Security laminates with interlaminated transparent embossed polymer hologram

Abstract

A method for interlaminating a transparent embossed hologram, the transparent embossed hologram comprising a support having two sides, at least one of the two sides either itself being embossed or having a layer thereon which is embossed and a layer of a HRI-material contiguous with the embossed side or embossed layer, comprising the steps of: a) providing the outermost surface of the layer of inorganic HRI-material with a layer of an adhesive composition containing a solution or dispersion of at least one polymer in an organic solvent medium; b) drying the layer of the adhesive composition on the outermost surface of the HRI-material thereby providing a conditioned outermost surface of the layer of inorganic HRI-material with a transparent continuous adhesive layer; and c) laminating the transparent continuous laminatable layer to a foil, wherein the organic solvent medium is selected from the group consisting of ketones, ethers, heterocyclic ethers, lactams, amides, halo-aliphatic compounds, nitriles and esters; wherein at least one of the support and the foil is transparent; and wherein the HRI material is a material with a refractive index of at least 0.3 higher than that of the embossed material. A laminate and a security document comprising the laminate obtainable by the above-disclosed process are also disclosed.

Description

FIELD OF INVENTION[0001]This invention relates to security laminates with interlaminated transparent embossed polymer hologram with an inorganic HRI-material-coating and a method for realizing same.BACKGROUND OF THE INVENTION[0002]Security laminates are traditionally used to protect documents or packages to ensure that the underlying items are not altered by containing an authentification feature making them difficult to counterfeit. Security laminates are particularly useful on identification cards such as driver's licenses, ID-cards and passports, and on other important documents such as certificates of title. Security laminates are also useful as tamper proof seals on medications, video cassettes, and compact discs. Five features are particularly important when producing and using security laminates. First, once applied to an article it is important that the laminate is difficult to remove to ensure that the underlying item is not altered or subjected to tampering. Second, a desi...

AI Technical Summary

Benefits of technology

[0017]Moreover, adhesion to a microporous surface would conventionally be viewed as requiring a degree of penetration of the microporous layer to provide anchor points for the layer, which as pointed out above will inevitably reduce the brilliance of the hologram.

[0018]Surprisingly it has been found that a transparent polymeric coating applied from a solution of a polymer in a theta solvent for that polymer or polymer mixture not only provides good adhesion to a polyethylene, polyethylene terephthalate, PET, PVC or polycarbonate foil, but also at least maintains the brilliance of the hologram a thoroughly counter-intuitive observation i.e. an adhesion is realized between the HRI-layer and the adjoining polyethylene foil which resists delamination in the standard delamination tests according to ISO 10373-1 and the cohesion of the HRI-layer is also able to resist splitting under the conditions of the standard delamination tests and a visually perceivable increase in brilliance is observed.

Problems solved by technology

Commercially available transparent embossed holograms coated with an inorganic HRI-material do not lend themselves to tamper-proof interlamination in the multiplex system making up a multiplex identity document.

Using standard adhesives it was found impossible to obtain sufficient adhesion of the outermost surface of the HRI-layer, e.g. a ZnS- or a TiO2-layer, to a polyethylene or PETG film to avoid integral delamination.

The brilliance of the hologram is adversely affected by penetration of a lower refractive index entity into the pores of this ultrathin HRI-layer.

Such porous layers are intrinsically weak.

Macroscopic delamination of the HRI layer includes both a failure of the bond between the HRI-layer and foil to which it is laminated and the HRI being unable to resist splitting under the conditions of the standard delamination tests.

Moreover, adhesion to a microporous surface would conventionally be viewed as requiring a degree of penetration of the microporous layer to provide anchor points for the layer, which as pointed out above will inevitably reduce the brilliance of the hologram.