Patent Application
20150231912
The present invention relates to a magnetic security element showing a three-dimensional (3D) moving hidden image effect and a method of printing the same, and more particularly to a magnetic security element showing a 3D moving hidden image effect, which is produced by printing a predetermined pattern on a substrate using magnetic ink, applying a magnetic field to the pattern-printed substrate by magnets having various shapes to form magnetically induced images, and drying and curing the substrate having the magnetically induced image formed thereon, and to a method of producing the magnetic security element.
Various cards such as cash cards or credit cards, various certificates such as passports, policies or driver licenses, checks, securities, paper money, brand products, industrial product materials that are imparted with information such as fabrication history, food labels that are imparted with information with production places or production dates, etc., can be forged or altered. Security features for identifying forgery and preventing forgery by copying include sophisticated guilloche patterns, intricate screen traps, complex drawings composed of lines having different thicknesses, and various special security features. With the development of printing techniques, many studies on the development of special functional materials and the production of specialty inks from the functional materials have been conducted, and the development of a technology for adding security features to printed images is also increasing.
As this technology for preventing the counterfeit of articles, various types of optically variable devices have been used. Among them, optically variable ink (OVI) that changes color depending on viewing angle is particularly important, and is used to print the surface and witness that show a viewing angle-dependent color.
In recent years, in order to maximize such optically variable effects, printing inks or magnetic optically variable inks that allow magnetically induced images, designs and patterns to be produced in a coating by the application of a magnetic field have been used. Such magnetic optically variable inks allow a coating to be dried and cured after the orientation of magnetic optically variable pigment particles in the coating, so that magnetically induced images, designs or patterns are recognized to have a three-dimensional or relief-type appearance, even though the images, designs or patterns are still in a geometrically flat state.
Korean Patent Laid-Open Publication No. 10-2009-0068249 discloses a device or method of magnetically transferring indicia, such as a design or an image, to a wet coating layer comprising magnetic or magnetizable particles, applied to a sheet or a substrate. However, a magnetically induced design produced by the method merely shows an optically variable effect, and the patent publication does not disclose that a magnetically induced image, design or pattern shows reversible appearance and disappearance effects by tilting or rotation together with 3D mobility by a change in the intensity of a magnetic field.
Accordingly, the present inventors have made extensive efforts to solve the above-described problems, and as a result, have found that a magnetic security element showing a 3D moving hidden image effect can be produced by printing a predetermined pattern comprising magnetic ink-printed regions alternating with non-printed regions, applying a magnetic field to the pattern-printed substrate by magnets having various shapes to form a magnetically induced image, and drying and curing the substrate having the magnetically induced image formed thereon, thereby completing the present invention.
It is an object of the present invention to provide a magnetic security element showing a 3D moving hidden image effect, which is produced by printing a predetermined pattern on a substrate using a magnetic ink, applying a magnetic field to the pattern-printed substrate by magnets having various shapes to form a desired image, and drying and curing the substrate having the image formed thereon, and a method of producing the magnetic security element.
To achieve the above object, the present invention provides a magnetic security element having a 3D moving hidden image effect, comprises: a substrate having an alternating pattern of a printed region and non-printed region of a magnetic ink on surface of the substrate, wherein in case that a magnetic field is applied to the pattern-printed substrate by a magnet, a magnetically induced image is formed, thereby showing a 3D moving hidden image effect.
The present invention also provides a method of producing a magnetic security element having a 3D moving hidden image effect, comprising the steps of: (a) printing an alternating pattern of a printed region and non-printed region on a surface of a substrate using magnetic ink; (b) applying a magnetic field to the pattern-printed substrate by a magnet to form a magnetically induced image; and (c) drying and curing the substrate having the magnetically induced image formed thereon.
a and 2b are cross-sectional views showing lines 1 printed on an opaque substrate 2 or a transparent substrate 3 by screen printing.
c is a partially enlarged view of
a is a top plan view showing a printed material having a donut-shaped, magnetically induced image formed thereon, and
a and 7b are top plan views showing that the color of an optically variable pigment is changed from magenta to gold by a change in viewing angle or the position of a light source while a 3D pattern portion applied with a magnetic field appears like it moves (d and d′) from the original position (solid dotted line).
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Generally, the nomenclature used herein and the experiment methods are those well known and commonly employed in the art.
In the present invention, a 3D moving hidden image is realized by the printing of a specific pattern, the use of magnets having various shapes, and the control of intensity of a magnetic field, and the effect thereof can be identified by tilting and rotation. As used herein, the term “3D moving” means the dynamic effect of the image, and the term “hidden image” means an image that appears depending on viewing angle, and is a security feature for preventing forgery, which cannot be realized by copying.
In one aspect, the present invention is directed to a magnetic security element having a 3D moving hidden image effect, comprises: a substrate having an alternating pattern of a printed region and non-printed region of a magnetic ink on surface of the substrate, wherein in case that a magnetic field is applied to the pattern-printed substrate by a magnet, a magnetically induced image is formed, thereby showing a 3D moving hidden image effect.
In another aspect, the present invention is directed to a method of producing a magnetic security element having a 3D moving hidden image effect, comprising the steps of: (a) printing an alternating pattern of a printed region and non-printed region on a surface of a substrate using magnetic ink; (b) applying a magnetic field to the pattern-printed substrate by a magnet to form a magnetically induced image; and (c) drying and curing the substrate having the magnetically induced image formed thereon.
As shown in
In the pattern, a printed distance (pd) may be larger than a non-printed distance (npd).
In the present invention, a silk screen printing technique was used to print the pattern, but is not limited thereto, and other methods capable of applying ink may also be used. Specifically, gravure printing, lithographic printing, flexographic printing, letterpress printing, intaglio printing, or conventional methods known to apply ink may be used, in which ink can be applied to different regions to form lines having different thicknesses or colors. The mesh size of a silk screen for forming a designed solid line pattern may be 150-250 meshes, but is preferably 150 meshes, because an increase in the number of meshes leads to an increase in the thickness of ink.
In the present invention, the ratio of the non-printed distance (npd) to the printed distance (pd) in the line pattern may be 0.25-1.25. In the present invention, in order to examine the 3D moving hidden image effect of a printed pattern, an experiment was performed using a printed distance of 1-2 mm while changing the non-printed distance to 0.25 mm, 0.5 mm, 0.75 mm, 1.25 mm, 1.5 mm and 1.75 mm. As a result, it was shown that the 3D moving hidden image effect was better as the printed distance was larger and the non-printed distance was smaller, and that when the printed distance was larger than the non-printed distance, the 3D moving hidden image effect appeared, and when the printed distance was smaller than the non-printed distance, the effect did not appear or was insignificant (see Tables 1 to 3). Particularly, it was shown that when the ratio of the non-printed distance (npd) to the printed distance (pd) was 0.25-1.25, the 3D moving hidden image effect was good, and when the ratio was 0.5-0.75, the 3D moving hidden image effect was better.
In addition, the effect of the ratio of lightness background (Lb) to lightness print (Lp), (Lb/Lp), was examined. As a result, it was shown that the 3D moving effect was regardless of lightness. However, in order to realize a hidden image, the ratio of lightness background (Lb) to lightness print (Lp) may be 1.2-100, preferably 60-100, and more preferably 80-100. When the ratio of lightness background (Lb) to lightness print (Lp) is less than 1.2, the hidden image effect does not appear.
In the present invention, a substrate having a thickness of 50-150 μm is used as a base on which a magnetic ink is to be printed. As shown in
A magnetic ink (1 in
The UV curable ink may be prepared by mixing 30-35 wt % of an oligomer, 35-40 wt % of a monomer, 3-5 wt % of a photopolymerization initiator, and 10-20 wt % of a magnetic pigment and stirring the mixture, but is not limited thereto. The oligomer may be a urethane-based acrylic resin, and the monomer may be a low-viscosity monomer consisting of a mixture of pentaerythritol hexaacrylate and pentaerythritol triacrylate. In addition, the photopolymerization initiator may be Micure MS-7 (MOWONSC) comprising 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone.
The solvent-evaporating ink may be prepared by mixing 25-30 wt % of thermoplastic resin, 30-40 wt % of a solvent, 5-10 wt % of a drying retarder, and 10-20 wt % of a magnetic pigment, but is not limited thereto. The thermoplastic resin may be a copolymer of polyvinyl alcohol with polyvinyl acetate, and the solvent may be a mixture of cyclohexane and ethylbenzene.
In the case of the solvent-evaporating ink among the two kinds of inks, the separation of some of the components occurs during curing, and for this reason, the selection of hot-air intensity and drying time (1-2 minutes), which influence the orientation of a magnetic pigment that is aligned by magnetic patterning, is particularly important. Thus, in order to obtain a screen-printed material having a highly reproducible, magnetically induced image, UV curable ink is preferably used.
A magnet is used to apply a magnetic field to the wet, screen-printed material after screen printing, but curing. The magnet is characterized by a uniaxial magnetization direction, and may be an NdFeB magnet, an SmCo magnet, a ferrite magnet, a ferrite magnet, an Alnico magnet, a Fe—Cr—Co magnet, an Sm—Fe—N magnet or an electromagnet. However, an NdFeB magnet or a ferrite magnet is more preferable in terms of availability, durability and strength.
a is a top plan view showing UV-cured 3D pattern images caused by the directional patterning of optically variable pigment particles oriented by applying a magnetic field to a wet, screen-printed material before curing as shown in
When UV curable ink is used to maintain the orientation of pigment particles oriented in the direction of magnetic field lines, a 3D moving hidden image is realized by the orientation of the magnetic pigment particles after drying the ink by UV irradiation, and when solvent-evaporating ink is used, a 3D moving hidden image is realized by the orientation of the magnetic pigment particles after naturally drying the ink by solvent evaporation, followed by curing.
In order to examine the 3D moving effect of the present invention, a cured substrate with donut-shaped magnetically induced images were tilted in a certain direction (upward and downward).
a and 7b schematically show color and mobility, which change upon tilting. As shown therein, when a printed material is tilted upward (
In addition, as shown in
Thus, the magnetic security element according to the present invention, which shows the 3D moving hidden image effect, can be used as a security element for preventing the forgery or alteration of paper money, securities, identification cards, cash or credit cards, bills, etc., and provides 3D dynamic effects that can be visually identified. In addition, images in prior security features for preventing forgery were transferred by copying, whereas the 3D moving hidden image according to the present invention is visible only under a specific condition, and cannot be transferred using current printers, scanners and duplicators.
Hereinafter, the present invention will be described in further detail with reference to examples. It will be obvious to a person having ordinary skill in the art that these examples are illustrative purposes only and are not to be construed to limit or change the scope of the present invention.
36 wt % of an oligomer, 40 wt % of a monomer, 4 wt % of a photopolymerization initiator and 20 wt % of a magnetic pigment were mixed and stirred to prepare a UV curable ink. As the monomer, a low-viscosity monomer consisting of a mixture of pentaerythritol hexaacrylate and pentaerythritol triacrylate was used. As the photopolymerization initiator, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone was used, and as the optically variable pigment, Colorcrypt M (Merck) was used.
Using the UV curable ink prepared in Example 1, solid line patterns as shown in
The distance between the magnet and the substrate was controlled to 5 mm while the same experimental conditions were used. As a result, it was shown that, as the distance of the magnet from the substrate decreased, the orientation of the magnetic pigment particles was improved, and thus the 3D moving hidden image effect was better (Table 2).
In order to examine the effect of the screen mesh number, an experiment was performed using 200 screen meshes under the same conditions (the distance between the magnet and the substrate: 3 mm) as shown in Table 1. As a result, it was shown that, as the number of meshes increased, the amount of ink decreased, and thus the 3D moving hidden image effect was reduced compared to when 150 screen meshes were used (Table 3).
Using the UV curable magnetic ink prepared in Example 1, a solid line pattern as shown in
After printing, donut-shaped magnetically induced images were formed by applying a magnetic field to the wet printed material using an NdFeB magnet in a state in which the distance between the substrate and the magnet was controlled to 1.5 mm. After the magnetic pigment particles were oriented, the printed material was dried and cured using a UV curing device in order to maintain the particles in the oriented state, thereby obtaining a magnetic security element having 3D moving hidden images (
As described above, the magnetic security element according to the present invention, which shows a 3D moving hidden image effect, can be produced by various printing methods, and can be applied to various cards such as cash cards or credit cards, various certificates such as passports, policies or driver licenses, checks or securities, which can be forged or altered. In addition, it offers a 3D moving hidden image effect, which can be visually identified by tilting or rotation and cannot be realized by copying. Thus, it is particularly useful for the prevention of counterfeit.
Although the present invention has been described in detail with reference to the specific features, it will be apparent to those skilled in the art that this description is only for an embodiment and does not limit the scope of the present invention. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2012-0102110 | Sep 2012 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2013/008323 | 9/16/2013 | WO | 00 |
