Showing papers on "Electrochromism published in 1977"

Dependence of WO 3 Electrochromic Absorption on Crystallinity

Abstract: The optical absorption of amorphous electrochromic display layers is explained as small polaron absorption. The necessary W5+ 5d‐electron localization is favored by the lattice disorder. This is concluded from the change of the optical properties to free‐electron‐like behavior upon crystallization of the layers. The increased electrocoloration stability of amorphous layers and the blue shift of the absorption peak in Mo‐doped films can also be explained within the model given.

Optical properties of mixed‐oxide WO3/MoO3 electrochromic films

Abstract: The electrochromic optical absorption of mixed‐oxide WO3/MoO3 amorphous films occurs at higher energy than either pure oxide alone. The systematics of the energy shifts as a function of MoO3 concentration and coloration density is determined. The data is explained by the intervalency charge‐transfer model if we assume that electrons trapped at Mo6+ ions lie 0.73 eV deeper than electrons on W6+ ions. Measurements of electron diffusion in mixed oxides support this hypothesis. The maximum absorption peak of mixed oxides is 2.15 eV compared with 1.4 eV for WO3. This is close to the peak in eye sensitivity, thereby leading to improved electrochromic display devices.

Electrochromism and local order in amorphous WO3

Abstract: WO3 films prepared under different conditions (evaporation, reactive sputtering and spraying of aqueous solutions of metatungstic acid) differ by orders of magnitude in their electrochromic sensitivity. Diffuse X-ray studies show the evaporated and sputtered films to be amorphous and to consists of a disordered network of corner sharing WO6 octahedra. Sprayed films have different degrees of crystallinity depending on spraying conditions. From differential scanning calorimetry we conclude that the crystal water present in most films strongly affects the local order of the corner sharing octahedra. We find that crystal water not only provides a high ionic conductivity which is conditional for a fast electrochromic reaction but also stabilises electrocatalytically active surface sites for fast hydrogen or Li exchange with the adjacent electrolyte.

Electro-optic device

Abstract: An electro-optic device comprising a transparent conductive layer and an electrochromic layer applied thereon together constituting an electrode, a counter-electrode spaced from said electrode and an intermediate electrolyte; the electrolyte containing a reductant capable of forming, during operation of the device, an electrochemical couple whose potential is more anodic than the oxidation potential of the electrochromic layer to prevent an increase of the potential during bleaching of the electrochromic layer markedly reducing deterioration of the electrolyte.

Color in ''tungsten trioxide'' thin films

Abstract: We show that evaporated tungsten trioxide amorphous layers commonly used in electrochromic displays actually have the composition WO2.7Hy (0.2

Electrochromism in the composite material Au‐WO3

Abstract: We have produced for the first time an electrochromic cermet composed of Au grains dispersed in the electrochromic WO3. The electrochromism arises from a shift in the wavelength of the dielectric absorption characteristic of gold cermets. The shift is due to a change in the dielectric constant of the WO3 matrix as a result of the coloring process. This is to be contrasted with the coloring in pure WO3 which results from the appearance of a broad absorption band in the red and infrared.

Electronic structure of tetragonal tungsten bronzes and electrochromic oxides

Abstract: X-ray photoemission spectra of the band structures of WO3, crystalline HxWO3 and the tetragonal and cubic bronzes MxWO3 (M=Li, Na) exhibit great similarity. In the bronzes tungsten 5d conduction band states are occupied. The tungsten 4f core level spectra of these materials have an unusual, but characteristic structure attributed to a combination of final state screening and hydrogen or alkali ion neighbor effects. The band structure of amorphous electrochromic WO3 films differs in characteristic ways from that of the crystalline bronzes.

Electrochromic display apparatus

Abstract: In a container which contains an electrochromic solution, a pair of electrodes, namely an indication electrode and a counter-electrode are disposed and an electric circuit is constituted in a manner such that a D.C. pulse is impressed across the electrodes and thereafter the electrodes are shortcircuited to each other. By means of the shortcircuiting, a color indicating substance formed on the indication electrode by the electrochemical reduction reaction or electrochemical oxidation reaction is reversably dissolved from the indication electrode into the solution so as to erase the indication, and therefore contamination of the indication electrode is less and hence a longer life is achieved in comparison with conventional apparatus where such shortcircuiting is not made and simply an inverse pulse is impressed across the electrodes for erasing.

Electrochromic devices having protective interlayers

Abstract: The incorporation of one or more protective layers between the electrochromic material and the polymeric electrolyte in an electrochromic device produces longer lasting, more uniform devices. The further placing of a protective layer between the electrolyte and the counterelectrode yields still better devices.

Reversible electrochromic display device having memory

Abstract: This invention is concerned with a reversible electrochromic display device wherein its electrochromic activity is derived from an electrochromic active molecules which are attached to a porous polymeric resin

Electrochromic display device

Abstract: An electrochromic display device which includes a transparent front substrate, at least one transparent display electrode formed on the front substrate, a counter substrate parallel to the front substrate, at least one display electrode provided on the counter substrate adjacent the display electrode on the front substrate, a spacer which maintains the front and counter substrate parallel to each other, a transparent electrolyte which is enclosed between the front and counter substrates and which is in contact with the front and counter substrates and which contains electrochromic material, a counter electrode which is in contact with the electrolyte and a means for selectively applying voltage between the counter electrode and the display electrodes.

Electrochromic cell with protective overcoat layer

Abstract: An electrochromic device having an electrochromic layer and an electrolyte sandwiched between electrodes. A charge compensator ion permeable layer is interposed between the electrochromic layer and the electrolyte. The latter-mentioned interposing layer serves as a protective overcoat for the electrochromic layer and minimizes the structural decay of the cell which might otherwise occur. SU FIELD OF THE INVENTION The present invention relates to electrochromic devices and, more particularly, to such a device having a protective overcoat layer interposed between an electrochromic layer and an electrolyte. BRIEF DESCRIPTION OF THE PRIOR ART The prior art has recognized the usefulness of electrochromic devices wherein the electromagnetic absorption characteristics may be reversibly altered by a controlled electric field. The device is particularly useful as a display device or in light valve-type applications. U.S. Pat. No. 3,708,220 issued to Meyers describes a device which consists of an electrochromic material in contact with a semisolid electrolyte gel sandwiched between a pair of electrodes. U.S. Pat. No. 28,188, issued to Deb et al, discloses a completely solid state electrochromic device which utilizes a current carrier permeable layer positioned between an electrochromic layer and a conductive layer. The reissue patent states that the structure set forth therein is an improvement over basic electrochromic cells that had previously included only an electrochromic layer sandwiched between two conductive layers. In U.S. Pat. No. 3,840,287, issued to Witzke et al, there is an electrochromic device which is described as including two electrochromic layers in different states and an electrolyte layer which is not limited to semisolid gels. In the Meyers and Witzke patents, the structure included an electrolyte or color assisting agent, respectively, which is described as being in direct contact with an electrochromic layer. This contact was thought necessary to insure ionic charge transport from the electrolyte to the electrochromic layer. However, these prior art structures have been found to lack a certain desirable cycling capability of lifetime due to an observable decay in the cell due to a deterioration of the electrochromic layer -- electrolyte interface, which is due to the contact therebetween. BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention relates to a novel structure for extending the life of an electrochromic device, having an electrolyte or color assisting agent, by interposing a protective overcoat layer between the electrolyte or color assisting agent and the electrochromic layer. More particularly, the electrochromic device comprises a pair of electrodes, there being between the electrodes at least one layer of electrochromic material, an electrolyte layer, and a protective overcoat layer between the electrochromic layer and the electrolyte layer. The protective overcoat layer is a substantially insulating dielectric layer. Normally, one would expect that the placement of a substantially insulating dielectric layer separating the electrochromic layer and the electrolyte would inhibit the necessary current flow of the device and be detrimental to the normal operation of the device. Contrary to this, an unexpected synergistic result is obtained. It has been discovered that the insertion of certain substantially insulating materials in the form of thin films not only does not adversely affect the operation of the device, but rather substantially increases the life of the device by inhibiting attack and degradation of the electrochromic layer.

Optical regeneration of aged WO3 electrochromic cells

Abstract: Continuously cycled display cells of evaporated WO3 on tin oxide show a progressive reduction in contrast with time. Partial restoration of the cells was observed when the WO3 was irradiated with uv, particularly if the cell was biased into the bleaching mode. The observed effect is consistent with optical depopulation and subsequent removal of trapped charge.

Solid state electrical switch employing electrochromic material

Abstract: A solid state electrical switch is described which exhibits high off/on resistance ratios and low insertion loss. An additional advantage is that removal of the switching energy does not alter the status (off or on) of the switch. The active solid state material in the switch is an electrochromic material (e.g., tungsten trioxide) which undergoes a transformation from insulator to metallic conductor on injection of certain ions.

Matrix addressed electrochromic display

Abstract: A matrix addressed electrochromic display includes first and second spaced apart opposed planar panels, a dielectric spacer peripherally sealing the panels to provide an interior cavity therebetween to define a display region, an electrochromic fluid filling the interior cavity, a plurality of parallel rows and columns of electrodes disposed in the mating surfaces of the first and second panels respectively and a low output impedance electrical refresh circuit coupled to electrically energize the electrodes in a repetitive matrix selection pattern to provide a selected dot matrix display.

A.C. and D.C. voltage polarity indicator utilizing electrochromic cells

Abstract: An electrochromic voltage indicator for detecting the presence and polarity of d.c. voltage, as well as for detecting the presence of a.c. voltage, includes two electrochromic cells, two contact terminals, two capacitors, two resistors and two diodes. First leads of each of the diodes are interconnected and are connected to first leads of each of the resistors and to first leads of each of the electrochromic cells. A second lead of each of the electrochromic cells is electrically connected via a respective capacitor to a second lead of the respective resistor to a second lead of the respective diode and to the respective contact terminal.

Method and apparatus for forming visible images

Abstract: A method and apparatus for causing coloration of an electrochromic material includes passing through the material an electrical pulse above a coloration threshold potential for the material and of a predetermined polarity and subsequently applying a D C potential of the same polarity to the material of a magnitude less than the threshold potential

Electrochromic device with cationic ion exchange resin separator

Abstract: An electrochromic display device in layered form having a first transparent substrate with a selectively actuable transparent electrode thereon and a first electrochromic layer on said transparent electrode, in combination with a counterelectrode having a second electrochromic layer thereon, and a solid electrolyte-separator layer between said first and said second electrochromic layers, said electrolyte-separator being comprised of a cationic ion exchange resin, specifically, a membrane of the acid form of a soluble polystyrene sulfonic acid polymer chemically wetted with water.

Electrochromic display device

Abstract: An electrochromic display device composed of a pair of oppositely disposed electrode plates at one of which is transparent, and an electrochromic composition sealed between the pair of electrode plates. The electrochromic composition is composed of an electrochromic compound coloring in a reduced state and a solvent. The electrochromic compound coloring in a reduced state is sealed between the electrode plated in a reducing atmosphere. The solubility of the electrochromic compound to the solvent is 10 -2 mol/(100 g solvent) or more in a reduced state and 10 -1 mol/(100 g solvent) or more in an oxidized state. The solvent is preferably composed of water and at least 70% by weight of alcohol. The alcohol is desirably polyhydric alcohol.

Electrochromic display device

Abstract: In an electrochromic display device having a plural number of indication electrodes displaying an information by repetition of coloring mode and discoloring mode, both modes of the indication electrodes being caused by an electrochemical oxidation-reduction reaction at the indication electrodes, and having an auxiliary electrode and counter-electrode to the indication electrodes and to the auxiliary electrode, the improvement is that an auxiliary electrode is further provided so as to act as the same acting mode as that of at least one of the indication electrodes, thereby removing an irregularity of color density of displaying at the acting indication electrodes.

Multilayered electroplatographic element comprising ion conductive and electrochromic layers

Abstract: Electrophotographic element typically comprising in sandwiched arrangement a transition metal oxide layer and a photoconductive layer. When an electric field is applied across the element, preferably after inserting the element between a pair of electrode layers, and an optical image is projected onto the photoconductive layer, the resulting conductivity pattern in the photoconductive layer causes corresponding coloration in the transition metal oxide layer, thereby visibly recording the optical image.

Electrochromic cermet material and device including the same

Abstract: An electrochromic display device includes a cermet electrochromic film. The cermet may comprise a conventional electrochromic material, such as tungsten oxide, and a noble metal, such as gold. In a preferred embodiment, the electrochromic cermet material includes a metal content of about 25 atomic percent. The electrochromic cermet is blue as prepared, and, when colored, is red. This electrochromic cermet material can be used in combination with other electrochromic materials, such as tungsten oxide, so as to result in a multicolor electrochromic display.

Electrochromic display body

Abstract: PURPOSE:Inactive gas such as Ar, He, Kr, N, etc. and dissolved in an electrochromi solution to remove remaining enzyme in the solution to provide long-life display body without causing further reducing reaction.

Method of driving electrochromic display means and electrochromic display means therefor

Abstract: A method of driving an electrochromic display means and the electrochromic display means therefor which includes an electrochromic display cell having a counter electrode and a plurality of display electrodes, and a constant voltage source coupled through switching means to the electrochromic display cell in such a manner that the display electrodes to be colored are maintained at the same potential as that of the counter electrode, while the display electrodes to be erased are impressed with a predetermined positive voltage with respect too the counter electrode.

Thin electrochromic display

Abstract: A thin electrochromic display suitable for manufacture in a continuous process on a backing tape which becomes part of the display. The display is a sandwich structure comprised of a transparent substrate, transparent electrodes having persistent electrochromic material thereon, a solid cationic ion exchange resin electrolyte in contact with the electrochromic material, a conductive metal foil member with electroreactive layer thereon, and an impervious adhesive backing tape adhered to the substrate around the foil member and also covering and adhered to the foil member to seal the display and having an aperture therein for permitting electrical contact to be made with the foil member.

Electrochromic display unit

Abstract: PURPOSE:To provide a display unit which has a low driving voltage, a longer life and a high response speed by doping a minor amount of a metal having a high hydrogen overvoltage into an oxide of a metal with electrochromic property or a nesa electrode provided thereunder.