DE102012025740B3 - Production of microstructured stamps - Google Patents

Abstract

Method for producing a lens (10) with a microstructure (18/18') on at least one curved lens surface, comprising:
- providing a substantially planar foil (20);
- Generating a microstructure (18/18') in or on the substantially planar film (20);
- Reshaping of the film (20) to produce a curved surface which defines the at least one curved lens surface of the lens (10) to be produced with the microstructure (18/18');
- Transferring the microstructure (18/18') from the shaped film (20) to the lens (10) to be produced, characterized in that the influence of the shaping of the film (20) on the geometry of the microstructure (18/18') already is taken into account when generating the microstructure (18/18') on the essentially planar film (20), in that the deformation of the microstructure (18/18') caused by the forming is already precompensated,
wherein transferring the microstructure (18/18') from the curved foil (20) to a lens (10) comprises:
- Transferring the microstructure (18/18') from the curved film (20) to a stamp; and
- Embossing the lens (10) by means of the stamp.

Description

The invention presented relates to a method for producing a lens, in particular a spectacle lens, which has an in particular diffractive microstructure on at least one side. In this case, the desired microstructure is produced by casting in particular by using a correspondingly structured casting mold in the production of the semi-finished product (blank) or finished product (spectacle lens), or the desired microstructure is formed in particular by using a correspondingly structured stamp in the semi-finished product (blank) or finished product ( Spectacle lens) introduced by forming.

Diffractive optics often use a combination of a refractive and a diffractive effect on at least one surface or interface. This means that very good imaging qualities can be achieved with comparatively few lens elements, even in complex optics with a high functional density. Especially for applications in which only a single lens is used, a combination of refractive and diffractive effects can reduce aberrations that can otherwise only be suppressed by multi-layer lenses or lenses with refractive index gradients. In particular in the case of lenses, such as spectacle lenses, which are constructed from a dispersing material, diffractive microstructures are occasionally used on a lens surface in order, for example, to reduce color fringes due to chromatic errors in the lens. Some examples for a design of diffractive structures for color fringe correction are, for example, from DE 10 2010 051 627 A1 , DE 10 2010 051 637 A1 , DE 10 2010 051 645 A1 and DE 10 2010 051 762 A1 known.

DE 698 33 226 T2 discloses a method of obtaining an ophthalmic lens having on the surface a dedicated antireflection microstructure, a step of transferring the microstructure from a mold having an internal surface bearing the microstructure and having a vision correction geometry, the transfer consisting in: forming a layer of a first curable optical material in the mold, one face of which bears a replica/duplicate of the microstructure carried by the internal face of the mold; Allowing the layer of the first optical material to be cured to cure in the mold, the transferring step being characterized in that the first optical material, after curing, forms a hard coating having abrasion-resistant properties and further consisting of: introducing a second curable optical material material between the surface of the hardened layer of the first optical material opposite the surface bearing the microstructure and a wall of the mold; and allowing the second optical material to harden.

US 2011/0 233 799 A1 discloses a method of making a lens with a functional nanostructure. A photonic crystal structure is formed on a mold, and the mold is pressed against one side of the lens, which is coated with a curable polymer. The curable polymer thus adapts to the photonic crystal structure and is cured in a curing step.

However, one of the challenges in using diffractive structures is their high production costs. Machining processes (e.g. diamond turning) have become established, especially for the production of rotationally symmetrical structures. Either the lens to be produced can be machined directly, or a mold or stamp is machined to form a negative of the microstructure to be provided on the lens, which is then formed by casting the lens or by stamping or embossing on the appropriate lens surface is transferred. However, these machining processes have certain limits with regard to the structure sizes that can be achieved and the freedom to deviate from rotational symmetry.

Another approach is optical structuring by means of direct laser exposure, as described, for example, in "Diffractive structures on curved surfaces for hybrid imaging systems" by Rene Reichle et al., Photonik 4/2010, pages 36 - 40. On the one hand, direct laser exposure offers a very high structural resolution and above all allows great freedom with regard to the shape of the structures. In this case, a substrate (eg a lens to be structured) is coated with photoresist, which is then exposed locally, in particular by means of a focused laser beam. After developing the photoresist, the resulting structures can be etched into the substrate. For a microstructuring of curved lens surfaces, for example of spectacle lenses, it is crucial that the surface to be structured always remains in the focus of the laser light during the exposure of the photoresist. This can be achieved, for example, by means of an autofocus system. But even the uniform deposition of the photoresist on a curved surface places certain demands on the deposition process. All in all, an optical method using laser direct exposure with the use of a corresponding technological effort allows a very high structure quality for microstructures even on curved surfaces and with a high degree of freedom with regard to the shape of the micro structures reachable. With this procedure, the curvature is (usually) limited.

The object of the present invention is to simplify the production of lenses, in particular spectacle lenses, with an in particular diffractive microstructure on at least one curved surface of the lens.

This object is achieved by a method having the features specified in claim 1. Preferred embodiments are subject of the dependent claims.

The invention thus offers a method for producing a lens, in particular a spectacle lens, with a microstructure on at least one curved lens surface. The at least one lens surface on which the desired microstructure is to be formed can in particular be a convex or a concave surface. It can therefore be either the front surface or the back surface of a spectacle lens. In a further preferred embodiment, corresponding microstructures could also be provided both on the front surface and on the back surface of a spectacle lens.

The method according to the invention comprises providing an essentially planar film and producing a microstructure in or on the essentially planar film. In other words, a microstructure is produced on at least one surface of the essentially planar foil. Depending on exactly how the manufacturing process proceeds, i.e. in particular depending on how many intermediate steps of a subsequent transfer of the microstructure still take place, the microstructure produced on the at least one surface of the essentially planar film essentially represents a positive or negative copy of the final, microstructure to be formed on the curved lens surface.

A microstructure is preferably produced on the at least one surface of the film by means of lithographic technology. In a preferred embodiment, the lithography can be carried out directly on the film. In another preferred embodiment, lithography is carried out on an essentially planar structure transfer substrate and the microstructure produced in the process is then transferred, in particular mechanically, to the planar film.

After the microstructure has been created on the surface of the substantially planar foil, the method includes reshaping the foil to create a curved surface that defines or replicates the at least one curved lens surface of the lens to be produced with the microstructure. The planar product created after the microstructure has been created in at least one surface of the film is thus brought into the desired global shape (e.g. sector of a sphere) by reshaping. The result can then preferably be used directly as a casting mold or stamp for the lens to be produced (in particular a spectacle lens) or as a master for one or more consecutive replication steps. According to the invention, the method thus includes transferring the microstructure from the formed film to the lens to be produced (in particular by casting and/or by an embossing or stamping process).

The invention presented here is a method for providing lenses, in particular spectacle lenses, which have a microstructure on at least one side. In this case, the structure is produced by casting, in particular by using a correspondingly microstructured casting mold in the manufacture of the semi-finished product (blank) or finished product (spectacle lens). As an alternative to this, the structure can also be brought into the semi-finished product (blank) or finished product (spectacle lens) by forming, in particular by using a correspondingly microstructured stamp.

Although it is also possible to produce microstructures on curved surfaces of casting molds and stamps with high precision using conventional mechanical methods, the structures naturally have dead zones due to the expansion of the tool, which can be disadvantageous for the application. On the other hand, a lithographic representation does not have this disadvantage. However, lithographic processes (such as single- and multi-stage mask exposure, direct laser exposure) on curved substrates are only possible with the comparatively high technological complexity described above, and even then lithography can only be reliably implemented technically on slightly curved substrates. In the field of spectacle lenses in particular, however, it is desirable to apply a microstructure to a surface (preferably the front surface) of the spectacle lens, which is typically curved to such an extent that the necessary casting mold or the necessary stamp can often not be produced, or only insufficiently, using conventional lithographic methods alone is possible.

With the help of the present invention, however, it is even possible to use a full-area lithographic method with very simple means and with high precision and reproducibility in order to define the desired microstructure kidneys - After the microstructure is first produced according to the invention on a substantially planar surface of a formable film, there are no "dead" (inaccessible) zones, as is known, for example, in the conventional machining of curved surfaces, nor does a complex, very rapid Autofocus control are used, as is necessary, for example, in conventional local direct laser exposures of curved surfaces. Rather, the essentially planar film can be structured lithographically with very simple means, preferably even over the entire surface (that is to say simultaneously over the entire surface to be structured), before the film is then reshaped in order to introduce the required global surface curvature.

As can be seen, it is not absolutely necessary for the film provided (or its surface to be structured) to be completely planar. Instead, the improvement according to the invention is already achieved when the global curvature of the film during the production of the microstructure is significantly smaller than the global curvature of the lens surface to be produced (e.g. spectacle lens surface), which is to have the desired microstructure. A mean curvature, which in particular ignores the microstructures, is preferably regarded as the global curvature. In particular, the curvature of a sphere or the mean curvature of a torus can be regarded as the global curvature, which best approximates the foil provided or the lens surface to be produced, in particular on the basis of mean square distances.

In this sense, the foil in a method according to the invention is considered to be “substantially planar” in particular if the curvature of the foil provided (i.e. before the forming) is no more than about one-fifth, preferably no more than about one-tenth, even more preferably no more than about one twentieth, more preferably no more than about one fiftieth, most preferably no more than about one hundredth the curvature of the lens surface to be produced. The deviation of the area of the film to be structured from a plane before the reshaping is particularly preferably not greater than about 1 mm, more preferably not greater than about 0.5 mm, even more preferably not greater than about 0.2 mm, particularly preferably not greater than about 0.1 mm, more preferably no greater than about 50 µm, or even no greater than about 10 µm, more preferably no greater than about 1 µm, most preferably no greater than about 0.1 µm, or even no once larger than about 0.05 µm or even not even larger than about 10 nm.

In particular, structures that serve as diffractive gratings for visible light are provided as the microstructure. In a preferred embodiment, the microstructure is produced directly in or on the film by means of lithography. For this purpose, a layer of photoresist is preferably applied directly to the film, which is exposed, for example, by means of a focused laser and/or by means of a lithographic shadow mask and/or by means of holographic interference structures and is then developed. This is preferably followed by an etching step, which transfers the microstructure produced in the photoresist to the film. In particular, after the remaining photoresist has been removed, the film can be subjected to further shaping.

In another preferred embodiment, the lithography does not take place directly on the foil to be formed, but on an essentially planar substrate, from which the microstructure is then transferred directly or indirectly, for example by an embossing or stamping process, to the essentially planar foil.

This substrate is thus used to transfer the microstructure from the planar lithography to the film. The substrate should therefore be referred to below as a structure transfer substrate. In this embodiment, the creation of a microstructure in or on the film thus preferably includes creating a microstructure by means of lithography in or on a structure transfer substrate and transferring the microstructure created on the structure transfer substrate into or onto the essentially planar film. As already mentioned, an embossing or stamping process can be used in particular. In this case, the microstructure produced in the structure transfer substrate is embossed into the essentially planar film, in particular by mechanical pressure. For this it is necessary that the film can be deformed much more easily than the structure transfer substrate. The structure transfer substrate must therefore have a mechanical stability that ensures that the microstructure produced therein is not significantly deformed during the embossing process. The film, in turn, should be able to be plastically deformed so that the embossed microstructure is retained on at least one surface of the film after the embossing process.

The preferred embodiment using an essentially planar structure transfer substrate offers a larger selection of the materials to be used, in particular for the foil to be formed, since the lithography and the forming into the curved shape are decoupled from one another. On the one hand, this makes it possible to use non-formable materials (such as relatively thick substrates made of nickel, aluminum or similar) in lithography (i.e. for the structure transfer substrate). liches) while for reshaping (i.e. as a foil) materials that cannot be lithographically processed (e.g. special organic compounds such as PMMA or PC) can also be used.

A multiplicity of foils, which are then each used for forming, are particularly preferably embossed using a single, lithographically structured structure transfer substrate. This can happen directly or via one or more intermediate steps (“fathers”). The later statements on possible downstream molding and forming steps apply here analogously.

Regardless of this intermediate step using a structure transfer substrate, the respective products (i.e. the results of the first step or the intermediate step) can be subjected to processes to optimize certain properties. Examples of this are chemical or thermal hardening steps or special coatings before use as a casting mold or stamp in molding or forming, as well as softening before forming.

Overall, the microstructure is first introduced into a planar (or only moderately curved) film, in particular by lithographic methods. A film is understood to mean a substrate that is sufficiently flexible for the forming in the subsequent step. Examples of this are thin foils made of organic material or (semi)metals (e.g. silicon, aluminum, nickel) with a preferred thickness of up to about 200 μm (particularly preferably 10-50 μm).

In a subsequent step, the resulting planar (or only moderately curved) product is formed into the desired global shape (e.g. base curve of the desired lens surface). A suitable possibility for this is, for example, a forming process under the influence of heat. Appropriate heating of the film can promote wrinkle-free and crack-free forming.

In a preferred embodiment, the film provided has a thickness of no more than about 0.5 mm, preferably no more than about 0.2 mm, even more preferably no more than about 0.1 mm, most preferably in the range of about 10 µm to about 50 µm. With these thicknesses, on the one hand in particular a good formation of diffractive microstructures and on the other hand a good, damage-free forming of the film is possible in a particularly efficient manner. For example, when using soft metals for the foil, but also for some organic foils, significantly thicker foils of up to a few millimeters could definitely also be used.

In a preferred embodiment, the foil provided comprises organic material, in particular PMMA and/or PC, and/or metal, in particular aluminum and/or nickel, and/or a semimetal and/or a semiconductor, in particular silicon. In these materials, on the one hand, the formation of diffractive microstructures with high precision and, on the other hand, a good, damage-free forming of the film is possible in a particularly efficient manner.

In the simplest case, the film is used directly after forming as (at least part of) a casting mold or as (at least part of) a stamp(s). However, since this foil is preferably relatively thin, it is particularly preferred to apply it to a more rigid substrate which has a corresponding curvature or shape. This substrate (also referred to below as carrier substrate) can not only be used to strengthen the mechanical stability, but also serve, for example, to improve the thermal properties during the casting or molding process. In this case, the carrier substrate can already be part of the casting mold or the stamp that is used to specify the curvature or the shape of the lens to be produced. Such a procedure has the additional advantage that there is no need for a corresponding removal from the mold after the film has been formed.

Thus, the reshaping of the film preferably includes arranging the film on a carrier substrate with a curved carrier surface. In this case, the film is arranged with the surface facing away from the at least one microstructured surface of the film on the curved carrier surface of the carrier substrate, so that it particularly adheres to it. The at least one microstructured surface of the film is thus turned away from the carrier substrate, so that the exposed microstructure can be transferred to the lens to be produced. In a preferred embodiment, the carrier substrate provided with the foil thus serves directly as a casting mold or as a stamp for the lens to be produced.

In a preferred embodiment, the transfer of the microstructure from the curved foil to a lens thus includes casting the lens using a mold in such a way that the foil shaped to produce a curved surface forms an inner surface of the mold which forms the at least one curved lens surface of the lens to be produced with the microstructure. The carrier substrate with the film adhering thereto as one is particularly preferred casting mold shell used. In a further preferred embodiment, the second surface of the lens to be produced can also be formed by means of a casting mold shell manufactured in an analogous manner. In a preferred embodiment, only one of the two lens surfaces, in particular the front surface of a spectacle lens, has a corresponding diffractive microstructure, while the other surface (in particular the rear surface of a spectacle lens) is subjected to further processing by appropriate grinding processes after casting.

In another preferred embodiment, the transfer of the microstructure from the curved foil to a lens comprises embossing by means of a stamp in such a way that the foil shaped to produce the curved surface forms a stamping surface of the stamp, which forms the at least one curved lens surface of the lens to be produced with the microstructure determines. The carrier substrate with the film adhering thereto is thus particularly preferably used directly as a stamp for forming the desired microstructure in the lens to be produced.

Irrespective of the use of said rear substrate, one or more additional processing steps (e.g. chemical or thermal curing, coating) can be carried out before use as a mold or stamp.

Deviating from a direct use of the formed film as part of a casting mold or a stamp, however, further forming and/or forming steps can also be stored in between. For several reasons, it can be advantageous not to use the film directly as (part of) a casting mold or as (part of a) stamp(s) after it has been formed, as described above, but to replace the casting mold or stamp by additional casting or To generate forming steps from the formed film. The formed film (possibly together with a corresponding carrier substrate) preferably serves as a master. This master can then be used to mold a mold or stamp directly from it (master -> mold or stamp) or one or more molding steps are interposed (master -> father -> mold or stamp or master -> father -> ... -> casting mold or stamp).

In a preferred embodiment, transferring the microstructure from the curved sheet to a lens thus includes directly or indirectly transferring the microstructure from the curved sheet to a mold (optionally via one or more intermediate steps) and casting the lens using the mold. Analogously, in another preferred embodiment, the - transfer of the microstructure from the curved foil to a lens includes a direct or indirect transfer of the microstructure from the curved foil to a stamp (if necessary via one or more intermediate steps and embossing the lens by means of the stamp.

In a preferred embodiment, the method includes molding the casting mold (or the stamp) or a father by electroplating. A technical advantage of this procedure is that the forming of the film is decoupled from the actual casting or embossing process. This means that materials can be used that are particularly suitable for the individual process steps (more durable, more stable, easier to clean, ...). Materials that cannot be formed or are difficult to form (e.g. thick substrates made of nickel, aluminum or similar) can act as a mold or stamp for the lenses (glasses or blanks), which are particularly suitable for this. On the other hand, materials (e.g. organic compounds such as PMMA or PC) that are less suitable for casting or stamping spectacle lenses or blanks can be used to shape the film.

Furthermore, this method can offer an economic advantage. The additional molding steps are often cheaper than direct production using lithographic processes and forming the foil.

Similar to the procedure described above, one or more additional processing steps (e.g. chemical or thermal hardening, coating) can also be carried out here before the respective molding or forming steps.

In order to obtain the desired structure in the lens to be produced (e.g. spectacle lens or blank), the following points in particular should be taken into account when designing the structure for lithography. Depending on the number of molding or forming processes (to produce the microstructure on the film and to transfer the microstructure from the film to the lens surface), the lithographically produced structure is the structure intended for the lens to be produced as a negative (none or an even number of molding steps) or as a positive (odd number) - reproduce.

Preferably, the influence of the reshaping of the film on the geometry of the microstructure is already taken into account during the production of the microstructure on the planar film, in that the deformation of the microstructure caused by the reshaping is already precompensated. The originally planar structure is thus curved by the deformation. The effects of this curvature as well the expansion or compression of the surface associated with the reshaping are likewise already taken into account in the structure produced in particular lithographically. Since diffractive microstructures mostly run essentially in a tangential direction, especially in spectacle lenses (i.e. microribs and microgrooves of such diffractive structures mostly run essentially transversely to the radial direction of a spectacle lens), the film can be reshaped in any case in such a way that the mutual distances between the diffractive structures hardly change when forming. The method according to the invention is therefore particularly well suited to producing spectacle lenses with diffractive structures (in particular for correcting color fringes) very efficiently.

Possible influences of other, optional process steps (e.g. intermediate steps during molding) which lead to changes in the structure (e.g. casting shrinkage, slight changes to the structure during casting or stamping, deformation during coating steps) are preferably also taken into account in advance.

Ultimately, the invention thus manages to provide spectacle lenses in particular that have a desired diffractive microstructure very efficiently and precisely with simple means. Correspondingly, changes in the structure that can occur during the manufacturing steps of the spectacle lens can also be taken into account. Such deformations can occur, for example, during the casting or stamping of the lens or blank, during further processing (e.g. distortions due to blocking or generating (grinding, cutting, polishing, ...) the prescription surface on the side facing away from the microstructure) as well as of finishing (e.g. deformations when applying coatings). Since these influences can depend on the materials and processes used for the lens, these corrections can also be selected product-, material- (e.g. with different shrinkage coefficients) or process-specific (e.g. temperatures during coating steps).

• 1 schematische Darstellungen von Linsen (Brillengläsern bzw. Brillenglasrohlingen) mit einer diffraktiven Mikrostruktur an einer ersten Oberfläche der jeweiligen Linse; und
• 2A - 2D schematische Darstellungen einzelner Verfahrensschritte in einem Herstellungsverfahren gemäß einer bevorzugten Ausführungsform der vorliegenden Erfindung.

The invention is described below using preferred embodiments with reference to the accompanying drawings. show:

• 1 schematic representations of lenses (spectacle lenses or spectacle lens blanks) with a diffractive microstructure on a first surface of the respective lens; and
• 2A - 2D schematic representations of individual process steps in a production process according to a preferred embodiment of the present invention.

1 FIG. 12 illustrates examples of spectacle lenses 10 with different powers and surface curvatures. A spectacle lens body 12 has a front surface 14 and a rear surface 16 (surface on the eye side). A diffractive microstructure 18 is formed on the front surface 14 in each case. The representation of the diffractive microstructure 18 should be regarded as purely schematic. In particular, the respective microstructure 18 is not shown to scale. The microstructure 18 is usually significantly smaller in comparison to the spectacle lens body 12 . Typical dimensions of diffractive microstructures are around 0.3 to 5 µm in the axial direction (ie in the thickness direction of the spectacle lens) and around 1 to 500 µm in the lateral direction.

From left to right are in 1 a plus lens with a convex base curve (front surface 14), a minus lens with a convex base curve (front surface 14), a plus lens with a flat base curve (front surface 14) and a minus lens with a flat base curve (front surface 14) are shown in succession. Precisely the production of spectacle lenses with a curved (eg convex) base curve and diffractive structures 18 is made possible in a particularly efficient manner by a method according to the invention.

In 2A until 2D an example of a manufacturing method according to a preferred embodiment of the invention is illustrated. Thus, in this preferred embodiment, an essentially planar film 20 is first provided, which has an essentially planar front surface 22 and a rear surface 24 . At least on the front surface 22, a microstructure 18' is formed, preferably by means of planar lithography, which essentially already defines a microstructure 18 to be formed in the spectacle lens to be produced. The microstructure 18' is preferably significantly smaller than the thickness of the film 20 in the axial direction (thickness direction of the film 20), which is why it is 2A until 2D is not represented as a visible structure. In addition, the microstructure 18 ′ is preferably produced essentially only on the front surface 22 but not on the back surface 24 of the film 20 . Depending on how many intermediate steps are to take place in a subsequent transfer of the microstructure to the spectacle lens, the microstructure 18' represents a positive or a negative of the microstructure 18 to be formed in the spectacle lens. In the example of the preferred method shown schematically here, it is a negative, since in In this example, the microstructure is transferred directly.

After the creation of the microstructure 18' in or on the essentially planar foil 20, in particular on its front surface 22, the foil 20 formed in such a way that it essentially follows the base curve of the lens to be produced, as is shown in 2C is illustrated. In the embodiment shown here, the reshaping preferably takes place by arranging the film 20 on a carrier substrate 26 with a curved carrier surface, which essentially defines the base curve of the spectacle lens to be produced. In this case, the foil 20 is arranged with its rear surface 24 on the carrier substrate 26, so that the microstructure 18′ is exposed. The carrier substrate 26 with the film 20 arranged thereon is then preferably used as a casting shell for a spectacle lens blank or a spectacle lens 10 . The front surface 22 of the film 20 with the microstructure 18' forms the casting surface for the front surface (base curve) 14 of the spectacle lens 10 to be produced. After the spectacle lens blank 10 has hardened, it is removed from the mold again, and preferably (but not necessarily) also the film 20 is removed from the front surface 14 of the spectacle lens blank 10 again.

In another preferred embodiment not shown here, the carrier substrate 26 is used together with the film 20 arranged thereon as a stamp for an embossing process.

Reference List

10

lens (blank)

12

lens body

14

Front surface (base curve) of the lens

16

back surface of the lens

18, 18'

microstructure

20

foil

22

front surface of the foil

24

back surface of the foil

26

carrier substrate

Claims (6)

A method of manufacturing a lens (10) having a microstructure (18/18') on at least one curved lens surface, comprising: - providing a substantially planar sheet (20); - Generating a microstructure (18/18') in or on the substantially planar film (20); - Reshaping of the film (20) to produce a curved surface which defines the at least one curved lens surface of the lens (10) to be produced with the microstructure (18/18'); - Transferring the microstructure (18/18') from the shaped film (20) to the lens (10) to be produced, characterized in that the influence of the shaping of the film (20) on the geometry of the microstructure (18/18') already is taken into account in the production of the microstructure (18/18') on the essentially planar film (20), in that the deformation of the microstructure (18/18') caused by the forming is already precompensated, the transfer of the microstructure (18/ 18') from the curved film (20) to a lens (10): - transferring the microstructure (18/18') from the curved film (20) to a stamp; and - embossing the lens (10) by means of the stamp. procedure after claim 1 , wherein the microstructure (18/18 ') is generated directly in or on the film (20) by means of lithography. procedure after claim 1 , wherein the creation of a microstructure (18/18') in or on the film (20) comprises: - creating a microstructure (18/18') by means of lithography in or on a structure transfer substrate; and - transferring the microstructure (18/18') produced on the structure transfer substrate into or onto the essentially planar film (20). Method according to one of the preceding claims, in which the forming of the foil (20) comprises arranging the foil (20) on a carrier substrate (26) having a curved carrier surface. A method according to any one of the preceding claims, wherein the film (20) provided has a thickness of no more than 0.5mm. Method according to one of the preceding claims, wherein the film (20) provided comprises organic material and/or metal and/or a semi-metal and/or a semiconductor.

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