JP5176269B2 - Anti-counterfeit medium and authenticity determination method - Google Patents

Description

  The present invention relates to an anti-counterfeit medium having a function of preventing faithful copying by a copying machine or the like and a method for determining authenticity thereof.

  In recent years, copying machines using electrophotographic technology have become widespread, and anyone can easily copy characters and images printed on paper or the like using this. In particular, according to recent color digital copying machines, it has become possible to easily create even a copy that is extremely difficult to distinguish between a manuscript and a copy.

  The copying principle of a general color digital copying machine is as follows. That is, first, when the CCD line sensor detects the reflected light of the light irradiated toward the document, the CCD line sensor generates a digital signal corresponding to the detected reflected light intensity and transmits it to the memory in the copying machine. . This reading process is performed for three colors of red (R), green (G), and blue (B), and the respective digital signals are stored in the memory. Next, based on the stored digital signal, the surface of the photosensitive drum is irradiated with laser light, and yellow (Y), magenta (M), cyan (C), and black (Bk) toners are sequentially and statically applied thereto. Electroadsorption is performed, and then these toners are sequentially transferred and fixed on a sheet such as paper to obtain a copy.

  While such color digital copying is convenient, it has the problem that securities such as stock certificates, bonds, promissory notes, checks, and printed materials such as admission tickets and boarding passes are easily forged. For this reason, various proposals have been made to take anti-duplication measures on printed matter so that faithful copying cannot be easily performed.

  For example, a technique has been proposed in which the color of a color copy is different from the color of an original. More specifically, securities that can be used as manuscripts are colored in a very pale color, and the copy color cannot be reproduced accurately. A technology that prevents the same pattern as the original from being reproduced by making use of the poor reproducibility of the small halftone dots, and the green and purple colors that are not found in color copier toner. , Orange, gold, silver, etc., and the technology that makes it difficult to faithfully reproduce the colors of these images on the copy, and 380 nm to 450 nm, which has low human visibility In addition, an image is formed using two types of inks having different reflectances in a wavelength range of about 650 to 780 nm, and a portion that appears to be the same color on the original is reproduced in a different color on the copy. I tried to end Surgery, and the like.

  However, in a color copying machine, it is possible to finely correct an output color by converting digital data that has been separated into three colors and stored in a memory. Also, digital presses that can correct digital data read by a color scanner with a computer and then output a copy that is inferior to a document by a color printer or color copier are becoming widespread. Therefore, with a little effort, it is possible to reproduce the color and image of an original using these devices, and it is difficult to completely prevent forgery by copying with the above-described technology. is there.

In addition, a technique has been proposed in which a special part that cannot be reproduced by a color copying machine is provided in a part of securities. Of these, OVD (Optical Varia) such as hologram foil
The technology of providing a ble device) foil on the surface of securities or the like has already been put into practical use. This is because the light on the silver surface of the hologram is specularly reflected, so that the reflected light does not enter the CCD line sensor, and the silver surface portion of the original is reproduced in black on the copy. In some cases, a special optical thin film formed by laminating a plurality of ceramic thin films having different refractive indexes with a predetermined thickness is provided in part so that the portion cannot be reproduced on a copy. Further, a technique for preventing forgery has been proposed in which printing is performed using ink mixed with fragments formed by finely pulverizing the optical thin film.

  However, in these techniques, it is necessary to form a hologram foil or a ceramic film by dry coating such as vapor deposition or sputtering, which complicates the process and has a problem that the manufacturing cost is extremely high.

However, in recent years, the use of circularly polarizing plates in display applications has become frequent, making it easy to obtain cholesteric liquid crystals, and the development of embossing technology has led to the formation of reflective layers using relief-type diffracted light. The anti-counterfeiting effect has been reduced due to the fact that it is relatively easy to perform. Therefore, it has been proposed to install cholesteric liquid crystals on the front and back sides of the phase element , and use the technology to control the rotation direction while the spiral direction of the cholesteric liquid crystal is the same to prevent counterfeiting, but the phase element itself is a familiar material. For example, since the performance similar to that of cellophane tape can be obtained, the degree of difficulty in preventing forgery is not so high.

  However, in recent years, the use of circularly polarizing plates in display applications has become frequent, making it easy to obtain cholesteric liquid crystals, and the development of embossing technology has led to the formation of reflective layers using relief-type diffracted light. The anti-counterfeiting effect has been reduced due to the fact that it is relatively easy to perform. Therefore, it has been proposed to install cholesteric liquid crystals on the front and back sides of the phase retarder, and to use the technology to control the rotation direction while keeping the spiral direction of the cholesteric liquid crystals in order to prevent counterfeiting. Since the material, for example, cellophane tape, can provide a similar performance, the difficulty of preventing forgery is not so high.

  The present invention solves the problems of the prior art, and the problem is that counterfeiting using a commercially available color copying machine is extremely difficult and can be manufactured at a low price. Furthermore, it is possible to easily set two, three or more states in which the cholesteric liquid crystal spiral axis direction and the spiral pitch are different on the same medium, and the genuine product and the counterfeit product can be clearly defined using a simple device. It is an object of the present invention to provide a forgery prevention medium using cholesteric liquid crystal and a method for determining the authenticity thereof that can be discriminated.

In order to achieve the above-described problems, the invention according to claim 1 is a polymer cholesteric liquid crystal layer that reflects clockwise or counterclockwise circularly polarized light, and a rotational direction of a spiral axis is right or left. fine and flaky cholesteric comprising at least one liquid crystal cholesteric liquid crystal flake layer is disposed on the substrate in a visible at the same time, the cholesteric liquid crystal flake layer comprises a rotating direction of the helical axis is right An anti-counterfeit medium characterized by containing both the left flaky cholesteric liquid crystal .

Furthermore, in the invention described in claim 2 , the polymer cholesteric liquid crystal layer and the cholesteric liquid crystal flake layer containing both flaky cholesteric liquid crystals whose helical axes rotate in the right and left directions are subjected to natural light irradiation. The anti-counterfeit medium according to claim 1, wherein the medium is recognized with the same hue.

Furthermore, in the invention described in claim 3 , the polymer cholesteric liquid crystal layer and the cholesteric liquid crystal flake layer containing both flaky cholesteric liquid crystals whose helical axes rotate in the right and left directions are subjected to natural light irradiation. The anti-counterfeit medium according to claim 1, wherein the medium is recognized with different hues.

Furthermore, in the invention according to claim 4 , the hue of the polymer cholesteric liquid crystal layer is irradiated with natural light of flake-like cholesteric liquid crystal having a spiral axis in the same direction as the rotation direction of the spiral axis of the polymer cholesteric liquid crystal constituting the layer. It may be recognized differently from the hue below, and it may be recognized differently from the hue of flake cholesteric liquid crystal having a helical axis opposite to the rotation direction of the helical axis of polymer cholesteric liquid crystal under natural light irradiation. The anti-counterfeit medium according to claim 1, wherein

Furthermore, according to the invention described in claim 5 , the hue of the polymer cholesteric liquid crystal layer is irradiated with natural light of flake cholesteric liquid crystal having a spiral axis in the same direction as the rotation direction of the spiral axis of the polymer cholesteric liquid crystal constituting the layer. The hue is recognized differently from the hue below, and the hue of flake-shaped cholesteric liquid crystal having a helical axis opposite to the rotation direction of the helical axis of the polymer cholesteric liquid crystal is recognized to be the same as that under natural light irradiation. The anti-counterfeit medium according to claim 1, wherein

Furthermore, the invention according to claim 6, according to any one of claims 1, characterized in that the light-absorbing layer is applied under the high polymer cholesteric liquid crystal layer and the cholesteric liquid crystal flake layer of 5 It is a medium for preventing forgery.

Furthermore, in the invention described in claim 7 , the anti-counterfeit medium according to any one of claims 1 to 6 is visually observed through a determination tool made of a circularly polarizing plate, and authenticity is determined based on a changing hue. Is a method for determining the authenticity of a forgery prevention medium.

  Since the present invention has the above-described configuration, it is possible to prevent faithful copying by a copying machine or the like, and an excellent practical effect as a medium having an anti-counterfeit effect is expected. In addition, when observed by changing the viewing angle under the irradiation of natural light, or when observed through a circular polarizing filter, a color shift is exhibited, and thus an anti-counterfeit medium having an unprecedented high design property is provided. It becomes possible.

  In addition, a predetermined color shift can be confirmed by simple means of observation through a clockwise or counterclockwise circular polarizing filter, and authenticity can be easily determined by visual inspection using these as verification elements.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic plan configuration of an anti-counterfeit medium according to the present invention, and FIG. 2 is an explanatory diagram showing a schematic configuration of a side cross-sectional portion in the XX plane of the anti-counterfeit medium shown in FIG. FIG. 3 is an explanatory view showing a state when the anti-counterfeit medium shown in FIG. 1 is observed through a clockwise circular polarizing filter, and FIG. 4 shows the anti-counterfeit medium as shown in FIG. FIG. 5 is an explanatory diagram schematically showing the principle of true / false judgment when observing, and FIG. 5 shows a state when the anti-counterfeit medium shown in FIG. 1 is observed through a counterclockwise circular polarizing filter. FIG. 6 is an explanatory diagram schematically showing the principle of authenticity determination when the anti-counterfeit medium is observed as shown in FIG.

  FIG. 7 is an explanatory view showing a schematic plan configuration according to another example of the forgery prevention medium of the present invention, and FIG. 8 is a schematic side sectional view of the forgery prevention medium shown in FIG. FIG. 9 is an explanatory diagram showing a configuration, and FIG. 9 is an explanatory diagram showing a state when the anti-counterfeit medium shown in FIG. 7 is observed through a clockwise circular polarizing filter, and FIG. 10 is shown in FIG. FIG. 11 is an explanatory diagram schematically showing the principle of authenticity determination when observing the anti-counterfeit medium, and FIG. 11 shows the anti-counterfeit medium shown in FIG. 7 observed through a counterclockwise circular polarizing filter. FIG. 12 is an explanatory diagram schematically showing the principle of authenticity determination when observing the anti-counterfeit medium as shown in FIG.

An anti-counterfeit medium 10 shown in FIG. 1 and FIG. 2 includes a polymer cholesteric liquid crystal layer 11 made of a polymer cholesteric liquid crystal having a helical axis rotation direction on the left, and a minute flaky cholesteric liquid crystal having a helical axis rotation direction on the right. The contained cholesteric liquid crystal flake layer 12 is visible at the same time, and is disposed on the light absorption layer 14 provided on one surface of the substrate 13. Since the cholesteric liquid crystals constituting the polymer cholesteric liquid crystal layer 11 and the cholesteric liquid crystal flake layer 12 have different helical pitches, they exhibit different reflection colors. That is, in the forgery-preventing printed matter 10, by changing the viewing angle, the apparent pitch of the cholesteric liquid crystal is reduced and the reflection wavelength is shifted to the short wave side. This blue shift causes a color change in the polymer cholesteric liquid crystal layer 11 and the cholesteric liquid crystal flake layer 12.

  Therefore, when the anti-counterfeit medium 10 is observed through the right rotation authenticity determination filter 18, the portion of the polymer cholesteric liquid crystal layer 11 becomes dark and the portion of the cholesteric liquid crystal flake layer 12 is visually observed as shown in FIG. Therefore, the cholesteric liquid crystal flake layer 12 can be recognized with a predetermined hue. If such a change in hue is used for verification, authenticity determination is performed.

  That is, as shown in FIG. 4, when natural light 15 is reflected by the anti-counterfeit medium 10, the rotation direction of the spiral axis corresponds to the spiral pitch of the cholesteric liquid crystal constituting the polymer cholesteric liquid crystal layer 11 on the left side. Left-handed polarized light 17 is reflected, and right-handed polarized light 16 is transmitted. The transmitted right-polarized polarized light 16 is absorbed by the light absorption layer 14. On the other hand, right-handed polarized light 16 is reflected by the cholesteric liquid crystal flake layer 12 whose spiral axis is rotated to the right, and left-handed polarized light 17 is transmitted and absorbed by the light absorbing layer 14. The left and right polarized light beams 17 and 16 reflected in this way pass only through the clockwise circular polarization filter 18 that transmits only the right polarized light beam, so that only the right polarized light beam 16 is transmitted. The liquid crystal layer 11 is dark, and the cholesteric liquid crystal flake layer 12 can be seen in the same manner as when there is no filter.

  On the other hand, FIG. 5 shows a state in which the anti-counterfeit medium 10 is observed through the counterclockwise circular polarizing filter 19 as described above. Although the cholesteric liquid crystal layer 11 is not visually changed, the cholesteric liquid crystal flake layer 12 whose spiral axis rotation direction is right becomes dark and only the high molecular cholesteric liquid crystal layer 11 can be visually recognized with a predetermined hue.

  That is, as shown in FIG. 6, when natural light 15 is reflected by the anti-counterfeit medium 10, in the polymer cholesteric liquid crystal layer 11 in which the rotation direction of the spiral axis is on the left, the polarized light 17 rotates counterclockwise according to the spiral pitch of the cholesteric liquid crystal. Is reflected, and right-polarized polarized light 16 is transmitted. The transmitted right-polarized polarized light 16 is absorbed by the light absorption layer 14. On the other hand, right-handed polarized light 16 is reflected by the cholesteric liquid crystal flake layer 12 whose spiral axis is rotated to the right, and left-handed polarized light 17 is transmitted and absorbed by the light absorbing layer 14. The left and right polarized light beams 17 and 16 reflected in this way are transmitted only by the counterclockwise circularly polarized light filter 19 that transmits only the counterclockwise polarized light beam, so that the cholesteric liquid crystal flakes are transmitted. The layer 12 is dark, and the polymer cholesteric liquid crystal layer 11 can be seen in the same manner as in the case without the filter.

  On the other hand, an anti-counterfeit medium 200 shown in FIGS. 7 and 8 includes a polymer cholesteric liquid crystal layer 211, a cholesteric liquid crystal flake layer 212 including two kinds of minute flaky cholesteric liquid crystals whose rotation directions of the spiral axis are right and left, However, it is arrange | positioned on the light absorption layer 214 provided in one surface of the base material 213 in the state which can be visually observed simultaneously. Different reflection colors are displayed by changing the spiral pitch of each flaky cholesteric liquid crystal. The cholesteric liquid crystal flake layer 212 containing both of the two types of flaky cholesteric liquid crystals having right and left spiral axes has different reflection colors individually, but is a mixed color by normal visual observation, and the two colors are mixed. Visible at.

  In the anti-counterfeit medium 200, the apparent pitch of the cholesteric liquid crystal is reduced by changing the viewing angle in the same manner as the anti-counterfeit medium 10, and the reflection wavelength is shifted to the short wave side. This blue shift causes a color change in the polymer cholesteric liquid crystal 211 and the cholesteric liquid crystal flake layer 212.

  FIG. 9 shows a state in which the anti-counterfeit medium is observed through the clockwise circular polarizing filter 18 as described above. In this case, the polymer cholesteric liquid crystal layer with the helical axis on the left is shown. The portion 211 is darkened, and the portion of the cholesteric liquid crystal flake layer 212 is visually recognized in a color different from that without the filter.

That is, as shown in FIG. 10, when the natural light 15 is reflected by the anti-counterfeit medium 200, in the polymer cholesteric liquid crystal layer 211 in which the rotation direction of the spiral axis is left, the polarized light 17 rotates counterclockwise according to the spiral pitch of the cholesteric liquid crystal. Is reflected, and right-polarized polarized light 16 is transmitted. The transmitted light is absorbed by the light absorption layer 214. On the other hand, the cholesteric liquid crystal flake layer and the liquid crystal layer 212 reflect both right and left polarized light beams 16 and 17. The right and left polarized light beams 16 and 17 reflected in this way are transmitted only by the right-hand polarized light beam 16 by the counterclockwise circular polarization filter 18 that transmits only the right-polarized light beam. Get dark. On the other hand, in the portion of the cholesteric liquid crystal flake layer 212, only right-handed polarized light is visually recognized, so that it can be visually recognized with a hue different from that without the filter.

  FIG. 11 shows the state when the anti-counterfeit medium 200 is observed through the counterclockwise circular polarizing filter 19 as described above. In this case, the polymer cholesteric liquid crystal with the helical axis on the left is shown. There is no visual change in the layer 211, and the cholesteric liquid crystal flake layer 212 containing the flaky cholesteric liquid crystals whose helical axes rotate in the right and left directions is confirmed with a hue different from that when viewed without a filter. The hue at this time is different from that when viewed through a right rotation authenticity determination filter.

That is, as shown in FIG. 12, when the natural light 15 is reflected by the anti-counterfeit medium, the rotation direction of the spiral axis is the left rotation corresponding to the spiral pitch of the cholesteric liquid crystal constituting the left in the polymer cholesteric liquid crystal layer 211. Polarized light 17 is reflected, and clockwise rotated polarized light 16 is transmitted. The transmitted right-polarized polarized light 16 is absorbed by the light absorption layer 214. On the other hand, the cholesteric liquid crystal flake layer 212 reflects right and left rotated polarized light 16 and 17. Polarized light of the reflected right and left rotation thus by the left-handed circularly polarizing filter 19 which transmits only polarized light of left turn, only polarized light 17 of the left rotation is transmitted. Therefore, the polymer cholesteric liquid crystal layer 211 can be visually recognized in the same manner as when there is no filter, and the cholesteric liquid crystal flake layer 212 is visually recognized only by the reflected color of the cholesteric liquid crystal whose helical axis is rotated counterclockwise.

  In the above, specific examples of the anti-counterfeit medium according to the present invention have been described. As other configurations, for example, a left-handed spiral with a handle is placed on a polymer cholesteric liquid crystal layer whose spiral axis is rotated clockwise It may be a laminate of cholesteric liquid crystal flake layers having axes, or a laminate of cholesteric liquid crystal flake layers containing two types of flake-like cholesteric liquid crystals having helical axes whose rotation directions are right and left. Moreover, when using a transparent thing as a base material which forms each liquid crystal layer, you may install a polymer cholesteric liquid crystal layer and a cholesteric liquid crystal flake layer separately on the front and back.

  Also, flaky cholesteric liquid crystals with right and left spiral axes and those with different spiral pitches are prepared, and these are mixed as appropriate to form a liquid crystal coating liquid, and a predetermined layer is arranged side by side by these. May be.

  Further, the light absorption layer provided for the purpose of clarifying the reflected light of the cholesteric liquid crystal may be other than black, and various hues can be appropriately selected in consideration of visual effects and the like. Further, if there is no problem in performance and manufacturing, the installation position may be installed anywhere in the layer structure as long as it is below the cholesteric liquid crystal and can be selected as appropriate. Further, a pressure-sensitive adhesive or adhesive may be applied to the surface opposite to the surface to be visually observed, and there is no problem even if a so-called protective layer is provided for the purpose of protecting the forgery prevention medium.

  The constituent materials of the forgery prevention medium of the present invention will be described in detail below.

The fine flaky cholesteric liquid crystals contained in the cholesteric liquid crystal flake layers 12 and 212 described above are, for example, aligned with a three-dimensional cross-linkable liquid crystal substance having a chiral phase and three-dimensionally cross-linked, and then pulverized to a desired particle size. It is a flaky pigment obtained as described above. The light reflected by this pigment is circularly polarized. Among liquid crystal substances, cholesteric liquid crystals have a twisted structure, and the refractive index of light periodically varies along the twisted axis (spiral axis). Therefore, light having a wavelength equal to the helical pitch of the twisted structure is selectively selected. reflect. Therefore, it is possible to create a desired reflection color by the cholesteric liquid crystal by controlling the helical pitch of the twisted structure using temperature and / or a chiral agent. In addition, a liquid crystal having a twisted structure has its molecules arranged in layers, and forms optical characteristics only when the molecules are uniformly arranged in the layer. In this case, the molecules change their preferred directions from layer to layer, resulting in a twisted structure. Orientation of each molecule, for example, can be controlled by the orientation layer or electric field or magnetic field. A typical method for immobilization is a method of immobilizing a twisted structure by combining a three-dimensional crosslinkable liquid crystal having a chiral phase and a polyfunctional polymer compound, and three-dimensionally cross-linking by irradiating ultraviolet rays. Can be mentioned.

  As the starting material of the polymer cholesteric liquid crystal, all cholesteric liquid crystal substances having a twisted structure with a helical pitch equal to the wavelength of ultraviolet to infrared light can be used. A cholesteric liquid crystal can be produced by adding a chiral substance to a liquid crystal having a nematic or smectic structure. At this time, the kind and molecular weight of the chiral substance determine the direction of the twisted structure, the helical pitch, and the wavelength of the reflected light. Furthermore, if the liquid crystal has an asymmetric carbon in the structure, a twisted structure can be formed without adding a chiral substance. Regardless of whether a chiral substance is added or not, changing the temperature is also effective for changing the helical pitch of the twisted structure. However, since the helical pitch is long when the temperature is low and short when the temperature is high, when the temperature is too low, the reflected light enters the infrared region, and when it is high, the reflected light enters the ultraviolet region except for absorption by molecules. Since this becomes an isotropic layer and may not exhibit liquid crystallinity, it is necessary to pay sufficient attention to these in order to obtain reflected light that satisfies the designability and anti-counterfeit effect of the anti-counterfeit medium.

  As the polymer cholesteric liquid crystal constituting the polymer cholesteric liquid crystal layer of the present invention, those having molecules having properties as a cholesteric liquid crystal incorporated in a flexible main chain or those having a side chain are used. obtain. For example, a polymer with an energy ray curable compound is used. As the energy ray curable compound, those containing monomers or oligomers having two or more energy ray curable groups in the molecule are particularly preferred. As the radical photopolymerizable monomer, for example, a polyfunctional monomer such as trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, etc. Other functional oligomers such as a polymer, polyurethane polyacrylate, epoxy resin polyacrylate, and acrylic polyol polyacrylate are preferably used.

Monofunctional monomers include alkyl (C1 to C18) (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, alkylene (C2 to C4) glycol (meth) acrylate, alkoxy (C1 -C10) alkyl (C2-C4) (meth) acrylate, polyalkylene (C2-C4) glycol (meth) acrylate, alkoxy (C2-C10) polyalkylene (C2-C4) glycol (meth) acrylate, and the like. Examples of the cationic photopolymerizable monomer include aromatic epoxy compounds, alicyclic epoxy compounds, and glycidyl ester compounds.

  As a polymerization initiator for causing energy ray curing, a known polymerization initiator having appropriate characteristics depending on the energy rays to be irradiated is used as necessary. For example, α-hydroxyacetophenone, acetophenone, such as α-aminoacetophenone, benzoin ether, benzyl ketal, α-dicarbonyl, α-acyl oxime ester, etc. are used as radical photopolymerization initiators. The More specifically, α-aminoacetophenone, acetophenone diethyl ketal, benzyldimethyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylphenylpropanone, benzophenone, Michler's ketone, isopropylthioxanthone, benzophenone and N-methyldiethanolamine Etc.

  Moreover, as a cationic photoinitiator, a conventionally well-known thing can be especially used without a restriction | limiting. When adding a cationic photopolymerization initiator, it is preferable to use it together with known sensitizers and peroxides as appropriate. For example, allyl iodonium salt-α-hydroxyacetophenone, triallyl sulfonium salt, metallocene compound-peroxide combination, metallocene compound-thioxanthone combination, metallocene compound-anthracene combination.

  In the production of fine flaky cholesteric liquid crystals, for example, first, a mixed solution of a three-dimensional crosslinkable liquid crystal polyorganosiloxane and a photopolymerization initiator is heated, and a metal blade or plastic support is applied while applying a shearing force with a doctor blade. The liquid crystal molecules are aligned by coating on a support such as a body or a glass support. Next, the thin film layer in which the liquid crystal molecules are aligned is irradiated with ultraviolet rays to be three-dimensionally crosslinked. Subsequently, the three-dimensionally crosslinked liquid crystal is peeled from the support and pulverized with a universal mill or the like to obtain a flake pigment.

  The flaky cholesteric liquid crystal has a particle size of 1 μm to 200 μm, preferably 0.5 to 100 μm, preferably 1 to 50 μm. Moreover, as a support body, you may use what has the orientation layer which consists of a polyimide or polyvinyl alcohol, for example. Further, as a method for aligning liquid crystal molecules, a method of shearing between two sheets can be employed.

  The polymer cholesteric liquid crystal layer uses ink or coating liquid made of the above-described constituent materials, and has a film thickness of 0.5 to 20 μm, preferably 2 by a known coating method or printing method such as comma coater or micro gravure coater offset. It is obtained by forming a thin film on a substrate so as to have a thickness of 10 μm and crosslinking by irradiation with active energy rays from a known active energy ray irradiation device such as a metal halide lamp high-pressure mercury lamp. In addition, in order to advance crosslinking | crosslinking rapidly, oxygen concentration can also be avoided by bonding an active energy ray irradiation environment using an inert gas, for example, nitrogen, reducing oxygen concentration, or bonding with films, such as polyethylene.

  Alternatively, an adhesive may be applied to the liquid crystal surface of the cholesteric liquid crystal film constructed on the base material, and transferred to another base material in a shape as required.

On the other hand, the cholesteric liquid crystal flake layer includes, for example, the above-described flake-shaped cholesteric liquid crystal (pigment), and for gravure printing, which is appropriately kneaded and selected from various binders, dispersants, auxiliary agents, and the like. It can be formed by various printing inks and coating liquids such as screen printing. These inks and coating liquids are preferably inks containing 10 to 50% by weight of flaky cholesteric liquid crystal. The blending ratio of the cholesteric liquid crystal flakes having the left and right rotating spiral axes is preferably about 1: 1 to 1: 3, although it depends on the color of the cholesteric liquid crystal.

  In addition, as a support used in the production of the cholesteric liquid crystal flakes, a plastic film, a plastic sheet, a plastic plate, or a glass plate is arbitrarily used. In particular, a film or sheet of polyethylene terephthalate or polycarbonate, or a glass plate is used. preferable.

  Further, the clockwise circular polarizing filter 18 and the counterclockwise circular polarizing filter 19 used in the authenticity determination method of the present invention are circularly polarizing plates. Specifically, it is a PVA-iodine type in which iodine is absorbed in a stretched PVA film, a dichroic dye type, a metal or metal compound containing type, a polyene type circular polarizing plate. In particular, a polarizing film using a PVA-iodine type or dichroic dye type film with a 1 / 4λ wavelength phase difference film is rotated right or left depending on whether the phase difference is advanced or delayed by 1 / 4λ. The direction is determined.

  Next, the present invention will be described more specifically with reference to examples.

  On a polyethylene terephthalate film with a thickness of 25 μm, after applying a UV curable cholesteric liquid crystal with a spiral axis rotation method to a thickness of 5 μm using a die coater, nitrogen having an oxygen concentration of 0.1% or less Under an atmosphere, ultraviolet rays were irradiated from a high-pressure mercury lamp under irradiation conditions of an integrated light amount of 500 mj, the coating film was cured, and a polymer cholesteric liquid crystal film was obtained. Next, after removing the central portion of the cholesteric liquid crystal thin film of this film in a star shape, a dry laminating adhesive was applied to the remaining cholesteric liquid crystal thin film to a thickness of 1 μm to produce a transfer film. .

  Subsequently, a thin film having a thickness of 2 μm made of black ink was formed on a triacetylcellulose film having a thickness of 80 μm using a gravure printing machine, and dried to provide a light absorption layer. And it laminated | stacked so that the adhesive agent surface on the polymer cholesteric-liquid-crystal layer of the said transfer film might face on a light absorption layer, it laminated, and the support body (reethylene terephthalate film) of the transfer film was peeled after that.

Then, after printing with a screen printer so that the thickness is 20 μm with the ink containing cholesteric liquid crystal flakes whose spiral axis rotation direction is right on the part extracted in a star shape in the above process, the integrated light quantity of 500 mj Ultraviolet rays were irradiated from a high-pressure mercury lamp under irradiation conditions to cure the printed portion, and the forgery prevention medium of the present invention according to Example 1 was obtained.

  When the anti-counterfeit medium obtained as described above was viewed from the front, the portion of the polymer cholesteric liquid crystal layer was glossy red, and the portion of the cholesteric liquid crystal flake layer was glittery green. Furthermore, by changing the viewing angle, the polymer cholesteric liquid crystal layer portion changed to green, and the cholesteric liquid crystal flake layer portion changed to blue, confirming a color shift. Further, when viewed through a right-rotating circularly polarizing filter (authenticity judgment filter), the portion of the polymer cholesteric liquid crystal layer became dark, and the portion of the cholesteric liquid crystal flake layer was confirmed to be green with a lamellar gloss. Next, when viewed through a left-rotating circularly polarizing filter (authenticity judgment filter), the portion of the polymer cholesteric liquid crystal layer was recognized as glossy red, and the portion of the cholesteric liquid crystal flake layer was recognized as dark. For these reasons, the anti-counterfeit medium of the present invention has a color shift effect using a circularly polarizing filter as well as a color shift effect as OVI (Optical Variable Ink) ink, and has a further anti-counterfeit effect. It was confirmed that it can be expected.

In addition, when the authenticity determination filter is placed on the OVI ink, it looks dark regardless of left-right rotation, and when viewed away from the filter so that light that does not pass through the filter hits the OVI, the color change does not matter regardless of left-right rotation. It didn't happen.

  As an ink containing minute cholesteric liquid crystal flakes, the cholesteric liquid crystal flakes with a blue rotation of the spiral axis on the right and a blue color and the cholesteric liquid crystal flakes with a purple rotation on the left and a purple axis are in a ratio of 1: 1. A forgery prevention medium of the present invention according to Example 2 was obtained in the same manner as Example 1 except that the blended ink was used.

When this anti-counterfeit medium was viewed from the front, the portion of the polymer cholesteric liquid crystal layer was glossy red, and the portion of the cholesteric liquid crystal flake layer was bluish green that gave a glittery appearance. Furthermore, by changing the viewing angle, the polymer cholesteric liquid crystal layer portion changed to green, and the cholesteric liquid crystal flake layer portion changed to blue, confirming a color shift. In addition, when viewed through a circular polarizing filter of the right rotation (authenticity determination filter) parts of the high polymer cholesteric liquid crystal layer is recognized dark, the portion of the cholesteric liquid crystal flake layer was recognized purple off a glossy lame shape.

  Next, when looking through the counterclockwise circular polarizing filter (authenticity judgment filter), the polymer cholesteric liquid crystal layer part is recognized as glossy red, and the cholesteric liquid crystal flake layer part is assumed to be green with a glittery luster. Recognized.

It is explanatory drawing which shows the schematic planar structure of the forgery prevention medium of this invention. It is explanatory drawing which shows the schematic structure of the side cross-section part in the XX plane of the forgery prevention medium shown in FIG. It is explanatory drawing which shows a mode when verifying the forgery prevention medium shown in FIG. 1 through the authenticity determination filter. It is explanatory drawing which shows typically the principle of authenticity determination when verifying the forgery prevention medium as shown in FIG. It is explanatory drawing which shows a mode when verifying the forgery prevention medium shown in FIG. 1 through the authenticity determination filter. It is explanatory drawing which shows typically the principle of authenticity determination when verifying the forgery prevention medium as shown in FIG. It is explanatory drawing which shows the schematic planar structure of the other example of the forgery prevention medium of this invention. It is explanatory drawing which shows the outline of the side cross-section part in the YY surface of the forgery prevention medium shown in FIG. It is explanatory drawing which shows a mode when verifying the forgery prevention medium shown in FIG. 7 through the authenticity determination filter. It is explanatory drawing which shows a mode when verifying the forgery prevention medium as shown in FIG. It is explanatory drawing which shows a mode when verifying the forgery prevention medium shown in FIG. 7 through the counterclockwise authenticity determination filter. FIG. 8 is an explanatory diagram illustrating the principle of authenticity determination when the forgery prevention medium is verified as illustrated in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Anti-counterfeiting medium 11 ... Polymer cholesteric liquid crystal layer 12 ... Cholesteric liquid crystal flake layer 13 ... Base material 14 ... Light absorption layer 15 ... Natural light 16 ... Right-handed polarization 17 ... Left-handed polarization 18 .. clockwise circular polarizing filter (authentication filter)
19 .. Counterclockwise circular polarization filter (authentication filter)
200 ... Anti-counterfeit medium 211 ... Polymer cholesteric liquid crystal layer 212 ... Cholesteric liquid crystal flake layer

Claims (7)

  A polymer cholesteric liquid crystal layer that reflects clockwise or counterclockwise circularly polarized light and a cholesteric liquid crystal flake layer that contains at least one of minute flaky cholesteric liquid crystals in which the rotation direction of the spiral axis is right or left The cholesteric liquid crystal flake layer is disposed on a substrate in a visible state, and the cholesteric liquid crystal flake layer contains both flaky cholesteric liquid crystals whose right and left flakes are rotated. .   The cholesteric liquid crystal flake layer that contains both the polymer cholesteric liquid crystal layer and the flaky cholesteric liquid crystals whose helical axis rotates in the right and left directions should be recognized with the same hue under natural light irradiation. The forgery prevention medium according to claim 1.   A cholesteric liquid crystal flake layer that contains both a polymer cholesteric liquid crystal layer and flake cholesteric liquid crystals whose helical axis rotates in the right and left directions can be recognized in different hues under natural light irradiation. The forgery prevention medium according to claim 1.   The hue of the polymer cholesteric liquid crystal layer is recognized differently from the hue of the flaky cholesteric liquid crystal having a spiral axis in the same direction as the rotation direction of the spiral axis of the polymer cholesteric liquid crystal constituting the polymer cholesteric liquid crystal layer. The flake cholesteric liquid crystal having a helical axis opposite to the rotation direction of the helical axis of the polymer cholesteric liquid crystal is recognized differently from the hue under natural light irradiation. The anti-counterfeit medium described in 1.   The hue of the polymer cholesteric liquid crystal layer is recognized differently from the hue of the flaky cholesteric liquid crystal having a spiral axis in the same direction as the rotation direction of the spiral axis of the polymer cholesteric liquid crystal constituting the polymer cholesteric liquid crystal layer. 2. The hue of flake-shaped cholesteric liquid crystal having a helical axis opposite to the rotational direction of the helical axis of the polymer cholesteric liquid crystal is recognized in the same manner as that of natural light irradiation. The anti-counterfeit medium described in 1. The medium for preventing forgery according to any one of claims 1 to 5, wherein a light absorbing layer is provided under the polymer cholesteric liquid crystal layer and the cholesteric liquid crystal flake layer. The anti-counterfeit medium according to any one of claims 1 to 6, wherein the anti-counterfeit medium is visually observed through a determination tool made of a circularly polarizing plate, and authenticity is determined based on a changing hue. False judgment method.

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