RU2587433C2 - Method of producing latent image - Google Patents

Abstract

FIELD: printing.

SUBSTANCE: invention relates to a method for obtaining latent image for protection against counterfeit secure printed products, in particular universal forms for implementation of railway transport. Technical result consists in improvement of reliability of protection. Template for concealed control element is applied on protective element, available on secure printing product. Template for concealed control element is made of transparent film or plastic. On template there is a periodic raster structure. Frequency of periodic raster structure of template matches screen frequency on background part of image on a universal document. Density of raster on control pattern is 5-15 % greater than density of raster on background part of image. Shape of raster structure on a reference pattern can vary from raster structure on background part of element.

EFFECT: image obtained has high degree of accuracy of reproduction of latent image.

1 cl, 10 dwg

Description

The invention relates to a method for obtaining a latent image, which can be used as a protective element in the manufacture of secure printing products, in particular universal forms for registration of rail transportation. Protected printing products are printing products that contain at least two elements of protection against counterfeiting and are manufactured using protection methods that prevent full or partial counterfeiting of these products.

Many methods are known in the art for protecting against document counterfeiting. Most of the known methods of protecting documents from counterfeiting are based on obtaining a latent image using a moire image.

From the patent US 2004076310 (date of access 16.10.2002), a method for authenticating objects, such as a document or product using a security device, is known. The protection device comprises a base layer with stripes containing a non-repeating sequence of basic strip patterns and a detecting layer containing a detecting linear network consisting of transparent lines, cylindrical microlenses. The essence of the method consists in superimposing the main layer and the detecting layer on each other, the formation of moire patterns and further comparison of these patterns with supporting moire patterns, which provides increased protection of the document or product.

In the anti-counterfeiting method in the documents disclosed in LT 4922 for identifying a latent image included in the main raster, it is necessary to apply a control pattern to the printed product, which in this case is a deformed raster applied to the substrate used to apply the latent image. When applying the template, any deviations in the geometry of the raster, not even exceeding one interval between the lines, will manifest themselves as the formed darker and lighter areas, which contributes to the image quality.

In the implementation of this method requires solving the algorithmically difficult task of constructing a raster with the introduction of additional variables into the usual screening algorithm, which significantly limits the possibilities.

Some sources of information, for example, in patent RU 2268152 (priority date 11.08.2004), describe a method for obtaining a latent image of a printed product by applying a control template to a printed product. Moreover, the latent image is made with the possibility of its visualization in grayscale or contour, when applying a control template. Moreover, the control template is a transparent substrate with a linear raster deposited on it, the angle and lineature of which are identical to those specified. Overlaying the optical key on the image at the appropriate angles will reveal two hidden images. In order not to cause moire when combining layers in such a composition, the deformation of the raster structure should be negligible. Whether the latent image will appear with the preservation of halftones or contour, depends on the set value of the deformation. When the optical key is shifted over the surface of the tested product, the latent image will change colors.

Unlike the known methods for obtaining a latent image in the claimed method, firstly, they do not use the moire effect when developing a latent image, and secondly, the security element itself consists of two components: a latent image made by an irregular raster and the background part of the element, performed by a regular raster, thirdly, to control the latent image, a template of transparent material is used with a periodic raster structure applied to it, the lineature of which coincides with the line of the raster on the background part of the image, and the density of the raster is 5-15% higher than the density of the raster on the background part of the protective element. An additional difference should be considered that for the development of a latent image using a control template, the exact positioning of the latter relative to the security element is not required, because the moire effect is not used, which greatly facilitates the control of the latent image. The moire that appears during inaccurate positioning of the control pattern relative to the background part of the security element has a side effect and is not a sign of determining a latent image, because does not occur on the latent image itself.

The technical result of the invention is the high protection of products of secure printing products, in particular universal forms for registration of railway transportation, and a high degree of accuracy of reproducing a latent image.

The achievement of the technical result is due to the fact that in the method for developing a latent image, the moire effect is not used. The method is based on masking the background part of the element with a template whose structure coincides with the structure of the template. This method can be applied both on opaque materials when monitoring a latent image in incident light, and on transparent materials when monitoring a latent image in transmitted light.

At the same time, the protection of products of secure printing products, in particular universal forms for processing railroad transportation, is facilitated by the fact that the template for controlling the latent image in this method is a thin transparent material (film, plastic, glass, etc.) up to 0, 5 mm, on which an opaque periodic raster structure is applied, the lineature of which coincides with the line of the raster in the background of the protective element, and the density of the raster is 5-15% higher than the density of the raster in the background of Szczytno element.

The security element is formed from two or more graphic structures so that its background part, which is not the main element, is made in the form of a raster structure with a known optical density or is part of a grayscale image made by standard printing methods using regular screening with a known lineature. By optical density should be understood a measure of reflection, absorption or transmission of light. The shape of the raster dot is not significant and can be any standard (round, oval, diamond-shaped, square, linear, etc.). The other part of the element, which is the hidden part, is formed using irregular screening, while the shape of the raster point does not really matter. As a special case, the shape of a raster dot in irregular rasterization can carry additional protective functions. In the simplest case, when a dashed (single-color) image is formed, the optical densities of the periodic and non-periodic structures that make up the protective element must be the same. This ensures the invisibility of the hidden element.

In FIG. 1 shows a view of an element with a latent image.

An indispensable condition for obtaining a latent image is the correspondence of the physical size of the raster points of a regular and irregular raster. In general, this correspondence can be obtained by calculating the physical size of the raster point of the regular raster. To do this, you need to calculate the linear size of the raster supercell of the background part of the element with a known lineature and output device parameters.

In FIG. 2 is an image of an example of a raster point.

The approximate size of the supercell of the raster point of the regular raster can be determined as follows:

Rsc = 1 / L2540,

where Rsc is the linear size of the supercell in microns;

L - lineature of a regular raster in lpi.

Knowing the optical density of the background part of the element, we can determine the size of the raster point, considering, in the general case, its shape as a square.

Rp = Rsc · Do / 100,

where Rp is the size of the raster point in microns;

Do is the optical density of the regular raster in%.

The above calculation is approximate, because the accuracy of calculations depends on the resolution of the output device for printing plates, the screening algorithm, the shape of the raster point, etc.

Additionally, the accuracy of calculating the size of the raster point of a square shape can be adjusted based on the graph, FIG. 3, obtained empirically.

The size of a single element of an irregular raster is most often known from the rasterization settings for an irregular raster. Examples of the type of raster structures of an irregular raster at various optical densities are presented in FIG. four.

By setting the rasterization parameters for a regular and irregular raster in such a way as to ensure approximate equality of the physical dimensions of the raster elements, it is possible to obtain a single-color image without visible manifestations of hidden elements.

A view of the print of the test element is shown in FIG. 5.

The template for monitoring the hidden element shown in FIG. 6 is a transparent medium (film, plastic) on which a periodic raster structure is applied, the lineature of which coincides with the line of the raster in the background part of the element, and the density of the raster is 5-15% higher than the density of the raster in the background part of the element. The shape of the raster structure in the control pattern may differ from the shape of the raster structure in the background of the element.

For the manifestation of the latent image, it is necessary to impose a template on the protective element. At the same time, there is no need for accurate positioning of the template, because the manifestation of the latent image does not use the moire effect. It is based on the masking by the template of the background part of the element, the structure of the raster on which coincides with the structure of the raster on the control template. The accuracy of the positioning of the control pattern affects the contrast of the appearance of the latent image, and the appearance of moire during the interaction of periodic raster structures of the control pattern and the background part of the protective element is a side effect. The maximum manifestation effect is achieved when combining raster structures and completely masking the background part of the image with a control template.

The method is convenient in operation and allows you to reproduce hidden images with a high degree of accuracy.

A view of the security element with the control template superimposed on it is shown in FIG. 7a and 7b.

Example.

The implementation of the method is as follows. The template for controlling the hidden element is superimposed on the security element available on secure printing products, for example, on a universal form for registering rail transportation. The latent image is made in the form of an irregular raster structure and the template does not have a masking effect to the extent that it affects the background (regular) structure. The optical densities of different parts of the element (latent image and background part) become different, due to this, the latent image becomes readable. As a result of the superposition of the control pattern on the security element, a latent image appears. The image thus obtained, as illustrated in FIG. 7b, has a high degree of fidelity of reproducing a latent image. In FIG. 7c and 7d illustrate the effect of the difference in the optical density of the template from the optimal one. A decrease in the readability contrast of the latent image is observed. High protection against fakes is provided by the fact that only the background part of the image is masked by the template, without significantly affecting the latent image, which provides a high degree of fidelity compared to other methods of obtaining a latent image known today.

Claims (1)

A method of obtaining a latent image for protection against counterfeiting of secure printing products, in particular, universal forms for processing rail transportation, which consists in the fact that the security element consists of two parts, namely, a latent image made by an irregular raster structure and a background part made in the form of a regular raster structure, while the optical densities of both parts of the protective element are the same, impose a template for controlling the latent image, made and of a transparent film or plastic on which a regular raster is applied, the line of the regular raster structure of the template coincides with the line of the raster in the background of the security element on the protected printing products, without precise positioning of the template, after which the latent image appears as a result of masking the background of the security element with the template, there is a difference in the optical densities of the background part and the latent image, while the density of the raster on the control template is 5-15% higher than the density of country on the background part of the security element and the shape of the raster structure on the control template may differ from the shape of the raster structure on the background part of the security element.

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