WO2014172913A1

WO2014172913A1 - Conductive retroreflective article and method of manufacturing the same

Info

Publication number: WO2014172913A1
Application number: PCT/CN2013/074885
Authority: WO
Inventors: Weiwei Gao; Weilin Shi; Bing Zhang; Xiaolong Jia
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2013-04-27
Filing date: 2013-04-27
Publication date: 2014-10-30
Anticipated expiration: 2015-10-27
Also published as: CN105190373B; CN105190373A

Abstract

The present application provides a conductive retroreflective article. One exemplary conductive retroreflective article comprises a retroreflective layer (130, 230, 330, 430) having a front surface and a back surface, and a conductive adhesive layer (140, 240, 340, 440) adjacent the back surface of the retroreflective layer; and an array of dissipating channels (160, 260, 360, 460) through which static electricity can be dissipated. The present application also provides a method of manufacturing the aforementioned conductive retroreflective article.

Description

CONDUCTIVE RETROREFLECTIVE ARTICLE AND METHOD OF

MANUFACTURING THE SAME

BACKGROUND

Field of the Invention

The present application relates to conductive retroreflective articles and methods of manufacturing the same.

Description of the Related Art

Retroreflective articles are generally employed for various safety and decorative purposes. For instance, such articles are useful at night time, when visibility is important because of low light conditions, due to their retroreflectivity. Retroreflective articles are widely used in plant areas, power signs and commercial advertising signs, etc., because of their manufacturing convenience and surface printable properties. Accordingly,

retroreflective articles are used in applications such as, for example, highway signs, traffic cone collars, license plates, and warning reflectors.

In some applications, retroreflective articles are used in power plants, mining areas, and manufacturing sites, wherein discharge of static electricity can create severe hazards. In industries dealing with flammable substances, for example, a small electrical spark may ignite explosive mixtures. In these environments it is desirable to reduce or eliminate electrostatic charge accumulation (static electricity) on the surface of numerous substrates, such as, for example, retroreflective articles.

SUMMARY

The present inventors sought to develop retroreflective articles with reduced surface electrostatic charge accumulation. Further, the present inventors sought to develop retroreflective articles that were also printable for decorative purposes.

The conductive retroreflective article of the present application overcomes or alleviates the above mentioned disadvantages existing in the conventional technical solutions. Accordingly, it is an object of the present application to provide a conductive retroreflective article capable of reducing and/or eliminating accumulated charge on its surface, so as to resolve potential safety concerns.

It is another object of the present application to provide a conductive retroreflective article which is surface printable and may be used for decorative purposes.

It is still another object of the present application to provide a method of

manufacturing the aforementioned conductive retroreflective article.

According to one aspect of the present application, there is provided a conductive retroreflective article comprising: a retroreflective layer having a front surface and a back surface; a conductive adhesive layer adjacent the back surface of the retroreflective layer; ; an array of dissipating channels on the retroreflective article; and at least some of the conductive adhesive in at least one of the dissipating channels.

According to another aspect of the present application, the conductive adhesive layer further comprises metal particles. In some embodiments, the adhesive layer comprises a pressure-sensitive adhesive (PSA) containing metal particles, wherein the content of metal particles ranges preferably from 5 to 30 weight percent, based on the total weight of the conductive adhesive layer. The metal particles are preferably any one selected from the group consisting of nickel, copper, lead, chromium and silver, and mixtures thereof. In some embodiments, the PSA is acrylic acid-based, with the content of acrylic resin being at least 30 percent, based on the total weight of the adhesive.

According to one aspect of the present application, the retroreflective layer may be one of a beaded layer and a prismatic layer. Specifically, the beaded layer may preferably comprise glass beads dispersed in a binding layer, and the prismatic layer may preferably comprise a structured surface having cube corner elements.

Further, the conductive retroreflective article according to the present application may also comprise a metal coating (layer) formed adjacent the glass beads or adjacent the cube corner elements.

According to one aspect of the present application, the metal coating comprises a metal selected from the group consisting of aluminum, aurum, silver, copper, and their alloys. In some embodiments, the metal is aluminum.

Furthermore, the conductive retroreflective article according to the present application may further comprise a release layer disposed on the conductive adhesive layer.

According to one aspect of the present application, the release layer may be selected from the group consisting of a release liner containing silicon or fluorine, and a polyester film.

According to one aspect of the present application, at least one dissipating channel may extend through the release layer.

According to another aspect of the present application, the conductive retroreflective article may further comprise a surface layer having a first side and a second side, wherein the second side of the surface layer is disposed on the front surface of the retroreflective layer, and wherein the surface layer is made of a transparent and/or printable polymer.

According to one aspect of the present application, the surface layer may be made from a polymer selected from the group consisting of polyvinyl chloride, acrylic, ethylene- acrylic acid, polyethylene terephthalate, polycarbonate and blends thereof.

According to yet another aspect of the present application, the conductive retroreflective article may further comprise a first adhesive layer disposed between the surface layer and the retroreflective layer, the first adhesive layer being used to bond the surface layer and the retroreflective layer together. According to one aspect of the present application, the first adhesive layer is formed by one of a primer composition, an adhesive composition and a surface treatment.

Preferably, the first adhesive layer is a polyurethane layer.

According to another aspect of the present application, the conductive retroreflective article may further comprise a carrier layer disposed on the first side of the surface layer.

According to yet another aspect of the present application, the conductive retroreflective article may further comprise a second adhesive layer disposed between the carrier layer and the surface layer, the second adhesive layer being used to bond the carrier layer and the surface layer together.

According to one aspect of the present application, the second adhesive layer is formed by one of a primer composition, an adhesive composition and a surface treatment. Preferably, the second adhesive layer is a polyurethane layer.

According to one aspect of the present application, the dissipating channels in the array of dissipating channels each have a diameter ranging from 1.0 mm to 10.0 mm. In some embodiments, the dissipating channels may be spaced apart by a distance ranging from 2.0 mm to 15.0 mm. In some embodiments, the dissipating channels in the array of dissipating channels may each have a cross-section shape selected from the group consisting of circular, square, triangular, rectangular and polygonal.

Meanwhile, the present application also provides a method of manufacturing the aforementioned conductive retroreflective article. The method at least comprising the steps of: providing a retroreflective layer having a front surface and a back surface; disposing a conductive adhesive layer on the back surface of the retroreflective layer to form a retroreflective article; and perforating the retroreflective article to form dissipating channels, wherein at least one dissipating channel extends through the retroreflective layer and conductive adhesive layer.

According to one aspect of the present application, the method further comprises a step of providing a metal coating adjacent the back surface of the retroreflective layer.

According to one aspect of the present application, the method further comprises a step of disposing a surface layer on the front surface of the retroreflective layer. In some embodiments, the surface layer is also perforated.

According to yet another aspect of the present application, the method further comprises a step of forming a first adhesive layer between the surface layer and the retroreflective layer.

According to one aspect of the present application, the method further comprises a step of providing a release layer on the conductive adhesive layer. In some embodiments, the release layer is also perforated.

As apparent from the above, the present application has the following advantages: the conductive retroreflective article according to the present application utilizes formation of an array of dissipating channels on a retroreflective article, wherein at least a portion of the conductive adhesive layer is displaced into at least one dissipating channel to form an electric path. This path allows for dissipation of electrostatic surface charges, and as a result, electrostatic charges accumulated on the surface of the conductive retroreflective article are reduced and/or eliminated. Further, the conductive retroreflective article according to the present application has a surface layer which may be printable for decorative purposes. Accordingly, the conductive retroreflective article according to the present application resolves potential safety concerns caused by static electricity. The conductive retroreflective article according to the present application may be used in, for example, highway signs, license plates, traffic cone collars, warning reflectors, electronic product signs, power signs, mining plants signs, and commercial advertising signs.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. la is a schematic view of a beaded retroreflective article according to one embodiment of the present application prior to perforation.

FIG. lb is a schematic view of the conductive beaded retroreflective layer depicted in 1 a after perforation.

FIG. 2 is a schematic view of a conductive beaded retroreflective article according to another embodiment of the present application.

FIG. 3 is a schematic view of a conductive prismatic retroreflective article according to one embodiment of the present application.

FIG. 4 is a schematic view of a conductive prismatic retroreflective article according to another embodiment of the present application.

The scope of the present application will in no way be limited to the simply schematic views of the drawings, the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of an embodiment.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure will be described hereinafter in detail with reference to the attached drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art.

Referring now to the Figures, FIG. la depicts a conductive retroreflective article according to the present application before perforation. Conductive retroreflective article 100 comprises a beaded retroreflective layer 130 having a front surface and a back surface. Light impinges onto the front surface of retroreflective layer 130 and returns towards the light source. Retroreflective layer 130 comprises glass beads 131 dispersed in a binding layer 132, and a metallic layer (metal coating) 133 adjacent the backside of binding layer 132. A surface layer 110 is adhered to the front surface of beaded retroreflective layer 130. Optionally, surface layer 110 is bonded to the retroreflective layer 130 by a first adhesive layer 120. In some embodiments, the first adhesive layer 120 is formed by one of a primer composition, an adhesive composition and a surface treatment (e.g., corona treatment). A conductive adhesive layer 140 adjacent the back surface of beaded retroreflective layer 130 is provided. In some embodiments, conductive adhesive layer 140 comprises metal particles (not shown). Optionally, a release layer 150 may be used to protect conductive adhesive layer 140. In some embodiments, conductive adhesive layer 140 is disposed on the release layer 150 and subsequently laminated to the retroreflective layer 130. In other embodiments, conductive adhesive layer 140 is formed on the retroreflective layer (e.g., by means ofcasting an adhesive composition or laminating and adhesive layer onto the back surface of the retroreflective layer).

FIG. lb depicts the conductive retroreflective article 100 shown in FIG. la after an array of dissipating channels 160 has been formed by perforating the conductive

retroreflective article 100, forming an electric path for static electricity. In some

embodiments the release layer 150 may also be perforated. In this embodiment, dissipating channels 160 extend through from the backside of release layer 150 to the front side of surface layer 110. Prior to forming the dissipating channels, a carrier layer 102 may optionally be adhered to the surface layer 110 by a second adhesive layer 103 to allow the conductive retroreflective article 100 to be positioned on the intended substrate (not shown) prior to effectively adhering the retroreflective article. The carrier layer 102 and second adhesive layer 103 remain intact (i.e., are not perforated) upon formation of dissipating channels 160. After application of the conductive retroreflective article on the substrate, carrier layer 102 and second adhesive layer 103 are removed (peeled from) from the conductive retroreflective article 100.

FIG. 2 depicts another embodiment of the conductive adhesive article of the present application. Conductive retroreflective article 200 comprises beaded retroreflective layer 230 having a front surface and a back surface. Beaded retroreflective layer 230 includes glass beads 231 at least partially embedded in a bead coat layer 234 and dispersed in a binding layer 232. A metal coating 233 is disposed on the back side of bead coat layer 234. The conductive retroreflective article 200 may also comprises a surface layer 210 disposed on the front surface of beaded retroreflective layer 230. First adhesive layer 220 may be used to help secure surface layer 210 to the beaded retroreflective layer 230. A conductive adhesive layer 240 is disposed adjacent metal coating 233 of retroreflective layer 230. In some embodiments, conductive adhesive layer 240 comprises metal particles (not shown). Optionally, a release layer 250 may be disposed adjacent conductive adhesive layer 240 to protect the adhesive before application of the retroreflective article to the intended substrate (not shown). An array of dissipating channels 260 is formed by perforating the conductive retroreflective article shown in FIG. 2. In some embodiments the release layer 250 may also be perforated. In other embodiments release layer 250 is not perforated to maintain integrity and handleability of conductive retroreflective article 200.

Alternatively to beaded retroreflective layer, prismatic retroreflective layer may be used. FIG. 3 depicts a conductive retroreflective article 300 comprising a prismatic retroreflective layer 330 having a front surface and a back surface. Prismatic retroreflective layer 330 comprises cube corner elements 334 disposed on a body layer 336. In some embodiments, body layer 336 is integral with cube corner elements 334 (not shown). A metal coating 333 is disposed adjacent cube corner elements 334. A surface layer 310 may optionally be disposed on the front surface of the prismatic retroreflective layer 330. In some embodiments, a first adhesive layer (not shown) is used to secure surface layer 310 to retrorefiective layer 330. A conductive adhesive layer 340 is disposed adjacent metal coating 333, and may further include metal particles (not shown). Optionally, a release layer 350 may be used to protect conductive adhesive layer 340. A carrier layer 302 may optionally be adhered to the surface layer 310 by a second adhesive layer 303 to allow the conductive retrorefiective article 300 to be positioned on the intended substrate (not shown) prior to effectively adhering the retrorefiective article. An array of dissipating channels 360 is formed on the conductive retrorefiective article 300, however carrier layer 302 and second adhesive layer 303 remain intact (i.e., are not perforated). In one embodiment, the array is formed by perforating the retrorefiective article.

FIG. 4 depicts another embodiment of a conductive retrorefiective article according to the present application. Conductive retrorefiective article 400 comprises a prismatic retrorefiective layer 430 having a front surface and a back surface. The prismatic

retrorefiective layer 430 includes cube corner elements 435, a body layer 436 integral with the cube corner elements 435, and a seal film 437 adjacent the back side of cube corner elements 435. Seal film 437 creates air pockets 438 on the back side of cube corner elements 435, enabling total internal reflection (TIR). A surface layer 410 may be optionally disposed on the front surface of the prismatic retrorefiective layer 430. In some embodiments, the surface layer 410 is adhered to the retrorefiective layer 430 by a first adhesive layer 420. A conductive adhesive layer 440 is disposed adjacent seal film 437, and may optionally comprise metal particles (not shown). A release layer 450 may be used to protect conductive adhesive layer 440 prior to application.

A third adhesive layer comprising optically inactive areas may be used in the prismatic retrorefiective layer of the present application. Such third adhesive layer further comprises first and second regions, wherein the second region is in contact with the structured surface of the prismatic retrorefiective layer. Said first and second regions have sufficiently different properties to form a low refractive index layer between the adhesive layer and the structured surface. An exemplary third adhesive layer is described in U.S.

Patent Publication No. 20130034682 (Free, et al), the disclosure of which is incorporated herein by reference. Alternatively, the conductive adhesive layer of the present application may include optically inactive areas, such as described above. In this embodiment, the conductive adhesive layer is positioned adjacent the structured surface of the retroreflective layer.

Preferably, at least part of the conductive adhesive layer (140, 240, 340, 440), as shown in FIGS. 1 - 4, is displaced (moved) into at least one of the dissipating channels (160, 260, 360, 460). As a result, electrostatic charges accumulated on the surface of the conductive retroreflective article are dissipated. In some embodiments, the conductive adhesive layer is cast as a liquid onto the retroreflective layer and flows into the channels upon formation of the dissipating channels. The conductive adhesive layer is subsequently dried and/or cured. In other embodiments, the adhesive is moved into the channels upon pressing the retroreflective article construction after perforation. In some embodiments, the conductive adhesive layer displaced into the dissipating channels contacts the metal coating (133, 233, 333).

In some embodiments, the perforated release layer (150, 350) may be replaced by a new, imperforated release layer, to provide improved handleability and adhesive protection.

In some embodiments of the present application, the dissipating channels are perforated in a direction generally perpendicular to the front surface of the conductive retroreflective article. Alternatively, the dissipating channels may be perforated in any inclination with respect to the front surface of the conductive retroreflective article.

Dissipating channels may have a cross-section of any shape, including, but not limited to, circular, triangular, rectangular, and other polygon. Typically, the diameter of the dissipating channels ranges from 1.0 to 10.0 mm each and the dissipating channels are spaced apart by a distance ranging from about 2.0 to about 15.0 mm. Preferably, the dissipating channels are spaced apart by a distance ranging from about 3.0 mm to about 6.0 mm. Dissipating channels in a given conductive retroreflective article may all have the same diameter. Alternatively, the diameter of the dissipating channels may vary throughout the retroreflective article. In some embodiments, the conductive retroreflective article is perforated so that the dissipating channels form a decorative pattern, such as, for example, a logo. Exemplary materials used in the conductive retroreflective article of the present application are listed below.

1 ) Surface Layer ( 110, 210, 310, 410), Body Layer (336, 436) and Carrier Layer (102, 302):

Exemplary materials for use as the surface layer, body layer and/or carrier layer are preferably light-transmissible (transparent) and may be selected from the group consisting of, polyester, polyvinyl chloride (PVC) , polyurethane (PU) , ethylene acrylic acid (EAA) , ethylene- vinyl acetate copolymer (EVA) , polypropylene (PP) , polyethylene terephthalate (PET) , acrylic acid, polymethyl methacrylate (PMMA), polycarbonate (PC), and polythene (PE). Preferably, the surface layer is made of any one selected from: PVC, acrylic resin, EAA, PET, PC, and PMMA. When PVC is used, the content of polyvinyl chloride is typically more than 60 percent. In addition, additives such as plasticizing agents, pigments, and ultraviolet-resistant absorbing agents, may be used. The surface layer's thickness typically ranges from 0.02 mm to 0.1 mm. The surface layer may be used to protect the retroreflective layer and/or provide a printable surface for the conductive retroreflective article of the present application.

2) First Adhesive Layer (120, 220, 420) and Second Adhesive Layer (103, 303) Exemplary materials useful for forming the first adhesive layer and/or second adhesive layer include, but are not limited to, primer compositions, adhesive compositions, adhesive polymer layers and surface treatments. Exemplary primer compositions include, but are not limited to, polyurethane and ethylene vinyl acetate based compositions.

Exemplary adhesive compositions include, but are not limited to acrylic adhesive or rubber based adhesive compositions. Exemplary surface treatments include, but are not limited to, corona treatment, chemical treatment or plasma treatment.

The first adhesive layer may be used to secure surface layer (110, 210, 410) to the retroreflective layer (130, 230, 430). The second adhesive layer (103, 303) may be used to secure carrier layer (102, 302) to the surface layer.

The thickness of the first adhesive layer preferably ranges from 0.01 mm to 0.2 mm.

3) Retroreflective layer (130, 230, 330, 430):

Two types of retroreflective layer (retroreflective sheeting) may be used in the conductive retroreflective article of the present application: beaded layer and prismatic layer. Beaded layer typically employs a multitude of glass or ceramic microspheres (beads) to retroreflect incident light (retroreflective elements). Said microspheres are typically at least partially embedded in a binding layer and having associated specular or diffuse reflecting materials (e.g., pigment particles, metal coatings, metal flakes or vapor coats, etc.) to retroreflect incident light. Due to the symmetrical geometry of microsphere-based retroreflectors, beaded layer exhibits the same light return regardless of orientation, i.e., when rotated about an axis normal to the surface of the sheeting. Such microspheres may optionally be at least partially embedded in a bead coat layer. The bead coat layer may have the same composition as the binding layer. Suitable glass beads used in beaded layer have refractive indices ranging from 1.5 - 2.2. Preferably, between 1.9 - 2.2. Suitable materials for use in the binding layer and/or bead coat layer include those with relatively high bond strength, such as, for example, polyurethane (PU), polyvinyl butyral (PVB), acrylic acid, ethylene- vinyl acetate copolymer (EVA), and, polyurethane (PU). Additives such as oxidation inhibitor, etc., may optionally be used.

Prismatic layer, on the other hand, typically employs a multitude of cube-corner elements to retroreflect incident light. Prismatic layer (also referred to as cube corner layer , prismatic sheeting or cube corner sheeting) typically comprises a thin transparent body layer having a substantially planar first surface and a second structured surface comprising a plurality of geometric structures. In some embodiments, the body layer is integral with the geometric structures.

In truncated cube corner sheeting some or all geometric structures include three reflective faces configured as a cube-corner element. The base edges of adjacent cube-corner elements of truncated cube-corner arrays are typically coplanar. Other cube-corner element structures, described as "full cubes" or "preferred geometry" typically comprise at least two non-dihedral edges that are not coplanar. Such structures typically exhibit a higher total light return in comparison to truncated cube-corner elements. Cube-corner sheeting having "preferred geometry" cube-corner elements may be manufactured by a laminae process (see, e.g., U. S. Pat. No. 7, 156,527 (Smith), incorporated herein by reference).

Prismatic retroreflective layer is commonly produced by first manufacturing a master mold that has a structured surface, such structured surface corresponding either to the desired cube corner element geometry in the finished sheeting or to a negative (inverted) copy thereof, depending upon whether the finished sheeting is to have cube corner pyramids or cube corner cavities (or both). The mold is then replicated using any suitable technique, such as nickel electroforming, to produce tooling for forming prismatic retroreflective layer by processes such as embossing, extruding, or cast-and-curing. U.S. Patent No. 5, 156,863 (Pricone et al.) provides an illustrative overview of a process for forming tooling used in the manufacture of prismatic retroreflective layer. Known methods for manufacturing the master mold include pin-bundling techniques, direct machining techniques, and techniques that employ laminae. These microreplication processes produce a retroreflective layer with prismatic structures that have been precisely and faithfully replicated from a microstructured tool having a negative image of the desired prismatic structure.

Exemplary polymers for forming cube corner elements include thermoplastic polymers, such as, for example, poly(carbonate), poly(methylmethacrylate),

poly(ethyleneterephthalate), aliphatic polyurethanes, as well as ethylene copolymers and ionomers thereof, and mixtures thereof. Cube corner sheeting may be prepared by casting directly onto a film, such as described in U.S. Patent No. 5,691,846 (Benson). Polymers for radiation cured cube corners include cross linked acrylates such as multifunctional acrylates or epoxies and acrylated urethanes blended with mono-and multifunctional monomers.

Further, cube corners such as those previously described may be cast on to plasticized polyvinyl chloride film for more flexible cast cube corner sheeting. These polymers are preferred for one or more reasons including thermal stability, environmental stability, clarity, excellent release from the tooling or mold, and capability of receiving a reflective coating. 4) Metal coating (133, 233, 333)

Exemplary materials for the metal coating include, but are not limited to, those selected from the group consisting of aluminum, aurum, silver, and copper, and their alloys. When aluminum is used, it should have a purity of more than 99 percent. A vacuum sputtering process may be used to form the metal coating, which typically has a thickness of about 100 angstrom (A).

5) Conductive adhesive layer (140, 240, 340, 440):

Exemplary materials for forming the conductive adhesive layer include pressure- sensitive adhesive compositions (PSA), radiation-curable adhesive compositions and hot- melt adhesive compositions. Electrically conductive metal particles may be used. In such embodiments, the content of the electrically conductive metal particles in the adhesive typically ranges from about 5 to about 30 weight percent based on the total weight of the adhesive. The electrically conductive metal particles may be selected from the group consisting of nickel, copper, lead, chromium and silver. Preferably, nickel is employed.

The adhesive preferably comprises an acrylic or acrylate PSA, with the content of acrylic or acrylate resin in the PSA being of about 30 weight percent based on the total weight of the adhesive composition. Other components may optionally include plasticizing agents, cross-linking agents, pigments, UV absorbers, and adhesion promoters. There is no certain demand on thickness of the conductive adhesive layer. The conductive adhesive layer is used to allow dissipation of electrostatic charges.

6) Release Layer (150, 250, 350, 450):

The release layer may be made of any one selected from the group consisting of silicon or fluorine-containing monomers, polyester, polyolefins, polyethylene terephthalate (PET), polypropylene (PP), and polythene (PE). There is no certain demand on thickness of the release layer. The release layer is used to provide support to the conductive

retroreflective article and protect the conductive adhesive layer prior to application of the retroreflective article to a substrate.

7) Seal film (437):

Exemplary seal films include, but are not limited to, those described in, for example, U. S. Pat. Nos. 5,691,846 (Benson et al), 5,784, 197 (Frey et al), 6,318,867 (Bacon et al), and 7,611,251 (Thakkar et al), all of which are incorporated herein by reference. The seal film maintains an air interface at the back side of the cubes to enhance retroreflectivity

The present application also provides a method of manufacturing the aforementioned conductive retroreflective article. Particularly, the method comprises the steps of: providing a retroreflective layer (130, 230, 330, 430) having a front surface and a back surface;

disposing a conductive adhesive layer (140, 240, 340, 440) on the back surface of the retroreflective layer to form a retroreflective article; and perforating the retroreflective article to form dissipating channels (260, 360, 460), wherein at least one dissipating channel extends through the retroreflective layer and conductive adhesive layer.

The method of the present application may further comprise the steps of: forming a light-transmittable and printable surface layer on the retroreflective layer; and forming a first adhesive layer between the surface layer and the retroreflective layer, to bond the surface layer and the retroreflective layer together. The surface layer and the retroreflective layer are perforated, thus forming an array of dissipating channels that form electric paths for dissipation of static electricity.

Further, the method of manufacturing the conductive retroreflective article according to the present application may also comprise the steps of providing a release layer; and forming the array dissipating channels by also perforating through the release layer.

Alternatively, the method of manufacturing the conductive retroreflective article according to the present application may also comprise the further step of replacing the perforated release layer with a new intact release layer.

These and/or other explanations and illustrations of the method of manufacturing the conductive retroreflective article according to the present application will more readily appreciated from the corresponding explanations and illustrations of the conductive retroreflective article in the context.

In conjunction with these following examples, retroreflectivity and surface contact resistance of the conductive retroreflective articles of the present application were measured.

EXAMPLES

The recitation of all numerical ranges by endpoint is meant to include all numbers subsumed within the range (i.e., the range 1 to 10 includes, for example, 1, 1.5, 3.33, and 10).

Those having skill in the art will appreciate that many changes may be made to the details of the above-described embodiments and implementations without departing from the underlying principles thereof. Further, various modifications and alterations of the present application will become apparent to those skilled in the art without departing from the spirit and scope of the invention. The scope of the present application should, therefore, be determined only by the following claims.

TEST PARAMETERS AMD TEST METHODS

Retroreflectivity:

Retroreflectivity (coefficient of retroreflection) was measured in the down web and cross web directions at an observation angle of 0.2° and entrance angle of -4° using a retroreflectometer (such as model "DELTA RETROSIGN GR3", from Delta, Denmark). Surface Contact Resistance:

Surface contact resistance was measured according to the procedure outlined in MIL- STD-202, "Test Method Standard, Electronic and Electrical Component Parts", (method 307#), using a micro ohmmeter such as available under the trade designation "TTi BS407", from Technology Transfer Initiative Company.

MATERIALS

Pressure sensitive adhesive (PSA)

An acrylic-based PSA was prepared by mixing at room temperature the ingredients listed in Table 1, below, in the order provided, for 6 hours. The amount of each ingredient is expressed in weight percent (wt %) based on the total weight of the composition.

Table 1 Ingredient Supplier Amount (wt%)

Isooctyl acrylate Chongqing Unisplendour 22

Chemical Co. Ltd, China

Butyl acrylate Chongqing Unisplendour 10

Chemical Co. Ltd

Methacrylate Chongqing Unisplendour 6

Chemical Co. Ltd

Ethyl acetate Sino Chemical Company, 30

Singapore

Toluene Sino Chemical Company 30

Acrylic acid Sino Chemical Company 2

Crosslinker

A crosslinker was prepared by mixing at room temperature the ingredients listed Table 2, below, in the order provided, for two hours. The amount of each ingredient is expressed in weight percent (wt %) based on the total weight of the composition.

Table 2

EXAMPLE 1

A surface layer was prepared using a polyvinyl chloride (PVC) homopolymer dispersion having a content of polyvinyl chloride greater than 60 percent (obtained under the trade designation "GEON 178", from PolyOne Corporation, Avon Lake, OH). The thickness of the surface layer (dried) was 0.03 mm. A first adhesive layer was prepared by coating a polyurethane dispersion (obtained under the trade designation "NEOREZ R9680", from DSM Company) onto the surface layer.

A retroreflective layer comprising a beaded retroreflective layer (such beaded retroreflective layer comprises a metal coating adjacent the glass beads) was obtained under the trade designation "3M Reflective Sheeting Series 610", from 3M Company, of St. Paul, MN.

The surface layer and first adhesive layer were then laminated to the front surface of the retroreflective layer.

A conductive adhesive layer was prepared mixing the acrylic pressure-sensitive adhesive (PSA), the crosslinker (both prepared as described above) with 10 weight percent (based on the total weight of the adhesive) of nickel flakes (obtained under the trade designation "HCA-l ", from Australian Metal Powders Supplies Pty Ltd., Sidney, Australia). The conductive adhesive mixture was coated onto the back surface of the retroreflective layer, and the construction passed through four consecutive ovens at a line speed of about 180 fpm (55 m/min), each oven set at a temperature of, respectively, 45°C, 70°C, 80°C, and 90°C. The coating thickness of the PSA (dried) was 0.5 mm.

A release layer comprising a silicon-containing kaolinic rolling kraft liner (obtained under the trade designation " 127G X/CCK 1100", from Loparex, Guangzhou, China) was providing. The release layer was adhered to the conductive adhesive layer.

Dissipating channels were created using a cutting plotter (obtained under the trade designation " JARGUAR TYPE Π", from Jarguar Company). Each dissipating channel had a circular cross-section and a diameter of 1.5 mm. The spacing between each channel was about 4 mm.

EXAMPLE 2

A retroreflective article was prepared as described in Example 1, except that the diameter of each dissipating channel was 1 mm, and the spacing between the dissipating channels was about 6

EXAMPLE 3

A retroreflective article was prepared as described in Example 1, except that the diameter of each dissipating channel was 3 mm, and the spacing between the dissipating channels was about 6 mm.

EXAMPLE 4

A retroreflective article was prepared as described in Example 1, except that the diameter of each dissipating channel was 2 mm, and the spacing between the dissipating channels was about 4 mm.

EXAMPLE 5

EXAMPLE 6

A retroreflective article was prepared as described in Example 1, except that the shape of the cross-section of each dissipating channel was an equilateral triangle, with the side length being 1.5 mm. The spacing between the dissipating channels was about 4 mm.

EXAMPLE 7

A retroreflective article was prepared as described in Example 1, except that the content of nickel flakes in the conductive adhesive layer was 5 weight percent based on the total weight of the adhesive composition, and the coating thickness of the PSA was

0.5g/inch² (0.5 g / 6.45 mm²).

EXAMPLE 8

A retroreflective article was prepared as described in Example 1, except that the content of nickel flakes in the conductive adhesive layer was 30 weight percent based on the total weight of the adhesive composition, and the coating thickness of the PSA was

0.5g/25.4 mm². COMPARATIVE EXAMPLE A

A retroreflective article was prepared as described in Example 1, except that no conductive adhesive layer was used.

Retroreflectivity and surface contact resistance of retroreflective articles prepared as described in Comparative Example A, and Examples 1 - 10 were measured as described above. Results are reported in Table 3, below.

Table 3

All references mentioned herein are incorporated by reference.

As used herein, the words "on" and "adjacent" cover both a layer being directly on and indirectly on something, with other layers possibly being located therebetween.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the present disclosure and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise.

As used in this disclosure and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

The phrases "at least one of and "comprises at least one of followed by a list refers to any one of the items in the list and any combination of two or more items in the list. All numerical ranges are inclusive of their endpoints and non-integral values between the endpoints unless otherwise stated.

Various embodiments and implementation of the present disclosure are disclosed.

The disclosed embodiments are presented for purposes of illustration and not limitation. The implementations described above and other implementations are within the scope of the following claims. One skilled in the art will appreciate that the present disclosure can be practiced with embodiments and implementations other than those disclosed. Those having skill in the art will appreciate that many changes may be made to the details of the above- described embodiments and implementations without departing from the underlying principles thereof. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows. Further, various modifications and alterations of the present invention will become apparent to those skilled in the art without departing from the spirit and scope of the present disclosure. The scope of the present application should, therefore, be determined only by the following claims.

Claims

What is claimed is:

1. A conductive retroreflective article comprising:

a retroreflective layer (130, 230, 330, 430) having a front surface and a back surface; a conductive adhesive layer (140, 240, 340, 440) adjacent the back surface of the retroreflective layer;

an array of dissipating channels (160, 260, 360, 460) on the retroreflective article_^ and

at least a portion of the conductive adhesive in_at least one of the dissipating channels.

2. The conductive retroreflective article according to Claim 1, wherein the conductive adhesive layer (140, 240, 340, 440) comprises metal particles.

3. The conductive retroreflective article according to Claim 2, wherein the content of the metal particles in the conductive adhesive layer ranges from 5 to 30 weight percent, based on the total weight of the conductive adhesive layer.

4. The conductive retroreflective article according to Claim 2, wherein the metal particles are selected from the group consisting of nickel, copper, lead, chromium and silver.

5. The conductive retroreflective article according to Claim 1, wherein the

retroreflective layer (130, 230, 330, 430) is one of a beaded retroreflective layer and a prismatic retroreflective layer.

6. The conductive retroreflective article according to Claim 5, wherein the beaded retroreflective layer comprises glass beads (131, 231) dispersed in a binding layer (132, 232).

7. The conductive retroreflective article according to Claim 6, wherein the beaded retroreflective layer further comprises a metal coating (133, 233) adjacent the glass beads (131, 231).

8. The conductive retroreflective article according to Claim 5, wherein the back surface of the prismatic retroreflective layer includes a structured surface having cube corner elements (334, 435)

9. The conductive retroreflective article according to Claim 8, wherein the prismatic retroreflective layer comprises one of a metal coating (333), a seal layer (437) and a third adhesive layer having optically inactive areas, adjacent the cube corner elements (334, 435).

10. The conductive retroreflective article according to Claim 7 or 9, wherein the metal in the metal coating (133, 233, 333) is selected from the group consisting of aluminum, aurum, silver, copper, and their alloys.

11. The conductive retroreflective article according to Claim 10, wherein the metal in the metal coating is aluminum.

12. The conductive retroreflective article according to Claim 1, further comprising a release layer (150, 250, 350, 450) disposed on a second side of the conductive adhesive layer, wherein the second side of the conductive adhesive layer is opposite to a first side of the conductive adhesive layer, which is adjacent the back surface of the retroreflective layer.

13. The conductive retroreflective article according to Claim 12, wherein the release layer (150, 250, 350, 450) is made of any one selected from the group consisting of silicon- containing polymer, fluorine-containing, and polyester.

14. The conductive retroreflective article according to Claim 12 or 13, wherein at least one dissipating channel (160, 260, 360, 460) extends through the release layer (250, 350, 450).

15. The conductive retroreflective article according to Claim 1, further comprising a surface layer (110, 210, 310, 410) having a first side and a second side, the second side of the surface layer being disposed on the front surface of the retroreflective layer.

16. The conductive retroreflective article according to Claim 15, wherein the surface layer is made of a transparent and printable polymer.

17. The conductive retroreflective article according to Claim 15 or 16, wherein the surface layer is made from a polymer selected from the group consisting of polyvinyl chloride, acrylic, ethylene-acrylic acid, polyethylene terephthalate, and polycarbonate.

18. The conductive retroreflective article according to Claim 15, further comprising a first adhesive layer (120, 220, 420) disposed between the surface layer (110, 210, 310, 410) and the retroreflective layer (130, 230, 330, 430).

19. The conductive retroreflective article according to Claim 18, wherein the first adhesive layer (120, 220, 420) is formed by one of a primer composition, an adhesive composition and a surface treatment.

20. The conductive retroreflective article according to Claim 18, wherein the first adhesive layer (120, 220, 420) is a polyurethane layer.

21. The conductive retroreflective article according to Claim 15, further comprising a carrier layer (102, 302) disposed on the first side of the surface layer.

22. The conductive retroreflective article according to Claim 21, further comprising a second adhesive layer (103, 303) disposed between the carrier layer (102, 302) and the surface layer.

23. The conductive retroreflective article according to Claim 22, wherein the second adhesive layer (103, 303) is formed by one of a primer composition, an adhesive

composition and a surface treatment.

24. The conductive retroreflective article according to Claim 1, wherein each dissipating channel has a diameter ranging from 1.0 to 10.0 mm, and the dissipating channels are spaced apart by a distance ranging from 2.0 to 15.0 mm.

25. The conductive retroreflective article according to Claim 1, wherein said dissipating channels have a cross-sectional shape selected from the group consisting of circular, square, triangular, rectangular and polygonal.

26. A method of making a conductive retroreflective article comprising the steps of: providing a retroreflective layer (130, 230, 330, 430) having a front surface and a back surface; disposing a conductive adhesive layer (140, 240, 340, 440) on the back surface of the retroreflective layer to form a retroreflective article; and

perforating the retroreflective article to form dissipating channels (160, 260, 360, 460), wherein at least one dissipating channel extends through the retroreflective layer and conductive adhesive layer.

27. The method according to claim 26, wherein the retroreflective layer further comprises a metal coating (133, 233, 333).

28. The method according to claim 26, further comprising the step of disposing a surface layer (110, 210, 310, 410) on the front surface of the retroreflective layer.

29. The method according to claim 28, wherein the surface layer (110, 210, 310, 410) is perforated.

30. The method according to claim 28, further comprising the step of forming a first adhesive layer (120, 220, 420) between said surface layer (110, 210, 310, 410) and the retroreflective layer (130, 230, 330, 430). 30. The method according to claim 26, further comprising the step of providing a release layer (150, 250, 350, 450) on the conductive adhesive layer (140, 240, 340, 440).

31. The method according to claim 30, wherein the release layer (150, 250, 350, 450) is perforated.