Note: Descriptions are shown in the official language in which they were submitted.
1090-62
-- 1 --
A method and an apparatus for fabricating a surface structure, particularly a
holographic surface structure, on a substrate
The invention relates to a method for fabricating a surface structure, particularly a
holographic surface structure, on a substrate and to an apparatus for the performance
of such a method.
The surface structure to be fabricated is generally a relief structure. A given or defined
surface structure or relief structure has to be applied to the substrate. The substrate can
then be used in particular as a die (relief master) for embossing holography.
The object of the invention is to provide a method and an apparatus of the type
described above with which an individualised fabrication of a surface structure,particularly of a holographic surface structure, is made possible in a simple manner.
In accordance with a first proposal, this object is solved for a method of the type
described above by the substrate being coated with a radiation-curable substance, in
particular with a radiation-curable monomer, by an embossing pattern being
introduced into the coating and by the embossing pattern being cured with a
modulated irradiation beam. The radiation-curable substance is preferably a fluid
substance. This substance can preferably be cured by means of electromagnetic rays,
for example W light. A regular embossing pattern can be applied. The radiation-
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curable substance is cured by the irradiation beam in those regions which are reached
by at least one modulated irradiation beam. Naturally, the iITadiation beam(s) must be
suitable to cure the radiation-curable substance.
Advantageous improvements are described in the dependent claims.
The embossing pattern is preferably applied by a cylinder. However, it may also be
applied by a plane element moved intermittently. The cylinder can possess a regular
relief structure on its surface.
The modulated radiation can be performed by means of a scanner, in particular bymeans of a line scanner. This is also particularly of advantage if the embossing pattern
is applied by means of a cylinder. The line of the line scanner then preferably runs
parallel to a circumferential line of the embossing cylinder or at a right-angle to the
direction of forward movement of the scanner.
A further advantageous improvement is characterised by the fact that the irradiation is
effected by an LCD. The LCD can be controlled by a PC or other computer so that the
surface structure regions to be cured individually can be programmed very quickly and
simply.
The method can be repeated once or several times. In this way, it is possible tofabricate one after the other on a substrate several surface structures which may differ
from one another as required and which can be positioned next to one another or
which may also overlap.
For example, the non-cured substance or the non-cured monomer is washed out after
the irradiation or the curing.
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An appalallls for the fabrication of a surface structure, in particular of a holographic
surface structure, on a substrate comprises in accordance with the invention a cylinder
over which a substrate coated with a radiation-curable substance, in particular with a
radiation-curable monomer, can be guided and an irradiation apparatus to irradiate the
coated substrate with a modulated irradiation beam.
Advantageous in~lovements are described in the further dependent claims.
Preferably, a coating apparatus for the coating of the substrate with a radiation-curable
substance, in particular a radiation-curable monomer, is connected in series prior to
the cylinder.
Preferably, the irradiation apparatus is located outside the cylinder. In this case, the
substrate is translucent for the rays of the irradiation apparatus. The irradiation
apparatus can, however, also be located within the cylinder. In this case, the surface of
the cylinder is transparent for the irradiation beams.
Preferably, the irradiation apparatus comprises a light modulator, for example ascanner, in particular a line scanner, and/or an LCD.
Preferably, several apparatuses are located in series one after the other. The substrate
passes through these apparatuses one after the other. In this way, several surface
structures, which may differ as required, can be fabricated one after the other on the
substrate which surface structures are then located next to one another and/or
overlapping on the substrate.
For example, a washing unit is connected subsequent to the cylinder to wash out the
non-cured substance or the non-cured monomer.
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The object forming the subject of the invention is solved for a method of the type
described above in accordance with a second proposal for which independent
protection is claimed by a radiation-curable substance, in particular a radiation-curable
monomer, being applied to the substrate in accordance with the surface structure to be
fabricated and the substance being irradiated with an irradiation beam. In this case,
therefore, the radiation-curable substance is not applied to the whole surface region of
the substrate, but only to that region where the surface structure should later be
located. There, the substance is then irradiated and thus cured. One advantage of this
procedure consists of a washing out of any liquid substance in those areas where no
surface structure should be located no longer being necessary.
The two methods in accordance with the invention differ by means of the following: in
accordance with the method first given, the radiation-curable substance is first applied
to the whole substrate or, however, at least to regions of the substrate which are
greater than that region on which the surface structure should later be located. The
surface structure is then manufactured in that only those regions on which the surface
structure should later appear are irradiated wlth an irradiation beam. In contrast, in the
second method, the radiation-curable substance is from the beginnin~ only applied to
the substrate where the surface structure should later appear. Here, the curing beam
does not need to be modulated (as long as no additional hologram is irradiated).
Advantageous improvements are described in the further dependent claims.
The radiation-curable substance or the radiation-curable monomer can be applied to
the substrate by specific application, for example by spraying or imprinting or by
another method. In accordance with another advantageous improvement, the radiation-
curable substance or the radiation-curable monomer can be applied to a cylinder with
surface relief and subsequent to curing by irradiation be applied to the substrate from
this. In this case, the radiation-curable substance or the radiation-curable monomer is,
CA 02244324 1998-07-28
for example, applied individually to the embossing cylinder by means of inkjet
nozzles. For the curing, only uniform, unmodulated radiation is required.
The method can be repeated once or several times to apply different surface structures
to the substrate as required and this to regions of the substrate which are next to one
another or which overlap.
An apparatus to fabricate a surface structure, in particular a holographic surface
structure, on a substrate comprises in accordance with the second proposal of the
invention an application apparatus to apply a radiation-curable substance, in particular
a radiation-curable monomer, to the substrate in accordance with the surface structure
to be fabricated and an irradiation apparatus to irradiate the substance.
Advantageous improvements are described in the further dependent claims.
The apparatus preferably comprises a cylinder. The application apparatus comprises,
for example, inkjet nozzles to apply the radiation-curable substance or the radiation-
curable monomer to the substrate andlor to the cylinder. It is advantageous if several
apparatuses are connected in series in order to fabricated different surface structures to
the substrate as required, and this to regions of the substrate which are next to one
another and/or which overlap.
By means of the invention, in particular holographic surface structures can be
fabricated. However, it is also possible to fabricate other surface structures, for
example, optical gratings. The surface structures are manufactured in the form of
casting or moulding.
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Embodiments of the invention are described in detail below by means of the enclosed
drawing in which
Fig. 1 shows an apparatus for fabricating a surface structure on a substrate with
a cylinder in a side view;
Fig. 2 shows the apparatus shown in Fig. 1 with, in addition, a coating
apparatus and a line scanner in a perspective view;
Fig. 3 shows a modification of the apparatus shown in Fig. 2 with an LCD
Fig. 4 shows a washing unit in a side view;
Fig. S shows two apparatuses from Fig.2 connected in series one after the
other;
Fig. 6 shows an apparatus for fabricating a surface structure on a substrate with
inkjet nozzles in a perspective view; and
Fig. 7 shows an apparatus for fabricating a surface structure on a substrate with
inkjet nozzles to apply thé surface structure to a cylinder in a
perspective view.
In the apparatus shown in schematic form in Fig. 1, a foil 4, which is coated with a
liquid, radiation-curable monomer 5, is supplied to a rotating cylinder 10. The cylinder
. 10 comprises a cylindrical surface (cylinder wall) 3 to whose outside a surface
structure 2 is applied. It is, for example, a hologram surface structure. The foil 4 is
first guided round a first guide roller 7. It then comes into contact with the surface
structure 2 in such a way that the liquid, radiation-curable monomer 5 is positioned on
the side of the foil 4 facing the surface structure 2. The feed rate 11 of the foil 4 is
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precisely the same as the circumferential speed of the cylinder wall 3. Then, the foil is
deflected by a further guide roller 7' and transported away.
While the foil 4 is in contact with the surface structure 2, the embossing pattern is
applied to the monomer coating 5 of the foil 4, that is the (negative) embossing pattern
of the surface structure 2. This embossing pattern is irradiated with a modulated
irradiation beam la and/or lb. The irradiation can be effected by a modulated
irradiation beam la from the inside, that is from the interior of the cylinder. In this
case, the cylinder wall 3 must be translucent. However, the irradiation can also be
effected by means of a modulated irradiation beam lb from the outside or the inside.
In the case of irradiation from the outside, the foil 4 should be translucent; in the event
of irradiation from the inside, the embossing cylinder be translucent in order to allow
an irradiation and curing of the monomer 5.
The Irradiation beam la and/or lb is modulated in such a way that only certain
predetermined regions of the embossing pattern are irradiated with light. These
regions are shown in black in Fig. 1. In these regions, the monomer 5 is cured. In this
way, the predetermined surface structure is formed on the foil with monomer 6 cured
by means of irradiation. Liquid monomer 5 can still be found between the cured
reglons.
In Fig. 2, the coating apparatus positioned prior to the cylinder is shown which coating
apparatus comprises a tank 8 filled with liquid monomer, a lower coating roller 9 and
an upper coating roller 9'. The lower coating roller 9 dips into the liquid monomer in
the tank 8. It rotates counter-clockwise and is in contact with the upper coating roller
9' which rotates clockwise and whose circumferential speed is the same as the
transportation rate 11 of the film 4.
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In the embodiment of Fig.2, irradiation is effected with the mo~ te-l irradiation
beam 1 by means of a line scanner 2 which consists of a rotating polygon mirror and
which is irradiated by the beam source 3 with modulation capability. The line of the
line scanner 2 runs parallel to a circumferential line of the cylinder 10. In this way,
regions 14 with cured monomer are applied to the foil 4.
The version shown in Fig. 3 differs from that in Fig. 2 in that the line scanner has been
replaced by an irradiation apparatus with an LCD 23 which irradiation apparatus is
irr~ te~l by an expanded irradiation beam 1 through a lens system 22. The
predetermined surface structure is fabricated on the LCD 23. The expanded irradiation
beam 1 is guided onto the LCD 23 by the lens system 22 and modulated there. The
LCD is located above the cylinder 10 parallel and at a distance to one of its
circumferential lines.
In Fig.4, a washing unit for the non-irradiated monomer is shown. It consists of a
washing drum 34 which rotates in a container with washing solution 33. The foil 31,
on which regions with cured monomer and with liquid monomer are located, is led via
a first rubber scraper 32 to a guide roller 35. From there, the foil 31 comes to the
outside circumference of the washing drum 34 in such a way that the monomer
regions are located on the outside circumference. In the washing solution 33, the liquid
monomer is then removed from the foil 1. The foil 31 washed in this way is then
guided through a rubber roller 36 after one wrap around the washing drum 34. By
means of the rubber roller 36, which is in contact with the washing drum 34, anysolvent still adhering to the foil 31 is simultaneously squeezed off.
The foil 37 with cured monomer is subsequently led to further rubber scrapers 32 on
both sides of the foil 37 which scrape off any residues of monomer andlor solvent.
Following on from these are hot-air nozzles 38 on both sides of the foil 31 which blow
off any monomer and/or solvent residues still rem~ining.
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Fig. 5 shows two a~palaluses of the type shown in Fig. 2 connected one after theother. Identical parts are identified by the same symbols so that they do not need to be
described again. By means of the first inscription beam 1, a first surface structure 14 is
applied to the foil 4. The second inscription beam 1 ' applies a second surface structure
14' to the film 4. In the embodiment of Fig. 5, the regions 14 and 14' are next to each
other. However, they may also overlap in full or in part.
In Figs. 6 and 7, embodiments in accordance with the second solution in accordance
with the invention are shown. In the embodiment of Fig. 6, a radiation-curable
monomer is applied in accordance with the surface structure 44 to the foil 4 by inkjet
nozzles 41. It is then found on the foil 4 as a sprayed monomer 42 in the pre-
determined surface structure. This pre-determined surface structure is fabricated by
means of a corresponding control ofthe inkjet nozzles 41. While passing the cylinder
10, the foil 4 is irradiated with the expanded irradiation beam 43. In this way, the
monomer located at the pre-determined areas is cured. On the regions 44, cured
monomer is then found on the foil 4.
Fig. 7 shows a modified embodiment in which the inkjet nozzles 41 do not apply the
monomer directly to the foil 4, but first to the cylinder 10 provided with a regular
surface structure or relief structure. The inkjet nozzles 41 are located below the
cylinder. After one rotation of the cylinder 10, its surface is irradiated by an expanded
irradiation beam 52. The inkjet nozzles 41 have applied the monomer to the cylinder
10 only on those pre-determined areas on which the surface structure 57 should be
fabricated. There, the monomer is then cured by the expanded irradiation beam 52.
Subsequently, it is transferred to the foil 4.
-
The foil 4 is first deflected downwards by a guide roller 55 which is located above thecylinder 10. It is brought into contact with the surface of the cylinder 10 by a pressure
roller 56. The foil 4 is then guided away by a further guide roller 55.
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As in the embodiments of Figs. 6 and 7, the monomer is only applied to the pre-
determined areas on which the surface structure should be fabricated, no washing unit
is required.
By means of the invention, the copying capability and the imitation of security
holograms is made substantially more difficult. It is possible to fabricate
microstructures which make counterfeiting difficult in a simple manner. These
microstructures can be fabricated by means of an individ~ tion such as a
numbering, a bar code, personal images (for I.D.s, etc.) or similar.
By means of the invention, a method and an apparatus are provided for the
individualised transfer of surface structures onto translucent and non-translucent
substrates. No expensive holographic equipment is needed. In particular, among other
things, the irradiation can be effected with a non-coherent light source. The
individll~ ation of the information to be transferred can be performed with very low
effort and by the utilisation of existing technologies such as LCD displays (projectors),
modulated lasers (laser printers), inkjet monomer application (inkjet printers),electron beam scanners (welding, drilling), electro-mechanically adjustable masks,
thermal transfer technology (printers, facsimile machines) and/or electrostatic
discharging with laser scanners (laser printers).
By means of a combination or overlapping of different structures, complex structures
can be manufactured simply in one workstep. Even structures with a large area can be
manufactured with minimum equipment effort. The invention allows a simple and
direct preparation of relief masters for embossing holography with and without the use
of coherent lasers and holographic equipment. By mixing in different dyestuffs,
fluorescent dyestuffs, reversible thermal dyestuffs and/or ferro-magnetic substances in
micro-encapsulated form (or also directly) to the monomer, imitation or counterfeiting
is made more difficult. By means of a multiple application onto overlapping regions,
elevations or relief structures can be fabricated on the substrate.
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In accordance with the first solution in accordance with the invention, the substrate is
coated with a radiation-curable substance, in particular with a radiation-curable
monomer. This process step can, however, be omitted if a pre-coated substrate is used
for the process. In this case, the embossing pattern is applied to the coating of the pre-
coated substrate and this embossing pattern is then irradiated with the modulated or
unmodulated irradiation beam.
In the multiple application of monomer shown in Fig. 5, elevations of the cured
monomer layer can be fabricated if the regions which are coated in each case overlap.
These elevations can be tangible or measurable by means of which an additional
authenticity feature is created. In addition, it is possible to provide the first cylinder 10
with a first structure and the second cylinder 10' with a second or multiple structures.
The structures can correspond to a first and a second colour.
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