RU2598413C2 - Method for producing aluminium foil with integrated security features - Google Patents

Abstract

FIELD: metal processing.

SUBSTANCE: invention relates to rolling aluminium foil. Method includes production of aluminium foil (1), as well as aluminium foil with integrated security features (6); the aluminium foil is rolled to a thickness of less than 150 µm in multiple cold rolling passes and simultaneously a texture (5a, 5b) which runs in the rolling direction is produced on both faces (4a, 4b) of the aluminium foil. Higher reliability of identification of the produced foil and reduced probability of forgery is ensured by the following: at least two aluminium foils (4) form a loose composite (8), which is fed into a pair of working rollers (9) in a final cold rolling pass, wherein on at least one of the surfaces (11) of the pair of working rollers the relief-like surface structure (11a) which is produced in the rolling direction by means of a polishing process has been reduced by 10 to 50% with respect to the average roughness height in one region (6') in a contrast- and motif-dependent manner on at least one roller surface (11) in order to form a motif for a security feature (6). Security feature is transferred onto the aluminium foil face (2a) that faces the roller surface, and the loose composite (8) of aluminium foils (1, 4') is then separated.

EFFECT: higher reliability of identification of the produced foil and reduced probability of forgery.

10 cl, 8 dwg

Description

The invention relates to a method for manufacturing an aluminum foil with integrated protective elements, as well as an aluminum foil made in this way with integrated protective elements.

Medical products that are usually packaged with aluminum foil are often fake targets. Therefore, anti-counterfeiting elements should be as close as possible to the medical product, i.e. The best prerequisite for this is the direct application of protective elements during the primary packaging process.

Therefore, as is usual with banknotes, attempts were made to supply holograms also with packaging materials for the pharmaceutical industry. It turned out that also holograms, although their production is relatively time-consuming, can be faked.

This invention may be useful here.

In accordance with the invention, a method of the aforementioned type is provided, wherein the aluminum foil is rolled in several passes of cold rolling to a thickness of less than 150 μm, and at the same time, texturing in the direction of rolling occurs on two sides of the surface of the aluminum foil, at least of these two aluminum a non-bonded layered structure is formed, which in the last pass of cold rolling is fed to a pair of work rolls with a shaft at least on one surface and the relief surface structure created in the direction of rolling due to polishing was pressed depending on the contrast and motive in the range from 10 to 50% relative to the average roughness depth in order to form a motive of the protective element, which is transferred onto the surface side of the aluminum foil facing the roll surface, after bringing the non-bonded layered structure of aluminum foils separated.

Other embodiments of this method are disclosed in accordance with dependent claims 2-5.

The invention also relates to aluminum foil with integrated security elements, which is manufactured by the method of the invention and which has security elements in an amount of at most 30% per unit area.

Other embodiments of this inventive aluminum foil are disclosed in accordance with dependent claims 7-10.

Below the invention is explained in more detail on one of the possible embodiments of the invention, as well as using FIG. 1-8.

In this case, Fig. 1 shows a pair of work rolls for implementing the method of the invention, Fig. 2 is a detailed view of one of the work rolls, as well as its surface configuration, Fig. 3 is a Stribek graph for documenting the relevant process parameters in a roll gap, and also in figure 4 - the process of implementing the method of manufacturing integrated security elements. 5-8 show possible embodiments of an integrated security element.

The manufacturing process of the inventive aluminum foil 1, equipped with integrated protective elements 6, first consists of separate processes of continuous casting, homogenization, hot rolling, cold rolling and subsequent firing above the crystallization temperature. They are followed by the process of cold rolling the foil. In this case, the aluminum foil 4 is rolled into several thicknesses of cold rolling to a thickness of less than 150 μm, while at the same time on two sides 4a, 4b of the surface of the aluminum foil there is a texture passing in the rolling direction 5a, 5b, see FIG. 4b. This structured roughness formed in the direction of movement leads to directional reflection of the incident light, so that due to this directional reflection, the sides 4a and 4b of the surface become brilliant.

For the last pass of the rolling, a retooling is carried out, see FIG. 1, as well as FIG. This motif 6 'is created when the surface structuring 11a created in the rolling direction by grinding is contrasted and depending on the motive is pressed in the range from 10 to 50% relative to the average roughness depth. This can, for example, occur under the influence of laser beams, see fig.2b, 2c and 4c. For the last pass of cold rolling, for example, from two shiny aluminum foils 4 by means of a separating means 7, an unfastened layered structure 8 is formed, see FIGS. 1 and 4b. This loose laminate structure 8 is fed to a closed roll gap 9 ', which is made between two work rolls 10, 11. The motive of the protective element 6 is now transferred to the side 4a of the surface of the aluminum foil facing the work roll. In the region of the protective element 6 of the aluminum foil 1 - cm Fig. 4d - now appears already opaque disordered texturing, which rises significantly above the remaining apparent shiny region 2a of the surface with directional texturing 3. In the area of the protective element 6 as a result of this disordered texturing, diffuse reflection of the incident light occurs, so that the region of the security element 6 appears dull. The side 2b of the surface of the aluminum foil 1 turned away from the surface of the roll is coated with release agent 7, as well as a second aluminum foil, for clarity, indicated by 4 '. The contact sides of these two foils differ in grooves from rolling of the previous rolling pass and roughness that arose during double rolling, which is mainly oriented across the direction of movement. Due to the disordered texturing of these surfaces, diffuse scattering occurs. After cold rolling, the non-bonded laminated structure of the aluminum foil 1 made in accordance with the invention, equipped with an integrated protective element 6, as well as aluminum 4 'is separated. The aluminum foil 4 'on its side 4'a of the surface has directional patterning 5'a, so that this side of the surface appears shiny, in contrast to which the second side 4'b of the surface has a disordered structure and therefore has a matte surface.

However, if both work rolls are equipped with one motif 6 ', then instead of aluminum foil 4' another aluminum foil 1 is obtained, equipped with an integrated protective element 6.

The rolling of the foil underlying the inventive method relates to the subgroup “rolling with flattening” and, in particular, is determined by the end products of the method with a thickness of 20 μm. The cold rolling process in this thickness range requires the specific application of surface roughness values for tools in combination with process fluids in order to create the tribological conditions necessary for plastic deformation in the roll gap.

To document process-relevant process parameters, we refer to the Stribek graph, see FIG. 3.

The friction coefficient is plotted along the abscissa, and the velocity, pressure, and viscosity are shown along the ordinate. For cold rolling foils, a mixed friction region is required. In the area of limited lubrication, there is constant contact with the rental; compression of the material in this area is impossible and subsequently leads to poor surface properties and damage to the roll. In the field of hydrodynamic lubrication — see also reference designation 14 in FIG. 2a about this — the work roll 11 “pops up”, so that targeted regulation of the rolling process and, in particular, reduction of the material thickness is no longer possible. Therefore, by varying the parameters v, p, and n, we can establish the region of mixed friction.

Only in the area of mixed friction can longitudinal tensile and compressive stresses be created that load the material above the deformation resistance and thus lead to deformation, i.e., a decrease in the thickness of the material. Regulation of the rolling oil parameters 12 necessary for the deformation process, namely viscosity, pressure resistance, lubricating action, is carried out by accurately selecting a base oil, namely a kerosene-like highly refined hydrocarbon with a precisely defined viscosity, and by adding about 5 vol. % additives to rolling oil, which, on the one hand, bring the pressure resistance of the medium to a certain level, but also have a decisive effect on the friction conditions in the 9 'roll gap.

The coordination of these parameters is the main prerequisite for the proposed invention method. Therefore, these parameters are constantly monitored and additionally adjusted. In a specific application, the concentration of additives to the rolling oil is measured directly by sampling from the buffer capacity of the rolling stand and is maintained within precisely defined limits by introducing additives. For the purpose of accurate dosing, the process fluid is sprayed onto the work rolls 10, 11 by means of a nozzle beam.

The conditions of mixed friction in the roll gap 9 'are necessary, since only a certain coefficient of friction allows the application of longitudinal tensile stresses. These longitudinal tensile stresses act against deformation resistance and during rolling of the foil are an essential factor in achieving deformation resistance. Reducing the thickness without these longitudinal tensile stresses is technically impossible in any case.

During cold rolling with a closed roll gap, the compression resulting from the method and at the same time the thickness of the strip at the exit of the rolls is controlled by the primary parameters of the input voltage (input tension), since they act against the deformation resistance of the aluminum foil 4. Upon reaching maximum tension at the input, a secondary control parameter, the speed of the rolls, is used to vary the thickness of the lubricating film (hydrodynamic lubricant supply).

In cold rolling, they tend to a state of mixed friction, which is characterized by the simultaneous occurrence of boundary friction and liquid friction. With liquid friction, that is, hydrodynamic lubricant 14, both surfaces are completely separated from each other. The shear stress transmitted depends on the dynamic viscosity of the lubricant and the speed difference between the work roll and aluminum foil. In case of boundary friction, on the contrary, both surfaces are separated only by a lubricant layer with a thickness of several molecular layers, while the viscosity of the lubricant plays only a secondary role. The relationship between boundary friction and liquid friction over the length of the roll gap depends on the thickness of the layer of supplied lubricant and the roughness of the work roll and aluminum foil.

The mechanisms for influencing the thickness 13 of the lubricating film are affected by the hydrodynamic supply of the lubricant, the supply of lubricant to the roughness depressions 11b, and also the deposition of lubricant particles, see FIG. 2b.

Hydrodynamic supply 14 of lubricant occurs primarily in the area of entry into the roll gap 9 '. In this case, the entry zone forms a wedge-shaped gap 12, whereby the work roll 11 and the aluminum foil 4, as they bound surfaces when moving in the direction of the wedge tip, drag the lubricant 13 in the form of a film with them, see Fig. 2a. The rise in hydrodynamic pressure caused by this in the rolling oil depends on the rolling speed, the viscosity of the lubricant and the geometry of the roll gap. As soon as the yield condition for the aluminum foils 4 is satisfied, they are plastically deformed and the thickness of the lubricant layer available at this point is drawn into the roll gap 9 '.

In the roll gap 9 ', lubricants enter the surface recesses, the so-called roughness troughs 11b, on the work roll 11 and aluminum foil 4, see Fig. 4c. This process depends, along with the contained oil volume of these surfaces, also on the orientation of the surface structure.

This mechanism can be used to purposefully change the friction conditions and also serves to create an altered surface texture due to the arising liquid friction. This is due to the lack of contact of the work roll and the absence due to this texturing in the rolling direction.

On the surface of the work roll and aluminum foil due to physical sorption and chemical sorption of lubricant components, such as, for example, surface-active additives, boundary layers are formed, which are sent to the roll gap 9 '. This mechanism is affected by the material of the rolls and rolled products, as well as the chemical composition of the rolling oil 12 and its temperature. Since the temperature and composition of the rolling oil 12 from the point of view of deposition of the components of the lubricant in the proposed invention, the method does not differ from the traditional method of cold rolling, we will not dwell on this mechanism in detail.

However, a combination of the above effects makes it possible to reduce the thickness of the lubricating film and the associated change in the tribological conditions in the roll gap of the mixed friction region in the motive region into the hydrodynamic region by means of targeted partial destruction of the grinding roll grinding structure. Due to this, the work roll emerges, and a disordered texture arises, which, although measurably almost does not differ in the measured roughness values, however, due to the reflection properties, it is optically noticeably different from other areas of the surface that, due to partial contact with the work roll, have a surface structured in the direction of rolling.

The manufactured aluminum foil 1, equipped with integrated protective elements 6, is subjected to optical photocopying for several passes for analytical purposes. To visualize the surface structure, representative foil samples are produced in A4 format. To measure the surface structure of the tools required for manufacturing, surface prints are made on epoxy resin and measured using a microscope for examination in reflected light and infinite focus.

Using this analytical method, it is now possible to perform optical identification in order to confirm the security elements 6 made in accordance with the invention. Thus, Fig. 5 shows an image of the security element 6, consisting of the inscription Security in combination with the medical image of an esculap snake. Here, it is obvious without claiming any exclusive rights is shown only as an example. In any case, it is important to indicate that the side of the surface shown in FIG. 5b, which was turned away from the surface of the rolls during the rolling process, does not have any undesirable motifs for inverting the aforementioned security element.

Figure 6 shows a fantasy image of the protective element 6, and on the fragment B, see about fig.6b, we can say that in the area of the protective element 6 the surface is dull, however, in the correspondingly adjacent regions of the surface, the structuring 3 in the longitudinal direction is still retained, making this surface appear shiny.

7 also shows the image of the protective element 6 taken by scanning electron microscopy. In the area of the protective element, the surface is dull, in contrast to which the surface in the adjacent areas of the surface appears shiny. The detailed views shown in figa or 7b show that this different effect is caused by the fact that in the area of the protective element 6 the surface is rough, but in the adjacent areas it is structured in the longitudinal direction.

The same applies to the image shown in FIG. 8 of an aluminum foil 1 made in accordance with the invention, provided with an integrated security element Security by means of endless focus analysis. Also, from the corresponding images in accordance with FIGS. 8a, 8b, 8c and 8d, it can be seen that there is disordered texturing in the region of the security element 6, in contrast to which there is directional structuring 13 in the bordering regions.

To summarize, the essential distinguishing elements of accurate identification of the method proposed by the invention are listed:

- the application of the protective element 6 directly and simultaneously with a decrease in the thickness of the aluminum foil 4; therefore, no additional work step is required;

- high efficiency due to high speeds in the manufacture of the invention of aluminum foil 1;

- difficult fake due to the complexity of the main process;

- unambiguous identification of the method of the rolling process due to the shape and location of the structuring 3 of the surface;

- the inability to remove the protective elements 6 without destroying the surface of the aluminum foil 1;

- lack of bursting of the protective element 6 on the reverse side of the aluminum foil 1;

- the absence of changes in the physical and / or chemical properties of aluminum foil 4, such as roughness, folding ability, longitudinal deformation, tensile strength and wettability;

- change in surface quality within the 4th order, measurable by the average roughness depth Rz;

- the absence of a significant change in the arithmetic average value of the roughness Ra in the region of the protective element 6;

- absence of deformation within the 1st order (shape deviations, such as non-flatness or non-circularity), 2nd order (waviness) or 3rd order (grooves).

When cold rolling is used in accordance with the invention, optical elements, such as protective elements 6, are introduced by the targeted application of various surface textures of aluminum foils within the 4th order. No significant difference in the values of the depth of roughness is observed, but a difference is achieved by the type of texture of the grooves and scales. Changing the shape of the aluminum foil 4 is not detected, therefore, there is also no punching on the back of the foil.

The graphic relief configuration of flexible packaging materials using common manufacturing methods and refinement technologies, such as, for example, embossing (indentation method), differs significantly with respect to the starting material, manufacturing technology and method, as well as optical or, accordingly, mechanical properties of the final product from the method proposed by the invention, since with the indentation method the embossing motif is often undesirably pressed on the back side of the embossed material .

When rolling in the course of the method proposed by the invention, the surface structure of the aluminum foil 4 changes during the deformation process, which makes it possible to make the surface with one or more protective elements 6. Counterfeiting using common refinement technologies is impossible or, accordingly, can be easily identified as such. The manufacture and further processing of the aluminum foil 1 according to the invention, equipped with integrated protective elements 6, does not differ in the number of technological steps from the processing of conventional aluminum-foil-riveted rolling foils and can thus be simply incorporated into the manufacturing process common for pharmaceutical products.

Claims (10)

1. A method of manufacturing aluminum foil (1) with integrated protective elements (6), comprising cold rolling of aluminum foil (4) in several passes to a thickness of less than 150 microns with the simultaneous formation of ordered relief texture on two sides (4a, 4b) of the surface of the aluminum foil (5a, 5b) extending in the rolling direction, after which at least two aluminum foils (4) are joined without bonding to form an unfastened layered structure (8), which, in the last cold rolling pass they are attached to a pair (9) of work rolls, the surface (11) of at least one of which has a relief structure (11a) formed by grinding in the rolling direction and the relief element pattern (6 ′) made by forcing said surface structure (11a) of the roll to a depth of 10-15% relative to the average depth of the roughness of structuring (11a), depending on the contrast and relief of the pattern of the protective element, which during the rolling process is transferred to the surface side (2a) facing the roll surface of aluminum foil, after which the non-bonded layered structure (8) of aluminum foil (1, 4 ′) is separated. 2. The method according to p. 1, characterized in that the last cold rolling pass is performed with a closed roll gap (9 ′), and the mixed friction region is established by means of the Stribek graph, depending on the parameters of the friction coefficient, dynamic viscosity of the rolling oil, rolling speed and rolling pressures, and simultaneously with rolling in a closed roll gap (9 ′), longitudinal tensile stresses opposite the deformation resistance of the aluminum foil are applied to the aluminum foil (4). 3. The method according to p. 1, characterized in that in the last pass of cold rolling on the surface (11) of the roll, the relief structuring (11a) of the surface along the average roughness depth is reduced by laser processing. 4. The method according to p. 1, characterized in that the non-bonded layered structure (8) has a release agent (7) to prevent bursting of the relief (6 ′) of the pattern of the protective element (6) on the other side (2b) of the surface of the aluminum foil (1) . 5. The method according to p. 1, characterized in that the rolling in a closed roll gap (9 ′) is performed in compliance with tribological conditions ensuring the conservation of physical and / or chemical properties in the finished aluminum foil (4). 6. Aluminum foil (1) made by the method according to claim 1, containing integrated protective elements (6) in an amount of not more than 30% per unit area. 7. Foil according to claim 6, characterized in that the protective elements (6) are made in the form of letters, fantasy characters or lines. 8. The foil according to claim 6, characterized in that it is made with the possibility of removing the protective elements (6) only when its surface is destroyed. 9. The foil according to claim 6, characterized in that it does not have shape deviations in the form of flatness, waviness and grooves. 10. The foil according to claim 6, characterized in that it has a shiny surface with a matte area of the protective element (6).

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