EP2925825A1

EP2925825A1 - Transparent security film

Info

Publication number: EP2925825A1
Application number: EP13789816.9A
Authority: EP
Inventors: Christoph HELLERMANN
Original assignee: Tesa SE
Current assignee: Tesa SE
Priority date: 2012-11-28
Filing date: 2013-11-14
Publication date: 2015-10-07
Also published as: WO2014082867A1; CN104812862B; CN104812862A; DE102012221796B3

Abstract

The invention relates to a multi-layer transparent security film, which is adhesively bonded to a substrate (5), wherein the security film comprises the following layers: an outer carrier layer (1), a separating lacquer layer (2), a partially applied release lacquer layer (3), an at least partially applied adhesive layer (4) for adhesively bonding to the substrate (5), wherein the adhesive force between the carrier layer (1) on one side and the separating lacquer layer (2) and possibly the release lacquer layer (3) on the other side and the adhesive force between the adhesive layer (4) on one side and the separating lacquer layer (2) and the substrate (5) on the other side are each greater than the cohesive force of the separating lacquer layer (2), wherein the cohesive force of the separating lacquer layer (2) is greater than the adhesive force between the release lacquer layer (3) and the separating lacquer layer (2) and the adhesive force between the release lacquer layer (3) and the separating lacquer layer (2) is possibly greater than the adhesive force between the release lacquer layer (3) and the adhesive layer (4), such that in the regions without the release lacquer layer (3) the security film separates due to a cohesive fracture or due to a mixed fracture that is mostly formed as a cohesive fracture, wherein both the cohesive fracture and the mixed fracture extend substantially horizontally through the separating lacquer layer (2), and in the regions having the release lacquer layer (3) the security film separates along an adhesive fracture between the release lacquer layer (3) and the separating lacquer layer (2) or possibly between the release lacquer layer (3) and the adhesive layer (4).

Description

description

Transparent security film

The invention relates to a multi-layer transparent security film, a portion of the security film and a use of the section.

Packaging, especially packaged goods, containers and doors, flaps and the like should often - at least temporarily - be protected against unauthorized opening. For these objects are for example provided with a seal, which consists of a section of adhesive film provided on one side with an adhesive. The seal may be attached with its sticky side across an opening of the article or else passed around a package or container to be sealed and adhered to itself. Such a seal usually changes visually when you open it; after that, for example, it is torn or plastically deformed. The changes are irreversible, so that a manipulation attempt is clearly detectable. Such security systems for detecting unauthorized opening are known from the prior art. Thus, EP 1 403 190 A2 describes a tamper-evident seal in the form of a section of an adhesive tape provided at least partially on one side, which is guided around an object to be sealed and adhered to itself with the existing adhesive, the adhesive tape having a splittable carrier, see above that when breaking the tamper-evident seal by pulling on both ends of the section, the carrier irreversibly splits.

Among these security systems, there is a need for such security seals, which are transparent, so that, for example, the substrate, so the surface of the packaging, the container, the door or flap, under the Security seal remains recognizable. Also, a transparent security seal is less noticeable and is therefore often perceived as more aesthetically pleasing because, for example, it does not influence or disturb a packaging design. EP 0 770 251 B1 describes a transparent multilayer film which is particularly suitable for protecting data on documents. The multilayer film comprises a cover layer, a damagable layer which is irreversibly damaged upon separation of the multilayer film, an adhesion-regulating material partially patterned between the layers, and an adhesive layer for bonding with a substrate. The adhesion forces between the various layers and the cohesive force of the damagable layer are adjusted to destroy or irreversibly deform the damagable layer in the regions complementary to the pattern of adhesion-regulating material. The patent uses the term "destroyed" in connection with the damageable layer so that the layer is irreversibly damaged, for example, by a brittle fracture or by tearing across the layer, in any case such that a continuous layer does not persist For example, starting with the state of the art, it is the object of the present invention to provide a transparent security film of simple construction and a section of a transparent security film which in a separation test is irreversible and Furthermore, it is an object of the invention to close a package, a container, a door, flap or the like by a section of a security film so that a manipulation attempt on the section can be detected.

The object is achieved by a multilayer transparent security film having the features of claim 1, a portion of such a security film and a use of such a portion for closure of a package, a container, a door, flap or the like.

The multilayer transparent security film according to claim 1 is adhered to a substrate, which may be the surface of a package, a container, a door or a flap, and comprises the following layers: an outer carrier layer, a release lacquer layer, a partially applied release lacquer layer and an at least partially applied adhesive layer for bonding to the substrate. After the security film has been bonded to the substrate, the carrier layer lies on the outside, that is, on the side facing away from the substrate. The separating lacquer layer is usually applied over the entire surface. The partially applied release lacquer layer is advantageously applied in the manner of a pattern or a lettering.

The adhesion forces between the individual layers and the cohesive force of the release lacquer layer are now set as follows: The adhesion between the carrier layer on the one hand and the release lacquer layer and optionally the release lacquer layer on the other hand, the adhesion between the adhesive layer on the one hand and the release lacquer layer and the substrate on the other hand are larger optionally, the cohesive force of the release varnish layer, the cohesive force of the release varnish layer is greater than the adhesion force between the release varnish layer and the release varnish layer, and the adhesion force between the release varnish layer and the release varnish layer may be greater than the adhesion force between the release varnish layer and the adhesive layer. In this way, in the areas in which no release lacquer layer is applied, the security film separates by a cohesive fracture, which runs essentially horizontally through the release lacquer layer. In the areas in which a release lacquer layer is applied, the security foil either separates along an adhesion break between the release lacquer layer and the release lacquer layer or, if appropriate, between the release lacquer layer and the adhesive layer.

As an advantage of the security film of the invention, it turns out that a high-contrast tamper evidence is obtained when the security film separates, although the security film does not comprise a pigmented or colored print layer. Without a pigmented or colored layer, the transmission of the security film according to the invention is markedly higher-as a rule more than 95%-than the transmission of security films with pigmented or colored layers, which is usually below 75%.

[001 1] The high-contrast proof of manipulation results from the fact that in the areas in which the security film has separated by an adhesion break, the smooth surfaces of the release lacquer layer and the release lacquer layer or optionally the adhesive layer come to light. In the areas where the Separates security film by a cohesive failure through the release lacquer layer, the rough surfaces of the release lacquer layer come to light, which scatter the incident light and thus produce a strong turbidity of the surfaces. Smooth surfaces hardly scatter the light. If you wanted to close the security film again, so would the coincidence of the rough surfaces of the release coating layer air bubbles, so that the strong turbidity would remain, caused by the scattering of light at the interface between the rough surface of the release coating layer and the air bubbles. When the smooth surfaces of the release lacquer layer and the release lacquer layer or optionally the adhesive layer meet, air bubbles hardly occur. The areas of adhesion break would therefore remain largely transparent, contrasting with the cloudy areas with a cohesive fracture that would be dull and less transparent.

In an advantageous embodiment of the security film, the side of the carrier layer, which is remote from the surface of the security film, roughened. In this case, although the cohesive fracture runs substantially horizontally through the release lacquer layer, the surface of the cohesive failure that runs on the side of the support layer shows points where small tips of the cohesive fracture run along the cohesive fracture Carrier layer protrude, the surface is thus a little rougher and the areas of such a cohesive fracture become even cloudier. Strictly speaking, this is a mixed fracture, because most of the two surfaces are exposed by a cohesive failure, but at the points where protrude small tips of the support layer, it is an adhesion break. Another advantage of a roughened side of the carrier layer, which faces away from the surface of the security film, is that a release lacquer layer adheres better to the carrier layer.

A surface can roughen by mechanically or chemically processed. A chemical treatment is, for example, an etching by an acid or a lye.

It is advantageous to use a release lacquer layer with a release lacquer which is uncrosslinked and therefore has a low cohesive power. Often it is desirable to install additional color features in addition to a high-contrast tamper evidence in the form of blunt and transparent areas. For this purpose, for example, a partially applied opaque layer in the security film is suitable. The opaque layer may be a lettering disposed between the layers such that a first portion of the opaque layer remains on the backing of the security film and a second portion of the opaque layer remains on the adhesive layer of the security film as the security film separates.

The separating lacquer layer is preferably either applied over the entire surface of the carrier layer, then release lacquer layer and adhesive layer can touch each other, or the release lacquer layer is applied over the entire surface of the adhesive layer, then carrier layer and release lacquer layer can touch each other. In both cases, the full-surface job simplifies the manufacturing process. If the release coating layer is applied over the entire surface of the carrier layer, it is particularly easy to partially apply an additional opaque layer and position, for example, that a pattern formed by the opaque layer is destroyed when opening a security film by parts of the pattern on the Part of the security film remaining on the substrate, and other parts of the pattern are on the part of the security film, which is separated from the substrate.

If the release coating layer is applied over the entire surface of the adhesive layer, so the safety film when opening separates according to experience particularly reliable and precise in the manner provided. In addition, remain after the separation of the security film no open adhesive surfaces. Thus, the attempt to seal the security film unnoticed again after a separation would be further complicated.

Furthermore, the security film may comprise an at least partially applied UV protective layer. The UV protective layer is usually located between the adhesive layer and the remaining layers of the security film. In the production of the security film, the UV protective layer is applied before the adhesive is applied to the security film. Thereby, the adhesive can be added in a hot melt or wet coating process, without the aqueous release coating by the action of heat when applying a hot melt adhesive or through the Dissolving with water from a water-based dispersion adhesive loses its good separation properties. If no additional UV protection layer is provided on the security film, it is advisable to conceal the adhesive. A security film according to the invention can be processed further, in which they are cut to size, for example as a tape, as a strip or label. Which form of section you choose depends on the application. For example, a strip is advantageous for the sealing of a door or flap. When sealing a package, it is often recommended to use a label that allows labeling or, if the portion of the security film is also intended to seal the package, a tape that is wrapped around the package and glued to itself.

For such a portion of a security film, it is provided in a preferred embodiment that the adhesive layer is partially applied in such a way that one surface of the portion of the security film remains uncoated by adhesive.

This surface is preferably sized so that the fingers of a hand through the

Area defined area of the section can take to separate the security film. In this way, the adhesive-free surface fulfills the function of a handle for easy gripping of the portion. Alternatively, it is conceivable to apply the adhesive layer over the entire surface, but in an area that should be available as a handle, non-adhesive cover.

Security films according to the invention are described below by way of example with reference to FIGS. 1-8. Show it

1 shows a schematic cross section of a closed security film,

2 shows a schematic cross section of a closed security film with opaque layer, a schematic cross section of a closed security film with UV protective layer, 4 shows a schematic cross section of a closed security film with opaque layer and UV protective layer,

5 shows a section of a schematic cross-section of a closed security film with a roughened carrier layer, which represents the boundary region between the carrier layer and release lacquer layer,

6 shows the detail from FIG. 5 after the security film has separated by a mixed fracture, which runs essentially as cohesive fracture horizontally through the release lacquer layer,

Fig. 7 in the left half of the sheet three schematic plan views of a security film of FIG. 1 from top to bottom in each case closed, in just over half open and in resealed state, and in the right half of the sheet from top to bottom in each case the corresponding cross sections the security foil,

Fig. 8 analogous to Fig. 7 in the left half of the sheet three schematic plan views of a security film of FIG. 2 from top to bottom in each case closed, in just over half open and in resealed state, and in the right half of the picture from above below each of the corresponding cross sections of the security film.

1 shows a schematic cross-section of a closed security film with a carrier layer 1, a release lacquer layer 3 partially applied thereon, a release lacquer layer 2 applied over its entire surface and an adhesive layer 4 applied over its entire surface. The adhesive layer 4 provides the connection to a substrate 5 which may be, for example, the surface of a package, a container, a door or a flap. The security film of Fig. 1 is in the closed, that is in the intact and non-separated state.

2 shows a schematic cross section of a closed security film with an opaque layer. The security film differs from the security film in Fig. 1 in that the release coating layer 2 over the entire surface of the Carrier layer 1 and not as in Fig. 1 over the entire surface of the adhesive layer 4 borders. In addition, an opaque layer 7 is applied partially, which is located either between the release lacquer layer 2 and the release lacquer layer 3 or between the release lacquer layer 2 and the adhesive layer 4.

3 shows a schematic cross section of a closed security film with UV protection layer. The security film differs from the security film in FIG. 1 in that the entire surface is provided with a UV protective layer 6 between the release lacquer layer 2 and the adhesive layer 4. With the aid of the UV protective layer 6, it is easily possible to add the adhesive required for the adhesive layer 4 in a hotmelt or wet coating process.

4 shows a schematic cross section of a closed security film with opaque layer and UV protective layer. The security film differs from the security film in FIG. 2 in that, in addition, a UV protective layer 6 is provided which borders the adhesive layer 4 on the side of the adhesive layer 4 facing away from the substrate 5 over its entire surface.

5 shows a schematic section of a closed security film with roughened carrier layer 1, which represents the boundary region between carrier layer 1 and release lacquer layer 2. The carrier layer 1 is roughened on its side facing away from the surface of the security film and adjoins the release lacquer layer 2 with this roughened side.

Fig. 6 shows the detail of Fig. 5, after the security film has separated by a mixed fracture, which runs essentially as a cohesive failure horizontally through the release lacquer layer 2. The surface of the mixed fracture, which runs on the side of the roughened carrier layer 1, shows points at which some tips of the carrier layer 1 protrude from the surface of the release lacquer layer 2. Exactly at these points would be precise to speak of an adhesion break between the carrier layer 1 and release lacquer layer 2, but because these places together make up a small - measured on the entire surface of the composite fracture - small area or possibly not occur, the surface as well as her opposite surface referred to in this context as a cohesive failure. Fig. 7 shows in the left half of the sheet three schematic plan views of a security film according to FIG. 1 from top to bottom in each case closed, in just over half open and in resealed state, and in the right half of the sheet from above below each the corresponding cross sections of the security film, wherein the central cross section represents a completely opened security film, although the corresponding middle plan view represents a just over half opened security film. The middle plan view shows in both the part of the security film left on the substrate 5 and on the part of the security film which is separated from the substrate 5 a checkerboard pattern of rough-surfaced areas 2a exposed by cohesive failure and transparent Fields 2b with a smooth surface, exposed by an adhesion break. The surface of the part of the security film remaining on the substrate 5 is the surface of a continuous release varnish layer 2 which is respectively smooth and smooth in checkerboard-type panels 2a and 2b. The surface of the part of the security foil which is separated from the substrate 5 is a checkerboard pattern of transparent panels 3b of a smooth-faced release lacquer layer 3 and of cloudy panels 2a of a rough-surfaced release lacquer layer 2. The lower plan view shows the resealed security foil with a checkerboard pattern of almost transparent fields 13, ie where the surfaces of an adhesion fracture, namely the surface of a release lacquer layer 2 and the surface of a release lacquer layer 3, meet again, and from cloudy fields 12, so there, where the surfaces of a cohesive fracture, namely the surfaces of two release lacquer layers 2, meet. Smooth, transparent fields are shown mottled in FIGS. 7 and 8, respectively, and rough, cloudy fields are each shown in white.

FIG. 8 shows analogous to FIG. 7 in the left half of the sheet three schematic plan views of a security film according to FIG. 2 from top to bottom in each case closed, in just over half open and in resealed condition, and in the right half of the image from top to bottom in each case the corresponding cross sections of the security film. On the side facing away from the carrier layer 1 side of the release coating layer 2, an opaque layer 7 is partially applied, in the form of four digits one, two, three and four. The position of the opaque layer 7 within the layer sequence of the security film can be seen in each of the three cross sections of the right half of the sheet. The middle section shows the opened one Security film partially separated by an adhesion break and partly by a cohesive failure. Depending on the position of the opaque layer 7, the opaque layer 7a is either in the part of the security film remaining on the substrate 5, between the release varnish view 2 and the adhesive layer 4, or the opaque layer 7b is in the part of the security film which is separated from the substrate 5 between the release varnish layer 2 and the release varnish layer 3.

backing

The backing layer may comprise a paper, a thermoplastic film or a laminate of at least one of the two components. As far as thermoplastic material is contained in the carrier layer, a coextrudate is also suitable. The thermoplastic material may comprise polyethylene, in particular HDPE (high density polyethylene), polyester, in particular PET (polyethylene terephthalate), PP (polypropylene) and PVC (polyvinyl chloride) and is preferably monoaxially or biaxially oriented. Monoaxially stretched PP is characterized by its very high tensile strength and low elongation in the longitudinal direction and is used for example as a carrier material for so-called "strapping tapes." The carrier layer is transparent, preferably with a transmission rate of more than 95% in that for the human eye The reciprocal of the transmission rate is logarithmically related to the optical density of a carrier layer and can be determined by Lambert-Beer's law if the optical density of a carrier layer is known.

The carrier layer, often a laminate based on PET, is generally between 20 and 100 μm, preferably between 30 and 50 μm thick. The surface of a backing layer may be roughened by being chemically treated, for example, etched by a strong acid or alkali. As the acid, for example, an oxidizing acid such as chromosulfuric acid or potassium permanganate in combination with sulfuric acid in question. In particular, PET films are often etched with trichloroacetic acid or with potassium hydroxide solution.

The Italian companies Coveme SPA and Polifibra SPA treat film surfaces with trichloroacetic acid accordingly. Coveme distributes one Both sides treated film under the trade name Kemafoil® HPH 100. The trichloroacetic acid is used very concentrated and acts on the film surface for a long time. In a continuous etching process, therefore, the web speed of the film surface to be etched is low and is about 30 to 50 meters per minute, and the drying temperature is only slightly higher than 100 ° C. During the etching process of a PET film, the ester groups are hydrolyzed on the surface, resulting in polar hydroxyl, carboxyl and carboxylate groups. The film surface thus provides a better bonding substrate for most release coatings and release coatings, which are also polar. In addition, the etching process destroys the crystallinity in the near-surface region of the film. The result is a clear roughening of the surface.

The term surface roughness refers to the height deviations of the actually measured interface from an ideally smooth averaged boundary plane. The measured values can be evaluated, for example, with the average roughness, an average value of the height deviations, or the square roughness, an averaged scattering of the height deviations. The average surface roughness of the carrier film is approximately 2 μm and is in the range between 1.5 and 2.5 μm, preferably in the range between 1.8 and 2.2 μm.

A roughened and thus enlarged film surface usually serves to strengthen the composite to a pressure-sensitive adhesive or laminating adhesive. Another significant effect of the roughened film surface in the context of the present invention is the increased light scattering at a boundary to air or other materials with densities greatly different from the film density. In this way, strong contrasts arise between these boundary regions and those boundary regions in which the roughened film surface is adjacent to materials which have a density similar to the film density and in which the light scattering is very low. In a closed security film according to the invention, the roughened film surface only adjoins materials which have a density similar to the film density, so that no contrasts occur. Upon separation of a security film according to the invention, both types of boundary regions occur, so that an opened section of a security film according to the invention can be clearly distinguished from an unopened section. Release coating layer

In particular, the release lacquer comprises transparent, water-based, solvent-based and UV-curing, that is to say ultraviolet curing, clearcoats which can be applied to the support material by different printing methods, such as flexo, offset, screen, tampon and inkjet printing. To improve a release effect, silicone-containing substances can be added to the release lacquer, which reduce its surface energy. The application weight of the release lacquer is preferably 1 to 7 g / m ² . Release varnish layer

As a release coating materials are particularly low cohesion, especially printable or squeegee, water-based or solvent-containing substances. A low cohesion can be achieved by a high content of fillers, for example barium sulfate, kaolin, talc or chalks, which are advantageously added as colloidal filler dispersions having particle sizes of less than 1 μm, in order to preserve the highest possible transparency of the release coating. Examples of such a release varnish are resin dispersions, acrylate dispersions or polymer dispersions in general and solvent-containing polymer solutions whose polymeric binder components are preferably low molecular weight and uncrosslinked and thus have a very low cohesion. Particularly good results can be achieved with an aqueous dispersion of waxes. The coating weight of the release coating is preferably 2 to 12 g / m ² .

UV-protective layer

As a UV protective layer, water-based or solvent-containing, UV-curing lacquers are used. The paints can be applied for example by a printing process or by a doctor blade method. adhesive layer

As adhesives come essentially all known adhesives with high bond strength on a substrate, such as a primer to be packaged, in Question, such as synthetic rubber, natural rubber and Acrylatklebmassen. These may be adhesive mass solutions, dispersions or hotmelts. The application rate of the adhesive to the printed substrate is preferably 15 to 60 g / m ² , more preferably 20 to 30 g / m ² .

In particular, for one embodiment of the security film according to the invention in which the release coating layer is applied over the entire surface of the carrier layer, the partially applied release coating between the release coating and the adhesive layer and no UV protective layer is provided, the adhesive layer is matched to the release coating layer in that the adhesion force between the release lacquer layer and the adhesive layer is less than the adhesion force between the release lacquer layer and the release lacquer layer. Particularly suitable for this purpose are polar adhesives having a moderate bond strength to steel between 1.5-4 N / cm, which are laminated onto the printed substrate.

Opaque layer

As an opaque layer, all customary coloring or pigmented, water-based or solvent-containing, UV-curing printing inks or printing inks are suitable. Preference is given to using UV-curable printing inks, as produced by Flint, Zeller + Gmelin or Siegwerk.

LIST OF REFERENCE NUMBERS

Carrier layer 1

Release lacquer layer 2 Field of a release lacquer layer with rough surface 2a

Field of a release coating layer with smooth surface 2b

Release lacquer layer 3

Field of Releasable Layer with Smooth Surface 3b

Adhesive layer 4 Substrate 5

UV protection layer 6 opaque layer 7 opaque layer between release varnish view 2 and adhesive layer 4 7a opaque layer between release varnish layer 2 and release varnish layer 3 7b cloudy field with superposed surfaces of a cohesive rupture 12 transparent field with superimposed surfaces of an adhesion rupture 13

Claims

Patent claims

Multilayer transparent security film that is glued to a substrate (5), the security film comprising the following layers:

an outer carrier layer (1),

a separating lacquer layer (2),

a partially applied release varnish layer (3),

an at least partially applied adhesive layer (4) for bonding to the substrate (5),

wherein the adhesion force between the carrier layer (1) on the one hand and the release varnish layer (2) and optionally the release varnish layer (3) on the other hand, the adhesion force between the adhesive layer (4) on the one hand and the release varnish layer (2) and the substrate (5) on the other hand are each greater than are the cohesive strength of the release varnish layer (2),

wherein the cohesive force of the release varnish layer (2) is greater than the adhesion force between the release varnish layer (3) and the release varnish layer (2) and the adhesion force between the release varnish layer (3) and the release varnish layer (2) may be greater than the adhesion force between the release varnish layer (3 ) and the adhesive layer (4),

so that the security film separates in the areas without a release varnish layer (3) through a cohesive fracture or through a mixed fracture, which is mostly designed as a cohesive fracture, both the cohesive fracture and the mixed fracture running essentially horizontally through the release varnish layer (2), and the security film in the areas with the release varnish layer (3) along an adhesion break between the release varnish layer (3) and the release varnish layer

(2) or, if necessary, between the release varnish layer

(3) and adhesive layer (4) separates.

Security film according to claim 1, characterized in that the side of the carrier layer (1) facing away from the surface of the security film is roughened.

Security film according to claim 2, characterized in that the side of the carrier layer (1) facing away from the surface of the security film is etched.

4. Security film according to one of the preceding claims, characterized in that the release varnish layer (2) either borders the entire surface of the carrier layer (1) or the entire surface of the adhesive layer (4).

5. Security film according to one of the preceding claims, characterized in that the release varnish layer (2) comprises an aqueous release varnish.

6. Security film according to one of the preceding claims, characterized in that the security film comprises a partially applied opaque layer (7).

7. Security film according to claim 5, characterized in that the opaque layer (7) is arranged so that a first part of the opaque layer (7b) on the carrier layer (1) and a second part of the opaque layer (7a) on the adhesive layer (4) remain when the security film separates.

8. Security film according to one of the preceding claims, characterized in that the security film comprises an at least partially applied UV protective layer (6).

9. Section of a security film according to one of claims 1 to 8, characterized in that the section is designed as a band, as a strip or as a label.

10. Section according to claim 9, characterized in that the adhesive layer (4) is partially applied in such a way that a surface of the section of the security film remains uncoated with adhesive, which is dimensioned such that the fingers of a hand are defined by the surface area of the section in the manner of a handle to separate the security film.

1 1 . Use of a section according to claim 9 or 10 for closing a package, container, door, flap or the like.