This patent application is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "Daylighting methods for increasing the amount of available light within structures are well known. Conventional daylighting methods typically employ prisms or other microstructures to guide/re-direct and/or diffuse light beams of sunlight by refraction and/or reflection to increase illumination into the interior of a room uniformly while reducing glare. Daylighting constructions frequently utilize microstructures such as a series of grooves provided in films or sheets that are capable of refracting and/or reflecting incident light through the microstructures by total internal reflection (TIR).
"Daylighting methods are becoming widely adopted. Daylighting increases ambient light within a building and can result in significant energy savings by reducing or eliminating the need for electric lighting during daytime hours. One disadvantage of a building without a sunlight redirecting apparatus, or daylighting film, is the inability to project light into the interior of a building. For example, if there is no apparatus, such as a reflector positioned inside or outside the window, sunlight cannot be directed to an interior space far away from the window. That is, typical, unguided sunlight will fall on the floor near the window when incident into a room. Thus, the illuminating effect is often wasted on undesired areas.
"Accordingly, methods have been introduced in an attempt to overcome this disadvantage by using unique, daylighting constructions. One such method employs a light redirecting film adapted for engagement against a window. Such light redirecting films or sheets generally include a planar base and at least one light redirecting microstructure provided on the side of the sheet opposite the base. The planar base is attached to the window such that the microstructures on the opposite side face away from the window.
"However, conventional attachment methods interfere with the optical properties of the microstructure, and disadvantageously degrade light projecting properties of the daylighting film. For example, conventional attachment methods put the adhesive on the planar side or base of the micro structured film, or sheet, and adhere the base to the light incident glazing to avoid degrading the optical re-directing/daylighting properties of the microstructure defining surface opposite the base. Note, that in such a conventional assembly, the daylighting microstructures generally are disposed opposite the base and face inward into the room to be illuminated. It is generally assumed that it is not possible to provide an adhesive on the light guiding microstructures without substantially degrading optical properties and thereby defeating the daylighting effect. For this reason, conventional methods of attaching daylighting microstructures to a glazing surface face the microstructures inward into a room, and avoid covering the microstructure with adhesive.
"Therefore, what is needed is an attachment system for securing a daylighting sheet comprising a series of light redirecting microstructures directly to a glazing surface without degrading the light redirecting optical properties of the resulting assembly.
"A further disadvantage of conventional attachment methods of a daylighting film to a glazing, such as a window surface, is the thermal expansion coefficient mismatch between the different materials comprising the glass or glazing, heated by incident light, and the adjacent planar base of the plastic daylighting sheet or film that must be covered with adhesive to a maximum extent in order to adhere to the glazing surface. Further, PSA adhesives can migrate, which means they can flow and further change the optical properties of the daylighting sheet after time has passed. Therefore, what is needed is a new way of mounting a daylighting sheet comprising a series of microstructures to a glazing surface using a PSA formulation that does not substantially migrate, and enhances optical properties, or at a minimum does not substantially degrade optical properties of the daylighting sheet
"What is also needed is an attachment system that would facilitate cost effective ease of re-attachment and/or replacement of such daylighting film without damage to a glazing surface. For example, it would be desirable for an attachment method to facilitate changing position of a daylighting film to remove air bubbles or deformations without adversely affecting optical properties of the microstructures. And, such an attachment system advantageously would facilitate cost effective implementation of daylighting, thus saving energy costs for electric lighting."
In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "In order to achieve the foregoing and other objectives, a first aspect of the invention provides a method for mounting a daylighting sheet comprising a series of light redirecting microstructures, such that the microstructures advantageously are provided directly against a transparent, light incident surface, such as a single or double pane window or other glazing, wherein optical performance and efficiency of the daylighting microstructures are improved. Such improvement of optical performance and efficiency of the daylighting microstructures may be found in the employment of the invention with a daylighting sheet that defines a series of microstructures having a series of light redirecting V grooves, such as taught in Milner et al. U.S. Pat. No. 5,880,886, incorporated herein by reference as if set forth in full. (Please refer to Operational Example, infra.
"Alternatively, optical performance and efficiency of other daylighting microstructures, with the exception of prisms, employed with the attachment methods of the present invention remain substantially unaltered, or at a minimum are not substantially degraded. Light transmission properties of a prism are inherently affected by the application of an adhesive. An aspect of the invention describes ways to minimize or substantially mitigate the effect of an adhesive on overall optical performance of prism type daylighting microstructures.
"An aspect of the invention provides an optical adhesive for mounting a daylighting sheet or film directly against a glazing. Glazing as used herein refers to architectural applications including clear and tinted float glass, tempered glass, and laminated glass, as well as coated glasses, all of which can be glazed singly or as double, or even triple, glazing units. The optical adhesive transmits light while minimizing adverse impacts on the light re-directing properties of the daylighting microstructures. This substantially seals grooves, prisms or other light redirecting microstructures directly against a glazing, thereby protecting the microstructures from dust, moisture, and other contaminants to provide enhanced long-term optical performance. This is not possible in conventional attachment methods wherein daylighting microstructures face outward into a room, and are open and unprotected as described above.
"The foregoing aspect of the invention can facilitate ease of removal of daylighting sheets from a glazing surface without damage to the glazing or deformation of the light redirecting microstructures This facilitates ease of re-positioning a daylighting sheet to alleviate deformation and errors in positioning, or to remove formed air bubbles, or for removing the daylighting sheet without damage to the glazing at the end of the daylighting sheet's useful life. Ease of removal occurs due to selective patterning of the adhesive, i.e., less surface area contact is needed between the adhesive and the daylighting microstructures. Ease of removal also can be facilitated by the use of low tack adhesives.
"In another aspect of the invention, an optical construction comprises a daylighting sheet having a base and a second surface opposite the base that defines the series of daylighting microstructures. Raised or elevated portions--relative to the base--of the daylighting microstructures are adapted to provide selected points of adhesive contact for an applied transparent adhesive. The set or locus of all adhesively contacted points define an optical, light transmissive adhesive surface or layer, for securing the daylighting microstructures directly against a glazing facing the incident light; effectively sealing the formerly open ended microstructures against ingress of dust and contaminants that would reduce optical efficiency. The light transmissive adhesive surface advantageously enables the daylighting microstructures to face outward toward the incident light and performs the optical function of facilitating the transmission of light directly to the microstructures with minimal adverse effect on the light redirecting properties of the underlying microstructures. In the case of microstructures comprising a series of light redirecting V grooves, such as taught in Milner et al. U.S. Pat. No. 5,880,886, the optical surface provided by the light transmissive adhesive allows the V groove microstructures to face outward toward the incident light. This facilitates the transmission of light over a wider range of sun elevation angles than is possible when the microstructures face inward, away from incident light.
"The light transmissive adhesive surface advantageously eliminates the need for a cover sheet. This also results in a daylighting assembly that is readily moveable to facilitate installation without deformation. Ease of removal is driven by application flexibility and the need to prevent damage to expensive windows, or glazing surfaces if it ever becomes necessary to replace the daylighting film. This aspect further protects the grooves in the microstructures against deformation and degradation of optical efficiency through dust or other contaminants by adhering wide or open ends of V grooves or daylighting microstructures directly against the light incident glazing.
"Both the area and depth of the adhesive applied to the grooved surface of the daylighting film readily may be controlled. Controlling the area of applied adhesive as well as controlling the depth to which the adhesive is applied within the grooves makes possible a precise adjustment of the optical properties of the daylighting film.
"In another aspect, the invention comprises direct attachment of a daylighting sheet to a glazing surface, wherein the daylighting sheet defines a series of V structures having flat top grooves, such as in such as Milner et al. U.S. Pat. No. 5,880,886. This aspect of the invention enables the flat regions between V grooves to be attached directly to a glazing surface with adhesive touching only the tops of the flat regions defining the grooves. Advantageously, the adhesive does not alter the optical properties of the daylighting sheet in this configuration, but rather improves light redirecting properties as shown in the computer modeling set forth in the operational example described with reference to FIGS. 12-15 infra. Further, this aspect of the invention encases the troughs of the grooves of the microstructures directly against the glazing and thereby protects the light redirecting microstructures from dust, moisture, and other contaminants. This aspect of the invention advantageously eliminates need for a cover sheet to protect the light redirecting microstructures. It also eliminates the need for the exposed open ends of the microstructure to face inward, unprotected, into the room to be illuminated.
"A further aspect of the invention provides a daylighting sheet comprising one or more microstructures defining a series of V grooves, such as Milner et al. U.S. Pat. No. 5,880,886, attached directly to a glazing surface with adhesive touching only a percentage, for example,
"Another way of attaching a daylighting optical structure comprises attaching a series of V grooves having flat tops between adjacent grooves (such as in U.S. Pat. No. 5,880,886) directly to a glazing using no adhesive. In this embodiment, the material for the microstructures, and in particular the material for the flat top structures, is selected from a group of polymer materials having self-adhering properties.
"Another aspect of the invention provides a method for attaching a daylighting optical design defining a series of prisms (any groove form) directly to a glazing surface with adhesive having a percentage of contact,
"In a further aspect, a daylighting sheet defining a series of prisms comprising any groove form having built-in posts enables the daylighting sheet to be adhered directly to a glazing with adhesive contacting only the posts. This construction also advantageously protects the grooves and eliminates the need for a cover sheet.
"In another aspect of the invention, a daylighting sheet such as described in Milner U.S. Pat. No. 5,880,886, defining a series of V grooves, or a prism-form daylighting optical design may be attached directly to a glazing on the groove side with adhesive touching only a percentage,
"Note: for the V grooves with a logo, the viewer will see the rolled edges of the adhesive. For prisms with logo adhesive, wherever the adhesive contacts the prism, the prism function is canceled and becomes 'clear.' A viewer will then see more than the edges in this scenario.
BRIEF DESCRIPTION OF THE DRAWINGS
"The foregoing and other aspects and advantages of the invention may be appreciated from the following detailed description together with the drawings--heuristic for clarity--in which:
"FIGS. 1A and 1B show cross-sectional end views of daylighting microstructures and placement of an adhesive for direct attachment of a daylighting sheet or film to a glazing surface in accordance with an aspect of the invention.
"FIG. 2 shows a perspective view of another variation where a V grooved microstructure of a daylighting sheet or film may be adhered directly to a glazing.
"FIGS. 3A and 3B show perspective assembly and side views, respectively, of a daylighting sheet or film adhered directly to the glazing along the grooved interface according to an aspect of the invention.
"FIGS. 4A and 4B show perspective and side views of another attachment variation where the grooved interface of the daylighting sheet or film may be attached directly to the glazing without adhesives according to an aspect of the invention.
"FIG. 5A shows a perspective view of another variation wherein the adhesive is patterned linearly over a grooved interface for attachment to a glazing according to an aspect of the invention.
"FIG. 5B shows a perspective view of another variation wherein the adhesive is patterned in various configurations over a grooved microstructure defining surface according to an aspect of the invention.
"FIG. 5C shows a perspective view of yet another variation wherein an adhesive border is applied to a periphery around the grooved microstructure defining surface according to an aspect of the invention.
"FIGS. 6A and 6B show perspective assembly and side views, respectively, of a daylighting sheet or film attached directly to a glazing by an adhesive border according to an aspect of the invention.
"FIG. 6C shows a variation of a peripheral border shown in FIGS. 6A and 6B.
"FIG. 7A shows a perspective view of a daylighting sheet or film having its microstructures formed as prisms with a border of adhesive applied directly to the prism interface surface for direct attachment to a glazing according to an aspect of the invention.
"FIG. 7B shows a perspective view of a prism daylighting sheet or film wherein the adhesive is patterned (
"FIGS. 8A and 8B show side views of a prism daylighting sheet or film having a patterned adhesive for direct attachment to a glazing according to an aspect of the invention.
"FIGS. 9A and 9B show side views of a prism daylighting sheet having a patterned adhesive applied directly upon the sheet at a controlled partial depth according to an aspect of the invention.
"FIG. 10 shows a perspective view of a patterned adhesive applied at a controlled partial depth upon a daylighting sheet or film according to an aspect of the invention.
"FIGS. 11A, 11B, and 11C show side views of daylighting microstructures characterized by various forms, such as a series of alternating V grooves, prisms, and flat-topped prisms, separated by a series of troughs or depressions.
"FIG. 12 shows an operational example of the invention for enhancing optical performance, efficiency and light transmission through a daylighting film or sheet comprising a series of V groove microstructures at a sun elevation angle of 70 degrees according to an aspect of the invention.
"FIG. 13 shows an operational example of a negative effect on optical performance at a sun angle of 70 degrees in a conventional configuration for adhering a daylighting sheet or film to a glazing.
"FIG. 14 shows a graphical representation of a comparison of optical performance between the orientations of daylighting microstructures shown in FIGS. 12 and 13.
"FIG. 15 shows a graphical representation or plot of the approximate values of light transmission below the horizontal for the daylighting orientations shown in FIGS. 12 and 13."
URL and more information on this patent application, see: Gardiner,
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