Composite pigment, identification medium and authenticity determination method

Abstract

The composite pigment contains a first cholesteric liquid crystal pigment, and a second cholesteric liquid crystal pigment. The first cholesteric liquid crystal pigment is a pigment having a selective reflection bandwidth of 150 nm or narrower and having a center wavelength for the selective reflection band that falls in a wavelength range of between 400 nm an 800 nm inclusive. The second cholesteric liquid crystal pigment is a pigment having a selective reflection bandwidth of 200 nm or wider within a range of between 400 nm and 800 nm wavelength. The selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment overlap one another at least partially. The content of the first cholesteric liquid crystal pigment is over 30% by weight but no greater than 80% by weight relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment.

Description

[Technical field]

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

[0002] 2. Description of the Related Art By attaching an identification medium to an article and identifying the authenticity of the identification medium, it is possible to prevent counterfeiting of the article. Cholesteric liquid crystal resin is obtained by cholesterically orienting a liquid crystal compound and curing it while maintaining the orientation. Such cholesteric liquid crystal resin has a circular polarization separation function that reflects one of left and right circularly polarized light and transmits the other circularly polarized light. It is known that in cholesteric liquid crystal resin materials, the wavelength of the reflected circularly polarized light shifts to the short wavelength side as the viewing angle θ from the front direction increases. This characteristic can be used to identify the authenticity of an identification medium that uses cholesteric liquid crystal resin.

[0003] As an example of using such a cholesteric liquid crystal resin, there is known an anti-counterfeiting printed matter that contains a cholesteric liquid crystal resin as a pigment (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-73600 A Summary of the Invention [Problem to be solved by the invention]

[0005] The anti-counterfeiting printed matter described in Patent Document 1 has a printed layer using ink containing either or both of a right-polarizing pigment that reflects a portion of right-circularly polarized light of incident light and a left-polarizing pigment that reflects a portion of left-circularly polarized light of incident light. The authenticity of this anti-counterfeiting printed matter can be determined by visual inspection through an authenticity determination filter using a circular polarizing plate.

[0006] However, in the case of printed matter using ink containing a conventional cholesteric liquid crystal resin as a pigment, there is a limit to the colors that can be expressed. Therefore, there is a demand for an identification medium that has excellent design and anti-counterfeiting effects. [Means for solving the problem]

[0007] As a result of studies to solve the above problem, the present inventor found that by using a composite pigment containing a specific first cholesteric liquid crystal pigment and a specific second cholesteric liquid crystal pigment in a predetermined ratio, a color lighter than the color derived from the first cholesteric liquid crystal pigment can be visually recognized, and thus an identification medium having excellent design and anti-counterfeiting effect can be provided. Specifically, it was found that such an effect can be obtained when the first cholesteric liquid crystal pigment has a selective reflection band center wavelength within a wavelength range of 400 nm to 800 nm and a selective reflection bandwidth of 150 nm or less, and the second cholesteric liquid crystal pigment has a selective reflection bandwidth of 200 nm or more within a wavelength range of 400 nm to 800 nm. That is, the present invention provides the following.

[0008] [1] A liquid crystal composition comprising a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment, the first cholesteric liquid crystal pigment has a selective reflection band center wavelength in a wavelength range of 400 nm or more and 800 nm or less, and a selective reflection band width of 150 nm or less; The second cholesteric liquid crystal pigment has a selective reflection bandwidth of 200 nm or more within a wavelength range of 400 nm or more and 800 nm or less, a selective reflection band of the first cholesteric liquid crystal pigment and a selective reflection band of the second cholesteric liquid crystal pigment at least partially overlap with each other; A composite pigment, wherein 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. [2] The composite pigment according to [1], wherein the content of the first cholesteric liquid crystal pigment is 75% by weight or less relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment. [3] The composite pigment according to [1] or [2], wherein the first cholesteric liquid crystal pigment has a selective reflection bandwidth of 120 nm or less. [4] 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 the same twist direction. [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 mutually different twist directions. [6] At least one of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is a flake; The composite pigment according to any one of [1] to [5], wherein the average particle size of the flakes is 20 μm or more and 120 μm or less. [7] An ink composition comprising the composite pigment according to any one of [1] to [6] and a binder resin. [8] A binder resin and a pigment dispersed in the binder resin, The pigment is the composite pigment according to any one of [1] to [6]. [9] A method for determining the authenticity of an identification medium according to [8], comprising: The method for determining authenticity includes step 1 of observing the reflected light from the identification medium through a left circular polarizing plate and a right circular polarizing plate, and determining whether or not there is a difference in one or more selected from the hue, brightness, and saturation of the reflected light. Effect of the Invention

[0009] According to the present invention, it is possible to provide a composite pigment that can realize an identification medium that has excellent design and anti-counterfeiting effects, an ink composition and an identification medium that use the composite pigment, and a method for identifying the authenticity of the identification medium. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a front view that shows a schematic diagram of a manufacturing apparatus for producing a peeled piece of a thin resin film used in the production of the composite pigment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view that typically shows a cross section of a corner portion of a bar of the manufacturing apparatus of FIG. 1 cut along a plane perpendicular to the width direction of the support. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be modified and practiced as desired without departing from the scope of the claims of the present invention and the scope of equivalents thereto.

[0012] In the following description, unless otherwise specified, a "composition" includes not only a mixture of two or more substances but also a material consisting of a single substance, and an "agent" includes not only a material consisting of a single substance but also a mixture of two or more substances.

[0013] In the following description, unless otherwise specified, "(meth)acrylate" means "acrylate" or "methacrylate", or both. Additionally, "(meth)acrylic" means "acrylic" or "methacrylic", or both. Additionally, "(thio)epoxy" means "epoxy" or "thioepoxy", or both. Additionally, "iso(thio)cyanate" means "isocyanate" or "isothiocyanate", or both.

[0014] [1. Composite pigments] The composite pigment of the present invention includes a first cholesteric liquid crystal pigment and a second cholesteric liquid crystal pigment. The first cholesteric liquid crystal pigment has a selective reflection band center wavelength within a wavelength range of 400 nm to 800 nm, and a selective reflection bandwidth of 150 nm or less. The second cholesteric liquid crystal pigment has a selective reflection bandwidth of 200 nm or more within a wavelength range of 400 nm to 800 nm. The selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment at least partially overlap. 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 more than 30% by weight and not more than 80% by weight.

[0015] The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are each composed of a cholesteric liquid crystal resin.

[0016] The term "cholesteric liquid crystal resin" refers to a resin material having cholesteric regularity, and means that the molecules or molecular parts constituting the resin are aligned in a state having cholesteric regularity within the resin. Here, the molecules in the resin "have cholesteric regularity" means that the molecules in the resin have a specific regularity described below. When the molecules in the resin have cholesteric regularity, the molecules are aligned in the resin in a manner that forms a number of molecular layers. In each molecular layer, the molecules are aligned so that the molecular axis is in a certain orientation direction. The orientation direction in a second plane that overlaps the first plane is shifted at a slight angle from the orientation direction in a first plane inside the resin layer. The orientation direction in a third plane that further overlaps the second plane is further shifted at a slight angle from the orientation direction in the second plane. In this way, in the multiple planes that are arranged in an overlapping manner, the angles of the molecular axes in the planes are sequentially shifted (twisted). A structure in which the direction of the molecular axis is twisted in this way becomes an optically chiral structure.

[0017] Cholesteric liquid crystal resins having an optically chiral structure usually have a circularly polarized light selective reflection function that selectively reflects circularly polarized light. When a cholesteric liquid crystal resin "selectively reflects" light in a predetermined wavelength range, it means that it reflects one circularly polarized component of unpolarized light (i.e., natural light) in a predetermined wavelength range and transmits the other circularly polarized component. In the present invention, the "selective reflection band" refers to the range of wavelengths of circularly polarized light that is selectively reflected. In the present invention, the "selective reflection bandwidth" refers to the width of the selective reflection band, and specifically, can be the half-width of the selective reflection band.

[0018] [Selective reflection band of cholesteric liquid crystal pigments] In the present invention, the selective reflection band of the first cholesteric liquid crystal pigment and the selective reflection band of the second cholesteric liquid crystal pigment at least partially overlap. 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 even more preferably 100% or less, based on 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, and preferably 50% or less, more preferably 40% or less, based on 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 equal to or greater than the lower limit with respect to the entire selective reflection band of the first cholesteric liquid crystal pigment, the action of the second cholesteric liquid crystal pigment makes it easy to express a color lighter than the color originating from the first cholesteric liquid crystal pigment in visual observation. 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 equal to or greater than the lower limit with respect to the entire selective reflection band of the second ... is equal to or less than the upper limit, it is possible to prevent the color originating from the first cholesteric liquid crystal pigment from becoming too light and becoming achromatic.

[0019] 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 having a narrower (narrow band) selective reflection bandwidth than the second cholesteric liquid crystal pigment, and the second cholesteric liquid crystal pigment is a cholesteric liquid crystal pigment having a wider (wide band) selective reflection bandwidth than the first cholesteric liquid crystal pigment. When an identification medium using a cholesteric liquid crystal pigment having a narrow selective reflection bandwidth alone is observed under natural light, an appearance having a color according to the reflection bandwidth can be visually recognized. When an identification medium using a cholesteric liquid crystal pigment having a wide selective reflection bandwidth alone is observed under natural light, an appearance of silver close to a mirror surface can be visually recognized. In the present invention, the composite pigment contains a predetermined amount of a first cholesteric liquid crystal pigment having a selective reflection bandwidth of 150 nm or less, and a second cholesteric liquid crystal pigment having a selective reflection bandwidth of 200 nm or more. Therefore, when such an identification medium is observed under natural light, a color lighter than the color derived from the first cholesteric liquid crystal pigment can be visually recognized.

[0020] The selective reflection bandwidth of the first cholesteric liquid crystal pigment is preferably 120 nm or less, more preferably 110 nm or less, and preferably 30 nm or more, 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. There is no particular upper limit to the selective reflection bandwidth of the second cholesteric liquid crystal pigment, but it is preferably 2000 nm or less, more preferably 1000 nm or less.

[0021] The first cholesteric liquid crystal pigment has a central wavelength of a selective reflection band within a wavelength range of 400 nm or more and 800 nm or less. In the present invention, the central wavelength of the selective reflection band of each cholesteric liquid crystal pigment can be the central wavelength of the region related to the half-width of the selective reflection band. That is, the reflection spectrum of the cholesteric liquid crystal pigment is measured at an incident angle of 5°, and in the obtained reflection spectrum, a peak having a maximum intensity and a base having a minimum intensity are determined, and a wavelength λ1 on the short wavelength side of the peak and a wavelength λ2 on the long wavelength side showing an intensity of minimum intensity + (maximum intensity - minimum intensity) / 2 are obtained. Furthermore, the average value of these ((λ1 + λ2) / 2) is obtained, and the average value can be used as the central wavelength. In this case, the selective reflection band of each cholesteric liquid crystal pigment is the range (λ1 to λ2) from the wavelength λ1 on the short wavelength side to the wavelength λ2 on the long wavelength side of the peak that shows an intensity of minimum intensity + (maximum intensity - 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.

[0022] When the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are cholesteric liquid crystal resins in the form of powder or fiber, the central wavelength of the selective reflection band of each cholesteric liquid crystal pigment is the central wavelength of the selective reflection band observed when a thin film containing the pigment is formed.

[0023] When a thin film containing each cholesteric liquid crystal pigment is observed at a viewing angle θ from the front direction, the central wavelength λ (nm) of the selective reflection band is expressed by the following formula, where n is the average refractive index of the cholesteric liquid crystal resin and P (nm) is the pitch length of the chiral structure (helical structure) of the cholesteric liquid crystal resin. λ=n×P×cosθ Therefore, when a thin film containing each cholesteric liquid crystal pigment is observed at a viewing angle θ from the front direction (cosθ<1), the central wavelength λ of the selective reflection band is shorter than the central wavelength λ of the selective reflection band when observed from the front direction (cosθ=1). The front direction of a thin film containing a cholesteric liquid crystal pigment refers to the normal direction of the thin film when the thin film containing the cholesteric liquid crystal pigment is formed.

[0024] The central wavelength λ of the selective reflection band when the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are observed from the front direction at a viewing angle θ can be increased by, for example, increasing the pitch length P of the chiral structure (helical structure), and can be decreased by decreasing the pitch length P.

[0025] The pitch length of each cholesteric liquid crystal resin can be adjusted, for example, by adjusting the type of chiral agent or the amount of the chiral agent.

[0026] [Content of first cholesteric liquid crystal pigment] In the present invention, the content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is more than 30% by weight and not more than 80% by weight. The content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is preferably 35% by weight or more, more preferably 45% by weight or more, and preferably 75% by weight or less, more preferably 65% ​​by weight or less.

[0027] By setting the content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment within the above range, the reflected color of the second cholesteric liquid crystal pigment can be visually recognized together with the reflected color of the first cholesteric liquid crystal pigment by visual observation, and as a result, a color lighter than the color derived from the first cholesteric liquid crystal pigment can be visually recognized, thereby providing a composite pigment that can realize an identification medium having excellent designability and anti-counterfeiting effects.

[0028] When the content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is equal to or less than the upper limit, the reflected color of the second cholesteric liquid crystal pigment becomes visible together with the reflected color of the first cholesteric liquid crystal pigment, and a color paler than the color derived from the first cholesteric liquid crystal pigment can be visually recognized. When the content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is equal to or less than 30% by weight, the reflected color of the first cholesteric liquid crystal pigment may be difficult or impossible to visually recognize, but when the content of the first cholesteric liquid crystal pigment is more than 30% by weight, the reflected color of the first cholesteric liquid crystal pigment becomes visible together with the reflected color of the second cholesteric liquid crystal pigment, and a color paler than the color derived from the first cholesteric liquid crystal pigment can be visually recognized.

[0029] From the viewpoint of excellent dispersibility when the composite pigment is made into an ink composition, it is preferable that at least one of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment is a flake. When the first cholesteric liquid crystal pigment, the second cholesteric liquid crystal pigment, or both of the 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, and 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 the lower limit or more, decorativeness can be obtained, and when the average particle size of the flakes is the upper limit or less, printability can be obtained.

[0030] The average particle diameter of the flakes can be determined, for example, by measuring the particle size distribution by a laser scattering method and measuring the average particle diameter from the particle size distribution. In the particle size distribution, the particle diameter at which the integrated value of the volume is 50% can be defined as the average particle diameter. In this application, the average particle diameter of the flakes is the volume average unless otherwise specified.

[0031] [Twist direction of cholesteric liquid crystal pigments] The first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment may have the same twist direction or different twist directions. The twist direction can be determined by observing the reflected light when non-polarized light is incident on a sample containing each cholesteric liquid crystal pigment through left and right circular polarizers. That is, the twist direction can be determined by irradiating the sample with non-polarized light from the observer side and observing the reflected light that is reflected by the sample and reaches the observer side. If the reflected light is right-handed circularly polarized, it can be determined as right-handed twist, and if it is left-handed circularly polarized, it can be determined as left-handed twist.

[0032] [Cholesteric liquid crystal pigment materials] The cholesteric liquid crystal resin used as the material for 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 used as the material for the second cholesteric liquid crystal pigment is a cured product of a second liquid crystal composition containing a liquid crystalline compound. The liquid crystal compound contained in the first liquid crystal composition and the second liquid crystal composition is preferably a polymerizable liquid crystal compound. A liquid crystal composition containing a polymerizable liquid crystal compound can be easily cured while maintaining the alignment state by polymerizing the liquid crystal compound.

[0033] As the liquid crystal compound, a cholesteric liquid crystal compound can be used. The cholesteric liquid crystal compound is a compound that can exhibit cholesteric liquid crystal properties. By using a liquid crystal composition containing such a cholesteric liquid crystal compound and curing the liquid crystal composition in a state of exhibiting a cholesteric liquid crystal phase, a cholesteric liquid crystal resin, which is a resin material having cholesteric regularity, can be obtained.

[0034] The liquid crystal compound contained in the first liquid crystal composition and the second liquid crystal composition may be, for example, a rod-shaped liquid crystal compound having two or more reactive groups in one molecule. An example of the rod-shaped liquid crystal compound is a compound represented by formula (1). R 3 -C 3 -D 3 -C5 -MC 6 -D 4 -C 4 -R 4 Formula (1)

[0035] In formula (1), R 3 and R 4 are reactive groups, each independently representing a group selected from the group consisting of a (meth)acrylic group, a (thio)epoxy group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, a vinyl group, an allyl group, a fumarate group, a cinnamoyl group, an oxazoline group, a mercapto group, an iso(thio)cyanate group, an amino group, a hydroxyl group, a carboxyl group, and an alkoxysilyl group. By having these reactive groups, a cholesteric liquid crystal resin with high strength can be obtained when the liquid crystal composition is cured.

[0036] In formula (1), D 3 and D. 4 each independently represents a group selected from the group consisting of a single bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and a linear or branched alkylene oxide group having 1 to 20 carbon atoms.

[0037] In formula (1), C 3 ~C 6 each independently represents a group selected from the group consisting of a single bond, -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH-, -OCH-, -CH=NN=CH-, -NHCO-, -O-(C=O)-O-, -CH-(C=O)-O-, and -CHO-(C=O)-.

[0038] In formula (1), M represents a mesogenic group. Specifically, M represents a group in which 2 to 4 skeletons, which may be unsubstituted or substituted, selected from the group consisting of azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoates, cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles, are bonded by a bonding group such as -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH=NN=CH-, -NHCO-, -O-(C=O)-O-, -CH2-(C=O)-O-, and -CHO-(C=O)-.

[0039] Examples of the substituent that the mesogenic group M may have include a halogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, a cyano group, a nitro group, -OR 5 , -OC(=O)-R 5 , -C(=O)-OR 5 , -OC(=O)-OR 5 , -NR 5 -C(=O)-R 5 , -C(=O)-NR 5 R 7 or -OC(=O)-NR 5 R 7 Here, R 5 and R 7 R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 5 and R 7 is an alkyl group, the alkyl group may include -O-, -S-, -OC(=O)-, -C(=O)-O-, -OC(=O)-O-, -NR 6 -C(=O)-, -C(=O)-NR 6 -, -NR 6 - or -C(=O)- may be present (excluding the case where there are two or more adjacent -O- and -S-). 6represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0040] Examples of the substituent in the "alkyl group having 1 to 10 carbon atoms which may have a substituent" include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkoxy group having 2 to 8 carbon atoms, an alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, an alkylcarbonyloxy group having 2 to 7 carbon atoms, and an alkoxycarbonyloxy group having 2 to 7 carbon atoms.

[0041] The rod-shaped liquid crystal compound preferably has an asymmetric structure. Here, the asymmetric structure is defined as a structure in which, in formula (1), R 3 -C 3 -D 3 -C 5 -and-C 6 -D 4 -C 4 -R 4 By using a rod-like liquid crystal compound having an asymmetric structure, the alignment uniformity can be further improved.

[0042] Preferable specific examples of the rod-shaped liquid crystal compound include the following compounds (B1) to (B9). These may be used alone or in combination of two or more in any ratio.

[0043] [ka]

[0044] The first liquid crystal composition and / or the second liquid crystal composition preferably contains a compound represented by the above formula (1) as a liquid crystal compound, and more preferably contains one or more compounds selected from the above compounds (B1) to (B9).

[0045] The first liquid crystal composition and / or the second liquid crystal composition may contain a compound represented by the following formula (2) in addition to a liquid crystal compound: The compound of formula (2) may function as an alignment assistant.

[0046] R 1 -A 1 -BA 2 -R 2 (2) In formula (2), R 1 and R 2 are each independently a group selected from the group consisting of a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or branched alkylene oxide group having 1 to 20 carbon atoms, a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acrylic group which may have an arbitrary bonding group interposed therebetween, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

[0047] The alkyl group and the alkylene oxide group may be unsubstituted or may be substituted with one or more halogen atoms. Furthermore, the halogen atom, the hydroxyl group, the carboxyl group, the (meth)acrylic group, the epoxy group, the mercapto group, the isocyanate group, the amino group, and the cyano group may be bonded to the alkyl group having 1 to 2 carbon atoms and the alkylene oxide group.

[0048] R 1 and R 2 Preferred examples of the alkyl group include a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acrylic group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

[0049] Also, R 1 and R 2 At least one of R is preferably a reactive group. 1 and R 2By having a reactive group as at least one of the above, the compound represented by formula (2) is fixed in the cholesteric liquid crystal resin during curing, and a stronger resin can be formed. Examples of the reactive group include a carboxyl group, a (meth)acrylic group, an epoxy group, a mercapto group, an isocyanate group, and an amino group.

[0050] In formula (2), A 1 and A 2 each independently represents a group selected from the group consisting of a 1,4-phenylene group, a 1,4-cyclohexylene group, a cyclohexen-1,4-ylene group, a 4,4'-biphenylene group, a 4,4'-bicyclohexylene group, and a 2,6-naphthylene group. The 1,4-phenylene group, the 1,4-cyclohexylene group, the cyclohexen-1,4-ylene group, the 4,4'-biphenylene group, the 4,4'-bicyclohexylene group, and the 2,6-naphthylene group 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. A 1 and A 2 In each of the groups, when two or more substituents are present, they may be the same or different.

[0051] A 1 and A 2 Particularly preferred examples of the aromatic ring structure include a group selected from the group consisting of a 1,4-phenylene group, a 4,4'-biphenylene group, and a 2,6-naphthylene group. These aromatic ring structures are relatively rigid compared to alicyclic structures, and have a high affinity with the mesogens of rod-like liquid crystal compounds, resulting in higher alignment uniformity.

[0052] In formula (2), B is selected from the group consisting of a single bond, -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH=NN=CH-, -NHCO-, -O-(C=O)-O-, -CH2-(C=O)-O-, and -CHO-(C=O)-. Particularly preferred values ​​for B include a single bond, -O-(C=O)-, and -CH=NN=CH-.

[0053] Particularly preferred specific examples of the compound represented by formula (2) include the following compounds (A1) to (A10). These may be used alone or in combination of two or more in any ratio. Among the following compounds (A1) to (A10), at least one selected from compounds (A2) and (A10) is particularly preferred. Compounds (A2) and (A10) can lower the temperature at which a liquid crystal phase appears in a liquid crystal composition, and can maintain the temperature range at which the liquid crystal compound exhibits a liquid crystal phase in a wide range.

[0054] [ka]

[0055] In the above compound (A3), "*" represents a chiral center.

[0056] In the first or second liquid crystal composition, the weight ratio represented by (total weight of the compounds represented by formula (2)) / (total weight of the rod-shaped liquid crystal compounds) is preferably 0.05 or more, more preferably 0.1 or more, particularly preferably 0.15 or more, and preferably 1 or less, more preferably 0.65 or less, particularly preferably 0.55 or less. By making the weight ratio equal to or more than the lower limit of the range, the alignment uniformity of the liquid crystal composition can be improved. By making the weight ratio equal to or less than the upper limit, the alignment uniformity can be increased. In addition, the stability of the liquid crystal phase of the liquid crystal composition can be increased. Here, the total weight of the compounds represented by formula (2) refers to the weight when only one type of compound represented by formula (2) is used, and refers to the total weight when two or more types are used. Similarly, the total weight of the rod-shaped liquid crystal compounds refers to the weight when only one type of rod-shaped liquid crystal compound is used, and refers to the total weight when two or more types are used.

[0057] In addition, when the compound represented by formula (2) is used in combination with a rod-shaped liquid crystal compound, the molecular weight of the compound represented by formula (2) is preferably less than 600, and the molecular weight of the rod-shaped liquid crystal compound is preferably 600 or more. This allows the compound represented by formula (2) to enter into the gaps of the rod-shaped liquid crystal compound having a larger molecular weight, thereby improving the alignment uniformity.

[0058] The first liquid crystal composition and the second liquid crystal composition may each contain a chiral agent. Usually, the twist direction of the cholesteric liquid crystal resin can be appropriately selected depending on the type and structure of the chiral agent used. Specific examples of the chiral agent include those described in JP2005-289881A, JP2004-115414A, JP2003-66214A, JP2003-313187A, JP2003-342219A, JP2000-290315A, JP6-072962A, U.S. Patent No. 6468444A, WO98 / 00428A, JP2007-176870A, etc., and can be appropriately used, for example, BASF Paliocolor LC756. As the chiral agent, a compound represented by the following formula (3) can also be used. The chiral agent may be used alone or in combination of two or more kinds in any ratio.

[0059] [ka]

[0060] The amount of the chiral agent can be set arbitrarily within a range that does not deteriorate the desired optical performance. The specific amount of the chiral agent in the liquid crystal composition is usually 1% by weight to 60% by weight.

[0061] The first liquid crystal composition and the second liquid crystal composition may each contain a polymerization initiator. Examples of the polymerization initiator include a photopolymerization initiator, and a compound capable of generating a radical or an acid by ultraviolet light or visible light can be used. Specific examples of the photopolymerization initiator include benzoin, benzyl dimethyl ketal, benzophenone, biacetyl, acetophenone, Michler's ketone, benzyl, 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 ketone, and the like. 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methylbenzoyl formate, 2,2-diethoxyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-amylcinnamic aldehyde, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, pp'-dichlorobenzophenone, pp'-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, anthracenebenzophenone, α-chloroanthraquinone, diphenyl disulfide, hexachlorobutadiene, pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,Examples of the carbazole oxime compounds include 2-octanedione-1-[4-(phenylthio)-2-(o-benzoyloxime)] and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(o-acetyloxime), (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate, 3-methyl-2-butynyltetramethylenesulfonium hexafluoroantimonate, and diphenyl-(p-phenylthiophenyl)sulfonium hexafluoroantimonate. As the polymerization initiator, IRGACURE 184 and IRGACURE OXE02 manufactured by BASF can also be used. These may be used alone or in combination of two or more in any ratio. Furthermore, if necessary, a known tertiary amine compound as a photosensitizer or polymerization accelerator may be used to control the curability.

[0062] 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 equal to or more than the lower limit of the above range, the degree of polymerization can be increased, and the mechanical strength of the cholesteric liquid crystal resin can be increased. Also, by making the amount equal to or less than the upper limit, the liquid crystal compound can be well aligned, and the liquid crystal phase of the liquid crystal composition can be stabilized.

[0063] The first liquid crystal composition and the second liquid crystal composition may each contain a surfactant as a leveling agent. For example, a surfactant that does not inhibit alignment may be appropriately selected and used. For example, a nonionic surfactant containing a siloxane or a fluorinated alkyl group in the hydrophobic group portion is suitable as such a surfactant. Among them, an oligomer having two or more hydrophobic group portions in one molecule is particularly suitable. Specific examples of these surfactants include PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, and PF-652 of PolyFox from OMNOVA Co., Ltd.; FTX-209F, FTX-208G, and FTX-204D of Futergent from NEOS Co., Ltd.; and KH-40 and S420 of Surflon from Seimi Chemical Co., Ltd. The surfactant may be used alone or in combination of two or more types at any ratio.

[0064] The amount of the surfactant is preferably 0.05% by weight to 3% by weight in the cholesteric liquid crystal resin. By making the amount of the surfactant equal to or greater than the lower limit of the range, the alignment control force of the liquid crystal composition at the air interface can be increased, thereby preventing alignment defects. By making the amount equal to or less than the upper limit, surface defects caused by the formation of a micelle structure by an excess surfactant can be suppressed.

[0065] Each of the first liquid crystal composition and the second liquid crystal composition may further contain optional components as necessary. Examples of the optional components include a polymerization inhibitor for improving pot life, an antioxidant, an ultraviolet absorber, and a light stabilizer for improving durability. These optional components may be used alone or in combination of two or more at any ratio. The amount of these optional components may be set as desired within a range that does not deteriorate the desired optical performance.

[0066] The method for producing the first and second liquid crystal compositions is not particularly limited, and the first and second liquid crystal compositions can be produced by mixing the above-mentioned components.

[0067] [Production of the first cholesteric liquid crystal pigment] The first cholesteric liquid crystal pigment can be produced by applying a coating liquid containing the first liquid crystal composition and a solvent onto a suitable support, drying it if necessary to form a layer of the first liquid crystal composition, and curing this layer to form a thin film of the first cholesteric liquid crystal resin, and then peeling the thin film of the first cholesteric liquid crystal resin from the support and crushing it.

[0068] (Production of thin film of first cholesteric liquid crystal resin) Prior to application of the coating solution containing the first liquid crystal composition, the surface of the support may be subjected to a treatment for imparting an alignment control force. Examples of such treatment include a rubbing treatment of the support surface, a stretching treatment of the support film, etc. Furthermore, a surface treatment such as a corona treatment may be performed to increase the affinity between the surface of the support and the first liquid crystal composition.

[0069] The support may be a film having a resin layer made of a resin. Examples of the polymer contained in the resin constituting the resin layer include linear olefin polymers, cycloolefin polymers, polycarbonates, polyesters, polysulfones, polyethersulfones, polystyrenes, polyvinyl alcohols, cellulose acetate polymers, polyvinyl chlorides, and polymethacrylates.

[0070] The resin may contain one type of polymer alone or two or more types of polymers in any combination at any ratio. The resin may also contain any compounding agent as long as it does not significantly impair the effects of the present invention.

[0071] The support may be a film having a single layer structure, or a film having a multilayer structure, including two or more layers. Thus, the support may be a film having only the resin layer, or a film having any layer in addition to the resin layer.

[0072] For example, from the viewpoint of favorably aligning the liquid crystal composition, the support may have an alignment film on its surface. The alignment film may be formed of a resin containing a polymer such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, etc. Moreover, these polymers may be used alone or in combination of two or more at any ratio. The alignment film may be produced by applying a solution containing the polymer, drying it, and carrying out a rubbing treatment. The thickness of the alignment film is preferably 0.01 μm or more, more preferably 0.05 μm or more, and is preferably 5 μm or less, more preferably 1 μm or less.

[0073] The support may be an unstretched film that is not stretched, or may be an oriented film that is stretched. The support may be an isotropic film or an anisotropic film. Furthermore, the support may be one that has been subjected to a surface treatment on one or both sides. By performing the surface treatment, it is possible to improve the adhesion with other layers that are formed directly on the surface of the support. Examples of the surface treatment include energy ray irradiation treatment, corona treatment, and chemical treatment.

[0074] From the viewpoints of ease of handling during production, material costs, thinness and weight reduction, the thickness of the support is preferably 30 μm or more, more preferably 60 μm or more, and is preferably 300 μm or less, more preferably 200 μm or less.

[0075] The coating solution containing the first liquid crystal composition can be applied by a known coating method, such as extrusion coating, direct gravure coating, reverse gravure coating, die coating, spin coating, and bar coating.

[0076] After forming a layer of the first liquid crystal composition by applying a coating liquid containing the first liquid crystal composition, an alignment treatment may be carried out as necessary before carrying out a curing step. The alignment treatment may 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 carrying out the alignment treatment, the liquid crystal compound in the first liquid crystal composition can be well aligned.

[0077] The first liquid crystal composition layer can be cured by one or more energy ray irradiations. Examples of the energy ray include ultraviolet light, visible light, and other electromagnetic waves. Specifically, the energy ray irradiation can be performed by irradiating light having a wavelength of 200 to 500 nm for 0.01 seconds to 3 minutes. When the first liquid crystal composition layer is cured, a thin film of the first cholesteric liquid crystal resin is formed on the support.

[0078] (Production of pigment using thin film of first cholesteric liquid crystal resin) The method for peeling and crushing the thin film of the first cholesteric liquid crystal resin from the support is not particularly limited, and may be, for example, the method described in JP 2015-27743 A. In this method, the thin film of the first cholesteric liquid crystal resin can be peeled from the support using a peeled piece manufacturing device shown in FIG. 1. The method for peeling the thin film of the first cholesteric liquid crystal resin using the device shown in FIG. 1 will be described below. Hereinafter, the "thin film of the first cholesteric liquid crystal resin" will also be simply referred to as the "first resin thin film."

[0079] Fig. 1 is a front view showing a schematic diagram of a manufacturing apparatus for producing peeled pieces of a resin thin film used in the manufacture of the composite pigment of the present invention. The peeled piece manufacturing apparatus 100 shown in Fig. 1 includes a film delivery section 120 capable of delivering a multilayer film 110 including a support 111 and a first resin thin film (see 112 in Fig. 2), a peeling section 130 capable of peeling the first resin thin film 112 from the delivered multilayer film 110, and a recovery section 140 capable of recovering the support 111 from which the first resin thin film 112 has been peeled off.

[0080] The peeling section 130 is equipped with a bar 134 having a corner portion 135 provided at an acute angle, and a nozzle 136 capable of spraying air, which is provided immediately downstream of the corner portion 135. The angle of the corner portion 135 of the bar 134 is set so that the multilayer film 110 can be folded back at an angle θ, and the corner portion has a chamfered structure.

[0081] Peeling of the first resin thin film using the device 100 can be performed as follows. The multilayer film 110 is attached to the film delivery section 120 in a direction that allows the multilayer film 110 to be folded back at the corner portion 135 of the bar 134 with the first resin thin film 112 facing outward relative to the support 111. Then, the multilayer film 110 is delivered from the film delivery section 120 in a state in which tension is applied to the multilayer film 110 in the transport direction by the film recovery section 140.

[0082] The multilayer film 110 sent out from the film delivery section 120 enters the peeling chamber 131 through the slit 132 and is folded back at the corner 135 of the bar 134. The support 111 bent at the corner 135 is usually not broken. On the other hand, the first resin thin film 112 bent at the corner 135 is subjected to stress due to the bending deformation, and the first resin thin film 112 is broken by this stress, forming a crack 113. Thereafter, the first resin thin film 112 with the crack formed therein is peeled off and blown away by the air jetted from the nozzle 136, becoming a peeled piece 114. A part of the peeled piece 114 is separated from the support 111 and is sent to a recovery path following the flow of the air jetted from the nozzle 136. Another part of the peeled piece 114 is carried together with the support 111 while it is placed on the support 111 or while it is attached to the support 111 by a force such as electrostatic attraction.

[0083] The support 111 from which the first resin thin film 112 has been peeled off at the corner portion 135 of the bar 134 is transported downstream. As shown in FIG. 1, when the support 111 reaches the installation position of the nozzle 136, air jetted from the nozzle 136 is blown onto the portion of the first resin thin film 112 where the crack has been formed. The air blows off the peeled pieces 114 contained in the portion of the first resin thin film 112 where the crack has been formed, and sends them to a recovery path 137. In addition, the first resin thin film (not shown) that has only formed a crack 113 but has not been peeled off from the support 111 and remains on the support 111 is also peeled off from the support 111 by the pressure of the air jetted from the nozzle 136, and becomes peeled pieces 114, which are sent to the recovery path 137.

[0084] The peeled pieces 114 sent to the recovery path 137 are carried by the air current to a recovery device (not shown) and recovered. The support 111 from which the first resin thin film 112 has been peeled off is transported through the slit 133 to the film recovery section 140, taken up around a winding core 141, and recovered.

[0085] The first cholesteric liquid crystal pigment having a desired particle size is obtained by pulverizing the pieces of the first cholesteric liquid crystal resin peeled off from the support. The pulverization process 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, and a stone mill type pulverizer.

[0086] [Manufacture of the second cholesteric liquid crystal pigment] The second cholesteric liquid crystal pigment can be produced by forming a thin film of the second cholesteric liquid crystal resin on a support, peeling the thin film of the second cholesteric liquid crystal resin from the support, and crushing it.

[0087] (Manufacture of thin film of second cholesteric liquid crystal resin) In producing a thin film of the second cholesteric liquid crystal resin, instead of curing a layer of the first liquid crystal composition to form a thin film of the first cholesteric liquid crystal resin in the above "Production of a thin film of a first cholesteric liquid crystal resin", a layer of the second liquid crystal composition is cured in a state in which the pitch of the helical structure is continuously changed by one or more light irradiation and / or heating treatment to form a thin film of the second cholesteric liquid crystal resin.

[0088] The operation of curing the layer of the second liquid crystal composition in a state in which the pitch of the helical structure is continuously changed by irradiating the layer with light and / or heating one or more times is called a band-widening treatment because it is an operation for widening the reflection band of the thin film of the cholesteric liquid crystal resin. By performing the band-widening treatment, a wide reflection band can be realized even in a thin film of the cholesteric liquid crystal resin having a thickness of, for example, 5 μm or less.

[0089] (Production of pigments using thin films of second cholesteric liquid crystal resin) The peeling and crushing of the thin film of the second cholesteric liquid crystal resin can be performed by using a thin film of the second cholesteric liquid crystal resin instead of the thin film of the first cholesteric liquid crystal resin (first resin thin film) in the above ``Peeling and crushing of the thin film of the first cholesteric liquid crystal resin.''

[0090] [2. Ink composition] The ink composition contains the composite pigment of the present invention and a binder resin. The binder resin contains a polymer. Examples of such a polymer include polyester polymers, acrylic polymers, polystyrene polymers, polyamide polymers, polyurethane polymers, polyolefin polymers, polycarbonate polymers, and polyvinyl polymers. The binder resin may be used alone or in combination of two or more kinds in any ratio.

[0091] The method for producing the ink composition of the present invention is not particularly limited, and the ink composition can be produced by mixing the above-mentioned components.

[0092] The ink composition of the present invention can be printed on a substrate to form an ink layer, and then the ink layer can be cured to form an identification medium. The material of the substrate on which the ink layer is formed is not particularly limited, and examples thereof include resin, metal, glass, and paper.

[0093] The method for printing the ink composition is not particularly limited, but examples thereof include screen printing, gravure printing, flexographic printing, letterpress printing, offset printing, and the like.

[0094] The ink layer can be cured by heating or by irradiating with energy rays one or more times. An example of heating is heat treatment at 150°C or higher. By thermally curing the ink layer by heat treatment, an identification medium can be obtained in which a printed layer containing the composite pigment of the present invention is formed on a substrate. Examples of energy rays include ultraviolet light, visible light, and other electromagnetic waves. Specifically, the energy ray irradiation can be performed by irradiating with light having a wavelength of 200 to 500 nm for 0.01 seconds to 3 minutes. By curing the ink layer, an identification medium can be obtained in which a printed layer containing the composite pigment of the present invention is formed on a substrate.

[0095] [3.Identification medium] The discrimination medium of the present invention includes a binder resin and a pigment dispersed in the binder resin. The pigment contained in the discrimination medium is the composite pigment of the present invention.

[0096] The discrimination medium may be in the form of including a layer containing a binder resin and the composite pigment of the present invention dispersed in the binder resin, and an optional layer. The optional layer may include a substrate and an adhesive layer. The substrate may be made of the material described in 2.

[0097] When the discrimination medium has an optional layer on the viewing 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 is preferably a layer with small in-plane retardation Re (for example, 5 nm or less).

[0098] [Use of identification medium] The identification medium is preferably used to identify the authenticity of an article by attaching or transferring it to the article. Examples of the article for which the authenticity should be identified include a gift certificate, a coupon, a ticket, a certificate, a security card, etc. The identification medium can also be used in the form of a label, a sticker, etc. for authenticity identification.

[0099] [4. Methods for verifying the authenticity of identification media] The method for determining the authenticity of an identification medium of the present invention includes step 1 of observing reflected light from the identification medium through a left circular polarizer and a right circular polarizer to determine whether or not there is a difference in one or more selected from the hue, brightness, and saturation of the reflected light.

[0100] [Process 1] Step 1 is a step of observing the light reflected from the discrimination medium through a left circular polarizer and a right circular polarizer to determine whether or not there is a difference in one or more selected from the hue, brightness, and saturation of the reflected light.

[0101] The discrimination medium used includes a binder resin and a pigment dispersed in the binder resin, the pigment being the composite pigment of the present invention, and the reflected light from the discrimination medium is observed through a left circular polarizing plate and a right circular polarizing plate. The reflected light is the light reflected when the discrimination medium is irradiated with natural light. Natural light means non-polarized light, and may be sunlight or artificial light.

[0102] Depending on the twist 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 discrimination medium is as follows. (1) When the twist directions of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are the same, the discrimination medium reflects only circularly polarized light having the same twist direction as the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment. (2) When the twist 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 twist direction as the first cholesteric liquid crystal pigment, and reflects the other circularly polarized light having the same twist direction as the second cholesteric liquid crystal pigment.

[0103] In the case of (1) above, when the identification medium is observed through a left circular polarizing plate and a right circular polarizing plate, 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, and therefore the reflected light of the identification medium is visible through one circular polarizing plate that transmits this one type of circularly polarized light, while the reflected light of the identification medium is not visible or is difficult to see through the other circular polarizing plate.

[0104] Therefore, when the reflected light from the identification medium is observed using a left-right circular polarizing plate, if there is a difference in one or more of the hue, brightness, and saturation of the reflected light of the identification medium by the left-right circular polarizing plate, the identification medium can be determined to be genuine.

[0105] Furthermore, if there is no difference in the hue, brightness, and saturation of the light reflected from the identification medium by the left and right circular polarizers, it can be determined that the identification medium does not have a selective reflection function that selectively reflects circularly polarized light, and the identification medium is not genuine.

[0106] In the case of (2) above, when the discrimination medium is observed through a left circular polarizing plate and a right circular polarizing plate, one of the circular polarizing plates transmits light reflected by the first cholesteric liquid crystal pigment and does not transmit light reflected by the second cholesteric liquid crystal pigment. Therefore, when the identification medium is observed from near the front using one of the circular polarizing plates, the light reflected by the first cholesteric liquid crystal pigment is visible as reflected light of the identification medium, but the light reflected by the second cholesteric liquid crystal resin does not pass through the other circular polarizing plate, and therefore the reflected light of the identification medium is not visible or is difficult to see.

[0107] 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. Therefore, when the identification medium is observed from near the front using the other circular polarizing plate, the light reflected by the first cholesteric liquid crystal pigment does not pass through the other circular polarizing plate, and the light reflected by the second cholesteric liquid crystal pigment is visible as reflected light of the identification medium.

[0108] If there is no difference in the hue, brightness, and saturation of the light reflected from the identification medium by the left and right circular polarizers, the identification medium does not have the selective reflection function of selectively reflecting circularly polarized light, and it can be determined that the identification medium is not genuine.

[0109] [Actions and Effects of the Invention] The identification medium of the present invention contains a composite pigment containing a first cholesteric liquid crystal pigment having a selective reflection band center wavelength within a wavelength range of 400 nm to 800 nm and a selective reflection bandwidth of 150 nm or less, and a second cholesteric liquid crystal pigment having a selective reflection bandwidth of 200 nm or more within a wavelength range of 400 nm to 800 nm, in a predetermined ratio. Therefore, when observed visually, both the reflected light of the first cholesteric liquid crystal pigment having a narrow selective reflection band and the reflected light of the second cholesteric liquid crystal pigment having a wide selective reflection band can be seen, and a color lighter than the color derived from the first cholesteric liquid crystal pigment can be seen. This effect is difficult to obtain even if two types of narrow-band cholesteric liquid crystal pigments are used. Therefore, according to the present invention, it is possible to provide a composite pigment that can realize an identification medium that is excellent in design and has a counterfeit prevention effect, since it is possible to express a pale color as described above and to express a counterfeit prevention effect.

[0110] In addition to visual evaluation, whether or not a color lighter than the color derived from the first cholesteric liquid crystal pigment can be quantitatively evaluated using a spectrophotometer or the like. Any color system can be used for quantitative evaluation, and for example, the XYZ color system or the L * a * b * A color system, etc. can be used. EXAMPLES

[0111] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples, and can be modified and practiced as desired without departing from the scope of the claims of the present invention and the scope of equivalents thereto. In the following description, the units "%" and "parts" are by weight unless otherwise specified. Furthermore, the operations described below were carried out in air at room temperature and normal pressure unless otherwise specified.

[0112] [Evaluation method] (Central wavelength of selective reflection band) 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. In the multilayer films A to F obtained in the following manufacturing examples 1 to 6, the layer of cholesteric liquid crystal resin was bonded to a black PET film with an adhesive layer (manufactured by Tomoegawa Paper 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. Next, the reflection spectrum of the liquid crystal resin layer was measured at an incidence angle of 5° using a spectrophotometer ("V570" manufactured by JASCO Corporation). From the obtained reflection spectrum, the half-width of the selective reflection band was obtained as the selective reflection bandwidth. That is, in the reflection spectrum, a base having a minimum intensity and a peak having a maximum intensity were determined, and the wavelength λ1 on the short wavelength side of the peak and the wavelength λ2 on the long wavelength side showing an intensity of minimum intensity + (maximum intensity - minimum intensity) / 2 were obtained, and the average value of these ((λ1 + λ2) / 2) was taken as the central wavelength of the selective reflection band of the cholesteric liquid crystal resin (pigment). In addition, the wavelength λ2 to wavelength λ1 was taken as the selective reflection band, and the width (the difference between λ2 and λ1: Δλ) was taken as the selective reflection bandwidth.

[0113] (Measurement of average particle size) The particle size distribution of each pigment was measured by a laser diffraction / scattering method, and the average particle size was measured from the particle size distribution. The measuring device used was a laser diffraction / scattering type particle size distribution measuring device (HORIBA, Ltd., LA-960).

[0114] (Determining the twist direction) The twist direction of each pigment was determined by observing the reflected light through left and right circular polarizers when non-polarized light was incident on the multilayer films A to F (films containing each pigment) obtained in Production Examples 1 to 6. That is, non-polarized light was irradiated onto the multilayer film from the observer side, and the reflected light that was reflected by the multilayer film and reached the observer side was observed. If the reflected light was right-handed circularly polarized, it was determined to be right-handed twisted, and if it was left-handed circularly polarized, it was determined to be left-handed twisted.

[0115] (Evaluation by visual observation) The discrimination media to be evaluated were visually observed under natural light, and the colors that were visible were evaluated.

[0116] (Evaluation of the reflective color of the identification medium: listed as "reflective characteristics" in the table) The reflection spectrum was measured at an incidence angle of 5° from the printed layer side of the discrimination medium to be evaluated using a spectrophotometer (V570 manufactured by JASCO Corporation). The obtained reflection spectrum was used to measure the L * a * b * Calculate the chromaticity coordinates, and then use the color difference based on the origin (Δa * b * ), and the color difference based on the chromaticity of the discrimination medium of Reference Examples 2 to 6 containing only the first cholesteric liquid crystal pigment (pigment A, C, D or E) (pigment 1 reference Δa * b * ), and the color difference based on the chromaticity of the discrimination medium of Reference Example 1 containing only the second cholesteric liquid crystal pigment (pigment B) (pigment 2 reference Δa * b * ) was calculated.

[0117] (STEP.1) The tristimulus values ​​X, Y, and Z were calculated using the measured reflectance spectrum R(λ) and the following equations (11) to (13).

[0118]

number

[0119] Here, S(λ) is the spectrum of the light source, and in this embodiment, the value of light source C is used. Also, x(λ), y(λ), and z(λ) represent color matching functions.

[0120] (STEP.2) Using the tristimulus values ​​X, Y, and Z calculated in STEP.1, * a * b * Color space luminosity L * , a * , b * The following formulas (14) to (16) were used for the calculation.

[0121]

number

[0122] where X n , Y n , Z n are the tristimulus values ​​calculated by equations (17) to (19), respectively.

[0123]

number

[0124] Also, f(X / X n ), f(Y / Y n ), f(Z / Z n ) are expressed by equations (20) to (22), respectively.

[0125]

number

[0126] Furthermore, for each example obtained, * , b * From the value of * b * ), the color difference based on the chromaticity of the identification medium containing only the first cholesteric liquid crystal pigment (pigment 1 standard Δa * b* ), the color difference based on the chromaticity of the identification medium containing only the second cholesteric liquid crystal pigment (pigment 2 standard Δa * b * ) was calculated. Δa * b * =((a * 1-a * 2) 2 +(b * 1-b * 2) 2 ) 1 / 2 ···(twenty three)

[0127] Origin reference Δa * b * When calculating, a in formula (23) * 1 is a for each example * , a * 2 is 0, b * 1 is the b of each example * , b * 2 indicates 0.

[0128] Pigment 1 standard Δa * b * When calculating, a in formula (23) * 1 is a for each example * , a * 2 is a of the identification medium containing only the pigment corresponding to the first cholesteric liquid crystal pigment used in each example * , b * 1 is the b of each example * , b * 2 is the identification medium b containing only the pigment corresponding to the first cholesteric liquid crystal pigment used in each example. * For example, the reference pigment 1 Δa * b * When calculating the a of the discrimination medium of Reference Example 2 containing only pigment A * and b * a * 2 and b * 2, and the reference Δa of Pigment 1 in Example 4 * b * When calculating the a of the discrimination medium of Reference Example 3 containing only pigment C, * and b * a * 2 and b* Let's say it's 2.

[0129] Pigment 2 standard Δa * b * When calculating, a in formula (23) * 1 is a for each example * , a * 2 is the a of the discrimination medium of Reference Example 1 (discrimination medium containing only the second cholesteric liquid crystal pigment) * , b * 1 is the b of each example * , b * 2 is the identification medium b of Reference Example 1 * Shows.

[0130] Origin reference Δa * b * is less than 25, pigment 1 standard Δa * b * is 5 or more and pigment 2 standard Δa * b * If the value is 10 or more, when the discrimination medium is visually observed, a color lighter than the color derived from the first cholesteric liquid crystal pigment can be visually recognized.

[0131] (Observation with a circular polarizer) The reflected light from the printed surface of the discrimination medium was observed through a left circular polarizing plate and a right circular polarizing plate. It was judged by visual inspection whether the reflected light was visible or not, and if it was visible, what color it appeared to be.

[0132] [Production Example 1: Production of multi-layer film A as a material for pigment A] As a support, a polyethylene terephthalate (PET) film ("Cosmoshine (registered trademark) A4100" manufactured by Toyobo Co., Ltd., thickness 100 μm) was prepared, and one side was subjected to a rubbing treatment. A liquid crystal composition (coating solution L1) containing liquid crystal compounds was prepared by mixing the materials shown in the table below. The liquid crystal compound (compound (B3)) and the compound of formula (2) (compound (A2)) are compounds represented by the following formulas.

[0133] [ka]

[0134] [Table 1]

[0135] (1-1. Coating process) The coating liquid L1 was applied onto 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 performed using a die coater, with the discharge amount adjusted so that the thickness of the liquid crystal composition layer before drying was 15 μm.

[0136] (1-2. Drying process) Next, the layer of the liquid crystal composition formed on the support was subjected to a drying step in which the layer was heated in an oven at 140° C. for 2 minutes.

[0137] (1-3. Polymerization process) After the drying process, a process of irradiating the liquid crystal composition layer with ultraviolet light from a high-pressure mercury lamp was carried out to polymerize the liquid crystal composition layer. The ultraviolet light irradiation conditions were as follows: in a nitrogen gas atmosphere with an oxygen concentration of 400 ppm or less, illuminance of 280 mW / cm at a wavelength of 365 nm. 2 The exposure dose at a wavelength of 365 nm was 2300 mJ / cm 2 It was decided.

[0138] By carrying out a polymerization process and curing the layer of the liquid crystal composition having cholesteric regularity, the cholesteric liquid crystal composition was cured while maintaining the cholesteric regularity, and a thin film of the cholesteric liquid crystal resin, which is a layer of the resin having cholesteric regularity, was formed. As a result, a multilayer film A having a structure of (support) / (thin film of cholesteric liquid crystal resin) was obtained. The thickness of the thin film of the cholesteric liquid crystal resin of the multilayer film A was 3 μm.

[0139] (Production Example 2: Production of multi-layer film B as a material for pigment B) (2-1. Coating process) In (1-1. Coating step) of Production Example 1, except that Coating Liquid L2 obtained by mixing the materials shown in the table below was used instead of Coating Liquid L1, and that the amount of Coating Liquid L2 discharged was adjusted so that the coating layer before drying had a thickness of 25 μm, a layer of a liquid crystal composition was formed on a support by carrying out the same operation as in (1-1) of Production Example 1.

[0140] [Table 2]

[0141] (2-2. Drying process) Next, the layer of the liquid crystal composition formed on the support was subjected to a drying step in which the layer was heated in an oven at 140° C. for 2 minutes.

[0142] (2-3. Wideband processing) After the drying process, the process of ultraviolet irradiation using a high-pressure mercury lamp and subsequent heat treatment at 100° C. for 1 minute was carried out twice.

[0143] The conditions for the first UV irradiation treatment were: in air, with an illuminance of 5 mW / cm at a wavelength of 365 nm. 2 The exposure dose at a wavelength of 365 nm was 300 mJ / cm 2 The second UV irradiation treatment was performed under the conditions of air atmosphere with an illuminance of 30 mW / cm at a wavelength of 365 nm. 2 The exposure dose at a wavelength of 365 nm was 1800 mJ / cm 2 The heat treatment was carried out in an oven.

[0144] (2-4. Polymerization process) After the band-widening treatment, a process of irradiating the liquid crystal composition layer with ultraviolet light using a high-pressure mercury lamp was carried out to polymerize the liquid crystal composition layer. The ultraviolet light irradiation conditions were as follows: in a nitrogen gas atmosphere with an oxygen concentration of 400 ppm or less, illuminance of 280 mW / cm at a wavelength of 365 nm. 2 The exposure dose at a wavelength of 365 nm was 2300 mJ / cm 2 It was decided.

[0145] By carrying out a polymerization process and curing the layer of the liquid crystal composition having cholesteric regularity, the cholesteric liquid crystal composition was cured while maintaining the cholesteric regularity, and a thin film of the cholesteric liquid crystal resin, which is a layer of the resin having cholesteric regularity, was formed. As a result, a multilayer film B having a structure of (support) / (thin film of cholesteric liquid crystal resin) was obtained. The thickness of the thin film of the cholesteric liquid crystal resin of the multilayer film B was 5 μm.

[0146] (Production Example 3: Production of multi-layer film C as a material for pigment C) The same operations as in Production Example 1 were carried out except that Coating Liquid L3 obtained by mixing the materials shown in the table below was used instead of Coating Liquid L1 in Production Example 1, to obtain a multilayer film C. The thickness of the thin film of the cholesteric liquid crystal resin in Multilayer Film C was 3 μm.

[0147] [Table 3]

[0148] (Production Example 4: Production of multilayer film D as a material for pigment D) The same operations as in Production Example 1 were carried out except that Coating Liquid L4 obtained by mixing the materials shown in the table below was used instead of Coating Liquid L1 in Production Example 1, to obtain a multilayer film D. The thickness of the thin film of the cholesteric liquid crystal resin in Multilayer Film D was 3 μm.

[0149] [Table 4]

[0150] (Production Example 5: Production of multilayer film E as a material for pigment E) The same operations as in Production Example 1 were carried out except that Coating Liquid L5 obtained by mixing the materials shown in the table below was used instead of Coating Liquid L1 in Production Example 1, to obtain a multilayer film E. The thickness of the thin film of the cholesteric liquid crystal resin in Multilayer Film E was 3 μm.

[0151] [Table 5]

[0152] The compound (3) contained in the coating liquid L5 is a compound represented by the following formula.

[0153] [ka]

[0154] (Production Example 6: Production of multilayer film F as a material for pigment F) The same operations as in Production Example 1 were carried out except that Coating Liquid L6 obtained by mixing the materials shown in the table below was used instead of Coating Liquid L1 in Production Example 1, to obtain a multilayer film F. The thickness of the thin film of the cholesteric liquid crystal resin in Multilayer Film F was 3 μm.

[0155] [Table 6]

[0156] [Production Example 7. Production of Pigments A to F] (Production of peeled pieces of thin films of cholesteric liquid crystal resin) Using the multilayer films A to F produced in Production Examples 1 to 6, peeled pieces of thin films of cholesteric liquid crystal resins were produced by the following method using the production apparatus shown in FIG. As shown in Fig. 1, a manufacturing apparatus 100 was prepared that included a film delivery unit 120, a peeling unit 130, and a film recovery unit 140. The peeling unit 130 included a bar 134 having a corner 135 formed at an acute angle, and a nozzle 136 capable of spraying air that was provided immediately downstream of the corner 135. In this case, the angle of the corner 135 of the bar 134 was set so that the multilayer film 110 could be folded back at an angle θ (60°). The corner had a chamfered structure with R = 0.2 mm to 0.3 mm.

[0157] Multilayer film 110 was attached to film delivery section 120 in a direction that allowed multilayer film 110 to be folded back with first cholesteric liquid crystal resin thin film 112 (or second cholesteric liquid crystal resin thin film) facing outward from support 111 (PET film) at corner portion 135 of bar 134. Then, multilayer film 110 was delivered from film delivery section 120 in a state in which tension was applied to multilayer film 110 in the transport direction by film recovery section 140. At this time, the magnitude of tension applied to multilayer film 110 was set to 80 N / m. Air was sprayed from nozzle 436 at a pressure of 0.5 MPa.

[0158] The multilayer film 110 was folded back at the corners 135 of the bar 134, and many cracks were formed. Thereafter, the thin film 112 of the first cholesteric liquid crystal resin (or the thin film of the second cholesteric liquid crystal resin) in which the cracks were formed was peeled off and blown away by air jetted from a nozzle 136, and a peeled piece 111A was obtained.

[0159] (Pigment manufacturing) The peeled piece 111A was collected, pulverized with a cutter mill, and classified with a 51 μm sieve, and only the particles that passed through the sieve were collected to obtain a pigment. The average particle size, center wavelength of the selective reflection band, selective reflection band, and selective reflection bandwidth of the obtained pigment were measured. The results are shown in Tables 7 to 11. From these measurement results, pigments A, C, D, E, and F were first cholesteric liquid crystal pigments having a center wavelength of the selective reflection band within a wavelength range of 400 nm or more and 800 nm or less, and a selective reflection bandwidth of 150 nm or less. Pigment B was a second cholesteric liquid crystal pigment having a selective reflection bandwidth of 200 nm or more within a wavelength range of 400 nm or more and 800 nm or less.

[0160] The color derived from pigment A was green, the color derived from pigment B was silver, the color derived from pigment C was blue, the color derived from pigment D was red, the color derived from pigment E was green, and the color derived from pigment F was red.

[0161] [Reference examples 1~6] (Preparation of Ink Composition) Using the pigments A to F produced in Production Example 7, ink compositions were prepared by the following method. The pigments and binders (UV-curable binders, Jujo Chemical Co., Ltd.'s "Raycure OP 4300-2" series FG-20SC thick medium) shown in Tables 7 and 8 were mixed to prepare ink compositions with a solids concentration of 10%.

[0162] (Manufacture of identification media) The prepared ink composition was screen-printed on a substrate (black paper). A screen plate with 120 thousandths 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 ultraviolet light irradiation conditions were as follows: in a nitrogen gas atmosphere with an oxygen concentration of 400 ppm or less, illuminance of 280 mW / cm at a wavelength of 365 nm. 2 The exposure dose at a wavelength of 365 nm was 400 mJ / cm 2 It was decided. The obtained discrimination media of Reference Examples 1 to 6 were visually observed, evaluated for reflection characteristics, and observed with a polarizing plate. The evaluation results and information on the pigment used in each example (type, center wavelength of selective reflection band, selective reflection band, selective reflection bandwidth, average particle size, and twist direction) are shown in the following table.

[0163] [Table 7]

[0164] [Table 8]

[0165] [Examples 1 to 9, Comparative Examples 1 to 2] (Preparation of Ink Composition) An ink composition was prepared by the following method using pigment A, C, D, E or F produced in Production Example 7 as the first cholesteric liquid crystal pigment and pigment B produced in Production Example 7 as the second cholesteric liquid crystal pigment. An ink composition with a solid concentration of 10% was prepared by mixing the first cholesteric liquid crystal pigment, the second cholesteric liquid crystal pigment, and a binder (UV curable binder, Jujo Chemical Co., Ltd.'s "Raycure OP 4300-2" series FG-20SC thick medium) shown in Tables 9 to 11. The content of the first cholesteric liquid crystal pigment relative to the total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment was set to the amount shown in Tables 9 to 11 (shown as "content of first cholesteric liquid crystal pigment" in the tables).

[0166] (Manufacture of identification media) The prepared ink composition was screen-printed on a substrate (black paper). A screen plate with 120 thousandths 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 ultraviolet light irradiation conditions were as follows: in a nitrogen gas atmosphere with an oxygen concentration of 400 ppm or less, illuminance of 280 mW / cm at a wavelength of 365 nm. 2 The exposure dose at a wavelength of 365 nm was 400 mJ / cm 2 It was decided. The obtained discrimination medium was visually observed, and the reflection characteristics were evaluated, and the discrimination medium was observed using a polarizing plate.

[0167] [result] The following table shows the evaluation results of the examples and comparative examples, as well as information on the pigments used in each example (type, center wavelength of selective reflection band, selective reflection band, selective reflection bandwidth, average particle size, and twist direction).

[0168] [Table 9]

[0169] [Table 10]

[0170] [Table 11]

[0171] From the above results, the following points can be seen. In the discrimination medium containing the composite pigment of the present invention, a color lighter than the color derived from the first cholesteric liquid crystal pigment was visible by visual observation, and a difference in hue of the reflected light of the discrimination medium by the left and right circular polarizers was observed by circular polarizer observation. In contrast, in Comparative Example 1, in which the content of the first cholesteric liquid crystal pigment is less than that specified in the present invention, the color derived from the second cholesteric liquid crystal pigment was visible by visual observation, but a color lighter than the color derived from the first cholesteric liquid crystal pigment was not visible. In Comparative Example 2, in which the content of the first cholesteric liquid crystal pigment is greater than that specified in the present invention, the color derived from the first cholesteric liquid crystal pigment was visible by visual observation, but a color lighter than the color derived from the first cholesteric liquid crystal pigment was not visible. From the above results, it is apparent that the present invention can realize an identification medium that is excellent in design and has an anti-counterfeiting effect. [Explanation of symbols]

[0172] 100 Manufacturing equipment for peeled pieces of thin resin films 110 Multi-layer film 111 Support 112 Thin film of first cholesteric liquid crystal resin 113 Crack 114 Peeling Piece 120 Film sending section 130 Peeling part 131 Stripping Room 132 Slit 133 Slit 134 Bar 135 Bar corner 136 Nozzle 137 Recovery Route 140 Film Collection Section 141 Winding core

Claims

1. a first cholesteric liquid crystal pigment; and a second cholesteric liquid crystal pigment, both the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment are flakes; The average particle size of the flakes is 20 μm or more and 120 μm or less, the first cholesteric liquid crystal pigment has a selective reflection band center wavelength in a wavelength range of 400 nm or more and 800 nm or less, and a selective reflection band width of 150 nm or less; the second cholesteric liquid crystal pigment has a selective reflection bandwidth of 200 nm or more within a wavelength range of 400 nm or more and 800 nm or less; a selective reflection band of the first cholesteric liquid crystal pigment and a selective reflection band of the second cholesteric liquid crystal pigment at least partially overlap with each other; A composite pigment, wherein a content of the first cholesteric liquid crystal pigment is more than 30% by weight and 75% by weight or less with respect to a total amount of the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment, A composite pigment comprising as the flakes a mixture of flakes of the first cholesteric liquid crystal pigment and flakes of the second cholesteric liquid crystal pigment.

2. The composite pigment according to claim 1 , wherein the first cholesteric liquid crystal pigment has a selective reflection bandwidth of 120 nm or less.

3. 3. The composite pigment according to claim 1, wherein the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment have the same twist direction.

4. 3. The composite pigment according to claim 1, wherein the first cholesteric liquid crystal pigment and the second cholesteric liquid crystal pigment have different twist directions.

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

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

7. A method for determining authenticity of an identification medium according to claim 6, comprising the steps of: The method for determining authenticity includes a step 1 of observing the reflected light from the identification medium through a left circular polarizing plate and a right circular polarizing plate, and determining whether or not there is a difference in one or more selected from the hue, brightness, and saturation of the reflected light.

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