JP5691567B2 - Anti-counterfeit structure - Google Patents

Description

  The present invention relates to an anti-counterfeit structure used for anti-counterfeiting, for example, for securities such as gift certificates and credit cards, or stickers for branded goods and luxury goods.

  In recent years, an OVD (Optically Variable Device) including a hologram has been used as a proof of authenticity such as banknotes, gift certificates, credit cards, branded goods, and luxury goods. A synonym for OVD is DOVID (Differential Optically Variable Imaging Device).

This OVD is used as an effective anti-counterfeiting means because it requires advanced manufacturing technology, has a unique visual effect, and can determine authenticity at a glance. Recently, in addition to securities, it is affixed to sports equipment, computer parts and other electrical product software, etc., as an authentication sticker to prove the authenticity of the product, and as a seal sticker to be affixed to the package of those products However, in recent years, due to the spread of hologram manufacturing technology, OVD has become easier to forge than before.

  Therefore, in order to improve the anti-counterfeiting effect, an anti-reflection function by a proposal of a complicated design with a finer structure than the conventional one, and an element (sub-wavelength structure element) made of a fine periodic uneven pattern below the wavelength of light, Proposals have been made for articles having a polarization separation function, a phase difference function, etc., and computer generated holograms (see, for example, Patent Documents 1, 2, and 3).

  By the way, the conventional relief-type diffraction grating has a concavo-convex structure with a width of about 1.0 μm and a depth of about 100 nm. When the sub-wavelength structure element is used for this, it is fine and has a depth of 100 to 800 nm. Since the irregularities have a high aspect ratio of 250 nm or more, forgery is difficult, but on the other hand, there is a problem that manufacture is difficult.

  Technologies such as the hot embossing method and the photopolymer method are used as a method for forming this concavo-convex shape, but the resin is easy to stick to the relief mold during molding due to the fine structure, making it difficult to process at high speed Have the problem of being.

  In order to solve this problem, there has been proposed a technique for efficiently manufacturing a sub-wavelength diffraction grating structure having a narrow width and a high aspect ratio without using a conventional molding method (see, for example, Patent Document 4).

  However, the technique of the above-mentioned Patent Document 4 is a technique for obtaining a high-aspect ratio sub-wavelength diffraction grating by arranging monodisperse fine particles, and the result of the diffraction depends greatly on the arrangement of the particles. Therefore, there is a problem that it is indispensable to regularly arrange and fill.

Japanese Patent Laid-Open No. 2002-040219 JP 2004-205990 A Japanese Patent Laying-Open No. 2005-010231 JP 2009-116857 A

  The present invention has been made in view of the above circumstances, and promotes the regular arrangement of spherical fine particles to improve the diffraction effect, so that the sub-wavelength diffraction grating can be efficiently narrowed and has a high aspect ratio. An object of the present invention is to provide a forgery prevention structure that realizes the structure.

The invention of claim 1 is a spherical fine particle diffractive structure in which a fine particle layer and a reflective layer are arranged and fixed on a lattice layer made of a polymer resin, and the lattice layer is formed in an uneven shape comprising a groove portion and a bank portion. In the groove portion of the lattice layer, a plurality of spherical fine particles having a particle size distribution having an average particle size of 2.5 μm or less and a particle number of 70% or more in a range of 0.8 to 1.2 times the average particle size are provided. And forming the fine particle layer by fixing the entire surface or an arbitrary shape so that more than half of the height of each spherical fine particle is not buried in the groove, and the reflective layer, The fine particle layer is disposed so as to cover at least a part of a portion not buried in the groove portion, and the lattice layer includes a plurality of the groove portions and a plurality of bank portions, and the plurality of the groove portions and the plurality of the plurality of groove portions. Banks are alternately aligned along one direction. And each of the groove portions and each of the bank portions has a width such that a plurality of the fine particles are arranged along a direction orthogonal to the one direction, and the groove portions along the one direction width Ri particle diameter or less on der of cycle the particles is the sum of the width of the bank portion in the grating layer, wherein the period includes two or more pitches, and the grooves of the same pitch A bank portion is formed in each unique region, and the plurality of spherical fine particles are composed of one kind of spherical fine particles .

  According to the above configuration, by providing the grating layer having the grooves for arranging the spherical fine particles, the regular arrangement of the spherical fine particles is promoted, and a diffraction grating structure with a narrower width and a high aspect ratio of a sub-wavelength with a higher diffraction effect is obtained. Can be obtained.

  According to the above configuration, it is possible to arrange spherical fine particles having the same shape with two different periodic structures by using two types of groove and bank period (sum of the width of the groove and bank) in the lattice layer, Different color changes can be imparted. Thereby, the improvement of visibility and the improvement of the forgery prevention effect can be aimed at.

  According to the present invention, an anti-counterfeit structure that realizes a sub-wavelength diffraction grating structure with a narrow width and a high aspect ratio efficiently by promoting the regular arrangement of spherical fine particles and improving the diffraction effect. The body can be provided.

It is sectional drawing which showed the basic composition of the forgery prevention structure of this invention. It is sectional drawing shown in order to demonstrate the lattice layer of this invention. It is the top view shown in order to demonstrate the lattice layer of this invention. It is sectional drawing which showed the sticker structure of the forgery prevention structure of this invention.

  Hereinafter, the forgery prevention structure of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a basic configuration of an anti-counterfeit medium according to an embodiment of the present invention, in which a lattice layer 3, a fine particle layer 4, and a reflective layer 5 are sequentially stacked.

  The fine particle layer 4 is formed of spherical fine particles having an average particle diameter of 2.5 μm or less and a particle number of 70% or more in a range of 0.8 times or more and 1.2 times or less of the average particle diameter. The spherical fine particles have an effect of diffracting incident light. When the light is diffracted by the fine particles, the spherical fine particles exhibit a color that changes in color tone depending on the viewing angle. The diffraction by the fine particles can be considered that light is diffracted when the contour of the fine particles has the same uneven shape as the diffraction grating, and is an effect obtained by regularly filling the uniform fine particles. In particular, the shape of fine particles, the particle size distribution, and the filling shape necessary for obtaining high color developability and vivid color tone change depending on the observation angle will be described in detail below.

  The shape of the spherical fine particles is preferably a spherical shape, and by making it more spherical, the difference in shape depending on the direction of the particle size is reduced, the variation in the periodic structure of the particles is reduced, and a vivid color tone change can be obtained. it can. The spherical fine particles refer to particles in which the ratio of the maximum diameter to the minimum diameter of one particle is 1.0 or more and 1.2 or less.

  The particle size distribution of the spherical fine particles is preferably in a narrower range. This is because by narrowing the particle size distribution, the variation in diffraction angle is reduced and a vivid color tone change can be obtained.

  Further, the spherical fine particles are characterized in that they are spherical fine particles having a particle number of 70% or more in a range of 0.8 times or more and 1.2 times or less of the average particle diameter and having a narrow particle size distribution. Preferably, the number of particles is 90% or more in a range of 0.9 times to 1.1 times the average particle size. By using spherical particles having such a sharp particle size distribution, a more vivid color tone change can be obtained. Here, as a confirmation method of the average particle diameter and a confirmation method of having a particle number of 70% or more in a range of 0.8 times or more and 1.2 times or less of the average particle diameter, SEM (scanning electron) It is preferable to confirm with an observation photograph using a microscope) or a TEM (transmission electron microscope).

  Furthermore, the spherical fine particles have a ratio of the maximum diameter and the minimum diameter of one particle of 1.0 or more and 1.2 or less in an observation photograph in SEM (scanning electron microscope) or TEM (transmission electron microscope). Refers to particles that are For this reason, in the measurement of the particle diameter, it is necessary to collect data by unifying either the maximum diameter or the minimum diameter of one particle. In this specification, the maximum diameter is displayed.

  Moreover, it is preferable that the filled shape of the spherical fine particles is more densely arranged in a single plane. When particles are stacked randomly in a double layer or more, light of each wavelength diffracted in the first layer is scattered in a random direction in the second and subsequent layers. As a result, the color intensity is reduced, A vivid color change due to the viewing angle cannot be obtained.

As a parameter related to the filling factor, the degree of accumulation of spherical fine particles is defined by the area filling factor. Here, the area filling rate is observed from the upper direction perpendicular to the plane of the anti-counterfeit structure by SEM (scanning electron microscope) or TEM (transmission electron microscope), and the particle area per unit area ( The area of the area to be measured is preferably 400 μm ² or more.

In addition, the area range was arbitrarily selected from five ranges of 2500 μm ² , the number of particles in the range was counted, and the area filling rate of the particles was calculated. When the area filling rate is less than 30%, the color intensity is reduced, and a vivid color tone change depending on the observation angle cannot be obtained. Therefore, it is preferable that particles are accumulated with an area filling rate of 30% or more. More preferably, it is 60% or more.

  As the spherical fine particles, organic material-based or inorganic material-based monodispersed spherical fine particles are preferable. Specific examples of the organic material-based fine particles include acrylic, polystyrene, polyester, polyimide, polyolefin, and poly (meth) acrylate. And resins such as polyethylene, polypropylene, polyethylene, polyether sulfone, polyamide, nylon, polyurethane, polyvinyl chloride, polyvinylidene chloride, and acrylamide, and copolymer resins composed of two or more resins. Similarly, monodisperse spherical fine particles of inorganic materials include calcium carbonate, barium carbonate, magnesium carbonate, calcium silicate, barium silicate, magnesium silicate, calcium phosphate, barium phosphate, magnesium phosphate, silica, titanium oxide, iron oxide. , Cobalt oxide, zinc oxide, nickel oxide, manganese oxide, aluminum oxide, iron hydroxide, nickel hydroxide, aluminum hydroxide, calcium hydroxide, chromium hydroxide, zinc silicate, aluminum silicate, zinc carbonate, basic copper carbonate, Examples include zinc sulfide, glass, and various metal particles. Examples include surface-modified fine particles, core-shell particles, laminated spherical particles, and bead-shaped spherical particles using two or more of the above organic materials and inorganic materials.

  Examples of the spherical fine particles include hollow spherical particles using the above organic materials and inorganic materials, spherical aggregates of fine particles, porous spherical particles, thermally expandable spherical particles, and the like, but are not limited thereto. Not a thing.

  As the particle diameter, when the observed wavelength region covers all of the ultraviolet light region, visible light region, and infrared light region (wavelength 2500 nm or less), the particle size is preferably 2.5 μm or less. If it is 2.5 μm or less, all diffracted light of 2500 nm or less, which is the light beam region to be observed, can be obtained.

  As a method for forming the fine particle layer 4, for example, the above-described spherical fine particles are mixed with a polymer resin, diluted with a solvent, applied by a known printing method, and then dried by a solvent medium. It is also possible to more firmly fix the spherical fine particles on the lattice layer 3 by using a crosslinking reaction, thermosetting reaction, or photopolymerization reactive material as the polymer resin component.

  Next, the lattice layer 3 will be described. As shown in FIGS. 2 and 3, the lattice layer 3 has a groove portion 21 and a bank portion 22 for urging the regular arrangement of spherical fine particles, and particles are arranged in the groove portion 21 to form a spherical shape. Fine particles are fixed. As a method of creating the groove portion 21, a method of forming using a metal mold can be cited. Therefore, as a material, a polymer resin material that can be molded is used. For example, a thermoplastic resin such as an acrylic resin, an epoxy resin, a cellulose resin, or a vinyl resin, or an acrylic polyol having a reactive hydroxyl group. UV or electron beam curing such as urethane resin, cross-linked urethane resin, melamine resin, phenolic resin, etc., epoxy (meth) acryl, urethane (meth) acrylate, etc. Resins etc. are mentioned, and these are used alone or in combination.

  The width of the groove portion 21 and the bank portion 22 is determined by the particle size of the spherical fine particles to be used. In order to arrange the particles one by one in the groove portion 21, the sum (period) of the groove portion 21 and the bank portion 22 is the particle size. The size needs to be equal to or larger than that, and the depth is preferably equal to or smaller than the radius of the spherical particles.

  In addition, the lattice layer 3 may be formed so as to be divided into regions of a size that can be visually recognized using two or more types of cycles (the sum of the groove portion 21 and the bank portion 22). According to this, the arrangement structure of the spherical fine particles can be changed, and a plurality of color changes can be imparted using one kind of spherical fine particles.

  The reflective layer 5 is a layer provided to increase the diffraction efficiency. As a material, a high refractive index material such as TiO2, Si2O3, SiO, Fe2O3, ZnS, Al, Sn, Cr, Examples thereof include metal materials such as Ni, Cu, and Au, and these materials are used alone or in layers. These materials are formed by a well-known thin film forming technique such as a vacuum deposition method or sputtering, and the film thickness is about 5 to 1000 nm.

  Moreover, the high gloss light reflection ink obtained by disperse | distributing the said metal material and ceramic microparticles | fine-particles to organic polymer resin can also be used. Further, the reflective layer 5 may be provided in a partial pattern. Examples of this processing method include pasta processing, flushed sealight processing, oil ablation processing, and laser processing.

  Although the basic lattice layer 3, fine particle layer 4, and reflective layer 5 have been described in detail above, specific examples according to the present invention and comparative examples will be manufactured and compared as follows.

(Example)
As an example, a forgery prevention structure having a sticker configuration shown in FIG. 4 was prepared, and a support 41 made of a transparent polyethylene terephthalate (PET) film having a thickness of 38 μm was stacked as follows.

(1) The lattice layer 3 was formed by applying a paint described later by 2 μm by a gravure method.

(2) Using a press plate made of nickel, a forming process is performed by a roll embossing method, and a lattice layer 3 having a groove 21 having a width of 0.4 μm, a depth of 0.1 μm, and a bank 22 having a thickness of 0.1 μm is formed. did.

(3) The fine particle layer 4 was formed by applying 0.5 μm of a paint described later by a bar coating method.

(4) The reflective layer 5 was formed by applying a 50 nm aluminum metal thin film over the entire surface by vacuum deposition.

(5) A pressure-sensitive adhesive for forming the adhesive layer 46 was applied in advance to a release paper (separator) to a thickness of 20 μm and pasted onto the reflective layer 5 of the film to form a label.

[Lattice layer 3 paint]
Vinyl chloride-vinyl acetate copolymer ... 15 parts Urethane resin ... 10 parts Methyl ethyl ketone ... 50 parts Toluene ... 25 parts
[Fine particle layer 4 paint]
Styrene particles (particle size 500 nm) 40 parts Vinyl alcohol resin 2 parts Water (solvent) 58 parts In addition, the number of styrene particles is 90% or more in the range of 0.8 to 1.2 times the average particle diameter. Particles made by Moritex Co., Ltd. having

[Adhesive layer 46 paint]
Acrylic adhesive ... 30 parts Ethyl acetate ... 40 parts Butyl acetate ... 30 parts (Comparative example)
As a comparative example, an anti-counterfeit structure using spherical fine particles was produced without forming the groove portion 21 and bank portion 22 of the lattice layer 3. In this comparative example, the other parts were molded using the same processing methods and materials as in the above examples.

(Study results)
For the packing area ratio, the ratio of the particle area per unit area was calculated by SEM (scanning electron microscope) observation.

As shown in Table 1, the results of the comparison are shown in Table 1. By the action of the groove portions 21 and the bank portions 22 of the lattice layer 3 in the example, a regular arrangement is promoted compared to the comparative example, and the filling area ratio is improved. It was confirmed that the color developed by clearer diffracted light.

  According to the present invention, a regular arrangement of spherical fine particles is promoted, and the diffraction effect can be improved, so that an anti-counterfeit structure having a diffraction grating structure with a narrow width and a sub-wavelength with a high aspect ratio can be achieved. The body can be realized.

DESCRIPTION OF SYMBOLS 3 ... Diffraction layer 4 ... Fine particle layer 5 ... Reflective layer 21 ... Groove part 22 ... Bank part 41 ... Support body 46 ... Adhesive layer

Claims (1)

A spherical fine particle diffractive structure in which a fine particle layer and a reflective layer are arranged and fixed on a lattice layer made of a polymer resin,
The lattice layer is formed in a concavo-convex shape including a groove portion and a bank portion, and the groove portion of the lattice layer has an average particle diameter of 2.5 μm or less and a range of 0.8 to 1.2 times the average particle diameter of 70% or more. A plurality of spherical fine particles having a particle size distribution having a number of particles are fixed in a single plane and fixed in the entire surface or in an arbitrary shape so that more than half of each height of the spherical fine particles is not buried in the groove. Forming the fine particle layer, and disposing the reflective layer so as to cover at least a portion of the fine particle layer that is not buried in the groove,
The lattice layer includes a plurality of the groove portions and a plurality of the bank portions, and the plurality of groove portions and the plurality of bank portions are arranged alternately and continuously along one direction, and the groove portions Each of the bank portions has a width such that a plurality of the fine particles are arranged along a direction orthogonal to the one direction, and the width of the groove portion and the bank portion along the one direction. Ri particle diameter or less on der of cycle the particles is the sum of the width,
In the lattice layer, the period includes two or more types of pitches, and a groove portion and a bank portion having the same pitch are formed in unique regions, respectively.
Wherein the plurality of spherical particles, counterfeit prevention structure characterized by being composed of one spherical particle.

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