Structured release liner and adhesive article including same

Abstract

A release liner includes a first polymeric layer having a first major surface including a substantially planar portion and a plurality of protruding structures protruding from the substantially planar portion along a thickness direction of the release liner and defining a regular two-dimensional pattern of substantially rhombus shapes. Each substantially rhombus shape has first and second sides meeting at an apex of the shape and defining an angle of no more than 55 degrees therebetween. Each of the first and second sides can have a length in a range of about 400 to 800 micrometers. The protruding structures can have an average height in the thickness direction in a range of about 10 to 20 micrometers and an average width along an in-plane transverse direction in a range of about 25 to 55 micrometers. The first major surface is a release surface.

Description

[0001] PA101604W002

[0002] STRUCTURED RELEASE LINER AND ADHESIVE ARTICLE INCLUDING SAME

[0003] TECHNICAL FIELD

[0004] The present description relates generally to release liners and adhesive articles.

[0005] BACKGROUND

[0006] A release liner may be structured to provide air release channels in an adhesive layer disposed on the release liner.

[0007] SUMMARY

[0008] In some aspects, the present description provides a release liner including a first polymeric layer having a first major surface including a substantially planar portion and a plurality of protruding structures protruding from the substantially planar portion along a thickness direction of the release liner and defining a regular two-dimensional pattern of substantially rhombus shapes. Each substantially rhombus shape has first and second sides meeting at an apex of the shape and defining an angle of no more than 55 degrees therebetween. Each of the first and second sides can have a length in a range of about 400 to 800 micrometers. The protmding structures can have an average height in the thickness direction in a range of about 10 to 20 micrometers and an average width along an in-plane transverse direction in a range of about 25 to 55 micrometers. The first major surface is a release surface.

[0009] In some aspects, the present description provides a release liner including a first polymeric layer having a first major surface including a plurality of substantially parallel first protruding structures extending substantially linearly along an in-plane first direction and arranged along an orthogonal inplane second direction at a first pitch; and a plurality of substantially parallel second protruding structures extending substantially linearly along an in-plane third direction and arranged along an orthogonal inplane fourth direction at a second pitch. Each of the first and second pitches can be in a range of about 250 to 600 micrometers. The first and second protruding structures have respective first and second average widths along the respective second and fourth directions and respective first and second average heights along a thickness direction of the release liner. Each of the first and second average widths can be in a range of about 25 to 55 micrometers. Each of the first and second average heights can be in a range of about 10 to 20 micrometers. The first and third directions define an angle therebetween of no more than 55 degrees such that the first and second protruding structures intersect one another. The first major surface is a release surface.

[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 top view of a release liner, according to some embodiments.FIGS. 2-3 are schematic cross-sectional views of a release liner, according to some embodiments. FIG. 4 is a schematic cross-sectional view of an adhesive article, according to some embodiments.

[0012] FIG. 5 is a schematic cross-sectional view of a roll of a release liner or of an adhesive article, according to some embodiments.

[0013] DETAILED DESCRIPTION

[0014] 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.

[0015] Structured release liners are generally known in the art and are described in U.S. Pat. Nos.

[0016] 6,197,397 (Sher et al.); 6,524,649 (Sher et al.); 9,085,121 (Mikami et al.); and 10,723,919 (Free), for example. The structures of a structured release liner can be formed via embossing a polymeric layer or film, for example. The structures can include protruding structures that define a plurality of channels in an adhesive layer when the adhesive layer is disposed on the structured surface of the release liner. The channels can provide passageways for air release when the adhesive layer is removed from the release liner and applied to a surface. However, it has now been found that the traditional geometries of the protruding stmctures can result in air entrapment and incomplete adhesive filling near the protruding structures when an adhesive is coated onto the structured release liner at high (e.g., 45 meters per minute or higher) coating line speeds.

[0017] According to some embodiments of the present description, it has been found that the geometry of protruding structures can be modified from traditional geometries to provide improved filling and reduced or substantially eliminated air entrapment. The improved geometry, according to some embodiments, may be described as including regularly arranged substantially rhombus shapes elongated along a direction, such as a machine direction in a roll-to-roll coating process, along which an adhesive layer is to be coated onto the release liner. This elongated direction can correspond to a circumferential direction in a roll of the release liner or a roll of an adhesive article including the release liner, since when the roll is wound or unwound, the circumferential direction can correspond to the machine direction in the coating process. The elongated rhombus can have an angle (e.g., 55 degrees or less, such as about 40 degrees) between adjacent sides that is significantly smaller than a corresponding angle of a conventional release liner.

[0018] FIG. 1 is a schematic top view of a release liner 100, according to some embodiments. The release liner has a thickness along a z-direction and extends generally along x- and y-directions. In some embodiments, the release liner 100 has a first major surface 121 including a plurality of protruding structures 131 and 132 which are schematically represented in FIG. 1 by centerlines of the stmctureswhich can extend in respective x'- and x"-directions and can be arranged along respective y'- and y"-directions. FIGS. 2-3 are schematic cross-sectional views of a release liner 100 in respective y'z- and y"z-cross-sections illustrating respective protruding structures 131 and 132, according to some embodiments. The first major surface 121 is typically a release surface.

[0019] In some embodiments, a release liner 100 includes a first polymeric layer 110 having a first major surface 121 including a substantially planar portion 125 and a plurality of protruding structures 131, 132 protruding from the substantially planar portion 125 along a thickness direction (z-direction) of the release liner 100 and defining a regular two-dimensional pattern of substantially rhombus shapes 140, where each substantially rhombus shape has first and second sides 141 and 142 meeting at an apex 145 of the shape and defining an angle Al of no more than 55, 52, 50, 48, 46, 45, 44, 43, 42, 41, or 40 degrees therebetween. In some such embodiments, or in other embodiments, each of the first and second sides has a length LI, L2 in a range of about 400 to 800 micrometers, or about 500 to 700 micrometers, or about 525 to 750 micrometers, or about 550 to 700 micrometers. In some such embodiments, or in other embodiments, the protruding stmctures 131, 132 have an average height Hl, H2 in the thickness direction (the average height can be understood to be an unweighted mean of the heights of the structures 131 and 132) in a range of about 10 to 20 micrometers, or about 11 to 18 micrometers, or about 12 to 17 micrometers. In some such embodiments, or in other embodiments, the protruding structures 131, 132 have an average width Wl, W2 along an in-plane transverse direction (y'- or y "-direction) in a range of about 25 to 55 micrometers, or about 30 to 50 micrometers, or about 35 to 45 micrometers. In some such embodiments, or in other embodiments, the protruding stmctures 131, 132 have a radius of curvature Rl, R2 in a range of about 10 to 30 micrometers, or about 15 to 26 micrometers, or about 18 to 24 micrometers. The substantially rhombus shapes 140 can be rhombus shapes, nominally rhombus shapes, or can have a rhombus shape up to deviations substantially smaller (e.g., by at least a factor of 3, 5, 10, or 20) than the length LI, L2.

[0020] In some embodiments, a release liner 100 includes a first polymeric layer 110 having a first major surface 121 including a plurality of substantially parallel first protruding structures 131 extending substantially linearly along an in-plane first direction (x'-direction) and arranged along an orthogonal inplane second direction (y ’-direction) at a first pitch Pl; and a plurality of substantially parallel second protruding structures 132 extending substantially linearly along an in-plane third direction (x"-direction) and arranged along an orthogonal in-plane fourth direction (y"-direction) at a second pitch P2. In some embodiments, each of the first and second pitches Pl and P2 is in a range of about 250 to 600 micrometers, or about 300 to 500 micrometers, or about 325 to 450 micrometers, or about 350 to 400 micrometers. In some such embodiments, or in other embodiments, the first and second protruding structures 131 and 132 have respective first and second average widths W 1 and W2 along the respective second and fourth directions where each of the first and second average widths Wl and W2 is in a range of about 25 to 55 micrometers, or about 30 to 50 micrometers, or 35 to 45 micrometers. In some such embodiments, or in other embodiments, the first and second protruding structures 131 and 132 haverespective first and second average heights Hl and H2 along a thickness direction (z-direction) of the release liner 100 where each of the first and second average heights Hl and H2 is in a range of about 10 to 20 micrometers, or about 11 to 18 micrometers, or about 12 to 17 micrometers. In some such embodiments, or in other embodiments, the first and third directions define an angle Al therebetween of no more than 55, 52, 50, 48, 46, 45, 44, 43, 42, 41, or 40 degrees such that the first and second protruding structures 131 and 132 intersect one another. In some such embodiments, or in other embodiments, the first and second protruding stmctures 131 and 132 protrude from a substantially planar portion 125 of the first major surface 121. In some such embodiments, or in other embodiments, the first and second protruding structures 131 and 132 have respective first and second radii of curvature R1 and R2, where each of the first and second radii of curvature R1 and R2 is in a range of about 10 to 30 micrometers, or about 15 to 26 micrometers, or about 18 to 24 micrometers.

[0021] In some embodiments, the angle Al (between the first and second sides of the substantially rhombus shape and / or between the first and third directions) is at least 10, 15, 20, 25, 30, or 35 degrees. The angle Al may be in any of these ranges in any of the embodiments where the angle is less than 55 degrees, for example. For example, in some embodiments, the angle Al is in a range of 10 to 55 degrees, or 15 to 50 degrees, or 20 to 50 degrees, or 25 to 48 degrees, or 30 to 46 degrees, or 35 to 45 degrees.

[0022] In some embodiments, the substantially planar portion 125 comprises 70 to 90 percent, or 75 to 85 percent, by area of the first major surface 121 in a top plan view (e.g., by area in the xy -plane of FIG.

[0023] 1). The substantially planar portion 125 can be planar, or nominally planar, or planar up to deviations substantially smaller (e.g., by at least a factor of 3, 5, 10, or 20) than the average height Hl, H2. A substantially planar surface portion may have a roughened surface or a substantially smooth surface. If a substantially planar surface portion is roughened, it generally has a surface roughness substantially smaller than the average height Hl, H2.

[0024] In some embodiments, the release liner has a volume factor in a range of 0.19 to 0.27, or 0.2 to 0.25 mm3 / (100 mm2). Here, volume factor is a total volume of the protruding structures 131, 132 per area in a top plan view (e.g., total area in xy -plane in FIG. 1).

[0025] The release liner 100 may be made by conventional means (e.g., embossing) for making structured release liners and may include materials conventionally used for release liners. Suitable exemplary methods and materials are described in the release liner references provided elsewhere herein, for example.

[0026] In some embodiments, the first polymeric layer 110 comprises polyolefin. In some embodiments, the polyolefin comprises polypropylene, polyethylene, or a blend thereof. In some embodiments, the polyolefin comprises a blend of low -density polyethylene (LDPE) and high-density polyethylene (HDPE). LDPE typically has a density in a range of 917 to 930 kg / m3while HDPE typically has a density in a range of 930 to 970 kg / m3. The density of HDPE used in the blend can be at least 5, 10, or 15 kg / m3greater than the density of LDPE used in the blend.In some embodiments, the release liner 100 further includes a second polymeric layer 112 and an inner layer 114 disposed between the first and second polymeric layers 110 and 112 (see, e.g., FIGS. 2-3). In some embodiments, the inner layer 114 is polymeric. In some embodiments, the inner layer 114 comprises paper (e.g., kraft paper, which may be bleached kraft paper). In some embodiments, the first and second polymeric layers 110 and 112 comprise first and second polyolefins. The first and second polyolefins can have a same composition or can have different compositions. The second polyolefin can be any of the polyolefins described for the first polymeric layer 110. In some embodiments, the first and second layers 110 and 112 and the inner layer 114 are substantially coextensive with one another.

[0027] Layers can be described as substantially coextensive with each other if at least about 60% by area of each layer is coextensive with at least about 60% by area of each other layer. In some embodiments, for layers describes as substantially coextensive, at least about 70%, or at least about 80%, or at least about 90% by area of each layer is coextensive with at least about 70%, or at least about 80%, or at least about 90% by area of each other layer.

[0028] In some embodiments, the first polymeric layer 110 comprises a release coating 129 thereon, wherein the release coating 129 comprises the release surface 121. Any suitable release coating conventionally used with release liners may be utilized. In some embodiments, the release coating 129 comprises a silicone coating. In some embodiments, the release coating 129 comprises a non-silicone, non-fluorinated release coating.

[0029] In some embodiments, the release liner 100 further includes a plurality of particles 137 distributed across the first major surface 121 of, and partially embedded in, the first polymeric layer 110. In some embodiments, when an adhesive layer is disposed on the first major surface 121 of the first polymeric layer 110, the particles 137 become at least partially embedded in, and attached to, the adhesive layer such that when the adhesive layer is removed from the release liner 100, the particles are removed with the adhesive layer. The particles can allow for, or enhance, repositionability of the adhesive layer. The particles 137 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.

[0030] FIG. 4 is a schematic cross-sectional view of an adhesive article 300, according to some embodiments.

[0031] In some embodiments, an adhesive article 300 includes an adhesive layer 310 disposed on the release liner 100, where the adhesive layer 310 is releasably attached to the first major surface 121 of the first polymeric layer 110. In some embodiments, an adhesive article 300 includes an adhesive layer 310 disposed on, and releasably attached to, the release liner 100. In some embodiments, the adhesive layer 310 includes a major surface 321 disposed on, and physically contacting, the first major surface 121 of the first polymeric layer 110. In some embodiments, the adhesive layer 310 and the first polymeric layer 110 are substantially coextensive with one another. In some embodiments, the adhesive layer includes amajor surface 321 substantially conforming (e.g., nominally conforming, or nominally conforming except for the presence of particles 137 between the major surfaces 321 and 121, or conforming up to deviations substantially smaller (e.g., by at least a factor of 3, 5, 10, or 20) than Hl, H2) to the first major surface 121 of the first polymeric layer 110 except possibly for presence of particles 137). In some embodiments, the adhesive article 300 further includes a backing layer 315 disposed on the adhesive layer 310 opposite the release liner 100. In some embodiments, the backing layer 315, the adhesive layer 310, and the liner 100 are substantially coextensive with one another. The release liner 100 of the adhesive article 300 may further include a second polymeric layer 112 and an inner layer 114 as described further elsewhere herein (see, e.g., FIGS. 2-3).

[0032] In some embodiments, the backing layer 315 is polymeric. In some embodiments, the backing layer 315 comprises polyvinylchloride (PVC), polyurethane, polyester, poly lactic acid (PLA), polyvinyl acetate, cellulose acetate propionate, polyvinyl butyral, or a blend thereof. In some embodiments, the backing layer 315 further comprises a plasticizer. In some embodiments, the backing layer 315 comprises paper.

[0033] In some embodiments, the backing layer 315 comprises a primer 319 disposed on a major surface 317 thereof, where the major surface 317 of the backing layer 315 faces the adhesive layer 310.

[0034] The adhesive layer 310 can be any suitable adhesive commonly used with a release liner. In some embodiments, the adhesive layer 310 comprises one or more of a pressure sensitive adhesive (PSA), a hot-melt adhesive, a solvent-coated adhesive, a solventless-coated adhesive, and a water-based adhesive. In some embodiments, the adhesive layer 310 comprises a hot-melt adhesive, which may be coated onto the release liner 100 at elevated temperatures, where the hot-melt adhesive is a pressure sensitive adhesive (e.g., at elevated temperature).

[0035] FIG. 5 is a schematic cross-sectional view of a roll 200 of a release liner 100 or an adhesive article 300, according to some embodiments. In some embodiments, a roll 200 of the release liner 100 is provided, where a circumferential direction 203 of the roll 200 substantially bisects the angle Al at the apex 145 and / or substantially bisects the angle Al between the first (x'-direction) and third (x"-direction) directions. In some embodiments, a roll 200 of the adhesive article 300 is provided, where a circumferential direction 203 of the roll 200 substantially bisects the angle Al at the apex 145 and / or substantially bisects the angle Al between the first (x'-direction) and third (x"-direction) directions. Such rolls may be used in, or produced by, a roll-to-roll adhesive coating process where the circumferential direction 203 defines a wind or unwind direction corresponding to a machine direction of the coating process.

[0036] EXAMPLES

[0037] A release liner having the general structure shown in FIGS. 1-3 was formed by embossing the release liner to provide four lanes extending along a length of the release liner and arranged adjacent to one another along a width of the release liner. The release liner included outer polyethylene layers and aninner bleached kraft paper layer with a silicone release coating on an outer surface one of the polyethylene layers. Patterns were embossed into the silicone side of the liner. The four lanes had four different embossed patterns that can be characterized by (see, e.g., FIGS. 1-3): angle Al, length L=L1=L2, pitch P=P1=P2, height H=H1=H2, width W=W1=W2, radius R=R1=R2, and piano area (area of substantially planar regions 125 as a percent of total area in a top plan view (e.g., area in xy -plane)). Each of the four lanes included protruding structures (ridges) having a nominal radius of curvature R of about 20.9 micrometers, a nominal width W of about 39.7 micrometers, and a nominal cross-sectional area of the protruding structures of about 418 micrometers2. Lane 4, but not lanes 1-3, had a roughened planar portion. Volume factor (volume of ridges per total area in top plan view) and other geometric parameters are provided in the following table. The geometry of Lane 3 was exemplary while the geometries of Lanes 1-2 and 4 were comparative.

[0038]

[0039] A hot-melt adhesive formulation was coated onto a release liner described above along the length direction (e.g., y-direction in FIG. 1) of the release liner with a line speed of 150 feet per minute (45.72 meters per minute) and a coating temperature of 330 deg. F (165.6 deg. C). The hot-melt adhesive was an acrylic adhesive formulation including an acrylic polymer and a tackifier at 10 parts per hundred resin by weight (phr), where the acrylic polymer had a weight average molecular weight Mw of 568,000 Daltons, a number average molecular weight Mn of 148,000 Daltons, a poly dispersity of 3.84 and an intrinsic viscosity (IV) of 0.777 dL / g. Intrinsic viscosity is measured at 0.3 g / dL in ethyl acetate at 27 deg. C, unless indicated differently. Magnified images of the coated liner in Lanes 1-4 were evaluated to determine the degree of filling and air entrapment. Significant undesired air entrapment was observed in Lanes 1 and 4; significantly reduced air entrapment was observed in Lane 2; and substantially further reduced air entrapment was observed in Lane 3.Pressure sensitive adhesives (PSAs) 1-3 were solvent coated onto a release liner described above along the length direction (e.g., y-direction in FIG. 1) of the release liner with a line speed varying from 50 to 300 feet per minute (FPM) and magnified images of the coated liner in Lanes 1-3 were evaluated (Lane 4 was not evaluated in this test) to determine the amount of air bubbles that were entrapped. The amounts of air bubbles were characterized as none, some, few, or many, with “some” meaning more than “none” and less than “few”. PSA 1 was a solvent-bome acrylic PSA with an IV of 1.00 dL / g and 33% solids; PSA 2 was a solvent-bome acrylic PSA and had an IV of 0.8 dL / g and 38.5% solids; and PSA 3 was a solvent-bome acrylic PSA with an IV of 0.8 dL / g and 36% solids. PSA 2 included tackifier at 16 phr, while PSA 1 and PSA 3 did not include tackifier. Results are provided in the following table, where it can be seen that only Lane 3 allowed a line speed of 200 FPM (60.96 meters per minute) for each adhesive with few or less entrained bubbles.

[0040]

[0041] 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.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 the art 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.

[0042] 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.

[0043] 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 release liner comprising a first polymeric layer having a first major surface comprising a substantially planar portion and a plurality of protruding structures protruding from the substantially planar portion along a thickness direction of the release liner and defining a regular two-dimensional pattern of substantially rhombus shapes, each substantially rhombus shape having first and second sides meeting at an apex of the shape and defining an angle of no more than 55 degrees therebetween, each of the first and second sides having a length in a range of about 400 to 800 micrometers, the protruding structures having an average height in the thickness direction in a range of about 10 to 20 and an average width along an in-plane transverse direction in a range of about 25 to 55 micrometers, the first major surface being a release surface.

2. The release liner of claim 1, wherein the substantially planar portion comprises 70 to 90 percent by area in a top plan view of the first major surface.

3. The release liner of claim 1, wherein the protruding structures comprise a radius of curvature in a range of about 10 to 30 micrometers.

4. The release liner of claim 1, wherein the angle is no more than 45 degrees.

5. The release liner of claim 1, wherein the angle is at least 10 degrees.

6. The release liner of claim 1, wherein the first polymeric layer comprises polyolefin.

7. The release liner of claim 1, further comprising a second polymeric layer and an inner layer disposed between the first and second polymeric layers.

8. The release liner of claim 1, further comprising a plurality of particles distributed across the first major surface of, and partially embedded in, the first polymeric layer.

9. An adhesive article comprising an adhesive layer disposed on the release liner of claim 1, the adhesive layer being releasably attached to the first major surface of the first polymeric layer.

10. The adhesive article of claim 9 further comprising a backing layer disposed on the adhesive layer opposite the release liner.

11. A roll of the adhesive article of claim 10, wherein a circumferential direction of the roll substantially bisects the angle at the apex.

12. A release liner comprising a first polymeric layer having a first major surface comprising:a plurality of substantially parallel first protruding structures extending substantially linearly along an in-plane first direction and arranged along an orthogonal in-plane second direction at a first pitch; anda plurality of substantially parallel second protruding structures extending substantially linearly along an in-plane third direction and arranged along an orthogonal in-plane fourth direction at a second pitch,wherein each of the first and second pitches is in a range of about 250 to 600 micrometers, wherein the first and second protruding structures have respective first and second average widths along the respective second and fourth directions and respective first and second average heights along a thickness direction of the release liner, each of the first and second average widths being in a range of about 25 to 55 micrometers, each of the first and second average heights being in a range of about 10 to 20 micrometers,wherein the first and third directions define an angle therebetween of no more than 55 degrees such that the first and second protruding structures intersect one another, andwherein the first major surface is a release surface.

13. The release liner of claim 12, wherein the angle is in a range of 35 to 45 degrees.

14. An adhesive article comprising an adhesive layer disposed on the release liner of claim 12, the adhesive layer being releasably attached to the first major surface of the first polymeric layer, the adhesive article further comprising a backing layer disposed on the adhesive layer opposite the release liner.

15. A roll of the adhesive article of claim 14, wherein a circumferential direction of the roll substantially bisects the angle between the first and third directions.

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