Composite Pigment, Identification Medium and Authenticity Judgment Method

Abstract

The present invention provides a composite pigment, which comprises a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment. The above-mentioned first cholesteric liquid crystal pigment is a pigment having a center wavelength of a selective reflection band in the range of 400 nm or more and 800 nm or less and a selective reflection bandwidth of 150 nm or less. The above-mentioned second cholesteric liquid crystal pigment is a pigment having a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less. At least a part of the selective reflection band of the above-mentioned first cholesteric liquid crystal pigment overlaps with the selective reflection band of the above-mentioned second cholesteric liquid crystal pigment. With respect to the total amount of the above-mentioned first cholesteric liquid crystal pigment and the above-mentioned second cholesteric liquid crystal pigment, the content of the above-mentioned first cholesteric liquid crystal pigment is more than 0% by weight and 30% by weight or less.

Description

Technical Field

[0001] The present invention relates to a composite pigment, an identification medium, and a method for authenticity determination. Background Art

[0002] By attaching an identification medium to an article and identifying the authenticity of the identification medium, anti-counterfeiting of the article and the like can be achieved.

[0003] A cholesteric liquid crystal resin can be obtained by orienting a liquid crystalline compound into a cholesteric phase and curing it while maintaining the orientation. Such a cholesteric liquid crystal resin has the following circularly polarized light separation function: reflecting one of the right- and left-handed circularly polarized lights and transmitting the other. In a cholesteric liquid crystal resin material, as the viewing angle θ from the front direction increases, the wavelength of the reflected circularly polarized light shifts to the short wavelength side. Utilizing this property, the authenticity of an identification medium using a cholesteric liquid crystal resin can be identified.

[0004] As a product using such a cholesteric liquid crystal resin, an anti-counterfeiting printed matter containing a cholesteric liquid crystal resin as a pigment is known (see Patent Document 1).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-73600. Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In the anti-counterfeiting printed matter described in Patent Document 1, a printing layer using an ink is provided, and the ink contains either one or both of a right-polarizing pigment that reflects a part of the right-handed circularly polarized light in incident light and a left-polarizing pigment that reflects a part of the left-handed circularly polarized light in incident light. The authenticity of this anti-counterfeiting printed matter is judged visually using a authenticity judgment filter using a circular polarizer, and thus the authenticity can be judged by a simple device.

[0010] In recent years, forgery techniques have become sophisticated. Therefore, there is a need for an identification medium with improved anti-counterfeiting effect.

[0011] Solutions to the Problems

[0012] The inventor of the present invention conducted research to solve the above problems and found that when using a composite pigment containing a specific first cholesteric liquid crystal pigment and a specific second cholesteric liquid crystal pigment in a specified ratio, the color from the first cholesteric liquid crystal pigment cannot be observed or is difficult to observe by visual inspection, but can be observed by microscopic observation, thereby improving the anti-counterfeiting effect. Specifically, a pigment having a center wavelength of a selective reflection band in the range of 400 nm or more and 800 nm or less and a selective reflection bandwidth of 150 nm or less is used as the first cholesteric liquid crystal pigment, and a pigment having a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less is used as the second cholesteric liquid crystal pigment. In this case, this effect can be obtained. That is, the present invention provides the following.

[0013] [1] A composite pigment comprising a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment,

[0014] The above-mentioned first cholesteric liquid crystal pigment is a pigment having a center wavelength of a selective reflection band in the range of 400 nm or more and 800 nm or less and a selective reflection bandwidth of 150 nm or less,

[0015] The above-mentioned second cholesteric liquid crystal pigment is a pigment having a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less,

[0016] At least a part of the selective reflection band of the above-mentioned first cholesteric liquid crystal pigment overlaps with the selective reflection band of the above-mentioned second cholesteric liquid crystal pigment,

[0017] With respect to the total amount of the above-mentioned first cholesteric liquid crystal pigment and the above-mentioned second cholesteric liquid crystal pigment, the content of the above-mentioned first cholesteric liquid crystal pigment is greater than 0% by weight and 30% by weight or less.

[0018] [2] The composite pigment according to [1], wherein, with respect to the total amount of the above-mentioned first cholesteric liquid crystal pigment and the above-mentioned second cholesteric liquid crystal pigment, the content of the above-mentioned first cholesteric liquid crystal pigment is 20% by weight or less.

[0019] [3] The composite pigment according to [1] or [2], wherein the selective reflection bandwidth of the above-mentioned first cholesteric liquid crystal pigment is 120 nm or less.

[0020] [4] The composite pigment according to any one of [1] to [3], wherein the above-mentioned first cholesteric liquid crystal pigment and the above-mentioned second cholesteric liquid crystal pigment have the same twisting direction as each other.

[0021] [5] The composite pigment according to any one of [1] to [3], wherein the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment have different twisting directions from each other.

[0022] [6] The composite pigment according to any one of [1] to [5], wherein at least one of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is a flake,

[0023] The average particle diameter of the flakes is 20 μm or more and 120 μm or less.

[0024] [7] An ink composition comprising the composite pigment according to any one of [1] to [6] and a binder resin.

[0025] [8] An identification medium comprising a binder resin and a pigment dispersed in the binder resin,

[0026] The pigment is the composite pigment according to any one of [1] to [6].

[0027] [9] A method for authenticity determination, which is a method for authenticity determination of the identification medium according to [8], and the method includes the following steps:

[0028] Step 1, observing the reflected light from the identification medium through a left-handed circular polarizer and a right-handed circular polarizer, and determining whether there are differences in one or more of hue, lightness, and chroma of the reflected light;

[0029] Step 2, visually observing the identification medium and determining whether the color from the second cholesteric liquid crystal pigment can be observed; and

[0030] Step 3, observing the identification medium through a microscope and determining whether both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed.

[0031] Advantages of the Invention

[0032] According to the present invention, it is possible to provide a composite pigment with improved anti-counterfeiting effect, an ink composition and an identification medium using the composite pigment, and a method for identifying the authenticity of the identification medium. Brief Description of the Drawings

[0033] Figure 1 A front view schematically showing a manufacturing apparatus for a release sheet of a resin film used in the manufacture of the composite pigment of the present invention.

[0034] Figure 2 Schematically showing for Figure 1A sectional view of a cross-section when a corner of a bar of a manufacturing apparatus is cut by a plane perpendicular to the width direction of the support body. Detailed Description of the Invention

[0035] Hereinafter, embodiments and examples will be shown to describe the present invention in detail. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily changed and implemented within the scope of the claims of the present invention and its equivalent scope.

[0036] In the following description, unless otherwise specified, "composition" includes not only mixtures of two or more substances but also materials formed from a single substance, and "agent" includes not only materials formed from a single substance but also mixtures of two or more substances.

[0037] In the following description, unless otherwise specified, "(meth)acrylate" means "acrylate" or "methacrylate" or both of them. Further, "(meth)acryloyl" means "acryloyl" or "methacryloyl" or both of them. "(Thio)epoxy" means "epoxy" or "thioepoxy" or both of them. Further, "isothiocyanate" means "isocyanate" or "isothiocyanate" or both of them.

[0038] [1. Composite Pigment]

[0039] The composite pigment of the present invention contains a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment. The first cholesteric liquid crystal pigment is a pigment having a center wavelength of a selective reflection band in the range of 400 nm or more and 800 nm or less and a selective reflection bandwidth of 150 nm or less. The second cholesteric liquid crystal pigment is a pigment having a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less. At least a part of the selective reflection band of the first cholesteric liquid crystal pigment overlaps with the selective reflection band of the second cholesteric liquid crystal pigment. The content of the first cholesteric liquid crystal pigment is more than 0% by weight and 30% by weight or less based on the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment.

[0040] The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are each composed of a cholesteric liquid crystal resin.

[0041] "Cholesteric liquid crystal resin" means a resin material having cholesteric regularity, and means that molecules or partial molecules constituting the resin are arranged in a state having cholesteric regularity in the resin.

[0042] Here, "having a cholesteric regularity" of the molecules in the resin means that the molecules in the resin have the specific regularity described below. When the molecules in the resin have a cholesteric regularity, the molecules are arranged in multiple molecular layers within the resin. In each molecular layer, the molecules are arranged such that the molecular axes are along a certain orientation direction. The orientation direction of the next second plane overlapping the first plane within the resin layer is slightly angularly deviated with respect to the orientation direction of the first plane. The orientation direction of the next third plane further overlapping the second plane is further slightly angularly deviated from the orientation direction of the second plane. Thus, in the multiple planes arranged in an overlapping manner, the angles of the molecular axes in these planes are sequentially deviated (twisted). The structure in which the direction of the molecular axes is continuously twisted like this is an optically chiral structure.

[0043] A cholesteric liquid crystal resin having an optically chiral structure usually has a circularly polarized light selective reflection function of selectively reflecting circularly polarized light. That the cholesteric liquid crystal resin "selectively reflects" light in a specified wavelength range means that the cholesteric liquid crystal resin reflects one circularly polarized light component in the non-polarized light (i.e., natural light) in the specified wavelength range and transmits the other circularly polarized light component. The "selective reflection band" in the present invention refers to the wavelength range of the circularly polarized light that is selectively reflected. In the present invention, the "selective reflection bandwidth" is the width of the selective reflection band. Specifically, it can be the half-width of the selective reflection band.

[0044] [Selective Reflection Band of Cholesteric Liquid Crystal Pigment]

[0045] In the present invention, at least a part of the selective reflection band of the first cholesteric liquid crystal pigment overlaps with the selective reflection band of the second cholesteric liquid crystal pigment. The overlapping range of the selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment is preferably 80% or more, more preferably 90% or more, and further preferably 100% with respect to the whole of the selective reflection band of the first cholesteric liquid crystal pigment. The overlapping range of the selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment is preferably 10% or more, more preferably 20% or more, preferably 50% or less, and more preferably 40% or less with respect to the whole of the selective reflection band of the second cholesteric liquid crystal pigment. If the overlapping range of the selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment is above the above lower limit value with respect to the whole of the selective reflection band of the first cholesteric liquid crystal pigment, it becomes difficult to recognize the difference in color between the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment in visual observation, and thus the anti-counterfeiting effect is improved. If the overlapping range of the selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment is above the above lower limit value with respect to the whole of the selective reflection band of the second cholesteric liquid crystal pigment, it becomes difficult to recognize the difference in color between the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment in visual observation, and thus the anti-counterfeiting effect is improved. In addition, if it is below the above upper limit value, it becomes easy to recognize the difference in color between the first cholesteric pigment and the second cholesteric liquid crystal pigment by microscopic observation.

[0046] In the present invention, the selective reflection bandwidth of the first cholesteric liquid crystal pigment is 150 nm or less, and the selective reflection bandwidth of the second cholesteric liquid crystal pigment is 200 nm or more. That is, the first cholesteric liquid crystal pigment is a cholesteric liquid crystal pigment with a narrower selective reflection bandwidth (narrow-band) than the second cholesteric liquid crystal pigment, and the second cholesteric liquid crystal pigment is a cholesteric liquid crystal pigment with a wider selective reflection bandwidth (broad-band) than the first cholesteric liquid crystal pigment. If an identification medium using a cholesteric liquid crystal pigment with a narrow selective reflection bandwidth is observed through natural light, an appearance with a color corresponding to the reflection band can be observed. If an identification medium using a cholesteric liquid crystal pigment with a wide selective reflection bandwidth is observed through natural light, an appearance close to silver like a mirror surface can be observed. In the present invention, since the composite pigment contains the first cholesteric liquid crystal pigment with a selective reflection bandwidth of 150 nm or less and the second cholesteric liquid crystal pigment with a selective reflection bandwidth of 200 nm or more, when observing an identification medium using such a composite pigment through natural light, it becomes easy to determine whether the observed color is the color from either the first cholesteric liquid crystal pigment or the second cholesteric liquid crystal pigment.

[0047] The selective reflection bandwidth of the first cholesteric liquid crystal pigment is preferably 120 nm or less, more preferably 110 nm or less, preferably 30 nm or more, and more preferably 50 nm or more. The selective reflection bandwidth of the second cholesteric liquid crystal pigment is preferably 200 nm or more, more preferably 300 nm or more. The upper limit of the selective reflection bandwidth of the second cholesteric liquid crystal pigment is not particularly limited, preferably 2000 nm or less, and more preferably 1000 nm or less.

[0048] The first cholesteric liquid crystal pigment has a central wavelength of the selective reflection band in the range of 400 nm or more and 800 nm or less. In the present invention, the central wavelength of the selective reflection band of each cholesteric liquid crystal pigment may be the central wavelength of the region of the half peak width of the selective reflection band. That is, the reflection spectrum of the cholesteric liquid crystal pigment is measured at an incident angle of 5°. In the obtained reflection spectrum, the peak with the maximum intensity and the bottom of the peak with the minimum intensity are determined, and the wavelength λ1 on the short wavelength side and the wavelength λ2 on the long wavelength side of the peak showing the intensity of the minimum intensity + (maximum intensity - minimum intensity) / 2 are obtained. Furthermore, their average value ((λ1 + λ2) / 2) is obtained, and this average value is used as the central wavelength. In this case, the selective reflection band of each cholesteric liquid crystal pigment is the range (λ1~λ2) from the wavelength λ1 on the short wavelength side of the peak showing the intensity of the minimum intensity + (maximum intensity - minimum intensity) / 2 in the reflection spectrum to the wavelength λ2 on the long wavelength side, and the selective reflection bandwidth of each cholesteric liquid crystal pigment is the difference (λ2 - λ1) between the wavelength λ2 on the long wavelength side and the wavelength λ1 on the short wavelength side.

[0049] In the case where the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are in the form of powders or fibers of a cholesteric liquid crystal resin, the central wavelength of the selective reflection band of each cholesteric liquid crystal pigment is the central wavelength of the selective reflection band observed when a film containing the pigment is formed.

[0050] When the average refractive index of the cholesteric liquid crystal resin is set to n and the pitch length of the chiral structure (helical structure) of the cholesteric liquid crystal resin is set to P (nm), the central wavelength λ (nm) of the selective reflection band when observing the film containing each cholesteric liquid crystal pigment from the front direction at a viewing angle θ is represented by the following formula.

[0051] λ = n × P × cosθ

[0052] Therefore, when observing the film containing each cholesteric liquid crystal pigment from the viewing angle θ in the front direction (cosθ < 1), the central wavelength λ of the selective reflection band is shorter than the central wavelength λ of the selective reflection band when observing from the front direction (cosθ = 1). The front direction of the film containing the cholesteric liquid crystal pigment refers to the normal direction of the film when the film containing the cholesteric liquid crystal pigment is formed.

[0053] When observing the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment from the perspective of the viewing angle θ in the front direction, the central wavelength λ of the selective reflection band can be increased, for example, by increasing the pitch length P of the chiral structure (helical structure), and can be decreased by decreasing the pitch length P.

[0054] As a method for adjusting the pitch length of each cholesteric liquid crystal resin, for example, a method of adjusting the type of chiral agent and a method of adjusting the amount of chiral agent can be cited.

[0055] [Content of the first cholesteric liquid crystal pigment]

[0056] In the present invention, relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment, the content of the first cholesteric liquid crystal pigment is greater than 0% by weight and 30% by weight or less. Relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment, the content of the first cholesteric liquid crystal pigment is preferably 10% by weight or more, more preferably 15% by weight or more, preferably 25% by weight or less, and more preferably 20% by weight or less.

[0057] By making the content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment be below the above upper limit value, in visual observation, the color from the first cholesteric liquid crystal pigment cannot be observed or is difficult to observe, while the color from the second cholesteric liquid crystal pigment can be observed, and in microscopic observation, both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed. Thereby, the anti-counterfeiting effect can be improved.

[0058] By making the content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment greater than 0% by weight, in microscopic observation, the color from the second cholesteric liquid crystal pigment and the color from the first cholesteric liquid crystal pigment can be observed simultaneously.

[0059] From the viewpoint of excellent dispersibility when the composite pigment is made into an ink composition, at least one of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is preferably a flake. When the first cholesteric liquid crystal pigment, the second cholesteric liquid crystal pigment, or both cholesteric liquid crystal pigments are flakes, the average particle diameter of the flakes is preferably 20 μm or more, more preferably 30 μm or more, preferably 120 μm or less, more preferably 100 μm or less, and particularly preferably 80 μm or less. If the average particle diameter of the flakes is above the above lower limit value, the decorativeness can be improved, and if the average particle diameter of the flakes is below the above upper limit value, the printing adaptability can be improved.

[0060] The average particle size of the flakes can be measured by, for example, the laser scattering method to measure the particle size distribution, and the average particle size is determined based on the particle size distribution. In the particle size distribution, the particle size at which the cumulative value of the volume is 50% can be used as the average particle size. In the present application, unless otherwise specified, the average particle size of the flakes is the volume average particle size.

[0061] [Twisting direction of cholesteric liquid crystal pigment]

[0062] The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment may have the same twisting direction as each other or may have different twisting directions from each other. The determination of the twisting direction can be carried out by observing the reflected light when unpolarized light is incident on a sample containing each cholesteric liquid crystal pigment through left- and right-handed circular polarizers. That is, unpolarized light is irradiated on the sample from the observer side, and the reflected light that reaches the observer side after being reflected by the sample is observed, thereby determining the twisting direction. In the case where the reflected light is right-handed circularly polarized light, it can be judged as right-handed twisting, and in the case where it is left-handed circularly polarized light, it can be judged as left-handed twisting.

[0063] [Material of cholesteric liquid crystal pigment]

[0064] The cholesteric liquid crystal resin as the material of the first cholesteric liquid crystal pigment is a cured product of a first liquid crystal composition containing a liquid crystalline compound. The cholesteric liquid crystal resin as the material of the second cholesteric liquid crystal pigment is a cured product of a second liquid crystal composition containing a liquid crystalline compound.

[0065] As the liquid crystalline compounds contained in the first liquid crystal composition and the second liquid crystal composition, liquid crystalline compounds having polymerizability are preferably used. A liquid crystal composition containing a liquid crystalline compound having polymerizability can be easily cured in a state where the orientation state is maintained by polymerizing the liquid crystalline compound.

[0066] As the liquid crystalline compound, a cholesteric liquid crystalline compound can be used. The cholesteric liquid crystalline compound is a compound that can exhibit cholesteric liquid crystallinity. By using a liquid crystal composition containing such a cholesteric liquid crystalline compound and curing the liquid crystal composition in a cholesteric liquid crystal phase state, a cholesteric liquid crystal resin as a resin material having cholesteric regularity can be obtained.

[0067] As the liquid crystalline compounds contained in the first liquid crystal composition and the second liquid crystal composition, for example, rod-shaped liquid crystalline compounds having two or more reactive groups in one molecule can be used. As such a rod-shaped liquid crystalline compound, for example, the compound represented by the formula (1) can be cited.

[0068] R 3 -C 3 -D 3 -C 5 -M-C 6 -D4 -C 4 -R 4 Formula (1)

[0069] In Formula (1), R 3 and R 4 are reactive groups, each independently representing a group selected from (meth)acryloyl, (thio)epoxy, oxetanyl, thietanyl, aziridinyl, pyrrolyl, vinyl, allyl, fumarate, cinnamoyl, oxazolinyl, mercapto, isothiocyanate, amino, hydroxy, carboxy, and alkoxysilyl. By having these reactive groups, when the liquid crystal composition is cured, a cholesteric liquid crystal resin with high strength can be obtained.

[0070] In Formula (1), D 3 and D 4 each independently represent a group selected from a single bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and a linear or branched epoxyalkyl group having 1 to 20 carbon atoms.

[0071] In Formula (1), C 3 ~C 6 each independently represent a group selected from a single bond, -O-, -S-, -S-S-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH=N-N=CH-, -NHCO-, -O-(C=O)-O-, -CH2-(C=O)-O-, and -CH2O-(C=O)-.

[0072] In Formula (1), M represents a mesogenic group. Specifically, M represents a group selected from unsubstituted or optionally substituted azomethines, azoxides, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoates, phenyl cyclohexanecarboxylates, cyano phenyl cyclohexanes, cyano-substituted phenyl pyrimidines, alkoxy-substituted phenyl pyrimidines, benzene di alkanes, diphenylacetylenes, alkenyl cyclohexyl benzonitriles, etc., in which two to four identical or different skeletons are bonded through linking groups such as -O-, -S-, -S-S-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH=N-N=CH-, -NHCO-, -O-(C=O)-O-, -CH2-(C=O)-O-, and -CH2O-(C=O)-.

[0073] Examples of the substituents that the above mesogenic group M may have include, for example, a halogen atom, an alkyl group having 1 to 10 carbon atoms that may have a substituent, a cyano group, a nitro group, -O-R 5 、-O-C(=O)-R5 、 -C(=O)-O-R 5 、 -O-C(=O)-O-R 5 、 -NR 5 -C(=O)-R 5 、 -C(=O)-NR 5 R 7 or -O-C(=O)-NR 5 R 7 。 Here, R 5 and R 7 represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When R 5 and R 7 are alkyl groups, -O-, -S-, -O-C(=O)-, -C(=O)-O-, -O-C(=O)-O-, -NR 6 -C(=O)-, -C(=O)-NR 6 -, -NR 6 - or -C(=O)- (except for the cases where two or more -O- are inserted adjacent to each other and two or more -S- are inserted adjacent to each other) can be inserted between these alkyl groups. Here, R 6 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0074] As substituents in the above-mentioned "alkyl group having 1 to 10 carbon atoms that may have substituents", examples include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkoxy group having 2 to 8 carbon atoms, an alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, an alkylcarbonyloxy group having 2 to 7 carbon atoms, an alkoxycarbonyloxy group having 2 to 7 carbon atoms, etc.

[0075] Furthermore, the above-mentioned rod-like liquid crystalline compound is preferably an asymmetric structure. Here, the asymmetric structure means that with the mesogenic group M as the center in formula (1), R 3 -C 3 -D 3 -C 5 - is different from -C 6 -D 4 -C 4 -R 4 in structure. By using a compound with an asymmetric structure as the rod-like liquid crystalline compound, the alignment uniformity can be further improved.

[0076] As specific examples preferred for the rod-like liquid crystalline compound, the following compounds (B1) to (B9) can be cited. In addition, these can be used alone or two or more of them can be used in any ratio in combination.

[0077] [Chemical Formula 1]

[0078]

[0079] The first liquid crystal composition and / or the second liquid crystal composition preferably contain the compound represented by the above formula (1) as a liquid crystal compound, and more preferably contain one or more selected from the above compounds (B1) to (B9).

[0080] In addition to the liquid crystal compound, the first liquid crystal composition and / or the second liquid crystal composition may contain the compound represented by the following formula (2). The compound of formula (2) can function as an alignment aid.

[0081] R 1 -A 1 -B-A 2 -R 2 (2)

[0082] In formula (2), R 1 and R 2 are each independently a group selected from linear or branched alkyl groups having 1 to 20 carbon atoms, linear or branched epoxyalkyl groups having 1 to 20 carbon atoms, hydrogen atom, halogen atom, hydroxyl group, carboxyl group, (meth)acryloyl group which can insert any bonding group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group.

[0083] The above alkyl and epoxyalkyl groups may be unsubstituted or substituted with one or more halogen atoms. Further, the above halogen atom, hydroxyl group, carboxyl group, (meth)acryloyl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group may be bonded to alkyl and epoxyalkyl groups having 1 to 2 carbon atoms.

[0084] As preferred examples of R 1 and R 2 halogen atom, hydroxyl group, carboxyl group, (meth)acryloyl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group can be cited.

[0085] In addition, it is preferred that at least one of R 1 and R 2 is a reactive group. By having at least one of R 1 and R 2 be a reactive group, the compound represented by the above formula (2) can be fixed in the cholesteric liquid crystal resin during curing to form a more firm resin. Here, as the reactive group, for example, carboxyl group, (meth)acryloyl group, epoxy group, mercapto group, isocyanate group, and amino group can be cited.

[0086] In formula (2), A 1 and A2 each independently represents a group selected from 1,4-phenylene, 1,4-cyclohexylene, cyclohexene-1,4-diyl, 4,4'-biphenylene, 4,4'-bicylcohexylidene, and 2,6-naphthylene. The above 1,4-phenylene, 1,4-cyclohexylene, cyclohexene-1,4-diyl, 4,4'-biphenylene, 4,4'-bicylcohexylidene, and 2,6-naphthylene may be unsubstituted or substituted with one or more substituents such as a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, etc. In A 1 and A 2 when there are two or more substituents in each, these substituents may be the same or different.

[0087] As particularly preferred groups for A 1 and A 2 groups selected from 1,4-phenylene, 4,4'-biphenylene, and 2,6-naphthylene can be mentioned. These aromatic ring skeletons are more rigid than the alicyclic skeleton, have a high affinity for the mesophase of the rod-like liquid crystal compound, and the orientation uniformity becomes higher.

[0088] In formula (2), B is selected from a single bond, -O-, -S-, -S-S-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH=N-N=CH-, -NHCO-, -O-(C=O)-O-, -CH2-(C=O)-O-, and -CH2O-(C=O)-.

[0089] As particularly preferred groups for B, a single bond, -O-(C=O)-, and -CH=N-N=CH- can be mentioned.

[0090] As particularly preferred specific examples of the compound represented by formula (2), the following compounds (A1) to (A10) can be mentioned. These can be used alone, or two or more of them can be used in any ratio in combination.

[0091] Among the following compounds (A1) to (A10), one or more selected from compounds (A2) and (A10) are particularly preferred. Compounds (A2) and (A10) can lower the appearance temperature of the liquid crystal phase in the liquid crystal composition and can maintain the temperature range of the liquid crystal phase of the liquid crystal compound in a wide range.

[0092] [Chemical formula 2]

[0093]

[0094] In the above compound (A3), "*" represents a chiral center.

[0095] In the first liquid crystal composition or the second liquid crystal composition, the weight ratio represented by (total weight of the compounds represented by formula (2)) / (total weight of the rod-like liquid crystalline compounds) is preferably 0.05 or more, more preferably 0.1 or more, particularly preferably 0.15 or more, preferably 1 or less, more preferably 0.65 or less, and particularly preferably 0.55 or less. By making the above weight ratio 0.05 or more, the alignment uniformity of the liquid crystal composition can be improved. In addition, by making the above weight ratio 1 or less, the alignment uniformity can be improved. In addition, the stability of the liquid crystal phase of the liquid crystal composition can be improved. Here, the total weight of the compounds represented by formula (2) represents the weight of the compound when only one compound represented by formula (2) is used, and represents the total weight when two or more compounds are used. Similarly, the total weight of the rod-like liquid crystalline compounds represents the weight of the compound when only one rod-like liquid crystalline compound is used, and represents the total weight when two or more compounds are used.

[0096] In addition, when the compound represented by formula (2) and the rod-like liquid crystalline compound are used in combination, it is preferable that the molecular weight of the compound represented by formula (2) is less than 600, and it is preferable that the molecular weight of the rod-like liquid crystalline compound is 600 or more. Thereby, the compound represented by formula (2) can enter the gaps of the rod-like liquid crystalline compounds having a larger molecular weight than itself, and thus the alignment uniformity can be improved.

[0097] The first liquid crystal composition and the second liquid crystal composition may each contain a chiral agent. Generally, the twisting direction of the cholesteric liquid crystal resin can be appropriately selected according to the type and structure of the chiral agent used. As specific examples of the chiral agent, chiral agents described in JP-A-2005-289881, JP-A-2004-115414, JP-A-2003-66214, JP-A-2003-313187, JP-A-2003-342219, JP-A-2000-290315, JP-A-6-072962, U.S. Patent No. 6468444, WO 98 / 00428, JP-A-2007-176870, etc. can be appropriately used, and for example, LC756 of BASF's Paliocolor can be obtained. As the chiral agent, the compound represented by the following formula (3) can also be used. The chiral agent can be used alone or two or more kinds can be used in combination at any ratio.

[0098] [Chemical formula 3]

[0099]

[0100] The amount of the chiral agent can be arbitrarily set within a range that does not reduce the desired optical properties. In the liquid crystal composition, the specific amount of the chiral agent is usually 1% by weight to 60% by weight.

[0101] The first liquid crystal composition and the second liquid crystal composition may each contain a polymerization initiator. As the polymerization initiator, for example, a photopolymerization initiator can be mentioned, and a compound that can generate free radicals or an acid by ultraviolet rays or visible light can be used. Specific examples of the photopolymerization initiator include: benzoin, benzyl dimethyl ketal, benzophenone, biacetyl, acetophenone, Michler's ketone, benzil, benzyl isobutyl ether, tetramethylthiuram mono(di)sulfide, 2,2-azobisisobutyronitrile, 2,2-azobis-2,4-dimethylvaleronitrile, benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methyl benzoylformate, 2,2-diethoxyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-amylcinnamaldehyde, p-dimethylaminobenzophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin n-butyl ether, diphenyl sulfide, bis(2,6-methoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, anthraquinone, α-chloroanthraquinone, diphenyl disulfide, hexachlorobutadiene, pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,2-octanedione-1-[4-(phenylthio)-2-(o-benzoyl oxime)], 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(o-acetoxime) and other carbazole oxime compounds, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate, 3-methyl-2-butynyltetramethylenesulfonium hexafluoroantimonate, diphenyl-(p-phenylphenylthio)sulfonium hexafluoroantimonate, etc. As the polymerization initiator, IRGACURE 184 and IRGACURE OXE02 manufactured by BASF can also be used. These can be used alone as one kind, or two or more kinds can be used in any ratio in combination. Furthermore, a known photosensitizer or a tertiary amine compound as a polymerization accelerator can be used as needed to control the curability.

[0102] The amount of the polymerization initiator is preferably 0.03% by weight to 7% by weight in the liquid crystal composition. By making the amount of the polymerization initiator be above the lower limit value of the above range, the degree of polymerization can be increased, and thus the mechanical strength of the cholesteric liquid crystal resin can be improved. In addition, by making the amount of the polymerization initiator be below the upper limit value of the above range, the orientation of the liquid crystalline compound can be made good, and thus the liquid crystal phase of the liquid crystal composition can be stabilized.

[0103] The first liquid crystal composition and the second liquid crystal composition may each contain a surfactant as a leveling agent. As the surfactant, for example, a surfactant that does not hinder the orientation can be appropriately selected and used. As such a surfactant, for example, a nonionic surfactant containing a siloxane or a fluorinated alkyl group in the hydrophobic group part can be preferably selected. Among them, an oligomer having two or more hydrophobic group parts in one molecule is particularly preferred. As specific examples of these surfactants, PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652 of PolyFox of OMNOVA Corporation; FTX-209F, FTX-208G, FTX-204D of FTERGENT of Neos Corporation; KH-40, S420 of Surflon of Seimi Chemical Co., Ltd. can be used. In addition, the surfactant can be used alone as one kind, or two or more kinds can be used in combination at any ratio.

[0104] The amount of the surfactant is preferably an amount such that the amount of the surfactant in the cholesteric liquid crystal resin is 0.05% by weight to 3% by weight. By making the amount of the surfactant be above the lower limit value of the above range, the orientation restricting force at the air interface of the liquid crystal composition can be increased, and thus orientation defects can be prevented. In addition, by making the amount of the surfactant be below the upper limit value of the above range, the poor surface condition caused by the formation of a micelle structure due to an excessive amount of the surfactant can be suppressed.

[0105] The first liquid crystal composition and the second liquid crystal composition may each further contain optional components as needed. As the optional components, for example, polymerization inhibitors for improving the pot life; antioxidants, ultraviolet absorbers, light stabilizers, etc. for improving the durability can be cited. In addition, these optional components can be used alone as one kind, or two or more kinds can be used in combination at any ratio. The amounts of these optional components can be arbitrarily set within a range that does not reduce the desired optical properties.

[0106] The production methods of the first liquid crystal composition and the second liquid crystal composition are not particularly limited, and the first liquid crystal composition and the second liquid crystal composition can be respectively produced by mixing the above-mentioned respective components.

[0107] [Manufacture of the First Cholesteric Liquid Crystal Pigment]

[0108] The first cholesteric liquid crystal pigment can be manufactured as follows: A coating liquid containing the first liquid crystal composition and a solvent is coated on a suitable support, dried as needed to form a layer of the first liquid crystal composition, and the layer is cured to form a film of the first cholesteric liquid crystal resin. Then, the film of the first cholesteric liquid crystal resin is peeled off from the support and pulverized.

[0109] (Manufacture of the Film of the First Cholesteric Liquid Crystal Resin)

[0110] Before coating the coating liquid containing the first liquid crystal composition, a treatment for imparting an orientation restricting force can be performed on the surface of the support. Examples of such treatment include rubbing treatment of the support surface, stretching treatment of the support film, etc. In addition, surface treatments such as corona treatment for improving the affinity between the surface of the support and the first liquid crystal composition can also be performed.

[0111] As the support, a film having a resin layer made of resin can be used. When giving examples of polymers contained in the resin constituting the resin layer, examples include chain olefin polymers, cycloolefin polymers, polycarbonates, polyesters, polysulfones, polyethersulfones, polystyrenes, polyvinyl alcohols, cellulose acetate-based polymers, polyvinyl chlorides, polymethacrylates, etc.

[0112] Here, the resin can be a resin containing only one kind of polymer alone, or a resin containing two or more kinds of polymers combined at any ratio. In addition, as long as the effects of the present invention are not significantly impaired, the resin can also contain any compounding agent.

[0113] In addition, the support can be a single-layer structure film having only one layer, or a multi-layer structure film having two or more layers. Therefore, the support can be a film having only the above resin layer, or a film having any layer in addition to the above resin layer.

[0114] For example, from the viewpoint of enabling the liquid crystal composition to be oriented well, the support can have an alignment film on its surface. The alignment film can be formed of a resin containing polymers such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, etc. In addition, these polymers can be used alone or two or more kinds can be used in combination at any ratio. The alignment film can be manufactured by coating a solution containing the above polymers, drying it, and performing a rubbing treatment.

[0115] The thickness of the alignment film is preferably 0.01 μm or more, more preferably 0.05 μm or more, preferably 5 μm or less, and more preferably 1 μm or less.

[0116] The support can be an unstretched film or a stretched film.

[0117] In addition, the support can be an isotropic film or an anisotropic film.

[0118] Furthermore, the support can also be a support whose one or both surfaces have been surface-treated. By performing the surface treatment, the adhesion with other layers directly formed on the surface of the support can be improved. Examples of the surface treatment include energy ray irradiation treatment and chemical treatment.

[0119] From the viewpoints of operability during manufacturing, cost of materials, thinning, and lightening, the thickness of the support is preferably 30 μm or more, more preferably 60 μm or more, preferably 300 μm or less, and more preferably 200 μm or less.

[0120] Coating of the coating liquid containing the first liquid crystal composition can be carried out by known coating methods. Examples of the coating method include extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method, spin coating method, and bar coating method.

[0121] Orientation treatment can also be carried out as needed after coating the coating liquid containing the first liquid crystal composition to form a layer of the first liquid crystal composition and before the curing process. The orientation treatment can be carried out, for example, by heating the layer of the first liquid crystal composition at 50 to 150 °C for 0.5 to 10 minutes. By performing this orientation treatment, the liquid crystalline compounds in the first liquid crystal composition can be oriented well.

[0122] The curing treatment of the layer of the first liquid crystal composition can be carried out by energy ray irradiation one or more times. Examples of the energy ray include ultraviolet rays, visible light, and other electromagnetic waves. Specifically, the energy ray irradiation can be carried out, for example, by irradiating light with a wavelength of 200 to 500 nm for 0.01 seconds to 3 minutes. When curing the layer of the first liquid crystal composition, a thin film of the first cholesteric liquid crystal resin is formed on the support.

[0123] (Manufacture of pigments using the thin film of the first cholesteric liquid crystal resin)

[0124] The method of peeling the thin film of the first cholesteric liquid crystal resin from the support and pulverizing it is not particularly limited, and examples include the method described in Japanese Patent Laid-Open No. 2015-27743. In this method, the Figure 1 manufacturing apparatus for the release sheet shown can be used to peel the thin film of the first cholesteric liquid crystal resin from the support. Hereinafter, the method of peeling the thin film of the first cholesteric liquid crystal resin using the Figure 1 apparatus shown will be described. Hereinafter, the "thin film of the first cholesteric liquid crystal resin" will also be simply referred to as the "first resin thin film".

[0125] Figure 1The front view of a manufacturing apparatus for a release sheet of a resin film used in the production of the composite pigment of the present invention is schematically shown. Figure 1 The shown release sheet manufacturing apparatus 100 has: a film feeding section 120 that can feed a multilayer film 110 having a support 111 and a first resin film (refer to Figure 2 112); a peeling section 130 that can peel the first resin film 112 from the fed multilayer film 110; and a recovery section 140 that can recover the support 111 from which the first resin film 112 has been peeled.

[0126] The peeling section 130 has a block 134 having a corner portion 135 set at an acute angle; and a nozzle 136 provided downstream of the corner portion 135 and capable of jetting air. The angle of the corner portion 135 of the block 134 is set such that the multilayer film 110 is folded back at an angle θ, and the corner portion has a chamfered structure.

[0127] The peeling of the first resin film using the apparatus 100 can be carried out as follows. The multilayer film 110 is mounted on the film feeding section 120 in a specified orientation such that at the corner portion 135 of the block 134, the first resin film 112 is located outside the support 111, and the multilayer film 110 is folded back. Then, the multilayer film 110 is fed from the film feeding section 120 in a state where tension is applied to the multilayer film 110 in the conveying direction by the film recovery section 140.

[0128] The multilayer film 110 fed from the film feeding section 120 enters the peeling chamber 131 through the slit 132 and is folded back at the corner portion 135 of the block 134. The support 111 bent at the corner portion 135 generally does not break. On the other hand, the first resin film 112 bent at the corner portion 135 generates stress due to the bending deformation, and the first resin film 112 breaks due to the stress, forming a crack 113. Then, the first resin film 112 having the crack formed is peeled and blown away by the air jetted from the nozzle 136 to become a release sheet 114. A part of the release sheet 114 detaches from the support 111 and is conveyed to the recovery passage along with the air flow jetted from the nozzle 136. In addition, another part of the release sheet 114 is carried together with the support 111 in a state of being placed on the support 111 or in a state of being attached to the support 111 by a force such as electrostatic attraction.

[0129] The support 111 from which the first resin film 112 has been peeled at the corner portion 135 of the block 134 is conveyed downstream. As Figure 1As shown, when the support 111 reaches the position where the nozzle 136 is provided, the air jetted from the nozzle 136 blows onto the portion of the first resin film 112 where cracks are formed. By this air, the release sheet 114 contained in the portion of the first resin film 112 where cracks are formed is blown away and conveyed to the recovery passage 137. In addition, the first resin film (not shown) that only forms cracks 113 but does not peel off from the support 111 and remains on the support 111 is also peeled off from the support 111 due to the pressure of the air jetted from the nozzle 136, becomes a release sheet 114, and is conveyed to the recovery passage 137.

[0130] The release sheet 114 conveyed to the recovery passage 137 is conveyed to a recovery device (not shown) along with the air flow and is recovered. The support 111 from which the first resin film 112 has been peeled off is transported to the film recovery section 140 through the slit 133 and wound around the core 141 for recovery.

[0131] By pulverizing the first cholesteric liquid crystal resin release sheet peeled off from the support, a first cholesteric liquid crystal pigment having a desired particle size is obtained. The pulverization treatment is usually carried out using a pulverizer. Examples of the pulverizer include a ball mill, a bead mill, a roll mill, a rod mill, a jet mill, a mortar type pulverizer, etc.

[0132] [Manufacture of the second cholesteric liquid crystal pigment]

[0133] The second cholesteric liquid crystal pigment can be manufactured by the following method: forming a film of the second cholesteric liquid crystal resin on a support, then peeling off the film of the second cholesteric liquid crystal resin from the support, and pulverizing it.

[0134] (Manufacture of the film of the second cholesteric liquid crystal resin)

[0135] In the manufacture of the film of the second cholesteric liquid crystal resin, instead of curing the layer of the first liquid crystal composition to form the film of the first cholesteric liquid crystal resin in the above-mentioned "manufacture of the film of the first cholesteric liquid crystal resin", the layer of the second liquid crystal composition is cured by performing light irradiation and / or heat treatment one or more times in a state where the pitch of the helical structure is continuously changed, thereby forming the film of the second cholesteric liquid crystal resin.

[0136] The operation of curing the layer of the second liquid crystal composition by performing light irradiation and / or heat treatment one or more times in a state where the pitch of the helical structure is continuously changed is an operation to widen the reflection band of the film of the cholesteric liquid crystal resin, and thus is called a broadbanding treatment. By performing the broadbanding treatment, even a film of the cholesteric liquid crystal resin with a thickness of, for example, 5 μm or less can achieve a wide reflection band.

[0137] (Manufacture of the pigment using the film of the second cholesteric liquid crystal resin)

[0138] The peeling and pulverization of the film of the second cholesteric liquid crystal resin can be carried out by using the film of the second cholesteric liquid crystal resin instead of the film of the first cholesteric liquid crystal resin (the first resin film) in the above-mentioned "peeling and pulverization of the film of the first cholesteric liquid crystal resin".

[0139] [2. Ink composition]

[0140] The ink composition contains the composite pigment of the present invention and a binder resin.

[0141] The binder resin contains polymers. Examples of such polymers include polyester-based polymers, acrylic-based polymers, polystyrene-based polymers, polyamide-based polymers, polyurethane-based polymers, polyolefin-based polymers, polycarbonate-based polymers, and polyethylene-based polymers. The binder resin can be used alone as one kind, or two or more kinds can be used in any ratio in combination.

[0142] The manufacturing method of the ink composition of the present invention is not particularly limited and can be manufactured by mixing the above-mentioned respective components.

[0143] After the ink composition of the present invention forms an ink layer by printing on a substrate and then cures the ink layer, an identification medium can be constituted. The material of the substrate for forming the ink layer is not particularly limited, and examples include resins, metals, glasses, and papers.

[0144] The printing method of the ink composition is not particularly limited, and examples include screen printing, intaglio printing, flexographic printing, letterpress printing, offset printing, etc.

[0145] The curing treatment of the ink layer can be carried out by heating or irradiation with energy rays one or more times. Examples of heating include heat treatment at 150 °C or higher. By the thermal curing of the ink layer using heat treatment, an identification medium having a printed layer containing the composite pigment of the present invention formed on a substrate can be obtained. Examples of energy rays include ultraviolet rays, visible light, and other electromagnetic waves. Specifically, the energy ray irradiation can be carried out, for example, by irradiating light with a wavelength of 200 to 500 nm for 0.01 second to 3 minutes. By the curing treatment of the ink layer, an identification medium having a printed layer containing the composite pigment of the present invention formed on a substrate can be obtained.

[0146] [3. Identification medium]

[0147] The identification medium of the present invention contains a binder resin and a pigment dispersed in the binder resin. The pigment contained in the identification medium is the composite pigment of the present invention.

[0148] The identification medium may be in the form of a layer containing a binder resin and the composite pigment of the present invention dispersed in the binder resin, and any arbitrary layer. As the arbitrary layer, a substrate and an adhesive layer can be cited. As the material of the substrate, the materials described in 2. can be cited.

[0149] When the identification medium has an arbitrary layer on the observation side, the arbitrary layer is preferably a layer with high light transmittance, more preferably a layer with a total light transmittance of 70% or more, and further preferably a layer with a small in-plane retardation Re (for example, 5 nm or less).

[0150] [Use of the identification medium]

[0151] The identification medium is preferably used for pasting, transferring, etc. on an article to identify the authenticity of the article. As the article for identifying authenticity, articles such as exchange vouchers, commodity vouchers, tickets, certificates, security cards, etc. can be cited. The identification medium can be used in the form of a label, sticker, etc. for authenticity identification.

[0152] [4. Method for identifying the authenticity of the identification medium]

[0153] The method for judging the authenticity of the identification medium of the present invention includes: Step 1 of observing the reflected light from the identification medium through a left-handed circular polarizer and a right-handed circular polarizer and judging whether there is a difference in one or more of hue, lightness, and chroma of the reflected light; Step 2 of visually observing the identification medium and judging whether the color from the second cholesteric liquid crystal pigment can be observed; and Step 3 of observing the identification medium through a microscope and judging whether both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed.

[0154] [Step 1]

[0155] Step 1 is a step of observing the reflected light from the identification medium through a left-handed circular polarizer and a right-handed circular polarizer and judging whether there is a difference in one or more of hue, lightness, and chroma of the reflected light.

[0156] As the identification medium, an identification medium containing a binder resin and a pigment dispersed in the binder resin and the pigment being the composite pigment of the present invention is used, and the reflected light from the identification medium is observed through a left-handed circular polarizer and a right-handed circular polarizer. The reflected light is the reflected light when natural light is irradiated on the identification medium. Natural light means non-polarized light, which can be sunlight or artificial light.

[0157] According to the twisting directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment contained in the composite pigment of the present invention, the polarized light reflected by the identification medium is as described below.

[0158] (1) When the twist directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are the same: the identification medium reflects only circularly polarized light in the same direction as the twist directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment.

[0159] (2) When the twisting directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are different from each other: the identification medium reflects one circularly polarized light having the same twisting direction as the first cholesteric liquid crystal pigment, and reflects another circularly polarized light having the same twisting direction as the second cholesteric liquid crystal pigment.

[0160] In the above-mentioned case (1), when the identification medium is observed using a left-handed circular polarizer and a right-handed circular polarizer, since the light reflected by the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment only includes one type of circularly polarized light, the reflected light of the identification medium can be observed using a circular polarizer that transmits the circularly polarized light, while the reflected light of the identification medium cannot be observed or is difficult to be observed using the other circular polarizer.

[0161] Therefore, when observing the reflected light from the identification medium through a left-handed circular polarizer, if there is a difference in one or more of the hue, brightness and chroma of the reflected light of the identification medium observed through the left-handed circular polarizer, the identification medium can be judged to be authentic.

[0162] Furthermore, when there is no difference in hue, brightness, and saturation of the reflected light of the identification medium observed by the left-handed circular polarizing plate, it can be determined that the identification medium does not have a selective reflection function of selectively reflecting circularly polarized light and the identification medium is not authentic.

[0163] In the above case (2), when the identification medium is observed using a left-handed circular polarizing plate and a right-handed circular polarizing plate, one of the circular polarizing plates transmits light reflected by the first cholesteric liquid crystal pigment and does not transmit light reflected by the second cholesteric liquid crystal pigment.

[0164] Therefore, when the identification medium is observed from the front direction using this circular polarizer, although the light reflected by the first cholesteric liquid crystal pigment is observed as the reflected light of the identification medium, the light reflected by the second cholesteric liquid crystal resin does not pass through this circular polarizer, so the reflected light of the identification medium cannot be observed or is difficult to observe.

[0165] In addition, the other circular polarizing plate does not transmit the light reflected by the first cholesteric liquid crystal resin, but transmits the light reflected by the second cholesteric liquid crystal resin.

[0166] Therefore, when the identification medium is observed from the front direction through the circular polarizing plate, the light reflected by the first cholesteric liquid crystal pigment does not pass through the circular polarizing plate, and the light reflected by the second cholesteric liquid crystal pigment is observed as reflected light of the identification medium.

[0167] When there is no difference in the hue, lightness, and chroma of the reflected light of the recognition medium observed through left- and right-handed circular polarizing plates, it can be determined that the recognition medium does not have the selective reflection function of selectively reflecting circularly polarized light, and the recognition medium is not genuine.

[0168] [Process 2]

[0169] Process 2 is a process of visually observing the recognition medium to determine whether the color from the second cholesteric liquid crystal pigment can be observed.

[0170] In the composite pigment of the present invention included in the recognition medium, while including the second cholesteric liquid crystal pigment, it also includes the first cholesteric liquid crystal pigment in an amount greater than 0% by weight and 30% by weight or less relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment. When visually observing such a recognition medium of the present invention, as described below, the color from the second cholesteric liquid crystal pigment can be observed, while the color from the first cholesteric liquid crystal pigment cannot be observed or is hardly observable.

[0171] In the composite pigment of the present invention, since the content of the first cholesteric liquid crystal pigment is less than that of the second cholesteric liquid crystal pigment, the circularly polarized light component reflected by the first cholesteric liquid crystal pigment is hardly observable during visual observation. As a result, when visually observing the recognition medium, the color from the second cholesteric liquid crystal pigment can be observed, while the color from the first cholesteric liquid crystal pigment cannot be observed or is hardly observable.

[0172] When the color from the second cholesteric liquid crystal pigment cannot be observed during visual observation of the recognition medium, and when the color from the second cholesteric liquid crystal pigment and the color from the first cholesteric liquid crystal pigment can be recognized to a recognizable degree during visual observation of the recognition medium, it can be determined as not genuine.

[0173] Regarding whether the color from the second cholesteric liquid crystal pigment and the color from the first cholesteric liquid crystal pigment can be recognized to a recognizable degree, it can be quantitatively evaluated using a spectrophotometer or the like. As the colorimetric system during quantitative evaluation, any system can be used, such as the XYZ colorimetric system, the L*a*b* colorimetric system, etc.

[0174] [Process 3]

[0175] Process 3 is a process of observing the recognition medium through a microscope to determine whether both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed.

[0176] As the microscope used in Step 3, an optical microscope can be used. The magnification during microscope observation is preferably 50 or more, more preferably 100 or more, preferably 1000 or less, and more preferably 500 or less. By setting the magnification during microscope observation to be not less than the above lower limit value, it is easier to observe the color from the first cholesteric liquid crystal pigment.

[0177] When observing the identification medium of the present invention with a microscope, both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed whether the twisting directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are the same or different from each other.

[0178] Therefore, in the case where one or both of the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment cannot be observed by microscope observation, it can be determined as not genuine.

[0179] [Effects of the Present Invention]

[0180] The identification medium of the present invention contains a composite pigment containing a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment in a specified ratio. The first cholesteric liquid crystal pigment has a center wavelength of a selective reflection band in the range of 400 nm or more and 800 nm or less, and the selective reflection bandwidth is 150 nm or less. The second cholesteric liquid crystal pigment has a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less. Therefore, the color from the first cholesteric liquid crystal pigment with a narrow selective reflection band cannot be observed or is difficult to observe by visual inspection but can be observed by microscope observation. As a result, according to the present invention, the criterion for authenticity judgment becomes higher, and thus the anti-counterfeiting effect can be improved.

[0181] Examples

[0182] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples and can be arbitrarily modified within the scope of the claims of the present invention and their equivalent scope.

[0183] In the following description, unless otherwise specified, "%" and "parts" representing amounts are based on weight. In addition, unless otherwise specified, the operations described below are carried out in the normal temperature and pressure atmosphere.

[0184] [Evaluation Method]

[0185] (Center Wavelength of Selective Reflection Band)

[0186] The selective reflection band and the center wavelength of the selective reflection band of the pigments (Pigments A to E) used in each example were measured according to the following method.

[0187] The layer of the cholesteric liquid crystal resin in the multilayer films A to E obtained in Production Examples 1 to 5 below was bonded to a black PET film with an adhesive layer (manufactured by TOMOEGAWA CO., LTD.) via the adhesive layer, and then the support was peeled off to transfer the liquid crystal resin layer to the black PET film.

[0188] Next, using a spectrophotometer (JASCO Corporation's "V570"), the reflection spectrum of the liquid crystal resin layer was measured at an incident angle of 5°. Based on the obtained reflection spectrum, the full width at half maximum of the selective reflection band, which is the selective reflection bandwidth, was determined. That is, in the reflection spectrum, the bottom of the peak with the minimum intensity and the peak with the maximum intensity were identified, and the wavelength λ1 on the short wavelength side and the wavelength λ2 on the long wavelength side of the peak showing the intensity of the minimum intensity + (the maximum intensity - the minimum intensity) / 2 were determined, and their average value ((λ1 + λ2) / 2) was taken as the center wavelength of the selective reflection band of the cholesteric liquid crystal resin (pigment). In addition, the wavelength range from λ2 to λ1 was taken as the selective reflection band, and its width (the difference between λ2 and λ1: Δλ) was taken as the selective reflection bandwidth.

[0189] (Measurement of average particle size)

[0190] The particle size distribution of each pigment was measured by the laser scattering method, and the average particle size was determined based on the particle size distribution. As the measuring instrument, a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, Ltd., LA-960) was used.

[0191] (Determination of the twisting direction)

[0192] The twisting direction of each pigment was determined as follows: The reflected light when unpolarized light was irradiated on the multilayer films A to E (films containing each pigment) obtained in Production Examples 1 to 5 was observed through left- and right-handed circular polarizers. That is, unpolarized light was irradiated on the multilayer film from the observer side, and the reflected light that reached the observer side after being reflected by the multilayer film was observed. When the reflected light was right-handed circularly polarized light, it could be judged as right-handed twisting, and when the reflected light was left-handed circularly polarized light, it could be judged as left-handed twisting.

[0193] (Evaluation based on visual observation)

[0194] Visual observation of the identification medium, which is the object of evaluation, was carried out under natural light, and it was evaluated whether the color from the first cholesteric liquid crystal pigment could be observed. If it could be observed, it was judged as observable, and if it was difficult to observe or could not be observed, it was judged as unobservable.

[0195] (Evaluation based on a spectrophotometer)

[0196] Using a spectrophotometer (V570, manufactured by JASCO Corporation), the reflectance spectrum was measured at an incident angle of 5° on the printed layer side of the identification medium, which is the object of evaluation. The obtained reflectance spectrum was used to calculate L according to the following method. * a * b * The chromaticity coordinates. Furthermore, based on the chromaticity of the identification medium in Comparative Example 1 containing only the second cholesteric liquid crystal pigment (Pigment B), the color difference Δa * b * .

[0197] (Step 1)

[0198] Using the measured reflectance spectrum R(λ) and the following equations (11) to (13), the tristimulus values X, Y, and Z were calculated.

[0199] [Mathematical formula 1]

[0200]

[0201]

[0202]

[0203] Here, S(λ) is the spectrum of the light source, and the value of the C light source was used in this example. In addition, x(λ), y(λ), and z(λ) represent the color matching functions.

[0204] (Step 2)

[0205] Using the tristimulus values X, Y, and Z calculated in Step 1, the CIE 1976L * a * b * brightness L in the color space * , a * , b * . were calculated using the following (Equation 14) to (Equation 16).

[0206] [Mathematical formula 2]

[0207]

[0208]

[0209]

[0210] Here, X n , Y n , Z n are the tristimulus values calculated according to Equations (17) to (19), respectively.

[0211] [Mathematical formula 3]

[0212]

[0213]

[0214]

[0215] In addition, f(X / X n ), f(Y / Y n ), f(Z / Z n ) are respectively represented by Formulas (20) to (22).

[0216] [Mathematical formula 4]

[0217]

[0218]

[0219]

[0220]

[0221]

[0222]

[0223] Furthermore, from the obtained values of a * and b * for each example, Δa * b * is calculated using the following Formula (23).

[0224] Δa*b* = ((a*1 - a*2) 2 + (b*1 - b*2) 2 ) 1 / 2 ··· (23)

[0225] In Formula (23), a * 1 represents a * for each example, a * 2 represents a * of Comparative Example 1, b * 1 represents b * for each example, b * 2 represents b * of Comparative Example 1.

[0226] If Δa * b * is less than 10, it is difficult to identify the difference in color between the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment. If it is 5 or less, it is even more difficult to identify the difference in the above colors. If Δa* b * If it is 10 or more, the difference in color between the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment can be recognized.

[0227] (Microscopic observation)

[0228] The printed surface of the medium is observed by magnifying it with an optical microscope (magnification: 100 times). By microscopic observation, it is judged whether the color from the first cholesteric liquid crystal pigment can be observed, and if it can be observed, what color can be seen is judged.

[0229] (Circular polarizer observation)

[0230] The reflected light from the printed surface of the identification medium is observed through a left-handed circular polarizer and a right-handed circular polarizer. It is visually judged whether the reflected light can be observed, and if it can be observed, what color can be seen is judged.

[0231] [Production Example 1: Production of Multilayer Film A as Material for Pigment A]

[0232] As a support, a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO., LTD., "COSMOSHINE (registered trademark) A4100", thickness: 100 μm) was prepared, and one side was subjected to rubbing treatment.

[0233] The following materials shown in the table were mixed to prepare a liquid crystal composition (coating liquid L1) containing a liquid crystal compound. The liquid crystal compound (compound (B3)) and the compound of formula (2) (compound (A2)) are respectively compounds represented by the following formulas.

[0234] [Chemical formula 4]

[0235]

[0236] [Table 1]

[0237] Table 1

[0238] Coating liquid L1

[0239] Liquid crystalline compound Compound (B3) 16.02 parts by weight Compound of formula (2) Compound (A2) 4.00 parts by weight Chiral agent "LC756" manufactured by BASF 1.29 parts by weight Polymerization initiator "IRGACURE184" manufactured by BASF 0.66 parts by weight Leveling agent "SURFLON S420" manufactured by AGC SEIMI CHEMICAL CO., LTD. 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0240] (1-1. Coating process)

[0241] The coating liquid L1 was coated on the rubbed surface of the support to form a layer of the liquid crystal composition (coating layer). The coating of the coating liquid L1 was carried out by a die coater, and the discharge amount was adjusted so that the film thickness of the liquid crystal composition layer before drying was 15 μm.

[0242] (1-2. Drying process)

[0243] Next, a drying process is performed by heating the layer of the liquid crystal composition formed on the support with an oven at 140°C for 2 minutes.

[0244] (1 - 3. Polymerization process)

[0245] After the drying process, the layer of the liquid crystal composition is irradiated with ultraviolet light from the layer side of the liquid crystal composition using a high - pressure mercury lamp to perform a process of polymerizing the layer of the liquid crystal composition. The conditions for ultraviolet irradiation are in a nitrogen atmosphere with an oxygen concentration of 400 ppm or less, the illuminance at a wavelength of 365 nm is 280 mW / cm 2 , and the exposure dose at a wavelength of 365 nm is 2300 mJ / cm 2 .

[0246] By performing the polymerization process, the layer of the liquid crystal composition having cholesteric regularity is cured, and the cholesteric liquid crystal composition is cured while maintaining the cholesteric regularity, forming a thin film of cholesteric liquid crystal resin as a resin layer having cholesteric regularity. As a result, a multilayer film A having a structure of (support) / (thin film of cholesteric liquid crystal resin) is obtained. The thickness of the thin film of cholesteric liquid crystal resin of the multilayer film A is 3 μm.

[0247] (Production Example 2: Production of Multilayer Film B as Material for Pigment B)

[0248] (2 - 1. Coating process)

[0249] In the (1 - 1. Coating process) of Production Example 1, instead of the coating liquid L1, a coating liquid L2 obtained by mixing the materials shown in the following table is used, and the discharge amount is adjusted so that the film thickness of the coating layer before drying is 25 μm to perform the coating of the coating liquid L2. Otherwise, the same operations as in (1 - 1) of Production Example 1 are performed to form a layer of the liquid crystal composition on the support.

[0250] [Table 2]

[0251] Table 2

[0252] Coating liquid L2

[0253] Liquid crystalline compound Compound (B3) 16.09 parts by weight Compound of formula (2) Compound (A2) 4.02 parts by weight Chiral agent "LC756" manufactured by BASF 1.20 parts by weight Polymerization initiator "IRGACURE184" manufactured by BASF 0.66 parts by weight Leveling agent "SURFLON S420" manufactured by AGC SEIMI CHEMICAL CO., LTD. 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0254] (2 - 2. Drying process)

[0255] Next, a drying process is performed by heating the layer of the liquid crystal composition formed on the support with an oven at 140°C for 2 minutes.

[0256] (2 - 3. Broadband processing)

[0257] After the drying process, a process consisting of two ultraviolet irradiation treatments using a high-pressure mercury lamp and a subsequent heat treatment at 100 °C for 1 minute is carried out.

[0258] The conditions for the first ultraviolet irradiation treatment are that in an atmospheric environment, the illuminance at a wavelength of 365 nm is 5 mW / cm 2 , and the exposure at a wavelength of 365 nm is 300 mJ / cm 2 . The conditions for the second ultraviolet irradiation treatment are that in an atmospheric environment, the illuminance at a wavelength of 365 nm is 30 mW / cm 2 , and the exposure at a wavelength of 365 nm is 1800 mJ / cm 2 . The heat treatment is carried out in an oven.

[0259] (2-4. Polymerization process)

[0260] After the broadbanding treatment, ultraviolet rays are irradiated from the layer side of the liquid crystal composition using a high-pressure mercury lamp to carry out a process of polymerizing the layer of the liquid crystal composition. The conditions for the ultraviolet irradiation are that in a nitrogen environment with an oxygen concentration of 400 ppm or less, the illuminance at a wavelength of 365 nm is 280 mW / cm 2 , and the exposure at a wavelength of 365 nm is 2300 mJ / cm 2 .

[0261] By carrying out the polymerization process, the layer of the liquid crystal composition having cholesteric regularity is cured, and the cholesteric liquid crystal composition is cured while maintaining the cholesteric regularity, forming a thin film of cholesteric liquid crystal resin as a resin layer having cholesteric regularity. As a result, a multilayer film B having a structure of (support) / (thin film of cholesteric liquid crystal resin) is obtained. The thickness of the thin film of cholesteric liquid crystal resin of the multilayer film B is 5 μm.

[0262] (Production Example 3: Production of Multilayer Film C as a Material for Pigment C)

[0263] In Production Example 1, instead of coating liquid L1, coating liquid L3 obtained by mixing the materials shown in the following table was used, and otherwise, the same operations as in Production Example 1 were carried out to obtain multilayer film C. The thickness of the thin film of cholesteric liquid crystal resin of multilayer film C is 3 μm.

[0264] [Table 3]

[0265] Table 3

[0266] Coating liquid L3

[0267] Liquid crystalline compound Compound (B3) 15.80 parts by weight Compound of formula (2) Compound (A2) 3.95 parts by weight Chiral agent "LC756" manufactured by BASF 1.56 parts by weight Polymerization initiator "IRGACURE184" manufactured by BASF 0.66 parts by weight Leveling agent "sURFLON s420" manufactured by AGC SEIMI CHEMICAL Co., LTD. 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0268] (Production Example 4: Production of Multilayer Film D as a Material for Pigment D)

[0269] In Production Example 1, instead of coating liquid L1, coating liquid L4 obtained by mixing the materials shown in the following table was used, and other than this, the same operations as in Production Example 1 were carried out to obtain multilayer film D. The thickness of the cholesteric liquid crystal resin thin film of multilayer film D was 3 μm.

[0270] [Table 4]

[0271] Table 4

[0272] Coating liquid L4

[0273] Liquid crystalline compound Compound (B3) 16.17 parts by weight Compound of formula (2) Compound (A2) 4.04 parts by weight Chiral agent "LC756" manufactured by BASF 1.10 parts by weight Polymerization initiator "IRGACURE184" manufactured by BASF 0.66 parts by weight Leveling agent "SURFLON s420" manufactured by AGC SEIMI CHEMICAL CO., LTD. 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0274] (Production Example 5: Production of Multilayer Film E as a Material for Pigment E)

[0275] In Production Example 1, instead of coating liquid L1, coating liquid L5 obtained by mixing the materials shown in the following table was used, and other than this, the same operations as in Production Example 1 were carried out to obtain multilayer film E. The thickness of the cholesteric liquid crystal resin thin film of multilayer film E was 3 μm.

[0276] [Table 5]

[0277] Table 5

[0278] Coating liquid L5

[0279]

[0280] Compound (3) contained in coating liquid L5 is a compound represented by the following formula.

[0281] [Chemical formula 5]

[0282]

[0283] [Production Example 6. Production of Pigments A to E]

[0284] (Production of Release Sheet of Cholesteric Liquid Crystal Resin Thin Film)

[0285] Using the multilayer films A to E produced in Production Examples 1 to 5, using Figure 1 the production apparatus shown, a release sheet of a cholesteric liquid crystal resin thin film was produced by the following method.

[0286] As Figure 1 shown, a production apparatus 100 having a film feeding section 120, a peeling section 130, and a film recovery section 140 was prepared. The peeling section 130 has a block 134 having an angled portion 135 set at an acute angle; and a nozzle 136 provided downstream of the angled portion 135 and capable of ejecting air. At this time, the angle of the angled portion 135 of the block 134 was set so that the multilayer film 110 was folded back at an angle θ (60°). The angled portion has a chamfered structure with R = 0.2 mm to 0.3 mm.

[0287] The multilayer film 110 is installed at the film delivery section 120 in a specified orientation such that at the corner 135 of the block 134, the thin film 112 of the first cholesteric liquid crystal resin (or the thin film of the second cholesteric liquid crystal resin) is located outside the support 111 (PET film), and the multilayer film 110 is folded back. Then, the multilayer film 110 is delivered from the film delivery section 120 in a state where tension is applied to the multilayer film 110 in the transport direction by the film recovery section 140. At this time, the magnitude of the tension applied to the multilayer film 110 is set to 80 N / m. In addition, air is ejected from the nozzle 436 at a pressure of 0.5 MPa.

[0288] The multilayer film 110 is folded back at the corner 135 of the block 134, forming a large number of cracks. Then, the thin film 112 of the first cholesteric liquid crystal resin (or the thin film of the second cholesteric liquid crystal resin) with cracks formed is peeled off and blown away by the air ejected from the nozzle 136, obtaining the peeled sheet 111A.

[0289] (Manufacture of Pigment)

[0290] The peeled sheet 111A is recovered, pulverized with a cutter mill, classified using a 51 μm sieve, and only the particles that passed through the sieve are recovered as the pigment. The average particle diameter, the center wavelength of the selective reflection band, the selective reflection band, and the selective reflection bandwidth of the obtained pigment are measured. The results are shown in Tables 5 and 6. Based on these measurement results, pigments A, C, D, and E are the first cholesteric liquid crystal pigments having the center wavelength of the selective reflection band in the range of 400 nm or more and 800 nm or less and the selective reflection bandwidth of 150 nm or less. Pigment B is the second cholesteric liquid crystal pigment having a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less.

[0291] The color from pigment A is green, the color from pigment B is silver, the color from pigment C is blue, the color from pigment D is red, and the color from pigment E is red.

[0292] [Examples 1 to 7, Comparative Example 2]

[0293] (Preparation of Ink Composition)

[0294] As the first cholesteric liquid crystal pigment, pigment A, C, D, or E manufactured in Production Example 6 is used, and as the second cholesteric liquid crystal pigment, pigment B manufactured in Production Example 6 is used, and an ink composition is prepared by the following method.

[0295] Mix the 1st cholesteric liquid crystal pigment, 2nd cholesteric liquid crystal pigment, and binder (UV curable binder, "RAYCURE OP 4300-2" series FG-20SC thick medium manufactured by JUJO CHEMICAL CO., LTD.) described in Table 6 and Table 7 to prepare an ink composition with a solid content concentration of 10%. With respect to the total amount of the 1st cholesteric liquid crystal pigment and the 2nd cholesteric liquid crystal pigment, the content of the 1st cholesteric liquid crystal pigment is the amount described in Table 6 and Table 7 (recorded as "content of the 1st cholesteric liquid crystal pigment" in the table).

[0296] (Manufacture of identification medium)

[0297] Screen print the prepared ink composition onto a substrate (black paper). As the screen printing plate, use a screen printing plate with 120 lines per inch. Irradiate the printed surface of the substrate with ultraviolet light using a high-pressure mercury lamp to obtain an identification medium. The conditions for ultraviolet irradiation are in a nitrogen environment with an oxygen concentration of 400 ppm or less, an illuminance of 280 mW / cm at a wavelength of 365 nm 2 , and an exposure dose of 400 mJ / cm at a wavelength of 365 nm 2 .

[0298] Evaluate the obtained identification medium by visual observation, spectrophotometer evaluation, microscopic observation, and polarizer observation.

[0299] [Comparative Example 1]

[0300] In the preparation of the ink composition of Example 1, do not use the 1st cholesteric liquid crystal pigment, and otherwise, perform the same operations as in Example 1 to obtain an identification medium. Evaluate the obtained identification medium by visual observation, spectrophotometer evaluation, microscopic observation, and polarizer observation.

[0301] [Results]

[0302] The evaluation results of the examples and comparative examples are shown in the following table, and information on the pigments used in each example (type, center wavelength of the selective reflection band, selective reflection band, selective reflection bandwidth, average particle size, and twist direction) is also shown.

[0303] [Table 6]

[0304] Table 6

[0305]

[0306] [Table 7]

[0307] Table 7

[0308]

[0309] Based on the above results, the following matters can be known.

[0310] For the identification medium containing the composite pigment of the present invention, when observed through a circular polarizer, it can be confirmed that the difference in the hue of the reflected light of the identification medium observed with the left- and right-handed circular polarizers comes from the color of the first cholesteric liquid crystal pigment, which cannot be observed by visual inspection but can be observed by microscopic observation. In contrast, in Comparative Example 2 where the content of the first cholesteric liquid crystal pigment is more than the content specified in the present invention, the color from the first cholesteric liquid crystal pigment can be confirmed by both visual inspection and microscopic observation.

[0311] From the above results, it can be seen that according to the present invention, the criterion for authenticity judgment can be improved, thereby improving the anti-counterfeiting effect.

[0312] Explanation of reference numerals

[0313] 100: Manufacturing apparatus for release sheet of resin film

[0314] 110: Multilayer film

[0315] 111: Support

[0316] 112: Film of first cholesteric liquid crystal resin

[0317] 113: Crack

[0318] 114: Release sheet

[0319] 120: Film feeding section

[0320] 130: Peeling section

[0321] 131: Peeling chamber

[0322] 132: Gap

[0323] 133: Gap

[0324] 134: Block

[0325] 135: Corner of block

[0326] 136: Nozzle

[0327] 137: Recovery channel

[0328] 140: Film recovery section

[0329] 141: Core

Claims

1. An identification medium comprising a binder resin and pigments dispersed in the binder resin, wherein the pigments are composite pigments as follows: The composite pigments include a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment; The first cholesteric liquid crystal pigment, or both the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are flakes; The average particle size of the flakes is 20 μm or more and 120 μm or less; The first cholesteric liquid crystal pigment is a pigment having a center wavelength of a selective reflection band in the range of 400 nm or more and 800 nm or less and a selective reflection bandwidth of 150 nm or less; The second cholesteric liquid crystal pigment is a pigment having a selective reflection bandwidth of 200 nm or more in the range of 400 nm or more and 800 nm or less; At least a part of the selective reflection band of the first cholesteric liquid crystal pigment overlaps with the selective reflection band of the second cholesteric liquid crystal pigment; and The content of the first cholesteric liquid crystal pigment is more than 0% by weight and 30% by weight or less with respect to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment, When the identification medium is observed with a microscope, both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed.

2. The identification medium according to claim 1, wherein, In the composite pigment, the content of the first cholesteric liquid crystal pigment is 20% by weight or less with respect to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment.

3. The identification medium according to claim 1 or 2, wherein, The selective reflection bandwidth of the first cholesteric liquid crystal pigment is 120 nm or less.

4. The identification medium according to claim 1 or 2, wherein The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment have the same twisting direction as each other.

5. The identification medium according to claim 1 or 2, wherein, The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment have different twisting directions from each other.

6. A method for authenticity determination, which is a method for authenticity determination of the identification medium according to any one of claims 1 to 5, and the method for authenticity determination includes the following steps: Step 1, observing the reflected light from the identification medium through a left-handed circular polarizer and a right-handed circular polarizer, and determining whether there is a difference in one or more of hue, lightness, and chroma of the reflected light; Step 2, visually observing the identification medium and determining whether the color from the second cholesteric liquid crystal pigment can be observed; and Step 3, observing the identification medium with a microscope and determining whether both the color from the first cholesteric liquid crystal pigment and the color from the second cholesteric liquid crystal pigment can be observed.

Images