Barrier film or sheet and laminated packaging material comprising the film or sheet and packaging container made therefrom

Abstract

Barrier films comprising a PECVD barrier coating from diamond-like carbon are disclosed, along with methods of manufacturing such films, and laminated packaging materials comprising such films, in particular for liquid food packaging, are disclosed. Packaging containers comprising the laminated packaging material or being made from the laminated packaging material, in particular a packaging container for liquid food packaging, are also disclosed.

Claims

1. A barrier film for use in laminated packaging materials for liquid food products, comprising: a polyethylene terephthalate (PET) film substrate having a thickness of 4-12 μm; a durable vapor-deposited diamond-like carbon (DLC) barrier coating on a first side of the substrate at a thickness from 10 to 35 nm, the DLC barrier coating configured to inhibit the passage of gas and water vapor, the DLC barrier coating comprising a single-layer gradient of DLC and a DLC barrier coating thickness; and an adhesion-promoting primer coating on a second side of the substrate, opposite the first side deposited with the DLC barrier coating, wherein the adhesion-promoting primer coating is a second DLC barrier coating; wherein the DLC barrier coating thickness extends from an interface of the DLC barrier coating with the PET film substrate to a surface of the DLC barrier coating, the DLC barrier coating exhibiting a decreasing gradient of oxygen ion concentration from the interface to a minimum value and a subsequent increasing gradient of oxygen ion concentration from the minimum value to the surface of the DLC barrier coating; and wherein the decreasing gradient comprises a slope of 5.Math.10.sup.4 to 5.Math.10.sup.5 counts per nanometer coating thickness as depicted by a Dynamic Time of Flight Secondary ion Mass Spectroscopy (ToF-SiMS) intensity-versus thickness surface analysis diagram calibrated to a TEM microscopy thickness measurement, the minimum value located at 40 to 60% of the DLC barrier coating thickness as measured from the surface of the DLC barrier coating, and wherein the barrier film has a crack onset strain (COS) equal to or greater than 2%.

2. The barrier film as claimed in claim 1, wherein a local and temporary concentration depletion of hydrogen and carbon ions is located 10-15 nm from the surface of the substrate.

3. The barrier film as claimed in claim 1, wherein the polymer film substrate is an oriented PET film.

4. The barrier film as claimed in claim 1, wherein the DLC barrier coating has a sp2 hybrid bond content of 60 to 70%, based on the total content of sp2 and sp3 hybrid bonds.

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

6. The laminated packaging material as claimed in claim 5, further comprising a first outermost liquid tight, heat sealable polyolefin layer and a second innermost liquid tight, heat sealable polyolefin layer.

7. The laminated packaging material as claimed in claim 5, further comprising a bulk layer comprising paper, paperboard or other cellulose-based material, a first outermost liquid tight, heat sealable polyolefin layer and a second innermost liquid tight, heat sealable polyolefin layer, wherein the barrier sheet is positioned between the bulk layer and the second innermost liquid tight, heat sealable polyolefin layer.

8. The laminated packaging material as claimed in 7, wherein the barrier film is bonded to the bulk layer by an intermediate thermoplastic polymer bonding layer, wherein the intermediate thermoplastic polymer bonding layer binds the surface of the DLC barrier coating to the bulk layer.

9. The laminated packaging material as claimed in claim 8, wherein the adhesion-promoting primer coating bonds the barrier film to the second innermost liquid tight, heat sealable polyolefin layer.

10. The laminated packaging material as claimed in claim 5, wherein the barrier film is a double barrier film, wherein the double barrier film comprises a first barrier film, a second barrier film and an interjacent thermoplastic bonding layer, and wherein the interjacent thermoplastic bonding layer bonds the first barrier film and the second barrier film.

11. The laminated packaging material as claimed in claim 10, further comprising a first outermost liquid tight, heat sealable polymer layer and a second innermost liquid tight, heat sealable polymer layer, wherein the first outermost liquid tight, heat sealable polymer layer is positioned on a second side of the first barrier film, wherein the second side of the first barrier film is opposite the first side of the first barrier film bonded with the interjacent thermoplastic bonding layer, wherein the second innermost liquid tight, heat sealable polymer layer is positioned on a second side of the second barrier film, and wherein the second side of the second barrier film is opposite the first side of the second barrier film bonded with the interjacent thermoplastic bonding layer.

12. A packaging container comprising the laminated packaging material as claimed in claim 5.

13. The barrier film as claimed in claim 1, wherein the concentrations of hydrogen and carbon ions remain at a substantially constant level throughout the DLC barrier coating thickness.

14. The barrier film as claimed in claim 1, wherein the decreasing gradient comprises a slope of about.Math.10.sup.5 counts per nanometer coating thickness as depicted by a Dynamic Time of Flight Secondary ion Mass Spectroscopy (ToF-SiMS) intensity-versus thickness surface analysis diagram calibrated to a TEM microscopy thickness measurement.

15. The barrier film as claimed in claim 1, wherein the decreasing gradient comprises a slope of about.Math.8.Math.10.sup.4 to 1.2.Math.10.sup.5 counts per nanometer coating thickness as depicted by a Dynamic Time of Flight Secondary ion Mass Spectroscopy (ToF-SiMS) intensity-versus thickness surface analysis diagram calibrated to a TEM microscopy thickness measurement.

Description

EXAMPLES AND DESCRIPTION OF PREFERRED EMBODIMENTS

(1) In the following, preferred embodiments of the invention will be described with reference to the drawings, of which:

(2) FIG. 1a is schematically showing, a barrier film in cross-section, comprising a polymer film substrate and a durable DLC barrier coating deposited thereon, according to the invention,

(3) FIG. 1b shows a similar film coated on its other side with an adhesive primer,

(4) FIG. 1c schematically shows a similar barrier film in cross-section, comprising a polymer film substrate which has been vapour deposition coated on both sides with the durable DLC barrier coating, in two consecutive vapour deposition coating steps,

(5) FIG. 2a is showing a schematic, cross-sectional view of a laminated packaging material according to an embodiment of the invention,

(6) FIG. 2b is showing a schematic, cross-sectional view of a further laminated packaging material according to an embodiment of the invention, comprising the durable barrier film of FIG. 1c,

(7) 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,

(8) 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,

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

(10) 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,

(11) FIG. 7 shows a Dynamic Time of Flight Secondary ion Mass Spectroscopy diagram, ToF-SiMS, in which the elementary composition of the durable DLC coating is analysed through the depth of the coating, from the polymer film substrate surface C, over the interface to the barrier coating A, and up to the surface of the barrier coating B, wherein the polymer film substrate is a PET film,

(12) FIG. 8 shows a Dynamic Time of Flight Secondary ion Mass Spectroscopy diagram, ToF-SiMS, in which the elementary composition of the durable DLC coating is analysed through the depth of the coating, from the polymer film substrate surface C, over the interface A to the barrier coating and up to the surface of the barrier coating B, wherein the polymer film substrate is a polyamide, PA, film.

EXAMPLES

(13) A 12 μm 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. The plasma being capacitively coupled to the power delivered at 40 kHz frequency, and being magnetically confined by unbalanced magnetron electrodes placed at a distance from the circumferential surface of a rotating drum, combined film-web transporting means and electrode. The film was first pre-treated with argon gas at a flow of 3 standard litres per minute, slm, and a pre-treatment power of 5 kW. Subsequently, the film was coated by depositing an amorphous, hydrogenated diamond-like coating DLC from a plasma formed from pure acetylene gas, at a total coating power of 24 kW and a total acetylene flow of 12 slm and a process gas pressure of about 0.03 mbar. The polymer film substrate was cooled to a constant temperature below 10 degrees Celsius by cooling means within the drum web-transporting means. The DLC coating was applied to a thickness of about 23 nm.

(14) Different settings of the process were tried between different coating batches, and were evaluated by measurement of oxygen transmission, OTR, and water vapour transmission, WVTR.

(15) The OTR of the uncoated BOPET film, measured at room temperature 23° C. and 50% RH is determined to be 110 cm.sup.3/m.sup.2/day at 1 atm. OTR was measured with Oxtran 2-60 (Mocon Inc.) equipment based on coulometric sensors, with a standard deviation of the results being ±0.5 cm.sup.3/m.sup.2/day.

(16) The method for determining OTR identifies the amount of oxygen per surface and time unit at passing through a material at a defined temperature, given atmospheric pressure, and chosen driving force.

(17) Water vapour transmission rate (WVTR) measurements were carried out by a Lyssy instrument (norm: ASTM F1249-01 using a modulated Infrared sensor for relative humidity detection and WVTR measurement) at 38° C. and 90% driving force. This test method is dedicated to measure Water Vapor Transmission Rate (WVTR) properties of films. The procedure is done according to ASTM F1249-01 using a modulated Infrared sensor for relative humidity detection and WVTR measurement.

(18) TABLE-US-00001 TABLE 1 OTR Power C2H2 flow (cm.sup.3/m.sup.2/day/atm Sample (kW) (slm) Ratio 23° C., 50% RH) F2-140922-A test 1 24 12 2.0 1.2 F2-140922-A test 2 24 14 1.7 6.1 F2-140922-A test 3 32 10 3.2 2.4 F2-140922-A test 4 24 13 1.8 1.0 F2-140922-A test 5 24 12 2.0 1.4 F2-140922-A test 6 24 14 1.7 5.6 F2-140922-A test 7 32 10 3.2 2.6 F2-140922-A test-8 24 13 1.8 1.1

(19) The precursor gas pressure in the plasma reaction zone during the sample test runs in Table 1 was kept at 42-52 μbar.

(20) As seen from the results of the test runs in Table 1, a ratio between the power and the flow of between 1.8 and 3.5, may be preferable for optimal OTR results.

(21) It has been seen that too large amount of gas precursor for the plasma seems to destroy the barrier properties.

(22) Lowering the amount of precursor gas, on the other hand, slowly dilutes the plasma such that the barrier properties gradually decrease, i.e. the OTR and WVTR increase away from the optimal values of Table 1.

(23) The durable barrier films obtained by samples 1, 3, 4, 5, 7 and 8, moreover showed excellent aroma barrier properties, chemical resistance and odour barrier properties. Importantly, the films exhibited high crack on-set strain, COS, above 2%. The good effects from this in lamination handling and in package forming from a laminated packaging material comprising the barrier film, are that the barrier coating is durable by being i.a. heat resistant and by having good mechanical properties at winding, rewinding, laminating, fold forming and sealing into packages.

(24) Moreover, the barrier film and the surface of the durable DLC coating has excellent adhesion to an adjacent polyolefin laminate layer, which has been measured to be above 200 N/m, such as above 300 N/m, in adhering to an adjacent polyethylene layer.

(25) TABLE-US-00002 TABLE 2 n C2H2 (number OTR μ* Power flow of (cm.sup.3/m.sup.2/day/atm Sigma, Pressure Sample (kW) (slm) samples) 23° C., 50% RH) δ* USL (μbar) F2-150204-A 24 12 6 1.5 1.2 2.3 32 S3 F2-150204-A 24 12 6 1.5 1.3 3.0 32 S2 F2-150205-A 24 12 6 0.8 1.3 1.7 32 S3* F2-150205-A 24 12 6 1.0 1.4 2.6 32 S6* F2-141009-A 24 12 9 1.3 1.3 2.8 33 S2 F2-141009-A 24 12 9 0.9 1.2 1.5 33 S3 F2-141009-A 24 12 9 1.4 1.3 2.8 33 S6 F2-150128-A 24 12 6 0.8 1.1 1.2 32 S2* F2-150128-A 24 12 6 0.8 1.4 2.4 32 S6* F2-141104-A 24 12 9 1.0 1.3 2.2 33 S4 F2-141015-A 24 12 9 1.1 1.2 1.9 33 S4 F2-141017-A 24 12 9 1.2 1.2 2.1 33 S4 F2-141006-A 24 12 6 1.6 1.2 3.0 33 S2 F2-141006-A 24 12 6 1.6 1.2 2.7 33 S3 F2-141006-B 24 12 6 1.7 1.2 2.9 33 S2 F2-141006-B 24 12 6 1.3 1.1 1.5 33 S3 F2-141008-A 24 12 6 1.6 1.1 2.2 34 S2 F2-141008-A 24 12 6 1.5 1.2 2.5 34 S3

(26) The oxygen transmission rates in Table 2 were measured on Mocon 2/60 at 23° C. and 50% RH. In all test runs of Table 2, the polymer film substrate was a 12 μm thick film of oriented PET. All samples except F2_150205* and F2_150128* were made from the same polymer film substrate as used in Table 1, i.e. (BOPET Hostaphan RNK12 by Mitsubishi). F2_150205* and F2_150128* were made from a different BOPET film having the thickness of 12 μm, also.

(27) μ* is the median value of the OTR and σ* is the multiplicative standard deviation. The USL is the upper specification limit given at 3 sigma (σ*.sup.3) in a lognormal distribution.

(28) n is the number of samples, i.e. the number of samples taken from the barrier film to do measurements on.

(29) Water vapor transmission rates (WVTR) were not measured systematically for samples tabulated in Table 2. Other tests, performed with the same settings and conditions, reported WVTR of from 0.6 to 1.0 g/day/m.sup.2 with 38° C. and 90% RH either on Mocon Permatran or on LYSSY equipments.

Examples—Adhesion Test

(30) Films from 12 μm 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, wherein (y+z)/x is from 1 to 1.5. 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.

(31) 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.

(32) 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.

(33) The SiOx coatings were coated to a thickness of about 10 nm.

(34) 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.

(35) 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.

(36) TABLE-US-00003 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 <3 cc at N/A 40-50  0 (x = 1.5-2.2) 3  Mean 1.5 cc SiOxCy <3 cc at 1 40-50 40-50 (y/x = 1-1.5) 3  Mean 1.5 cc SiOxCyNz <3 cc at 1 200-300 100 (y + z/x = 1-1.5) 3  Mean 1.5 cc DLC ~25 nm <3 cc at 0.8 350-400 350-400 3  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

(37) 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.

(38) 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.

(39) 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.

(40) 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 is actually no notable barrier properties obtained any longer. This is the case both regarding dry and wet conditions for the sample films.

(41) Of course, 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. Double-sided applications of DLC coatings onto the polymer film substrate would have to be carried out in two consecutive process steps, however.

Further Example in Line with Adhesion Tests

(42) 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.

(43) 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.

(44) TABLE-US-00004 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

(45) 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.

(46) 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.

(47) Further, relating to the attached figures:

(48) 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 or PA or polyolefin, preferably BOPET, film substrate coated with a durable, amorphous DLC coating 12, by means of plasma enhanced chemical vapour deposition, PECVD, coating, in order to improve the oxygen barrier (decrease the OTR value). The vapour deposited coating 12 is a carbon coating (C:H) which is evenly deposited to a brownish transparent coating colour. The thickness of the durable DLC coating is preferably from 5 to 50 nm, more preferably from 5 to 30 μm.

(49) In FIG. 1b, a similar polymer film substrate 11 as in FIG. 1a, in this case a BOPET film substrate, was vapour deposition coated on the coating side with a similar, durable, amorphous DLC coating 12, by means of plasma enhanced chemical vapour deposition, PECVD, coating, in order to improve the oxygen barrier (decrease the OTR value). On its other side, opposite to the durable DLC barrier coating, the film substrate is coated with a thin layer of an adhesion-promoting primer 13, such as 2-DEF, a polyethyleneimine-based priming composition from Mitsubishi Chemicals.

(50) In FIG. 1c, a similar polymer film substrate 11 as in FIGS. 1a and 1b, in this case a BOPET film substrate, was vapour deposition coated with a 20 nm thick durable DLC coating, in accordance with the present invention, on both sides, 12a, 12b. The OTR of the film was measured to be lower than 1 cc/day/m.sup.2/atm at 23° C. and 50% RH.

(51) 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).

(52) The bulk layer 21 is laminated to a durable barrier film 28, comprising a polymer film substrate 24, which is coated on a first side with a layer of a thin PECVD vapour deposited layer of amorphous, durable DLC barrier material, in accordance with the present invention, 25, at a thickness of from 20 to 30 nm. On its second, opposite, side, the polymer film substrate is coated 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 μm, more preferably from 12-18 μm. 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.

(53) 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).

(54) The bulk layer 21 is laminated to a durable barrier film 28, which is coated on both sides with a thin PECVD vapour deposited layer of amorphous, durable DLC barrier material, in accordance with the present invention, 25a and 25b, each at a thickness of from 10 to 30 nm, in two consecutive PECVD coating operations, one per side of the substrate 24 polymer film. The thus durable barrier coated film 28 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 μm, more preferably from 12-18 μm. 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.

(55) In FIG. 3, the lamination process 30 is shown, for the manufacturing of the packaging laminate 20, of FIG. 2, respectively, wherein the bulk layer 31 is laminated to the durable barrier film 10a or 10b (33) of FIGS. 1a and 1 b, by extruding an intermediate bonding layer of LDPE 34 from an extrusion station and pressing together in a roller nip 36. The durable barrier film 10a; 10b; 33 has a durable DLC barrier coating, 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; 10b 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.

(56) 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 is formed from one or more gaseous organic hydrocarbon, such as acetylene or methane, and the coating is applied to a thickness of 1-500 nm, preferably 2-100 nm, such that a deposition coated film 1a or 1b is formed, respectively.

(57) 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.

(58) 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.

(59) 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.

(60) 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.

(61) 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.

(62) FIG. 7 shows an intensity-versus-time diagram from surface analysis by Time of Flight Secondary ion Mass Spectroscopy ToF-SiMS at varying depths of the durable DLC barrier coating, deposited onto a polyethyleneterephthalate, PET, film substrate.

(63) FIG. 8 shows an intensity-versus-time diagram from surface analysis by Time of Flight Secondary ion Mass Spectroscopy ToF-SiMS at varying depths of the durable DLC barrier coating, deposited onto a polyamide, PA, film substrate.

(64) Secondary ion mass spectrometry (SiMS) is a technique used to analyze the composition of solid surfaces and thin films by sputtering the surface of the sample with a focused primary ion beam and collecting and analyzing ejected secondary ions. The mass/charge ratios of these secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface to a depth of 1 to 2 nm. Due to the large variation in ionization probabilities among different materials, SiMS is generally considered to be a qualitative technique, and is a very sensitive surface analysis technique, with elemental detection limits ranging from parts per million to parts per billion.

(65) The ToF-SiMS method measures the composition of solid surfaces and thin films, and can thus do this at different depths of the material, in order to determine the chemical structure of and within the coating.

(66) The ToF-SiMS measurements were performed using a TOF 5 equipment from IONTOF GmBH company

(67) Analysis Conditions:

(68) Primary ion Bi.sup.+ 25 keV, I˜1.86 pA Analysed area 70×70 μm.sup.2, 256×256 pixels Negative secondary ions analysed Charge compensation (<20 eV)
Sputtering Conditions: Primary ion Cs.sup.+ 500 eV, 40 nA Sputtering area: 250×250 μm.sup.2
Analysis/Sputtering cycling: 2 analysis scans from 0 to 300 uma (time of flight max=50 μs) sputtering: 1.638 seconds
Pause Between Sputtering and Analysis: 0.5 Second.

(69) Thickness measurements were performed by Transmission Electronic Microscopy using on a Titan 80-300, FEI equipment. Samples are prepared by ultramicrotomy on an EM UC6 Microtome from Leica.

(70) The diagrams 7-8, show that there is a greatly decreasing gradient of oxygen ion concentration, from below the surface of the polymer film substrate C at a first zone, through a second zone at the interface A between the substrate surface and the coating, to a third zone, i.e. the zone of the coating surface B, and a rapid increase again of the oxygen concentration within this third zone, to more or less recover the level of the initial concentration again. Thus, the PECVD coating process first modifies the surface of the polymer film at zone C, starting from below the initial polymer surface, and starts building the barrier coating at the interface A, up to the full thickness of the barrier coating, at the top surface thereof, at B. The concentrations of the carbon and hydrogen ions remain at a substantially constant level throughout the three coating zones. According to an embodiment, the durable DLC coating of the invention characteristically exhibits a relatively smaller, temporary depletion of hydrogen and triple-carbon ions, during the second zone A, while the concentrations of single- and double-carbon ions remain substantially constant throughout all three zones and the depth of the coating. Although the diagram becomes a little different when the coating is applied and analysed on a polyamide film substrate compared to a PET film substrate, it can be seen that the characteristics and change patterns regarding the ion contents in the coatings are very similar.

(71) We have thus seen that the specific DLC barrier coatings made by our method, and having these characteristics when analysed by ToF-SiMS, provide both optimal initial oxygen barrier and water vapour barrier properties of a coated film, and excellent durability regarding said barrier properties after being exposed to mechanical strain, i.e. when the film is used in lamination and fold-forming and sealing of laminated materials comprising the films, into packages. The temporary depletion of the hydrogen and triple-carbon ion concentration at the interface A between the coating and the film surface, indicates that there is covalent bonding between the coating and the film, which is believed to be at least a contributing factor to the good mechanical properties at strain, including adhesion of the coating to the film substrate and internal cohesion within the coating.

(72) The invention is not limited by the embodiments shown and described above, but may be varied within the scope of the claims.