阅读说明：本技术 安全颜料 (Security pigments ) 是由 V·P·拉克沙 C·J·德尔斯特 于 2021-06-04 设计创作，主要内容包括：本发明公开了包括抗磁材料层和至少一个附加层的薄片。薄片,例如多个薄片,可以分散在液体介质中以形成组合物。可以将组合物施加到基材的表面以形成安全装置。还公开了一种制造所述安全装置的方法。(The invention discloses a sheet comprising a layer of diamagnetic material and at least one additional layer. Flakes, e.g., a plurality of flakes, can be dispersed in a liquid medium to form a composition. The composition may be applied to the surface of a substrate to form a security device. A method of manufacturing the security device is also disclosed.)

1. A sheet, comprising:

a layer of diamagnetic material; and

at least one additional layer.

2. The wafer of claim 1, wherein the diamagnetic material is bismuth.

3. The lamina of claim 1 wherein the diamagnetic material has a thickness of about-2.00 x 10⁶To about-300.0X 10⁶The volume magnetic susceptibility of (a).

4. The lamina of claim 1 wherein the layer of diamagnetic material has a physical thickness ranging from about 950nm to about 2000 nm.

5. The sheeting of claim 1, wherein the at least one additional layer is selected from the group consisting of a reflector layer, an absorber layer, and a dielectric layer.

6. The wafer of claim 1, wherein the wafer is symmetrical.

7. The wafer of claim 1, wherein the wafer is asymmetric.

8. The lamina of claim 1 wherein the layer of diamagnetic material is a central layer of lamina.

9. A security device, comprising:

a substrate; and

a composition applied to a surface of the substrate; wherein the composition comprises a plurality of the flakes of claim 1 dispersed in a liquid medium.

10. A method of manufacturing a security device, comprising:

dispersing flakes comprising a layer of diamagnetic material and at least one additional layer in a liquid medium to form a composition;

applying the composition to a substrate to form a security device; and

applying a magnetic field to the security device such that the plane of the flakes is aligned perpendicular to the magnetic field.

11. The method of claim 10, wherein the application of the magnetic field is for a time greater than 10 seconds.

12. The method of claim 10, wherein the application of the magnetic field is from a magnet having a maximum energy product greater than about 3.5.

13. The method of claim 10, further comprising curing flakes aligned perpendicular to the magnetic field; and wherein the cured, aligned flakes form opaque regions on the substrate.

Technical Field

The present invention generally relates to a sheet comprising a layer of diamagnetic material; and at least one additional layer. Flakes, e.g., a plurality of flakes, can be dispersed in a liquid medium to form a composition. The composition may be applied to the surface of a substrate to form a security device. A method of manufacturing the security device is also disclosed.

Background

Banknotes often contain many security features to prevent counterfeiting. Among these features are optical security devices that exhibit different illusive optical effects. These effects are caused by the reflection of light by the colour-changing platelets (platelets) dispersed in the layer of security ink printed on the surface of the banknote.

Security inks comprise magnetizable platelets of a colour-changing interference pigment randomly oriented in an organic vehicle (binder). The platelets are ordered along the direction of the lines of the applied magnetic field. In the magnetic field, the patches align with their longest diagonal of the plane along the field lines of the magnetic field, organizing themselves in a head-to-tail chain projecting in the direction of the field lines. The known magnetizable color-changing interference pigments in platelet form are multilayer thin-film structures comprising a plurality of materials.

The platelets contain several different metals. One of the metals is ferromagnetic so that the platelets respond to an applied magnetic field. Many thin films of magnetosensitive metals and their alloys have been described. They include Ni, Co, Fe, Gd, Tb, Dy, Er and their alloys, FeSi, FeNi, FeCo, FeNiMo, SmCo₅、NdCo₅、Sm₂Co₁₇、Nd₂FeI₄B、Sr₆Fe₂O₃、TbFe₂、AlNiCo、Fe₃O₄、NiFe₂O₄、MnFe₂O₄、CoFe₂O₄Or YIG or GdIG type garnet. These metals exhibit a directional dependence.

The directional dependence of the magnetic properties of a material is its magnetic anisotropy. Ferromagnets exhibit several different types of magnetic anisotropy, such as magnetocrystalline anisotropy, shape anisotropy, magnetoelastic anisotropy, exchange anisotropy, induced magnetic anisotropy, and texture induced anisotropy. The bulk magnetic anisotropy of the platelet is the sum of all these factors. However, these factors contribute differently to the directionality of the patch. The shape anisotropy contributes most to the platelet orientation when exposed to an external field. In this case, the longest dimension of the magnetised body is similar to the "easy" magnetisation axis, in the case of a patch the longest dimension of the magnetised body is one of its diagonals.

There is a need for another class of magnetic materials that can be used to make banknotes with different illusive optical effects to prevent counterfeiting.

Disclosure of Invention

In one aspect, a sheet is disclosed that includes a layer of diamagnetic material; and at least one additional layer.

In another aspect, a method of manufacturing a security device is disclosed that includes dispersing flakes comprising a diamagnetic material layer and at least one additional layer in a liquid medium to form a composition; applying the composition to a substrate to form a security device; a magnetic field is applied to the security device such that the plane of the lamellae is aligned perpendicular to the magnetic field.

Additional features and advantages of embodiments will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments. The objectives and other advantages of the embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description herein.

Drawings

Several aspects and embodiments of the present invention can be more fully understood from the detailed description and the accompanying drawings, in which:

FIG. 1 shows a magnet;

FIG. 2A shows an enlarged view of a portion of FIG. 2B;

fig. 2B illustrates a magnetic field generated by the magnet of fig. 1 shown in cross-section.

FIG. 3A shows an enlarged view of a portion of FIG. 3B;

FIG. 3B shows magnetic flakes aligned parallel to the magnetic field of FIG. 2B;

FIG. 4A shows an enlarged view of a portion of FIG. 4B;

FIG. 4B illustrates flakes aligned perpendicular to the magnetic field of FIG. 2B, according to one aspect of the present application;

FIG. 5 illustrates the optical effect obtained, for example, from FIGS. 3A and 3B; and

figure 6 shows a security banknote with magnetic pigment (left) and security pigment according to one aspect of the invention (right).

Like reference numerals identify like parts throughout the specification and drawings.

Detailed Description

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide an explanation of various embodiments herein. The layers/components shown in each figure may be described with respect to a particular figure, but it should be understood that the description of a particular layer/component will apply to equivalent layers/components in other figures.

In a wide range and varied embodiment of the present invention, disclosed herein is a sheet comprising a layer of diamagnetic material; and at least one additional layer. Flakes, e.g., a plurality of flakes, can be dispersed in a liquid medium to form a composition. The composition may be applied to the surface of a substrate to form a security device. A method of manufacturing the security device is also disclosed.

The sheet may comprise a layer of diamagnetic material. Electrons in diamagnetic materials can rearrange their orbitals, thereby generating a small persistent current that opposes the magnetic field. In this way, the diamagnetic material can be repelled by the magnetic field. Non-limiting examples of diamagnetic materials include bismuth, copper, mercury, silver, gold, palladium, beryllium, calcium, zinc, lead, cadmium, thallium. In one aspect, the diamagnetic material is bismuth. The diamagnetic material can be an inorganic compound, such as AgCl and BiCl₃. In another aspect, the diamagnetic material can include organic compounds such as aniline, benzene, methane, octane, naphthalene, and diphenylamine.

In order for the diamagnetic material to be affected by a magnetic field, the diamagnetic material should have a specific volume susceptibility range determined by the following formula: XvH, where M is the magnetization of the material (amperes/meter), H is the magnetic field strength (amperes/meter), and XV is negative. In one aspect, the diamagnetic material has a range of about-2.00 x 10⁶To about-300.0X 10⁶The volume magnetic susceptibility of (a); for example, from about-5.00X 10⁶To about-290.0X 10⁶(ii) a As a further example, from about-10.00 x 10⁶To about-285.0X 10⁶。

The layer of diamagnetic material can be present in any suitable physical thickness that allows the diamagnetic material to be affected by a magnetic field. To this end, typically, the layer of diamagnetic material is typically thicker than the layer of magnetic material (e.g., ferromagnetic or paramagnetic material). In one aspect, the diamagnetic material can be present in a layer having a physical thickness ranging from about 250nm to about 3000 nm; for example, from about 500nm to about 3000 nm; as a further example, from about 750nm to about 2500 nm. In another aspect, the layer of diamagnetic material has a physical thickness ranging from about 950nm to about 2000 nm.

The sheet may comprise at least one additional layer, such as a reflector layer, a dielectric layer or spacer layer, and an absorber layer. The at least one additional layer may be present on the first surface of the layer of diamagnetic material. For example, the sheet may have the following structure: diamagnetic material/reflector/dielectric/absorber. In this form, the sheet is asymmetric.

In another aspect, the at least one additional layer may be present on both the first surface and the second surface of the layer of diamagnetic material. For example, the sheet may have the following structure: absorber/dielectric/reflector/diamagnetic material/reflector/dielectric/absorber. In this form, the lamellae are symmetrical. The layer of diamagnetic material can be a central layer or core in the sheet. In another aspect, the sheet may include any and all combinations of layer structures including a layer of diamagnetic material and at least one additional layer. The choice of the material present in the at least one additional layer and the structure of the foil may be designed according to the intended use of the foil.

The reflector layers for the flakes disclosed herein can comprise a metal and/or metal alloy. In one example, any material having reflective properties may be used. Non-limiting examples of materials having reflective properties include aluminum, silver, copper, gold, platinum, tin, titanium, palladium, nickel, cobalt, rhodium, niobium, chromium, and compounds, combinations, or alloys thereof. Examples of other suitable reflective alloys and compounds include bronze, brass, titanium nitride, and the like, as well as alloys of the above listed metals, such as silver-palladium. The reflector layer may have an inherent color such as copper, gold, silver-copper alloy, brass, bronze, titanium nitride, and compounds, combinations, or alloys thereof.

The absorber layer may comprise any absorber material, including selectively absorbing materials and non-selectively absorbing materials. For example, the absorber layer may be formed of a non-selectively absorbing metallic material deposited to a thickness at least partially absorbing or translucent to the absorber layer. Examples of non-selective absorbing materials may be grey metals such as chromium or nickel. Examples of selective absorbing materials may be copper or gold. In one aspect, the absorbing material may be chromium. Non-limiting examples of suitable absorber materials include metal absorbers such as chromium, aluminum, silver, nickel, palladium, platinum, titanium, vanadium, cobalt, iron, tin, tungsten, molybdenum, rhodium, niobium, carbon, graphite, silicon, germanium, cermets, and various combinations, mixtures, compounds, or alloys of the above absorber materials that can be used to form the absorber layer.

Examples of suitable alloys for the absorber material described above may include Inconel (Ni-Cr-Fe), stainless steel, Hastelloy (Ni-Mo-Fe; Ni-Mo-Fe-Cr; Ni-Si-Cu), and titanium-based alloys, such as titanium mixed with carbon (Ti/C), titanium mixed with tungsten (Ti/W), titanium mixed with niobium (Ti/Nb), titanium mixed with silicon (Ti/Si), and combinations thereof. Other examples of suitable compounds for the absorber layer include titanium-based compounds such as titanium silicide (TiSi2), titanium boride (TiB2), and combinations thereof. Alternatively, the absorber layer may be composed of a titanium-based alloy disposed in a Ti matrix, or may be composed of Ti disposed in a titanium-based alloy matrix.

The dielectric layer may act as a spacer in the sheet. The dielectric layer may be formed to have an optical thickness effective for a specific wavelength. The dielectric layer may optionally be transparent or may be selectively absorbing to aid in the color effect of the pigment. Optical thickness is a well-known optical parameter defined as the product η d, where η is the refractive index of the layer and d is the physical thickness of the layer. Typically, the optical thickness of the layers is expressed in terms of a quarter-wave optical thickness (QWOT) equal to 4 η rf/λ, where λ is the wavelength at which the QWOT condition occurs. Depending on the desired color change, the optical thickness of the dielectric layer may be from about 2QWOT at a design wavelength of about 400nm to about 9QWOT at a design wavelength of about 700nm, such as about 2-6QWOT at 400-700 nm. Depending on the desired color characteristics, the dielectric layer may have a physical thickness of about 100nm to about 800nm, for example about 140nm to about 650 nm.

Suitable materials for the dielectric layer include materials having a "high" index of refraction (defined herein as greater than about 1.65), as well as materials having a "low" index of refraction (defined herein as about 1.65 or less). The dielectric layer may be formed of one material or a combination and configuration of materials. For example, the dielectric layer may consist of only a low refractive index material or only a high refractive index material, or a mixture or plurality of sub-layers of two or more low refractive index materials, a mixture or plurality of sub-layers of two or more high refractive index materials, or a mixture or plurality of sub-layers of low and high refractive index materials. Furthermore, the dielectric layer may be partially or completely formed by the high/low dielectric optical stack. When the dielectric layer is formed in part by a dielectric optical stack, the remaining portions of the dielectric layer may be formed of one material or various material combinations and configurations as described above.

Non-limiting examples of suitable high refractive index materials for the dielectric layer include zinc sulfide (ZnS), zinc oxide (ZnO), zirconium oxide (ZrO)₂) Titanium dioxide (TiO)₂) Diamond-like carbon, indium oxide (InO)₃) Indium Tin Oxide (ITO) and tantalum pentoxide (Ta)₂O₅) Cerium oxide (CeO)₂) Yttrium oxide (Y)₂O₃) Europium oxide (Eu)₂O₃) Iron oxides such as iron (II) oxide (FeO)₄) And iron oxide (Fe)₂O) (ferric oxide), hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO)₂) Lanthanum oxide (La)₂O₃) Magnesium oxide (MgO), neodymium oxide (Nd)₂O₃) Praseodymium oxide (Pr)₆O₁₁) Samarium oxide (Sm)₂O₃) Antimony trioxide (Sb)₂O₃) Silicon monoxide (SiO), selenium trioxide (Se)₂O₃) Tin oxide (SnO)₂) Tungsten trioxide (WO), combinations thereof, and the like.

Non-limiting examples of suitable low refractive index materials for the dielectric layer include silicon dioxide (SiO)₂) Aluminum oxide (Al)₂O₃) Such as magnesium fluoride (MgF)₂) Aluminum fluoride (AlF)₃) Cerium fluoride (CeF)₃) Lanthanum fluoride (LaF)₃) Sodium aluminum fluoride (e.g., Na)₃AlF₆、Na₅Al₃F₁₄) Neodymium fluoride (NdF)₃) Samarium fluoride (SmF)₃) Barium fluoride (BaF)₂) Calcium fluoride (CaF)₂) Lithium fluoride (LiF), combinations thereof or metal fluorides having a refractive index of about 1.65 or lessAny other low refractive index material. For example, organic monomers and polymers may be used as the low refractive index material, including dienes or olefins, such as acrylates (e.g., methacrylates), perfluoroolefins, polytetrafluoroethylene (Teflon), Fluorinated Ethylene Propylene (FEP), combinations thereof, and the like.

Flakes, e.g., a plurality of flakes, can be dispersed in a liquid medium to form a composition. Non-limiting examples of liquid media include polyvinyl alcohol, polyvinyl acetate polyvinyl pyrrolidone, poly (ethoxyethylene), poly (methoxyethylene), poly (acrylic acid), poly (acrylamide), poly (oxyethylene), poly (maleic anhydride), hydroxyethylcellulose, cellulose acetate, poly (saccharides) such as gum arabic and pectin, poly (acetals) such as polyvinyl butyral, poly (vinyl halides) such as polyvinyl chloride and polyvinylidene chloride (polyvinylidene chloride), poly (dienes) such as polybutadiene, poly (olefins) such as polyethylene, poly (acrylates) such as polymethyl acrylate, poly (methacrylates) such as polymethyl methacrylate, poly (carbonates) such as poly (oxycarbonyloxymethylene), poly (esters) such as polyethylene terephthalate, polyurethane, poly (siloxanes), poly (sulfides), poly (oxyethylene), poly (meth) acrylate, poly (meth) acrylate, poly (meth) acrylate, poly (meth) acrylate, poly (meth, Poly (sulfones), poly (vinyl nitriles), poly (acrylonitrile), poly (styrene), poly (phenylene) such as poly (2,5 dihydroxy-1, 4-phenylethene), poly (amides), natural rubber, formaldehyde resins, other polymers and mixtures of polymers with solvents.

The composition may be applied to the surface of a substrate to form a security device. The substrate may be made of a flexible material. The substrate may be any suitable material that can receive the deposited layers during the manufacturing process. Non-limiting examples of suitable substrate materials include polymeric meshes such as polyethylene terephthalate (PET), glass foils, glass sheets, polymeric foils, polymeric sheets, metal foils, metal sheets, ceramic foils, ceramic sheets, ionic liquids, paper, silicon wafers, and the like. The thickness of the substrate may vary, but may range, for example, from about 2 μm to about 100 μm, with a further example ranging from about 10 μm to about 50 μm.

A method of manufacturing a security device comprising dispersing flakes comprising a layer of diamagnetic material and at least one additional layer in a liquid medium to form a composition; applying the composition to a substrate to form a security device; a magnetic field is applied to the security device such that the plane of the lamellae is aligned perpendicular to the magnetic field.

The application of the magnetic field comprises placing the substrate with the applied composition on a magnet. The magnet can be a permanent magnet, such as neodymium iron boron, samarium cobalt, ceramic magnet, ferrite magnet, AlNiCo, and the like; or an electromagnet. In one aspect, the magnet may be any magnet capable of generating a magnetic field strength for planarizing a sheet comprising a layer of diamagnetic material. For example, the magnet may have a maximum energy product (BH) greater than about 3.5_{Maximum of}) For example, greater than about 5.5, and as a further example, greater than about 26. In particular, the application of the magnetic field may result from a magnet having a maximum energy product greater than about 3.5.

Planarization of a sheet comprising diamagnetic material can take several seconds to more than a minute, e.g., several minutes. For this purpose, the application of the magnetic field may last for a time greater than 10 seconds, such as greater than 30 seconds, for example greater than one minute.

Factors such as the time available for planarization, the viscosity of the liquid medium, the size of the flakes, and the magnetic properties of the flakes can affect the desired flake alignment. In this application, the flakes comprising the layer of diamagnetic material are aligned perpendicular to the magnetic field.

The method may further comprise curing the flakes aligned perpendicular to the magnetic field. The curing step may comprise any drying and/or curing process that fixes the aligned flakes, for example using ultraviolet light, visible light, infrared or electron beams. In this manner, the cured, aligned flakes can form opaque regions on the substrate.

In optical security devices printed with magnetisable pigments, the optical effect is based on the reflection of light falling on flat pigment platelets towards the viewer, as shown in fig. 5. The magnetic platelets 18 are arranged along the magnetic field lines 20 as a fresnel-like convex cylindrical reflector. Light 22 from a light source 24 extends into the plane of the die 18. The smooth surface of the differently oriented platelets reflects light rays 22 into the surrounding space in a number of directions governed by the law of reflection. The light ray 26 that enters the eye of the viewer 28 without loss appears brightest. All other reflected rays are perceived as different shades of gray. In the viewer's mind, all the light rays together look like a bright band 30 on a dark background, creating an optical effect. The differences in optical effects produced by the lamellae are explained in detail below.

Examples

Preparing a flake having the following structure: Cr/MgF₂/Al/Bi1000nm/Al/MgF₂and/Cr. The flakes are dispersed in a liquid medium to form a composition, such as a UV curable ink. The composition is applied to a paper substrate using screen printing techniques to form a security device. The composition was exposed to a magnetic field from a ring magnet as shown in fig. 1.

The magnet exhibits a magnetic field as shown in fig. 2A and 2B. As shown in fig. 2A, the magnetic field lines in the middle of the top surface of the magnet are oriented perpendicular (middle arrow) to the surface. In addition, the magnetic field line direction near the edges of the surface is horizontal, as indicated by the arrows to the right and left.

Fig. 4A and 4B show the composition when exposed to the magnetic field shown in fig. 2A and 2B. As shown in fig. 4B, a substrate 10, such as a paper card, is coated with a layer 12 of the composition, i.e., flakes 16, dispersed in a liquid medium. The substrate 10 is placed on a magnet 14, the magnet 14 being shown in cross-section in fig. 1. The flakes 16 are repelled by the magnetic field and oriented in the liquid medium as follows: the plane of the lamellae 16 is perpendicular to the magnetic field lines. Fig. 4A shows an enlarged view of a portion of fig. 4B.

Comparative example

Preparing a flake having the following structure: Cr/MgF₂/Al/Ni60nm/Al/MgF₂and/Cr. The flakes are dispersed in a liquid medium to form a composition, such as a UV curable ink. The composition is applied to a paper substrate using screen printing techniques to form a security device. The composition was exposed to a magnetic field from a ring magnet as shown in fig. 1. The magnetic field is shown in fig. 2A and 2B.

Fig. 3A and 3B illustrate the composition when exposed to the magnetic field illustrated in fig. 2A and 2B. As shown in fig. 3B, a substrate 10, such as a paper card, is coated with a layer 12 of the composition, i.e., a sheet 18, dispersed in a liquid medium. The substrate 10 is placed on a magnet 14, the magnet 14 being shown in cross-section in fig. 1. The flakes 18 themselves are oriented in the liquid medium as follows: the plane of the lamellae 18 is parallel to the magnetic field lines. Fig. 3A shows an enlarged view of a portion of fig. 3B.

Referring now to fig. 6, two ink-filled circular areas 1 and 2 of the same size were printed onto a substrate (paper test banknote) through the same screen and aligned using a colorless transparent UV curable composition containing flakes of the invention (containing Bi) and comparative flakes (containing Ni) dispersed at similar concentrations. Each printed feature was placed on top of the same permanent magnet and after aligning the flakes in a magnetic field, the composition was cured with UV light.

The composition in region 1 comprises a comparative flake with a magnetizable nickel core layer. The area 1 shows a semi-transparent gray filled circle and two narrow bright circular outlines 3. The gray filled regions appeared because the nickel-containing flakes were aligned perpendicular to the substrate surface, i.e., the longest plane of the flakes was aligned parallel to the magnetic field, as shown in fig. 3A and 3B. The aligned flakes are at a very steep angle relative to the substrate surface, spaced far apart, allowing the substrate pattern to be viewed through the cured colorless composition. The bright outline 3 refers to the position where the flakes are aligned parallel to the substrate surface at the magnet edges, as indicated by the horizontal left and right arrows in fig. 2A.

Returning to fig. 6, the areas 2 printed with the composition comprising flakes having a layer of diamagnetic material (e.g., bismuth) have a completely different appearance. It has no transparent areas. The flakes in the features are at a small angle to the substrate and reflect incident light in different directions. The patches with planes parallel to the substrate surface (and perpendicular to the magnetic field) form a bright profile 4, as shown in fig. 4A and 4B. Appearance and cross-sectional analysis of the composition demonstrated the repulsion of the applied magnetic field to the flakes containing the diamagnetic material.

Those skilled in the art can now appreciate from the foregoing description that the teachings herein can be implemented in a variety of forms. Therefore, while these teachings have been described in connection with particular embodiments and examples thereof, the true scope of the teachings herein should not be so limited. Various changes and modifications may be made without departing from the scope of the teachings herein.

The scope of the disclosure herein should be construed broadly. The present disclosure is intended to disclose equivalents, means, systems and methods for obtaining the devices, activities and mechanical actions disclosed herein. For each device, article, method, means, mechanical element, or mechanism disclosed, the present disclosure is also intended to include and teach in its disclosure equivalents, means, systems, and methods for practicing the many aspects, mechanisms, and devices disclosed herein. Further, the present disclosure relates to coatings and many aspects, features and elements thereof. Such devices may be dynamic in their use and operation, and the present invention is intended to encompass the use of such devices and/or the manufacture of optical devices and their equivalents, means, systems and methods in many respects, all of which are consistent with the description and spirit of the operation and function disclosed herein. The claims of this application are to be construed broadly as well. The description of the invention herein in many embodiments is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.