Showing papers on "Electrochromism published in 1987"

Single-compartment, self-erasing, solution-phase electrochromic devices, solutions for use therein, and uses thereof

Abstract: Single-compartment, self-erasing, solution-phase electrochromic devices, solutions of electrochromic compounds for use as media of variable transmittance in such devices, and electrochromic compounds for such solutions are provided. The devices of the invention are surprisingly stable to cycling between light and dark states, have continuously variable transmittance to light as a function of electrical potential applied across the solution in a device, and have transmittance that can be varied over more than a factor of 10, from clear to dark or from dark to clear, in several seconds. Thus, the devices are especially suitable as variable transmittance components of variable transmission light filters, including windows, and variable reflectance mirrors, including anti-glare rearview mirrors in automobiles. Also provided are improved variable reflectance mirrors, wherein transmittance of reflected light is varied by thermochromic, photochromic or electro-optic means and wherein the reduction in transmittance which is required to eliminate perceptible reflection of an object to the eyes of an observer is reduced by disposing the plane of the highly reflective surface of the mirror at an angle with respect to the plane of the surface through which light from the object enters the mirror.

Electrochromic display device

Abstract: An electrochromic display device which comprises a display electrode comprising a transparent substrate, a transparent electrode formed on an inner surface of the transparent substrate and an electrochromic material layer for display made of tungsten oxide and formed on the transparent electrode; a counter electrode comprising a substrate, a conductive layer formed on an inner surface of the substrate and an activated carbon fiber material; and a spacer provided between the display electrode and the counter electrode with their inner surfaces facing each other to define, between them, an electrolyte chamber, which is filled with an electrolyte comprising a lithium salt and at least one of the tertiary alkyl ammonium salts and quarternary alkyl ammonium slats dissolved in a non-aqueous medium containing a small amount of water, which device has increased original injected charge which can last for a long time.

Electrochromic Switching of the Optical Properties of Polyisothianaphthene

Abstract: We present a detailed study of the electrochromic switching phenomena in the novel conducting polymer, polyisothianaphthene. We find reversible electrochromic switching with a characteristic switching time of a few hundred milliseconds. Since the results indicate that the rate limiting step in the electrochromic switching involves diffusion of the dopant species into the bulk of the polymer, we present a series of electron micrographs which provide an initial characterization of the morphology of PITN. The observation of a very open honeycomb‐like structure with morphological subunits on the 20A scale is consistent with the relatively rapid doping kinetics and the associated electrochromism of PITN. Our conclusion is that the detailed morphology plays a critical role in determining the electrochromic switching; by controlling the morphology so as to minimize dopant diffusion distance in conductive polymers, it should be possible to achieve sufficient speed to be of interest for a variety of technological applications.

Method for deposition of electrochromic layers

Abstract: A method of coating a substrate with electrochromic coatings comprises dipping a substrate having a conductive surface into, or spraying, or spin coating with, a solution prepared by reacting an anhydrous halide of an electrochromically active transition metal with a C₁ to C₅ anhydrous alcohol, preferably under a stream of inert gas, at 0 to 80 °C. The dipped substrate is removed at a rate necessary to give a desired thickness, and the resulting coating is dried and hydrolysed and further condensed to create an electrochromically active coating.

Electrochromic coating and method for making same

Abstract: Transition metal nitrates such as nickel nitrate are dissolved in monoalcohols having from 1 to 5 carbon atoms The coatings are applied to a substrate material and fired to convert the coating to an electrochromically active state

Electrochromic effects of charge separation in bacterial photosynthesis: theoretical models

Abstract: The primary charge separation in photosynthetic bacteria generates a dimeric bacteriochlorophyll (BChl) cation and a bacteriopheophytin (BPheo) anion which lie within close proximity of each other (approx. 10 A). The two radicals also lie within van der Waals contact on opposite sides of a lone BChl bridging molecule. Spectral changes in the red (Q/sub y/) band of the bridge BChls have been observed on picosecond time scales following excitation of the reaction center (RC) and have been variously attributed to the formation of a BChl anion, to a charge-transfer state, or to electrochromic effects. They present calculations here which suggest that electrochromic effects caused by the photogenerated cation and/or anion can rationalize the optical changes observed in the flash photolyses as well as in trapping experiments.

Electrodeposited Films from Aqueous Tungstic Acid-Hydrogen Peroxide Solutions for Electrochromic Display Devices

Abstract: Electrodeposited tungsten oxide films from aqueous tungstic acid-hydrogen peroxide solutions were investigated for applications to electrochromic devices. These films exhibited electrochromism in aprotic electrolyte solutions containing Li-salts. When the films were heat-treated for an hour at temperatures between 100 and 200°C, the electrochromic reactions were rich in reversibility. The coloring efficiency and response rate for the films were favorable and comparable to those for tungsten trioxide evaporated films. A cell life-test was performed on several clock-size cells by applying a 1.2-V, 1-Hz, continuous square wave. The typical amount of charge required for coloration was about 50 C / m2 and remained unchanged even after 107 coloration-bleaching cycles.

Hexacyanoferrate layers as electrodes for secondary cells

Abstract: It is known that intercalation compounds represent highly reversible electroactive materials in secondary cells, as the change of structure of the host lattice is negligibly small during cycling. Thus inorganic materials such as TiS2 [1] and graphite salts [2] are successfully used as positives in secondary cells. The zeolite-like hexacyanoferrates, which intercalate cations such as K + and N H [ , have been investigated recently with regard to their application to electrochromic displays [3, 4], electrocatalysts [5] and ion-selective electrodes [6, 7]. Their suitability for use as electrodes in secondary cells, however, has not been described so far. This preliminary report shows that thin layers of hexacyanoferrates of iron and copper are promising electrodes for reversible charging in secondary cells.

Electrochromic properties of alkylviologen-cyclodextrin systems

Abstract: Electrochromic properties of methyl, ethyl, n-hexyl and n-heptyl viologens, and α-, β-, γ-cyclodextrin systems were studied using cyclic voltammetry and absorption spectroscopy Colourations of red-violet (λ max = 530 or 560 nm), blue (λ max = 600nm) and light purple (λ max = 560 and 600 nm) could be obtained by changing the length of the alkyl chain of viologens or the radius of cyclodextrin The intermolecular interaction between viologen radicals is weakened when the radicals form inclusion complexes so the blue colour inherent in the monomer of viologen radical appears The red-violet colour is ascribed to the dimer of the reduced viologen With the addition of γ-cyclodextrin, viologens were found to be included as dimer The light purple colour is ascribed to the mixed colour of the monomer and the dimer Furthermore, since the ratio of monomer and dimer depends upon the concentration of cyclodextrin, any colour between the red-violet of the dimer and the blue of the monomer can be obtained by adjusting the concentration of cyclodextrin The redox reaction of an inclusion complex was found to depend upon the length of the alkyl viologen and the size of the cavity in cyclodextrin

Conducting substituted polyisothianophthenes

Abstract: Polyisothianaphthene substituted in the 5 and/or 6 positions so as to have an oxygen atom adjacent to C5 or C6. Substituents include alkoxys, hydroxys and dioxyalkylenes. The polymers are conducting and useful in electrochromic displays and as electrode materials.

Electrochromic Properties of V2O5 Thin Films Colloid-Chemically Deposited onto ITO Glasses

Abstract: The dynamic properties of a V2O5 ECD cell prepared by the sol-get method are mentioned. The V2O5 thin film was electrochemically deposited onto ITO glass from a poly-vanadic acid sol. The response time of the ECD cell was 2–20 seconds, depending upon the cell voltage. The repeating time was more than 8×104 times. It is possible to fabricate large-area ECD cells by this method.

Encapsulated electrochromic mirror and method of making same

Abstract: Electrochromic mirrors are protected against environmental and mechanical damage by an encapsulant system comprising a shatterproofing backing and a hermetic seal. The shatterproofing backing entirely covers the surfaces of the electrochromic cell elements and is itself entirely covered by the hermetic seal.

Optical properties of electrochromic hydrated nickel oxide coatings made by rf sputtering

Abstract: Electrochromic NiOxHy coatings were produced by rf magnetron sputtering of Ni in the presence of H2 and O2 followed by treatment of the films in KOH. Spectral transmittance and reflectance were measured in the 0.35 ≤ λ ≤ 2.5-μm wavelength range. The integrated luminous and solar transmittance could be varied between ≈75 and 10% and between ≈75 and 20%, respectively. Electrochromic coloration was found to be associated with the formation of a broad absorption band centered at λ ≈ 0.8 μm.

Electrochromic variable color tone nonglaring mirror

Abstract: The invention relates to a nonglaring mirror which is an electrochromic (EC) device in principle. The mirror comprises a transparent front substrate provided with a transparent first electrode layer, a back substrate provided with a second electrode layer opposite to the first electrode layer, first and second EC layers formed on the first and second electrode layers, respectively, an electrolyte liquid which fills up the space between the two substrates and reflecting means for providing a reflective surface to the second substrate. The material of the first EC layer is an organic polymer which is colorless or very pale in color in its electrochemically reduced state and undergoes electrochemical oxidation in two stages to assume a characteristic color in the first-stage oxidized state and another color in the second-stage oxidized state, and intermediate colors in intermediately oxidized states. It is very favorable to use a polymer made up of repeating structural units of N,N,N',N'-tetraphenyl-p-phenylenediamine. The second EC layer is usually formed of a transition metal oxide, e.g. WO3, which takes on color in its electrochemically reduced state.

Preparation and aging of sputtered tungstic oxide films

Abstract: Conditions for the preparation of electrochromic tungstic oxide films with high efficiency for coloration have been investigated. Tungstic oxide films were deposited on glass substrates by rf sputtering in Ar‐O2 mixture from a compressed powder WO3 target. As‐deposited films require an ‘‘aging process,’’ in which the density of charges extracted in bleaching is smaller than that injected in coloring. It is considered that a part of the protons introduced during the aging combine with bonds of unstable oxygen contained in the as‐deposited films. After the aging period, sputtered films have reversible coloration and bleaching cycles. Maximum electrochromic coloration efficiencies are 0.09 and 0.04 cm2/mC at wavelengths of 800 and 500 nm, respectively. They are obtained when the sputtering atmosphere is 0.04–0.05‐Torr total pressure and 5% oxygen content. At any rate, substrate temperature should be kept at 100 °C or less.

Polymerisable thiophene monomers, their production and polymers prepared therefrom

Abstract: Thiophene derivatives of the formula wherein R 1 and R 2 are certain specified substituent groups can be homopolymerised or copolymerized to form polymers which are electroconductive. These polymers find many uses, for example, as EMI/RF shielding materials, in electrochromic display systems, as antistatics, as ion and pH sensors, as battery electrode materials etc.

Electrochromic Characteristics of Organic Materials with a Simple Molecular Structure

Abstract: Electrochromic characteristics of familiar organic materials with relatively simple molecular structures, such as dimethyl terephthalate, are described. Coloration occurred at the cathode of all cells examined; the color spontaneously bleached upon removing the voltage. Electrochemically induced optical absorption was measured for organic compounds with various types of terminal groups. As a result, the induced color was found to depend upon the type of terminal groups as well as its position placed in the compound. The time response of the optical density during a coloration and bleaching sequence was also investigated. An empirical formula fitting with the observed response curves is proposed.