Security feature and method of manufacture thereof

Abstract

The present disclosure relates to methods of producing substrate level multi-tonal images.

Claims

1. A security feature comprising: a substrate including a first surface and a second surface, a first image layer applied to the first surface of the substrate, by depositing a coloured ink in selected regions of the substrate to form a first image, a second image layer applied to the substrate, wherein the second image layer is a layer of semi-opaque material including transparent or translucent regions in which the semi-opaque material is omitted or reduced, at least some of the transparent or translucent regions overlap with the first image, wherein the first and the second image layer collectively define a coloured multi-tonal image that is visible both in transmission and reflection when the security feature is viewed from a first side of the substrate, and wherein when the security feature is viewed from a second side of the substrate a mono-tonal version of the first image layer is visible, both in reflection and transmission.

2. The security feature of claim 1, wherein coloured ink is deposited on less than 50% surface area of the substrate, or less than 30%, or less than 20%.

3. The security feature of claim 1, wherein the first and the second image layers are provided on opposing first and second surfaces of the substrate, or on the same surface of the substrate.

4. The security feature of claim 1, wherein the transparent or translucent regions of the second image layer are arranged to form one or more tonal values of the multi-tonal image.

5. The security feature of claim 4, wherein the transparent or translucent regions of the second image layer correspond to darker tone(s) of the multi-tonal image compared to non-transparent or non-translucent regions of the second image layer.

6. The security feature of claim 4, wherein the first image layer defines a mono-tonal version of the multi-tonal image, and the second image layer provides tonal variations for the mono-tonal image.

7. The security feature of claim 1, wherein the first and the second image layers are both printed using a gravure printing unit in an in-line printing process.

8. The security feature of claim 7, wherein the printing surface of the gravure printing unit includes an array of ink cells configured to receive ink during an image printing process, wherein the ink cells are modulated to form tonal variation that is required to produce a multi-tonal effect.

9. The security feature of claim 1, wherein one or more additional layers of opacifying material are applied to the first and/or the second surface of the substrate.

10. The security feature of claim 1, wherein the multi-tonal image appears substantially similar in reflection and transmission when viewed from the first side of the substrate.

11. The security feature of claim 1, wherein the second printed image layer is formed in a substantially white or grey colour, and the first printed image layer is formed in a different colour which visually contrasts with white or grey.

12. The security feature of claim 1, wherein the security feature is formed in a window or a half-window region of a security substrate, wherein said security substrate can be printed upon and further processed into a security document.

13. The security feature of claim 1, wherein the substrate is substantially transparent and is made from a polymeric material.

14. A security feature comprising: a substrate including a first surface and a second surface, a first image layer applied to the first surface of the substrate, by depositing a coloured ink in selected regions of the substrate to form a first image, a second image layer applied to the substrate, wherein the second image layer is a layer of semi-opaque material including transparent or translucent regions in which the semi-opaque material is omitted or reduced, at least some of the transparent or translucent regions overlap with the first image, wherein the first and the second image layer collectively define a coloured multi-tonal image that is visible both in transmission and reflection, wherein one or more additional layers of opacifying material are applied to the first and/or the second surface of the substrate, and wherein the one or more additional layers of opacifying material are applied such that the first image layer is sandwiched between two misregistered half-windows, the two misregistered half-windows creating a region of reduced opacity in the substrate.

15. The security feature of claim 14, wherein the one or more additional layers of opacifying material are applied such that the first image layer is sandwiched between four misregistered half-windows, two on each side of the substrate, the four misregistered half-windows creating a region of reduced opacity in the substrate.

16. The security feature of claim 14, wherein a different coloured multi-tonal effect is observed from each side of the substrate.

17. A security feature comprising: a substrate including a first surface and a second surface, a first printed working and a second printed working applied to the substrate, wherein the first printed working and the second printed working at least partially overlap and are registered to one another, the first printed working is multi-tonal, the first printed working and the second printed working are each formed in a single printed layer and in contrasting colours, the first printed working and the second printed working collectively provide a coloured multi-tonal image visible both in reflection and transmission, wherein the first printed working and the second printed working are both printed in an in-line printing process, and wherein a printing surface of a printing unit in the in-line printing process includes an array of ink cells configured to receive ink during an image printing process, wherein the ink cells are modulated to form tonal variation to produce the multi-tonal first printed working.

18. The security feature of claim 17, wherein the second printed working is free of tonal variation.

19. The security feature of claim 17, wherein the second printed working is multi-tonal.

20. The security feature of claim 17, wherein the first printed working and the second printed working are both printed using a gravure printing unit in the in-line printing process, and wherein the printing unit is a gravure printing unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures. It is to be appreciated that the embodiments are given by way of illustration only and the invention is not limited by this illustration. In the drawings:

(2) FIG. 1a shows a security document including a security feature according to a first embodiment of the invention in a plan view;

(3) FIG. 1b shows a security document including two security features according to a first and a second embodiment of the invention in a plan view;

(4) FIG. 1c shows a security document including three security features according to a first, second and third embodiment of the invention in a plan view;

(5) FIG. 2a shows a cross-section of FIG. 1a along ling A-A;

(6) FIG. 2b shows a cross-section of FIG. 1b along line B-B;

(7) FIG. 2c shows a cross-section of FIG. 1c along line C-C; and

(8) FIGS. 2d-2g illustrate other alternative embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) For the purposes of the following discussion, the figures are to be considered illustrative and not to scale, unless otherwise indicated. The figures illustrate simplified depictions of the embodiments described.

(10) “Colour” as used herein refers to a colour as perceived, and may correspond to a single range of wavelengths or a mixing of different ranges of wavelengths.

First Embodiment

(11) Referring to FIG. 1a, a security document 1 includes an exemplary first embodiment of the present invention. The security document 1 includes a window region 2, and a security feature provided as a multi-tonal image 3 in a selected region of the document 1. The multi-tonal image 3 is a coloured multi-tonal image, meaning that it has a colour that visually contrasts with the colour of the rest of the security document 1, which, in this example, is generally white or light grey.

(12) FIG. 2a shows a cross-section of the embodiment of FIG. 1a along line A-A. The security document 1 is formed by applying various printed layers on opposing surfaces of a polymer based base substrate 1a, which is typically substantially transparent.

(13) The multi-tonal image 3 comprises two image layers 31 and 32. The first image layer 31 is applied as a coloured ink layer over a selected region of the base substrate 1a. The coloured ink layer can be either continuous, or discontinuous. It generally forms a mono-tonal, that is having equal tone throughout, version of the final multi-tonal image that is to be observed by a viewer through the use of the presence or absence of the layer. Hence, a mono-tonal version of layer 31 provides for an image layer, being a representation of a particular image (such as a cloud as in FIG. 2a) with no variation in the image other than at its outline. The image represented by layer 31 may be such that the outline provides for a discontinuous image layer. The second image layer 32 is then applied over the first image layer 31 to introduce tonal variation by including regions 32a in which the material used to form the second image layer 32 is either completely omitted or at least reduced. For example, the second image layer 32 can include one or more gaps, openings, in accordance with a desired tonal value and tonal pattern of image pixels of the multi-tonal image 3. In regions 32a, portions of the second image layer 32 are shown through the first image layer 31 directly, whereas in regions outside of 32a, a combination colour effect of the first image layer 31 and the second image layer 32 is observed. As such, when viewed from a first side of the security document 1, the multi-tonal image 3 will display a darker tone or a more vibrant colour tone in regions 32a and a lighter tone or a pale colour in the rest of the imagery area.

(14) In this embodiment, the first and the second image layers 31 and 32 are applied on the same side of the base substrate 1a. In another embodiment, the first and second image layers 31 and 32 may be provided on opposing surfaces of the base substrate 1a.

(15) Typically, the first image layer 31 only occupies less than 50% of the surface area of the substrate 1a, or less than 30%, or more preferably less than 20%. This is to allow further and additional security features to be applied to the security document 1, thereby enhancing its security.

(16) When viewed from the top side, the multi-tonal effect is clearly visible both in reflection and transmission. When viewed from the bottom side, a mono-tonal version of the image layer 31 is visible, both in reflection and transmission. In addition, the appearances of the multi-tonal effect are substantially similar in reflection and transmission.

(17) In another embodiment, a tonal variation may be directly introduced into the first or the second image layers 31 or 32 by suitable means. This embodiment will create a more complex multi-tonal imagery effect, as an increased number of tonal values, that is more than two tones, can be created across the multi-tonal image 3. In this embodiment, a multi-tonal image is observable from both sides of the security document 1. Details of how a tonal variation can be created in a single imagery layer will be described below and specifically in relation to FIGS. 1b and 2b.

Second Embodiment

(18) FIG. 1b shows a second embodiment of the invention, and FIG. 2b shows a cross-section of second embodiment along line B-B.

(19) In this embodiment, there is a multi-tonal image 4 being provided in the window region 2 of the security document 1. The multi-tonal image 4 is visible both in reflection and transmission, and is visible from either side of the security document 1.

(20) The multi-tonal image 4 is formed in a single printed working, meaning all the tonal variation is introduced in a single printing step and at one printing station. In a preferred form, the multi-tonal image 4 is printed by a gravure printing unit including a gravure cylinder. The gravure cylinder includes an array of ink cells, arranged to receive a printing ink stored in an ink tank. As the gravure cylinder rotates in the ink tank, it contacts with the base substrate 1a and transfers the ink stored in the ink cells to the base substrate 1a in order to form an image. The ink cells of a gravure cylinder can be formed by directly engraving a metal surface of the gravure cylinder. After engraving, an optional protective surface material can be applied to enhance durability of the cylinder. The ink cells are formed to have a specific shape profile and location, which correspond to the image to be printed on the base substrate 1a. It will be appreciated that the ink cells can be modulated so that different ink cells have different shape profiles, (depth, diameter, density, and the like) and/or different locations on the gravure cylinder. In this manner, a multi-tonal image can be printed in one printing step, by having a set of specific shape profiles of ink cells on the cylinder representing a corresponding set of tonal ranges.

(21) The second embodiment aims to provide a simple yet effective multi-tonal image, which is very easy to identify and authenticate by the public. Further, the tonal information is created in a single printing step, so it greatly reduces the material costs associated with manufacturing such features.

(22) The multi-tonal image 4 is in a colour which visually contrasts with the rest of the security document, which is generally white or grey. However, it should be appreciated that other colours can also be chosen, depending on the requirement of such security features.

Third Embodiment

(23) FIGS. 1c and 2c illustrate a third embodiment of the invention in a plan view and in a cross-sectional view, FIG. 2c being a cross-section along line C-C.

(24) Similar to the first embodiment, a multi-tonal image 6 is formed by two printed layers 33 and 35. In this embodiment, the corresponding image region 7 is partially located in a window region 2, and partially located in an opacified region, overlapping one or more opacifying layers 36. It should be appreciated that the multi-tonal image 6 displays a tonal effect when viewed from a bottom side of the security substrate 1, both in reflection and transmission, and regardless of whether it is located in the window region 2 or outside of the window region.

(25) The first image layer 33 is an opacifying layer including a region 33a with tonal variation formed by methods described above. For example, this could be achieved by varying the sizes of ink cells of a gravure cylinder, so that different amount of ink is deposited in different regions to generate tonal variation. The second image layer 35 is a coloured layer applied in registration with the first image layer, and is free of tonal variation. The second image layer 35 is applied to cover a small area of the base substrate, so that the overall appearance of the security substrate 1 is still of a white or grey colour, allowing further security features to be formed thereon.

(26) In another embodiment, both layers 33 and 35 may be formed such that a tonal variation subsists in each layer. That is, tonal variation is included in layer 35 as well. In this embodiment, a coloured multi-tonal image will be observable from both sides of the substrate. However, the image may appear differently depending on from which side the user is examining the security feature.

(27) In the past, substrate level multi-tonal images are generally formed by overlapping a plurality of opacifying layers and by deliberately introducing openings of different sizes in the plurality of opacifying layers. While it is possible to produce a multi-tonal image in this manner, it requires multiple printed layers to achieve this effect, hence requiring multiple printing stations and multiple printing cylinders, as each printing cylinder could only print one layer of opacifying material, thereby increasing material cost and time required to produce such security features.

(28) Another common issue with such images is that the image is generally more visible in transmission, and a lot less visible in reflection, which means sometimes it can be a bit difficult for the public to locate such images.

(29) Another common issue with such images is that the plurality of opacifying layers must be registered to each other, as each layer contributes to a portion of the overall multi-tonal imagery effect. If one of the plurality of layers is outside of an allowable registration tolerance, the multi-tonal image will be distorted and the general public may not even recognise the existence of a security feature.

(30) In contrast, the first and the third embodiments of the present disclosure require only two image layers to produce a coloured multi-tonal imagery effect, wherein each image layer is printed in a single printed working. The second embodiment above requires only a single printed working which simplifies the manufacturing process even further. In addition, the multi-tonal effect displayed by the embodiments of the present disclosure is equally visible in both reflection and transmission, thereby avoiding causing potential confusion for the general public.

OTHER EMBODIMENTS

(31) FIGS. 2d to 2g illustrate other alternative embodiments of the present disclosure. In these embodiments, opacifying layers 3, 10, 11 and 12 are provided on each side of the base substrate 1a to create a dynamic multi-tonal effect. Specifically, the opacifying layers 3, 10-12 are applied to create a plurality of misregistered half windows 2a, 2b, 2c, 2d. The first imagery layer 31 is then sandwiched between these misregistered half windows. By ‘misregistered half windows’ it is meant that these windows, for example, misregistered half windows 2a and 2b, are displaced relative to each other such that there is no overlap between their corresponding window regions, but one of their edges is aligned, as indicted by line D-D in respect of FIG. 2d. PCT application WO2016149762A1 discloses details of how such misregistered half windows are formed, and the contents of this application is incorporated herein by reference.

(32) With reference to FIG. 2d, two misregistered half windows 2a and 2b are provided on each side of the base substrate 1a. In this embodiment, different coloured multi-tonal effects will be observed from each side of the security document 1, thus making it more difficult to counterfeit, and easier to recognize by the general public. It will also be appreciated that the two misregistered half windows 2a and 2b by themselves do not create a multi-tonal effect. They are included to merely create a region A of reduced opacity comparing to the rest of the substrate, and the region A has different impact on the perceived colour of the coloured image layer 31 depending on which side a viewer is observing the image. Region A includes three layers of opacifying layers, whereas outside of Region A four layers of opacifying layers are provided to the substrate 1a.

(33) Coloured image layer 31 has two regions in this example, a region 31a with no tonal variation (mono-tonal) and a region 31b with tonal variation. Optionally, as shown in the embodiment of FIG. 2d, opacifying layer 3 may have sub-regions with tonal variation, such as sub-regions 3a, 3b. Tonal variation in these layers can be generated by the methods disclosed in other embodiments, such as by variance in the amount of ink laid down in the layer according to a pre-defined tone. In embodiments which relies on the tonal variation in the image layer 31 alone, the opacifying layer 3 is mono-tonal in sub-regions 3a and 3b.

(34) The multi-tonal image generated by this embodiment will be visible in both transmission and reflection from each side. However, its appearances may change depending on which side it is viewed from.

(35) Turning to FIG. 2e, four misregistered half windows 2a-2d are provided to the security document 1. In this embodiment, Region A is again created to form a region of reduced opacify comparing to the rest of the substrate, with only two layers of opacifying material within this region. Layer 31, in this embodiment is a mono-tonal coloured image layer. As with FIG. 2d, opacifying layer 3 may have sub-regions, such as sub-region 3a, with tonal variation. Once again, tonal variation in the sub-regions of layer 3 can be generated by the methods disclosed in other embodiments. In embodiments which relies on the tonal variation in the image layer 31 alone, the opacifying layer 3 is mono-tonal in sub-region 3a.

(36) FIG. 2f shows another embodiment, which is similar to the embodiment of FIG. 2e, however, tonal variation is introduced into the coloured image layer 31 using methods described herein. Coloured image layer 31 has two regions, in this example, a region 31a with no tonal variation (mono-tonal) and a region 31b with tonal variation. Optionally, opacifying layers 3 and 11 may have sub-regions, such as sub-region 3a, 11a and 11b, with tonal variation. Once again, tonal variation in the sub-regions of layer 3 and 11 can be generated by the methods disclosed in other embodiments. In embodiments which relies on the tonal variation in the image layer 31 alone, the opacifying layers 3 and 11 are mono-tonal in sub-regions 3a, 11a and 11b.

(37) FIG. 2g shows another embodiment, similar to the embodiment of FIG. 2f, in which a second coloured imagery layer 32 is included to create more complex multi-tonal image. Coloured image layer 31 and 32 each have two regions, in this example, a region 31a, 32b with no tonal variation (mono-tonal) and a region 31b, 32a with tonal variation. Optionally, opacifying layers 3 and 11 may have sub-regions, such as sub-region 3a, 3b, 11a and 11b, with tonal variation. Once again, tonal variation in the sub-regions of layer 3 and 11 and regions of the coloured image layers 31 and 32 can be generated by the methods disclosed in other embodiments. In embodiments which relies on the tonal variation in the image layers 31 and 32 alone, the opacifying layers 3 and 11 are mono-tonal in sub-regions 3a, 3b, 11a and 11b

(38) It will be understood that the invention is not limited to the specific embodiments described herein, which are provided by way of example only. The scope of the invention is as defined by the claims appended hereto.