WO2025149523A1

WO2025149523A1 - 3d effect printing method

Info

Publication number: WO2025149523A1
Application number: PCT/EP2025/050343
Authority: WO
Inventors: Roger Jacot; Joachim LACHMANN; Stefan KÜFFER; Achim KURRECK
Original assignee: Sun Chemical BV
Current assignee: Sun Chemical BV
Priority date: 2024-01-09
Filing date: 2025-01-08
Publication date: 2025-07-17
Anticipated expiration: 2026-07-09

Abstract

A method of creating a 3-D effect printed image, which may also have a holographic effect, and a gravure printing press apparatus that can be used in said method.

Description

3D EFFECT PRINTING METHOD

Background

The concept of a magnetically induced pattern with magnetizable pigments is known, but the method of the present application is not described and no such magnetized patterns have been observed on the market. This is due to the preparation of the counterpressure cylinder of a gravure printing press with the permanent magnets being very difficult and impractical due to time and cost concerns.

In preliminary tests either (a) the desired pattern from a magnetic foil must be cut out and inserted into a former plate (underlay sheet) in the counterpressure cylinder, which is impractical due to being very time consuming; or (b) the magnet is filled as a hot-melt paste (magnetic particles in a thermoplastic polymer) into a cut out form in the underlay sheet in the counterpressure cylinder and additionally axially magnetized, which is also very time consuming and technically difficult. Alternatively, the pattern is directly magnetized on a magnetic foil and mounted on the counterpressure cylinder, which is not economically viable since each desired pattern requires a specific magnetic coil for the impulse magnetization.

WO 2007/131833 Al discloses a coating composition for the production of a magnetically induced image, consisting of volatile and non-volatile components and the use of the composition for the production of a magnetically induced image coating on a substrate with the help of applied magnetic fields.

Summary of the invention

A solution to the problems described above and the subject of the present application is to inverse the process, i.e. the desired pattern is demagnetized in an axially magnetized magnetic foil, such as a NdFeB (neodymium iron boron) magnetic foil, which is mounted around the counterpressure cylinder. This can be done thermally and very efficiently with a laser. By varying the power of the laser, a different magnetic force of the magnetic foil can be reached. In this method magnets do not have to be adjusted. Instead, only the laser needs to be adjusted, which is a much easier and faster process. The laser may comprise one or more lenses to increase the energy density of the laser beam.

The present invention provides a method of creating a 3D effect printed image, comprising the steps of:

A. mounting an axial magnetized magnetic foil on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press;

B. lasering a pattern on the magnetic foil by laser-thermal demagnetization;

C. printing the desired pattern on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image;

D. curing the ink or coating with UV radiation to fix the printed 3D effect.

Step B of lasering a pattern on the magnetic foil by laser-thermal demagnetization can take place whilst the magnetic foil is mounted on a cylinder of the gravure printing press as specified in step A, or can take place before the magnetic foil is mounted on a cylinder of the gravure printing press as specified in step A. Preferably, step B takes place before step A. When step B takes place before step A, the laser-thermal demagnetization is preferably conducted using a laser engraver. Further detail regarding how a laser engraver may be used to laser a pattern onto a magnetic foil by laser-thermal demagnetization is provided below.

The present invention also provides a method of reconditioning a magnetic foil mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press, comprising the steps of: a. completely demagnetizing the magnetic foil mounted on the counterpressure and/or gravure cylinder and/or additional cylinder; b. magnetizing the magnetic foil with magnets or coils to form an axial magnetized magnetic foil; c. lasering a pattern on the magnetic foil by laser-thermal demagnetization; d. printing the desired pattern on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image; e. curing the ink or coating with UV radiation to fix the printed 3D effect.

Preferably, the magnetic foil that is completely demagnetized in step (a) comprises a pattern of magnetized and demagnetized areas prior to being completely demagnetized.

The present invention also provides a method of reconditioning a magnetic foil mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press, comprising the steps of: i. removing the magnetic foil from the cylinder on which it is mounted on a gravure printing press; ii. completely demagnetizing the magnetic foil; iii. magnetizing the magnetic foil with magnets or coils to form an axial magnetized magnetic foil; iv. lasering a pattern onto the magnetic foil by laser-thermal demagnetization; v. re-mounting the magnetic foil on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press; vi. printing the desired pattern on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image; vii. curing the ink or coating with UV radiation to fix the printed 3D effect. Preferably, the magnetic foil that is reconditioned comprises a pattern of magnetized and demagnetized areas prior to step (i).

Step (iv) of lasering a pattern onto the magnetic foil by laser-thermal demagnetization may take place after remounting the magnetized magnetic foil on a cylinder of the gravure printing press in step (v), or can performed after step (iii) and before step (v), i.e. before mounting the magnetized magnetic foil on a cylinder of the gravure printing press. Preferably, step (iv) is performed after step (iii) and before step (v), in which case it preferably comprises transferring the axial magnetized magnetic foil obtained in step (iii) to a laser engraver and using the laser engraver to laser a pattern onto the magnetic foil by laser-thermal demagnetization.

The present invention also provides a gravure printing press apparatus comprising an axial magnetized magnetic foil mounted on the counterpressure cylinder of the gravure printing press and/or the gravure cylinder of the gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of the gravure printing press, wherein the magnetic foil is partially demagnetized such that it bears a pattern of magnetized and demagnetized areas.

Further details of the invention are provided in the detailed description below and in the appended dependent claims.

Detailed description of the invention

The present application describes a method for producing a 3D effect by gravure printing, which may also result in holographic effects. The 3D effect is produced by permanent magnetic foil from the backside of a non-magnetic substrate (preferably carton board but could also be a plastic foil, aluminum foil, laminated carton board, etc.) which interacts with the orientation of a magnetic pigment that is embedded in a UV-curable gravure printing ink. The oriented pigments in the UV ink are fixed directly after the gravure cylinder by UV light. The magnetization of the pigments can also occur with permanent magnets in the gravure cylinder and/or an additional cylinder on the backside of the substrate between the printing unit and drying station.

A scheme of the printing procedure with magnets on the counterpressure cylinder and magnetic ink is depicted in Figure 1.

The ink with the magnetic pigments are printed on the substrate (e.g. board). The pigments in the ink are aligned by a magnetic field, which is induced by axially magnetized magnetic foils, which are mounted on the counterpressure cylinder and/or gravure cylinder and/or an additional cylinder on the backside of the substrate between the printing unit and drying station. Preferably, the axially magnetized magnetic foil is fixed on the counterpressure cylinder of the gravure printing press.

The ink is dried while the pigments are still aligned. Curing is performed when the ink film is still in liquid form, preferably immediately (within several seconds) after printing. Preferably, the ink or coating is cured 0.01-10 seconds after being applied to the substrate, more preferably 0.01-5 seconds after being applied to the substrate and even more preferably 0.01-2 seconds after being applied to the substrate. The ink is preferably cured by UV radiation.

The magnetic foil used in the present invention preferably comprises a magnetic material selected from the group consisting of NdFeB, ferrite, SmCo, and other alloys, wherein said other alloys comprise Fe in combination with at least one of Ni and Co, and optionally further comprise other additional metals besides Ni and/or Co. Most preferably, the magnetic foil is a NdFeB magnetic foil (e.g. a Nd2Fei4B foil). The term “NdFeB magnetic foil” preferably means a material is sheet form that comprises NdFeB powder (e.g. Nd2Fei4B powder) dispersed in a polymer material.

The magnetic foil used in the present invention is preferably a material in sheet form. The magnetic foil is preferably provided in the form of a sheet (e.g. as a tape), which may be cut to the required size before mounting on a cylinder of the gravure printing press. The magnetic foil is removable (i.e. detachable) in sheet form from the cylinder on which it is mounted on the gravure printing press without damaging the integrity of the magnetic foil, such that it can later be remounted on a cylinder of the gravure printing press. This facilitates reconditioning of the magnetic foil by removing it from the printing press, completely demagnetizing it, then axially remagnetizing it and lasering on a new pattern by laser-thermal demagnetization, preferably using a laser engraver which is a particularly efficient way of lasering on a new pattern. This enables the magnetic foil to be reused many times (theoretically forever), which is a significant advantage over systems where a polymer material (e.g. a hot-melt polymer) containing magnetic powder may be applied to a cylinder of a printing press in molten form and then hardened in situ, such that the magnetic polymer material cannot be removed from the cylinder without destroying the material. Naturally, the magnetic foil used in the present invention should be sufficiently flexible to be wound around a cylinder of a gravure press.

The magnetic foil preferably comprises magnetic powder dispersed in a polymer material. The content of the magnetic powder in the polymer is preferably at least about 50% by mass, more preferably in the range from about 60% to about 80% by mass, relative to the overall mass of the magnetic foil. The magnetic powder may be any of the magnetic materials listed above (NdFeB, ferrite, SmCo, and other alloys, wherein said other alloys comprise Fe in combination with at least one of Ni and Co, and optionally further comprise other additional metals besides Ni and/or Co), and is most preferably NdFeB (e.g. Nd2Fei4B powder). The polymer may be a plastic or rubber material, preferably a rubber polymer material. A preferred rubber polymer material is nitrile butadiene rubber (NBR).

Therefore, a preferred magnetic foil for use in all methods and gravure printing press apparatuses of the present invention is a material in sheet form (e.g. a tape) comprising NdFeB powder dispersed in a rubber polymer material, preferably nitrile butadiene rubber. This magnetic foil preferably comprises in the range from about 60% to about 80% NdFeB powder by mass, relative to the overall mass of the magnetic foil. This magnetic foil is removable from the cylinder of the gravure printing press on which it is mounted. In a preferred embodiment, an axial magnetized NdFeB magnetic foil is fixed on the counterpressure cylinder of a gravure printing press. Preferably, the axial magnetized NdFeB magnetic foil has a thickness of l-2mm.

The term “axial magnetized magnetic foil” refers to a foil that is magnetized such that the magnetization is from one side of the foil to the other, i.e. the magnetic induction lines go from one pole to the other from top to bottom of the foil. This means that one face of the foil has north polarity and the other face has south polarity.

Axial magnetized magnetic foil is preferred rather than multipolar magnetized foil, wherein the 3D effect is either lost or greatly diminished. Axial and multipolar magnetized foils are depicted in Figure 2.

The term “lasering a pattern on the magnetic foil by laser-thermal demagnetization” refers to using a laser to thermally demagnetize or partially demagnetize certain areas of the magnetic foil.

The printed samples produced on an industrial scale gravure printing press using the method of the present invention show a 3D pattern, with a simulated depth of about 2-5 mm and with a shadow which moves with the visual point of view and with the movement of the prints. Additionally, an unexpected holographic effect could be observed on a printed parquet pattern (see Figure 4).

The method of the present application was successfully tested with small 2mm magnetic plates (2mm x 300mm x 100mm) to print desirable 3D patterns (see Figures 3 & 4). For these tests a puzzle pattern (Fig. 3) and a parquet pattern (Fig. 4). were printed. Both prints show a 3D effect with a simulated depth of about 2-3 mm. Even the shadow of the “higher” parts in the pattern shifts by moving the sample. Additionally, some parts of the parquet pattern disappear or rise by moving the sample, giving a holographic effect. Scale-up was successfully carried out on industrial scale with a MOOG gravure printing press with similar 3D and holographic effects seen.

MOOG press conditions: 3000 - 7000 sheets / hour (specifically 5000 sheets / hour); the dimension of one sheet is 700 x 1000 mm.

The examples of the present application use magnetic gold and green pearl pigments, which are flat pigment plates that orientate in the direction of the magnetic field. However, it is understood that the present invention is not limited to gold and green and many other pearl pigment colors may also be used in the methods of the present invention.

In one preferred embodiment, relatively large particle size pearl pigments are used as this generally enhances the 3D and holographic effects. Preferably, the D(v,0.9) value of the pigment particles as measured by laser diffraction is less than about 100 microns. Preferably, the D(v,0.5) value of the pigment particles as measured by laser diffraction is about 5-50 microns, more preferably 5-30 microns. Therefore, preferably the D(v, 0.5) value of the pigment particles as measured by laser diffraction is about 5-50 microns and D(v, 0.9) as measured by laser diffraction is less than about 100 microns. More preferably, the D(v, 0.5) value of the pigment particles as measured by laser diffraction is about 5-30 microns and D(v, 0.9) as measured by laser diffraction is less than about 100 microns.

In the context of the present invention, the “D(v,0.5)” value refers to the volume distributed median particle diameter (equivalent spherical diameter corresponding to 50% of the volume of all the particles, read on the cumulative distribution curve relating volume % to the diameter of the particles). D(v,0.9) refers to the equivalent spherical diameter corresponding to 90% of the volume of all the particles, read on the cumulative distribution curve relating volume % to the diameter of the particles, i.e. 90% of the particles by volume have a particle size below this value. Particle size distributions can be determined by routine laser diffraction techniques. Unless otherwise stated, particle size distribution measurements as specified or reported herein are as measured by Malvern Instruments’ conventional Malvern Mastersizer 3000 particle size analyzer. A preferred magnetic pearl pigment content of the ink or coating composition is 5-25% by weight of the ink or coating, more preferably 10-20% by weight of the ink or coating, most preferably 12.5-17.5% by weight of the ink or coating. These ranges typically provide the best 3D effect.

Different background colors were tested and can be used, but the results showed that darker background colors (especially black) are preferred as they visually enhance the 3D effect. Therefore, it is preferred that the magnetic ink or coating is printed on black primed board, as this exhibits enhanced 3D and holographic effects. However, it is not mandatory that black primed board is used and other types and colors of substrates may be used.

The 3D effect is also visually enhanced by the use of strong magnets and axial magnetized magnetic foil as opposed to multipolar magnetized magnetic foil. It will naturally be appreciated that the magnetic strength of the axial magnetized foil must be at least the magnetic strength which has an influence on the one or more magnetic pearl pigments in the ink or coating, such that the pigments are applied to the desired area of the substrate which has not been demagnetized. A preferred range for the magnetic strength of the axial magnetized magnetic foil is about 0.05-6.0 kg/cm² (0.49-59 N/cm²), more preferably about 0.08-3.50 kg/cm² (0.8-34 N/cm²). The magnetic strength may also be in the range of about 0.10-2.80 kg/cm² (1-27 N/cm²). The magnetic strength may be measured by placing the magnetic foil on an iron plate and lifting the magnetic foil axially (i.e. vertically upwards) until the magnetic foil tears from the iron plate. The force required to tear the magnetic foil in this way is measured using a tensometer. The iron plate should have a thickness of about 10 mm and may be a technical pure iron plate such as M2/ARMC0 iron with DIN EN 10027-2 material number 1.1003 and a minimum purity of 99.85% iron.

A preferred viscosity for the ink or coating is 20 sec. ± 5 sec. measured with a DIN 53211 flow cup (4.0 mm orifice diameter, 100 ml capacity) at 25 °C.

In the laser-thermal demagnetization step, the laser beam should heat the areas on the magnetic foil that are desired to be demagnetized until they reach a temperature of around the Curie temperature of the magnetic material in areas where full demagnetization is required. However, some degree of demagnetization may be observed below the Curie temperature. Therefore, the areas of the magnetic foil to be demagnetized are preferably heated in this step to a temperature that is at least about 75% of the Curie temperature in Kelvin, preferably at least about 90% of the Curie temperature in Kelvin. The areas of the magnetic foil to be demagnetized may be heated to the Curie temperature or above the Curie temperature, in areas where full demagnetization is required. In the case of NdFeB, the material should be heated by the laser beam to at least about 440 K, preferably at least about 525 K, in the areas to be demagnetized. For full demagnetization, the NdFeB magnetic foil should be heated to about 583K or higher in the desired areas (the Curie temperature of NdFeB magnets is 583 K).

In some cases, such as the ink composition used in Example 1 below, pigment settling over the course of 2-6 months to the bottom of the vessel can create a very thick clay-like material that is difficult to stir and mix homogenously.

In a series of tests aimed at minimizing pigment settling to improve package stability, additives were tested to prevent or minimize pigment settling. In one test, the ink was made more viscous or even thixotropic by employing additives such as like Ca- or Mg- stearate or colloidal silica (e.g. Aerosil®). This was partially successful and represents one possible approach. However, a thixotropic ink can be difficult to homogenously mix and the pigments may not be mixed homogenously during the printing process.

In another test, anti-agglomeration additives were tested. There are many such commercial additives available. It was found that liquid surfactants worked particularly well as antisettling rheological additives in this context. With the use of such additives, the pigment still does show some evidence of settling but can be easily stirred to return the ink to a homogenous state. Therefore, the ink or coating used in the method of the present invention may contain one or more of calcium stearate, magnesium stearate, colloidal silica or a liquid surfactant. Preferably, the ink or coating contains a liquid surfactant.

After the printing process is complete, the magnetic foil can be completely demagnetized by heating to provide fresh and homogeneous demagnetized foil that can be axially magnetized with coils or magnets, which can then be used to create a new pattern by laserthermal demagnetization as described above. The great advantage with this method is that the magnetic foil can be re-used indefinitely (theoretically forever) which eliminates waste and makes the process much more cost effective.

The complete demagnetization of the magnetic foil may take place whilst the magnetic foil is mounted on a cylinder that is part of the gravure printing press or after removing the magnetic foil from the cylinder of the gravure printing press on which it is mounted. Complete demagnetization may be accomplished by heating the magnetic foil to around the Curie temperature of the magnetic material in the foil, or above. Preferably, the magnetic foil is heated to above the Curie temperature of the magnetic material in the foil, in order to achieve complete demagnetization.

Preferably, complete demagnetization is achieved by irradiating the magnetic foil with an infrared heater (e.g. infrared lamp) in the case complete demagnetization takes place whilst the magnetic foil is mounted on a cylinder of the gravure printing press. In the case where the magnetic foil is completely demagnetized after being removed from a cylinder of the gravure printing press, complete demagnetization may be achieved by irradiating the magnetic foil with an infrared heater (e.g. infrared lamp) or by heating the magnetic foil in an oven.

Following complete demagnetization, the magnetic foil is axially magnetized using coils or magnets. A pattern is then lasered onto the magnetic foil by laser-thermal demagnetization. In the case where the magnetic foil has been removed from a cylinder of the gravure printing press, a laser engraver is preferably used for lasering on the pattern by laser-thermal demagnetization.

Laser engravers are also known as “laser engraving machines” or “laser plotter tables”. Those skilled in the art will be familiar with the design of laser engravers. Laser engravers typically comprise a laser, a controller and a flat surface (the flat surface may be referred to as the plotter table). A substrate (in the present case, the magnetic foil) is placed on the flat surface and the laser shines a beam on the substrate. The controller controls the position of the laser. Those skilled in the art can routinely adjust the power of the laser in order to achieve the desired degree of demagnetization by heating to a temperature around the Curie temperature of the magnetic material in the magnetic foil, or above. When a laser engraver is used to laser a pattern onto the magnetic foil, the areas to be demagnetized in order to form the pattern are irradiated with the laser to heat them to a temperature that is preferably at least about 75% of the Curie temperature in Kelvin, more preferably at least about 90% of the Curie temperature in Kelvin. The areas of the magnetic foil to be demagnetized may be heated to the Curie temperature or above the Curie temperature, in areas where full demagnetization is required.

As a less preferred alternative, the magnetic foil may be re-mounted on a cylinder of the gravure printing press and then a pattern may be lasered onto it by laser-thermal demagnetization. A laser mounted on the gravure press may be used to laser on the pattern.

Next, the desired pattern can then be printed on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image, which is then cured by UV radiation in the manner described above.

The magnetic foil bearing a pattern of magnetized and demagnetized areas may then be removed from the cylinder of the gravure press on which it is mounted and demagnetized again, preferably using an oven or an infrared lamp as described above, following which it can be axially remagnetized. Then, a new pattern lasered is onto it using laser-thermal demagnetization and it can be remounted on a cylinder of the gravure printing press (as described above, the new pattern may be lasered onto the magnetic foil after it has been remounted, although this is less preferred). The process of the invention thus facilitates the magnetic foil being re-used indefinitely (theoretically forever) which eliminates waste and makes the process much more cost effective.

The gravure printing press apparatus may have any of the attributes described above in the context of the disclosed methods of the invention.

In particular, the axial magnetized magnetic foil is preferably mounted on the counterpressure cylinder of the gravure printing press. The axial magnetized magnetic foil is preferably a NdFeB magnetic foil (but may also be any other type of magnetized foil, including others described above).

The magnetic foil mounted on a cylinder of a gravure printing press apparatus of the invention is as described above. Thus, the magnetic foil is preferably a material in sheet form. The magnetic foil is preferably provided in the form of a sheet (e.g. as a tape), which may be cut to the required size before mounting on a cylinder of the gravure printing press. The magnetic foil is removable in sheet form from the cylinder (i.e. the foil remains in the form of a sheet (e.g. tape) after being removed from the cylinder) on which it is mounted on the gravure printing press without damaging the integrity of the magnetic foil, such that it can later be remounted on a cylinder of the gravure printing press. This facilitates reconditioning of the magnetic foil by removing it from the printing press, completely demagnetizing it, then axially remagnetizing it and lasering on a new pattern by laserthermal demagnetization, preferably using a laser engraver which is a particularly efficient way of lasering on a new patern. This enables the magnetic foil to be reused many times (theoretically forever), which is a significant advantage over systems where a polymer material (e.g. a hot-melt polymer) containing magnetic powder may be applied to a cylinder of a printing press in molten form and then hardened in situ, such that the magnetic polymer material cannot be removed from the cylinder without destroying the material. Naturally, the magnetic foil used in the present invention should be sufficiently flexible to be wound around a cylinder of a gravure press.

Preferably, the gravure printing press apparatus of the invention is obtained by providing an axially magnetized magnetic foil in sheet form as described above, cutting it to the required size and mounting it on the counterpressure cylinder of the gravure printing press and/or the gravure cylinder of the gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of the gravure printing press. Thus, those skilled in the art will appreciate that the axially magnetized magnetic foil is preferably a sheet of material that is wound around the cylinder of the gravure printing press on which it is mounted.

Therefore, a preferred magnetic foil in the gravure printing press apparatus of the present invention is a material in sheet form comprising NdFeB powder dispersed in a rubber polymer material, preferably nitrile butadiene rubber. This magnetic foil preferably comprises in the range from about 60% to about 80% NdFeB powder by mass, relative to the overall mass of the magnetic foil. This magnetic foil is removable in sheet form from the cylinder of the gravure printing press on which it is mounted.

The gravure printing press apparatus may further comprise an ink tank comprising a magnetic ink, wherein the magnetic ink contains magnetic pearl pigments.

Examples

Example 1

A first test was performed to form a figure, induced by magnetic forces. The first test was carried out with 15% magnetic pearl pigment in a UV-printing ink according to the following formula:

Table 1 : Gold magnetic pearl ink

¹ Sunmica Dark Gold Pigment (Sun Chemical) is a pearl pigment (particles in the 10-60 micron range, with D(v,0.5) = 20 microns).

²UV Primer Heliopac UVLM Coating is solvent free UV-curing coating.

In this set of tests, the magnetic pearl ink in Table 1 was coated with a 24 pm bar coater onto carton board. The coated board was held above a permanent magnet¹ for about 1 second. The 0.6mm distance was controlled by placing a 0.6mm sheet of printing blanket between the permanent (NdFeB) magnet and the substrate in order to simulate the magnetcounterpressure cylinder system. The printed carton board was then cured immediately by UV light. During these tests, the background color on the board was tested, as well as the influence of the strength of a permanent magnet on the magnetic pearl ink and its influence of the viscosity were tested. ’For these experiments NdFeB rod magnets (Diameter 3mm, length = 6mm were used with a magnetic strength of 5.634 kg/cm² (55.267 N/cm²). Ferrite magnets are less preferred as they are typically weaker, but may still be used in the present invention.

Using a round magnet on the Example 1 ink produced an intense 3D figure like a crater with a simulated depth of about 3-5 mm. For this experiment NdFeB disk magnets with a diameter of 13 mm and a thickness of 1mm were used. The magnetic force of such magnet disks is 0.684 kg/cm² (6.712 N/cm²; Supermagnete S-13-01-N; see https://www. supermagnete. ch/eng/).

A second set of experiments was performed using the following magnetic pearl pigments: Sun Chemical: Black Olive™ 90C0Z (SAP: 95950563) Merck: Colorona® Blackstar Red Merck: Colorona® Blackstar Blue Merck: Colorona® Blackstar Gold Merck: Colorona® Blackstar Green

The formulas were the same as in Table 1 (15 parts pigment : 85 parts UV Primer Heliopac UVLM Coating). Testing was performed using the same protocol as described in the paragraph beneath Table 1 (i.e. coating with a 24 pm bar coater onto carton board).

All of the additional magnetic pearl pigments performed very similarly to the Sunmica Dark Gold C025 in Example 1.

Subsequently, tests were performed on an industrial scale printing press from MOOG using the Example 1 ink from Table 1. The permanent magnets with different shapes were sunk into the carton on the counterpressure cylinder, directly below the rubber blanket. During this set of experiments, NdFeB disk magnets (S-13-01-N) were compared to cut-out letters (A, B, C etc.) from a multipolar magnetized NdFeB magnetic foil (NMS-A4-STIC) with a thickness of 1.5mm and a magnetic strength of 0.450 kg/cm² (4.414 N/cm²). The axial magnetized disk magnet was more effective in creating a 3D effect than the multipolar magnetized magnetic foil, even though the magnetic disk was thinner. Therefore an axial magnetized foil with a magnetic strength of 1.27 N/cm² (= 0.13 Kg /cm²) was used for the next experiment.

The MOOG press results using the Example 1 ink from Table 1 were equally as good as the laboratory experiments involving coating with a 24 pm bar coater onto carton board.

Example 2

Table 2: Magnetic pearl ink with anti-settling additive

Forming of the permanent magnets to patterns / letters

In the initial experiments to get a formed magnet, hotmelt polymer, such as polycaprolactone (very low melting point), with NdFeB powder was poured into a recessed mold and axially magnetized. But the handling of these hot melt polymers was very difficult. When axial magnetized NdFeB foil became available, it was decided to test this new material instead of using magnetic hot melt plastics. It was still problematic to cut out the desired figures since this foil is difficult to cut by laser due to it being very temperature stable. Mechanically cutting was also difficult as this material is very brittle and breaks easily.

Subsequently, a new idea was developed - demagnetizing the desired pattern into the magnetic foil by heating with a laser. The difference between magnetization and nonmagnetization can be seen in Figures 3-5. This became the basis for the most preferred embodiments of the present invention. Figures 3 & 4 show examples using a MOOG industrial scale gravure printing press with demagnetized patterns. The pattern for the demagnetization on the magnetic foil was chosen in such a way that there are only two or three alternating “colors”. In Figure 3, the puzzle pattern was chosen, as only the black sections were laser-thermal demagnetized and the white sections were untreated. In Figure 4 one color in the pattern was completely demagnetized, the other color was partially demagnetized and the third color was untreated.

The magnetic foil was heated by laser¹ with varying laser power². A puzzle pattern (Figure 3) was tested in which every second single puzzle was heated with maximum laser power and the single puzzle between was not. A parquet pattern was also tested (Figure 4), where three different laser powers (not demagnetized, semi-demagnetized and completely demagnetized).

’The laser used is LaserPro Spirit GE (GCC). The maximal power is 30 Watt with a wavelength of 10.57 to 10.63 micrometer for the CX P-laser.

²100% laser power output corresponds to 30 Watt; therefore, 40% laser power output corresponds to 12 Watt.

With these thermal treated NdFeB magnetic foils, according to Figures 3 & 4, we prepared the counterpressure cylinder on a MOOG industrial scale gravure printing machine.

MOOG Industrial Scale Print Results

Patterns were printed at an ink viscosity of 15-20 seconds (DIN 53211 flow cup with an orifice diameter of 4.0 mm and a capacity of 100 ml, measured at 25 °C). The printed samples show the expected 3D effect with the puzzle pattern. Every second heightened single puzzle piece appears 2-3mm higher than the deeper neighbor single puzzle. Even the shadow of the imaginary higher single puzzles moves by moving the carton sample. The parquet pattern shows a holographic-like effect. Parts of the pattern disappears with the direction of view. Only one of the three parts from Fig. 4 can be seen (Figure 5). Some parts of the parquet pattern rise, and some parts disappears by moving the print. This is not only a 3D effect, but also produces a holographic-like effect. In a further experiment, a laser plotter table (laser engraver) was successfully used to laser a pattern onto the foil by laser-thermal demagnetization using the following protocol: Apparatus: GCC LaserPro Laser Systems

Model: LaserPro Spirit GE Print Driver

Laser Type: CO2 Laser

Energy Used: Maximum (100%) Power - 30 Watt; 40% Power - 12 Watt

Wavelength: 10.57 - 10.63 mm

Working Area: 812mm (31.968 inches) x 460mm (18.110 inches)

Magnetic Foils: NdFeB Tromaflex magnetic foils 2 x 100 x 297mm.

Using the laser plotter table method, a pattern was lasered onto an axially magnetized magnetic foil by laser-thermal demagnetization using the laser plotter table (laser engraver) and then used on a MOOG gravure printing press (on the counterpressure cylinder) to produce printed examples of the puzzle and parquet patterns (see Figures 3, 4 below). Testing was performed using the MOOG Industrial Scale Print Results protocol above and similar print results were observed (3D and holographic effect).

Embodiments of the invention

The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The method of any one of embodiments 1 to 5", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to " The method of any one of embodiments 1, 2, 3, 4 and 5". Further, it is explicitly noted that the following set of embodiments is not the set of claims determining the extent of protection, but represents a suitably structured part of the description directed to general and specific aspects of the present invention. Embodiments

1. A method of creating a 3D effect printed image, comprising the steps of:

B. lasering a pattern on the magnetic foil by laser-thermal demagnetization;

D. curing the ink or coating with UV radiation to fix the printed 3D effect.

2. A method of reconditioning a magnetic foil mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press, comprising the steps of: a. completely demagnetizing the magnetic foil mounted on the counterpressure and/or gravure cylinder and/or additional cylinder; b. magnetizing the magnetic foil with magnets or coils to form an axial magnetized magnetic foil; c. lasering a pattern on the magnetic foil by laser-thermal demagnetization; d. printing the desired pattern on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image; e. curing the ink or coating with UV radiation to fix the printed 3D effect.

3. A method of reconditioning a magnetic foil mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press, comprising the steps of: i. removing the magnetic foil from the cylinder on which it is mounted on a gravure printing press; ii. completely demagnetizing the magnetic foil; iii. magnetizing the magnetic foil with magnets or coils to form an axial magnetized magnetic foil; iv. lasering a pattern onto the magnetic foil by laser-thermal demagnetization; v. re-mounting the magnetic foil on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press; vi. printing the desired pattern on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image; vii. curing the ink or coating with UV radiation to fix the printed 3D effect. The method of any preceding paragraph, where the printed image has a holographic effect. The method of paragraph 1 , wherein step B takes place before step A, such that a pattern is lasered onto an axial magnetized magnetic foil by laser-thermal demagnetization prior to it being mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press. The method of paragraph 5, wherein the step of lasering a pattern onto an axial magnetized magnetic foil by laser-thermal demagnetization comprises using a laser engraver to perform the laser-thermal demagnetization. The method of any one of paragraphs 1, 5 and 6, comprising mounting the axial magnetized magnetic foil on the counterpressure cylinder of a gravure printing press. 8. The method of paragraph 3, wherein step (iv) is performed after step (iii) and before step (v) and comprises transferring the axial magnetized magnetic foil obtained in step (iii) to a laser engraver and using the laser engraver to laser a pattern onto the magnetic foil by laser-thermal demagnetization.

9. The method of paragraph 2 or paragraph 3, wherein the magnetic foil is mounted on the counterpressure cylinder of a gravure printing press.

10. The method of any one of paragraphs 2, 3, 8 or 9, wherein the step of completely demagnetizing the magnetic foil comprises heating the magnetic foil in an oven or irradiating it with an infrared lamp, preferably wherein the magnetic foil is heated to above the Curie temperature of the magnetic material in the magnetic foil.

11. The method of any preceding paragraph, wherein the ink or coating comprises about 5-25% by weight of one or more magnetic pearl pigments.

12. The method of any preceding paragraph, wherein the D(v,0.9) value of the one or more magnetic pearl pigments is less than 100 microns.

13. The method of any preceding paragraph, wherein the magnetic foil is made from materials selected from the group consisting of NdFeB, ferrite, SmCo, and other alloys, wherein said other alloys comprise Fe in combination with at least one of Ni and Co, and optionally further comprise other additional metals besides Ni and/or Co.

14. The method of any preceding paragraph, wherein the magnetic foil is a NdFeB magnetic foil.

15. The method of any preceding paragraph, wherein the magnetic foil is a NdFeB magnetic foil that is mounted on the counterpressure cylinder of a gravure printing press. 16. The method of any preceding paragraph, wherein the ink has a viscosity of 20 seconds ± 5 seconds, measured with a DIN 53211 flow cup with a 4.0 mm orifice diameter, at 25 °C.

17. The method of any preceding paragraph, wherein the ink or coating is cured about 0.01- 10 seconds after being applied to the substrate, more preferably about 0.01-5 seconds after being applied to the substrate, most preferably about 0.01-2 seconds after being applied to the substrate.

18. The method of any preceding paragraph, wherein the substrate is a board substrate, preferably a black primed board substrate.

19. The method of any preceding paragraph, wherein the magnetic foil is a material in sheet form which is removable from the cylinder on which it is mounted on the gravure printing press.

20. The method of any preceding paragraph, wherein the magnetic foil comprises a magnetic powder dispersed in a polymer material, preferably wherein the polymer material is a rubber polymer material.

21. The method of paragraph 20, wherein the magnetic foil comprises NdFeB powder dispersed in nitrile butadiene rubber.

22. A gravure printing press apparatus comprising an axial magnetized magnetic foil mounted on the counterpressure cylinder of the gravure printing press and/or the gravure cylinder of the gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of the gravure printing press, wherein the magnetic foil is partially demagnetized such that it bears a pattern of magnetized and demagnetized areas.

23. The gravure printing press apparatus of paragraph 22, wherein the axial magnetized magnetic foil is a NdFeB magnetic foil that is mounted on the counterpressure cylinder of the gravure printing press. 24. The gravure printing press apparatus of paragraph 22 or 23, wherein the axial magnetized magnetic foil is a material in sheet form which is removable in sheet form from the cylinder on which it is mounted on the gravure printing press.

25. The gravure printing press apparatus of paragraph 24, wherein the magnetic foil comprises a magnetic powder dispersed in a polymer material, preferably wherein the polymer material is a rubber polymer, most preferably wherein the magnetic foil comprises NdFeB powder dispersed in nitrile butadiene rubber.

26. A printed substrate prepared by the method of any one of paragraphs 1-21.

In the present application, “A and/or B” means A or B, or A and B. “A and/or B and/or C” means any of A, B, C, A and B, A and C, B and C, or A, B and C. Thus “the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press” encompasses:

• the counterpressure cylinder, gravure cylinder and additional cylinder (i.e. all three options);

• the counterpressure cylinder or the gravure cylinder or the additional cylinder (i.e. one of the three options); and

• any combination of two of the counterpressure cylinder, gravure cylinder and additional cylinder (i.e. any two of the three options).

The present invention has been described in detail, including various embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on this invention that fall within the scope and spirit of the invention.

Claims

1. A method of creating a 3D effect printed image, comprising the steps of:

B. lasering a pattern on the magnetic foil by laser-thermal demagnetization;

D. curing the ink or coating with UV radiation to fix the printed 3D effect.

3. A method of reconditioning a magnetic foil mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press, comprising the steps of: i. removing the magnetic foil from the cylinder on which it is mounted on a gravure printing press; ii. completely demagnetizing the magnetic foil; iii. magnetizing the magnetic foil with magnets or coils to form an axial magnetized magnetic foil; iv. lasering a pattern onto the magnetic foil by laser-thermal demagnetization; v. re-mounting the magnetic foil on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press; vi. printing the desired pattern on a substrate using an ink or coating containing one or more magnetic pearl pigments to form a 3D effect printed image; vii. curing the ink or coating with UV radiation to fix the printed 3D effect.

4. The method of any preceding claim, where the printed image has a holographic effect.

5. The method of claim 1, wherein step B takes place before step A, such that a pattern is lasered onto an axial magnetized magnetic foil by laser-thermal demagnetization prior to it being mounted on the counterpressure cylinder of a gravure printing press and/or the gravure cylinder of a gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of a gravure printing press.

6. The method of claim 5, wherein the step of lasering a pattern onto an axial magnetized magnetic foil by laser-thermal demagnetization comprises using a laser engraver to perform the laser-thermal demagnetization.

7. The method of any one of claims 1, 5 and 6, comprising mounting the axial magnetized magnetic foil on the counterpressure cylinder of a gravure printing press.

8. The method of claim 3, wherein step (iv) is performed after step (iii) and before step (v) and comprises transferring the axial magnetized magnetic foil obtained in step (iii) to a laser engraver and using the laser engraver to laser a pattern onto the magnetic foil by laser-thermal demagnetization.

9. The method of claim 2 or claim 3, wherein the magnetic foil is mounted on the counterpressure cylinder of a gravure printing press.

10. The method of any one of claims 2, 3, 8 or 9, wherein the step of completely demagnetizing the magnetic foil comprises heating the magnetic foil in an oven or irradiating it with an infrared lamp, preferably wherein the magnetic foil is heated to above the Curie temperature of the magnetic material in the magnetic foil.

11. The method of any preceding claim, wherein the ink or coating comprises about 5-25% by weight of one or more magnetic pearl pigments.

12. The method of any preceding claim, wherein the D(v,0.9) value of the one or more magnetic pearl pigments is less than 100 microns.

13. The method of any preceding claim, wherein the magnetic foil is made from materials selected from the group consisting of NdFeB, ferrite, SmCo, and other alloys, wherein said other alloys comprise Fe in combination with at least one of Ni and Co, and optionally further comprise other additional metals besides Ni and/or Co.

14. The method of any preceding claim, wherein the magnetic foil is a NdFeB magnetic foil.

15. The method of any preceding claim, wherein the magnetic foil is a NdFeB magnetic foil that is mounted on the counterpressure cylinder of a gravure printing press.

16. The method of any preceding claim, wherein the ink has a viscosity of 20 sec. ± 5 sec. measured with a DIN 53211 flow cup with an orifice diameter of 4.0 mm, at 25 °C.

17. The method of any preceding claim, wherein the ink or coating contains a liquid surfactant.

18. The method of any preceding claim, wherein the ink or coating is cured 0.01-10 seconds after being applied to the substrate, more preferably 0.01-5 seconds after being applied to the substrate, most preferably 0.01-2 seconds after being applied to the substrate.

19. The method of any preceding claim, wherein the substrate is a board substrate.

20. The method of claim 19, wherein the board substrate is a black primed board.

21. The method of any preceding claim, wherein the laser energy in the laser-thermal demagnetization step is in the range of 6-30 watts.

22. The method of any preceding claim, wherein the laser-thermal demagnetization is performed using a laser that comprises one or more lenses to increase the energy density of the laser beam.

23. The method of any preceding claim, where the areas of the magnetic foil to be demagnetized in the laser-thermal demagnetization step are heated to a temperature of at least 75% of the Curie temperature of the magnetic foil in Kelvin, preferably at least about 90% of the Curie temperature of the magnetic foil in Kelvin.

24. The method of any preceding claim, wherein the magnetic foil is a material in sheet form which is removable from the cylinder on which it is mounted on the gravure printing press.

25. The method of any preceding claim, wherein the magnetic foil comprises a magnetic powder dispersed in a polymer material, preferably wherein the polymer material is a rubber polymer material.

26. The method of claim 25, wherein the magnetic foil comprises NdFeB powder dispersed in nitrile butadiene rubber.

27. A gravure printing press apparatus comprising an axial magnetized magnetic foil mounted on the counterpressure cylinder of the gravure printing press and/or the gravure cylinder of the gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of the gravure printing press, wherein the magnetic foil is partially demagnetized such that it bears a pattern of magnetized and demagnetized areas.

28. The gravure printing press apparatus of claim 27, wherein the axial magnetized magnetic foil is mounted on the counterpressure cylinder of the gravure printing press.

29. The gravure printing press apparatus of claim 27 or claim 28, wherein the axial magnetized magnetic foil is a NdFeB magnetic foil.

30. The gravure printing press apparatus of any one of claims 27-29, wherein the axial magnetized magnetic foil is a material in sheet form which is removable in sheet form from the cylinder on which it is mounted on the gravure printing press.

31. The gravure printing press apparatus of claim 30, wherein the magnetic foil comprises a magnetic powder dispersed in a polymer material, preferably wherein the polymer material is a rubber polymer material, most preferably wherein the magnetic foil comprises NdFeB powder dispersed in nitrile butadiene rubber.

32. The gravure printing press of any one of claims 27-31, wherein the gravure printing press is obtained by providing an axially magnetized magnetic foil in sheet form and mounting it on the counterpressure cylinder of the gravure printing press and/or the gravure cylinder of the gravure printing press and/or an additional cylinder on the backside of the substrate between the printing unit and drying station of the gravure printing press, preferably wherein the axially magnetized magnetic foil is cut to the required size before mounting it.

3. The gravure printing press apparatus of any one of claims 27-32, wherein the apparatus further comprises an ink tank comprising a magnetic ink, wherein the magnetic ink contains magnetic pearl pigments.