Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2001-07-06
2002-12-31
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Composite
Of metal
C430S275100
Reexamination Certificate
active
06500555
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to laminates which absorb or reflect electromagnetic radiation in a predictably variable manner and can thus be used to control the heat absorbed or directed away from an underlying structure. Laminates of the present invention comprise at least one thermochromic layer and at least one reflective layer and vary predictably with response to their properties of heat absorption and reflection. They are thus thermoabsorptive-reflective dynamic laminates useful, for example, in effecting methods for controlling the absorption or reflection of radiant or heat energy into or away from of structures that underlie the laminates.
BACKGROUND OF THE INVENTION
It is known that thermochromic compositions change color in response to temperature fluctuations. In their simplest form, thermochromic compositions are special combinations of chemical compounds and organic materials that exhibit color or transparency to light in response to temperature fluctuations. Typically, upon reaching or exceeding a trigger temperature, a thermochromic composition exhibits transparency to thermal or “UVI” radiation and, upon falling below a trigger temperature, the thermochromic material will exhibit color, and, correspondingly, opacity to radiant energy. The thermal or “UVI” radiation range is the range of frequencies in the Ultraviolet, Visible and Infrared ranges which produce heat in objects, which absorb those frequencies. The relative transparency/opacity of a thermochromic material is dynamic with respect to the trigger temperature or trigger temperature range of the specific thermochromic material. For example, a thermochromic material having a trigger temperature of precisely 72 degrees Fahrenheit would be opaque to light and thus would absorb thermal radiation in the UVI range at temperatures below 72 degrees Fahrenheit and transparent, or non-absorptive, to UVI light at temperatures above 72 degrees Fahrenheit.
Materials are known that possess the properties of color-exhibiting and color-extinguishing to a transparent state when exposed to temperature change above their trigger temperatures. Materials are known which can go through numerous cycles of changing between color-exhibition and color-extinguishing to transparency. Such materials are described, for example, in U.S. Pat. Nos. 5,919,404 and 5,558,700, which are incorporated herein by reference.
All patents cited herein are incorporated by reference.
It is known that modifying ratios of the compounds used to produce a thermochromic composition can control the trigger temperature and relative sensitivity of coloration/transparency of thermochromic materials. In addition, the maximum density of the color displayed when the thermochromic composition is in the color-exhibiting state can also be controlled to be either translucent (i.e. partially transparent) in varying degrees or to be fully opaque. For example, U.S. Pat. No. 5,585,425 describes a method for creating a thermochromic opaque/transparent composition, laminate member. Other patents relevant to methods for manipulating the properties of thermochromic materials are described in U.S. Pat. Nos. 4,028,118 and 5,919,404.
It is also known that thermochromic compositions can be produced in a range of different colors. For example, U.S. Pat. No. 5,919,404 describes a method for creating reversible thermochromic compositions that exhibit a wide range of traditional colors, while U.S. Pat. No. 5,558,700 describes a method for creating reversible thermochromic compositions that exhibit fluorescent colors. It is likewise known that thermochromic compositions can be laminated to various substrates depending on the desired application, i.e. U.S. Pat. Nos. 5,352,649 pertaining to a thermochromic laminate member, and composition and sheet for producing the same; U.S. Pat. No. 5,688,592 (“Shibahashi '592”); and U.S. Pat. No. 5,585,425.
In a more complex form, thermochromic compositions can be produced in the form of microcapsules using conventionally known methods to protect the material from external elements, maintain their functionality and to endow them with desirable properties and characteristics. U.S. Pat. Nos. 4,028,118 and 5,919,404 are good examples of patents that describe known properties of thermochromic compositions.
It is also known that thermochromic materials can be added to thermoplastics, polyvinyl chloride (PVC) or other resins and molded into any shape or design or made into sheets (as described in U.S. Pat. Nos. 4,826,550 and 5,919,404). For example, U.S. Pat. No. 5,798,404 describes a method in which hair curlers are manufactured with a thermochromic thermoplastic elastomer body.
Significant research has gone into increasing the light-fastness of the colors of thermochromic materials as perceived by the human eye, increasing luminosity (brightness) and reducing the fading of colors that may be caused by the cycling of sunlight, and especially by ultraviolet frequencies. The purpose of such research is to develop formulations of thermochromic materials that are more resistant to damage from light, which impinges upon them. The Shibahashi '592 patent describes an example of a layer of thermochromic material (blue in color) which was covered with a UV filter layer, which is dark yellow in color. When the thermochromic material was in the color developed stage, the additive color rule applies, that is, yellow+blue=green. Therefore the perceived color of the material in its color-developed stage is green and not blue. A solution to this problem presented in the Shibahashi '592 patent is to combine two layers the first of which is a color reflecting layer comprising particulates of natural mica coated with a reflective metallic luster pigment such as titanium oxide sprinkled on the layer. An additional feature is to provide, over the thermochromic layer, a layer of UV absorber, which filters out UV light. One of the functions of the reflective layer is to reflect some of the light before it hits the UV absorber and the thermochromic layer to thereby present the true color of the underlying layer. The Shibahashi '592 patent does not, however, recognize the advantages of utilizing the variable transmissivity of thermochromic materials to control the thermal absorption or reflectance of a structure.
SUMMARY AND OBJECTS OF THE INVENTION
Thermochromic laminates of the present invention, and methods for using them, comprise a passive system that automatically varies the reflection or absorption of electromagnetic energy in response to temperature changes. Thus, the present laminates function with respect to predetermined temperature trigger points or ranges without the input of energy except from that of the incident radiation. Laminates of the invention comprise at least two layers, a thermochromic layer having a trigger temperature or a trigger temperature range, and a reflective, or partially reflective layer that is concealed from or exposed to radiant energy incident upon the outer laminate by the change in transmissivity and corresponding color change of the thermochromic layer. The interaction of the at least two layers with respect to the absorption or reflection of radiant or thermal energy can be used to control or modulate the absorption of heat or other energy by an underlying structure. By doing so, the present invention diminishes the need for the use of conventional energy sources such as electricity or natural gas to control the temperature of the underlying structure. Further objectives and advantages will become apparent from a consideration of the following description and attached drawings.
It is an object of the present invention to provide thermochromic laminates that can be utilized to control the heat gain or loss of an underlying structure without the necessity for an external power source.
It is a similar object of the present invention to provide thermochromic laminates that predictably vary their absorption or reflectance of incident radiant energy in response to temperature ch
Cygnet Works, Inc.
Evans Elizabeth
Venable Baetjer Howard & Civiletti LLP
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