JP7698249B2 - Ink composition and printed matter - Google Patents

Description

The present invention relates to an ink composition and printed matter that have the effect of absorbing infrared rays.

Banknotes, passports, stock certificates, gift certificates, revenue stamps, postage stamps, various tickets, and other securities have monetary value, and therefore require advanced anti-counterfeiting and authenticity discrimination technologies. Widely used anti-counterfeiting and authenticity discrimination technologies include a method of visually or mechanically discerning a coating of an ink composition that has absorption characteristics in a specific wavelength range to distinguish between counterfeit and genuine products.

For example, a method is known in which a coating of an ink composition having a certain level of infrared absorption properties is used to reliably detect and determine authenticity in a high-speed authenticity discrimination device such as a cash processing machine. In this case, for example, an ink composition containing a large amount of infrared absorbing pigment is used to form an image line while suppressing the thickness of the ink coating.

For example, a known technique for visually determining authenticity is to use the fact that by appropriately selecting an illuminating light source, multiple printed parts may appear to be the same color or different colors. For example, this method uses two or more metameric ink compositions (metameric pair inks (inks that appear the same color as normal but contain a pair of inks with different color-producing components)) and uses the absorption characteristics of the pigments contained in the ink compositions in a specific wavelength range. Under normal light, the inks appear to be the same color, but when using a different light source or viewed through a color filter, the ink coatings of the metallic pair inks appear to be different colors from each other, and are also reproduced in different colors on a color copier, making it possible to visually determine the authenticity of printed matter.

The following are known as technologies relating to authenticity discrimination in which a coating of an ink composition having absorption characteristics in a specific wavelength region is visually or mechanically discriminated _to distinguish between counterfeit and genuine products. Patent Document 1 describes an infrared absorbing transparent ink composition containing cesium tungsten oxide ( _Cs0.33WO3 ) and an infrared absorbing black ink composition containing cesium tungsten oxide ( _Cs0.33WO3 ) 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 the use of an ink composition containing carbon black to impart an image having infrared absorption characteristics to a metallic pair print.

Patent No. 6160830 JP 2011-225782 A Patent No. 4863118

The infrared absorbing transparent or black ink composition of Patent Document 1 does not use chromatic color pigments, and is not capable of forming a vivid and bright ink coating. Therefore, if chromatic color pigments are simply mixed to make the ink composition of Patent Document 1 vivid and bright, there is a risk that printed matter with the same infrared absorbing effect can be counterfeited by using carbon black instead of cesium tungsten oxide and mixing color pigments of the desired color.

In addition, the ink composition of Patent Document 2 is not an ink composition containing cesium tungsten oxide, but further uses an organic dye, so there is a risk that the color tone will change over time compared to when a color pigment is used.

In addition, the ink composition and printed matter of Patent Document 3 contain carbon black, and increasing the infrared absorption properties results in an ink composition with high black density and low brightness due to the increased amount of carbon black used, which darkens the color tone of the ink coating and limits color and design properties.

The problem that the present invention aims to solve is to provide an ink composition and printed matter that can form a chromatic ink coating film with infrared absorbing properties and can prevent counterfeiting using an ink composition containing carbon black. Furthermore, it is an object of the present invention to provide a printed matter that can form a printed pattern with unlimited color and can prevent counterfeiting of a metallic effect printed matter using an ink composition containing carbon black, and that can determine the authenticity of the printed matter in the infrared wavelength range and has a metallic effect.

As a result of intensive research into solving the above problems, the inventors have discovered that the above problems can be solved by (a) an ink composition containing cesium tungsten oxide and a color pigment, in which the ink coating formed from the ink composition satisfies specific requirements, and (b) a printed matter in which the ink coating formed from the ink composition containing cesium tungsten oxide and a color pigment on a substrate satisfies specific requirements, and have thus completed the present invention. In other words, the present invention provides the following ink composition and printed matter.

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

It is.

である。 [Section 2]
An ink composition comprising cesium tungsten oxide and a color pigment, wherein an ink coating film formed from the ink composition satisfies the following requirements (3) and (4).
(3) The reflectance of infrared rays with a wavelength of 850 nm is greater than 30% and less than 50%.
(4) The coordinates (L ^* , a ^* , b ^* ) of the CIE 1976 L ^* a ^* b ^* color space are outside the following coordinates: plane 1 including A'E'H', plane 2 including A'H'D', plane 3 including D'G'H', plane 4 including D'C'G', plane 5 including A'F'E', plane 6 including A'B'F', plane 7 including A'B'D', plane 8 including D'C'B', plane 9 including F'E'H', and plane 10 including H'G'F';
Coordinates A' to H' are shown in Table 2, respectively.

It is.

である。 [Section 3]
3. The ink composition according to item 1 or 2, wherein an ink coating film formed from the ink composition further satisfies the following requirement (5):
(5) The coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space are within the following planes: plane 1 including aeh, plane 2 including ahd, plane 3 including dgh, plane 4 including dcg, plane 5 including afe, plane 6 including abf, plane 7 including abd, plane 8 including dcb, plane 9 including feh, and plane 10 including hgf, and the coordinates a to h are respectively shown in Table 3;

It is.

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

It is.

である。 [Section 5]
A printed matter having an ink coating formed on a substrate from an ink composition containing cesium tungsten oxide and a color pigment, the ink coating satisfying the following requirements (8) and (9).
(8) The reflectance of infrared rays with a wavelength of 850 nm is greater than 30% and less than 50%.
(9) The coordinates (L ^* , a ^* , b ^* ) of the CIE 1976 L ^* a ^* b ^* color space are outside the following coordinates: plane 1 including A'E'H', plane 2 including A'H'D', plane 3 including D'G'H', plane 4 including D'C'G', plane 5 including A'F'E', plane 6 including A'B'F', plane 7 including A'B'D', plane 8 including D'C'B', plane 9 including F'E'H', and plane 10 including H'G'F';
Coordinates A' to H' are shown in Table 5, respectively.

It is.

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

It is.

[Section 7]
7. The printed matter according to any one of items 4 to 6, comprising a first pattern formed by an ink coating film formed from an ink composition containing cesium tungsten oxide and a color pigment, and a second pattern having a color identical to that of 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.

The present invention makes it possible to form a chromatic ink coating film with infrared absorbing properties, and to provide an ink composition and printed matter that can prevent counterfeiting using an ink composition containing carbon black. Furthermore, in a printed matter with a metallic effect, it is possible to determine the authenticity in the infrared wavelength range, and it is possible to form a printed pattern with no color restrictions, and it is possible to provide a printed matter that can prevent counterfeiting of a printed matter with a metallic effect using an ink composition containing carbon black.

1 is a diagram showing provisional color coordinates in the CIE 1976 L ^* a ^* b ^* color space and a plane connecting the color coordinates. FIG. 1 is a diagram showing color coordinates in the CIE1976 L ^* a ^* b ^* color space in a first embodiment of the ink composition of the present invention, and a plane connecting the color coordinates. FIG. 2 is a diagram showing color coordinates in the CIE1976 L ^* a ^* b ^* color space in a second embodiment of the ink composition of the present invention, and a plane connecting the color coordinates.

The following describes in detail the form for carrying out the present invention. Note that the present invention is not limited to the following embodiment, and should be understood to include various modified forms that are implemented within the scope that does not change the gist of the present invention.

[Ink composition]
The ink composition of the present invention is an ink composition containing cesium tungsten oxide and a color pigment, and when an ink coating film of a predetermined thickness is formed, it satisfies the following requirements. The properties of the ink coating film are in two forms, which will be explained in order.

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

It is.

The reason why the reflectance of the ink coating to infrared rays with a wavelength of 850 nm is set to 30% or less is to enable stable readings by an optical sensor that is generally used to read infrared absorption characteristics in an environment in which a medium to which the ink coating is applied is transported at high speed. The infrared reflectance of the ink coating can be measured, for example, by the method described in the Examples.

(CIE 1976 L ^* a ^* b ^* color space coordinates (L ^* , a ^* , b ^* ))
In the present invention, the color characteristics of the ink coating film are expressed using the CIE1976 L ^* a ^{* b *} color space, in which lightness is represented by L ^* , and chromaticity indicating hue and saturation is represented by a ^* and b ^{* .} Lightness L ^* ranges from 0 to 100, with 0 indicating the black direction and 100 indicating the white direction. Chromaticity a ^* and b ^* indicate the color direction, with the +a ^* direction being the red direction, the -a ^* direction being the green direction, the +b ^* direction being the yellow direction, and the -b ^* direction being the blue direction. The larger the absolute values of the ^a* and b ^* values ^, the more vivid the color, and the smaller the absolute values (the closer the a ^* and b ^* values are to 0), the duller the color. Note that saturation is represented by the square root of the sum of the squared values of a ^* and b ^* . The coordinates (L ^* , a ^* , b ^* ) of the ink coating in the CIE 1976 L ^* a ^* b ^* color space can be measured, for example, by the method described in the Examples section below.

In the present invention, the configuration of colors outside a plurality of planes including the coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space will be described. Fig. 1(a) is a schematic diagram of a color space of a plane connecting provisional coordinates _A0 to _H0 different from the coordinates shown in Table 7, and is an example in which the shape connecting the coordinate points _A0 to _H0 is a cube in order to easily explain the coordinates of the color space. The cube shown in FIG. 1( a) is surrounded by plane 1 including coordinates A ₀ B ₀ C ₀ D ₀ , plane 2 including coordinates C ₀ D ₀ G ₀ H ₀ , plane 3 including coordinates D ₀ G ₀ E ₀ A ₀ , plane 4 including coordinates A ₀ E ₀ F ₀ B ₀ , plane 5 including coordinates C ₀ H ₀ F ₀ B ₀ , and plane 6 including coordinates H ₀ G ₀ E ₀ F _0. "Outside" the multiple planes refers to colors that are outside planes 1, 2, 3, 4, and 5, and does not include the outside of plane 6, which is the lower lightness side of the cube.

FIG. 1B is a diagram for explaining the color outside the plane 1 to plane 5, and for plane 1, it is a color in the direction of the arrow (V1) in which the value of lightness L ^* increases. Furthermore, for plane 2, it is a color in the direction of the arrow (V2) (the direction in which the value of -a ^* increases), for plane 3, it is a color in the direction of the arrow (V3) (the direction in which the value of ^{-b* increases} ), for plane 4, it is a color in the direction of the arrow (V4) (the direction in which the value of a* increases), and for plane 5, it is a color in the direction of the arrow (V5) (the direction in which the value of b ^* increases). Furthermore, the color outside the plane 1 to plane 5 may be a color in the direction of the arrow (V6) shown in FIG. 1B (the direction in which the value of L ^* increases and the value of -a ^* increases) common to plane 1 and plane 2, or a color in the direction of the arrow (V7) (the direction in which the value of L ^* increases and the value of a ^* increases) common to plane 1 and plane 4. Also, it may be a color common to planes 4 and 5 in a direction in which the a ^* value and the b ^* value increase (not shown), a color common to planes 2 and 3 in a direction in which the -a ^* value and the -b ^* value increase (not shown), or a color common to planes 1, 4, and 5 in a direction in which the lightness L ^* value, a ^* value, and b ^* value increase (not shown). However, this does not include colors in the direction in which the L ^* value decreases from plane 1 to plane 5.

Figure 2 is a schematic diagram of a three-dimensional diagram connecting the coordinates A through H shown in Table 7. In more detail, the plane connecting the points of the coordinates A through H forms a three-dimensional shape formed by the contact of triangular planes connecting three of the coordinates A through H, but for the sake of simplicity, Figure 2 shows a three-dimensional shape connecting four of the coordinates A through H.

In the three-dimensional shape shown in FIG. 2, the colors on the outside of plane 1 including coordinates AEH, plane 2 including AHD, plane 3 including DGH, plane 4 including DCG, plane 5 including AFE, plane 6 including ABF, plane 7 including ABD, plane 8 including DCB, plane 9 including FEH, and plane 10 including HGF can be used as the color of the coating, and some of the outside directions are indicated by arrows (v1 to v6). In FIG. 2, some of the outside directions from plane 1 to plane 10 are illustrated, but the directions that are outside the planes shown in FIG. 1(b) and the directions described in paragraph (0027) are the same for the planes shown in FIG. 2. Note that the area outside the GCBF plane on the low-lightness side is a dark color, and therefore the effect of the present invention cannot be achieved.

The ink coating film of the present invention can be made to have sufficient infrared absorbing properties and high brightness or chroma by printing an ink composition containing cesium tungsten oxide, and can expand the range of design. The present inventors have found that when a coating film of an ink composition containing carbon black as an infrared absorbing pigment is produced, if the reflectance of infrared rays at a wavelength of 850 nm is set to 30% or less, the color of the ink composition becomes dark due to the carbon black, and it is difficult for the coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space to satisfy the color requirements outside the above plane. Therefore, the ink composition using carbon black can reduce the risk of counterfeiting.

である。 (Characteristics of ink film 2)
The second ink coating property satisfies the following requirements (3) and (4).
(3) The reflectance of infrared rays with a wavelength of 850 nm is greater than 30% and less than 50%.
(4) The coordinates (L ^* , a ^* , b ^* ) of the CIE 1976 L ^* a ^* b ^* color space are outside the following coordinates: plane 1 including A'E'H', plane 2 including A'H'D', plane 3 including D'G'H', plane 4 including D'C'G', plane 5 including A'F'E', plane 6 including A'B'F', plane 7 including A'B'D', plane 8 including D'C'B', plane 9 including F'E'H', and plane 10 including H'G'F', and the coordinates A' to H' are respectively shown in Table 8;

It is.

FIG. 3 is a schematic diagram showing a three-dimensional figure connecting the coordinates A' to H' shown in Table 8, and a three-dimensional figure connecting the coordinates A to H shown in Table 7 for comparison. In FIG. 3, the three-dimensional figure connecting the coordinates A' to H' shown in Table 8 is shown with a thick line, and the three-dimensional figure connecting the coordinates A to H shown in Table 7 has the same shape as FIG. 2. As shown in FIG. 3, the three-dimensional figure connecting the coordinates shown in Table 8 tends to be in a direction of higher lightness overall and has larger absolute values of a ^* and b ^* than the three-dimensional figure connecting the coordinates shown in Table 7. In other words, the second ink coating is brighter than the first ink coating, and has a color range with higher saturation.

The reason why the reflectance of the ink coating to infrared rays with a wavelength of 850 nm is set to more than 30% and not more than 50% is that, unlike the first embodiment, the infrared absorption characteristics of the printed matter are read using an infrared camera or infrared viewer. When using an infrared camera or infrared viewer, the observation environment is more stable than when reading infrared rays from a medium transported at high speed, so the ink coating pattern can be obtained stably, and since the human eye can interpolate and distinguish slight smudges and stains in the pattern, it is possible to make a distinction even if the infrared absorption characteristics are lower than in the first configuration.

Regarding the color range, which is the second characteristic of the ink coating film, by printing an ink composition containing cesium tungsten oxide, it is possible to obtain an ink composition with sufficient infrared absorption properties and high brightness, which makes it possible to expand the range of design. The inventors have found that even when the reflectance of infrared rays at a wavelength of 850 nm is 50%, the color of the ink composition becomes dark due to carbon black, and it is difficult for the coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space to satisfy the color requirements outside the above plane. In the case of forming an ink coating film with an infrared reflectance of 30% using an ink composition containing carbon black, the amount of carbon black needs to be increased compared to the case of forming an ink coating film with an infrared reflectance of 50% using an ink composition containing Kern black, so the color range of the ink coating film that can be reproduced at that time is narrower (dull color, dark color). Therefore, the range of colors that cannot be reproduced with an ink composition containing carbon black when the infrared reflectance is 50% as shown in Table 8 cannot be reproduced even when the infrared reflectance is in the range of 50% or less.

The infrared reflectance can be adjusted by the amount of cesium tungsten oxide contained in the ink composition and the ink film thickness, and the color of the coating can be adjusted by the color pigment contained in the ink composition and the ink film thickness. In either case, an ink composition that satisfies the above requirements (1) and (2) or (3) and (4) will produce an effect that cannot be reproduced by an ink composition containing carbon black. The thickness of the ink coating that satisfies the above requirements for infrared reflectance and color may be within the range that can be formed by the method of printing the ink composition described below. For example, in the case of offset printing, in which the ink coating is thin, the thickness of the ink coating is about 0.5 μm to 2 μm, and in the case of screen printing, in which the ink coating can be thickened, the ink coating can be printed to a thickness of up to 200 μm. In each printing method, it is sufficient to satisfy the requirements for infrared reflectance and color.

<Cesium tungsten oxide>
The 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 metals 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, and the like.

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 prevented. When z/y is 2.2 or more, the chemical stability of the material can be further improved, and when it is 3.0 or less, infrared rays can be sufficiently shielded.

The cesium tungsten oxide microparticles represented by the above general formula (I) have excellent durability when they have a hexagonal, tetragonal, or cubic crystal structure, so it is preferable that they contain one or more crystal structures selected from the hexagonal, tetragonal, and cubic crystal structures, and it is particularly preferable that they have a hexagonal crystal structure. A specific example of the cesium tungsten oxide represented by the above general formula (I) is _{Cs0.33WO3 .}

The cesium tungsten oxide is preferably fine particles, and the volume average particle diameter of the 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 this range, the cesium tungsten oxide is less likely to block visible light due to light scattering, so that the translucency in the visible light region can be more reliably achieved. From the viewpoint of avoiding light scattering, the smaller the average particle diameter, the more preferable, but from the viewpoint of manufacturing costs, ease of handling, and the like, the volume average particle diameter of the cesium tungsten oxide is usually 1 nm or more. As the cesium tungsten oxide, a commercially available product may be used. 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.

The content of cesium tungsten oxide in the ink composition may be adjusted according to the application, the function of the ink coating, etc. Even when forming a coating film with the same infrared reflectance, if the content of cesium tungsten oxide is low, the thickness can be made thicker, and if the content of cesium tungsten oxide is high, the thickness can be made thinner. In the present invention, it is necessary to form a coating film with an infrared reflectance of 50% or less, and it is necessary to make it at least 0.1% by mass or more when the total solid content of the ink composition is 100% by mass. 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 decreases, which may affect the transparency and color tone of the ink coating film, so it is preferable to make it 10% by mass or less.

<Coloring pigment>
The color pigment, which is a component of the ink composition of the present invention, is not particularly limited, and an appropriate inorganic pigment or organic pigment may be used to obtain a desired color.

Examples of inorganic pigments that can be used include carbon black, titanium oxide, zinc oxide, red iron oxide, calcium carbonate, barium sulfate, silica, clay, talc, alumina, zinc yellow, Prussian blue, ultramarine, graphite, and aluminum powder. Examples of organic pigments that can be used include azo, diazo, condensed azo, azomethine, indanthrone, carbonyl, anthraquinone, nitro, phthalocyanine, indigo, thioindigo, benzodifuranone, benzimidazolone, methine, polyene, polymethine, dioxazine, quinacridone, isoindoline, quinophthalone, perylene, perinone, triarylmethane, diketopyrrolopyrrole, and carotene. Color pigments may be used alone or in combination of two or more of these.

The content of the color 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 may be mixed and used according to the desired color of the ink coating. However, taking into consideration the printability of the ink composition on the substrate for printing and the robustness of the ink coating, the content is 50% by mass or less, preferably 40% by mass or less, when the total solid content of the ink composition is 100% by mass.

<Solvent>
The ink composition of the present invention may contain a solvent for the purpose of adjusting viscosity, imparting printability, etc. Examples of the solvent that can be used include mineral oil, alcohol-based solvents, ether-based solvents, ester-based solvents, and hydrocarbon-based solvents.

<Other ingredients>
The ink composition of the present invention may be used by adding, as necessary, pigments other than "cesium tungsten oxide and color pigments" (hereinafter, sometimes referred to as "other pigments"), coating film-forming components such as resins and photopolymerizable compounds, gelling agents, surfactants, antioxidants, anti-settling agents, defoamers, anti-blocking agents, magnetic materials, luminescent materials, conductive materials, drying agents, etc. In the present invention, only one of these other components may be used alone, or two or more may be used in combination.

である。 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) The coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space are within the following planes: plane 1 including aeh, plane 2 including ahd, plane 3 including dgh, plane 4 including dcg, plane 5 including afe, plane 6 including abf, plane 7 including abd, plane 8 including dcb, plane 9 including feh, and plane 10 including hgf, and the coordinates a to h are respectively shown in Table 9;

It is.

The coordinates shown in Table 9 represent the range of colors that can be reproduced using the process inks cyan ink, magenta ink, yellow ink, and black ink as the color pigments contained in the ink composition. Cyan ink, magenta ink, yellow ink, and black ink are preferred because they are common and inexpensive, and the range of colors that can be reproduced by combining each color ink is wide. Note that by using special color inks in addition to the above process inks, colors outside the range shown in Table 9 can also be reproduced.

<Method of producing ink composition>
The method for producing the ink composition of the present invention is not particularly limited as long as it is a method that can uniformly mix the components of the ink composition. When mixing the components in the method for producing the ink composition, for example, a mixer such as a planetary mixer, a tumbler, a bead mill, a sand mill, a stirrer, an agitator, a mechanical homogenizer, an ultrasonic homogenizer, a paint shaker, a V-type blender, a Nauta mixer, or a three-roll mill can be used.

<Applications of ink composition>
The ink composition of the present invention can be used as an anti-counterfeit ink composition or a metameric pair ink composition utilizing infrared absorbing properties. Examples of products to which the ink composition is applied include ink for printed matter requiring anti-counterfeiting, such as banknotes (paper money), revenue stamps, postage stamps, securities, identification cards, passports, security labels, and cards.

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

である。 The first ink film characteristic 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) The coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space are outside the following coordinates: plane 1 including AEH, plane 2 including AHD, plane 3 including DGH, plane 4 including DCG, plane 5 including AFE, plane 6 including ABF, plane 7 including ABD, plane 8 including DCB, plane 9 including FEH, and plane 10 including HGF, and the coordinates A to H are respectively shown in Table 10;

It is.

である。 The second characteristic of the ink coating is that the printed matter satisfies the following requirements (8) and (9).
(8) The reflectance of infrared rays with a wavelength of 850 nm is greater than 30% and less than 50%.
(9) The coordinates (L ^* , a ^* , b ^* ) of the CIE 1976 L ^* a ^* b ^* color space are outside the following coordinates: plane 1 including A'E'H', plane 2 including A'H'D', plane 3 including D'G'H', plane 4 including D'C'G', plane 5 including A'F'E', plane 6 including A'B'F', plane 7 including A'B'D', plane 8 including D'C'B', plane 9 including F'E'H', and plane 10 including H'G'F', and the coordinates A' to H' are respectively shown in Table 11;

It is.

The first and second ink film properties of the ink film formed on the printed matter of the present invention shown in Tables 10 and 11 correspond to the infrared reflectance of the environment in which the ink composition of the present invention is read, as described above, and the color range that cannot be reproduced by an ink composition containing carbon black that has each infrared reflectance.

である。 In addition, it is preferable that the ink coating film formed on the printed matter of the present invention further satisfies the following requirement (10).
(10) The coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space are within the following coordinate plane 1 including aeh, plane 2 including ahd, plane 3 including dgh, plane 4 including dcg, plane 5 including afe, plane 6 including abf, plane 7 including abd, plane 8 including dcb, plane 9 including feh, and plane 10 including hgf, and the coordinates a to h are respectively shown in Table 12;

It is.

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 the process inks cyan ink, magenta ink, yellow ink, and black ink, which are common and inexpensive, and are preferable because a wide range of colors can be expressed by combining each color ink. Note that by using special color inks in addition to the above process inks, colors outside the range shown in Table 12 can also be reproduced.

The substrate is not particularly limited as long as it has a surface to which an ink coating can be applied, and examples of the substrate that can be used include paper, plastic film, glass, metal, wood, and composites of these. The substrate may be white or colored in red, blue, yellow, or other colors. In the case where the color of the substrate affects the color of the ink coating in the printed matter of the present invention (if the ink coating is thin, the color of the substrate may show through), the color of the area to which the ink coating is applied may be configured to satisfy requirement (7) or requirement (9).

The cesium tungsten oxide, color pigment, and ink composition containing them, the reflectance of infrared light with a wavelength of 850 nm, and the coordinates (L ^* , a ^* , b ^* ) in the CIE 1976 L ^* a ^* b ^* color space described in the configuration of the printed matter of the present invention are the same as those described in the above-mentioned [Ink Composition].

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

<Use of printed matter>
The printed matter of the present invention can be used for various purposes. In particular, it can be used for security printed matter or printed matter requiring design, such as banknotes (paper money), revenue stamps, postage stamps, securities, identification cards, passports, security labels, etc. For example, it can be used for printed matter in which an infrared absorbing ink coating film is formed on a substrate and the absorption of infrared light is detected to determine authenticity. It can also be used for anti-counterfeit printed matter having a metallic property that is visually recognized as a uniform color under visible light, but allows a pattern to be recognized under a specific light source or through a specific wavelength transmission filter.

In the case of making a counterfeit prevention printed matter having a metallic property, a first pattern is formed by an ink containing cesium tungsten oxide in the color range according to the infrared reflectance shown in Table 10 or Table 11, and a second pattern is formed by a normal colored ink such as cyan ink, magenta ink, or yellow ink (not including carbon black or cesium tungsten oxide) to have a color identical to that of the first pattern when observed under visible light. Note that the first and second patterns are formed by combining pigments with different spectral reflectances so that they are color identical under visible light, as in the case of conventional metallic pair inks, and blending them into the inks that form the respective patterns. In the present invention, "color identical" refers to a state in which two colors are so close that an observer can perceive them as the same color when observing the two patterns without paying attention. For the two patterns to have colors close to each other and indistinguishable under visible light, the color difference ΔE between the two patterns (based on the CIE 1976 ^L* a ^* b ^* color difference formula in this invention) is preferably 7 or less, and more preferably 3 or less.

The first and second patterns may be, for example, predetermined designs (letters, symbols, figures, etc., background patterns, colored patterns, etc.) arranged in a negative-positive relationship, or two of the same designs arranged side by side. As long as two patterns are arranged on the substrate, there are no particular limitations, and the first and second patterns may be arranged apart.

In the case of a counterfeit prevention printed matter having a metameric effect, a red wavelength region (610 nm to 700 nm) can be used as a condition under a specific light source or a characteristic wavelength transmission filter, and in this case, it is preferable because the contrast between the two patterns visually recognized when a red light source or a red transmission filter is used is high. The color of the ink coating film made of the ink forming the first pattern containing cesium tungsten oxide corresponding to this and the ink forming the second pattern of the same color is a reddish purple to yellowish red hue, specifically, the hue angle is in the range of 144 degrees from -52 degrees (reddish purple) to 92 degrees (yellowish red). In the present invention, the hue angle is an angle representing each hue such as red, blue, yellow, etc. in the CIE1976 L ^* a ^* b ^* color space, and is represented as a positive angle in the counterclockwise direction and a negative angle in the clockwise direction based on the a ^* axis.

The above hue angle range corresponds to the hue that can be expressed by mixing yellow ink and red ink that disappear when a red light source or red transmission filter is used, based on the hue of the magenta ink that disappears when a red light source or red transmission filter is used (hue angle of -52 degrees). By appropriately mixing yellow ink and red ink with magenta ink, it is possible to express colors with a hue angle of up to 92 degrees. On the other hand, when blue ink, which does not have the disappearing effect when a red light source or red transmission filter is used, is mixed, the disappearing effect is not obtained, so this is used as the ink for forming the first pattern. Details of the ink blend for forming a printed matter with a metallic effect will be explained in the examples.

In a counterfeit prevention printed matter having metallic properties, a first pattern formed with ink containing cesium tungsten oxide and a second pattern of the same color are recognized as the same color under visible light, but when a specific light source or a specific wavelength transmission filter is used, a color difference occurs between the two patterns, which allows for authenticity discrimination. Fluorescent lamps and sunlight can be used as a light source for irradiating the counterfeit prevention printed matter with visible light. Furthermore, when the counterfeit prevention printed matter is observed under infrared light, authenticity can be discriminated by confirming that the first pattern absorbs a specified proportion of infrared light. In other words, compared to conventional printed matter having a metallic effect, authenticity discrimination using infrared wavelengths is possible, and the counterfeit prevention effect is improved.

The present invention will be explained in more detail below using examples and comparative examples of ink compositions and ink coatings printed with the ink compositions that were specifically prepared according to the above-mentioned embodiment of the invention, but the present invention is not limited to these examples. In addition, unless otherwise specified, "parts" in each example means parts by mass and "%" means "% by mass".

[Ink raw materials]
The ink ingredients used in the examples and comparative examples are as follows, and ink compositions were prepared by mixing the ink ingredients in a predetermined ratio, and coating films using each ink composition were evaluated. Details of the examples and comparative examples are described below.

<Cesium tungsten oxide paste (CWO paste)>
Cesium tungsten oxide paste (Sumitomo Metal Mining Co., Ltd., CWO (registered trademark) YMDM-05A) was used. The cesium tungsten oxide paste used in this example had a cesium tungsten oxide pigment concentration of 65.9 wt %.

<Carbon Black (CB)>
A black pigment (No. 6UVL Carton Black CW, manufactured by T&K Toka Corporation) was used.

<Yellow ink>
A yellow pigment (No. 6UVL Carton Yellow CW, manufactured by T&K Toka Co., Ltd.) was used.

<Red ink>
A red pigment (No. 6UVL Carton Red CW, manufactured by T&K Toka Co., Ltd.) was used.

<Indigo ink>
A yellow pigment (No. 6UVL Carton Indigo CW, manufactured by T&K Toka Co., Ltd.) was used.

<Fluorescent medium>
A fluorescent pigment (UV Fluorescent Medium B manufactured by T&K Toka Co., Ltd.) was used.

[Evaluation of ink coating]
<Creating printed matter>
The prepared ink composition was printed on fine paper at a printing speed of 1.0 m/min and a printing pressure of 20 kgf using a universal printability tester (Kumagaya Riki Kogyo Co., Ltd.) to produce a print.
<Infrared reflectance>
The infrared reflectance of the printed portion of the obtained print was measured using a spectrophotometer (UH4150, Hitachi High-Tech Science Corporation). The wavelength of infrared rays was 850 nm, which is a wavelength generally used to determine the authenticity of counterfeit products. The lower the infrared reflectance value, the higher the infrared absorptance of the ink coating.

<CIE1976 L ^* a ^* b ^* color space coordinates (L ^* , a ^* , b ^* )>
Measurements were made using a Spectroeye spectrophotometer (manufactured by Gretag Macbeth) under conditions of a light source of D65 and a visual field of 10° to obtain the L ^* value, a ^* value and b ^* value of the absolute white standard.

[Example 1]
An ink composition was prepared by mixing 15 parts of cesium tungsten oxide paste (Sumitomo Metal Mining Co., Ltd., CWO (registered trademark) YMDM-05A) and 85 parts of fluorescent medium using a mixer. The composition of the resulting ink composition, the infrared reflectance of a coating film made from the ink composition, and the coordinates (L ^* , a ^* , b ^* ) in the CIE1976 L ^* a ^* b ^* color space are shown in Table 13.

[Examples 2 to 8, Comparative Examples 1 to 8]
For the ink compositions of Examples 2 to 8, the ink compositions were prepared in the same manner as in Example 1, except that the components of the ink compositions were the components shown in Table 13. The infrared reflectance and coordinates (L ^* , a ^* , b ^* ) in the CIE1976 L ^* a ^* b ^* color space of the coating film of the ink compositions are shown in Table 13. For the ink compositions of Comparative Examples 1 to 8, carbon black was blended to provide infrared reflectance characteristics substantially equivalent to those of the ink compositions of Examples 1 to 8, and colored inks of the respective colors were blended to provide the same color. The composition of the obtained ink compositions, infrared reflectance, coordinates (L ^* , a ^* , b ^* ) in the CIE1976 L ^* a ^* b ^* color space, and coating film thickness are shown in Table 14.

From Tables 13 and 14, it can be seen that the ink composition containing cesium tungsten oxide and a color pigment has a higher lightness L ^* (a color tone toward whiter side) and a larger absolute value of chromaticity a ^* and b ^* than the comparative example, and therefore can form a coating film with a high lightness and a vivid color tone. On the other hand, it can be seen that the ink composition containing carbon black has a smaller lightness L ^* (a color tone toward darker side) and a smaller absolute value of chromaticity a ^* and b ^* when the ink composition containing cesium tungsten oxide and a color pigment has the same infrared reflectance as the ink composition containing cesium tungsten oxide and a color pigment. In other words, it can be seen that the ink composition containing carbon black cannot reproduce the color of the ink composition containing cesium tungsten oxide.

The infrared reflectance of the ink compositions of Comparative Examples 1 to 8 is about 33%, but to make an ink composition with a lower reflectance (higher infrared absorptance) than that, it is necessary to increase the amount of carbon black blended, and the lightness L ^* value will be smaller and the absolute values of chromaticity a ^* and b ^* will be smaller than the colors shown in Table 14. In other words, when the infrared reflectance of a coating film made of an ink composition containing cesium tungsten oxide is set to 30% or less, it is not possible to reproduce colors beyond the range shown in Table 14.

In Examples 1 to 7, the thickness of the ink coating is approximately 1 μm, but as mentioned above, a coating film with a thickness of 0.5 to 200 μm can be formed depending on the printing method. Therefore, by adjusting the composition of cesium tungsten oxide according to the desired thickness to make the infrared reflectance of the coating film 30% or less and creating an ink composition with a color that satisfies the above-mentioned requirement (2), it is possible to prevent counterfeiting using an ink composition that contains carbon black.

[Comparative Examples 9 to 16]
For the ink compositions of Comparative Examples 9 to 16, carbon black was blended and colored inks of each color were blended so that the infrared reflectance was 50%. The composition, infrared reflectance, and coordinates (L ^{* ,} a ^* , b ^{* )} of ^the resulting ink compositions are shown in Table 15.

The infrared reflectance of the ink compositions of Comparative Examples 9 to 16 is about 50%, and the amount of carbon black blended is less than that of the ink compositions of Comparative Examples 1 to 8. As a result, the ink coating film has higher lightness and brighter color than the ink compositions of Comparative Examples 1 to 8. However, a coating film made of an ink composition containing cesium tungsten oxide having an infrared reflectance similar to that of the ink compositions of Comparative Examples 9 to 16 can reproduce colors with higher lightness L ^* values and chroma values than the colors shown in Table 15 because the cesium tungsten oxide paste is transparent. In other words, when the infrared reflectance of the coating film of the ink composition containing cesium tungsten oxide is set to 50% or less, it is not possible to reproduce colors beyond the range of colors shown in Table 15.

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

The infrared reflectance, CIE1976 L ^* a ^* b ^* color space coordinates (L ^* , a ^* , b ^* ) and hue angle of the first and second patterns in the printed matter of Examples 9 to 11 are shown in Table 16. The first and second patterns of Example 9 are reddish purple, the first and second patterns of Example 10 are red, and the first and second patterns of Example 11 are light purple.

In the printed matter of Examples 9 to 11, when observed under visible light, the two patterns are indistinguishable because they are of the same color, but when observed using a red filter (Fujifilm Corporation, sharp cut filter SC64), the second pattern disappears and becomes invisible, and the first pattern is confirmed without disappearing. This is because the CWO paste forming the first pattern is almost transparent to the naked eye, but contains a small amount of blue components, so it does not disappear when using a red filter. In addition, when observed using a near-infrared camera (Japan CDR Corporation, MS-40), the second pattern disappears and only the first pattern can be seen, confirming that it is possible to distinguish between genuine and counterfeit. The infrared reflectance of the ink compositions of Examples 9 to 11 was about 37%, which was outside the range of coordinates (L ^* , a ^* , b ^* ) of the CIE1976 L ^* a ^* b ^* color space shown in Comparative Examples 9 to 16 in Table 15, and when the hue angle was in the range of -52 degrees to 92 degrees, it was not possible to reproduce the ink compositions using carbon black.

Although the present invention has been described in detail above, various modifications can be made in the above configuration without departing from the scope of the present invention. Therefore, all matters contained in the above description or shown in the accompanying drawings should be interpreted as illustrative.

1. Plane of virtual color coordinates in L ^* a ^* b ^* color space
2 Plane 2 consisting of virtual color coordinates in L ^* a ^* b ^* color space
3. Plane of virtual color coordinates in L ^* a ^* b ^* color space 3
4. Plane of virtual color coordinates in the L ^* a ^* b ^* color space
5. Plane of virtual color coordinates in the L ^* a ^* b ^* color space
6 Plane of virtual color coordinates in L ^* a ^* b ^* 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 (5)

An ink composition comprising cesium tungsten oxide and a color pigment, wherein an ink coating film formed from the ink composition satisfies the following requirements (3) and (4):
(3) The reflectance of infrared rays with a wavelength of 850 nm is greater than 30% and less than 50%.
(4) CIE1976 L ^* a ^* b ^* Color space coordinates (L ^* , a ^* , b ^* ) are outside the following planes: Plane 1 including A'E'H', Plane 2 including A'H'D', Plane 3 including D'G'H', Plane 4 including D'C'G', Plane 5 including A'F'E', Plane 6 including A'B'F', Plane 7 including A'B'D', Plane 8 including D'C'B', Plane 9 including F'E'H', and Plane 10 including H'G'F', and the coordinates A' to H' are as shown in Table 2;

It is. The ink composition according to claim 1, wherein an ink coating film formed from the ink composition further satisfies the following requirement (5):
(5) CIE1976 L ^* a ^* b ^* Color space coordinates (L ^* , a ^* , b ^* ) are inside the plane 1 including the coordinates aeh, the plane 2 including ahd, the plane 3 including dgh, the plane 4 including dcg, the plane 5 including afe, the plane 6 including abf, the plane 7 including abd, the plane 8 including dcb, the plane 9 including feh, and the plane 10 including hgf, and the coordinates a to h are respectively shown in Table 3;

It is. A printed matter having an ink coating formed on a substrate from an ink composition containing cesium tungsten oxide and a color pigment, the ink coating satisfying the following requirements (8) and (9).
(8) The reflectance of infrared rays with a wavelength of 850 nm is greater than 30% and less than 50%.
(9) CIE1976 L ^* a ^* b ^* Color space coordinates (L ^* , a ^* , b ^* ) are outside the following planes: Plane 1 including A'E'H', Plane 2 including A'H'D', Plane 3 including D'G'H', Plane 4 including D'C'G', Plane 5 including A'F'E', Plane 6 including A'B'F', Plane 7 including A'B'D', Plane 8 including D'C'B', Plane 9 including F'E'H', and Plane 10 including H'G'F', and the coordinates A' to H' are as shown in Table 5;

It is. The printed matter according to claim 3, wherein the ink coating film formed on the substrate by the ink composition further satisfies the following requirement (10):
(10) CIE1976 L ^* a ^* b ^* Color space coordinates (L ^* , a ^* , b ^* ) are inside the plane 1 including the coordinates aeh, the plane 2 including ahd, the plane 3 including dgh, the plane 4 including dcg, the plane 5 including afe, the plane 6 including abf, the plane 7 including abd, the plane 8 including dcb, the plane 9 including feh, and the plane 10 including hgf, and the coordinates a to h are respectively shown in Table 6;

It is. 5. The printed matter according to claim 3 or 4, comprising: a first pattern formed by an ink coating film formed from an ink composition containing cesium tungsten oxide and a color pigment; and a second pattern having a color equivalent to that of the first pattern under visible light, wherein the first pattern and the second pattern have different spectral reflectances in a red wavelength range and a hue angle of -52 degrees to 92 degrees.

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