KR102559246B1 - Security ink composition for screen process comprising AlNiCo based magnetic particle - Google Patents

Abstract

In the security ink composition according to the present invention, the AlNiCo-based magnetic particles contained are ultra-fine particles having a D ₅₀ of 12 μm or less, and at the same time, the variation in composition is remarkably small, so that each particle can have uniform magnetic properties, it is possible to implement a security element having a high degree of shape, it has a light-coloring characteristic that can hide dark-colored magnetic particles, has enhanced security that can be recognized by being distinguished from hard magnetic materials only with expensive recognition equipment, and has printability, so it is suitable for conventional inks for various purposes. There are advantages. In addition, since the AlNiCo-based magnet is used, the ink composition according to the present invention prevents problems in which viscosity is lowered due to dispersion and processing processes in ink manufacturing processes such as screen printing, and oxidation due to surface damage. Problems such as color degradation and reflectance degradation are prevented, and security characteristics are remarkably improved while having high viscosity, uniform elasticity, and high durability.

Description

Security ink composition for screen printing comprising AlNiCo-based magnetic particles

The present invention relates to a security ink composition for screen printing comprising AlNiCo-based magnetic particles.

Security materials can be said to be essential in areas where forgery prevention is required. For example, in the field of security printing, security materials are used for valuable documents such as checks, postage stamps, gift certificates, certificates, and bonds.

Currently, among security materials, magnetic particles having a core-shell structure formed by coating an inorganic material on a magnetic material are known, and coating the inorganic material to brighten the dark color of the magnetic material or improving the mechanical properties of the magnetic particle It is known to further coat another type of inorganic material (Korean Patent Publication No. 2013-0072444).

Recently, studies have been attempted to maximize the security of security products using security materials. As a first step of the research, the possibility of maximizing the security of a security product was suggested as a method of positioning the coercive force and magnetization density of magnetic particles within a specific region.

However, due to the evolution of highly developed measuring equipment, if the security material has a simple pattern or the coercive force difference of the mixed magnetic particles is too large, it may be easily recognized by general equipment. Therefore, it is required that the security material has the coercive force and magnetization density of a specific window so that it can be recognized only by expensive high-resolution recognition equipment (hereinafter referred to as "expensive recognition equipment").

However, conventional magnetic particles solve these problems, but the following problems still exist. 1) If the magnetization density of the magnetic particles is too large or too small, expensive recognition equipment has difficulty measuring the unique signal of the magnetic particles. 2) If the size of the magnetic particles is too large or too small, it is difficult for the magnetic particles to effectively reflect sunlight, so it is difficult to conceal the magnetic particles that are originally dark in color, and this drastically reduces the security, and may cause problems such as poor printing during the security printing process.

As a solution to this problem, i) a method of preparing relatively small nanoparticles by aggregating them with a binder, and ii) a method of pulverizing relatively large particles to a desired size may be proposed.

However, since the binder aggregation method of i) causes swelling of the binder when agglomerated with the magnetic particles, it is difficult to manufacture magnetic particles for security having a specific size and specific shape.

Compared to the binder aggregation method of i), the pulverization method of ii) may be advantageous in terms of coercive force, magnetization density, purity, and cost because no binder is added.

However, the pulverization method of ii) is generally prepared by the crush method, and the crush method was found to be difficult to control the particle size at the level of several microns. In addition, the coercive force of the powder, which started with a relatively large coercive force as a starting material, decreased significantly as the size decreased.

In addition to these two methods, an atomizing method is known as a method of producing magnetic particles with a specific size. The atomizing method is classified into a gas spray method, a water spray method, and a mixed spray method according to the type of cooling medium. In general, in the atomizing method, molten metal of an alloy is sprayed into a cooling medium through a nozzle or the like, and droplets of the molten metal are cooled by colliding the molten metal with the cooling medium. Through this, fine magnetic particles having a particle size of about tens or hundreds of μm can be manufactured.

However, since the water atomization process uses water (H ₂ O) as a main cooling medium, oxidation of the powder to be produced is problematic.

In addition, since the gas atomization method uses inert gas (N ₂ , Ar, He) or air as a cooling medium, it is possible to manufacture high-quality powder due to low oxidation and contamination problems during powder manufacturing. However, the cooling effect is relatively low, so there is a risk of micro-segregation during the manufacturing process, and technical difficulties in manufacturing magnetic particles of a specific shape follow, and the yield is very low, around 5%, resulting in very low commercial viability.

Accordingly, the present applicant has provided a manufacturing technology of AlNiCo-based magnetic particles that can effectively reflect sunlight to hide dark-colored magnetic particles, have magnetic properties capable of being operated as a strong security element, and have printability (Korean Patent No. 1718505).

Republic of Korea Patent Publication No. 2013-0072444 Republic of Korea Patent No. 1718505

An object of the present invention is to provide a security ink composition for screen printing comprising AlNiCo-based magnetic particles having improved security.

In detail, the present invention is to provide a security ink composition containing AlNiCo-based magnetic particles capable of stably forming a fine linear security pattern, having magnetic properties that can be distinguished from paramagnetic particles by expensive recognition equipment, having bright colors, excellent printability, and at the same time having a designed composition and an extremely uniform composition.

Another object of the present invention is to prevent the problem of lowering the viscosity due to dispersion and processing during the ink manufacturing process such as screen printing, to prevent problems such as oxidation, color degradation, and reflectance degradation caused by surface damage, and to provide a security ink composition having remarkably excellent security characteristics while having high viscosity, uniform elasticity, and high durability.

The security ink composition for screen printing according to the present invention includes AlNiCo-based magnetic particles and has a viscosity of 1000 cps to 30000 cps at 20° C., wherein the AlNiCo-based magnetic particles include core particles containing Al, Ni, and Co; and an inorganic shell surrounding the core particle, wherein the core particle is an ultrafine particle having a D ₅₀ of 12 μm or less, which is a particle size corresponding to 50% in the cumulative distribution of particle diameters of the core particle, and has compositional uniformity of Equation 1, Equation 2, and Equation 3 below.

Equation 1: 10 ≤ UNF(Al)

Equation 2: 10 ≤ UNF(Ni)

Equation 3: 10 ≤ UNF(Co)

In Equation 1, UNF(Al) is the value obtained by dividing the average Al composition between core particles by the standard deviation of the Al composition, based on the weight percent composition, and in Equation 2, UNF (Ni) is the value obtained by dividing the average Ni composition between core particles by the standard deviation of the Ni composition, based on the weight percent composition.

A security ink composition according to an example of the present invention may satisfy Equations 11 and 12 below.

Equation 11: INK _ST ≤ BNK _γc

Equation 12: BNK _γc ≤ INK _SE ≤ SUB _SE

In Equations 1 and 2, INK _ST is the initial surface tension of the ink composition, BNK _γc is the wet critical surface tension of the coated substrate, INK _SE is the surface energy of the ink coating on the coated substrate, and SUB _SE is the surface energy of the printed material.

The security ink composition according to the present invention may further include a base ink, and the base ink may include a polymer resin and a solvent.

The security ink composition according to an example of the present invention may include 0.1 to 70 parts by weight of the AlNiCo-based magnetic particles based on 100 parts by weight of the base ink.

In one example of the present invention, the base ink may include 1 to 500 parts by weight of the solvent based on 100 parts by weight of the polymer resin.

In one example of the present invention, the base ink may further include additives, and the additives may include any one or two or more selected from pigments, dispersants, drying agents, drying retardants, plasticizers, antifoaming agents, leveling agents, coupling agents, ultraviolet absorbers, antioxidants, slipping agents, color separation inhibitors, precipitation inhibitors, flame retardants, antistatic agents, and curing agents.

AlNiCo-based magnetic particles according to an example of the present invention may have an infrared reflectance of 60% or more based on a wavelength of 900 nm.

The AlNiCo-based magnetic particles according to an example of the present invention may have an L* value of 60 or more as measured by a color difference meter.

A security ink composition according to an example of the present invention may satisfy Equations 7 and 8 below.

Equation 7: 3 μm ≤ D ₅₀ ≤ 12 μm

Equation 8: 10 μm ≤ D ₉₀ ≤ 20 μm

In Equation 7, D ₅₀ is the particle size corresponding to 50% of the cumulative distribution of the particle diameter of the core particles, and in Equation 8, D ₉₀ is the particle size corresponding to 90% of the cumulative distribution of the particle diameter of the core particles.

In the AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention, the inorganic shell includes a metal shell, and the metal shell may satisfy Equations 6 and 7 below.

Equation 9: 50 nm ≤ t _m ≤ 100 nm

Equation 10: σ _t ≤ 30 nm

In Equation 9, t _m is the average thickness of the metal shell, and in Equation 10, σ _t is the standard deviation of the metal shell thickness.

In the AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention, the inorganic shell may further include a dielectric shell positioned below or above the metal shell.

In the AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention, the saturation magnetization (Ms) of the magnetic particles may be 50 to 150 emu/g, and the residual magnetization (Mr) may be 10 to 40 emu/g.

In the AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention, the coercive force of the magnetic particles may be 100 to 500 Oe.

In the AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention, the core particle may further include one or two or more fourth elements selected from Cu, Ti, Fe, and Si.

In the AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention, the value obtained by dividing the average composition of the fourth element between the core particles by the standard deviation of the composition of the fourth element based on the weight percent of the core particles may be 10 or more.

In the AlNiCo-based magnetic particles (I and II) according to an embodiment of the present invention, the core particles further contain Ti, Fe, and Cu, and may include 4 to 12% of Al, 10 to 20% of Ni, 15 to 25% of Co, 1 to 10% of Ti, 0.5 to 5% of Cu, the balance of Fe, and other unavoidable impurities by weight.

The AlNiCo-based magnetic particles (I, II) according to an embodiment of the present invention may have an infrared reflectance of 60% or more based on a wavelength of 900 nm.

The present invention may include a value certificate including the above-described AlNiCo-based magnetic particles, which may be printed with the security ink composition.

In the security ink composition for screen printing according to the present invention, the AlNiCo-based magnetic particles for security are ultra-fine particles having a D ₅₀ of 12 μm or less and have a strictly designed composition, so that there is an effect of having improved security.

In the security ink composition according to the present invention, the AlNiCo-based magnetic particles for security according to the present invention are ultra-fine particles having a D ₅₀ of 12 μm or less, and at the same time, the variation in composition is remarkably small, so that each particle can have uniform magnetic properties, and it is possible to implement a security element having a high degree of shape.

By using the AlNiCo-based magnet, the ink composition according to the present invention prevents problems in which viscosity is lowered due to dispersion and processing processes in the ink manufacturing process such as screen printing, and oxidation due to surface damage. Problems such as color degradation and reflectance degradation are prevented, and security characteristics are remarkably improved while having high viscosity, uniform elasticity, and high durability.

In the security ink composition containing AlNiCo-based magnetic particles according to an embodiment of the present invention, the AlNiCo-based magnetic particles have a pale color property that can hide dark-colored magnetic particles, and are distinguished from hard magnetic materials only with expensive recognition equipment.

Even if the effects are not explicitly mentioned in the present invention, the effects described in the specification expected by the technical features of the present invention and the inherent effects thereof are treated as described in the specification of the present invention.

1 is a scanning electron microscope photograph of AlNiCo-based magnetic particles prepared according to an embodiment of the present invention;
2 is a scanning electron microscope photograph of a cross section of an AlNiCo-based magnetic particle manufactured according to an embodiment of the present invention and a diagram showing a measurement of the thickness distribution of a silver shell;

Hereinafter, a security ink composition including AlNiCo-based magnetic particles according to the present invention will be described in detail with reference to the accompanying drawings.

The drawings described in this specification are provided as examples to sufficiently convey the spirit of the present invention to those skilled in the art. Therefore, the present invention may be embodied in other forms without being limited to the drawings presented, and the drawings may be exaggerated to clarify the spirit of the present invention.

Technical terms and scientific terms used herein have meanings commonly understood by those of ordinary skill in the art to which this invention belongs, unless there is another definition in the technical terms and scientific terms used herein, and descriptions of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted in the following description and accompanying drawings.

Singular forms of terms used in this specification may be construed as including plural forms unless otherwise indicated.

In this specification, the unit of % used without particular notice means weight % unless otherwise defined.

The present applicant confirmed that, in the process of actually manufacturing a security element for a valid certificate using fine AlNiCo-based hard magnetic particles having a size of micrometer order, when a security element is designed in a fine linear shape, even with expensive recognition equipment, it is not reproducibly recognized as a paramagnetic particle-based security element or the shape of the designed security element is not reproducibly recognized. As a result of intensifying research to solve these problems, it was confirmed that in order to stably implement a fine linear security element, uniform compositional characteristics between AlNiCo-based magnetic particles, that is, suppression of compositional deviation between manufactured magnetic particles is essential. As a result of long-term continuous research to ensure uniform compositional characteristics, the conventional gas injection method (atomizing method using gas as a cooling medium) has a limitation in preventing segregation that causes an aluminum-rich phase or an Fe-rich phase due to a slow cooling rate, and uses water as a cooling medium to induce rapid cooling, but suppresses oxidation of easily oxidizable elements (e.g., Al, Ti, etc.) during the cooling process to prevent oxidation of easily oxidized elements It was confirmed that particles having uniform magnetic properties and substantially the same composition as the designed composition were produced, and the present invention was filed.

The security ink composition for screen printing according to the present invention includes AlNiCo-based magnetic particles and has a viscosity of 1000 cps to 30000 cps at 20° C., preferably 2000 cps to 20000 cps. The security ink composition according to the present invention contains the AlNiCo-based hard magnetic particles described later, has excellent printability, has a designed composition and an extremely uniform composition, and can also stably form a fine linear security pattern, It prevents the problem of viscosity being lowered due to dispersion and processing in the ink manufacturing process such as screen printing, and has high viscosity, uniform elasticity, and high durability while having significantly improved security characteristics.

Accordingly, the present invention includes one aspect of magnetic particles (I) in which compositional variation between particles is suppressed, and another aspect of magnetic particles (II) having a designed composition, that is, a composition substantially the same as that of the molten metal used in atomizing. In describing the present invention in detail, unless a particular aspect is specifically limited and described, all of the above applies to both one aspect (magnetic particle (I)) and another aspect (magnetic particle (II)).

In detailing the present invention, the AlNiCo-based alloy may mean an alloy containing Al, Ni, and Co, and the AlNiCo-based magnetic particles may mean hard magnetic alloy particles containing Al, Ni, and Co, and may mean security magnetic particles used for security of securities. Hard magnetism particles are difficult to magnetize, but are difficult to demagnetize once magnetized, which means that the coercive force (Hc) and residual magnetization density (Mr) are higher than those of soft magnetism particles. In the case of AlNiCo-based magnetic particles, hard magnetism may mean a magnetic property having a coercive force of 100 to 500 Oe. In contrast, soft magnetic particles mean that they can be easily magnetized by a relatively weak magnetic field, and magnetization rapidly disappears over time when the external magnetic field is removed. Soft magnetism may mean a magnetic property having a coercive force of 10 to 90 Oe.

In detailing the present invention, the water-based atomizing method may mean a process or manufacturing method using a cooling medium containing water when spraying molten metal of an alloy through a nozzle or the like. At this time, the water-based atomizing method should not be construed as limited to a method using only water as a cooling medium, and water and gas (eg, N ₂ , Ar, He, inert gas such as Ne) is used as a cooling medium at the same time. It should be interpreted as including.

In detailing the present invention, the AlNiCo-based magnetic particles may mean a group of magnetic particles, that is, an aggregate of individual magnetic particles, and may mean a group of independent individual magnetic particles excluding an aggregate of magnetic particles or an aggregate of core particles. At this time, the meaning of 'group' means at least a number that is not changed by the number of magnetic particles constituting the 'group', such as average magnetic characteristics. That is, it may refer to a group composed of magnetic particles having a size (number) or greater to which the magnetic characteristics of the group of magnetic particles may be uniformly displayed. In another sense, the 'group' may refer to a particle group having a size enough to obtain reliable average size, average composition, and variance values. In terms of the above, the AlNiCo-based magnetic particles may mean a group of at least 50 or more magnetic particles, specifically at least 100 or more, more specifically at least 300 or more, even more specifically at least 500 or more, and still more specifically at least 1000 or more. In terms of the manufacturing method, the AlNiCo-based magnetic particles are integrally obtained by atomizing an AlNiCo-based alloy molten metal having a designed composition using a refrigerant containing water, that is, integrally obtained in a single water-based spraying method. It may mean a group of magnetic particle(s) manufactured using particle(s) as core particles.

Al-based magnetic particles (I) according to one aspect of the present invention are magnetic particles in which compositional variation between magnetic particles is suppressed. Specifically, the AlNiCo-based magnetic particles (I) according to the present invention include core particles containing Al, Ni, and Co; and an inorganic shell surrounding the core particle, wherein the core particle is an ultrafine particle having a D ₅₀ of 12 μm or less, which is a particle size corresponding to 50% in the cumulative distribution of the particle diameter of the core particle, and the core particle has compositional uniformity of Equation 1, Equation 2, and Equation 3 below.

Equation 1: 10 ≤ UNF(Al)

Equation 2: 10 ≤ UNF(Ni)

Equation 3: 10 ≤ UNF(Co)

In Equation 1, UNF(Al) is the value obtained by dividing the average Al composition between core particles by the standard deviation of the Al composition, based on the weight percent composition, and in Equation 2, UNF (Ni) is the value obtained by dividing the average Ni composition between the core particles, based on the weight percent composition, by the standard deviation of the Ni composition, and in Equation 3, UNF(Co) is the value obtained by dividing the average Co composition between the core particles, based on the weight percent composition, by the standard deviation of the Co composition.

That is, UNF (Al) is the value obtained by dividing the average Al composition (average Al wt%) between core particles by the standard deviation of Al composition (standard deviation of Al wt% between core particles) based on the total weight of core particles as 100%, and UNF (Ni) is the value obtained by dividing the average Ni composition (average Ni wt%) between core particles by the standard deviation (standard deviation of Ni weight% between core particles) of Ni composition based on the total weight of core particles as 100%, and UNF ( Co) is a value obtained by dividing the average Co composition (average Co wt%) between core particles by the standard deviation of the Co composition (standard deviation of Co wt% between core particles) based on the total weight of the core particles as 100%.

As described above, the magnetic particle may mean a magnetic particle group, and in Equations 1, 2, and 3, the average Al composition (or Ni composition or Co composition) of the core particles may mean the average value of the Al composition (or Ni composition or Co composition), which is the weight percent Al content of each of the core particles of the magnetic particles constituting the magnetic particle group, and the standard deviation of the Al composition (or the standard deviation of the Ni composition or the standard deviation of the Co composition) is the core particles of the magnetic particles constituting the magnetic particle group Of course, it can mean the standard deviation in each Al composition (or Ni composition or Co composition). In addition, in the UNF of any element, as the uniformity of the composition increases, the UNF increases, so it is meaningless to limit the upper limit of the UNF, but in practice, the upper limit of the UNF may reach 200.

The compositional uniformity of AlNiCo-based magnetic particles satisfying Equations 1, 2, and 3 is the compositional uniformity of AlNiCo-based particles that cannot be obtained by the conventionally known gas atomization process and the conventional water atomization process in which oxidation by water occurs, and the average particle is on the order of several micrometers. This is a compositional uniformity that has never been reported for Co-based magnetic particles.

As described above, the AlNiCo-based magnetic particles according to the present invention are characterized in that the core particles are ultra-fine particles having a D50 of 12 μm or less, and that the composition uniformity, which is the main factor determining the magnetic uniformity of the AlNiCo-based magnetic particles, satisfies Equations 1, 2, and 3, and is a magnetic particle aggregate having a remarkably low compositional deviation. As a result, even when the security element is designed in a fine linear shape, the security element is stable without damaging the designed shape by expensive recognition equipment. It can be reproducibly recognized, and even when the micro-linear security element is mixed with the paramagnetic particle-based security element, it is stably distinguished/recognized, thereby significantly improving security. AlNiCo-based magnetic particles according to a more characteristic and advantageous example may satisfy UNF(Al) of 11 or more, UNF(Ni) of 40 or more, and UNF(Co) of 30 or more. Due to such high degree of compositional uniformity, AlNiCo-based magnetic particles can exhibit highly uniform magnetic properties.

Together with or independently of the aforementioned aspect, the magnetic particles according to another aspect of the present invention are magnetic particles (II) having a designed composition, that is, a composition substantially the same as that of the molten metal used in atomizing. Specifically, the magnetic particle (II) according to another aspect of the present invention includes a core particle containing Al, Ni, and Co; and an inorganic shell surrounding the core particle, wherein the core particle is an ultrafine particle having a D ₅₀ of 12 μm or less, which is a particle size corresponding to 50% in the cumulative distribution of the particle diameter of the core particle, and the core particle is manufactured by an atomizing method using a refrigerant containing at least water, and has a composition satisfying the following formulas 4, 5, and 6 based on the design composition, which is a composition of an alloy molten metal containing Al, Ni, and Co used during atomization. .

Equation 4:

Equation 5:

Equation 6:

In Equation 4, C _m (Al) is the average Al composition between core particles based on weight percent composition, C ₀ (Al) is the Al composition of the design composition based on weight percent composition, C _m (Ni) is the average Ni composition among core particles based on weight percent composition, C ₀ (Ni) is the Ni composition based on weight percent composition and design composition, C _m (Co) is the average Co composition between core particles based on weight percent composition, and C ₀ (Co) is the Co composition based on weight percent composition and design composition. That is, C _m (Al) in Equation 4 corresponds to the average Al composition described above in relation to Equation 1, C _m (Ni) in Equation 5 corresponds to the average Ni composition described above in relation to Equation 2, and C _m (Co) in Equation 6 corresponds to the average Co composition defined in Equation 3. In addition, C ₀ (Al) may be the weight percent of Al contained in the molten AlNiCo-based alloy used for atomizing, C ₀ (Ni) may be the weight percent of Ni contained in the molten AlNiCo-based alloy used for atomizing, and C ₀ (Co) may be the weight percent of Co contained in the molten AlNiCo-based alloy used for atomizing. At this time, in order to improve composition uniformity, it is advantageous to prepare an ingot by melting and solidifying metal powders constituting an alloy according to a predetermined composition in an inert atmosphere, and then melting the manufactured ingot in an inert atmosphere. In this advantageous example, the design composition, which is the composition of the molten alloy, may be a composition based on a mixture of metal powders constituting an alloy for manufacturing an ingot. However, the design composition cannot be interpreted as being limited to only the standard composition of the mixture of these raw metal powders, and may mean the composition of the ingot itself or the composition of the ingot (alloy molten metal) itself melted for atomizing. Of course.

As shown in relational expressions 4, 5, and 6, the AlNiCo-based magnetic particles according to the present invention are characterized in that the composition of the core particles determining the magnetic properties is substantially the same as the designed composition, and the magnetic particles in which deviation from the designed composition is suppressed.

In terms of the manufacturing method, ingot and molten metal are manufactured under an inert atmosphere, and at the same time, when the molten metal is sprayed, it is quickly cooled by an aqueous refrigerant (refrigerant containing water) to prevent segregation, and at the same time, the antioxidant contained in the water-based refrigerant prevents compositional change due to oxidation during the spraying process, especially when the compositional change between particles due to oxidation of a highly oxidizing element such as Al is prevented. core particles having can be produced, and furthermore, compositional uniformity satisfying relations 1, 2, and 3 can be secured.

In terms of deviation from the design composition and compositional deviation between particles, the magnetic particle according to the present invention may include the above two aspects, but these two aspects should not be interpreted as being independent of each other, and the present invention should be interpreted as including magnetic particles belonging to both the first and second aspects.

That is, the magnetic particle according to an example of the present invention includes a core particle containing Al, Ni, and Co; and an inorganic shell surrounding the core particle, wherein the core particle is an ultrafine particle having a particle size D ₅₀ of 50% or less in the cumulative distribution of the particle diameter of the core particle, which is 12 μm or less, and the core particle has the above-described formulas 1, 2 and 3. The composition uniformity is obtained, the core particles are prepared by an atomizing method using a refrigerant containing at least water, and the core particles are for an alloy containing Al, Ni, and Co used during atomization. Based on the design composition, which is the composition of the hot water, it may have a composition that satisfies Equations 4, 5, and 6 described above.

The core particles may be alloys containing Al (aluminum), Ni (nickel), and Co (cobalt), which are excellent in coercive force, saturation magnetization, and residual magnetization. As a specific example, the core particle may include one or two or more fourth elements selected from Fe, Cu, Ti, and Si, and other unavoidable impurities. As a specific and practical example, the core particle contains Al, Ni, and Co, and is selected from one or more nonferrous metals selected from the group consisting of Cu, Si, and Ti; iron-based containing Fe; And other unavoidable impurities; it may be an AlNiCo-based alloy containing.

Similar to the compositional uniformity of Al, Ni, and Co, the AlNiCo-based magnetic particles are characterized by extremely uniformly containing the fourth element as well. In detail, the core particles have a compositional uniformity in which the value obtained by dividing the average composition of the fourth element (average content based on weight%) among the core particles by the standard deviation of the composition of the fourth element, based on weight percent, is 10 or more. That is, UNF (fourth element) may be 10 or more, and UNF (fourth element) may be a value obtained by dividing the average fourth element composition (average fourth element weight %) between core particles by the standard deviation of the fourth element composition (standard deviation of fourth element weight %) on a composition basis in weight%. At this time, the average composition of the fourth element among the core particles may refer to an average value of the composition of each fourth element of the core particles of the magnetic particles constituting the group of magnetic particles, and the standard deviation of the composition of the fourth element may mean the standard deviation in the composition of each fourth element of the core particles of the magnetic particles constituting the group of magnetic particles.

As a practical example, the core particle may further contain Ti, Fe, and Cu together with Al, Ni, and Co, and UNF (Ti) in which the fourth element is Ti, UNF (Fe) in which the fourth element is Fe, and UNF (Cu) in which the fourth element is Cu may each be 10 or more. As a more practical example, UNF(Ti) may be 15 or more, UNF(Fe) may be 35 or more, and UNF(Cu) may be 30 or more.

That is, in a practical and advantageous example, the core particles may contain Ti, Fe, and Cu together with Al, Ni, and Co, and may have a high degree of compositional uniformity that satisfies UNF (Al) of 11 or more, UNF (Ni) of 40 or more, UNF (Co) of 30 or more, UNF (Ti) of 15 or more, UNF (Fe) of 35 or more, and UNF (Cu) of 30 or more.

In the AlNiCo-based magnetic particles according to a practical and advantageous example, the core particles may include 4 to 12% Al, 10 to 20% Ni, 15 to 25% Co, 1 to 10% Ti, 0.5 to 5% Cu, the balance Fe and other unavoidable impurities, based on weight% based on 100% of the total weight of the core particles. In the AlNiCo-based magnetic particles according to another practical and advantageous embodiment, the core particles may include 4 to 12% Al, 10 to 20% Ni, 15 to 25% Co, 1 to 10% Ti, 0.5 to 5% Cu, 0.1 to 1% Si, the balance Fe and other unavoidable impurities, based on weight% based on 100% of the total weight of the core particles. At this time, the composition of the core particles means an average weight % of the weight % of one element contained in each of the core particles of the magnetic particles constituting the magnetic particle group, and may correspond to the composition of the average element used in the UNF definition of one element.

The core particles may contain 4 to 12% by weight of Al, advantageously 5 to 10% by weight, and even more advantageously 6 to 9% by weight of Al. When the content of aluminum satisfies this composition range, the sintering prevention effect is sufficient during subsequent heat treatment for segregation relief and magnetic property control, so that the shape of the fine particles secured by the waterless method can be maintained, and mechanical properties of the core particles are prevented.

The core particles may contain 10 to 20% by weight of Ni, advantageously 12 to 18% by weight and even more advantageously 13 to 16% by weight of Ni. When the content of nickel satisfies these compositional ranges, it is advantageous because coercive force and remanent magnetization can be simultaneously increased.

The core particles may contain 15 to 25% Co by weight, advantageously 17 to 25% by weight and even more advantageously 17 to 23% by weight Co. When the content of cobalt satisfies these compositional categories, it is advantageous to increase the coercive force and reduce cost.

Ti and Cu can further improve the coercive force of the Al-Ni-Co alloy. In order to prevent the residual magnetization decrease and improve the coercive force, the core particles may contain 1 to 10 wt% Ti, advantageously 2 to 8 wt%, and even more advantageously 3 to 6 wt% Ti. In addition, in order to prevent a decrease in remanent magnetization and improve coercive force, the core particles may contain 0.5 to 5% by weight of Cu, advantageously 1 to 4% by weight, and more advantageously 1 to 3% by weight of Cu.

The core particles may contain 0.1% by weight or more of Si, but it is preferable to contain less than 1% by weight so that the magnetic properties are not deteriorated. Specifically, the core particles may contain 0.4 to 0.7% by weight of Si in terms of deoxidation, maintaining the shape of fine particles, and suppressing deterioration of magnetic properties. However, as shown in the examples, in the case of manufacturing an ingot in an inert atmosphere, melting the ingot in an inert atmosphere, and using a refrigerant (cooling medium) containing an antioxidant along with water when spraying the molten metal, oxidation can be sufficiently suppressed during the granulation process of the molten metal, so that magnetic particles having composition uniformity and substantially the same composition as the design composition described above can be manufactured without the molten metal containing a deoxidizer such as Si that deteriorates magnetic properties. .

In the AlNiCo-based magnetic particles according to an embodiment of the present invention, the core particles may further satisfy Equations 7 and 8 below.

Equation 7: 3 μm ≤ D50 ≤ 12 μm

Equation 8: 10 μm ≤ D90 ≤ 20 μm

As described above, D ₅₀ in Equation 7 is the particle size corresponding to 50% of the cumulative distribution of the particle diameter of the core particles, and D ₉₀ in Equation 8 is the particle size corresponding to 90% of the cumulative distribution of the particle diameter of the core particles. Practically, the D ₅₀ may be 3 to 9 μm and the D ₉₀ may be 10 to 15 μm.

When the core particles are ultrafine particles having a D ₅₀ of 12 μm or less, the particle size distribution may also affect the magnetic properties. When the AlNiCo-based magnetic particles satisfy Equations 7 and 8, printability can be secured, printing defects such as nozzle clogging during the printing process can be improved, and change in magnetic properties due to size variation can be suppressed, so that the AlNiCo-based magnetic particles can have more uniform magnetic properties.

In order to use a magnetic material as a security element, it is necessary to conceal the dark color inherent to magnetic particles. Therefore, as suggested by the present applicant, the dark color inherent in magnetic particles can be concealed by using a technique of lightening the magnetic body by covering it with a particulate magnetic metal shell (refer to Korean Registered Patent No. 1341150).

In the AlNiCo-based magnetic particles, the inorganic shell may serve to hide the inherent dark color of the core particles containing Al, Ni, and Co, and to allow the AlNiCo-based magnetic particles to have a pale color.

Specifically, the inorganic shell may include a metal shell, and may further include a dielectric shell positioned on the top of the metal shell (ie, the surface side of the metal shell) and / or the bottom of the metal shell (on the core particle side of the metal shell). The dielectric shell may serve to improve the binding force between the metal shell and the core particles or to improve durability by protecting the metal shell from the outside.

Through various preceding experiments over a long period of time, it was confirmed that the uniformity of the metal shell, which is the main component for whitening, along with the compositional uniformity and particle size distribution of the core particles, also have a significant effect on the magnetic properties of the AlNiCo-based magnetic particles.

Accordingly, in the AlNiCo-based magnetic particles according to an embodiment of the present invention, the inorganic shell may include a metal shell, and the metal shell may have thickness uniformity satisfying Equations 9 and 10 below.

Equation 9: 50 nm ≤ t _m ≤ 100 nm

Equation 10: σ _t ≤ 30 nm

In Equation 9, t _m is the average thickness of the metal shell, and in Equation 10, σ _t is the standard deviation of the metal shell thickness. At this time, the average thickness and standard deviation of the thickness in Equations 9 and 10 are the average thickness of the thickness according to the position of one metal shell surrounding one core particle with respect to one magnetic particle, and the deviation is also the standard deviation of the thickness in one metal shell. Magnetic particles belonging to the group of AlNiCo-based magnetic particles may satisfy Expressions 9 and 10, respectively.

That is, the average thickness of the metal shell of each magnetic particle belonging to the AlNiCo-based magnetic particle group is 50 to 100 nm, and the deviation of the thickness of the metal shell of each magnetic particle belonging to the AlNiCo-based magnetic particle group may be within 30 nm, substantially 1 nm to 10 nm.

The metal shell may be one or more metals selected from copper, nickel, gold, platinum, silver, aluminum, and chromium, and silver is more effective in whitening, and furthermore, the silver shell is more advantageous because it can impart infrared reflective ability to AlNiCo-based magnetic particles.

The upper, lower, or upper and lower dielectric shells of the metal shell may be dielectrics selected from one or more of titanium oxide, silicon oxide, aluminum oxide, zinc oxide, zirconium oxide, calcium carbonate, magnesium fluoride, and zinc sulfide. The thickness of the dielectric shell may be 10 to 100 nm in terms of stably improving durability and improving color whitening, but is not limited thereto.

AlNiCo-based magnetic particles according to an embodiment of the present invention may have a coercive force of 100 to 500 Oe, a saturation magnetization (Ms) of 50 to 150 emu/g, and a residual magnetization (Mr) of 10 to 40 emu/g. Specifically, the AlNiCo-based magnetic particles may have a coercive force of 100 to 500 Oe, a saturation magnetization (Ms) of 50 to 70 emu/g, and a residual magnetization (Mr) of 15 to 30 emu/g. These magnetic properties of coercive force, saturation magnetization, and residual magnetization are indistinguishable from soft magnetic particles by general recognition equipment, and can be distinguished from soft magnetic particles by expensive recognition equipment and are magnetic characteristics that can secure enhanced security performance.

The AlNiCo-based magnetic particles have a strictly designed composition to secure the above-described composition uniformity and planned magnetism, and advantageously have composition uniformity, design composition, particle size uniformity, and metal shell thickness uniformity, so that a security element designed in a high-level shape such as a fine linear is also reliably classified and detected with soft magnetic particles by expensive recognition equipment, and the security characteristics can be greatly improved.

Furthermore, generally, magnetic particles have a characteristic of absorbing infrared rays, but AlNiCo-based magnetic particles according to an advantageous embodiment of the present invention may have a characteristic of reflecting infrared rays. Furthermore, the AlNiCo-based magnetic particles according to an advantageous embodiment of the present invention have a metal shell with a uniform thickness and very low surface roughness, so that they reflect infrared rays (infrared rays of a 900 nm wavelength) of 60% or more based on a wavelength of 900 nm. It can have very good infrared reflectance. This means that the magnetic particles according to an embodiment of the present invention can implement a security element having a high degree of shape including a fine linear shape, along with magnetic characteristics that cannot be distinguished from soft magnetic particles by general recognition equipment, and have a security characteristic of high infrared reflection. That is, it means that multi-faceted security such as magnetic properties, security pattern (shape of security element), and infrared rays are achieved with AlNiCo-based magnetic particles, which are a single material. In particular, since the AlNiCo-based magnetic particles according to an embodiment of the present invention can implement soft magnetic characteristics with substantially the same composition, the difference between the soft magnetic particles and the soft magnetic particles cannot be distinguished with a conventional composition analysis device and a general magnetic recognition device, and therefore, counterfeiting of the security element is substantially impossible.

In addition, in the AlNiCo-based magnetic particles according to the present invention, the hard magnetic particles may have a lightness (L*) value of 60 or more, preferably 70 or more, as measured by a color difference meter. At this time, it is meaningless to limit the upper limit value, but in practice, the upper limit of the L* value may be 95. When the hard magnetic particle has an L* value in the above range, the concealment property is further improved, and thus the security thereof may be further improved.

The present invention includes the above-described method for producing AlNiCo-based magnetic particles. The manufacturing method according to the present invention includes all of the above-described contents of the AlNiCo-based magnetic particles.

In the manufacturing method of the present invention, terms such as the cooling medium containing water, the water-based spray, and/or the water-based cooling medium should be interpreted as meaning including at least water, and should not be construed as being limited to meaning that the cooling medium is made of a liquid. It should not be construed as including the case where the cooling medium includes a gaseous phase of an inert gas together with water.

A method for producing AlNiCo-based magnetic particles according to the present invention includes a) preparing an ingot by melting and solidifying raw materials including Al, Ni, and Co in an inert atmosphere; b) melting the prepared ingot in an inert atmosphere and producing fine particles by atomization using a cooling medium containing water and an antioxidant; c) heat-treating the prepared microparticles; d) preparing AlNiCo-based core particles having a D ₅₀ of 12 μm or less by air stream classifying the heat-treated particles; and e) forming an inorganic shell on the prepared AlNiCo-based core particles.

As described above, when the gas atomization method is used, it is practically very difficult to manufacture particles having uniform magnetic properties due to a slow cooling rate, and furthermore, the size required for printing (eg, D ₅₀ ≤ 12 ㎛) As the yield of ultrafine particles is only around 5%, there is a disadvantage that is not suitable for mass production.

The manufacturing method according to the present invention can be prepared by using a cooling medium comprising water, and the ultra -fine particles of a precise tissue in which the segregation prevents the segregation can be prepared with a very good yield (35% or more), and as the cooling medium contains an antioxidant, certain elements having a strong oxidative element in the particles prepared by water are indefinitely oxidized. By preventing, as described above, it has excellent composition uniformity (low composition deviation), and a core particle having a designed composition can be prepared.

As compositional deviation is caused by heterogeneous oxidation of elements with strong oxidizing properties (eg, Al, Ti, etc.), ingotization (a) by melting raw materials in an inert gas atmosphere and remelting (b) of the ingot for spraying in an inert atmosphere) are performed, thereby suppressing the occurrence of compositional deviation up to the step immediately before spraying, and suppressing the occurrence of compositional deviation in the spraying process by using a water-based cooling medium containing an antioxidant during spraying.

Thereafter, the fine particles produced by spraying can be heat treated to improve the coercive force, and by performing airflow classification on the fine particles subjected to the heat treatment, D50 of 12 μm or less, preferably D ₅₀ and D ₉₀ of Equations 7 and 8. Core particles having a very narrow size distribution and having an ultrafine size can be manufactured.

In addition, when the metal shell is formed in the inorganic shell forming step after the core particles are produced, the metal shell is formed using electroless plating, but electroless plating is performed at a low temperature of 5 ° C or less, specifically 1 to 5 ° C. A thin, uniform and very low surface roughness satisfying Equations 9 and 10 can be manufactured.

Hereinafter, a detailed manufacturing method will be described, but in detailing the manufacturing method, the size, distribution, composition, element content, magnetic properties, material of the inorganic shell, thickness, etc. of the core particles are similar to or the same as those described above for the AlNiCo-based magnetic particles. Accordingly, the method for manufacturing AlNiCo-based magnetic particles includes all of the above-described related components of the AlNiCo-based magnetic particles.

The ingot may be manufactured by melting a raw material obtained by mixing powders of each element including Al, Ni, and Co to have the same composition as the designed core particle to produce molten metal in an inert atmosphere, and cooling the manufactured molten metal in an inert atmosphere. However, when the core particles contain iron, medium carbon steel (steel containing 0.15 to 0.3% by weight of C) having an antioxidant effect can be used instead of iron powder, but ingotization and melting of the ingot are performed in an inert atmosphere, and spraying is performed by an aqueous cooling medium containing an antioxidant, so medium carbon steel is not necessarily required and can be optionally used. Accordingly, it goes without saying that the present invention cannot be limited by the type of iron raw material. Accordingly, the ingot may be an AlNiCo alloy ingot containing Al, Ni, and Co, and specifically, an element selected from one or more selected from Fe, Cu, Si, and Ti together with Al, Ni, and Co, and other unavoidable impurities. It may be an AlNiCo alloy ingot containing impurities. More substantially, the ingot may be an AlNiCo alloy ingot containing Ti, Fe, Cu and other unavoidable impurities along with Al, Ni and Co. As another practical example, the ingot may be an AlNiCo alloy ingot containing Ti, Fe, Cu, Si, and other unavoidable impurities along with Al, Ni, and Co.

The composition of the raw material, the composition of the ingot, or the composition of the molten metal corresponding to the design composition according to a practical and advantageous example may include 4 to 12% of Al, 10 to 20% of Ni, 15 to 25% of Co, 1 to 10% of Ti, 0.5 to 5% of Cu, the balance of Fe, and other unavoidable impurities on a weight percent basis. The composition of the raw material, the composition of the ingot, or the composition of the molten metal corresponding to the design composition according to another practical and advantageous embodiment may include 4 to 12% Al, 10 to 20% Ni, 15 to 25% Co, 1 to 10% Ti, 0.5 to 5% Cu, 0.1 to 1% Si, the balance Fe and other unavoidable impurities, based on weight% based on 100% of the total weight of the core particles.

At this time, the composition of the raw material corresponding to the design composition, the composition of the ingot, or the composition of the molten metal may contain 4 to 12% by weight, advantageously 5 to 10% by weight, and more advantageously 6 to 9% by weight of Al. In addition, the composition of the raw material corresponding to the design composition, the composition of the ingot or the composition of the molten metal may contain 10 to 20% by weight, advantageously 12 to 18% by weight, and more advantageously 13 to 16% by weight of Ni. In addition, the composition of the raw material corresponding to the design composition, the composition of the ingot, or the composition of the molten metal may contain 15 to 25% by weight, advantageously 17 to 25% by weight, and more advantageously 17 to 23% by weight of Co. In addition, the composition of the raw material corresponding to the design composition, the composition of the ingot, or the composition of the molten metal may contain 1 to 10% by weight of Ti, advantageously 2 to 8% by weight, and more advantageously 3 to 6% by weight of Ti. In addition, the composition of the raw material corresponding to the design composition, the composition of the ingot, or the composition of the molten metal may contain 0.5 to 5% by weight of Cu, advantageously 1 to 4% by weight, and more advantageously 1 to 3% by weight of Cu. In addition, the composition of the raw material, the composition of the ingot, or the composition of the molten metal corresponding to the design composition may contain 0.1% by weight or more of Si, specifically 0.4 to 0.7% by weight of Si, but, similar to the reason described above for carbon steel, Si may be selectively used when necessary.

The melting of the ingot in step b) may be a process of melting the ingot in an inert atmosphere, and in detail, may be a process of melting the ingot by induction heating for high frequency in an inert atmosphere, but in an inert atmosphere in which oxidation is prevented. It is not limited by the sphere heating method as long as the melting is performed. As a specific and non-limiting example, the temperature at high frequency melting in an inert atmosphere may be 1300 to 1800 °C.

Spraying in step b) may be performed using a water-based cooling medium containing water and an antioxidant, and may be performed by spraying the water-based cooling medium through a ring-shaped spray nozzle.

When the ingot melt melted for spraying is referred to as an AlNiCo-based molten metal, in order to suppress oxidation during granulation of the AlNiCo-based molten metal by a water-based fluid, the water-based cooling medium may contain water and an antioxidant, and the antioxidant may include one or two or more selected from a reducing organic solvent and a reducing organic compound. In particular, the antioxidant may contain a reducing organic compound including urea, and when spraying is performed by an aqueous cooling medium containing urea and water, heterogeneous oxidation during granulation of the AlNiCo-based molten metal to be granulated is significantly suppressed, and core particles satisfying the above-described relational expressions 1, 2, and 3 can be manufactured, and furthermore, oxidation itself during granulation is significantly suppressed to satisfy relational expressions 4, 5, and 6, substantially conforming to the designed composition. Core particles that do can be prepared.

Specifically, the cooling medium may contain 10 to 100 parts by weight of urea, advantageously 15 to 100 parts by weight of urea, and more advantageously 20 to 100 parts by weight of urea based on 100 parts by weight of water. The urea content is such that oxidation by water and heterogeneous oxidation by water can be substantially completely suppressed during granulation of AlNiCo-based molten metal.

However, in the present invention, the antioxidant contained in the cooling medium cannot be interpreted as being limited to urea alone, and if necessary, the cooling medium may further include a reducing organic solvent together with the aforementioned reducing organic compound including urea. Of course. As a reducing organic solvent, an alkanolamine having excellent miscibility with water and a high boiling point and excellent reducibility is advantageous, and the alkanolamine may include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropylamine (MIPA), diisopropylamine (DIPA), or a mixture thereof, but the present invention is not limited thereto.

When the cooling medium further includes a reducing organic solvent, the cooling medium may contain 30 parts by weight or less of the reducing organic solvent, specifically 1 to 30 parts by weight, more specifically 5 to 20 parts by weight based on 100 parts by weight of water, so as not to impair the quenching effect by water, but the present invention is not limited thereto.

In addition, when the cooling medium further includes a gas phase containing an inert gas, it is advantageous that the volume ratio of water: the gas phase containing an inert gas is in the range of 1: 0.05 to 0.3 so that the quenching effect by water that prevents segregation and formation of unwanted anomalies (eg, Al-rich phase) can be maintained.

The temperature of the cooling medium itself, that is, the temperature of the cooling medium at the beginning of use is not particularly limited, and may be, for example, -30 to 15°C.

When spraying, the spraying pressure of the cooling medium containing water and an antioxidant is 500 bar or more, which is advantageous for producing ultrafine particles having a D ₅₀ of 12 μm or less. Specifically, in order to obtain ultrafine particles having a D ₅₀ of 12 μm or less in excellent yield, the injection pressure of the cooling medium may be 500 to 1000 bar, more specifically 500 to 800 bar.

AlNiCo-based fine particles may be obtained by the above-described spraying process, and then a step of heat-treating the AlNiCo-based fine particles produced by spraying may be performed. In the case of the gas spray method, heat treatment should be performed to improve magnetic properties and remove segregation and unwanted abnormalities (specifically, γ phase) caused by slow cooling, but in the case of AlNiCo-based fine particles obtained by the manufacturing method according to an embodiment of the present invention, as segregation and phase separation (formation of abnormalities) are prevented by rapid cooling, it is sufficient to perform heat treatment under favorable conditions for improving the magnetic properties of AlNiCo-based fine particles. Specifically, the heat treatment of step c) may be performed at a temperature of 700 to 800° C. in an ordinary inert to reducing atmosphere. The heat treatment time may be performed as long as the desired magnetic property improvement is achieved and the AlNiCo-based fine particles are not strongly bound, and as a practical example, it may be performed for 30 to 2 hours, but the present invention is performed. Of course, it cannot be limited by the time.

If necessary, after the first heat treatment at 700 to 800 ° C., the second heat treatment at a temperature relatively lower than the first heat treatment, and the third heat treatment at a temperature relatively lower than the second heat treatment temperature. This multi-stage heat treatment can further improve the coercive force of the AlNiCo-based particles. Specifically, if necessary, after a first heat treatment performed at 700 to 800 ° C., a second heat treatment may be performed at a temperature of 600 to 700 ° C. (excluding 700 ° C.) for 2 to 4 hours, and after the second heat treatment is performed, a third heat treatment may be performed at 550 to 600 ° C. (excluding 600 ° C.) for 10 to 15 hours.

Step d) may be a step of preparing core particles having a D ₅₀ of 12 μm or less by performing airflow classification on the heat-treated microparticles. As is well known, in the air flow classification of the cyclone method, coarse particles move to the outer wall of the classifier by the centrifugal force and fluid drag of the high-speed air flow and are recovered by turning along the wall surface, and fine particles move to the center (inside) of the classifier and swirl together with air to be exhausted and recovered, and the control of the classification point can be mainly controlled by the rotation speed of the classifier and the amount of air injected. Air flow classification is very suitable for the present invention because it is possible to precisely classify very fine particles and the classified particles have a very narrow particle size distribution. As a specific and non-limiting example, in order to classify and recover core particles having a D ₅₀ of 12 μm or less, advantageously satisfying Equations 7 and 8, the rotational speed during air flow classification may be 2500 to 8000 rpm, and the air injection amount may be 2 to 10 m ³ /min. However, those engaged in the field of controlling particle size distribution by air flow classification can perform the desired classification by controlling the main variables of known classifiers to obtain particles having a desired average size and distribution according to the detailed structure of various commercially available air flow classifiers.

Core particles having a D ₅₀ of 12 μm or less, obtained by air flow classification, and particles advantageously satisfying Equations 7 and 8 are very suitable for fine linear pattern printing, and difficult problems such as printing defects that may occur during the printing process are prevented, and it is advantageous because it can prevent changes in magnetic properties due to particle size deviation.

Step e) is a step of forming a shell for the core particles obtained by air flow classification, and step e) may include forming a metal shell. Specifically, forming a dielectric shell on the core particle; And forming a metal shell on top of the dielectric shell; may include, but, if necessary, a homogenous or heterogeneous dielectric shell forming step to protect the metal shell again may be further performed, of course.

In the step of forming a dielectric shell, any method commonly used for coating a dielectric on a particle may be used, but it is advantageous to use a sol-gel method in terms of forming a thin and uniform film. Specifically, it may be performed using an alkoxide sol-gel method or a colloid sol-gel method in consideration of the dielectric material of the shell to be formed. As a specific and non-limiting example, when a titanium oxide shell is to be formed, a titanium precursor such as titanium tetrabutoxide is dissolved in titanium sol. After mixing the dispersed core particles in a dispersion medium containing water, the core particles are separated and recovered and dried to prepare a core particle having a titanium oxide shell.

In the step of forming the metal shell, any method commonly used for coating metal on particles may be used, but it is advantageous to use electroless plating in terms of forming a thin and uniform film. It is advantageous to form a metal shell. Various electroless plating solutions may be used in consideration of the metal material of the metal shell. According to an advantageous example, when forming a silver shell with a metal shell, the plating bath for electroless plating may include a silver precursor (typically, silver nitrate, etc.), a pH adjusting agent (typically, KOH, etc.), a complexing agent (typically, ammonia water, ammonium salt, etc.), a solvent, a reducing agent, and the like. At this time, the reducing agent is monosaccharides, glucose, fructose, galactose, potassium sodium tartrate (Seignette salt), sodium tartrate (sodium tartrate), potassium tartrate (potassium tartrates), potassium sodium tartrate (potassium sodium tartrate), calcium tartrate (calcium tartrate), stearyl tartrate (stearyl tartrate), formaldehyde, and the like. At this time, the pH of the plating bath may be adjusted to 7 to 10 by a pH adjusting agent, and the plating bath may further include known additives for uniform plating.

The security ink composition according to the present invention exhibits printing characteristics suitable for a plate-type printed object having an uncurved surface shape as well as a curved flexible plate printed object, and is suitable for screen printing applications, such as printing on a printed object after applying the ink composition to a coating substrate such as a screen cloth. In detail, the security ink composition according to the present invention prevents the problem of viscosity being lowered due to dispersion and processing in the process of manufacturing ink for screen printing, and oxidation of AlNiCo-based magnetic particles due to surface damage, color degradation, and reduction of reflectance. It prevents problems such as high viscosity, uniform elasticity, and high durability while improving security characteristics. Therefore, the security ink composition according to the present invention can freely control the thickness of the ink according to the thickness of the screen, and enables strong and luxurious printing. However, in addition to this, it can be applied without limitation as long as it uses a screen printing method such as a use that can be printed on a flexible or curved substrate, a flat plate use, etc.

As described above, the ink composition according to the present invention can realize printing quality suitable for a plate-type printed object having an uncurved surface shape as well as a printed object having a curved and flexible surface shape, and thus, the printed object has an advantage that not only a plate-type object having an uncurved surface shape can be used, but also a curved and flexible one can be used. Examples of the printed material may include various materials such as paper, plastic, fiber, metal, and glass, but are not limited thereto.

The security ink composition according to the present invention may have a viscosity range as described above, and it may be more preferable to satisfy Equations 11 and 12 below. When the above viscosity range and/or the following Equations 11 and 12 are satisfied, high viscosity, uniform elasticity, and high durability can be secured, and physical properties more suitable for screen printing can be implemented. The viscosity range may be adjusted according to the type and content of components to be described later that may be included in the security ink composition, and Equations 11 and 12 below may be included in the security ink composition.

Equation 11: INK _ST ≤ BNK _γc

Equation 12: BNK _γc ≤ INK _SE ≤ SUB _SE

In Equations 11 and 12, INK _ST is the initial surface tension of the ink composition, BNK _γc is the wet critical surface tension of the coated substrate, INK _SE is the surface energy of the ink film on the coated substrate, and SUB _SE is the surface energy of the printed material.

After coating the security ink composition on the coating substrate, application may proceed in a state in which most of the solvent, particularly the highly volatile solvent is volatilized. Therefore, the main components of the ink coating film coated on the coating substrate may be magnetic particles, high-viscosity components, and trace amounts of low-volatility liquid components. Therefore, in order to satisfy Equation 12, it may be preferable that at least one of the surface tension of the high-viscosity component and the surface tension of the low-volatility liquid satisfy at least the wet critical surface tension of the surface of the coated substrate of Equation 12.

In one example of the present invention, in Equations 11 and 12, even if there is no difference between each element, it is suitable for the printing method, but if there is a difference of 2 mN / m or more between each element, the fine pattern realization effect is better. For example, the effect is more effective when the difference between INK _ST and BNK _γc in Equation 11 is 2 mN/m or more. In Equation 12, the effect is more effective when the difference between BNK _γc and INK _SE is 2 mN/m or more. In addition, in Equation 12, the effect is more effective when the difference between INK _SE and SUB _SE is 2 mN/m or more.

In Equations 11 and 12, INK _ST and BNK _γc depend on the type and content of the components contained in the security ink composition, the coating substrate, the printed material, etc., but are not limited thereto, but are independently 5 to 50 mN / m. In addition, INK _SE and SUB _SE depend on the type, content or coating substrate of the component, and the substrate to be printed, so it is not limited, but may be 30 to 80 mN / m independently of each other.

Hereinafter, the composition and composition ratio of the security ink composition according to the present invention that can satisfy the above-described desirable characteristics and the like will be described as a specific example.

As described above, the security ink composition according to the present invention includes AlNiCo-based magnetic particles, and at this time substantially further includes a base ink, and may further include additives as necessary to suit the required purpose and characteristics. It goes without saying that other additional components not mentioned herein may be further included. In addition, the content and content ratio of the composition described below are only described as specific and preferred examples, and the present invention is not limited thereto, of course.

The base ink may include a polymer resin and a solvent. At this time, the polymer resin and the solvent are not limited as long as they are used as components of ink in the printing field, specifically in the screen printing field, and specific examples thereof are as follows, but are not limited thereto.

The polymer resin serves to form a film on the surface of the object to be printed during screen printing, which can influence ink performance such as workability, gloss, adhesiveness, hardness, plasticity, water resistance, oil resistance, chemical resistance, and weather resistance. It can be referred to as a base resin. These polymer resins can be largely classified into thermoplastic resins, thermosetting resins, and photocurable resins. Specific examples of the thermoplastic resin include petroleum resin, casein, shellac, rosin-modified maleic acid resin, rosin-modified phenolic resin, nitrocellulose, cellulose acetate butyrate, cyclized rubber, chlorinated rubber, oxidized rubber, hydrochloric acid rubber, phenol resin, alkyd resin, polyester resin, unsaturated polyester resin, amino resin, epoxy resin, vinyl resin, vinyl chloride resin, vinylidene chloride resin, vinyl chloride acetate resin, ethylene vinyl acetate resin , acrylic resins, methacrylic resins, polyurethane resins, silicone resins, fluororesins, drying oils, synthetic drying oils, styrene-maleic acid resins, styrene-acrylic resins, polyamide resins, or butyral resins. Examples of the thermosetting resin include epoxy resins, phenol resins, benzoguanamine resins, melamine resins, and urea resins. As the photocurable resin (photosensitive resin), a linear polymer having a reactive substituent such as a hydroxyl group, a carboxyl group, or an amino group is reacted with a (meth)acrylic compound or cinnamic acid having a reactive substituent such as an isocyanate group, an aldehyde group, or an epoxy group, and a resin obtained by introducing a photocrosslinkable group such as a (meth)acryloyl group or a styryl group into the linear polymer can be used. In addition, it is also possible to use a half-esterified linear polymer containing an acid anhydride such as styrene-maleic anhydride copolymer or α-olefin-maleic anhydride copolymer with a (meth)acrylic compound having a hydroxyl group such as hydroxyalkyl (meth)acrylate. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

The solvent can dissolve or disperse the polymer resin to impart fluidity to the polymer resin, can play a role in transferring the composition to a printed object in screen plate making, and can be any solvent that can be adjusted within the above-mentioned viscosity range. -Dimethylformamide, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, acetone, hexane, methyl ethyl ketone, cyclohexanone, cyclopentanone, cyclohexane, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 3-methoxypropanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, It may include any one or two or more selected from ethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, and water. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

In the security ink composition according to the present invention, the weight ratio of the base ink and the AlNiCo-based magnetic particles may be appropriately adjusted according to the purpose and use, so it is not limited, and for example, the AlNiCo-based magnetic particles may be 0.1 to 70 parts by weight based on 100 parts by weight of the base ink. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

In the base ink, the weight ratio of the polymer resin and the solvent is not limited because it can be appropriately adjusted according to the purpose and use, for example, the required viscosity, and for example, 1 to 500 parts by weight of the solvent relative to 100 parts by weight of the polymer resin. It may be 5 to 300 parts by weight. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

In the base ink, since the additives may be appropriately selected and used according to the purpose and required purpose, they are not limited, and may include, for example, any one or two or more selected from pigments, dispersants, drying agents, drying retardants, plasticizers, antifoaming agents, leveling agents, coupling agents, ultraviolet absorbers, antioxidants, slipping agents, color separation inhibitors, precipitation inhibitors, flame retardants, antistatic agents, adhesion reagents, flow reagents, flame retardants, and curing agents. However, this is only described as a specific example, and the present invention is not construed as being limited thereto, and various other additives may be used, of course.

In the above additives, the pigment is not particularly limited as long as it can realize color, and for example, soluble azo pigments, insoluble azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, perylene pigments, perinone pigments, dioxazine pigments, anthraquinone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, andanthrone pigments, indanthrone pigments, flavanthrone pigments, pyranthrone pigments, or diketopyrrolopyrrole pigments; and the like. As a more specific example, red pigments include C.I. Pigment Red 7, 9, 14, 41, 48:1, 48:2, 48:3, 48:4, 81:1, 81:2, 81:3, 97, 122, 123,146, 149, 168, 177, 178, 180, 184, 185 . At this time, a yellow pigment and an orange pigment may be used in combination with the red pigment. In addition, C.I. Pigment Yellow 1, 2,3, 4, 5, 6, 10, 12, 13, 14, 15, 16, 17, 18, 20, 24, 31, 32, 34, 35, 35:1, 36, 36:1, 37, 37:1, 40, 42,43 ,53,55,60,61,62,63,65,73,74,77,81,83,86,93,94,95,97,98,100,101,104,106,108,109,210,113,114,115, 116, 117, 118, 119, 120, 123, 125, 126, 127, 128, 129, 137, 138, 139, 147, 148, 150, 151, 152, 153, 154, 155, 156, 161, 162, 164, 166, 167, 168, 169, 240, 171, 172, 173, 174, 175, 176, 177, 179, 180, 181, 182, 185, 187, 188, 193, 194, 199 and the like can be used. In addition, as an orange pigment, C.I. Pigment orange 36, 43, 51, 55, 59, 61, etc. can be used. In addition, as a green pigment, C.I. Pigment Green 7, 10, 36, 37, etc. can be used. In addition, as a blue pigment, C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 60, 64, etc. can be used. At this time, a purple pigment (for example, C.I. Pigment Violet 1, 19, 23, 27, 29, 30, 32, 37, 40, 42, 50, etc.) may be used in combination with the blue pigment. In addition, as the magenta pigment, a purple pigment (eg C.I. Pigment Violet 1, 19, etc.) and a red pigment (eg C.I. Pigment Red 144, 146, 177, 169, 81, etc.) may be mixed and used. At this time, a yellow pigment may be used in combination with the magenta pigment. In addition, carbon black having a particle size of 200 nm or less may be used as a black pigment.

In the above additives, the dispersant is not limited in kind, but may include at least one or two or more selected from the group consisting of fluorinated surfactants, polymerizable fluorinated surfactants, siloxane surfactants, polymerizable siloxane surfactants, polyoxyethylene surfactants, and derivatives thereof. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

In the above additives, the drying retardant may include any one or two or more selected from monoethylene glycol, diethylene glycol, triethylene glycol, and dimethyl sulfoxide. The antifoaming agent is used to remove harmful bubbles, and may include any one or two or more selected from silicone-based antifoaming agents such as dimethylpolysiloxane, methylethylpolysiloxane, and diethylpolysiloxane, and non-silicone-based antifoaming agents such as mineral oil, alcohol, and organic phosphate. The leveling agent is an auxiliary agent for preventing cracking or smoothing the ink film, and may include any one or two or more selected from silicone-based leveling agents selected from silicone diacrylate and silicone polyacrylate, alcohol-based leveling agents selected from methanol, ethanol, butanol, and the like. The plasticizer may include any one or two or more selected from phthalate-based plasticizers such as dioctyl phthalate, didodecyl phthalate, triethylene glycol dicaprylate, and dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, and triacetyl glycerin. The coupling agent is used when the object to be printed is mainly made of glass or metal, and a silane coupling agent may be mainly used. The UV absorber is for improving the weatherability of the printed material against light, and may include at least one selected from benzotriazole-based compounds and benzophenone-based compounds. The antioxidant is to prevent components in the ink from being oxidized or the surface of a screen-printed object from being oxidized, and may include any one or two or more selected from tocopherol, sesamol, zingerone, gosypol, capshacin, quercetin, gallic acid BHA, BHT, TBHQ, sulfur-containing compounds, amino acids, hydroxy acids, citric acid, and ascorbic acid. The slipping agent is an auxiliary agent that improves friction resistance by making the ink film smooth, and may include any one or two or more selected from oleic acid, LC-102N, LC-104N, LC-140B/P, and LC-402F. The color separation inhibitor is an additive added to prevent color separation when two or more types of pigments are used in a single ink or when a plurality of inks are mixed to match colors. The anti-settling agent is an auxiliary agent that prevents the pigment from settling to the bottom during ink storage when the specific gravity of the pigment is large. The curing agent is an auxiliary agent for accelerating the formation of a film of a polymer resin and improving the strength of the film formed, and is an isomeric mixture of ethylene diamine, propylene diamine-1,2 and -1,3, tetramethylene diamine-1,4, hexamethylene diamine-1,6, 2,2,4- and 2,4,4-trimethyl hexamethylene diamine, 2-methyl pentamethylene diamine and bis-(β-aminoethyl) amine (both It may include any one or two or more selected from an aliphatic polyamine-based curing agent such as ethylene triamine) or a mixture of aliphatic polyisocyanate and ethyl acetate in a weight ratio of 4:1 to 6:1. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

In the base ink, when the additive is further included, the weight ratio of the polymer resin and the additive may be appropriately adjusted according to the purpose and use, so it is not limited. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

The present invention can provide a security print containing the above-described AlNiCo-based magnetic particles, and can be specifically applied to ink for printing certificates and commercial screen ink applicable to other general security prints. In detail, the present invention includes banknotes, checks, postage stamps, gift certificates, certificates, bonds, etc., or general security printed materials in which the above-described AlNiCo-based magnetic particles are included as security elements. At this time, of course, the security element including the AlNiCo-based magnetic particles may have a shape designed for security, such as an image (including a part of a shape constituting an image), numbers, letters, geometric patterns, and the like.

A method of forming the security ink composition according to the present invention on a subject to be printed may use a conventional screen printing method. As a specific example, in the silk screen printing method using a conventional silk screen printing device, a mesh screen such as a mesh screen woven with silk fiber or general chemical fiber yarn or a metal mesh screen woven with metal yarn such as stainless is tightly fixed to a fixed frame, and then a photoresist is applied to the entire surface of the screen in a uniform thickness. It can be performed by film removal. After the screen manufactured in this way is brought close to the surface of the object to be printed, printing ink is dispensed into the screen frame and the printing ink is pushed while applying pressure to the screen using a squeegee. The ink dispersed by the squeegee penetrates the film-off portion, that is, the part composed of patterns or characters, and is printed on the surface of the object to be printed. However, this is only described as a specific example, and the present invention is not necessarily construed as being limited thereto.

Hereinafter, the present invention will be described in detail through examples, but these are for explaining the present invention in more detail, and the scope of the present invention is not limited by the following examples.

According to the design composition of 6 wt% Al, 15 wt% Ni, 22 wt% Co, 4 wt% Ti, 3 wt% Cu, and 50 wt% Fe, raw material powders (aluminum powder, nickel powder, cobalt powder, titanium powder, copper powder, and iron powder, purity of the raw material powder ≥ 99.9%) were mixed, melted in an inert atmosphere, and solidified to prepare an ingot. 1 kg of the prepared ingot was placed in a crucible heated by a high-frequency generator and placed under an inert atmosphere, and then the temperature was maintained at 1650° C. to form an AlNiCo-based molten metal. For atomization, the molten metal was injected into a vacuum atomization confinement, and a cooling medium, which was an aqueous solution of urea in which urea was dissolved at 25% by weight, was sprayed at 600 bar through an annular spray nozzle.

The prepared microparticles were heat treated at 750° C. for 1 hour under an argon gas atmosphere.

The particles obtained after the heat treatment were air-classified by a cyclone method under conditions of a rotational speed of 7500 rpm and an air injection amount of 2.8 m ³ /min to obtain core particles having a D ₅₀ of 7.8 μm and a D ₉₀ of 14.1 μm. Thereafter, the core particles obtained by air flow classification were washed twice with ethanol and dried at 60 °C.

After sampling about 1 g at random from the obtained core particles, elemental analysis (10kV, 100sec) was performed on the central region of the particle cross section by EDS (Energy Dispersive X-Ray Spectroscopy, FEI company, Magellan400), and elemental analysis was performed on each of 50 particles. , Fe analysis results). In addition, the value specified by Equations 4, 5, and 6, that is, the degree of deviation from the design composition was set as 'DEV' and shown in Table 2.

Separately, 1 g of core particles, 1 ml of tetrabuthoxy titanium (TBOT) (Aldrich), 1 ml of distilled water, and 170 ml of ethanol were added to the washed core particles, and then stirred at a rotational speed of 300 rpm for 2 hours at a temperature of 85 ° C. The surface of the core particles was coated with a titanium oxide shell (50 nm thick). After separating and recovering the core particles coated with the titanium oxide shell with a magnet, they were washed twice with ethanol and dried.

Thereafter, 21 g of silver nitrate (AgNO ₃ ) and 4 g of sodium hydroxide (NaOH) were added to 1200 ml of distilled water, followed by 34 ml of ammonium hydroxide (NH4OH), and stirring was performed to change the brown precipitate into a transparent silver amine complex solution. After adding 60 g of titanium oxide shell-coated core particles to the silver amine complex solution maintained at 3° C., the mixture was stirred at a speed of 300 rpm for 30 minutes. A solution (3 ° C) in which 20 g of glucose and 1.5 g of potassium tartrate were dissolved in 400 ml of distilled water was added to the silver amine complex solution (3 ° C) in which core particles coated with titanium dioxide shells were dispersed, and then stirred at a speed of 300 rpm for 1 hour to form a silver shell with a thickness of 58.4 nm on the core particles on which the titanium oxide shell was formed, thereby forming an AlNiCo-based Magnetic particles were prepared. Thereafter, the prepared magnetic particles were separated with a magnet, washed twice with ethanol, and dried at 60°C.

The coercive force, saturation magnetization (Ms), and residual magnetization (Mr) of the prepared magnetic particles were measured using a vibrating sample magnetometer (VSM, Lakeshore, 7400 series), and the results are summarized in Table 3.

[Comparative Example 1]

Core particles were prepared in the same manner as in Example 1, except that water was used as a cooling medium during spraying, and then magnetic particles were prepared in the same manner as in Example 1, except that a room temperature solution was used when preparing the silver shell.

The core particles prepared in Comparative Example 1 also confirmed the compositional uniformity of the core particles in the same manner as in Example 1, which is summarized in Table 1, and also values specified by Equations 4, Equation 5, and Equation 6, that is, the degree of deviation from the design composition was set as 'DEV' and summarized in Table 2. In addition, the magnetic properties of the prepared magnetic particles were also measured in the same manner as in Example 1, and the results are summarized in Table 3.

[Table 1-1]

[Table 1-2]

In Table 1 (Table 1-1 and Table 1-2), C _m (A) is the average weight percent of element A of core particles, σ (A) is the standard deviation of element A among core particles (wt %), and UNF (A) is C _m (A) / σ (A). In addition, the reason why the sum of C _m between elements in Table 1 does not become 100 is due to unavoidable impurities.

As can be seen from Table 1, in the case of the AlNiCo-based magnetic particles according to the present invention, the D ₅₀ of the core particles is 7.8 μm and the D ₉₀ is 14.1 μm, while having remarkably improved composition uniformity. It can be seen that it has a very fine and very narrow particle size distribution.

[Table 2]

As can be seen from Table 2, in the case of the core particles prepared in Examples, it can be seen that magnetic particles having substantially the same composition as the designed raw material are produced.

[Table 3]

As can be seen from Table 3, segregation and abnormality are prevented by rapid cooling and composition deviation by oxidation is prevented, so that hard magnetic particles having magnetic properties that are indistinguishable from soft magnetic properties and improved security can be obtained through a simple and very short heat treatment of 750 ° C. for 1 hour.

1 is a scanning electron microscope photograph of AlNiCo-based magnetic particles prepared in Example 1; As can be seen from FIG. 1, it can be seen that substantially spherical particles are produced, and it can be confirmed that a silver shell is formed uniformly and stably by electroless plating at a low temperature of 3 ° C.

2 is a scanning electron microscope photograph of a cross-section of the prepared AlNiCo-based magnetic particles and a diagram showing a measurement of the thickness distribution of the silver shell. As can be seen from FIG. 2, it can be seen that the silver shell has an extremely uniform thickness with an average thickness of 58.4 nm and a standard deviation of only 7.9 nm. In addition, as in the concentration uniformity test, 50 AlNiCo-based magnetic particles were randomly selected and the thickness and thickness distribution of the formed silver shells were measured through cross-section observation. As a result, the average thickness of the silver shell (average thickness of the silver shell in each magnetic particle) of all measured AlNiCo-based magnetic particles was in the range of 56.2 to 59.7 nm, and the standard deviation of the thickness of the silver shell (standard deviation of the thickness of the silver shell in each magnetic particle) was 7.1 to 8.3 belonged to the nm category.

In addition, as a result of measuring the infrared reflectance of the magnetic particles prepared by irradiating a 900 nm laser using a spectrophotometer (Carry 5000), it was confirmed that they had a reflectance of 64%.

In addition, as a result of measuring the lightness (L*) value of the CIELAB color system using a color difference meter (Spectrophotometer CM-5), it was confirmed that it had 78.

A security ink composition was prepared using the AlNiCo-based magnetic particles prepared in Example 1. In detail, after mixing 55% by weight of the first polymer resin (polyvinyl chloride-based resin, SOLBIN-A, Nissin), 40% by weight of the second polymer resin (urethane varnish, Samhwa paint), and 5% by weight of the AlNiCo-based magnetic particles, the mixture was put into a meat softener and subjected to tenderization 4 to 5 times in a meat tenderizer to prepare a security ink composition. At this time, the viscosity (at 20 ℃) of the security ink composition was 3900 cps.

Using a screen printing device, the mesh screen is brought close to the surface of the object to be printed, and then the security ink composition is dispensed into the screen frame and pushed while applying pressure to the screen using a squeegee, so that the security ink composition dispersed by the squeegee permeates into the film removal portion to form a coating film on the surface of the object to be printed. Thereafter, the printed object on which the coating film was formed was sufficiently dried at 70° C. to obtain a security print. At this time, the screen is a silk screen made of a polyester material with a standard of 150 mesh, and the printed object is a fabric made of a polyester material having a curved and flexible surface shape.

A security ink composition was prepared using the AlNiCo-based magnetic particles prepared in Example 1. Specifically, 12 wt% of the first polymer resin (polyvinyl chloride-based resin, SOLBIN-A, Nissin), 14 wt% of the second polymer resin (urethane varnish, Samhwa paint), 10 wt% of the AlNiCo-based magnetic particles, 20 wt% of the extender pigment (Dongho calcium, TL-2000), 30 wt% of the first solvent (3-ethoxypropionic ethyl ester), and the second solvent (dipropylene) Glycol monomethyl ether) 10% by weight, dispersant (surfactant, Koremul-263Na, Hannong Chemical) 2% by weight, desiccant (ALP 98, Jinyang Chemical) 1% by weight and plasticizer (DBP, Aekyung Oil) 1% by weight were mixed, and then put into a tenderizer and tenderized 4 to 5 times in a tenderizer to prepare a security ink composition. At this time, the viscosity (at 20 ℃) of the security ink composition was 2200 cps.

Using a screen printing device, the mesh screen is brought close to the surface of the object to be printed, and then the security ink composition is dispensed into the screen frame and pushed while applying pressure to the screen using a squeegee, so that the security ink composition dispersed by the squeegee permeates into the film removal portion to form a coating film on the surface of the object to be printed. Thereafter, the printed object on which the coating film was formed was sufficiently dried at 70° C. to obtain a security print. At this time, the screen is a silk screen made of a polyester material with a standard of 150 mesh, and the printed object is a fabric made of a polyester material having a curved and flexible surface shape.

As a result, even though the security ink composition was printed on a curved flexible substrate having a different surface shape than a flat plate, both Examples 2 and 3 had excellent bonding properties to the substrate and durability of the coating film itself.

In addition, the printed matter was optically observed in the visible and infrared regions. As a result, it was confirmed that the color of the part printed with the ink containing the AlNiCo-based magnetic particles according to the present invention was very bright.

In addition, in the soft magnetic image obtained by taking the magnetic image in the soft magnetic mode using the magnetic image measuring device (G&D), the soft magnetic mode has magnetic properties similar to those of general soft magnetic pigments, so it is practically impossible to distinguish them. However, in the hard magnetic image taken in the hard magnetic mode using the same magnetic image measuring device, the AlNiCo-based magnetic particles according to the present invention are stably detected in the hard magnetic mode and form a clear image, but the general soft magnetic pigment is not detected. It can be seen. In addition, in an infrared image taken using an infrared image measuring device (Foster & Freeman, VSC 4 PLUS), the AlNiCo-based magnetic particles according to the present invention did not appear as an image due to infrared reflection characteristics.

As described above, the present invention has been described by specific details and limited embodiments and drawings, but this is only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. Those skilled in the art can make various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described embodiments and should not be determined, and it will be said that not only the claims to be described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the present invention.

Claims (17)

A security ink composition for screen printing comprising AlNiCo-based magnetic particles and having a viscosity of 1000 cps to 30000 cps at 20 ° C,
The AlNiCo-based magnetic particles include core particles containing Al, Ni, and Co; and an inorganic shell surrounding the core particle.
The core particle is an ultra-fine particle that has compositional uniformity of Formulas 1, 2 and 3 below and further satisfies Formulas 7 and 8 below, a security ink composition for screen printing.
Equation 1: 10 ≤ UNF(Al)
Equation 2: 10 ≤ UNF(Ni)
Equation 3: 10 ≤ UNF(Co)
(In Equation 1, UNF(Al) is the value obtained by dividing the average Al composition between core particles by the standard deviation of the Al composition, based on the weight percent composition. In Equation 2, UNF (Ni) is the value obtained by dividing the average Ni composition between the core particles, based on the weight percent composition, by the standard deviation of the Ni composition. In Equation 3, UNF (Co) is the value obtained by dividing the average Co composition between the core particles, based on the weight percent composition, by the standard deviation of the Co composition.)
Equation 7: 3 μm ≤ D ₅₀ ≤ 12 μm
Equation 8: 10 μm ≤ D ₉₀ ≤ 20 μm
(In Equation 7, D ₅₀ is the particle size corresponding to 50% of the cumulative distribution of the particle diameter of the core particles, and in Equation 8, D ₉₀ is the particle size corresponding to 90% of the cumulative distribution of the particle diameter of the core particles) According to claim 1,
A security ink composition for screen printing that satisfies Formulas 11 and 12 below.
Equation 11: INK _ST ≤ BNK _γc
Equation 12: BNK _γc ≤ INK _SE ≤ SUB _SE
(In the above formulas 1 and 2, INK _ST is the initial surface tension of the ink composition, BNK _γc is the wet critical surface tension of the coated substrate, INK _SE is the surface energy of the ink coating on the coated substrate, and SUB _SE is the surface energy of the printed material) According to claim 1,
A security ink composition for screen printing further comprising a base ink comprising a polymer resin and a solvent. According to claim 3,
The security ink composition for screen printing includes 0.1 to 70 parts by weight of the AlNiCo-based magnetic particles based on 100 parts by weight of the base ink,
The base ink is a security ink composition for screen printing comprising 1 to 500 parts by weight of the solvent based on 100 parts by weight of the polymer resin. According to claim 3,
The base ink is a pigment, a dispersant, a drying agent, a drying retardant, a plasticizer, an antifoaming agent, a leveling agent, a coupling agent, a UV absorber, an antioxidant, a slipping agent, a color separation inhibitor, an anti-settling agent, a flame retardant, an antistatic agent, and a curing agent. delete According to claim 1,
The AlNiCo-based magnetic particles are security ink composition for screen printing having an infrared reflectance of 60% or more based on a wavelength of 900 nm. According to claim 1,
The hard magnetic particle is a security ink composition for screen printing having an L * value of 60 or more as measured by a colorimeter. According to claim 1,
The inorganic shell is a security ink composition for screen printing comprising a metal shell satisfying the following formulas 9 and 10.
Equation 9: 50 nm ≤ t _m ≤ 100 nm
Equation 10: σ _t ≤ 30 nm
(In Equation 9, t _m is the average thickness of the metal shell, and in Equation 10, σ _t is the standard deviation of the thickness of the metal shell) According to claim 9,
The inorganic shell further comprises a dielectric shell located below or above the metal shell security ink composition for screen printing. According to claim 1,
Saturation magnetization (Ms) of the magnetic particles is 50 to 150 emu / g, residual magnetization (Mr) is 10 to 40 emu / g security ink composition for screen printing. According to claim 1,
The coercive force of the magnetic particles is 100 to 500 Oe security ink composition for screen printing. According to claim 1,
The core particle is a security ink composition for screen printing further comprising one or two or more fourth elements selected from Cu, Ti, Fe and Si. According to claim 13,
The core particle is a security ink composition for screen printing in which the value obtained by dividing the average composition of the fourth element between the core particles by the standard deviation of the composition of the fourth element, based on the weight percent, is 10 or more. According to claim 1,
The core particles further contain Ti, Fe, and Cu, and, by weight, Al 4 to 12%, Ni 10 to 20%, Co 15 to 25%, Ti 1 to 10%, Cu 0.5 to 5%, the balance Fe and other unavoidable impurities A security ink composition for screen printing containing. A security print formed from the security ink composition for screen printing according to any one of claims 1 to 5 and 7 to 15. A certificate of value containing the security printout of clause 16.

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