Multilayer film for tear-open packages

Abstract

The invention relates to a multilayer film (1) for tear-open packages, the film (1) comprising at least one laser-removable carrier layer (2) and at least one barrier layer (3). According to the invention, at least one laser stop layer (4) for protecting the at least one barrier layer (3) from removal of the at least one barrier layer (3) by a laser is located between the at least one carrier layer (2) and the at least one barrier layer (3).

Description

[0001] Multilayer film for tear-open packaging

[0002] The invention relates to a multilayer film for tear-open packaging according to the preamble of patent claim 1.

[0003] Single- and multi-layer film packaging has long been known and of great importance, particularly in the food and pharmaceutical industries.

[0004] It is known that commercially available tear-open packaging has a weakened area or line of weakness where the packaging can be opened, particularly torn, with minimal force to access the contents. Such weakened lines enable easy handling of the tear-open packaging.

[0005] A line of weakness is a locally limited weakening of a film material and can be created, for example, by precision punching. Lasers, particularly CO2 lasers, can also be used to create lines of weakness. The line of weakness is created by reducing the local film layer thickness or by locally embrittlement of the film material.

[0006] The disadvantage is that during so-called "laser scribing," the scoring of the film to create a line of weakness and make it easier for the user to open the packaging, a barrier layer of the film is often damaged, thus no longer providing an effective barrier against the outside atmosphere. This is particularly the case when using similar polymers, where the laser cannot distinguish between the material being removed on the outside of the film composite and the barrier layer on the inside, which must remain intact. If the barrier layer is removed or damaged, oxygen and moisture can penetrate the packaging contents and damage the packaged goods.

[0007] The object of the invention is therefore to provide a multilayer film for

[0008] To specify tear-open packaging of the type mentioned above, with which the disadvantages mentioned can be avoided, with which a tear-open packaging can be easily opened and with which the tear-open packaging has an intact barrier layer when unopened.

[0009] According to the invention, this is achieved by the features of patent claim 1.

[0010] The fact that at least one laser stop layer is arranged between the carrier layer and the at least one barrier layer to protect the at least one barrier layer from being ablated by a laser results in the advantage that the contents of tear-open packaging are protected from the atmosphere surrounding the tear-open packaging, thereby preventing the penetration of harmful substances such as moisture, oxygen, and also the penetration of viruses and bacteria into the packaging. The barrier layer is not damaged when the laser creates a weakened area or line of weakness in the carrier layer, whereby the contents of the package remain protected from the aforementioned external influences, and the shelf life of the contents of the package is not reduced. This is particularly important for food and for medical or pharmaceutical products.Furthermore, this still allows for safe and easy opening of the tear-off packaging.

[0011] The invention further relates to a method for forming a weakened region in a multilayer film according to claim 11.

[0012] According to the invention, this is achieved by the features of patent claim 10.

[0013] The invention therefore further aims to provide a method for forming a weakened area in a multilayer film using a laser, which avoids the aforementioned disadvantages and enables a simple formation of a weakened area in a tear-open packaging, while maintaining an intact barrier layer of the tear-open packaging. The advantages of the method correspond to the advantages of the aforementioned multilayer film.

[0014] The subclaims relate to further advantageous embodiments of the invention.

[0015] Express reference is hereby made to the wording of the patent claims, whereby the patent claims are incorporated into the description at this point by reference and are deemed to be reproduced verbatim.

[0016] The invention will be described in more detail with reference to the accompanying drawings, in which only preferred embodiments are shown by way of example. In the drawings:

[0017] Fig. 1 is an exemplary representation of a first preferred embodiment of a multilayer film comprising a carrier layer, a barrier layer and a laser stop layer as a section and

[0018] Fig. 2 is an exemplary representation of a second preferred embodiment of a multilayer film comprising a carrier layer, two sealing layers, two barrier layers and two blocking layers, wherein the blocking layers form a laser stop layer, as a section.

[0019] 1 and 2 show at least parts of a multilayer film 1 for tear-open packaging, wherein the film 1 comprises at least one laser-ablatable carrier layer 2 and at least one barrier layer 3, wherein at least one laser stop layer 4 is arranged between the at least one carrier layer 2 and the at least one barrier layer 3 to protect the at least one barrier layer 3 from being ablated by a laser.

[0020] Furthermore, a method for forming a weakened region in a multilayer film 1 with a laser is proposed, wherein the laser ablates at least one carrier layer 2 of the multilayer film 1 in a weakened region, wherein the laser impinges on at least one laser stop layer 4 arranged between the at least one carrier layer 2 and at least one barrier layer 3 in the weakened region, wherein the laser power 7 in the at least one laser stop layer 4 is locally attenuated such that the at least one barrier layer 3 is not ablated by the laser.

[0021] Furthermore, a tear-open packaging comprising a multilayer film 1 is provided. The tear-open packaging comprises the multilayer film 1, with at least one weakened area, in particular at least one weakening line, being incorporated into the carrier layer 2. This makes it easier for a user to open the packaging at the weakened area or along the weakening line.

[0022] The fact that at least one laser stop layer 4 is arranged between the carrier layer 2 and the at least one barrier layer 3 to protect the at least one barrier layer 3 from being ablated by a laser results in the advantage that the contents of tear-open packages are protected from the atmosphere surrounding the tear-open package, thereby preventing the penetration of harmful substances such as moisture, oxygen, and also the penetration of viruses and bacteria into the package. The barrier layer 3 is not damaged when the laser creates a weakened area or line of weakness in the carrier layer 2, whereby the contents of the package remain protected from the aforementioned external influences, and the shelf life of the contents of the package is not reduced. This is particularly important for food and for medical or pharmaceutical products.Furthermore, this still allows for safe and easy opening of the tear-off packaging.

[0023] It is preferable for the laser to be a CO2 laser. Using a CO2 laser, the attenuation zone can be formed particularly well.

[0024] The multilayer film 1 comprises several layers which are not detachably connected to one another in a non-destructive manner. The at least one carrier layer 2 of the multilayer film 1 can be ablated by a laser. The ablation of the at least one carrier layer 2 preferably takes place only in one area to be ablated, the so-called weakened area or along the so-called weakening line, along which the multilayer film 1 can be torn open in a processing or usage state, namely as a tear-open package. The carrier layer 2 ensures the mechanical strength of the multilayer film 1. The tensile strength of the carrier layer 2 is preferably higher than that of the other individual layers. Preferably, only a single carrier layer 2 is provided. However, two or more carrier layers 2 can also be provided, at least one of which can be ablated by the laser.

[0025] Furthermore, the multilayer film 1 comprises at least one barrier layer 3, which preferably forms a packaging inner side of a tear-open packaging in the processing or use state of the multilayer film 1.

[0026] The at least one barrier layer 3 protects the contents of the package from the external atmosphere surrounding the tear-open package. The at least one barrier layer 3 is preferably oxygen-impermeable and / or moisture-impermeable.

[0027] It can preferably be provided that the multilayer film 1 comprises several barrier layers 3. The barrier layers 3 can preferably be connected or attached to one another.

[0028] Alternatively, 3 other layers can be arranged between the individual barrier layers.

[0029] The at least one barrier layer 3 may preferably comprise ethylene-vinyl alcohol copolymer (EVOH) or consist of EVOH.

[0030] The tear-open packaging can preferably be packaging for food, medical products, pharmaceutical products or other consumer goods.

[0031] The multilayer film 1 further comprises at least one laser stop layer 4, which is arranged between the at least one carrier layer 2 and the at least one barrier layer 3 to protect the at least one barrier layer 3 from laser ablation. The at least one laser stop layer 4 causes absorption and / or reflection and / or scattering of the laser beam in the at least one laser stop layer 4. A combination of the effects mentioned can also be used here. The at least one laser stop layer 4 is designed such that ablation of the at least one barrier layer 3 is prevented. The at least one laser stop layer 4 attenuates or reduces the local laser power 7 to such an extent that ablation of the at least one barrier layer 3 does not occur.The at least one barrier layer 3 thus remains intact after the processing of the multilayer film 1 with a laser and the protective effect of the at least one barrier layer 3 for the packaging contents is thus maintained.

[0032] A simple structure of a first preferred embodiment of a multilayer film 1 with a laser stop layer 4 arranged between a carrier layer 2 and a barrier layer 3 is shown by way of example in Fig. 1. Furthermore, the change in the laser power 7 upon penetration of the individual layers is indicated by way of example. In Fig. 1, the left-hand side shows the case in which the laser power 7 decreases due to absorption in the laser stop layer 4 and is completely absorbed. The right-hand side shows the case in which the laser beam is reflected and scattered in the boundary region between the carrier layer 2 and the laser stop layer 4, which is indicated by the arrows. In both cases, no laser power 7 is apparent in the barrier layer 3 any longer.

[0033] The thickness ratios of the layers shown in the figures do not correspond to the actual thickness ratios.

[0034] It can particularly preferably be provided that the at least one carrier layer 2 and the at least one barrier layer 3 consist of a jointly recyclable material. This allows the carrier layer 2 and the barrier layer 3 to be recycled together, and no complex steps are required to separate these layers from one another prior to recycling. The jointly recyclable material can, in particular, be the same polymer or the same plastic. Therefore, the at least one carrier layer 2 and the at least one barrier layer 3 can consist of the same polymer or the same plastic.

[0035] The at least one laser stop layer 4 can be formed as a single layer or in multiple layers. In a multi-layer configuration, the laser stop layer 4 preferably consists of several interconnected layers.

[0036] Preferably, the thickness of the at least one laser stop layer 4 can be less than 6 pm, in particular less than 3 pm, preferably less than 1 pm. Such thicknesses are already sufficient to enable stopping of the laser beam or a sufficient reduction of the local laser power 7 in the at least one laser stop layer 4 to prevent the barrier layer 3 from being removed.

[0037] It can particularly preferably be provided that the at least one laser-stop layer 4 comprises at least one laser-absorbing substance, in particular at least one inorganic pigment or at least one organic dye. The laser beam impinging on the laser-stop layer 4 is absorbed by the laser-stop layer 4. As a result, the at least one barrier layer 3 arranged downstream of the at least one laser-stop layer 4 is not removed, and the at least one barrier layer 3 remains intact. The inorganic pigments preferably comprise transparent, colored, fluorescent, and phosphorescent pigments.

[0038] It can also preferably be provided that the at least one laser stop layer 4 comprises at least one laser-reflecting substance, in particular at least one metal. This allows the laser or at least a large part of the laser beam, and thus also the laser power 7 of the laser, to be reflected, whereby the at least one barrier layer 3 arranged beneath the at least one laser stop layer 4 is not ablated and remains intact. The laser-reflecting substance preferably comprises aluminum, copper, platinum, gold, silver, aluminum oxides (AlOx), and silicon oxides (metallized SiOx). It can also preferably be provided that the at least one laser stop layer 4 comprises at least one structure for scattering laser beams. By scattering the laser beam, it can be attenuated to such an extent that the laser does not ablate the at least one barrier layer 3 and the at least one barrier layer 3 remains intact.

[0039] The laser stop layer 4 can preferably be formed as a surface structure of the carrier layer 2 and / or the barrier layer 3.

[0040] It can be provided that the at least one laser stop layer 4 is produced by crosslinking. The crosslinking creates a three-dimensional structure. This crosslinking leads to scattering of the laser beam at the three-dimensional structure, whereby the laser beam is attenuated. Crosslinking of partial regions of the multilayer film 1 can be preferred. For this purpose, the areas not to be crosslinked are covered by masks which are printed on or which are pulled over the crosslinking device. The masks can consist of metal coatings. Crosslinked and non-crosslinked regions can be combined by lamination. The mechanical properties of the multilayer film 1, in particular its durability and printability, can preferably be improved by partial crosslinking.

[0041] The raw materials for crosslinking must be adjusted to ensure good crosslinkability. The degree of crosslinking is controlled by the power of the crosslinking system. Crosslinking can be achieved using electron beams, ultraviolet rays (UV), X-rays, and magnetic waves.

[0042] It can preferably be provided that the at least one laser stop layer 4 has one or more embossings or is formed by one or more embossings. The embossing can create structures that deflect or scatter the laser beam, thereby attenuating the laser beam's power.

[0043] However, it can also be provided that the at least one laser stop layer 4 is printed, thereby enabling simple production of the at least one laser stop layer 4. Printing can preferably be carried out using defined, modified raster dots, analogous to the Digimarc printing technique.

[0044] Preferably, the at least one laser stop layer 4 can be printed using gravure printing, flexographic printing, digital printing, offset printing, or screen printing. It can also be provided that the at least one laser stop layer 4 is formed using two or more of the aforementioned printing methods. This can be the case, in particular, with a multilayer laser stop layer 4.

[0045] It can also be provided that the at least one laser stop layer 4 is produced over the entire surface of the at least one barrier layer 3 by means of screen rollers and / or smooth rollers in the same direction and in the opposite direction or by means of reverse engraving.

[0046] It can preferably be provided that the at least one laser stop layer 4 further comprises one or more of the following compounds and / or elements and / or modifications, namely silica in the master patch, ethylene-vinyl alcohol copolymer (EVOH), acrylates, polyvinyl alcohol (PVOH), conductive pigments such as conductive carbon black and / or silver and / or tin and / or antimony, magnetizable pigments such as magnetite and / or organic and inorganic printing.

[0047] For example, the at least one laser stop layer 4 may comprise at least one pigment or at least one dye and / or an organic or inorganic binder and at least one solvent.

[0048] It can further be provided that the at least one laser stop layer 4 is arranged only partially in that region of the at least one barrier layer 3 in which the laser beam is to be stopped. The weakening region or line of weakness is preferably predetermined. Accordingly, the at least one laser stop layer 4 can preferably be arranged only in this region of the multilayer film 1, thereby saving costs and resources.

[0049] It can be provided that the at least one laser stop layer 4 forms the weakened region or weakened line in such a way that several, for example, point-shaped, weakened subregions are arranged along the weakened line. However, it can also be provided that the weakened region has a weakened line that is essentially continuous across the weakened region. The at least one laser stop layer 4 is arranged specifically at the locations or regions where the laser beam is to be stopped.

[0050] Alternatively, it can be provided that the at least one laser stop layer 4 is arranged over the entire surface, thereby enabling simple production of the multilayer film 1.

[0051] It can also be provided that the at least one laser stop layer 4 is vapor-deposited. For example, a vapor-deposited metal layer can be structured by means of etching processes or other metal-removing processes or masking.

[0052] In particular, it can preferably be provided that the at least one laser stop layer 4 consists of a material that is recyclable together with the at least one carrier layer 2 and the at least one barrier layer 3. This allows the multilayer film 1 to be easily recycled, and there is no need to separate different plastics. This also makes it easy to meet strict recycling requirements. Polymers of the same type are essential for a functioning circular economy and thus for the recyclability of the multilayer film 1. By reducing the material components of the multilayer film 1, the recyclability of the film can be optimized.

[0053] It can preferably be provided that the at least one laser stop layer 4 is formed as a surface structure of the at least one barrier layer 3 and / or the at least one carrier layer 2. For this purpose, the surface of the laser stop layer 4 and / or at least one barrier layer 3 can, for example, have a structure and / or inorganic pigments and / or a metal coating. As a result, the at least one laser stop layer 4 can be formed particularly thin. For this purpose, it can be provided that the at least one laser stop layer 4 covers the entire surface of the at least one barrier layer 3 or that it is arranged partially in the weakened region or along the weakened line.

[0054] It can furthermore preferably be provided that the multilayer film 1 comprises at least one additional removal layer. The at least one removal layer can preferably be arranged on the at least one carrier layer 2, which is not shown in the figures.

[0055] Alternatively, the at least one removal layer can be formed as a part of the at least one carrier layer 2 or the at least one removal layer can correspond to the at least one carrier layer 2.

[0056] The at least one ablation layer can preferably be provided with additives that facilitate absorption of the laser beam. A layer that absorbs the laser beam more heavily is preferably arranged downstream of the at least one ablation layer, thereby enabling precise control of the penetration depth of the laser beam. The additives used for the at least one ablation layer can be applied or incorporated during blow coating, flat coating, extrusion coating, or printing.

[0057] The at least one removal layer can be applied partially and thus only to specific areas of the multilayer film 1, in particular partially to specific areas of the at least one carrier layer 2. The additives used here facilitate the penetration of the laser beam. The additives can also amplify the laser beam. Additives for amplifying the laser beam include, in particular, polyethylene terephthalate (PET) and / or polyamide. The laser beams can be further amplified by adding glass fibers.

[0058] It can be provided that the multilayer film 1 comprises at least one additional sealing layer 6. This sealing layer 6 can, in particular, form the inside of the packaging, as shown by way of example in Fig. 2. Furthermore, the sealing layer 6 can be adjacent to the barrier layer 3. The at least one sealing layer 6 can preferably consist of polyethylene or polypropylene.

[0059] Furthermore, it can particularly preferably be provided that the film 1 has two blocking layers 5 which are blocked together and which form a non-destructively detachable blocking of two layers, wherein the laser stop layer 4 comprises the two blocking layers 5. The blocking layers 5 form at least part of the at least one laser stop layer 4 or the laser stop layer 4 entirely. Such a blocking can be produced, for example, by means of a blown film extrusion system at a predefined temperature and at a predefined pressure. In this case, each of the layers can preferably be designed identically. Furthermore, it can be provided that each layer has a barrier layer 3 and a blocking layer 5. The blocking can easily create a complex layer structure in which the blocking layers 5 are arranged between two barrier layers 3.In this case, one of the barrier layers 3 can be removed by the laser beam, since another intact barrier layer 3 remains. By blocking, a multilayer and absorbent region can be easily provided in the multilayer film 1.

[0060] A multilayer film 1 produced by the blocking technique is shown as an example in Fig. 2. This multilayer film 1 essentially comprises two layers. Both layers have a sealing layer 6, a barrier layer 3 arranged on the sealing layer 6, and a blocking layer 5 arranged on the barrier layer 3. The two layers are connected to one another in the blocking layer 5, and the blocking layers 5 form the laser-stop layer 4. Additionally, a carrier layer 2 is arranged on one of the layers.

[0061] The sealing layers 6 can preferably comprise polyethylene or polypropylene or consist of polyethylene or polypropylene. The sealing layers 6 can in particular be fusible layers, whereby a package can be closed. For example, two sealing layers 6 can be fused together to close a package. The blocking layers 5 can preferably comprise ethylene-vinyl acetate copolymer (EVA) or consist of EVA. The barrier layers 3 shown in Fig. 2 form a barrier for oxygen and moisture and protect the package contents from oxygen and moisture. At least one barrier layer 3 facing the package contents remains intact during and after the creation of the weakened region by means of the laser.

[0062] A laser beam penetrating through the carrier layer 2 and a first sealing layer 6 is stopped in the laser stop layer 4, which in the second preferred embodiment is formed by two blocking layers 5. The laser beam is indicated by a triangle in Fig. 2. Thus, in this example, a barrier layer 3 facing the packaging contents and a sealing layer 6 facing the packaging contents remain intact. A package can be fused to the sealing layer 6 during its production, with the intact barrier layer 3 protecting the packaging contents from oxygen and moisture.

[0063] The following are principles for understanding and interpreting the disclosure in question.

[0064] Characteristics are usually introduced with an indefinite article, "ein, eine, eines, einer." Therefore, unless the context indicates otherwise, "ein, eine, eines, einer" is not to be understood as a number.

[0065] The conjunction "or" is to be interpreted as inclusive and not exclusive. Unless the context indicates otherwise, "A or B" also includes "A and B," where "A" and "B" represent any characteristics.

Claims

PATENT CLAIMS 1. Multilayer film (1) for tear-open packaging, wherein the film (1) comprises at least one laser-ablatable carrier layer (2) and at least one barrier layer (3), characterized in that at least one laser stop layer (4) is arranged between the at least one carrier layer (2) and the at least one barrier layer (3) to protect the at least one barrier layer (3) from ablation by a laser.

2. Multilayer film (1 ) according to claim 1 , characterized in that the at least one laser stop layer (4) comprises at least one laser-absorptive substance, in particular at least one inorganic pigment or at least one organic dye.

3. Multilayer film (1 ) according to claim 1 or 2, characterized in that the at least one laser stop layer (4) comprises at least one laser-reflecting substance, in particular at least one metal.

4. Multilayer film (1 ) according to one of claims 1 to 3, characterized in that the at least one laser stop layer (4) comprises at least one structure for scattering laser beams.

5. Multilayer film (1 ) according to one of claims 1 to 4, characterized in that the at least one laser stop layer (4) is arranged only partially in relation to that area of ​​the barrier layer (3) in which the laser beam is to be stopped.

6. Multilayer film (1 ) according to one of claims 1 to 5, characterized in that the at least one carrier layer (2) and the at least one barrier layer (3) consist of a jointly recyclable material.

7. Multilayer film (1) according to claim 6, characterized in that, that the at least one laser stop layer (4) consists of a material which, together with the at least one support layer (2) and the at least one barrier layer (3), is recyclable.

8. Multilayer film (1 ) according to one of claims 1 to 7, characterized in that the at least one laser stop layer (4) is formed as a surface structure of the at least one barrier layer (3) and / or the at least one carrier layer (2).

9. Multilayer film (1 ) according to one of claims 1 to 8, characterized in that the film (1 ) has two interlocking interlocking layers (5) which form a non-destructive interlocking of two layers, wherein the laser stop layer (4) comprises the two interlocking layers (5).

10. Tear-open packaging comprising a multilayer film (1 ) according to any one of claims 1 to 9.

11. Method for forming a weakening region in a multilayer film (1) using a laser, wherein the laser ablates at least one carrier layer (2) of the multilayer film (1) in a weakening region, wherein the laser in the weakening region hits at least one laser stop layer (4) arranged between the at least one carrier layer (2) and at least one barrier layer (3), wherein the laser power in the at least one laser stop layer (4) is locally attenuated such that the at least one barrier layer (3) is not ablated by the laser.

12. Method according to claim 11, characterized in that the weakening area ends at the at least one laser stop layer (4) and that the laser does not ablate the at least one laser stop layer (4).

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