WO2020101514A1

WO2020101514A1 - Latent image security feature, method of producing it and security document

Info

Publication number: WO2020101514A1
Application number: PCT/PL2019/050053
Authority: WO
Inventors: Dariusz DĄBROWSKI; Piotr Dymała
Original assignee: Polska Wytwórnia Papierów Wartościowych Spółka Akcyjna
Priority date: 2018-11-15
Filing date: 2019-09-24
Publication date: 2020-05-22
Also published as: PL3880488T3; PT3880488T; EP3880488B1; PL427757A1; HUE060562T2; EP3880488A1; ES2929175T3

Abstract

A latent image security feature for a security document, comprises a substrate with a convex structure emerging by superimposing at least two images, wherein one of the images is defined by at least one pattern of lines extending in the first direction, the other of the images is defined by a pattern of lines extending in the second and third directions forming together a latent image, with the first, second and third directions being different. The security feature is characterised in that the convex structure is defined by the resultant latent image formed by performing one of three logical operations on the first image and the second image, wherein the operations are as follows: negation of implication, simultaneous negation, reverse implication.

Description

LATENT IMAGE SECURITY FEATURE, METHOD OF PRODUCING IT AND

SECURITY DOCUMENT

Technical field

The present invention relates to the field of security features protecting valuable documents against counterfeiting, in particular including banknotes, passports, bank cards, and other documents having some value, which are being protected because of possible counterfeiting. More specifically, the invention relates to a latent image security feature, a document protected with such a security feature, and a method for production thereof.

Prior art

The beginnings of using latent images printed with Intaglio technique with the use of an ink date back to the 1980s and 1990s. With the development of digital image processing technology and the production of Intaglio printing forms, their implementation has become increasingly easier. The first such solutions were developed by a Russian company Goznak (KIPP-security feature) and a UK company De La Rue (LIFT-security feature), they quickly became recognizable world-wide and nowadays there is virtually no banknote that would not comprise the aforementioned or similar solutions.

The latent image is filled with parallel lines of a given thickness and with strictly defined spacing. It is placed on the background of another image, which is also filled with lines, which in this case are, however, perpendicular to those in the latent image. The latent image can be a freely "suspended" graphic element or a part of a larger image. Elements combined in such a way are printed using the Intaglio technique. This means that the pattern is convex in relation to the substrate. When viewing an element made as described above at an acute angle, the convexity of the lines perpendicular to the observer results in an optical masking of gaps between given images. Thus, a uniform surface becomes visible. Lines that are parallel to the line of sight do not merge, but form a bright plane that is in contrast to the remaining part of the pattern.

Upon rotation of the element by 90 degrees, the lines that were previously perpendicular are then visible as parallel ones to the line of sight. Therefore, the colours "rotate" with respect to previous observations.

There are also products on the market that use multiple graphics, so called "latent images", matched up with each other. This effect can be achieved by dividing the image into adjacent segments, in which the latent image is visible both at a 90 degrees angle and at a 45 degrees angle. It is to be noted, however, that it is not a double latent image, but only two latent images which are matched up graphically with each other. They do not share a common area and, at a given moment, only segments that meet the principle of optical line mixing are visible.

There are also known solutions that instead of adjacent segments combine latent images by using many smaller areas, such as those disclosed in EP2941356. The advantage of this type of solutions is that, for the observer, there is no visible division of the graphics between latent images. The disadvantage is, however, that many small areas are cut out from a single latent image, which results in a lower legibility thereof, and the very pattern cannot always match up the remainder of the graphic pattern.

EP1093414B1 discloses also a security feature comprising a pattern consisting of convex elements formed by overlapping two latent images, wherein the convex elements are formed only where the lines filling these images intersect. The disadvantage of the solution is a strong distortion of the resulting pattern with respect to the original pattern before processing.

Summary of the invention

The present invention provides a solution that will eliminate the above drawbacks and guarantee a protection that is effective and difficult to counterfeit, while at the same time being simple and cheap to produce. A latent image security feature for a security document, according to the first invention, comprises a substrate with a convex structure emerging by superimposing at least two images, wherein one of the images is defined by at least one pattern of lines extending in the first direction, the other of the images is defined by a pattern of lines extending in the second and third directions forming together a latent image, with the first, second and third directions being different. The security feature is characterised in that the convex structure is defined by the resultant latent image formed by performing one of three logical operations on the first image and the second image, wherein the operations are as follows:

a. Negation of implication

b. Simultaneous negation

c. Reverse implication

Preferably, the pattern of lines defining the images consists of solid or dashed lines. Preferably, the pattern of lines defining the images consists of straight lines or curves or polylines or is a combination of the mentioned types of lines.

Preferably, the pattern of lines defining the images consists of lines 50 to 300 micrometres wide, and the spacing between the lines is 25 to 300 micrometers, preferably the thickness of the lines or the spacing is constant or variable.

Preferably, the pattern of lines defining the images consists of lines with a width of up to 25% of the width of the first image lines.

Preferably, the pattern of lines defining the images consists of lines whose spacing is greater than the spacing of the lines of the first image.

Preferably, the second image is the first image or a reduced or enlarged copy thereof, preferably rotated by 0 to 360 degrees, or a mirror image.

Preferably, the first of the images is also defined by a pattern of lines extending in a fourth direction other than the first, second and third direction of the lines.

Preferably, the security feature of the invention also comprises a third image that is superimposed on the first two images, wherein the third image consists of at least one line pattern with a different direction than the lines in the first and second images. Preferably, the second image may be a resultant image.

According to the second invention, a security document is characterised in that it has a security feature according to the first invention. The method for production of a latent image security feature for a security document, according to the third invention, comprises production of a convex structure on a substrate, in which method at least two images are superimposed, wherein one of the images is defined by at least one pattern of lines extending in the first direction, the other image is defined by a pattern of lines extending in the second and third directions and a latent image is formed, wherein the first, second and third directions are different. The method is characterised in that the convex structure defined by the resultant latent image is obtained by performing one of three logical operations on the first image and the second image, wherein the operations are as follows:

a. Negation of implication

b. Simultaneous negation

c. Reverse implication

Preferably, a standard or optically variable ink is used.

Preferably, an opaque or transparent ink is used.

Preferably, the ink is applied or the embossing is made with a printing technique, in particular the Intaglio technique.

Preferred embodiments of the invention

Now the invention will be illustrated in more detail in a preferred embodiment with reference to the attached drawings, wherein:

Fig. la - shows the first image P as defined in the form of the first pattern of lines in the first direction 1 and the fourth direction 4.

Fig. lb - shows the second image Q as defined in the form of the second pattern of lines in the second direction 2 and the third direction 3.

Fig. lc - shows the first image P as defined in the form of the first pattern of lines in the first direction 1.

Fig. Id - shows the second image Q as defined in the form of the second pattern of lines in the second direction 2.

Fig. 2 - shows the resultant image 5.

Fig. 3 - shows a cross section of the convex structure 6, the ink-covered areas 7 and the embossing 8.

Fig. 4 - shows a cross section of the convex structure 6, the embossing 8. Fig. 5 - shows the resultant image 9.

Fig. 6 - shows the resultant image 10.

Fig. 7 - shows the resultant image 11.

Fig. 8 - shows the resultant image 12.

In the first preferred embodiment of the invention, the latent image security feature is made in a document by Intaglio printing technique as an overprint with an opaque ink combined with embossing. The security feature forms a convex structure consisting of convex lines covered with the printing ink.

The first image P, shown in Fig. la, is defined in the form of the first pattern of lines extending in the first direction 1 and the fourth direction 4. The first direction 1 consists of lines with a constant width of 80 micrometres, extending at an angle of 0 degrees to the vertical axis, with a constant line spacing of 80 micrometres. The fourth direction 4 consists of lines with a constant width of 80 micrometres, extending at an angle of 90 degrees to the vertical axis, and a constant spacing between the lines is 80 micrometres. The second image Q, shown in Fig. lb, is defined in the form of the second pattern of lines extending in the second direction 2 and the third direction 3. The second direction 2 consists of lines with a constant width of 20 micrometres, extending at an angle of 45 degrees to the vertical axis, with a constant line spacing of 200 micrometres. The third direction 3 consists of lines with a constant width of 20 micrometres, extending at an angle of 135 degrees to the vertical axis, with a constant width of 20 micrometers, and a constant spacing between the lines is 200 micrometers.

The convex structure 6 is defined by the resultant image 5 formed by performing a logical operation of negation of implication on the first image P and the second image Q. The logical operation of negation of implication can be written in the form of a logical sentence:

P ® Q

where " " marks the operation of negation of implication.

As a result of the above logical operation, the resultant image 5 shown in Fig. 2 is obtained. The resultant image 5 is mapped on a security document by overprinting with an opaque ink using the Intaglio printing technique. The convex structure 6 obtained in this way, shown in Fig. 3, has the ink-covered areas 7 and the embossing 8 which map the resultant image 5, forming a latent image. In the second preferred embodiment of the invention, the resultant image 5 of the first embodiment is used. The resultant image 5 has been mapped on a security document by embossing with the Intaglio printing technique. The convex structure 6 obtained in this way, visible in Fig. 4, has the embossing 8 which maps the resultant image 5 forming a latent image.

In the third, preferred embodiment of the invention, the latent image security feature is made in a document with the Intaglio printing technique as an overprint with an opaque ink combined with embossing. The security feature forms a convex structure consisting of convex lines covered with the printing ink.

The convex structure 6 is defined by the resultant image 9 formed by performing a logical operation of simultaneous negation on the first image P and the second image Q. The logical operation of simultaneous negation can be written in the form of a logical sentence:

P I Q

where "

" marks the operation of simultaneous negation.

As a result of the logical operation of alternative, followed by the logical operation of negation, the resultant image 9 shown in Fig. 5 is obtained. The resultant image 9 is mapped on a security document by overprinting with an opaque ink using a printing technique, in particular the Intaglio. The convex structure 6 obtained in this way has the ink-covered areas 7 and the embossing 8 which map the resultant image 5, forming a latent image. In the fourth, preferred embodiment of the invention, the latent image security feature is made in a document with Intaglio printing technique as an overprint with an opaque ink combined with embossing. The security feature forms a convex structure consisting of convex lines covered with the printing ink.

The first image P and the second image Q are defined as in the third embodiment.

The convex structure 6 is defined by the resultant image 10 formed by performing a logical operation of reverse implication on the first image P and the second image Q. The logical operation of reverse implication can be written in the form of a logical sentence:

where " " marks the operation of reverse implication.

As a result of the logical operation of reverse implication, followed by the logical operation of negation, the resultant image 10 shown in Fig. 6 is obtained. The resultant image 10 is mapped on a security document by overprinting with an opaque ink using a printing technique, in particular Intaglio. The convex structure 6 obtained in this way has the ink- covered areas 7 and the embossing 8 which map the resultant image 10, forming a latent image.

In the fifth embodiment, the first image P, shown in Fig. lc, is defined in the form of the first pattern of lines extending in the first direction 1. The first direction 1 consists of lines with a constant width of 80 micrometres, extending at an angle of 0 degrees to the vertical axis, with a constant line spacing of 80 micrometres. The second image Q, shown in Fig. lb, is defined in the form of the second pattern of lines extending in the second direction 2 and the third direction 3. The second direction 2 consists of lines with a constant width of 20 micrometres, extending at an angle of 45 degrees to the vertical axis, with a constant line spacing of 200 micrometres. The third direction 3 consists of lines with a constant width of 20 micrometres, extending at an angle of 135 degrees to the vertical axis, with a constant width of 20 micrometers, and a constant spacing between the lines is 200 micrometers.

The convex structure 6 is defined by the resultant image 11 formed by performing a logical operation of negation of implication on the first image P and the second image Q. The logical operation of negation of implication can be written in the form of a logical sentence:

P Q

where " " marks the operation of negation of implication. As a result of the above logical operation, the resultant image 11 shown in Fig. 7 is obtained. The resultant image 11 is mapped on a security document by overprinting with an opaque ink using the Intaglio printing technique. The convex structure 6 obtained in this way, shown in Fig. 3, has the ink-covered areas 7 and the embossing 8 which map the resultant image 11, forming a latent image.

In the sixth embodiment of the invention, the first image P, shown in Fig. la, is defined in the form of the first pattern of lines extending in the first direction 1 and the fourth direction 4. The first direction 1 consists of lines with a constant width of 80 micrometres, extending at an angle of 0 degrees to the vertical axis, with a constant line spacing of 80 micrometres. The fourth direction 4 consists of lines with a constant width of 80 micrometres, extending at an angle of 90 degrees to the vertical axis, and a constant spacing between the lines is 80 micrometres. The second image Q, shown in Fig. lb, is defined in the form of the second pattern of lines extending in the second direction 2. The second direction 2 consists of lines with a constant width of 20 micrometres, extending at an angle of 45 degrees to the vertical axis, with a constant line spacing of 200 micrometres.

The convex structure 6 is defined by the resultant image 12 formed by performing a logical operation of negation of implication on the first image P and the second image Q. The logical operation of negation of implication can be written in the form of a logical sentence:

P Q

where " " marks the operation of negation of implication.

As a result of the above logical operation, the resultant image 12 shown in Fig. 8 is obtained. The resultant image 12 is mapped on a security document by overprinting with an opaque ink using the Intaglio printing technique. The convex structure 6 obtained in this way, shown in Fig. 3, has the ink-covered areas 7 and the embossing 8 which map the resultant image 12, forming a latent image.

Claims

1. A latent image security feature for a security document comprising a substrate with a convex structure emerging by superimposing at least two images, wherein one of the images is defined by at least one pattern of lines extending in a first direction, the other of the images is defined by a pattern of lines extending in a second and third directions forming together a latent image, with the first, second and third directions being different, characterised in that the convex structure (6) is defined by a resultant latent image (5, 9, 10) formed by performing one of three logical operations on the first image (P) and the second image (Q), wherein said operations are as follows: a. Negation of implication

b. Simultaneous negation

c. Reverse implication

2. The security feature according to claim 1, characterised in that the pattern of lines defining the images (P, Q) consists of solid or dashed lines.

3. The security feature according to claim 1 or 2, characterised in that the pattern of lines defining the images (P, Q) consists of straight lines or curves or polylines or is a combination of the mentioned types of lines.

4. The security feature according to claim 1, 2 or 3, characterised in that the pattern of lines defining the images (P, Q) consists of lines 50 to 300 micrometres wide, and the spacing between the lines is 25 to 300 micrometers, preferably the thickness of the lines or the spacing is constant or variable.

5. The security feature according to claim 1, 2, 3, or 4, characterised in that the pattern of lines defining the images (P, Q) consists of lines with a width of up to 25% of the width of the first image (P) lines.

6. The security feature according to any claim 1 to 5, characterised in that the pattern of lines defining the images (P, Q) consists of lines whose spacing is greater than the spacing of the lines of the first image (P).

7. The security feature according to any claim 1 to 6, characterised in that the second image (Q) is the first image (P) or a reduced or enlarged copy thereof, preferably rotated by 0 to 360 degrees, or a mirror image.

8. The security feature according to any claim 1 to 7, characterised in that the first image (P) is also defined by a pattern of lines extending in a fourth direction (4) other than the first (1), second (2) and third direction (3) of the lines.

9. The security feature according to any claim 1 to 8, characterised in that it also comprises a third image that is superimposed on the first two images, wherein the third image consists of at least one line pattern with a different direction than the lines in the first (P) and second images (Q).

10. The security feature according to any claim 1 to 9, characterised in that the second image (Q) may be a resultant image.

11. A security document having a security feature according to any claim 1 to 10.

12. A method for production of a latent image security feature for a security document, comprising production of a convex structure on a substrate, in which method at least two images are superimposed, wherein one of the images is defined by at least one pattern of lines extending in the a direction, the other image is defined by a pattern of lines extending in a second and third directions and a latent image is formed, wherein the first, second and third directions are different, characterised in that the convex structure (6) defined by a resultant latent image (5, 9, 10) is obtained by performing one of three logical operations on the first image (P) and the second image (Q), wherein said operations are as follows: a. Negation of implication

b. Simultaneous negation

c. Reverse implication

13. The method for production of a latent image security feature according to claim 12, characterised in that a standard or an optically variable ink is used.

14. The method for production of a latent image security feature according to claim 12 or 13, characterised in that an opaque or transparent ink is used.

15. The method for production of a latent image security feature according to claim 12, 13, or 14 characterised in that the ink (7) is applied or embossing (8) is made with a printing technique, in particular Intaglio technique.