KR102101798B1 - Photonic crystal film for security feature, and method of manufacturing the same, and security articles using the same - Google Patents

Abstract

The present invention relates to a photonic crystal film for security elements, a method for manufacturing the same, and an anti-counterfeiting article comprising the same. More particularly, the present invention relates to a photonic crystal film for a security element and a security article including the same, having high transmittance and reflection characteristics, excellent visibility, and particularly maintaining its performance despite repeated and continuous folding.

Description

Photonic crystal film for security feature, and security article using the same, and method of manufacturing the same, and security articles using the same}

The present invention relates to a photonic crystal film for security elements, a method for manufacturing the same, and an anti-counterfeiting article comprising the same. More particularly, the present invention relates to a photonic crystal film for a security element and a security article including the same, having high transmittance and reflection characteristics, excellent visibility, and particularly maintaining its performance despite repeated and continuous folding.

Photonic crystal (photonic crystal) refers to a material having a wide band gap by periodically changing the dielectric constant at a level of half the wavelength of light as a matrix and particles having different refractive indices are regularly arranged to form a crystal lattice.

The optical bandgap controls photons in a photonic crystal in the same way that the electrons' bandgap controls electrons in a semiconductor. When light having a broad spectrum from the outside enters a photonic crystal, the wavelength band corresponding to the optical bandgap Only light does not propagate inside the material and is selectively reflected. When such an optical bandgap exists in the visible light region, selective reflection by the optical bandgap appears as a reflection color.

The fact that the regular arrangement of colloidal particles shows a reflective color is based on the same principle, and is a color corresponding to the optical band gap of a photonic crystal. The reflective color of colloidal photonic crystals is determined by the refractive index, crystal structure, particle size, and spacing between particles. Therefore, by controlling this, a photonic crystal having a desired reflection color can be produced.

The film-type photonic crystal can increase the reflectance by increasing the thickness of the film to produce a reflective color with excellent visibility, but the mechanical strength of the photonic crystal film itself is very weak and is not easy to handle due to durability problems such as easily breaking. There are limitations in application to areas such as bills and security documents that require flexibility.

Therefore, it is necessary to research and develop a photonic crystal film having excellent anti-rolling property and high reflectance and transmittance by overcoming the limitation of durability to be used as a security element for preventing forgery and alteration.

Republic of Korea Patent Publication No. 10-2015-0031862 (2015.03.25.)

The present invention has a high reflectance characteristic, excellent visibility, and can maintain the above characteristics despite particularly continuous and repetitive folding, and thus has excellent durability, and furthermore, can provide a transparent window film made of photonic crystals for security performance. It is an object to provide a photonic crystal film for a security element further improved.

In addition, an object of the present invention is to provide a method of manufacturing a photonic crystal film for manufacturing a photonic crystal film for a security element as described above simply and efficiently.

In addition, an object of the present invention is to provide a security article for forgery prevention comprising the photonic crystal film for the security element.

In order to achieve the above object, an aspect of the present invention

As a cured product of a photonic crystal composition comprising a polymer matrix, colloidal particles dispersed in the polymer matrix and arranged in a crystal lattice structure, and a photoinitiator,

The polymer matrix is selected from the group consisting of ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate and trimethylolpropane triacrylate Any one or more first acrylate-based compounds and any one or more second acrylates selected from the group consisting of polypropylene glycol acrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate It relates to a photonic crystal film characterized in that the polymer is derived from a mixture of compounds based.

In the photonic crystal film according to an embodiment of the present invention, the weight mixing ratio of the first acrylate-based compound and the second acrylate-based compound may be 55:45 to 25:75.

In the photonic crystal film according to an embodiment of the present invention, the polymer matrix may have a refractive index difference with colloidal particles of 0.02 or more.

In the photonic crystal film according to an embodiment of the present invention, the polymer matrix may have a refractive index of 1.4 to 1.5, and the colloidal particles may have a refractive index of 1.3 to 3.0.

The photonic crystal film according to an embodiment of the present invention has a thickness of 10 to 200 μm, and a transmittance in a wavelength range of 400 to 800 nm may be 60% or more. In addition, the average reflectance at a wavelength of 300 to 800 nm may be 30% or more.

In the photonic crystal film according to an embodiment of the present invention, the average particle diameter of the colloidal particles may be 50 to 350 nm.

In the photonic crystal film according to an embodiment of the present invention, the colloidal particles may satisfy relational expression 1 below.

[Relationship 1]

Da × 0.95 ≤ Ds ≤ Da × 1.05

(In the relational expression 1 above, Ds is the particle diameter (nm) of the colloidal particles, and Da is the average particle diameter (nm) of the colloidal particles.)

In the photonic crystal film according to an embodiment of the present invention, the colloidal particles may be any one or more selected from metal nanoparticles, metal oxide nanoparticles, organic nanoparticles, and carbon structure nanoparticles.

Another aspect of the present invention relates to a security article comprising the photonic crystal film.

The security article according to an embodiment of the present invention may include any one selected from the group consisting of bank notes, securities, gift certificates, lotteries, passports, ID cards, credit cards, and product labels.

In addition, another aspect of the present invention is a step of injecting a dispersion comprising a mixture of a first acrylate-based compound and a second acrylate-based compound, colloidal particles, and a photoinitiator into the hole on a substrate having a hole that is perforated and the photonic crystal. It relates to a method for producing a photonic crystal film comprising the step of curing the composition layer by light irradiation.

In the method of manufacturing a photonic crystal film according to an embodiment of the present invention, the first acrylate-based compound is ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol triacrylate , Dipentaerythritol pentaacrylate and trimethylolpropane triacrylate, any one or more selected from the group consisting of, the second acrylate-based compound is polypropylene glycol acrylate, polypropylene glycol dimethacrylate, polyethylene glycol It may be any one or more selected from the group consisting of diacrylate and polyethylene glycol dimethacrylate.

In the method of manufacturing a photonic crystal film according to an embodiment of the present invention, the weight mixing ratio of the first acrylate-based compound and the second acrylate-based compound may be 55:45 to 25:75.

In the method of manufacturing a photonic crystal film according to an embodiment of the present invention, the step of injecting the dispersion may further include a transparent polymer film on one surface of the substrate.

In the method of manufacturing a photonic crystal film according to an embodiment of the present invention, the dispersion may be applied at 60 to 100 ℃.

The photonic crystal film for security elements according to the present invention has the advantage of minimizing damage such as cracking or peeling of the film despite continuous and repeated folding by maximizing flexibility and strength. From this, the durability of the film is improved and the film can be easily handled, and thus it has the advantage that it can be applied as a security element to anti-counterfeiting articles such as bills and security documents that require flexibility. Furthermore, the photonic crystal film according to the present invention is a transparent window film made of a photonic crystal, and can be applied at an early stage of manufacturing a security article, and has the advantage of realizing excellent flexibility and strength by securing product stability and reliability.

1 schematically shows a perspective view of a banknote according to an embodiment of the present invention.

Hereinafter, a photonic crystal film for a security element according to the present invention, a method for manufacturing the same, and a security article including the same will be described in more detail. The present invention can be better understood by the following examples. The following examples are for illustrative purposes of the present invention and are not intended to limit the scope of protection defined by the appended claims. At this time, the technical terms and scientific terms used have a meaning that is understood by a person having ordinary knowledge in the technical field to which this invention belongs, unless otherwise defined.

The term “(meth) acrylate” is meant to include “acrylate” and “methacrylate” unless otherwise noted in the present invention.

Although the conventional photonic crystal film has excellent reflectance, there is a limit in practical application as a security element because the film is easily broken or damaged when a high degree of physical deformation such as folding or bending is applied. Accordingly, the present inventors intend to present a photonic crystal film for a security element that is not easily damaged by a high degree of physical deformation. Furthermore, the present invention intends to provide a transparent photonic crystal film having excellent visibility as well as improved durability by maintaining flexibility and strength that does not degrade its properties even after continuous and repeated folding.

One aspect of the present invention is to have a reflection spectrum for a specific wavelength, a polymer matrix derived from two or more different acrylate-based compounds, a security element that is a cured product of a photonic crystal composition comprising colloidal particles dispersed in the polymer matrix It is to provide a photonic crystal film for. At this time, the colloidal particles are characterized by being arranged in a crystal lattice structure by inducing self-assembly of the colloid by a polymer derived from two or more different acrylate-based compounds.

According to an aspect of the present invention, by including a polymer matrix derived from the two or more different acrylate-based compounds can absorb the wavelength of a specific region to express the structure color, secure excellent optical properties and excellent reflection properties and high transparency Of course, it has an advantage of maximizing mechanical strength and flexibility without deteriorating the optical properties because it has excellent folding endurance even in continuous and repetitive folding. This has the advantage of being able to easily handle the film by enhancing durability, and in particular, it can be applied in the early stages of manufacturing security items, and can be applied to security items such as bills and security documents that can secure flexibility and reliability of mechanical properties. Have

Specifically, the photonic crystal film for security elements according to an aspect of the present invention is maintained in its original form without damaging the photonic crystal film for security elements even in an environment in which a high degree of physical deformation is continuously and repeatedly applied through maximization of flexibility and mechanical strength. The high reflectivity and light transmittance that the photonic crystal film for the security element must have can be maintained continuously, from which the physical properties as the security element can be secured.

According to one aspect of the invention, the polymer matrix is characterized in that it is derived from a mixture of a first acrylate-based compound and a second acrylate compound. These combinations have the property of maximizing flexibility while inducing self-assembly of the colloid, and realizing strength corresponding to foldability, thereby minimizing degradation of optical properties even when continuous and repetitive folding is applied to the film.

Specifically, the first acrylate-based compound is ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol triacrylate ), Dipentaerythritol pentaacrylate, and may be any one or more selected from the group consisting of trimethylolpropane triacrylate. These components provide excellent reflectance and high light transmittance of the photonic crystal film, and can secure excellent coating properties in combination with a second acrylate-based compound to be described later, and have high optical properties despite continuous and repetitive folding. It can be implemented, it has the property of maintaining the physical properties of strength and flexibility, which is difficult to implement by polymerization according to single use. More specifically, the first acrylate-based compound may be ethoxylated trimethylolpropane triacrylate (ETPTA).

The second acrylate-based compound is a glycol-based (meth) acrylate compound having an alkylene glycol as a repeating unit, and as a specific example, polypropylene glycol acrylate (Poly (propylene glycol) diacrylate: PPGDA), Polypropylene glycol dimethacrylate (PPGDMA), Polyethylene glycol diacrylate (PEGDA) and Polyethylene glycol dimethacrylate (PEGDMA) It includes any one or more from the group consisting of, but is not limited thereto. More specifically, it is effective that the second acrylate-based compound is a glycol-based diacrylate compound having an acrylate group at the sock end, and preferably, the first acrylate-based compound is polypropylene glycol dimethacrylate. It is more effective in terms of improving physical properties due to its excellent compatibility with compounds.

The second acrylate-based glycol-based (meth) acrylate compound is not limited in molecular weight, but has a weight average molecular weight of 300 to 3,000 g / mol, specifically a weight average molecular weight of 700 to 1,800 g / mol, More specifically, it may be 500 to 1,000 g / mol, and when it satisfies the above range, in combination with the first acrylate-based compound, an excellent coating property and a property of a cured product by photocuring, and flexibility and strength are realized. In particular, it is more effective in terms of maximizing the improvement of anti-theft. The second acrylate-based compound is not limited to a molar fraction of an acrylate functional group compared to the repeating unit in the structure, but it is controlled in combination with the first acrylate-based compound to improve curing reactivity as well as flexibility and strength. It is more effective.

One more preferred aspect of the present invention is to control the weight mixing ratio of the first acrylate-based compound and the second acrylate-based compound. The weight mixing ratio can be adjusted within the range of implementing the desired effect of the present invention, specifically, the weight mixing ratio of the first acrylate-based compound and the second acrylate-based compound is 55:45 to 25:75, more Specifically, it may be 50:50 to 30:70. In the case of satisfying the above range, it is possible to implement excellent visibility with high optical transmittance and reflectivity while minimizing damage such as colloidal particle detachment or film breakage even during continuous and repeated folding, and thus requires flexibility in articles requiring flexibility. Its application as a security element has an excellent effect. On the other hand, if it is out of the above range, it may be difficult to achieve the desired effect of the present invention because it is difficult to obtain a physical property balance that realizes excellent optical properties along with flexibility, strength, and durability.

According to an aspect of the present invention, the polymer matrix is difficult to achieve the object of the present invention when the polymer is derived from the first acrylate-based compound alone or the second acrylate-based compound alone, and the first acrylate-based compound and agent The desired effect can be realized by including a combination of 2 acrylate-based compounds.

According to an aspect of the present invention, the photonic crystal composition is characterized in that it comprises colloidal particles uniformly dispersed in the polymer matrix.

The colloidal particles are dispersed in the polymer matrix to form a crystal lattice structure through self-assembly of the colloid so that the photonic crystal film for the security element can have photonic crystal properties. The colloidal particles are not limited in their kind, and specifically, any one or more selected from metal nanoparticles, metal oxide nanoparticles, organic nanoparticles, and carbon structure nanoparticles may be used. More specifically, the metal nanoparticles are gold (Au), silver (Ag), copper (Cu), nickel (Ni), zinc (Zn), aluminum (Al), tin (Sn), palladium (Pd), platinum It may be any one selected from (Pt) and silicon (Si) or a mixture thereof or an alloy thereof, and the metal oxide nanoparticles may be oxides of the metal nanoparticles. The organic nanoparticle is any one or two selected from polyethylene, polypropylene, polyacrylate, polymethyl methacrylate, polystyrene, polydimethylsiloxane, polyimide, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, and polycarbonate. The above-described polymer nanoparticles may be used, and the carbon structure nanoparticles may include graphite, graphene, carbon fiber, and carbon nanotubes, but are not limited thereto.

The colloidal particles are not limited in size, but specifically, the average particle diameter may be 50 to 350 nm, and more specifically, 80 to 320 nm. The size of the colloidal particles can be adjusted differently according to the volume occupied by the colloidal particles in the photonic crystal film. That is, the size of the colloidal particles used may vary according to the volume ratio of the colloidal particles, and when the volume of the colloidal particles is 5 to 25% by volume based on the total volume of the crystal film, the average particle diameter of the colloidal particles is 50 to 50 It may be 180 nm, when the volume of the colloidal particles is greater than 25 to 60% by volume, the average particle diameter of the colloidal particles may be greater than 180 nm to 250 nm, and when the volume of the colloidal particles is greater than 60 to 90% by volume, The colloid particles may have an average particle diameter of more than 250 nm to 350 nm, but are not limited thereto. As a more specific example, based on the total volume of the photonic crystal film, when the volume of the colloidal particles is 33% by volume, the average particle diameter of the colloidal particles may be 140 to 220 nm, and when the volume is 5% by volume, the average of the colloidal particles The particle diameter may be 50 to 120 nm, and when the volume is 90% by volume, the average particle diameter of the colloidal particles may be 180 to 320 nm. If it is out of the above range, it may be difficult to secure the visibility of the photonic crystal film for the security element beyond the reflection wavelength of the visible light region. At this time, the shape of the colloidal particles is not greatly limited, but it is effective to use spherical nanoparticles.

Further, in terms of having excellent reflectance by forming a regularly arranged crystal lattice dispersed in a polymer matrix, the colloidal particles may satisfy the following relational expression 1.

[Relationship 1]

Da × 0.95 ≤ Ds ≤ Da × 1.05

(In the relational expression 1 above, Ds is the particle diameter (nm) of the colloidal particles, and Da is the average particle diameter (nm) of the colloidal particles.)

That is, when the average particle diameter of the colloidal particles is 200 nm, the particle diameter of each colloidal particle may satisfy a particle diameter of 190 to 210 nm. At this time, the particle size and the average particle diameter (D50) of the colloidal particles may be calculated from particle size distribution, and the particle size distribution may be measured using a laser particle size analyzer.

As described above, by using colloidal particles having a uniform particle diameter, a highly precise and regularly arranged crystal lattice structure can be achieved, whereby the photonic crystal film for the security element has excellent reflectance and can secure excellent visibility. It has characteristics.

In addition, the photonic crystal is a material in which particles having different refractive indices from the polymer matrix are regularly arranged to form a crystal lattice. The photonic crystal film for a security element according to an aspect of the present invention is also very important in the refractive index of the polymer matrix and the refractive index of the colloidal particles Do.

According to an aspect of the present invention, the polymer matrix may have a refractive index difference with colloidal particles of 0.02 or more, and specifically, may be 0.03 to 1.55. When the above range is satisfied, the photonic crystal film for a security element may have an excellent reflection spectrum with respect to a specific wavelength, and specifically has an average reflectance of 30% or more and more specifically 40% or more at 300 to 800 nm. By implementing the reflectance within the above range, it has excellent visibility and discrimination. More preferably, the maximum reflectance may be 48% or more. The upper limit of the maximum reflectance is not particularly limited, but the upper limit of the practical maximum reflectance may be 60% or less. At this time, the wavelength region where the maximum reflectance appears may vary depending on the size of the colloidal particles used, and of course, the wavelength region cannot be limited. As a specific example, when a spherical silica having an average particle diameter of 170 nm is used as colloidal particles, the maximum reflectance may appear in the wavelength range of 530 to 535 nm, and the reflection color may be green. In addition, when a spherical silica having an average particle diameter of 200 nm is used as colloidal particles, the maximum reflectance may appear in the wavelength range of 620 to 630 nm, and the reflection color may be red.

In addition, the refractive index of the polymer matrix may be 1.4 to 1.5, and the refractive index of the colloidal particles may be 1.3 to 3.0. More specifically, as a non-limiting example, the refractive index of the polymer matrix may be 1.45 to 1.49, preferably 1.47 to 1.49, and the refractive index of the colloidal particles may vary depending on the type of colloidal particles, but for example silica In the case of nanoparticles, the refractive index may be 1.43 to 1.5.

Although the thickness of the photonic crystal film according to an aspect of the present invention is not greatly limited, the thickness may be 10 to 200 μm, specifically 30 to 150 μm, in order to realize the desired effect of the present invention. When the above range is satisfied, the mechanical strength of remarkably excellent flexibility, flexural strength, and impact strength is maintained, so that even in an environment where a high degree of physical deformation is repeatedly applied, the film can be maintained intact without damage. More specifically, the thickness of the photonic crystal film may be 50 to 100 μm.

At the same time, the photonic crystal film according to an aspect of the present invention may have a transmittance of 60% or more, specifically 70% to 99%, at a wavelength of 400 to 800 nm, specifically, at a wavelength of 500 to 700 nm.

The photonic crystal film according to an aspect of the present invention is not greatly limited in its manufacturing method and can be manufactured using a conventional method. Specifically, the method for manufacturing a photonic crystal film according to an aspect of the present invention is perforated and provided with holes. Injecting a dispersion comprising a mixture of a first acrylate-based compound and a second acrylate-based compound, colloidal particles, and a photoinitiator into the hole on a substrate and curing the light by irradiating the photonic crystal composition layer. At this time, the mixture comprising the mixture of the first acrylate-based compound and the second acrylate-based compound, colloidal particles, and a photoinitiator is applied to form a photonic crystal composition layer.

The substrate is made of a photonic crystal on the substrate by partially punching the hole, and then raising the substrate with the hole on the substrate, and then injecting a dispersion into the hole and preparing a photonic crystal film by light irradiation. A transparent window film can be formed. The transparent window film can improve process efficiency by applying it in the initial stage when manufacturing security items such as banknotes, and it has its own flexibility and strength to prevent damage from external factors, and further improve security performance. It has a characteristic. At this time, the substrate may be a transparent polymer film. Preferably, the step of injecting the dispersion may be performed on a transparent polymer film on one surface of the substrate. In addition, another transparent polymer film may be further included on the other side of the substrate, thereby providing a security article that is a laminate including a substrate having a photonic film layer laminated between the transparent polymer films.

Another aspect of the method for manufacturing the photonic crystal film is to apply a dispersion on a substrate and then photocur it to produce a photonic crystal film, or to inject the dispersion between two transparent flat plates with a gap equal to the thickness of the desired film, By photo-curing this, a photonic crystal film for a security element having a film form can be produced, but a certain area is punched in advance to prevent damage by external factors in the process efficiency and process, and a dispersion liquid is injected onto a substrate having holes. It is more effective to include a process. That is, according to an aspect of the present invention, a part of a security article, such as a banknote, is removed, and the dispersion is applied to the removed portion using the above-described substrate, followed by curing to form a photonic crystal having the same thickness as the target security article. By providing a transparent window film, a photonic crystal film provided with a function as a security element can be manufactured.

The dispersion according to an aspect of the present invention can control the volume fraction of the polymer matrix and colloidal particles. The volume fraction of the polymer matrix and the colloidal particles may be 0.9: 0.1 to 0.5: 0.5, and when the above range is satisfied, the repulsive force between the colloidal particles effectively acts so that the colloidal particles can be arranged in a crystal lattice structure, and a specific reflection spectrum To improve visibility and discrimination, but this is only a non-limiting example and is not limited to the numerical range. Preferably in terms of arranging the colloidal particles in a crystal lattice structure, the volume fraction of the polymer matrix: colloidal particles may be 0.8: 0.2 to 0.6: 0.4.

The photoinitiator may be used without being particularly limited as long as it is capable of photocuring the photonic crystal composition. At this time, the photoinitiator may be included in an amount of 0.3 to 3% by weight, specifically, 0.5 to 2% by weight, based on the total weight of the composition. This is only a non-limiting example and is not limited by the above numerical range.

The photoinitiators include 1-hydroxy-cyclohexyl-phenol-ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, benzyldimethylketone, 1- (4- Dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydride Hydroxy-2-methylpropan-1-one, benzophenone, 2,2-dimethoxy-2-phenylacetphenone, 2,2-diethoxy-2-phenylacetphenone, 2-hydroxy-2-methyl-1 -Propan-1-one, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2, It may be any one or more selected from 4-dimethyl thioxanthone and 2,4-diethyl thioxanthone, but is not limited.

The method of applying or injecting the dispersion onto the substrate is not particularly limited and a conventional method can be used. As an example, the application method is spin coating, doctor blading, dip coating, spray coating, casting, screen printing, inkjet printing, electrostatic hydraulic printing, micro contact printing, imprinting, gravure printing, reverse offset printing or gravure offset Printing may be used, and the injection method may fill the dispersion between two substrates through capillary forces.

At this time, the dispersion may be applied or injected at a temperature of 60 to 100 ℃, in this case has excellent coating properties and can form a uniform photonic crystal composition layer, it has the effect of shortening the process time.

At this time, the substrate can be used without particular limitation as long as it can easily separate the photonic crystal film, for example, a glass plate or the like can be used.

The curing step is performed by irradiating light, wherein the light may mean ultraviolet light, and may specifically have a wavelength region of 200 to 600 nm, and more specifically, a wavelength region of 250 to 450 nm. It may be an excitation light, but is not limited thereto.

According to an aspect of the present invention, the light irradiation process is adjusted according to conditions such as the size of the photonic crystal film, and in a non-limiting example, it may be performed by irradiating light having an output of 5 to 20 mW / cm 2 for 3 to 30 seconds. Specifically, it may be performed by irradiating light of 7 to 15 mW / cm 2 for 5 to 10 seconds, but is not limited thereto.

Thereafter, a process of separating the photonic crystal film for a security element prepared on a substrate and removing uncured unreacted materials may be additionally performed.

In addition, the present invention provides a security article comprising the above-described photonic crystal film for security elements.

Specifically, the security article may include a photonic crystal layer formed by a photonic crystal composition comprising a substrate, a mixture of a first acrylate-based compound and a second acrylate-based compound, colloidal particles, and a photoinitiator.

Further, the security article may include an object article requiring anti-counterfeiting and a photonic crystal film formed through one or both sides of the object article or through the object article. That is, the security article may be a structure in which a photonic crystal film is laminated or inserted through a security object article, and may be manufactured through a known lamination method.

1 schematically shows a banknote 1 as a security article according to an embodiment of the present invention. Specifically, as described above, by forming a photonic crystal layer by applying a dispersion on a substrate in the manufacturing method of the photonic crystal film, and inserting the formed photonic crystal layer in the initial stage of manufacturing the banknote, so that the banknote has a transparent window film of photonic crystal in some areas. can do. At this time, the photonic crystal layer 3 may be formed by using only the polymer matrix 2 without a transparent polycarbonate (PC) or transparent polyethylene terephthalate (PET) film. In addition, the photonic crystal layer 3 may be formed in a pattern using a photonic crystal.

The security article according to an aspect of the present invention is not particularly limited as long as it is intended to prevent forgery, and may include any one selected from the group consisting of bank notes, securities, gift certificates, lottery tickets, passports, ID cards, credit cards, and product labels. have.

Hereinafter, an example of a photonic crystal film for a security element according to an aspect of the present invention, a method for manufacturing the same, and a security article including the same will be described, but the present invention is not limited to the following examples.

(Example 1)

After dispersing the dispersion between two glass plates with a separation distance of 50 μm at 80 ° C. and irradiating with UV (wavelength 365 nm, output 12 mW / cm 2) for 7 seconds, the dispersion was photocured, and then the two glass plates were removed. To prepare a photonic crystal film for security elements.

The dispersion is ethoxylated trimethylol propane triacrylate (ETPTA; ethoxylated trimethylolpropane triacrylate, weight average molecular weight 428 g / mol) and polypropylene glycol diacrylate (PPGDA; polyprophylene glycol diacrylate, weight average molecular weight 800 g / mol) Was prepared by mixing 50:50 parts by weight of a polymer matrix mixture, silica nanoparticles having an average particle diameter of 210 nm and 2-hydroxy-2-methyl-1-phenyl-1-propanone (Darocur 1173), The volume fraction of the matrix mixture and the silica nanoparticles was 67:33, and the photoinitiator Darocur 1173 was added at 1% by weight relative to the mixture. At this time, the viscosity of the dispersion at 80 ° C was 1,200 cps.

(Example 2)

In Example 1, the same method as in Example 1, except that the weight mixing ratio of ethoxylated trimethylol propane triacrylate and polypropylene glycol diacrylate (ETPTA: PPGDA) in the dispersion was 30:70. Was carried out.

(Example 3)

In Example 1, the same method as in Example 1 except that the weight mixing ratio (ETPTA: PPGDA) of ethoxylated trimethylol propane triacrylate and polypropylene glycol diacrylate in the dispersion was 20:80. Was carried out.

(Example 4)

In Example 1, the same method as in Example 1, except that the weight mixing ratio (ETPTA: PPGDA) of ethoxylated trimethylol propane triacrylate and polypropylene glycol diacrylate in the dispersion was 60:40 Was carried out.

(Example 5)

In Example 1, Example 1, except that a polypropylene glycol diacrylate having a weight average molecular weight of 2,100 g / mol was used in the dispersion instead of a polypropylene glycol diacrylate having a weight average molecular weight of 800 g / mol. It was carried out in the same manner as.

(Example 6)

In Example 1, Example 1, except that a polypropylene glycol diacrylate having a weight average molecular weight of 470 g / mol was used in the dispersion instead of polypropylene glycol diacrylate having a weight average molecular weight of 800 g / mol. It was carried out in the same manner as.

(Comparative Example 1)

It was carried out in the same manner as in Example 1, except that only ethoxylated trimethylol propane triacrylate was used alone without using polypropylene glycol diacrylate as the polymer matrix.

(Comparative Example 2)

It was carried out in the same manner as in Example 1, except that only propylene glycol diacrylate was used alone without using ethoxylated trimethylol propane triacrylate as the polymer matrix.

(evaluation)

(1) Reflectance and transmittance

For the films prepared from Examples 1 to 7, Comparative Examples 1 and 2, reflectance in a wavelength region of 400 to 800 nm was measured using an optical microscope (Nikon, L150). In addition, the transmittance is a value measured at 540 nm with relative reflectance based on 100% of the barium sulfate standard white plate using an ultraviolet-visible light spectrometer (UV-VIS-NIR spectrophotometer, Cary 5000, Varian). Is 3 ° 20 ”, the average time for detecting a signal from the detector is 0.1 s, the interval of analysis data is 1 nm, and the scan speed is 600 nm / min.

(2) Folding endurance

When the film produced from Examples 1 to 5 and Comparative Examples 1 to 3 was repeatedly performed by folding the film at 150 ° based on a predetermined portion, and then visually confirming that deformation occurred with the naked eye, and when the initial damage was applied The number of repetitions was measured, and if it is 25 times or more, it is indicated by ○, if it is 10 or more times and less than 25 times, and △ if it is less than 10 times.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 reflectivity
(%) 50 38 30 54 25 29 57 20 Transmittance
(%) 73 78 82 63 83 90 63 92 Foldability ○ ○ △ △ △ △ × △

As can be seen from Table 1, the embodiment according to the present invention absorbs the wavelength of a specific region and has excellent reflection characteristics to express the structure color, and at the same time has a high transmittance, thereby confirming that the application value for the security element is high. Could. In addition, through the foldability test, it was confirmed that the films prepared from Examples 1 and 2 exhibited very good flexibility and foldability. On the other hand, the films prepared from Examples 3 to 6 are somewhat inflexible, and the reflective properties are slightly deteriorated compared to high transmittance. On the other hand, the film prepared from Comparative Example 1 lacks flexibility, and thus a brittle property occurs easily even though the number of repetitions is low, resulting in a problem that the film is broken due to folding, and the film according to Comparative Example 2 has a reflective property. It was confirmed that it is very low and difficult to use for security elements.

Although the preferred embodiments of the present invention have been described above, it is clear that the present invention can use various changes, modifications, and equivalents, and can be equally applied by appropriately modifying the above embodiments. Therefore, the above description is not intended to limit the scope of the present invention as defined by the following claims.

1: Banknote, 2: Polymer matrix, 3: Photonic crystal layer

Claims (14)

As a cured product of a photonic crystal composition comprising a polymer matrix, colloidal particles dispersed in the polymer matrix and arranged in a crystal lattice structure, and a photoinitiator,
The polymer matrix is selected from the group consisting of ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate and trimethylolpropane triacrylate Any one or more first acrylate-based compounds and any one or more second acrylates selected from the group consisting of polypropylene glycol acrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate It is a polymer derived from a mixture of compounds based,
The second acrylate-based compound has a weight average molecular weight of 300 to 3,000 g / mol,
A photonic crystal film for a security element, having a thickness of 10 to 200 µm and a transmittance of 60% or more in a wavelength range of 400 to 800 nm. According to claim 1,
A photonic crystal film for a security element, characterized in that the weight mixing ratio of the first acrylate-based compound and the second acrylate-based compound is 55:45 to 25:75. According to claim 1,
The polymer matrix is a photonic crystal film for a security element having a refractive index difference of 0.02 or more with colloidal particles. According to claim 3,
The polymer matrix has a refractive index of 1.4 to 1.5, and the colloidal particles have a refractive index of 1.3 to 3.0. delete According to claim 1,
The colloidal particles are photonic crystal films for security elements that satisfy the following relational expression 1.
[Relationship 1]
Da × 0.95 ≤ Ds ≤ Da × 1.05
(In the relational expression 1 above, Ds is the particle diameter (nm) of the colloidal particles, and Da is the average particle diameter (nm) of the colloidal particles.) The method of claim 6,
The colloidal particles have an average particle diameter of 50 to 250 nm. According to claim 1,
The colloidal particles are one or two or more selected from metal nanoparticles, metal oxide nanoparticles, organic nanoparticles, and carbon structure nanoparticles. A security article comprising the photonic crystal film for a security element according to any one of claims 1 to 4 and 6 to 8. Forming a layer of a photonic crystal composition by injecting a dispersion comprising a mixture of a first acrylate-based compound and a second acrylate-based compound, colloidal particles and a photoinitiator into the hole on the substrate having a hole, and
Method of manufacturing a photonic crystal film for a security element comprising the step of curing by irradiating the photonic crystal composition layer. The method of claim 10,
The first acrylate compound is ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate and trimethylolpropane triacrylate Any one or more selected from the group consisting of, the second acrylate-based compound is selected from the group consisting of polypropylene glycol acrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate and polyethylene glycol dimethacrylate Method for manufacturing a photonic crystal film for any one or more security elements. The method of claim 10,
Method of manufacturing a photonic crystal film for a security element, characterized in that the weight mixing ratio of the first acrylate-based compound and the second acrylate-based compound is 55:45 to 25:75. The method of claim 10,
The step of injecting the dispersion is a method of manufacturing a photonic crystal film for a security element further comprising a transparent polymer film on one surface of the substrate. The method of claim 10,
The dispersion is a method of manufacturing a photonic crystal film for security elements that are applied at 60 to 100 ℃.

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