Multilayer windshield film having progressive thickness layers - Patents.com

Abstract

The protective barrier is adapted to be applied to a curved substrate, such as an automobile windshield. The protective barrier may comprise a stack of three or more lenses. Each of the three or more lenses may comprise a thermoplastic film, preferably a polyethylene terephthalate (PET) film, and an adhesive layer on a first surface of the thermoplastic film. The three or more lenses may have thicknesses that define a monotonically decreasing function in a stacking direction of the stack and that comprise at least three different thicknesses. The protective barrier is placed on the curved substrate with the adhesive layer of the innermost lens of the stack in contact with the curved substrate. The stack may be conformed to the shape of the curved substrate by application of heat and pressure. The outermost lens of the stack may then be peeled away to reveal the next lens in the stack.

Description

[Technical field]

[0001] This application relates to a multi-layer windshield film having progressive thickness layers. [Background technology]

[0002] (CROSS REFERENCE TO RELATED PATENT APPLICATIONS) This application is related to U.S. Provisional Application No. 63 / 267,686, filed February 8, 2022, and entitled "MULTILAYER WINDSHIELD FILM HAVING PROGRESSIVE THICKNESS LAYERS." This application claims the benefit of the U.S. Provisional Application, the entire contents of which are expressly incorporated by reference.

[0003] For participants in motor sports such as stock car racing and off-road racing, maintaining visibility of the track is important as mud, bugs, and other debris accumulate on the windshield of the vehicle, causing the windshield to be punctured by hard debris such as rocks. This is also true for general street vehicles. Additionally, auto racers and general street vehicle owners alike have a need to protect the windshield substrate from punctures and cracks, given the high cost and inconvenience of replacing a windshield. In fact, this aspect of the problem is even more pronounced for street vehicles, as there are far more street vehicles in existence and the cost of glass windshields is higher than polycarbonate windshields, such as those commonly used in race cars. To address this need, tear-off films are commonly employed. Tear-off films can be applied individually or in laminated stacks to any type of vehicle windshield. If the outermost tear-off film becomes contaminated with debris or becomes punctured or damaged, the driver simply peels it away to reveal the next clean film underneath. Depending on the number of films in the stack, this process may be repeated several times before the stack is replaced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2004 / 0121105 [Patent Document 2] US Patent Application Publication No. 2021 / 0162645 [Patent Document 3] US Patent Application Publication No. 2021 / 0283994 [Patent Document 4] US Patent Application Publication No. 2022 / 0032591 [Patent Document 5] U.S. Patent No. 9,128,545 [Patent Document 6] U.S. Patent No. 9,295,297 [Patent Document 7] US Patent Application Publication No. 2021 / 0070017 [Patent Document 8] US Patent Application Publication No. 2020 / 0247102 [Non-patent literature]

[0005] [Non-Patent Document 1] Wolfel(o is umlaut) B, Seefried A, Allen V, Kaschta J, Holmes C, Schubert DW, “Recycling and Reprocessing of Thermoplastic Polyurethane Materials towards Nonwoven Processing”, Polymers, 2020,12(9),1917 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have found that much of the protective benefit of a laminate stack of tear-off films comes from the total thickness acting to cushion the impact of hard debris. Unfortunately, this potential benefit is at odds with the functionality of the laminated stack, as the thickness of the stack is dramatically reduced with each removal of film. As a result, the stack is less resistant to impact and may be subject to a significantly increased risk of damage from debris to the underlying windshield during use. Furthermore, there may be a performance trade-off between impact cushioning and increased distortion associated with the use of thicker films. [Means for solving the problem]

[0007] The present disclosure contemplates various systems and methods for overcoming the above-mentioned shortcomings associated with the related art. One aspect of the present disclosure is a protective barrier that can be applied to a curved substrate. The protective barrier may comprise a stack of three or more lenses. Each of the three or more lenses may comprise a thermoplastic film, preferably a polyethylene terephthalate (PET) film or a thermoplastic polyurethane (TPU) film, and an adhesive layer on a first surface of the thermoplastic film. The three or more lenses may define a monotonically decreasing function in the stacking direction of the stack and have thicknesses of at least three different thicknesses.

[0008] The thermoplastic films of the three or more lenses may have thicknesses that define a monotonically decreasing function in the stack direction and have at least three different thicknesses. The thermoplastic film of the innermost lens of the stack may be at least twice as thick, preferably at least three times as thick, as the thermoplastic film of the outermost lens of the stack.

[0009] The thermoplastic film of the innermost lens of the stack may have a thickness of 5 mils (0.127 mm) or more. The thermoplastic film of the innermost lens of the stack may have a thickness of 7 mils (0.1778 mm) or less, preferably 6 mils (0.1524 mm) or less.

[0010] The thermoplastic film of the outermost lens of the stack may have a thickness of 3 mils (0.0762 mm) or less. The thermoplastic film of the outermost lens of the stack may have a thickness of 2 mils (0.0508 mm) or more.

[0011] The adhesive layers of the three or more lenses may define a monotonically decreasing function in the stacking direction and have respective thicknesses of at least three different thicknesses. The adhesive layer of the innermost lens of the stack may be at least twice as thick as the adhesive layer of the outermost lens of the stack. The adhesive layer of the innermost lens of the stack may be at least three times as thick as the adhesive layer of the outermost lens of the stack.

[0012] The thermoplastic films of the three or more lenses can have respective thicknesses that comprise at least two different thicknesses. The adhesive layers of the three or more lenses may have respective thicknesses that comprise at least two different thicknesses.

[0013] The number of the three or more lenses is at least four (four, four). At least two (two, two) of the lenses may have the same thickness. The total thickness of the stack may be between 10 mils (0.254 mm) and 30 mils (0.762 mm). The total thickness of the stack may be between 15 mils (0.381 mm) and 25 mils (0.635 mm).

[0014] Another aspect of an embodiment of the present disclosure is a system. The system may include a vehicle windshield and a protective barrier affixed to the vehicle windshield. The protective barrier may comprise a stack of three (three, three) or more lenses. Each of the three or more lenses may comprise a thermoplastic film, preferably a polyethylene terephthalate (PET) film or a thermoplastic polyurethane (TPU) film, and an adhesive layer on a first surface of the thermoplastic film. The three or more lenses may have thicknesses that define a monotonically decreasing function in a stacking direction of the stack and include at least three different thicknesses.

[0015] The vehicle windshield may be a road vehicle windshield. Another aspect of an embodiment of the present disclosure is a method. The method may include stacking three or more lenses. Each of the three or more lenses may comprise a thermoplastic film, preferably a polyethylene terephthalate (PET) film or a thermoplastic polyurethane (TPU) film, and an adhesive layer on a first side of the thermoplastic film. The three or more lenses may have thicknesses that define a monotonically decreasing function in a stacking direction of the stack and have at least three different thicknesses. The method may further include placing the stack of three or more lenses on a curved substrate with an adhesive layer of an innermost lens of the stack in contact with the curved substrate, and applying heat and pressure to conform the stack of three or more lenses to a shape of the curved substrate.

[0016] The method may include peeling an outermost lens of a stack of three or more lenses after applying said heat and pressure. Another aspect of an embodiment of the present disclosure is a protective barrier that can be applied to a curved substrate. The protective barrier can be configured with a stack of two or more lenses. Each of the two or more lenses can include a thermoplastic film, preferably a polyethylene terephthalate (PET) film or a thermoplastic polyurethane (TPU) film, and an adhesive layer on a first side of the thermoplastic film. The adhesive layers of the two or more lenses can have thicknesses that define a monotonically decreasing function in the stack direction and have at least two different thicknesses.

[0017] Another aspect of an embodiment of the present disclosure is a protective barrier that is applicable to a curved substrate. The protective barrier comprises a stack of one or more lenses, each of which comprises a thermoplastic polyurethane (TPU) film and an adhesive layer on a first side of the thermoplastic polyurethane TPU film.

[0018] These and other features and advantages of the various embodiments disclosed herein will become better understood with regard to the following description and drawings. [Brief description of the drawings]

[0019] [Figure 1] 1 illustrates a cross-sectional view of a protective barrier according to one embodiment of the present disclosure. [Diagram 2] Exploded view of the protective barrier. [Diagram 3] 4 is a cross-sectional view of another protective barrier according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is an exemplary operational flow diagram according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present disclosure encompasses various embodiments of a protective barrier that can be applied to a curved substrate, such as a vehicle windshield, as well as methods of making, installing, and using the same. The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of some currently contemplated embodiments, and is not intended to represent the only manner in which the disclosed invention may be developed or utilized. This specification defines functions and features in conjunction with the illustrated embodiments. However, it is understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the scope of the present disclosure. Furthermore, it should be understood that relationship terms such as first and second are used only to distinguish one entity from another, without necessarily requiring or implying an actual relationship in the order between such entities.

[0021] FIG 1 is a cross-sectional view of a protective barrier 100 according to one embodiment of the present disclosure. The protective barrier 100 may be applied to a substrate 10, such as an automobile windshield, or may comprise a stack of three or more lenses 110, such as lenses 110a, 110b, and 110c shown in FIG 1. Each of the lenses 110 may comprise a thermoplastic film (preferably a polyethylene terephthalate (PET) film) 112 and an adhesive layer 114 on a first side for adhering the lenses 110 to each other and to the substrate 10. Unlike a stack of conventional tear-off films, the three or more lenses 110 may have respective thicknesses that define a monotonically decreasing function (i.e., decrease or remain the same, not increase) in the stacking direction of the stack (i.e., from the lens 110 closest to the substrate 10 to the lens 110 furthest from the substrate 10). The respective thicknesses of the three or more lenses 110 may further include at least three different thicknesses arranged accordingly. Thus, each change in thickness is a decrease, so that the thinner lens 110 is arranged later in the stacking direction (although the stack may include adjacent lenses 110 with the same respective thickness). As shown by way of example in FIG. 1, the three illustrated lenses 110a, 110b, 110c all have different respective thicknesses D. a , D b , D c , and has a thickness D a , D b , D c , decreases from the first (innermost) lens 110a, which is closest to the substrate 10, to the last (outermost) lens 110c, which is farthest from the substrate 10. That is, D a >D b >D cThe described structure allows the protective barrier 100 to maintain a greater total remaining thickness as each lens 110 is removed, as compared to a conventional stack in which all layers have the same thickness. As a result, the cushioning effect of the stack is not significantly reduced as each lens 110 peels off during the life of the protective barrier 100, while improving protection of the substrate 10 against harmful impacts. At the same time, the novel structure of the protective barrier 100 allows a desired balance of performance to be achieved by combining the cushioning effect of a relatively thick film with the reduced distortion of a relatively thin film.

[0022] FIG. 2 is an exploded view of the protective barrier 100 shown in FIG. a , D b , D c can be achieved by adjusting the thickness of any sub-layer of each lens 110. Thus, in the illustrated example where each lens 110 has a thermoplastic film 112 and an adhesive layer 114, the different thicknesses D a , D b , D c , may be the result of varying the thickness of one or both of these two layers (112, 114) of each lens 110. For illustrative purposes, Figures 1 and 2 show one such possibility, where both the thickness of the thermoplastic film 112 and the thickness of the adhesive layer 114 are reduced in the stacking direction. In particular, in the illustrated example, d in Figure 2 1a , d 1b , and d 1c , the thickness of each of the thermoplastic films 112 identified as 1a >d 1b >d 1c In Fig. 2, d 2a , d 2b , and d 2c , d 2a >d 2b >d 2cHowever, any of these relationships may by themselves be inconsistent, e.g., with the thickness of the other layer (i.e., the thickness of the thermoplastic film 112, or the thickness of the adhesive layer 114) remaining constant or having a different relationship, D a >D b >D c This may result in a relationship of

[0023] More generally, considering embodiments in which adjacent lenses 110 may have the same thickness, the thermoplastic films 112 of three or more lenses 110 may have thicknesses that define a monotonically decreasing function in the stacking direction. Additionally or alternatively, the adhesive layers 114 of three or more lenses 110 may have thicknesses that define a monotonically decreasing function in the stacking direction. Furthermore, either or both of the thicknesses of the thermoplastic films 112 or the adhesive layers 114 may include at least two different thicknesses, or even three or more thicknesses. For example, in one practical embodiment, three or more different thicknesses of thermoplastic films 112 are produced, so that the thermoplastic films 112 are stacked together to have a monotonically decreasing thickness in the stacking direction. In some cases, it is considered to keep the thickness of the adhesive layers 114 constant. In such a stack, the thermoplastic film 112 of the innermost lens 110 of the stack may be at least twice as thick, for example, preferably at least three times as thick, as the thermoplastic film 112 of the outermost lens 110 of the stack. Another practical embodiment would be to produce thermoplastic films 112 having the same thickness, but with different amounts of adhesive applied such that the adhesive layers 114 have a monotonically decreasing thickness in the stacking direction. In such a stack, the adhesive layer 114 of the innermost lens 110 of the stack may be at least twice as thick, for example, preferably at least three times as thick, as the adhesive layer 114 of the outermost lens 110 of the stack. Between these two extremes, the thickness of the thermoplastic film 112 or the adhesive layer 114 is allowed to gradually transition from the thickest thermoplastic film 112 or the thickest adhesive layer 114 of the innermost lens 110 to the thinnest thermoplastic film 112 or the thinnest adhesive layer 114 of the outermost lens 110.Preferably, as described in more detail below, the thickness of the thermoplastic film 112 or adhesive layer 114 may transition in discrete steps, rather than perfectly uniformly, as each lens 110 is removed in order to maximize the total thickness remaining of the stack as much as possible.

[0024] FIG. 3 is a cross-sectional view of another protective barrier 300 according to an embodiment of the present disclosure. Similar to the protective barrier 100, the protective barrier 300 may be applied to a substrate 10, such as an automobile windshield, and may be configured with a stack of three or more lenses 110 (possibly two or more lenses 110), in this case lenses 110a, 110b, 110c, and an additional lens 110c. Each of the lenses 110 may be the same as described in connection with FIG. 1, or may include a thermoplastic film (preferably a polyethylene terephthalate (PET) film) 112 and an adhesive layer (114) on a first side of the thermoplastic film 112 for bonding the lenses 110 together and to the substrate 10. The example of the protective barrier 300 of FIG. 3 is provided to illustrate that the monotonically decreasing function described above may allow adjacent lenses 110 that are the same thickness. In this regard, FIG. 3 illustrates the thickness of the thinnest lens 110c (thickness D c 1 illustrates a specific case where lenses 110 are repeated. More generally, any of the lenses 110 may be repeated any number of times within the meaning of the monotonically decreasing function contemplated herein. For example, there may be two lenses 110a, two lenses 110b, and two lenses 110c. Or there may be three lenses 110a, one lens 110b, and three lenses 110c. Thus, for example, the three or more lenses 110 contemplated may be four or more, with two (or more) of the lenses having the same thickness. It should also be noted that there is no limit to the number of lenses 110 made differently with different thicknesses. That is, the number of lenses 110 with different thicknesses D d (Here, D d <D c) and one or more lenses 110d having a thickness D e (Here, D e <D d ), and so on. Typically, however, the total number of lenses 110 may be five (five, five) or less, so as not to introduce too much optical distortion into the protective barrier 100.

[0025] In general, the thickness of the lenses 110 of the protective barriers 100, 300 contemplated herein may transition evenly or, preferably, in discrete steps from the thickest (innermost) lens 110 to the thinnest (outermost) lens 110 to maximize the total remaining thickness of the stack as each lens 110 is removed. As a numerical example, Table 1 below compares the remaining stack thickness in mils for three hypothetical protective barriers as each lens 110 is removed. In each case, the starting total thickness (total thickness) of the stack is 20.00 mils (0.508 mm) and there are four lenses 110. The particular constraints on the thickness of each lens will depend on the quality or strength of the polyethylene terephthalate PET used (e.g., a higher quality polyethylene terephthalate PET may allow for a thinner thermoplastic film 112) and the particular application (e.g., a thicker thermoplastic film 112 may be made usable where a higher degree of optical distortion is acceptable), and in each case it is assumed that the thinnest thermoplastic film 112 usable is 2.00 mils (0.0508 mm) and the thickest thermoplastic film 112 usable is 7.00 mils (0.1778 mm) (note, however, that a stronger polyethylene terephthalate PET may allow for a thermoplastic film 112 of 1.00 mils (0.0254 mm) in some cases). In this example, it is assumed that the thickness of the adhesive layer 114 is held constant at 0.50 mils (0.0127 mm) for each lens 110, and that the thickness of each lens 110 ranges from 2.50 mils (0.0635 mm) to 7.50 mils (0.1905 mm).

[0026]

Table 1

[0027] In Table 1, the protective barrier labeled as "Constant Thickness" has four lenses 110 of equal thickness, each 5.0 mil (0.127 mm). Meanwhile, the two protective barriers labeled as "Progressive Thickness 1" and "Progressive Thickness 2" show monotonically decreasing thicknesses from the innermost lens to the outermost lens, with at least three thicknesses, as described herein. As can be seen from the comparison between the different hypothetical protective barriers in Table 1, the total remaining thickness in the "Progressive Thickness 1" and "Progressive Thickness 2" examples is significantly greater than that in the "Constant Thickness" example as each lens 110 is removed. Such a remaining stack provides a superior cushioning effect to withstand impact. For example, after the outermost lens (lens number 4) was removed, the "constant thickness" stack dropped from a total thickness of 20.00 mils (0.508 mm) to a total thickness of 15.00 mils (0.381 mm), while the two "progressive thickness" examples only dropped to a total thickness of 17.50 mils (0.4445 mm). The "progressive thickness" examples continue to maintain more total thickness as lenses 110 are removed. The monotonically decreasing thickness of "progressive thickness 1" represents a constant even transition in thickness change from one lens 110 to the next. The monotonically decreasing thickness of "Progressive Thickness 2" represents an uneven transition exhibited by discrete steps, such that there are relatively thin stages of lenses 110 at the outermost portions of the stack (2.50 mils (0.0635 mm) and 3.00 mils (0.0762 mm)) while there are relatively thicker stages of lenses 110 at the innermost portions of the stack (7.00 mils (0.1778 mm) and 7.50 mils (0.1905 mm)). Arranging the thicknesses of the lenses 110 in this manner allows for further optimization of the thickness remaining when each lens 110 is removed.For example, "Progressive Thickness 2" retains a total thickness of 14.50 mils (0.3683 mm) after the second lens 110 is removed, while "Progressive Thickness 1" only retains a total thickness of 13.33 mils (still far superior to the 10.00 mils (0.254 mm) total thickness retained in the "Constant Thickness" example). Thus, the non-uniform transition between the thickest and thinnest lenses 110 may further optimize the protective barrier 100 for protection against impact during use, since a greater total thickness remains after each lens 110 is removed.

[0028] In the above examples described in connection with Table 1, it is assumed that the thickness of the adhesive layer 114 is held constant at 0.50 mils (0.0127 mm), with the thickness of the thermoplastic film 112 being 4.50 mils (0.1143 mm) for the "constant thickness" example and transitioning from 7.00 mils (0.1778 mm) to 2.00 mils (0.0508 mm) for the two progressive thickness examples ("Progressive Thickness 1" and "Progressive Thickness 2"). In general, when implementing the disclosed monotonic thickness decrease, it is contemplated that the thermoplastic film 112 of the innermost lens 110 in the stack and the thermoplastic film 112 of the lens 110 closest thereto are preferably allowed to be relatively thick (e.g., 5 mils (0.127 mm) or greater) so that the greatest portion of the total thickness of the protective layer (100) is concentrated at the innermost part of the stack. At the same time, the thickness of this innermost thermoplastic film 112 is preferably not more than 7 mils (0.1778 mm), more preferably not more than 6 mils (0.1524 mm), to keep the degree of optical distortion within a range suitable for a windshield application. For the outermost lens 110 of the stack and the thermoplastic film 112 of the lens 110 nearest it, the thickness is preferably not more than 3 mils (0.0762 mm), so that the first lens 110 removed from the stack does not significantly reduce the total thickness of the stack. At the same time, the thickness of the outermost thermoplastic film 112 (i.e., minimum film thickness) is typically at least 2 mils (0.0508 mm) or more so that it has sufficient strength to withstand the forces associated with a user peeling the lens 110 from the stack during use. However, it should be noted that because the outermost thermoplastic film 112 does not need to bear the tensile force of the previous (i.e., higher) adhesive layer, the thermoplastic film 112 of the outermost lens 110 may, in some cases, be significantly thinner than the thermoplastic film 112 of the lens 110 below it.

[0029] As mentioned above, the different thicknesses D a , D b , D cThis can be accomplished by adjusting the thickness of any sub-layer of each lens 110 that includes adhesive layer 114. In this regard, the thickness of adhesive layer 114 can typically vary between a minimum thickness of, for example, 0.050 mils (0.00127 mm) or more and a maximum thickness of 2.00 mils (0.0508 mm) or less.

[0030] FIG. 4 is an exemplary process flow according to an embodiment of the present disclosure. The process flow of FIG. 4 may serve as an exemplary method of manufacturing, installing, and using a protective barrier 100, 300 comprising a stack of lenses 110 as shown and described in connection with FIGS. 1-3. The process flow may begin with providing a thermoplastic film 112 to be used for each of the three or more lenses 110 (step 410). The thermoplastic film 112 for each lens 110 may be biaxially oriented polyethylene terephthalate (BoPET) and may be selected for specific MTF (modulation transfer function) data. Alternatively, the thermoplastic film 112 for each lens 110 may be manufactured in a continuous or batch-to-batch process with active monitoring of modulation transfer function MTF data, as described in either U.S. Pat. No. 6,399,411 entitled "Method and Apparatus for Reducing Non-Normal Incidence Distortion in Glazing Films," U.S. Pat. No. 6,399,411 entitled "Protective Barriers for Safety Glazing," or in U.S. Pat. No. 6,399,433 entitled "Method and Apparatus for Reducing Non-Normal Incidence Distortion in Glazing Films," which is a commonly owned U.S. patent application Ser. No. 17 / 505,433. The entire contents of each of these are incorporated herein by reference. In this regard, providing the thermoplastic film 112 may include, for example, melting a resin, extruding the molten resin through a die to produce a polymer film, and cooling the polymer film. Each thermoplastic film 112 may be coated on one side with an adhesive layer 114 (step 420). This adhesive layer 114 is preferably wet deposited, but may be applied according to any suitable method including spin coating, dip coating, or vacuum deposition. The adhesive layer 114 may be a wet mount adhesive, such as disclosed in U.S. Patent No. 5,399,633, entitled "Touch Screen Shield," or a dry mount adhesive, such as disclosed in U.S. Patent No. 5,399,633, entitled "Adhesive Mountable Stack of Removable Layers," the entire contents of each of which are incorporated herein by reference.The adhesive (114) may be an acrylic or silicone adhesive, such as an acrylic pressure sensitive adhesive (PSA) or a silicone PSA.

[0031] With the thermoplastic film 112 coated with the adhesive layer 114, the operational flow of FIG. 4 can be continued by laminating three or more of the resulting lenses 110 to produce a stack of progressive thickness (step 430). For example, as described above, either or both of the thickness of the thermoplastic film 112 and the thickness of the adhesive layer 114 can vary according to a monotonically decreasing function from the innermost lens 110 to the outermost lens 110. The thickness of each lens 110 can be less than or equal to the thickness of the previous lens 110 in the stacking direction. In addition to the thermoplastic film 112 and the adhesive layer 114, each lens 110 can include a hard coat, such as described in the aforementioned U.S. Pat. No. 5,994,333 (the '994 patent), a UV blocking layer, or a thermochromic film, such as described in U.S. Pat. No. 5,994,333 entitled "Nanoparticle Solar Control Film," the entire contents of which are incorporated herein by reference. The thickness of such additional layers can likewise be controlled to maintain the monotonically decreasing thicknesses described herein. The total thickness of the stack of lenses 110 is preferably between 10 mils (0.254 mm) and 30 mils (0.762 mm), more preferably between 15 mils (0.381 mm) and 25 mils (0.635 mm) (e.g., 20 mils (0.508 mm) as in the above example of Table 1). To keep optical distortion as low as possible, the refractive indices of the thermoplastic film 112, adhesive layer 114, and other layers within each lens 110 and between each of the lenses 110 can be matched to within 0.2 as described in the '297 patent mentioned above.

[0032] Once the protective barrier 100 comprising the stack of lenses 110 has been assembled, the operational flow can continue by placing the protective barrier 100 on a curved substrate (curved substrate 10), such as a windshield (front glass) of an automobile or other vehicle. Continuing with the operational flow of FIG. 4, the protective barrier 100 comprising the stack of lenses 110 can be placed (step 440) on a windshield or other curved substrate (10) with the adhesive layer (114) of the bottom lens 110a (see FIGS. 1-3) in contact with the curved substrate (10). To facilitate attachment, the protective barrier 100 can be roughly cut (e.g., using an electric film cutter) so that it does not protrude too far outside the windshield (10). The operational flow can continue by applying heat and pressure to conform the stack of three or more lenses 110 to the shape of the curved substrate (10) (step 450). In particular, the application of heat and pressure may be performed at least partially before the adhesive layer 114 of each of the three or more lenses 110 is fully cured, for example, before the adhesive layer 114 exceeds a peel strength of 25 grams per inch (25.4 mm), determined as the constant load per unit width required for peeling. The protective barrier 100 may be fully conformed to the shape of the curved substrate (10) before the adhesive layer 114 is fully cured. In some cases, the protective barrier 100 may be applied to the substrate 10 by using a sacrificial layer that acts as a female cavity to sandwich the stack of lenses 110 between the sacrificial layer and the substrate 10, as described in U.S. Patent Application Publication No. 2005 / 0139994, entitled “THERMOFORM WINDSHIELD STACK WITH INGLATED FORMABLE MOLD,” the entire contents of which are incorporated herein by reference. After the protective barrier 100 is allowed to cool, the attachment may be completed by final trimming to fit the windshield or other substrate 10.

[0033] As discussed above, it is contemplated that in a protective barrier 100 having more than one lens 110, the outermost lens 110 may be peeled away and removed to expose an unused surface of the underlying lens 110. In this regard, the operational flow of FIG. 4 may be allowed to continue throughout the life of the protective barrier 100 installed on a vehicle windshield or other substrate 10. If the outermost lens 110 unacceptably degrades over time (e.g., after six months, a year, after wiper blade scratches begin to appear, etc.), it may be peeled away to expose the next underlying lens 110 (step 460). The timing of peeling away the outermost lens 110 may depend on the particular climate in which the protective barrier 100 is used, such as climates that have high sun exposure or require frequent wiper blade use. Because the thickness of the stack of lenses 110 is gradual, the total thickness of the protective barrier 100 remains significantly greater after removal of the outermost lens 110 than a stack of conventional tear-off lenses, resulting in a longer lasting cushioning effect against impacts over the life of the protective barrier 100.

[0034] It is noted in the above disclosure that polyethylene terephthalate PET (e.g., biaxially oriented polyethylene terephthalate BoPET) may be the preferred thermoplastic film 112. However, the material of the thermoplastic film 112 is not necessarily limited in this respect. For example, any or all of the thermoplastic films 112 of the lens 110 may instead be thermoplastic polyurethane (TPU) films, such as optically clear thermoplastic polyurethane TPU films. The thermoplastic polyurethane TPU films may be manufactured to have a visible light transmission (VLT) of 85% or more (e.g., 90-95%) while having low haze (e.g., 1% or less). The thermoplastic polyurethane TPU films may be, for example, 2 mils (0.0508 mm) or more. Advantageously, the use of thermoplastic polyurethane TPU for the thermoplastic film 112 of the protective barrier 100 may require less expertise on the part of the installer and may allow for a faster installation process compared to the use of polyethylene terephthalate PET. This is because no heat needs to be applied to thermoform the film or stack, or only very little heat is needed to thermoform the thermoplastic polyurethane TPU in a few seconds when the film is installed, and the thermoplastic polyurethane TPU is easy to apply to 2D or 3D curved surfaces. Notably, the thermoplastic polyurethane TPU is not only more stretchable than polyethylene terephthalate PET, but also requires less heat to achieve the desired stretchability. Common problems such as fingering (imperfect application of air bubbles under the film) that occur when installing polyethylene terephthalate PET-based stacks must be avoided and corrected with specific thermoforming techniques. Correcting such imperfections is time-consuming and increases the time required for professional installation. In contrast, the thermoplastic polyurethane TPU, with its strong elasticity and elongation properties, does not require as much skill and may not even require professional skills in some cases.

[0035] As a result of the above advantages, the use of thermoplastic polyurethane TPU for the thermoplastic film(s) 112 allows for significantly lower installation costs than polyethylene terephthalate PET-based thermoplastic film(s) 112. This can result in a very affordable product, which is particularly important as a protective barrier for the underlying windshield as windshield costs increase due to advanced driver assistance systems (ADAS) technology, increased windshield curvatures in new vehicle designs, and larger windshield sizes in new vehicle designs. It is also contemplated that the thermoplastic polyurethane TPU-based film (112) can outlast the polyethylene terephthalate PET-based film (112), with or without a protective hard coat. Thus, the use of thermoplastic polyurethane TPU in the disclosed embodiments (as well as protective films in general, whether in a single layer stack as described below) can result in lower cost films, significantly shorter installation times (e.g., one-fifth the installation time), longer life, and lower cost per windshield per year (e.g., one-tenth the cost of polyethylene terephthalate PET-based protective films) because the underlying windshield is protected from damage, cracking, or punctures.

[0036] Furthermore, when a windshield is replaced in the United States, over 95% of the time the old windshield is not recycled, even if it could be recycled by being sent to a third-party recycling company. The majority of the estimated 15 million broken windshields are dumped into landfills every year in the United States alone, causing massive pollution (Recycling and Reprocessing of Thermoplastic Polyurethane Materials for Nonwoven Fabric Processing (https: / / doi.org / 10.3390 / polym12091917)). A significant portion of such waste can be avoided by using one or more protective TPU films in layers. Meanwhile, TPU itself is easily recycled, making it a 100% recyclable and biodegradable material. TPU is recyclable and biodegrades in 3 to 5 years, making it a much more environmentally friendly advanced material than alternatives such as polyvinyl chloride (PVC). Assuming that glass windshield materials, which can take hundreds of thousands of years to decompose in landfills, do not decompose at all, TPU is a much more environmentally friendly material.

[0037] It is contemplated that the thermoplastic polyurethane TPU-based film (112) can advantageously replace the polyethylene terephthalate PET-based film (112) of the protective barrier 100 disclosed above. However, the above disclosure regarding the advantages of using the thermoplastic polyurethane TPU-based film (112) is not intended to be limited to use only in the protective barrier 100 described herein. The thermoplastic polyurethane TPU-based film (112) can be used, for example, in other multi-layer stacks of lenses 110 or in a single layer stack of a single lens 110. A single layer stack, for example, of a single lens 110, can comprise, for example, a thermoplastic polyurethane TPU film (112), an adhesive layer 114 for adhering the lens 110 to the substrate 10, and optionally a hard coat, a UV blocking layer, a thermochromic film, etc., as described above.

[0038] The above description is provided for illustrative purposes and not for limitation. Given the above disclosure, those skilled in the art will be able to devise variations that are within the scope and spirit of the invention disclosed herein. Furthermore, the various features of the embodiments disclosed herein can be used alone or in various combinations with each other and are not intended to be limited to the specific combinations described herein. Thus, the claims are not limited by the illustrated embodiments.

Claims

1. 1. A protective barrier applicable to a curved substrate, the protective barrier comprising a stack of three or more lenses; each of the three or more lenses comprises a thermoplastic film and an adhesive layer on a first surface of the thermoplastic film; The three or more lenses define a monotonically decreasing function in a stacking direction of the stack and have respective thicknesses among at least three different thicknesses. Protective barrier.

2. the thermoplastic films of the three or more lenses define a monotonically decreasing function in the stacking direction of the stack and have respective thicknesses of at least three different thicknesses; The protective barrier of claim 1 .

3. the thermoplastic film of the innermost lens of the stack is at least twice as thick as the thermoplastic film of the outermost lens of the stack; The protective barrier of claim 2.

4. the thermoplastic film of the innermost lens of the stack has a thickness of 5 mils (0.127 mm) or greater; The protective barrier of claim 1 .

5. the thermoplastic film thickness of the innermost lens of the stack is 7 mils (0.1778 mm) or less; 5. The protective barrier of claim 4.

6. the thermoplastic film of the outermost lens of the stack has a thickness of 3 mils (0.0762 mm) or less; The protective barrier of claim 1 .

7. the thermoplastic film thickness of the outermost lens of the stack is 2 mils (0.0508 mm) or greater; 7. The protective barrier of claim 6.

8. the adhesive layers of the three or more lenses define a monotonically decreasing function in the stacking direction of the stack and have respective thicknesses of at least three different thicknesses; The protective barrier of claim 1 .

9. the adhesive layer of the innermost lens of the stack is at least twice as thick as the adhesive layer of the outermost lens of the stack; 9. The protective barrier of claim 8.

10. the adhesive layer of the innermost lens of the stack is at least three times as thick as the adhesive layer of the outermost lens of the stack; 10. The protective barrier of claim 9.

11. The thermoplastic films of the three or more lenses have respective thicknesses among at least two different thicknesses. The protective barrier of claim 1 .

12. The adhesive layers of the three or more lenses have respective thicknesses among at least two different thicknesses. The protective barrier of claim 1 .

13. The number of the three or more lenses is at least four. The protective barrier of claim 1 .

14. At least two of the lenses have the same thickness.

14. The protective barrier of claim 13.

15. the total thickness of said stack is between 10 mils (0.254 mm) and 30 mils (0.762 mm); The protective barrier of claim 1 .

16. the total thickness of the stack is between 15 mils (0.381 mm) and 25 mils (0.635 mm); 16. The protective barrier of claim 15.

17. The thermoplastic film is a polyethylene terephthalate (PET) film; The protective barrier of claim 1 .

18. The thermoplastic film is a thermoplastic polyurethane (TPU) film; The protective barrier of claim 1 .

19. A vehicle windshield; a protective barrier affixed to the vehicle windshield, the protective barrier comprising a stack of three or more lenses, each of the three or more lenses comprising a thermoplastic film and an adhesive layer on a first surface of the thermoplastic film, the three or more lenses defining a monotonically decreasing function in a stacking direction of the stack and having respective thicknesses of at least three different thicknesses; The system comprises:

20. The vehicle windshield is a windshield of a road vehicle.

20. The system of claim 19.

21. The thermoplastic film is a polyethylene terephthalate (PET) film; 20. The system of claim 19.

22. The thermoplastic film is a thermoplastic polyurethane (TPU) film; 20. The system of claim 19.

23. 1. A method, comprising: stacking three or more lenses, each of the three or more lenses comprising a thermoplastic film and an adhesive layer on a first side of the thermoplastic film, the three or more lenses defining a monotonically decreasing function in a stacking direction of the stack and having respective thicknesses of at least three different thicknesses; placing the stack of three or more lenses onto the curved substrate such that the adhesive layer of an innermost lens of the stack contacts the curved substrate; applying heat and pressure to cause the stack of three or more lenses to conform to the shape of the curved substrate; The method comprises:

24. The method further comprises peeling an outermost lens of the stack of three or more lenses after the applying of the heat and the pressure.

24. The method of claim 23.

25. The thermoplastic film is a polyethylene terephthalate (PET) film; 25. The method of claim 24.

26. The thermoplastic film is a thermoplastic polyurethane (TPU) film; 25. The method of claim 24.

27. 1. A protective barrier applicable to a curved substrate, the protective barrier comprising a stack of two or more lenses; each of the two or more lenses comprises a thermoplastic film and an adhesive layer on a first surface of the thermoplastic film; the adhesive layers of the two or more lenses define a monotonically decreasing function in a stacking direction of the stack and have respective thicknesses of at least two different thicknesses; Protective barrier.

28. The thermoplastic film is a polyethylene terephthalate (PET) film; 28. The protective barrier of claim 27.

29. The thermoplastic film is a thermoplastic polyurethane (TPU) film; 28. The protective barrier of claim 27.

30. A protective barrier applicable to a curved substrate, the protective barrier comprising a stack of one or more lenses; Each of the one or more lenses comprises a thermoplastic polyurethane (TPU) film and an adhesive layer on a first surface of the thermoplastic polyurethane film. Protective barrier.

Images