DE102022103817B4 - Security fiber, in particular for use in security documents and security documents - Google Patents

Abstract

The invention relates to a security fiber, comprising at least one surface (51, 52); wherein at least three types (10, 20, 30) of points are arranged on the at least one surface (51, 52);wherein the three types (10, 20, 30) of points are arranged such that the density of the points is a first Type (10) varies over a region of the surface (51, 52) and the density of the points of a second type (20) varies over a region of the surface (51, 52), and the points of the first (10) and the Gradually mixing dots of the second (20) type to form an area of mixed dots (10, 20); wherein the area of mixed dots (10, 20) is overlaid with a third type (30) of dots; the at least three types (10, 20, 30) of dots upon irradiation with visible light having a wavelength between 380 nm and 780 nm have essentially no color; andwherein when irradiated with a UV wavelength between 315 nm and 380 nm or between 280 to 315 nm, the first type (10) of points glows in a first color (1), the second type (20) of points glows in a second color ( 2) glows, the area of mixed dots (10, 20) glows in a third color (3) and the third type (30) of dots is invisible; andwherein when irradiated with a UV wavelength between 100 nm and 280 nm, the first type (10) of dots glows in the first color (1), the second type (20) of dots glows in the second color (2) and the with The surface of mixed points (10, 20) superimposed on the third type (30) of points lights up in a fourth color (4).

Description

The present invention relates to an improved security fiber, the use of the security fiber in security documents and security documents.

Security fibers are used as a security feature in security documents, for example banknotes, identification documents such as ID cards, passports and visa documents, lottery tickets and certificates.

The ideal security feature is one that is easy to verify authenticity while also being difficult to reproduce by a counterfeiter.

An example of the use of security fibers is in inclusion in security paper. Paper is made from paper pulp containing cellulosic fibers such as wood, hemp, straw, and cotton linters (note that while these cellulosic fibers are used to make paper, they are not actually made from paper). A known security technique is to replace some of the cellulosic fibers used in the manufacture of a security paper with synthetic fibers made from materials such as polyester, nylon and rayon. A relatively small number of the synthetic fibers can become entrapped in the paper pulp along with a majority of the cellulosic fibers, resulting in the security paper made from the pulp having the synthetic fibers embedded and randomly scattered therein. The synthetic fibers can be colored or coated, resulting in the paper containing a random pattern of small printed areas. The dye may be an ultraviolet (UV) sensitive dye such that the random colored pattern is only visible under UV light.

Such synthetic fibers are generally fibrous (ie predominantly one-dimensional rather than two-dimensional or sheet-like) like the cellulosic fibers they replace. In the WO 2004/025028 A1 describes security features referred to as "fibers" because they replace and bind to the cellulosic fibers used in the manufacture of security paper and because they provide a visual impression in the paper produced suggesting that they are similar to such fibres . In fact, however, the fibers described in this document are small strips of paper and not fibrous.

Security fibers that are invisible in daylight and appear monochromatic when exposed to ultraviolet light are a well-known security feature. However, counterfeiters can use highlighter-type fluorescent markers to draw an imitation of the fibers on the security documents. The feature must be closely examined to identify the counterfeit, for example with a microscope, thus there is a need for a more secure or harder to counterfeit security fiber.

Describes for improving the security of security fibers WO 2004/025028 A1 Security fibers with two or more differently colored bands or areas, the colors being visible only under ultraviolet light. The areas on these security fibers may butt against each other at the edges of the areas without color overlap.

Also describes the WO 2020/ 089 625 A1 a security device that may be a security fiber for incorporation into a security document, the security device comprising a substrate having a first surface and a second surface. A first printed area may be provided on at least one of the first and second surfaces. The first printed area may have a varying tone density and/or be printed in an ink that fluoresces under ultraviolet light to emit light in a first color. A second printed area may be provided on at least one of the first and second surfaces. The second printed area may have a varying tone density and/or be printed in an ink that fluoresces under ultraviolet light to emit light in a second color. It may be that the first and second printed areas are arranged on the at least one of the first and second surfaces such that the colored light emitted from the fluorescent printed areas mixes to generate light of further, different colors.

Security fibers with different printed areas are also from the WO 2021/ 048 539 A1 known.

The U.S. 2008/0 305 313 A1 teaches security fibers with parallel stripe markings printed in two or more colors using UV and/or IR fluorescent inks.

The DE 103 61 131 A1 relates to security elements and documents of value, the security element having a color-coded latent image with different image components.

The U.S. 4,897,300A relates to security papers in which security fibers are embedded.

The problem to be solved by the invention is to provide a security fiber which has an improved level of security compared to the security fibers described in the prior art. Another object of the invention is to provide a security document with an improved level of security.

This object is achieved by a security fiber having the features of claim 1.

Furthermore, the above object is achieved by the security document containing the security fiber according to the invention.

According to the invention there is provided a security fiber comprising at least one surface, wherein at least three types of points are arranged on the at least one surface. The three types of points are arranged such that the density of points of a first type varies over an area of the surface and the density of points of a second type varies over an area of the surface, and where the points of the first type and the points of the second type vary gradually blend to form an area of blended dots. The area of mixed dots is overlaid with a third type of dots. The at least three types of dots appear substantially colorless when irradiated with visible light in the wavelength range between 380 nm and 780 nm, and when irradiated with a UV wavelength in the range between 315 nm and 400 nm or between 280 and 315 nm, the first type of glows dots in a first color, the second type of dots glows in a second color, the area of mixed dots glows in a third color and the third type of dots is invisible, i.e. the third type of dots does not glow when irradiated in this wavelength range. Further, upon irradiation with a UV wavelength between 100 nm and 280 nm, the first type of dots light up in the first color, the second type of dots light up in the second color, and the area of mixed dots superimposed with the third type of dots light up in a fourth Color.

There are generally three types of UV light, Ultraviolet A (UV-A or Long Wave UV), which can have a wavelength between 315 and 380 nm and is often provided at a wavelength of 365 nm; Ultraviolet B (UV-B or medium wave UV), which can have a wavelength between 280 and 315 nm and is often provided at a wavelength of 313 nm; and Ultraviolet C (UV-C or shortwave UV), which has a wavelength between 100 and 280 nm and is often provided at a wavelength of 254 nm. Visible light or artificial light generally has a wavelength between 380 nm and 780 nm.

When irradiated with visible or artificial light, the security fiber is essentially colorless, i.e. the security fiber is colorless under daylight or artificial light and is essentially non-absorbing.

Depending on how high-energy the wavelength of the UV light is, with which the respective points are irradiated, luminescent light can be generated at the respective type of points or not. In the case of the points of the first and second type, excitation with UV-A or UV-B light is already sufficient to generate the emission of luminescent light of the first and second color. In the case of the third type of dots, however, no luminescence light is emitted when irradiated with UV-A or UV-B light, and the third type of dots therefore remains invisible with this lower-energy irradiation.

However, if the points of the first, second and third type are excited with the high-energy UV-C light, the excitation energy is sufficient for the points of the third type to also emit luminescence light.

When the fiber is irradiated with UV radiation in the wavelength range between 315 nm and 380 nm or between 280 and 315 nm, the first type of dots light up in the first color, the second type of dots light up in the second color and the surface lights up of mixed dots, i.e. the area in which the first and second kind of dots are mixed, in a third color.

For example, the first type of dots can glow green through the excitation of luminescence by irradiation with the UV-A or UV-B radiation and the second type of dots can glow red since green or red luminescence light is emitted.

If there is now a surface with mixed points of the first and second type, the mixed points appear green at the point of the first type and red at the point of the second type when irradiated according to the above example. Since the dots are very small, the irradiated area with the mixed dots lights up in a third color, yellow in this example (additive color mixing green + red = yellow). However, it can be observed under the microscope that the light of the third color, namely yellow, differs from the luminescent light of the first color, green, produced by irradiating the point of the first kind, and the luminescent light of the second color, im Example red, composed. By the separate ones that can be generated by irradiation and are visible under the microscope green and red luminescence, it can be verified that the light appearing in the third color, for example yellow, comes from additive color mixing on two differently colored luminescences, green and red, originating from the two different points of the first and second type. This aspect of the invention further increases the security of the security thread.

Of course, it is possible to add a further type of dots that glow in a further color when irradiated, the luminescence of which can gradually mix with the luminescence of the first and/or the second type of dots to additionally produce a further luminescent light in a further Color and, if necessary, the additional mixed colors associated with it.

As a security feature, the security fiber not only has the above-described luminescence in a first, second and third color that occurs when irradiated with UV-A or UV radiation, but also makes it possible to check with a microscope whether the mixed color produced (third color) is really based on the mixture of luminescence light of the first and second color or whether there is a forgery. This increases the security of the security fiber since it is difficult for a counterfeiter to imitate the security fiber according to this aspect.

A further security aspect of the security fiber according to the invention is that when irradiated with short-wave UV light with a wavelength between 100 nm and 280 nm, the first type of dots continue to glow in the first color and the second type of dots in the second color, but the area of mixed dots superimposed with the third type of dots lights up in a fourth color.

This is because, in the superimposed area, when short-wavelength ultraviolet light is irradiated, the area superimposed by the superimposed first and second dots glows in the third color (mixed color) on which the color of the third kind of dots is superimposed.

According to the invention, the security fiber shows a first color scheme when irradiated with UV-A and UV-B light, in the above example green, red and the additive mixed color yellow, and when irradiated with UV-C light a different color scheme (e.g. green, red, mixed color white) if the third type of dots luminesces blue, for example, because with additive color mixing red + green + blue = white.

As the first type of dots (green) and the second type of dots (red) gradually mix, there are no "sharp" edges from one color to the other, but the colors appear from red through red-orange through yellow in this example, from yellow-green to green, the transition is diffuse.

The dots of the first and second type each have the same color under UV-C irradiation as under UV-A and UV-B irradiation. The surface of the mixed dots is overlaid with dots of a third type, namely dots that have no color under UV-A and UV-B radiation but appear in another further color when exposed to UV-C radiation. So if the fiber appears to change from green to yellow - orange to red under UV-A and under UV-B light, it could appear green to white to red under UV-C light if the third type of dots emits blue (with additive color mixing, red, green and blue = white). Thus a further level of security is provided which can be easily authenticated by comparing the different colors exhibited by the security fiber under UV-A/UV-B light and under UV-C light.

The area of mixed dots overlaid with dots of the third type can be made by printing the dots of the third type on the area of mixed dots of the first and second types. This means that the points of the third kind can overlap with the points of the first and the second kind. 2 exemplifies the third type dots overlapping the area of mixed dots of the first type and the second type.

In a further variant, the points of the first, second and third type are printed simultaneously.

The variation in the density of the dots can be provided by halftone printing. Halftone printing is a well-known reprographic technique that uses dots of different sizes, patterns, and/or spacing to give the appearance of different tones. The density of the different types of dots (at least first, second and third type) can vary continuously over the surface(s) of the fiber, i.e. increase and decrease, so that a color gradient can be achieved. The color pattern that can be achieved can thus have diffuse transitions between different colors. The density of each type of dot may vary between 0% and 100%, for example along the area of at least one or all of the surfaces of the fibre. The density of a type of dots may also vary in one or more increments or discrete levels, such as in increments of ten degrees (e.g., with densities of 10%, 20%, 30%, etc.).

The density of the points is understood to mean the area covered by the points in relation to the area spanned by the points as a whole.

The dots of the first, second and third type can be printed on the first and/or second surface of the security fiber with a first, second and third fluorescent ink. Printing the dots onto the fiber surface(s) allows for more accurate positioning of the dots than, for example, dyeing the fibers. A more precise positioning allows better distinguishability between the points of the first and second type under a microscope. Thus, the safety fiber is made safer.

Furthermore, the first and second types of dots are preferably arranged such that the color appearing upon irradiation varies continuously over a portion of at least one surface upon irradiation with a UV wavelength of 315 nm to 400 nm or 280 to 315 nm. A graded spectrum or rainbow effect pattern may be produced. A rainbow pattern can be achieved by adding a fourth, fifth, and so on type of dots. The more types of dots, i.e. the more colors seen under UV-A and UV-B, the more difficult it is for a counterfeiter to imitate the security fiber of the present invention.

Furthermore, it is preferred that the first, second and third type of dots are arranged such that the luminous color of the third type dots does not have a continuous transition to the other colors but when irradiated with a UV wavelength of 100 nm to 280 nm, an abrupt color change takes place at the transition to the fourth color. Since the third type of dots has no color under UV-A or UV-B light, the authenticity of the security fiber can be easily checked by comparing the color produced under UV-A/UV-B light versus that under UV-C -Light color shown can be achieved.

The security fiber of the present invention may exhibit color when irradiated under NIR (near infrared light having a wavelength of 780 to 2500 nm). Such a fiber can be provided by mixing luminescent particles having anti-Stokes properties into the fluorescent inks used in at least the first, second and third types of dots. However, it is preferred that the first, second and third types of dots do not fluoresce or have no color when irradiated with NIR light. Instead, an additional type of dots that fluoresces or has a color when irradiated with NIR light can be used. The addition of another type of dots on one or both surfaces of the security fiber according to the present invention adds another level of security.

It is further preferred that the dots of the first and second types are provided using an ink which fluoresces and generates red, blue or green light when irradiated with UV-A, UV-B and UV-C light. Each of the first and second types of dots can be provided using a single color ink. Cyan and magenta inks can also be used as an alternative to red, blue and green inks.

In addition, each of the first and second types of dots can also be made using an ink that includes a mixture of two or more differently colored pigments (e.g., yellow, red, green, and blue pigments) that fluoresce to light of one color to generate, which results from the mixture of the different colors.

Likewise, the dots of the third type can be provided using an ink that fluoresces under UV-C light to produce, for example, red, blue or green light. The third type of dots can be created using an ink that fluoresces to produce a color different from the color produced by the area of mixed dots of the first and second types of dots. Each of the third type of dots can be provided using a single color ink. Cyan and magenta inks can also be used as an alternative to red, blue and green inks. The third type of dots can also be made using an ink that includes a mixture of two or more differently colored pigments (e.g., yellow, red, green, and blue pigments) that fluoresce to produce light of a color that consists of the mixture of the different colors results.

Different types of dots exist when the dots have different luminescence spectra at the same excitation wavelength or different excitation wavelengths (UV-A, UV-B and UV-C).

The different types of dots can be provided using inks comprising microencapsulated fluorescent organic or organometallic dyes. The microencapsulated inks may each include a fluorescent dye of more than one color. The different types of dots can be provided using inks, which have a lightfastness of at least 3 on the blue wool scale.

Furthermore, it is preferable that the first type of dots has a different shape than the second type of dots. Further, the third type of dots may have a different shape than the first type of dots and the second type of dots. A different shape means, for example, that one type of dots can have a round shape and the other type can have an oval shape. There may be different degrees of ovality, i.e. different degrees of longitude of the oval shape. Additionally, a different shape may mean a difference in diameter of a round point, for example, one shape may have a smaller diameter of round points than the other shape. In addition, the orientation of the different oval shapes can differ with respect to the longitudinal axis of the fiber. Another shape difference can be caused by the dots having smooth edges or rough edges. These shape differences can be observed under the microscope, adding another security feature to the security fiber of the present invention.

Preferably, the points of the first and second type are arranged side by side. However, they can also be superimposed.

The security fiber generally has at least a first and second surface. The first and second surfaces of the security fiber can be opposite surfaces. The first, second and third types of dots can be provided on only one surface of the fiber or on the first and second surfaces of the fiber. Preferably the points are provided on both surfaces. This allows the fiber to be authenticated regardless of the orientation of the fiber in the security document.

The fiber of the present invention can be made, for example, from a synthetic material such as polyester, nylon and rayon, or from paper or cellulose. In a preferred embodiment, the security fiber of the present invention may be made from strips of paper, particularly soft paper, more preferably it may be prepared from strips of tissue paper, particularly small strips of tissue paper, or an alternative thin paper. The paper can be without optical brighteners. A “small” strip of paper is to be understood as meaning a strip of paper which is preferably between 3 and 10 mm long and between 0.15 and 0.5 mm wide and in particular between 4 and 7 mm long and 0.3 mm wide.

Further, the paper may be a high porosity, high wet strength tissue paper having a basis weight rating of between 22 and 28 gsm. More preferably, the paper may be a high porosity, high wet strength tissue paper having a basis weight rating of 25 gsm. These properties enable optimal printing and cutting conditions of the paper. It is preferred that the fiber is made from paper, as the paper fiber is easier to integrate into the papermaking process, which means it allows for easier integration of the fiber into a security document made primarily of paper.

The length of the security fiber of the present invention may be any of 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm and 10mm or variations of these lengths. The width can be any of 0.125mm, 0.15mm, 0.2mm, 0.225mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm and 0.5mm or variations of these widths.

The security fiber may further comprise a lacquer layer on at least the first, second and third types of dots. The security device may further include a layer of lacquer on at least one of the first and second surfaces. The application of a varnish layer protects the types of dots from abrasion and/or improves the affinity of the fibers for a paper product in which the fiber is incorporated.

According to another aspect of the invention, there is provided a security document containing the security fiber described above. Due to the advantageous security properties of the fibre, the security document is made more secure by including the fibre. A security document according to the present invention can be, for example, a bank note, an identification document such as an ID card, passport and visa document, a lottery ticket and a certificate.

An example of a security fiber according to the present invention is in 1 and 2 shown.

• 1 zeigt eine beispielhafte Verteilung der ersten Art 10 von Punkten und der zweiten Art 20 von Punkten auf einer Oberfläche 51 einer Sicherheitsfaser 8. Gegenüber der in der Abbildung dargestellten Oberfläche 51 weist die Sicherheitsfaser noch eine zweite, dieser Oberfläche 51 gegenüberliegende Oberfläche 52 auf der anderen Seite auf. Bei Bestrahlung mit sichtbarem oder künstlichem Licht sind alle Arten 10, 20, 30 von Punkten farblos. Bei Anregung mit UV-A- oder UV-B-Licht leuchtet die erste Art 10 von Punkten in einer ersten Farbe 1 und die zweite Art 20 von Punkten in einer zweiten Farbe 2. Die Fläche der gemischten Punkte 10, 20 der ersten Art 10 und der zweiten Art 20 leuchtet, wie in 1 unten angegeben, in einer dritten Farbe 3.
• 2 zeigt eine beispielhafte Verteilung der ersten 10, zweiten 20 und dritten 30 Art von Punkten. Wie beispielhaft in 1 veranschaulicht, bilden die erste 10 und die zweite 20 Art von Punkten eine gemischte Fläche von Punkten aus. Diese gemischten Punkte werden von der dritten Art 30 von Punkten überlagert.

The invention and other advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings. The features to be found in the description and the drawings can be used according to the invention individually or collectively in any combination. Show it:

• 1 shows an exemplary distribution of the first type 10 of points and the second type 20 of points on a surface 51 of a security fiber 8. Compared to the surface 51 shown in the figure, the Safety fiber has a second surface 52 opposite this surface 51 on the other side. When irradiated with visible or artificial light, all types 10, 20, 30 of dots are colorless. When excited with UV-A or UV-B light, the first type 10 of dots glows in a first color 1 and the second type 20 of dots glows in a second color 2. The area of the mixed dots 10, 20 of the first type 10 and the second type 20 lights, as in 1 given below, in a third color 3.
• 2 shows an exemplary distribution of the first 10, second 20 and third 30 types of points. As exemplified in 1 As illustrated, the first 10 and second 20 kinds of dots form a mixed area of dots. The third type 30 of dots is superimposed on these mixed dots.

In 2 For demonstration purposes, the third type 30 of dots is shown with a black outline at the top of the blended dots area (the dots in the blended area are shown in a lighter shade of grey). No color appears upon irradiation of the first 10, the second 20 or the third 30 kind of points with visible or artificial light. When excited with UV-A or UV-B light, the first type 10 of dots glows in a first color 1 and the second type 20 of dots glows in a second color 2. The area of the mixed dots of the first type 10 and the second type 20 lights up in a third color 3 (cf. 1 ). The third type 30 of dots has no color. When excited with UV-C light, the first type 10 of dots glows in a first color 1 and the second type 20 of dots glows in a second color 2. The area of mixed dots overlaid with the third type 30 of dots , lights up in a fourth color 4, cf. 2 .

Reference List

1

First color

2

second color

3

third color

4

fourth color

8th

safety fiber

10

First kind of points

20

Second type of points

30

Third type of points

51

First surface

52

second surface

Claims (13)

Security fiber comprising: at least one surface (51, 52); wherein at least three kinds (10, 20, 30) of points are arranged on the at least one surface (51, 52); the three types (10, 20, 30) of dots being arranged such that the density of dots of a first type (10) varies over a region of the surface (51, 52) and the density of dots of a second type (20) varies over a portion of the surface (51, 52) and wherein the dots of the first (10) and second (20) types gradually blend to form an area of blended dots (10, 20); the area of mixed dots (10, 20) being overlaid with a third type (30) of dots; wherein the at least three kinds of dots (10, 20, 30) have substantially no color when irradiated with visible light having a wavelength between 380 nm and 780 nm; and wherein when irradiated with a UV wavelength between 315 nm and 380 nm or between 280 and 315 nm the first type (10) of dots emits a first color (1), the second type (20) of dots emits a second color ( 2) glows, the area of mixed dots (10, 20) glows in a third color (3) and the third type (30) of dots is invisible; and wherein, upon irradiation with a UV wavelength between 100 nm and 280 nm, the first type (10) of dots glows in the first color (1), the second type (20) of dots glows in the second color (2) and the with the surface of mixed dots (10, 20) superimposed on the third type (30) of dots lights up in a fourth color (4). security fiber after claim 1 , where dots (10, 20, 30) contain fluorescent printed ink. security fiber after claim 1 or 2 wherein the first (10) and second (20) types of dots are arranged such that the irradiated color is continuous over a portion of at least one surface (51, 52) when irradiated with a UV wavelength between 315 nm and 380 nm nm or between 280 and 315 nm. security fiber after claim 3 wherein the first (10), second (20) and third (30) types of dots are arranged such that the color luminous upon irradiation is not continuous over a portion of at least one surface (51, 52) upon irradiation with a UV wavelength varies between 100 nm and 280 nm. Security fiber after one of Claims 1 until 4 , wherein the at least three types of dots (10, 20, 30) have substantially no color when irradiated in NIR. Security fiber after one of Claims 1 until 5 wherein the first type (10) of dots are printed in an ink which fluoresces when exposed to UV light to produce yellow light, red light, blue light or green light or a mixture thereof. security fiber after claim 6 wherein the second type (20) of dots is printed in an ink that fluoresces in a different color than the first type (10) of dots when exposed to UV light. security fiber after claim 6 or 7 , wherein the third type (30) of dots is printed with an ink that fluoresces when irradiated with a UV wavelength between 100 nm and 280 nm to produce a light of yet another different color than the luminescent light of the dots of the first (10) and second ( 20) Art to produce. Security fiber after one of Claims 1 until 8th wherein at least the first type (10) of dots and the second type (20) of dots have different shapes. Security fiber after one of Claims 1 until 9 wherein the first (10), second (20) and third (30) types of dots are provided on only one surface (51, 52) of the fiber or on the first (51) and second (52) surfaces of the fiber are. Security fiber after one of Claims 1 until 10 wherein the fiber is made of paper strips, especially soft paper, more preferably small strips of paper or tissue paper, especially small strips of tissue paper. Security fiber after one of Claims 1 until 11 for use in security documents. Security document that contains the security fiber according to one of Claims 1 until 11 contains.

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