CA3145610A1 - Security feature with metallization for security documents - Google Patents

Abstract

Disclosed herein is a monolithic laminated multi-layer thermoplastic polymer security document and method of making same with an improved, difficult-to-counterfeit security device. The security device comprises at least one selective metallized feature located on an embedded or enclosed surface within the monolithic document, by virtue of the fact that the polymer layers are laminated together. The embedded or enclosed surface comprises a selectively metallized feature. In some embodiments, the security device may comprise the selectively metallized feature in combination with one or more laser engraved data.

Description

SECURITY FEATURE WITH METALLIZATION FOR SECURITY DOCUMENTS
FIELD OF THE INVENTION
The invention relates generally to a security feature for security documents.
In particular, the present invention provides security devices comprising selectively metallized portions, for use in printed security documents including but not limited to identification cards, driver's licenses, passports, and banknotes.
BACKGROUND
Security documents such as identification cards, data pages, driver's licenses, passports and banknotes may include one or more features formed by printing, laser engraving and/or by applying metallization. For example, a security document in the form of an identification card, a driver's license or personal identification sheet of a passport may be made of a thermoplastic polymer substrate and may bear data or a feature that is laser engraved onto the thermoplastic substrate. In order to render the security feature more difficult to copy or counterfeit, metallization, including complex selective or patterned metallization may be incorporated as well.
Integration of the metallization with other security features such as a window, multiple laser images (MLI), personalization, optically variable devices, or background print, etc will make the security device difficult to counterfeit. Screen/selective metallization techniques can be used to metallize polymer surfaces to achieve complex patterns which are difficult to achieve by common commercial flood metallization process.
Finsted (U520180282551A1) describes a method for producing metallized polycarbonate (polymer) sheets. A mask layer is applied onto the polymer surface by means of a printing process. Preferably, the printing process is a flexographic printing process with 400Ipi or higher anilox. The most preferred anilox is 1000Ipi+, which would produce a higher resolution print. The mask layer comprises a water or solvent soluble ink.
Once the mask layer has dried, flood metallization is applied over the mask layer. In the third step, the Date Recue/Date Received 2022-01-14 mask layer is washed off by water or solvent to achieve the final screen/selective metallized image.
The manufacture of polycarbonate-based security documents involves collating together layers of polycarbonate, then exposing them to high heat (-160 C) and pressure during lamination. The polycarbonate softens at 160 C and adjacent layers fuse together to form a monolithic document. In order to achieve such fusion, it is important that sufficient surface area of the polycarbonate is exposed in each layer. Areas which are printed or metallized may not fuse together. In the absence of enough exposed polycarbonate surface area, adhesive may be used to improve the bonding strength between layers.
However, the use of adhesive is not recommended for polycarbonate-based security documents. Layers secured together by means of adhesive can potentially be separated, thereby compromising the security of the document.
The flood metallization process that is typically used for metallizing polycarbonate will produce a polycarbonate film with 100% metal at the surface. Such metallized films would not be suitable for forming a monolithic polycarbonate document, as the metallization would prevent adhesion or bonding between layers of polycarbonate during lamination.
Thus, to adhere metallized polycarbonate layers, adhesive would have to be used to improve bonding strength.
Moreover, if it is desired to laser engrave a security document, for example to add personalized data, the laser engraving process may cause bubbling if the polymer layers are insufficiently bonded or fused together. Laser engraving may cause gas/pressure within the document or between layers of the document (due to localized combustion). If the document, due to metallization, includes unbonded or unfused portions, the gas or pressure will lead to delamination/bubbling/lifting of layers in a localized area, thus compromising security of the document.
Accordingly, there is a need for a method to incorporate metallized thermoplastic polymer layers into a monolithic laminated/fused security document, while maintaining the ability for the polymer layers to fuse together, thus avoiding the need for adhesive.

2 Date Recue/Date Received 2022-01-14 Summary Disclosed herein is a monolithic security document comprising a security device. The security document comprises a substrate having at least three thermoplastic polymer layers laminated together to form the monolithic document. At least one layer is transparent or semi-transparent and laser engravable, and at least one layer is a core layer. At least one embedded or enclosed surface is within the monolithic document, by virtue of the fact that the polymer layers are laminated together. The embedded or enclosed surface comprises a selectively metallized feature. The security device comprises the selectively metallized feature. In some embodiments, the security device may comprise the selectively metallized feature in combination with one or more laser engraved data or features on the at least one laser engravable layer.
In an embodiment, the security document is laser engraved to add data for personalization of the document.
In an embodiment, the security device further comprises a lenticular lens. The security document further comprises a non-laser engravable transparent or semi-transparent filler layer, and the core layer is opaque. Further, first and second transparent or semi-transparent laser engravable layers are located, respectively, above and below the filler layer, and the second laser engravable layer comprises one or more laser engraved data or features. The selectively metallized feature is located either on the filler layer or on a bottom surface of the first laser engravable layer, and comprises at least one gap in metallization in registration with the lenticular lens and through which the one or more laser engraved data or features are visible.
The security document is laser engraved, for example, during the personalization process. The laser personalization creates slits/gaps in the metal layer and black marking on the laser engravable layer that is located beneath the metal layer. The laser engraved images will be visible through the lenticular lens located on the surface of the security device. The flip effect of the security device will be optimal due to the presence of the metal layer and the slit between the lens and laser engraved data, which allows for a parallax effect.

3 Date Recue/Date Received 2022-01-14 In an embodiment, the monolithic security document may comprise a security device which is a combination of a laser engraved tactile data or feature on the at least one laser-engravable layer, and the selectively metallized feature. In some embodiments, laser engraved non-tactile data may also be included. In an embodiment, a laser engravable layer comprises the selectively metallized surface ¨ if the selectively metallized surface is on the outermost layer of the document, it must be located on the inner surface of such layer. In an embodiment, the laser engravable layer may be laser engraved with tactile and non-tactile text. The metal can also be ablated using the same laser engraving process which creates the tactile or non-tactile text. The security device, such as personalized information, may therefore include a combination of tactile data, non-tactile data and laser ablated metal.
In an embodiment, the core layer is an opaque polycarbonate film. At least one transparent or semi-transparent layer must be located, respectively, above and below the opaque core layer. The number of transparent or semi-transparent films on either side of the opaque core layer is determined by the security features and print layers to be used.
In an embodiment, the thermoplastic layers are laminated together under heat and pressure to create a monolithic card or document.
In an embodiment, the thermoplastic layer to be metallized has a surface roughness (Ra value) of less than 5pm, or less than 3pm, prior to metallization.
Also disclosed herein is a method for making a monolithic security document comprising a security device. The method comprises the steps of applying a soluble coating over at least a portion of a first surface of a thermoplastic substrate layer;
applying flood metallization to the first surface; and washing the first surface to remove the soluble coating, thereby forming a selectively metallized feature on the first surface of the thermoplastic substrate layer. The thermoplastic substrate layer is laminated together with at least two additional thermoplastic substrate layers, including a core layer, through application of heat and pressure, such that the selectively metallized feature is embedded or enclosed within the fused thermoplastic substrate layers, thereby forming the monolithic security document. The selectively metallized substrate layer and/or at least

4 Date Recue/Date Received 2022-01-14 one of the additional thermoplastic substrate layers may be transparent or semi-transparent and laser engravable. The laser engravable layer(s) is/are then laser engraved, for example to add personalized data. The security device comprises the selectively metallized feature, optionally in combination with one or more laser engraved data or features on the laser engravable layer.
In an embodiment, the laminating step further comprises forming a lenticular lens on a surface of the security document. Further, the thermoplastic substrate layer or at least one of the least two additional thermoplastic substrate layers comprises a non-laser engravable transparent or semi-transparent filler layer. First and second transparent or semi-transparent laser engravable layers are located, respectively, above and below the filler layer. The selectively metallized feature is located either on the filler layer or on a bottom surface of the first laser engravable layer. The laser engraving step comprises laser engraving one or more data or features onto the second laser engravable layer, thereby ablating a portion of the metal and creating at least one gap in metallization in registration with the lenticular lens, through which the one or more laser engraved data or features are visible.
In an embodiment, the laser engraving step further comprises laser ablating the selectively metallized feature, and laser engraving tactile data onto the at least one laser engravable layer. The security device comprises a combination of a laser engraved tactile data or feature on the at least one laser engravable layer and the selectively metallized laser ablated feature. Optionally, laser engraved non-tactile data may be present as well.
In an embodiment, the laser engraving step further comprises laser ablating the selectively metallized feature, for example to personalize the security document.
In an embodiment, the laser ablated selective metallization or the combination of tactile laser engraving and laser ablated selective metallization may be used for personalization of the security document, such as for an identification number.
In an embodiment, the thermoplastic substrate layers are polycarbonate layers.
Non-polycarbonate layers can also be incorporated such as polyurethane (PU) film and/or Date Recue/Date Received 2022-01-14 Polyethylene terephthalate glycol (PETG) film. In an embodiment, the core layer is opaque, but in other embodiments the core layer may be semi-transparent or transparent.
In an embodiment, the thermoplastic layer to be metallized has a surface roughness (Ra value) of less than 5pm, or less than 3pm, prior to metallization.
Brief Description of the Drawings Fig. 1 illustrates a cross-sectional view of an exemplary construction for a security document comprising selective metallization in combination with a lenticular lens.
Figs. 2a and 2b illustrate cross-sectional views of an exemplary construction for a security document featuring a lenticular lens and selective metallization.
Figs. 3a and 3b illustrate an exemplary embodiment of a security document comprising selective metallization in the window and a personalized photographic image.
Figs. 4a and 4b illustrate exemplary embodiments of patterns or designs for security documents, created by selective metallization.
Fig. 5 illustrates an exemplary embodiment of a security document, wherein a portion of the document is metallized prior to laser ablation.
Fig. 6 is a close-up image of the ID number portion of the security document illustrated in Fig. 5.
Fig. 7 illustrates the security document of Fig. 5 after laser ablation has been used to create the ID number.
Detailed Description As used herein, the term "thermoplastic substrate" or "polymer" refers to thermoplastic polymers which are capable of fusing together under heat and pressure to form a monolithic document. Suitable thermoplastic substrates include polycarbonate or polycarbonate in combination with polyurethane and/or polyethylene terephthalate glycol (PETG). However, other polymers may be suitable as well.

Date Recue/Date Received 2022-01-14 The manufacture of the security documents described herein involves collating together layers of thermoplastic polymer, then exposing them to high heat (-160 C) and pressure during lamination. The polymer softens at 160 C and adjacent layers fuse together to form a monolithic document.
By selectively metallizing only a portion of the polymer, it is possible to design a metallization pattern which allows for enough of the polymer surface to be exposed for bonding during lamination. Therefore, the resulting document would be less vulnerable to tampering or alteration. Further, during laser engraving of the metal, blistering will not occur or will be minimal. Fused thermoplastic polymer will prevent or minimize bubbling or blistering.
As used herein, the term "selective metallization" is defined as metallization of a specific, less than whole, portion of a thermoplastic substrate layer. The metallization may be accomplished by, for example, applying a mask layer is applied onto a substrate surface by means of a printing process. The mask layer comprises a water or solvent soluble ink.
Once the mask layer has dried, flood metallization is applied over the mask layer. Finally, the mask layer is washed off by water or solvent to achieve the final selective metallized image.
Metallization refers to the application of a thin layer of metal by, for example, chemical vapor deposition from a radiation sensitive precursor. In an embodiment, the metal comprises aluminum. Other suitable metals may also be used, such as gold, silver, vanadium, copper, zinc, tin, chromium, or titanium. Alloys of suitable metals may also be used.
Both glossy and matte polymer films can be selectively metallized in accordance with the methods described herein. Glossy polymer film, when metallized, will produce a mirror-like effect, while matte polymer will not produce such an effect. For application of the mask layer, a 1000 1pi (lines per inch) or higher anilox may be used in order to obtain higher resolution images. The volume of ink deposited onto the polycarbonate film would in that case be low, since the higher the number of anilox, the lower the volume of ink transferred to the print plate. Matte films have higher roughness at the surface thereof, Date Recue/Date Received 2022-01-14 i.e. there will be peaks and valleys. When a low volume of ink is used, the amount of ink used may be insufficient to fill the valleys. Therefore, application of a mask layer on a matte polycarbonate film may be ineffective since portions of the film surface intended to be covered by the mask layer will instead be exposed. Exposed portions not covered by the mask layer will result in metallization in the unintentionally unmasked areas, thereby causing "noise" in the masked area. Therefore, it is preferable in this process to use a glossy film, or a matte film with low roughness. For example, in an embodiment, a film having a surface roughness (Ra value) of less than 5pm, or less than 3pm, is preferred.
In an embodiment, the selectively metallized image includes at least a portion of non-metallization in order to allow for exposure of polymer within the selective metallization design. This allows for sufficient fusing of polymer layers to produce a monolithic document as well as reduced blistering upon laser engraving of the document.
As illustrated in Figure 1, first and second layers of transparent or semi-transparent laser engravable polymer are located, respectively, above and below a non-laser engravable filler layer. In the figure, selective metallization is applied to the filler layer, but it is possible that the selective metallization may be applied to the inner surface of the first laser engravable layer. A core polymer layer is also present, which in the figure is opaque.
In an embodiment, as further discussed below, lenticular lenses are used to produce laser engraved images with an illusion of depth or the ability to change or move as the image is viewed from different angles.
As illustrated in Figures 2a and 2b, where the security document comprises lenticular personalization, metallization may be used to achieve an enhanced effect. To achieve lenticular personalization on security documents, a lens is initially formed at the surface of the document. Typically, this is achieved by laminating the card with a lamination plate that has the lens structure engraved/formed on it.
The lenticular lens has a focal distance (focal length). The second laser engravable layer is placed at the focal distance, and a filler layer may be included between the lenticular lens and the laser engravable layer to ensure that the laser engravable layer is correctly Date Recue/Date Received 2022-01-14 positioned vis-a-vis the lenticular lens. The density of the laser beam is higher at the focal distance than it is near the lens.
In the second step, the second laser-engravable polymer layer is laser-engraved with one or more data features at various angles though the lens. Typically, two separate data features are engraved, such as a secondary photo and an ID number. For example, the secondary photo may be engraved at a +12 angle and the ID number may be engraved at a -10 angle. Each personalized laser engraved data or feature will be visible through the lens at specific angles. The transition/flip effect and the quality of the flip is in part determined by the quality of the lenticular lens, the angle of engraving, and the thickness of the laser engravable layer. The transition/flip effect can be improved by placing a metal layer between the lens and laser engravable layer. During the step of personalization by laser engraving, the laser will form a slit on the metal layer (by ablating the metal) before engraving the laser engravable layer located underneath the metal layer. When viewing the laser engraved data, the slit will control the visibility of the engraved data only at a narrow view angle due to the parallax effect. Due to the narrow view angle, it is possible to engrave more than two data sets or data features under the lenticular lens and still able to achieve a good flip affect. This is otherwise difficult to achieve (i.e.
without a metallized layer).
As illustrated in Figures 3a and 3b, selective metallization may be used to add a personalized security feature such as a photograph. The photograph may be combined with a window in the security document. As shown in Figure 3a, selective metallization is applied only in the window portion, while in Figure 3b the metallized portion has been laser ablated to create a photographic image.
Without selective metallization, metallization can be incorporated into a security document by, for example, hot-stamping, or by plugging a metallized polymer.
This is costly and/or necessitates the use of adhesive layers. As previously discussed, flood metallization, which is currently commonly used, covers the entire polymer layer, rendering it difficult to use where a monolithic document is desired. By contrast, selectively adding metal by vapor deposition onto the polymer allows the metal to bond to the surface of the polymer without adhesive, and is cost effective. The selective Date Recue/Date Received 2022-01-14 metallization process, as discussed, only results in metallization where the mask layer is not present, thus allowing for selection of the portion or portions on the document for metallization. In an embodiment, the resolution of the metallized image or feature can be up to 1200dpi. This selective metallization by vapor deposition method would eliminate use of adhesive on one or both sides of the polymer, depending on how the metallization is selected or designed. Complex patterns can be created as well, using selective metallization by vapor deposition, for example as shown in Figs. 4a and 4b.
Selective metallization may be used when adding text to the security document.
Text may include personalized features such as an ID number. As illustrated in Figs. 5-7, for example, a portion of an ID number may be metallized. In the illustrated embodiment, selective metallization is used for the last 5 digits of the ID number.
Initially, metallization may be applied over the entire area where the number is to appear. Next, the security document may be personalized by laser ablation to remove the metal around the ID
number "80904". Further, a portion or portions of the personalized information may be laser engraved so as to be tactile(see Fig. 7). Tactile effect laser engraving disrupts the top surface of the security document and can be felt as a raised area with one's fingertips.
The combination of tactile, non-tactile, and metallized personalization is possible with laser engraving and would be difficult to counterfeit by other means.
Moreover, registration (alignment) of these features would be difficult to achieve using counterfeiters' methods. For example, to create a similar effect, counterfeiters may use inkjet/thermal transfer for black print, UV curable inkjet for tactile print and hot-stamping/screen print for metallization.
The above disclosure and figures are intended to be illustrative and not exhaustive. The description will suggest many variations and alternatives to one of ordinary skill in the art.
Those familiar with the art may recognize other equivalents to the specific embodiments described herein within, without departing from the spirit and scope thereof.
Date Recue/Date Received 2022-01-14

Claims (10)

We claim:

1. A security document comprising a security device, the security document comprising at least three thermoplastic substrate layers, wherein the at least three thermoplastic substrate layers are fused together to form a monolithic document, wherein the at least three thermoplastic substrate layers comprise at least one transparent or semi-transparent laser engravable layer, a core layer and at least one embedded or enclosed surface within the monolithic document, the embedded or enclosed surface comprising a selectively metallized feature, and wherein the security device comprises the selectively metallized feature, optionally in combination with one or more laser engraved data or features on the at least one laser engravable layer.

2. The security document of claim 1, wherein the security device comprises a lenticular lens, wherein the at least three thermoplastic substrate layers further comprise a non-laser engravable transparent or semi-transparent filler layer, and the core layer is opaque, wherein the at least one laser engravable layer comprises at least first and second laser engravable layers located, respectively, above and below the filler layer wherein the second laser engravable layer comprises one or more laser engraved data or features, and wherein the selectively metallized feature is located either on the filler layer or on a bottom surface of the first laser engravable layer, and comprises at least one gap in metallization in registration with the lenticular lens and through which the one or more laser engraved data or features are visible.

3. The security document of any one of claims 1-2, wherein personalization of the security document is achieved at least in part by the laser engraved data.

Date Recue/Date Received 2022-01-14

4. The security document of any one of claims 1-3, wherein the at least three thermoplastic substrate layers comprise polycarbonate layers.

5. The security document of claim 1, wherein the selectively metallized feature is laser ablated, and the security device comprises a combination of laser engraved tactile data or text and the laser ablated selectively metallized feature.

6. A method for making a monolithic security document comprising a security device, the method comprising the steps of:
a) applying a soluble coating over at least a portion of a first surface of a thermoplastic substrate layer;
b) applying flood metallization to the first surface;
c) washing the first surface to remove the soluble coating, thereby forming a selectively metallized feature on the first surface of the thermoplastic substrate layer;
d) laminating the thermoplastic substrate layer together with at least two additional thermoplastic substrate layers, including a core layer, through application of heat and pressure, such that the selectively metallized feature is embedded or enclosed within the fused thermoplastic substrate layers, thereby forming the monolithic security document, wherein the thermoplastic substrate layers comprise at least one transparent or semi-transparent laser engravable layer; and e) laser engraving at least the laser engravable layer, thereby forming the security device which comprises the selectively metallized feature, optionally in combination with one or more laser engraved data or features on the at least one laser engravable layer.

7. The method of claim 6, wherein the laminating step further comprises forming a lenticular lens on a surface of the security document, Date Recue/Date Received 2022-01-14 wherein the thermoplastic substrate layer or the at least two additional thermoplastic substrate layers comprise a non-laser engravable transparent or semi-transparent filler layer and the core layer is opaque, wherein the at least one laser engravable layer comprises first and second laser engravable layers located, respectively, above and below the filler layer, wherein the selectively metallized feature is located either on the filler layer or on a bottom surface of the first laser engravable layer, wherein the laser engraving step comprises laser engraving one or more data or features onto the second laser engravable layer, thereby ablating a portion of the metal and creating at least one gap in metallization in registration with the lenticular lens, through which the one or more laser engraved data or features are visible.

8. The method of any one of claims 6-7, wherein personalization of the security document is achieved at least in part by the laser engraving step.

9. The method of claim 7 or 8, wherein the laser engraving step further comprises laser ablating the selectively metallized feature, and laser engraving tactile data onto the at least one laser engravable layer, and wherein the security device comprises:
a combination of the laser engraved tactile data or feature on the at least one laser engravable layer, the laser ablated selectively metallized feature, and optionally, laser engraved non-tactile data.

10. The method of any one of claims 6-9, wherein the thermoplastic substrate layers comprise polycarbonate.

Date Recue/Date Received 2022-01-14