Film stack including polyurethane pressure sensitive adhesive layer and method of making same

Abstract

A film stack includes a polymeric film; a polyurethane pressure sensitive adhesive layer having opposing first and second major surfaces where the first major surface is disposed on, and physically contacts, the polymeric film and where the second major surface includes a plurality of structures defining fluid egress passageways; and a structured release liner having a structured major surface disposed on, and substantially conforming to the second major surface of the polyurethane pressure sensitive adhesive layer. When the structured release liner is removed from the film stack and the polyurethane pressure sensitive adhesive layer is placed on a support surface with the second major surface physically contacting the support surface, the plurality of structures substantially disappears within about 2 weeks at room temperature.

Description

[0001] PA103360W002

[0002] FILM STACK INCLUDING POLYURETHANE PRESSURE SENSITIVE ADHESIVE LAYER AND METHOD OF MAKING SAME

[0003] TECHNICAL FIELD

[0004] The present description relates generally to film stacks, and more specifically, to a film stack including an adhesive layer and a release liner.

[0005] BACKGROUND

[0006] A release liner may include a structured release surface for forming air release channels in an adhesive layer.

[0007] SUMMARY

[0008] In some aspects, the present description provides a film stack including a polymeric film; a polyurethane pressure sensitive adhesive layer having opposing first and second major surfaces where the first major surface is disposed on, and physically contacts, the polymeric film and where the second major surface includes a plurality of structures defining fluid egress passageways; and a structured release liner having a structured major surface disposed on, and substantially conforming to the second major surface of the polyurethane pressure sensitive adhesive layer. When the structured release liner is removed from the film stack and the polyurethane pressure sensitive adhesive layer is placed on a support surface with the second major surface physically contacting the support surface, the plurality of structures substantially disappears within about 2 weeks at room temperature.

[0009] In some aspects, the present description provides a method of making a film stack. The method includes coating a polyurethane pressure sensitive adhesive formulation onto a structured major surface of a structured release liner where the polyurethane pressure sensitive adhesive formulation includes polyurethane polymer in a solvent; drying the coated formulation; curing the dried coating to form a cured polyurethane pressure sensitive adhesive layer having opposing first and second major surfaces, where the second major surface is disposed on, and substantially conforms to, the structured major surface of the structured release liner such that the second major surface comprises a plurality of structures defining fluid egress passageways; and laminating a polymeric film to the first major surface of the polyurethane pressure sensitive adhesive layer to form the film stack.

[0010] These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a film stack, according to some embodiments.FIG. 2A is a schematic cross-sectional view showing an adhesive layer disposed on a support surface before structures of the adhesive layer have substantially disappeared, according to some embodiments.

[0012] FIG. 2B is a schematic cross-sectional view showing an adhesive layer disposed on a support surface after structures of the adhesive layer have substantially disappeared, according to some embodiments.

[0013] FIG. 3 A is a schematic cross-sectional view showing an adhesive layer disposed on a support surface where the adhesive layer includes protruding structures, according to some embodiments.

[0014] FIG. 3B is a schematic cross-sectional view showing an adhesive layer disposed on a support surface where the adhesive layer includes both protmding and recessed structures, according to some embodiments.

[0015] FIG. 4 is a schematic cross-sectional view showing an adhesive layer disposed on a support surface where the adhesive layer has ridge structures, according to some embodiments.

[0016] FIGS. 5-6 are schematic top views showing different patterns of structures of an adhesive layer, according to some embodiments.

[0017] FIG. 7 is a schematic illustration of light transmission through a layer or film, according to some embodiments.

[0018] FIG. 8 is a schematic illustration of a method of making a film stack, according to some embodiments.

[0019] DETAILED DESCRIPTION

[0020] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0021] Structured release liners are generally known in the art and are described in U. S. Pat. Appl. Pub. Nos. 2021 / 0095166 (Seth et al.); 2020 / 0009843 (Sherman et al.); 2015 / 0298446 (Mikami et al);

[0022] 2007 / 0128396 (Sher et al.); and 2003 / 0152695 (Sher et al.), for example, and in U. S. Pat. Nos. 7,087,279 (Callahan et al.); 10,723,919 (Free); 11,879,081 (Schonfelder et al.); 12,117,635 (Toy et al.); 6,197,397 (Sher et al.), for example. The structures of a structured release liner can be formed via embossing a polymeric layer or film, for example. The structures can define passageways for air release in an adhesive layer when the adhesive layer is disposed on the structured surface of the release liner. Release liners may further define features (e.g., non-adhesive protrusions or particles) in an adhesive layer for repositionability as generally known in the art and described in U. S. Pat. Nos. 3,314,838 (Erwin);

[0023] 5,141,790 (Calhoun et al.); 5,296,277 (Wilson et al.); 5,362,516 (Wilson et al); and 6,197,397 (Sheret al.), for example.While structured release liners can result in air passageways that disappear over time for various adhesives, it has previously been believed that polyurethane (PU) pressure sensitive adhesives (PSAs) would not allow the passageways to disappear over time due to the properties of typical PU PSAs. However, according to some embodiments of the present description, it has now been found that a structured release liner can define air passageways in certain PU PSAs that disappear over time. For example, it has been found that the polyurethane of a PU PSA can include groups configured to reduce crystallinity of the polyurethane and that this can lead to the air passageways disappearing over time. Further, it has been found that the passageways more completely disappear than when conventional adhesives are utilized. For example, an adhesive with air release passageways may be used to bond a transparent film to a surface (e.g., the painted surface of an automobile where the transparent film may be a protective film), for example, where the air release passageways may be visible if they do not sufficiently disappear after application. It has been found that for conventional adhesives, but not for a PU PSA according to some embodiments of the present description, that the air release passageways are visible to the unaided eye of a person of 20 / 20 vision and / or result in undesired visible haze to the unaided eye and are visible under an optical microscope at a 50x magnification, for example.

[0024] Principles of polyurethane formulation are known in the art and are described, for example, in Chapter 1 of Felipe M. de Souza, Pawan K. Kahol, Ram K. Gupta (2021); Polyurethane Chemistry: Renewable Polyols and Isocyanates', ACS Symposium Series, Vol. 1380; and in Chapter 7 of Kumbar, Sangamesh G. Laurencin, Cato T. Deng, Meng (2014); Natural and Synthetic Biomedical Polymers,' Elsevier. Polyurethanes typically comprise a plurality of alternating hard and soft segments.

[0025] Polyurethanes can be formed as a reaction product of a formulation comprising at least one isocyanate and at least one polyol. The at least one isocyanate can define the hard segments of the polyurethane and the at least one polyol can include diols of long-chain molecules of poly ether, polyesters, poly siloxane, and / or polycarbonate, for example, to define the soft segments. Mechanical properties of polyurethanes can be varied by suitably selecting the hard and soft segments and / or by varying the ratio of the soft and hard segments. Generally, increasing the hard segment fraction increases strength of the polyurethane while increasing the soft segment fraction increases the elasticity of the polyurethane. A polyurethane can be a pressure sensitive adhesive (PSA) when the polyurethane forms a bond with minimal pressure, without needing heat, water, or other activation methods. The pressure sensitive adhesive properties (e.g, tack, peel adhesion) can be generally contributed by an alkylene group of the polyurethane (e.g.. contributed by an aromatic or aliphatic polyester or polycarbonate polyol). Without intending to be bound by theory', the tack and peel adhesion can be increased by use of a longer branched alkylene group and / or by reducing the crosslinking. Conversely, the tack and peel adhesion can be decreased by use of a shorter branched alkylene group or by increasing the crosslinking. The adhesion can also be adjusted by the addition of other aliphatic polyols having longer or shorter alkylene groups. Polyurethane PSAs are known in the art and are described in U. S. Pat. No. 11.629,273 (Lu et al.) and International Appl. Pub. No. WO 2025 / 046451 (Xia et al.), for example.In some embodiments, a film stack includes a polyurethane pressure sensitive adhesive layer disposed on a structured release liner as described further elsewhere herein.

[0026] In some embodiments, the polyurethane pressure sensitive adhesive layer comprises a polyurethane comprising at least one of pendent groups and non-planar cyclic backbone groups. The at least one of pendent groups and non-planar cyclic backbone groups may be configured to reduce crystallinity of the polyurethane (e.g., as reflected in a lower glass transition temperature when the groups are included compared to when they are not). In some embodiments, the polyurethane pressure sensitive adhesive layer comprises a polyurethane having groups configured to reduce crystallinity of the polyurethane, where the groups may comprise at least one of pendent groups and non-planar cyclic backbone groups.

[0027] In some embodiments, the groups (e.g., the at least one of pendent groups and non-planar cyclic backbone groups and / or the groups configured to reduce crystallinity of the polyurethane) comprise the pendent groups. In some embodiments, the pendent groups comprise C2-C30 aliphatic units. In some embodiments, the pendent groups comprising C2-C30 aliphatic units further comprises one or more of an oxygen atom, a nitrogen atom, and a cyclic group. In some embodiments, the pendent groups comprising C2-C30 aliphatic units comprise

[0028] -CO(OC2H4)nOCO(CH2)mCH3,

[0029] where n is a positive integer and m is an integer in a range of 2 to 25, or 8 to 20, or 10 to 18, or 12 to 16 or 14. A suitable isocyanate for providing such groups is TOLONATE X FLO 100 (available from Vencorex, Saint-Priest, France), for example. In some embodiments, at least one of the pendent groups comprising C2-C30 aliphatic units is attached to a backbone chain of the polyurethane through an allophanate group having an -N- along the backbone chain.

[0030] In some embodiments, the groups (e.g., the at least one of pendent groups and non-planar cyclic backbone groups and / or the groups configured to reduce crystallinity of the polyurethane) comprise the non-planar cyclic backbone groups. In some embodiments, the non-planar cyclic backbone groups comprise aliphatic rings. In some embodiments, at least one of the non-planar cyclic backbone groups comprises a 6-member aliphatic ring. In some embodiments, at least one of the non-planar cyclic backbone groups comprises dicyclohexylmethane. A suitable isocyanate for providing such groups is 4,4'-diisocyanato dicyclohexylmethane (H₁₂MDI) which may be obtained under the trade name DESMODUR W from Covestro LLC (Pitsburgh, PA).

[0031] In some embodiments, the groups (e.g., the at least one of pendent groups and non-planar cyclic backbone groups and / or the groups configured to reduce crystallinity of the polyurethane) comprise the pendent groups and the non-planar cyclic backbone groups.

[0032] In some embodiments, the polyurethane comprises a reaction product of isocyanates and at least one polyol, where at least 50, 60, 70, 80, 90, or 100 mol% of the isocyanates comprise at least one of pendent groups and non-planar cyclic backbone groups. The pendent groups and / or non-planar cyclic backbone groups may be as described elsewhere herein. The at least one polyol can include one or morepolyester polyols. Suitable polyester polyols include those available from Stepan Company (Northbrook, IL) under the STEPANPOL tradename and those available from Kuraray (Japan) under the Kuraray Polyol P-series tradename, for example. The at least one polyol can further include one or more (meth)acrylate polyols, such as bisphenol A glycerolate dimethacrylate, to provide (meth)acrylate functionality for post-curing (e.g., via actinic radiation) the polyurethane pressure sensitive adhesive layer after it has been formed on a structured release liner. Here, (meth)acrylate encompasses acrylate and methacrylate. The polyurethane may alternatively be thermally cured. The isocyanates can further include at least one of 4,4'-MDI (methylene diphenyl diisocyanate), carbodiimide modified 4,4'-MDI, and allophanate modified 4,4’ -MDI. Useful isocyanates include those available from Huntsman Corporation (The Woodlands, TX) under the RUBINATE tradename and those available from Covestro (Leverkusen, Germany) under the MONDUR tradename, for example. The polyurethane layer may be formed by coating a polyurethane formulation, drying the coated formulation, and then curing the dried polyurethane. The polyurethane formulation can include a polyurethane solution (e.g., polyurethane polymer in a solvent such as methyl ethyl ketone (MEK), for example) and may further include one or more additives. A photoinitiator such as ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (available from IGM resins (Waalwijk, The Netherlands), for example) can be included in the polyurethane formulation. A hydrolysis stabilizer such as N, N, N’, N’-tetraglycidyl-m-xylenediamine (available from Huntsman Corporation as ERISYS GA240, for example) may also be included in the polyurethane formulation. Other useful ingredients for making the polyurethane include those described in the Examples and those described in U. S. Pat. No. 11,629,273 (Lu et al.) and International Appl. Pub. No. WO 2025 / 046451 (Xia et al.), for example.

[0033] In some embodiments, the polyurethane has a glass transition temperature (Tg) less than 37, 35, 30, 25, 20, 15, 10, 5, 0, -5, -10, -15, -20, -25, or -30 degrees C. The Tg is typically greater than -100 degrees C or greater than -80 degrees C. The Tg of a PU PSA can be adjusted by selecting monomers of the PU formulation that have suitable Tgs. For example, a low Tg polyol may be selected to result in a low Tg PU. A low glass transition temperature may correspond to a low crystallinity of the polyurethane. Glass transition temperature can be determined by differential scanning calorimetry (DSC), for example, and / or may be determined according to ASTM E2602-24, for example.

[0034] FIG. 1 is a schematic cross-sectional view of a film stack 100, according to some embodiments. In some embodiments, a film stack 100 includes a polymeric film 110; a polyurethane pressure sensitive adhesive layer 120 having opposing first and second major surfaces 121 and 122, where the first major surface 121 is disposed on, and physically contacts, the polymeric film 110, and the second major surface 122 comprises a plurality of structures 125 defining fluid egress passageways 128; and a structured release liner 130 having a structured major surface 132 disposed on, and substantially conforming (e.g., nominally conforming or conforming up to variations small (e.g., less than 20% or less than 10%) compared to the average structure height H) to the second major surface 122 of the polyurethane pressure sensitive adhesive layer 120.In some embodiments, the plurality of structures 125 comprises a plurality of channels such as a plurality of intersecting channels and / or a plurality of irregularly arranged channels. The plurality of structures 125 may alternatively include protruding structures as described further elsewhere herein. In some embodiments, the plurality of channels has an in-plane average channel width W (which may alternatively be referred to as an average structure width) in a range of about 5 to 100 micrometers. In some such embodiments, or in other embodiments, W is at least about 7, 10, 15, or 18 micrometers. In some such embodiments, or in other embodiments, W is no more than about 80, 60, 40, 30, or 25 micrometers. In some such embodiments, or in other embodiments, the plurality of channels has an average channel height H (which may alternatively be referred to as an average channel depth or average structure height or depth) along a thickness direction (z-direction) of the polyurethane pressure sensitive adhesive layer 120 that is in a range of about 5 to 30 micrometers. In some such embodiments, or in other embodiments, H is at least about 8, 10, 12 micrometers. In some such embodiments, or in other embodiments, H is no more than about 25, 20, 18, or 16 micrometers. In some embodiments, the structures 125 have an average structure height H in a range of about 5 to 25 micrometers, and the polyurethane pressure sensitive adhesive layer comprises a polyurethane comprising at least one of pendent groups and non-planar cyclic backbone groups. It has been found, according to some embodiments, that this can accelerate the substantial disappearance of the fluid egress passageways.

[0035] In some embodiments, the polyurethane pressure sensitive adhesive layer 120 has a total thickness T of no more than about 200, 150, 100, 80, 60 micrometers. In some such embodiments, or in other embodiments, the total thickness T is at least 10, 20, 30, 35, or 40 micrometers. Generally, a thin (e.g., no more than about 200 micrometers) adhesive layer is typically preferred, but it has been found that a thicker adhesive layer can accelerate the substantial disappearance of the structures 125 after the adhesive layer 120 is disposed on a support so a sufficient thickness (e.g., at least 10 micrometers, or preferably at least 20 or 30 micrometers, or more preferably at least 35 or 40 micrometers) is also typically preferred.

[0036] In some embodiments, the film stack 100 further includes a plurality of particles 140 distributed along the second major surface of, and at least partially embedded in, the polyurethane pressure sensitive adhesive layer 120. The particles 140 are typically non-adhesive particles and may be inorganic particles such as hollow glass microspheres. Adhesive layers having such features for repositionability are generally known in the art and are described in U. S. Pat. Nos. 3,314,838 (Erwin); 5,141,790 (Calhoun et al.); 5,296,277 (Wilson et al.); 5,362,516 (Wilson et al); and 6,197,397 (Sher et al.), for example. In some embodiments, the film stack 100 further includes a plurality of non-adhesive protrusions 140 distributed along, and protruding from, the second major surface 122 of the polyurethane pressure sensitive adhesive layer 120.

[0037] In some embodiments, structures 125 of the adhesive layer 120 substantially disappear over time after the adhesive layer has been bonded to a support surface.FIG. 2A is a schematic cross-sectional view showing an adhesive layer 120 disposed on a support surface 142 before structures 125 of the adhesive layer 120 have substantially disappeared, according to some embodiments. FIG. 2B is a schematic cross-sectional view showing an adhesive layer 120 disposed on a support surface 142 after structures 125 of the adhesive layer 120 have substantially disappeared, according to some embodiments.

[0038] In some embodiments, when the structured release liner 130 is removed from the film stack 100 and the polyurethane pressure sensitive adhesive layer 120 is placed on a support surface 142 (of support of 144) with the second major surface 122 physically contacting the support surface 142, the plurality of structures 125 substantially disappears within about 2, 1.8, 1.6, 1.4, 1.2 or 1 week, or 6, 5, 4, 3, 2, or 1 day, or 18, 12, 10, 8, 6, or 5 hours at room temperature (e.g., 25 deg. C). For example, the plurality of structures 125 may substantially disappear within about 5 days at room temperature. In some embodiments, the polymeric film 110 and the adhesive layer 120 are sufficiently transparent that the disappearance of the structures 125 can be determined by looking through the polymeric film 110 and the adhesive layer 120 toward or to the support surface 142. Accordingly, in some embodiments, the substantial disappearance of the structures 125 can be tested by laminating the polymeric film 110 with the adhesive layer 120 to a painted panel, for example, and observing (e.g., under an optical microscope) the stmctures 125 through the polymeric film 110 and adhesive layer 120. In some embodiments, the substantial disappearance of the structures 125 can be tested by laminating the polymeric film 110 with the adhesive layer 120 to a surface 142 of a transparent substrate (e.g., glass or transparent plastic) and then observing the structures 125 through the transparent substrate.

[0039] As used herein, structures that “substantially disappear" are not visible to a person of normal 20 / 20 vision when viewed under an optical microscope at 50x magnification using ordinary microscope lighting (e.g., substantially white light provided by a light emitting diode ring illuminator). It will be understood that the structures 125 are observed through sufficiently transparent layer(s) (e.g., polymeric film 110 and adhesive layer 120 can be sufficiently transparent that the structures 125 can be observed through these layers and / or the support surface can be a surface of a transparent substate) such that the structures 125 are initially visible under the 50x magnification.

[0040] The plurality of structures 125 may be a plurality of channels as schematically illustrated in FIGS.

[0041] 1 and 2A, for example, or other structures may be utilized. Any structured release liner known in the art for creating fluid egress (e.g., air release) passageways in an adhesive layer may be used with the PU PSAs of the present description. Suitable release liners include those described in the release liner references provided elsewhere herein, those available from 3M Company (St. Paul, MN) under the COMPLY, MICROCOMPLY, and CONTROLTAC tradenames, those available from Mondi PLC (Weybridge, England) under the AIRXLINER tradename; and those available from LOPAREX (Cary, NC) under the POLYSILK tradename, for example. In some embodiments, the release liner defines in the adhesive layer channels such as a plurality of intersecting channels or regularly or irregularly arranged protruding structures such as an array of protruding structures or a plurality of intersecting ridges.FIG. 3 A is a schematic cross-sectional view showing an adhesive layer 120 disposed on a support surface 142 where the adhesive layer 120 includes protruding structures 125, according to some embodiments. The protruding structures may have an average width W and an average height H. H and / or W may be in any of the respective ranges described elsewhere herein for channels. The protruding structures may be a two-dimensional array of protruding structures such as those described in US Pat. No.

[0042] 7,087,279 (Callahan et al.), for example. In some embodiments, the plurality of structures 125 comprises a plurality of protruding structures. In some such embodiments, the fluid egress passageways 128 extend between the protruding structures.

[0043] FIG. 3B is a schematic cross-sectional view showing an adhesive layer 120 disposed on a support surface 142 where the adhesive layer 120 includes structures 125 that include both protruding and recessed structures, according to some embodiments. In this case, the average width and height of the structures 125 (which may be in any of the respective ranges described elsewhere herein for channels, for example) is the average (mean) of the widths and heights over all structures 125 including the protruding structures (e.g., having widths and heights W and H, respectively, as schematically illustrated in FIG. 3A) and the recessed structures (e.g., having widths and heights W and H, respectively, as schematically illustrated in FIG. 2A). Including recessed structures with the protruding structures can provide improved air release performance with reduced time for the structures to disappear compared to including only the protruding structures, for example.

[0044] FIG. 4 is a schematic cross-sectional view showing an adhesive layer 120 disposed on a support surface 142 where the adhesive layer 120 has ridge structures 125, according to some embodiments. In some embodiments, the plurality of structures comprises a plurality of protruding structures 125, where the protruding structures have an irregular height defining the fluid egress passageways 128. In some embodiments, the plurality of protruding structures 125 include a plurality of intersecting ridges which may be a plurality of intersecting ridges and / or may be a plurality of irregularly arranged ridges (see, e.g., FIGS. 5-6). In some embodiments, the plurality of structures 125 comprises a plurality of intersecting ridges, where the ridges have an irregular height defining the fluid egress passageways 128. In some embodiments, a standard deviation of the irregular height is in a range of 0.01 to 0.8 times an average height of the ridges, for example.

[0045] FIGS. 5-6 are schematic top views showing different patterns of structures 125 of an adhesive layer 120, according to some embodiments. The structures 125 in these figures are extended structures and may schematically represent channels and / or ridges, for example. In FIG. 5, the structures 125 form a regular array of intersecting structures. In FIG. 6, the structures 125 are irregularly arranged intersecting structures.

[0046] In some embodiments, the plurality of channels (or ridges) defines a plurality of channel-free regions 127 (or, respectively, ridge-free regions) bounded by channels of the plurality of channels (or, respectively, bounded by ridges of the plurality of ridges), where the regions 127 have an average largest lateral dimension D in a range of about 100 micrometers to about 800 micrometers. In some suchembodiments, or in other embodiments, D is at least about 125, 150, 175, 200, 250, 300, or 350 micrometers. In some such embodiments, or in other embodiments, D is no more than about 750, 700, 650, or 600 micrometers. The average largest lateral dimension D may be determined by taking the mean of the largest lateral dimensions determined for the regions 127. For example, for a regular array of rectangles having a same size, the average largest lateral dimension D is the diagonal dimension of the rectangles. In some embodiments, a plurality of channels and ridges is included, and the plurality of channels and ridges defines a plurality of channel and ridge-free regions 127 bounded by channels and ridges of the plurality of channels and ridges, where the regions 127 have an average largest lateral dimension D in any of the ranges described above.

[0047] In some embodiments, after the structured release liner 130 is removed from the film stack 100 and the polymeric film 110 is laminated to an aluminum substrate (e.g., support 144 may be an aluminum substrate such as a Fruehauf panel), a 180 degree peel force of the polymeric film 110 from the aluminum substrate is no less than about 20, 25, 30, 40, or 50 N / dm (and may be up to about 140, 120, or 105 N / dm) after a 24 hour dwell time at room temperature. In some embodiments, after the stmctured release liner 130 is removed from the film stack 100 and the polymeric film 110 is laminated to an aluminum substrate (e.g., a Fruehauf panel), a 180 degree peel force of the polymeric film 110 from the aluminum substrate is no less than about 40, 45, 50, 70, 75, or 100 N / dm (and may be up to about 160, 150, or 140 N / dm) after a 24 hour dwell time at 60 deg. C.

[0048] In some embodiments, the polymeric film 110 is or includes at least one of a polyester film (e.g., a polyethylene terephthalate (PET) film); a vinyl film; a polyolefin film (e.g., polyethylene film); a polyurethane film; an acrylic film; a poly lactic acid (PLA) film; or a bio-derived film (e.g., a PLA film made from bio-derived lactic acid, or polyurethane or polyester with bio-derived components).

[0049] In some embodiments, the polymeric film 110 is or includes one or more of a multilayer optical film reflecting or transmitting light primarily by optical interference; a paint protection film; a decorative film (e.g., a film with an embossed pattern to create a desired look and / or with a printed pattern and / or a multilayer optical film with a color that shifts with viewing angle); and a window film (e.g., a fdm for preventing a window from shattering and / or an infrared reflective film for reflecting infrared solar radiation).

[0050] Layers may be described as reflecting or transmitting light primarily by optical interference when the reflectance and transmittance of the interference layers can be reasonably described by optical interference or reasonably accurately modeled as resulting from optical interference. Multilayer optical films reflecting or transmitting light primarily by optical interference are known in the art and are described in U. S. Pat. Nos. 5,882,774 (Jonza et al.); 6,783,349 (Neavin et al.); 6,949,212 (Merrill et al.); 6,967,778 (Wheatley et al.); 9,162,406 (Neavin et al.); and 11,493,677 (Haag et al.), for example. Such films may provide reflection in certain wavelength ranges while providing transmittance in other wavelength ranges and / or may substantially reflect a first polarization state and substantially transmit anorthogonal second polarization state. A window film may be a multilayer optical film (e.g., transmitting visible wavelengths and reflecting near-infrared wavelengths).

[0051] The polymeric film 110 may be a paint protection film. Paint protection films typically protect a vehicle’s paint from scratches, chips, or other damage and are conventionally applied with a wet solution for ease of installation. A dry installation may be preferred, but air release structures are preferred in this case since air bubbles would otherwise be undesirably visible and air release structures of conventional adhesives do not sufficiently disappear. For example, the PU PSA may be used to bond a transparent paint protection film to an automobile, for example, where the air release passageways may be readily visible if they do not sufficiently disappear after application. A paint protection film may have a thickness of no less than about 100, 110, or 120 micrometers. In some embodiments the thickness is no more than about 550, 475, 400, 325, 275, 225, or 200 micrometers. For example, a paint protection film may have a thickness in a range of about 100 micrometers to about 550 micrometers, or about 110 micrometers to about 400 micrometers, or about 120 micrometers to about 325 micrometers, or about 120 micrometers to about 200 micrometers. A paint protection film may be or include a polyurethane film, for example.

[0052] The polymeric film 110 and / or the polyurethane pressure sensitive adhesive layer 120 may be substantially optically transparent (e.g., having an average optical transmittance of greater than 60% in a wavelength range of 400 nm to 700 nm for substantially normally incident light and for each of two orthogonal polarization states) or at least optically transmissive for at least some range of visible wavelengths. It has been found that for conventional adhesives, but not for a PU PSA according to some embodiments of the present description, that the fluid egress (e.g., air release) passageways 128 are visible through the polymeric film 110 and through the adhesive layer 120 to the unaided eye of a person of 20 / 20 vision and / or result in undesired visible haze to the unaided eye and are visible under an optical microscope at a 50x magnification, for example.

[0053] FIG. 7 is a schematic illustration of light transmission through a layer or film 115, according to some embodiments. The layer or film 115 may correspond to adhesive layer 120, or to polymeric film 110, or to a stack of the adhesive layer 120 and the polymeric film 110, for example. In some embodiments, for substantially normally incident (e.g., within 25, 20, 15, or 10 degrees of normally incident) light 162 and for at least one polarization state (e.g., one or both of polarization states 165 and 167), the polymeric film 110 has an average optical transmittance (see, e.g., transmitted light 163) of greater than 20, 30, 40, 50, 60, 70, 80% in a visible wavelength range at least 50, 75, 100, 150, 200, or 250 nm wide (e.g., a range of wavelengths from W1 to W2 where 400 nm < W1 < W2 < 700 nm and where W2-W1 is at least 50 nm). In some embodiments, the polymeric film 110 and the adhesive layer 120 are sufficiently transparent that the structures 125 are visible (e.g., to the unaided eyes of a person of 20 / 20 vision under ordinary daylight and / or under an optical microscope at 50x magnification) through the polymeric film 110 and the adhesive layer 120 when the adhesive layer is first applied to the support surface 142. In some embodiments, for substantially normally incident light 162 and for each of orthogonal first and second polarization states 165 and 167, the polymeric film 110 has an average opticaltransmittance of greater than 80, 85, or 90 percent in a wavelength range of 400 nm to 700 nm. In some embodiments, for substantially normally incident light 162 and for each of orthogonal first and second polarization states 165 and 167, the adhesive layer 120 has an average optical transmittance of greater than 80, 85, or 90 percent in a wavelength range of 400 nm to 700 nm.

[0054] FIG. 8 is a schematic illustration of a method 500 of making a film stack, according to some embodiments. In some embodiments, a method 500 of making a film stack 100 is provided, where the method 500 includes coating (step 502) a polyurethane pressure sensitive adhesive formulation onto a structured major surface 132 of a structured release liner 130, where the polyurethane pressure sensitive adhesive formulation includes polyurethane polymer in a solvent (e.g., methyl ethyl ketone (MEK)); drying (step 504) the coated formulation (e.g., to remove solvent); curing (step 506) the dried coating to form a cured polyurethane pressure sensitive adhesive layer 120 having opposing first and second major surfaces 121 and 122, where the second major surface 122 is disposed on, and substantially conforms to, the structured major surface 132 of the structured release liner 130 such that the second major surface 122 includes a plurality of structures 125 defining fluid egress passageways 128; and laminating (step 508) a polymeric film 110 to the first major surface 121 of the polyurethane pressure sensitive adhesive layer 120 to form the film stack 100. Before drying, the polyurethane pressure sensitive adhesive formulation may have a solids content in a range of about 40 to 55 wt.%, for example. The curing step can include applying actinic radiation (e.g., ultraviolet (UV) curing) and / or applying heat (e.g., thermally curing).

[0055] The film stack resulting from the method 500 can have properties described elsewhere herein. For example, in some embodiments, as described further elsewhere herein, when the structured release liner 130 is removed from the film stack and the polyurethane pressure sensitive adhesive layer 120 is placed on a support surface 142 with the second major surface 122 physically contacting the support surface 142, the plurality of structures 125 substantially disappears within about 2, 1.8, 1.6, 1.4, 1.2 or 1 week, or 6, 5, 4, 3, 2, or 1 day, or 18, 12, 8, or 6 hours at room temperature (see, e.g., FIGS. 2A-2B). The polyurethane pressure sensitive adhesive layer 120 resulting from the method 500 can be as described elsewhere herein. For example, in some embodiments, the polyurethane pressure sensitive adhesive layer 120 comprises a polyurethane comprising a reaction product of isocyanates and at least one polyol, where at least 50, 60, 70, 80, 90, or 100 mol% of the isocyanates comprise one or more groups configured to reduce a crystallinity of the polyurethane, where the one or more groups comprise at least one of pendent groups and non-planar cyclic backbone groups. The polymeric film 110 laminated to the first major surface 121 may be any polymeric film described herein and / or can have any of the properties described herein. For example, in some embodiments, for substantially normally incident light and for at least one polarization state, the polymeric film 110 has an average optical transmittance of greater than 20, 30, 40, 50, 60, 70, 80% in a visible wavelength range at least 50 nm wide.

[0056] In some embodiments, a method of bonding a polymeric film (e.g., a paint protection film) to a support surface (e.g., a painted surface of an automobile) includes the steps of making a film stack 100according to the method 500, removing the release liner 130, and placing the polyurethane pressure sensitive adhesive layer 120 on the support surface.

[0057] EXAMPLES

[0058] Table 1: Materials

[0059] Designation Description Source

[0060] Polyester Polyol Mw = 2000, under the trade name Stepan Company, PH-56

[0061] STEPANPOL PH-56 Northbrook, IL RUBINATE MDI (methylene diphenyl diisocyanate)-based Huntsman Corporation, 9225 polyisocyanate The Woodlands, TX MONDUR Allophanate modified 4,4’-diphenylmethane- Covestro, Leverkusen, 2902 diisoayanate Germany

[0062] Aliphatic polyisocyanate, under the trade name Vencorex, Saint-Priest, X FLO 100

[0063] TOLONATE X FLO 100 France

[0064] Sigma Aldrich, St. Louis, bis-GMA Bisphenol A glycerolate dimethacrylate

[0065] MO

[0066] Bismuth carboxylate catalyst, under the trade name K- King Industries, Norwalk, XK-651

[0067] KAT XK-651 CT

[0068] N, N, N’, N’-tetraglycidyl-m-xylenediamine, under the Huntsman Corporation, GA240

[0069] trade name Erisys GA240 The Woodlands, TX TPO-L Ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate IGM Resins

[0070] EMD Millipore MEK Methyl ethyl ketone, solvent Corporation, Burlington,

[0071] MA

[0072] Aliphatic diisocyanate, under the trade name Covestro LLC, H₁₂MDI

[0073] DESMODUR W Pittsburgh, PA Aliphatic diisocyanate, under the trade name Covestro LLC, HDI DESMODUR H Pittsburgh, PA Polyester polyol with a MW of 2000, under the trade

[0074] P2050 Kuraray, JP

[0075] name Kuraray Polyol P-2050

[0076] MPD 3-methyl-l,5-pentandiol, a chain extender Sigma-Aldrich, MO Aliphatic diisocyanate under the trade name

[0077] TMDI Evonik, Parsipanny, NJ VESTANAT TMDI PU Film polyurethane film with 6 mil thickness Made by extrusion

[0078]

[0079] A polyethylene coated paper release liner with square

[0080] diamond structures, pitch of 417 micrometers, width of Made by embossing Liner- 1

[0081] 40 micrometers, depth of 14 micrometers, and protruded release liner beads on the surface.

[0082] A polyethylene coated polyethylene terephthalate

[0083] release liner with square diamond structures, pitch of Made by embossing Liner-2

[0084] 200 micrometers, width of 20 micrometers and depth of release liner 13 micrometers.

[0085] A polyethylene coated polyethylene terephthalate

[0086] release liner with square diamond structures, pitch of Made by embossing Liner-3

[0087] 200 micrometers, width of 20 micrometers and depth of release liner 13 micrometers, and protruded beads on the surface.

[0088] A polyethylene coated polyethylene terephthalate

[0089] release liner with linear structures, pitch of 340 Made by embossing Liner-4

[0090] micrometers, width of 60 micrometers and a depth of 30 release liner micrometers, and protmded beads on the surface.

[0091]

[0092] Wet Out Performance

[0093] Examples were hand laminated on a black color painted panel and a time series of pictures were recorded through the clear polyurethane film using KEYNCE optical microscope with 50X objective lens. Images of the interface were captured as the adhesive wet the surface of the painted panel and the air egress structure shrunk and eventually disappeared. Tests were run at ambient conditions. Light areas on the image correspond to air in the air egress structure. Dark areas show where the adhesive has wet the painted panel surface. The approximate time when light areas completely disappeared was recorded.

[0094] 180° Peel Adhesion

[0095] Examples were cut into 2.5 centimeters by 12.5 centimeters strips. The release liner was removed and the strip was laminated halfway on a Fruehauf panel (white painted aluminum panel). The laminated panel dwelled at room temperature for 24 hours, and at 65° C for 24 hours, and was tested for 180 degree peel adhesion using an Instron 5900 series tester (Model 59CP, commercially available from Instron®, Norwood, MA) at a rate of 30.5 cm per minute (12 inches per minute). Three replicates were tested for each Example, and the reported adhesion value is an average of the three replicates.

[0096] Polyurethane (PU) Synthesis

[0097] The compositions to synthesize the PU polymers are summarized in Table 2. To a resin reaction vessel equipped with a mechanical stirrer, a condenser and a nitrogen inlet were added polyols, isocyanates, catalyst XK-651 (500 ppm based on total solid) and MEK of 50.0 grams. The reactants werestirred and heated up to 78 °C for reaction. The temperature was maintained at 78 ± 2 °C until no free NCO group was observed by FT- IR at around 2270 cm-1. During the reaction, MEK was added to adjust the viscosity. After reaction, the PU solution with a solid content of 40-55 wt% was obtained with an IV range from 0.43-0.56.

[0098] Examples 1-13

[0099] Examples 1-12 were made according to the following procedures, where the polyurethane compositions are provided in Table 2 and a list of the PU PSA Examples are provided in Table 3. PU PSA compositions were roller mixed with GA240 and TPO-L (at the parts per hundred resin (phr) by weight indicated in Table 3) in glass jars for at least 8 hours until the formulations were fully homogeneous. The formulated adhesives were coated on structured liners using a Notch Bar and setting a wet gap in a range of 127 microns to 152 microns (5mil to 6mil). The coated liner was dried in 70°C oven for 15 mins, then went through D-bulb at a speed of 300 cm per minute with a power of 90 mJ / cm2 UVC. The PU film was laminated with adhesive coated liner right after.

[0100] Example 13 was made by coating PU322 formulation (see Table 3) on Liner-3 using Notch Bar and setting a wet gap of 127 microns. The coated liner was cured at 65 °C overnight, then laminated with the PU film.

[0101] Comparative Examples 1-2

[0102] Comparative Example 1 was Scotchgard™ Paint Protection Film Pro Series 200 film with acrylic PSA on Liner- 1.

[0103] Comparative Example 2 was Scotchgard™ Paint Protection Film Pro Series 200 (acrylic PSA on flat liner for applying via wet installation).Table 2: Polyurethane Compositions

[0104] »»»»»*»»*»»»»»»,»»»»»»»»»»»»»»»»» isacysmm "mm" AM IV Fsty&wr Rl'BIB. XPE Bin TMSI | HsAWI X-FIB FB- B? ( |

[0105] nf W

[0106] PUSS? os??.?! IBS | | 05 MS PUsTS W XS.1.5 IPS | | OS MS PUS?? IW RSS | | S B2 045

[0107] 2W IBS | t OJ 5,4S PBW 4B3 2§,4J IBS 1 ] S.65 SB pum W 4 IBS j 1 § §S 0,5 jOl S§ | 50 | §^3 o 0,43 PUP25 j 2. Si 292- | t 08 SB? PUSBS n..?s | 5S | 5S S. SS MS

[0108]

[0109] PW23 05 HB | | 05 0,52Table 3: List of Examples

[0110] TPO-L / GA240 / Example No. Liner Polymer

[0111] phr phr Example 1 Liner- 1 PU857 0.2 1 Example 2 Liner- 1 PU876 0.2 1 Example 3 Liner- 1 PU877 0.2 1 Example 4 Liner- 1 PU878 0.2 1 Example 5 Liner- 1 PU880 0.2 1 Example 6 Liner-2 PU877 0.2 1 Example 7 Liner-2 PU880 0.2 1 Example 8 Liner-3 PU878 0.2 1 Example 9 Liner-4 PU878 0.2 1 Example 10 Liner-3 PU901 0.2

[0112] Example 11 Liner-3 PU905 0.2

[0113] Example 12 Liner-3 PU906 0.2

[0114]

[0115] Example 13 Liner-3 PU322 1

[0116] Examples 1-13 and Comparative Example 1 were tested according to the Wet Out Performance test described elsewhere herein, and the results are provided in Table 4.

[0117] Table 4: Wet Out Performance

[0118] Example The approximate time when the air egress structure completely disappeared Example 1 4 days < t < 2 weeks Example 2 4 days < t < 2 weeks Example 3 4 days < t < 2 weeks Example 4 ~ 4 days

[0119] Example 5 ~ 4 days

[0120] Example 6 ~ 2 days

[0121] Example 7 ~ 1 day

[0122] Example 8 ~ 2 days

[0123] Example 9 2 weeks < t < 1 month Example 10 ~ 1 day

[0124] Example 11 ~ 4 hours

[0125] Example 12 Visible air egress passageways after 4 months Example 13 Visible air egress passageways after 40 days Comparative

[0126] Visible air egress passageways after 2 years Example 1

[0127]

[0128] Examples 9 and 12-13 exhibited longer times for the air egress structures to disappear than desired for many applications, but each of Examples 1-13 illustrate exemplary methods of making a film stack, according to some embodiments.

[0129] Examples 1-12 and Comparative Examples 1 and 2 were tested according to the 180° Peel Adhesive test described elsewhere herein, and the results are shown in Table 5.

[0130] Table 5: 180° Peel Adhesion Results

[0131] Example No. 180° Peel After 24 Hours Dwell 180° Peel After 24 Hours Dwell at Room Temperature (N / dm) at 65 Degree C (N / dm) Example 1 28.9 56.6 Example 2 25.0 50.3 Example 3 25.0 48.2 Example 4 28.9 52.0 Example 5 25.6 46.4 Example 6 26.1 n / a Example 7 n / a 49.2 Example 8 103.4 120.1 Example 9 26.8 50.4 Example 10 56.2 112.3 Example 11 74.0 139.2 Example 12 102.3 126.8 Comparative Example 1 49.6 61.1

[0132]

[0133] Comparative Example 2 93.3 114.0

[0134] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1.

[0135] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially” with reference to a property or characteristic is not otherwise clear to one of ordinary skill in theart in the context in which it is used and described in the present description and when it would be clear to one of ordinary skill in the art what is meant by an opposite of that property or characteristic, the term “substantially” will be understood to mean that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited.

[0136] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0137] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed is:

1. A film stack comprising:a polymeric film;a polyurethane pressure sensitive adhesive layer having opposing first and second major surfaces, the first major surface disposed on, and physically contacting, the polymeric film, the second major surface comprising a plurality of structures defining fluid egress passageways; and a structured release liner having a structured major surface disposed on, and substantially conforming to the second major surface of the polyurethane pressure sensitive adhesive layer, wherein when the structured release liner is removed from the film stack and the polyurethane pressure sensitive adhesive layer is placed on a support surface with the second major surface physically contacting the support surface, the plurality of structures substantially disappears within about 2 weeks at room temperature.

2. The film stack of claim 1, wherein the polyurethane pressure sensitive adhesive layer comprises a polyurethane having groups configured to reduce crystallinity of the polyurethane, the groups comprising at least one of pendent groups and non-planar cyclic backbone groups.

3. The film stack of claim 2, wherein the groups configured to reduce crystallinity of the polyurethane comprise the pendent groups.

4. The film stack of claim 3, wherein the pendent groups comprise C2-C30 aliphatic units.

5. The film stack of claim 4, wherein the pendent groups comprising C2-C30 aliphatic units comprise -CO(OC2H4)nOCO(CH2)mCH3, wherein n is a positive integer and m is an integer in a range of 2 to 25.

6. The film stack of claim 4, wherein at least one of the pendent groups comprising C2-C30 aliphatic units is attached to a backbone chain of the polyurethane through an allophanate group having an -N- along the backbone chain.

7. The film stack of claim 2, wherein the groups configured to reduce crystallinity of the polyurethane comprise the non-planar cyclic backbone groups.

8. The film stack of claim 7, wherein the non-planar cyclic backbone groups comprise aliphatic rings.

9. The film stack of claim 7, wherein at least one of the non-planar cyclic backbone groups comprises dicyclohexylmethane.

10. The film stack of claim 2, wherein the groups configured to reduce crystallinity of the polyurethane comprise the pendent groups and the non-planar cyclic backbone groups.

11. The film stack of claim 1, wherein the polyurethane pressure sensitive adhesive layer comprises a polyurethane comprising a reaction product of isocyanates and at least one polyol, at least 50 mol% of the isocyanates comprising at least one of pendent groups and non-planar cyclic backbone groups.

12. The film stack of any one of claims 1 to 11, wherein the polyurethane pressure sensitive adhesive layer has a glass transition temperature less than 37 degrees C.

13. The film stack of any one of claims 1 to 12, wherein the plurality of structures comprises a plurality of channels or a plurality of protruding structures.

14. The film stack of any one of claims 1 to 13, wherein for substantially normally incident light and for at least one polarization state, the polymeric film has an average optical transmittance of greater than 50% in a visible wavelength range at least 50 nm wide.

15. A method of making a film stack, the method comprising:coating a polyurethane pressure sensitive adhesive formulation onto a structured major surface of a structured release liner, the polyurethane pressure sensitive adhesive formulation comprising polyurethane polymer in a solvent;drying the coated formulation;curing the dried coating to form a cured polyurethane pressure sensitive adhesive layer having opposing first and second major surfaces, the second major surface disposed on, and substantially conforming to, the structured major surface of the structured release liner such that the second major surface comprises a plurality of structures defining fluid egress passageways; and laminating a polymeric film to the first major surface of the polyurethane pressure sensitive adhesive layer to form the film stack.

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