Patent Description:
The present disclosure relates generally to flexible retroreflective sheeting particularly useful for the labeling of traffic safety devices.

Traffic cones (pylons), are cone-shaped markers that are often placed on roads or footpaths to temporarily redirect traffic in a safe manner. The marker cones are frequently used, for example, to create separation or merge lanes during road construction projects or automobile accidents. In the United States, cones are required by the Federal Highway Administration's Manual on Uniform Traffic Control Devices (MUTCD) to be fitted with reflective white bands to increase night-time visibility. Reflective collars, such as white strips made from white reflective plastic, can be snugly slipped over the tops of cones and permanently or semi-permanently attached to the traffic cones with tape or adhesive. Similar reflective strips, tapes, or labels are also generally attached to other traffic safety devices, such as traffic barrels and barriers, to increase their visibility.

Because of their common locations on and near roads, traffic cones are highly susceptible to impacts from, for example, vehicular and pedestrian collisions, resulting in the crushing or bending of the cone surfaces. When traffic cones are deformed in this way, labels such as reflective collars attached to the cones are subjected to stresses that can damage the label integrity. This damage can create cracks within the label structure, revealing the surface of the cone beneath the cracked label, and disrupting the uniformity of the label appearance. The visual effect of the crack is particularly noticeable because of the significant contrast between the typical fluorescent orange color of traffic cones and other road safety devices, and the typical white color of reflective labels. In view of these undesirable effects, a need exists for improved flexible adhesive retroreflective sheeting. Relevant prior art can be found in <CIT> and <CIT>.

A flexible retroreflective sheeting according to the invention is defined in claim <NUM>. A method for producing a flexible retroreflective sheeting is defined in claim <NUM>. In one embodiment, the disclosure is to flexible retroreflective sheeting that includes an emboss layer, a flexible backing layer, a first adhesive layer, an interleaf layer, and a second adhesive layer. Preferably, the sheeting has a tensile strain ranging from <NUM>% to <NUM>%. The emboss layer has a back surface including a plurality of retroreflective elements. The flexible backing layer is in contact with the emboss layer back surface. The first adhesive layer is connected to the flexible backing layer opposite the emboss layer. The interleaf layer has an opacity greater than <NUM>% and is connected to the first adhesive layer opposite the flexible backing layer. Preferably, the interleaf layer has a CIEDE2000 color difference from the emboss layer color that is less than <NUM>. Preferably, the interleaf layer includes a cavitated or pigmented film. The second adhesive layer is connected to the interleaf layer opposite the first adhesive layer.

In another embodiment the disclosure relates to a method for producing a flexible retroreflective sheeting having a flexible backing layer. The method includes thermally embossing an emboss layer, thereby forming a plurality of retroreflective elements on the emboss layer back surface. The method further includes connecting a flexible backing layer to the emboss layer back surface. The method further includes coating a first face of an interleaf layer with a first adhesive layer, and an opposite second face of the interleaf layer with a second adhesive layer, thereby forming a transfer tape. The method further includes laminating the transfer tape to the flexible backing layer opposite the emboss layer.

In another embodiment, the disclosure is to a flexible retroreflective sheeting that includes an emboss layer, a metallized layer, a first adhesive layer, an interleaf layer, and a second adhesive layer. Preferably, the sheeting has a tensile strain ranging from <NUM>% to <NUM>%. The emboss layer back surface includes a plurality of retroreflective elements. The metallized layer is located directly on the emboss layer back surface. The first adhesive layer is connected to the metallized layer opposite the emboss layer. The interleaf layer is connected to the first adhesive layer opposite the metallized layer, has an opacity greater than <NUM>%, and has a CIEDE2000 color difference from the emboss layer color of less than <NUM>. Preferably, the interleaf layer includes a cavitated or pigmented film. The second adhesive layer is connected to the interleaf layer opposite the first adhesive layer.

In another embodiment, the disclosure is to a method for producing a flexible retroreflective sheeting having a metallized layer. The method includes thermally embossing an emboss layer, thereby forming a plurality of retroreflective elements on the emboss layer back surface. The method further includes connecting a metallized layer directly to the emboss layer back surface. The method further includes coating a first face of an interleaf layer with a first adhesive layer, and an opposite second face of the interleaf layer with a second adhesive layer, thereby forming a transfer tape. The method further includes laminating the transfer tape to the metallized layer opposite the emboss layer.

In another embodiment, the disclosure is to a method of applying a flexible retroreflective sheeting to a surface. The method includes providing a surface having an outer face. The method further includes providing a flexible retroreflective sheeting as disclosed herein. The method further includes adhering the second layer of the flexible retroreflective sheeting to the outer face of the surface.

In another embodiment, the disclosure is to an article labeled with a flexible retroreflective sheeting as described herein. The article includes a surface having an outer face, and the flexible retroreflective sheeting adhered to the outer face of the surface.

The disclosure references the appended drawings, wherein like numerals designate similar parts. <FIG> illustrates a flexible retroreflective sheeting construction in accordance with an embodiment.

The present disclosure generally relates to retroreflective sheeting that, when employed for example as a retroreflective label for articles subject to crushing and bending, provides advantageous improvements in label integrity and hiding ability. For example, it is beneficial for sheeting, e.g., a cone collar, applied to traffic safety devices, e.g., a traffic cone, to be strong and flexible enough to not experience delamination or cracking if the device is handled roughly, stepped on, or driven over. It is also beneficial for the retroreflective sheeting to continue to conceal the underlying labeled surface, even in cases in which the label does develop a crack in one or more constituent layers. The ability of the sheeting to prevent the labeled surface from being seen can advantageously improve the uniformity of the appearance of the label.

It is difficult, however, for conventional retroreflective sheeting, labels, or tapes to meet these demands. One reason for this is that sheeting intended for application to traffic safety devices must be able to conform to the highly curved surfaces of cones, barrels, and barriers if it is to form a tight adhesion to these devices. The properties of such sheeting that promote such conformability are counter to those that promote rigidity and toughness, though, making conventional sheeting highly susceptible to cracking under force. Retroreflective sheeting in particular can include structural features known to be particularly likely to break when impacted. For example, air backed retroreflective sheeting includes layers that are not in complete contact with one another, as these partially connected layers form air gaps conferring retroreflectivity to the sheeting, These locations of incomplete contact between the layers can be a weak point likely to fracture under stress.

The inventors have now discovered that specific combinations of layers having the compositions and geometries disclosed herein surprisingly provide improved performance characteristics to retroreflective sheeting. In particular, it has been found that the use of certain interleaf layers, together in a construction with certain adhesive and emboss layers, can produce a multilayer retroreflective sheeting having advantageous tensile properties. Beneficially, these improved properties can give the provided sheeting greater resistance to cracking. Moreover, the disclosure also provides certain combinations of colors among different layers of the sheeting. Further advantages are thus realized in that a durable and opaque interior layer of the sheeting, e.g., the interleaf layer, can have a significantly similar color to that of an upper layer, allowing the interleaf layer to continue to hide an underlying surface and to visually blend in with the upper layer when the upper layer, e.g., an emboss layer, has developed fissures or cracks.

In one aspect, a flexible retroreflective sheeting is disclosed. The sheeting includes a multilayer construction having an emboss layer with retroreflective elements on its back surface, a flexible backing layer and/or a metallized layer at least partially in contact with the retroreflective elements, and a transfer tape connected to the backing layer or to the metallized layer. The transfer tape includes an at least partially opaque interleaf layer that is sandwiched between a pair of adhesive layers. The first adhesive layer connects the transfer tape to the backing or metallized layer, and the second adhesive layer can be an outer face of the sheeting to be adhered to an article.

<FIG> illustrates an exemplary embodiment of the provided sheeting. Shown in the figure is a retroreflective sheeting construction <NUM>. The sheeting includes an emboss layer <NUM> having a pattern of retroreflective elements <NUM> embossed into the emboss layer back surface. In some embodiments, and as shown in <FIG>, the retroreflective elements are prisms or cube corner retroreflectors. The front surface of the emboss layer is attached to a face layer <NUM> that can provide, for example, a durable and/or printable exterior face of the sheeting. A flexible backing layer <NUM> is in contact with a portion of the emboss layer back surface, such that the backing layer and the retroreflective elements together define a plurality of air gaps <NUM>. A first adhesive layer <NUM> is attached to the flexible backing layer, and an interleaf layer <NUM> is disposed between the first adhesive layer and a second adhesive layer <NUM>. The sheeting also includes a release liner <NUM> attached to the second adhesive layer.

The composition and construction of the sheeting can be configured to provide the film with a tensile strain sufficient to allow the sheeting to deform with minimal or no breaking, e.g., cracking, when subjected to a tensile force. In this way, when the sheeting is applied to an object, such as a traffic cone, that is prone to being impacted or crushed by vehicular or pedestrian traffic, the likelihood that the integrity and uniformity of the sheeting will be affected can be reduced.

The tensile strain of the sheeting can, for example, range from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%. The tensile strain of the sheeting can range from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%. In terms of upper limits, the sheeting tensile strain can be less than <NUM>%, e.g., less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, or less than <NUM>%. In terms of lower limits, the sheeting tensile strain can be greater than <NUM>%, e.g., greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, or greater than <NUM>%. Higher tensile strains, e.g., greater than <NUM>%, and lower tensile strains, e.g., less than <NUM>%, are also contemplated. The tensile strain can be measured using, for example, the standard protocol ASTM D828-16e1 (<NUM>).

Similarly, the composition and construction of the sheeting can be configured to provide the film with a force at break sufficient to prevent the sheeting from breaking, e.g., cracking, when subjected to a force or load below a high threshold. The force at break of the sheeting can, for example, range from <NUM> lbf to <NUM> lbf, e.g., from <NUM> lbf to <NUM> lbf, from <NUM> lbf to <NUM> lbf, from <NUM> lbf to <NUM> lbf, from <NUM> lbf to <NUM> lbf, or from <NUM> lbf to <NUM> lbf. In terms of upper limits, the sheeting force at break can be less than <NUM> lbf, e.g., less than <NUM> lbf, less than <NUM> lbf, less than <NUM> lbf, less than <NUM> lbf, less than <NUM> lbf, less than <NUM> lbf, less than <NUM> lbf, less than <NUM> lbf, or less than <NUM> Ibf. In terms of lower limits, the sheeting force at break can be greater than <NUM> lbf, e.g., greater than <NUM> lbf, greater than <NUM> lbf, greater than <NUM> lbf, greater than <NUM> lbf, greater than <NUM> lbf, greater than <NUM> lbf, greater than <NUM> lbf, greater than <NUM> lbf, or greater than <NUM> lbf. Larger forces at break, e.g., greater than <NUM> lbf, and smaller forces at break, e.g., less than <NUM> lbf, are also contemplated. The force at break can be measured using, for example, standard protocol ASTM D828-16e1 (<NUM>).

The sheeting can also be configured to provide the film with a Young's modulus sufficient to permit the sheeting to withstand stretching or compression when under lengthwise forces. The Young's modulus of the sheeting can, for example, range from <NUM> ksi to <NUM> ksi, e.g., from <NUM> ksi to <NUM> ksi, from <NUM> ksi to <NUM> ksi, from <NUM> ksi to <NUM> ksi, from <NUM> ksi to <NUM> ksi, or from <NUM> ksi to <NUM> ksi. In terms of upper limits, the sheeting Young's modulus can be less than <NUM> ksi, e.g., less than <NUM> ksi, less than <NUM> ksi, less than <NUM> ksi, less than <NUM> ksi, less than <NUM> ksi, less than <NUM> ksi, less than <NUM> ksi, less than <NUM> ksi, or less than <NUM> ksi. In terms of lower limits, the sheeting Young's modulus can be greater than <NUM> ksi, e.g., greater than <NUM> ksi, greater than <NUM> ksi, greater than <NUM> ksi, greater than <NUM> ksi, greater than <NUM> ksi, greater than <NUM> ksi, greater than <NUM> ksi, greater than <NUM> ksi, or greater than <NUM> ksi. Larger Young's moduli, e.g., greater than <NUM> ksi, and smaller Young's moduli, e.g., less than <NUM> ksi, are also contemplated. The Young's modulus can be measured using, for example, the standard protocol ASTM D828-16e1 (<NUM>).

The emboss layer can be colored or can be colorless. The emboss layer is generally substantially transparent but can in certain aspects be at least partially opaque. The material of the emboss layer can be selected from a wide variety of polymers, including, but not limited to, polycarbonates, polyesters, polystyrenes, polyarylates, styrene-acrylonitrile copolymers, urethane, acrylic acid esters, cellulose esters, ethylenically unsaturated nitrites, hard epoxy acrylates, acrylics and the like, with acrylic, polycarbonate, and polyurethane polymers being preferred. In some embodiments, the emboss layer comprises acrylic. In some embodiments, the emboss layer comprises polycarbonate. In some embodiments, the emboss layer comprises both acrylic and polycarbonate.

The emboss layer can have a thickness ranging, for example, from <NUM> mil to <NUM> mil, e.g., from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, or from <NUM> mil to <NUM> mil. In terms of upper limits, the emboss layer thickness can be less than <NUM> mil, e.g., less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, or less than <NUM> mil. In terms of lower limits, the emboss layer thickness can be greater than <NUM> mil, e.g., greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, or greater than <NUM> mil. Larger thicknesses, e.g., greater than <NUM> mil, and smaller thicknesses, e.g., less than <NUM> mil, are also contemplated.

In certain aspects, the retroreflective elements of the emboss layer include an arrangement or pattern of prismatic elements embossed into or disposed onto the back surface of the emboss layer. The prismatic elements can be prismatic elements of any three-dimensional shape. In some embodiments, the prismatic elements include prismatic cube corners. In certain aspects, the retroreflective elements include an arrangement or pattern of beads, e.g., glass or ceramic microspheres.

In some embodiments, a flexible backing layer is directly attached to a portion of the emboss layer back surface, and the flexible backing layer and the retroreflective elements define a plurality of air gaps. These air gaps can be at least partially responsible for the retroreflective properties of the sheeting, by providing a material, e.g., air, that has a significantly different refractive index than that of the emboss layer and that is in intimate contact with the retroreflective elements.

The backing layer can be colored or can be colorless. The backing layer can be substantially transparent or can be substantially opaque. The materials and construction of the backing layer can be selected for properties such as flexibility. The flexible backing layer can include, for example, polyvinyl chloride, polycarbonate, ethylene-vinyl acetate, polyolefin, polyurethane, or a combination thereof. In some cases, the flexible backing layer comprises polycarbonate or polyvinyl chloride.

In some embodiments, the sheeting includes, in place of or in addition to a backing layer, a metallized layer. The metallized layer or metallic coating can include a metal such as aluminum, silver, or chromium. The metallized layer can be disposed directly onto the retroreflective elements. In certain aspects in which the sheeting includes a metallized layer, the sheeting further includes a backing layer that acts at least in part as a protecting layer protecting the metallic coating of the retroreflective elements.

The composition and construction of the interleaf layer can be selected to provide the layer with an opacity high enough to block the view of materials and surfaces underlying the interleaf layer. In this way, the interleaf layer can assist in preventing the labeled surface beneath the sheeting from being visible, and can contribute to a uniform appearance of the sheeting. As used herein, the term "opacity" refers to the ratio of the reflectance of a film on a black substrate to that of an identical film on a white substrate The opacity of the interleaf layer can range, for example, from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%. In terms of upper limits, the interleaf layer opacity can be less than <NUM>%, e.g., less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, or less than <NUM>%. In terms of lower limits, the interleaf layer opacity can be greater than <NUM>%, e.g., greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, or greater than <NUM>%. Lower opacities, e.g., less than <NUM>%, are also contemplated. Opacity can be measured using, for example, the standard protocol ASTM D1003-<NUM> (<NUM>). The inventors have found that the use of these durable and sufficiently opaque interleaf layers, as disclosed herein, surprisingly provides the combined and synergistic benefits of resistance to cracking and the ability to hide cracks that may occur.

The composition and construction of the interleaf layer can also be selected to provide the layer with an color closely matching that of a covering layer of the sheeting. This can allow the interleaf layer to contribute to a uniform appearance of the sheeting in the event that the interleaf layer becomes visible through the covering layer, e.g., if the covering layer develops cracks. In certain aspects, the interleaf layer has a white color. In some embodiments, the interleaf layer is pigmented. In certain aspects, the interleaf layer has a yellow, e.g., fluorescent yellow, color. In certain aspects, the interleaf layer has a green, e.g., fluorescent green, color. In certain aspects, the interleaf layer has a yellow-green color. The difference between the colors of the interleaf layer and the covering layer can be expressed in terms of formulae, such as CIEDE2000 (<NUM>), developed by the International Commission on Illumination (CIE). These formulae define a distance metric (ΔE*) having a value from <NUM> to <NUM>, with values less than <NUM> indicating a color difference that is imperceptible to human vision, and a value of <NUM> indicating a difference between colors that are exact opposites of one another.

In some embodiments, the interleaf layer has a similar color to that of the emboss layer of the sheeting. The CIEDE2000 color difference between the interleaf layer color and the emboss layer color can range, for example, from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the difference between the interleaf color and the emboss color can be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of lower limits, the difference between the interleaf color and the emboss color can be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. Larger color differences, e.g., greater than <NUM>, are also contemplated.

In some embodiments, the interleaf layer has a similar color to that of a backing layer of the sheeting. The CIEDE2000 color difference between the interleaf layer color and the backing layer color can range, for example, from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the difference between the interleaf color and the backing color can be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of lower limits, the difference between the interleaf color and the backing color can be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. Larger color differences, e.g., greater than <NUM>, are also contemplated.

In some embodiments, the interleaf layer is cavitated, e.g., the interleaf layer includes a cavitated film. Cavitation agents of the cavitated film can include one or more inorganic and/or organic particulate solids. The cavitation agents can include an organic solid such as calcium carbonate. In some embodiments, the cavitation agents include one or more polymers, such as polyesters or polycarbonates. In certain aspects, the cavitation agents include polar polymers. The cavitation agents can include, for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene <NUM>,<NUM>-naphthalate (PEN), polycarbonate (PC), or a combination thereof. The cavitation agent can added to the film in the form of a particulate solids concentrate or additive concentrate at <NUM> wt% to <NUM> wt% in a thermoplastic polymer carrier, such as a propylene polymer mixture.

In addition to color properties, the structural integrity of the interleaf layer can also be considered in selecting the materials and construction of the layer. The interleaf layer can include, for example, polyethylene terephthalate, polyvinyl chloride, polycarbonate, ethylene-vinyl acetate, polyolefin, polyurethane, or a combination thereof. In some embodiments, the interleaf layer comprises polyethylene terephthalate. In some embodiments, the interleaf layer comprises pigmented polyethylene terephthalate.

The interleaf layer can have a thickness ranging, for example from <NUM> mil to <NUM> mil, e.g., from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, or from <NUM> mil to <NUM> mil. In terms of upper limits, the interleaf layer thickness can be less than <NUM> mil, e.g., less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, or less than <NUM> mil. In terms of lower limits, the interleaf layer thickness can be greater than <NUM> mil, e.g., greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, or greater than <NUM> mil. Larger thicknesses, e.g., greater than <NUM> mil, and smaller thicknesses, e.g. less than <NUM> mil, are also contemplated.

The ratio of the emboss layer thickness to the interleaf layer thickness can, for example, range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the thickness ratio of the emboss layer to the interleaf layer can be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of lower limits, the thickness ratio of the emboss layer to the interleaf layer can be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. Higher ratios, e.g., greater than <NUM>, and lower ratios, e.g., less than <NUM>, are also contemplated. The inventors have found that maintaining the ratio of the emboss layer thickness to the interleaf layer thickness within these ranges and/or limits surprisingly provides for improvements in the ability to hide cracks that may occur. It is postulated that the interleaf layer must have sufficient thickness (with respect to the emboss layer, to conceal cracks. Without sufficient thickness, cracks will either occur in the interleaf layer or will be unable to be hidden due to the lack of opaque layering.

The composition of the first adhesive layer can be selected to provide strong adhesion to the materials of the backing layer, metallized layer, or other layer to which the first adhesive layer will be attached. The composition of the second adhesive layer can be selected to provide strong adhesion to the surface materials of the article, e.g., a traffic device, to which the second adhesive layer will be attached. The compositions of the first and second adhesive layers can also be selected to provide strong adhesion to the materials of the interleaf layer. In certain aspects, the second adhesive layer is not present in the sheeting construction. In these cases, the interleaf layer can be an outer layer of the sheeting, and the sheeting can be configured to wrap tightly around the surface of an object, e.g., a traffic cone, such that an adhesive bond between the sheeting and the object is not required.

The first adhesive layer and the second adhesive layer can each independently include a pressure sensitive adhesive. In certain aspects, one or both of the first and second adhesive includes an emulsion. In certain aspects, one or both of the first and second adhesives includes a hot melt adhesive. In some embodiments, the adhesive may be formed from an acrylic based polymer. The adhesive can also be rubber-based, or a radiation curable mixture of monomers with initiators and other ingredients. Tackifiers, plasticizers, and other additives can be included in the adhesives to impart desired properties. Additives can include cutting agents such as waxes and surfactants, light stabilizers, heat stabilizers, ultraviolet absorbers, heat absorbers, and combinations thereof.

In certain aspects the sheeting includes a single face layer. The sheeting can also include two face layers, or more than two layers, arranged in a stacked configuration with different face layers having different properties and imparting different benefits to the multilayer sheeting. Each face layer of the sheeting can independently be colored or can be colorless. Each face layer of the sheeting can independently be substantially transparent or can be substantially opaque. The materials and construction of the layer can be selected for properties such as flexibility and printability. The face layer can include, for example, polyvinyl chloride, acrylic, polycarbonate, polyolefin, polyurethane, or a combination thereof. In some embodiments, the face layer comprises polyvinyl chloride.

The face layer can have a thickness ranging, for example, from <NUM> mil to <NUM> mil, e.g., from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, from <NUM> mil to <NUM> mil, or from <NUM> mil to <NUM> mil. In terms of upper limits, the face layer thickness can be less than <NUM> mil, e.g., less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, less than <NUM> mil, or less than <NUM> mil. In terms of lower limits, the face layer thickness can be greater than <NUM> mil, e.g., greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, greater than <NUM> mil, or greater than <NUM> mil. Larger thicknesses, e.g., greater than <NUM> mil, and smaller thicknesses, e.g., less than <NUM> mil, are also contemplated.

The ratio of the face layer thickness to the emboss layer thickness can, for example, range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the thickness ratio of the face layer to the emboss layer can be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of lower limits, the thickness ratio of the face layer to the emboss layer can be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. Higher ratios, e.g., greater than <NUM>, and lower ratios, e.g., less than <NUM>, are also contemplated.

The inventors have found that the relationship between the thickness of the face layer and the thickness of the interleaf layer can be critical in providing the sheeting with advantageous properties particularly useful in, for example, outdoor traffic safety applications. Importantly, by maintaining a sufficient face layer thickness relative to the interleaf thickness, the emboss layer and other underlying layers are protected from environmental degradation associated with outdoor use. In addition, if the interleaf thickness is not sufficiently large relative to the face layer thickness, then the aforementioned benefits in visible crack mitigation are not significantly realized. The ratio of the face layer thickness to the interleaf layer thickness can, for example, range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the thickness ratio of the face layer to the interleaf layer can be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of lower limits, the thickness ratio of the face layer to the interleaf layer can be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>.

In some embodiments, a release liner is connected to the second adhesive layer. The releasable liner can function as a protective cover such that the release liner remains in place until the sheeting is ready for attachment to an object or surface. If a liner or release liner is included in the sheeting, a wide array of materials and configurations can be used for the liner. In many embodiments, the liner is a paper or paper-based material. In many other embodiments, the liner is a polymeric film of one or more polymeric materials. Typically, at least one face of the liner is coated with a release material such as a silicone or silicone-based material. As will be appreciated, the release coated face of the liner is placed in contact with the otherwise exposed face of the second adhesive layer. Prior to application of the label to a surface of interest, the liner is removed to thereby expose the adhesive face of the label. The liner can be in the form of a single sheet. Alternatively, the liner can be in the form of multiple sections or panels.

The disclosure also relates to methods for producing the provided retroreflective sheeting. The methods include thermally embossing an emboss layer to form a plurality of retroreflective elements on the back surface of the emboss layer. The thermal embossing can include feeding the emboss layer to an embossing tool, heating the layer to allow the pattern on the tool to be pressed into the emboss layer material, and then cooling the layer. In certain aspects, the thermal embossing forms retroreflective elements on a back side of the emboss layer, and attaches a flexible face layer to an opposite front side of the emboss layer.

In some embodiments, the method includes connecting a flexible backing layer to the emboss layer back surface. In certain aspects, the connecting includes sealing the flexible backing layer to a portion of the emboss layer back surface, thereby defining a plurality of air gaps with the flexible backing layer and the retroreflective elements. In some embodiments, the method includes connecting a metallized layer to the emboss layer back surface. In certain aspects, the metallized layer is applied vacuum metallization. In certain aspects, the metallized layer is applied by sputtering or plasma coating.

The method also includes coating an interleaf layer with adhesive. A first face of the interleaf layer is coated with a first adhesive layer, and a second face of the interleaf layer is coated with a second adhesive layer. The interleaf layer and the adhesive layers together form a transfer tape that is then laminated to the backing layer or metallized layer of the sheeting. In some embodiments, a release liner is also attached to the exposed face of the second adhesive layer.

The following embodiments are contemplated. All combinations of features and embodiments are contemplated, as defined in the appended set of claims.

The present disclosure will be better understood in view of the following non-limiting example.

A series of retroreflective sheeting constructions were assembled as shown in Table <NUM> below. Each sheeting included a polyvinyl chloride (PVC) face layer, a white acrylic emboss layer, and a polyvinyl chloride backing layer. Examples <NUM> and <NUM> included a clear interleaf layer sandwiched between two layers of S-<NUM> adhesive, commercially available from Avery Dennison (Glendale, CA). Examples <NUM>, <NUM>, and <NUM> included a white pigmented interleaf layer between two S-<NUM> adhesive layers. Two comparative retroreflective sheeting constructions were also prepared. These Comparative A and Comparative B samples included similar face, emboss, and backing layers to those of Examples <NUM>-<NUM>, but did not include an interleaf layer.

Each of the sheeting constructions was applied in the form of top and bottom cone collars to polyvinyl chloride traffic cones. These cones were then subjected to tests that included stepping on the collars in an indoor environment, and driving on the collars with a car in two passes in an outdoor environment after the cones were stored at a temperature of <NUM> °F for <NUM> hours. Results from these crush tests, as well as from tests of different tensile properties, are also presented in Table <NUM> below.

The results in Table <NUM> demonstrate that the inclusion of an interleaf layer in the flexible retroreflective sheeting as described herein allows the sheeting to better withstand the stresses of a step crush test simulating pedestrian collisions with traffic safety devices such as traffic cones. The results further demonstrate that the color matching of the interleaf layer with the emboss layer of the sheeting constructions allows the sheeting to minimize or prevent the formation of visible cracks under the greater force of a car crush test simulating vehicular collisions.

Claim 1:
A flexible retroreflective sheeting (<NUM>) comprising:
an emboss layer (<NUM>) having a front surface and an opposite back surface comprising a plurality of retroreflective elements (<NUM>);
a flexible backing layer (<NUM>) in contact with the emboss layer back surface;
a first adhesive layer (<NUM>) connected to the flexible backing layer opposite the emboss layer;
an interleaf layer (<NUM>) having an opacity greater than <NUM>% and connected to the first adhesive layer opposite the flexible backing layer; and
a second adhesive layer (<NUM>) connected to the interleaf layer opposite the first adhesive layer
wherein the emboss layer has an emboss color, and wherein the interleaf layer has an interleaf color with a CIEDE2000 color difference from the emboss color of less than <NUM>, or
wherein the emboss layer is transparent and wherein the flexible backing layer has a backing color, and wherein the interleaf layer has an interleaf color with a CIEDE2000 color difference from the backing color of less than <NUM>.