WO1995035553A1

WO1995035553A1 - Surface component with a spatial, locally coated micro-structure and its use

Info

Publication number: WO1995035553A1
Application number: PCT/DE1995/000776
Authority: WO
Inventors: Heinrich Wild
Original assignee: Leonhard Kurz Gmbh & Co.
Priority date: 1994-06-18
Filing date: 1995-06-08
Publication date: 1995-12-28
Also published as: DE4421407C1; AU2668095A; TW320604B

Abstract

The proposal is for a surface component, especially for use as a safety feature for a valuable document or the like, having a micro-structure (3, 14) in which essentially only the projecting regions (6) of the micro-structure have a coating (4, 15), e.g. a reflective metal layer. Local application of the micro-structure only in the projecting regions is made possible by the suitably oblique irradiation or vapour-deposition of particles of the coating material.

Description

Surface element with a spatial, regionally coated micro structure and use of such a surface element

The invention relates to a surface element with a base layer arranged on a support and projecting from its main plane and forming a spatial, diffraction-optically effective microstructure made of a first, transparent material, the microstructure of the

The base layer is partially provided with a coating made of a second material that has different optical properties than the first material.

U.S. Patents 5,128,779 and 5,145,212 are such

Area elements known. The microstructure is coated in the form of dots, strips or the like, the dimensions of these dots and strips being substantially greater than, for example, the line spacing of one formed by the microstructure

Hologram is. The procedure according to the prior art has the purpose, despite the presence of a diffraction-optically effective microstructure with a reflective coating, of being able to view further information present on a carrier, for example alphanumeric information or image information, through the microstructure , In the state of the art essentially only holograms are considered as microstructure which are visible from a certain viewing angle, while when viewing the support with the additional information from a direction essentially perpendicular to the plane of the support, they are hardly recognizable. According to the two US patents, it is further provided to arrange two hologram structures one above the other, the hologram information of one hologram being able to be read out about the reflecting points, strips, etc., while the information of the other hologram is about the respective spaces between the reflecting ones Points etc. are accessible.

A disadvantage of the prior art is that in order to achieve sufficient brightness of the holograms on the one hand and good visibility of the other information on the other hand, the ratio between the reflecting surfaces reflecting the hologram and the areas which are quasi-transparent must be selected very precisely . In addition, the design options for the known surface elements are very limited.

From DE-32 06 062 an authentication or security device for a counterfeit-prone object is known, in which a diffraction grating structure is used, whereby not the entire surface of the diffraction grating is coated with a reflective coating. It is namely the case in the prior art that a rectangular grating is used in which only the grating surfaces parallel to the main plane of the surface element or grating are vapor-coated while the surfaces running perpendicular to the main plane are not provided with a reflective coating. The main disadvantage of such a diffraction grating structure is that, although it does not cover the entire surface with a reflective coating, but is not transparent.

The invention is based on the object of forming a surface element with a spatial microstructure in such a way that, on the one hand, if necessary it has a certain transparency, even if a reflective coating is present, on the other hand, however, a multitude of design options with regard to. of the achievable optical effects, with the possibility of machine identification of the microstructure taking into account above all.

To achieve this object, it is proposed according to the invention to design a surface element of the type mentioned at the outset in such a way that the coating of the base layer is essentially only provided in the projecting regions of the microstructure, the coating being carried out by blasting particles of the second material onto the microstructure Base layer at an angle of

5 to 60 ° relative to the main plane of the surface element is applied.

If in the context of this registration of "projecting

Areas of the microstructure "are meant the areas of greatest layer thickness of the base layer having the microstructure, the projecting areas depending on the respective microstructure being able to have very different shapes. These can be line-like areas, but also point-like areas , the contour of the areas depending on the respective microstructure can be different, for example rectangular, wavy or the like.

The surface element according to the invention is now distinguished from the prior art in that the coating of a material different from the material of the base layer is only provided where the microstructure has projecting areas. This means that the coating corresponds in structure to the structure of the microstructure and not one coating area over several elements, e.g. Grooving that stretches microstructure. Nevertheless, the transparency of the material of the base layer is retained, so that either an information carrier located under the base layer is visible through the base layer that has the microstructure and the region-by-layer coating, or a use of the surface element is possible in application areas where the effect of the microstructure in transmitted light is Validity comes. It is obvious that, due to the application of the coating according to the invention, the finest optical effects achieved by the microstructure can be observed perfectly only in the projecting areas of the microstructure, whereas in the prior art, where a punctiform or the like. reflective coating, each covering several lines of the microstructure, is provided, impairments of the optical effect produced by the microstructure cannot be ruled out. As a result of the oblique radiation of the particles of the second material onto the microstructure of the

Base layer, for example in the form of oblique vapor deposition, is achieved in a simple manner that in fact only the projecting areas of the microstructure are given a corresponding coating. The type and scope the coating can be changed by changing the radiation angle. A particular advantage of such a type of coating is that an asymmetrical coating of the projecting areas of the microstructure is also possible, namely that more coating material is deposited on the side of the projecting areas of the microstructure facing the radiation source than on the side facing away from the radiation source Page. This fact is of particular interest if the coating of the microstructure is a reflective coating, since different intensities of the reflected light are obtained in this way depending on the angle of reflection. For example, it can be achieved in this way that, in the case of a reflection grating serving as a microstructure, the reflection diffraction signal of the + diffraction order differs considerably in intensity from the -th diffraction order.

A surface element according to the invention can be used for a wide variety of applications. Its use as a security element, e.g. to secure banknotes, checks, credit cards or valuable objects.

Depending on the respective application, a wide variety of microstructures can then be used, for example holograms and diffraction structure images that appear to change depending on the viewing angle.

However, it is particularly expedient if, in the case of a surface element according to the invention, the microstructure is a diffraction-optical grating structure. Using The lattice structure allows the area-by-area coating to be applied particularly uniformly by means of the oblique radiation, and in addition, precisely defined effects can be achieved by varying the radiation angle.

According to the invention, lattice structures are advantageously used which have a lattice constant, i.e. a line spacing between the individual grid lines, and a structure depth, i.e. maximum dimensions between the most protruding areas of the lattice structure and the most distant areas, between 0.2 and 10 microns. Such grating structures can be used to achieve most of the optical effects desired in the relevant field, for example color effects, movement effects, etc., the respective grating structure varying in a manner known per se over the total area of the surface element or the microstructure of the surface element from areas with each different lattice structure can be composed.

It is further provided according to the invention that the non-raised areas of the microstructure of the base layer after the application of the coating with material to form an essentially smooth surface of the

Surface element are filled, wherein the material used to fill the non-raised areas of the microstructure is identical to the material of the base layer, but can also be a different material. If the non-raised areas of the microstructure are filled in, a smooth surface is obtained in any case, with the result that the mechanical resistance of the coating of the microstructure or of the microstructure as a whole is improved. However, it is particularly favorable if the material used to fill the microstructure corresponds in terms of its optical properties to the first material of the base layer. In this way, one can

Create a surface element in which the coating forms a very fine grating or other diffraction-optically effective structure. With such a structure it is possible to achieve optical effects that were previously only possible with spatial diffraction structures that e.g. were metallized, could be achieved. While these known structures were of course not transparent, surface elements according to the invention either allow a view of an underlying information-carrying object, for example an image, or offer the possibility of utilizing optical effects based on transmitted light. A particular advantage of this embodiment when the surface element is used as a security element is the fact that it is not possible to take an impression of the microstructure which provides the optical security because of the smooth surface produced. Much finer, optically effective structures can also be produced according to the invention, as would be possible, for example, in a printing process. The reason for this is to be seen in the fact that with modern processes very fine microstructures in layers, e.g. can be produced in lacquer layers, which, according to the invention, leads to the fact that the region-by-region coating is also correspondingly finely structured.

The base layer can advantageously be coated with the

Microstructure can be covered by a transparent cover layer, which primarily fulfills a protective function. In a further development of the invention, the transparent cover layer can also be provided with a spatial microstructure, the projecting regions of the microstructure of the cover layer expediently having a coating which consists of a material whose optical properties are different from the cover layer. In this way, the surface element according to the invention can also be equipped with two superimposed microstructures, the advantage over the prior art, as described in US Pat. Nos. 5,128,779 and 5,145,212, primarily to be seen therein that the two microstructures are arranged extremely evenly over the surface of the surface element, and therefore undesired differences in the reflection or diffraction behavior do not result as a result of a correspondingly relatively coarse grid.

The manufacture of the surface element according to the invention is particularly simple if

A transparent lacquer layer is used in the base layer and possibly the top layer, into which the microstructure is embossed in a replication process, known per se, it being possible here to use the replication processes mentioned in the prior art in accordance with the aforementioned US Pat.

In general, the surface element according to the invention will be designed in such a way that the coating on the projecting areas of the microstructure of the base layer and / or the cover layer is reflective, the coating advantageously being made of metal, expediently applied by means of oblique vapor deposition, for example Aluminum, chrome, silver, gold or corresponding, suitable metal alloys.

Especially when the surface element is used as a security element and accordingly on a

If the substrate is to be applied, it is advantageous if the surface element is part of a transfer layer consisting of several layers and detachable from a carrier film, an embossing film, in particular a hot stamping film. The composition and manufacture of such embossing foils are described, for example, in DE 34 22 908 C2 by the applicant, wherein according to the invention there is no full-surface metallization of the structure having an optical diffraction effect, but only a region-by-region coating of the regions of the microstructure which have been embossed into the corresponding lacquer layer.

As already mentioned, the surface element according to the invention is particularly suitable for use as

Security feature for a value document, an object or the like Suitable, the document of value or the object can either be equipped directly with a corresponding surface element, for example by embossing and subsequent oblique radiation with the second material, or, which should generally be preferable, the surface element is produced in a first step and then , for example by lamination or hot stamping, is transferred to the object to be secured.

Further features, details and advantages of the invention result from the following description of preferred exemplary embodiments of surface elements on the basis of the Drawing, in which the surface elements are each shown without a carrier, ie essentially only the base layer and a possible cover layer.

Show it:

Fig. La - Id four different embodiments of

Base layers of the surface element with different microstructures and correspondingly different coatings;

2 shows a base layer with a microstructure and asymmetrical coating; Fig. 3 shows the intensity distribution of the

Diffraction structure according to Figure 2 reflected or transmitted light.

4a, 4b two further base layers with lattice

Microstructure and different

Coating; 5a - 5c different manufacturing stages of a surface element according to the invention and

6a, 6b two manufacturing stages of a further surface element according to the invention as

Development of the surface element according to FIG.

5c.

As already mentioned, only the most essential components of the surface element are shown in the drawing. For reasons of clarity and easier understanding, the generally available support for the base layer with the microstructure has been omitted. For example, a carrier or another substrate suitable for receiving a lacquer chic as the base layer comes in as the carrier Consider, for example, a document of value, an object to be marked accordingly or the like.

A base layer 1 is shown in each of FIGS. 1a to 1d, 2 and 4a to 6b. This base layer 1 is expediently a layer of a lacquer suitable for receiving a microstructure, with respect to the lacquers that can be used, their thickness and the embossing of the microstructure are expressly referred to the explanation in DE 34 22 908 C2. However, other lacquers and other layers which can be deformed by means of an embossing matrix to form a microstructure can also be used as the base layer.

The base layer 1 is attached, at least during the production of the surface element according to the invention, with the underside 2 on the carrier, not shown. On its side opposite the flat surface 2, which corresponds to the main plane of the surface element, the base layer 1 is provided with a microstructure, generally designated by the reference number 3, the design of the microstructure being different.

In Fig. La the microstructure is e.g. from a regular triangular lattice structure. In FIG. 1b, as can be seen in the drawing, the microstructure 3 is of irregular design, the microstructure 3 of FIG. 1b being a hologram structure, for example.

1c, 1d, 2, 4a, 4b, 5a and 5b, the microstructure 3 is in each case a rectangular grating, although the ratio between the grating constant g and the structure depth t of the grating (see FIG. 2) in each case can be different. In addition, the different rectangular grids differ in the respective relationships between web width a and web spacing b, the ratio a / b being large in FIG. 1c and small in FIG. 1d.

As can be seen from the drawing, according to the invention only the areas of the microstructures 3 of the base layer 1 which protrude the most from the surface 2 are provided with a coating 4 or 4a, the coating 4 being able to be formed, for example, by a vapor-deposited metal layer while the coating 4a (FIG. 4b) is formed by a dielectric which has different optical properties than the first material from which the base layer 1 is made.

In FIG. 1 a, the coating 4 is found only in the area of the tips 5 of the base layer 1. The same applies to FIG. 1 b, where only the most protruding “waves” 5 a of the hologram microstructure have a coating 4.

In the rectangular grid according to FIGS. 1c, 1d and 2 to 5b, the coating 4, 4a is essentially only present on the end faces 6 of the grid webs 7 opposite the surface 2. The recessed surfaces 8 between the webs 7, however, do not carry any coating material.

This type of coating of the base layer 1 is achieved according to the invention in that particles of the material forming the coating 4, 4a are sprayed onto the base layer at a predetermined angle. This spraying of the particles forming the coating at an angle (see dashed lines in FIGS. 1a to 1d and 2) leads to the areas of a Lattice web or the microstructure, which are covered by an adjacent web or projection during spraying, are not coated.

The respective coated surface depends on the one hand on the exact shape of the microstructure 3 and on the other hand on the irradiation angle, it generally being the case that the larger the irradiation angle, the larger the coated surface.

The dependence of the coating area on the irradiation conditions on the one hand and on the respective microstructure on the other hand can be seen particularly clearly when comparing FIGS. 1c, 1d and 2.

The surface elements according to FIGS. 1c and 1d differ essentially only in that the ratio between web width a and web spacing b is different, while the radiation angle α coincides. In the lattice according to FIG. 1c, a coating 4 is obtained which actually covers essentially only the end face 6 of the lattice webs 7 and extends only to a very small extent into the space between the lattice webs 7. In contrast, the coating 4 in the microstructure according to FIG. 1d extends significantly further into the space between the grid bars, which can only be attributed to the greater distance between the grid bars 7 compared to FIG. 1c, because in this case the grid bars less the respectively adjacent grid bar cover.

In the embodiment according to FIG. 2, a thicker coating of the one (in the figure right) side surface 9 of the lattice webs 7 is provided, which thereby What is achieved is that the irradiation angle at which the particles of the coating material strike the microstructure 3 of the base layer 1 is significantly increased in comparison to FIGS. 1a to 1d.

From Fig. 2 it follows that a surface element according to the invention can have special optical properties in the sense of a clear asymmetry. It is obvious that a grating of a design according to FIG. 2 reflects light relatively strongly in the Oth order or, because the regions between the webs are transparent, also transmits it strongly. With reflection - and possibly also transmission - of the light and the corresponding diffraction are then obtained in the + lth or -lth order of strongly different light intensities, as is sketched in FIG. 3. This property of the surface element according to FIG. 2 can, for example, be used to great advantage to ensure the authenticity of a document or the like. to be checked by machine. It is possible without great difficulty to measure the light beams of the + lth and -lth order at the same time and then to check their intensity ratio, which ratio can be used as a security feature.

Basically you get a procedure according to the

Invention, as illustrated in Fig. 4a and 4b, when the microstructure is a lattice structure, each lattice, in which - when using metal as a coating - alternating, metallized, opaque and conductive sections on the one hand and non-metallized, translucent and non-conductive subareas are present on the other hand. This is indicated in Fig. 4a by the arrows. When using a dielectric as the coating 4a, as in 4b, areas corresponding to alternately different optical properties are obtained. According to the invention, it is thus possible to create a surface element which, depending on the microstructure and coating chosen in each case, is semitransparent, for example, or also has very special optical effects or diffraction effects, it being possible to achieve both phase and amplitude diffraction effects.

5a to 5c, starting from the surface elements of FIGS. 1c to 4a, show the production of a special surface element according to the invention.

5a, the base layer is provided with a microstructure 3, for example a rectangular lattice structure, in a conventional manner, for example by molding.

This microstructure 3 is then provided with a coating 4 in the manner explained in connection with FIGS. 1 a to 2, for example by oblique vapor deposition with a metal, oblique vapor deposition processes e.g. for films or other substrates are generally known. According to FIG. 5b, a surface element is then obtained which basically corresponds to that of FIGS. 1c, 1d, 2 and 4a.

The surface element according to FIG. 5c is now modified compared to the surface element according to FIG. 5b in that the spaces 10 between the lattice webs 7 are filled, as a result of which a smooth surface 11 is formed on the side of the base layer 1 opposite the surface 2.

The material used to fill the gaps 10 may vary depending on the desired effect. In any case, the material should be transparent. However, it is particularly expedient if the intermediate spaces 10 are filled with a material that corresponds to the material of the base layer 1, because then the interfaces 12 (dashed lines in FIG. 5c) between the original base layer 1 and the filled material 10 are not visible.

The surface element according to FIG. 5d thus gives the impression that lattice structures formed by the coating 4 are only present in the region of the surface 11, without the surface 11 in any way spatially, i.e. is three-dimensional. 5c therefore acts like an amplitude grating. A particular advantage of the surface element of FIG. 5c can be seen in the fact that there is no possibility of transferring the structures of the surface 11 by molding, for example for the purpose of forgery.

Of course, further optical effects can be achieved by using material to fill the gaps 10 which differs from that of the base layer 1, e.g. with respect to the refraction factor, since then not only amplitude but also phase effects can occur.

To protect the coating 4, a transparent cover layer 13 can be attached to the surface elements of FIGS. 1a to 5c on the side of the base layer facing away from surface 2, which covers the microstructure and e.g. protective purposes only.

A particularly advantageous embodiment of such a cover layer 13 is shown in FIGS. 6a and 6b. The cover layer 13 according to FIGS. 6a and 6b is also with a Provided microstructure, for example also in the form of a rectangular grid with different grid parameters than the grid of FIGS. 5a, 5b, wherein, as shown in FIG. 6b, the grid structure 14 of the cover layer 13 can also be provided with a coating 15. The coating 15 of the lattice structure 14 of the cover layer 13 can match the coating 4 of the base layer 1, but can consist of a different material. E.g. one of the coatings 4, 15 could be made of metal, the other of a dielectric.

6b, a surface element according to FIG. 5c is first created in the manner explained above, whereby not only the gaps 10 between the lattice webs 7 are filled in one work step, but the cover layer 13 is simultaneously applied. This is possible if the cover layer 13 is made of the same material that is also used to fill the spaces 10. If a different material is provided for the cover layer 13, only that

5c finished and then the cover layer 13 applied in a further operation, for example after curing the mass used to fill the spaces 10.

The further microstructure 14, e.g. by means of a suitable embossing die. The further coating 15 is then applied to the microstructure 14 of the cover layer 13, it being assumed in FIG. 6b that the

Coating 15 is produced by correspondingly oblique radiation of the microstructure 14 of the cover layer 13. Of course, it would also be conceivable to cover the microstructure 14 with a coating over the entire surface provided, which can be easily accomplished that the radiation angle is chosen to be correspondingly large, usually about 90 °.

The surface element according to FIG. 6b comprises two optically effective microstructures which can certainly produce different optical effects. This ensures that either the optical effect produced by the coating 4 through the regionally coating 15 of the microstructure 14 is visible or, conversely, the optical effect generated by the microstructure 14 with the coating 15 is visible through the regionally coating 4, provided that for the Cover layer 13 or the base layer 1 can be used in accordance with transparent materials. If only reflection effects are to be observed, the base layer 1 could possibly be non-transparent, provided that the surface element of FIG. 6b is observed from the side of the coating 15.

Of course, it is also possible to cover the microstructure 14 and, if necessary, the coating 15 of the cover layer 13 with a further material layer, which may also only fill the depressions of the microstructure 14 in order to achieve a smooth surface.

Experiments have shown that in practice those surface elements are best used in which the base layer 1 or cover layer 13 is provided with a lattice structure as a microstructure, the lattice structure expediently having a lattice constant g and a structure depth t between 0.2 and 10 μm should have. A coating in certain areas is expediently achieved in that the irradiation of the lattice webs 7 or projecting Areas of the microstructure 3 with particles of the coating material take place at an angle between 5 and 60 ', which can be achieved by appropriate alignment of the carrier with the base layer with respect to the source of the coating composition.

Claims

Expectations

1. surface element with a base layer arranged on a support and forming a spatial microstructure with diffractive optics that protrudes from its main plane, the microstructure of the base layer being partially provided with a coating of a second material that has different optical properties from the first material, characterized in that that the coating (4, 4a) of the base layer (1) is essentially only provided in the protruding areas (7) of the microstructure (3), the coating being formed by blasting particles of the second material onto the microstructure (3) of the base layer ( 1) is applied at an angle () of 5 to 60 'with respect to the main plane (2) of the surface element.

2. Surface element according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the microstructure (3) is a diffraction-optically effective grating structure.

3. surface element according to claim 1 or 2, characterized in that the structure has a structure constant (g) and a structure depth (t) between 0.2 and 10 μm.

4. Surface element according to claim 1 or 2, characterized in that the non-raised areas (10) of the microstructure (3) of the base layer (1) after the application of the coating (4, 4a) with material to form a substantially smooth surface (11th ) of the surface element are filled.

5. surface element according to claim 4, d a d u r c h g e k e n n z e i c h n e t that the material used to fill the microstructure (3) corresponds in terms of its optical properties to the first material of the base layer (1).

6. Surface element according to one of the preceding claims, that the base layer (1) with the microstructure (3) is covered by a transparent cover layer (13).

7. surface element according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the transparent cover layer (13) is also provided with a spatial microstructure (14).

8. Surface element according to claim 7, characterized in that the projecting regions of the microstructure (14) of the cover layer (13) have a coating (15) which consists of a material whose optical properties compared to the cover layer (13) are different.

9. Surface element according to one of the preceding claims, that a transparent coating layer is used as the base layer (1) and possibly the top layer (13), into which the microstructure is embossed in a replication process.

10. Surface element according to one of the preceding claims, characterized in that the coating (4, 4a, 15) on the projecting areas (7) of the microstructure (3, 14) of the base layer (1) and / or the cover layer (13) is reflective is.

11. Surface element according to claim 10, d a d u r c h g e k e n n z e i c h n e t that the coating (4, 15) consists of metal.

12. Surface element according to one of the preceding claims, that the surface element is part of a transfer layer of an embossing foil, consisting of several layers, removable from a carrier foil, in particular. Hot stamping foil, is.

13. Use of a surface element according to one of the preceding claims 1 to 12 as Security feature for a document of value or an object prone to forgery.