A typical electrochromic device comprises five superimposed layers deposited on one substrate or positioned between two substrates in a joined together configuration. The central part of the five-layer electrochromic stack is an ion conductor (electrolyte). The ion conductor is in contact with an electrochromic film, capable of conducting electrons as well as ions. On the other side of the ion conductor is an electron and ion conducting counter electrode film serving as an ion storage layer. The central three-layer structure is positioned between electron conducting layers. Such a device is colored/bleached by applying an external voltage pulse between the electron conducting layers on the two sides of the stack, causing the electrons and ions to move between the electrochromic layer and the counter electrode layer. Applications of electrochromic devices include architectural windows, information displays, light filters and modulators, rear-view mirrors, sunroofs and windows in vehicles, eyewear, helmet visors, ski goggles, surfaces with variable thermal emissivity or camouflage.
Historically, the first electrochromic coatings were deposited on glass substrates. The possibility of using plastic substrates is described, for example, in WO9923528. Electrochromic devices on plastic substrates are characterized by their light weight, flexibility, and the ease of cutting to complex shapes.
A typical procedure for manufacturing of electrochromic devices with two substrates comprises the following steps. First, two substrates are provided.
Each substrate is coated by an electron conducting layer and an electrochromic alternatively a counter electrode layer. The coated substrates are typically cut to their final size and shape. Secondly, the two substrates are joined together with an electrolyte layer interposed between the substrates. A hermetic sealing to the device edges is provided. Finally, means of electrical contacting are applied so as to connect the electrochromic device to the power supply.
There are many prior art disclosures presenting different types of sealing procedures. Just a few examples will be presented here. WO 9923528 discloses a thermal hardening, photochemical hardening or photochemically initiated thermal hardening epoxy adhesive applied to the edges of electrochromic devices with glass or plastic substrates.
U.S. Pat. No. 6,952,299 discloses electrochromic devices sealed by a liquid-state sealing resin applied to the outer circumferential edge of a laminated structure and cured to seal the laminated structure, so the entire structure is made into a body.
JP 2005266185 discloses plastic sheets, disposed on both surfaces of a dimming layer comprised of a photochromic material, thermochromic material or electrochromic material that changes in state according to external stimulation. The edges of the sheets are sealed by ultrasonic welding in order to eliminate the need for adhesives and bonding in unnecessary regions. The method describes welding of individual pre-cut devices having a periphery with a bare plastic welding area.
U.S. Pat. No. 6,193,379 discloses an electrochromic assembly including a front and/or rear elements made of aliphatic hydrocarbons. A transparent conductive material layer is disposed on the rear surface of the front element, and another layer on the front surface of the rear element. The elements of pre-cut size and shape are joined to form a chamber containing electrochromic material in solution with the organic solvent. The front and rear elements may be joined by a thermal, ultrasonic, or laser weld, or by an epoxy seal. The sealing area is an uncoated part of bare front or rear elements.