Optical: systems and elements – Glare or unwanted light reduction – Display window
Reexamination Certificate
2001-07-31
2002-10-29
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Glare or unwanted light reduction
Display window
C359S602000, C359S603000, C359S604000, C359S266000
Reexamination Certificate
active
06471360
ABSTRACT:
The present invention relates to switchable electrochromic devices that are capable of uniform switching throughout the entire structure and of preferential switching to selected areas. More particularly, the present invention is directed to switchable electrochromic devices, particularly large scale window transparencies and window transparencies of non-uniform shape, which can uniformly switch from an activated to an unactivated state, and which can simultaneously include both an activated area and an unactivated area.
Commercial electrochromic devices are well known in the art for use as mirrors in motor vehicles. The patent literature also discusses uses of flat types of electrochromic devices for automotive windows, aircraft window assemblies, sunroofs, skylights, and architectural windows. Such electrochromic devices typically include a sealed chamber defined by two pieces of glass that are separated by a gap or space that contains an electrochromic medium. The electrochromic medium typically includes anodic compounds and cathodic compounds together in a solution. The glass substrates typically include transparent conductive layers coated on facing surfaces of the glass and in contact with the electrochromic medium. The conductive layers on both glass substrates are connected to electronic circuitry. When the conductive layers are electrically energized, an applied potential is introduced into the chamber of the device, which electrically energizes the electrochromic medium and causes the medium to change color. For example, when the electrochromic medium is energized, it can darken and begin to absorb light. For the electrochromic rear-view mirror assemblies for motor vehicles, a photocell can be incorporated into the electrochromic cell to detect a change in light reflected by the mirror and activate the electrical potential to dim the mirror.
In the other proposed applications of electrochromic devices, various problems become prevalent as the size of the electrochromic device is enlarged. For instance, rear-view mirror assemblies involve small-scale electrochromic assemblies, typically about 2 inches by 10 inches (5.08 cm to 25.4 cm) in size. In such electrochromic devices, an anodic bus bar is typically arranged at the top portion of the mirror assembly, and a cathodic bus bar is typically arranged at the bottom portion of the mirror assembly.
Automotive windows, architectural windows, and some aircraft windows on the other hand, are much larger in scale. As a result, switching between the lightened and darkened state in an electrochromic rear-view mirror assembly is typically quick and uniform, whereas switching between the lightened and darkened state in a larger scale electrochromic device can be slow and non-uniform. Gradual, non-uniform coloring or switching is a common problem associated with larger scale electrochromic window assemblies, commonly referred to as the “iris effect”. This effect is typically due to the potential drop across the surface of the transparent conductive coatings present on the surfaces of the substrates, which results in the applied potential being highest adjacent to the bus bars along the edge of the surface coating and lowest at the center of the cell as the electrical current passes through the electrochromic solution. Accordingly, the electrochromic medium will typically display non-uniform coloring by initially coloring the perimeter of the cell where the bus bars are located, i.e., closest to the point where the applied potential comes in contact with electrochromic medium, and thereafter coloring toward the center of the cell. Traditionally, conductive films having high sheet resistance are used. However, such high sheet resistance films require higher voltages and longer time periods to switch. Moreover, in conventional electrochromic devices, the entire assembly is shaded upon application of electrical potential.
Various attempts have been made to provide more uniform coloring of electrochromic devices to eliminate this iris effect. For example, various electrochromic chemical solutions have been chemically altered to increase uniform coloring.
A need exists for electrochromic devices that are capable of more uniform switching and coloring, can be easily manufactured and can optionally include preferential areas of shading.
The present invention provides an electrochromic window assembly comprising: a first transparent substrate including a first conductive coating on a surface thereof; a second transparent substrate including a second conductive coating on a surface thereof, the first transparent substrate and the second transparent substrate being spaced from each other to define a chamber therebetween; an electrochromic medium contained in the chamber, the electrochromic medium having a luminous transmittance that varies upon application of an electrical potential through the electrochromic medium; a plurality of first spaced facilities contacting the first conductive coating and capable of delivering electrical current to the first conductive coating; and a plurality of second spaced facilities contacting the second conductive coating and capable of delivering electrical current to the second conductive coating to establish the electrical potential through the electrochromic medium. In one nonlimiting embodiment of the invention, the plurality of first spaced facilities and the plurality of second spaced facilities are bus bars arranged about the perimeter of the window assembly. In another nonlimiting embodiment, the window assembly further comprises a controller capable of controlling delivery of electrical current to selected ones of the plurality of first spaced facilities and selected ones of the plurality of second spaced facilities, such that the luminous transmittance through a first portion of the electrochromic medium is different from the luminous transmittance through a second portion of the electrochromic medium.
The present invention also provides a method for providing uniform coloring to an electrochromic window assembly comprising: providing an electrochromic window assembly comprising first and second spaced apart transparent substrates defining a chamber therebetween, the first transparent substrate having a first conductive coating and the second transparent substrate having a second conductive coating, the chamber containing an electrochromic medium capable of coloring upon application of electrical potential thereto to provide reduced luminous transmittance; and applying an electrical current to opposing ends of the first conductive coating and to opposing ends of the second conductive coating to establish the electrical potential through the electrochromic medium, the opposing ends of the first conductive coating and the second conductive coating being spaced from each other, wherein the coloring of the electrochromic medium is uniform.
The present invention further provides a method for providing preferential coloring to a portion of an electrochromic window assembly, comprising: providing an electrochromic window assembly comprising first and second spaced apart transparent substrates defining a chamber therebetween, the first transparent substrate having a first conductive coating and the second transparent substrate having a second conductive coating, the chamber containing an electrochromic medium capable of coloring upon application of electrical potential thereto to provide reduced luminous transmittance; electrically connecting a plurality of first spaced facilities to the first conductive coating for providing the electrical potential to the first conductive coating; electrically connecting a plurality of second spaced facilities to the second conductive coating for providing the electrical potential to the second conductive coating; applying an electrical current to selected ones of the plurality of first spaced facilities and to selected ones of the plurality of second spaced facilities to establish the electrical potential through a selected portion of the electrochromic medium such th
Lin Chia-Cheng
Rukavina Thomas G.
PPG Industries Ohio Inc.
Sikder Mohammad
Siminerio Andrew C.
LandOfFree
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