BARRIER FILM

Abstract

A barrier film for use in laminated packaging materials for liquid food products, comprising a polymer film substrate and coated onto a first side of the polymer film substrate, by plasma-enhanced chemical vapor deposition (PECVD) in a vacuum process, a first coating layer of silicon oxide having the general composition formula SiOxCy, wherein x is from 1.5 to 2.2, and y is from 0.15 to 0.8, and a second coating layer of an amorphous diamond-like carbon (DLC), which is directly adjacent and contacting the first coating layer, the barrier film providing gas and water vapor barrier properties and mechanical durability in a packaging material and packages made thereof.

Claims

1. A barrier film, for use in laminated packaging materials for liquid food products, comprising a polymer film substrate and coated onto a first side of the polymer film substrate, by plasma-enhanced chemical vapor deposition (PECVD) in a vacuum process, a first coating layer of silicon oxide having the general composition formula SiOxCy, wherein x is from 1.5 to 2.2, and y is from 0.15 to 0.8, and a second coating layer of an amorphous diamond-like carbon (DLC), which is directly adjacent and contacting the first coating layer, the barrier film providing gas and water vapor barrier properties and mechanical durability in a packaging material and packages made thereof.

2. The barrier film as claimed in claim 1, wherein x is from 1.7 to 2.1, and y is from 0.39 to 0.47.

3. The barrier film as claimed in claim 1, wherein the polymer film substrate is selected from the group consisting of films comprising a polymer based on any of polyesters, polyamides, ethylene vinyl alcohol copolymers (EVOH), polyolefins, blends of any of said polymers, and a multilayer film having a surface layer comprising any of said polymers or blends thereof.

4. The barrier film as claimed in claim 1, wherein the polymer film substrate is a film selected from the group consisting of films comprising a polymer based on any of polyethylene terephthalate (PET), mono-oriented PET (OPET), biaxially oriented PET (BOPET), oriented or non-oriented polybutylene terephthalate (PBT), non- or mono- or biaxially oriented polyethylene furanoate (PEF), polyethylene napthanate (PEN), non-oriented polyamide (PA) or oriented polyamide (OPA or BOPA), blends of two or more of said polymers, and multilayer films having a surface layer comprising such polymers or blends thereof.

5. The barrier film as claimed in claim 1, wherein the total thickness of the first and second coating layers is from 7 to 10 nm.

6. The barrier film as claimed in claim 1, wherein a pre-coating layer of an amorphous DLC is first applied directly adjacent and in direct contact with the surface of the polymer film substrate, and further coated on its free side with said first coating layer.

7. The barrier film as claimed in claim 1, wherein the polymer film substrate has an adhesion-promoting primer coating on its other, uncoated side.

8. The barrier film as claimed in claim 1, wherein the adhesion-promoting primer coating is a fourth coating layer of DLC.

9. The barrier film (10a; 10b; 10c), according to claim 1, having a crack-onset strain of 5% or higher.

10. A laminated packaging material comprising the barrier film as claimed in claim 1.

11. The laminated packaging material according to claim 10, further comprising a first outermost liquid tight, heat sealable polyolefin layer and a second innermost liquid tight, heat sealable polyolefin layer.

12. The laminated packaging material according to claim 10, further comprising a bulk layer of paper or paperboard or other cellulose-based material, a first outermost liquid tight, heat sealable polyolefin layer, a second innermost liquid tight, heat sealable polyolefin layer and, arranged on the inner side of the bulk layer of paper or paperboard, between the bulk layer and the innermost layer, said barrier film.

13. The laminated packaging material according to claim 12, wherein the barrier film is bonded to the bulk layer by an intermediate thermoplastic polymer bonding layer, binding the surface of the second barrier coating layer of DLC to the bulk layer.

14. The laminated packaging material according to claim 13, wherein the polymer film substrate of the barrier film has an adhesion-promoting primer coating on its other side, opposite the side coated with the first and second barrier coating layers, and wherein the barrier film is bonded to the second innermost liquid tight, heat sealable polyolefin layer by means of the adhesion-promoting primer coating.

15. A packaging container comprising the laminated packaging material as defined in claim 10.

16. A method of manufacturing the barrier film as claimed in claim 1, comprising: a first step of providing a polymer film substrate as a moving web in a roll to roll system, a second step of depositing a first coating layer of a silicon oxide having the general formula SiOxCy, wherein x is from 1.5 to 2.2 and y is from 0.15 to 0.8, onto the moving polymer film substrate, by subjecting an organosilicon gas precursor to a vacuum plasma in a PECVD coating operation, and a third step of further depositing onto the first coating layer on the moving polymer film substrate, a second coating layer of an amorphous diamond-like carbon, DLC, by subjecting a hydrocarbon gas precursor to a vacuum plasma in a PECVD coating operation.

17. The method as claimed in claim 16, wherein there is a fourth step carried out before the second step, of depositing a pre-coating layer of an amorphous diamond-like carbon, DLC, onto the moving polymer film substrate, by subjecting a hydrocarbon gas precursor to a vacuum plasma in a PECVD coating operation.

18. The barrier film as claimed in claim 3, wherein the polyesters are selected from the group consisting of polyethylene terephthalate (PET), mono-oriented PET (OPET) or biaxially oriented PET (BOPET), non- or mono- or biaxially oriented polyethylenefuranoate (PEF), oriented or non-oriented polybutylene terephthalate (PBT) and polyethylene napthanate (PEN).

19. The barrier film as claimed in claim 3, wherein the polyamides are selected from the group consisting of non-oriented polyamide (PA) and oriented polyamide (OPA or BOPA).

20. The barrier film as claimed in claim 3, wherein the polyolefins are selected from the group consisting of polypropylene, mono-oriented polypropylene (PP) or biaxially oriented polypropylene (OPP or BOPP).

21. The barrier film as claimed in claim 3, wherein the polyolefin is a polyethylene.

22. The barrier film as claimed in claim 21, wherein the polyethylene is selected from the group consisting of oriented or non-oriented high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and cyclo-olefin co-polymers (COC).

Description

EXAMPLES AND DESCRIPTION OF PREFERRED EMBODIMENTS

[0098] In the following, preferred embodiments of the invention will be described with reference to the drawings, of which:

[0099] FIG. 1a schematically shows a barrier film according to the invention in cross-section, coated with first and second barrier coating layers,

[0100] FIG. 1b shows a similar barrier film having a further pre-coating layer,

[0101] FIG. 1c schematically shows a similar barrier film, comprising a polymer film substrate which has been coated also on its opposite side with a DLC coating functioning as an adhesion-promoting layer,

[0102] FIG. 2a is showing a schematic, cross-sectional view of a laminated packaging material according to the invention, comprising the barrier film of FIG. 1a,

[0103] FIG. 2b is showing a schematic, cross-sectional view of a further laminated packaging material comprising the barrier film of FIG. 1c,

[0104] FIG. 3 shows schematically a method, for laminating the durable barrier film of the invention into a laminated packaging material for liquid packaging, having a core or bulk layer of paperboard or carton,

[0105] FIG. 4 is showing a diagrammatic view of a plant for plasma enhanced chemical vapour deposition (PECVD) coating, by means of a magnetron plasma, onto a substrate film,

[0106] FIGS. 5a, 5b, 5c and 5d are showing typical examples of packaging containers produced from the laminated packaging material according to the invention,

[0107] FIG. 6 is showing the principle of how such packaging containers are manufactured from the packaging laminate in a continuous, roll-fed, form, fill and seal process,

[0108] FIG. 7 shows a diagram of comparable barrier films, on of which is according to the invention.

EXAMPLES

[0109] A 12 m thick film of biaxially oriented polyethyleneterephthalate (BOPET Hostaphan RNK12 by Mitsubishi) was deposition coated in a roll-to-roll plasma reactor, by plasma enhanced chemical vapour deposition (PECVD) under vacuum conditions.

[0110] One film sample was coated according to the invention, i.e. with a first coating layer of SiOxCy, wherein x is from 1.5 to 2.2, and y is from 0.15 to 0.8, and a second coating layer of an amorphous DLC. The total thickness of the two coating layers was determined to be from 8 nm. A comparison film sample was coated with a single coating of SiOxCy, wherein x is from 1.5 to 2.2, and y is from 0.15 to 0.8, preferably from 0.39 to 0.47. The single SiOxCy coating was deposited to a thickness of about 20 nm. A further comparison film sample was deposition coated with DLC to a thickness of 13.7 nm. The OTR as a function of the percentage of strain of each barrier film is shown in the diagram, and the point where the OTR completely takes off above useful levels, like about 10 cc/m.sup.2/day/atm at 23 C. and 50% RH.

ExamplesAdhesion to Laminated Layers

[0111] Films from 12 m thick biaxially oriented polyethyleneterephthalate (BOPET Hostaphan RNK12 and RNK12-2DEF by Mitsubishi) were deposition coated with various coatings by plasma enhanced chemical vapour deposition (PECVD) under vacuum conditions, in a roll-to-roll plasma reactor. A diamond-like amorphous hydrogenated carbon coating, DLC, was coated on some film samples, in line with the invention, while other PECVD barrier coatings were coated on other samples. The other PECVD barrier coatings, subject of comparative examples, were SiOx, wherein x varied between 1,5 and 2,2, SiOxCy coatings and SiOxCyNz coatings, respectively. These other silicon-containing barrier coatings were formed from organosilane pre-cursor gas compounds. The film samples according to the invention, were coated by depositing an amorphous, hydrogenated diamond-like coating DLC from a plasma formed from pure acetylene gas.

[0112] The plasma employed was capacitively coupled to the power delivered at 40 kHz frequency, and magnetically confined by unbalanced magnetron electrodes placed at a distance from the circumferential surface of a rotating drum, which functioned as a combined film-web transporting means and electrode. The polymer film substrate was cooled by cooling means within the drum web-transporting means.

[0113] The DLC coating was in a first example applied to a thickness of about 15-30 nm, and in a second example to a thickness of only about 2-4 nm.

[0114] The SiOx coatings were coated to a thickness of about 10 nm.

[0115] The thus barrier-coated substrate film samples, were subsequently extrusion coated with a 15 g/m2 thick layer of low density polyethylene (LDPE), of a type corresponding to LDPE materials of the laminate bonding layer that is conventionally used in order to extrusion laminate paperboard to aluminium foil in liquid carton packaging laminates.

[0116] The adhesion between the thus extrusion coated LDPE layer and the barrier-coated substrate PET film, was measured by a 180 peel test method under dry and wet conditions (by putting distilled water at the peeling interface) as described above. An adhesion of more than 200 N/m ensures that the layers do not delaminate under normal manufacturing conditions, e.g. when bending and fold-forming the laminated material. A wet adhesion of this same level ensures that the layers of the packaging laminate do not delaminate after filling and package formation, during transport, distribution and storage.

TABLE-US-00001 TABLE 1 PE-laminate PE-laminate Water Peel force Peel force Oxygen Vapour (N/m) Dry (N/m) wet Coating type Barrier Barrier adhesion adhesion SiOx (x = 1.5-2.2) <3 cc at 3 6 N/A 40-50 0 Mean 1.5 cc SiOxCy <3 cc at 3 6 1 40-50 40-50 Mean 1.5 cc SiOxCyNz <3 cc at 3 6 1 200-300 100 Mean 1.5 cc DLC ~25 nm <3 cc at 3 6 0.8 350-400 350-400 Mean 1.5 cc DLC ~25 nm on 0.5 0.05 0.5 350-400 350-400 both sides of film DLC 2-4 nm 60-80 5-6 350-400 350-400 DLC 2-4 nm on 60-80 5-6 350-400 350-400 both sides of film

[0117] As can be seen from the results summarised in Table 1, there is some insufficient dry adhesion between pure SiOx barrier coatings and there onto extrusion coated LDPE, while the adhesion deteriorates completely under wet/humid conditions.

[0118] When experimenting with more advanced SiOx formulas, containing also carbon and nitrogen atoms, some improvement is seen in the dry and/or wet adhesion properties, as compared to the pure SiOx coating, but the wet adhesion properties remain insufficient, i.e. below 200 N/m.

[0119] The dry adhesion of a DLC coating to extrusion coated LDPE is slightly better than for the best of the tested SiOxCyNz coatings. The more important and unforeseeable difference, compared to the SiOxCyNz coatings is that the adhesion remains constant under wet or humid conditions, such as are the conditions for laminated beverage carton packaging.

[0120] Furthermore, and rather surprisingly, the excellent adhesion of DLC coatings at values above 200 N/m, remain unaffected also when the DLC coating is made thinner, and as thin as 2 nm, i.e. where there are actually no notable barrier properties obtained any longer. This is the case both regarding dry and wet conditions for the sample films.

[0121] When such films are laminated into packaging laminates of paperboard and thermoplastic polymer materials, it is advantageous to coat such a DLC coating on both sides of the film, in order to provide excellent adhesion on both sides of the film. Alternatively, the adhesion to adjacent layers on the opposite side of the substrate film, may be secured by a separately applied chemical primer composition, such as the 2 DEF primer from Mitsubishi. A DLC adhesion-promoting layer is preferable from both environmental and cost perspective, since it only involves carbon atoms in the adhesion layer, and since it may be made very thin in order to just provide adhesion, or thicker in order to provide also barrier properties. At any thickness of a DLC-coating, the adhesion obtained is at least as good as that of a chemical primer (such as the 2 DEF from Mitsubishi) under both dry and wet conditions. Application of DLC coatings onto both sides of the polymer film substrate would have to be carried out in two consecutive process steps, however.

[0122] Further Example in Line with Adhesion Tests:

[0123] A similar BOPET film to the one used in the above Example was coated with similar thin DLC coatings on one and two sides, as described in Table 2. OTR was measured as cc/m.sup.2/day/atm at 23 C. and 50% RH, by the same method as in the above Example. The DLC-coated films were subsequently laminated into packaging material structures including a paperboard with an outer LDPE layer, by means of a bonding layer of 15 g/m.sup.2 of LDPE, and by being further coated on the opposite side of the film with an inside layer of a blend of LDPE and mLLDPE at 25 g/m.sup.2. The OTR was measured on the laminated packaging material by the same method as described previously.

[0124] Subsequently, the laminated packaging materials were reformed into 1000 ml standard Tetra Brik Aseptic packaging containers, on which the total oxygen transmission was further measured, by a Mocon 1000 equipment at 23 C. and 50% RH. The results from the measurements are presented in table 2.

TABLE-US-00002 TABLE 2 Thickness Thickness OTR DLC 1 DLC 2 OTR packaging OTR Test coating coating Film material Package ID Film structure (nm) (nm) (mean) (mean) (mean) A /BOPET/DLC2/ 3.4 21.8 A /DLC1/BOPET/DLC2/ 11.9 3.4 1.1 1.6 0.037 B /BOPET/DLC2/ 3.4 19.3 B /DLC1/BOPET/DLC2/ 3.5 3.4 10.5 1.8 0.027

[0125] Very surprisingly, it was found that when measured on laminated packaging material, and on packages from the packaging material, the oxygen barrier properties were on the same level or even improved by the film of Test B, although the film in Test B was coated with only two very thin DLC coatings, while in Test A, one of the coatings was thicker and actually intended for providing the resulting oxygen barrier properties of the film. By the measurements on the barrier-coated films, the film of Test A was indeed better, but when laminated into a final laminated packaging material structure, and used in a packaging container, both the two films were performing very well, and the film of Test B was even performing better than the film of Test A.

[0126] Thus, by the DLC-coated barrier films described above, high-integrity packaging laminates are provided, which have maintained excellent adhesion between layers also when used in liquid packaging, i.e. at subjecting the packaging material to wet conditions, and which may consequently protect other layers of the laminate from deterioration, in order to provide as good laminated material properties as possible. Since the durable DLC coatings in accordance with the invention provide both good oxygen barrier properties and water vapour barrier properties, it is a highly valuable type of barrier coating to be used in carton package laminates for liquid food products.

Further, relating to the attached figures:

[0127] In FIG. 1a, there is shown, in cross-section, a first embodiment of a barrier film 10a, of the invention. The polymer film substrate 11 is a PET, preferably BOPET, film substrate coated with a first silicon oxide coating layer 13 having the general composition formula SiOXCy, wherein x ranges from 1.5 to 2.2 and y ranges from 0.15 to 0.80, such as from 0.39 to 0.47, and a subsequent second coating layer of an amorphous DLC coating 12, both coating layers being applied by means of vacuum plasma enhanced chemical vapour deposition, PECVD. The PECVD coatings provide the film with good oxygen barrier (low OTR value). The second DLC coating 12 is a carbon coating (C:H) which is evenly deposited to a brownish transparent coating colour. The total thickness of first and second coating layers together is from 7 to 10 nm, such as from 7 to 8 nm, where the first SiOxCy coating layer has a greater thickness than the second DLC coating.

[0128] In FIG. 1b, a similar polymer film substrate 11 as in FIG. 1a, a BOPET film substrate, was vacuum PECVD coated with first and second coating layers 13 and 12 as in FIG. 1a, however first pre-coated with a thin coating layer of an amorphous DLC pre-coating layer 14, also by means of vacuum PECVD coating, in order to improve the adhesion of the first coating layer to the surface of the polymer film substrate.

[0129] In FIG. 1c, a similar polymer film substrate 11 as in FIG. 1a, a BOPET film substrate, was vacuum PECVD coated with first and second coating layers 13 and 12 as in FIG. 1a. On its other side, opposite to the first and second barrier coating layers, the film substrate is PECVD coated with a thin layer of an adhesion-promoting DLC 16, in order to provide improved adhesion to adjacent polymer layers to be laminated to the barrier film on this, opposite side.

[0130] In FIG. 2a, a laminated packaging material 20a of the invention, for liquid carton packaging, is shown, in which the laminated material comprises a paperboard bulk layer 21 of paperboard, having a bending force of 320 mN, and further comprises an outer liquid tight and heat sealable layer 22 of polyolefin applied on the outside of the bulk layer 21, which side is to be directed towards the outside of a packaging container produced from the packaging laminate. The polyolefin of the outer layer 22 is a conventional low density polyethylene (LDPE) of a heat sealable quality, but may include further similar polymers, including LLDPEs. An innermost liquid tight and heat sealable layer 23 is arranged on the opposite side of the bulk layer 21, which is to be directed towards the inside of a packaging container produced from the packaging laminate, i.e. the layer 23 will be in direct contact with the packaged product. The thus innermost heat sealable layer 23, which is to form the strongest seals of a liquid packaging container made from the laminated packaging material, comprises one or more in combination of polyethylenes selected from the groups consisting of LDPE, linear low density polyethylene (LLDPE), and LLDPE produced by polymerising an ethylene monomer with a C4-C8, more preferably a C6-C8, alpha-olefin alkylene monomer in the presence of a metallocene catalyst, i.e. a so called metallocene-LLDPE (m-LLDPE).

[0131] The bulk layer 21 is laminated to a durable barrier film 28a, comprising a polymer film substrate 24, which is coated on a first side with first and second coating layers 25, as in FIG. 1a. On its second, opposite, side, the polymer film substrate is pre-primed with an adhesion-promoting primer 27, in this case 2-DEF, a polyethyleneimine-based priming composition from Mitsubishi Chemicals. The first side of the thus durable barrier-coated film 24 is laminated to the bulk layer 21 by an intermediate layer 26 of bonding thermoplastic polymer or by a functionalised polyolefin-based adhesive polymer, in this example by a low density polyethylene (LDPE). The intermediate bonding layer 26 is formed by means of extrusion laminating the bulk layer and the durable barrier film to each other. The thickness of the intermediate bonding layer 26 is preferably from 7 to 20 m, more preferably from 12-18 m. The innermost heat sealable layer 23 may consist of two or several part-layers of the same or different kinds of LDPE or LLDPE or blends thereof. Excellent adhesion will be obtained in the laminated material, in that the second PECVD DLC coating layer is containing substantial amounts of carbon material, which exhibits good adhesion compatibility with polymers, such as polyethylene and polyethylene-based co-polymers.

[0132] In FIG. 2b, a laminated packaging material 20b of the invention, for liquid carton packaging, is shown, in which the laminated material comprises a paperboard core layer 21, having a bending force of 320 mN, and further comprises an outer liquid tight and heat sealable layer 22 of polyolefin applied on the outside of the bulk layer 21, which side is to be directed towards the outside of a packaging container produced from the packaging laminate. The polyolefin of the outer layer 22 is a conventional low density polyethylene (LDPE) of a heat sealable quality, but may include further similar polymers, including LLDPEs. An innermost liquid tight and heat sealable layer 23 is arranged on the opposite side of the bulk layer 21, which is to be directed towards the inside of a packaging container produced from the packaging laminate, i.e. the layer 23 will be in direct contact with the packaged product. The thus innermost heat sealable layer 23, which is to form the strongest seals of a liquid packaging container made from the laminated packaging material, comprises one or more in combination of polyethylenes selected from the groups consisting of LDPE, linear low density polyethylene (LLDPE), and LLDPE produced by polymerising an ethylene monomer with a C4-C8, more preferably a C6-C8, alpha-olefin alkylene monomer in the presence of a metallocene catalyst, i.e. a so called metallocene-LLDPE (m-LLDPE).

[0133] The bulk layer 21 is laminated to a durable barrier film 28b, which is PECVD coated on both sides in accordance with FIG. 1c, thus having first and second barrier coating layers 25a as in FIG. 1a, and an adhesion-promoting DLC coating layer 25b on the opposite side of the substrate 24 polymer film, the DLC coating layers each having a thickness lower than 5 nm. The thus durable barrier coated film 28b is laminated to the bulk layer 21 by an intermediate layer 26 of bonding thermoplastic polymer or by a functionalised polyolefin-based adhesive polymer, in this example by a low density polyethylene (LDPE). The intermediate bonding layer 26 is formed by means of extrusion laminating the bulk layer and the durable barrier film to each other. The thickness of the intermediate bonding layer 26 is preferably from 7 to 20 m, more preferably from 12-18 m. The innermost heat sealable layer 23 may consist of two or several part-layers of the same or different kinds of LDPE or LLDPE or blends thereof. Excellent adhesion will be obtained in the laminated material, in that the PECVD-coated durable DLC barrier coating is containing substantial amounts of carbon material, which exhibits good adhesion compatibility with polymers, such as polyolefins, such as in particular polyethylene and polyethylene-based co-polymers.

[0134] In FIG. 3, the lamination process 30 is shown, for the manufacturing of the packaging laminate 20a or 20b, of FIGS. 2a and 2b, respectively, wherein the bulk layer 31 is laminated to the durable barrier film 10a or 10c (33) of FIGS. 1a and 1c, by extruding an intermediate bonding layer of LDPE 34 from an extrusion station 35 and pressing together in a roller nip 36. The durable barrier film 10a; 10c; 33 has a first SiOxCy and a second DLC barrier coating layers, deposited on the surface of the polymer film substrate, whereby the DLC coating is to be directed towards the bulk layer when laminated at the lamination station 36. Subsequently, the laminated paper bulk and the barrier film passes a second extruder feedblock 37-2 and a lamination nip 37-1, where an innermost heat sealable layer 23; 37-3 is coated onto the barrier-film side 10a;10c of the paper-film laminate forwarded from 36. Finally, the laminate, including an innermost heat sealable layer 37-3, passes a third extruder feedblock 38-2 and a lamination nip 38-1, where an outermost heat sealable layer of LDPE 22; 38-3 is coated onto the outer side of the paper layer. This latter step may also be performed as a first extrusion coating operation before lamination at 36, according to an alternative embodiment. The finished packaging laminate 39 is finally wound onto a storage reel, not shown.

[0135] FIG. 4 is a diagrammatic view of an example of a plant for plasma enhanced vapour deposition coating, PECVD, of hydrogenated amorphous diamond-like carbon coatings onto a polymer film substrate. The film substrate 44 is subjected, on one of its surfaces, to continuous PECVD, of a plasma, 50, in a plasma reaction zone created in the space between magnetron electrodes 45, and a chilled film-transporting drum 46, which is also acting as an electrode, while the film is forwarded by the rotating drum, through the plasma reaction zone along the circumferential surface of the drum. The plasma for deposition coating of the first SiOxCy coating layer is formed from an organosilicon gas precursor composition, while the plasma for the second DLC coating layer is formed from one or more gaseous organic hydrocarbons, such as acetylene or methane, and the coatings are applied to a total thickness of 7-10 nm, preferably 7-8 nm, in two consecutive coating steps or separate plasma reaction chambers, such that the barrier film of the invention is formed.

[0136] FIG. 5a shows an embodiment of a packaging container 50a produced from the packaging laminate 20 according to the invention. The packaging container is particularly suitable for beverages, sauces, soups or the like. Typically, such a package has a volume of about 100 to 1000 ml. It may be of any configuration, but is preferably brick-shaped, having longitudinal and transversal seals 51a and 52a, respectively, and optionally an opening device 53. In another embodiment, not shown, the packaging container may be shaped as a wedge. In order to obtain such a wedge-shape, only the bottom part of the package is fold formed such that the transversal heat seal of the bottom is hidden under the triangular corner flaps, which are folded and sealed against the bottom of the package. The top section transversal seal is left unfolded. In this way the half-folded packaging container is still is easy to handle and dimensionally stable when put on a shelf in the food store or on a table or the like.

[0137] FIG. 5b shows an alternative, preferred example of a packaging container 50b produced from an alternative packaging laminate 20 according to the invention. The alternative packaging laminate is thinner by having a thinner paper bulk layer 21, and thus it is not dimensionally stable enough to form a parallellepipedic or wedge-shaped packaging container, and is not fold formed after transversal sealing 52b. It will thus remain a pillow-shaped pouch-like container and be distributed and sold in this form.

[0138] FIG. 5c shows a gable top package 50c, which is fold-formed from a pre-cut sheet or blank, from the laminated packaging material comprising a bulk layer of paperboard and the durable barrier film of the invention. Also flat top packages may be formed from similar blanks of material.

[0139] FIG. 5d shows a bottle-like package 50d, which is a combination of a sleeve 54 formed from a pre-cut blanks of the laminated packaging material of the invention, and a top 55, which is formed by injection moulding plastics in combination with an opening device such as a screw cork or the like. This type of packages are for example marketed under the trade names of Tetra Top and Tetra Evero. Those particular packages are formed by attaching the moulded top 55 with an opening device attached in a closed position, to a tubular sleeve 54 of the laminated packaging material, sterilizing the thus formed bottle-top capsule, filling it with the food product and finally fold-forming the bottom of the package and sealing it.

[0140] FIG. 6 shows the principle as described in the introduction of the present application, i.e. a web of packaging material is formed into a tube 61 by the longitudinal edges 62 of the web being united to one another in an overlap joint 63. The tube is filled 64 with the intended liquid food product and is divided into individual packages by repeated transversal seals 65 of the tube at a pre-determined distance from one another below the level of the filled contents in the tube. The packages 66 are separated by incisions in the transversal seals and are given the desired geometric configuration by fold formation along prepared crease lines in the material.

[0141] FIG. 7 shows a diagram of the OTR of three BOPET substrate polymer films, each being coated with three different vacuum PECVD coatings, as a function of the strain of the film, and indicating and comparing the point of crack onset strain for each film, i.e. the point of strain at which the oxygen barrier properties begin to deteriorate beyond being useful in a barrier film. The diagram shows that a COS of about 2% or above, may be obtained with a good amorphous DLC coating by PECVD under vacuum. With a good silicon oxide coating, having a general composition formula SiOx or SiOxCy wherein x ranges from 1.5 to 2.2, by PECVD under vacuum, a COS of about 3-4% may be obtained by coating onto a similar film. However, when vacuum-coating by PECVD a similar PET-based film with a first coating of SiOxCy, followed by a coating of amorphous DLC, the COS is synergetically improved to a value of 5-6% and above, and in addition, it seems that the total coating thickness may be thinner, while still achieving the same level of barrier properties as compared to comparable, but thicker, single-layer coatings. In some cases, a COS of from 7 to 8% was achieved for similar films having the combined first and second coating layers. The particular example films behind the diagram were coated BOPET films of thickness 12 m, but similar COS values were for example also obtained for biaxially oriented films of polypropylene (BOPP) having a thin coating-receiving layer of polyimide, such as from 1-2 m thick.

[0142] As a final remark, the invention is not limited by the embodiments shown and described above, but may be varied within the scope of the claims.