Infrared Absorbing Ink Print

Abstract

To provide printed matter that is printed matter in which an information pattern is formed on a substrate with an infrared absorption ink and that makes an observer difficult to recognize the presence of the information pattern under visible light.SOLUTION: The present invention relates to infrared absorption ink printed matter that is printed matter 1 in which an information pattern 3 is formed on a base material 2 using an infrared absorption ink, wherein the infrared absorption ink contains at least cesium tungsten oxide, a coloring material that makes the hues of the base material and information pattern the same, and an extender pigment, and when the infrared reflectance when the information pattern formed on the base material is irradiated with a wavelength of 850 nm is less than 40%, a hue difference between the base material and the information pattern formed on the base material is 3.9 or less, and when the infrared reflectance is 40% or more, the hue difference is 2.7 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a printed matter using an infrared absorption ink that has absorption in the infrared region but no absorption in the visible region, and particularly to a printed matter that is difficult to visually recognize even when the ink is used alone.

Background Art

[0002] Security printed matters such as banknotes, passports, stamps, postage stamps, securities, identity certificates, various tickets, security labels, etc. 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 having absorption characteristics in a specific wavelength region to distinguish a counterfeit product from a genuine product.

[0003] As a technology related to authenticity discrimination for visually or mechanically discriminating a coating film of an ink having absorption characteristics in a specific wavelength region to distinguish a counterfeit product from a genuine product, for example, as an inexpensive and easily available material having a high infrared absorption effect in a small amount, it is generally known to form an information pattern on a security printed matter using a black ink containing a black pigment such as carbon black. The information held by this information pattern is read by irradiating infrared light and measuring the infrared reflected light.

[0004] However, since the information pattern printed with the infrared absorption ink using carbon black also has light absorbency under visible light, its presence is easily recognized visually. Therefore, it is not sufficient as a means for effectively preventing forgery and alteration.

[0005] Security prints are difficult to forge and alter because the presence of information patterns is difficult to discern. Therefore, in order to prevent information from being easily read by visible light, the information pattern made with infrared absorption ink using carbon black or the like is covered with a concealment layer that transmits infrared light, so that the information pattern is not visible under visible light. However, a technique is known in which the information pattern made with infrared absorption ink can be discriminated in the infrared region (see, for example, Patent Document 1).

[0006] However, in the technique such as Patent Document 1, even when the information pattern made with infrared absorption ink is covered with a concealment layer, the coating film of the concealment layer is visible. Therefore, further measures have been demanded as countermeasures against forgery and alteration. In addition, when a concealment layer is provided, not only specific wavelength light is blocked, but there is also a risk of affecting the reading of the information pattern in the lower layer.

[0007] Under such a technical background, as a technique that does not require a concealment layer and is difficult to visually recognize the presence of infrared absorption ink alone, the ink itself has little absorption under visible light and absorbs in other wavelength regions. In particular, as an infrared absorption material, an ink containing a pulverized heat ray absorption glass or infrared absorption glass and pigmented thereof is known. By forming an information pattern on a substrate using this infrared absorption ink, the information pattern on the substrate can be made difficult to see with the naked eye.

[0008] However, when an infrared absorption material such as the above heat ray absorption glass or infrared absorption glass is made into ink and an information pattern is formed on a printed matter, although the absorption under visible light is reduced, the absorption in the infrared region is inferior to that of conventional ink containing carbon black or the like. Therefore, it is necessary to increase the film thickness in order to improve the absorbency in the infrared region. However, when the film thickness of the ink is increased, a step is generated between the substrate and the portion where the information pattern is formed, and the presence of the information pattern can be easily understood due to the step caused by the film thickness.

[0009] Therefore, in recent years, as the infrared absorption ink other than the above, cesium tungstate (Cs0.33 There is known a forgery-proof printed matter using an infrared-absorbing transparent ink containing WO3 (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, according to the technique of Patent Document 2, although the infrared-absorbing transparent ink containing cesium tungstate (Cs 0.33 WO3) has excellent absorption characteristics in the infrared region and high transparency, it is not colorless and transparent but exhibits a slight blue tint. Therefore, when a printed matter in which an information pattern is formed on a substrate using the ink alone is visually observed under visible light, the information pattern formed by the ink can be visually recognized even if it is a thin coating film. And when a large amount of cesium tungstate is blended in the ink, the information pattern is significantly visually recognized.

[0012] Also, although the technique of Patent Document 2 describes that the infrared-absorbing ink can contain a coloring pigment that transmits near-infrared light, and the colored infrared-absorbing ink can visually recognize the same color as the coloring pigment in the visible light region, a configuration for making it difficult to easily read information under visible light is not described.

[0013] Therefore, the problem to be solved by the present invention is to provide a printed matter in which an information pattern is formed on a substrate only with an infrared-absorbing ink without requiring a concealment layer as in the prior art, and in which the presence of the information pattern under visible light is difficult to be visually recognized, and to provide a printed matter with an improved forgery-proof effect and alteration-proof effect.

Means for Solving the Problems

[0014] As a result of intensive studies to solve the above problems, the inventors have found that the above problems can be solved by a printed matter in which an ink coating film formed from an ink composition containing cesium tungsten oxide and a coloring pigment on a substrate satisfies specific requirements, and have completed the present invention. That is, the present invention provides the following printed matter.

[0015] The infrared absorption ink printed matter of the present invention is an infrared absorption ink printed matter in which an information pattern is formed by an ink containing a material having infrared absorption characteristics on at least a part of a substrate, The aforementioned ink contains cesium tungsten oxide, which is at least a material having infrared absorption characteristics, a coloring material for making the hue of the substrate and the information pattern equal in color, and an extender pigment. When the infrared reflectance when irradiated with a wavelength of 850 nm on the information pattern formed on the substrate is less than 40%, the CIE1976L of the substrate and the information pattern formed on the substrate * a * b * The color difference represented as the distance on the ab plane in the color space is characterized by being 3.9 or less.

[0016] Also, the infrared absorption ink printed matter of the present invention is an infrared absorption ink printed matter in which an information pattern is formed by an ink containing a material having infrared absorption characteristics on at least a part of a substrate. The aforementioned ink contains cesium tungsten oxide, which is at least a material having infrared absorption characteristics, a coloring material for making the hue of the substrate and the information pattern equal in color, and an extender pigment. When the infrared reflectance when irradiated with a wavelength of 850 nm on the information pattern formed on the substrate is 40% or more, the CIE1976L of the substrate and the information pattern formed on the substrate * a * b * The color difference represented as the distance on the ab plane in the color space is characterized by being 2.7 or less.

[0017] In addition, when the base material of the infrared absorption ink printed matter of the present invention is a white base material, the coloring material has a hue in a complementary color relationship with the hue of cesium tungsten oxide.

[0018] Further, the infrared absorption ink printed matter of the present invention is characterized in that the information pattern is formed by a pattern formed of an ink having infrared absorption characteristics different from those of the infrared absorption ink.

Effect of the Invention

[0019] The infrared absorption ink printed matter of the present invention is a printed matter in which an information pattern is formed by infrared absorption ink and the presence of the information pattern under visible light is difficult to be visually recognized, and it is possible to improve the forgery prevention effect and alteration prevention effect of the printed matter.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0021] Hereinafter, modes 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 modified examples implemented without changing the gist of the present invention.

[0022] (Embodiment) Embodiments of the present invention will be described with reference to FIG. 1. As shown in FIG. 1, the printed matter (1) of the present invention is an ink (hereinafter referred to as "infrared absorption ink") (3) containing cesium tungsten oxide, which is at least an infrared absorption material, a coloring material, and a extender pigment, on at least a part of a base material (2). The information pattern (3) is formed by the ink. Further, in the present invention, the base material (2) and the information pattern (3) on the base material (2) are configured to be indistinguishable visually. However, on the drawing, for easy understanding of the explanation, the base material (2) and the information pattern (3) are shown separately.

[0023] (Base material) First, the base material (2) constituting the printed matter (1) of the present invention preferably has the property of reflecting infrared rays. The infrared reflectance of the base material is preferably 60 to 100%, more preferably 70 to 100% with respect to the irradiated infrared rays (for example, infrared rays having a wavelength of 850 nm). Further, the base material (2) is not particularly limited as long as it has a surface to which the information pattern (3) can be applied. For example, high-quality paper, coated paper, art paper, pasted paper, etc. used for security printed matter such as banknotes, passports, stamps, postage stamps, securities, identity certificates, various papers including plastic sheets and films used for cards, composites thereof, etc. are included, but the present invention is not limited thereto.

[0024] Regarding the color of the base material (2), there is no particular limitation. However, since it is used for the above-described security printed matter, it preferably has a very light coloration such as white, cream color based on white, skin color, etc. (hereinafter referred to as "white base material"). In the present embodiment, an example using a white base material will be described below.

[0025] (Information pattern) The infrared absorption ink used in the printed matter (1) of the present invention will be described later. First, the information pattern (3) formed by the infrared absorption ink on the base material (2) will be described.

[0026] As long as the shape of the information pattern (3) can detect the absorption of infrared light and be used for authenticity discrimination, as shown in FIG. 1, it may be formed by solid printing, or as shown in FIG. 2(a), it may be a figure, a mark, etc., or as shown in FIG. 2(b), it may be characters, numbers, etc. Further, as shown in FIG. 2(c), in addition to a myriad of lines (curved myriad lines, straight myriad lines), it may be a colored pattern, a kagome pattern, etc., or as shown in FIG. 2(d), it may be code information such as a barcode or a two-dimensional code. Also, as shown in FIG. 2(e), the information pattern (3) may be adjacent to a pattern (5) formed by an ink with different infrared absorption characteristics from the infrared absorption ink, or a part of the information pattern (3) and the pattern (4) may overlap, or as shown in FIG. 2(f), the information pattern (3) may be surrounded by a pattern (5) formed by an ink with different infrared absorption characteristics from the infrared absorption ink. FIG. 2(f) is an effective configuration for making it more difficult to visually distinguish between the base material (2) and the information pattern (3) on the base material (2) because the information pattern (3) is not adjacent to the base material (2). In this form, the information pattern (3) and the pattern (4) may be adjacent, or there may be a slight gap between the information pattern (3) and the pattern (4) and they may be close to each other, or a part of the information pattern (3) and the pattern (4) may overlap.

[0027] Also, in the above, the inks with different infrared absorption characteristics are those that do not affect the detection of the information pattern (3) in the printed matter (1) when reading the infrared absorption characteristics by an optical sensor, an infrared camera, an infrared viewer, etc. For example, an ink without infrared absorption characteristics such as a general coloring ink, or an ink with higher infrared absorption characteristics or lower infrared absorption characteristics than the infrared absorption ink forming the information pattern (3) may be used as long as the information pattern (3) can be detected separately.

[0028] In addition, in FIGS. 1 and 2, an example is shown in which the pattern (4) is formed on one surface of the base material (2), but the present invention is not limited thereto, and the pattern (4) may be formed on both surfaces of the base material (2). Further, when the information patterns (3) are formed on both surfaces of the base material (2), the respective patterns may partially overlap each other via the base material (2), or may be formed in separate regions.

[0029] (Infrared Absorbing Ink) Next, the infrared absorbing ink in the present invention will be described. The infrared absorbing ink of the present invention contains at least cesium tungstate as an infrared absorbing material, a coloring material, and a extender pigment. First, cesium tungstate, which is an infrared absorbing material, will be described.

[0030] Cesium tungstate contained as an infrared absorbing material in the infrared absorbing ink 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 elements selected from 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, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I.

[0031] When x / y is 0.001 or more, infrared rays can be sufficiently shielded, and when it is 1.1 or less, generation of an impurity phase 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.

[0032] The fine particles of cesium tungsten oxide represented by the general formula (I) have excellent durability when having a crystal structure of hexagonal, tetragonal, or cubic crystal system. Therefore, it preferably contains one or more crystal structures selected from the hexagonal, tetragonal, and cubic crystal systems, and particularly preferably has a hexagonal crystal structure. Specific examples of the cesium tungsten oxide represented by the general formula (I) include Cs 0.33 WO3 and the like.

[0033] 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, and more preferably 100 nm or less. When the volume average particle diameter is in 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 more reliably ensured. 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 of cesium tungsten oxide may be used. For example, YMF-02, YMF-02A, YMS-01A-2, YMF-10A-2, YMDM-05A, YMDS-874, YMW-D20, etc. manufactured by Sumitomo Metal Mining Co., Ltd. can be used.

[0034] (Coloring material) Examples of the coloring material used in the infrared absorption ink of the present invention include coloring pigments, coloring dyes, fluorescent pigments, fluorescent dyes, and the like. The coloring material is blended to make the hues of the base material (2) and the information pattern (3) formed on the base material (2) equal. In particular, when the base material (2) is a white base material, since the above-mentioned cesium tungsten oxide exhibits a light blue color, a coloring material having a complementary color relationship with blue is used alone as a component of the infrared absorption ink of the present invention, or two or more kinds are used in combination. In the present invention, the complementary color relationship means that even if the hues of both are not in a perfect complementary color relationship, the effect of the present invention appears as long as the hues are substantially in a complementary color relationship. Specifically, the substantial complementary color relationship means, in the Munsell color phase ring, the color phase and the color phase adjacent to this color phase that are opposed by a diagonal line with respect to the color phase position of the light blue presented by cesium tungsten oxide, and the color phase (red (R), orange (YR), yellow (Y)) that is located in the range of ±50° expressed in terms of angle.

[0035] Although details will be described later, by mixing a coloring material having a complementary color relationship with the blue color of cesium tungsten oxide in this way to obtain an achromatic color such as white or gray or a color close to an achromatic color, when made into ink, the hues of the base material (2) and the information pattern (3) can be made equal, so that the information pattern (3) is assimilated with the base material (2) and visually recognized. Strictly speaking, the hue of the information pattern (3) formed on the base material (2) is adjusted so that the hues of the base material (2) and the information pattern (3) on the base material (2) are equal, taking into account the type and amount of the coloring material and the ink film thickness formed on the base material (2) described later.

[0036] If a red fluorescent pigment is used as the coloring material, the information pattern (3) formed on the base material (2) with the infrared absorption ink can be selectively used for authenticity discrimination based on infrared absorption characteristics using an infrared camera, an infrared viewer, etc., and authenticity discrimination based on fluorescence emission characteristics using a black light, etc. Either one or both, so the convenience in authenticity discrimination is enhanced, and the forgery prevention and alteration prevention effects are further improved.

[0037] (Extender pigment) Next, the extender pigment, which is a component of the infrared-absorbing ink of the present invention, will be described. The extender pigment is used to lower the concentrations of cesium tungsten oxide and the coloring material in the infrared-absorbing ink and to adjust the hue based on white for achromatic colors or colors close to achromatic colors. As the extender pigment, white extender pigments such as calcium carbonate, calcium phosphate-based pigments, barium sulfate, alumina white, titanium oxide, and silicon oxide can be used.

[0038] (Other components) The infrared-absorbing ink 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 solvents, ether-based solvents, ester-based solvents, hydrocarbon-based solvents, etc. can be used. Further, if necessary, pigments other than "cesium tungsten oxide, coloring material, and extender pigment" (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, drying agents, etc. may be added and used. 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.

[0039] (Mixing ratio) In the present invention, if an ink coating film with an infrared reflectance of 50% or less can be formed, the contents of cesium tungsten oxide, coloring material, and extender pigment in the infrared absorbing ink are not particularly limited. For example, the content of cesium tungsten oxide can be adjusted according to the use and the required infrared reflectance, etc. However, for example, when using the infrared absorbing ink as offset ink or gravure ink, when the total solid content of the infrared absorbing ink is 100% by mass, cesium tungsten oxide is preferably 0.1% by mass or more and 10% by mass or less. When the content of cesium tungsten oxide is less than 0.1% by mass, infrared absorption characteristics cannot be obtained, which is not preferable. Further, when the content of cesium tungsten oxide exceeds 10% by mass, it may affect the transparency and color tone of the ink coating film, so it is preferably 10% by mass or less. Also, regarding the coloring material and extender pigment, they may be blended and used according to the printing method, printability, and desired hue. However, in order to express a light hue based on white, the coloring material is preferably 20% by mass or less, and the extender pigment is preferably 2% by mass or more and 45% by mass or less.

[0040] In the present invention, the film thickness obtained by the infrared absorbing ink is adjusted so that the infrared reflection characteristics, the type of coloring material, the amount of coloring material, and the hues of the base material (2) and the information pattern (3) on the base material (2) are the same. Further, in order to prevent a step difference from occurring between the film thicknesses of the base material (2) and the information pattern (3), the film thickness is preferably 3 μm or less.

[0041] (Method for manufacturing ink) The method for manufacturing the infrared absorbing ink is not particularly limited as long as it is a manufacturing method capable of uniformly mixing the above-described ink constituent components. When mixing the constituent components in the method for manufacturing the infrared absorbing ink, for example, mixers such as a planetary mixer, tumbler, bead mill, sand mill, stirrer, agitator, mechanical homogenizer, ultrasonic homogenizer, paint shaker, V-type blender, Nauta mixer, three-roll mill, etc. can be used.

[0042] (Printing method) In addition, the printed matter (1) of the present invention can form an information pattern (3) on a substrate (2) by using the above-described infrared-absorbing ink in various printing methods. However, in order to form a thin film thickness on the substrate (2), it is preferable to use offset printing, letterpress printing, flexographic printing, gravure printing, inkjet printing, or the like.

[0043] (Hue) Subsequently, the hue and color difference, which are the characteristic points of the printed matter (1) of the present invention, will be described. The "hue" in the present invention refers to a in the CIE1976 (L * , a * , b * ) color space recommended by the CIE (International Commission on Illumination) in 1976, and is defined in Japanese Industrial Standard (JIS Z 8729). Further, the "color difference" in the present invention refers to a distance on the ab plane in the CIE1976 (L * , b * ) color space. * a * b * ) color space.

[0044] (Color difference) There are two conditions for the color difference (ΔH) in the present invention. The first is that when the infrared reflectance when the information pattern (3) formed on the substrate (2) is irradiated with a wavelength of 850 nm, which is a wavelength generally used for authenticity determination of counterfeit products, is less than 40%, the CIE1976L * a * b * The color difference (ΔH) expressed as the distance on the ab plane in the color space (hereinafter referred to as "color difference (ΔH)") is 3.9 or less. When the color difference (ΔH) is 3.9 or less, when an observer observes the printed matter under visible light without paying attention, the difference in the two hues between the substrate (2) and the information pattern (3) on the substrate (2) cannot be distinguished and recognized by the naked eye. On the other hand, when the color difference (ΔH) exceeds 3.9, it is not preferable because the substrate (2) and the information pattern (3) can be visually distinguished by the naked eye under visible light.

[0045] The second condition is that when irradiated with light having a wavelength of 850 nm, if the infrared reflectance is 40% or more, the color difference (ΔH) should be 2.7 or less. When the color difference (ΔH) is 2.7 or less, when an observer observes the printed matter under visible light without paying attention, the difference in the two hues between the base material (2) and the information pattern (3) on the base material (2) cannot be distinguished and recognized by the naked eye. On the other hand, when the color difference (ΔH) exceeds 2.7, it is not preferable because the base material (2) and the information pattern (3) can be visually distinguished by the naked eye under visible light.

[0046] Next, the reason for dividing the cases into when the infrared reflectance is less than 40% and when it is 40% or more in the above will be explained. The printed matter (1) with an infrared reflectance of 40% or more has a relatively high infrared reflectance, and since the information pattern (3) is formed of a relatively thin film (about 0.1 μm to 1.45 μm), the printing color density does not greatly affect the color difference (ΔH). However, when the infrared absorbing ink does not have a coloring material, the blue color of cesium tungsten oxide will be visually recognized. Therefore, by adding a coloring material and making the color difference (ΔH) 2.7 or less, the difference in the two hues between the base material (2) and the information pattern (3) on the base material (2) cannot be distinguished and recognized by the naked eye.

[0047] On the other hand, in the present invention, the printed matter (1) with an infrared reflectance of less than 40% has a lower infrared reflectance than the printed matter (1) with an infrared reflectance of 40% or more described above, and since the information pattern (3) is formed of a thick film (1.45 μm or more), the printing color density becomes high and more affects the color difference (ΔH). However, in the present invention, by adding a coloring material and making the color difference (ΔH) 3.9 or less, even if the information pattern (3) is formed of a thick film, it can be made difficult to recognize. In particular, in the present invention, since the effect of reducing the color difference (ΔH) when adding a coloring material is higher when the information pattern (3) is formed of a thick film than when it is formed of a thin film, even if it is a thick film, as long as the step between the base material (2) and the information pattern (3) cannot be visually recognized, it has the advantage of preventing the observer from recognizing the presence of the information pattern (3) on the base material (2).

[0048] (Method for calculating color difference) The method for calculating the color difference in the present invention will be described. First, for the substrate (2), L * a * b * The hue (a1 * , b1 * ) in the color space is obtained using a spectrophotometer (UH4150, manufactured by Hitachi High-Technologies Corporation). Next, on the substrate (2), using a universal printing suitability tester manufactured by Kumagai Riki Kogyo Co., Ltd., a sample is prepared in which an information pattern (3) is formed with an infrared absorption ink at an arbitrary film thickness (a film thickness adjusted to the required infrared reflectance). In the same manner as the measurement method for the substrate (2), for the information pattern formed on the substrate (2), L * a * b * The hue (a2 * and b2 * ) in the color space is obtained. Next, the difference between the hue (a1 * , b1 * ) of the substrate (2) and the hue (a2 * and b2 * ) of the information pattern (3) on the substrate (2) is obtained by the following formula according to Japanese Industrial Standard (JIS Z 8729).

[0049] [Equation]

[0050] In the present invention, as described above, the difference in hue is used, and the lightness L * is not included in this calculation. The reason is that for the substrate (2) and the information pattern (3) on the substrate (2), it is easier to be perceived as unevenness when visually observed with the naked eye by expressing the difference in hue rather than the difference in lightness.

[0051] In the above description, the printed matter (1) having the information pattern (3) on the base material (2) has been described. However, the printed matter (1) in the present invention may further include a pattern (4) different from the information pattern (3) as shown in FIG. 3. For example, as shown in FIG. 3(a) or FIG. 3(b), by further forming a pattern (4) different from the information pattern (3) on at least a part of the information pattern (3) formed on the base material (2), it is possible to make it more difficult to recognize the information pattern (3) on the base material (2). In this case, the pattern (4) different from the information pattern (3) can be a ground pattern as shown in FIG. 3(a), halftone dots as shown in FIG. 3(b), and can be a predetermined pattern such as characters, symbols, figures, and colored patterns, and is not particularly limited. The ink used for forming the pattern (4) is not particularly limited as long as it does not affect the detection of the infrared absorption characteristics of the information pattern (3). Also, the printing method is not particularly limited.

[0052] (Use of the printed matter) The printed matter (1) of the present invention is used for various applications, and in particular, it is used for security printed matters such as banknotes, passports, stamps, postage stamps, securities, identity certificates, security labels, etc. For example, by forming an information pattern (3) of the same color as the base material (2) on the base material (2), it is not recognized by the naked eye that there is an information pattern (3) under visible light, but it can be used for a printed matter that detects the absorption of infrared light for authenticity discrimination, so the effect of preventing forgery and alteration is improved.

[0053] Also, by including cesium tungstate oxide in the infrared absorption ink, while having sufficient infrared absorption characteristics, the information pattern (3) formed by the infrared absorption ink is made invisible under visible light, so that it is possible to widen the range of designability as a security printed matter that requires designability.

Example

[0054] Hereinafter, the embodiments of the printed matter (1) of the present invention will be described in detail according to the embodiments for carrying out the invention, but the present invention is not limited to this embodiment.

[0055] (Ink) As the infrared absorption inks in Examples 1 to 4, Comparative Example 1 and Comparative Example 2, the following materials were used to prepare inks at the blending ratios shown in Table 1. The numbers in Table 1 are in "mass %". Note that Comparative Example 1 and Comparative Example 2 are the same infrared absorption inks without a coloring material, and Examples 1 to 4 are infrared absorption inks containing a coloring material. Also, Comparative Example 1 is a comparative example for Examples 1 to 3, and Comparative Example 2 is a comparative example for Example 4.

[0056] <Cesium tungsten oxide paste (CWO paste)> As the infrared absorption material, cesium tungsten oxide paste (Sumitomo Metal Mining Co., Ltd., CWO (registered trademark) YMDM-05A) was used. Note that the cesium tungsten oxide paste with a pigment concentration of cesium tungsten oxide of 65.9 wt% was used.

[0057] <Coloring material> As the coloring materials, Pigment Red 188 red pigment having a complementary color relationship with cesium tungsten oxide, yellow pigment Pigment Yellow 97, and orange pigment Pigment Orange 16 were used. Also, as the fluorescent pigment, a red fluorescent pigment (YVB-F, Konnichi Special Chemical Co., Ltd.) was used.

[0058] <Extender pigment> As the extender pigments, calcium carbonate and silicon oxide (manufactured by High Purity Chemical Research Institute Co., Ltd.) were used.

[0059] <UV offset varnish> As the UV offset varnish, a non-reactive resin, urethane oligomer, polyfunctional acrylate, and bifunctional acrylate were prepared by heating and stirring and used.

[0060] <Photoinitiator> As the photoinitiators, Irgacure 907 and Irgacure 379 (BASF) were used.

[0061]

Table 1

[0062] (Base material) As the base materials (2) of Examples 1 to 3 and Comparative Example 1, white high-quality paper (Kishu high-quality underpaper N, basis weight 81.4 g / m 3 , manufactured by Kishu Paper Co., Ltd.) was used. Also, as the base materials (2) of Example 4 and Comparative Example 2, skin color (High Color - light skin color, manufactured by Honshu Paper Co., Ltd.) was used.

[0063] (Printing conditions) In Examples 1 to 4, Comparative Example 1 and Comparative Example 2, using a universal printing suitability tester manufactured by Kumagai Riki Kogyo Co., Ltd., printed matter was produced by printing the information pattern (3) as a solid pattern at two levels, level 1 and level 2, at a printing speed of 1.0 m / min and a printing pressure of 20 kgf. For level 1, using a spectrophotometer (UH4150 manufactured by Hitachi High-Technologies Corporation), the information pattern (3) was formed on the base material (2) so that the infrared reflectance at 850 nm, which is a wavelength generally used for authenticity determination of counterfeits, was 40%. For level 2, the information pattern (3) was formed on the base material (2) under the same conditions as above so that the infrared reflectance was 30%.

[0064] (Evaluation conditions) The evaluation of the base material (2), Examples 1 to 4, Comparative Example 1 and Comparative Example 2 was carried out under the following conditions.

[0065] <CIE1976 L * a * b * Color space coordinates (L * ,a * ,b * )> Using the data of the spectral reflectance measured with a spectrophotometer (UH4150 manufactured by Hitachi High-Technologies Corporation), under the conditions of light source D65 and viewing angle 10°, the L * value, a * value and b * value were obtained using the color calculation program (conforming to JIS) attached to the spectrophotometer, and the color difference was calculated from the obtained a * value and b * value.

[0066] <Film thickness> The printing film thickness was calculated from the ink specific gravity, printing area, and ink transfer amount in Examples 1 to 4 and Comparative Example 1.

[0067] <Visual evaluation> When the obtained printed matter (1) was observed with the naked eye under visible light, it was evaluated whether the base material A (2) and the information pattern (3) on the base material A (2) could be distinguished and recognized with the naked eye. "〇" indicates that they could not be distinguished and recognized, "△" indicates that they could be slightly distinguished and recognized, and "×" indicates that they could be distinguished and recognized.

[0068] [Examples 1 to 3] The paper was white paper For each of Level 1 and Level 2, in Examples 1 to 3, as the base material A (2), white high-quality paper (Kishu high-quality lower paper N (basis weight 81.4 g / m 3 ), Kishu Paper Co., Ltd.) was used. Also, at the mixing ratios shown in Table 1 for Examples 1 to 3, a mixer was used for mixing to prepare an infrared-absorbing ink, and using the prepared infrared-absorbing ink, the printed matter (1) shown in FIG. 1 was prepared.

[0069] [Comparative Example 1] For each of Level 1 and Level 2, in Comparative Example 1, similar to Examples 1 to 3, white high-quality paper (Kishu high-quality lower paper N (basis weight 81.4 g / m 3 ), Kishu Paper Co., Ltd.) was used as the base material A (2). Also, under the condition of not blending a coloring material and not performing hue adjustment at the blending ratio shown in Table 1 for Comparative Example 1, a mixer was used for mixing to prepare an infrared-absorbing ink, and using the prepared infrared-absorbing ink, the printed matter (1) shown in FIG. 1 was prepared.

[0070] [Example 4] The paper was skin color For each of Level 1 and Level 2, in Example 4, skin color (Hi-Kara skin color light tone, Honshu Paper Co., Ltd.) was used for the base material B (2). Also, at the mixing ratios shown in Table 1 for Example 4, a mixer was used for mixing to prepare an infrared-absorbing ink, and using the prepared infrared-absorbing ink, the printed matter (1) shown in FIG. 1 was prepared.

[0071] [Comparative Example 2] For each of Level 1 and Level 2, in Comparative Example 2, similar to Example 4, skin color (High-color skin color light shade, manufactured by Nippon Paper Industries Co., Ltd.) was used for the base material B(2). Also, under the condition of not blending the coloring material and not performing hue adjustment at the blending ratio of Comparative Example 1 shown in Table 1, it was mixed using a mixer to prepare an infrared absorption ink, and using the prepared infrared absorption ink, the printed matter (1) shown in FIG. 1 was prepared.

[0072] For Examples 1 to 4, Comparative Example 1, and Comparative Example 2 at Level 1, the film thickness, CIE1976 L * a * b * coordinates in the color space (L * ,a * ,b * ), color difference (ΔH), and visual evaluation are shown in Table 2.

[0073]

Table 2

[0074] Also, for Examples 1 to 4, Comparative Example 1, and Comparative Example 2 at Level 2, similar to Level 1, the film thickness, CIE1976 L * a * b * coordinates in the color space (L * ,a * ,b * ), and color difference (ΔH) are shown in Table 3.

[0075]

Table 3

[0076] (Results of Level 1) The visual evaluations of Comparative Example 1 and Comparative Example 2 related to Level 1 were both "△", while the visual evaluations of Examples 1 to 4 related to Level 1 were all "〇".

[0077] (Results of Level 2) The visual evaluation of Comparative Example 1 according to Level 2 was "Δ", and the visual evaluation of Comparative Example 4 according to Level 2 was "×", whereas the visual evaluations of Examples 1 to 4 according to Level 2 were all "〇".

[0078] That is, as shown in Table 2, at Level 1, when the color difference (ΔH) was 3.01 as shown in Comparative Example 1, it was slightly distinguishable and recognizable by the naked eye under visible light. However, it was found that if the color difference (ΔH) was 2.7 or less as shown in Examples 1 to 4, it could not be distinguished and recognized by the naked eye under visible light. Also, as shown in Table 3, at Level 2, when the color difference (ΔH) was 4.32 as shown in Comparative Example 1, it was slightly distinguishable and recognizable by the naked eye under visible light. However, it was found that if the color difference (ΔH) was 3.9 or less as shown in Examples 1 to 4, it could not be distinguished and recognized by the naked eye under visible light.

[0079] Also, compared with Level 1, since Level 2 has a thicker film thickness, the color difference (ΔH) becomes slightly larger due to the influence of the printing color density. However, in Level 2, since the difference in the color difference (ΔH) between the comparative example and the example becomes larger compared to the result of Level 1, it was found that even when the printing film thickness is large, the effect of making the information pattern (3) on the substrate (2) unrecognizable by the naked eye is high.

[0080] According to the present invention, when the infrared reflectance at the time of irradiating the information pattern (3) formed on the substrate (2) with a wavelength of 850 nm is less than 40%, it is necessary to increase the ink film thickness to improve the absorbency in the infrared region, or to contain a large amount of cesium tungsten oxide in the infrared absorbing ink. However, even in that case, if the color difference (ΔH) is 3.9 or less, it cannot be distinguished and recognized by the naked eye under visible light. Also, when the infrared reflectance is 40% or more and authenticity discrimination is performed by reading the infrared absorption characteristics of the printed matter using an infrared camera, an infrared viewer, etc., since the ink film thickness can be made thinner or the content of cesium tungsten oxide in the infrared absorbing ink can be reduced compared to the above, if the color difference (ΔH) is 2.7 or less, it cannot be distinguished and recognized by the naked eye under visible light.

[0081] Figure 4 shows the white substrate which is the base material A at level 1 and the spectral reflectance distributions of Examples 1 to 3 and Comparative Example 1. It was found that in Examples 1 and 3, by including Pigment Red 188 which is a red pigment and Pigment Yellow 97 which is a yellow pigment as coloring materials, the spectral reflectance near 450 nm is lower compared to Comparative Example 1 at level 1 where the hue adjustment was not performed. Also, at levels 1 and 2, Example 2 which particularly had a small color difference (ΔH) contains, in order to reduce the concentration of the infrared absorbing ink, together with calcium carbonate which is an extender pigment, Fluorescent Pigment YVB-F whose body color is light yellow as a coloring pigment. As shown in Figure 4, as a result, the reflectance in the vicinity of 360 nm to 420 nm (blue region from long-wavelength ultraviolet to visible wavelength region) decreases, and the effect of reducing the blueness of cesium tungsten oxide is obtained. Further, Figure 5 shows the skin-color substrate which is the base material B at level 1 and the spectral reflectance distributions of Example 4 and Comparative Example 2. A decrease in reflectance in the visible light region was also confirmed in the skin-color substrate.

[0082] Although the present invention has been described in detail above, various changes can be made without departing from the scope of the present invention in the above configuration. Therefore, all matters included in the above description or shown in the attached drawings should be construed as illustrative.

Explanation of Reference Numerals

[0083] 1 Printed matter 2 Base material 3 Information pattern 4 Pattern 5 Pattern by inks having different infrared absorption characteristics

Claims

1. An infrared absorption ink printed matter in which an information pattern is formed by an ink containing a material having infrared absorption characteristics on at least a part of a substrate, wherein the ink contains tungsten oxide cesium which is at least the material having the infrared absorption characteristics, a coloring material for making the hues of the substrate and the information pattern equal in color, and an extender pigment, when the information pattern formed on the substrate is irradiated with infrared rays having a wavelength of 850 nm, the infrared reflectance is i) less than 40%, or ii) when it is 40% or more, the color difference represented as the distance on the ab plane in the CIE1976L*a*b* color space between the substrate and the information pattern formed on the substrate is 3.9 or less in the case of i), or 2.7 or less in the case of ii), an infrared absorption ink printed matter characterized by this.

2. The infrared absorption ink printed matter according to claim 1, characterized in that when the substrate is a white substrate, the coloring material has a hue complementary to the hue of the tungsten oxide cesium.

3. The infrared absorption ink printed matter according to claim 1 or 2, characterized in that the information pattern is formed surrounded by a pattern formed by an ink having infrared absorption characteristics different from those of the ink.

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