Process for the production of micro picture elements on a substrate

专利摘要:
The invention provides a method for manufacturing micro-picture elements on a substrate for a security document, the method comprising: producing a plurality of micro-structure units comprising three-dimensionally structured formations in a transparent or matt relief layer on the substrate; and applying an ink fluid to the relief layer, the ink fluid preferably accumulating in regions of high surface curvature on each microstructure unit to provide contrasting areas with different ink density.
公开号:AT521806A2
申请号:T9209/2018
申请日:2018-06-29
公开日:2020-05-15
发明作者:Ivan Jolic Karlo；Fairless Power Gary
申请人:Ccl Secure Pty Ltd；
IPC主号:

专利说明:

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Technical field
The present invention relates to methods for producing micro-picture elements on a substrate for a security document and micro-optical devices on a substrate, which comprises such micro-picture elements. The methods include, in particular, the manufacture of microstructure units comprising three-dimensionally structured formations in a transparent or matt relief layer on a substrate, the application of an ink fluid to the relief layer and the enabling of the ink fluid preferably in areas with a high surface curvature on each microstructure unit, around contrasting areas with different
To provide ink density.
General state of the art
It is important that security documents such as banknotes, credit cards, identification papers (including passports), land titles, share certificates and certificates, packaging materials for high-quality goods, security labels and security cards from counterfeiters are difficult to replicate and have features
should allow their authentication.
A number of different strategies for securing and authenticating such security documents have been disclosed. The use of polymer films as substrates offers due to the greater difficulty of copying and printing on such temperature sensitive materials and because of the accessibility to integrate a variety of visible ones
and hidden security features an inherent advantage.
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One type of security feature that has been proposed for use in security documents is disclosed in US 5712731. This security feature involves a combination of microlenses and microimages to create optically variable effects. The microimages are formed by printing on a surface of a substrate and the microlenses can be formed as a separate component or on a transparent plastic film adhered to the microimages. A slight mismatch between the division or rotational alignment of the microimages and the microlenses can have optically variable effects, such as an enlarged image (known as a Moire6 lens as described in M. Hutley et al, "The moire magnifier", Pure and Applied Optics 1994 Vol 3, pp. 133 to 142). These security features can produce images that appear to move and / or float below or above the plane of the substrate
shine as the viewing angle changes.
However, the resolution and size of the micro images that can be produced by the processes of US 5712731 are limited by the dependence on traditional printing processes, such as gravure, flexographic and gravure printing. Usually, such printing methods cannot be used to produce images that have a resolution of less than approx.
Require 50 microns.
In particular, roll-to-roll gravure printing is limited by high resolution features by phenomena known in the printing industry as dot-skip, drying, feathering and screening. Such phenomena result in errors in printed images in the form of small missing sections that can be random in their position. The errors are magnified and seen through an arrangement of microlenses
generate images by the user as an inferior
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Perceived quality. The enlarged images may have a grainy appearance that appears to have "rashes" or "streaks" of missing points. This limits in particular the usability of the security features in the case of thin, flexible security documents, such as banknotes or the like. Apart from aesthetic considerations, a poor or inconsistent quality of security features in banknotes can give counterfeiters the opportunity to reproduce
of poor quality as original banknotes.
Embossing and related techniques were previously used to produce security features with higher resolutions than can be achieved by conventional printing techniques. A radiation-curable lacquer layer is usually embossed with an embossing disk and hardened at the same time in order to produce a microstructured layer on the security document substrate. The microstructured coatings can be designed to produce a number of optical effects, including refractive and holographic effects. The color contrast of such three-dimensional ones formed in a monochromatic coating
Micrographs can be unsatisfactory.
Embossing techniques have also been used to produce microimages that produce optical effects when viewed through an array of microlenses. Refractive structures were formed in an image layer on a substrate by embossing flat lattice formations into a monochromatic UV-curing coating. The contrast in the enlarged image seen through the microlenses is therefore due to the refractive properties of the lattice microstructures versus the non-refractive ones
Background regions of the embossed image layer set generated.
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A multicolored enlarged image is therefore observed by an observer. However, due to the refractive nature of the pixels, the enlarged image must generally have a
Point source lighting instead of indirect lighting
be considered.
More complex techniques have been reported for producing high resolution, high contrast color micrographs that can be viewed with a wide range of lighting conditions. A pigmented UV-curing printing ink can, for example, be applied directly to an embossing roller into which a three-dimensional microstructure is engraved. Excess ink is wiped off the roller, leaving only ink in the recessed regions of the embossing roller surface, and the ink is partially cured on the roller with UV radiation. The partially cured ink microstructures are then transferred to the substrate surface and fully cured on the surface. Although this technique is useful for producing high contrast, color contrasted microimages for certain niche applications, it is difficult to enlarge for high throughput manufacturing. This multi-step approach also suffers from a number of other disadvantages including the inherent process complexity, the rapid wear that the embossing roller experiences due to ink application and wiping, and the effects on ink adhesion to the substrate due to pigmentation and pre-curing and limitation on a
individual color choice per printing unit.
There is therefore a constant need for new processes for
Production of color-contrasted micro images with a high
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Resolution on substrate surfaces, with one or more of the
aforementioned disadvantages are at least partially addressed.
Reference herein to a patent document or other subject matter identified as prior art should not be construed as an admission that the document or subject matter was known, or that the priority date information contained therein
of any of the claims is part of general knowledge
were. Summary of the invention
According to a first aspect, the invention provides a method for producing micro-picture elements on a substrate for a security document, the method comprising: producing a plurality of micro-structure units comprising three-dimensionally structured formations in a transparent or matt relief layer on the substrate; and applying an ink fluid to the relief layer, the ink fluid preferably accumulating in regions with high surface curvature on each microstructure unit in order to create contrasting areas with different
To provide ink density.
Three-dimensional microstructures with micrometer scale (or even submicrometer scale) features can be produced precisely in a relief layer by embossing or the associated techniques. The inventors have found that an ink fluid which is applied in a transparent or matt relief layer produced in this way preferably accumulates on the three-dimensional microstructures, which provides an excellent color contrast between contrasting ones
Provides areas with different ink density.
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The contrasting areas with different ink density generally comprise areas with high ink density in the regions with high surface curvature on the microstructure units and contrasting areas with low ink density on adjacent areas of the relief layer. It is obvious that the areas with low ink density can either be essentially free of ink or can have a sufficiently low ink density relative to the areas with high ink density so that a visible contrast is perceived. Microimage elements formed in this way, which comprise printing ink that has accumulated at least in the regions with a high surface curvature, can have a higher degree of resolution and a higher reproducibility,
than it can be made using conventional printing techniques
can.
Without wishing to be bound by theory, it is believed that the ink fluid flows over the surface of the relief layer in regions with high surface curvature on the microstructure units in order to minimize the surface energy. The ink fluid spreads over the surface to balance the cohesive forces that hold the ink fluid together and the adhesive forces between the ink fluid and the microstructure surface. By controlling the three-dimensional configuration of the microstructure units, ink fluid properties, and ink fluid loading, the method of the invention can be used to create a wide variety of high resolution symbols, characters and patterns on one
To produce substrate surface.
As used herein, a region with high
Surface curvature of any surface region with a sufficiently large area
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Be curvature relative to nearby surface regions, with ink fluid preferably accumulating therein in such a way that contrasting regions with different ink density are produced. It is understood that regions with high surface curvature, within which an ink fluid can preferentially accumulate, are both essentially angular (ie, angles <180 °) features, such as corner regions defined by cutting planes, as well as more curved features with concave Surfaces, of which the configuration can be in practice by the method of manufacturing the microstructure units
can be influenced.
In some embodiments, a repeating arrangement of substantially identical microstructure units is made in the relief layer. In such embodiments, the ink fluid accumulates in a substantially equal distribution on each substantially identical microstructure unit, so that a repeating arrangement of substantially identical microimage elements is produced. The repetitive arrangement of micro picture elements can be arranged in rows and / or columns with a pitch of less than approximately 100 micrometers, preferably less than approximately 70 micrometers.
be configured.
In some embodiments, the viscosity of the ink fluid, as measured using a # 2 tooth cup, ranges from 16 to 25 seconds (10 to 50 centipoise), preferably 16 to 18 seconds (10 to 20 centipoise). The printing ink fluid can be applied with a wet loading of approximately 0.5 g / m 'up to approximately 10 g / m. The use of ink fluids with viscosities
and loads in these areas may be particularly preferred
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to accumulate the ink fluid preferably on microstructure units with formation features with a resolution between 1 and 3 microns and therefore
produce high-resolution micro images.
In some embodiments, the multiple microstructure units are manufactured by embossing the three-dimensionally structured formations into the relief layer. In some such embodiments, the relief layer is made by applying a transparent or matt embossable coating to the substrate. The three-dimensionally structured formations are then embossed into the embossable coating. The embossable coating is preferably a radiation-curable coating. The three-dimensionally structured formations can then be embossed into the embossable coating at the same time and cured with radiation, such as UV radiation, in order to produce a cured coating. The embossable coating can with
an embossing disc or roller.
In some embodiments, the plurality of microstructure units are manufactured by: filling a plurality of depressions in a surface of a printing tool with a transparent or matt lacquer; and transferring the varnish from the depressions to the substrate by contacting the surface of the printing tool with the substrate. In some such embodiments, the method further includes increasing the viscosity of the paint in the wells prior to contacting
the area of the printing tool with the substrate.
Filling the plurality of wells may include applying the varnish to the surface of the printing tool. The method can then further remove excess lacquer from the
Area of the printing tool outside of the wells, such as
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for example with a wiping tool such as a shovel or a sponge. In this way, essentially only the lacquer in the depressions is transferred to the substrate in the subsequent contact step, as a result of which a relief layer is provided which comprises discrete three-dimensionally structured lacquer formations and the surrounding surface of the substrate. In these embodiments, the viscosity of the lacquer in the depressions can be increased before and / or after, but preferably before, the removal of the excess lacquer. In other embodiments, excess varnish is not removed from the surface of the printing tool outside the depressions. In this way, paint can be transferred from regions of the printing tool surface, which surround the depressions, to the substrate. In some such embodiments, a continuous varnish coating is transferred to the surface of the printing tool, thereby covering the substrate with a continuous varnish coating as the relief layer, the varnish that is transferred from the depressions forming the three-dimensionally structured formations in the relief layer. Aside from the greater simplicity, this has the advantage that the surface of the printing tool is not an object
of wear as a result of wiping.
In some embodiments, increasing the viscosity of the paint in the wells prior to contacting the surface of the printing tool with the substrate at least partially includes curing the paint. In this way, the paint in the wells can develop a level of structural integrity sufficient to protect the configuration of the paint formations during transfer to the substrate. In some embodiments, the method further includes at least partially curing the paint during the
Contacting the surface of the printing tool with the substrate.
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Curing the paint while in contact with the substrate can improve the adhesiveness of the paint formations and / or layer to the substrate. In some embodiments, the varnish is a radiation curable varnish and the varnish is at least partially irradiated by the varnish
cured with radiation such as UV radiation.
The microstructure units comprising three-dimensionally structured formations can generally have any suitable configuration that allows the ink to preferentially accumulate in regions with high surface curvature, thereby producing color-contrasted micro picture elements. In some embodiments, the microstructure units include at least one formation sidewall that intersects with a surrounding surface region formation portion of the microstructure unit or an adjacent relief layer surface. The intersection of the side wall and the surrounding surface region therefore defines a region with a high surface curvature, so that the printing ink fluid preferably accumulates next to the side wall. In some such embodiments, the surrounding surface region is aligned in substantial alignment with the plane of the relief layer. The sidewall may be at a steep, including a substantially perpendicular, angle to that
Level of the relief layer.
In some embodiments, the microstructure units include at least one formation in the form of a depression that is recessed into surrounding regions of the relief layer. The recess generally has side walls and a recess base surface between the side walls, although it is apparent that the recess, in some embodiments, has a substantially curved surface
may include that the side walls and the
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Well base area not through angled intersections
are separated.
In some embodiments, the recess has a minimum width between 0.5 and 10 microns, and preferably between 1 and 3 microns. The minimum width of a depression is the minimum distance between opposite side walls of the depression and therefore correlates with the resolution of the microstructure units. In some embodiments, the depression is a groove formed in the plane of the relief layer. In such embodiments
the minimum width of the recess the width of the groove.
In some embodiments, the ink fluid, when applied to the relief layer, accumulates in regions of high surface curvature within the well by flowing into the well from the surrounding regions. The flow of ink fluid into the well is believed to minimize surface energy because the well has regions with high curvature
on the relief layer surface.
In some embodiments, the ink fluid preferably accumulates within the well and covers the well base surface. The well base surface is therefore completely covered by a layer of ink fluid, although typically the ink fluid does not fill the well. A color contrast is therefore produced between the ink-covered depression of the microstructure units and the surrounding regions which are devoid of or at least depleted from ink fluid. In other embodiments, the ink fluid preferentially collects within the depression in regions with high surface curvature
at an intersection of the side walls and the
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Well base area, the contrasting areas with different ink density areas having high ink density areas adjacent to the side walls and a contrasting area with low ink density area on the well base area between the side walls. There is therefore a color contrast due to the selective distribution of the printing ink fluid within the depressions
produced.
In some embodiments, the microstructure units include at least one formation in the form of a protrusion that protrudes from surrounding regions of the relief layer. The protrusion generally has sidewalls, although it is obvious that in some embodiments the protrusion may comprise a substantially curved surface such that the sidewalls are from the surrounding regions
are not separated by angled intersections.
In some embodiments, the protrusion has a minimum width between 0.5 and 10 microns, and preferably between 1 and 3 microns. The minimum width of a projection is the minimum distance between opposite side walls of the projection and therefore correlates with the resolution of the microstructure units. In some embodiments, the protrusion is a protrusion formed at the level of the relief layer above. In such embodiments, the minimum width of the protrusion is that
Width of increase.
In some embodiments, the ink fluid, when applied to the relief layer, preferably collects in regions of high surface curvature at an intersection of the side walls and the surrounding regions of the
Relief layer. Areas with high ink density are
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therefore provided adjacent to the side walls. These areas of high ink density contrast with areas of low ink density that are further away from the side walls on the surrounding regions of the relief layer and / or on the protrusion itself. The flow of ink fluid is believed to minimize area energy because the intersection between the sidewalls and the surrounding regions is a high region
Surface curvature forms on the relief layer surface.
In some embodiments, the plurality of microstructure units comprise a coherent network of raised regions that extend across the relief layer and connect adjacent microstructure units. The inclusion of air bubbles in the relief layer can be avoided if several microstructure units with this
Configuration can be embossed into the relief layer.
In some embodiments, micro-pixels that include ink accumulated in the high curvature regions, seen through an array of focusing elements disposed on the substrate, such as on a surface of the substrate opposite the relief layer, produce a visible optical effect. In some embodiments, the substrate is therefore transparent. The visible optical effect can be an enlarged moire image, a holistic image, a contrast-changing image, a nested image or a flip image. In some embodiments, the ink fluid, when viewed directly on the substrate, forms a design element that is opposite to the
visible optical effect is distinguishable.
In some embodiments, the ink fluid is one
solvent-based printing ink with a solid content
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between about 15 percent by mass and about 25 percent by mass. The ink fluid can be applied by gravure printing. The method of the invention may further include drying or
Include curing the ink fluid.
In some embodiments, the method of the invention further includes, after applying the ink fluid, applying a transparent protective coating over the relief layer. In other embodiments, the method of the invention further includes applying a contrast coating over the relief layer after the ink fluid is applied, the contrast coating being a different color from the ink fluid so that micro-pixels that have ink accumulated in the regions with high surface curvature are reflected in reflected light seen through the substrate against the
Contrast the contrast coating.
In a second aspect, the invention provides micro-pixels on a substrate for a security document by the method according to any of the embodiments disclosed herein
is made.
According to a third aspect, the invention provides a micro-optical device on a substrate for a security document, comprising: a plurality of micro-structure units comprising three-dimensionally structured formations in a transparent or matt relief layer on the substrate; and a printing ink on the relief layer, the printing ink preferably being accumulated in regions with a high surface curvature on each microstructure unit, whereby contrasting areas with
Different ink density can be provided.
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The contrasting areas with different ink density generally include areas with high ink density in the regions with high surface curvature on the microstructure units and contrasting areas with low ink density on adjacent areas of the
Relief layer.
In some embodiments of the third aspect, the relief layer comprises a coating on the substrate and the microstructure units are embossed into the coating. The relief layer can comprise a repeating arrangement of essentially identical microstructure units, the printing ink being in a substantially uniform distribution on each substantially identical
Microstructure unit is accumulated.
The micro-optic device may further comprise an arrangement of focusing elements arranged on the substrate, micro-image elements comprising the printing ink accumulated in the regions with high surface curvature being seen through the arrangement of focusing elements
create optical effect.
Where the terms "comprise", "comprises" and "comprehensive" are used in the patent specification (including the claims), these are intended to specify the features mentioned, whole numbers, steps or components, but the presence of one or more other features, integers, steps or components or a group of them
not be interpreted exclusively.
Further aspects of the invention are described in the following
detailed description of the invention.
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Embodiments of the invention are given herein by way of example only with reference to the accompanying drawings
illustrates, where:
FIG. 1 shows a top view of a cut-out area of a relief layer with microstructure units that comprise recessed three-dimensionally structured formations,
which are made according to an embodiment of the invention.
Figure 2 is a side view (not to scale) of the relief layer of Figure 1 along that indicated in Figure 1
Section line A-B represents.
Figure 3 illustrates the relief layer of Figure 2 after an ink fluid is applied thereon and preferably on the microstructure units according to one embodiment of the
Invention was accumulated.
FIG. 4 shows a top view of the colored relief layer from FIG. 3, on the micro-picture elements contrasting in color due to the preferred accumulation of the printing ink fluid
were formed.
FIG. 5 shows the relief layer of FIG. 2 after an ink fluid has been applied to it and preferably on the microstructure units according to a further embodiment of the
Invention was accumulated.
Figure 6 is a top view of the colored relief layer of
Figure 5 represents on the result of the preferred accumulation
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of the ink fluid, color-contrasted micro-picture elements
were formed.
FIG. 7 shows a top view of a cut-out area of a relief layer with microstructure units which comprise the above three-dimensionally structured formations,
which are made according to an embodiment of the invention.
Figure 8 in side view (not to scale)
Relief layer of Figure 7 along that given in Figure 7
Section line A-B represents.
FIG. 9 shows the relief layer of FIG. 8 after an ink fluid has been applied to it and preferably on the microstructure units according to a further embodiment of the
Invention was accumulated.
FIG. 10 shows a top view of the colored relief layer from FIG. 9, on the micro-picture elements contrasting in color due to the preferred accumulation of the printing ink fluid
were formed. Detailed description
The present invention relates to a method for producing micro picture elements on a substrate for a security document. The method comprises producing a plurality of microstructure units which comprise three-dimensionally structured formations in a transparent or matt relief layer on the substrate. An ink fluid is then applied to the relief layer, so that the ink fluid is preferentially in regions with high
Area curvature accumulates on each microstructure unit
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contrasting areas with different
To provide ink density.
Substrate
The substrate can be any suitable substrate for security documents. The substrate can be paper or other fibrous material such as cellulose; a plastic or polymer material, including but not limited to polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET); or a composite material of two or more materials, such as a laminate of paper and at least one plastic material or two or more polymer materials. The use of plastic or polymer materials in the manufacture of security documents, which paved the way in Australia, has been very successful because polymer banknotes are more durable than their paper counterparts and also new security features (such as
Micro-optic devices).
In preferred embodiments, the substrate is a transparent or translucent material. Transparent substrates are particularly preferred since microimage elements produced on one surface of the substrate can then be viewed by an arrangement of focusing elements arranged on the opposite surface of the substrate. The thickness of the transparent substrate is preferably over 50 micrometers in order to enable the micro picture elements to be arranged at or just within the focal length of focusing elements on the opposite surface. In some embodiments, the substrate is 60 to 100
Microns thick and preferably 65 to 90 microns thick.
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A particularly suitable transparent substrate is polypropylene and in particular biaxially oriented
Polypropylene.
A common security feature for polymer banknotes made for Australia and other countries is a transparent area or window. In one embodiment, the micro-picture elements of the invention are fabricated on a window region of a transparent substrate. The substrate may then include one or more opacifying layers over other regions of the substrate surface. The transparent substrate may alternatively be inserted into a cut region of a substantially opaque material, such as paper or
Fiber material.
Manufacture of microstructure units in a transparent
or matt relief layer
The invention comprises a step of producing a plurality of microstructure units, which comprise three-dimensionally structured formations, in a transparent or matt relief layer on the substrate. The relief layer is preferably transparent or transparent. Transparent relief layers are particularly preferred because they enable the subsequently applied printing ink fluid to be viewed with a strong contrast against a transparent background. In embodiments in which the color-contrasting micro-picture elements on one side of a substrate are to be viewed by focusing elements which are arranged on the opposite side of the substrate, this is
Furthermore, a sufficient degree of transparency of the
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Relief layer (and substrate) is required to ensure that the micro picture elements are viewed
can.
The relief layer is preferably colorless and therefore provides a strong contrast for the printing ink fluid. However, it is not excluded that the relief layer may have a matt color, provided that the subsequently applied printing ink fluid has sufficient contrast to color-contrasted micro-picture elements sufficiently compared to the background color of the coating
define.
The multiple microstructure units can be produced by embossing the three-dimensionally structured formations in the relief layer. The microstructure units can be embossed directly into the substrate to form the relief layer as a structured surface layer of the substrate itself, such as by hot stamping a suitable polymer substrate. Typically, however, the relief layer comprises a transparent or matt coating applied to the substrate, the microstructure units which comprise the three-dimensionally structured formations being embossed into the coating. The plurality of microstructure units can, for example, be applied to the substrate
thermoplastic coating can be hot stamped.
In a preferred embodiment, the transparent or matt coating is a radiation-curable coating. The radiation-curable coating can be any varnish or other coating that can be applied to the surface of the substrate and then embossed while it is soft to form microstructure units
to form three-dimensionally structured formations, and the
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or which can be hardened with radiation in order to harden the embossed microstructure units. The radiation-curable coating is preferably curable by ultraviolet (UV) radiation. Alternatively, the radiation-curable coating can be formed by other forms of radiation, such as, for example
Electron beams or X-rays, be curable.
In a particularly preferred embodiment, the transparent or matt radiation-curable coating comprises an acrylic-based, embossable UV-curing transparent lacquer. Such UV curing varnishes can be obtained from various manufacturers, including Kingfisher Ink Limited, product Ultraviolet type UVF-203 or the like. These coatings have been reported to be particularly suitable for embossing microstructures including refractive structures such as diffraction gratings and holograms, microlenses and lens assemblies, and non-refractive optically variable devices. The radiation-curable embossable coatings can alternatively be applied to other compounds such as
For example, nitrocellulose.
In some embodiments, the clear or matte radiation curable coating, when applied to the substrate, has a viscosity that falls in the range from about 20 to about 175 centipoise, and more preferably from about 30 to about 150 centipoise. The viscosity can be determined by measuring the time until the paint expires from a # 2 Zahn cup. A sample that expires in 20 seconds has a viscosity of 30 centipoise and a sample that expires in 63 seconds has a viscosity of 150 centipoise. Viscosities in this range can allow the coating to pass through
Gravure printing techniques can be applied and shaped.
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The radiation-curable coating can be applied to the substrate using a gravure printing process and then embossed in a second step. In some embodiments, the coating is embossed with an embossing disk or roller with a three-dimensionally structured surface in accordance with the configuration of the relief layer to be embossed. A slice, as is known in the industry, is typically a thin piece of metal formed from structures created using photolithography techniques or the like using electroplating or similar processes. A roller can be formed using similar techniques, but is typically made using etching, engraving, or laser ablation techniques
educated.
The curing of the coating generally does not begin before the radiation curable coating is embossed, but it is possible that the curing step occurs either after the embossing or at substantially the same time as the embossing step. The radiation-curable coating is preferably embossed and cured at the same time by ultraviolet (UV) radiation. In such embodiments, the UV light coating can be through the substrate (if suitably transparent) or
be irradiated by a transparent embossing tool.
Although the invention is described herein with particular reference to embossed microstructure units, it is apparent that the principles of the invention can also be applied to microstructure units made by other techniques in a relief layer. In such an alternative approach, the microstructure units are created by directly applying
preformed three-dimensional formations on the substrate
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prepared as described for example in W02011 / 102800
is.
In some embodiments, therefore, depressions of suitable configuration in the surface of a printing tool are filled with a transparent or matt lacquer. The printing tool can be, for example, an embossed, etched or laser-removed roller. Suitable paints include, but are not limited to, the radiation curable coatings described in relation to embodiments herein in which the microstructure units are embossed into a coating on the substrate. The viscosity of the varnish is suitable for filling at least the depressions on the printing tool surface and optionally also providing a layer of essentially the same thickness over the surface of the tool. After application, the viscosity of the paint is increased in at least the wells. The viscosity of the paint can be increased by any suitable means, typically by at least partially curing the paint, to provide sufficient structural integrity to the molded paint during subsequent transfer. The varnish can be applied by irradiating the varnish on the printing tool surface
UV radiation can be partially cured.
Excess paint is optionally removed from the surface of the printing tool outside the depressions, for example with a wiping tool, such as a sponge or scoop, in such a way that only paint within the depressions is transferred to the substrate in the subsequent contact step. A layer of lacquer covering an extended portion of the printing tool surface including the depressions can alternatively be provided and viscoused
so that the entire layer including the
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well-formed formations in the subsequent
Contact step is transferred to the substrate.
The varnish is transferred from the depressions and optionally also from the surrounding varnish-coated areas of the printing tool to the substrate by contacting the surface of the printing tool with the substrate. If the printing tool is a roller, the roller and the substrate can be brought into rolling contact. The lacquer can be at least partially hardened while the surface of the printing tool is in contact with the substrate in order to adhere the lacquer to the substrate. If, for example, a radiation-curable lacquer is used, the lacquer can be hardened by irradiating the lacquer with UV radiation through a transparent substrate and / or through the printing tool surface. The printing tool is then removed, leaving the three-dimensionally structured formations of hardened lacquer in a relief layer on the substrate surface. Optionally, the varnish after
Removing the printing tool can be further hardened.
For some polymer substrates, it may be necessary or desirable to apply an intermediate layer to the substrate before applying the radiation-curable coating or the formed paint formations to improve the adhesion of the coating or varnish to the substrate. The intermediate layer preferably comprises a primer layer and more preferably the primer layer comprises a polyethyleneimine. The primer layer can also include a crosslinker, such as a multifunctional isocyanate. Examples of other primers suitable for use include: hydroxyl-terminated polymers; hydroxyl-terminated polyester-based copolymers; cross-linked or uncross-linked hydroxylated acrylates; Polyurethanes; and UV-curing
anionic or cationic acrylates. Examples of suitable ones
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Crosslinkers include: isocyanates; Polyaziridines; Zirconium complexes; Aluminum acetylacetone; Melamine; and carbodiimides. The type of primer can vary for different substrates and a radiation-curable coating. A primer is preferably selected which has the optical properties of the embossed coating or applied
Paint formations essentially not affected.
Multiple microstructure units
In the method of the invention, a plurality of microstructure units comprising three-dimensionally structured formations are produced in the transparent or matt relief layer on the substrate. The microstructure units may not be identical or substantially identical, and the microstructure units may be arranged as an ordered (such as a uniformly repeating) pattern of microstructure units or an unordered arrangement. The preferred configuration of both the microstructure units themselves and their relative positioning on the relief layer depends on the intended visual effect that is to be created by the color-contrasted microimage elements that are subsequently produced by applying an ink fluid to the microstructures. In some embodiments, the microstructure units may have at least one dimension in the plane of the relief layer of less than about 100 microns, preferably less than about 7/0 microns, more preferably less than about 50 microns. In some embodiments, the microstructure units on the relief layer can be arranged in rows and / or columns with a pitch of less than approximately 100 micrometers, preferably less than approximately 70 micrometers.
be configured. In some embodiments, the
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Relief layer is a repeating arrangement of essentially identical microstructure units. The repetitive arrangement of essentially identical microstructure units can be arranged in rows and / or columns
be configured.
The three-dimensional configuration of the microstructure units produced in the relief layer is selected such that the subsequently applied printing ink fluid preferably accumulates on the surface thereof in order to produce color-contrasting micro-picture elements with the intended dimensions and the intended resolution on the surface of the substrate. Therefore, any configuration that can be produced in a relief layer, for example by embossing, and that can act as a three-dimensional template and allow flow and accumulation of subsequently applied ink fluid is considered to be within the scope of the invention. However, the microstructure units generally do not include any refractive structures because the visualization of the micro picture elements formed by the ink fluid accumulation on the microstructure units does not result in a contrast between refractive and non-refractive ones
Regions of the relief layer.
The microstructure units can therefore comprise any suitable formation features produced three-dimensionally in the relief layer. Suitable features can include geometric shapes such as squares, rectangles or circles, or discrete images. The microstructure units can comprise lines which are formed as recessed grooves or protruding elevations in the relief layer. The lines can be customized
coherent symbols or characters, such as letters
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or numeric characters. Alternatively, you can define patterns, such as repeating patterns. In some embodiments, the microstructure units are unit cells of a larger repeating pattern that is two-dimensional across the
Relief layer extends.
The microstructure units can include formation features which are recognizably deepened or protrude from the surrounding regions of the relief layer. The microstructure units can comprise, for example, one or more depressions which are recessed into the base surface plane of the relief layer or one or more projections which protrude from the base surface plane of the relief layer. It can be imagined that the microstructure units can comprise both depressions and protrusions in the base surface plane of the relief layer. As used herein, the base surface plane of a relief layer is the substantially flat surface of the relief layer that is defined by regions without three-dimensionally structured formations. The indentations and protrusions generally have formation sidewalls, which in some embodiments may be steeply inclined, including substantially perpendicular relative to the surrounding regions and / or the
Base surface level of the relief layer.
While a number of embodiments are described herein with reference to formation features such as "depressions", "protrusions", "sidewalls", etc., those skilled in the art understand that these terms are idealized representations and that more complex microstructure units are also made in accordance with the invention in which individual formation characteristics are not without
More than either indentations or protrusions
28
can be identified, or where a base surface level of the coating is not easily
is defined.
The method of the invention is particularly useful for, but is not limited to, the production of micro picture elements with finely resolved features that are too small to be made by conventional printing techniques. In some embodiments, the microstructure units therefore have three-dimensionally structured formation features, such as recessed grooves or protruding elevations with a width of less than 50 micrometers, preferably less than 10 micrometers, most preferably less than 5 micrometers, such as between
1l and 3 microns.
The microstructure units can have a depth of less than 5 micrometers, preferably less than 3 micrometers. The inventors have found that depths of approximately 2 micrometers are sufficient to enable preferred ink accumulation on three-dimensionally structured relief layers in such a way that micro picture elements with satisfactory color contrast and high resolution
getting produced.
Deeper formation features can be formed in the relief layer by embossing an embossable coating with a disc or roller with corresponding protruding embossing elements, while protruding formation features can be formed by embossing with a disc or roller with corresponding recessed embossing elements which are in contact with the embossable coating composition during the embossing step to fill. If a coating is embossed and
is hardened, it is an important consideration to blow air
x
29
to be excluded, which can impair the appearance of the micro-picture elements and any resulting visual optical effects which are produced thereby. In some embodiments, the configuration of the embossing tool can therefore be designed such that it involves the risk of trapping air bubbles in the hardened embossed coating.
minimized.
For example, where the embossing surface of a disc (or roller) has closed areas that isolate portions of a coating during embossing (whether as recessed shapes in the base surface of the disc or as portions of the base surface of the disc that are within closed above features such as one “O” shaped, insulated) increases the likelihood of trapping air bubbles in a coating embossed with the disc. It may therefore be preferred that any recessed areas within the disc form a coherent network that allows air bubbles to escape during the stamping step. This in turn affects the configuration of the multiple microstructure units made with the disk. In some embodiments, the multiple microstructure units therefore comprise a coherent network of raised regions that extend across the relief layer and connect adjacent microstructure units. The contiguous network of raised regions can be formed in the base surface plane of the coating if the microstructure units include recess features. The contiguous network of raised regions may alternatively be formed as a network of embossed protrusions, such as ridges, that are at the base surface level of the
Coating are formed above.
*
30th
Applying and accumulating ink fluid to the
Microstructure units
After the multiple microstructure units are fabricated, an ink fluid is applied to the relief layer. In the method of the invention, the plurality of color-contrasted micro picture elements are applied to the three-dimensionally structured surface of the micro structure units by the preferred accumulation of the printing ink fluid. The inventors have found that using this alternative approach, small (such as micrometer-scale) microimages with excellent resolution and
Color contrast can be made.
Without wishing to be bound by theory, it is believed that the ink fluid accumulates on the relief layer surface to minimize its surface energy. The inevitability of minimizing surface energy causes the ink fluid to flow over the three-dimensional surface of the microstructure units and to accumulate in a predictable distribution that is not primarily determined by the application process or gravitational forces. Rather, it is believed that the ink fluid accumulates such that there is a balance between the cohesive forces that hold the fluid together and the adhesive forces between the fluid and the microstructure surface
manufactures.
The composition of the relief layer and the printing ink fluid can therefore be selected in such a way that adhesion forces relative to the cohesion forces are suitably balanced, i. that is, the relief layer is suitably wettable by the ink fluid. The wettability should be sufficient
be high, causing the ink fluid in
* &
31
Regions of high surface curvature flow on the surface of the microstructure units, but not so high as to cause the ink fluid to cause the entire surface of the
Relief layer covers.
The ink fluid should have a suitable viscosity to allow preferential accumulation on the microstructure units. An ink fluid with an unacceptably high viscosity will not be able to flow on the three-dimensional relief layer surface, while an ink fluid with an unacceptably low viscosity will flow too freely to provide precise control of the ink distribution. Those skilled in the art will appreciate with the benefit of this disclosure that the optimal viscosity for a particular application will depend on an appropriate balance between these competing needs when combined with other factors including the size and configuration of the three-dimensional formation features of the microstructure units and the intended visual effect is looked at. In some embodiments, the viscosity of the ink fluid, as measured using a # 2 tooth cup, ranges from 16 to 25 seconds (10 to 50 centipoise), preferably 16 to 18 seconds (10 to 20 centipoise). Ink fluids of this viscosity have been found to be preferred by accumulation on microstructure units with formation features with a resolution between 1 and 3 microns and a depth of
produce approximately 2 microns of high resolution micro images.
The ink fluid is applied with a suitable mass load such that an accumulation on the microstructure units provides the desired micro picture elements. If the ink fluid is too high
Mass load is applied, the distribution of
32
Ink fluid on the three-dimensional microstructures does not produce a satisfactory color contrast between areas with different ink density. In extreme cases, the printing ink fluid covers the entire surface of the relief layer with a layer of sufficient consistency so that no color contrast is achieved. If the ink fluid loading is too low, regions of the three-dimensional microstructures that are intended to be covered by ink fluid remain uncovered, so that the micro picture elements are not manufactured satisfactorily. Those skilled in the art will appreciate with the benefit of this disclosure that the optimal ink fluid loading for a particular application depends on a number of factors including the three-dimensional configuration of the microstructure units, ink viscosity and the intended visual effect. In some embodiments, the ink fluid becomes in the range of approximately when wet loaded
0.5 g / m “applied up to approximately 10 g / m”.
In some embodiments, the ink fluid may be a solvent-based ink having a solids content that is between about 10 percent by mass to about 60 percent by weight, such as between about 15 percent by mass and about 25 percent by weight. The preferred solids content can be selected, at least in part, to provide the ink fluid with a suitable viscosity
gives.
The ink fluid can be applied to the relief layer by any suitable technique, such as roll-to-roll gravure. Gravure printing or other conventional printing techniques are used to make the
Micro picture elements of the present invention despite the
.
33
Resolution limitations of these techniques are suitable, since the production of the color-contrasted micro-picture elements is based on the preferred accumulation of the printing ink fluid on the three-dimensionally structured surfaces of the microstructure units, due to surface energy considerations and not through a precise arrangement of the printing ink on the surface of the relief layer
is determined.
The ink fluid can be of any suitable color capable of providing satisfactory color contrast to the relief layer, including black and white inks. In some embodiments, a single ink fluid is applied to the relief layer. In other embodiments, two or more different colored ink fluids are applied. The differently colored printing ink fluids can be applied to different sections of the relief layer in such a way that each microstructure unit on the relief layer only absorbs a single printing ink fluid. However, it is not excluded that differently colored printing ink fluids could be applied to the same section of the relief layer, for example in sequential application steps, so that regions
are made up of composite colors.
Optionally, the printing ink fluid applied to the relief layer forms a separate design element that is not based on every microstructure unit for its visual influence on the preferred accumulation of the printing ink fluid. Such a design element, such as one or more colored regions on the surface, generally extends over the plurality of microstructure units or a substantial portion thereof and is therefore not limited to that
Resolution requirements of traditional
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Ink application process restricted. The optional design element, seen directly on the surface of the substrate, may be distinguishable from any visible optical effect created by the color-contrasted micro-picture elements when it is arranged on the opposite surface of the substrate
arranged focusing elements is viewed.
It is apparent that the distribution of the ink fluid in the contrasting areas with different ink density (such as areas with high ink density that contrast with areas with low or substantially zero ink density) and therefore the shapes and / or the contrast of the micro picture elements from that three-dimensional configuration of the microstructure units depends. In some embodiments, the ink fluid preferably collects in regions with high surface curvature next to one or more sidewalls of the microstructure units, i.e. that is, at the intersection between the side walls and surrounding area regions. For recessed microstructure unit formation features, the ink fluid can therefore accumulate at the corners (either substantially angular or more curved) where the sidewalls and base of the recess intersect, or accumulate throughout the recess, thereby filling it at least partially. With the foregoing microstructure unit formation features, the ink fluid may be at the corners (either substantially angular or more curved) where the side walls and the
Cut the base surface level of the relief layer and collect it. In some embodiments, the ink fluid collects
only in selected areas of the three-dimensional
Microstructures while other areas of microstructures
35
and / or surrounding areas of the relief layer are essentially free of printing ink fluid. However, it is not excluded that ink fluid can cover the entire area of the three-dimensional microstructures or even the entire relief layer, provided that a sufficiently selective accumulation of ink fluid occurs in order to achieve a satisfactory color contrast between the contrasting areas with different
To produce ink density.
In embodiments in which the relief layer comprises a repeating arrangement of substantially identical microstructure units, the ink fluid can accumulate in a substantially equal distribution on each microstructure unit in the arrangement, especially if the ink fluid has a constant load over the relief layer is applied. This enables the creation of a repeating arrangement of essentially identical color-contrasted micro-picture elements on the surface of the substrate. A number of visual optical effects, including enlarged moiré images, require such an orderly arrangement of identical ones
Images to create the desired effect.
In some embodiments, the microstructure units include at least one depression that is recessed in surrounding regions of the relief layer. When the ink fluid is applied to the relief layer, it can flow from the surrounding regions into the well £ and therefore provide a color contrast between the ink accumulated in at least a portion of the well and the surrounding regions depleted with ink. It is believed that the flow of ink fluid into the
Deepening minimizes the surface energy of the system, since the
36
Recess includes regions with high surface curvature on the relief layer surface. For example, the entire inner surface of the recess (including the side walls) can be concave. As another example, the side walls may be relatively flat, but are inclined steeply relative to a base surface of the recess to have a high region along the intersection (corner region) between the side walls and the base surface of the recess
To provide surface curvature.
In some embodiments, the ink fluid preferably accumulates such that it covers the base surface of the recess between the side walls with a layer of the ink fluid. The micro-picture elements are therefore formed by the color contrast between the high ink density area, the ink fluid filling the recess and the low ink density area defined by the surrounding regions of the relief layer which are devoid of or depleted of ink fluid. Where the depression is, for example, a groove recessed in the relief layer, the printing ink fluid preferably accumulated in the depression appears as a colored line on the transparent relief layer, which has the thickness of the groove. In such embodiments, it is not necessary for the recess to be completely filled with ink fluid to produce a satisfactory color contrast, and it is generally preferred that the recess not be completely filled, as this is likely to result from the ink accumulates both in the deepening and on the surrounding regions,
leads to a poor contrast.
In some embodiments, the ink fluid collects
within the depression in regions with high surface curvature
37
at the intersection of the side walls and the well base surface. In such embodiments, the ink fluid selectively accumulates against at least one side wall of the recess and preferably selectively accumulates against two opposite side walls of the recess. The ink fluid may preferably only accumulate along the corners where the side walls and the base of the recess intersect, leaving an intermediate portion of the base of the recess as a contrasting area with a low ink density. The micro-picture elements of these embodiments are at least partially formed by the color contrast that is generated by the selective distribution of printing ink within the recess. If the depression is, for example, a groove recessed in the relief layer, the preferably accumulated printing ink fluid in the depression can form a pair of printing ink lines against the opposite side walls of the
Form a groove.
It is apparent that the loading of ink fluid is an important factor that can determine whether the ink fluid prefers to be filled by at least partially filling a well feature or by selectively accumulating only in selected regions with high surface curvature within the wells, such as against the sidewalls, accumulates. However, other factors such as the viscosity of the ink fluid, the coating wettability, and the dimensions (such as the width) of the well feature can help determine the ink fluid distribution for a given load
also play a role.
In some embodiments, the
Microstructure units at least one protrusion from
x,
38
surrounding regions of the relief layer. When the ink fluid is applied to the relief layer, it can flow from the surrounding regions and preferably accumulate in a region with high surface curvature at the intersection of at least one side wall of the projections and the surrounding regions of the relief layer and preferably against both opposite side walls. The flow of ink fluid is believed to minimize the surface energy of the system because the intersection between the side walls of the protrusions and the surrounding regions forms a region of high surface curvature on the relief layer surface. The ink fluid may therefore preferentially accumulate in areas of high ink density along the corners where the sidewalls and base plane of the relief layer intersect, leaving other regions of the base plane and the top portions of the protrusion free of or depleted of ink fluid. The micro-picture elements are therefore formed by the color contrast created by the selective accumulation of ink that circumscribes the protrusions. For example, if the protrusion is a protrusion formed on the relief layer, the ink fluid may form a pair of ink lines, preferably against that
opposite side walls of the elevation are accumulated.
Additional characteristics
As soon as the ink fluid has preferably accumulated on the microstructure units, the ink fluid can be dried and / or cured. The drying or hardening of the ink can prevent further ink flows, constantly fix the ink and adhere to the relief layer and therefore that
Preserve the appearance of the micro picture elements. If that
39
Ink fluid is a solvent-based ink, for example, a drying step can be carried out with heating ovens
blow the warm air onto the substrate.
In some embodiments, a transparent protective layer is applied over the relief layer after the ink fluid has been applied and preferably accumulated (and optionally dried or cured). The transparent protective coating can be a solvent-containing printing ink which is applied by means of gravure printing in order to fill the three-dimensionally structured relief layer and to provide a smooth and flat surface. The transparent protective layer can then be dried using heater ovens that blow warm air onto the substrate. The transparent protective coating can protect against physical damage due to wear as well as counterfeiting due to mechanical damage
Protect lifting.
In other embodiments, the method of the invention further includes applying a contrast coating over the relief layer after the ink fluid has been applied and preferably accumulated (and optionally dried or cured). The contrast coating should have a different color than the ink fluid, so that the micro-picture elements are contrasted with the contrast coating when they are reflected in a reflected light
the substrate can be viewed.
In some embodiments, the color-contrasted micro-picture elements made by the methods of the invention are capable of producing a visible optical effect, such as an enlarged image, when arranged by an array on the substrate
Focusing elements is viewed. The enlarged image can be viewed on
*
40
are best viewed in reflected light to achieve a bright color that matches the color of the first ink fluid. However, the enlarged image can also be viewed in transmitted light, appearing in color when the ink fluid is sufficiently transparent, or in black and white when the ink fluid is substantially opaque. As used herein, "transmitted light" means light transmitted through the substrate from a source on the opposite side of the substrate from the viewer, and "reflected light" means light coming from a source on the same side of the substrate as the viewer and is reflected back to the viewer by the micro picture elements. Advantageously, when the micro-picture elements are viewed through an array of focusing elements, the enlarged images produced have satisfactory contrast under a wide variety of lighting conditions (including indirect lighting) because the micro-picture elements tend to have color contrast rather than refractive
Effects are based.
The visible optical effect when viewing the micro picture elements can include an enlarged moiré picture, a holistic picture, a contrast-changing picture, a nested picture or a flip picture. Due to the high resolution and complex micro picture elements that can be produced on a substrate surface with the method of the invention, a large variety of optical effects can be generated. The visual optical effect is preferably an enlarged moiré image or a holistic image and more
prefers an enlarged Moire image.
The extremely fine resolution of the color-contrasted
Micro-picture elements made according to the invention
+ x
41
can, is particularly advantageous for producing enlarged optical effects. For example, microimage elements that are intended for imaging as an enlarged moiré image effect through a 2D array of microlenses must be configured as an array of image "symbols" that are approximately the size of a microlens. The finer the resolution of the features in the symbols, the greater the complexity of the enlarged image that is produced
can.
Micro-optic devices and security features
The present invention also relates to a micro-optical device on a substrate for a security document. The micro-optic device comprises a plurality of microstructure units which comprise three-dimensionally structured formations in a transparent or matt relief layer on the substrate. The micro-optical device further comprises a printing ink on the relief layer, the printing ink preferably being accumulated in regions with a large surface curvature on each microstructure unit. Contrasting areas with different ink densities are therefore provided. The contrasting areas, which typically include areas of high ink density and contrasting areas of low (including substantially zero) ink density, at least partially form the plurality of colors
contrasted micro picture elements on the substrate.
The micro-optic device can be manufactured by any of the methods described herein. In this regard, the substrate, the composition of the relief layer, the multiple microstructure units produced thereon and the
several color-contrasted micro-picture elements the same
4th
42
as described in relation to some of the method embodiments disclosed herein. The ink that is accumulated on the microstructure units in regions of high surface curvature can be arranged by applying an ink fluid to the relief layer such that it enables the ink fluid to preferentially accumulate on the microstructure units and optionally to dry or harden the ink fluid, how
it is described herein.
In some embodiments, the relief layer comprises a coating on the substrate and the three-dimensionally structured formations of the microstructure units are embossed into the coating. The coating can be a hardened coating, such as a radiation-hardened coating, such as a UV-hardened coating. In other embodiments, the relief layer comprises three-dimensionally structured formations, which are formed as discrete pre-formed lacquer structures (or pre-formed coating layers) that extend from the surface of a printing tool onto the
Substrate can be transferred as described herein.
In some embodiments, the relief layer of the micro-optic device comprises a repeating arrangement of substantially identical microstructure units and the ink is accumulated in an essentially equal distribution on each substantially identical microstructure unit. A repetitive arrangement of essentially identical color-contrasted micro-picture elements is therefore provided on the surface of the substrate. A number of visual optical effects, including an enlarged moiré image, require such an orderly arrangement of identical images to achieve the desired effect
to manufacture.
Oil
43
In some embodiments, the micro-optic device further comprises an arrangement of focusing elements arranged on the substrate. In such embodiments, the color-contrasted micro-picture elements can be configured to produce a visible optical effect, such as, for example, an enlarged moiré picture, a holistic picture, a contrast-changing picture, a nested picture or a tilt picture, when arranged by the arrangement of focusing elements be considered. In some embodiments, the arrangement of focusing elements on a surface of the substrate is arranged opposite the surface of the substrate on which the relief layer is arranged. However, it is not excluded that the arrangement of focusing elements on top of the relief layer and optionally spaced apart by an inserted transparent layer could be arranged. In such embodiments, the arrangement of focusing elements can optionally be configured to be based on a reflection of the micro-picture elements in one on the opposite surface of the substrate
Focus reflection layer.
The arrangement of focusing elements is generally arranged at a distance from the plurality of micro picture elements that is substantially equal to or lies within the focal length of the focusing elements. For use in security documents, the focal lengths of the focusing elements are preferably in the range from 20 to 130 micrometers, more preferably from 65 to 90 micrometers, corresponding to the typical thickness of transparent substrates
for security documents.
The arrangement of focusing elements can be any
Include devices previously considered for viewing
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Micro-picture elements on a substrate and in particular a substrate have been reported as being suitable for a security document. In some embodiments, the arrangement of focusing elements may include refractive microlens structures including conventional microlenses and Fresnel lenses. In other embodiments, refractive focusing elements, such as zone plates or photon screens, can be used. Fresnel lenses and refractive focusing elements can be particularly suitable for integration into a micro-optical device on a security document, since such focusing elements are thinner than conventional ones for a given focal length
Microlens structures.
The arrangement of focusing elements can be in register with the plurality of micro picture elements on the substrate. The orientation between the focusing elements and the micro-image elements can alternatively be offset by one
to produce the desired visual optical effect.
The arrangement of focusing elements can be produced as a separate layer that is adhered to the substrate. In preferred embodiments, however, the arrangement of focusing elements is produced by applying a transparent radiation-curable coating to the substrate and embossing and curing the coating with radiation in order to form the focusing elements. The transparent coating into which the focusing elements are embossed can optionally have the same composition as the relief layer into which the
Microstructure units are characterized. The micro-optic device can be on a substrate for any
Security documents are formed, including but not
limited to the following: Currency items, such as
45
For example banknotes and coins, credit cards, checks, passports, ID cards, security and share certificates, driver's licenses, ownership certificates, travel documents, such as airline tickets and train tickets, entrance tickets and tickets, birth, death and marriage certificates and academic transcripts. In some embodiments, the micro-optic device is placed on the substrate of banknotes or identification documents, such as
for example, ID cards or passports.
The micro-optical device according to the invention can form a component of a security device on a security document. The security device may be provided on the security document in addition to one or more of a large number of other security devices, elements or features that are intended to protect a security document or feature from being tampered with, copied, modified or tampered with. Security devices can take a wide variety of forms, such as security threads embedded in layers of the security document, security printing inks such as a fluorescent substance, luminous and phosphorescent printing inks, metal printing inks, iridescent printing inks, photochromic, thermochromic, hydrochromic or piezochromic printing inks; printed and embossed features including relief structures; Interference layers; Liquid crystal devices; Lenses and lenticular structures; optically variable devices (OVDs) such as refractive devices including diffraction gratings, holograms and refractive optical devices
Elements (DOEs).
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Embodiments
An embodiment of the invention will now be described with specific reference to Figures 1-4. FIG. 1 shows a top view of a cut-out area of the relief layer 10, which was produced in accordance with the invention by embossing and curing a transparent radiation-curable coating which is applied to a transparent substrate. The relief layer 10 comprises a uniformly repeating arrangement of essentially identical microstructure units including the individual microstructure units 1la, 11b, 11c and 11d (only 1l1ld is completely contained within the cut-out area of the relief layer 10 shown in FIG. 1). The microstructure units l1la to 11d comprise three-dimensionally structured formations as recessed grooves in the form of “O” shapes and are characterized by embossing the coating with a disk with corresponding “O” -shaped embossing elements which protrude from the surface of the disk and simultaneously hardening the
Coating made with UV light.
Figure 2 shows a side view (not to scale) of the relief layer 10, as shown in Figure 1 along the section line AB. The relief layer 10 is located on the first surface 12 of the transparent substrate 13. The grooves 14a and 14b are as depressions in the Base surface plane 15 of the relief layer 10 is formed, which corresponds to the sections of the microstructure unit 11d cut through the section line AB. The grooves 14a and 14b have a width of approximately 2
Microns and a depth of about 2 microns. FIG. 3 again shows the relief layer 10 in a side view
after the ink fluid 16 on the relief layer 10
was applied according to the invention. The ink fluid 16
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has preferably accumulated by flowing from the surrounding regions of the base surface plane 15 into the grooves 14a and 14b. In the embodiment shown in Figure 3, the ink fluid 16 has a viscosity and has been applied with a load that is suitable to cover the base surface, but the grooves 14a and 14b (and therefore the entire recessed "O" -shaped groove of the microstructure unit 11d ) not to be filled completely. Due to the preferred accumulation of ink fluid 16 in the grooves 14a and 14b are surrounding
Regions of the base surface level 15 essentially free of
Printing ink.
FIG. 4 shows the relief layer 10 again in a top view after the printing ink fluid 16 has been applied as shown in FIG. 3 and after the printing ink fluid 16 has been dried or hardened. The color-contrasted micro-picture elements 17a, 17b, 17c and 17d are applied to the substrate surface due to the preferred accumulation of the ink fluid 16 in the form of positive (ie, ink-filled) "O" -shaped symbols around areas with high ink density on the grooves 14a and 14b and contrasting areas with low ink density
to provide on the surrounding regions of the base surface 15.
Another embodiment of the invention will now be described with specific reference to Figures 1, 2, 5 and 6. Figures 1 and 2 are as above
described.
FIG. 5 shows the relief layer 10 again in a side view after the printing ink fluid 18 has been applied to the relief layer 10 according to the invention. In the embodiment shown in FIG. 5, the printing ink fluid 18
a viscosity and was applied with a load,
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which is suitable to flow both from the surrounding regions of the base surface plane 15 into the grooves 14a and 14b and within the grooves 14a and 14b against the opposite side walls 19a and 19b. The ink fluid 18 has therefore preferably accumulated at the corner regions (i.e., regions with high surface curvature) of the grooves 14a and 14b where the side walls 19a and 19b intersect the recess base surfaces 20. Due to the preferred accumulation of the ink fluid 18 within the grooves 14a and 14b and against the side walls 19% 9a and 19b, surrounding regions of the base surface plane 15 and intermediate portions of the
Well base surfaces 20 substantially free of ink.
FIG. 6 shows the relief layer 10 again in a top view after the ink fluid 18 has been applied as shown in FIG. 5 and after the ink fluid 18 has been dried or hardened. The color-contrasted micro-picture elements 21a, 21b, 21c and 21d are applied to the substrate surface due to the preferred accumulation of the printing ink fluid 18 in the form of negative “O” -shaped symbols. The symbols are provided by the lines of the ink fluid 18 (ie, areas with a high ink density) which have accumulated against the opposite side walls of the grooved depressions of the microstructure units 11a to 11d, which the color contrast for the negative (ie, outlined with ink) " O "-shaped micro-picture elements 21a, 21b, 21c and
Outline and deploy 21d.
Another embodiment of the invention will now be described with specific reference to Figures 7-10. FIG. 7 shows a top view of a cutout area of the relief layer 30, which according to the invention is embossed and
Curing a transparent radiation-curable coating,
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which is applied to a transparent substrate. The relief layer 30 comprises a uniformly repeating arrangement of essentially identical microstructure units including the individual microstructure units 31a, 31b, 31c and 31d (only 31d is completely contained within the cut-out area of the relief layer 30 shown in FIG. 7). The microstructure units 31a to 31d comprise three-dimensionally structured formations as protruding elevations in the form of “O” shapes and are characterized by embossing the coating with a disk with corresponding “O” -shaped embossing elements, which are recessed into the surface of the disk, and hardening at the same time
the coating is made with UV light.
FIG. 8 shows a side view (not to scale) of the relief layer 30, as shown in FIG. 7 along the section line AB. The relief layer 30 is located on the first surface 32 of the transparent substrate 33. The elevations 34a and 34b are protrusions from that Base surface plane 35 of the coating 30 is formed, which corresponds to the sections of the microstructure unit 31d cut by the section line AB. The elevations 34a and 34b have a width of approximately 2 micrometers and a height of approximately 2
Micrometer on.
FIG. 9 shows the relief layer 30 again in a side view after the printing ink fluid 36 has been applied to the relief layer 30 according to the invention. In the embodiment shown in FIG. 9, the ink fluid 36 has a viscosity and was applied with a load which is suitable for flowing from the surrounding regions of the base surface plane 35 and against the two opposite side walls 39a and 39b of the elevations 34a
and 34b accumulate. The ink fluid 36 has therefore become
b +
50
preferably accumulated at the corners (i.e., regions of high surface curvature) where the side walls 39a and 39b and the base surface plane 35 intersect. Due to the selective accumulation of the ink fluid 36, the bump tops 40 and at least the regions of the base surface plane 35 are the bumps 34a and 34b
surrounded, essentially free of ink.
FIG. 10 shows the relief layer 30 again in a top view after the ink fluid 36 has been applied as shown in FIG. 9 and after the ink fluid 36 has been dried or hardened. The color-contrasted micro-picture elements 37a, 37b, 37c and 37d are provided on the substrate surface due to the preferred accumulation of the printing ink fluid 36 in the form of negative “O” -shaped symbols. The symbols are provided by the lines of ink fluid 36 (ie, areas of high ink density) that have accumulated against the opposite side walls of the protruding elevations of the microstructure units 31a to 31d, which contrast the color for the negative (ie, outlined with ink) " O "-shaped micro-picture elements 37a, 37b, 37c and
Outline and deploy 37d.
EXAMPLES
The present invention will be described with reference to the following examples. It is understood that the
Examples of the invention described herein
are illustrative and not limiting.
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51
Example 1 (comparative)
A disc (300 mm x 300 mm) was produced by spinning a photoresist layer on a substrate and then exposing the photoresist to UV light transmitted through a mask, the mask having UV-transparent sections corresponding to the desired microstructure pattern. The photoresist exposed to UV light was then chemically developed to produce recessed regions in the photoresist surface that expose the underlying substrate. A galvanic seeding layer was deposited on the chemically developed photoresist structures and the exposed substrate underneath. The seed layer was then electroplated with nickel to form the finished disc. The finished disc was on one
Roller attached for use as an embossing tool.
A colorless transparent relief layer, which comprises three-dimensionally structured microstructure units, was applied by applying a layer of transparent UV-curing resin on a 75 micron thick transparent substrate and then simultaneously embossing and irradiating the coating through the
Substrate made with UV light.
The embossed relief layer comprised a regular hexagonal arrangement of microstructure units in the form of individual: sections of recessed “E” symbols that extended across the surface of the relief layer in a configuration that was designed to project a holistic image seen through microlenses. The hexagonal arrangement had a pitch of approximately 53 micrometers. The embossing depth in the relief layer (i.e., the depths of the embossed grooves, the
the height of the protruding embossing elements on the disc
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52
correspond) was approximately 1.8 micrometers. The width of the grooves,
which form the “E symbols” was approximately 2 micrometers.
A separate transparent film (approx. 85 microns thick) comprising a hexagonal arrangement of embossed hemispherical microlenses (53 microns division, 51 microns lens width, 10 microns sag height, approx. 115 microns focal length) was then the embossed relief layer (ie, overlaid on the same side of the substrate as the relief layer) such that the hexagonal arrangement of microstructure units was aligned with and in direct contact with the hexagonal arrangement of microlenses (a water droplet was applied between the microstructure units and the lens substrate for direct contact ensure). The embossed microstructure units are therefore close to the focal length of the
Microlenses just inside of it.
Seen through the microlenses in the transmitted or reflected light, the embossed relief layer created a grayscale, holistic image with only limited contrast. The ink-free relief layer is also susceptible to being filled with liquid contaminants such as user sweat, which would cause the contrast to completely disappear and the relief layer to be susceptible to mechanical copying.
because the structures are exposed.
Example 2
The embossed relief layer from Example 1 was then coated with a silver printing ink (solvent-based, solids content of 30
Vol .-%, application over RK Coater dipstick No. 0) overprinted.
After the ink dried, which was a dry load
+
53
of 0.2 g / m ”, the layer of microlenses was renewed
overlying the relief layer as in Example 1.
Seen through the microlenses in transmitted light, a holistic image of an enlarged “E” symbol with excellent contrast was clearly visible. The "E" symbol was approx. 1 cm X 1 cm in size and appeared to hover approx. 1 cm above the level of the microlenses. It was evident from the holistic image that the ink had accumulated in a substantially equal distribution on each of the microstructure units and from the immediately surrounding regions of the "E" shaped microstructure units (which compared to more distant regions in the basal plane of the relief layer in the integrated image were visibly depleted of printing ink) flowed into the recessed grooves of the microstructure units. The contrast between the depressions filled with printing ink and the surrounding areas depleted in printing ink in each of the micro-picture elements (as shown schematically in FIGS. 3 and 4) therefore contributed to the projection of a color
contrasted holistic picture. Example 3
Another colorless, transparent relief layer comprising microstructure units was produced in accordance with the method of Example 1. In this case, the embossed relief layer comprised an arrangement of microstructure units in the form of protruding “O” projections on the surface of the relief layer. The embossing height in the relief layer (i.e., the protrusion heights of the embossed features that corresponded to the depth of the recessed embossing elements on the disc) was approximately 1.8 micrometers. The width of the
Elevations forming "O" shapes were approximately 2 microns.
€ -
54
The embossed relief layer was then overprinted with a silver printing ink (containing solvent, solids content of 30% by volume, application via RK Coater dipstick No. 0. After the printing ink had dried in an oven, this resulted in a dry load of 0.2 g / m " , the layer of microlenses of the relief layer became again as in Example 1
overlaid.
Seen through the microlenses in transmitted light, an enlarged moiré image with a pattern of “O” shapes with excellent contrast was clearly visible. It was evident from the moiré image that the ink had accumulated preferentially on the surface of the relief structure against the side walls of the protrusions. The contrast between the ink that accumulated in addition to the microstructure sidewalls and the elevations devoid of ink (or at least depleted in ink) in each of the micro picture elements (as shown schematically in Figures 9 and 10) therefore contributed to the protrusion
color contrasted enlarged moire image.
Example 4
Another colorless, transparent relief layer comprising microstructure units was produced in accordance with the method of Example 1. In this case, the microstructure units were hexagonally packed unit cells of a repeating hexagon pattern that extended across the surface of the relief layer. The fine lines of the hexagon pattern were recessed grooves embossed in surrounding regions of the relief layer. The hexagonal pattern had a pitch of approximately 53 microns. The embossing depth in the
Relief layer was approximately 1.7 to 1.8 micrometers. The
t *
55
The minimum width of the grooves that formed the pattern was approximately 1
up to 2 micrometers.
The embossed relief layer was then overprinted with a black ink (solvent-based, solids content of 20% by volume, viscosity of 19 seconds as measured with a Zahn cup # 2; application via RK Coater dipstick No. 0) with a wet load of 4 g / m ". After the ink was dry, the layer of microlenses of the relief layer became as in
Example 1 overlaid again.
Seen through the microlenses in transmitted light, an enlarged moiré image with a hexagon pattern with excellent contrast was clearly visible. It was evident from the moire image that the ink had preferentially accumulated on the surface of the relief structure and at least partially filled the recessed grooves of the hexagon pattern microstructures. The contrast between the depressions filled with ink and surrounding areas in each of the micro-picture elements (as shown schematically in FIGS. 3 and 4) free of printing ink (or at least depleted of printing ink) therefore contributed to the projection of a color
contrasted enlarged moire image.
Those skilled in the art will recognize that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all of these variations and modifications
encompasses that within the spirit and scope of the present
Invention fall.
Future patent applications may be filed in Australia or overseas based on the present application or on priority claim. It is understood that the following preliminary claims only
provided by way of example and are not intended to
f *
36
limit the scope of what may be claimed in any such future application. Features may be added to or omitted from the provisional claims at a later date to further define or redefine the invention or inventions
define.

权利要求:
Claims (10)
[1]
1. A method of making micro-picture elements on a substrate for a security document, the method comprising:
Producing a plurality of microstructure units comprising three-dimensionally structured formations in a transparent or matt relief layer on the substrate; and
Applying an ink fluid to the relief layer,
the ink fluid preferably accumulates in areas with high surface curvature on each microstructure unit to contrast areas with different
To provide ink density.
[2]
2. The method of claim 1, wherein a repeating array of substantially identical microstructure units is made in the relief layer, and wherein the ink fluid is in a substantially uniform distribution on each substantially identical
Microstructure unit is accumulated.
[3]
3. The method of claim 1 or 2, wherein the microstructure units comprise at least one formation sidewall that intersects with a surrounding area region, the ink fluid preferably located in a region with high area curvature at the intersection of the sidewall
and the surrounding area accumulates.
[4]
4. The method according to any one of claims 1 to 3, wherein the
Microstructure units comprise at least one depression that is recessed into surrounding regions of the relief layer, the depression being side walls and a depression base surface between
has the side walls.
"
r +
58
[5]
5. The method according to any one of claims 1 to 4, wherein the microstructure units comprise at least one protrusion that protrudes from surrounding regions of the relief layer, wherein the
Has projection sidewalls.
[6]
6. The method according to any one of claims 1 to 5, wherein micro picture elements, which comprise printing ink accumulated in the regions with high surface curvature, by an arrangement of focusing elements arranged on the substrate
seen create a visible optical effect.
[7]
7. The method according to any one of claims 1 to 6, further comprising applying a contrast coating over the relief layer after applying the ink fluid, the contrast coating having a different color than the ink fluid, so that micro-image elements have ink accumulated in the regions with high surface curvature , seen in reflected light through the substrate
contrast against the contrast coating.
[8]
8. micro picture elements on a substrate for a security document, which according to the method according to one of the
Claims 1 to 7 is made.
[9]
9. A micro-optic device on a substrate for a security document, comprising:
a plurality of microstructure units comprising three-dimensionally structured formations in a transparent or matt relief layer on the substrate; and
an ink on the relief layer,
wherein the printing ink is preferably accumulated in regions with a high surface curvature on each microstructure unit and thus contrasting areas with different
Ink density are provided.
59
[10]
10. The micro-optical device according to claim 9, further comprising an arrangement of focusing elements arranged on the substrate, wherein micro-image elements comprising the printing ink accumulated in the regions with high surface curvature are seen through the arrangement of focusing elements
create a visible optical effect.
Vienna, December 30, 2019 Registrant:
Haffner umü Kebchmdnn Patentanwälte GmbH

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同族专利:

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公开号 | 公开日

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GB201918293D0|2020-01-29|

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GB2576679A|2020-02-26|

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US20200130397A1|2020-04-30|

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US11167580B2|2021-11-09|

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WO2019000048A1|2019-01-03|

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AU2018293928A1|2020-01-16|

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DE112018003093T5|2020-03-26|

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SE2050084A1|2020-01-29|

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法律状态:

优先权:

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申请号 | 申请日 | 专利标题

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AU2017902534A|AU2017902534A0|2017-06-30|Method of producing micro-image elements on a substrate|

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PCT/AU2018/050670|WO2019000048A1|2017-06-30|2018-06-29|Method of producing micro-image elements on a substrate|

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