DE19627638A1 - Stamping cylinder for the production of stamping foils - Google Patents

Abstract

The invention concerns a process for producing a seamless embossing mould with defracting structures in the form of a relief pattern (10). This is done by producing an embossing tool that has defracting structures in the form of a relief structure. This embossing tool is impressed onto an intermediate mould that has at least one sleeve surface of malleable plastic material in order to transfer the defracting structures (10) to the malleable plastic material. The embossed surface is then duplicated, for example, into a metal surface (15) that produces a stable mould that is removed from the surface in a final stage.

Description

The invention relates to a method for producing a seamless cylinder shape, the diffraction structures in the form of a relief structure has and a method for producing an embossing cylinder, which a clamping cylinder and a metallic embossing mold.

Holograms, kinegrams or the like based on diffraction effects Elements set up due to their change in viewing angle occurring color interplay and the possibility of viewing angle Generate legible information, a popular authenticity feature because this so-called "optically variable effect" is practically impossible simple means can be imitated. They also offer a very good one Protection against counterfeiting using color copiers. Because that Copier can only he from a certain viewing angle reproduce recognizable information and color of the hologram, the optical variable effect, however, is lost.

Usually the holo used in security technology grams produced as embossed holograms, d. H. that in the diffraction structure Ren stored holographic information is converted into a relief structure puts. The holographic image is taken in a photo resist plate, which has the desired relief structure after development. This re Delivery structure is galvanically molded into a nickel foil, the so-called "Master Shim". This master shim also galvanically toch ter-Shims molded in the form of nickel foils. The individual plate-shaped daughter shims serve as an embossing mold. Several of these forms of embossing which is glued or stretched on a tensioning cylinder to make a continuous to enable a later hologram stamping foil to be embossed.

The This method is described in more detail, for example, in EP 0 338 378 A1.  

In a somewhat modified procedure, the first ones are molded Nickel foils for embossing a large number of benefits in a thermo plastic plastic plate, e.g. B. plexiglass used. This plastic plate is then electroplated and the molded metal layer in the form of a large embossing mold, which has many uses of the original Shims has attached to the tension cylinder.

Since the embossing dies made by the described process plana re are metal foils, the one with the finished embossing cylinder (consisting of Embossing mold and clamping cylinder) embossed hologram foil in the areas in which the individual embossing molds on each other on the clamping cylinder delimit a disturbing dividing line.

In order to avoid this disadvantage, it has also already been proposed Provide photo resist for holographic exposure on a cylinder and in a so-called "step repeat feed process" in certain To repeat intervals with the same holographic information The developed cylinder is then in a rubber mold and this in turn in a durable ceramic material on a steel core molded, which represents the embossing cylinder ("Holography News", Vol. 8 No. Sept. 1994, pages 1 to 7).

The last described procedure for producing a hologram The embossing cylinder, however, is very complex since the exposure of the entire photo-resist cylinder takes several days. In addition errors can occur during repeated exposure, which may which make the entire cylinder unusable. Also the impression processes ge require a lot of effort.

The invention is based on the object of specifying a method which avoids the disadvantages of the prior art.

This object is achieved by those mentioned in the independent claims Features resolved. Developments can the dependent claims be removed.

The invention is based on the basic idea of a small stamp to produce the desired diffraction structure in the form of a relief has, and this stamp for embossing a thermoplastic, zy lindric intermediate form to use. The embossing stamp can be used here be made planar and the relief structure by smooth rolling of the stamp are transferred into the cylindrical intermediate shape. Before however, the stamp is also given the same curvature as the cylinder cal intermediate form, so that the stamp by known step-repeat Devices pressed into the thermoplastic material in one step can be. The term stamp is also not intended to refer to the usual stamp The meaning should be limited, but within the scope of the invention it should be of any kind of embossing devices with which transfer individual benefits can be, for example, a high pressure roller, which in the area of Elevations has the holographic relief structure.

The cylindrical intermediate shape does not necessarily have to be one thermoplastic material, but can be of any plastically deformable material are formed. Also cylindrical intermediate Shaped shapes are conceivable, preferably from any core material however, metal, and a plastic plastic arranged thereon coating exist.  

The embossing is preferably carried out seamlessly over the entire cylinder tel surface. Then the cylinder is galvanically metallized and finally the resulting cylindrical metal foil by chemical dissolution, Heating, melting, etc. of the cylindrical intermediate shape from this taken. Since the cylindrical metal foil created in this way the Has embossed structures on the inside of the cylinder, must plating of the embossing mold again, so that a cylindrical metal foil is created, which on its outer surface has the desired diffraction structures. This metal foil forms the Embossing mold, d. H. a cylindrical, closed, seamless shim, which on a clamping cylinder is attached and together with the embossing cylinder forms.

For mounting the embossing form on the clamping cylinder come in green de All clamping techniques common in printing technology are taken into account. So can For example, the clamping cylinder material can be chosen so that it is Cooling shrinks. In this state, the embossing shape is on the clamping cylinder and then the clamping cylinder material again heated so that the embossing form adheres firmly to the clamping cylinder. Alternatively it is possible to expand the embossing material by heating that Pull the embossing mold onto the clamping cylinder and the embossing mold material then cool down again. According to a further variant, the Clamping cylinders are also pressed onto the embossing mold with the aid of compressed air will.

According to an alternative production variant, the cylindrical intermediate be shaped as a hollow cylinder, the thermoplastic Has coating on the inside of the outer surface. In this case The embossing is of course also carried out on the inside of the Hollow cylinder. This procedure has the advantage that the subsequent  molded metal foil can be used directly as an embossing mold as it the diffraction structures are already on the outer surface of the cylin has metallic foil.

Another embodiment according to the invention further provides that apply thermoplastic coating directly to the clamping cylinder, to emboss the thermoplastic coating with the embossing stamp and then harden the thermoplastic material. The advantage of this The method is that this embossed clamping cylinder directly as an embossing cylinder can be used for the production of stamping foils. For the thermoplastic coating come in this embodiment but only materials in question, which are very wi when hardened have a durable and hard surface, such as UV-curable lacquers that polymerize into solid plastics. But also poly mermaterials that are cross-linked by irradiation with high-energy ions offer the desired properties, such as abrasion resistance, chemical resistance etc.

Further advantages and exemplary embodiments are described below of the figures explained.

Show it:

Fig. 1 Scheme of the known process sequence in the production of stamping foils,

FIGS. 2a-f diagram of the process steps according to an embodiment of the invention,

Fig. 3 cross section of a possible embodiment of the zy-cylindrical intermediate form of FIG. 2a,

Fig. 4 the cross section of a possible embodiment of the zy-cylindrical intermediate form of FIG. 2a,

Fig. 5 another embodiment of the invention,

Fig. 6 further embodiment according to the invention.

Fig. 1 illustrates the usual method for producing hologram stamping foils. In the simplest case, a substrate, usually a transparent plastic substrate 1 , is coated with a thermoplastic material 2 . The thermoplastic material is softened in the area of the heated embossing roller 3 and provided with the holographic information in the form of the relief structure. Here, the embossing cylinder 3 has on its order the corresponding negative structure of the holographic information to be impressed. Following the embossing, the holographic structure is preferably metallized in a vacuum metallization chamber 5 . Finally, if desired, the metal layer can also be coated with an adhesive layer and a silicone layer covering it.

The stamping foils produced in this or a similar manner can be used for precipitation security of all kinds of value documents are used, by parts of the stamping foil either via selective activation of full surface applied glue or selective coating with glue transferred to the document.

The manufacture of the embossing cylinder 3 according to the invention will now be explained with reference to FIGS . 2a-f. However, it is pointed out that the use of the embossing cylinder according to the invention is in no way limited to the method described above. Rather, the cylinders produced by the method according to the invention can advantageously be used wherever continuously repeating relief structures are to be transferred into a deformable material.

In a first step, a small stamp 6 is produced according to the methods known from the prior art. Here, a diffraction structure produced by any method, such as a hologram, kinegram, excel, etc., is converted into a relief structure on an embossing die 6 of any shape. The embossing die 6 preferably has the same curvature as the cylinder subsequently to be embossed, since in this case the embossing die only has to be moved along an axis (in FIG. 2a, for example along the arrow) during the embossing process, and in this way very easily a uniform one Embossing depth or relief quality can be guaranteed.

According to Fig. 2a of this die 6 is used to the plastic upper surface of a cylinder 7, which is hereinafter referred to as a cylindrical intermediate molded to shape. If it is a mold made of thermoplastic material, the stamp is preferably heated.

Fig. 3 shows a possible embodiment of the cylinder 7 in cross section. It consists of a core 9 made of any suitable material, e.g. B. metal, and a thermoplastic coating 8 together . Alternatively, the cylinder 7 could also consist entirely of a plastic, especially thermoplastic material.

Fig. 4 shows a further possible embodiment of the cylinder in cross section. The intermediate form 7 here consists of three parts 25 , 26 , 27 , made of any material, but preferably metal. The parts 25 , 26 , 27 are connected to each other in the area of the inner lateral surface, for. B. glued, screwed or clamped together so that a stable cylindri cal shape is created. The outer surface of this intermediate form 7 is now coated with thermoplastic material.

The relief structures 10 transferred with the embossing stamp 6 can, as shown in FIG. 2a, be arranged at certain intervals on the cylinder 7 or can also adjoin one another without gaps. A spaced arrangement may e.g. B. be useful if instead of an embossing foil an end loss substrate, such as. B. endless banknote paper placed with a diffraction structure to be provided. It is also conceivable to make several different dies 6 and use them for embossing the cylinder jacket 8 . The order can be determined according to a fixed pattern or randomly.

The described embossing variants can of course also be used with the other embodiments of the invention find application.

FIG. 2b shows schematically the subsequent to the embossing Galvanisie tion 11 of the cylinder 7. The surface relief is preferably molded in the form of a nickel foil. However, other metallization processes are also conceivable, which lead to a stable, self-supporting metal foil.

After the galvanic impression 11 , the metal foil 12 has to be removed from the cylinder 7 , the detachment being able to take place, for example, by heating and thereby melting the thermoplastic material 8 , as indicated in FIG. 2 by the reference number 13 . If the Zy cylinder 7 consists of a metal core, cooling of the cylinder would also be conceivable, as a result of which the cylinder material shrinks and the metal foil can be removed. Further possibilities according to the invention are chemical loosening or bending of the cylinder.

If the cylindrical intermediate shape 7 is formed by a hollow cylinder, as shown in FIG. 4, the metal foil 12 can also be made by dismantling the cylinder 7 . By pulling out the cylinder part 25 in the direction of the arrow 28 shown in FIG. 4, the parts 26 and 27 can be easily removed. The thermoplastic coating 8 is destroyed here, the metal foil 12, however, remains intact.

Since the metal foil 12 carries the relief structure on the inside of the cylinder jacket, a further galvanic impression 14 must take place, as shown in FIG. 2d. If the first metal foil 12 is made of the same material as the second impression to be made (e.g. nickel), the first metal foil 12 can be covered with a separating layer, for example by spraying on a corresponding material. Subsequently, the deposited metal foil 15 , preferably also a nickel foil, is separated from the first foil 12 in accordance with one of the procedures according to the invention. The new metal foil 15 now represents the seamless embossing shape (shim). In a last step, it is attached to a tensioning cylinder 16 (see FIG. 2f).

Here, too, the cylinder material can be shrunk by cooling or the embossing mold material can be stretched by heating in order to allow the seamless embossing mold 15 to be pulled onto the cylinder 16 .

The clamping cylinder 16 and the stamping die 15 fastened thereon represent the finished stamping cylinder 3 , which can be used for the production of stamping foils.

A variant of the method described in FIG. 2 is shown in FIG. 5. The cylindrical intermediate shape 17 shown here consists of a hollow cylinder 18 made of any material that is coated with the thermoplastic material 8 on the inside of its cylinder jacket. Correspondingly, the embossing takes place with the possibly heated embossing die 6 in the interior of the intermediate cylindrical shape 17 . The further processing steps run analogously to those shown in FIGS. 2b and 2c. A further impression can, however, be dispensed with, since the first metal foil already carries the relief structure on the outer lateral surface and can therefore be attached directly to the clamping cylinder 16 as an embossing mold 15 (see FIG. 2f).

A special embodiment of this variant provides for the cylinder 18 to be produced from two halves, which preferably consist of plastic or metal, which are screwed together before the embossing process in FIG. 2a, ground to a smooth, cylindrical surface and only then with the thermoplastic material 8 can be coated. After the galvanic impression 11 (see Fig. 2b), the plastic mold 18 forms the outer man tel of the metal foil, which forms the subsequent embossing mold. In this case, the two shapes can also be separated by dismantling the screwed cylinder halves of the cylindrical intermediate shape 18 .

Another embodiment according to the invention is shown in FIG. 6. Here, a clamping cylinder is coated with a hardenable thermoplastic material 22 and embossed as in FIG. 2a with an embossing stamp. At closing, the thermoplastic material is hardened, whereby it becomes abrasion-resistant and resistant, so that the cylinder 20 prepared in this way can be used directly as an embossing cylinder 3 .

For the thermoplastic material, for example, polymer materials can be used that can be cross-linked by ion irradiation 21 , as shown in FIG. 6.

However, this particularly simple way of producing embossing cylinders is not limited to the manufacture of cylindrical dies, son can be used for any kind of embossing stick.

Claims (19)

1. A method for producing a seamless, cylindrical embossing mold which has diffraction structures in the form of a relief structure, characterized by the following steps:

• Producing an embossing stamp which has diffraction structures in the form of a relief structure,
• Provision of a cylindrical intermediate shape which has at least one jacket surface made of plastically deformable plastic material,
• Embossing the stamp into several areas of the plastically deformable plastic material in order to transfer the diffraction structures into the plastic material,
• Metallizing the embossed cylinder surface in such a way that a stable metal foil is produced,
• - Removal of the seamless, cylindrical metal layer, which has the diffraction structures.

2. The method according to claim 1, characterized in that the embossing stamp is made so that it has the same curvature as the cylindrical Has intermediate shape. 3. The method according to claim 1 or 2, characterized in that the Embossing stamp is a metal stamp that is used at least during embossing is heated.   4. The method according to claim 1 to 3, characterized in that the on diffraction structure provided in a step-repeat Process seamlessly into the thermoplastic surface of the cylindrical Intermediate form is impressed. 5. The method according to at least one of claims 1 to 4, characterized ge indicates that the metallization takes place in a galvanic process. 6. The method according to at least one of claims 1 to 5, characterized ge indicates that the embossing in the surface of the cylindrical surface Intermediate form takes place. 7. The method according to at least one of claims 1 to 6, characterized ge indicates that the cylindrical intermediate shape is a hollow cylinder which is made up of several detachably connected parts, and that the hollow cylinder with a thermoplastic layer is provided. 8. The method according to claim 6 or 7, characterized in that the taken, cylindrical metal layer is molded again, so that a cylindrical embossing shape is created, which on its outer surface which has diffraction structures. 9. The method according to at least one of claims 1 to 5, characterized ge indicates that the cylindrical intermediate shape is a hollow cylinder and the embossing takes place in the inner surface. 10. The method according to at least one of claims 1 to 9, characterized ge indicates that the cylindrical intermediate form by chemical dissolution,  Heating, melting, bending, disassembly of the cylindrical metal foil lie is being replaced. 11. Method for producing an embossing mold which has diffraction structures in the form of a relief structure, characterized by the following steps:

• Producing an embossing stamp which has the diffraction structure in the form of a relief structure,
• Provision of a carrier form,
• - coating the carrier shape with plastically deformable plastic material,
• Embossing the stamp into several areas of the plastically deformable material in order to transfer the diffraction structures into this material,
• - hardening of the thermoplastic material.

12. The method according to claim 11, characterized in that the thermoplastic material is cured with UV or ion radiation. 13. The method according to claim 11 or 12, characterized in that for the carrier shape uses a planar plate or a cylindrical shape becomes. 14. The method according to at least one of claims 1 to 13, characterized ge indicates that the plastically deformable material with the on the diffraction structure provided for the die.   15. The method according to at least one of claims 1 to 13, characterized ge indicates that the plastically deformable material with multiple embossing stamp that have different diffraction structures. 16. A method for producing an embossing cylinder consisting of a Clamping cylinder and at least one embossing mold, characterized in that that an embossing die according to a method according to the clamping cylinder at least one of claims 1 to 10 is attached. 17. Embossing cylinder, consisting of a clamping cylinder and one on top of it fastened embossing mold, characterized in that the embossing mold according to a method according to at least one of claims 1 to 10 is. 18. Embossing mold for the production of diffraction structures in the form of Re Delivery structures consisting of a support form and one arranged thereon netem plastically deformable material, characterized in that the plastically deformable material is a curable with UV or ion radiation Is plastic material. 19. Embossing mold according to claim 18, characterized in that the carrier is cylindrical and the plastically deformable material the outer jacket surface of the carrier shape is arranged.