Infrared heat-assisted drying of thin films

Abstract

The method of applying a paint film to a substrate may include wetting a surface of the substrate or an adhesive layer of the paint film to form a fluid layer thereon. The paint film may further include a polymeric film layer. The method may further include applying the paint film to the substrate such that the fluid layer is disposed between the adhesive layer and the surface. The applied paint film may be heated with infrared heat to facilitate removal of the fluid layer and adhere the adhesive layer to the surface. Systems and devices for applying a paint film to a substrate are also disclosed.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 149,193, filed February 12, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] Incorporation by Reference All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0003] FIELD OF THE INVENTION The present invention relates generally to paint films, methods of applying and using same, and articles containing same. [Background technology]

[0004] In recent years, paint films have gained popularity as an alternative to traditional surface painting methods in many different types of applications, particularly in motorized vehicles such as automobiles, airplanes, boats, etc. This popularity is at least in part a result of paint films being more durable and sustainable compared to traditional paints.

[0005] One exemplary paint film is Aero Satin Clean 200 film, a transparent film used to modify the surface of vehicles. These films and methods of making are described in U.S. Publication No. 20190161646, which is incorporated herein by reference in its entirety.

[0006] Typically, paint films are applied by a wet installation process. However, wet installation processes are often incomplete, especially when adapted by installers after the fact. For example, thick blisters may form under the applied paint film. Unless the blisters are completely dry, the paint film cannot properly adhere to the surface (e.g., the surface of a vehicle). As a result, film adhesion typically requires at least 24 hours to allow for complete adhesion. This drying time is particularly burdensome on OEM product production lines. Therefore, it would be beneficial to have a faster paint film drying method that could also minimize installation defects. Summary of the Invention

[0007] Described herein is an improved method for applying paint films using infrared (IR) heat assisted drying.

[0008] Generally, in one embodiment, a method of applying a paint film to a substrate includes wetting the surface of the substrate or the adhesive layer of the paint film with a polymeric film layer to form a fluid layer thereon, applying the paint film to the substrate such that the fluid layer is disposed between the adhesive layer and the surface, and heating the applied paint film with infrared heat to facilitate removal of the fluid layer and to bond the adhesive layer to the surface.

[0009] This and other embodiments may include one or more of the following features: The wetting step may include wetting both the surface and the adhesive layer. The method may further include removing a portion of the fluid layer using a squeegee before heating. The portion may include at least 80% of the fluid layer. The polymer film layer may have a thickness of at least 1 g / m 2The paint film may include a 24-hour moisture vapor transmission rate (MVTR). The polymer film layer may include a polyurethane. The adhesive layer may include a pressure-sensitive adhesive. The adhesive layer may include a polyacrylate. Heating the applied paint film with infrared heat can increase the water vapor transmission rate of the paint film by at least two times. The paint film can adhere to the surface of the substrate in less than 60 minutes. The drying time of the paint film can be reduced by at least 75% compared to drying at room temperature. Heating includes heating the paint film to between 30°C and 100°C. The substrate can include a motor vehicle. [Brief explanation of the drawings]

[0010] The novel features of the invention are set forth with particularity in the following claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

[0011] [Figure 1] 1 shows a paint film on the surface of a substrate.

[0012] [Figure 2] FIG. 1 shows an exemplary flow diagram for applying a paint film to a substrate using infrared heat assisted drying.

[0013] [Figure 3] 1 illustrates the use of a squeegee to remove fluid from between the paint film and the substrate.

[0014] [Figure 4] 1 illustrates a residual fluid layer that may remain during the wet application process of a paint film to a substrate.

[0015] [Figure 5] 1 illustrates the use of heat to dry the residual fluid layer.

[0016] [Figure 6] 1 shows an exemplary setup for infrared heat-assisted drying of a paint film on the surface of a car.

[0017] [Figure 7] Illustrates the basic drying process of a paint film when exposed to air.

[0018] [Figure 8] 1 illustrates the effect of heat on the drying process of a paint film.

[0019] [Figure 9] 1 is a graph of experimental results comparing peel force over time when a paint film is dried using infrared heat assisted drying versus when the film is dried at room temperature.

[0020] [Figures 10A-10F] 1 illustrates the formation of defects during drying after a wet lay process.

[0021] [Figure 11] 1 is a graph of illumination power versus wavelength. DETAILED DESCRIPTION OF THE INVENTION

[0022] Described herein are improved methods for applying paint films to substrates. Specifically, described herein are methods for applying paint films to motorized vehicles using infrared heat to efficiently adhere the film to the vehicle, such as in less than an hour. The disclosed paint film application method using IR heat can advantageously reduce drying time by at least 75% compared to drying the paint film at room temperature. In addition, the methods described herein can help reduce defects in the applied paint film. The methods described herein can be particularly useful for accelerating the cycle time of film application to motorized vehicles (e.g., for automotive production lines at OEM facilities).

[0023] 1 shows an exemplary paint film 101 on a surface 102 (e.g., the surface of a motorized vehicle). The paint film 101 includes a polymer film layer 108 and an adhesive layer 106. The paint film 101 may be a polymer laminate having the ability to transmit moisture. For example, the paint film 101 may have a thickness of at least 1 g / m 2 / 24-hour moisture vapor transmission rate (MVTR). In one embodiment, the polymer film layer 108 can be a polyurethane or polyacrylate. For example, the polymer film layer 108 can be a polymer containing urethane (also known as carbamate) linkages, urea linkages, or a combination thereof (i.e., in the case of poly(urethane-urea)). Thus, the polymer film layer 108 can contain at least urethane linkages, urea linkages, or a combination thereof. In some embodiments, the polymer film layer 108 can have a polymer backbone with at least 40%, at least 60%, or at least 80% urethane and / or urea repeat linkages formed in situ during the polymerization process. The adhesive layer 106 can include a pressure-sensitive adhesive. In some embodiments, the pressure-sensitive adhesive can include (meth)acrylates (i.e., acrylates and methacrylates). For example, the pressure-sensitive adhesive can include 2-ethylhexyl acrylate, vinyl acetate, and acrylic acid monomers polymerized and crosslinked with conventional aluminum or melamine crosslinkers. In some embodiments, adhesive layer 106 may include synthetic and natural rubber, polybutadiene and its copolymers, polyisoprene and its copolymers, and / or silicones (e.g., polydimethylsiloxane and polymethylphenylsiloxane). In some embodiments, paint film 101 may further include a pigmented base coat. Further features of exemplary paint films are described in U.S. Publication No. 20190161646, entitled "Paint Film Appliques with Reduced Defects, Articles and Methods," which is incorporated herein by reference in its entirety.

[0024] 2 , a method of applying a paint film 101 (illustrated by flow diagram 1100) may include, in step 1104, applying (e.g., spraying) a fluid (e.g., water) to the exposed surface of the adhesive layer 106 of the paint film 101. Similarly, in step 1105, a fluid may be applied to the surface 102 of the substrate. Then, in step 1106, a wetted adhesive layer 106 may be applied to the wetted surface 102 of the substrate. In step 1108, a majority of the fluid between the film 101 and the surface 102 of the substrate may be physically removed (e.g., by using a squeegee to press the film against the surface 102 of the substrate, thus forcing the fluid from the interface). In one embodiment, the amount of fluid between the film 101 and the surface 102 of the substrate is initially 200 g / m 2 Super, 300g / m 2 Over 400g / m 2 After physical removal of the fluid (e.g., using a squeegee), 2 Less than 10g / m 2 Less than 5g / m 2 Less than 50g / m 2 In step 1110, infrared heat can be applied to the paint film 101 to further remove fluid (e.g., less than 2 g / m 2 Less than 1g / m 2 Less than 0.1g / m 2 Less than 0.01g / m 2 (e.g., less than 100°C remains fluid). Infrared heat between 30°C and 100°C, such as between 40°C and 90°C, may be applied. The infrared heat may advantageously penetrate the paint film 101 and be absorbed by polymers and water molecules within the film 101. Advantageously, infrared heat may be used to allow the paint film 101 to dry in less than 2 hours, such as less than 1 hour, such as less than 45 minutes, such as less than 30 minutes.

[0025] FIG. 3 illustrates the first step of removing fluid between the paint film 101 and the surface 102 during a wet installation process (e.g., during step 1108 above). Shown in FIG. 3 is the surface 102 having the fluid 103 (shown by the wavy lines) and the paint film 101 (which is transparent and not visible). Also shown are squeegees 302 and 304 being moved in the directions indicated by arrows 306, 310, and 312 to remove fluid molecules 308. Portion 301 illustrates the surface 102 after the squeegee has been applied, and portion 303 illustrates the surface 102 before the squeegee has been applied. In some embodiments, the pressure and / or overlap of the squeegee strokes can be adjusted to maximize the amount of fluid removed from between the paint film 101 and the surface 102.

[0026] 4, even after optimizing the squeegee process, residual fluid 104 may remain behind and underneath the paint film 101. In some embodiments, the residual fluid 104 at this stage may be less than 10 microns thick and / or less than 10% of the thickness of the adhesive layer 106. While this small residual layer 104 may not seem significant, the fluid may prevent complete contact between the adhesive layer 106 and the substrate (especially if the adhesive layer 106 is hydrophilic).

[0027] 5 (e.g., as described in step 1110 above), infrared heat can be applied to the paint film 101 to remove the residual fluid layer 104. As shown, an IR heat source 902 can be directed at the paint film 101 to remove the residual fluid layer 104. Referring to FIG. 11 , in some embodiments, infrared heat can be applied to the paint film 101 at a “mid-wave” IR wavelength, which can better allow for interaction with and / or preferential heating of polymer and water molecules in or around the paint film 101. Advantageously, the mid-wave IR wavelength can prevent strong interaction with the surface 102 of any underlying substrate, such as paint, on the surface 102. The mid-wave IR wavelength can also have less variation when interacting with different colors or pigments within the paint film 101.

[0028] 6 shows an exemplary setup for infrared heat-assisted drying of a paint film on a surface 1002 of a vehicle 1001. As shown, a paint film 101 is disposed on the surface 1002 of the vehicle 1001. A residual fluid layer 104, an adhesive film layer 106, and a polymer film layer 108 are also visible. As shown, the polymer film layer 108 is directly exposed to an IR heat source 902. In some embodiments, a single IR heat source 902 may be used. For example, the heat source may be a tunnel configured to apply heat circumferentially around the vehicle 1001. In other embodiments, a row of heat sources may be used.

[0029] FIG. 7 illustrates the basic drying process of a paint film 101 when exposed to air. As shown, the drying process occurs as individual water molecules diffuse through the polymer network within the polymer film 108 into the air 702. The diffusion of water molecules is indicated by arrows 704. FIG. 8 then illustrates the effect of heat on the drying process of the paint film 101 (e.g., as described with respect to step 1110). As is well known in the art, the rate at which water molecules diffuse through the polymer network of a polymer film is referred to as the moisture vapor transmission rate (MVTR) of the polymer film. Therefore, the MVTR of a film generally determines how fast a wet-laid film will dry. Additionally, the MVTR increases with temperature by approximately 5% for every 1° C. increase in temperature. Thus, as shown in FIG. 8, the paint film 101 may dry faster at 35° C. than at 25° C., for example. Because the MVTR of a film increases with temperature, IR heating can improve adhesion of the paint film 101 to the surface 102 by more quickly removing water molecules in the fluid layer, thus reducing the time it takes for the adhesive layer 106 to fully adhere to the surface 102. In some embodiments, the use of IR heat as described herein can increase the MVTR of the paint film 101 by 2x, 5x, or 10x or more. Additionally, in some embodiments, the use of IR heat can reduce drying time by at least 75%, such as at least 85%, such as at least 95%, compared to drying at room temperature.

[0030] Drying the film using IR heat may also have additional and unexpected benefits. Specifically, the use of IR heat during drying of the paint film 101 can result in significantly stronger or more effective adhesion of the paint film 101 to the surface 102. When adhesion values ​​are used to express the degree of adhesion, it has been discovered that the adhesion values ​​of the paint film 101 to the surface 102 using IR heating even exceed the maximum values ​​obtained at room temperature, indicating that the improved adhesion levels cannot be simply attributed to the removal of water molecules. Rather, if the adhesive layer 106 is a pressure-sensitive adhesive (PSA), IR heating may improve the van der Waals forces that traditionally bind the PSA to the surface 102. This unexpected improvement may be the result of a synergistic effect between the presence of water molecules in the fluid layer 104 and the application of IR heat. That is, plasticization occurs when solvent-type molecules (e.g., water) diffuse between polymer chains, disrupting the polymer network and causing a decrease in the viscosity of the polymer within the PSA. This lower viscosity allows the PSA to flow into small cavities in surface 102, promoting stronger van der Waals forces and therefore stronger adhesive forces.

[0031] FIG. 9 shows a graph 1200 of experimental results achieved by applying a paint film (as described herein) to a surface with or without IR heat-assisted drying. During the experiment, panels were painted using a wet-lay process to apply paint film samples. One set of panels was maintained at room temperature. The other set was placed under a bank of infrared lamps. At designated intervals, one film sample from each set was tested to determine how quickly adhesion occurred under each condition. After the first hour, adhesion in the samples exposed to infrared light was significantly higher than samples dried at room temperature. In fact, it was discovered that the samples exposed to the infrared lamps developed higher adhesion after one hour than did the room-temperature samples after as much as 72 hours.

[0032] Continuing with reference to FIG. 9 , curve 1202 shows experimental data from the drying of a set of room temperature and curve 1204 shows experimental data from IR heat-assisted drying of paint film 101. As can be seen from curve 1204, the IR heat-exposed film can withstand a peel force of over 60 oz / in (approximately 63 oz / in) after about 18 hours, while the room temperature film can withstand a peel force of less than 40 oz / in (approximately 45 oz / in) after about 18 hours. Furthermore, within 72 hours, the room temperature film can only withstand a peel force in the range of 35 oz / in to 40 oz / in, while the IR heat-exposed film can withstand a peel force in the range of 43 oz / in to 63 oz / in. Since the ability to withstand a higher peel force is indicative of adhesion, it can be interpreted from the experimental results that IR heat exposure bonds paint films faster than room temperature drying.

[0033] In some embodiments, IR heating can also improve the defect correction process for wet-deposition of thin films. That is, with reference to FIGS. 10A-10F, during drying (either air or IR heat), fluid from the residual fluid layer 104 may migrate laterally and, over time, coalesce into thicker pockets of fluid. The lateral movement of fluid may also allow small trapped air bubbles to coalesce over time, which can result in the formation of larger, visible bubbles. The coalescence of water and / or air can result in film defects 602. FIGS. 9A-9F show the formation of defects 602 in the film 101, which can result from air or water bubbles. Advantageously, the use of IR can reduce the number of defects formed by decreasing drying time, thus reducing the amount of time available for water and / or air to converge into the defects.

[0034] Various modifications and alterations to the present invention will become apparent to those skilled in the art without departing from the spirit and scope of the present invention, which is defined by the appended claims. It should be noted that the steps recited in any method claims below do not necessarily have to be performed in the order in which they are recited. Those skilled in the art will recognize variations from the recited order in performing the steps.

[0035] Any theory set forth herein is subject to change pending further testing and analysis, and thus, the inventors do not intend to be bound by any theory presented herein as to, for example, what factors contribute to the physical properties described in conjunction with the paint film decoration and the individual layers therein.

[0036] It is to be understood that any feature described herein with respect to one embodiment may be used in addition to, or instead of, any feature described with respect to another embodiment.

[0037] When a feature or element is referred to herein as being "on" another feature or element, it may be directly on the other feature or element, or intervening features and / or elements may also be present. In contrast, when a feature or element is referred to as being "directly on" another feature or element, there are no intervening features or elements present. When a feature or element is referred to as being "connected," "attached," or "coupled" to another feature or element, it will be understood that it may be directly connected, attached, or coupled to the other feature or element, or that intervening features or elements may also be present. In contrast, when a feature or element is referred to as being "directly connected," "directly attached," or "directly coupled" to another feature or element, there are no intervening features or elements present. Although described or illustrated with respect to one embodiment, features and elements so described or illustrated may apply to other embodiments. It will also be understood by those skilled in the art that a reference to a structure or feature located "adjacent" to another feature may overlap with or have a portion underneath the adjacent feature.

[0038] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting of the present invention. For example, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that as used herein, the terms "comprises" and / or "comprising" specify the presence of stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ."

[0039] Spatial terms such as "under," "below," "lower," "over," and "upper" are used herein for ease of description and to describe the relationship of one element or feature to another element or feature shown in the figures. It will be understood that spatial terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. For example, if a device is inverted in the figures, an element described as "under" or "beneath" the other element or feature would be oriented "above" the other element or feature. Thus, the exemplary term "under" can encompass both an orientation of over and under. A device may be oriented differently (rotated 90 degrees or at other orientations) and the spatial descriptions used herein interpreted accordingly. Similarly, terms such as "upward," "downward," "vertically," "horizontally," and the like are used herein for descriptive purposes only, unless specifically indicated otherwise.

[0040] The terms "first" and "second" may be used herein to describe various features / elements (including steps), but these features / elements should not be limited by these terms unless the context indicates otherwise. These terms may be used to distinguish one feature / element from another. Thus, a first feature / element discussed below may be referred to as a second feature / element, and similarly, a second feature / element discussed below may be referred to as a first feature / element without departing from the teachings of the present invention.

[0041] Throughout this specification and the claims that follow, unless the context otherwise requires, the word "comprise," and variations such as "comprises" and "comprising," mean that various components may be used together simultaneously in methods and articles (e.g., compositions and apparatuses, including devices and methods). For example, the term "comprising" will be understood to mean the inclusion of any stated element or step, but not the exclusion of any other element or step.

[0042] As used herein in the specification and claims, including when used in the examples, unless expressly specified otherwise, all numbers may be read as if preceded by the word "about" or "approximately," even if the term is not expressly stated. The terms "about" or "approximately" may be used when a description of a size and / or location to indicate a stated value and / or location is within a reasonable expected range of values ​​and / or locations. For example, a numerical value may have a value that is + / - 0.1% of the stated value (or range of values), + / - 1% of the stated value (or range of values), + / - 2% of the stated value (or range of values), + / - 5% of the stated value (or range of values), + / - 10% of the stated value (or range of values), etc. Any numerical range recited herein is intended to include all subranges contained therein.

[0043] While various exemplary embodiments have been described above, any of numerous modifications may be made to the various embodiments without departing from the scope of the invention as set forth in the claims. For example, the order in which various described method steps are performed may often be changed in alternative embodiments, and one or more method steps may be omitted altogether in other alternative embodiments. Optional features of the various device and system embodiments may be included in some embodiments and not included in other embodiments. Accordingly, the foregoing description has been provided primarily for illustrative purposes and should not be construed as limiting the scope of the invention as set forth in the claims.

[0044] The examples and illustrations contained herein illustrate, by way of illustration and not limitation, specific embodiments in which the subject matter may be practiced. As stated, other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of the present disclosure. Such embodiments of the inventive subject matter may be individually or collectively referred to herein by the term "the invention" merely for convenience and without intending to intentionally limit the scope of this application to any single invention or inventive concept where more than one is actually disclosed. Thus, while specific embodiments have been shown and described herein, any adjustments calculated to achieve the same purpose may be substituted for the specific embodiments shown. The present disclosure is intended to cover any and all modifications or variations of the various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will become apparent to those skilled in the art upon reviewing the above description. One embodiment of the present invention will be described below, but the present invention is not limited thereto. [Invention 1] 1. A method of applying a paint film to a substrate, said method comprising: wetting a surface of a substrate or an adhesive layer of a paint film to form a fluid layer thereon, the paint film further comprising a polymer film layer; applying the paint film to the substrate such that the fluid layer is disposed between the adhesive layer and the surface; heating the applied paint film with infrared heat to facilitate removal of the fluid layer and to adhere the adhesive layer to the surface. [Invention 2] 2. The method of claim 1, wherein the wetting step includes wetting both the surface and the adhesive layer. [Invention 3] 2. The method of claim 1, further comprising removing a portion of the fluid layer using a squeegee before heating. [Invention 4] 4. The method of claim 3, wherein said portion constitutes at least 80% of said fluid layer. [Invention 5] the polymer film layer having a thickness of at least 1 g / m 2 / The method according to claim 1, including 24-hour water vapor transfer rate (MVTR). [Invention 6] 2. The method of claim 1, wherein the polymer film layer comprises polyurethane. [Invention 7] 2. The method of claim 1, wherein the adhesive layer comprises a pressure-sensitive adhesive. [Invention 8] 2. The method of claim 1, wherein the adhesive layer comprises a polyacrylate. [Invention 9] 3. The method of claim 2, wherein heating the applied paint film with infrared heat increases the water vapor transmission rate of the paint film by at least two times. [Invention 10] 2. The method of claim 1, wherein the paint film is adhered to the surface of the substrate in less than 60 minutes. [Invention 11] 2. The method of claim 1, wherein the drying time of the paint film is reduced by at least 75% compared to drying at room temperature. [Invention 12] 2. The method according to claim 1, wherein the heating step comprises heating the paint film to 30°C to 100°C. [Invention 13] 2. The method of claim 1, wherein the substrate comprises a motorized vehicle.

Claims

1. 1. A method of applying a paint film to a substrate, said method comprising: wetting a surface of a substrate or an adhesive layer of a paint film to form a fluid layer thereon, the paint film further comprising a polymer film layer; applying the paint film to the substrate such that the fluid layer is disposed between the adhesive layer and the surface; heating the applied paint film with infrared heat to facilitate removal of the fluid layer and to adhere the adhesive layer to the surface.

2. The method of claim 1 , wherein the wetting step includes wetting both the surface and the adhesive layer.

3. The method of claim 1 , further comprising removing a portion of the fluid layer using a squeegee before heating.

4. The method of claim 3 , wherein the portion comprises at least 80% of the fluid layer.

5. The method of claim 1 , wherein the polymeric film layer comprises polyurethane.

6. The method of claim 1 , wherein the adhesive layer comprises a pressure sensitive adhesive.

7. The method of claim 1 , wherein the adhesive layer comprises a polyacrylate.

8. 10. The method of claim 1, wherein the paint film adheres to the surface of the substrate in less than 60 minutes.

9. The method of claim 1 , wherein the substrate comprises a motorized vehicle.

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