Laminate structure

Details Laminate structure Laminate structure

2000-05-05

2001-11-13

Lam, Cathy (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C428S913300, C428S914000, C428S915000, C283S072000, C283S083000, C283S100000

Reexamination Certificate

active

06316082

ABSTRACT:

The present invention relates to the field of laminated materials and, in particular, to laminates for stamping foils and security threads.
Stamping foils, including hot-stamping foils, are used to provide decorative surface effects on articles and typically comprise a film laminate of a carrier layer, a release layer, a lacquer or colour layer, a light-reflecting layer usually formed from aluminium, and an adhesive layer or size coat. During stamping, the foil is positioned adjacent to the surface of the article to be marked and heat and/or pressure is applied. This causes the foil to adhere to the surface of the article via the adhesive layer. At this stage, the carrier layer is designed to separate from the other layers and this is facilitated by the release layer. After the carrier layer has been separated from the other layers, the uppermost layer of the foil on the surface of the article is the lacquer layer. This is a transparent or translucent colour layer through which the underlying metal layer is viewed. The lacquer layer may have a pre-printed design thereon. The metal layer provides the foil with reflectiveness and opacity.
Holographic hot-stamping foils find application in the packaging and security industries. A holographic element containing a pattern or information, such as letters, numerals, graphic symbols or the like, is provided within the laminate structure.
Conventional holographic stamping foils are made by the following procedure. A Polyester carrier layer has a release layer applied on to its surface using, for example, direct gravure coating. Next, a thermo-plastic lacquer layer is applied on top of the release layer, again by direct gravure coating for example. The top (free) surface of the thermo-plastic lacquer layer is then holographically embossed using heat and pressure in combination with nickel shims engraved with a holographic pattern or image. Once embossed, the lacquer layer is then metallised with aluminium in a standard metal evaporator to render the foil reflective. Alternatively, the lacquer layer may be metallised prior to the embossing step. A heat and/or pressure activated adhesive or size coat is then applied to form the completed stamping foil. For partially transparent holographic foils the aluminium layer may be discontinuous or replaced by a transparent material of high refractive index which causes a percentage of the incident light to be transmitted.
Security threads or filaments are used for authenticating security documents such as bank notes and generally have a similar laminate structure to the stamping foils described above, but usually do not contain a release layer or an adhesive layer.
U.S. Pat. Nos. 5,044,707, 5,145,212 and 5,411,296 relate to partially transparent holographic foils for authenticating security documents. The foil disclosed in each of these patents comprises a discontinuous metallic reflective layer formed from a plurality of discrete aluminium portions and an overlying continuous lacquer layer having a surface relief pattern formed therein. If the lacquer layer has a yellow dye added then this can give the underlying discrete aluminium portions a gold-like appearance. In this case, however, the regions between the discrete aluminium portions will have a yellow colour. Consequently, when the foil is applied on to the surface of a substrate, the surface will appear yellow in those regions not covered by the aluminium portions. It will be appreciated that this effect is not always desired. For example, if the surface of the substrate comprises a photograph, the coloured lacquer layer will act as a yellow filter through which the photograph is viewed and this will affect the photographic image.
In a first aspect, the present invention provides a laminate for a security thread comprising a translucent or transparent support layer, a translucent or transparent coloured first lacquer layer, a translucent or transparent second lacquer layer disposed between the support layer and the first lacquer layer and a light-reflecting layer adjacent to the first lacquer layer, wherein the first lacquer layer is incomplete in a region substantially in register with an incomplete region in the light-reflecting layer such that the support layer is partially covered by the first lacquer layer and the light-reflecting layer.
If desired, the support layer may comprise a colouring agent, such as a dye, pigment or colourant.
In a second aspect, the present invention provides a laminate for a stamping foil comprising a carrier layer, a translucent or transparent coloured first lacquer layer, a translucent or transparent second lacquer layer disposed between the carrier layer and the first lacquer layer and a light-reflecting layer adjacent to the first lacquer layer, wherein the first lacquer layer is incomplete in a region substantially in register with an incomplete region in the light-reflecting layer such that the carrier layer is partially covered by the first lacquer layer and the light-reflecting layer.
The stamping foil is preferably a hot-stamping foil.
In both aspects of the present invention, the second lacquer layer may comprise a colouring agent, such as a dye, pigment or colourant.
In both aspects of the present invention it will be appreciated that the substantially in register incomplete regions in the first lacquer layer and the light-reflecting layer are complemented by substantially in register complete regions in the said layers. The in register complete regions in the said layers may comprise a plurality of discrete portions or may be continuous.
It will be appreciated that the laminate according to the present invention is not limited solely to the layers described herein and may also include additional layers.
Preferably, the substantially in register incomplete regions in the first lacquer layer and the light-reflecting layer result in a visual element which comprises a pattern, design, marking or a combination of two or more thereof. When the visual element comprises a marking, this may be in the form of alpha-numeric characters, micro-print, graphic symbols, indicia or the like. The visual element may be formed by the substantially in register incomplete regions in the first lacquer layer and the light-reflecting layer or by the complementary substantially in register complete regions or by a combination of the incomplete and complete regions. For instance, the visual element could comprise the alpha-numeric characters “A1” and the shape of one or both of these characters could be provided by the substantially in register complete regions.
A pattern, design, marking or a combination of two or more thereof may be provided on a surface of the first lacquer layer and may be pre-printed thereon. The pattern, design or marking may be three-dimensional and may be formed as a surface relief. In this case, the pattern, design or marking is preferably provided on the surface of the first lacquer layer which faces the light-reflecting layer. The three-dimensional pattern, design or marking may be contained in a hologram or a diffraction grating or a combination thereof. The three-dimensional pattern, design or marking may be formed by processes conventional in the art, such as embossing or stamping. The marking may be in the form of alpha-numeric characters, micro-print, graphic symbols, indicia or the like. Similarly, the second lacquer layer may also have a pattern, design, marking or a combination of two or more thereof as described above.
Advantageously, the laminate according to both aspects of the present invention further comprises a protective layer on a surface of the light-reflecting layer, which surface faces away from the first lacquer layer. The protective layer may be incomplete in a region substantially in register with the incomplete region in the light-reflecting layer and may comprise a resist material. If desired, the protective layer may comprise a colouring agent, such as a dye, pigment or colourant.
The light-reflecting layer of the laminate of the present invention is preferably formed f

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