DE20215153U1 - Printed security mark for e.g. banknotes has a latent intaglio image of strongly-reflecting ink visible from certain angles and giving a flickering effect, optionally together with a non-intaglio image - Google Patents

Abstract

A printed security mark for a document has a latent intaglio printed image with a strongly-reflecting ink, the image being visible from a first angle close to the perpendicular and also from a second angle nearer to the image plane but not visible from an angle in-between so that by altering the viewing angle the latent image switches from visible to invisible or vice-versa.

Description

PRINTED SECURITY FEATURE

Scope of the invention

This invention relates generally to printing as applied to documents such as securities (e.g. banknotes), passports, identity cards and the like, and more particularly to printing in the form of a security feature to facilitate verification of the authenticity of the document by simple visual inspection.

General state of the art ·

Intaglio printing is generally used to produce securities such as banknotes, where counterfeiting and fraud issues need to be considered. This printing process involves pressing a substrate, such as high-quality paper, against an engraved and inked plate at very high pressure, so that the substrate is pressed into the ink-filled engraved recesses in the plate, creating a color print on the substrate whose appearance is determined by the engravings and which is difficult to reproduce without an intaglio printing press.

However, with the advent of improved photocopying techniques, there has been an increased risk that documents produced by intaglio printing could be forged using photographic processes. With these new techniques, it is possible to reproduce documents produced by intaglio printing in a quality sufficient to be undetectable by laypersons relying on a mere visual inspection of the reproduced document. There is therefore a need for means to enable the authenticity of such documents to be verified simply by visual inspection of the document (i.e. without the use of special knowledge or experience, inspection screens, special lights or similar aids).

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Various special printed security features are already known to enable such authentication, but due to their mode of application and limited visibility, they are mainly aimed at trained or knowledgeable security personnel and are less suitable for laypersons. For example, U.S. Patent No. 4,033,059 (Hutton et al.) describes an intaglio printing process which uses different orientations or depths of the intaglio prints to print two images, one as a background image and the other as a latent image, so that when viewed from a normal angle, approximately perpendicular to the document, the latent image and the background image are indistinguishable and appear as a single image, but when viewed from the side (i.e., at a shallow angle to the document plane), the latent image appears as a separate image, separate from the background and distinguishable. For this security feature, it is necessary to reduce the viewing angle (i.e., the angle to the document plane) to make the latent image visible and then to improve its visibility. A similar security feature is described in US Patent No.

5,199,744 (Shenton et al.) and consists of a substrate embossed with a transient image in an area of the substrate that is only visible from a specific angle and not from other angles, and with a linear area around the image that is visible from any angle, so that when the feature is viewed from an angle other than the specific angle, a uniform image is seen and the transient image (in the form of a latent or moving image) is indistinguishable (which is only visible as a separate image when viewed from the specific angle). These two known security features are therefore suitable for effective use for a

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intended for a group of people who are familiar with the viewing angles to be used.

Another example is a security feature described in Canadian Patent No. 1,172,282 (Merry) in which a first image in the form of a first serpentine pattern, which is detectable by means of an overlying inspection screen, is superimposed on a second image in the form of a second serpentine pattern, which is detectable by means of an overlying inspection screen. The two patterns are printed at different orientation angles so that each image is detectable separately by means of an inspection screen oriented at those different angles.

A similar security feature is described in Canadian Patent No. 2,071,795 (Merry et al.). This involves an arrangement of microcharacters in which one group of characters is out of phase with the others and together defines an image, whereby the characters appear uniform when viewed with the naked eye and the image is not discernible but can be made visible using a review screen. Effective use of these security features requires that the user has knowledge of the correct application and also has a special review screen.

There is therefore a need for a security feature that can be applied without prior knowledge on the part of the user. There is also a need for a security feature that can be applied to a document using conventional printing methods, is relatively simple and avoids high manufacturing costs. And finally there is a need for a security feature that creates a different visual effect than those caused by the known latent images and wandering images as described in the above patent literature.

Brief description of the invention

According to one aspect of the invention, a printed security feature for documents is provided. A latent image is printed by intaglio printing on a substrate having a highly reflective ink such that the latent intaglio image is visible when viewed at a first angular range ranging from approximately perpendicular to the plane of the latent image to further towards the image and also at a second angular range closer to the image plane and is not visible when viewed at an angular range between the first and second angular ranges. This has the effect that when the viewing angle is changed from one angular range to an adjacent angular range, a visible latent image becomes invisible or vice versa (thereby creating a tilting effect of image visibility).

According to a further aspect of the invention, a second image is non-intaglio printed such that the second image is visible when viewed at a third angle range lying between the first and second angle ranges (e.g., in the illustrated embodiment, the third angle range begins at about 12-17° from the perpendicular to the image plane) and is not visible when viewed from other angles. This causes a change in viewing angle between the first angle range and the third angle range to make a visible latent image invisible and an invisible non-intaglio printed second image visible, or vice versa. Furthermore, a change in viewing angle between the third angle range and the second angle range to make a visible non-intaglio printed second image invisible and an invisible latent image visible, or vice versa (also creating a tilting effect of image visibility, but with the improvement that the visible image is tilted between the two

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different images, namely between the latent and the second image).

The highly reflective ink is preferably a luster bronze ink having the following composition by weight: 30% - 60% varnish, 0 - 15% solvent, 0-5% wax, 24% - 60% metallic pigment and 0-5% drier. The second image is printed with an iridescent ink which may, for example, have the following composition by weight: about 65% clear varnish, about 23% thinner and about 12% iridescent pigment. Preferably, the second image is screen printed onto the substrate and the latent intaglio image is printed over the second image.

Description of the drawings

The present invention will now be described with reference to the following drawings, in which like reference numerals designate like elements throughout. In the drawings:

' Figure 1 is an exemplary illustration of a banknote on which a security feature according to the invention has been printed, showing the appearance of the security feature when viewed approximately at a right angle to the image plane, so that at this approximately vertical viewing angle a latent intaglio image is visible (in this example the word "OKAY");

Figure 2 is a further image of the banknote of Figure 1 with the security feature, but viewed at a different angle (in this example 17°) within an angular range adjacent to a first angular range in which the latent image of Figure 1 is visible, such that at this different angle a second image not printed by intaglio printing is visible instead of the latent image shown in Figure 1 (in this example the letter "A" with a circular pattern); and

Figure 3 is an exaggerated sectional view of the security feature shown in Figure 1 (or Figure 2) along the section line I-I showing the printing substrate and the printing layers of the security feature of the document shown in Figures 1 and 2.

Description of the illustrated embodiment

Prior to this invention, the prevailing view in intaglio printing circles was that latent intaglio images "can only be seen at shallow angles (acute angles to the image plane) and cannot be seen at approximately vertical viewing angles (perpendicular to the image plane) because this was the effect resulting from the different orientation or depth of the intaglio used to create the latent image (for a basic description of how a latent intaglio image is created, see, for example, U.S. Patent No. 4,033,059 (Hutton et al.)). This effect is referred to, for example, in U.S. Patent No. 5,199,744 (Shenton et al.) at column 6, lines 19-21, where it is stated that a latent intaglio image must be outlined with a perimeter line so that the location of the latent image can be seen from above, implying that latent images are only seen at a shallow viewing angle. meant to be.

The inventors have unexpectedly and surprisingly discovered that when using a highly reflective intaglio printing ink (here alternatively referred to as gloss bronze intaglio printing ink) to print a latent image using intaglio printing technology, the visibility of the latent image is significantly different than when using a non-reflective (normal) intaglio printing ink. In particular, this has the effect that when using a highly reflective intaglio printing ink, the latent image is not only visible at the previously flat viewing angle (i.e. at an acute angle to the image plane), but

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is also visible at a viewing angle of approximately 90 degrees (i.e. approximately perpendicular to the image plane). In the context of latent images according to the known prior art, this visibility of the latent image when viewed approximately vertically would be undesirable, since the latent image is supposed to be secret and known only to initiated persons whose job it is to look for this image in order to authenticate documents. However, the inventors have recognized that this steep-flat double visibility is in itself a useful advance for the security and authenticity of a document, because this ability to see the image of a printed security feature when viewed normally (i.e. approximately vertically) enables the layperson to assess the authenticity of the security feature. At the same time, simple manipulation of the security feature by slowly moving the security feature in different directions to continuously change the viewing angle from steep to flat will cause the latent image to repeatedly appear and disappear as it becomes visible at steep and flat angles and invisible at angles in between, thereby creating a hologram or tilting effect for the security feature.

The specific angles of visibility of a latent intaglio image printed with highly reflective ink vary from one intaglio printing situation to another, as the viewing angles associated with a given latent image depend on the different patterns, orientation, widths and heights of the engraved lines. In a given viewing situation, the brightness and direction of the light source also affect the visibility of the latent image, i.e. the angle at which the light falls on the document (for example, the tilt effect occurs at different angles depending on whether the viewer is facing a window

or lateral to it). Generally, however, for a latent intaglio image printed with a highly reflective ink, the inventors have found that the latent intaglio image is visible when viewed at a first angular range that extends from approximately perpendicular to the plane of the latent image (i.e., about 90° to the image plane) to further toward the image, and also at a second angular range that is different from the first angular range and extends from a point closer to the image plane (i.e., about 10° to the image plane) to further toward the image (i.e., horizontal). When viewed at an angular range between these first and second angular ranges, the latent image is not visible.

Thus, a change in the viewing angle from one angle range to an adjacent angle range

(i.e. when moving from an angle in the first angular range to an angle in the angular range between the first and second angular ranges or vice versa or from an angle in the angular range between the first and second range to an angle in the second angular range or vice versa) that a visible latent image becomes invisible or that an invisible latent image becomes visible. The aforementioned first angular range, which begins approximately at the perpendicular to the image, is new here and occurs with latent intaglio images that are printed with normal

(i.e. not highly reflective) colors.

In addition, the inventors have developed an even more improved security feature consisting of two separately printed, different images 80, 90, each of which is visible when viewed at a different angle or range of angles than the other, so that the resulting visual effect is a clear change between the two images depending on how the document is held. Examples of these two images 80, 90

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are illustrated in Figures 1 and 2, one representing a latent intaglio image 80 and the other a non-intaglio printed image 90. The use of an intaglio printing process advantageously increases the security level of the document, since intaglio printing is inherently more secure than other printing processes due to the expensive special printing equipment required.

The latent intaglio image 80 is printed with highly reflective ink and provides steep angle visibility (actually steep-flat dual visibility). A second printed image 90 produced by a printing process other than intaglio and with iridescent ink provides intermediate angle visibility such that the second image is visible when viewed at an angle within a third angular range that is intermediate between the first and second visibility angle ranges of the latent image 80. Thus, the latent image 80 is visible at approximately perpendicular angles to the security feature plane. Then, as the viewing angle moves away from these approximately perpendicular angles and into the third angular range of visibility of the second image (which is closer to the horizontal of the security feature plane, but not so close that it reaches the flat viewing angle range of the latent image 80), the non-intaglio printed second image 90 becomes visible. Again, it should be noted that it is not possible to give precise viewing angle ranges for images 80, 90 as these depend on many variable factors, including the brightness and direction of the light source. In the illustrated embodiment (where the non-intaglio image 90 is first screen printed with a specially selected iridescent ink prior to intaglio printing), the non-intaglio image 90 is viewed at approximately 12° to

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17° from the perpendicular to the image plane and remains visible within a third angular range which lies between the first and second angular ranges of visibility of the intaglio image. Thus, a change in viewing angle from one angular range to an adjacent angular range (i.e. from the first to the third angular range or vice versa, or from the third to the second angular range or vice versa) causes a visible latent image to become invisible and an invisible second image to become visible, or vice versa.

In the illustrated embodiment of the security feature 10, the images 80, 90 occupy the print layers 50 and 40 respectively on a substrate 30 which is of sufficiently high quality to be printed by intaglio printing, such as banknote paper (see Figure 3). In this example, the non-intaglio image 90 is first printed by means of a screen printing press and forms a first print layer 40 on the substrate 30. Screen printing offers the advantage over other non-intaglio printing processes such as lithography, doctor blade printing, flexography and letterpress printing that a thick layer of ink can be applied, and this is important because the visibility of iridescent color images such as image 90 depends on the thickness of the ink layer applied. By appropriately selecting the color to be used for this printing process and arranging the printed image, the second image 90 not produced by intaglio printing is only visible within a predetermined angular range in which the latent image is no longer visible, i.e. the image 90 becomes invisible at angles outside the predetermined visibility angle range (here referred to as the third angular range).

To achieve this additional visibility of the non-intaglio printed image 90, a suitable iridescent ink (i.e. an ink containing iridescent pigments) is selected. Such inks are

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is well known in the printing industry and one skilled in the art will readily be able to make an appropriate choice. In the illustrated embodiment, the ink formulation set forth in Table A below is used to screen print the non-intaglio image 90. Although in the illustrated embodiment, the non-intaglio image 90 is preferably printed first and then the latent intaglio image, it is understood that it is also possible to print the latent image first and then print the second non-intaglio image over it. Likewise, it is understood that other printing processes are possible in addition to the preferred screen printing process for the non-intaglio image 90, such as lithography, flexography or doctor blade printing.

Table A: Color recipe for example screen print image

component Portion (in mass %) Clearcoat MPI 17O ¹ 65 Thinner MPI 182G ¹ 23 Pigment Afflair 205 ² 12 In total: 100

Remarks:

1 Product name available from Tecknecal Screen Print Supplies Inc., Clarence Creek, Ontario, Canada.

2 Product name, available from EM Industries, Hawthorne, New York, USA.

If desired, this formula can also be modified so that the color acquires other special properties in addition to being visible only in a predetermined angular range, such as fluorescent, phosphorescent or thermochromic properties.

In the illustrated embodiment,

the intaglio printing of the latent image 80 is carried out as a second step with a highly reflective ink so that the image 80 is visible at an approximately right angle to the image plane. The impressions 60 produced by intaglio printing form a second printing layer 50 above the first printing layer 40.

The highly reflective ink used for the illustrated embodiment is the bright bronze intaglio ink developed by the assignee of the present invention as described in U.S. Patent No. 6,063,176. Other suitable bright bronze inks are well known in the art and are readily available commercially. These inks contain metallic pigments, iridescent pigments, or special effect pigments such as Paliocrom* pigments (* trademark) available from BASF, Germany. Also suitable is OVI*^ intaglio ink (* trademark) manufactured by Sicpa, Switzerland. In the illustrated embodiment, the ink formulation shown in Table B below is used to intaglio print the latent image 80.

Table Bj Color recipe for example intaglio print

Component proportion (in mass %) [and

optional percentage range]

Lacquer 35 [30-60]

Solvent 6 [0-15]

Wax 3 [0-5]

Metallic pigment 55 [25-60]

Dryer _1 [0-5]

Total: 100

Experts in the field of security printing technology will be able to easily

It is therefore to be understood that the specific embodiment described herein for illustrative purposes is not intended to limit the scope of the invention claimed by the inventors herein and defined by the appended ^claims .

Claims (9)

1. A printed security feature for a document, characterized in that the security feature includes a latent intaglio image printed with highly reflective ink onto a printing substrate, this latent intaglio image being visible when viewed in a first angular range extending from approximately perpendicular to the plane of the latent image to further towards the image, and also in a second angular range closer to the image plane, and not visible when viewed in an angular range between the first and second angular ranges, so that when the viewing angle is changed from one angular range to an adjacent angular range, a visible latent image becomes invisible or an invisible latent image becomes visible. 2. A printed security feature according to claim 1, further comprising a non-intaglio printed second image, said second image being visible when viewed at a third angle range between said first and second angle ranges and not visible when viewed at other angles, such that upon changing the viewing angle between said first angle range and said third angle range, a visible latent image becomes invisible and an invisible non-intaglio printed second image becomes visible, or vice versa. 3. A printed security feature according to claim 2, wherein upon a change in the viewing angle between the third angular range and the second angular range, a visible, non-intaglio printed second image becomes invisible and an invisible latent image becomes visible, or vice versa. 4. A printed security feature according to claim 1, wherein the highly reflective ink is a bright bronze ink having the following composition by weight: 30%-60% varnish, 0-15% solvent, 0-5% wax, 24%-60% metallic pigment and 0-5% drier. 5. A printed security feature according to claim 3, wherein the second image is printed with iridescent ink. 6. A printed security feature according to claim 5, wherein the highly reflective ink is a glossy bronze ink having the following composition by weight: 30-60% varnish, 0-15% solvent, 0-5% wax, 24-60% metallic pigment and 0-5% drier. 7. A printed security feature according to claim 6, wherein the iridescent ink has the following composition by mass: about 65% clear varnish, about 23% thinner and about 12% iridescent pigment. 8. A printed security feature according to claim 7, wherein a printing layer defined by the non-intaglio printed image is arranged between the printing substrate and a printing layer defined by the latent intaglio printed image. 9. A printed security feature according to claim 8, wherein the non-intaglio printed image is visible at about 12 to 17° from the perpendicular to the image plane.