Polymeric Safety Glazing for Vehicles

Abstract

The laminate includes a polycarbonate substrate and an ultraviolet hard-coat film disposed on the polycarbonate substrate. The ultraviolet hard-coat film may include a polyethylene terephthalate (PET) layer, an adhesive interposed between the PET layer and the polycarbonate substrate, and an outer hard-coat disposed on the PET layer opposite the polycarbonate substrate. The outer hard-coat may include a UV stabilizer. The laminate may also include an additional ultraviolet hard-coat film laminated on the ultraviolet hard-coat film. The laminate can be thermoformed into the shape of a curved vehicle windshield.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to safety glazing, and more particularly to polymeric safety glazing for vehicle windows, including windshields. [Background technology]

[0002] Safety glazing has historically been made of glass. Glass has a hardness that allows it to withstand scratches from windshield wipers and some abrasive debris. It is also very economical and lends itself to mass production techniques. However, glass is prone to breaking and can produce dangerous sharp shards that can injure passengers and cause personal injury. This problem has been mitigated to some extent by strengthening the glass, breaking it into small shards (1 / 2”), and laminating two pieces of glass with a flexible polymer polyvinyl butyral (PVB) core between them to hold the small shards together.

[0003] Unfortunately, glass safety glazing is susceptible to pitting from small agglomerates and dust in the air, which can reduce visibility when moving toward the sun. Over 15 million glass windshields are replaced each year in the United States alone due to pitting and breakage. Additionally, laminated glass-PVB-glass windshields cannot be recycled because the PVB core contaminates the glass.

[0004] Considering the shortcomings of glass safety glazing, passenger lacerations are a long-standing problem with no ideal solution. For example, 30 years of research has attempted to place polymer coatings or layers on the interior of glass windshields, but without any commercial success.

[0005] Polycarbonate exhibits excellent impact resistance and is used for vehicle glazing in auto racing and off-road vehicles. However, polycarbonate is a very soft material, making it too susceptible to scratches and punctures for use in commercial and public vehicles. To date, there are no direct hard coatings available to overcome these durability issues. Thus, polycarbonate windshields are currently restricted to motorcycles on public roads. For example, Saudi Basic Industries Corporation (SABIC) is a producer of LEXAN brand polycarbonate. A 2016 Department of Transportation (DOT) guidebook for LEXAN sheet products states, "With the exception of motorcycle windshields, SABIC thermoplastic materials generally cannot be used for forward-facing exterior glazing." Summary of the Invention

[0006] The present disclosure contemplates various systems and methods for overcoming the above-mentioned shortcomings associated with the related art. One aspect of an embodiment of the present disclosure is a laminate including a polycarbonate substrate and an ultraviolet hard-coat film disposed on the polycarbonate substrate. The ultraviolet hard-coat film may include a polyethylene terephthalate (PET) layer, an adhesive interposed between the PET layer and the polycarbonate substrate, and an outer hard-coat disposed on the PET layer opposite the polycarbonate substrate. The outer hard-coat, the PET layer, and / or the adhesive may include a UV stabilizer.

[0007] The polycarbonate substrate may be 3-8 mm thick. The PET layer may be 2-6 mils thick. The outer hard coat may be 2-10 microns thick. The outer hard coat may have a gouge pencil hardness of greater than 8H. The adhesive may be a pressure sensitive adhesive.

[0008] The laminate may include an inner hardcoat disposed on the polycarbonate substrate opposite the PET layer. The inner hardcoat may have a gouge pencil hardness of 6H to 8H.

[0009] The UV hard-coat film may be a first UV hard-coat film of a plurality of UV hard-coat films laminated on a polycarbonate substrate. The plurality of UV hard-coat films may include a second UV hard-coat film disposed on the first UV hard-coat film, the second UV hard-coat film including a second PET layer, a second adhesive interposed between the second PET layer and the first UV hard-coat, and a second outer hard-coat disposed on the second PET layer opposite the first UV hard-coat film. The second outer hard-coat, the second PET layer, and / or the second adhesive may include a UV stabilizer. The adhesive of the first UV hard-coat film may be stronger than the second adhesive.

[0010] The laminate can be thermoformed into the shape of a curved vehicle windshield. Another aspect of an embodiment of the present disclosure is a method that may include depositing a UV stabilized hard coat on a first side of a polyethylene terephthalate (PET) carrier, coating a second side of the PET carrier opposite the first side with an adhesive, and adhering the second side of the PET carrier to a polycarbonate substrate using the adhesive.

[0011] The PET carrier, the UV stabilized hard coat, and the adhesive can define an ultraviolet hard coat film. The method may include winding the ultraviolet hard coat film onto a roll prior to adhering the second side of the PET carrier to the polycarbonate substrate. The method may include applying a removable liner to the second side of the PET carrier after coating. The method may include removing the removable liner from the second side of the PET carrier prior to adhering the second side of the PET carrier to the polycarbonate substrate. The method may include thermoforming the polycarbonate substrate with the adhered ultraviolet hard coat film into the shape of a curved vehicle windshield.

[0012] The PET carrier, the UV stabilized hard coat, and the adhesive can define a first ultraviolet hard coat film. The method may further include depositing a second UV stabilized hard coat on a first side of a second PET carrier, coating a second side of the second PET carrier opposite the first side with a second adhesive, and adhering the second side of the second PET carrier to the first ultraviolet hard coat film with the second adhesive. The adhesive of the first ultraviolet hard coat film may be stronger than the second adhesive. The second PET carrier, the second UV stabilized hard coat, and the second adhesive can define a second ultraviolet hard coat film.

[0013] The method may include thermoforming the polycarbonate substrate with the adhered first and second ultraviolet hardcoat films into the shape of a vehicle windshield. The method may include peeling away the second ultraviolet hardcoat film to expose the first ultraviolet hardcoat film. The method may include depositing a new second UV stabilized hardcoat on a first side of a new second PET carrier, coating a second side of the new second PET carrier opposite the first side with a new second adhesive, and adhering the second side of the new second PET carrier to the first ultraviolet hardcoat film with the new second adhesive. [Brief description of the drawings]

[0014] These and other features and advantages of the various embodiments disclosed herein will become better understood with regard to the following description and drawings, in which like numbers refer to like parts throughout. [Figure 1] FIG. 2 illustrates a laminate thermoformed into the shape of a vehicle windshield and installed in a vehicle according to one embodiment of the present disclosure. [Diagram 2] 2 is a cross-sectional view of the laminate taken along line 2-2 of FIG. 1. [Diagram 3] FIG. 2 illustrates an exemplary operational flow according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present disclosure encompasses various embodiments of laminates for use as vehicle windshields and methods of manufacture thereof. 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. The description sets forth functions and features associated with the illustrated embodiments. However, it should be understood that the same or equivalent functions may be accomplished by different embodiments that are also intended to be encompassed within the scope of the present disclosure. Furthermore, it is understood that relational terms such as first, second, etc. are used only to distinguish one entity from another and do not necessarily require or imply an actual sequential relationship between such entities.

[0016] FIG. 1 illustrates a laminate 100 thermoformed into the shape of a vehicle windshield and installed in a vehicle 10 according to one embodiment of the present disclosure. FIG. 2 illustrates a cross-sectional view of the laminate 100 taken along line 2-2 of FIG. 1. As shown in FIG. 2, the laminate 100 may include a polycarbonate substrate 110 and one or more UV hard coat films 120 (120a, 120b, etc.) disposed on the polycarbonate substrate 110. By disposing one or more UV hard coat films 120 on the polycarbonate substrate 110, the polycarbonate substrate 110 may be protected from scratching and pitting from windshield wipers and debris during use. In this manner, the laminate 100 may combine the impact resistance of polycarbonate with the durability required for extensive vehicle use while avoiding the safety hazards associated with glass windshields.

[0017] Unlike previous attempts to apply hard coatings to polycarbonate, the UV hard coat film 120a includes a polyethylene terephthalate (PET) layer 122a that acts as a carrier, which may be adhered to the polycarbonate substrate 110 by an intervening adhesive 124a. A UV stabilized outer hard coat 126a may be disposed on the PET layer 122a on the side opposite the polycarbonate substrate 110, with the PET layer 122a, adhesive 124a, and outer hard coat 126a defining the UV hard coat film 120a. The outer hard coat 126a may have a gouge pencil hardness of greater than 8H, making the laminate 100 much more durable than the polycarbonate substrate 110 alone. Using the PET layer 122a as a carrier allows the outer hard coat 126a to be applied without the difficulties that may arise if one were to attempt to apply the outer hard coat 126a directly to the polycarbonate substrate 110. For example, the polycarbonate substrate 110 may be too soft to support the hardcoat 126a, differences in the coefficient of thermal expansion between the polycarbonate substrate 110 and the hardcoat 126a may cause the hardcoat 126a to break down over time, and / or the hydrophilic nature of the polycarbonate substrate 110 may cause absorbed water to lift off the hardcoat 126a. These concerns can be avoided by applying the hardcoat 126a to the PET layer 122a and "floating" the PET layer 122a on the polycarbonate substrate 110 with an adhesive 124a in between.

[0018] As shown in the example of FIG. 2, the UV hard-coat film 120a may be a first UV hard-coat film of a plurality of UV hard-coat films 120 (120a, 120b, etc.) laminated on the polycarbonate substrate 110. By way of example, the second UV hard-coat film 120b includes and is defined by a PET layer 122b, an adhesive 124b, and an outer hard-coat 126b, which may be the same as the PET layer 122a, the adhesive 124a, and the outer hard-coat 126a, respectively, except that the adhesive 124b is interposed between the PET layer 122b and the first UV hard-coat film 120 (e.g., its outer hard-coat 126a). Additional (e.g., third, fourth, etc.) UV hard-coat films 120 may be applied in a similar manner. If the laminate 100 having multiple UV hard-coat films 120 unacceptably deteriorates over time (e.g., due to chipping, oxidation, etc.) during the life of a vehicle windshield or other window, the outermost UV hard-coat film 120 can simply be peeled away to expose a fresh UV hard-coat film 120 underneath. To this end, the adhesive 124a of the first UV hard-coat film 120a may be stronger than the adhesives 124b, etc. used for the additional UV hard-coat films 120 (and in some cases the adhesives 124b, etc. may be even weaker with each additional UV hard-coat film 120). In this way, the first UV hard-coat film 120a can remain adhered to the polycarbonate substrate 110 while another UV hard-coat film 120 is peeled away. For example, the first UV hard coat film 120a may be intended to remain on the polycarbonate substrate 110 for the life of the laminate 100, with the additional hard coat films 120 being intended to be removable (and possibly replenished, as described below) as needed. Similarly, each such additional UV hard coat film 120 beyond the first 120a may be provided with a tab or other means for easy peeling during the life of the laminate 100.

[0019] The PET layer 122a of the UV hardcoat film 120a may be 2-6 mils thick (1 mil = 1 / 1000th of an inch) and may be, for example, biaxially-oriented polyethylene terephthalate (BoPET) sold under the registered trademark Mylar owned by DuPont. The outer hardcoat 126a may be 2-10 microns thick (e.g., 5 microns) and may be, for example, a UV-curable polysiloxane-acrylic hybrid resin, such as a UV-curable resin sold by DIC. In addition to having a gouge pencil hardness of greater than 8H, the outer hardcoat 126a may pass the abrasion test #18 specified in the American National Standards Institute (ANSI) Z26.1-1996 standard and the one-year weather test #16 specified in the ANSI Z26.1-1996 standard. As noted above, the outer hardcoat 126a may be UV stabilized, for example, by including a UV stabilizer such as a hydroxyphenyl-benzotriazole or hydroxyphenyl-triazine UV absorber. By including a UV stabilizer in the outer hardcoat 126a, degradation (e.g., yellowing or embrittlement) of the PET carrier 122a and adhesive 124a caused by ultraviolet radiation in sunlight may be prevented or slowed down during the life of the ultraviolet hardcoat film 120a. It is contemplated that a UV stabilizer may additionally or alternatively be included in the PET carrier 122a and / or adhesive 124a. The adhesive 124a may be 10-25 microns (e.g., 25 microns) thick and may be a pressure sensitive adhesive (PSA), such as a low tack PSA, for example, with a peel strength determined as a constant load per unit width required for peeling, of about 30 grams per inch. The components of the additional ultraviolet hardcoat film 120 other than the first ultraviolet hardcoat film 120a may have the same or similar specifications. The underlying polycarbonate substrate 110 may be 3-8 mm (eg, 4 mm) thick.

[0020] As shown in FIG. 2, the laminate 100 may further include an inner hardcoat 130 disposed on the polycarbonate substrate 110 opposite the PET layer 122a. The inner hardcoat 130 will be the inward facing surface of the windshield and therefore will not be subject to the same wear and impact as the outer hardcoat 126a and need not be held to the same standards. Thus, the inner hardcoat 130 may be softer than the outer hardcoat 126a, thus mitigating the difficulties discussed above with respect to applying the outer hardcoat 126a directly to the polycarbonate substrate 110. The inner hardcoat 130 may have a gouge pencil hardness of only 6H to 8H, for example. The inner hardcoat 130 does not necessarily need to pass the abrasion test #13 specified in the ANSI Z26.1-1996 standard or the one-year weather test #16 specified in the ANSI Z26.1-1996 standard. Like the outer hardcoat 126a, the inner hardcoat 130 may be 2-10 microns (e.g., 5 microns) thick and may be, for example, a UV-curable polysiloxane-acrylic hybrid resin, such as those sold by DIC Corp. Since it is not exposed to direct sunlight, the inner hardcoat 130 may or may not have UV stabilizers.

[0021] FIG. 3 illustrates an exemplary operational flow according to one embodiment of the present disclosure. The operational flow may begin with depositing a UV stabilized hard-coat that functions as an outer hard-coat 126a on a first side of the PET carrier 122a (step 310). The outer hard-coat 126a is preferably wet deposited on the PET carrier 122a, but may be applied according to any suitable method, including spin coating, dip coating, or vacuum deposition. Before or after the outer hard-coat 126a is applied, the PET carrier 122a may be coated on the opposite side with an adhesive 124a (step 320). These three elements, the PET carrier 122a, the adhesive 124a, and the outer hard-coat 126a, may be permanently adhered to each other and may be collectively considered as an ultraviolet hard-coat film 120a. Once the adhesive 124a is coated on the PET carrier 122a, a removable liner may be applied to the same side of the PET carrier 122a to protect the adhesive 124a (step 330). The UV hard-coated film 120a can then be wound onto a roll to form a roll-to-roll process web that may be about 2 meters wide (step 340). The operational flow of steps 310-340 can produce a roll of the UV hard-coated film 120a at a speed of about 30 meters per minute.

[0022] Once the UV hard coat film 120a is unwound from the roll, the removable liner can be removed to expose the adhesive 124a (step 350), and the PET carrier 122a can be adhered to the polycarbonate substrate 110 by the exposed adhesive 124a (step 360). For example, the UV hard coat film 120a can be dry nipped by a roller to the flat polycarbonate substrate 110. With the UV hard coat film 120a adhered to the polycarbonate substrate 110, the laminate 100 can be ready to be thermoformed into the desired final shape of a windshield or other window. However, as described above and shown in FIG. 2, the laminate 100 can include additional UV hard coat films 120b, etc., which degrade with use and can later be peeled off one by one. In this case, steps 310-360 may be repeated for each additional UV hard coat film 120, except that in step 360, each subsequent UV hard coat film 120 is adhered to the preceding UV hard coat film 120 in the stack rather than to the polycarbonate substrate 110. Once the desired number of UV hard coat films 120 have been laminated onto the polycarbonate substrate 110, the entire stack 110, including the polycarbonate substrate 110 and one or more adhered UV hard coat films 120, may be 2D or 3D thermoformed to create a windshield or other window (step 370). The thermoforming temperature may typically be around 180 degrees Celsius, and a windshield-shaped pattern or mold surface may be utilized to form a 2D or 3D shaped vehicle windshield of appropriate size for installation into the vehicle 10 (see FIG. 1).

[0023] As explained above, it is contemplated that a laminate 100 having two or more UV hard coat films 120 may have the outermost UV hard coat film 120 peeled away to expose a fresh UV hard coat film 120 underneath. In this regard, the operational flow of FIG. 3 may continue for the life of the laminate 100 installed in the vehicle 10. If the outermost UV hard coat film 120 unacceptably degrades over time, it may be peeled away to expose the next UV hard coat film 120 underneath (step 380).

[0024] Following removal of one or more UV hard-coat films 120 in step 380, it is further contemplated that, in some cases, a set of UV hard-coat films 120 may be replenished to avoid degradation to the first, innermost UV hard-coat film 120a and extend the life of the laminate 100. It is contemplated that this first UV hard-coat film 120a will generally not be removed, as doing so would expose the softer polycarbonate substrate 110, which may not meet the same standards for use in the vehicle 10. Thus, the operational flow of FIG. 3 may include a step of applying one or more new UV hard-coat films 120 to the first UV hard-coat film 120a or the remaining stack of UV hard-coat films 120 (step 390). For example, steps 310-360 may be performed for each additional new UV hardcoat film 120, except that in step 360, the new UV hardcoat film 120 may be added to the laminate 100 after the laminate 100 has already been attached to the vehicle 10 and thus thermoformed. This may be done, for example, by wet laminating the new UV hardcoat film(s) 120 into the stack and shrinking them with a heat gun or blow dryer while applying pressure with a card or squeegee to conform to the existing shape of the laminate 100. In some cases, such additional UV hardcoat film(s) may be applied using a sacrificial layer that acts as a female mold cavity, as described in commonly owned U.S. patent application Ser. No. 16 / 778,928, entitled "THERMOFORM WINDSHIELD STACK WITH INTEGRATED FORMABLE MOLD," filed Jan. 31, 2020, the entire contents of which are expressly incorporated herein by reference.

[0025] At the end of the life of the laminate 100, there is no contamination as with conventional laminated glass-PVB-glass windshields, and therefore the polycarbonate substrate 110 can be easily recycled, resulting in less waste and benefiting the environment.

[0026] In the above example of laminate 100, it is assumed that at least one UV hardcoat film 120 is adhered to the polycarbonate substrate 110 prior to thermoforming into the desired shape of a windshield or other window. However, the disclosure is not intended to be so limited, and it is contemplated that one or more UV hardcoat films 120 may be applied after the polycarbonate substrate 110 has already been thermoformed. For example, the original one or more UV hardcoat films 120 can be applied using the same techniques described above in connection with refilling the stack of UV hardcoat films 120 in step 390.

[0027] The above description is illustrative and not limiting. In light of the above disclosure, those skilled in the art may devise modifications that are within the scope and spirit of the invention disclosed herein. Furthermore, the various features of the embodiments disclosed herein may be used alone or in various combinations with each other, and are not intended to be limited to the specific combinations described herein. Therefore, the scope of the claims should not be limited by the illustrated embodiments.

Claims

1. A laminate comprising: A polycarbonate substrate; an ultraviolet hardcoat film disposed on the polycarbonate substrate, the ultraviolet hardcoat film including a first polyethylene terephthalate (PET) layer, a first adhesive interposed between the first PET layer and the polycarbonate substrate, and a first outer hardcoat disposed on the first PET layer opposite the polycarbonate substrate, the first outer hardcoat including a UV stabilizer; an inner hardcoat disposed on the polycarbonate substrate opposite the first PET layer; wherein the inner hard coat is softer than the first outer hard coat; Laminate.

2. The laminate of claim 1, wherein the polycarbonate substrate is 3 to 8 mm thick.

3. The laminate of claim 1, wherein the first PET layer is 2 to 6 mils thick.

4. The laminate of claim 1, wherein the first outer hardcoat is 2 to 10 microns thick.

5. 10. The laminate of claim 1, wherein the first outer hardcoat has a gouge pencil hardness of greater than 8H.

6. The laminate of claim 1 , wherein the first adhesive is a pressure sensitive adhesive.

7. 10. The laminate of claim 1, wherein the inner hard coat has a gouge pencil hardness of 6H to 8H.

8. The laminate of claim 7, wherein the first outer hard coat has a gouge pencil hardness greater than 8H.

9. 2. The laminate of claim 1, wherein the ultraviolet hard coat film is a first ultraviolet hard coat film of a plurality of ultraviolet hard coat films laminated on the polycarbonate substrate, the plurality of ultraviolet hard coat films including a second ultraviolet hard coat film disposed on the first ultraviolet hard coat film, the second ultraviolet hard coat film including a second PET layer, a second adhesive interposed between the second PET layer and the first ultraviolet hard coat film, and a second outer hard coat disposed on the second PET layer opposite the first ultraviolet hard coat film, the second outer hard coat including a UV stabilizer.

10. The laminate of claim 9 , wherein the first adhesive is stronger than the second adhesive.

11. The laminate of claim 1 , wherein the laminate is thermoformed into the shape of a curved vehicle windshield.

12. 1. A method comprising: depositing a first UV stabilized hard coat on a first surface of a polyethylene terephthalate (PET) carrier; coating a second side of the PET carrier opposite the first side with an adhesive; adhering the second surface of the PET carrier to a first surface of a polycarbonate substrate using the adhesive. depositing an inner hardcoat on a second side of said polycarbonate substrate opposite said first side; wherein the inner hardcoat is softer than the first UV stabilized hardcoat.

13. 13. The method of claim 12, wherein the PET carrier, the first UV stabilized hard coat, and the adhesive define an ultraviolet hard coat film, the method further comprising winding the ultraviolet hard coat film onto a roll prior to the bonding.

14. applying a removable liner to the second surface of the PET carrier after said coating; removing the removable liner from the second surface of the PET carrier prior to said bonding. The method of claim 12 further comprising:

15. 13. The method of claim 12, wherein the PET carrier, the first UV stabilized hard coat, and the adhesive define an ultraviolet hard coat film, the method further comprising thermoforming the polycarbonate substrate having the ultraviolet hard coat film adhered thereto into the shape of a curved vehicle windshield.

16. The PET carrier, the first UV stabilized hard coat, and the adhesive define a first ultraviolet hard coat film, and the method further comprises: depositing a second UV stabilized hard coat on the first surface of the second PET carrier; coating a second side of the second PET carrier opposite the first side with a second adhesive; Adhering the second surface of the second PET carrier to the first ultraviolet hard coat film using the second adhesive. The method of claim 12 further comprising:

17. 17. The method of claim 16, wherein the adhesive of the first UV hard coat film is stronger than the second adhesive.

18. 17. The method of claim 16, wherein the second PET carrier, the second UV stabilized hardcoat, and the second adhesive define a second ultraviolet hardcoat film, the method further comprising thermoforming the polycarbonate substrate having the first and second ultraviolet hardcoat films adhered thereto into the shape of a vehicle windshield.

19. 20. The method of claim 18, further comprising peeling off the second UV hardcoat film to expose the first UV hardcoat film.

20. depositing a new second UV stabilized hardcoat on the first surface of the new second PET carrier; coating a second surface of the new second PET carrier opposite the first surface with a new second adhesive; Adhering the second surface of the new second PET carrier to the first ultraviolet hard coat film using the new second adhesive.

20. The method of claim 19, further comprising:

21. The method of claim 12, wherein the first UV stabilized hard coat on the first surface of the PET carrier has a gouge pencil hardness of greater than 8H and the inner hard coat has a gouge pencil hardness of 6H to 8H.

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