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United States Patent
LeCompte et al.
(io) Patent No.: (45) Date of Patent:
US 7,457,027 B2 Nov. 25, 2008
(54) FABRICATION OF CELL CAVITIES FOR ELECTROOPTIC DEVICES
(75) Inventors: Robert S. LeCompte, Tucson, AZ (US);
Juan Carlos Lopez Tonazzi, Tuscson,
(73) Assignee: ElectroChromix, Inc., Tucson, AZ (US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 257 days.
(21) Appl.No.: 11/185,261
(22) Filed: Jul. 20, 2005
(65) Prior Publication Data
US 2006/0027260 Al Feb. 9, 2006
Related U.S. Application Data
(60) Provisional application No. 60/589,492, filed on Jul. 20, 2004.
(51) Int. CI.
(52) U.S. CI 359/265; 359/272; 345/49;
(58) Field of Classification Search 359/265,
359/272; 345/49, 105; 349/154; 264/4 See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
This invention discloses methods to dispense adhesives for fabricating electrooptic devices. In addition the invention also discloses on how the cavities of these electrooptic devices may be filled using detachable tabs. The Electrooptic devices of this invention may comprise liquid or solid electrolytes.
16 Claims, 2 Drawing Sheets
FABRICATION OF CELL CAVITIES FOR
RELATED APPLICATIONS/CLAIM OF
This application is related to and claims benefit of and priority to U.S. provisional applications 60/589,492 filed on Jul. 20, 2004.
BACKGROUND OF THE INVENTION
Electrooptic devices are used for many applications, such as electrochromic (EC) devices, including displays, rear-view mirrors for transportation and windows; liquid crystal 15 devices, solar cells and light emitting devices. Many of these devices require two substrates to be bonded in a spaced apart geometry, so that the space between the substrates may be filled with a medium. Examples of the mediums are electrolytes and liquid crystal compositions. 20
This disclosure provides novel ways of fabricating devices with cavities formed using two substrates which are sealed at the perimeter; applying perimeter sealants and filling the cavities with appropriate mediums.
BRIEF SUMMARY OF THE INVENTION
This invention discloses methods to fabricate electrooptic devices comprising of a cavity formed by two substrates assembled in a spaced apart relationship by using an adhesive 30 (or sealant) bond close to their perimeter. The disclosure provides methods to dispense the adhesive so that uniform bond widths may be obtained. In addition the invention also discloses on how the cavities of these electrooptic devices may be filled using detachable tabs. 35
DESCRIPTION OF THE DRAWINGS
FIG. la is a schematic view of a portion of an EC mirror being formed by a process according to the present invention, 40 showing an EC mirror with a tab comprising a port for filling;
FIG. lb shows another schematic view of an EC mirror at another stage in the process, in which the tab is removed after filling with the electrolyte and the plug areas are sealed; and
FIG. 2 shows a schematic view of the cavity filling process, 45 taken from the direction A-A in FIG. la, and also showing an injector that can be used in the cavity filling process.
DETAILED DESCRIPTION OF THE INVENTION
Liquid crystal mirrors, displays (Kmetz, A. R., et al., NonEmissive Electrooptic Displays, Plenum Press, NY (1976)) and electrochromic mirrors (Lynam N. R. et al, Automotive Applications of Chromogenic Materials, Lampert C. M., et al editor, "Large Area Chromogenics: Materials and Devices for 55 Transmittance Control", SPIE Optical Eng Press, Bellingham, Wash. (1990)) have been made commercially for many years, in addition electrochromic displays (US published patent application 2002/0021482) and dye sensitized solar cells (M. Gratzel, Platinum Metals Rev., 38, 151-159 (1994) 60 Highly efficient nanocrystalline photovoltaic devices: CT sensitizers based on Ru and Os achieve outstanding performance) have also been demonstrated which utilize two substrates with conductive and optionally with other coatings on the walls which face each other inside the cavity. The sub- 65 states may be planar or non-planar. In most of these devices, the cavity is pre-fabricated by dispensing a sealant (called
main sealant) on the surface of one of the substrates near the perimeter, and then lowering the second substrate so that the adhesive is sandwiched between the two forming a cavity between the two substrates. The cavity thickness (or spacing between the two substrates) is usually determined by adding spacers to the adhesive or sprinkling the spacers on the surface of one of the substrates before assembling them. The second substrate is lowered and the two substrates are held together by springs, clips or a pressure while the sealant is cured. Any pressure may be used as long as the spacer beads do not get crushed prior to the curing of the sealant. Pressure may also be applied by enclosing the assembled plates in a vacuum bag and then evacuating the bag prior to curing. To ensure that the plates do not move relative to each other in operations prior to the seal cure, one may also use localized application (a few spots) of quick curing adhesives, e.g., UV curable types, thermoplastic glues which may further cure by reaction with moisture. Curing of the main seal is done by heating and/or by subjecting the assembly to radiation, e.g., UV, infrared and microwave. Generally a small gap is left in the sealant which is then used to backfill the liquid medium and then it is plugged with another sealant (called plug sealant) which is generally cured by UV. Details on sealants, devices and processing may be found in many references. Some of the exemplary references on electrochromic devices are U.S. Pat. Nos. 6,606,183; 6,111,684; 6,195,193; 5,724, 187 and published US patent application 2004/0233537. The descriptions of devices, sealants and processing of devices described in these references are incorporated herein by reference.
The sealants for these devices are generally based on epoxy resins due to their inertness, good adhesion and temperature performance. For example in many EC devices for automotive rear-view mirrors there are requirements to subject these to 85° C./85% RH for extended periods of time or to steam autoclave testing at 121° C. Important tests for automotive EC mirrors are summarized in U.S. Pat. No. 6,245,262. However, sealants based on acrylics, urethanes, butyls and silicones may also be used as long as they do not compromise any of the performance parameters of the device. Hybrid materials such as acrylic silicones, urethane-acrylics, urethane-silicones, acrylic-epoxies, etc. may also be used. In the hybrid materials typically one of the moieties is pre-formed and the other one is responsible for reacting and curing. For example, in an epoxy acrylic, the curing mechanism of the adhesive is by reaction related to acrylate groups, whereas the base material (resin) for the adhesive is formed by reacting epoxy groups. Adhesives based on interpenetrating networks may also be used where two different mechanisms of polymerization (and/or crosslinking) may be used resulting in interlocked polymers. One may also have systems where both epoxy and the acrylics react during cure, e.g., acrylic may be UV activated to result in partial cure and quick green strength for handling, etc, and epoxy groups react later when subjected to heat to result in the final properties. Particularly, the barrier of the non-epoxy sealants may be considerably improved by adding nano-particles (see published US patent application 2004/0233537) which may be added along with conventional inorganic fillers. The filler content in the adhesives is usually kept lower than about 65% by weight and of the nano-particles lower than 30%. Those main sealants are preferred so where no volatiles are given out as they cure. As an example RTV silicones which cure due to hydrolysis and condensation giving off acetic acid or alcohol are less preferred over those two component silicones where platinum chemistry is used for addition crosslinking. The reaction mechanism of such systems are known widely (e.g., Handbook of Adhesives and