KR20140077159A - Method for producing an aluminum foil with integrated security features - Google Patents

Abstract

The present invention relates to an aluminum foil having an integrated safety device (6) and a method for producing the aluminum foil (1). The aluminum foil 4 is rolled up to a thickness of less than 150 占 퐉 in a plurality of cold rolling passes and at the same time a structure 5a, 5b is formed on both sides of the aluminum foil in the rolling direction. A loose composite 8 is formed from at least two of the aluminum foils 4 and such composite is fed to a pair of drive rollers 9 in a final cold rolling pass to form a relief Of surface structure 11a is reduced by 10 to 50% with respect to the average roughness height in one zone 6 'in a contrast and motif-dependent manner on at least one roller surface to form a motif relating to the security feature Respectively. This security feature is transferred onto the aluminum foil face 2a facing the roller surface, and then the loose composite 8 of the aluminum foil 1, 4 'is separated.

Description

[0001] METHOD FOR PRODUCING ALUMINUM FOIL WITH INTEGRATED SECURITY FEATURES [0002]

The present invention relates to a method of manufacturing an aluminum foil with integrated security features and an aluminum foil with integrated security features made by such a manufacturing method.

Medical products, which are typically packaged with the help of aluminum foils, are often targets for counterfeiting. Therefore, anti-counterfeiting devices should be as close as possible to such medical products, which means that direct application of security features during the manufacturing of primary packaging provides the best conditions for it.

Therefore, as is common in banknotes, the pharmaceutical industry has been trying to provide holograms for packaging materials. However, it turns out that the hologram can be counterfeited even if it is complex on the production side.

The present invention therefore provides a solution to this.

According to the present invention, a method of the above-mentioned type is proposed, in which aluminum foil is rolled to a thickness of less than 150 [mu] m and at the same time texturing extending in the rolling direction is produced on both sides of the aluminum foil, A loose composite is formed from at least two of the aluminum foils and the composite is guided to the drive roller pair in the last rolling pass and is transferred onto the outer surface of the aluminum foil facing the roller surface on at least one roller surface The relief type surface structure made by grinding is reduced according to the contrast and motif in the range of 10 to 50% with respect to the average depth of roughness, The loose composite of aluminum foils is separated after the type surface structure is reduced .

Further embodiments of the manufacturing method of the present invention are disclosed in the dependent claims 2 to 5.

The present invention also relates to an aluminum foil with integrated security features, which is manufactured according to the manufacturing method of the present invention and has security features of up to about 30% per unit surface.

Further embodiments of the aluminum foil according to the present invention are disclosed in dependent claims 7 to 10.

The invention is also illustrated by the following description in Figures 1 to 8 and by way of possible exemplary embodiments for the embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a drive roller for carrying out a process according to the invention; Fig.
2 is a detailed view of one drive roller and its surface design.
Figure 3 shows a Stribeck curve for documentation of related process parameters in the roller gap.
Fig. 4 shows a processing sequence of a process for making integrated safety devices; Fig.
Figures 5-8 illustrate possible embodiments of an integrated safety device.

A method of manufacturing an aluminum foil (1) according to the present invention, incorporating safety devices (6), comprises firstly a sub-process of strand casting, homogenization, hot rolling, cold rolling, and subsequent annealing above the recrystallization temperature annealing). This is followed by a foil cold rolling process. This causes the aluminum foil 4 to be rolled in several cold rolling passes to a thickness of less than 150 microns so that at the same time both the external faces 4a and 4b of the aluminum foil as shown in Figure 4 (b) Texturing (5a, 5b) is produced in the rolling direction as well. This structured roughness formed in the rolling direction leads to an induced reflection of the incident light such that the external faces 4a and 4b have a glossy appearance due to such induced reflection.

This method is modified not only in FIG. 4 (a) but also for the last rolling pass, as shown in FIG. 1, so that at least one roller surface is used for the drive roller pair 9 with the motif 6 ' do. Such a motif 6 'may be formed by a motif having a surface structure 11a such as a relief made in the rolling direction by grinding in a range of 10% to 50% with respect to the average roughness depth, . This can be done, for example, by the action of laser beams as shown in Figs. 2 (b), 2 (c) and 4 (c). During the last cold rolling step, a loose composite 8 is formed from two shiny aluminum foils 4 by release agent 7, for example as shown in Figures 1 and 4 (b). This loose composite 8 is fed into a closed roller gap 9 'formed between the two drive rollers 10,11. The motif relating to the safety device 6 is now transferred onto the outer surface 4a of the aluminum foil facing towards the drive roller. The random texturing which now appears blurry is formed in the area of the safety device 6 of the aluminum foil 1 - see figure 4 (d), which is followed by the remainder of the outer surface area 2a ) Is clearly distinguished from. Because of this random texturing, the diffuse reflection of the incident light is made in the area of the safety device 6, so that the area of the safety device 6 appears blurred. The outer surface 2b of the aluminum foil 1 facing away from the roller surface is covered by a release agent 7 with a second aluminum foil, designated 4 'for clarity. The two contact sides of the foil are identified by the roller grooves of the advancing rolling stage and the newly generated roughness during the combined rolling, and this roughness is mainly directed transverse to the rolling direction. Because of the random structuring of these surfaces, diffuse scattering occurs. After cold rolling, the loose composite of the integrated safety device 6 made according to the invention and the aluminum foil 1 with the aluminum foil 4 'is separated. The aluminum foil 4 'has a directional structuring 5'a on its outer surface 4'a such that the outer surface is shiny and the second outer surface 4'b has a random structuring Thus providing a hazy surface.

However, both drive rollers are provided with motifs 6 ', and another aluminum foil 1 with integral safety device 6 is made instead of aluminum foil 4'.

The thin rolling process underlying the process according to the invention falls within the subcategory "flat rolling" and is defined in particular by process final products having a thickness of 20 [mu] m. The cold rolling process in this thickness range requires a clear application of the surface roughness values to the tools in combination with the procedure liquid to create the friction conditions in the rotor cap required for plastic deformation.

A streamback curve for documenting the process parameters associated with the procedure - see Figure 3 - is referenced. Friction coefficients appear on the X-axis, and functions of velocity, pressure, and viscosity appear on the Y-axis. Mixed friction ranges are required for cold rolling of foils. In areas where there is little lubrication, continuous contact with the rolled material occurs, and the reduction of material in these areas is not possible, and then results in poor surface properties and damage to the rollers. In the fluid lubrication zone - see point 14 in Figure 2 (a) for this point - the drive roller 11 begins to rise so that the rolling process, especially direct control of material thickness reduction, is no longer possible. Whereby the range of the mixed friction can be adjusted by changing the parameters V, P and N. [

It is possible to generate longitudinal and pressure tensions that load materials beyond the shape change resistance to effect reshaping only in the mixed friction range, which means a reduction in material thickness. The adjustment of the parameters of the rolling oil 12 required for the reshaping process, namely viscosity, pressure, safety, and lubrication effects, is based on the precise selection of base oils such as kerosene, a highly refined hydrocarbon with precisely defined viscosity, On the one hand only by the addition of about 5 parts by volume of rolling oil additives which brings the pressure stability of the medium to a certain level but which also significantly affects the friction conditions in the rolling gap 9 '.

The adjustment of these parameters represents a basic requirement for the method according to the invention. Therefore, these parameters are permanently monitored and readjusted. In a specific application, the concentration of the rolling oil additive is measured directly through sampling from a buffer container of a roller rack and is maintained within the precisely specified range by additive adjustment. For accurate dose control, the treatment liquid is sprayed onto the drive rollers 10, 11 by a nozzle beam.

In the roller gap 9 ', a mixed friction condition is required, because only the specified frictional conditions allow the application of longitudinal tension stresses. This longitudinal tensile stress acts against the deformation strength and is an essential factor for achieving the deformation resistance during the foil rolling. This thickness reduction without longitudinal tension stress is not technically feasible.

A reduction is made from this method during cold rolling to a closed roller gap whereby the band thickness in the roller output is controlled by the primary parameter of the entry tension, Since the parameter acts against the deformation resistance of the aluminum foil 4. After achieving the maximum admission tension, the roller speed is used as the secondary control parameter to change the lubricant film thickness (fluid lubricant input).

During cold rolling, mixed friction conditions characterized by simultaneous occurrence of boundary friction and liquid friction are required. During liquid friction, which is the fluid lubrication 14, both surfaces are completely separated from each other. The transferred shear stress depends on the kinematic viscosity of the lubricant and the speed difference between the drive roller and the aluminum foil. On the contrary, during boundary friction, both sides are separated only by a lubricating layer, which is a small number of thick molecular layers, and the viscosity of the lubricant plays a subordinate role. The ratio between boundary friction and liquid friction with respect to the length of the roller gap is dependent on the layer thickness of the input lubricant and the roughness of the drive roller and the aluminum foil.

The mechanism for influencing the lubricant film thickness 13 is dependent on the fluid lubricant input, the input of the lubricant into the roughness valley 11b, and the attachment of the lubricant particles, as shown in Figure 2 (b).

The fluid lubricant input 14 mainly occurs in the input zone to the roller gap 9 '. The input zones form wedge-shaped gaps 12 through which the drive rolls 11 and aluminum (not shown) as limiting surfaces while moving in the direction of the wedge tip pull along the lubricant 13 in the form of a membrane, Forming a foil 4, which is illustrated in Figure 2 (a). The fluid pressure composition resulting from the rolling oil thereby depends on the rolling speed, the viscosity of the lubricant, and the geometry of the roller gap. As soon as the yield criterion for the aluminum foil 4 is satisfied, the aluminum foils are flexibly deformed and the layer thickness of the lubricant present at this position is pulled into the roller gap 9 '.

In the roller gap 9 ', the lubricant enters the surface depression, referred to as the roughness valley 11b, on the drive roller 11 and the aluminum foil 4, see FIG. 4 (c). This process, independent of the oil reserves of the surfaces, is also dependent on the orientation of the surface structure. This mechanism can be used for the induced change of the friction condition and serves to create a changed surface texture due to the subsequent friction of the liquid. This is because it misses the contact with the drive roller and thus misses the texturing in the rolling direction.

On the surface of the drive rollers and the aluminum foil conveyed into the roller gap 9 'boundary layers are formed, which is due to the physical and chemical adsorption properties of lubricant components such as, for example, surface active additives. This mechanism is influenced by the chemical composition and temperature of the roller material and the rolled material, and the rolling oil 12. This mechanism is not discussed further, since the temperature and composition of the rolling oil 12 with respect to the attachment of the lubricant components in the process according to the invention is not different from the conventional cold rolling process.

However, it is the ground-in of the drive roller which makes it possible to bring the lubricant film thickness and the associated changes of friction conditions in the roller gap from the mixed friction range in the region of the motif into the hydrodynamic range, It is a combination of the above effects by directed partial destruction of the structure. This results in a floating of the drive roller and a randomly distinct structure visually distinct, although it can be easily distinguished measurably in the measured roughness, since partial contact with the drive roller Due to the reflectivity of the remaining surface areas having a surface made in the rolling direction.

Aluminum foil 1 made with integrated security features 6 is replicated through optical processes in multiple passes for analytical purposes. For a clear illustration of the surface structure, representative thin samples are made in format A4. For measurement of the surface structure of the tools required for fabrication, epoxy resin imprints of the surface are made and measured by a reflection optical microscope and infinite focus.

With the aid of this analysis procedure it is now possible to carry out optical recognition to identify the security features 6 made in accordance with the invention. Figure 5 illustrates a security feature 6 that consists of lettering security combined with an example of an Asclepius customary staff in the healthcare industry. Of course, the latter is only an example in this case and does not claim rights for any exclusion. It is important to point out, however, that the outer surface illustrated in Figure 5 (b), which is directed away from the roller surface during the rolling process, does not include unwanted negative print motifs, whatever the aforementioned security features.

A fantasy example of the security device 6 is shown in Figure 6 and in section b as in Figure 6b there is a blurry surface in the area of the security feature 6, In the surface zones, the longitudinal (3) orientation is maintained and the surface looks glossy.

Figure 7 also shows an image taken by scanning electron microscopy of the security feature (6). In areas with security features, the surface is blurry, which makes the surface look glossy in the bounding surface areas. The detailed drawings according to Fig. 7 (a) or 7 (b) show that these different effects are caused by surface roughness in the zone of the security feature 6, and are configured longitudinally in the bounding zones Show.

This is applied analogously to the image shown in Fig. 8 of the aluminum foil 1 produced in accordance with the present invention with integrated security features 6, secured according to infinite focus analysis. From the ones shown in Figures 8 (a), 8 (b), 8 (c) and 8 (d), there is random texturing in the zone of the security feature 6, It is also evident that there is an induced structure 13 in Fig.

In summary, the following fundamental differentiating features are enumerated for correct recognition of the method according to the invention:

- Direct application of security features (6) with aluminum foil (4) thickness reduction; So no additional processing steps are required;

High operating efficiency at high speeds during fabrication of the aluminum foil according to the invention;

- more complex imitation due to the complexity of the basic process;

Due to the shape and arrangement of the surface structure (3), a clear association of the treatment with the rolling process;

- no possibility of removal of the destructive security features (6) of the aluminum foil surface;

The security feature (6) does not break through the back side of the aluminum foil (1);

- no change in the physical and / or chemical properties of the aluminum foil (4) such as roughness, foldability, stretch, tensile strength and hygroscopicity;

A change in the surface composition in the range of the fourth order, which can be measured by the average roughness depth (RZ);

There is no significant change in the arithmetic mean roughness index (RA) in the zone of security feature (6);

- in the range of a first degree (shape changes such as unevenness or out of roundness), a second degree (waviness), or a third degree (grooves) No change in shape of

In the cold rolling used in accordance with the present invention, optical features such as security feature 6 are applied by the induced application of different surface textures of aluminum foils in the fourth order range. No significant difference in roughness depth can be determined, but a difference in the type of texturing of the scaling with the grooves is achieved. The change in the shape of the aluminum foil is not detectable, so passing through the back of the foil does not occur either.

Finishing techniques such as shaping and embossing of the graphic relief type of flexible packaging materials with the help of conventional fabrication methods may be advantageous because of the optical or mechanical properties of the final product, Technology, and fabrication processes, it is quite different from the method according to the present invention, because the motif to be laid down during the stamping process is often pierced in an undesired manner on the back side of the material to be laid.

During rolling in the process according to the invention, the surface structure of the aluminum foil 4 is changed during the machining operation, making it possible to construct one or more security features 6 on its surface. Imitation by conventional finishing techniques is not possible or is readily identifiable as such. The production and further processing of the aluminum foil 1 according to the invention with integrated security features 6 is not indistinguishable from the processing of conventional rolled aluminum foils in the number of manufacturing steps, The present invention can be easily implemented in a conventional manufacturing method.

Claims (10)

A method of manufacturing an aluminum foil (1) having integrated safety devices (6)
The aluminum foil 4 is rolled in several cold rolling passes to a thickness of less than 150 탆 while at the same time texturing 5a and 4b is produced in the rolling direction on the outer faces 4a and 4b of the aluminum foil, A loose composite 8 is formed from at least two of the aluminum foils 4 and the composite is fed to the drive roller pair 9 in the last cold rolling pass and on at least one roller surface 11, Depending on the contrast and motifs in the range 6 'in the range of 10 to 50% relative to the average depth of the roughness, for the formation of motifs on the security features 6 that are transferred to the outer surface 2a of the aluminum foil Characterized in that the relief-type surface structure produced by grinding is reduced and the loose composite (8) of the aluminum foil (1, 4 ') is separated after the relief-type surface structure is reduced. Gt; The method according to claim 1,
The last cold rolling pass is performed with a closed roller gap 9 'and the prescribed mixed friction range is adjusted according to the streak back curve by parameters such as friction coefficient, dynamic viscosity of the rolling oil, rolling speed, and rolling pressure And at the same time a tension in the longitudinal direction is applied to the aluminum foil (4) acting against the shape change resistance of the aluminum foils in the closed roller gap (9 '). 3. The method according to claim 1 or 2,
Characterized in that for the last cold rolling pass on the roller surface (11), the relief-type surface structure (11a) made in the rolling direction is reduced in the average depth of roughness by the laser beams. 4. The method according to any one of claims 1 to 3,
In the aluminum foil 4 used, the release of the motif 6 'relative to the security feature 6 onto the remaining outer surface 2b of the aluminum foil 1, due to the provision of the release agent 7, ) Of the aluminum foil does not cause any unwanted strikethrough of the aluminum foil. 5. The method according to any one of claims 1 to 4,
Characterized in that the physical and / or chemical properties of said aluminum foil (4) are retained in the final product (1) of said manufacturing process, owing to the frictional conditions in said closed roller gap (9 ' . An aluminum foil (1) having an integrated security feature (6) produced according to any one of claims 1 to 5,
The security feature (6) is present in an amount of at most 30% per unit surface. The method according to claim 6,
Characterized in that the security feature (6) is in the form of letters, fantasy signs or lines. 8. The method according to any one of claims 5 to 7,
Characterized in that the security feature (6) can only be removed by fracture of the foil surface. 9. The method according to any one of claims 5 to 8,
Characterized in that the aluminum foil (1) does not undergo a shape change in the first, second or third zone after the last cold rolling pass. 10. The method according to any one of claims 5 to 9,
Security Feature (6) The aluminum foil is characterized in that the area appears blurred and the surface 2a appears glossy due to the induced texturing.

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