Ink composition and printed matter

Abstract

To provide an ink composition capable of forming a chromatic color ink coating film having an infrared absorption characteristic, and preventing forgery using a carbon black-containing ink composition, and to provide a printed matter.SOLUTION: An ink composition containing cesium tungstic oxide and a coloring pigment is such that: an ink coating film formed by the ink composition has an infrared reflectance of a wavelength of 850 nm of 30% or less; and coordinates (L*,a*,b*) of the CIE1976 L*a*b* color space are in the outsides of a plane 1 including a coordinate AEH shown in a table 1, a plane 2 including AHD, a plane 3 including DGH, a plane 4 including DCG, a plane 5 including AFE, a plane 6 including ABF, a plane 7 including ABD, a plane 8 including DCB, a plane 9 including FEH, and a plane 10 including HGF.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an ink composition having an effect of absorbing infrared rays and a printed matter.

Background Art

[0002] Banknotes, travel documents, stock certificates, gift certificates, revenue stamps, postage stamps, various tickets, and other valuable securities have a monetary value, and thus are required to be provided with advanced anti-counterfeiting technologies and authenticity discrimination technologies. As these anti-counterfeiting technologies and authenticity discrimination technologies, there are widely used authenticity discrimination methods such as visually or mechanically discriminating a coating film of an ink composition having absorption characteristics in a specific wavelength region to distinguish between a counterfeit product and a genuine product.

[0003] For example, in order to surely detect and determine authenticity with an authenticity discrimination device that is processed at high speed such as a cash processing machine, a method of using a coating film of an ink composition having infrared absorption characteristics of a certain amount or more is known. In this case, for example, a method of forming a line by suppressing the thickness of an ink coating film using an ink composition containing a large amount of an infrared absorbing pigment is used.

[0004] For example, as a technique for visually discriminating authenticity, there is known a method that uses the fact that when appropriately selecting a light source for illumination, a plurality of printed portions may appear the same color or different colors. For example, two or more ink compositions having characteristics of conditional metamerism (metameric pair ink (ink in which inks having different color developing components etc. are included in a pair although the apparent color is usually the same)) are used, and absorption characteristics in a specific wavelength region of the pigments contained in the ink compositions are used. Although they appear to be the same color under normal light, when different light sources are used or when viewed through a color filter, the ink coating films by the metameric pair ink appear different colors from each other, and are also reproduced as different colors by a color copier, and this action enables visual discrimination of the authenticity of a printed matter.

[0005] As a technique for discriminating between counterfeits and genuine products by visually or mechanically discriminating a coating film of an ink composition having absorption characteristics in a specific wavelength region, the following are known. Patent Document 1 describes an infrared-absorbing transparent ink composition containing cesium tungsten oxide (Cs 0.33 WO3) and an infrared-absorbing black ink composition containing cesium tungsten oxide (Cs 0.33 WO3) and a black organic pigment. Patent Document 2 describes an ink composition containing antimony-doped tin oxide and an organic dye. Patent Document 3 describes using an ink composition containing carbon black to impart an image having infrared absorption characteristics to a metametric pair print.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] The infrared-absorbing transparent or black ink composition of Patent Document 1 does not use a colored pigment and cannot form an ink coating film with vivid and bright colors. Therefore, when simply mixing and using a colored pigment to make the ink composition of Patent Document 1 have vivid and bright colors, there is a risk that a printed matter having the same effect of absorbing infrared rays may be counterfeited by using carbon black instead of cesium tungsten oxide and mixing a colored pigment of a desired color.

[0008] In addition, since the ink composition of Patent Document 2 does not contain cesium tungsten oxide and further uses an organic dye, there is a possibility that the color tone may change over time as compared with the case of using a coloring pigment.

[0009] In addition, the ink composition and the printed matter of Patent Document 3 contain carbon black. When the infrared absorption characteristics are enhanced, the amount of carbon black used increases, resulting in an ink composition with a high black density and low brightness. Therefore, the color tone of the ink film becomes dark, and the color and designability are restricted.

[0010] The problems to be solved by the present invention are to provide an ink composition and a printed matter that can form a colored ink film having infrared absorption characteristics and can prevent forgery using an ink composition containing carbon black. Further, in a printed matter having a metameric effect, it is possible to determine authenticity in the infrared wavelength range, form a printed pattern with unrestricted colors, and provide a printed matter that can prevent forgery of a printed matter having a metallic effect using an ink composition containing carbon black. [Means for Solving the Problems]

[0011] As a result of intensive studies to solve the above problems, the inventors have found that (a) an ink film formed from an ink composition containing cesium tungsten oxide and a coloring pigment satisfies specific requirements, and (b) on a substrate, an ink film formed from an ink composition containing cesium tungsten oxide and a coloring pigment satisfies specific requirements, and have found that the above problems can be solved, leading to the completion of the present invention. That is, the present invention provides the following ink composition and printed matter.

[0012] [Item 1] An ink composition containing cesium tungsten oxide and a coloring pigment, wherein the ink film formed by the ink composition satisfies the following requirements (1) and (2). (1) The infrared reflectance at a wavelength of 850 nm is 30% or less. (2) CIE1976 L * a * b * The coordinates of the color space (L * , a * , b * ) are outside the planes 1 including the following coordinates AEH, 2 including AHD, 3 including DGH, 4 including DCG, 5 including AFE, 6 including ABF, 7 including ABD, 8 including DCB, 9 including FEH, 10 including HGF, and the coordinates A to H are respectively shown in Table 1;

Table 1

[0013] [Item 2] An ink composition containing cesium tungsten oxide and a coloring pigment, wherein the ink film formed by the ink composition satisfies the following requirements (3) and (4). (3) The reflectance of infrared rays with a wavelength of 850 nm is higher than 30% and 50% or less. (4) CIE1976 L * a * b * The coordinates of the color space (L * , a * , b * ) are outside the planes 1 including the following coordinates A’E’H’, 2 including A’H’D’, 3 including D’G’H’, 4 including D’C’G’, 5 including A’F’E’, 6 including A’B’F’, 7 including A’B’D’, 8 including D’C’B’, 9 including F’E’H’, 10 including H’G’F’, and the coordinates A’ to H’ are respectively shown in Table 2;

Table 2

[0014] [Item 3] The ink composition according to Item 1 or Item 2, wherein the ink film formed by the ink composition further satisfies the following requirement (5). (5) CIE1976 L* a * b * The coordinates (L * , a * , b * ) of the color space are inside the planes 1 including the following coordinates aeh, 2 including ahd, 3 including dgh, 4 including dcg, 5 including afe, 6 including abf, 7 including abd, 8 including dcb, 9 including feh, and 10 including hgf, and the coordinates a to h are respectively shown in Table 3;

Table 3

[0015] [Item 4] A printed matter having an ink coating film formed from an ink composition containing cesium tungsten oxide and a coloring pigment on a substrate, and the ink coating film satisfies the following requirements (6) and (7). (6) The infrared reflectance at a wavelength of 850 nm is 30% or less. (7) CIE1976 L * a * b * The coordinates (L * , a * , b * ) of the color space are outside the planes 1 including the following coordinates AEH, 2 including AHD, 3 including DGH, 4 including DCG, 5 including AFE, 6 including ABF, 7 including ABD, 8 including DCB, 9 including FEH, and 10 including HGF, and the coordinates A to H are respectively shown in Table 4;

Table 4

[0016] [Item 5] A printed matter having an ink coating film formed from an ink composition containing cesium tungsten oxide and a coloring pigment on a substrate, and the ink coating film satisfies the following requirements (8) and (9). (8) The reflectance of infrared rays at a wavelength of 850 nm is higher than 30% and 50% or less. (9) CIE1976 L *a * b * The coordinates (L * , a * , b * ) of the color space are outside the planes 1 including the following coordinates A’E’H’, 2 including A’H’D’, 3 including D’G’H’, 4 including D’C’G’, 5 including A’F’E’, 6 including A’B’F’, 7 including A’B’D’, 8 including D’C’B’, 9 including F’E’H’, and 10 including H’G’F’. The coordinates A’ to H’ are respectively shown in Table 5;

Table 5

[0017] [Item 6] The printed matter according to item 4 or item 5, wherein the ink film formed by the ink composition on the substrate further satisfies the following requirement (10). (10) CIE1976 L * a * b * The coordinates (L * , a * , b * ) of the color space are inside the planes 1 including the following coordinates aeh, 2 including ahd, 3 including dgh, 4 including dcg, 5 including afe, 6 including abf, 7 including abd, 8 including dcb, 9 including feh, and 10 including hgf. The coordinates a to h are respectively shown in Table 6;

Table 6

[0018] [Item 7] The printed matter according to items 4 to 6, comprising a first pattern formed by an ink film formed from an ink composition containing cesium tungstate oxide and a coloring pigment, and a second pattern that is isochromatic with the first pattern under visible light, wherein the first pattern and the second pattern have different spectral reflectances in the red wavelength range and a hue angle of -52 degrees to 92 degrees.

Effect of the Invention

[0019] According to the present invention, it is possible to form a colored ink film having infrared absorption characteristics, and to provide an ink composition and a printed matter capable of preventing forgery using an ink composition containing carbon black. Further, in a printed matter having a metameric effect, it is possible to determine authenticity in the infrared wavelength range, to form a printed pattern with unlimited colors, and to provide a printed matter capable of preventing forgery of a printed matter having a metameric effect using an ink composition containing carbon black.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments for carrying out the present invention will be described in detail. It should be understood that the present invention is not limited to the following embodiments, and includes various modifications implemented without changing the gist of the present invention.

[0022] [Ink Composition] The ink composition of the present invention is an ink composition containing cesium tungsten oxide and a coloring pigment, and is an ink composition that satisfies the following requirements when an ink film having a predetermined thickness is formed. Note that the characteristics of the ink film have two forms, which will be described in order.

[0023] (Characteristic 1 of Ink Film) The characteristics of the first ink coating satisfy the following requirements (1) and (2). (1) The reflectance of infrared rays with a wavelength of 850 nm is 30% or less. (2) CIE1976 L * a * b * The coordinates in the color space (L * , a * , b * ) are outside the planes 1 including the following coordinates AEH, 2 including AHD, 3 including DGH, 4 including DCG, 5 including AFE, 6 including ABF, 7 including ABD, 8 including DCB, 9 including FEH, and 10 including HGF, and the coordinates A to H are shown in Table 7 respectively;

Table 7

[0024] The reason for setting the reflectance of infrared rays with a wavelength of 850 nm in the ink coating to 30% or less is to enable stable reading by an optical sensor generally used for reading infrared absorption characteristics in an environment where the medium to which the ink coating is applied is conveyed at high speed. The infrared reflectance of the ink coating can be measured, for example, by the method described in the examples.

[0025] (CIE1976 L * a * b * The coordinates in the color space (L * , a * , b * )) In the present invention, regarding the color characteristics of the ink coating, the CIE1976 L * a * b * color space is used for representation. In the CIE1976 L * a * b * color space, the lightness is L * , and the chromaticity indicating the hue and saturation is a * and b * . The lightness L *is in the range of 0 to 100, where 0 indicates the black direction and 100 indicates the white direction. Chromaticity a * and b * indicate the color direction, and the +a * direction is the red direction, the -a * direction is the green direction, the +b * direction is the yellow direction, and the -b * direction is the blue direction. As the absolute values of the numerical values of a * and b * increase, the color becomes more vivid, and as the absolute values decrease (when the numerical values of a * and b * approach 0), the color becomes duller. Note that the chroma is represented by the square root of the sum of the square of the value of a * and the square of the value of b * . The CIE1976 L * a * b * coordinates in the color space (L * , a * , b * ) can be measured, for example, by the method described in the examples below.

[0026] In the present invention, the color configuration on the outside of a plurality of planes including the CIE1976 L * a * b * coordinates in the color space (L * , a * , b * ) will be described. FIG. 1(a) is a schematic diagram of the color space of a plane connecting the hypothetical coordinates A0 to H0 different from the coordinates shown in Table 7. For easy explanation of the coordinates in the color space, an example is shown where the shape connecting the coordinate points A0 to H0 is a cube. The cube shown in FIG. 1(a) is surrounded by plane 1 including coordinates A0B0C0D0, plane 2 including coordinates C0D0G0H0, plane 3 including coordinates D0G0E0A0, plane 4 including coordinates A0E0F0B0, plane 5 including coordinates C0H0F0B0, and plane 6 including coordinates H0G0E0F0. The outside of the plurality of planes refers to the colors outside planes 1, 2, 3, 4, and 5, and does not include the outside of plane 6 on the side with lower brightness in the cube.

[0027] Figure 1(b) is a diagram for explaining the outer color with respect to Planes 1 to 5. For Plane 1, the color is in the direction of arrow (V1) where the value of lightness L * increases. For Plane 2, the color is in the direction of arrow (V2) (the direction where the value of -a * increases). For Plane 3, the color is in the direction of arrow (V3) (the direction where the value of -b * increases). For Plane 4, the color is in the direction of arrow (V4) (the direction where the value of a * increases). For Plane 5, the color is in the direction of arrow (V5) (the direction where the value of b * increases). Furthermore, the outer color with respect to Planes 1 to 5 may be a color that is common to Plane 1 and Plane 2 and is in the direction of arrow (V6) shown in Figure 1(b) (the direction where the value of L * increases and the value of -a * increases), or a color that is common to Plane 1 and Plane 4 and is in the direction of arrow (V7) (the direction where the value of L * increases and the value of a * increases). Also, it may be a color that is common to Plane 4 and Plane 5 and is in the direction (not shown) where the values of a * and b * increase, a color that is common to Plane 2 and Plane 3 and is in the direction (not shown) where the values of -a * and -b * increase, or a color that is common to Plane 1, Plane 4, and Plane 5 and is in the direction (not shown) where the values of lightness L * , a * , and b * increase. However, colors in the direction where the value of L * decreases are not included with respect to Planes 1 to 5.

[0028] Figure 2 is a schematic diagram of a three-dimensional figure connecting coordinates A to H shown in Table 7. Specifically, the plane connecting the points of each of coordinates A to H is a three-dimensional shape formed by the contact of triangular planes connecting three of the coordinates A to H. However, in Figure 2, for simplicity of explanation, a three-dimensional shape connecting four of the coordinates A to H is shown.

[0029] Even in the three-dimensional shape shown in Fig. 2, a color outside the planes 1 including the coordinates AEH, 2 including AHD, 3 including DGH, 4 including DCG, 5 including AFE, 6 including ABF, 7 including ABD, 8 including DCB, 9 including FEH, and 10 including HGF can be used as the color of the coating film, and for a part of the outer direction, it is indicated by the direction of the arrows (from v1 to v6). In Fig. 2, a part of the outer direction of the planes 1 to 10 is illustrated, but the outer direction with respect to each plane shown in Fig. 1(b) and the direction described in paragraph (0027) are the same with respect to the planes shown in Fig. 2. Note that since the region outside the GCBF surface on the side with lower lightness becomes a dark color, the effects of the present invention cannot be achieved.

[0030] The ink coating film of the present invention can be an ink composition with high lightness or chroma while having sufficient infrared absorption characteristics by printing an ink composition containing cesium tungsten oxide, and it becomes possible to widen the range of designability. The inventor of the present invention, when producing a coating film of an ink composition containing carbon black as an infrared absorbing pigment, when the reflectance of infrared rays with a wavelength of 850 nm is 30% or less, due to carbon black, the color of the ink composition becomes dark, and CIE1976 L * a * b * It has been found that it is difficult for the coordinates in the color space (L * ,a * ,b * ) to satisfy the color requirements outside the above planes. For this reason, the possibility of being counterfeited by an ink composition using carbon black can be reduced.

[0031] (Characteristic 2 of the ink coating film) The second characteristic of the ink coating film satisfies the following requirements (3) and (4). (3) The reflectance of infrared rays with a wavelength of 850 nm is higher than 30% and 50% or less. (4) CIE1976 L * a * b * The coordinates in the color space (L * ,a * ,b* ) is outside the planes 1 including the following coordinates A’E’H’, 2 including A’H’D’, 3 including D’G’H’, 4 including D’C’G’, 5 including A’F’E’, 6 including A’B’F’, 7 including A’B’D’, 8 including D’C’B’, 9 including F’E’H’, and 10 including H’G’F’, and the coordinates A’ to H’ are respectively shown in Table 8;

Table 8

[0032] Figure 3 is a diagram schematically showing a three-dimensional figure connecting each of the coordinates A’ to H’ shown in Table 8 and a three-dimensional figure connecting each of the coordinates A to H in Table 7 for comparison. In Figure 3, the three-dimensional figure connecting each of the coordinates A’ to H’ shown in Table 8 is indicated by a thick line, and the three-dimensional figure connecting each of the coordinates A to H shown in Table 7 has the same shape as Figure 2. As shown in Figure 3, the three-dimensional figure connecting each of the coordinates shown in Table 8 is, as a whole, in a direction with higher brightness than the three-dimensional figure connecting each of the coordinates shown in Table 7, and the absolute values of a * and b * tend to be larger. That is, the second ink coating film is brighter than the first ink coating film and has a higher chroma range of colors.

[0033] The reason for setting the reflectance of infrared rays with a wavelength of 850 nm in the ink coating film to be higher than 30% and not more than 50% is that, unlike the first form, it is for reading the infrared absorption characteristics of printed matter by an infrared camera or an infrared viewer. When using an infrared camera or an infrared viewer, since the observation environment is more stable than when reading the infrared rays of a medium conveyed at high speed, the pattern of the ink coating film can be obtained stably, and since a person's eyes can interpolate and discriminate slight scratches or dirt on the pattern, even if the infrared absorption characteristics are lower than those of the first configuration, discrimination can be performed.

[0034] Regarding the color range, which is a characteristic of the second ink coating film, by printing an ink composition containing cesium tungsten oxide, it is possible to obtain an ink composition that has sufficient infrared absorption characteristics while having a high brightness, thereby expanding the range of design possibilities. The inventor has also found that even when the reflectance of infrared light with a wavelength of 850 nm is 50%, the color of the ink composition becomes dark due to carbon black, and the coordinates (L * a * b * in the color space (L * , a * , b * ) have difficulty meeting the color requirements outside the above plane. When forming an ink coating film with a 50% infrared reflectance using an ink composition containing carbon black, compared to when forming an ink coating film with a 30% infrared reflectance using an ink composition containing carbon black, it is necessary to increase the amount of carbon black, and thus the range of colors of the ink coating film that can be reproduced at that time becomes narrower (duller colors, darker colors). Therefore, for the color range that cannot be reproduced by an ink composition containing carbon black when the infrared reflectance is 50% as described in Table 8, it cannot be reproduced even in the range where the infrared reflectance is 50% or less.

[0035] Regarding the infrared reflectance, it can be adjusted by the blending amount of cesium tungsten oxide contained in the ink composition and the film thickness of the ink. Regarding the color of the coating film, it can also be adjusted by the coloring pigment contained in the ink composition and the film thickness of the ink. In any case, as long as it is an ink composition that satisfies the requirements of (1) and (2) or (3) and (4) above, it has an effect that cannot be reproduced by an ink composition containing carbon black. Regarding the thickness of the ink coating film for the ink coating film to satisfy the above-mentioned infrared reflectance and color requirements, it may be within the range that can be formed by the method of printing the ink composition described later. For example, in the case of offset printing where the ink coating film becomes thinner, the thickness of the ink coating film is about 0.5 μm to 2 μm. In the case of screen printing where the ink coating film can be made thicker, the ink coating film can be printed up to 200 μm. In each printing method, it is sufficient to satisfy the infrared reflectance and color requirements.

[0036] <Cesium tungsten oxide> Cesium tungsten oxide is preferably a compound represented by the following general formula (composition formula) (I). M x W y O z ···(I) M represents a metal containing cesium, W represents tungsten, and O represents oxygen. 0.001 ≦ x / y ≦ 1.1 2.2 ≦ z / y ≦ 3.0 M is a metal containing cesium, and examples of metals other than cesium include one or more selected from the group consisting of alkali metals, alkaline earth metals, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Sn, Pb, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, etc.

[0037] When x / y is 0.001 or more, infrared rays can be sufficiently shielded, and when it is 1.1 or less, the generation of impurity phases in cesium tungsten oxide can be more reliably avoided. When z / y is 2.2 or more, the chemical stability as a material can be further improved, and when it is 3.0 or less, infrared rays can be sufficiently shielded.

[0038] The fine particles of cesium tungsten oxide represented by the above general formula (I) have excellent durability when having a crystal structure of hexagonal, tetragonal, or cubic crystal, so it preferably contains one or more crystal structures selected from the hexagonal, tetragonal, and cubic crystals, and particularly preferably has a hexagonal crystal structure. Specific examples of cesium tungsten oxide represented by the above general formula (I) include Cs 0.33 WO3, etc.

[0039] Cesium tungsten oxide is preferably in the form of fine particles. The volume average particle diameter of cesium tungsten oxide is 800 nm or less, preferably 200 nm or less, more preferably 100 nm or less. When the volume average particle diameter is within such a range, cesium tungsten oxide is less likely to block visible light by light scattering, so that the light transmittance in the visible light region can be made more reliable. From the viewpoint of avoiding light scattering, the smaller the average particle diameter, the better. However, due to manufacturing costs, ease of handling, etc., the volume average particle diameter of cesium tungsten oxide is usually 1 nm or more. Commercially available products may be used for cesium tungsten oxide. For example, YMF-02, YMF-02A, YMS-01A-2, YMF-10A-1, YMDF-05A, YMDS-874, YMW-D20, etc. manufactured by Sumitomo Metal Mining Co., Ltd. can be used.

[0040] The content of cesium tungsten oxide in the ink composition may be adjusted according to the use, the function of the ink film, etc. Even when forming a coating film with the same infrared reflectance, if the content of cesium tungsten oxide is small, a correspondingly thicker film thickness can be used to cope, and if the content of cesium tungsten oxide is large, a thinner film thickness can be used to cope. In the present invention, it is necessary to form a coating film with an infrared reflectance of 50% or less, and at least when the total solid content of the ink composition is 100% by mass, it is necessary to be 0.1% by mass or more. On the other hand, if the content of cesium tungsten oxide in the ink composition exceeds 10% by mass when the total solid content of the ink composition is 100% by mass, the haze value of the ink coating film may decrease, which may affect the transparency and color tone of the ink coating film. Therefore, it is preferably 10% by mass or less.

[0041] <Coloring pigment> The coloring pigment, which is a constituent of the ink composition of the present invention, is not particularly limited. Appropriate ones are used from inorganic pigments and organic pigments in order to obtain a desired color.

[0042] As inorganic pigments, for example, carbon black, titanium oxide, zinc oxide, red iron oxide, calcium carbonate, barium sulfate, silica, clay, talc, alumina, zinc yellow, ultramarine blue, graphite, aluminum powder, etc. can be used. As organic pigments, for example, azo-based, diazo-based, condensed azo-based, azomethine-based, indanthrone-based, carbonyl-based, anthraquinone-based, nitro-based, phthalocyanine-based, indigo-based, thioindigo-based, benzodifuranone-based, benzimidazolone-based, methine-based, polyene-based, polymethine-based, dioxazine-based, quinacridone-based, isoindoline-based, quinophthalone-based, perylene-based, perinone-based, triallylmethane-based, diketopyrrolopyrrole-based, carotenoid-based, etc. can be used. The coloring pigment may be used alone or in combination of two or more thereof.

[0043] The content of the coloring pigment in the ink composition is not particularly limited as long as it satisfies the above requirements (1) and (2) or requirements (3) and (4), and it may be blended and used according to the desired color of the ink film. However, considering the printability of the ink composition on the printing substrate and the hardness of the ink film, when the total solid content of the ink composition is 100% by mass, it is 50% by mass or less, preferably 40% by mass or less.

[0044] <Solvent> The ink composition of the present invention may contain a solvent for the purpose of viscosity adjustment, imparting printability, etc. As the solvent, for example, mineral oil, alcohol-based solvent, ether-based solvent, ester-based solvent, hydrocarbon-based solvent, etc. can be used.

[0045] <Other components> The ink composition of the present invention may, if necessary, contain pigments other than "cesium tungsten oxide and coloring pigments" (hereinafter sometimes referred to as "other pigments"), film-forming components such as resins and photopolymerizable compounds, gelling agents, surfactants, antioxidants, anti-settling agents, defoaming agents, anti-blocking agents, magnetic materials, luminescent materials, conductive materials, desiccants, etc. In the present invention, only one of these other components may be used alone, or two or more of them may be used in combination.

[0046] When the ink composition of the present invention forms an ink coating film of a predetermined thickness, it is preferable that the ink coating film further satisfies the following requirement (5). (5) CIE1976 L * a * b * The coordinates in the color space (L * , a * , b * ) are inside the planes 1 including the following coordinates aeh, 2 including ahd, 3 including dgh, 4 including dcg, 5 including afe, 6 including abf, 7 including abd, 8 including dcb, 9 including feh, and 10 including hgf, and the coordinates a to h are respectively shown in Table 9;

Table 9

[0047] Each coordinate shown in Table 9 is a range of colors that can be reproduced using cyan ink, magenta ink, yellow ink, and black ink, which are process inks, as the coloring pigments contained in the ink composition. Cyan ink, magenta ink, yellow ink, and black ink are common and inexpensive, and since the range of colors that can be expressed is wide by combining inks of each color, they are preferable. In addition to the above process inks, by using special inks, colors outside the region shown in Table 9 can also be reproduced.

[0048] <Method for manufacturing ink composition> The manufacturing method of the ink composition of the present invention is not particularly limited as long as it can uniformly mix the constituent components of the ink composition. When mixing the constituent components in the manufacturing method of the ink composition, for example, mixers such as planetary mixers, tumblers, bead mills, sand mills, stirrers, agitators, mechanical homogenizers, ultrasonic homogenizers, paint shakers, V-type blenders, Nauta mixers, and three-roll mills can be used.

[0049] <Use of the ink composition> The ink composition of the present invention can be used as an anti-counterfeiting ink composition utilizing infrared absorption characteristics or a metameric pair ink composition. Examples of products to which the ink composition is applied include inks for printed matter that require anti-counterfeiting, such as banknotes (paper money), stamps, postage stamps, securities, identity certificates, passports, security labels, and cards.

[0050] [Printed matter] The printed matter of the present invention has an ink coating film formed from an ink composition containing cesium tungsten oxide and a coloring pigment on a substrate. The characteristics of the ink coating film are in two forms, which will be described in order.

[0051] The first characteristic of the ink coating film is a printed matter that satisfies the following requirements (6) and (7). (6) The reflectance of infrared rays with a wavelength of 850 nm is 30% or less. (7) CIE1976 L * a * b * The coordinates (L * , a * , b * ) in the color space are outside the planes 1 including the following coordinates AEH, 2 including AHD, 3 including DGH, 4 including DCG, 5 including AFE, 6 including ABF, 7 including ABD, 8 including DCB, 9 including FEH, and 10 including HGF, and the coordinates A to H are respectively shown in Table 10;

Table 10

[0052] The characteristics of the second ink coating film are those of a printed matter that satisfy the following requirements (8) and (9). (8) The reflectance of infrared rays with a wavelength of 850 nm is higher than 30% and 50% or less. (9) CIE1976 L * a * b * The coordinates (L * , a * , b * ) in the color space are outside the planes 1 including the following coordinates A’E’H’, 2 including A’H’D’, 3 including D’G’H’, 4 including D’C’G’, 5 including A’F’E’, 6 including A’B’F’, 7 including A’B’D’, 8 including D’C’B’, 9 including F’E’H’, and 10 including H’G’F’, and the coordinates A’ to H’ are shown in Table 11 respectively;

Table 11

[0053] The characteristics of the first ink coating film and the characteristics of the second ink coating film provided by the ink coating film formed on the printed matter of the present invention shown in Table 10 and Table 11 correspond to the infrared reflectance of the environment for reading the ink composition of the present invention described above and the range of colors that cannot be reproduced by the ink composition having each infrared reflectance. In the case of an ink composition containing carbon black.

[0054] Also, it is preferable that the ink coating film formed on the printed matter of the present invention further satisfies the following requirement (10). (10) CIE1976 L * a * b * The coordinates (L * , a * , b *) is inside the planes 1 including the following coordinates aeh, 2 including ahd, 3 including dgh, 4 including dcg, 5 including afe, 6 including abf, 7 including abd, 8 including dcb, 9 including feh, and 10 including hgf, and the coordinates a to h are respectively shown in Table 12;

Table 12

[0055] The characteristics of the ink coating film formed on the printed matter of the present invention shown in Table 12 are the range of colors that can be reproduced using cyan ink, magenta ink, yellow ink, and black ink, which are process inks. They are common and inexpensive, and the combination of inks of each color can also represent a wide range of colors, so they are preferable. In addition to the above process inks, by using special inks, colors outside the area shown in Table 12 can also be reproduced.

[0056] The base material is not particularly limited as long as it has a surface to which an ink coating film can be applied. For example, paper, plastic film, glass, metal, wood, composites thereof, etc. can be used. Also, the base material may be white or colored in colors such as red, blue, and yellow. However, in the printed matter of the present invention, when the color of the base material affects the color of the ink coating film (when the thickness of the ink coating film is thin, the color of the base material may be seen through), the color of the area where the ink coating film is applied only needs to satisfy the conditions of requirement (7) or requirement (9).

[0057] Regarding the tungsten oxide cesium, coloring pigment, and ink composition containing them, the reflectance of infrared rays with a wavelength of 850 nm, and CIE1976 L * a * b * coordinates in the color space (L * , a * , b * ) described above are the same as those described in [Ink Composition].

[0058] <Printing method> The printed matter of the present invention can be produced by using an ink composition containing cesium tungsten oxide and a coloring pigment and using a printing method such as intaglio printing, letterpress printing, offset printing, screen printing, flexographic printing, gravure printing, inkjet printing, etc. on a substrate.

[0059] <Use of the printed matter> The printed matter of the present invention is used for various purposes. In particular, it is used for security printed matter and printed matter that requires design, such as banknotes (paper money), stamps, postage stamps, securities, identity certificates, passports, security labels, etc. For example, it can be used for a printed matter that forms an ink coating film that absorbs infrared rays on a substrate and detects the absorption of infrared light to discriminate authenticity. In addition, although it is visually recognized as having the same color under visible light, it can be used for anti-counterfeiting printed matter having a metameric property that allows a pattern to be recognized when viewed under a specific light source or through a specific wavelength transmission filter.

[0060] When making an anti-counterfeiting printed matter having a metameric property, in the color range corresponding to the infrared reflectance shown in Table 10 or Table 11, a first pattern formed by an ink containing cesium tungsten oxide and a second pattern formed by a normal coloring ink such as cyan ink, magenta ink, yellow ink (not including carbon black and cesium tungsten oxide) are provided so as to have the same color when observed under visible light. The first pattern and the second pattern are formed by combining pigments having different spectral reflectances so as to have the same color under visible light, similar to conventional metameric pair inks, and blending them into the inks forming the respective patterns. In the present invention, "the same color" refers to a state where two colors are close enough that an observer feels they have the same color when observing the two patterns without paying attention. As a configuration where the colors of the two patterns are close and indistinguishable under visible light, the color difference ΔE (in the present invention, CIE1976L * a * b * by the color difference formula.) is preferably 7 or less, and more preferably 3 or less.

[0061] Examples of arranging the first pattern and the second pattern include arranging a predetermined design (characters, symbols, figures, etc., or ground patterns, colored patterns, etc.) in a negative-positive relationship, arranging two identical designs side by side, etc. As long as two patterns are arranged on the substrate, there is no particular limitation, and the first pattern and the second pattern may be arranged separately.

[0062] In the anti-counterfeiting printed matter having a metameric effect, as a condition of a specific light source or a characteristic wavelength transmission filter, a red wavelength range (610 nm to 700 nm) can be used. At this time, it is preferable because the contrast between the two patterns visually recognized when using a red light source or a red transmission filter becomes high. The colors of the ink films formed by the ink for forming the first pattern containing cesium tungsten oxide and the ink for forming the second pattern having the same color as this are in a hue from red-violet to yellowish-red. Specifically, the hue angle is in the range of 144 degrees from -52 degrees (red-violet) to 92 degrees (yellowish-red). In the present invention, the hue angle is CIE1976 L * a * b * In the color space, it is the angle representing each hue such as red, blue, and yellow. With respect to the a * axis as a reference, the counterclockwise direction is represented as a positive angle, and the clockwise direction is represented as a negative angle.

[0063] The above range of the hue angle is based on the hue of the red-violet ink that disappears when using a red light source or a red transmission filter (the hue angle is -52 degrees), and corresponds to the hue that can be expressed by mixing the yellow ink and the red ink that disappear when using a red light source or a red transmission filter. By appropriately mixing the yellow ink and the red ink with the red-violet ink, colors with a hue angle up to 92 degrees can be expressed. On the other hand, when mixing a blue ink that has no disappearing effect when using a red light source or a red transmission filter, the disappearing effect cannot be obtained, so this is used as the ink for forming the first pattern. The details of the ink formulation for forming a printed matter having a metameric effect will be described in the examples.

[0064] In an anti-counterfeiting printed matter having a metameric property, a first pattern formed by an ink containing cesium tungstate oxide and a second pattern having the same color as the first pattern are recognized as having the same color under visible light. However, when observed under a specific light source or through a specific wavelength transmission filter, a color difference between the two patterns occurs, enabling the authenticity to be discriminated thereby. Note that as the light source for irradiating the anti-counterfeiting printed matter with visible light, a fluorescent lamp or sunlight can be used. Further, when the anti-counterfeiting printed matter is observed under infrared light, the authenticity can be discriminated by confirming that the first pattern absorbs infrared rays at a predetermined ratio. That is, for a conventional printed matter having a metameric effect, it is possible to further discriminate authenticity using the wavelength of infrared rays, and an effect of improving the anti-counterfeiting effect can be obtained.

[0065] Hereinafter, according to the embodiments for carrying out the above-described invention, the present invention will be described in more detail with reference to examples and comparative examples of a specifically prepared ink composition and an ink film printed with the ink composition. However, the present invention is not limited to these examples. Note that unless otherwise specified, "parts" in each example are parts by mass and "%" is "% by mass".

Examples

[0066] [Ink raw materials] The ink raw materials used in the examples and comparative examples are as follows. Each ink raw material was blended at a predetermined ratio to prepare an ink composition, and the coatings formed by each ink composition were evaluated. Details of the examples and comparative examples will be described below.

[0067] <Cesium tungstate oxide paste (CWO paste)> Cesium tungstate oxide paste (Sumitomo Metal Mining Co., Ltd., CWO (registered trademark) YMDM-05A) was used. Note that the cesium tungstate oxide paste used in this example has a pigment concentration of cesium tungstate oxide of 65.9 wt%.

[0068] <Carbon black (CB)> A black pigment (No. 6UVL Carton Ink CW manufactured by T&K TOKA Co., Ltd.) was used.

[0069] <Yellow Ink> A yellow pigment (No. 6UVL Carton Yellow CW manufactured by T&K TOKA Co., Ltd.) was used.

[0070] <Red Ink> A red pigment (No. 6UVL Carton Red CW manufactured by T&K TOKA Co., Ltd.) was used.

[0071] <Blue Ink> A yellow pigment (No. 6UVL Carton Blue CW manufactured by T&K TOKA Co., Ltd.) was used.

[0072] <Fluorescent Medium> A fluorescent pigment (UV Fluorescent Medium B manufactured by T&K TOKA Co., Ltd.) was used.

[0073] [Evaluation of Ink Film] <Production of Printed Matter> The prepared ink composition was printed on high-quality paper at a printing speed of 1.0 m / min and a printing pressure of 20 kgf using a universal printing suitability tester (manufactured by Kumagai Riki Kogyo Co., Ltd.) to produce a printed matter. <Infrared Reflectance> Using a spectrophotometer (UH4150 manufactured by Hitachi High-Technologies Corporation), the infrared reflectance of the printed part of the obtained printed matter was measured. The wavelength of the infrared light was set to 850 nm, which is a wavelength generally used for authenticity determination of counterfeits. A lower numerical value of the infrared reflectance means a higher infrared absorption rate of the ink film.

[0074] <CIE1976 L * a * b * Color space coordinates (L * ,a * ,b * )> Using a Spectroeye spectrophotometer (manufactured by Gretag Macbeth), measurements were taken under the conditions of light source D65 and a viewing field of 10°. The L * value, a *Value and b * The value was obtained.

[0075] [Example 1] 15 parts of cesium tungsten oxide paste (Sumitomo Metal Mining Co., Ltd., CWO (registered trademark) YMDM-05A) and 85 parts of fluorescent magnesium were mixed using a mixer to prepare an ink composition. The composition of the obtained ink composition, the infrared reflectance of the coating film formed from the ink composition, and the CIE1976 L * a * b * Coordinates in the color space (L * , a * , b * ) are shown in Table 13.

[0076] [Examples 2 to 8, Comparative Examples 1 to 8] Regarding the ink compositions of Examples 2 to 8, ink compositions were prepared in the same manner as in Example 1, except that the constituent components of the ink compositions were the components described in Table 13, respectively. The infrared reflectance of the coating film formed from the ink composition and the CIE1976 L * a * b * Coordinates in the color space (L * , a * , b * ) are shown in Table 13. Regarding the ink compositions of Comparative Examples 1 to 8, carbon black was blended to achieve infrared reflection characteristics substantially equivalent to those of the ink compositions of Examples 1 to 8, and colored inks of each color were blended to obtain the same color. The composition, infrared reflectance, and CIE1976 L * a * b * Coordinates in the color space (L * , a * , b * ) and the film thickness of the coating film are shown in Table 14.

[0077]

Table 13

[0078]

Table 14

[0079] From Tables 13 and 14, it can be seen that the ink composition containing cesium tungsten oxide and a coloring pigment has a higher lightness L (a color tone in the white direction) than the comparative examples, and the absolute values of chromaticity a * and b * are large, indicating that a coating film with a high lightness and vivid color tone can be formed. On the other hand, when the ink composition containing carbon black has the same infrared reflectance as the ink composition containing cesium tungsten oxide and a coloring pigment, the lightness L * is small (a color tone in the dark direction), and it can be seen that the absolute values of chromaticity a * and b * are small. That is, it can be seen that the ink composition containing carbon black cannot reproduce the color of the ink composition containing cesium tungsten oxide. *

[0080] The infrared reflectance of the ink compositions of Comparative Examples 1 to 8 is about 33%. However, when making an ink composition with a lower reflectance (higher infrared absorption rate) than this, it is necessary to increase the blending amount of carbon black. Compared with the colors shown in Table 14, the value of lightness L * becomes smaller, and the absolute values of chromaticity a * and b * become smaller. That is, when the infrared reflectance of the coating film by the ink composition containing cesium tungsten oxide is set to 30% or less, it cannot be reproduced beyond the color range shown in Table 14.

[0081] In Examples 1 to 7, the film thickness of the ink coating film is generally 1 μm. However, as described above, depending on the printing method, a coating film with a film thickness of 0.5 to 200 μm can be formed. Therefore, according to the desired film thickness, adjust the blending amount of cesium tungsten oxide to make the infrared reflectance of the coating film 30% or less, and make an ink composition with a color that satisfies the above-mentioned requirement (2), thereby preventing forgery by the ink composition containing carbon black.

[0082] [Comparative Examples 9 - 16]​ Regarding the ink compositions of Comparative Examples 9 to 16, carbon black was blended so that the infrared reflectance would be 50%, and colored inks of each color were blended. The composition, infrared reflectance, and CIE1976 L * a * b * coordinates in the color space (L * ,a * ,b * ) are shown in Table 15.

[0083]

Table 15

[0084] The infrared reflectance of the ink compositions of Comparative Examples 9 to 16 is about 50%, and the blending amount of carbon black is less than that of the ink compositions of Comparative Examples 1 to 8. As a result, the ink film has a higher brightness and a vivid color than the ink compositions of Comparative Examples 1 to 8. However, for a coating film formed by an ink composition containing cesium tungsten oxide having an infrared reflectance similar to that of the ink compositions of Comparative Examples 9 to 16, since the cesium tungsten oxide paste is transparent, the value of L * and the value of chroma can reproduce a color with a higher value. That is, when the infrared reflectance of the coating film of the ink composition containing cesium tungsten oxide is 50% or less, it cannot reproduce beyond the color range shown in Table 15.

[0085] [Printed matter having a metameric effect in Examples 9 to 11] Examples 9 to 11 are examples of printed matter having a metameric effect. A first pattern was formed with an ink composition containing cesium tungsten oxide, and a second pattern having the same color as the first pattern was formed under visible light. Regarding the materials constituting each ink composition for forming the first pattern and the second pattern of the printed matter of Examples 9 to 11, the materials used in Examples 1 to 8 and a red-violet ink (Hostaperm Red Violet ER02 manufactured by Clariant) as an ink that disappears when a red light source or a red transmission filter is used were used and blended at the ratios shown in Table 16 to prepare each ink composition.

[0086] The infrared reflectance and CIE1976 L * a * b * coordinates in the color space (L * , a * , b * ) and the hue angle are shown in Table 16. The first pattern and the second pattern of Example 9 are red-violet, the first pattern and the second pattern of Example 10 are red, and the first pattern and the second pattern of Example 11 are light purple.

[0087]

Table 16

[0088] In the printed matters of Examples 9 to 11, when observed under visible light, the two patterns are of the same color and thus indistinguishable. However, when observed using a red filter (Sharp Cut Filter SC64 manufactured by Fuji Film), the second pattern disappears and cannot be seen, while the first pattern is confirmed without disappearing. This is because the CWO paste forming the first pattern is substantially transparent to the naked eye but contains a slight blue component, so it does not disappear when using a red filter. Also, when observed using a near-infrared camera (MS-40 manufactured by Nippon SDR Co., Ltd.), it was confirmed that the second pattern disappeared and only the first pattern could be visually recognized, enabling authenticity discrimination. The infrared reflectance of the ink compositions of Examples 9 to 11 was about 37%, and the CIE1976 L * a * b * coordinates (L * ,a * ,b * ) outside the range and with the hue angle in the range of -52 degrees to 92 degrees cannot be reproduced using carbon black.

[0089] As described above, the present invention has been described in detail. However, within the above configuration, various changes can be made without departing from the scope of the present invention. Therefore, all matters included in the above description or shown in the accompanying drawings should be construed as illustrative.

Explanation of Reference Numerals

[0090] 1 L * a * b * Plane 1 composed of provisional color coordinates in the color space 2 L * a * b * Plane 2 composed of provisional color coordinates in the color space 3 L * a * b * Plane 3 composed of provisional color coordinates in the color space 4 L* a * b * Plane 4 consisting of provisional color coordinates in color space 5 L * a * b * Plane 5 consisting of provisional color coordinates in color space 6 L * a * b * Plane 6 consisting of provisional color coordinates in color space A color coordinates (L * +61.0, a * +0.9, b * +4.1) B color coordinates (L * +44.4, a * +22.7, b * -3.4) C color coordinates (L * +36.9, a * +3.6, b * -14.4) D color coordinates (L * +49.2, a * -16.2, b * -13.4) E color coordinates (L * +56.5, a * -1.9, b * -34.4) F color coordinates (L * +47.9, a * +15.1, b * +9.8) G color coordinates (L * +47.6, a * -2.1, b * +0.8) H color coordinates (L * +48.9, a * -19.5, b * +11.0)

Claims

**Claim 1**: An ink composition containing cesium tungsten oxide and a coloring pigment, wherein the ink film formed by the ink composition satisfies the following requirements (3) and (4). (3) The reflectance of infrared rays with a wavelength of 850 nm is higher than 30% and 50% or less. (4) The coordinates (L*, a*, b*) in the CIE1976 L*a*b* color space are outside the planes 1 including the following coordinates A’E’H’, 2 including A’H’D’, 3 including D’G’H’, 4 including D’C’G’, 5 including A’F’E’, 6 including A’B’F’, 7 including A’B’D’, 8 including D’C’B’, 9 including F’E’H’, and 10 including H’G’F’, and the coordinates A’ to H’ are respectively shown in Table 2; 【Table 2】 It is as follows. **Claim 2**: The ink composition according to claim 1, wherein the ink film formed by the ink composition further satisfies the following requirement (5). (5) The coordinates (L*, a*, b*) in the CIE1976 L*a*b* color space are inside the planes 1 including the following coordinates aeh, 2 including ahd, 3 including dgh, 4 including dcg, 5 including afe, 6 including abf, 7 including abd, 8 including dcb, 9 including feh, and 10 including hgf, and the coordinates a to h are respectively shown in Table 3; 【Table 3】 It is as follows. **Claim 3**: A printed matter having an ink film formed from an ink composition containing cesium tungsten oxide and a coloring pigment on a substrate, wherein the ink film satisfies the following requirements (8) and (9). (8) The reflectance of infrared rays with a wavelength of 850 nm is higher than 30% and 50% or less. (9) The coordinates (L*, a*, b*) in the CIE1976 L*a*b* color space are outside the planes 1 including the following coordinates A’E’H’, 2 including A’H’D’, 3 including D’G’H’, 4 including D’C’G’, 5 including A’F’E’, 6 including A’B’F’, 7 including A’B’D’, 8 including D’C’B’, 9 including F’E’H’, and 10 including H’G’F’, and the coordinates A’ to H’ are respectively shown in Table 5; 【Table 5】 It is as follows. **Claim 4**: The printed matter according to claim 3, wherein the ink film formed by the ink composition on the substrate further satisfies the following requirement (10). The coordinates (L*, a*, b*) in the CIE1976 L*a*b* color space are inside the plane 1 containing the following coordinates aeh, the plane 2 containing ahd, the plane 3 containing dgh, the plane 4 containing dcg, the plane 5 containing afe, the plane 6 containing abf, the plane 7 containing abd, the plane 8 containing dcb, the plane 9 containing feh, and the plane 10 containing hgf, and the coordinates a to h are respectively shown in Table 6; 【Table 6】 That is. **Claim 5**: A printed matter according to claim 3 or 4, comprising a first pattern formed by an ink film formed from the ink composition containing cesium tungsten oxide and a coloring pigment, and a second pattern having the same color as the first pattern under visible light, wherein the first pattern and the second pattern have different spectral reflectances in the red wavelength range and a hue angle of -52 degrees to 92 degrees.

Images