Abstract:
An exemplary thin film appliqué includes a polymer film having first and second sides. A pattern layer has first and second sides, and the first side of the polymer film and the first side of the pattern layer are positioned adjacent each other. A pressure-sensitive adhesive underlies one of the second side of the pattern layer and the second side of the polymer film. A clearcoat covers one of the second side of the polymer film and the second side of the pattern layer that is not overlying the pressure-sensitive adhesive, and thickness of the clearcoat is equalized toward a combined thickness of the polymer film, the pattern layer, and the pressure-sensitive adhesive. The polymer film, the pattern layer, and the pressure-sensitive adhesive exhibit chemical affinity for each other.

Description:
BACKGROUND  
       [0001]     Decal systems or appliqués are currently used for exterior decoration of vehicles, including aircraft and land vehicles such as automobiles, trucks, and motorcycles. Because land vehicles typically operate in relatively benign environments (compared to aircraft operating environments), decal systems for land vehicles may be as simple as a sticker covered with paint. However, such a simple decal system for land vehicles would not be able to withstand erosion due to wind and/or rain that can occur in aircraft operating environments.  
         [0002]     A typical decal system used for aircraft includes a pigmented polymer film/pressure-sensitive adhesive (PSA) laminate. The laminate is provided to a printer, who prints graphics on top of the laminate and applies a topcoat on top of the decal system. The decal system is applied to an aircraft skin and edge sealer, such as a border of clear paint, is brushed onto edges of the decal system. Another typical decal system consists of a clear polymer film which is provided to a printer, who prints graphics on the bottom side of the film, then applies the pressure-sensitive adhesive. This system is then applied to the aircraft skin and edge sealer is applied around its borders in similar fashion.  
         [0003]     Conventional decal systems and appliqués for aircraft application typically have a thickness of around 5/1000 inch (5 mils) or so. The sharp edge creates a step of around 5 mils thickness that may be exposed and subject to wind- and rain-erosion at aircraft cruise speeds. The thicker the edge, the harder it is to cover the edge step, thereby resulting in exposure of part of the edge step. As a result, conventional decal systems and appliqués that are applied to an aircraft, especially in the nose section and on leading edges of flight control surfaces, may be subject to delamination, peeling, or complete removal.  
         [0004]     Delamination and peeling may shorten the service life of the decal system or appliqué. Moreover, if a decal is used for mandatory markings on an aircraft and is removed during flight (such as by wind- or rain-erosion), then Federal Aviation Administration (FAA) rules mandate that the aircraft be taken out of service. The mandatory markings must be replaced to return the aircraft to service. When the aircraft is a commercial aircraft, it is desirable to return the aircraft to revenue service as soon as possible.  
         [0005]     One approach to addressing the above problems of conventional decal systems and appliqués on aircraft is by use of stenciling. Stenciling, though, also has shortcomings. For example, there is a limit in how small a font can be used. Further, stenciling is time- and labor-intensive. Finally, characters must be exact, thereby increasing time consumption for proofreading and correcting errors.  
         [0006]     The foregoing examples of related art and limitations associated therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.  
       SUMMARY  
       [0007]     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the problems described above in the Background have been reduced or eliminated, while other embodiments are directed to other improvements.  
         [0008]     Embodiments provide a thin film appliqué. The exemplary embodiments of thin film appliqués described herein advantageously may be more resistant to wind- or rain-erosion than conventional appliqués when used on aircraft, and may thereby reduce frequency of removing an aircraft from service for replacement of mandatory markings.  
         [0009]     An exemplary appliqué includes a polymer film having first and second sides. A pattern layer has first and second sides, and the first side of the polymer film and the first side of the pattern layer are positioned adjacent each other. A pressure-sensitive adhesive underlies one of the second side of the pattern layer and the second side of the polymer film. A clearcoat covers one of the second side of the polymer film and the second side of the pattern layer that is not overlying the pressure-sensitive adhesive, and thickness of the clearcoat is equalized toward a combined thickness of the polymer film, the pattern layer, and the pressure-sensitive adhesive.  
         [0010]     According to aspects, the polymer film, the pattern layer, and the pressure-sensitive adhesive exhibit chemical affinity for each other. The polymer film may include polyvinyl fluoride, polyvinyl chloride, polyester, a urethane film or an epoxy film. Also, the pattern layer may include an ink layer.  
         [0011]     According to further aspects, the clearcoat may be applied after the pressure-sensitive adhesive is adhered to a substrate.  
         [0012]     In addition to the exemplary embodiments and aspects described above, further embodiments and aspects will become apparent by reference to the drawings and by study of the following detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.  
         [0014]      FIGS. 1A and 1B  are side views of embodiments of a thin film appliqué applied to a substrate;  
         [0015]      FIGS. 2A and 2B  are side views of the thin film appliqués of  FIGS. 1A and 1B , respectively, before application to the substrate; and  
         [0016]      FIG. 3  is an illustration of the exemplary appliqués of  FIGS. 1A  and/or  1 B applied to an aircraft. 
     
    
     DETAILED DESCRIPTION  
       [0017]     Referring to  FIGS. 1A and 1B  and by way of overview, an appliqué  10  ( FIG. 1A ) or an appliqué  10 ′ ( FIG. 1B ) according to exemplary embodiments is applied to a substrate  12 , such as without limitation an aircraft skin. The appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) suitably are covered completely by a clearcoat  14 . Advantageously and as a result, the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) may be more resistant to wind- or rain-erosion than conventional appliqués when used on aircraft, and may thereby reduce frequency of removing an aircraft from service for replacement of mandatory markings. Details regarding exemplary embodiments will be set forth below.  
         [0018]     Still referring to  FIGS. 1A and 1B  and given by way of non-limiting example, the substrate  12  may be an aircraft skin, such as without limitation a fuselage skin, a vertical stabilizer skin, an engine nacelle, or the like. While embodiments of the thin film appliqué described herein are well-suited to aircraft applications because of increased resistance to wind- or rain-erosion than conventional appliqués, the exemplary thin film appliqués described herein may be used on any substrate as desired for a particular application. For example, the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) may be applied to substrates such as land vehicle body panels, maritime vessel hulls and superstructures, spacecraft skins, and the like. In certain applications, the substrate  12  may be coated with a primer  16 , such as without limitation an anodize coating, a chromate conversion coating like Alodine, or the like, and a basecoat  18  of paint, as desired.  
         [0019]     The appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) each includes a polymer film  20 , a pattern layer  22 , and a pressure sensitive adhesive (PSA)  24 . The total combined thickness of the polymer film  20 , the pattern layer  22 , and the PSA  24  is on the order of around 0.0017-0.0023 inches (1.7-2.3 mils). The thickness of the clearcoat  14  on the top layer (either the polymer film  20  or the pattern layer  22 ) is equalized toward the combined thickness of the polymer film  20 , the pattern layer  22 , and the PSA  24  and therefore is also on the order of around 1.7-2.3 mils. Because of the low profile of the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ), the covering of the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) by the clearcoat  14 , and the selection of materials for the components of the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ), the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) are able to withstand the harsh conditions and environment presented by an aircraft in flight. Each of the components of the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) will be discussed in turn below. In addition, certain combinations of exemplary materials for the components of the appliqué  10  ( FIG. 1A ) and the appliqué  10 ′ ( FIG. 1B ) will be highlighted below.  
         [0020]     The polymer film  20  is a thin film that is made of a suitable material that can withstand temperatures and high-speed wind and rain impingement associated with flight conditions. The polymer film  20  suitably has a thickness in a range between around 0.5 mil and around 1.0 mil. The polymer film  20  preferably has other desirable characteristics. For example, the polymer film  20  preferably is thermally resistant to temperatures encountered during flight conditions, such as temperatures in a range between around −65 degrees Fahrenheit to around +160 degrees Fahrenheit. As a further example, the polymer film  20  preferably is resistant to fluids, such as phosphate ester-based hydraulic fluid (e.g., SKYDROL®). The polymer film  20  preferably has surface characteristics that promote strong adherence of the clearcoat  14 , the pattern layer  22 , and the PSA  24  to the polymer film  20 . Finally, the polymer film  20  preferably is impact-resistant and flexible, with a flexibility on the order of around 5-10 percent extension.  
         [0021]     The polymer film  20  may be embodied in any suitable polymeric film as desired. For example, the polymer film  20  may be a urethane film, an acrylic film, or an epoxy film. In addition, the polymer film  20  may be a vinyl, such as polyvinyl chloride (PVC) or polyvinyl fluoride like TEDLAR®, available from DuPont. Further, the polymer film  20  may be a polyester such as MYLAR®, available from DuPont. If desired, a binder additive may be included with the polymer film  20  to improve cohesive strength.  
         [0022]     The polymer film  20  may be clear or pigmented, as desired for a particular application. When the polymer film  20  is clear, the pattern layer  22  may provided between the polymer film  20  and the PSA  24  (as shown in  FIG. 1A ). Alternately, when the polymer film  20  is clear, the pattern layer  22  may be provided on top of the polymer film  20  (as shown in  FIG. 1B ). When the polymer film  20  is pigmented, the pattern layer  22  may likewise be provided on top of the polymer film  20  (as shown in  FIG. 1B ). The polymer film  20  may be impregnated with a material, such as without limitation TiO 2 , that causes the polymer film  20  to act as a reflective background that brings out the color of the pattern layer  22 .  
         [0023]     The pattern layer  22  suitably is a layer of ink. The pattern layer has a thickness on the order of around 0.2-0.3 mils. The ink desirably has a fairly high opacity, such that the pattern layer  22  is fully opaque when the pattern layer  22  has a thickness on the order of around 0.2-0.3 mils. The surface tension of the ink should be compatible with the surface tension of the polymer film  20 . In the embodiment shown in  FIG. 1A , the surface tension of the ink should also be compatible with the surface tension of the PSA  24 . In the embodiments shown in  FIGS. 1A and 1B , the surface tension of the ink should also be compatible with the surface tension of the clearcoat  14 . The ink used for the pattern layer  22  may be any acceptable commercial-off-the-shelf ink. Non-limiting examples of acceptable inks include pigmented acrylic ink, pigmented fast-dry acrylic ink, urethane ink with pigment, epoxy ink, a urethane enamel coating such as Desothane®, and the like. If desired, an adhesion promoter may be included with the pattern layer  22 .  
         [0024]     The PSA  24  suitably is any acceptable, commercially-available, acrylic PSA. If desired, the PSA  24  may be ultraviolet (UV) resistant. The PSA  24  suitably has a thickness on the order of around 1 mil. The PSA  24  desirably has a surface tension that is compatible with the surface tension of the clear coat  14 . The PSA  24  preferably does not contain volatile or mobile components that may tend to migrate to the outer surface of the appliqué  10  or to an interface within the appliqué  10 , where they may promote delamination of the appliqué  10  or impede wetting of the appliqué  10  by the clearcoat  14 . Also, the PSA  24  desirably is resistant to fluids, such as water, hydraulic fluids, SKYDROL®, and the like, and will adhere strongly to the basecoat  18  and overlying polymer film  20  and pattern layer  22 .  
         [0025]     Unless indicated otherwise, all further references in the Detailed Description to the appliqué  10  are intended to also include the appliqué  10 ′ and are not intended to refer only to the appliqué  10  to the exclusion of the appliqué  10 ′. The clearcoat  14  provides a means for encapsulating the appliqué  10 . As such, the clearcoat  14  suitably provides UV protection, has a smooth finish, provides high gloss on the order of around 80-90 gloss units, and provides resistance to impacts and to fluids such as water, hydraulic fluid, SKYDROL®, and the like. To that end, the clearcoat  14  contributes to resistance of the appliqué  10  to wind- and rain-erosion. In one embodiment, the clearcoat  14  is applied over the appliqué  10  after the appliqué  10  is applied to the substrate  12 . Given by way of non-limiting example, the clearcoat  14  may be sprayed as a layer that covers the entire appliqué  10 . In addition, if desired, the clearcoat  14  may be painted around edges of the appliqué  10 . Non-limiting examples of acceptable clearcoat include polyurethane coatings such as Desothane HS® BAC 900 (CA8000/B900A or CA8000/B900B) from PRC/DeSoto or Eclipse® BAC 900 clearcoat from Akzo-Nobel, and the like.  
         [0026]     The polymer film  20 , the pattern layer  22 , and the PSA  24  advantageously are selected to adhere strongly to each other. To that end, certain key chemical parameters of the polymer film  20 , the pattern layer  22 , and the PSA  24 , such as surface tension and the polarizability of chemical species (moieties) on the surfaces thereof, are similar in value such that the polymer film  20 , the pattern layer  22 , and the PSA  24  all have a high chemical affinity for each other. For example, the surface tension of the polymer film  20 , the pattern layer  22 , and the PSA  24  suitably are all within around +/−5 dyn/cm of each other. Furthermore, it is desirable that the surface tension of the polymer film  20 , the pattern layer  22 , and the PSA are all compatible with the surface tension of the clearcoat  14 . This is because the polymer film  20 , the pattern layer  22 , and the PSA  24  are all in contact at their edges with the clearcoat  14 . Further, in the embodiment shown in  FIG. 1A , the top of the polymer film  20  is covered by the clearcoat  14  and, in the embodiment shown in  FIG. 1B , the top of the pattern layer  22  is covered by the clearcoat  14 .  
         [0027]     While various materials have been discussed for the components of the appliqué  10  (that is, the polymer film  20 , the pattern layer  22 , and the PSA  24 ), certain combinations of components of the appliqué  10  may be better suited for use with each other than other combinations. Table 1 below shows, by way of non-limiting examples, combinations of components of the appliqué  10  that are well suited to each other.  
                               TABLE 1                                   Polymer Film 20   Pattern Layer 22   PSA 24                           Urethane   Pigmented fast-dry acrylic   Acrylic           Urethane   Urethane with pigment   Acrylic           Urethane   Desothane   Acrylic           Urethane   Epoxy   Acrylic           Acrylic   Pigmented fast-dry acrylic   Acrylic           Epoxy   Epoxy   Acrylic                      
 
         [0028]     Referring now to  FIGS. 2A and 2B , before the appliqué  10  or the appliqué  10 ′ is applied to the substrate  12 , ( FIGS. 1A and 1B ), the appliqués  10  and  10 ′ are covered by a carrier sheet  26  and a liner  28 . The carrier sheet  26  and the liner  28  protect the appliqués  10  and  10 ′ before application, and provide for ease of handling and ease of application. In the embodiment shown in  FIG. 2A , the carrier sheet  26  covers the polymer film  20 . In the embodiment shown in  FIG. 2B , the carrier sheet  26  covers the pattern layer  22 . In certain embodiments (not shown), the carrier sheet  26  may be omitted if deemed to be not needed to assist in application of the appliqués  10  and  10 ′. In the embodiments shown in both  FIGS. 2A and 2B , the liner  28  underlies the PSA  24 . In addition to assisting in application of the appliqués  10  and  10 ′ the liner  28  protects the PSA  24  from damage by unintentional contact with other surfaces. The carrier sheet  26  adheres to the polymer film  20  ( FIG. 2A ) or to the pattern layer  22  ( FIG. 2B ) with an adhesion strength that is stronger than the adhesion strength with which the liner  28  adheres to the PSA  24 . However, both of these adhesion strengths are less than the adhesion strength between the PSA  24  and the substrate  12  ( FIGS. 1A and 1B ).  
         [0029]     Referring now to  FIGS. 1A, 1B ,  2 A, and  2 B, this ordering of adhesion strengths ensures that the liner  28  can come off the PSA  24  when preparing to apply the appliqué  10  or  10 ′ to the substrate  12  while permitting the carrier sheet  26  to still adhere to the polymer film  20  or the pattern layer  22 . Once the liner  28  has been removed and the PSA  24  adheres to the substrate  12 , the carrier sheet  26  can be removed from the polymer film  20  or the pattern layer  22 .  
         [0030]     At this point, the appliqué  10  or  10 ′ is applied to the substrate  12  but the polymer film  20  or the pattern layer  22  is not yet covered by the clearcoat  14 . If desired, the polymer film  20  or the pattern layer  22  may be rinsed and wiped down with a cleaning agent, such as without limitation isopropyl alcohol, to remove any contamination before the clearcoat  14  is applied. With the appliqué  10  or  10 ′ thus applied to the substrate  12 , the clearcoat  14  can be applied as desired (such as by spraying) to completely cover the polymer film  20  or the pattern layer  22 .  
         [0031]     Referring now to  FIGS. 1A, 1B , and  3 , the appliqués  10  and  10 ′ are well suited for use on skin of an aircraft  30 . Because of the materials selected for the polymer film  20 , the pattern layer  22 , and the PSA  24 , and because of the thin overall thickness of the appliqués  10  and  10 ′ that is on the order of around 1-2 mils, and because the appliqués  10  and  10 ′ are completely covered by the clearcoat  14 , the appliqués  10  and  10 ′ are more resistant to wind- and rain-erosion than are conventional appliqués.  
         [0032]     Given by way of non-limiting example, the appliqués  10  and/or  10 ′ may be applied to skin of a fuselage  32  of the aircraft  30 . The aircraft  30  may be any type of known aircraft that includes an airframe and skin. In this non-limiting example, the pattern layers  22  may give effect to an image such as airline livery (not shown), to solid colors (such as the solid white color or the dark stripes shown on the fuselage  32 , to mandatory markings such as an aircraft tail number, and to stylized text such as BOEING  777  shown on the fuselage  32  and  777  shown on skin of a vertical stabilizer  34 . As another non-limiting example, the pattern layers  22  of the appliqué  10  and/or  10 ′ that are applied to an exterior skin of an engine nacelle  36  may give effect to an image of an jet engine manufacturer.  
         [0033]     While a number of exemplary embodiments and aspects have been illustrated and discussed above, those of skill in the art will recognize certain modifications, permutations, additions, and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, and sub-combinations as are within their true spirit and scope.