This invention relates generally to optically variable pigments, films, devices, and images, and more particularly to aligning or orienting magnetic flakes, such as during a painting or printing process, to obtain an illusive optical effect.
Optically variable devices are used in a wide variety of applications, both decorative and utilitarian. Optically variable devices can be made in multitude of ways to achieve a variety of effects. Optically variable devices (OVDs) such as holograms are imprinted on credit cards and authentic software documentation; color-shifting images are printed on banknotes, and OVDs enhance the surface appearance of items such as motorcycle helmets and wheel covers.
Optically variable devices can be made as a film or a foil that is pressed, stamped, glued, or otherwise attached to an object, and can also be made using optically variable pigments. One type of optically variable pigment is commonly called a color-shifting pigment because the perceived color of images appropriately printed with such pigments changes as the angle of view and/or illumination is tilted. A common example is the number “20” printed with color-shifting pigment in the lower right-hand corner of a U.S. twenty-dollar banknote, which serves as an anti-counterfeiting device.
Some anti-counterfeiting devices are covert, while others are overt intended to be noticed. Unfortunately, some optically variable devices that are intended to be noticed are not widely known because the optically variable aspect of the device is not sufficiently dramatic or distinguishable from its background. For example, the amount of color-shift of an image printed with color-shifting pigment might not be noticed under uniform fluorescent ceiling lights, but may be more noticeable in direct sunlight or under single-point illumination. This can make it easier for a counterfeiter to pass counterfeit notes without the optically variable feature because the recipient might not be aware of the optically variable feature, or because the counterfeit note might look substantially similar to the authentic note under certain conditions.
Optically variable devices can also be made with magnetic pigments. These magnetic pigments may be aligned with a magnetic field after applying the pigment (typically in a carrier such as an ink vehicle or a paint vehicle) to a surface. However, painting with magnetic pigments has been used mostly for decorative purposes. For example, use of magnetic pigments has been described to produce painted cover wheels having a decorative feature that appears as a three-dimensional shape. A pattern was formed on the painted product by applying a magnetic field to the product while the paint medium still was in a liquid state. The paint medium had dispersed magnetic non-spherical particles that aligned along the magnetic field lines. The field had two regions. The first region contained lines of a magnetic force that were oriented parallel to the surface and arranged in a shape of a desired pattern. The second region contained lines that were non-parallel to the surface of the painted product and arranged around the pattern. To form the pattern, permanent magnets or electromagnets with the shape corresponding to the shape of desired pattern were located underneath the painted product to orient in the magnetic field non-spherical magnetic particles dispersed in the paint while the paint was still wet. When the paint dried, the pattern was visible on the surface of the painted product as the light rays incident on the paint layer were influenced differently by the oriented magnetic particles.
Similarly, a process for producing of a pattern of flaked magnetic particles in fluoropolymer matrix has been described. After coating a product with a composition in liquid form, a magnet with desirable shape was placed on the underside of the substrate. Magnetic flakes dispersed in a liquid organic medium orient themselves parallel to the magnetic field lines, tilting from the original planar orientation. This tilt varied from perpendicular to the surface of a substrate to the original orientation, which included flakes essentially parallel to the surface of the product. The planar oriented flakes reflected incident light back to the viewer, while the reoriented flakes did not, providing the appearance of a three dimensional pattern in the coating.
By way of background prior art, United States Patent Application 20050106367, incorporated herein by reference, published May 19, 2005 in the name of Raksha et al., assigned to JDS Uniphase Corporation, describes a method and apparatus for orienting magnetic flakes such as optically variable flakes.
Although some of the aforementioned methods for providing visually appealing and useful optical effects are now nearly ubiquitous, these devices require enhancements and additional features to make them more recognizable as an authentic article; for example it would be preferable to have the ability to provide yet additional security features.
For example it would be highly desirous to have a security device which provided a color shift with change in incident light or viewing angle including magnetically aligned flakes and optical features associated therewith; and, providing such a device which had a reasonable amount of tactility would be highly advantageous. It would also be preferably to have such a device wherein there was significant contrast and sharpness between regions of the device that Were functionally different. For example a magnetically aligned region of thin film color shifting flakes directly adjacent an embossed region could offer benefits not realizable in two adjacent different magnetically aligned regions.
It is an object of this invention to provide a method for forming an image of a plurality of contrasting, discernible regions, wherein at least one region has magnetic flakes thereon aligned by an applied magnetic field having a predetermined orientation, and another of the discernible regions adjacent to the first discernible region having flakes thereon or an absence of flakes caused by mechanically impressing or pushing away flakes from said second region.
It is an object of this invention to provide a tactile image wherein a tactile transition can be sensed by touching a transition between at least the first and second discernible regions.
It is an object of this invention to provide a banknote or security document which has tactile properties to assist the blind in verifying the authenticity of the note or document.
It is an object of this invention to provide an image having an optically variable region and having a tactile region about the optically variable region.
In accordance with the invention, there is provided, an image comprising:
said orientation of the flakes in the second region being a result of mechanically impressing flakes within the second region, or
ii) said second region having an absence of flakes caused by or pushing away flakes from said second region,
the image forming a tactile image wherein a tactile transition can be sensed by touching a transition between the at least first and second discernible regions.
In accordance with the invention, there is further provided an image having a plurality of discernible tactile regions wherein two adjacent tactile discernible regions have different optical characteristics, and wherein one of the regions have magnetic flakes aligned differently and by different means than flakes within the adjacent region.
In accordance with this invention there is provided an image comprising a plurality of contrasting, discernible regions thereon, together defining an image, at least a first of the discernible regions having magnetic flakes thereon aligned by an applied magnetic field having a predetermined orientation, and a second of the discernible regions adjacent the first discernible region having flakes thereon or an absence of flakes caused by mechanically impressing or pushing away flakes from said second region, the image forming a tactile image wherein a tactile transition can be sensed by touching an interface between the at least the first and second discernible regions.
In accordance with another aspect of the invention, there is provided, a method of forming an image, comprising the steps of:
providing a substrate;
coating at least a first region of the substrate with magnetic non-spherical flakes;
magnetically orienting the magnetic non-spherical flakes within the first region by exposing the non-spherical flakes to a magnetic field oriented in a predetermined direction; and,
so as to form the image, wherein the sub-region has a visual appearance that is different from the first region outside of the sub-region.
Exemplary embodiments of the invention will now be described in accordance with the drawings, in which:
a is a side view of an image being formed by applying an engraving tool to a pre-inked substrate wherein the flakes within the ink have been magnetically aligned to be up-standing and substantially perpendicular with respect to the substrate.
b is a side view of the image formed by the process depicted in
c is a side view of a side of an image being formed by applying an engraving tool to a pre-inked substrate wherein the flakes within the ink have been magnetically aligned to be up-standing and substantially perpendicular with respect to the substrate, and wherein the engraving tool has forced ink out from under the tool leaving voids of ink on the substrate.
d is a side view of the image formed by the process depicted in
Intaglio printing also known as recessed printing is a well accepted method to produce images. Intaglio printing can be used to print optically variable interference devices (OVIDs). In accordance with the method of this invention,
Turning now to
c illustrates another embodiment of this invention wherein the engraving tool 48 is formed to remove most or all of the high aspect ratio flakes as the tool makes contact with the substrate. The bottom of the engraved areas 49 may or may not contain ink depending of the depth, pressure, and the shape or material of the tool used to produce the engraved image. In this embodiment shown, the engraving tool 48 has a flat bottom and wedged sides which force out most of the ink under it. In
The images formed by the processes of
Other print process, like letterpress, screen, flexo, pad printing, ink jet, may present varying degrees of tactility based on the final thickness of the dried ink layer
Referring now to
In contrast to standard printed devices where the image may display some degree of tactility from the raised areas of the printed image, the tactility of this security device comes from the special optical effect areas that have been engraved into the low brightness background.
Within this specification, the term applied magnetic field connotes providing a magnetic field that is sufficient to align magnetic flakes along the magnetic field lines. This may be achieved by disposing the inked or painted substrate near or adjacent to a magnet, or by providing a means for generating a magnetic field and exposing the flakes to the field.
Mechanically impressing the flakes can be done by impressing the flakes with an engraving tool, a pen, or pencil or any form of mechanical means which will push or sweep the flakes aside or that will mechanically force the flakes into a different orientation from an upstanding substantially vertical position with respect to the substrate. The term mechanically impressing is to include wiping away magnetically aligned flakes within a target region.
For example after the flakes are oriented by the magnetic field to be upstanding with respect to the substrate, one can use a pen or pencil to scribe text or a signature that will be visually and tactilely distinguishable from its background as shown in
Providing a signature that is recessed from it's background and visually distinguishable from it's background wherein color shifting features are associated therewith, offers a significant advantage in the field of security enhancements.
In addition to realizing the image shown in
Turning now to
Alternatively, in another embodiment of this invention, one can provide a magnetic optically variable coating to a substrate and align the magnetic optically variable flakes in a particular desired pattern by using magnetic fields to provide an optical feature such as a rolling bar, for example, forming one or more rolling bars, and subsequently scribe the substrate to provide a tactile feature prior to curing the coating.
An optically variable image was produced using a 7 layer magnetic Gold to Green Optical variable design as follows:
10 nm Cr/4 QW MgF2 @ 604 nm/80 nm Al/50 nm Ni/80 nm Al/4 QW MgF2 @ 604 nm/10 nm Cr.
The particle size distribution is between 10 to 30 microns by 1.1 microns in thickness.
An ink was formulated comprising 80% by weight of a UV curable silk screen ink base and 20% of pigment. The ink was applied by silk screen printing over the black and white areas of a Leneta card. Once the ink was applied, the printed sample, containing no engraved image, was passed over a strong permanent magnet. The magnet's pole orientation was such that the magnetic flux lines were perpendicular to the plane of the Leneta card. As a result, a significant number of the high aspect ratio flakes aligned themselves perpendicular to the substrate, producing the dark areas of the device. The dark areas are due to the trapping of light from the pigment alignment, and occur independently of the substrate lightness.
An image was created using a metallic stamp under controlled, light pressure which causes the flakes to realign in such a way that light is now reflected by the pigment. The observed color changes from gold to green in accordance with the previously referenced optical interference design. The Leneta card was then passed under a high power UV lamp to cure the ink and permanently fix the pigment alignment.
An optically variable image was produced using a 7 layer magnetic Gold to Green Optical variable design as follows:
10 nm Cr/4 QW MgF2 @ 604 nm/80 nm Al/50 nm Ni/80 nm Al/4 QW MgF2 @ 604 nm/10 nm Cr.
The particle size distribution is between 10 to 30 microns by 1.1 micron thick.
Similar to Example 1, an ink was formulated comprising 80% by weight of a UV curable silk screen ink base and 20% of pigment. The ink was applied by silk screen printing over the black and white areas of a Leneta card. Once the ink was applied, the printed sample, containing no engraved image, was passed over a strong permanent magnet. The magnet's pole orientation was such that the magnetic flux lines were perpendicular to the plane of the Leneta card.
In this embodiment, the image was manually engraved using a stylus. Due to the nature of the stylus, the bottom of the engravings do not contain any ink as it pushes all of the ink aside. The walls of the engraved areas change from gold to green as the sample is tilted from near normal to high angles of viewing. As in Embodiment 1, the sample was UV cured afterwards.
An optically variable image was produced using a 7 layer magnetic Magenta to Green Optical variable design as follows:
10 nm Cr/4 QW MgF2 @ 665 nm/80 nm Al/50 nm Ni/80 nm Al/4 QW MgF2 @ 665 nm/10 nm Cr.
The particle size distribution is between 10 to 30 microns by 1.2 micron thick.
The method preparation is similar to the one described in Example 1, with the difference that in this example, a rubber stamp in the shape of a hummingbird was used to create the image. In this case, the color of the image changes from Magenta to Green as the sample is tilted from near normal to high angles of viewing.
An image was produced using a 7 layer magnetic Green to Blue diffractive Optical variable design as follows:
10 nm Cr/4 QW MgF2 @ 530 nm/80 nm Al/50 nm Ni/80 nm Al/4 QW MgF2 @ 530 nm/10 nm Cr.
A foil with a linear grating frequency of 500 l/mm, corresponding to a 2 micron separation between grooves, was used as the substrate to produce the pigment's diffractive properties. The particle size distribution is between 10 to 30 microns by 1 micron thick.
As in the case of the previous embodiments, the flakes were aligned perpendicular to the substrate. In this case the flakes have a tendency to have their diffractive grooves align parallel to the applied field, and thus perpendicular to the plane of the substrate.
As in the case of Example 2, the image was manually engraved using a stylus.
In this embodiment, an extra alignment was produced after the engraving step by passing the sample over a second permanent magnet positioned in such a way that the magnetic flux lines were oriented in a predetermined direction as is shown in
The OVID was produced using a 7 layer magnetic Magenta to Green Optical variable design as follows:
10 nm Cr/4 QW MgF2 @ 665 nm/80 nm Al/50 nm Ni/80 nm Al/4 QW MgF2 @ 665 nm/10 nm Cr.
The particle size distribution is between 10 to 30 microns by 1.2 micron thick.
An ink was formulated comprising 80% by weight of a UV curable silk screen ink base and 20% of pigment. The ink was this time applied using a doctor blade over the black and white areas of a Leneta card. As previous embodiments, once the ink was applied, the printed sample, containing no engraved image, was passed over a strong permanent magnet to align the flakes perpendicular to the substrate producing a dark area. As in previous embodiments, the image can be produced using a stylus, a rubber stamp, passing the sample under an engraved cylindrical roll, or any other method to produce an engraved image. The engraved areas, over the dark background, change from magenta to green in accordance to its optical interference design. Finally, the samples are UV cured to fix the position of the pigment.
Although a UV curing ink was used, other types of curing ink can be used in accordance with this invention.
Of course numerous other embodiments may be envisaged without departing from the spirit and scope of the invention. Preferred embodiments of this invention utilize optically variable magnetically alignable flakes or particles, however, magnetically alignable flakes having other optical properties can be utilized, such as diffractive flakes or other metallic flakes.
The present invention claims priority from U.S. Patent Application No. 60/660,837 filed Mar. 11, 2005, which is incorporated herein by reference.
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