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 central 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 30% by weight and 80% 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 aligning a liquid crystalline compound into a cholesteric phase and curing it while maintaining the alignment. Such a cholesteric liquid crystal resin has a circularly polarized light separation function of reflecting one of the right- and left-handed circularly polarized lights and transmitting the other. In a cholesteric liquid crystal resin material, it is known that as the viewing angle θ from the front direction increases, the wavelength of the reflected circularly polarized light shifts to the short wavelength side. This property can be used to identify the authenticity of an identification medium using a cholesteric liquid crystal resin.

[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 Unexamined Patent Application Publication 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 printed layer using an ink is provided, and the ink contains either or both of a right-polarizing pigment that reflects a part of the right-handed circularly polarized light in the incident light and a left-polarizing pigment that reflects a part of the left-handed circularly polarized light in the incident light. The authenticity of this anti-counterfeiting printed matter can be visually determined by a authenticity determination filter using a circular polarizer.

[0010] However, in a printed matter using an ink containing an existing cholesteric liquid crystal resin as a pigment, the colors that can be exhibited are limited. Therefore, there is a need for an identification medium with excellent design and an anti-counterfeiting effect.

[0011] Solutions to the Problems

[0012] The inventors 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, a color lighter than the color from the first cholesteric liquid crystal pigment can be observed. Thus, an identification medium with excellent design and an anti-counterfeiting effect can be provided. Specifically, it was found that this effect can be obtained when using 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 as the first cholesteric liquid crystal pigment, and using 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 as the second cholesteric liquid crystal pigment. That is, the present invention provides the following content.

[0013] [1] A composite pigment, which contains 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] Relative 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 30% by weight and 80% by weight or less.

[0018] [2] The composite pigment according to [1], wherein, relative 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 75% 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 flake 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], the method comprising:

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

[0029] Advantages of the Invention

[0030] According to the present invention, it is possible to provide a composite pigment capable of realizing an identification medium having excellent design and an anti-counterfeiting effect, an ink composition using the composite pigment, an identification medium, and a method for authenticating the authenticity of the identification medium. Description of the Drawings

[0031] 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.

[0032] Figure 2 Schematically showing Figure 1 A cross-sectional view of a cross-section when a corner of a block of the manufacturing apparatus is cut by a plane perpendicular to the width direction of the support. Detailed Description

[0033] Hereinafter, the present invention will be described in detail with reference to embodiments and exemplifications. However, the present invention is not limited to the embodiments and exemplifications shown below, and can be arbitrarily modified within the scope of the claims of the present invention and the equivalent scope thereof.

[0034] 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.

[0035] In the following description, unless otherwise specified, "(meth)acrylate" means "acrylate" or "methacrylate" or both. Further, "(meth)acryloyl" means "acryloyl" or "methacryloyl" or both. "(Thio)epoxy" means "epoxy" or "thioepoxy" or both. Further, "isothiocyanate" means "isocyanate" or "isothiocyanate" or both.

[0036] [1. Composite Pigment]

[0037] The composite pigment of the present invention comprises 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 30% by weight and 80% by weight or less based on the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment.

[0038] The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are each composed of a cholesteric liquid crystal resin.

[0039] "Cholesteric liquid crystal resin" means a resin material having cholesteric regularity, and refers to a state in which molecules or partial molecules constituting the resin are arranged in a cholesteric regular state within the resin.

[0040] Here, "having a cholesteric regularity" of the molecules in the resin means that the molecules in the resin have the following specific regularity. When the molecules in the resin have a cholesteric regularity, the molecules are arranged in the resin in a manner that forms multiple molecular layers. In each molecular layer, the molecules are arranged such that the molecular axis assumes a certain orientation direction. The orientation direction in a next second plane that overlaps with a certain first plane within the layer of the resin is slightly angularly deviated from the orientation direction in the first plane. The orientation direction in a next third plane that further overlaps with the second plane is further slightly angularly deviated from the orientation direction in the second plane. Thus, in the multiple planes arranged in an overlapping manner, the angle of the molecular axis in this plane is sequentially deviated (twisted). Thus, the structure in which the direction of the molecular axis is continuously twisted is an optically chiral structure.

[0041] A cholesteric liquid crystal resin having an optically chiral structure generally 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 one circularly polarized light component in unpolarized light (i.e., natural light) in the specified wavelength range is reflected and the other circularly polarized light component is transmitted. In the present invention, the "selective reflection band" means 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, and specifically, it can be the full width at half maximum of the selective reflection band.

[0042] [Selective Reflection Band of Cholesteric Liquid Crystal Pigment]

[0043] 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% or less with respect to the entire 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 entire selective reflection band of the second cholesteric liquid crystal pigment. When 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 entire selective reflection band of the first cholesteric liquid crystal pigment, in visual observation, due to the action of the second cholesteric liquid crystal pigment, a color lighter than the color from the first cholesteric liquid crystal pigment is likely to appear. When 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 entire selective reflection band of the second cholesteric liquid crystal pigment, in visual observation, due to the action of the second cholesteric liquid crystal pigment, a color lighter than the color from the first cholesteric liquid crystal pigment is likely to appear. In addition, when it is below the above upper limit value, it is possible to prevent the color from the first cholesteric liquid crystal pigment from becoming too light and turning into achromatic color.

[0044] 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 (wide-band) than the first cholesteric liquid crystal pigment. When observing an identification medium using only a cholesteric liquid crystal pigment with a narrow selective reflection bandwidth through natural light, an appearance with a color corresponding to the reflection band can be observed. When observing an identification medium using only a cholesteric liquid crystal pigment with a wide selective reflection bandwidth through natural light, an appearance close to silver like a mirror can be observed. In the present invention, since the composite pigment contains a specified amount of the first cholesteric liquid crystal pigment with a selective reflection bandwidth of 150 nm or less and contains the second cholesteric liquid crystal pigment with a selective reflection bandwidth of 200 nm or more, when observing such an identification medium through natural light, a color lighter than the color from the first cholesteric liquid crystal pigment can be observed.

[0045] 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.

[0046] The first cholesteric liquid crystal pigment has a center wavelength of the selective reflection band in the range of 400 nm or more and 800 nm or less. In the present invention, the center wavelength of the selective reflection band of each cholesteric liquid crystal pigment can be the center 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 at an incident angle of 5° is measured. 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 + (the maximum intensity - the minimum intensity) / 2 are obtained. Further, their average value ((λ1 + λ2) / 2) is obtained, and this average value can be used as the center 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 to 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 in the reflection spectrum, 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.

[0047] When the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are in the form of powder or fiber of the cholesteric liquid crystal resin, the center wavelength of the selective reflection band of each cholesteric liquid crystal pigment is the center wavelength of the selective reflection band observed when forming a film containing the pigment.

[0048] When the average refractive index of the cholesteric liquid crystal resin is set as n and the pitch length of the chiral structure (helical structure) of the cholesteric liquid crystal resin is set as P (nm), the center wavelength λ (nm) of the selective reflection band when observing the film containing each cholesteric liquid crystal pigment from the viewing angle θ in the front direction is represented by the following formula.

[0049] λ = n × P × cosθ

[0050] Therefore, compared with the center wavelength λ of the selective reflection band in the case of observing from the front direction (cosθ = 1), the center wavelength λ of the selective reflection band in the case of observing the film containing each cholesteric liquid crystal pigment from the viewing angle θ in the front direction (cosθ < 1) is a short wavelength. The front direction of the film containing the cholesteric liquid crystal pigment refers to the normal direction of the film when forming the film containing the cholesteric liquid crystal pigment.

[0051] When observing the central wavelength λ of the selective reflection band of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment from the perspective θ in the front direction, it 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.

[0052] 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.

[0053] [Content of the first cholesteric liquid crystal pigment]

[0054] In the present invention, with respect 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 more than 30% by weight and 80% by weight or less. With respect 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 35% by weight or more, more preferably 45% by weight or more, preferably 75% by weight or less, and more preferably 65% by weight or less.

[0055] By making the content of the first cholesteric liquid crystal pigment with respect to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment within the above range, the reflected color of the first cholesteric liquid crystal pigment and the reflected color of the second cholesteric liquid crystal pigment can be simultaneously observed by visual observation. As a result, a color lighter than the color from the first cholesteric liquid crystal pigment can be observed, and thus, a composite pigment capable of providing an identification medium with excellent design and having an anti-counterfeiting effect can be provided.

[0056] By making the content of the first cholesteric liquid crystal pigment with respect 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, the reflected color of the first cholesteric liquid crystal pigment and the reflected color of the second cholesteric liquid crystal pigment can be simultaneously observed, and a color lighter than the color from the first cholesteric liquid crystal pigment can be observed. If the content of the first cholesteric liquid crystal pigment with respect to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is 30% by weight or less, the reflected color of the first cholesteric liquid crystal pigment is sometimes difficult to observe or cannot be observed. By making the content of the above first cholesteric liquid crystal pigment more than 30% by weight, the reflected color of the second cholesteric liquid crystal pigment and the reflected color of the first cholesteric liquid crystal pigment can be simultaneously observed, and a color lighter than the color from the first cholesteric liquid crystal pigment can be observed.

[0057] From the viewpoint of excellent dispersibility when preparing a composite pigment 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 size 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. When the average particle size of the flakes is at least the above lower limit value, the decorativeness can be improved, and when the average particle size of the flakes is at most the above upper limit value, the printing adaptability can be improved.

[0058] The average particle size of the flakes can be measured by, for example, a laser scattering method to measure the particle size distribution, and the average particle size can be determined from the particle size distribution. In the particle size distribution, the particle size at which the cumulative value of its volume is 50% can be used as the average particle size. In this application, unless otherwise specified, the average particle size of the flakes is the volume average particle size.

[0059] [Twisting direction of cholesteric liquid crystal pigment]

[0060] 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 polarizing plates. That is, unpolarized light is irradiated on the sample from the observer side, and the reflected light that is reflected by the sample and reaches the observer side is observed, whereby the twisting direction can be determined. When the reflected light is right-handed circularly polarized light, it can be judged as right-handed twisting, and when it is left-handed circularly polarized light, it can be judged as left-handed twisting.

[0061] [Materials of cholesteric liquid crystal pigment]

[0062] 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.

[0063] As the liquid crystalline compounds contained in the first liquid crystal composition and the second liquid crystal composition, liquid crystalline compounds having polymerizability are preferred. A liquid crystal composition containing a liquid crystalline compound having polymerizability can be easily cured in a state maintaining the alignment state by polymerizing the liquid crystalline compound.

[0064] As the liquid crystalline compound, a cholesteric liquid crystalline compound can be used. The cholesteric liquid crystalline compound is a compound capable of exhibiting cholesteric liquid crystallinity. By using a liquid crystal composition containing such a cholesteric liquid crystalline compound and curing the liquid crystal composition in a state where a cholesteric liquid crystal phase is exhibited, a cholesteric liquid crystal resin as a resin material having cholesteric regularity can be obtained.

[0065] As the liquid crystalline compounds contained in the first liquid crystal composition and the second liquid crystal composition, for example, rod-like liquid crystalline compounds having two or more reactive groups in one molecule can be used. As such a rod-like liquid crystalline compound, for example, the compound represented by the formula (1) can be cited.

[0066] R 3 -C 3 -D 3 -C 5 -M-C 6 -D 4 -C 4 -R 4 Formula (1)

[0067] In formula (1), R 3 and R 4 are reactive groups, and each independently represents a group selected from (meth)acryloyl, (thio)epoxy, oxetanyl, thietanyl, aziridinyl, pyrrolyl, vinyl, allyl, fumarate, cinnamoyl, oxazolinyl, mercapto, isothiocyanate, amino, hydroxy, carboxy, and alkoxysilyl groups. By having these reactive groups, when the liquid crystal composition is cured, a cholesteric liquid crystal resin having high strength can be obtained.

[0068] In formula (1), D 3 and D 4 each independently represents 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.

[0069] In formula (1), C 3 to C 6 each independently represents 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)-.

[0070] In formula (1), M represents a mesogenic group. Specifically, M represents 2 to 4 skeletons selected from unsubstituted or substituted azomethines, azoxides, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoates, phenyl cyclohexanecarboxylates, cyanophenyl cyclohexanes, cyanophenyl pyrimidines, alkoxy-substituted phenyl pyrimidines, benzene di alkanes, diphenylacetylenes, vinyl cyclohexyl benzonitriles, which are the same or different from each other, and are bonded through bonding 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)-.

[0071] Examples of the substituents that the mesogenic group M can 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)-R 5 , -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 case where two or more -O- are inserted adjacent to each other and the case where two or more -S- are inserted adjacent to each other) can be inserted into the alkyl group. Here, R 6 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0072] Examples of the substituent in the above-mentioned "alkyl group having 1 to 10 carbon atoms which may have a substituent" include, for example, 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, and the like.

[0073] In addition, the above-mentioned rod-like liquid crystalline compound is preferably an asymmetric structure. Here, the asymmetric structure means that in formula (1), with the mesogenic group M as the center, R 3 -C 3 -D 3 -C 5 - and -C 6 -D 4 -C 4 -R 4 are different structures. By using a compound having an asymmetric structure as the rod-like liquid crystalline compound, the orientation uniformity can be further improved.

[0074] Specific examples of the preferred rod-like liquid crystalline compound include the following compounds (B1) to (B9). In addition, these can be used alone or in combination of two or more in any ratio.

[0075] [Chemical formula 1]

[0076]

[0077] The first liquid crystal composition and / or the second liquid crystal composition preferably contains the compound represented by the above formula (1) as a liquid crystalline compound, and more preferably contains one or more selected from the above compounds (B1) to (B9).

[0078] The first liquid crystal composition and / or the second liquid crystal composition can further contain the compound represented by the following formula (2) in addition to the liquid crystalline compound. The compound of formula (2) can function as an alignment aid.

[0079] R 1 -A 1 -B-A 2 -R 2 (2)

[0080] In formula (2), R 1 and R 2Each independently represents 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, a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acryloyl group which may have an arbitrary bonding group inserted therein, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

[0081] 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.

[0082] As R 1 and R 2 Preferred examples include a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acryloyl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

[0083] 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 have 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 stronger resin. Here, examples of the reactive group include a carboxyl group, a (meth)acryloyl group, an epoxy group, a mercapto group, an isocyanate group, and an amino group.

[0084] In formula (2), A 1 and A 2 each independently represent a group selected from 1,4-phenylene, 1,4-cyclohexylene, cyclohexene-1,4-diyl, 4,4'-biphenylene, 4,4'-bicyclohexylidene, and 2,6-naphthylene. The above 1,4-phenylene, 1,4-cyclohexylene, cyclohexene-1,4-diyl, 4,4'-biphenylene, 4,4'-bicyclohexylidene, 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, and a halogenated alkyl group. When there are two or more substituents in each of A 1 and A 2 , these substituents may be the same or different.

[0085] 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 and have a higher affinity for the mesophase of the rod-like liquid crystalline compound, and the orientation uniformity becomes higher.

[0086] 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)-.

[0087] As particularly preferred groups for B, a single bond, -O-(C=O)-, and -CH=N-N=CH- can be mentioned.

[0088] 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.

[0089] 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 in which the liquid crystalline compound exhibits a liquid crystal phase within a wide range.

[0090] [Chemical formula 2]

[0091]

[0092] In the above compound (A3), "*" represents a chiral center.

[0093] The weight ratio represented by (total weight of the compound represented by formula (2)) / (total weight of the rod-like liquid crystalline compound) in the first liquid crystal composition or the second liquid crystal composition 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 equal to or higher than the lower limit value of the above range, the orientation uniformity of the liquid crystal composition can be improved. In addition, by making the above weight ratio equal to or lower than the upper limit value, the orientation 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 compound represented by formula (2) represents the weight of the compound in the case where only one compound represented by formula (2) is used, and represents the total weight in the case where two or more are used. Similarly, the total weight of the rod-like liquid crystalline compound represents the weight of the compound in the case where only one rod-like liquid crystalline compound is used, and represents the total weight in the case where two or more are used.

[0094] In addition, in the case of using a compound represented by formula (2) and a rod-like liquid crystalline compound 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. Thus, the compound represented by formula (2) can enter the gaps of the rod-like liquid crystalline compound having a larger molecular weight than itself, and thus the alignment uniformity can be improved.

[0095] The first liquid crystal composition and the second liquid crystal composition can 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 Japanese Unexamined Patent Application Publication No. 2005-289881, Japanese Unexamined Patent Application Publication No. 2004-115414, Japanese Unexamined Patent Application Publication No. 2003-66214, Japanese Unexamined Patent Application Publication No. 2003-313187, Japanese Unexamined Patent Application Publication No. 2003-342219, Japanese Unexamined Patent Application Publication No. 2000-290315, Japanese Unexamined Patent Application Publication No. 6-072962, U.S. Patent No. 6468444, International Publication No. 98 / 00428, Japanese Unexamined Patent Application Publication No. 2007-176870, etc. can be appropriately used, and for example, LC756 of BASF's Paliocolor can be obtained. As the chiral agent, a compound represented by the following formula (3) can also be used. In addition, the chiral agent can be used alone in one kind, or two or more kinds can be used in combination at any ratio.

[0096] [Chemical formula 3]

[0097]

[0098] The amount of the chiral agent can be arbitrarily set within the 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.

[0099] The first liquid crystal composition and the second liquid crystal composition can each contain a polymerization initiator. Examples of the polymerization initiator include, for example, a photopolymerization initiator, and a compound capable of generating 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-benzoyloxime)], 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 and the like. As the polymerization initiator, IRGACURE 184 and IRGACURE OXE02 manufactured by BASF can also be used. These can be used alone, or two or more of them 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.

[0100] 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 crystal compound can be made good, and thus the liquid crystal phase of the liquid crystal composition can be stabilized.

[0101] The first liquid crystal composition and the second liquid crystal composition can each contain a surfactant as a leveling agent. As the surfactant, for example, a surfactant that does not hinder 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 moiety can be preferably selected. Among them, an oligomer having two or more hydrophobic moieties 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 Corporation, etc. can be used. In addition, the surfactant can be used alone or two or more kinds can be used in any ratio.

[0102] 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.

[0103] The first liquid crystal composition and the second liquid crystal composition can 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 durability can be cited. In addition, these optional components can be used alone or two or more kinds can be used in any ratio. The amounts of these optional components can be arbitrarily set within a range that does not reduce the desired optical properties.

[0104] 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.

[0105] [Production of the First Cholesteric Liquid Crystal Pigment]

[0106] The first cholesteric liquid crystal pigment can be produced as follows: A coating solution 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.

[0107] (Manufacture of the film of the first cholesteric liquid crystal resin)

[0108] Before coating the coating solution 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 film of the support, etc. In addition, surface treatment such as corona treatment for improving the affinity between the surface of the support and the first liquid crystal composition can also be performed.

[0109] As the support, a film having a resin layer made of resin can be used. When examples of the polymer contained in the resin constituting the resin layer are cited, examples include chain olefin polymers, cycloolefin polymers, polycarbonates, polyesters, polysulfones, polyethersulfones, polystyrenes, polyvinyl alcohols, cellulose acetate polymers, polyvinyl chlorides, polymethacrylates, etc.

[0110] 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.

[0111] 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.

[0112] For example, from the viewpoint of making the liquid crystal composition orient 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.

[0113] 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.

[0114] The support can be an unstretched film or a stretched film.

[0115] In addition, the support can be an isotropic film or an anisotropic film.

[0116] 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, corona treatment, and chemical treatment.

[0117] 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.

[0118] 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.

[0119] 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 step, alignment treatment can be carried out as needed. The alignment 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 alignment treatment, the liquid crystalline compounds in the first liquid crystal composition can be aligned well.

[0120] 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.

[0121] (Manufacture of pigments using the thin film of the first cholesteric liquid crystal resin)

[0122] 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 thereof include the method described in Japanese Patent Laid-Open No. 2015-27743. In this method, Figure 1 The shown manufacturing apparatus for the peeling sheet can be used to peel the thin film of the first cholesteric liquid crystal resin from the support. Hereinafter, the peeling method of the thin film of the first cholesteric liquid crystal resin using Figure 1 The shown apparatus 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".

[0123] Figure 1 The front view of the manufacturing apparatus of the release sheet of the resin film used in the manufacture 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 capable of feeding a multilayer film 110 having a support 111 and a first resin film (refer to Figure 2 112); a peeling section 130 capable of peeling the first resin film 112 from the fed multilayer film 110; and a recovery section 140 capable of recovering the support 111 from which the first resin film 112 has been peeled.

[0124] The peeling section 130 has: a block 134 having an angled portion 135 set at an acute angle; and a nozzle 136 disposed downstream of the angled portion 135 and capable of ejecting air. The angle of the angled portion 135 of the block 134 is set such that the multilayer film 110 is folded back at an angle θ, and the angled portion has a chamfered structure.

[0125] The peeling of the first resin film using the apparatus 100 can be performed as follows. The multilayer film 110 is mounted in the film feeding section 120 in a specified orientation such that at the angled 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, with a state in which tension is applied to the multilayer film 110 in the conveying direction by the film recovery section 140, the multilayer film 110 is fed from the film feeding section 120.

[0126] 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 angled portion 135 of the block 134. The support 111 bent at the angled portion 135 generally does not break. On the other hand, the first resin film 112 bent at the angled portion 135 generates stress due to this bending deformation, and the first resin film 112 breaks due to this stress, forming a crack 113. Then, the first resin film 112 having formed the crack is peeled and blown away by the air ejected 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 ejected 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.

[0127] The support 111 from which the first resin film 112 has been peeled at the angled 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 set, the air ejected from the nozzle 136 is blown 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 dispersed and conveyed to the recovery passage 137. In addition, the first resin film (not shown) that only forms the crack 113 but remains on the support 111 without peeling off from the support 111 is also peeled off from the support 111 due to the pressure of the air ejected from the nozzle 136, becomes a release sheet 114, and is conveyed to the recovery passage 137.

[0128] 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.

[0129] 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 performed 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 pulverizer, etc.

[0130] [Manufacture of the second cholesteric liquid crystal pigment]

[0131] 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.

[0132] (Manufacture of the film of the second cholesteric liquid crystal resin)

[0133] In the manufacture of the film of the second cholesteric liquid crystal resin, in the above-mentioned "manufacture of the film of the first 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, the layer of the second liquid crystal composition is cured by performing one or more light irradiations and / or heat treatments in a state where the pitch of the helical structure is continuously changed to form the film of the second cholesteric liquid crystal resin.

[0134] The operation of curing the layer of the second liquid crystal composition by performing one or more light irradiations and / or heat treatments 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.

[0135] (Manufacture of the pigment using the film of the second cholesteric liquid crystal resin)

[0136] 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".

[0137] [2. Ink Composition]

[0138] The ink composition contains the composite pigment of the present invention and a binder resin.

[0139] 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 or two or more kinds can be used in any ratio in combination.

[0140] 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.

[0141] The ink composition of the present invention can form an ink layer by printing on a substrate and then curing the ink layer, and can constitute an identification medium. The material of the substrate for forming the ink layer is not particularly limited, and examples include resins, metals, glasses, and papers.

[0142] The printing method of the ink composition is not particularly limited, and examples include screen printing, intaglio printing, flexographic printing, letterpress printing, offset printing, and the like.

[0143] 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 seconds 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.

[0144] [3. Identification Medium]

[0145] 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.

[0146] The identification medium can 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 an optional layer. As the optional layer, a substrate and an adhesive layer can be mentioned. As the material of the substrate, the materials described in 2. can be mentioned.

[0147] When the identification medium has an optional layer on the observation side, the optional 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).

[0148] [Use of the identification medium]

[0149] The identification medium is preferably used for pasting, transferring, etc. onto an article to identify the authenticity of the article. As the article for identifying authenticity, articles such as exchange vouchers, gift vouchers, tickets, certificates, security cards, etc. can be mentioned. The identification medium can also be used in the form of labels, stickers, etc. for authenticity identification.

[0150] [4. Method for identifying the authenticity of the identification medium]

[0151] 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 are differences in one or more of hue, lightness, and chroma of the reflected light.

[0152] [Step 1]

[0153] 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 are differences in one or more of hue, lightness, and chroma of the reflected light.

[0154] 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 unpolarized light, which can be sunlight or artificial light.

[0155] 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 follows.

[0156] (1) When the twisting directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are the same: The identification medium only reflects circularly polarized light in the same direction as the twisting directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment.

[0157] (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.

[0158] In the above-mentioned case (1), when the identification medium is observed using a left-handed circular polarizer and a right-handed circular polarizer, the light reflected by the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment contains only one type of circularly polarized light. Therefore, 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.

[0159] Therefore, when observing the reflected light from the identification medium through a left-handed circular polarizing plate, 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 polarizing plate, it can be determined that the identification medium is authentic.

[0160] 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, the identification medium does not have a selective reflection function of selectively reflecting circularly polarized light, and it can be determined that the identification medium is not authentic.

[0161] 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 circular polarizing plate transmits light reflected by the first cholesteric liquid crystal pigment and does not transmit light reflected by the second cholesteric liquid crystal pigment.

[0162] Therefore, when the identification medium is observed from near 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 the circular polarizer, so the reflected light of the identification medium cannot be observed or is difficult to observe.

[0163] In addition, the other circular polarizing plate does not transmit the light reflected by the first cholesteric liquid crystal pigment but transmits the light reflected by the second cholesteric liquid crystal pigment.

[0164] 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.

[0165] 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, the identification medium does not have a selective reflection function of selectively reflecting circularly polarized light, and it can be determined that the identification medium is not authentic.

[0166] [Functions and Effects of the Present Invention]

[0167] The identification medium of the present invention contains a composite pigment. The above composite pigment contains a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment in a specified ratio. The above first cholesteric liquid crystal pigment has a central wavelength of a selective reflection band within the range of 400 nm or more and 800 nm or less, and the selective reflection bandwidth is 150 nm or less. The above second cholesteric liquid crystal pigment has a selective reflection bandwidth of 200 nm or more within the range of 400 nm or more and 800 nm or less. Therefore, in the case of visual observation, it is possible to observe both the reflected light of the first cholesteric liquid crystal pigment with a narrow selective reflection band and the reflected light of the second cholesteric liquid crystal pigment with a wide selective reflection band. Thus, it is possible to observe a color lighter than the color from the first cholesteric liquid crystal pigment. Such an effect is difficult to obtain even when using two narrow-band cholesteric liquid crystal pigments. Therefore, according to the present invention, it is possible to provide a composite pigment that can exhibit the above-mentioned light color and can achieve an anti-counterfeiting effect, so it is possible to realize an identification medium with excellent design and an anti-counterfeiting effect.

[0168] Regarding whether it is possible to observe a color lighter than the color from the first cholesteric liquid crystal pigment, in addition to using visual evaluation, it is also possible to quantitatively evaluate using a spectrophotometer or the like. As the colorimetric system for quantitative evaluation, any system can be used, and for example, the XYZ colorimetric system, L * a * b * colorimetric system, etc. can be used.

[0169] Examples

[0170] Hereinafter, examples are shown to specifically illustrate the present invention. However, the present invention is not limited to the following examples, and can be arbitrarily changed within the scope of the claims of the present invention and its equivalent scope.

[0171] In the following description, unless otherwise specified, "%" and "parts" representing amounts are based on weight standards. In addition, unless otherwise specified, the operations described below are performed in normal temperature and pressure atmosphere.

[0172] [Evaluation Method]

[0173] (Central Wavelength of Selective Reflection Band)

[0174] The selective reflection band and the central wavelength of the selective reflection band of the pigments (Pigments A to F) used in each example were measured according to the following method.

[0175] The layers of cholesteric liquid crystal resin in the multilayer films A to F obtained in the following Production Examples 1 to 6 were 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.

[0176] Next, using a spectrophotometer (JASCO Corporation's "V570"), the reflection spectrum of the liquid crystal resin layer at an incident angle of 5° was measured. 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 peak bottom with the minimum intensity and the peak with the maximum intensity were identified, and the wavelengths λ1 on the short wavelength side and λ2 on the long wavelength side of the peak showing the intensity of minimum intensity + (maximum intensity - minimum intensity) / 2 were found. The average value ((λ1 + λ2) / 2) was taken as the central wavelength of the selective reflection band of the cholesteric liquid crystal resin (pigment). In addition, the range from wavelength λ2 to wavelength λ1 is the selective reflection band, and its width (the difference between λ2 and λ1: Δλ) is the selective reflection bandwidth.

[0177] (Measurement of average particle size)

[0178] 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 device, a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., LA-960) was used.

[0179] (Determination of the twisting direction)

[0180] The twisting direction of each pigment was determined as follows: The reflected light when unpolarized light was incident on the multilayer films A to F (films containing each pigment) obtained in Production Examples 1 to 6 was observed through left and right 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. If the reflected light is right-handed circularly polarized light, it is judged as right-handed twist, and if it is left-handed circularly polarized light, it is judged as left-handed twist.

[0181] (Evaluation based on visual observation)

[0182] The evaluation object, the identification medium, was visually observed under natural light to evaluate what color could be observed.

[0183] (Evaluation of the reflected color of the identification medium: denoted as "reflection characteristics" in the table)

[0184] Using a spectrophotometer (manufactured by JASCO Corporation, V570), the reflection spectrum at an incident angle of 5° was measured from the printing layer side of the identification medium of the evaluation object. Using the obtained reflection spectrum, the following method was used to calculate L * a* b * Chromaticity coordinates, and further, calculate the color difference based on the origin (Δa based on the origin * b * ), the color difference based on the chromaticity of the identification media in Reference Examples 2 to 6 containing only the first cholesteric liquid crystal pigment (Pigment A, C, D, or E) (Δa based on Pigment 1 * b * ), and the color difference based on the chromaticity of the identification media in Reference Example 1 containing only the second cholesteric liquid crystal pigment (Pigment B) (Δa based on Pigment 2 * b * ).

[0185] (Step 1)

[0186] Calculate the tristimulus values X, Y, and Z using the measured reflection spectrum R(λ) and the following equations (11) to (13).

[0187] [Mathematical formula 1]

[0188]

[0189]

[0190]

[0191] Here, S(λ) is the spectrum of the light source, and the value of the C light source is used in this embodiment. In addition, x(λ), y(λ), and z(λ) represent the color matching functions.

[0192] (Step 2)

[0193] Calculate the lightness L * a * b * in the CIE 1976L * 、a * 、b * color space using the tristimulus values X, Y, and Z calculated in Step 1. Use the following equations (14) to (16) in the calculation.

[0194] [Mathematical formula 2]

[0195]

[0196]

[0197]

[0198] Here, X n 、Y n 、Z nThey are the tristimulus values calculated according to formulas (17) to (19), respectively.

[0199] [Mathematical formula 3]

[0200]

[0201]

[0202]

[0203] In addition, f(X / X n ), f(Y / Y n ), f(Z / Z n ) are represented by formulas (20) to (22), respectively.

[0204] [Mathematical formula 4]

[0205]

[0206]

[0207]

[0208] Furthermore, using the following formula (23), the color differences based on the origin (Δa*b* based on the origin), the color differences based on the chromaticity of the identification medium containing only the first cholesteric liquid crystal pigment (Δa*b* based on pigment 1), and the color differences based on the chromaticity of the identification medium containing only the second cholesteric liquid crystal pigment (Δa*b* based on pigment 2) are calculated from the obtained values of a and b for each example. * b * The color difference based on the origin (Δa*b* based on the origin), the color difference based on the chromaticity of the identification medium containing only the first cholesteric liquid crystal pigment (Δa*b* based on pigment 1), and the color difference based on the chromaticity of the identification medium containing only the second cholesteric liquid crystal pigment (Δa*b* based on pigment 2). * b * ), the color difference based on the chromaticity of the identification medium containing only the first cholesteric liquid crystal pigment (Δa*b* based on pigment 1) * b * ), and the color difference based on the chromaticity of the identification medium containing only the second cholesteric liquid crystal pigment (Δa*b* based on pigment 2) * b * ).

[0209] Δa*b* = ((a*1 - a*2) 2 + (b*1 - b*2) 2 ) 1 / 2 ···(23)

[0210] When calculating the color difference Δa*b* based on the origin, a*1 in formula (23) represents a for each example, a*2 represents 0, b*1 represents b for each example, and b*2 represents 0. * b * In the case of calculating the color difference Δa*b* based on the origin, a*1 in formula (23) represents a for each example, * a*2 represents 0, b*1 represents b for each example, * a * ), a*2 represents 0, b*1 represents b for each example, * b * ), and b*2 represents 0. * ), and b*2 represents 0.

[0211] When calculating the color difference Δa*b* based on pigment 1* b * In the case of a in formula (23) * a1 represents a of each example * a * a2 represents a of the identification medium containing only the pigment corresponding to the first cholesteric liquid crystal pigment used in each example * b * b1 represents b of each example * b * b2 represents b of the identification medium containing only the pigment corresponding to the first cholesteric liquid crystal pigment used in each example * For example, when calculating the pigment 1-based Δa * b * in the case of, the a * and b * of the identification medium of Reference Example 2 containing only Pigment A are respectively used as a * 2 and b * 2. When calculating the pigment 1-based Δa * b * in the case of Example 4, the a * and b * of the identification medium of Reference Example 3 containing only Pigment C are respectively used as a * 2 and b * 2.

[0212] When calculating the pigment 2-based Δa * b * in the case of, the a * 1 represents a of each example * a * a2 represents a of the identification medium of Reference Example 1 (the identification medium containing only the second cholesteric liquid crystal pigment) * b * b1 represents b of each example * b * b2 represents b of the identification medium of Reference Example 1 * .

[0213] When the origin-based Δa * b * is less than 25, the pigment 1-based Δa * b * is 5 or more, and the pigment 2-based Δa * b * is 10 or more, when visually observing the identification medium, a color lighter than the color from the first cholesteric liquid crystal pigment can be observed.

[0214] (Observation with circular polarizer)

[0215] The reflected light from the printed surface of the identification medium is observed through a left-handed circular polarizing plate and a right-handed circular polarizing plate. It is visually determined whether the reflected light can be observed, and if so, what color can be seen.

[0216] [Production Example 1: Production of Multilayer Film A as a Material for Pigment A]

[0217] 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.

[0218] 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.

[0219] [Chemical Formula 4]

[0220]

[0221] [Table 1]

[0222] Table 1

[0223] Coating Liquid L1

[0224] 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 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0225] (1-1. Coating Step)

[0226] 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, adjusting the discharge amount so that the film thickness of the layer of the liquid crystal composition before drying was 15 μm.

[0227] (1-2. Drying Step)

[0228] Next, the layer of the liquid crystal composition formed on the support was heated at 140 °C for 2 minutes in an oven to carry out the drying step.

[0229] (1-3. Polymerization Step)

[0230] After the drying step, ultraviolet rays were irradiated from the side of the layer of the liquid crystal composition using a high-pressure mercury lamp to carry out the step of polymerizing the layer of the liquid crystal composition. The conditions for ultraviolet irradiation were in a nitrogen atmosphere with an oxygen concentration of 400 ppm or less, the illuminance at a wavelength of 365 nm was 280 mW / cm 2 , and the exposure amount at a wavelength of 365 nm was 2300 mJ / cm 2 .

[0231] By performing a polymerization process, the layer of the liquid crystal composition having cholesteric regularity is cured. The cholesteric liquid crystal composition is cured while maintaining the cholesteric regularity, and a thin film of cholesteric liquid crystal resin is formed as a layer of the resin 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 in the multilayer film A is 3 μm.

[0232] (Production Example 2: Production of Multilayer Film B as Material for Pigment B)

[0233] (2-1. Coating Process)

[0234] 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 was used, and the coating liquid L2 was coated while adjusting the discharge amount so that the film thickness of the coating layer before drying was 25 μm. Otherwise, the same operations as in (1-1) of Production Example 1 were performed to form a layer of the liquid crystal composition on the support.

[0235] [Table 2]

[0236] Table 2

[0237] Coating Liquid L2

[0238] 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 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0239] (2-2. Drying Process)

[0240] Next, the layer of the liquid crystal composition formed on the support was heated at 140 °C for 2 minutes using an oven to perform the drying process.

[0241] (2-3. Broadbanding Treatment)

[0242] After the drying process, a process consisting of ultraviolet irradiation treatment using a high-pressure mercury lamp and subsequent heating treatment at 100 °C for 1 minute was performed twice.

[0243] The conditions for the first ultraviolet irradiation treatment were an illuminance of 5 mW / cm at a wavelength of 365 nm and an exposure dose of 300 mJ / cm at a wavelength of 365 nm in an atmospheric environment. 2 The conditions for the second ultraviolet irradiation treatment were an illuminance of 30 mW / cm at a wavelength of 365 nm and an exposure dose of 1800 mJ / cm at a wavelength of 365 nm in an atmospheric environment. 2 The heating treatment was performed using an oven. 2 The conditions for the second ultraviolet irradiation treatment were an illuminance of 30 mW / cm at a wavelength of 365 nm and an exposure dose of 1800 mJ / cm at a wavelength of 365 nm in an atmospheric environment. 2 The heating treatment was performed using an oven.

[0244] (2-4. Polymerization Process)

[0245] After the broadband processing, ultraviolet rays are irradiated from the layer side of the liquid crystal composition using a high-pressure mercury lamp to carry out a step of polymerizing the layer of the liquid crystal composition. The conditions for the 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 carrying out the polymerization step, 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, and a thin film of a cholesteric liquid crystal resin as a layer having cholesteric regularity is formed. 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 the cholesteric liquid crystal resin of the multilayer film B is 5 μm.

[0247] (Production Example 3: Production of Multilayer Film C as a Material for Pigment C)

[0248] In Production Example 1, instead of the coating liquid L1, a coating liquid L3 obtained by mixing the materials shown in the following table was used, and the same operations as in Production Example 1 were carried out except for this, to obtain a multilayer film C. The thickness of the thin film of the cholesteric liquid crystal resin of the multilayer film C is 3 μm.

[0249] [Table 3]

[0250] Table 3

[0251] Coating liquid L3

[0252] 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 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0253] (Production Example 4: Production of Multilayer Film D as a Material for Pigment D)

[0254] In Production Example 1, instead of the coating liquid L1, a coating liquid L4 obtained by mixing the materials shown in the following table was used, and the same operations as in Production Example 1 were carried out except for this, to obtain a multilayer film D. The thickness of the thin film of the cholesteric liquid crystal resin of the multilayer film D is 3 μm.

[0255] [Table 4]

[0256] Table 4

[0257] Coating liquid L4

[0258] 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 0.04 parts by weight Solvent Cyclopentanone 77.99 parts by weight

[0259] (Production Example 5: Production of Multilayer Film E as a Material for Pigment E)

[0260] 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 the same operations as in Production Example 1 were performed except for this, to obtain multilayer film E. The thickness of the cholesteric liquid crystal resin thin film of multilayer film E was 3 μm.

[0261] [Table 5]

[0262] Table 5

[0263] Coating liquid L5

[0264] Liquid crystalline compound Compound (B3) 15.87 parts by weight Compound of formula (2) Compound (A2) 3.97 parts by weight Chiral agent Compound (3) 1.48 parts by weight Polymerization initiator "IRGACURE184" manufactured by BASF 0.66 parts by weight Leveling agent "SURFLON S420" manufactured by AGC Seimi Chemical 0.04 parts by weight Solvent Cyclopentanone 77.98 parts by weight

[0265] The compound (3) contained in coating liquid L5 is a compound represented by the following formula.

[0266] [Chemical formula 5]

[0267]

[0268] [Production Example 6: Production of Multilayer Film F as a Material for Pigment F]

[0269] In Production Example 1, instead of coating liquid L1, coating liquid L6 obtained by mixing the materials shown in the following table was used, and the same operations as in Production Example 1 were performed except for this, to obtain multilayer film F. The thickness of the cholesteric liquid crystal resin thin film of multilayer film F was 3 μm.

[0270] [Table 6]

[0271] Table 6

[0272] Coating liquid L6

[0273] Liquid crystalline compound Compound (B3) 16.22 parts by weight Compound of formula (2) Compound (A2) 4.05 parts by weight Chiral agent Compound (3) 1.05 parts by weight Polymerization initiator "IRGACURE184" manufactured by BASF 0.66 parts by weight Leveling agent "SURFLON S420" manufactured by AGC Seimi Chemical 0.04 parts by weight Solvent Cyclopentanone 77.98 parts by weight

[0274] [Production Example 7. Production of Pigments A to F]

[0275] (Production of a Release Sheet of a Cholesteric Liquid Crystal Resin Thin Film)

[0276] Using the multilayer films A to F produced in Production Examples 1 to 6, using Figure 1 the production apparatus shown, a release sheet of a cholesteric liquid crystal resin thin film was produced by the following method.

[0277] As Figure 1As shown, a manufacturing apparatus 100 having a film feeding section 120, a peeling section 130, and a film recovery section 140 is prepared. The peeling section 130 has: a block 134 having an angled portion 135 set at an acute angle; and a nozzle 136 disposed 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 is set such that the multilayer film 110 is folded back at an angle θ (60°). The angled portion has a chamfered structure with R = 0.2 mm to 0.3 mm.

[0278] The multilayer film 110 is mounted on the film feeding section 120 in a specified orientation such that at the angled portion 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 fed out from the film feeding 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.

[0279] The multilayer film 110 is folded back at the angled portion 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 the formed cracks is peeled off and blown away by the air ejected from the nozzle 136, obtaining a peeled sheet 111A.

[0280] (Manufacture of Pigments)

[0281] The peeled sheet 111A is recovered, pulverized using a cutter mill, and classified using a 51 μm sieve, and only the particles that passed through the sieve are recovered as pigments. The average particle diameter, the center wavelength of the selective reflection band, the selective reflection band, and the selective reflection bandwidth of the obtained pigments are measured. The results are shown in Tables 7 to 11. Based on these measurement results, Pigments A, C, D, E, and F are first cholesteric liquid crystal pigments having a center wavelength of the 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. Pigment B is a 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.

[0282] 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, the color from Pigment E is green, and the color from Pigment F is red.

[0283] [Reference Examples 1 to 6]

[0284] (Preparation of Ink Composition)

[0285] Using Pigments A to F produced in Production Example 7, an ink composition was prepared by the following method.

[0286] The pigments and a binder (UV curable binder, "RAYCURE OP 4300-2" series FG-20SC thick medium manufactured by JUJO CHEMICAL CO., LTD.) described in Tables 7 and 8 were mixed to prepare an ink composition having a solid content concentration of 10%.

[0287] (Manufacture of Identification Medium)

[0288] The prepared ink composition was screen-printed onto a substrate (black paper). As the screen printing plate, a screen printing plate with 120 lines per inch was used. The printed surface of the substrate was irradiated with ultraviolet light using a high-pressure mercury lamp to obtain an identification medium. The conditions for ultraviolet irradiation were in a nitrogen atmosphere with an oxygen concentration of 400 ppm or less, the illuminance at a wavelength of 365 nm was 280 mW / cm 2 , and the exposure dose at a wavelength of 365 nm was 400 mJ / cm 2 .

[0289] The obtained identification media of Reference Examples 1 to 6 were visually observed, evaluated for reflection characteristics, and observed through a polarizing plate. The following table shows the evaluation results 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 twisting direction).

[0290] [Table 7]

[0291] Table 7

[0292]

[0293] [Table 8]

[0294] Table 8

[0295]

[0296] [Examples 1 to 9, Comparative Examples 1 to 2]

[0297] (Preparation of Ink Composition)

[0298] As the first cholesteric liquid crystal pigment, Pigment A, C, D, E, or F produced in Production Example 7 was used, and as the second cholesteric liquid crystal pigment, Pigment B produced in Production Example 7 was used. An ink composition was prepared by the following method.

[0299] 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 Tables 9 to 11 to prepare an ink composition with a solid content concentration of 10%. The content of the 1st cholesteric liquid crystal pigment is the amount described in Tables 9 to 11 (denoted as "Content of the 1st cholesteric liquid crystal pigment" in the table) relative to the total amount of the 1st cholesteric liquid crystal pigment and the 2nd cholesteric liquid crystal pigment.

[0300] (Manufacture of the identification medium)

[0301] 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 the 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 .

[0302] Visually observe, evaluate the reflection characteristics, and observe with a polarizer for the obtained identification medium.

[0303] [Results]

[0304] The following table shows the evaluation results of the examples and comparative examples 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).

[0305] [Table 9]

[0306] Table 9

[0307]

[0308] [Table 10]

[0309] Table 10

[0310]

[0311] [Table 11]

[0312] Table 11

[0313]

[0314] From the above results, the following matters can be known.

[0315] In the identification medium containing the composite pigment of the present invention, a color lighter than the color from the first cholesteric liquid crystal pigment can be observed by visual observation, and it is confirmed by observation through a circular polarizer that there is a difference in the hue of the reflected light of the identification medium observed with the left- and right-handed circular polarizers. In contrast, in Comparative Example 1 where the content of the first cholesteric liquid crystal pigment is less than the content specified in the present invention, the color from the second cholesteric liquid crystal pigment can be observed by visual observation, but a color lighter than the color from the first cholesteric liquid crystal pigment cannot be observed. Further, 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 observed by visual observation, but a color lighter than the color from the first cholesteric liquid crystal pigment cannot be observed.

[0316] From the above results, it can be seen that according to the present invention, an identification medium with excellent design and an anti-counterfeiting effect can be achieved.

[0317] Description of reference numerals

[0318] 100: Manufacturing apparatus for release sheet of resin film

[0319] 110: Multilayer film

[0320] 111: Support

[0321] 112: Film of first cholesteric liquid crystal resin

[0322] 113: Crack

[0323] 114: Release sheet

[0324] 120: Film feeding section

[0325] 130: Peeling section

[0326] 131: Peeling chamber

[0327] 132: Gap

[0328] 133: Gap

[0329] 134: Block

[0330] 135: Corner of block

[0331] 136: Nozzle

[0332] 137: Recovery passage

[0333] 140: Film recovery section

[0334] 141: Core

Claims

1. A composite pigment, which comprises a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment, wherein the first cholesteric liquid crystal pigment is in the form of flakes, or both the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are in the form of 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, 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 80% or more and 100% or less with respect to the whole of the selective reflection band of the first cholesteric liquid crystal pigment, and 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 10% or more and 50% or less with respect to the whole of the selective reflection band of the second cholesteric liquid crystal pigment, with respect 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 more than 30% by weight and 75% by weight or less, 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, 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, and the first liquid crystal composition and / or the second liquid crystal composition contains one or more selected from the compounds (B1) to (B9) represented by the following formulae (B1) to (B9), 2. The composite pigment according to claim 1, wherein, the selective reflection bandwidth of the first cholesteric liquid crystal pigment is 120 nm or less.

3. The composite pigment 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.

4. The composite pigment 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.

5. An ink composition, which comprises the composite pigment according to any one of claims 1 to 4 and a binder resin.

6. An identification medium, which comprises a binder resin and a pigment dispersed in the binder resin, wherein the pigment is the composite pigment according to any one of claims 1 to 4.

7. A method for authenticity judgment, which is a method for authenticity judgment of the identification medium according to claim 6, and the method includes: Step 1, observing the reflected light from the identification medium through a left-handed circular polarizer and a right-handed circular polarizer, and judging whether there are differences in one or more of hue, lightness and chroma of the reflected light.

Images