RU2748464C2 - Method and mask for making watermarked paper, method for making resulting watermarked paper mask, and method for authenticating watermarked paper - Google Patents

Abstract

FIELD: printing.

SUBSTANCE: invention relates to a method for the manufacture of protected paper, including a step consisting in the manufacture of a watermark using a mask (10) attached to the paper machine wire, with the mask containing a rack of elements (18) to form light zones on the watermark, connected by binding elements (15), in this case, the specified light zones are arranged as pixels of the raster image, while the specified binding elements are thin enough that at least certain specified elements (18) for forming light zones provide the formation of pixels of the raster image, which, when viewed with the naked eye in transmitted light, would look like isolated pixels.

EFFECT: invention is aimed at expanding technological capabilities of the process of obtaining a watermark in paper.

25 cl, 14 dwg

Description

The present invention relates to methods for making watermarked security paper and the resulting paper and documents.

Watermarks have long been used in the security document field and are formed during the manufacture of a paper substrate by changing its thickness and affecting fiber deposition and / or dewatering.

Many improvements have been made to the watermarking industry.

More specifically, the present invention relates to the field of halftone watermarks.

Patents EP1122360 B1 and EP1252389 B1 of the present applicant describe methods of making watermarks marketed by the applicant under the trademark Pixel Watermark. The masks used in the manufacture of such watermarks are usually obtained by mechanical treatment or chemical etching of a metal plate. This method complicates the manufacture of high-precision elements, since the spatial resolution of the part is usually at least 0.8 of the thickness. Thus, for a mask with a thickness of 0.5 mm, the holes that can be made in it must have a size of at least 0.4 mm.

The production of watermarks of this type also includes other publications, in particular WO2010 / 036104 A1, WO2011 / 117828 A1 and WO2011 / 081561 A1.

WO2013 / 140126 A1 discloses a watermark-forming mask formed by a mesh, to which elements are attached to form a watermark pattern. The zones formed by the elements in the watermark appear to be separated from each other, which is presented as an advantage in allowing the display of Arabic script. This publication does not cover bitmap reproduction.

There is a need for further improvements in at least partially rasterized watermarks and related manufacturing methods, namely to increase the degree of protection provided by such watermarks.

The present invention solves the aforementioned problem by means of a method for manufacturing security paper, including the step of:

making a watermark using a mask attached to the mesh of a paper machine, wherein the mask contains a network of elements for forming light zones on the watermark, said elements are connected by means of connecting elements, while said light zones are located as pixels of a bitmap image, said connecting elements being sufficiently thin that at least some of the indicated elements for forming the bright zones provide the formation of pixels of the raster image, which to the naked eye look, in transmitted light, as isolated pixels.

The expression "to the naked eye" or "through the naked eye" means observation by the human eye with normal visual acuity without the use of additional equipment at a distance of 25 cm in daylight.

The present invention makes it possible to produce visually attractive watermarks and improve the security against counterfeiting because they are difficult to imitate due to their potentially high resolution.

Another advantage is that the paper can be better dewatered during the forming process.

Whereas in the prior art the various elements placed and welded onto the moldable mesh with relative positioning corresponding to the displayed pattern are held together by webs, or even a frame, which remain visible when the watermark is viewed with the naked eye, in the present invention at least some the structure elements of the watermark appear to be separated from each other to the naked eye, which provides new visual effects perceived by the layman and expands the range of patterns produced.

In particular, the visual impression of mobility created by the constituent elements of the pattern can be used to improve the aesthetic appearance. A watermark may be easier to recognize by a layman. Thus, watermarks of a new type can be obtained, made at least partially no longer in the form of rasters of interconnected dots or rasters of interconnected lines, as is currently used in pixel-type watermarks, but in the form of clouds of dots or clouds of lines, the connections of which are no longer visible or barely visible.

Another object of the present invention is a mask for shaping a watermark for implementing the method according to the present invention, comprising a set of elements for the formation of light zones, the elements of which are connected by means of connecting elements and are arranged as pixels of a bitmap, for example, in the form of lines, which are similar to lines referred to in the sphere of banknotes with "gravure" lines, while the connecting elements are thin enough not to be visible on the watermark, and these elements for the formation of bright zones when viewed in transmitted light with the naked eye appear in the image as isolated pixels.

Bitmap

By "bitmap" is meant an image formed by pixels arranged in accordance with a raster with a variable spacing and / or size to reproduce a halftone image. Depending on the density of the pixels, their size, height and / or amplitude, even depending on the local opacity of the paper, several “grayscale” levels can be reproduced at the level of each pixel. In this case, several of the indicated shades of gray preferably create a three-dimensional effect, for example a relief effect.

The bitmap preferably displays a monument, landscape, animal, plant, or portrait. In particular, a bitmap can only display a portion of a monument, landscape, animal, plant, or portrait.

Alternatively, the raster image can display any geometric shape, forming, in particular, the background or part of the background of another image, for example, a monument, landscape, animal, plant or portrait. With this option, a bitmap allows you to accentuate another image.

When viewed with the naked eye in transmitted light, the pixels of the raster image, in particular, are indistinguishable from one another. In particular, they are distinguishable from one another when the raster image is observed in transmitted light with magnification, for example magnification of at least 10 times, preferably at least 20 times. This is the second level of protection.

In one embodiment, the pixels of the bitmap are distinguishable from one another when viewed with the naked eye in transmitted light, which is a first level of protection.

Pixels

By "pixel" is meant a single element in a watermark pattern, similar to pixels in a digital image.

The pixels can be of any shape, preferably the shape of dots, in particular round, oval or polygonal dots, or the shape of lines, or the shape of letters, alphanumeric characters, ideograms, or symbols. A bitmap can contain pixels of various shapes.

Pixels form the bitmap elements of the bitmap.

A raster image can contain pixels located at the angle of rotation of the raster, that is, located in accordance with lines that make a certain angle with the horizontal.

The thickness of the raster elements can be from 200 to 1500 microns.

In the case of pixels in the form of lines, the width of the screen elements, that is, lines, may be greater than 50 µm, in particular 70 µm, and preferably 100 µm.

In the case of pixels in the form of dots, letters, alphanumeric characters or ideograms, the largest dimension, excluding the width of the raster element, may be greater than 50 µm, in particular 70 µm, and preferably 100 µm.

The raster can be amplitude modulated, that is, there can be a change in pixel size while the pixels are evenly distributed, or frequency modulated, or even both. In particular, starting from a certain pixel size, the raster can be with amplitude modulation, and below it - with frequency modulation.

The raster can be stochastic, for example, with a fixed pixel size, the statistical frequency of which is varied to display different shades of gray. Pixels can have the same geometry depending on the amplitude, or alternatively, the pixel geometry can change with amplitude.

The arrangement of pixels in the image is preferably generated automatically by software.

Mask

The mask can be made of any suitable material, in particular metal and / or plastic.

The mask contains subtle binding elements.

The said connecting elements, due to their subtlety, do not leave or leave very few visible traces in the watermark and connect and ensure stability of the elements intended to form the visual pattern of the watermark. The bonding elements preferably have a thickness of 20 to 200 µm, more preferably 30 to 100 µm. The thickness of the bonding elements is preferably constant.

The bonding elements preferably have a thickness of 20 to 200 µm, more preferably 30 to 100 µm. The width of the binding members is preferably constant.

The bonding elements preferably have a width and a thickness of 20 to 200 µm, more preferably 30 to 100 µm. The thickness and width of the bonding elements are preferably constant.

The connecting elements are preferably elongated elements.

The bonding elements are preferably arranged in a lattice. In this case, the smallest lattice size l of the lattice may be greater than 300 μm, in particular from 300 μm to 5 mm, preferably from 500 μm to 3 mm.

Bonding elements can be positioned between the base and the top of the elements they connect to form light zones. They are preferably located between the bases or between the tops of the elements they connect to form light zones.

The height of the elements for the formation of light zones can be constant within the mask. Alternatively, the height of the elements for the formation of the light zones is variable within the mask in order to affect the formation of the watermark and make the pixels more or less dark when viewed in transmitted light.

The elements for shaping the light zones are preferably composed of the same material as the bonding elements. In particular, the elements for shaping the light zones and the bonding elements are preferably one monolithic piece, which gives the mask greater strength.

The mask may contain, in at least one area, elements for forming light zones arranged as pixels of a bitmap image, at least one area for forming another type of watermark, in particular an area without elements for forming light zones, arranged as pixels of a bitmap image. Thus, it is possible to obtain a kind of hybrid watermark resulting from the superposition and / or registration of at least one full raster watermark and at least one conventional watermark, such as a multi-tone watermark obtained by means of an embossed surface, for example, embossing. , or an electro-type watermark. This "hybrid" watermark is especially visually appealing. Thus, the raster image of the watermark according to the present invention can display only one part of the pattern, while the other part, in particular the additional part, is a watermark of a different type, in particular an embossed multi-tone watermark. This is especially preferable when the watermark displays an image, preferably a monument, landscape, animal, plant or portrait, since according to the first embodiment, the watermark according to the present invention can display only one part of the said image, while the other part, in particular an additional part, reproduced by another type of watermark, in particular by an embossed multi-tone watermark, and in accordance with the second embodiment, said image can display an embossed multi-tone watermark, while the other part, in particular a background or a part of the background of said image, will be reproduced by the watermark according to the present invention. In such a case, the portion reproduced by the watermark according to the present invention will be identified, or it will be used to identify and highlight one portion or all of the other portion of the watermark.

The mask can contain several elements for the formation of light zones, each of which appears in the image as an isolated pixel, preferably on at least one area of the mask with a density of elements ranging from 30 to 80 elements per cm ² , which gives, for example, the same number of isolated pixels. pixels in the resulting image.

In one area, the mask may include elements for shaping light zones, located as pixels of the bitmap, and in another area, holes that form zones that appear darker than the light zones, and these holes are also located as pixels of the bitmap. Both areas correspond, for example, to the dark and light areas of the image, respectively. Between both areas, the watermark can include areas where pixels corresponding to light areas converge and are no longer isolated in the image. Darker areas can have the same opacity as the vellum area and can also be considered mini-areas of vellum paper.

The largest dimension of at least one of the elements for forming the light zones can be less than or equal to 0.3 mm, in particular from 0.1 to 0.3 mm.

This level of detail is especially useful to make it difficult to simulate the resulting watermark.

If the elements for the formation of light zones are smaller than the thickness, for example, they are more than 1 mm in width, then holes of very small diameter, for example, not more than 0.3 mm, can be made in order to ensure dewatering at their level during the papermaking process.

Elements for generating light zones can have a cross-section subject to amplitude modulation along the raster row of an image, which allows reproducing raster dots or lines of variable size, and / or a height, subject to amplitude modulation along the raster row of an image, which allows raster dots or lines having a variable size. opacity. In the latter case, it is thus possible to vary not only the distribution of pixels, but also the local opacity, and therefore the brightness of the pixels when viewed in transmitted light, which creates new possibilities for the final appearance of the watermark.

The spatial frequency of these elements for the formation of light zones can be constant along at least one image raster. The spatial frequency of these elements for the formation of light zones can also be variable along at least one image raster. A combination of amplitude modulation of the cross-section of the elements to form light zones, amplitude modulation of their height and / or modulation of their spatial frequency to obtain the best visual reproduction of the image is possible.

Grid

The mesh is a section of a paper machine that serves to form fibrous layers by dewatering a slurry of paper fibers.

It can be a grid of a cylindrical grid or a flat grid machine.

Preferably it is a mesh of a cylindrical machine.

Preferably, a recess is provided on the mesh, oriented outwardly from the fibrous layer in the suspension, and a mask is placed in this recess. This allows you to protect the mask, make it easier to position the mask, and optimize the opacity (shadow / highlight distribution) of the watermark. The niche can be formed by embossing the mesh. Alternatively, the mask is placed on the surface of the mesh, rather than in a niche in it, and even placed on the "positive" relief of the mesh.

The mask can be attached to the mesh in any suitable way, for example, welded, in particular soldered, to the mesh, or glued, set or otherwise mechanically attached.

The mesh and mask can be made such that the watermark includes at least one raster zone and one non-raster zone. This is, for example, the juxtaposition and / or overlay of various types of watermarks, for example, embossing in the net and masks according to the present invention, such as described above.

The watermark can be used in conjunction with other security methods such as security threads, security fibers or strips embedded in the paper during or after production. More generally, the watermarked paper of the present invention may contain any additional security in addition to the watermark. Some of the additional security features can be detected with the naked eye in daylight or artificial light without the use of a special device. These security elements contain, for example, colored fibers or strips. These security features are called level 1 security features.

Other types of additional security features can only be detected with a relatively simple device such as an ultraviolet (UV) or infrared (IR) lamp or a magnifying glass. These security elements contain, for example, fibers, straps, particles or microtexts. These security features may or may not be visible to the naked eye, for example becoming luminescent when illuminated by a 365 nm Wood lamp. These security features are called second level security features.

Other types of additional security elements require a more sophisticated detector to detect them. These security elements, for example, are capable of generating a specific signal when they are simultaneously or not simultaneously acted upon by one or more external excitation sources. Automatic signal detection allows you to verify the authenticity of the document, if necessary. These security elements contain, for example, indicators in the form of radioactive substances, particles or fibers, capable of generating a specific signal when these indicators are exposed to optocoupler, electrical, magnetic or electromagnetic excitation. These security features are called level 3 security features.

The additional security element or additional security elements present in the paper according to the present invention or in the security document according to the present invention may have security characteristics of the first, second and / or third level.

The subject of the present invention is also a method for making a mask according to the present invention, in which the elements for forming the bright areas, and possibly the connecting elements, are made in an additive manner. This allows for a higher resolution than mechanical processing or chemical etching.

"Additive method" refers to a method carried out by adding material, as opposed to a method carried out by removing material, as in the case of machining or chemical etching.

Preferably, said elements for shaping the bright areas, and optionally the bonding elements, are electroformed, which can provide a higher resolution than chemical etching.

The bonding elements are preferably made in the same additive manner as the elements for the formation of the light zones, and, thus, they turn out to be monolithic with the latter.

Electroforming allows you to easily make changes in the amplitude of the height of elements to form bright zones if desired - changes that can be made continuously or discretely to create additional shades of gray in the watermark.

Electroforming method ensures high precision of mask elements manufacturing. You can get details on the order of one isolated 0.1 mm pixel and play on the space between the pixels to create a "degrade" effect. A detail size of 0.2 mm is particularly well suited to the resolution that the paper substrate allows. The largest elements are preferably at most 0.8 mm. Outside of this value, the elements are preferably made with very small holes for removing water, for example with a diameter of 0.2 to 1 mm.

The finest details on a watermark can be formed by light areas visible in transmitted light.

The subject of the invention is also watermarked paper, in particular paper obtained using a method such as that described above, comprising a watermark having light areas arranged as pixels of a bitmap image in which at least one light area appears when viewed in transmitted light with the naked eye as an isolated pixel in the image. A watermark can include many of these light areas.

The watermark can include at least one area where the pixels corresponding to the light areas are no longer isolated and converge. The watermark can also include at least one area with isolated pixels that are darker than light areas, with these darker pixels being arranged as pixels in a bitmap.

The watermark is preferably formed by extremely light areas arranged as pixels of the bitmap.

The watermark may include an area having a density of light zones, each of which appears, when viewed in transmitted light, as an isolated pixel of 30 to 80 per cm ² , this area preferably occupying more than 20 mm ² in the watermark.

The subject of the present invention is also a method for authenticating watermarked paper according to the present invention, comprising examining the watermark in transmitted light in order to detect the presence of a raster image, the pixels of which appear as bright areas with at least one isolated pixel in the image, preferably with several isolated pixels. pixels in the image, in particular along one raster line of the image.

The present invention is suitable for the manufacture of any security documents such as bank notes, passports and other valuable documents or identity documents.

The present invention will be better understood by reading the following detailed description of non-limiting examples of the use of the invention and by studying the accompanying drawings, in which:

- Figures 1A-1E show details of watermarking masks according to the present invention;

- Figures 2a-2c are cross-sectional views of examples of masks according to the present invention;

3 shows one example of a mask according to the present invention;

4 shows the resulting image when the watermark is viewed in transmitted light;

- Fig. 5 shows one detail from Fig. 4;

5a and 5b show, respectively, another example of a mask according to the present invention and the resulting image when observing the watermark in transmitted light, and

6 illustrates the placement of a mask according to the present invention in a recess on a mesh.

Figure 3 shows one example of a mask 10 according to the present invention. This mask includes connecting elements 15 arranged in a lattice, for example, with cells of constant cross-section, each of which in the illustrated example has a square or rectangular shape. Alternatively, the connecting elements 15 are not arranged in a grid.

Figure 1A shows one example of a mask.

Connectors 15 connect isolated elements 18 to form light zones, arranged as pixels in a bitmap. These elements 18 for the formation of light zones have the largest dimension w .

The elements 18 can be placed at the intersections of the lattice drawn by the connecting elements 15 and in other places.

1B-1E illustrate the possibility of using elements having a non-circular outline as image pixels.

These can be polygonal elements such as rectangular as illustrated in FIG. 1B, ruled as illustrated in FIG. 1C, or L-shaped as illustrated in FIG. 1D. Elements 18 with different geometries can be located on the same carrier grid, as illustrated in FIG. 1E.

The smallest mesh size l of the mesh can be, for example, more than 300 μm, in particular from 300 μm to 5 mm, preferably from 500 μm to 3 mm.

Referring to FIGS. 2a-2c, it can be seen that the thickness e _{g of the} bonding elements 15 is less than the thickness e _{e of the} elements 18 to form the light zones. The tie elements 15 can form strands that intersect at right angles. Part of the strands can be oriented parallel to the rasters of the image, and the gap between these strands can correspond to the gap between the rasters in the image.

The height e _e of the light zone shaping elements 18 can vary within the mask 10, as shown in FIGS. 2b and 2c. This can make it possible to obtain more or less bright pixels, which increases the number of parameters that can be played on to reproduce the image. Varying the height of the elements 18 to create light areas can provide a watermark that is more difficult to reproduce.

In the example shown in FIGS. 2a-2c, the elements 18 for generating light zones in a top view have a cross-section that can vary along the rasters depending on the size of the raster dots to be reproduced in the image.

As shown in FIGS. 2a-2c, the connecting elements 15 connect the bases of the elements 18 to form light zones. Alternatively, the connecting elements 15 connect the tops of the elements 18 to form light zones.

The present invention is not limited to connecting elements 15 connecting the bases or tops of elements 18 to form light zones. In fact, the connecting elements 15 can connect the elements 18 to form light zones at points other than their base or their apex. Alternatively, a combination of different possibilities is possible, whereby the connecting elements 15 can connect the elements 18 to form light zones at their base and / or at their top and / or at other points.

It can be seen that some of the elements 18 for generating the light areas of the mask are isolated and create light areas on the resulting watermark 30 that look like isolated pixels 20, such as illustrated in FIGS. 4 and 5. This is, for example, the case on the back helmet.

The area 21 surrounding the pixels 20 may have the same thickness as the vellum area 31. FIG. 6 illustrates the possibility of a niche 100 on the mesh T receiving the mask 10.

The mask 10 is located in the niche 100, with the connecting elements 15 resting on the flat bottom of the niche 100 (Fig. 6) or at least part of the elements 18 to form the light zones rests on the flat bottom of the niche 100.

According to one embodiment, all of the elements 18 for forming the light zones and / or all of the connecting elements 15 are supported on the flat bottom of the recess 100. In particular, when the members 18 for forming the light zones have a variable height, such a configuration is, for example, possible due to the recess 100, the bottom of which is not flat, and / or due to the connecting elements, repeating the relief of the elements to form light zones.

The present invention is not limited to these examples.

In particular, the watermark or watermarks of the present invention can be positioned on the paper in such a way as to interact with other security elements such as threads or foils.

The paper can be based on natural and / or synthetic fibers. Preferably, the paper contains natural fibers such as linen and / or cotton fibers, in particular cotton linters.

The paper can be single-ply or multi-ply. In the latter case, the layers can be colored differently.

Claims (26)

1. A method of manufacturing security paper, including the stage consisting in the following: - production of a watermark using a mask (10) attached to the mesh of a paper machine, the mask contains a lattice of elements (18) for the formation of light zones on the watermark, connected by connecting elements (15), while these light zones are located as pixels of a raster image, while the specified connecting elements are thin enough not to be visible on the watermark and that at least certain specified elements (18) for the formation of light zones provide the formation of pixels of the raster image, which to the naked eye look like isolated pixels in transmitted light , while the elements (18) for the formation of light zones are made of the same material as the connecting elements (15), while the elements (18) for the formation of light zones and the connecting elements (15) form a monolithic part. 2. A method according to claim 1, wherein the pixels are in the form of points, in particular points of a circular, oval or polygonal shape. 3. The method of claim 1, wherein the pixels are in the form of lines, or the form of letters, alphanumeric characters, ideograms or symbols. 4. A method according to any one of claims. 1-3, in which the mesh is the mesh of a cylindrical cylinder. 5. A method according to any of the preceding claims, wherein the mesh (T) comprises a niche (100), the mask (10) being located in said niche (100). 6. The method of claim 5, wherein the niche is formed by embossing the mesh. 7. A method according to any of the preceding claims, wherein the mask is welded or brazed to the mesh. 8. A method according to any one of claims. 1-7, in which the mesh and mask are designed such that the watermark contains at least one raster zone and one non-raster zone. 9. A method according to any of the preceding claims, wherein the height (e _e ) of the elements (18) for generating the light zones is constant within the mask. 10. The method according to any one of claims. 1-8, in which the height (e _e ) of the elements (18) for generating the light zones is variable within the mask. 11. Mask for forming a watermark for using the method according to any one of paragraphs. 1-10, containing a set of elements (18) for the formation of light zones, the elements of which are connected by means of connecting elements and are located as pixels of a bitmap image, while the connecting elements (15) are thin enough not to be visually visible on the watermark, and these elements for generating light zones provide the formation of pixels of the raster image, which to the naked eye look in transmitted light as isolated pixels in the image. 12. A mask according to claim 11, comprising in at least one area elements (18) for forming light zones, located as pixels of a bitmap image, and having at least one other area without elements for forming light zones, located as pixels of a bitmap image ... 13. A mask according to claim 11 or 12, containing several elements (18) for the formation of light zones, each of which looks like an isolated pixel in the image. 14. A mask according to claim 13, having, on at least one area of the mask, a density of elements (18) for the formation of light zones from 30 to 60 elements per cm ² . 15. Mask according to any one of paragraphs. 11-14, in which at least one of the elements (18) for forming the light zones has a maximum dimension (w) less than or equal to 0.3 mm, in particular from 0.1 to 0.3 mm. 16. Mask according to any one of paragraphs. 11-15, in which the specified elements (18) for the formation of light zones have a cross-section subject to amplitude modulation along the raster image line. 17. Mask according to any one of paragraphs. 11-16, in which the specified elements (18) for the formation of light zones have a height (e _e ), subject to amplitude modulation along the raster row of the image. 18. Mask according to any one of paragraphs. 11-17, in which the spatial frequency of said elements (18) for the formation of light zones is constant along at least one image raster. 19. Mask according to any one of paragraphs. 11-17, in which the spatial frequency of said elements (18) for the formation of light zones is variable along at least one image raster. 20. Mask according to any one of paragraphs. 11-19, in which the bonding elements (15) have a thickness (e _g ) of 30 to 200 μm. 21. A method for making a mask according to any one of paragraphs. 11-20, in which the elements (18) for the formation of light zones, providing the formation of pixels of the raster image, which look to the naked eye in transmitted light as isolated pixels in the image and are manufactured in an additive manner. 22. Paper with watermarks, obtained by carrying out the method according to any one of paragraphs. 1-10, comprising a watermark (30) having light zones arranged as pixels of a bitmap image, including at least one light zone, which, to the naked eye, appears in transmitted light as an isolated pixel (20) in the image. 23. The paper of claim 22, wherein the watermark is formed by exclusively light areas arranged as pixels of the bitmap. 24. Paper according to PP. 22 or 23, in which the watermark contains several light zones, each of which looks like an isolated pixel in the image (20), in particular, it contains one region with a density of light zones, each of which looks like an isolated pixel in transmitted light, ranging from 30 up to 80 per cm ² . 25. A method for establishing the authenticity of paper with watermarks according to any one of paragraphs. 22-24, including examination of the watermark in transmitted light to detect the presence of a raster image, the pixels (20) of which to the naked eye look like light zones with at least one isolated pixel in the image or several isolated pixels in the image, in particular along the raster image row.

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