Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-09-18
2001-10-16
Lester, Evelyn A (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S265000, C359S268000, C359S272000, C359S273000, C359S274000
Reexamination Certificate
active
06304363
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electro-optic devices for vehicles and, more particularly, to an enhanced vehicular rearview mirror or window glazing incorporating an electro-optic medium allowing variation in the transmission of light in response to application of an electric field to the electro-optic medium.
Specifically, in one aspect, the invention is a variable reflectance, electro-optic mirror including protection against laceration injuries and scattering of glass or other fragments if broken or damaged, against degradation from ultraviolet radiation, and against fogging and misting in high humidity conditions.
This invention also relates to glazing in vehicles and, more particularly, to an enhanced vehicular window, sun visor, shade band or sunroof incorporating an electrochromic medium allowing variation in the light transmitted by the glazing in response to application of an electric field to the electrochromic medium. Specifically, the invention is a variable transmission, electrochromic vehicular window including protection against laceration injuries and scattering of glass, other fragments, or chemicals if broken or damaged, against degradation from ultraviolet radiation, and including thin film means to reflect a substantial portion of incident, solar, near-infrared radiation. optionally, and preferably, the electrochromic glazing assembly is blue or green in transmission, as viewed from the vehicle interior, so as to reduce glare from the sun and to optimize visibility and a true-to-nature blue view of the sky.
In a collision, the glass typically used as the substrate in vehicular rearview mirrors poses potential hazards to the driver or other vehicle occupants. Since glass easily shatters into sharp, irregular fragments, there is a high likelihood of facial or other injury, typically lacerative in nature, in any collision. For this reason, prior known interior and exterior vehicular rearview mirrors, which typically consist of a single glass piece coated with reflective material, are conventionally protected by applying a tape or a plastisol-type plastic adhesive to the back surface of the glass piece. Accordingly, if impacted or broken in an accident, and shattered, glass fragments are retained by the tape or plastisol-type plastic adhesive.
More recently, however, a new generation of electro-optical mirrors has emerged which are fabricated using two pieces of glass separated by a gap or space which contains an electro-optic medium allowing variation in the light reflected by the assembly. For example, in liquid crystal rearview mirrors, the space between the transparent front and reflective coated rear glass pieces is filled with a semi-viscous liquid crystal material. In electrochemichromic or electrochromic mirrors, the gap or space contains a liquid, thickened liquid, gel or semi-solid material.
In these types of electro-optic, laminated mirror assemblies, scatterproofing of the rear glass piece is relatively easy since tape or plastisol-type plastic adhesives can be applied to its rear surface behind the reflective coating in the conventionally known manner. However, scatterproofing the front piece of glass in such a laminated assembly is difficult since the material used to fill the space between the front and rear glass pieces is usually insufficiently viscous or adhering to retain fragments of the front glass should it shatter in a collision.
Another problem encountered with electro-optic rearview mirrors and windows or glazing assemblies is degradation due to exposure to ultraviolet radiation over the life of the mirror or glazing. Ultraviolet (UV) radiation from the sun which penetrates the earth's atmosphere has a wavelength in the range between 290 and 400 nanometers (nm) and can cause breakdown in the operational characteristics of the electro-optical medium including chain scission, cross-linking and stimulation of chemical changes in the chemicals used to formulate the electro-optical medium. This interferes with electronic conjugation in the aromatic conjugated materials typically used and thus the electro-optic activity of those materials is impaired. Moreover, the medium will often discolor taking on a yellowish tint visible in light reflected or passing therethrough and drastically affect the usefulness of the rearview mirror or window. Such degradation from UV solar radiation is particularly problematic in electro-optical automotive windows which are typically exposed to the full solar radiation, often when the electro-optical medium is in its colored state.
In order to overcome ultraviolet radiation degradation in such electro-optic rearview mirrors and glazings, it is possible to add UV radiation absorbing materials to the electro-optic medium. However, such UV absorbing additives, especially in higher concentrations and with broad UV absorbance, themselves impart a yellowish tint to the materials to which they are added. Such yellow tint is also visible in light reflected or transmitted therethrough. Yellow is aesthetically displeasing in many applications, and is particularly displeasing when used in rearview mirrors. Consumer acceptance of rearview mirrors having a yellowish tint or cast in the reflected light has been poor. Moreover, yellow mirrors are efficient reflectors of headlamp glare which itself is yellow. Consequently, prolonged exposure to sunlight and UV radiation, or reducing UV degradation in electro-optic mirrors with UV absorbing additives, can create negative consumer reaction and acceptance. Likewise, a yellow tint in, for example, an automotive sunroof is consumer displeasing as it detracts from the consumer's appreciation of, and natural view of, the blue sky.
Another objective in the use of rearview mirrors is the matching of human sight sensitivity in various light conditions during the use of such mirrors to the glare sources and ambient lighting present. It is known that the spectral sensitivity of the human eye depends on its light adaptation. Thus, daylight and night driving conditions create differing human eye sensitivities. Further, nearly all night driving is affected by the reflection of light from the headlights of the driver's own vehicle on the road. The electro-optic mirror assemblies of this invention should, therefore, optimally be constructed to correspond as much as possible with the eye sensitivities in both day and night driving conditions.
The electro-optic media commonly used in electro-optic mirrors and windows are often constituted of materials and chemicals of a potential toxic or otherwise hazardous nature. Should the mirror glass break in an accident, there is a possibility of automobile occupants contacting the electro-optic media, either directly or by contact with glass particles to which these potentially hazardous media are still adhering. Sun contact presents a hazard to the occupants through toxic effects, and through skin irritation such as to eyes and facial areas. The anti-lacerative layers and laminate interlayers of this invention offer a barrier that ensures that contact with chemicals used within the mirror is minimized should the glass shatter in an accident.
Yet another problem is unwanted misting or fogging of the rearview mirror surface or the glazing surface when the vehicle encounters high humidity conditions. For example, in damp, cold conditions where the interior passenger compartment of a vehicle has a highly humid atmosphere, water droplets may tend to condense on the rearview mirror surface or window surface thereby obscuring vision in the mirror or through the window. Not only does such condensation prevent effective use of the mirror or window, but also requires frequent wiping by the vehicle driver which distracts his attention from driving.
Vehicular windows provide a field of view so that the driver can make safe driving decisions and allow occupants to comfortably view the surroundings. Glass vehicular sunroofs are luxury items that serve both aesthetic and functional needs. A transparent sunroof is primarily consumer
Donnelly Corporation
Lester Evelyn A
Van Dyke Gardner, Linn & Burkhart, LLP
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