FIELD OF THE INVENTION

|00011 This invention relates to glass. In particular, the invention relates to bird collision-averting window panes, glass railings or glass barriers that reduce the incidence of birds flying into glass.

BACKGROUND OF THE INVENTION

[ 00021 Birds flying into glass panes, particularly into windows in high rise structures which often make up the greater part of the surface of the walls in a high rise structure, is a significant ecological problem. Particularly in the case of migratory birds, during peak migration periods the number of bird fatalities from striking window panes is staggering. Some sources estimate that in North America alone over one billion birds die each year from flying into windows, glass railings and other glass barriers.

100031 The bulk of window collisions occur for two primary reasons. In daylight when the outdoor ambient light is bright, birds crash into windows when they see the reflection of a landscape off of the window, or when they see plants or other natural vegetation through the window. The second reason occurs at night when windows are illuminated from inside a structure, which for reasons that are not entirely clear seems to attract nocturnal migrant species and divert them from their intended flight path.

100041 There are many sources of information and suggestions on how to prevent birds from hitting windows. Some solutions involve substantially eliminating the illumination of a window by such actions as turning out interior lights or closing blinds or other window coverings at night. Turning out lights is not practical where there are persons in the premises at night, and further relies on individuals to remember to take such steps, as does closing window coverings. Outdoor coverings such as bird exclusion netting are not practical for use on high rise buildings due to wind and installation issues. Other solutions involve imprinting or forming the window with a material having an opaque or translucent pattern, which a bird processes as an obstruction, but applying a permanent pattern to the glass itself reduces visibility through the window to humans and occludes outdoor light coming into the structure, even at times when bird collisions are unlikely.

|0005| It would accordingly be advantageous to provide a means of encouraging birds to avoid flying toward glass panes, for example as used in windows, glass railings and other glass barriers, that does not require human intervention in order to be effective and does not substantially obscure the view through the window or occlude light shining into the premises.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In drawings which illustrate by way of example only a preferred embodiment of the invention,

|0007] Figure 1 is a perspective view of a first embodiment of a laminated window pane according to the invention.

100081 Figure 2 is a partially exploded view of the construction of the window pane of Figure 1.

|0009| Figure 3 is a perspective view of a further embodiment of a laminated window pane according to the invention.

|0010| Figure 4 is a partial cross-sectional elevation of the window pane of Figure 3.

100111 Figure 5 is a perspective view of a further embodiment of a window pane according to the invention.

100121 Figure 6 is a side elevation of the window pane of Figure 5.

|0013| Figure 7 is an enlarged partial cross-sectional elevation of the window pane of Figure 5. DETAILED DESCRIPTION OF THE INVENTION

|0014| The invention provides a glass pane coated, filled or laminated with at least one layer containing a sufficient quantity of an optical brightener to cause at least some birds to sense the glass pane as an obstacle and avoid colliding with the glass pane.

|0015| The invention further provides a method of reducing incidence of birds colliding with a glass pane in a structure, comprising the steps of: a. coating the pane with at least one layer containing a sufficient quantity of an optical brightener to cause at least some birds to sense the pane as an obstacle and avoid colliding with the window pane, and b. installing the coated glass pane into a frame affixed to the structure.

10016] The invention will be described in the context of a window pane by way of non- limiting example, however the description of the invention applies equally to outdoor glass barriers such as railings and the like.

|0017| According to the invention, in order to avert bird collisions at least one glass pane, for use for example as a window pane 10, is laminated or filled with at least one layer containing an optical brightener. As used herein the term 'laminate' includes the application of a coating in either solid form (for example as a sheet laminate) or liquid form (for example as a resin).

|0018| Optical brighteners, also known as "fluorescent whitening agents," are used to "whiten" or "brighten" the appearance of such materials as clothing fibers, plastics and other polymers, paints, inks and other materials where a white colour is considered to be aesthetically relevant or important. An optical brightener is a fluorescing compound which fluoresces by absorbing light in the ultraviolet (UV) portion of the electromagnetic radiation (EMR) spectrum, for example typically within the range generally between about 300 and about 400 nanometers, and emitting light in visible EMR wavelengths, generally within the visible blue portion of the spectrum between about 400 and about 500 nanometers. |0019| As used herein the term "optical brightener" means a compound that, either in solid form or in solution, fluoresces by absorbing ultraviolet light and emitting EMR of a longer wavelength, typically in the visible light portion of the EMR spectrum. An optical brightener, such as (by way of non-limiting example only) 2,2'-(l,2-ethenediyl)bis(4,l- phenylene)bisbenzoxazole, available for example from Mayzo, Inc. and sold under the name Benetex OB- 1 (Trademark), may be mixed into a resin, paint or other solvent-based composition in the liquid phase to produce an optical brightening layer that can be applied to a pane of glass to avert bird collisions, for example in the manners described below.

[0020| Other non-limiting examples of optical brighteners suitable for use in embodiments of the invention include: 2,2'-(2,5-fhiophenediyl)bis(5-tert- butylbenzoxazole), available for example from Mayzo, Inc. and sold under the name Benetex OB Plus (Trademark); 2,2'-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole), available for example from Mayzo, Inc. and sold under the name Benetex OB

(Trademark); and Benzenesulfonic acid, 2,2'-([l,T-biphenyl]-4,4'-diyldi-2,l- ethenediyl)bis-, sodium salt (1 :2), a water-soluble derivative of distyryl biphenyl (DSBP), available for example from Mayzo, Inc. sold under the name Benetex OB- Ml (Trademark).

|002l I An optical brightening layer may be formed from a mixture of at least about 0.1 grams of optical brightener per 1000 cubic centimetres (cc) of a thermoplastic, thermosetting, or ionoplastic polymer resin, for example polyester (PE), polyurethane (PUR), polyvinyl butyral (PVB), ethylene- vinyl acetate (EVA) or SentryGlas Plus (Trademark) (SGP). An optical brightening layer may alternatively be formed from a mixture of at least about 0.1 grams of optical brightener per lOOOcc of a suitable

(preferably but not necessarily clear) paint or other solvent-based composition.

Optical brightening laminate layer

100221 Figures 1 and 2 illustrates a first embodiment of a double-glazed window pane 10 comprising an optical brightening laminate layer 16 disposed between two glass panes 12, 14. The laminate layer may be formed from a polymer film such as (without limitation) polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) or an ionoplastic interlayer film such as SentryGlas Plus (Trademark) (SGP) that has been doped during manufacture with a suitable amount of an optical brightener. In this embodiment the doped laminate may be applied to the glass in conventional fashion, for example by interposing the optical brightening laminate layer 16 between the glass panes 12, 14.

|0023| In a further laminated embodiment, illustrated in Figures 3 and 4, a double- glazed window pane 20 is produced with an optical brightening laminate layer 22 between the two panes of glass 12, 14 formed from a liquid laminate, such as (without limitation) polyester (PE) or polyurethane (PUR) doped with an optical brightener. This double-glazed window pane 20 can be constructed, for example, by applying a 1/16 inch silicon-based double-sided adhesion tape 24 around the periphery of one glass pane 14, as shown in Figure 3, and adhering the second glass pane 12 to the tape 24. The void between the two panes 12, 14 is filled with the liquid laminate 22, which intrudes into the air gap between the panes 12, 14 by capillary action. Once the liquid laminate 22 has cured, the collision-averting window pane 20 is ready to be installed.

|0024| In this embodiment the base resin is doped with an optical whitener by mixing the optical whitener (which may for example be in powder form) into the resin in a desired proportion, for example at least about 0.1 grams per lOOOcc resin and preferably about 2 grams per lOOOcc resin. This proportion may vary depending upon the type of optical brightener, the type of resin and the desired degree of fluorescence.

|0025| Many species of birds are sensitive to wavelengths in the ultraviolet portion of the EMR spectrum, which is believed to be involved in mate selection, territorial displays and foraging for food. It is not clear whether it is the absorption of UV wavelengths or the emission of visible wavelengths by the doped resin layer 22 that makes the window pane 20 look unusual to a bird, however it has been found that the construction of a window pane with the doped resin layer 22 has the effect of averting a substantial number of bird collisions. In tests, the laminated embodiment of Figures 3 and 4 scored 82 to 86 aversions per 100 potential collisions. Optical brightening films and coatings

[0026| Further embodiments of a bird collision averting window pane 30 are illustrated in Figures 5 to 7. In these embodiments a single glass pane 32 is coated with a doped optical brightening film layer 34, with a clear coat paint containing an optical brightener, or with a sputtered or possibly pyrolytic optical brightening coating.

[00271 The doped film layer 34 may for example (without limitation) comprise conventional window film such as polyester (PE), polyethylene terephthalate (PET) or any other film capable of being doped with a suitable amount of optical brightener and adhered to a glass pane 32. This embodiment is particularly suitable for retrofitting the doped film layer 34 to an existing window pane, for example by conventional window application adhesives and methods.

[0028] The film layer 34 containing the optical brightener need not be homogeneous. While the optical brightener may be dispersed substantially uniformly throughout the coating, it is also possible to apply a shape or pattern utilizing for example the film illustrated in Figures 5 to 7. Optical brighteners have such a minimal effect on

transparency of the window pane in the visible wavelengths that it would ordinarily be unnecessarily complicated and costly to apply an optical brightening layer 34 in the shape of a pattern. However, it may in certain circumstances be advantageous to utilize a pattern or shape, for example the silhouette of a predator bird species that may appear to a bird as a hazard rather than merely an obstruction.

[0029[ Combinations of the embodiments described above are also possible. This allows for the creation of multiple optical brightening layers and as such would provide an opportunity to use different optical brighteners in a single window pane. Alternatively, it may be possible to combine different optical brighteners in a single layer.

[0030| It may also be possible to 'hard-coat' a glass pane with an optical brightener to achieve the desired collision-aversion effect. For example, a coating material doped with an optical brightener may be applied to the surface of glass in a molten state, typically during manufacture of the pane, known as "pyrolytic" coating. |003l I A clear coat or clear paint having a desired proportion of optical brightener mixed into the paint can be applied to the glass pane in any suitable fashion, preferably sprayed or roller coated in order to produce a relatively uniform layer once the paint cures. The optical brightener is mixed into the paint so that in the resulting transparent layer of cured paint the optical brightener is present in a sufficient quantity as to be visible to birds.

(00321 Alternatively, a doped solution may be applied to a glass pane 32 in the solid state by conventional sputtering techniques, for example by chemical vapour deposition or plasma vapour deposition in an arc coating reactor. In this embodiment it may be possible to apply the optical brightening layer 34 at the same time as a 'low-e' layer, commonly used in windows for high rise buildings, in which a metal oxide layer may be applied to the glass by various methods including magnetron sputtering.

Example I

|0033) A water-soluble derivative of distyryl biphenyl (DSBP), available for example from Mayzo, Inc. sold under the name Benetex OB-MI (Trademark) and having the chemical structure:

was mixed into a clear paint coating in the proportion of about 2 grams of optical brightener to 1 OOOcc of a clear glass coating paint, Linea Vetro (Trademark) from ICA Paints. The mixture was sprayed onto the 'air' side of a pane of glass to provide a substantially uniform coating having a thickness of between about 2 mils to 12 mils and allowed to cure. The 'air' side of a glass pane is generally rougher than the 'tin' side and therefore provides better adhesion, so there may be a slight preference for applying the coating to the air side of the pane, however the coating may be applied to either face of the pane. Depending upon the type of coating and method of its application, the coated face may form the interior face of the window pane to protect the coating from the elements.

Example 2

10034] A window pane was laminated using a polyester resin containing 2,2'-(l ,2- ethenediyl)bis(4,l-phenylene)bisbenzoxazole (Mayzo, Inc. OB-1) in the ratio of about 2 grams to lOOOcc of resin. The resin was allowed to cure, forming an interlayer about 1.5 mm thick.

100351 The glass pane formed in this example was tested in accordance with the standard testing protocol of the American Bird Conservatory, and achieved an avoidance index of 83% in sunny conditions, 100%) in cloudy conditions and 85% in partly cloudy conditions. These results are well above the 70%> bird avoidance minimum standard of the American Bird Conservatory.

100361 Experimentation with processed glass panes, for example sandblasted glass, anti -reflective glass etc. may yield improved collision-aversion results.