ES2443191T3 - Procedure for the orientation of magnetic scales - Google Patents

Abstract

A method for the formation of an illusory image on a substrate, the method comprising the operations of: (a) printing a field with magnetic pigment scales dispersed in a fluid carrier on the substrate; (b) move the substrate along and over a first elongated magnet extended in a direction of travel of the substrate to selectively orient the magnetic pigment scales to form the illusory image; in which a magnetic axis between the north and south faces of the elongated magnet is transverse to the direction of travel of the substrate; and (c) fix the illusory image.

Description

Procedure for the orientation of magnetic scales

Background of the invention

The present invention relates generally to pigments, films, devices, and optically variable images, and more particularly to the alignment or orientation of magnetic scales, such as during a painting or printing process, to obtain an illusory optical effect.

Optically variable devices are used in a wide variety of applications, decorative and utilitarian. Optically variable devices can be made in a variety of ways to achieve a variety of effects. Examples of optically variable devices include holograms printed on credit cards and authentic software documentation, color-changing images printed on bills, and that improve the surface appearance of items such as motorcycle helmets and wheel covers.

Optically variable devices can be made as a film or sheet that is pressed, stamped, glued, or otherwise fixed to an object, and can also be made using optically variable pigments. An optically variable type of pigment is commonly referred to as a pigment that changes color because the apparent color of images properly printed with such pigments changes by tilting the viewing angle and / or lighting. A common example is the "20" printed with the pigment that changes color in the lower right corner of a twenty-dollar bill, which serves as a counterfeit device.

Some anti-counterfeit devices are undercover, while others are designed to be notorious. Unfortunately, some optically variable devices that are meant to be notorious are not widely known because the optically variable aspect of the device is not dramatic enough. For example, changing the color of an image printed with a color-changing pigment may not be noticed under uniform fluorescent ceiling lights, but it is most noticeable in direct sunlight or under single-point lighting. This may make it easier for a forger to pass fake bills and without the optically variable feature because the recipient is not aware of the optically variable feature, or because the fake bill could be substantially similar to the authentic ticket under certain conditions.

Optically variable devices can also be made with magnetic pigments that are 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, magnetic pigment paint has been used primarily for decorative purposes. For example, the use of magnetic pigments to produce painted wheel covers having a decorative element that appears as a three-dimensional shape has been described. A pattern was formed on the painted product by applying a magnetic field to the product, while the painting medium was still in a liquid state. The paint medium had dispersed non-spherical magnetic particles that line 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 not 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 the desired pattern were placed under the painted product to orient in the magnetic field the 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, since the light rays incident on the paint layer were influenced differently by the oriented magnetic particles.

Similarly, a process for the production of a pattern of magnetic particles in fluoropolymer matrix flakes has been described. After coating a product with a liquid form composition, a magnet with a desirable shape was placed on the bottom of the substrate. The magnetic scales scattered in a liquid organic medium orient themselves parallel to the magnetic field lines, tilting from the original flat orientation. This inclination varied from perpendicular to the surface of a substrate to the original orientation, which included scales essentially parallel to the surface of the product. The flat oriented scales reflected the incident light back to the observer, while the reoriented scales did not, providing the appearance of a three-dimensional pattern on the coating.

Although these approaches describe procedures and apparatus for the formation of three-dimensional images in the paint layers, they are not suitable for high-speed printing processes, since they are essentially batch processes. It is desirable to provide procedures and apparatus for printing and painting at high speed in line that reorient magnetic pigment scales. In addition, it is desirable to create more sensitive optically variable security elements in financial documents and other products.

WO 02/090002 A2 published below discloses multilayer magnetic scales that can be oriented using a magnet arranged adjacent to a substrate, for example, a magnet in the form of a 2 10

character. In some examples of this document, the portions adjacent to the magnet appear black when viewed at a viewing angle of 90 degrees.

EP 0 556 449 A1 discloses the formation of patterns by bringing magnets adjacent to the substrates covered with a paint layer containing non-spherical magnetic particles, causing an alignment of the particles according to a magnetic field caused by the magnet. Some portions of the aligned particles may resemble an arc shape. With the procedure disclosed in this document, characters that appear in white can be formed, while the surrounding area appears in black.

US 3,853,676 A discloses the placement of magnetic pigments in a curved shape near reference points in the vicinity of a film using curved magnetic fields to create an illusion of depth.

US 6,103,361 A discloses the orientation of magnetic scales such that in a first part and a second part they are essentially parallel to a substrate, and between the first and second parts, the scales are perpendicular to the substrate. To orient the scales, magnetizable matrices can be used.

GB 1,131,038 A discloses the production of a particle pattern in a polytetrafluoroethylene matrix using magnets to create an illusion of depth. The particles can be oriented inclined with respect to a substrate in this way. For example, a magnet in the form of a star can be used.

US 2,570,856 A discloses a method in which a film containing magnetic particles is subjected to a magnetic field, for example, is rotated in a magnetic field. After hardening, the film can be removed from the magnetic field.

GB 1,107,395 A discloses devices and procedures for printing characters on a sheet using ink containing magnetizable particles and the use of magnets to move the ink containing the particles on the sheet. Some of the magnets used can be provided on a roller.

WO 88/07214 A discloses the orientation of preferably spherical particles, and preferably a hemisphere of which is coated by a light reflective material having magnetic properties

or electric The particles can be brought to a desired orientation with respect to a substrate using a magnetic or electric field, for example such that the light-reflecting material is placed in front of the substrate, in a continuous process where the substrate moves along of a magnetic device. The magnetic device may include a series of permanent bar magnets that are arranged end to end and extend transversely to the substrate.

EP 0 325 237 A2 discloses a method and apparatus for producing a magnetic recording medium where a substrate moves in a direction of field lines of a magnetic field.

Summary of the invention

The present invention provides articles and procedures related to images having an illusory optical effect as defined in the appended claims. The images are printed in a high speed continuous printing operation.

Brief description of the drawings

Figure 1A is a simplified cross section of a printed image that is known as a "changing" image.

Figure 1B is a simplified plan view of the image printed on a document at a first selected viewing angle.

Figure 1C is a simplified plan view of the printed image at a second selected viewing angle, obtained by tilting the image with respect to the viewing point.

Figure 2A is a simplified cross section of a printed image that is known as a "rolling bar" for purposes of the description.

Figure 2B is a simplified plan view of the image of the rolling bar at a first selected viewing angle.

Figure 2C is a simplified plan view of the image of the rolling bar in a second selected viewing angle.

Figure 3A is a simplified cross-sectional view of an apparatus for producing a changing type image.

Figure 3B is a simplified cross section of an apparatus for producing a changing type image. Figure 3C illustrates the calculated magnitude of the field strength through the apparatus of Figure 3B. Figure 4 is a schematic view of a magnetic assembly that can be installed in the printing equipment or

online painting.

Figure 5A is a simplified cross section of an apparatus for producing a changing type image with a more acute transition, in accordance with an embodiment of the present invention. Figure 5B is a simplified cross section of an apparatus for producing an image according to another

embodiment of the present invention.

Figure 5C is a simplified cross section of the apparatus illustrated in Figure 5B, showing the orientation of the scales on such a magnetic device. Figure 5D is a graph illustrating the calculated magnitude of field strength for the apparatus of Figures 5B

and 5C.

Figure 6 is a simplified schematic view of a magnetic assembly that can be installed in the equipment Print or paint online. Figure 7A is a simplified cross section of another embodiment of the invention to form an orientation.

Semicircular of paint or ink flakes for a rolling bar type image. Figure 7B is a simplified perspective view of an apparatus according to Figure 7A. Figure 7C is a simplified side view of an apparatus for forming a rolling bar image in accordance with

Another embodiment of the present invention.

Figure 8 is a simplified schematic view of an apparatus for printing rolling bar images according with an embodiment of the present invention that can be installed in the online printing or painting equipment. Figure 9A is a simplified cross section of another optical effect that can be achieved using

Magnetic alignment techniques in high speed printing processes.

Figure 9B is a simplified cross section of an apparatus according to an embodiment of the present. invention capable of producing the image illustrated in Figure 9A. Figure 9C is a simplified cross section of an apparatus according to another embodiment of the present.

invention.

Fig. 9D is a simplified cross section of an apparatus according to yet another embodiment of the present. invention. Figure 9E illustrates the calculated magnetic field strength for an apparatus of five associated magnets. Figure 10A is a simplified side view of an apparatus for printing illusory images that inclines scales

magnetic in a selected direction according to another embodiment of the present invention.

Figure 10B is a simplified side view of an apparatus for printing illusory images that includes magnets auxiliaries according to another embodiment of the present invention. Figure 10C is a simplified plot illustrating the magnetic field strength for the apparatus of the figures.

10A and 10B.

Figure 11A is a simplified side view of an apparatus for aligning magnetic pigment scales to the plane. of the substrate after printing that is not in accordance with the claimed invention. Figure 11B is a simplified side view of a portion of an apparatus for improving the visual quality of

an image printed with scales that can be magnetically aligned not according to the invention

claimed. Fig. 13A is a simplified flow chart of a method of printing an image according to An embodiment of the present invention.

Detailed description of the invention

1. Introduction

The present invention in its various embodiments solves the problem of the predetermined orientation of optically variable magnetic ink flakes in a high speed printing process. Normally, particles of an optically variable pigment that are dispersed in a paint or liquid ink vehicle generally orient themselves parallel to the surface when they are printed or painted on a surface. The orientation parallel to the surface provides a high reflection of the incident light from the coated surface. Magnetic scales may be inclined, while in the liquid medium by applying a magnetic field. The scales are usually aligned in such a way that the longest diagonal of a scale follows a magnetic field line. Depending on the position and intensity of the magnet, the magnetic field lines can penetrate the substrate at different angles, tilting the magnetic scales at these angles. An inclined scale reflects the incident light differently than a scale parallel to the surface of the printed substrate. The reflectance and tone may be different at angles of inclination. Sloping scales will typically look darker and have a different color than scales parallel to the surface at a normal viewing angle.

The orientation of magnetic scales in printed images poses several problems. Many modern printing processes are at high speed in relation to the batch process that applies a magnet on a static coated article (no movement) and keeps the magnet in position while the paint or ink dries. In some printing presses, the paper substrate moves at a speed of 100-160 meters per minute. The sheets of paper are stacked after a printing operation, and feed each other. The inks used in this type of operations are usually dried in a matter of milliseconds. Conventional processes are not suitable for such applications.

It was found that one way to obtain improved optical effects on the painted / printed image is by orientation of the magnetic scales perpendicular to the direction of the moving substrate. In other words, the paint or liquid ink medium painted or printed with the scales scattered on the substrate moves perpendicular to the magnetic lines of the field to cause reorientation of the scales. This type of orientation can provide remarkable illusory optical effects in the printed image. One type of optical effect is known as a kinematic optical effect for description purposes. An illusory kinematic optical effect generally provides an illusion of movement in the printed image when the image is tilted relative to the viewing angle, assuming a source of stationary lighting. Another illusory optical effect provides virtual depth to a printed, two-dimensional image. Some images can provide virtual movement and depth. Another type of illusory optical effect changed the appearance of a printed field, such as by alternating bright and dark colors when the image is tilted back and forth.

II. Examples of Illusory Printed Images

Figure 1A is a simplified cross section of a printed image 20 that is known as an "switching" or "changing" optical effect, for purposes of description in accordance with an embodiment of the present invention. The changing image includes a first printed portion 22 and a second printed portion 24, separated by a transition 25. The pigment flakes 26 surrounded by the carrier 28, such as an ink vehicle or paint vehicle, have been aligned parallel to a foreground in the first portion, and the pigment scales 26 'in the second portion have been aligned parallel to a second plane. The scales are shown as short lines in the cross-sectional view. The scales are magnetic scales, that is, pigment scales that can be aligned using a magnetic field. They may or may not retain the remaining magnetization. Not all scales in each portion are precisely parallel to each other or to the respective alignment plane, but the overall effect is essentially as illustrated. The figures are not drawn to scale. A typical scale could be twenty microns in diameter and approximately one micron thick, therefore, the figures are merely illustrative. The image is printed or painted on a substrate 29, such as paper, plastic film, laminate, cardboard, or other surface. For the convenience of the description, the term "printed" will be used to describe in general the application of pigments in a carrier to a surface, which may include other techniques, including other techniques that could be referred to as "painted."

Generally, scales seen normal to the scale plane appear bright, while scales seen along the edge of the plane appear dark. For example, light from a light source 30 is reflected outside the scales in the first region for a viewer 32. If the image is tilted in the direction indicated by an arrow 34, the scales in the first region 22 will be seen at the end, while the light will be reflected in the scales in the second region 24. Thus, in the first viewing position, the first region will appear bright and the second region will look dark, while in the second viewing position the fields will change, the first region will turn dark and the second region will become bright. This provides a very striking visual effect. Similarly, if the pigment scales change color, one portion may appear to be of a first color and the other portion of another color.

The carrier is typically transparent, either clear or dyed, and the scales are usually quite reflective. For example, the carrier could be dyed green and the scales could include a metallic layer, such as a thin film of aluminum, gold, nickel, platinum, or metal alloy, or be a metal scale, such as a scale of nickel or alloy. The light reflected by a layer of metal through the dyed carrier of

Green may appear bright green, while another portion with scales facing the end may appear dark green or another color. If the scales are merely metallic scales on a light carrier, then one part of the image might appear shiny metallic, while the other seems dark. Alternatively, the metal scales may be coated with a dyed layer, or the scales could include an optical interference structure, such as a Fabry Perot type absorber-separator-reflector structure.

Figure 1B is a simplified plan view of the printed image 20 on the substrate 29, which could be a document, such as a banknote or stock certificate, at a first selected viewing angle. The printed image can act as a security and / or authentication feature because the illusory image will not be photocopied and cannot be produced using conventional printing techniques. The first portion 22 appears bright and the second portion 24 appears dark. A section line 40 indicates the cross section shown in Figure 1A. The transition 25 between the first and second portions is relatively acute. The document could be a banknote, a stock certificate, or other valuable printed material, for example.

Figure 1C is a simplified plan view of the printed image 20 on the substrate 29 at a second selected viewing angle, obtained by tilting the image with respect to the point of view. The first portion 22 now appears dark, while the second portion 24 appears bright. The angle of inclination at which the image changes depends on the angle between the planes of alignment of the scales in the different portions of the image. In a sample, the image changes from bright to dark when tilted through about 15 degrees.

Figure 2A is a simplified cross section of a printed image 42 of a kinematic optical device that is known as a "rolling bar" for the purposes of the description. The image includes pigment scales 26 surrounded by the transparent support 28 printed on the substrate 29. The pigment scales are aligned in a curved manner. As with the changing image, the region (s) of the rolling bar that reflect light outside the faces of the pigment scales for the viewer appear brighter than areas that do not directly reflect light towards the viewer. This image provides a bright band (s) or bar (s) that appear to move ("roll") through the image when the image is tilted relative to the viewing angle (assuming a source (s) (s) of fixed lighting (s)).

Figure 2B is a simplified plan view of the image of the rolling bar 42 at a first selected viewing angle. A bright bar 44 appears in a first position in the image between two contrasting fields 46, 48. Figure 2C is a simplified plan view of the image of the rolling bar in a second selected viewing angle. The bright bar 44 'seems to have "moved" to a second position in the image, and the sizes of the contrast fields 46 ", 48" have changed. The alignment of the pigment scales creates the illusion of a bar that "rolls" down the image when the image is tilted (at a fixed viewing angle and fixed lighting). The tilt of the image in the other direction makes the bar appear to roll in the opposite direction (upwards).

The bar may also appear to have depth, even though it has been printed on a plane. The virtual depth may appear to be much greater than the physical thickness of the printed image. The inclination of the scales in a selected pattern reflects the light to provide the illusion of depth or "3D", as is commonly known. A three-dimensional effect can be achieved by placing a shaped magnet behind the paper or other substrate with magnetic pigment scales printed on the substrate in a fluid carrier. The scales line up along the magnetic field lines and create the 3D image after adjustment (for example, drying or curing) of the wearer. The image often seems to move when tilted, and therefore, 3D cinematic images can be formed.

Changing images and rolling bars can be printed with magnetic pigment scales, that is, pigment scales that can be aligned using a magnetic field. A printed changing type image provides an optically variable device with two distinct fields that can be obtained with a single printing stage and using a single ink formulation. A rolling bar type image provides an optically variable device that has a contrast band that appears to move when the image is tilted, similar to the semi-precious stone known as Tiger's Eye. These printed images are very sensitive and illusory aspects could not be photocopied. Such images can be applied to banknotes, share certificates, software documentation, security seals, and similar objects such as authentication and / or counterfeiting devices. They are particularly desirable for large volume printed documents, such as banknotes, containers and labels, since they can be printed in a high speed printing operation, as described below in Section III.

III. Exemplary Manufacturing Apparatus

Figure 3A is a simplified cross-sectional view of a portion of an apparatus 50 to produce an image of the changing type. The scales 26 are arranged in a V-shaped manner in which both branches of the V represent directions of inclination and the vertex represents a transition point. Such orientation of the

scales are possible when magnetic fields oppose each other. Two magnets 52, 54 are aligned with opposite poles (in this case north-north). For modeling purposes, the magnets have been assumed to be 40MOe NdFeB magnets 50.8 mm W by 38.1 mm H spaced 3.175 mm between the north poles. The type of magnet (material and intensity) is selected according to the scale material, viscosity of the paint vehicle, and a substrate translation speed. In many cases, a neodymium-borohierro, samarium-cobalt, and / or ALNICO magnet can be used. The optimal distance between magnets is important for the formation of the uniformity of the optical effect for a particular printed image size.

An image 56 is printed on a thin print or paint substrate 58, such as a sheet of paper, plastic, film, or card stock, in a previous printing operation, which is not illustrated in this figure. In the typical operation, several images are printed on the substrate, which is subsequently cut into individual documents, such as printing a sheet of banknotes from which it is cut into money. The carrier 28 is still wet or at least sufficiently fluid to allow the alignment of the magnetic scales with the magnets. The carrier typically hardens shortly after alignment to allow manipulation of the printed substrate without staining the image. The magnetic scales 26 follow the direction of the magnetic lines 60 and are inclined.

Figure 3B is a simplified cross-section of a portion of an apparatus for producing a changing type image where magnets 52, 54 are mounted on a base 62 made of a metal alloy with high magnetic permeability, such as SUPERMALLOY. It is easier to make a set of several magnets if they are attached to a base, and the base provides a path for the magnetic field on the opposite side of the magnet, and alters the magnetic field lines on the printed side of the assembly. The magnetic base acts as a shunt for the magnetic field and reduces the magnetic field behind the ("below") assembly, thus protecting objects near the back side of the magnetic fields and high forces. The magnetic base also keeps the magnets securely in position without screws, terms, welds, or the like. The magnetic field circulates inside the base 62 providing uniformity of the field between the magnets. The field is the most intense in the space between magnets and above them.

Figure 3C illustrates the calculated magnitude of the field strength through the apparatus of Figure 3B. The intensity is low near the edges of the magnets, and is very high in the center, providing a sharp transition between the scales in adjacent portions of the image.

Figure 4 is a simplified schematic view of a magnetic assembly 64 that can be installed in the online printing or painting equipment. Permanent magnets 66, 68, 70, 72, 74, 76 with their north and south poles indicated with "N" and "S", respectively, similar to those illustrated in Figure 3B, are attached to the base 62 by magnetic attraction. The magnets can be magnetic bars, or they can be segments. That is, rows of magnets can be used, for example 74, 76, etc. Plastic spacers (not shown in the image) can be inserted between magnets to prevent their collision and provide security. The assembly is enclosed in a box 78 with a lid 80. The box and the stage may be made of aluminum or other non-magnetic material, for example.

The plastic or paper substrate 29 with printed fields 20 '(for example square or other shapes) moves at high speed over the top of the assembly in the direction of the arrows 82 such that the intersections of the field lines Magnetic pass through the printed fields. It is possible to align the substrate to the magnetic assembly so that the intersections of the magnetic field lines pass through the center of the fields. Alternatively, the centers between the magnets can be displaced from the centers of the printed fields. Similarly, the substrate could be a continuous roll, rather than sequential sheets. In many cases, several sets of images are printed on a sheet, and the sheet is cut into individual documents, such as banknotes, after the printing is completed.

After tilting the scales, the image 20 has an illusory optical effect. A water or solvent-based paint or ink dryer (not shown in the image) or a UV light source for photopolymers typically follows the magnetic assembly shortly thereafter in the line to dry the ink or paint vehicle and fix the scales redirected in their aligned positions. It is generally desirable to avoid magnetizing the scales before application, since they can pile together. It has been found that pigment scales with nickel or SUPERMALLOY layers approximately 100-150 nm thick are suitable.

Figure 5A is a simplified cross section of an apparatus for producing a changing type image with a more acute transition, in accordance with an embodiment of the present invention. Two magnets 84 of NdFeB (modeled as being 50.8 mm W for 38.1 mm H each) are placed on the magnetic base 62 looking with their north poles "up." The distance between magnets is approximately 25.4 mm (one inch). A sheet 88 made of a high permeability metal or metal alloy, such as SUPERMALLOY, is attached to the base between the magnets. The point of attack of the tip 90 of the blade is of the order of about 5 degrees to about 150 degrees. The sheet reshapes the magnetic field lines, bringing them closer together and making the tip as a point where the magnetic field lines originate.

Figure 5B is a simplified cross section of an apparatus for producing an image according to another

embodiment of the present invention. The shaped SUPERMALLOY caps or caps 92 are placed on top of magnets 84 to bend the magnetic field lines, as illustrated. The hoods curve the field, bringing it closer to the tip, which makes the V-shaped transition of the lines even more acute.

Figure 5C is a simplified cross section of a portion of the apparatus illustrated in Figure 5B, showing the orientation of the scales on such a magnetic device. The substrate 29 is placed on top of the device that slides along the caps 92 (or magnets, in the case of Figure 5A) in the direction from the observer to the page. A printed image 85 is located above the tip. The scales 26 follow the magnetic lines 94 and are inclined accordingly. This view more clearly shows the pointed nature of the tip of the sheet, which produces an acute transition between the two areas of the illusory image.

Figure 5D is a graph illustrating the calculated magnitude of the field strength for the apparatus of Figures 5B and 5C. The field strength is narrower compared to the plot field intensity of Figure 3C, and produces a more acute transition.

Figure 6 is a simplified schematic view of a magnetic assembly 100 that can be installed in the online printing or painting equipment. Permanent magnets 84 with the north and south poles as illustrated in Figures 5A and 5B are mounted on the magnetic base 62. Alternatively, the south poles could be facing up. The cap plates 92 are magnetically attached to the top of the magnets. The sheets 88 are mounted on the base with their edges extending along the direction of translation 82 of the substrates 29 and 29 '. The magnets 84 in line can be installed either next to each other, or with a space 102 between them. The magnetic assembly is typically enclosed in a box 78 with a cover plate 80.

Fields 104 'printed on substrate 29 generally have non-oriented scales. Some alignment of the scales may occur as an artifact of the printing process, and some of the scales generally tend to line up in the substrate plane. When the substrate moves at high speed in the direction indicated by arrow 82 above the magnetic assembly, the scales change their orientation along lines of the magnetic field forming an illusory image 104 (changing). The image has two areas with light reflected in different directions and a boundary or border (transition) relatively sharp between them.

Figure 7A is a simplified cross section of another embodiment of the invention to form a semi-circular orientation of paint or ink flakes for an image of the rolling bar type. A thin permanent magnet 106 is magnetized through its thin section, as illustrated. The magnet has circular magnetic lines 108 at its ends. The substrate 29 with the printed magnetic scales dispersed in a fluid carrier moves along the magnet from the observer to the paper. The scales 26 are inclined along the direction of the magnetic lines 108 and form a semicircular pattern above the magnet.

Figure 7B is a simplified perspective view of an apparatus according to Figure 7A. The substrate 29 moves through the magnet 106 in the direction of the arrow. An image 110 forms a rolling bar feature 114, which will appear to move up and down when the image is tilted or the viewing angle is changed. The scales 26 are shown as inclined in relation to the magnetic field lines. The image is typically very thin, and the scales may not form a hump or protrusion, as illustrated, but generally align along the lines of the magnetic field to provide the desired arched reflective properties to create a rolling bar effect. . The bar seems to roll the image up and down when it is tilted through an angle of about 25 degrees in an example.

It has been found that the intensity of the rolling bar effect could be improved by chamfering 116 the back edge 118 of the magnet. It is believed that this gradually reduces the magnetic field as the image uncovers the magnet. Otherwise, the magnetic transition that occurs in a sharp corner of the magnet could again arrange the orientation of the scales and degrade the visual effect of the rolling bar. In a particular embodiment, the corner of the magnet was chamfered at an angle of thirty degrees from the plane of the substrate. An alternative approach is to fix the scales before they pass over the trailing edge of the magnet. This could be done by providing a source of UV partially down the path of the magnet, by a UV curing carrier, or a drying source for evaporator carriers, for example.

Fig. 7C is a simplified side view of another apparatus 120 for forming a rolling bar image in accordance with another embodiment of the present invention. The rolling bar effect is obtained using two magnets 122. The magnetic pigment scales 26 are oriented themselves in the liquid carrier 28 along the oval magnetic field lines.

Fig. 8 is a simplified schematic view of an apparatus 130 for printing rolling bar images in accordance with an embodiment of the present invention that can be installed in the online printing or painting equipment. Thin vertical magnets 106, with their north-south polarization as shown, are installed in a plastic housing 132 that separates the magnets at selected distances, generally in accordance with the

location of printed fields 110 'on the substrate 29. The magnets are aligned in such a way that they oppose each other. In other words, the north pole of a row of images faces the north pole of an adjacent row, while the south pole faces the south pole of an adjacent row of magnets on the other side.

In comparison with the magnetic devices shown in Figures 4 and 6, which have a base made of very permeable alloy for mounting the magnets and concentration of a field strength just above the center of the space or above the gasket. the sheet, the apparatus of figure 8 does not have a metal base. A base made of a metal that has a high magnetic permeability would reduce the intensity of the magnetic field on the side of the magnet that is responsible for the inclination of the scales. Instead of the base, the magnets are inserted into grooves of the plastic housing such that the upper part of the magnets passes below the center of the printed fields, but could be displaced from the center. The substrates 29, 29 'move at high speed on the magnets in the direction of the many 82. Passing over the magnets, the scales in the printed images orient themselves along lines of the magnetic field, creating an illusory optical effect on the rolling bar image 110.

Figure 9A is a simplified cross section of another optical effect that can be achieved using magnetic alignment techniques in high speed printing processes. The scales 26 of the pigment in the image 134 are generally aligned parallel to each other, but not parallel to the surface of the substrate 29. Again, it is not necessary that each scale be perfectly aligned with each of the other scales, but the visual impression obtained is essentially in accordance with the illustration. Alignment of most scales in the manner illustrated causes an interesting optical effect. The image appears dark when viewed from one direction 136 and bright when viewed from another direction 138.

Figure 9B is a simplified cross section of an apparatus 139 according to an embodiment of the present invention capable of producing the image illustrated in Figure 9A. A printed field 134 with still wet paint or ink is placed above the permanent magnet 140 with its position displaced relative to the axes of the magnet. The magnetic field analysis was modeled assuming a 40MOe NdFeB magnet of 50.8 mm by 38.1 mm. The magnitude of the field intensity is smaller in the center of the magnet and greater towards its edges.

In general, electromagnets could be used in some embodiments, but it is difficult to obtain magnetic fields as high as can be obtained by ordinary superimanes in the confined spaces of a high-speed printing machine. Electromagnets coils also tend to generate heat, which can affect the curing time of the ink or paint and add another variable to the process. However, electromagnets may be useful in some embodiments of the invention.

Figure 9C is a simplified cross section of an apparatus according to another embodiment of the present invention. Magnets 142, 142 'are used which have a diamond-shaped cross section to disperse the magnetic field and make it wider. The apparatus was modeled with three 50.8 mm by 38.1 mm NdFeB magnets arranged 25.4 mm apart. The magnets show a cross section of a magnetic assembly for reorienting scales in a magnetic field. The substrate 29 moves at a high speed in the direction of the observer to the drawing. Two magnets have their north pole facing up while the magnet 142 'that intervenes has their south pole facing up. Each magnet has the same field strength as the magnets illustrated in Figure 9B, but provides a wider area for placement of the field 134 'to orient the scales 26.

Figure 9D is a simplified cross section of an apparatus according to yet another embodiment of the present invention. An effect similar to that obtained with the apparatus illustrated in Figure 9C can be obtained with magnets 144, 144 'having a cross-section in the form of a roof, as well as with magnets with hexagonal, rounded, trapezoidal cross-section, or other cross-section. Different shapes of magnets provide different performance that can create different printed or painted images with slanted scales. For example, the magnitude of the intensity of the magnetic field can be very different for magnets with different shapes (cross sections).

Figure 9E illustrates the magnetic field strength calculated for an apparatus with five magnets. The first magnet 142 is a 40MOe NdFeB magnet with dimensions close to 50.8 mm by 38.1 mm with its north pole facing up. The second magnet 146 is a 50.8 mm by 38.1 mm rectangular NdFeB 40MOe magnet with its south pole facing the substrate 29. The third magnet 148 is a NdFeB 40MOe magnet with a rounded top. This magnet has its north pole facing the substrate. The fourth magnet 150 has the south pole facing up, and has a roof shape (the tip angle being approximately 185 °). The fifth magnet 152 also has a roof shape but the angle of the tip is approximately 175 °. Curve 160 shows the calculated magnitude of the magnetic field strength in this illustrative set. The forms of field strength are different for different magnets. The intensity of the field is low in the center of the rectangular, diamond-shaped and roof-shaped magnets while it is almost flat at 380,000 A / m for the rounded magnet 148. The curve shows that shaping the magnet helps to obtain an intensity field that will be enough to provide a pair of the scale to guide it.

Figure 10A is a simplified side view of an apparatus 162 according to an embodiment of the present invention.

It tilts scales in a preferred direction and is suitable for adaptation to a high speed printing process. Three magnets 164, 164 'of 40MOe of NdFeB of 50.8mm by 38.1mm are inclined 10 ° in relation to the substrate 29 and the printed images 166. The scales 26 follow the magnetic lines and reorient themselves. The magnets have the same alignment similar to the alignment shown in Figure 9D. Two of the magnets 164 have their north pole facing up and the magnet 164 'between them has their south pole facing the substrate 29. Printed images 166 must be placed above the central axis of the magnet to take advantage of the inclined magnetic field lines generated by inclined magnets. Such an arrangement produces a uniform inclination of the scale in an area that is larger for the magnetic assemblies described with reference to Figures 9A-9E.

The magnetic lines in the field are not parallel. The difference is smaller in the near order and is greater with the increase of a distance between the lines. It means that in a large printed image placed in a magnetic field, all scales would have different inclination resulting in an inconsistent image appearance. Inconsistency can be reduced by diverting the magnetic lines toward the center of the magnet to keep them more parallel. It is possible to do this with small auxiliary magnets.

Figure 10B is a simplified side view of an apparatus 168 according to an embodiment of the present invention that includes auxiliary magnets 170, 170 '. The inclined primary magnets 172, 172 'are arranged similarly to the magnets shown in Figure 10A, with alternating magnets having alternating poles (north-south) after the substrate 29. The minor auxiliary magnets are located below the substrate and between the widest main magnets. The auxiliary magnets are arranged so that the north pole of an auxiliary magnet faces the north pole of a main magnet, and its south pole faces the south pole of a main magnet. In such an arrangement, two fields (north-north, south-south) oppose each other and the magnetic lines are diverted towards the center of the main magnets.

Figure 10C is a simplified graph showing the intensity of the field calculated for the magnetic assemblies shown in Figures 10A and 10B, represented by curves 174 and 176, respectively. The substrate 29, the main magnets 172, 172 'and the auxiliary magnets 170, 170' are shown to illustrate how the paths relate to the dimensions of the assembly, although the auxiliary magnets are only important for drawing the second curve 176. The first curve 174 shows how the magnitude of the field strength of the assembly in Figure 10A changes in the direction from one edge of the substrate to another. The curve has two minimum 178, 180 corresponding to the center of the main magnets 172, 172 '. A central axis 182 of the central magnet 172 'shows where the center of the magnet and the plot of the field intensity coincide.

The inclusion of auxiliary magnets 170, 170 'in the assembly shifts the magnitude of field strength to the left. The second curve 176 shows the magnitude of the field strength of an assembly according to Figure 10B. The maximums 184, 186 on the curve are shifted to the left in relation to the first curve 174 associated with Figure 10A. This shows that opposite fields on auxiliary magnets divert the fields of the main magnets.

Figure 11A is a simplified side view of an apparatus 190 for aligning magnetic pigment scales on printed fields 192 in the plane of a substrate after printing. Magnets 194, 196 are arranged to produce lines 198 of magnetic field essentially parallel to the surface of the substrate 29. In some printing processes using pigment scales, the scales are aligned essentially parallel to the substrate when applied (printed), but are "removed" from the plane when the print screen is raised, for example. This disorganization of the scales tends to reduce the visual effect of printing, such as a reduction in chroma.

In one case, magnetic pigment scales with color shift were applied to a card using a conventional screen printing process. The same ink was applied to another cardboard, but before the ink carrier dried, a magnet was used to reorient the flakes in the cardboard plane. The difference in visual appearance, such as the intensity of the colors, was very dramatic. The measurements indicated that an improvement in chroma of 10% had been obtained. This level of improvement is very significant, and it is believed that it would be very difficult to achieve such improvement by modifications of the flake production techniques of the invention, such as changes in the substrate and thin film layers of the flake. It is believed that even greater improvement in chroma is possible, and that a 40% improvement could be obtained when magnetic realignment techniques are applied to images formed using a woodcut printing process.

Figure 11B is a simplified side view of a portion of an apparatus for improving the visual quality of an image printed with scales that can be magnetically aligned according to another embodiment of the present invention. The magnets 194, 196 create magnetic field lines 198 that are essentially parallel to the substrate 29, which causes the magnetic pigment scales 26 in the fluid carrier 28 to crush. The magnets can be separated by a distance to provide the desired magnetic field, and the apparatus can be adapted to an online printing process.

V. Exemplary Procedures

Figure 13A is a simplified flow chart of a method 300 of printing an image on a substrate according to an embodiment of the present invention. A field is printed on a thin flat substrate, such as a sheet of paper, plastic film, or laminated, using magnetic pigment scales in a fluid carrier (operation 302). Before the carrier dries or hardens, the substrate is moved in a linear manner relative to a set of magnets (operation 304) to orient the magnetic pigment scales (operation 306). After magnetically orienting the magnetic pigment scales, the image is fixed (ie dried or hardened) (operation 308) to obtain an optically variable image resulting from the alignment of the pigment scales. Typically, the substrate is moved beyond a stationary magnetic assembly. In some cases, the image may have optically additional variable effects, such as color shift. In a particular embodiment, the magnetic assembly is configured to provide a changing image. In another embodiment, the magnetic assembly is configured to provide a rolling bar image. In some embodiments, the flat substrate delegate is a sheet that is printed with several images. The images on the sheet can be the same or different, and different inks or paints can be used to print the images on the sheet. Similarly, different sets can be used

15 magnetic, to create different images on a single sheet of substrate. In other embodiments, the substrate may be an essentially continuous substrate, such as a roll of paper.

Claims (15)

1.-A procedure for the formation of an illusory image on a substrate, the procedure comprising the operations of:

(to)

 print a field with magnetic pigment scales dispersed in a fluid carrier on the substrate;

(b)

move the substrate along and over a first elongated magnet extended in a direction of substrate travel to selectively orient the magnetic pigment scales to form the illusory image;

in which a magnetic axis between the north and south faces of the elongated magnet is transverse to the direction of travel of the substrate; Y

(C)

 Fix the illusory image.

2. The method according to claim 1 wherein the fixing operation takes place before the illusory image moves beyond the first elongated magnet. 3. The method according to claim 1 wherein the substrate is a sheet of paper. 4. The method according to claim 1 wherein the substrate is a roll of paper. 5. The method according to claim 1 wherein a plurality of illusory images are printed at the same time. 6. The method according to claim 1 wherein the illusory image is an illusory three-dimensional image that has an apparent depth greater than the thickness of the image. 7. A method for forming several illusory images on the same substrate, wherein each of the several illusory images is formed using the method according to claim 1. 8. The method according to claim 7 further comprising an operation of cutting the substrate into individual documents. 9. The method according to claim 7, wherein the illusory images are changing images on a substrate printed in the linear printing process, and in which in operation (b) the magnetic pigment scales are oriented using a second elongated magnet that extends along the direction of travel of the substrate and attached to a base; and a sheet disposed between the first elongated magnet and the second elongated magnet, the sheet also extending along the direction of travel of the substrate. 10. The method according to claim 7, wherein the illusory images are rolling bar images printed on a substrate in a linear printing process, and wherein the first elongated magnet has a rear edge having a chamfered upper corner . 11. The method according to claim 10, wherein in operation (b) the scales of the magnetic invention are oriented using a second elongated magnet essentially identical to the first elongated magnet and having a second north face, a second south face, and a second upper edge, the first elongated magnet and the second elongated magnet being arranged in a non-magnetic housing such that the north face faces the second north face or such that the south face faces the second face south, and the upper edge is in a plane with the second upper edge. 12. The method according to claim 1 wherein the first elongated magnet is segmented. 13. The method according to claim 9 or 11 wherein the second elongated magnet is segmented. 14. A substrate (29) comprising an image (20) printed on it, the image comprising: a first image portion (22) having a first plurality of magnetic scales (26) aligned so as to reflect the light in a first direction; Y a second image portion (24) adjacent to the first image portion (22), having a second plurality of scales (26 ') aligned so that they reflect light in a second direction, the first image portion (22) appearing brighter than the second image portion (24) when viewed from a first viewing direction and the first image portion (22) appearing darker than the second image portion (24) when viewed from a second viewing direction , wherein the image is formed by the method according to claim 9. 15. A substrate (29) comprising an image (42) printed on it, the image comprising: a plurality of magnetic scales (26) in which a portion of the plurality of magnetic scales (26) are aligned with a pattern arched relative to a substrate surface (29) so that a contrast bar (44) is created across the image, appearing between a first adjacent field (46) and a second adjacent field (48), it seems that the Contrast bar moves relative to the first adjacent field (46) and the second adjacent field (48) when the image (42) is tilted, in which the image is formed by the method according to claim 10.