namely the “Cycled-Time-of-Flight” (CTOF) technique.

Dyes for optical recording systems such as laser optical recording systems, laser printing systems, cycolor and related systems, xerography and so on are reviewed. Infrared absorbing (IR) dyes are newly designed for laser optical recording systems such as DRAW and erasable type recording systems. The chemistry of IR dyes developed the new fields in dye chemistry. Many of functionalities in dye chromophores are newly developed for optical recording systems such as PHB and cycolor systems. New technology has developed new dye chemistry and new characteristics of dye chromophores advanced the technology for new optical recording systems.

We present a new type of streak camera to measure the temporal shape of pulses in the extreme ultraviolet (XUV) region: A cloud of noble gas atoms is used as a photocathode. The first results at 57 nm show a time resolution of 10 ps. Modifications to improve the time resolution are discussed. Using a noble gas as a photocathode has the potential to decrease the temporal resolution of the streak camera in the XUV to less than 0.5 ps.

Electroluminescence (EL) from organic materials was first observed in the early 1960s, during what might be considered a “golden age” of the physical chemistry of organic materials: the foundations of our current knowledge of electronic excitations, energy transport, and photochemistry were all laid in that era.1,2 The potential of these materials for commercial application was quickly recognized, and a great deal of work has been expended over the years in attempts to develop such products as solar cells, photochromic or holographic memories, nonlinear optical devices, displays, and transistors. Until recently, however, the only significant success story was in xerography: essentially all photocopiers today use organic photoconductors.3 Today a second contender has finally entered the arena: Pioneer Electronics now markets a 64 × 256 pixel organic EL (OEL) monochrome display for automobiles. Although they are first to market with a product, other companies are in close contention: Philips and Uniax have both built production facilities and are prepared to supply prototype samples of OEL displays, and the list of companies and universities with RD hence, external quantum efficiency, which is the quantity of practical interest, is much lower than internal quantum efficiency). By using two organic layers, having an interface with energy level offsets, the majority charge carriers can be slowed and prevented from flowing through the device without recombination, thus increasing quantum efficiency at the expense of higher bias. The appearance of organic electroluminescence as a practical display technology traces its origins to Tang and VanSlyke,4 who introduced the double-layer concept in 1987: this was the first publication that combined modern thin film deposition techniques with suitable materials and structure to give a moderately low bias voltage, attractive efficiency, and encouraging lifetimes. Their devices were made by subliming molecules of a triarylamine as hole transporter, followed by aluminatotris(8hydroxyquinolate) (Alq3) for electron injection and emission, and a magnesium-silver alloy cathode. In 1991 Burroughes et al.,5 at Cambridge University, reported a similar single-layer device made with a polymeric meJames R. Sheats received his B.S. in chemistry from Colorado State University in 1974, and his Ph.D. in physical chemistry in 1978 at Stanford University (under H. M. McConnell), with a thesis on molecular motion in lipid membranes. After postdoctoral work in nonlinear chemical dynamics at the Massachusetts Institute of Technology and Stanford, he joined HP Laboratories in 1982 where he has contributed to a wide range of applications of chemistry in electronics, including photolithography, high-temperature superconductors, and organic electroluminescence, described in 40 journal articles and several patents. While remaining active in the development of organic materials for electronics, he currently manages a program to analyze and develop technology opportunities motivated by environmental sustainability.

This paper is devoted to the scientific study and engineering application of cyclic systems. Cyclic systems are non-traditional plants, containing devices with rotating dynamics along with actuators and sensors fixed in inertial space. The combination of rotating dynamics and inertially-fixed inputs and outputs leads to one-per-revolution (or stroboscopic) actuation and sensing. Control of cyclic systems amounts to designing a regulator that uses stroboscopic actuation and sensing to force the system into the desired regime. Although cyclic systems are periodic, the general theory of periodic control is not immediately applicable due to stroboscopic actuation and sensing. Because of rotating dynamics, the theory of impulsive control is not applicable as well. This work develops an approach to the control of systems with both rotating dynamics and stroboscopic instrumentation, and reports the initial application to a xerographic process.