Method for producing a metal stamp for embossing a nano-and/or microstructure on a metal device as well as uses thereof and devices made therewith

Abstract

The invention relates to a method for producing a metal stamp for embossing a nano- or microstructure on a metal device ( 4 ), comprising the following steps for producing a 3D structured embossing area ( 3 ) on the stamp: a) providing a master ( 30 ) having a structured surface ( 30 a ), and replicating said master ( 30 a ) in the surface of a soft stamp ( 31 ); b) forming an imprint ( 32 ) on the soft stamp ( 31 a ) using a cross-linkable material to form an imprint structured surface ( 32 a ), before, while or after contacting an opposite side of the imprint ( 32 ) with said surface portion of the metal stamp, and removing said soft-stamp ( 31 ) exposing said imprint structured surface ( 32 a ); c) etch-opening said surface ( 32 a ) using a first set of etching conditions; d) using a second set of etching conditions, different from the first ones, etching the surface of the metal stamp to form said embossing area ( 3 ).

1 . Method for producing a metal stamp for embossing a nano- and/or microstructure on a metal device, wherein the method comprises at least the following steps in given order for producing a 3D topologically structured embossing area on at least a surface portion of the metal stamp:
 a) providing a master tool having a master 3D topologically structured surface representing said nano- and/or microstructure, and replicating said master 3D topologically structured surface in the surface of a soft stamp to form a soft stamp 3D topologically structured surface;   b) forming an imprint on the soft stamp 3D topologically structured surface using a polymerizable and/or cross-linkable organic imprint material to form an imprint 3D topologically structured surface on one face of the imprint, before, while or after contacting an opposite side of the imprint with said surface portion of the metal stamp, and removing said soft-stamp exposing said imprint 3D topologically structured surface;   c) etch-opening said imprint 3D topologically structured surface to expose back to air only most recessed portions of the imprint 3D topologically structured surface using a first set of etching conditions;   d) using a second set of etching conditions, different from the first ones, etching the metal surface of the metal stamp to form said 3D topologically structured embossing area.   
     
     
         2 . Method according to  claim 1 , wherein the nano- and/or microstructure is an optical diffractive element with a grating. 
     
     
         3 . Method according to  claim 1 , wherein prior to step a) and/or b) the surface portion of the metal stamp for the embossing area is polished. 
     
     
         4 . Method according to  claim 1 , wherein the master tool is made from a photoresist material, glass, a nickel shim, a fused silica master, a sol-gel replica or a combination thereof. 
     
     
         5 . Method according to  claim 1 , wherein the material of the soft stamp is a polymeric or oligomeric material selected from the group consisting of: silicon-based materials, urethane-based materials, polyethylene-based materials polyacrylates, polycarbonate (PC), polyester (PES), aliphatic or (semi-)aromatic polyamides (PA), halogenated polymers, polyimide (PI) as well as mixtures and/or copolymers thereof,
 and/or wherein within step a) replication of the master 3D topologically structured surface is carried out using hot or cold embossing, UV embossing, UV casting, heat casting or heat and UV casting or a combination thereof,   and/or wherein the soft stamp is casted or laminated on a support,   and/or wherein before step b) the soft stamp material is at least one of hardened, cross-linked, or polymerized.   
     
     
         6 . Method according to  claim 1 , wherein the polymerizable and/or cross-linkable organic imprint material is selected from the group consisting of: an acrylate based material including methacrylate based materials, a polyester-based material, an epoxy-based material or an urethane-based material, or mixtures and/or copolymers and/or grafted forms thereof;
 and/or wherein the polymerizable and/or cross-linkable organic imprint material is a two component material;   and/or wherein in step b) before or after removing said soft stamp the material of the imprint is cross-linked and/or polymerized using irradiation and/or heat,   and/or wherein in step b) the polymerizable and/or cross-linkable organic imprint material is deposited on the soft stamp using a coating technique,   and/or wherein application of the imprint on the metal stamp involves pressing imprint material located between the soft stamp and the metal stamp,   and/or wherein anti-sticking material is applied to the soft stamp 3D topologically structured surface before contacting with the polymerizable and/or cross-linkable organic imprint material.   
     
     
         7 . Method according to  claim 1 ,
 wherein etch opening within step c) is carried out using a dry etching technique including reaction ion etching (RIE)   and/or wherein the metal etching in step d) is carried out using reactive ion beam etching (RIBE) or ion beam milling (IBM);   and/or wherein after step d) residual imprint if present is cleaned from the surface.   
     
     
         8 . Metal stamp with a 3D topologically structured embossing area made using a method according to  claim 1 . 
     
     
         9 . Method of generating a nano- and/or microstructure, on a metal device, wherein a metal stamp according to  claim 8  carrying a topologically structured surface being essentially the negative of the nano- and/or microstructure to be generated on the device is embossed on an exposed metal surface of the device under plastic deformation conditions such that the topology of the topologically structured surface is imaged on the metal surface of the device. 
     
     
         10 . Method according to  claim 9 , wherein the metal stamp at least in the region of the topologically structured surface for embossing, consists of material of a higher hardness than the material of the device in the exposed region to be embossed. 
     
     
         11 . Method according to  claim 9 , wherein the nano- and/or microstructure, is embossed using an embossing pressure in the range of 0.1-5 kN/mm 2    and/or wherein the grating is embossed at a temperature of at most 150° C.   
     
     
         12 . Device essentially consisting of a structural load bearing part consisting of metal, with the exception of a medical prosthesis, medical osteosynthesis device, hearing aid or hearing aid housing,
 wherein the device comprises at least one nano- and/or microstructure, with a grating, which is directly embossed in an exposed metal surface of the load bearing part in the form of a security and/or identification element.   
     
     
         13 . Device according to  claim 12 , wherein the metal is selected from steel, or titanium or a titanium alloy with at least one of zinc, niobium, tantalum, vanadium, aluminium. 
     
     
         14 . Device according to  claim 12 , wherein the period of the nano- and/or microstructure, is in the range of 0.3-3 μm or in the range of 0.5-2 μm
 and/or wherein the depth of the nano- and/or microstructure, is in the range of 80-500 nm 
 and/or wherein the nano- and/or microstructure is embossed on a ground exposed metal part of the device, 
 and/or wherein the nano- and/or microstructure, is embossed on an exposed metal part of the device having a surface roughness Ra (as defined according to ISO 4287:1997) of at most 0.8 μm, 
 and/or wherein the nano- and/or microstructure, is embossed using an embossing pressure in the range of 0.1-5 kN/mm 2    
 and/or wherein the grating is embossed at a temperature of at most 150° C., 
 and/or wherein the nano- and/or microstructure, is provided such that the tips of the grating or essentially flush with the surface plane defined by the surrounding metal surface 
 and/or wherein the optical diffractive element generates the image at least one of a picture, letters, numbers or pictograms. 
 
     
     
         15 . Device according to  claim 12 , wherein the device is
 part of or a watch,   part of or a surgical tool,   part of or a medical system aid that can be implanted in human body with the exception of a medical prosthesis, medical osteosynthesis device or hearing aid or hearing aid housings,   part of or an entire automotive, aeronautics, military, power plant, consumer computer device.   
     
     
         16 . Method according to  claim 1 , wherein prior to step a) and/or b) the surface portion of the metal stamp for the embossing area is polished, using mechanical, chemical or combined mechanical and chemical polishing techniques. 
     
     
         17 . Method according to  claim 1 , wherein prior to step a) and/or b) the surface portion of the metal stamp for the embossing area is polished until a surface roughness Ra (as defined according to ISO 4287:1997) of at most 0.8 μm, or of at most 0.5 μm or at most 0.3 μm or at most 0.23 μm is established at least in the surface portion of the metal stamp for the embossing area. 
     
     
         18 . Method according to  claim 1 , wherein the material of the soft stamp, which is elastomeric, is a polymeric or oligomeric material selected from the group consisting of: PDMS, polyethylene terephthalate, polypropylene-based materials, polymethyl-methacrylate (PMMA), polymethacrylic acid ethylester (PMAA), polymethacrylic acid propylester (PMAP), polymethacrylic acid isopropylester, polycarbonate (PC), polyester (PES), aliphatic or (semi-)aromatic polyamides (PA), ETFE or PTFE, polyimide (PI) as well as mixtures and/or copolymers thereof,
 and/or wherein the soft stamp is casted or laminated on a flexible support, including a foil.   
     
     
         19 . Method according to  claim 1 , wherein the polymerizable and/or cross-linkable organic imprint material is selected from the group consisting of: an acrylate based material methacrylate based materials, a polyester-based material, an epoxy-based material or an urethane-based material, or mixtures and/or copolymers and/or grafter forms thereof;
 and/or wherein the polymerizable and/or cross-linkable organic imprint material is a two component material, based on a material selected from the group consisting of: an acrylate based material including methacrylate based materials, a polyester-based material, an epoxy-based material or an urethane-based material, or mixtures and/or copolymers and/or grafter forms thereof;   and/or wherein in step b) before or after removing said soft stamp the material of the imprint is cross-linked and/or polymerized using UV irradiation,   and/or wherein in step b) the polymerizable and/or cross-linkable organic imprint material is deposited on the soft stamp using slot coating, cast coating, spin coating, spray coating or a combination thereof,   and/or wherein application of the imprint on the metal stamp involves pressing imprint material located between the soft stamp and the metal stamp, using a deformable elastomeric tampon.   
     
     
         20 . Method according to  claim 1 , wherein etch opening within step c) is carried out using reaction ion etching (RIE), wherein an oxygen based plasma is used in vacuum and/or wherein the metal etching in step d) is carried out using reactive ion beam etching (RIBE) or ion beam milling (IBM), wherein an argon gas is ionized and projected onto the surface of the metal stamp. 
     
     
         21 . Metal stamp with a 3D topologically structured embossing area made using a method according to  claim 1 , wherein at least in the region of the 3D topologically structured embossing area the metal stamp is made from steel selected from the following steels: 1.2083, 1.2363, UM20 HIP, UM30 HIP, K110/1.2379, K340, K470, K890, Stavax ESR or ESU, Rigor 1.2363, Böhler K305, EN 1.2344, SKD61 1.2344, EN 1.2343, EN 1.2083, EN 1.2162, EN 1.2516, or RAMAX. 
     
     
         22 . Method of generating a nano- and/or microstructure, in the form of an optical diffractive element in the form of a grating, on a metal device, wherein a metal stamp according to  claim 8  carrying a topologically structured surface being essentially the negative of the nano- and/or microstructure to be generated on the device is embossed on an exposed metal surface of the device under plastic deformation conditions such that the topology of the topologically structured surface is imaged on the metal surface of the device, wherein the metal stamp has a grating depth in the range of 80-500 nm. 
     
     
         23 . Method according to  claim 22 , wherein the metal stamp has a grating depth in the range of in the range 200-400 nm, or in the range of 230-300 nm. 
     
     
         24 . Method according to  claim 9 , wherein the metal stamp at least in the region of the topologically structured surface for embossing, consists of material of a higher hardness than the material of the device in the exposed region to be embossed, wherein the metal stamp is essentially based on hardened steel, selected from the following steels: 1.2083, 1.2363, UM20 HIP, UM30 HIP, K110/1.2379, K340, K470, K890, Stavax ESR or ESU, Rigor 1.2363, Böhler K305, EN 1.2344, SKD61 1.2344, EN 1.2343, EN 1.2083, EN 1.2162, EN 1.2516, or RAMAX, or hardened steel with a coating of tungsten carbide, Si3N4 or ZrO2. 
     
     
         25 . Method according to  claim 9 , wherein the nano- and/or microstructure, the grating, is embossed using an embossing pressure in the range of 0.1-5 kN/mm 2 , or in the range 0.1-2 kN/mm 2    and/or wherein the grating is embossed at a temperature of in the range of 10-40° C.   
     
     
         26 . Device essentially consisting of a structural load bearing part consisting of metal, with the exception of a medical prosthesis, medical osteosynthesis device, hearing aid or hearing aid housing,
 wherein the device comprises at least one nano- and/or microstructure, in the form of an optical diffractive element with a grating, which is directly embossed in an exposed metal surface of the load bearing part in the form of a security and/or identification element, using a metal stamp made according to  claim 1 .   
     
     
         27 . Device according to  claim 12 , wherein the metal is selected from stainless steel, or a titanium alloy with at least one of zinc, niobium, tantalum, vanadium, aluminium. 
     
     
         28 . Device according to  claim 12 , wherein the most protruding elevations of the nano- and/or microstructure, the grating, are at the level of the surrounding surface of the structural load bearing part and with respect to the surrounding surface, or are recessed with respect to the surrounding surface by less than 40 microns, or by less than 20 microns. 
     
     
         29 . Device according to  claim 12 , wherein the period of the nano- and/or microstructure, the grating, is in the range of 0.3-3 μm or in the range of 0.5-2 μm, or in the range of 1-1.9 μm or 1.7-1.9 μm
 and/or wherein the depth of the nano- and/or microstructure, the grating, is in the range of 80-500 nm, or in the range of 200-400 nm, or in the range of 230-300 nm 
 and/or wherein the nano- and/or microstructure, the grating, is embossed on a ground exposed metal part of the device, 
 and/or wherein the nano- and/or microstructure, the grating, is embossed on an exposed metal part of the device having a surface roughness Ra (as defined according to ISO 4287:1997) of at most 0.8 μm, or of at most 0.5 μm or at most 0.3 μm or at most 0.23 μm, or in the range of 0.20-0.25 μm, 
 and/or wherein the nano- and/or microstructure, the grating, is embossed using an embossing pressure in the range of 0.1-5 kN/mm 2 , or in the range 0.1-2 kN/mm 2    
 and/or wherein the grating is embossed at a temperature of at most 150° C., or at most 100° C., or in the range of 10-40° C., 
 and/or wherein the nano- and/or microstructure, the grating, is provided such that the tips of the grating or essentially flush with the surface plane defined by the surrounding metal surface. 
 
     
     
         30 . Device according to  claim 12 , wherein the device is
 part of or a watch, the nano- and/or microstructure, the grating, being provided in for the track and trace or anticounterfeiting of the titanium or titanium alloy parts,   part of or a surgical tool, the nano- and/or microstructure, the grating, being provided for the track and trace or anticounterfeiting,   part of or a medical system aid that can be implanted in human body with the exception of a medical prosthesis, medical osteosynthesis device or hearing aid or hearing aid housings, the nano- and/or microstructure, the grating, being provided for the track and trace or anticounterfeiting of the titanium or titanium alloy parts,   part of or an entire automotive, aeronautics, military, power plant, consumer computer device, the nano- and/or microstructure, the grating, being provided for the track and trace or anticounterfeiting of the titanium or titanium alloy parts or for decorative purposes.