MULTI-LAYER FILM ASSEMBLY SUITABLE FOR USE IN A MULTI-LAYER CARD

Abstract

A multi-layer film comprising: (i) a polyester base layer (B) having a first and second surface wherein the polyester of the base layer is a crystals isabie polyester; and (ii) a heat-sealabie copolyester layer (A) disposed on one or both surfaces of said polyester base layer (B); wherein the polyester base layer (S) comprises titanium dioxide particles in an amount of from about 1 to about 30 wt % by total weight of the base layer, wherein said particles are coated with an organic coating; and a multi-layer card comprising said multi-layer film, a polymeric inlay layer and a polymeric overlay layer such that the layer order is polymeric inlay layer, first multi-layer film and first polymeric overlay layer.

Claims

1. A multi-layer film comprising: (i) a polyester base layer (B) having a first and second surface wherein the polyester of the base layer is a crystallisable polyester; and (ii) a heat-sealable copolyester layer (A) disposed on one or both surfaces of said polyester base layer (B), wherein the polyester base layer (B) comprises titanium dioxide particles in an amount of from about 1 to about 30 wt % by total weight of the base layer, wherein said particles are coated with an organic coating.

2. A multi-layer film according to any claim 1 wherein the polyester of the base layer is selected from polyethylene terephthalate (PET) and polyethylene 2,6-naphthalate (PEN).

3. A multi-layer film according to any preceding claim wherein the polyester base layer further comprises a copolyesterether, preferably in an amount of from about 0.2 to about 10 wt % relative to the total weight of the polyester base layer.

4. A multi-layer film according to claim 3 wherein the copolyesterether comprises at least one polyester block and at least one polyether block wherein the ratio of polyesterpolyether is in the range 25-55: 45-75 by weight % of the copolyesterether.

5. A multi-layer film according to claim 3 or 4 wherein the copolyesterether comprises at least one polyester block of an alkylene terephthalate, and wherein the copolyesterether comprises at least polyether block which is a poly(alkylene oxide) glycol selected from poly(ethylene oxide) glycol, poly(propylene oxide) glycol and poly(tetramethylene oxide) glycol.

6. A multi-layer film according to any preceding claim wherein the copolyester of the heat-sealable layer(s) is selected from copolyesters derived from repeating units comprising or consisting of a first aromatic dicarboxylic acid, a second aromatic dicarboxylic acid and an aliphatic glycol, and preferably copolyesters derived from repeating units consisting of terephthalic acid, isophthalic acid and ethylene glycol, preferably wherein the isophthalic acid is present in an amount of from about 15 to about 20 mol % of the acid fraction of the copolyester.

7. A multi-layer film according to any preceding claim wherein the polyester base layer (B) is biaxially oriented.

8. A multi-layer film according to any preceding claim wherein said multi-layer film is a coextruded multi-layer film.

9. A multi-layer film according to any preceding claim which is opaque, and preferably exhibits a Transmission Optical Density (TOD) of at least 1.0.

10. A multi-layer film according to any preceding claim which is white, and preferably exhibits a whiteness index of at least 95.

11. A multi-layer film according to any preceding claim which exhibits an L* value of greater than 92.00; an a* value in the range from 2.00 to 0.50; and a b* value in the range from 4.00 to 1.00.

12. A multi-layer film according to any preceding claim wherein said titanium dioxide is rutile titanium dioxide.

13. A multi-layer film according to any preceding claim wherein the amount of titanium dioxide in the polyester base layer is in the range from about 10 to about 15% by weight, relative to the total weight of the polyester layer.

14. A multi-layer film according to any preceding claim wherein said organic coating does not comprise or is not derived from a silane, and/or wherein the organic coating is not or does not comprise a polysiloxane, and/or wherein said organic coating is not or does not comprise a polyolefin resin, and/or wherein said titanium dioxide particles are not titanium dioxide particles coated with a coupling agent and a polyolefin resin.

15. A multi-layer film according to any preceding claim wherein said organic coating is an organophosphorus compound.

16. A multi-layer film according to any preceding claim wherein the titanium dioxide particles are coated with an alkylphosphonic acid or an ester of an alkylphosphonic acid wherein the alkylphosphonic acid contains from 6 to 22 carbon atoms.

17. A multi-layer film according to claim 16 wherein the alkylphosphonic acid or ester thereof has the formula P(R)(O)(OR.sup.1)(OR.sup.2), wherein: R is an alkyl group or a cycloalkyl group containing 6 to 22 carbon atoms; and R.sup.1 and R.sup.2 are each hydrogen, an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group.

18. A multi-layer film according to claim 17 wherein R.sup.1 and R.sup.2 are independently selected from hydrogen and hydrocarbyl groups containing up to 10 carbon atoms, and preferably R.sup.1 and R.sup.2 are hydrogen.

19. A multi-layer film according to claim 16, 17 or 18 wherein the alkyl group of said alkylphosphinic acid, or R, contains from 6 to 14 carbon atoms and is a straight chain alkyl group.

20. A multi-layer film according to claim 16, 17, 18 or 19 wherein the alkylphosphonic acid or ester thereof is selected from n-octylphosphonic acid and its esters, n-decylphosphonic acid and its esters, 2-ethylhexylphosphonic acid and its esters and camphyl phosphonic acid and its esters.

21. A multi-layer film according to any of claims 1 to 14 wherein said organic coating is a polymeric organic coating.

22. A multi-layer film according to claim 21 wherein the polymeric organic coating is derived from monomers containing carbon, hydrogen and oxygen atoms, and optionally further comprising nitrogen and/or phosphorus and/or sulphur atoms, and which preferably which do not contain silicon atoms.

23. A multi-layer film according to claim 21 or 22 wherein the polymeric backbone of said polymeric coating does not contain silicon atoms.

24. A multi-layer film according to any of claims 21 to 23 wherein said titanium dioxide particles are obtainable by dispersing titanium dioxide particles in water at a pH value higher than the isoelectric point of said titanium dioxide particles (and preferably at a pH above 7 and preferably at a pH of 9 to 11) in the presence of a dispersing agent comprising a polymeric polybasic acid or a salt thereof to produce particles having a modified isoelectric point; adjusting the pH of the dispersion to a value below 9 but above the modified isoelectric point of the particles; and polymerising in the presence of the dispersion so produced one or more ethylenically unsaturated monomer(s) so that said titanium dioxide particles are coated with polymerised monomer.

25. A multi-layer film according to any of claims 21 to 24 wherein said coated titanium dioxide particles comprise a coherent inner coating formed from a dispersing agent comprising a polymeric polybasic acid or a salt thereof and an outer coating formed from the polymerisation of one or more ethylenically unsaturated monomer(s).

26. A multi-layer film according to any of claims 21 to 25 wherein said coated titanium dioxide particles comprise a polymeric coating formed from the polymerisation of one or more ethylenically unsaturated monomer(s) wherein a dispersing agent comprising a polymeric polybasic acid or a salt thereof is incorporated into the polymeric coating during polymerisation.

27. A multi-layer film according to any of claims 24 to 26 wherein said polymeric polybasic acids are selected from polysulphonic acids, polyphosphonic acids and polycarboxylic acids, and preferably from polycarboxylic acids, or salts thereof.

28. A multi-layer film according to any of claims 24 to 27 wherein said polymeric polybasic acids are in salt form and wherein the acids are partially or fully neutralised, and/or the salts are the alkali metal salts or ammonium salts.

29. A multi-layer film according to claim 27 or 28 wherein said polymeric polybasic acids are selected from polysulphonic acids selected from lignosulphonates, petroleum sulphonates and poly(styrene sulphonates), including poly(sodium 4-styrene sulphonate), or wherein said polymeric polybasic acids are selected from polymaleic acids, polyacrylic acids, substituted acrylic acid polymers, acrylic copolymers, including copolymers of an acrylic acid with sulphonic acid derivatives, including 2-acrylamido, 2-methyl propane sulphonic acid.

30. A multi-layer film according to any of claims 24 to 29 wherein the amount of dispersing agent is from about 0.05 to about 5.0 wt %, preferably from about 0.1 to about 1.0 wt %, by weight of the titanium dioxide particle.

31. A multi-layer film according to any of claims 24 to 30 wherein said ethylenically unsaturated monomer is polymerisable in aqueous solvents, preferably wherein the polymer produced is insoluble in water and optionally cross-linked by a cross-linking agent.

32. A multi-layer film according to any of claims 24 to 31 wherein said ethylenically unsaturated monomer is selected from aliphatic and aromatic compounds containing a polymerisable unsaturated group, preferably wherein the polymerisable unsaturated group is selected from unsaturated carboxylic acids and unsaturated carboxylic acid esters.

33. A multi-layer film according to any of claims 24 to 32 wherein said ethylenically unsaturated monomer is an acidic monomer selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid or its anhydride, fumaric acid and crotonic acid, and esters of said acidic monomers, including methyl acrylate, ethyl acrylate, methyl methacrylate, butyl acrylate and ethyl methacrylate, and preferably wherein said ethylenically unsaturated monomer is selected from styrene, vinyl toluene, alpha methylstyrene, ethylene, vinyl acetate, vinyl chloride, acrylonitrile, and fluorinated monomers including fluorinated alkenes, fluorinated ethers, fluorinated acrylic and methacrylic acids and esters thereof and fluorinated heterocyclic compounds, and preferably wherein said ethylenically unsaturated monomer is selected from unsaturated carboxylic acids and unsaturated carboxylic acid esters, preferably from methyl acrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, vinyl acetate and vinyl isobutylether.

34. A multi-layer film according to any of claims 24 to 33 wherein said polymeric organic coating is cross-linked, preferably by virtue of the presence of one or more cross-linking agent(s), preferably wherein the cross-linking agent is selected from di- and poly-functional ethylenically unsaturated monomers, preferably from ethylene glycol dimethacrylate, ethylene glycol diacrylate, allyl methacrylate, allyl acrylate, 1,3-butanediol diacrylate, divinyl benzene and 1,3-butanediol dimethacrylate, preferably wherein said cross-linking agent in an amount of from about 1 wt % to about 20 wt %, preferably from about 1 wt % to about 10 wt %, based on the total weight of the ethylenically unsaturated monomer(s)

35. A multi-layer film according to any preceding claim wherein said coated titanium dioxide has a water content such that it exhibits a loss at 290 C. of no greater than 1.0%, preferably no greater than 0.5%, as measured by coulometric Karl Fischer titration.

36. A multi-layer film according to any preceding claim wherein said organic coated titanium dioxide is not hydrophobic, and is preferably hydrophilic.

37. A multi-layer film according to any preceding claim wherein the organic coating is present in an amount of from about 0.1 to about 200 wt %, preferably from about 0.1 to about 100 wt %, from about 0.5 to about 100 wt %, from about 2.0 to about 20 wt %, by weight of the titanium dioxide.

38. A multi-layer film according to any preceding claim wherein the volume ratio of the titanium dioxide particle particles to the organic coating is from 1:1 to 1:25 by volume, and preferably from 1:2 to 1:8.

39. A multi-layer film according to any preceding claim wherein said titanium dioxide particles carry an inorganic coating, and wherein the organic coating is coated onto said inorganic-coated titanium dioxide particles.

40. A multi-layer film according to any preceding claim wherein said titanium dioxide particles have a volume-distributed median primary particle diameter in the range from 0.15 to 0.25 m.

41. A multi-layer film according to any preceding claim wherein the thickness of the polyester base layer (B) is in the range from 100 to 350 m, and the thickness of the or each heat-sealable copolyester layer is in the range of from about 3 to about 30 m.

42. A multi-layer film according to any of claims 1 to 41 wherein the multi-layer film comprises a polyester base layer (B), a first heat-sealable copolyester layer (A1) disposed on a first surface of the polyester base layer and a second heat-sealable copolyester layer (A2) disposed on a second surface of the polyester base layer.

43. A multi-layer film according to any of claims 1 to 41 wherein the multi-layer film comprises a polyester base layer (B), a heat-sealable copolyester layer (A) disposed on a first surface of the polyester base layer and an ink-receptive layer disposed on the second surface of the polyester base layer, wherein said ink-receptive layer is different from said heat-sealable copolyester layer (A), and wherein the ink-receptive layer comprises an acrylic resin.

44. A multi-layer film according to claim 43 wherein the acrylic resin comprises at least one monomer derived from an ester of acrylic acid and/or an ester of methacrylic acid, preferably an alkyl ester of acrylic and/or methacrylic acid where the alkyl group contains up to ten carbon atoms, and preferably wherein the acrylic resin comprises an alkyl acrylate and an alkyl methacrylate, and preferably wherein the acrylate monomer is present in a proportion in the range from 20 to 80 mole % and the methacrylate monomer is present in a proportion in the range from 20 to 80 mole %.

45. A multi-layer film according to claim 43 or 44 wherein the thickness of the acrylic resin-containing layer is no more than 1.5 m.

46. A multi-layer film according to any preceding claim wherein the multi-layer film exhibits at least one and preferably all of the following properties: (i) an Ultimate Tensile Strength (UTS) in each of the longitudinal and transverse directions of the film of at least 1300 N/cm.sup.2; (ii) an Elongation To Break (ETB) in each of the longitudinal and transverse directions of the film of at least 250%; (iii) an F5 value in each of the longitudinal and transverse directions of the film of at least 860 N/cm.sup.2; and (iv) a heat-seal strength to itself, wherein two multi-layer films comprising a polyester base layer and a copolyester heat-sealable layer are heat-sealed together such the heat-sealable layers of each film are in contact with each other, of at least 12 N/cm, preferably at least 13 N/cm, preferably at least 14 N/cm, preferably at least 15N/cm.

47. A multi-layer card comprising a polymeric inlay layer having a first surface and a second surface, further comprising a first multi-layer film as defined in any of claims 1 to 46 which is disposed on the first surface of the polymeric inlay layer, and further comprising a first polymeric overlay layer which is disposed on said first multi-layer film, such that the layer order is polymeric inlay layer, first multi-layer film and first polymeric overlay layer.

48. A multi-layer card according to claim 47 further comprising a second multi-layer film as defined in any of claims 1 to 46 which is disposed on a second surface of the polymeric inlay layer, and optionally further comprising a second polymeric overlay layer disposed on said second multi-layer film, such that the layer order is second polymeric overlay layer, second multi-layer film, polymeric inlay layer, first multi-layer film and first polymeric overlay layer, preferably wherein said second multi-layer film is the same as the first multi-layer film, and preferably wherein said second polymeric overlay layer is the same as said first polymeric overlay layer.

49. A multi-layer card according to claim 47 or 48 wherein the or each multi-layer film comprises a single heat-sealable copolyester layer (A) and said multi-layer film is disposed in the multi-layer card such that its heat-sealable copolyester layer (A) is facing the polymeric inlay layer.

50. A multi-layer card according to any of claims 47 to 49 wherein the polymeric inlay layer and the polymeric overlay layer are independently selected from polyester, polycarbonate, polyolefin, PVC, ABS and paper, and preferably from PVC.

51. A multi-layer card according to any of claims 47 to 50 wherein said polymeric cover layer is optically clear.

52. A multi-layer card according to any of claims 47 to 51 wherein the multi-layer card has a thickness in the range from 250 to 850 m.

53. The use of the multi-layer film as defined in any of claims 1 to 46 as one or more layer(s) in a multi-layer card further comprising a polymeric inlay layer and one or more polymeric cover layer(s) as defined in any of claims 47 to 52, preferably for the purpose of improving the delamination resistance and/or durability of said multi-layer cards.

54. The use of titanium dioxide particles coated with an organic coating in a multi-layer film according to any of claims 1 to 46 for improving the delamination resistance of said multi-layer film.

55. The use according to claim 54 wherein said titanium dioxide particles are as defined in any of claims 12 to 40.

Description

EXAMPLES

[0148] In the following discussion, intrinsic viscosity values are those measured on the polymer chip unless otherwise specified.

Examples 1a and 1b

[0149] Polyester composition P1 comprised a PET polymer having IV=0.62, 4 wt % copolyesterether (Hytrel 4068; DuPont), 12.5 wt % of rutile TiO.sub.2 comprising an organic coating on its surface (TR28, available from Tioxide), and 3 wt % commercially available antioxidant.

[0150] Copolyester composition P2 comprised IPA-containing PET-based copolyester (TA:IPA=82:18) having IV=0.64 and containing 0.125 wt % china clay based on the weight of the copolyester.

[0151] An acrylic resin coating composition was prepared with the following ingredients: [0152] (i) Acrylic resin (46% w/w aqueous latex of methyl methacrylate/ethyl acrylate/methacrylamide in a molar ratio of 46/46/8 mole %; Primal AC201ER): 14.1 litres; [0153] (ii) Methoxylated melamine-formaldehyde (Cymel 385; aqueous): 7.1 litres; [0154] (iii) Ammonium nitrate (10% w/w aqueous solution): 90 ml; [0155] (iv) Alkyl (C7-C9) benzyl phthalate plasticizer (Santicizer 261A):1.5 litres; and [0156] (v) Demineralised water to 25.2 litres.

[0157] A multi-layer film comprising a base layer of polyester composition P1 and a heat-sealable layer of copolyester P2 was extruded and cast using a standard melt coextrusion system. The coextrusion system was assembled using two independently operated extruders which fed separate supplies of polymeric melt to a standard coextrusion block or junction at which these streams were joined. From the coextrusion block, the melt-streams were transported to a conventional, flat film extrusion die. The melt temperature of polyester P1 was 270 C., and the melt temperature of copolyester P2 was 265 C. The melt curtain was cast from the common coextrusion die, and then quenched in temperature onto a rotating, chilled metal drum. The cast film was collected at a process speed of about 3.8 m/min. The cast extrudate was stretched in the direction of extrusion to approximately 2.9 times its original dimensions at a temperature of 82 C. The stretched film was then coated on the surface of the polyester base layer with the acrylic resin coating composition. The coated film was then passed into a stenter oven at a temperature of 115 C. where the film was dried and stretched in the sideways direction to approximately 3.2 times its original dimensions. The biaxially stretched film was heat-set at about 230 C. The final film was 152 m in thickness and comprised three layers having an ABC structure, wherein the heat-sealable copolyester layer (A) was approximately 15 m thick, and the acrylic ink-receptive layer (C) was approximately 0.04 m thick. This film is referred to as Example 1a.

[0158] The process was also used to make a further multi-layer film, referred to herein as Example 1b, which had a final thickness 254 m, and in which the heat-sealable copolyester layer and the acrylic ink-receptive layer (C) were approximately the same thicknesses as Example 1a.

Comparative Examples 1a (152 m) and 1b (254 m)

[0159] Multi-layer films similar to those described in Example 1 were prepared, except that anatase TiO.sub.2 (AHR-F, available from Clariant), which does not have an organic coating, was used in the base layer. The film is therefore essentially the same as Example 4 in U.S. Pat. No. 7,232,602-B, and it was this structure on which the present inventors sought to improve.

Comparative Example 2 (254 m)

[0160] A multi-layer film similar to that described in Comparative Example 1b was prepared, except that anatase TiO.sub.2 (1071, available from Kronos), which does not have an organic coating, was used in the base layer.

[0161] The optical properties of the 254 m films of Example 1b and Comparative Examples 1b and 2 were tested as described herein. The results are presented in Table 1 below and demonstrate that the films of the present invention exhibit optical properties which are comparable to the current commercially available films, as represented by Comparative Example 1b, and well within the targeted and desirable optical properties.

TABLE-US-00001 TABLE 1 Film Identity L* a* b* Comp. Example 1b 93.34 1.26 3.17 Comp. Example 2 93.44 1.18 3.71 Example 1b 93.46 1.42 2.30

[0162] The optical density of the 152 m multi-layer films of Example 1a and Comparative Example 1a were measured as described herein. The optical density of the Example 1a film of the present invention exceeded 1.0 and was unexpectedly greater than that of the film of Comparative Example 1a.

[0163] The optical density of the 254 m multi-layer films of Example 1b and Comparative Example 1b were also measured as described herein. The optical density of the Example 1b film of the present invention exceeded 1.7 and was unexpectedly greater than that of the film of Comparative Example 1b.

[0164] Given that it was known in the art that anatase TiO.sub.2 normally provides superior optical properties in polyester films compared to rutile TiO.sub.2, these results are particularly surprising.

[0165] The delamination strength of the Examples was assessed using the test method described herein. It was observed that failure of the laminate normally occurs just beneath the surface of a polyester base layer, rather than at the interfacial boundary of the heat-sealable copolyester layers with each other, or the interfacial boundary of heat-sealable layer and polyester base layer. The results are presented in Table 2 below, and show that the 152 m multi-layer film of Example 1a unexpectedly exhibits statistically significantly greater cohesive strength within the polyester base layer, and hence provides significantly greater delamination resistance, compared to the current commercially available conventional films as represented by Comparative Example 1a. The same improvement is observed with the 254 m film of Example 1b when compared to Comparative Examples 1b and 2.

TABLE-US-00002 TABLE 2 Thickness Average Delamination Sample (m) strength (N/cm) Comparative Example 1a 152 11.1 Example 1a 152 14.3 Comparative Example 1b 254 9.8 Comparative Example 2 254 9.6 Example 1b 254 15.1

[0166] The mechanical properties of the films of Example 1b and Comparative Examples 1b and 2 were tested as described herein and the results are shown in FIG. 3 (UTS), FIG. 4 (ETB) and FIG. 5 (F5 value). The abbreviations MD and TD refer to the machine and transverse directions of the film, respectively. The results demonstrate the unexpectedly superior mechanical properties and cohesive strength of the films of the present invention.

[0167] The delamination susceptibility of multi-layer cards according to the present invention was tested using the corner impact test described herein, with up to 16 impacts. The results are presented in Table 3 below and demonstrate the unexpectedly superior delamination and tensile properties of the multi-layer cards of the present invention.

TABLE-US-00003 TABLE 3 Film Identity of the Card Corner Impact/16 Failure Mode Comp. Example 1b 12 3 Delamination; 1 Brittle Comp. Example 2 14 Delamination Example 1b 16 No failures; no delamination; no brittleness

[0168] The films and cards of the present invention thus exhibit unexpectedly superior delamination resistance, security and tamper-resistance.

Example 4

[0169] A multi-layer film comprising a base layer of polyester composition P1 above and two outer layers of copolyester composition P2 was extruded and cast using a standard melt coextrusion system. The coextrusion system was assembled using two independently operated extruders which fed separate supplies of polymeric melt to a standard coextrusion block or junction at which these streams were joined. From the coextrusion block, the melt-streams were transported to a conventional, flat film extrusion die. The melt temperature of polyester P1 was 270 C., and the melt temperature of copolyester P2 was 265 C. The melt curtain was cast from the common coextrusion die, and then quenched in temperature onto a rotating, chilled metal drum. The cast extrudate was stretched in the direction of extrusion to approximately 2.9 times its original dimensions at a temperature of 82 C. The cooled stretched film was then passed into a stenter oven at a temperature of 115C where the film was dried and stretched in the sideways direction to approximately 3.9 times its original dimensions. The biaxially stretched film was heat-set at about 230 C. The final film was about 254 m in thickness and comprised three layers having an ABA structure, wherein the outer layers (A1) and (A2) were each 15 m thick. The film exhibited excellent optical, properties, mechanical properties and delamination strength, measured according to the test methods described herein. Multi-layer cards incorporating these multi-layer films exhibited excellent overlay peel strength and low delamination susceptibility.