Liquid crystal cells – elements and systems – Liquid crystal system – Liquid crystal window
Reexamination Certificate
2001-11-06
2004-03-23
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Liquid crystal window
C349S015000, C349S115000, C349S176000
Reexamination Certificate
active
06710823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to an electro-optical glazing structure having total-reflection and semi-transparent and totally-transparent modes of operation which are electrically-switchable for use in dynamically controlling electromagnetic radiation flow in diverse applications.
2. Brief Description of the Prior Art
The use of windows in homes, commercial buildings, and automotive vehicles alike is very well known. The reasons for providing windows in such structures and systems are directly related to the functions they perform. For example, window structures provide for ventilation, lighting, a sense of spaciousness, as well as a way of making contact with the outdoors. Windows made of glazing (e.g. glass material) also permit selective transmission of electromagnetic radiation between the outdoors and the interior space of homes, commercial buildings, and automotive vehicles. While conventional forms of glazing serves many useful functions, such forms are not without problems.
An appreciation of the problems presented by the use of conventional glazing in windows, can be most easily attained by recognizing the nature and composition of electromagnetic radiation with which windows universally come in contact.
On a clear day at sea level, electromagnetic radiation is composed of 3% ultraviolet light (i.e. electromagnetic radiation in the UV band), 44% visible light (i.e. electromagnetic radiation in the visible band), and 53% infrared light (i.e. electromagnetic radiation in the IR band). In accordance with the laws of physics, 50% of all electromagnetic radiation produced is left hand circularly polarized (LHCP) while the other 50% thereof is right hand circularly polarized (RHCP). The total electromagnetic radiation striking a window surface is a combination of direct radiation from the Sun and diffuse radiation from the ambient environment. While electromagnetic radiation is broad-band in nature, it is the ultraviolet light component thereof which causes molecular decomposition in various types of plastic material and inorganic dyes, which results in color fading.
When electromagnetic radiation strikes a glass window, three different physical processes occur. Some of the radiant energy is transmitted through the glass; some of the radiant energy is reflected off the glass; and a small portion of the radiant energy is absorbed by the glass. The energy transmitted through the glass window is typically absorbed by furnishings or structures within the interior environment, and often becomes trapped therewithin causing an increase in interior temperature.
Depending on the season, electromagnetic radiation transmitted through glass windows can be either mitigate or worsen the thermal loading imposed upon the heating and cooling systems associated with the glass windows. Consequently, during the hot weather season, it is highly desired to shield windows and sliding glass doors from electromagnetic radiation in order to lessen thermal loading upon cooling systems. During cold weather season, it is highly desired to expose windows and sliding glass doors to electromagnetic radiation in order to lessen thermal loading on heating systems.
In short, it is highly desired to selectively control the transmission of electromagnetic radiation through window structures at different times of the day and year so that thermal loading upon the heating and cooling systems of residential, commercial and industrial building environments can be minimized. By minimizing such thermal loading, power can be used in an economical manner to control the internal temperature of residential, commercial and industrial building environments. Achievement of this goal would impact the natural environment in a positive manner, while improving the quality of life.
With such objectives in mind, great effort has been expended in recent times to improve the ways and means of selectively controlling the transmission of electromagnetic radiation through window structures.
One approach to electromagnetic radiation control involves using a window shade to reduce the transmission of electromagnetic radiation through windows. The most popular type of shade is the window blind. However, as window blind is mounted within the interior of the building or transportation environment, electromagnetic radiation is allowed transmit through the window, raise the temperature within the internal environment, and thus increase thermal loading on cooling systems during the hot weather season. Also, the operation of window blinds requires mechanical or electromechanical controls which tend to be bulky and expensive to manufacture, install and maintain.
Another approach to electromagnetic radiation control involves the use of sun control films which are physically applied to the surface of glass windows in building and automotive vehicles alike. Presently a variety of different types of sun control film are marketed by various firms. Such electromagnetic control films can be categorized into one of the three basic categories, namely: high reflectivity film; heat saving or winter film; and fade protection film.
High reflectivity electromagnetic films are most effective at blocking summer heat. The higher the reflectivity of electromagnetic film, the more effective it will be at blocking electromagnetic radiation. Electromagnetic reflectivity film having a silver, mirror-like surface is more effective in blocking electromagnetic radiation than the colored, more transparent films. Electromagnetic reflectivity films can lower the U-value of glass by more than 10%. Notably, in climates having long heating seasons, the use of high reflectivity film prevents using the winter sun to warm the interior of buildings during the cold weather season, and thus lessen thermal loading on building heating systems.
Heat-saving or winter films are designed to reduce winter heat losses through glazing. These films can lower the U-value of glass windows by more than 20%.
Fade-protection films are designed to filter out ultraviolet rays. Ultraviolet rays cause about 60-65% of color fading in most home furnishing fabrics and automobile dash boards.
While electromagnetic radiation control films of the types described above can be used to control heat and glare, eliminate sun damage, and to a lesser extent, reduce visibility into buildings during the daytime. The major disadvantages thereof are reduction in interior light, loss of visibility, and extra care required in cleaning. Moreover, prior art electromagnetic window films are incapable of changing from transmissive during winter months to reflective during summer months in order to effectively use electromagnetic radiation for dynamic temperature control of biological environments (e.g. human habitats, greenhouses and the like).
An alternative approach to electromagnetic radiation control involves using special glass panels having radiation transmission characteristics which effectively absorb (i.e. block) the infrared and ultra violet wavelengths, while transmitting the visible wavelengths thereby allowing window viewing and day light to enter the interior spaces of buildings using such window technology. While the light transmission characteristics of such glass provides a measure of electromagnetic radiation control during cooling seasons, where outdoor temperatures tend to be above 72 degrees Fahrenheit, its IR absorption characteristics prevents, during heating season, IR wavelengths of Sun light to warm the interior spaces of building structures in which such glass panels are installed. Consequently, during heating seasons, such glass fails to lessen the thermal loading on the heating systems of such buildings, as would be desired in an effort to conserve energy and heating resources during the winter months.
In recent times, there has been great interest in using variable light transmission glass or glazing, referred to as “smart windows”, to achieve electromagnetic radiation (i.e. energy) control in buildings and vehicles alike. The reas
Faris Sadeg M.
Li Jian-Feng
Li Le
Brill Gerow D.
Chowdhury Tarifur R.
Crispino Ralph J.
Reveo Inc.
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