U.S. patent application number 16/366433 was filed with the patent office on 2019-10-03 for method for producing a metal stamp for embossing a nano-and/or microstructure on a metal device as well as uses thereof and devi.
This patent application is currently assigned to CSEM Centre Suisse d'Electronique et de Microtechnique SA. The applicant listed for this patent is CSEM Centre Suisse d'Electronique et de Microtechnique SA. Invention is credited to Michael DE WILD, David KALLWEIT, Roger KRAHENBUHL, Angelique LUU-DINH, Romy Linda MAREK, Christian SCHNEIDER, Marc SCHNIEPER.
Application Number | 20190299266 16/366433 |
Document ID | / |
Family ID | 61832421 |
Filed Date | 2019-10-03 |
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United States Patent
Application |
20190299266 |
Kind Code |
A1 |
SCHNEIDER; Christian ; et
al. |
October 3, 2019 |
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 (30a), and replicating said master (30a) in
the surface of a soft stamp (31); b) forming an imprint (32) on the
soft stamp (31a) using a cross-linkable material to form an imprint
structured surface (32a), 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 (32a); c) etch-opening said surface
(32a) 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).
Inventors: |
SCHNEIDER; Christian;
(Oftringen, CH) ; LUU-DINH; Angelique; (Mulhouse,
FR) ; SCHNIEPER; Marc; (Onex, CH) ; KALLWEIT;
David; (Freiburg im Breisgau, DE) ; KRAHENBUHL;
Roger; (Arlesheim, CH) ; DE WILD; Michael;
(Bottmingen, CH) ; MAREK; Romy Linda; (Maur,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CSEM Centre Suisse d'Electronique et de Microtechnique SA |
Neuchatel |
|
CH |
|
|
Assignee: |
CSEM Centre Suisse d'Electronique
et de Microtechnique SA
Neuchatel
CH
|
Family ID: |
61832421 |
Appl. No.: |
16/366433 |
Filed: |
March 27, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21D 37/01 20130101;
B21D 37/20 20130101; B21D 47/005 20130101; G03F 7/0002 20130101;
B21D 22/02 20130101 |
International
Class: |
B21D 22/02 20060101
B21D022/02; B21D 47/00 20060101 B21D047/00; B21D 37/20 20060101
B21D037/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2018 |
EP |
18 164 630.8 |
Claims
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.sup.2 and/or wherein the grating is embossed
at a temperature of at most 150.degree. 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 .mu.m or in the
range of 0.5-2 .mu.m 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
.mu.m, and/or wherein the nano- and/or microstructure, is embossed
using an embossing pressure in the range of 0.1-5 kN/mm.sup.2
and/or wherein the grating is embossed at a temperature of at most
150.degree. 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 .mu.m, or of at most 0.5 .mu.m or at most
0.3 .mu.m or at most 0.23 .mu.m 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, Bohler 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, Bohler 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.sup.2, or in the range 0.1-2
kN/mm.sup.2 and/or wherein the grating is embossed at a temperature
of in the range of 10-40.degree. 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 .mu.m
or in the range of 0.5-2 .mu.m, or in the range of 1-1.9 .mu.m or
1.7-1.9 .mu.m 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 .mu.m, or of at most 0.5
.mu.m or at most 0.3 .mu.m or at most 0.23 .mu.m, or in the range
of 0.20-0.25 .mu.m, 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.sup.2, or in the range 0.1-2 kN/mm.sup.2 and/or
wherein the grating is embossed at a temperature of at most
150.degree. C., or at most 100.degree. C., or in the range of
10-40.degree. 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.
Description
TECHNICAL FIELD
[0001] The present invention relates to methods for producing a
metal stamp for embossing a nano- and/or microstructure on a metal
device, to methods of generating an optical diffractive element in
the form of a submicron grating on a metal device using such a
metal stamp, as well as to devices comprising at least one nano-
and/or microstructure which is directly embossed in an exposed
metal surface of a load bearing part using such a metal stamp.
PRIOR ART
[0002] Many established articles of commerce are being copied by
copycats as well as by newly founded producers having obtained the
characteristics by reengineering the products. This development is
unfavorable for the users, since reengineered products may not meet
the exact specifications of the engineered design, often do not
meet the quality standards and regularly failures are reported. On
the other hand, the market for copycats is growing fast due to
lower prices. Lower prices are mainly determined by a weaker
quality system and, for example in the medical field for the lack
of clinical studies, or in the automotive field for the lack of
approvals by other authorities. The influence of CADCAM as well as
3D printing solutions is likely to speed up this development
quickly.
[0003] Responsible users ask for original parts. However, for
example in the medical field, it is difficult for a surgeon to find
out if an original or a copied prosthetic part was used, since this
decision which product to use is made at the orthopaedic
technicians site and is not visible on the part. It is assumed that
the amount of all prosthetic parts purchased through copycats will
shift to 50% within the next 5 years in Europe and US. This is
equivalent to 40% of the complete prosthetic sales. Furthermore, it
is assumed that 50% of the surgeons would preferably use original
parts, if they could distinguish between. Therefore, a 20% loss of
sales of prosthetic products is expected, if no identification of
the original manufacturer will be applied. Similar figures are
assumed in other fields in industry.
[0004] A very important further topic is guaranty claims for
damaged parts. Guaranty claims have to be investigated carefully,
to assure original parts have been used. One has observed an
increasing use of guaranty claims which were based on cheaper
copied pieces over the last years.
SUMMARY OF THE INVENTION
[0005] Many attempts have been made to avoid copying or to track
and to trace metal parts. These attempts include packaging with
elaborated security features, but also laser marking of the devices
themselves or attaching security elements to the devices. The
problem with the former is that after the device has been unpacked
there is no possibility to check the identity and/or origin of the
device anymore. The problem with the latter is that laser markings
are conventional art and can be as easily reproduced as the device
itself. Attaching security elements to metal devices is a problem
since on the one hand for many applications these security elements
will have to be removed before use of the metal part, and attaching
them to the metal part requires adhesives which for example in the
medical field are not tolerated. Furthermore, attaching the
security elements to the metal parts also allows to remove them
fraudulently and to re-use or replicate the corresponding features
for deceptive use.
[0006] The invention solves this problem by providing on the one
hand a tool for embossing an optical security element on any kind
of metal device, a method for making a corresponding metal stamp
tool, as well as the method of using such a metal stamp tool for
applying the corresponding optical security feature directly onto
and into the desired metal device. At the end the device comprises
at least one optical security feature comprising diffractive
elements made of nano- and/or microstructures, for example with one
or more gratings which are directly embossed in an exposed metal
surface in the form of a security and/or identification
element.
[0007] Microstructuring is defined as the creation of surface
structures which are submicronic in dimensions (i.e. periodicity
smaller than 1 .mu.m, typically in the range of 200-800 nm), in the
micron-scale or of a few microns (typically at most 5 .mu.m or at
most 2 .mu.m) in dimensions. For example for periodic nano- and/or
microstructures such as gratings, the ridge/groove sizes can be
submicronic (i.e. smaller than 1 .mu.m, typically in the range of
200-800 nm) or up to a few microns (typically at most 10 .mu.m or
at most 5 .mu.m), the depth of the microstructure in the submicron
domain while the microstructure periodicity can be larger than one
micron, for example less than or 2 .mu.m.
[0008] The nano- and/or microstructures can comprise or consist of
non-periodic nano- and/or microstructures such as Fourier or
Fresnel Diffractive Optical Element (DOE), random microstructures,
Optically Variable Devices (OVDs), Diffractive Optical Variable
Image Devices (DOVIDs), micro-images, micro-structures encoding an
image, code or symbol based on a Moire encoding, diffusive and
scattering optical microstructures, zero-order color-generating
optical microstructures and a combination thereof.
[0009] More specifically, the present invention according to a
first aspect relates to the method of claim 1, i.e. to a method for
producing a metal stamp for embossing a nano- and/or
microstructure, preferably an optical security feature comprising a
diffractive element with a grating, on a metal device.
[0010] The method comprises at least the following steps in given
order for forming a 3D topologically structured embossing area on
at least a surface portion of the metal stamp: [0011] a) providing
a master tool having a master 3D topologically structured surface
representing said optical diffractive element, and replicating said
master 3D topologically structured surface in the surface of a soft
stamp to form a soft stamp 3D topologically structured surface;
[0012] 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 soft stamp, and removing said soft stamp exposing
said imprint 3D topologically structured surface; [0013] 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; [0014] 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.
[0015] According to a first preferred embodiment, the method is
characterized in that prior to step a) and/or b) the surface
portion of the metal stamp for the embossing area is polished,
preferably using mechanical, chemical or combined mechanical and
chemical polishing techniques, preferably until a surface roughness
Ra (as defined according to ISO 4287:1997) of at most 0.8 .mu.m,
preferably of at most 0.5 .mu.m or at most 0.3 .mu.m or at most
0.23 .mu.m is established at least in the surface portion of the
metal stamp for the embossing area.
[0016] The master tool is typically made from a photoresist
material, glass, a nickel shim, a fused silica master, a sol-gel
replica. Such a master tool can for example be produced using a
method and materials as described in the following literature:
Optical Document Security (R. L. Renesse, Optical Document
Security, Third Edition, 3rd edition, Artech House, Boston, Mass.,
2004).
[0017] The material of the soft stamp, which is preferably
elastomeric, can be selected from the group consisting of:
silicon-based elastomers such as PDMS, urethane-based elastomer,
polyurethane, polypropylene-based organic material, polyacrylates
such as polymethyl-methacrylate (PMMA) or polycarbonate (PC),
Polyester (PET), Polyamide (PA), a fluoropolymer such as ETFE or
PTFE, polyimide (PI) and any combination thereof.
[0018] The soft stamp can as well be made of a 2 layers composite
such as a foil and an elastomeric material. The elastomeric
material can be one of the above listed and the foil be flexible
and can be selected among polyamide, polyethylene terephthalate,
polycarbonate polyamide.
[0019] Within step a) replication of the master 3D topologically
structured surface can be carried out using hot or cold embossing,
UV embossing, UV casting, heat casting or heat and UV casting or a
combination thereof.
[0020] Before step b) the soft stamp material can be hardened
and/or cross-linked and/or polymerized.
[0021] The polymerizable and/or cross-linkable organic imprint
material is preferably an acrylate based material (including
methacrylate materials), a polyester-based material, an epoxy-based
material or an urethane-based material
[0022] The polymerizable and/or cross-linkable organic imprint
material can also be a two component material, possible 2 component
systems suitable for the present use are epoxy-based resins.
[0023] In step b) before or after removing said soft stamp the
material of the imprint is preferably cross-linked and/or
polymerized for example using irradiation and/or heat, preferably
UV irradiation. Preferably, the imprint material will be structured
with a 3D topologically structured surface being close to the
complementary 3D topologically structured surface of the soft
stamp, its negative copy. So a good fidelity of replication is
preferably targeted.
[0024] In step b) the polymerizable and/or cross-linkable organic
imprint material can be deposited on the soft stamp using a coating
technique, preferably slot coating, cast coating, spin coating,
spray coating or a combination thereof.
[0025] Application of the imprint on the soft stamp may involve
pressing imprint material located between the soft stamp and the
metal stamp, preferably using a tampon, preferably a deformable
elastomeric tampon.
[0026] On the opposite or in complement, the imprint can be applied
on the metal part area that will be structured with one or a
combination of the above listed coating techniques.
[0027] To avoid problems when removing the soft stamp from the
imprint material to free the corresponding 3D topologically
structured surface comprising one or more gratings of the surface
of the imprint material, anti-sticking material can be applied to
the soft stamp 3D topologically structured surface before
contacting with the polymerizable and/or cross-linkable organic
imprint material.
[0028] Etch opening within step c) is preferably carried out using
a dry etching technique including reactive ion etching (RIE) and
reaction ion beam etching (RIBE), wherein preferably the plasma
composition is tuned to provide a good etching anisotropy of the
imprint material.
[0029] The metal etching in step d) is preferably carried out using
a dry etching technique including reactive ion beam etching (RIBE),
also called ion beam milling (IBM), wherein preferably the
following conditions are used: the dry etching is stopped before
all the 3D structured imprint material is removed/etched away; the
dry etching technique is applied close to the normal of the area of
the metal part to be structured for marking, close to the normal to
the average orientation of the metal part marking area for a
non-planar metal part marking area.
[0030] After step d) residual imprint material if present can be
cleaned from the surface.
[0031] As pointed out above, the present invention also relates to
a metal stamp/metal stamp tool being produced using the above
mentioned method. Correspondingly the present invention relates to
a metal stamp with a 3D topologically structured embossing area
made using a method as given above, wherein preferably at least in
the region of the 3D topologically structured embossing area (3)
the metal stamp is made from steel, preferably hardened steel, more
preferably 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, Bohler K305, EN 1.2344, SKD61 1.2344, EN 1.2343, EN
1.2083, EN 1.2162, EN 1.2516, or RAMAX.
[0032] The present invention also relates to a method of generating
a nano- and/or microstructure, e.g. security feature comprising an
optical diffractive element with a grating on a metal device,
wherein a metal stamp as detailed above carrying a topologically
structured surface being essentially the negative of the nano-
and/or microstructure, e.g. the optical diffractive element with a
grating 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 preferably the
metal stamp has a grating depth in the range of 80-500 nm, more
preferably in the range 200-400 nm, and even more preferably in the
range of 230-300 nm.
[0033] The method is preferably characterized in that 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 preferably the metal stamp is essentially based
on hardened steel, preferably 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, Bohler 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 hard coating.
[0034] Hard coating can be made of tungsten carbide, Si3N4 or ZrO2,
cemented carbide such as tungsten carbide (WC), titanium carbide
(TiC), or tantalum carbide (TaC) as the aggregate. Mentions of
"carbide" or "tungsten carbide" in industrial contexts usually
refer to these cemented composites. Such a hard coating can also be
made of Cr Nitrides CrN or CrAlN, TiN, Diamond Like Carbon (DLC) or
other suitable materials.
[0035] The 3D topologically structured surface with one or more
nano- and/or microstructures, e.g. gratings, can be embossed using
the metal stamp using an embossing pressure in the range of 0.1-5
kN/mm.sup.2, preferably in the range of 0.2-2 or 0.5-1
kN/mm.sup.2.
[0036] The one or more gratings is for example embossed at a
temperature of at most 150.degree. C., preferably at most
100.degree. C., preferably in the range of 10-40.degree. C.
[0037] The present invention also relates to a device essentially
consisting of or comprising a structural load bearing part
consisting of metal, with the exception of a medical prosthesis,
medical osteosynthesis device or hearing aids (including housings
thereof), wherein the device comprises at least one nano- and/or
microstructure, e.g. a security feature comprising 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, preferably using a metal
stamp made as detailed above or a metal stamp as given above.
[0038] The metal of such a device to be protected can be selected
from steel, preferably stainless steel, or titanium or a titanium
alloy with at least one of zinc, niobium, tantalum, vanadium,
aluminium or aluminum or an aluminum alloy with for example
scandium.
[0039] Preferably the most protruding elevations of the nano-
and/or microstructure, preferably 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,
preferably by less than 20 microns. The absence of a recess can be
particularly advantageous in many applications. It is difficult or
impossible to achieve with other methods, as for example by
laminating/gluing a structured nickel shim on a metal tool to be
used as a composite metal stamp.
[0040] In such a device but also in the corresponding metal stamp
for making the embossing in the device, the period of the one or
more grating is in the range of 0.3-3 .mu.m or in the range of
0.5-2 .mu.m, preferably in the range of 1.1.9 .mu.m or 1.7-1.9
.mu.m.
[0041] The depth of the one or more nano- and/or microstructures,
e.g. the gratings in the metal stamp and/or the corresponding
mental device is preferably in the range of 80-500 nm, more
preferably 200-400 nm, even more preferably in the range of 230-300
nm.
[0042] The 3D topologically structured surface comprising one or
more nano- and/or microstructure or grating is for example embossed
on a ground exposed metal part of the metal device.
[0043] The one or more nano- and/or microstructure (grating) can be
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
.mu.m, preferably of at most 0.5 .mu.m or at most 0.3 .mu.m or at
most 0.23 .mu.m, preferably in the range of 0.20-0.25 .mu.m.
[0044] Typically, the one or more nano- and/or microstructure
(gratings) is embossed using an embossing pressure in the range of
0.1-5 kN/mm.sup.2, preferably in the range of 0.1-2
kN/mm.sup.2.
[0045] The grating can be embossed at a temperature of at most
150.degree. C., preferably at most 100.degree. C., preferably in
the range of 10-40.degree. C. The one or more nano- and/or
microstructures can be provided in the form of a patch with a
surface area of at most 5 mm.sup.2, preferably in the range of
2-4.5 mm.sup.2.
[0046] The one or more nano- and/or microstructures can e.g. be
provided such that the tips of the grating or essentially flush
with the surface plane defined by the surrounding metal surface.
The security feature comprising an optical diffractive element may
generate the image of a picture and/or letters and/or numbers
and/or pictograms.
[0047] The metal device to be embossed with the metal stamp can be
one of the following devices:
[0048] part of or a watch, the security feature being provided in
particular for the track and trace or anticounterfeiting in
particular of the titanium or titanium alloy parts,
[0049] part of or a surgical tool, the security feature being
provided in particular for the track and trace or
anticounterfeiting,
[0050] 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 aids, the security feature being
provided for the track and trace or anticounterfeiting of in
particular of the titanium or titanium alloy parts,
[0051] part of or an entire automotive, aeronautics, military,
power plant, consumer computer device, the security feature being
provided in particular for the track and trace or
anticounterfeiting of the in particular titanium or titanium alloy
parts or for decorative purposes.
[0052] Furthermore, the present invention relates to the use of a
method as detailed above for making a metal device identifiable
and/or for providing it with a security element and/or marking.
[0053] Further embodiments of the invention are laid down in the
dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] Preferred embodiments of the invention are described in the
following with reference to the drawings, which are for the purpose
of illustrating the present preferred embodiments of the invention
and not for the purpose of limiting the same. In the drawings,
[0055] FIG. 1 shows in a) a metal stamp for use in the context of
the present invention as well as in a magnified representation to
the right the corresponding topologically structured surface region
for embossing, in [0056] b) on the left side the metal stamp and
the element to be embossed before the step of embossing, in the
middle the metal stamp and the element after embossing, and on the
right side a magnified representation of the grating on the metal
stamp and the embossing, in [0057] c) on the left side the metal
stamp and the element in the form of a ring to be embossed before
the step of embossing, on the right side the embossed ring, and in
[0058] d) the embossing of a dental implant;
[0059] FIG. 2 shows the situation of embossing a curved surface,
wherein on the left side the situation before embossing, and on the
right side the situation after embossing is schematically
illustrated;
[0060] FIG. 3 shows on the left side the embossing of a conical
portion of the coronal collar of an implant and on the right side
the embossing of a conical portion on an abutment;
[0061] FIG. 4 shows in a) a laser scanning digital microscope image
of the topologically structured surface on the metal stamp for an
embodiment having a period of 1.8 .mu.m, and in b) the properties
along line 19 in a);
[0062] FIG. 5 shows in a) a laser scanning digital microscope image
of the resulting embossed grating on the object and in b) the
properties along line 19 in a);
[0063] FIG. 6 shows in a) a cut in a direction essentially
perpendicular to the grating direction through an embossing
generated in an abutment, in b) an image of an abutment with an
optical diffractive element, in c) a REM image of the embossed
grating and in d) the embossing region on the abutment;
[0064] FIG. 7 shows a nanoimprinted microstructure on a flat steel
stamp surface;
[0065] FIG. 8 shows an opened nanoimprint material and open steel
surface under AFM;
[0066] FIG. 9 shows a simple diffractive transferred into hardened
steel as seen under AFM;
[0067] FIG. 10 shows a schematic representation of the metal stamp
making process in schematic cut views showing the grating
schematically as a zigzag pattern and the embossing process,
wherein in a) the making of the soft stamp based on the master is
shown, in b) the generation of the imprint based on the soft stamp
is shown, in c) the attachment of the imprint on the metal stamp
portion is shown, in d) the etch opened imprint on the metal stamp,
in e) the front metal stamp portion after the metal etching and in
f) the starting position for the embossing on the device to be
embossed.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0068] The objectives of this invention is a microstructuring
transfer/embossing process into for example a medical device, in
particular into a titanium implant material of structures like
holograms and Optical Diffractive Elements (DOE). This, to add
optical security features consisting of nano- and/or
microstructures, like sophisticated holograms, covert laser
readable images, 2D/3D QR codes, logos, article or lot numbers or
micro-text, directly into the titanium implant material such to
create visual and appealing 1st level control security features on
the one hand side, and/or to provide unique identifying (hidden)
2nd level control security features for trademark protection, e.g.
to identify new or explanted fake implants and defeat product
counterfeiting, on the other hand.
[0069] In the security world one usually defines 3 levels of
security features:
[0070] First level are features visible by naked eyes and do not
need any external set-up, typically holograms are 1st order
security devices.
[0071] The second level features will need a simple external
set-up, like a UV lamp, a laser pointer etc. easy to find on the
market, UV inks and DOE's are often 2nd level security devices.
[0072] And the 3rd level are security features that can only be
identified in the laboratory, like the real composition of a
material, the measurement of traces of specific chemical compounds
or elements.
[0073] Here, focus is put on first and second level security
features.
[0074] Nano- and/or microstructure surface labelling is
tissue-compatible because the process is only based on a pure
physical structuring of the surface of the implant, and no
chemicals, acids, paints, pigments, coatings or solvents need to be
implemented.
[0075] Furthermore, the proposed markings are abrasion-resistant
and that they can be disinfected and sterilized.
[0076] A new way of hologram tooling is used. As already mentioned
this process permits to transfer complex holograms directly into
hard steel surfaces. By illuminating a certain area on the
micron-structured steel surface with a laser pointer, a logo and/or
a data code is projected on a screen.
[0077] The steel nano- and/or microstructuring technology can be
used to make high resistant stamping tools, capable to stamp the
holograms into the titanium alloys those implants are made of.
[0078] This can be accomplished by using a stamping/embossing
process after the production of the metal stamp.
[0079] Nano- and/or microstructuring is defined as the creation of
surface structures which are submicronic in dimensions, in the
micron-scale or of a few microns in dimensions. For example for
periodic microstructures such as gratings, the ridge/groove sizes
can be submicronic or up to a few microns, the depth of the
microstructure in the submicron domain while the microstructure
periodicity can be larger than one micron, for example 2
microns.
[0080] The making of the metal stamp 1 having a tip portion 2 with
a topologically structured grating structure which is complementary
to what is to be generated on the device is very schematically
illustrated in FIG. 1 a).
[0081] Such a metal stamp can be generated using a technique as
follows, using a new approach by directly transferring micro and
nano-structures into a typically hardened steel material for the
metal stamp. This increases drastically the stamp lifetime compared
to conventional stamp making techniques. The structuration of 2D
curved metal stamp surfaces with small radius of curvature is as
well demonstrated. This technique and the resultant stamps allow
the hot and cold embossing of various materials in very large
volumes.
[0082] The structuration of steel or other metallic stamps relies
on several process steps, some of which are optional depending of
the tool and result to be achieved: [0083] 1. In a first step, the
surface of the metal stamp, with which micro- and nanostructures
should be embossed on the final part, should to be polished. Most
steel grades have random rough surfaces in the scale to a few to
several microns, in order to create a matt or dull finish on the
polymer surfaces. To transfer successfully smaller structures with
a high coverage, this topography needs to be planarized using
polishing techniques. Various polishing technique, purely
mechanical, purely chemical or combined mechanical and chemical
etching can be used. The roughness target after this polishing step
should be lower than the micro- or nanostructures to be
transferred, in order get high surface coverage and optimal optical
quality of the diffractive structures. Typically the surface
roughness, should be lower than (as defined according to ISO
4287:1997) 0.8 .mu.m, preferably lower than 0.5 .mu.m or lower than
0.3 .mu.m or lower than 0.23 .mu.m, preferably lower than 0.05
.mu.m and more preferably as low as or lower than 0.020 .mu.m. When
possible and depending on the mold geometry, a so-called mirror
finish polishing is preferable. Ultimately the grain size of the
steel will limit the achievable planarization quality. To reach
very low roughness levels, as may be interesting for the transfer
of nanostructures, the use of cold-worked steels which have not be
annealed is preferable. Useful for the present purpose of making
metal stamps are steel types as follows: 1.2083; 1.2363; UM20 HIP;
UM30 HIP; K110/1.2379; K340; K470; K890, Stavax ESR or ESU, Rigor
1.2363, Bohler K305, EN 1.2344, SKD61 1.2344, EN 1.2343, EN 1.2083,
EN 1.2162, EN 1.2516, or RAMAX. [0084] 2. As a second step, a
master tool containing the diffractive nano- and/or
microstructures, whether simple grating or complex surface
holograms, is replicated in a soft stamp material. [0085]
Preferably the soft stamp material is a soft material allowing the
soft stamp to be flexible. The master tool can be made of a
photoresist material, a glass, a nickel shim, a fused silica
master, a sol-gel replica or any other material depending of the
origination, structure modification and structure assembly
processes. A method how to produce such a master tool as well as
possible materials for use is e.g. disclosed in Optical Document
Security (R. L. Renesse, Optical Document Security, Third Edition,
3rd edition, Artech House, Boston, Mass., 2004). The soft stamp
material is made of a flexible material, usually elastomeric, which
is either hot embossed, UV embossed, UV casted, heat casted or heat
and UV casted from the master tool. [0086] Possible specific
materials for the soft stamp are as follows: silicon-based
elastomers such as PDMS, urethane-based elastomer, polyurethane,
polypropylene-based organic material, polyacrylates such as
polymethyl-methacrylate (PMMA) or polycarbonate (PC), Polyester
(PET), Polyamide (PA), a fluoropolymer such as ETFE or PTFE,
polyimide (PI) and any combination thereof. [0087] If needed the
flexible and usually elastomeric material can be casted or
laminated on a flexible foil that will support it and limit its
lateral deformation. Especially during the imprinting step,
pressure can lead to stretching of the soft stamp material. [0088]
3. The third step consists in imprinting the structure transferred
from the master tool through the soft stamp to the actual polished
metal stamp surface. The imprint material is usually an acrylate
based, preferably cross-linkable organic material. Possible
specific materials for the imprint material are as follows: an
acrylate based material (including methacrylate materials), a
polyester-based material, an epoxy-based material or an
urethane-based material, or mixtures thereof. [0089] The
cross-linking of the imprint can be effected by UV exposure (UV
induced cross-linking), a heating step (heat-induce cross-linking),
UV and heat combined or using two-component cross-linkable
materials. [0090] The imprint material is deposited either on the
soft-stamp, for example using spin-coating or on the final metal
stamp surface, for example using spray-coating. [0091] The final
metal stamp surface is put it contact with the soft-stamp so that
the imprint material located in between is pressed between the two
materials. The pressure can be applied using a soft and deformable
elastomeric tampon. The tampon geometry is usually adapted to the
final metal stamp 3D shape to apply gradually a pressure for the
soft-stamp center to its outer edges. [0092] After the
cross-lining, the soft-stamp and metal stamp are demolded. To
prevent damaging the imprint material or to delaminate the imprint
material from the metal stamp surface, an anti-sticking agent can
be applied on the soft-stamp before it comes into contact with the
imprint material. [0093] 4. The imprint organic material
transferred to the polished mold surface then needs to be etched.
An AFM topography image of such a micro-structure can be seen in
FIG. 7. The imprint material contains a continuous imprint material
layer below its patterned upper surface. [0094] This residual layer
is etch opened, usually using a dry technique method such a
Reaction Ion Etching (RIE), preferably an oxygen based RIE.
Suitable etching conditions are as follows: oxygen reactive ion
beam etching of 4 minutes. [0095] This allows exposing back to air
a portion of the steel polished surface, as can be seen in FIG. 8
under AFM. [0096] 5. The steel tool is now etched using Reactive
Ion Beam Etching (RIBE) also called Ion Beam Milling (IBM),
typically using ionized argon gas. [0097] Suitable etching
conditions are as follows: Veeco RIBE plasma chamber with a
duration of 25 minutes. [0098] Such dry etchings have relatively
low selectivity between various metals. This allows the metal stamp
tool, possibly made of hardened steel, to be etched in its bulk
with relatively good depth as structure aspect ratio above 1 can be
realized. [0099] At the end of this transfer, the imprint material
and etching residues are either fully etched away or the residues
left can be easily cleaned so that the metal stamp tool is back to
its original composition. FIG. 9 shows a simple diffractive
transferred into hardened steel as seen under AFM.
[0100] The steps are schematically illustrated in FIG. 10.
[0101] FIG. 10 a) shows the first step of the generation of the
soft stamp. The master 30 is provided and its grating portion 30a
is for example hot embossed into the soft stamp 31, so that in the
corresponding surface of the soft stamp a replica of the grating
portion 30a is generated forming the soft stamp grating 31a.
[0102] In the next step this soft stamp is used for making the
imprint 32, this is illustrated in FIG. 10 b). To do so, for
example in a casting process, imprint material is cast at least on
the soft stamp grating portion 31a, so that the corresponding
grating is again replicated forming the imprint grating 32a.
[0103] In the next step the result of which is illustrated in FIG.
10 c), the imprint is then transferred to the surface portion of
the metal stamp 1 which shall be provided with the corresponding
grating. It is also possible to directly form the imprint between
the soft stamp 31 and the metal stamp 1, for example by providing
the imprint material on the surface of the metal stamp 1 as a layer
and then applying the soft stamp 32 to that coated surface
portion.
[0104] In this phase the imprint 32 still is fully covering the
corresponding area, the metallic surface of the metal stamp 1 not
being exposed anywhere.
[0105] In the next step the imprint material is etch opened leading
to the situation as illustrated in FIG. 10 d). The etch opened
imprint 3D topologically structured surface 33 exposes now the
corresponding metal portions as regular pattern.
[0106] In a following step, the result of which is illustrated in
FIG. 10 e), metal etching takes place such that the open portions
of the etch opened imprint 33 are etched a way leading to a
corresponding grating in the surface of the metal stamp 1.
[0107] Now the metal stamp 1 or rather the corresponding
topologically structured portion 3 thereof, can be used to emboss
the corresponding optically active pattern in the corresponding
device 4.
A Specific Example of a 1.2083 Steel Metal Stamp Production Method
is Described for Exemplary Purpose:
[0108] In a first step, the surface of a metal stamp made of steel
1.2083, with which micro- and nanostructures should be embossed, is
polished to be mirror-like. Most steel grades have random rough
surfaces in the scale to a few to several microns, in order to
create a matt or dull finish on the polymer surfaces. To transfer
successfully smaller structures with a high coverage, this
topography needs to be planarized using polishing techniques.
[0109] As a second step, a master tool containing the diffractive
nano- and/or microstructures, whether simple grating or complex
surface holograms is made of a nickel plate grown galvanically from
a previous master, so-called a nickel shim. The nickel shim is
coated with 10 mL of a fluorinated and no-fluorinated
acrylated/methacrylated mixture UV-Opti-Clad made by Ovation
Polymers. The structured nickel shim coated with the mixture is
pressed against a planar fused-silica wafer and flashed with 10
W/cm.sup.2 of 365 nm UV light. The cross-linked UV-Opti-Clad soft
stamp is peel-off from the structured nickel shim and fused-silica
wafer.
[0110] The structured surface of the soft stamp is activated with a
5 minutes thinned-air plasma in a Harrick PDC-32G plasma cleaner
oven. A thermal imprint material is spin-coated on the activated
structured surface at 2000 rotation per minute with a mr-I T85-5
imprint material from Micro-Resist Technology GmbH.
[0111] The third step consists in imprinting the structure
transferred from the master tool through the soft stamp to the
actual polished metal stamp surface. In order to press the imprint
material on the metal surface, the backside of the soft stamp is
pressed on with an elastomeric tampon with 50N/cm.sup.2 using a
pressing steel plate. The metal stamp is coated with, the imprint
material, the soft stamp, the elastomeric tampon and the pressing
steel plate is placed in an oven. The oven is heated up to
140.degree. C. for 2 h.
[0112] The pressing steel plate, the elastomeric tampon and the
soft stamp are removed during the cooldown, leaving the metal stamp
surface coated with a thin imprint material layer structured with
the opposite polarity of the soft stamp, having the same polarity
as the nickel shim used.
[0113] The fourth step consists of an oxygen etching in a Veeco
RIBE plasma chamber with the imprint material facing the plasma.
The duration of the oxygen reactive ion beam etching is of 4
minutes to etch open the grooves of the structures to the metal
stamp surface.
[0114] A second etching step is used to etch the micro- and
nanostructures into the metal stamp using a Veeco RIBE plasma
chamber with a duration of 25 minutes.
[0115] With the previously mentioned method, coated metal stamps
can also be nano- and/or microstructured, for example by hard
chrome electroplating. According to the method described above, a
diffractive microstructure 3 is created in the surface.
[0116] If necessary, the metal stamp 1 or its surface 3 may be
hardened after generating the microstructure by a subsequent heat
treatment or ion implantation.
[0117] The actual embossing on the device to be made identifiable
is illustrated in FIG. 1 b). The metal stamp 1 is pressed onto the
surface of the corresponding device 4 until an embossed region 5 is
formed under plastic deformation conditions. In this case the
result is a general indentation 7 in the region where the grating
of the patch is generated. However it is also possible to emboss
without having such an overall indentation. A grating 6, which
essentially corresponds to the complementary topologically
structured surface to the one in the metal stamp is generated on
the surface of the device 4.
[0118] So in essence the proposed method consists in hammering the
desired microstructure into the surface of the device to be
securitized by an embossing method using a main die in the form of
the metal stamp. This metal stamp can be nano- and/or
microstructured with the ionic etching method described above, it
may however also itself have been produced in an embossing
process.
[0119] To be able to hammer a diffractive microstructure with a
metal stamp into metal device, e.g. a metallic implant, the
following prerequisites should be met:
[0120] 1. The hardness of the metal stamp should be greater than
that of the metal device at the position of the patch.
[0121] 2. Young's modulus should be as high as possible for both in
order to minimize the elastic deformation.
[0122] 3. The applied stress should be higher than the yield point
but lower than the ultimate tensile stress of the compression die.
Furthermore, it should be lower than the yield point, if any, and
the ultimate tensile stress of the main die.
[0123] To be able to nano- and/or microstructure a device based on
stainless steel or titanium (alloys) as conventionally used in the
field of processes of prosthesis and implants, a main die of
hardened steel, for example, is advantageous and an embossing
pressure of approximately 0.1-5 kN/mm.sup.2 is required, preferably
in the range 0.1-2 kN/mm.sup.2. As an alternative to that, the main
die may also be made of hardened steel with a coating of tungsten
carbide, Si.sub.3N.sub.4 or ZrO.sub.2, for example, which carries
the microstructure. The latter embodiment is less expensive because
only the coating must be made of the very hard and
fracture-resistant material.
[0124] FIG. 1 c) and d) show that the corresponding process can be
used for different medical devices, and the corresponding optical
patches can be applied at different places in these devices. In
FIG. 1 c) the device 4' is a medical distance holder ring.
[0125] In FIG. 1 d) the device is an implant 9. The dental implant
9 comprises an apical threading region 11 and a coronal collar
region 10. Typically the apical threading region is provided with a
rough surface (by chemical treatment and/or mechanical treatment)
which is not suitable for the generation of a grating 6. On the
other hand the collar region 10, and in particular axial
circumferential surfaces such as the lower abutment surface 12 or
the upper terminal surface 13 are suitable for embossing the
corresponding optically variable grating patch.
[0126] As illustrated in FIG. 2, the embossing is not limited to
flat surfaces such as illustrated in FIG. 1, the embossing process
has the advantage of also being suitable for convex and/or concave
surfaces. Essentially any kind of surface can be embossed, all that
needs to be taken care of is that the general surface form on the
tip 3' of the metal stamp 1 should be complementary to the general
surface form of the section of the device 4'' where the grating
patches to be applied.
[0127] Other possibilities of locating a corresponding embossed
grating 6 on implants are illustrated in FIG. 3. On the left side
it is illustrated that an embossed grating 6 can be generated on
the radial surface 15 of the dental implant which is either
converging apically as illustrated in this figure, or also the
opposite, if the corresponding surface is converging coronally. On
the left side in FIG. 3 it is illustrated that the corresponding
embossed grating 6 can be generated on an abutment 17, specifically
on a frustoconical section 18 thereof. While not being illustrated
in FIG. 3 on the right-hand side, it is also possible to generate
corresponding patches in a lower apical region of the abutment 17,
for example in one of the contact surfaces contacting the implant
in use.
[0128] FIG. 4 illustrates the surface topology on the metal stamp,
using the methods as described above a nice grating can be
generated if for example a grating period of 1.8 .mu.m is used. The
grating has a depth of approximately 360 nm. The grating can be
generated over the full patch and it comprises only little lattice
imperfections.
[0129] FIG. 5 demonstrates that even after having been used
repeatedly, the corresponding metal stamp maintains the essential
properties of the topologically structured surface. After a series
of embossing's in titanium material still the grating has a depth
of approximately 360 nm, there is little deposition of titanium on
the surface of the metal stamp.
[0130] FIG. 6 shows a dental abutment 17 in the coronally
converging portion thereof there is provided a flattened region 20,
and where in this flattened region the optical diffractive element
with a grating 6' has been generated. As one can see from a) the
corresponding grating has a depth in the range of 250 nm, the
proper periodicity, and the structure was generated in an abutment
having a roughness value Ra of approximately 0.22 .mu.m. Oppressing
force of 4.5 kN was applied at room temperature resulting in a
grating as illustrated in c) and d).
TABLE-US-00001 LIST OF REFERENCE SIGNS 1 metal stamp 2 front
portion of 1 3 topologically structured front surface of 1 3'
topologically structured concave front surface of 1 3''
topologically structured inclined front surface of 1 4 object to be
provided with a grating 4' object in the form of a ring 4'' object
with convex surface 5 embossed region in 4 6 grating embossed in 4
6' grating in the form of a diffractive optical element 7 general
indentation 8 embossing force 9 dental implant 10 coronal collar
region of 9 11 apical threading region of 9 12 lower abutment
surface on 10 13 upper terminal surface on 10 14 interface (female)
for attaching an implant 15 conical portion of 10 16 interface
(male) for attaching the abutment to the implant 17 abutment 18
conical surface of the abutment 19 measurement line 20 flattened
portion on 18 with optical diffractive element 30 master tool 30a
master 3D topologically structured surface 31 soft stamp 31a soft
stamp 3D topologically structured surface 32 imprint 32a imprint 3D
topologically structured surface 33 etch opened imprint 3D
topologically structured surface
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