Laminate, Medium, and Method

Abstract

The problem addressed by the present invention is to provide: a laminate on which information representing, e.g., a variable pattern that is difficult to recognize with a visible light camera or naked eyes can be printed using a laser beam; a medium having a similar property; and a related method.　Provided is a laminate comprising a substrate and a near-infrared ray-absorbing layer formed by using a near-infrared ray-absorbing ink composition including a near-infrared ray-absorbing material. The near-infrared ray-absorbing material includes cesium tungsten oxide or lanthanum hexaboride. Irradiating a target section in the near-infrared ray-absorbing layer with a laser beam lowers the near-infrared ray absorption at least in a predetermined wavelength range in the target section.

Description

Technical Field

[0001] The present invention relates to a laminate including a near-infrared absorbing layer capable of printing or drawing (marking) characters, images, etc. that can be recognized by a near-infrared camera or the like, a medium having similar properties, and related methods.

Background Art

[0002] In recent years, regarding data pages, ID (identification) cards such as identity certificates, cards such as credit cards and cash cards, banknotes, etc., improving security has become an issue, and various proposals have been made for preventing forgery.

[0003] In Patent Document 1, a marking method has been proposed in which an infrared-absorbing pattern is formed by applying energy such as laser light to a base material containing ytterbium oxide. However, the infrared absorbency of ytterbium oxide is not sufficiently high, and there are also problems in terms of ease of handling.

[0004] In addition, techniques such as anti-counterfeiting using infrared-absorbing materials have been proposed as in Patent Documents 2 to 7, but problems remain in any of the techniques. For example, in Patent Document 2, variable variable information is printed by a printing method, and the following demerits exist: · When printing or transferring to the card surface, it is easily tampered with, resulting in low security. The resistance such as abrasion resistance also deteriorates. · When printing or transferring to the middle layer of the card, after printing (or issuing) personal information, press processing, card size finishing processing, etc. will be performed, so on-site issuance is considered difficult. Furthermore, if any problem occurs in the processing step, since the personal information is different, it will be necessary to start over from the first printing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In view of the above, an object of the present invention is to provide a laminate capable of printing information such as variable patterns, which is difficult to recognize with a general camera or the naked eye, on a laser beam, a medium having the same properties, and a related method. [Means for Solving the Problems]

[0007] To solve the above problems, the present invention provides a laminate including a base material layer and a near-infrared absorbing layer formed using a near-infrared absorbing ink composition containing a near-infrared absorbing material, the near-infrared absorbing material including cesium tungsten oxide or lanthanum hexaboride, and by applying a laser beam to a target portion of the near-infrared absorbing layer, the near-infrared absorption of the target portion is reduced at least in a predetermined wavelength range.

[0008] The laminate may further include an oversheet layer that is formed to overlap the near-infrared absorption layer and has near-infrared transmissivity.

[0009] In the laminate, the base material layer may be printed with a near-infrared transmissive colored ink composition or fluorescent ink composition so as to overlap at least a part of the near-infrared absorption layer.

[0010] In the laminate, the near-infrared absorptive ink composition may include a colored ink composition or fluorescent ink composition containing a near-infrared absorptive material.

[0011] The laminate may further include a near-infrared transmissive hologram layer that is formed to overlap at least a part of the near-infrared absorption layer.

[0012] In the laminate, a plurality of convex optical element portions may be formed in a region of the surface of the oversheet layer opposite to the near-infrared absorption layer that overlaps at least a part of the near-infrared absorption layer.

[0013] In the laminate, the base material layer may contain a near-infrared absorptive material.

[0014] The laminate may further include a near-infrared absorptive oversheet layer that is formed to overlap the near-infrared absorption layer and contains a near-infrared absorptive material.

[0015] The present invention also provides a medium including a near-infrared absorptive base material containing a near-infrared absorptive material, the near-infrared absorptive material including cesium tungsten oxide or lanthanum hexaboride, and when a laser beam is applied to a target portion of the near-infrared absorptive base material, the near-infrared absorptivity of the target portion in at least a predetermined wavelength range is reduced.

[0016] The present invention also provides a laminate comprising a base material layer and a near-infrared absorbing over-sheet layer containing a near-infrared absorbing material, wherein the near-infrared absorbing material contains tungsten oxide cesium or lanthanum hexaboride, and the near-infrared absorbency of at least a predetermined wavelength range of a target portion is reduced by applying laser light to the target portion of the near-infrared absorbing over-sheet layer.

[0017] The present invention also provides a method for reducing the near-infrared absorbency of at least a predetermined wavelength range of a target portion by applying laser light to the target portion of a near-infrared absorbing layer in a laminate comprising a base material layer and a near-infrared absorbing layer formed using a near-infrared absorbing ink composition containing a near-infrared absorbing material, wherein the near-infrared absorbing material contains tungsten oxide cesium or lanthanum hexaboride.

[0018] In the above method, the laminate may further comprise an over-sheet layer formed so as to overlap the near-infrared absorbing layer and having near-infrared transmissivity.

[0019] In the above method, laser light can be applied to the target portion so as to increase the reflectivity of the target portion for near-infrared light in at least a predetermined wavelength range to 5% or more.

[0020] In the above method, the base material layer of the laminate may be printed with a colored ink composition or a fluorescent ink composition having near-infrared transmissivity so as to at least partially overlap the near-infrared absorbing layer.

[0021] In the above method, the near-infrared absorbing ink composition may include a colored ink composition or a fluorescent ink composition containing a near-infrared absorbing material.

[0022] In the above method, the laminate may further comprise a near-infrared transmissive hologram layer formed so as to at least partially overlap the near-infrared absorbing layer.

[0023] In the above method, a plurality of convex optical element portions may be formed in a region of the surface of the oversheet layer of the laminate opposite to the near-infrared absorption layer and overlapping at least a part of the near-infrared absorption layer.

[0024] In the above method, the base material layer may contain a near-infrared absorbing material.

[0025] In the above method, the laminate may further include a near-infrared absorbing oversheet layer formed so as to overlap the near-infrared absorption layer and containing a near-infrared absorbing material.

[0026] The present invention also provides a method of applying laser light to a target portion of a near-infrared absorbing base material in a medium, the near-infrared absorbing base material including a near-infrared absorbing material containing cesium tungstate or lanthanum hexaboride, so as to reduce the near-infrared absorption of the target portion in at least a predetermined wavelength range.

[0027] The present invention also provides a method of applying laser light to a target portion of a near-infrared absorbing oversheet layer in a laminate including a base material layer and a near-infrared absorbing oversheet layer containing a near-infrared absorbing material, the near-infrared absorbing material including cesium tungstate or lanthanum hexaboride, so as to reduce the near-infrared absorption of the target portion in at least a predetermined wavelength range.

Advantages of the Invention

[0028] According to the present invention, in a colorless infrared-absorbing printed matter or medium, by changing the infrared absorption performance with laser light, a highly secure printed matter or medium having a variable pattern or the like that is difficult to recognize with a general camera or the naked eye but can be visually recognized using an infrared visualization device (infrared camera) equipped with a visible light spectrum cut filter can be produced. By producing a variable colorless infrared-absorbing printed matter or medium, the security is improved, and it becomes easier to determine the authenticity of any printed matter or medium such as identity cards, cards, banknotes, etc. In particular, by combining with security technologies for microdisplay printing such as micro characters, the security of the infrared-absorbing printed matter can be further improved.

Brief Description of the Drawings

[0029]

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Embodiments for Carrying Out the Invention

[0030] Hereinafter, a laminate, a medium, and a method, which are exemplary embodiments of the present invention, will be described with reference to the drawings. However, note that the laminate, the medium, and the method according to the present invention are not limited to the specific aspects described below, and can be appropriately changed within the scope of the present invention. Each function, element, etc. included in the embodiments described later can be appropriately deleted or changed within the scope of the present invention, and it is also possible to add any function, element, etc. not included in the embodiments within the scope of the present invention. For example, in the following embodiments, a laminate in which a visible colored ink layer is printed on a base material will be described. However, instead of the colored ink layer, or in addition to the colored ink layer, a fluorescent ink layer can be formed by printing using a fluorescent ink composition that emits light upon irradiation with excitation light, or a hologram layer can be formed. Alternatively, only a near-infrared absorption layer may be formed on the base material (FIG. 27). It is not essential to form the near-infrared absorption layer by offset printing, and it can also be formed by silk screen printing, gravure printing, flexographic printing, inkjet printing, etc. (it is not necessary to be microdisplay printing). The colored ink layer, the fluorescent ink layer, the hologram layer, etc. preferably have near-infrared transmissivity that allows at least a part of the irradiated near-infrared rays to pass through, but it is not essential for them to have near-infrared transmissivity. Further, in the following embodiments, a laminate in which oversheet layers are formed on the uppermost layer and the lowermost layer of the laminate will be described, but it is not essential to provide these oversheet layers. It is not essential to form the near-infrared absorbing ink layer by printing, and the near-infrared absorbing ink layer and the colored ink layer, etc. may be formed by the same method or different methods. In the embodiments described below, it is shown that it is effective to use near-infrared (ray) laser light as the laser light, and in each embodiment, the laser light is described as near-infrared laser light. However, the laser light that can be used in the present invention is not limited to this. That is, it is not essential to use near-infrared laser light by a near-infrared laser (e.g., Nd:YAG laser, YVO4 laser, fiber laser, etc.). It is also possible to use laser light by an ultraviolet laser (e.g., THG laser, etc.), a visible light laser (e.g., SHG laser, etc.), a far-infrared laser (e.g., CO2 laser, etc.).

[0031] In the following embodiments, "near-infrared rays" are defined as electromagnetic waves having a wavelength of 780 nm to 2000 nm (from "JIS Z 8117:2002 Terms for Far-Infrared Rays"). "Near-infrared laser light (near-infrared ray laser light)" is defined as laser light having a wavelength within the above wavelength range of near-infrared rays. Also, "visible light" is defined as electromagnetic waves having a wavelength of 400 nm to 780 nm. Further, in the following embodiments, "near-infrared absorbability" means the property of absorbing at least a part of the irradiated near-infrared rays, and "near-infrared transmittability" means the property of transmitting at least a part of the irradiated near-infrared rays. Similarly, in the following embodiments, "visible light absorbability" means the property of absorbing at least a part of the irradiated visible light, and "visible light transmittability" means the property of transmitting at least a part of the irradiated visible light. Also, in the following embodiments, "laser marking" of a near-infrared absorbing layer with near-infrared laser light means irradiating the near-infrared absorbing layer with near-infrared laser light to change the absorption characteristics of the near-infrared absorbing layer with respect to near-infrared rays, thereby drawing (or writing) some display content such as a pattern, characters, or other information on the near-infrared absorbing layer.

[0032] (First Embodiment) FIG. 1 is a diagram showing an observation image (visible light image) of the laminate in the first embodiment of the present invention under visible light. In the present embodiment and each subsequent embodiment, it is assumed that the laminate 1 is a printed matter for identifying an individual such as an identity card, but it is not limited thereto, and the laminate 1 can be produced as any laminate such as cards such as credit cards and cash cards, banknotes, etc. On the base material layer 8 of the laminate 1 (see FIGS. 3 and the like described later), a near-infrared transmissive colored ink (visible light absorbing colored ink) such as UV SOYBI SG Yellow (manufactured by DIC Graphics), UV SOYBI SG Red (manufactured by DIC Graphics), UV SOYBI SG Blue (manufactured by DIC Graphics), UV 161 Yellow S (manufactured by T&K TOKA), UV 161 Red S (manufactured by T&K TOKA), UV 161 Blue S (manufactured by T&K TOKA) is used, and a person image 2, person identification information 3, and a mark 4 are printed.

[0033] FIG. 2 is a diagram showing an observation image (near-infrared image) of the laminate in the first embodiment of the present invention by a near-infrared camera (note that the outer shape of the laminate is drawn for easy viewing of the figure. The same applies to other figures). Such an observation image can be obtained by observing using a near-infrared camera. In the observation image, the printed image 5 is formed by printing on the base material layer 8 using a near-infrared absorbing ink containing at least one of cesium tungsten oxide, which is a near-infrared absorbing material, and lanthanum hexaboride. As will be described later with reference to the experimental results, a near-infrared absorbing ink composition containing cesium tungsten oxide or lanthanum hexaboride has the property that the absorption rate for near-infrared rays in at least a predetermined wavelength range decreases (the reflectance increases) when irradiated with near-infrared laser light. By applying near-infrared laser light to the near-infrared absorbing ink layer formed by printing using such a near-infrared absorbing ink composition so as to draw characters, images (pictures, graphics, etc.), etc. (laser marking), the near-infrared absorption characteristics of the drawn portion change, and thus characters, images, etc. that can be recognized using an infrared camera or the like are formed on the near-infrared absorbing ink layer.

[0034] The portrait 6 is drawn by irradiating near-infrared laser light so as to draw a person by laser marking on the printed image 5. The person identification information 7 is drawn by irradiating near-infrared laser light so as to write the identification information (name, personal identification number, etc.) of the person by laser marking on the printed image 5.

[0035] As the cesium tungsten oxide-containing ink composition, an ink containing cesium tungsten oxide represented by the chemical formula (general formula) Cs x W y O z can be used (x, y, z are positive real numbers respectively). In one example, an ink containing fine particles represented by Cs 0.33 WO3 having a hexagonal crystal structure, described in Patent Document 8 (Japanese Patent No. 6160830), can be used. As the lanthanum hexaboride-containing ink composition, an ink containing fine particles represented by the chemical formula LaB6 can be used. The near-infrared absorbing ink contains a dispersant, a monomer, synthetic resins, auxiliaries, etc. in addition to cesium tungsten oxide or lanthanum hexaboride. The content of cesium tungsten oxide in the cesium tungsten oxide-containing ink is arbitrary, but in one example, it is shown in the following examples that good characteristics are obtained at a content rate of 0.5% by weight (weight percent) to 6% by weight. The content rate of lanthanum hexaboride in the lanthanum hexaboride-containing ink is also arbitrary, and in one example, it may be 0.05% by weight (weight percent) to 6% by weight, but it is shown in the following examples that good characteristics are obtained at a content rate of 0.3% by weight. Even when using a near-infrared absorbing ink containing both cesium tungsten oxide and lanthanum hexaboride, the respective content rates of cesium tungsten oxide and lanthanum hexaboride are similarly arbitrary. In any case, the preferable content rate can be changed according to the printing density (ink volume). Here, the "content rate (weight%) of cesium tungsten oxide" means the ratio of the weight of cesium tungsten oxide contained in the ink to the total weight of the ink, The content rate (wt%) of tungsten oxide cesium in the ink = {(weight of tungsten oxide cesium) / (weight of the whole ink)} × 100 is represented by the following formula. Similarly, the "content rate (wt%) of lanthanum boride 6" is the ratio of the weight of lanthanum boride 6 contained in the ink to the total weight of the ink, The content rate (wt%) of lanthanum boride 6 in the ink = {(weight of lanthanum boride 6) / (weight of the whole ink)} × 100 is represented by the following formula.

[0036] Figure 3 shows an example of the layer structure when the laminate shown in Figure 1 is viewed from the A-A' cross-section cut along the line A-A' in Figure 1 (viewed from below within the plane of the paper of Figure 1. Each layer is depicted separately to show the layer structure. The same applies to other figures showing the layer structure).

[0037] The base material layer 8 is formed of a sheet-like base material (white sheet) made of materials such as PVC (polyvinyl chloride), PET-G (copolyester), PC (polycarbonate), PET (polyethylene terephthalate), and PP (polypropylene). The base material layer 8 may be formed as a transparent sheet instead of a white sheet. In this case, for example, a transparent sheet can be produced using materials such as PVC (polyvinyl chloride), PET-G (copolyester), PC (polycarbonate), PET (polyethylene terephthalate), and PP (polypropylene). Also, when the over-sheet layers 11 and 12 are not used, the base material layer 8 may be a paper base material (such as high-quality paper or cord paper) (even when the over-sheet layers 11 and 12 are used, it is possible to use the above paper base material as the base material layer 8). Further, the base material layer 8 may contain one or both of cesium tungsten oxide and lanthanum hexaboride as a near-infrared absorbing material. For example, when molding the resin (plastic) sheet base material, a resin added with the near-infrared absorbing material is used, and such a near-infrared absorbing base material can be produced by a method of making a sheet such as extrusion molding or calendar molding. Also, in the case of a paper base material, a near-infrared absorbing material is added in advance to the pulp (raw material) used in the papermaking process and put into the papermaking process, or a near-infrared absorbing material is added in advance to the paint applied to the front side of the paper in the papermaking process, etc., whereby such a near-infrared absorbing paper base material can be produced.

[0038] A colored ink layer 9 is formed on the base material layer 8. As described above, the colored ink layer 9 is formed by printing a human image 2, human identification information 3, and a mark 4 on the base material layer 8 using a near-infrared transmissive colored ink. The method for forming the colored ink layer 9 is arbitrary. For example, printing methods such as letterpress printing, offset printing, inkjet printing, or any other arbitrary forming method can be used. Instead of, or in addition to, the colored ink layer 9, a fluorescent ink layer 9 may be formed using a near-infrared transmissive fluorescent ink such as UV fluorescent medium B (manufactured by T&K TOKA), UV fluorescent medium Y (manufactured by T&K TOKA), UV fluorescent medium R (manufactured by T&K TOKA). The fluorescent ink layer 9 can be formed by performing printing or the like on the base material layer 8 in the same manner as the colored ink layer 9 using a fluorescent ink composition, and a human image, human identification information, etc. can be printed in the same manner as in the case of colored ink printing. Alternatively, instead of the colored ink layer 9 or the fluorescent ink layer 9, or in addition to at least one of these layers, a near-infrared transmissive hologram layer 9 such as a transparent hologram may be formed.

[0039] Also, on the substrate layer 8, a near-infrared absorbing ink layer 10 is formed so as to at least partially overlap with a colored ink layer 9 (or a fluorescent ink layer, a hologram layer, etc.; the same applies in other descriptions). The near-infrared absorbing ink layer 10 is formed by printing a printed image 5 on the substrate 8 layer using a near-infrared absorbing ink as described above. However, the near-infrared absorbing ink layer 10 may be formed by any forming method other than printing. Also, it is not essential that the colored ink layer 9 and the near-infrared absorbing ink layer 10 at least partially overlap, and these may be formed completely separated on the substrate layer 8. Further, when the colored ink layer 9 and the near-infrared absorbing ink layer 10 at least partially overlap, which layer is located on top is also arbitrary (Fig. 4). In addition to the colored ink layer 9 and the near-infrared absorbing ink layer 10 being formed on the substrate layer 8 as shown in Fig. 3, Fig. 4, etc., for example, they may be formed on the back surface (the surface on the substrate layer 8 side) of one or both of the over-sheet layers 11, 12, or these layers 9, 10 may be formed on the back surface (the surface on the over-sheet layer 11 side) of the substrate layer 8 (illustration is omitted here).

[0040] On the uppermost layer of the laminate 1, an oversheet layer (transparent sheet) 12 having visible light transmittance and near-infrared light transmittance is formed, and on the lowermost layer of the laminate 1, an oversheet layer (transparent sheet) 11 having visible light transmittance and near-infrared light transmittance is formed. For the oversheet layers 11 and 12, for example, two sheets of PVC (polyvinyl chloride) with a thickness of about 0.05 mm to 0.2 mm are prepared, and one sheet is laminated on each of the lowermost layer and the uppermost layer of the laminate 1 before forming the oversheet layers 11 and 12, and the laminate 1 can be formed by applying heat and pressure to fuse them. As another example, the laminate 1 before forming the oversheet layers 11 and 12 may be laminated from above and below with any two transparent films, and adhesives may be used for adhesion between the layers. As already described, it is not essential to form the oversheet layers 11 and 12, and only one of the oversheet layers 11 and 12 may be formed, or the laminate 1 may be produced without forming either oversheet layer. Note that laser marking on the printed image 5 may be performed from the lowermost layer side or the uppermost layer side of the laminate 1. When performing laser marking from the lowermost layer side, that is, when performing laser marking through the base material layer 8, a material having near-infrared light transmittance is used as the material of the base material layer 8.). Note that one or both of the oversheet layers 11 and 12 may be a near-infrared light absorbing oversheet layer containing one or both of cesium tungsten oxide and lanthanum hexaboride as a near-infrared light absorbing material (for example, even if the oversheet layer 12 overlapping the near-infrared light absorbing ink layer 10 is a near-infrared light absorbing oversheet layer, if the irradiated (near-infrared) laser light is not completely absorbed by the oversheet layer 12 and at least a part of it passes through the oversheet layer 12 and reaches the near-infrared light absorbing ink layer 10, laser marking on the near-infrared light absorbing ink layer 10 is possible). For example, when molding the resin (plastic) sheet base material, a resin added with the near-infrared light absorbing material is used, and such a near-infrared light absorbing oversheet layer can be produced by a method of making a sheet such as extrusion molding or calender molding.

[0041] FIG. 5 is a view showing micro characters visible when a part of a printed image formed by a near-infrared absorbing ink shown in FIG. 1 is enlarged (near-infrared image). As can be seen from the enlarged view of a part 13 of the printed image 5 shown in FIG. 5, the printed image 5 includes micro characters 14 (the micro characters 14 are omitted in FIG. 2. In the following figures, minute displays such as micro characters are appropriately omitted). Instead of the micro characters, the printed image 5 may be printed including security designs such as colored patterns, minute symbols, relief patterns, etc., or these may be printed in combination. By printing minute displays such as micro characters (displays having a size that cannot be visually recognized by the naked eye. In addition to micro characters, for example, minute characters, symbols, and figures may also be used. Here, the "micro characters" are not limited to characters in μm units (characters having a diameter, width, or height of less than 1 mm), and characters having a diameter, width, or height of 1 mm or more may also be referred to as "micro characters". The same applies to the sizes of other minute displays.) (minute display printing), the forgery prevention effect of the laminate 1 can be enhanced. In particular, if micro characters having a line width and character size that are difficult to reproduce in laser marking (laser printing) described later are included, the forgery prevention effect of the laminate 1 becomes extremely high.

[0042] FIG. 6 is a diagram (near-infrared image) showing micro characters visible when a part of a printed image with near-infrared absorbing ink shown in FIG. 1 and a part of a portrait image generated by laser marking (laser drawing) are enlarged. Micro character 15 is a micro character formed during printing (micro display printing) using the near-infrared absorbing ink of printed image 5, and a part of it remains even after laser marking the portrait image 6. Micro character 16 is a micro character formed during printing using the near-infrared absorbing ink of printed image 5. In one example, printed image 5 is entirely formed by at least one of micro characters, colored patterns, fine symbols, relief patterns, etc. (security design. Note that the size of individual characters such as micro characters and fine symbols can be arbitrary, but in one example, the maximum diameter, maximum width, or maximum height can be 1000 μm (micrometers).), and thus patterns such as portrait image 6 and person identification information 7 drawn by laser marking also become security designs when enlarged with a near-infrared camera or the like. By adopting such a configuration, the effect of preventing forgery and alteration of laminate 1 can be further improved.

[0043] (Second Embodiment) FIG. 7 is a diagram (near-infrared image) showing micro characters generated by laser marking (laser printing) on the laminate in the second embodiment of the present invention. The layer structure of laminate 1 in FIG. 7 may be the same as that in the first embodiment (see FIGS. 3 and 4), and micro character 17 is written by laser marking on the near-infrared absorbing ink layer 10. The only difference from the first embodiment is that, as shown in FIG. 2, person identification information 7 is not laser marked (however, the content indicated by micro character 17 may be the same as the content indicated by person identification information 7 in FIG. 2).

[0044] (Third Embodiment) FIG. 8 is a diagram showing a near-infrared image of the laminate in the third embodiment of the present invention. Different from the laminate 1 of the first embodiment, a mark 18 is printed on a substrate 8 using a near-infrared absorbing ink so as to overlap with a mark 4 (see FIG. 1) by colored ink printing (near-infrared absorbing ink layer 10. However, the mark 18 may be formed using a near-infrared absorbing ink mixed with a colored ink. A layer formed using an ink in which other components such as a colored ink are added to the near-infrared absorbing ink is also referred to as a "near-infrared absorbing ink layer" here. The same applies to other embodiments.). Also, a portrait 19 is drawn by laser marking on the mark 18. In other respects, the laminate in the third embodiment is the same as the laminate in the first embodiment, and the layer structure may be the same in both embodiments. Note that the near-infrared absorbing ink layer (near-infrared absorption layer) may contain a near-infrared absorbing ink composition mixed with a near-infrared transmissive colored ink composition, or a near-infrared absorbing ink composition mixed with a near-infrared transmissive fluorescent ink composition, or a near-infrared absorbing ink composition mixed with both a near-infrared transmissive colored ink composition and a fluorescent ink composition. Further, the near-infrared absorbing ink composition may contain a colored ink composition containing a near-infrared absorbing material containing one or both of cesium tungstate and lanthanum hexaboride, or a fluorescent ink composition containing such a near-infrared absorbing material, or both a colored ink composition and a fluorescent ink composition containing such a near-infrared absorbing material.

[0045] (Fourth Embodiment) FIG. 9 is a view showing an observation image (visible light image) of the laminate in the fourth embodiment of the present invention by visible light (the lenticular lens is transparent but is drawn for the purpose of making the figure easier to view). FIG. 10 is a view showing an example of the layer structure when the laminate shown in FIG. 9 is viewed from the A-A' cross section cut along the line A-A' in FIG. 9 (viewed from below within the plane of FIG. 9), and FIG. 11 is a view showing another example of the layer structure when the laminate shown in FIG. 9 is viewed from the A-A' cross section cut along the line A-A' in FIG. 9 (viewed from below within the plane of FIG. 9). Different from the first embodiment shown in FIG. 1 and the like, a lenticular lens 20 is formed in a region that at least partially overlaps with the near-infrared absorbing ink layer 10 on the surface of the oversheet layer 12 opposite to the near-infrared absorbing ink layer 10 (completely overlaps in FIGS. 10 and 11, but may only partially overlap). The layer structures of FIGS. 10 and 11 may be the same as the layer structures of FIGS. 3 and 4 except that the lenticular lens 20 is formed.

[0046] FIG. 12 shows an example of the layer structure when the laminate shown in FIG. 9 is viewed along the cutting plane B-B' cut along the line B-B' in FIG. 9 (viewed from the right direction within the plane of FIG. 9). As an example of a plurality of convex optical element portions, the lenticular lens 20 has a shape such that when viewed from the direction as shown in FIG. 12, a plurality of convex lens portions appear to be arranged (along the vertical direction (B-B' line) within the plane of FIG. 9). In FIG. 12, 10 convex lens portions are drawn side by side, but this is a display for convenience of simplifying the explanation of the structure of the lenticular lens. In one example, the lenticular lens 20 can be formed to include more, for example, about 100 convex lens portions. Alternatively, the number of convex lens portions may be made smaller, and generally, the lenticular lens 20 can be formed to include any plurality of convex lens portions. As a method of forming the lenticular lens 20 on the oversheet layer 12, a previously fabricated lenticular lens may be adhered onto the oversheet layer 12 with an adhesive or the like, or the oversheet layer 12 may be formed by heat and pressure so as to have a shape that functions as the lenticular lens 20, or a lenticular lens base material may be formed on the oversheet layer 12 by a printing method and fixed by a method such as UV curing.

[0047] When viewing the patterns, characters, etc. drawn on the near-infrared absorbing ink layer 10 by laser marking using a near-infrared camera or the like, different displays (near-infrared images) can be seen depending on the viewing direction. In FIG. 12, when viewed in the direction of arrow C, the near-infrared image shown in FIG. 13 can be seen, and when viewed in the direction of arrow D in FIG. 12, the near-infrared image shown in FIG. 14 can be seen. In the example of FIG. 12, a printed image 21 is printed on the base material layer 8 using a near-infrared absorbing ink so as to overlap the lenticular lens 20 (near-infrared absorbing ink layer 10). By laser marking that irradiates the near-infrared absorbing ink layer 10 with near-infrared laser light in the direction (angle) of arrow C in FIG. 12, a portrait 22 shown in FIG. 13 is drawn on the near-infrared absorbing ink layer 10, and by laser marking that irradiates the near-infrared absorbing ink layer 10 with near-infrared laser light in the direction (angle) of arrow D in FIG. 12, the person identification information 23 shown in FIG. 14 is drawn on the near-infrared absorbing ink layer 10. In FIG. 12, the portrait 22 can be recognized by viewing the near-infrared absorbing ink layer 10 from the direction of arrow C using a near-infrared camera or the like, and the person identification information 23 can be recognized by viewing the near-infrared absorbing ink layer 10 from the direction of arrow D in FIG. 12 using a near-infrared camera or the like. That is, the latent pattern can be visually recognized by changing the observation angle, and a multiple laser image (MLI) of near-infrared absorption is realized.

[0048] FIG. 15 is a diagram conceptually explaining the principle of the lenticular (it does not need to match the specific configuration described with reference to FIGS. 10 to 14). When viewing the near-infrared absorbing ink layer 10 through the lenticular lens 20 from the first position P1 using an infrared camera or the like, each of the patterns etc. drawn on the plurality of printing portions IM1 is synthesized, and a first display (pattern) such as the portrait 22 can be recognized. When viewing the near-infrared absorbing ink layer 10 through the lenticular lens 20 from the second position P2 using an infrared camera or the like, each of the patterns etc. drawn on the plurality of printing portions IM2 is synthesized, and a second display (character) such as the person identification information 23 can be recognized.

[0049] (Fifth Embodiment) FIG. 16 is a diagram showing an observation image (visible light image) of the laminate in the fifth embodiment of the present invention by visible light, and FIG. 17 is a diagram showing an example of the layer structure when the laminate shown in FIG. 16 is viewed along the line A-A' cut in FIG. 16 (viewed from below within the plane of FIG. 16). In the base material layer 8, a clear window 24 made of a transparent material such as PVC (polyvinyl chloride), PET-G (amorphous polyester), PC (polycarbonate), PET (polyethylene terephthalate), PP (polypropylene), etc. is formed (for the two-dimensional shape, refer to FIG. 16. In the configuration of FIG. 17, the clear window 24 belongs to the base material layer 8). In one example, a part of the base material layer 8 may be opened according to the shape of the clear window 24, and a transparent resin having visible light transmittance and near-infrared transmittance may be poured into the resulting space and cured to produce the clear window 24. Alternatively, a transparent resin having visible light transmittance and near-infrared transmittance with the same size as the opened part of the base material layer 8 may be fitted and produced. Regarding the configuration other than the configuration related to the clear window 24, the laminate of the fifth embodiment may be the same as the laminate of the first embodiment.

[0050] In the laminate 1 of the fifth embodiment, a near-infrared absorbing ink layer 10 is formed so as to overlap the clear window 24 (FIG. 17). Therefore, when looking at the clear window 24 from above using a near-infrared camera or the like (defining the direction from the over-sheet layer 11 toward the over-sheet 12 in the layer structure of FIG. 17 as the "upward" direction and the opposite direction as the "downward" direction (the same applies to other embodiments). Refer also to FIG. 16. Here, the clear window 24 is viewed from above the over-sheet layer 12), the printed image 5 printed as the near-infrared absorbing ink layer 10 and the portrait image 6 drawn on the printed image 5 by laser marking can be recognized (FIG. 18). In addition, in the space formed by cutting out a part of the base material layer 8 to form the clear window 24, the above-described hologram layer as an embedded hologram or some security display may be arranged (these also belong to the base material layer 8).

[0051] FIG. 19 is a diagram schematically showing the configuration of a laser marker device for performing the laser marking (drawing, printing, etc.) described so far. The laser marker device 25 includes a control unit 26, a storage unit 27, a drive (scanning) unit 28, a laser light irradiation unit 29, and the like. While the head of the laser light irradiation unit 29 is driven by the drive unit 28, near-infrared laser light is irradiated from the head to the near-infrared absorption layer, so that the above-described laser marking on the near-infrared absorption layer (near-infrared absorbing ink layer 10) is performed. In the operation of such a laser marker device 25, a control unit 26 having various control circuits such as a CPU or an embedded control circuit (a separate computer outside the laser marker device 25 can also function as the control unit 26.) The drive unit 28, which is a drive device including a motor or the like, is controlled by the drive unit 28 above the near-infrared absorption layer (above the over-sheet layer 12 having near-infrared transparency. However, when the base material layer 8, the over-sheet layer 11, etc. have near-infrared transparency, it may be below the near-infrared absorption layer, that is, below the over-sheet layer 11.) While driving the head of the laser light irradiation unit 29 (moving (scanning) the head), the laser light irradiation unit 29 (in one example, a laser light irradiation device including a Nd:YAG laser that generates laser light with a laser wavelength of 1064 nm and includes various devices for irradiating the laser light to the target, such as a head.) irradiates near-infrared laser light (which may be a near-infrared laser beam) from the head toward the near-infrared absorption layer. Note that the storage unit 27 including a storage device such as a semiconductor memory and a magnetic disk stores various data for the control unit 26 to appropriately read and use in order to control the operation of the laser marker device 25, such as characters and images to be drawn by laser marking. The laser marker device 25 draws the characters, images, etc. stored in the storage unit 27 on the near-infrared absorption layer. Since there are many known laser marker devices, no more detailed description will be given here.

Example

[0052] The experimental results of various laminates (offset prints) of the present invention prepared using cesium tungsten oxide-containing ink and lanthanum hexaboride-containing ink are described below while comparing them with the experimental results of an offset print prepared using ytterbium oxide-containing ink as a comparative example.

[0053] (Comparative Example 1) An ink having a ytterbium oxide content of 25% by weight was prepared by mixing ytterbium(III) oxide, 3N5 powder, and an ink vehicle containing monomers, synthetic resins, and other non-infrared absorbing materials so that the weight ratio of ytterbium oxide to the ink vehicle was 25:75. Using the thus-prepared ytterbium oxide-containing ink, printing was performed on a part of the area of high-quality paper as a substrate by an offset printing machine (IGT C1 for offset printing suitability test machine, manufactured by IGT Testing Systems). The obtained printed matter was used as the laminate of Comparative Example 1, and was photographed with a VSC8000 (manufactured by Foster and Freeman), an infrared visualization device, with a filter that cuts light having a wavelength of 925 nm or less attached to the camera lens of the device.

[0054] (Example 1) Cesium tungsten oxide Cs 0.33 An ink having a cesium tungsten oxide content of 2% by weight was prepared by mixing a dispersion containing cesium tungsten oxide Cs

[0055] In the infrared photographs taken of the ytterbium oxide-containing ink and the cesium tungsten oxide-containing ink prepared in Comparative Example 1 and Example 1 respectively using the above infrared camera, and the infrared photographs taken of the respective printed materials offset-printed as described above using the respective inks, are shown in FIG. 20. From the photographs of the respective inks, it can be understood that both the ytterbium oxide-containing ink and the cesium tungsten oxide-containing ink exhibit near-infrared absorbency. However, near-infrared absorbency could not be visually recognized in the printed material offset-printed with the ytterbium oxide-containing ink. On the other hand, in the printed material offset-printed with the cesium tungsten oxide-containing ink with a low content, a difference in brightness could be visually recognized between the unprinted area and the printed area, and it was confirmed that the printed area has near-infrared absorbency.

[0056] The above experimental results are summarized in the following table.

Table 1

[0057] In the above table, the “film thickness” refers to the film thickness of the ytterbium oxide-containing ink layer or the cesium tungsten oxide-containing ink layer formed by offset printing. These are reference values assuming typical film thicknesses formed in offset printing, not measured values. The film thickness formed in the offset printing in each of the following examples is also estimated to be about 1 μm to about 3 μm. Note that experiments were conducted under the same conditions such as printing density for all examples in this specification, and theoretically, the film thickness is considered to be the same. Also, the “infrared absorption rate” in Example 1 is a value obtained using a reflectance measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation) (the reflectance is the ratio of the intensity of the reflected light when the irradiated light is reflected from the surface of the printed material, and is the ratio of the intensity of the reflected light from the surface of the target printed material to the intensity of the reflected light from the surface of the reference substrate (reference portion) serving as a reference).) (Absorption rate (%) = 100 - Reflectance (%))

[0058] Next, offset printing was performed using near-infrared absorbing ink with a cesium tungsten oxide (Cs 0.33 WO3) content (content rate) of 2% by weight on various base sheets. Laser printing was performed on each of the produced printed materials using a laser marker device, and the reflectance of electromagnetic waves in the wavelength range of visible light to near-infrared light was measured for the printed and unprinted portions. In the following examples, the "reflectance" is, as in Example 1, the ratio of the intensity of the reflected light when the irradiated light is reflected from the surface of the printed material, and is the ratio of the intensity of the reflected light from the surface of the target printed material to the intensity of the reflected light from the surface of the reference base material (reference portion) (a value obtained by measurement using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation)). The "reflectance" in the above-mentioned Example 1 and the following Examples 2 to 11 can be generally defined by the following formula. Reflectance (%) of the target portion (target surface) = {(intensity of the reflected light from the target portion (target surface)) / (intensity of the reflected light from the reference portion (reference surface))} × 100

[0059] (Example 2) A dispersion containing cesium tungsten oxide Cs 0.33 WO3, monomers, synthetic resins, auxiliaries, etc. were mixed so that the weight ratio of cesium tungsten oxide to all other components was 2:98 to prepare an ink with a cesium tungsten oxide content of 2% by weight. Using the thus-prepared cesium tungsten oxide-containing ink, printing was performed on a PC (polycarbonate) sheet as the base material using an offset printing machine (IGT C1 for offset printing suitability test machine, manufactured by IGT Testing Systems). The obtained printed material was used as the laminate of Example 2, and the reflectance of visible light to near-infrared light at wavelengths of 400 nm to 2000 nm on the printed surface before laser printing was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation). Furthermore, as a laser marker device,[[]] Using TIFF0007711592000002.tif876, laser printing was performed on the above printing surface with a laser beam from a Nd:YAG laser with a wavelength of 1064 nm. The reflectance of the laser-printed portion in the visible to near-infrared range from 400 nm to 2000 nm was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation).

[0060] (Example 3) Cesium tungstate Cs 0.33 A dispersion containing cesium tungstate WO3, monomers, synthetic resins, auxiliaries, etc. was mixed so that the weight ratio of cesium tungstate to all other components was 2:98, thereby preparing an ink with a cesium tungstate content of 2% by weight. Using the thus-prepared cesium tungstate-containing ink, printing was performed on a PET-G (copolyester) sheet as the substrate using an offset printing machine (IGT C1 for offset printing suitability testing machine, manufactured by IGT Testing Systems). The obtained printed matter was used as the laminate of Example 3, and the reflectance of the printing surface before laser printing in the visible to near-infrared range from 400 nm to 2000 nm was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation). Furthermore, as a laser marker device, Using TIFF0007711592000003.tif876, laser printing was performed on the above printing surface with a laser beam from a Nd:YAG laser with a wavelength of 1064 nm. The reflectance of the laser-printed portion in the visible to near-infrared range from 400 nm to 2000 nm was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation).

[0061] (Example 4) Cesium tungstate Cs 0.33A dispersion containing WO3, a monomer, synthetic resins, auxiliaries, etc. were mixed such that the weight ratio of cesium tungstate to all other components was 2:98, thereby preparing an ink with a cesium tungstate content of 2% by weight. Using the thus-prepared cesium tungstate-containing ink, printing was performed on a PVC (polyvinyl chloride) sheet as the substrate using an offset printing machine (IGT C1 printing suitability tester for offset, manufactured by IGT Testing Systems). The obtained printed matter was used as the laminate of Example 4, and the reflectance of visible light to near-infrared light at wavelengths from 400 nm to 2000 nm on the printed surface before laser printing was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation). Furthermore, as a laser marker device, TIFF0007711592000004.tif876 was used, and laser printing was performed on the above printed surface with laser light from a Nd:YAG laser with a wavelength of 1064 nm. The reflectance of visible light to near-infrared light at wavelengths from 400 nm to 2000 nm of the laser-printed portion was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation).

[0062] The measurement results of the reflectance performed in Examples 2 to 4 above are shown in FIG. 21. Also, the measurement results of the reflectance performed in Example 2 are shown in FIG. 22, the measurement results of the reflectance performed in Example 3 are shown in FIG. 23, and the measurement results of the reflectance performed in Example 4 are shown in FIG. 24, respectively, extracted from the graph of FIG. 21 and shown. In the graphs of FIGS. 21 to 24, the value on the horizontal axis is the wavelength of the electromagnetic wave (nm), and the value on the vertical axis is the reflectance (%) on the printed surface or the laser-printed portion of the electromagnetic wave with the wavelength indicated by the value on the horizontal axis.

[0063] As is clear from the graphs of FIGS. 21 to 24, it can be seen that the reflectance increases (the absorption rate decreases) in the near-infrared region by laser printing regardless of the substrate used. Although the increase width varies depending on the wavelength on the horizontal axis, in the near-infrared region of 780 nm to 2000 nm, it can be read that the reflectance increases by at least 5% or more, generally 10% to 15%, or more, due to laser printing. Also, as a general tendency, the change in reflectance before and after laser printing in the visible light wavelength range is small compared to the change in reflectance before and after laser printing in the near-infrared region. Therefore, it is considered that laser printing can be used to draw characters, images, etc. that are relatively difficult to visually recognize with the naked eye or a general camera.

[0064] Next, offset printing was performed on high-quality paper as a substrate sheet using six types of near-infrared absorbing inks having different cesium tungsten oxide (Cs 0.33 WO3) contents (content ratios) ranging from 0.5% by weight to 6% by weight, and the reflectance of electromagnetic waves in the wavelength range of visible light to near-infrared light of the printed surface (near-infrared absorbing ink layer) in each of the produced printed materials was measured. Note that the definition of reflectance and the equipment used for reflectance measurement are the same as those in Examples 1 to 4 described above.

[0065] (Examples 5 to 10) Cesium tungsten oxide Cs 0.33 A dispersion containing WO3, monomers, synthetic resins, auxiliaries, etc., with the weight ratio of cesium tungsten oxide to all other components being: (Example 5) 0.5:99.5 (Example 6) 1:99 (Example 7) 1.3:98.7 (Example 8) 2:98 (Example 9) 3:97 (Example 10) 6:94 By mixing them so as to obtain the following, six types of inks having a cesium tungsten oxide content of 0.5% by weight to 6% by weight were prepared. Using each of the thus-prepared cesium tungsten oxide-containing inks, printing was performed on the above high-quality paper sheet as the base material using an offset printing machine (offset printing suitability tester IGT C1 (manufactured by IGT Testing Systems)). The six types of printed matter obtained were used as the laminates of Examples 5 to 10, and the reflectance of visible light to near-infrared light at wavelengths of 400 nm to 2000 nm was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation).

[0066] The measurement results of the reflectance performed in Examples 5 to 10 above are shown in FIG. 25. In the graph of FIG. 25, the value on the horizontal axis is the wavelength (nm) of the electromagnetic wave, and the value on the vertical axis is the reflectance (%) of the electromagnetic wave having the wavelength indicated by the value on the horizontal axis on the printed surface. It can be seen that at least in the near-infrared wavelength range, the higher the content of cesium tungsten oxide, the lower the reflectance (the higher the absorption rate) at the same wavelength. A similar tendency can be read in the visible light wavelength range. That is, the higher the content of cesium tungsten oxide in the ink, the easier it is to recognize the image offset-printed using the ink with a near-infrared camera or the like. However, in this case, since the visible light reflectance also decreases, the possibility of visual recognition with the naked eye, a general camera, etc. also increases. Therefore, it is considered preferable to select an appropriate cesium tungsten oxide content in consideration of security.

[0067] Next, offset printing was performed using an infrared-absorbing ink with a lanthanum hexaboride (LaB6) content (content rate) of 0.3 wt% on a PC (polycarbonate) as a base sheet. Laser printing was performed on the produced printed matter using a laser marker device, and the reflectance of electromagnetic waves in the wavelength range of visible light to near-infrared light was measured for the printed part and the non-printed part, respectively. Also in this example, the reflectance is the ratio of the intensity of the reflected light when the irradiated light is reflected on the surface of the printed matter, and is the ratio of the intensity of the reflected light from the surface of the target printed matter to the intensity of the reflected light from the surface of the base material (reference part) used as a reference (a value obtained by measurement using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation)).

[0068] (Example 11) A dispersion containing lanthanum hexaboride (LaB6), monomers, synthetic resins, auxiliaries, etc. were mixed so that the weight ratio of lanthanum hexaboride to all other components was 0.3:99.7, thereby producing an ink with a lanthanum hexaboride content of 0.3 wt%. Using the thus-produced lanthanum hexaboride-containing ink, printing was performed on a PC (polycarbonate) sheet as a base material using an offset printing machine (IGT C1 for offset printing suitability test machine (manufactured by IGT Testing Systems)). The obtained printed matter was used as the laminate of Example 11, and the reflectance of visible light to near-infrared light at a wavelength of 400 nm to 2000 nm on the printed surface before laser printing was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation). Furthermore, as a laser marker device, TIFF0007711592000005.tif876 was used, and laser printing was performed on the above-mentioned printed surface with a laser beam from a Nd:YAG laser with a wavelength of 1064 nm. The reflectance of visible light to near-infrared light at a wavelength of 400 nm to 2000 nm for the laser-printed part was measured using a JASCO V-670 ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation).

[0069] The measurement results of the reflectance performed in the above-described Example 11 are shown in FIG. 26. In the graph of FIG. 26, the value on the horizontal axis is the wavelength (nm) of the electromagnetic wave, and the value on the vertical axis is the reflectance (%) in the printed surface or the laser-printed portion of the electromagnetic wave having the wavelength indicated by the value on the horizontal axis.

[0070] As is apparent from the graph of FIG. 26, it can be seen that the reflectance increases (the absorption rate decreases) in the near-infrared region by laser printing. Although the rising width varies depending on the wavelength on the horizontal axis, in the near-infrared region of 780 nm to 1400 nm, it can be read that the reflectance has increased by approximately 5% to 14% by laser printing. Also, as a general tendency, since the change in reflectance before and after laser printing in the wavelength range of visible light is smaller than the change in reflectance before and after laser printing in the near-infrared region of about 800 nm to 1200 nm, it is considered that characters, images, etc. that are relatively difficult to visually recognize with the naked eye or a general camera can be drawn by laser printing.

[0071] (Sixth Embodiment) FIG. 28 is a diagram showing an observation image (visible light image) of the medium according to the sixth embodiment of the present invention and the laminate in the seventh embodiment under visible light, and FIG. 29 is an observation image (near-infrared image) of the medium according to the sixth embodiment of the present invention and the laminate in the seventh embodiment by a near-infrared camera. First, the medium 1 of the sixth embodiment will be described.

[0072] FIG. 30 shows an example of the structure when the medium (sixth embodiment) shown in FIG. 28 is viewed from the A-A' cross-section cut along the line A-A' in FIG. 28. (Viewed from below within the plane of the paper of FIG. 28.) The medium 1 is configured as a near-infrared absorbing substrate 8 containing one or both of cesium tungsten oxide and lanthanum hexaboride as a near-infrared absorbing material. For example, when forming the resin (plastic) sheet substrate, a resin added with the near-infrared absorbing material is used, and such a near-infrared absorbing substrate can be produced by methods of making a sheet such as extrusion molding or calendar molding. Also, in the case of a paper substrate, a near-infrared absorbing material is added in advance to the pulp (raw material) used in the papermaking process and put into the papermaking process, or a near-infrared absorbing material is added in advance to the paint applied to the front side of the paper in the papermaking process, etc., whereby such a near-infrared absorbing paper substrate can be produced. In view of the experimental results described with reference to FIGS. 20 to 26, in the same manner as when printing on a substrate using a near-infrared absorbing ink composition containing cesium tungsten oxide or lanthanum hexaboride, by applying laser light to the target portion of the near-infrared absorbing substrate 8 containing cesium tungsten oxide or lanthanum hexaboride, the near-infrared absorption in at least a predetermined wavelength range (for a substrate containing cesium tungsten oxide, for example, the near-infrared region of 780 nm to 2000 nm; for a substrate containing lanthanum hexaboride, for example, the near-infrared region of 780 nm to 1400 nm) of the target portion is considered to decrease. Therefore, after performing laser marking by irradiating (near-infrared) laser light so as to write (draw) characters, symbols, patterns, etc. on the near-infrared absorbing substrate layer 8 in the same manner as in the first to fifth embodiments, if a near-infrared image is observed by photographing with a near-infrared camera, etc., it is considered that the characters, symbols, patterns, etc. written (drawn) by the laser marking can be confirmed.

[0073] Figure 29 shows an example of such a near-infrared image. Since the medium 1 is composed of the near-infrared absorbing substrate 8, the unlaser-marked areas have near-infrared absorption and are observed as dark in the near-infrared image. On the other hand, the human image 6 and the human identification information 7 drawn by laser marking have reduced near-infrared absorption in the drawn part (target part). Therefore, the near-infrared light irradiated from the near-infrared camera passes through the target part and is reflected by, for example, an object behind the medium 1 (if the medium 1 is placed on a stand, then that stand) and enters the near-infrared camera, etc., and is observed as bright in the near-infrared image. On the other hand, in the visible light image observed with a visible light camera, the human image 6 and the human identification information 7 formed by laser marking are invisible (Fig. 28) or at least difficult to visually recognize.

[0074] In the example of Fig. 30, the medium 1 has been described as being composed of only one layer of the near-infrared absorbing substrate 8. However, in the medium 1 according to the sixth embodiment of the present invention, an arbitrary layer such as a colored ink layer (or a fluorescent ink layer, or a hologram layer), a near-infrared absorbing ink layer, an oversheet layer, etc. may be further formed on the near-infrared absorbing substrate 8 (for example, in the oversheet layer, the lenticular lens already described may be formed). Also, as the substrate layer in the laminate according to the above-described first to fifth embodiments and the seventh embodiment described later, the above-described near-infrared absorbing substrate may be used.

[0075] (Seventh Embodiment) Next, the laminate 1 of the seventh embodiment will be described. As already described, Fig. 28 shows the observation image (visible light image) of the laminate in the seventh embodiment of the present invention under visible light, and Fig. 29 shows the observation image (near-infrared image) of the laminate in the seventh embodiment by a near-infrared camera.

[0076] FIG. 31 shows an example of the structure when the laminate (seventh embodiment) shown in FIG. 28 is viewed in the A-A' cross section cut along the line A-A' in FIG. 28. (Viewed from below in the plane of FIG. 28.) The laminate 1 may be a sheet-like base material (white sheet) made of a material such as PVC (polyvinyl chloride), PET-G (copolyester), PC (polycarbonate), PET (polyethylene terephthalate), or PP (polypropylene) used in Example 1 or the like, may be formed as a transparent sheet, or may be the near-infrared absorbing base material of the sixth embodiment. ) and oversheet layers 11 and 12 formed as upper and lower layers thereof. The oversheet layers 11 and 12 are configured as near-infrared absorbing oversheet layers containing one or both of cesium tungstate and lanthanum hexaboride as near-infrared absorbing materials. For example, when molding the resin (plastic) sheet base material, a resin added with the near-infrared absorbing material is used, and such a near-infrared absorbing oversheet layer can be produced by a method of making a sheet such as extrusion molding or calender molding. A near-infrared absorbing oversheet layer can be laminated on each of the upper and lower surfaces of the base material layer 8, one sheet each, and the laminate 1 can be formed by applying heat and pressure to fuse them. Note that only one of the oversheet layers 11 and 12 may be a near-infrared absorbing oversheet layer, or only one of the oversheet layer 11 and the oversheet layer 12 may be formed as a near-infrared absorbing oversheet layer (an oversheet layer is provided only on one side of the base material layer 8).

[0077] In view of the experimental results described with reference to FIGS. 20 to 26, similar to the case where printing is performed on a substrate using a near-infrared absorbing ink composition containing tungsten oxide cesium or lanthanum hexaboride, by applying laser light to the target portions of the near-infrared absorbing overcoat layers 11 and 12 containing tungsten oxide cesium or lanthanum hexaboride, the near-infrared absorbency in at least a predetermined wavelength range of the target portions (for example, in the near-infrared region of 780 nm to 2000 nm if the substrate contains tungsten oxide cesium, or in the near-infrared region of 780 nm to 1400 nm if the substrate contains lanthanum hexaboride) is considered to decrease. Therefore, after performing laser marking by irradiating (near-infrared) laser light so as to write (draw) characters, symbols, patterns, etc. on the near-infrared absorbing overcoat layers 11 and 12 in the same manner as in the first to fifth embodiments, and observing a near-infrared image by photographing with a near-infrared camera or the like, it is considered that the characters, symbols, patterns, etc. written (drawn) by the laser marking can be confirmed.

[0078] FIG. 29 shows an example of such a near-infrared image (for the sake of convenience, it is assumed that laser marking is performed on the near-infrared absorbing overcoat layer 12, and the near-infrared image is obtained by photographing the surface on the near-infrared absorbing overcoat layer 12 side in the laminate 1 with a near-infrared camera or the like). Since the overcoat layer 12 contains tungsten oxide cesium or lanthanum hexaboride as a near-infrared absorbing material, the unlaser-marked regions have near-infrared absorbency and are observed darkly in the near-infrared image. On the other hand, the human figure image 6 and the human identification information 7 drawn by the laser marking are brightly observed in the near-infrared image because the near-infrared absorbency of the drawn portions (target portions) is decreased, and the near-infrared light irradiated from the near-infrared camera passes through the target portions and is reflected by, for example, the substrate layer 8 behind the near-infrared absorbing overcoat layer 12 and enters the near-infrared camera. On the other hand, in the visible light image observed with a visible light camera, the human figure image 6 and the human identification information 7 formed by the laser marking are invisible (FIG. 28) or at least difficult to visually recognize.

[0079] In the example of FIG. 31, the laminate 1 has been described as being composed of three layers, namely the base material 8 and the over-sheet layers 11 and 12. However, in the laminate 1 according to the seventh embodiment of the present invention, after forming an arbitrary layer such as a colored ink layer (or a fluorescent ink layer, or a hologram layer), a near-infrared absorbing ink layer, etc. on the base material 8, at least one of the over-sheet layers 11 and 12 may be formed. Alternatively, for example, in at least one of the over-sheet layers 11 and 12, the lenticular lens described above may be formed. As at least one of the over-sheet layers 11 and 12 in the laminates according to the first to fifth embodiments described above, the above-described near-infrared absorbing over-sheet layer may be used.

[0080] (An example of use) In one example, the laminates and media in the above-described embodiments and examples can be used as printed materials such as identity certificates with high security. In FIG. 1, by comparing the portrait 2 and the personal identification information 3 printed with colored ink (visible to the naked eye) with the portrait 6 and the personal identification information 7 drawn by laser marking in the printed image 5 with near-infrared absorbing ink (recognizable by an infrared camera, etc.), it is possible to determine whether the person indicated by the portrait 2 and the personal identification information 3 (visible information) matches the person indicated by the portrait 6 and the personal identification information 7 (infrared information). Thus, it is possible to determine the authenticity of an identity certificate or the like (if they match, it can be determined that the identity certificate or the like is genuine, and if they do not match, it can be determined that the identity certificate or the like is not genuine.), and if it has been forged, it can be detected. The pattern drawn by the laser may not be limited to a monotonous pattern such as a barcode, number, or two-dimensional code, but may be a portrait or the like as described above. Also, by combining with security technologies for microdisplay printing such as micro characters, the security of the infrared-absorbing printed material can be further improved.

Industrial Applicability

[0081] The present invention can be used for ID cards such as identity certificates, cards such as credit cards and cash cards, banknotes, etc., but is not limited to these and can be used for any laminate or medium.

Explanation of Signs

[0082] 1 Laminate (printed matter), or medium 2 Portrait (printed with colored ink, fluorescent ink, or hologram) 3 Personal identification information (printed with colored ink, fluorescent ink, or hologram) 4 Mark (printed with colored ink, fluorescent ink, or hologram) 5 Printed image (printed with near-infrared absorbing ink) 6 Portrait (laser marking) 7 Personal identification information (laser marking) 8 Substrate layer (white sheet) or near-infrared absorbing substrate 9 Colored ink layer, fluorescent ink layer, or hologram layer 10 Near-infrared absorbing ink layer 11, 12 Overlay sheet layer (transparent sheet or near-infrared absorbing overlay sheet) 13 Part of printed image (printed with near-infrared absorbing ink) 14 Microtext included in printed image (printed with near-infrared absorbing ink) 15 Microtext (printed with near-infrared absorbing ink) 16 Microtext (printed with near-infrared absorbing ink) 17 Microtext (laser marking) 18 Mark (printed with near-infrared absorbing ink) 19 Portrait (laser marking) 20 Lenticular lens 21 Printed image (printed with near-infrared absorbing ink) 22 Portrait (laser marking) 23 Personal identification information (laser marking) 24 Clear window (transparent resin) 25 Laser marker device 26 Control unit 27 Memory unit 28 Drive (scanning) unit 29 Laser irradiation unit IM1 Printing unit (laser marking) IM2 Printing unit (laser marking)

Claims

1. A base material layer, and a near-infrared absorption layer formed using a near-infrared absorption ink composition containing a near-infrared absorbing material, comprising: the near-infrared absorbing material includes tungsten oxide cesium or lanthanum hexaboride, and by applying laser light to a target portion of the near-infrared absorption layer, the near-infrared absorbency of the target portion in at least a predetermined wavelength range is reduced, an opening is provided in the base material layer, and a transparent material having visible light transmissivity and near-infrared transmissivity is provided in the opening, and the near-infrared absorbing material is formed so as to overlap the transparent material, a laminate.

2. The laminate according to claim 1, further comprising an over-sheet layer formed so as to overlap the near-infrared absorption layer and having near-infrared transmissivity.

3. The laminate according to claim 1 or 2, wherein printing using a near-infrared transmissive colored ink composition or fluorescent ink composition is performed on the base material layer so as to at least partially overlap the near-infrared absorption layer.

4. The laminate according to any one of claims 1 to 3, wherein the near-infrared absorption ink composition includes a colored ink composition or a fluorescent ink composition containing the near-infrared absorbing material.

5. The laminate according to any one of claims 1 to 4, further comprising a near-infrared transmissive hologram layer formed so as to at least partially overlap the near-infrared absorption layer.

6. The laminate according to claim 2, wherein a plurality of convex optical element portions are formed in a region of the surface of the over-sheet layer opposite to the near-infrared absorption layer and overlapping at least a part of the near-infrared absorption layer.

7. The laminate according to any one of claims 1 to 6, wherein the base material layer contains the near-infrared absorbing material.

8. The laminate according to claim 1, further comprising a near-infrared absorption over-sheet layer formed so as to overlap the near-infrared absorption layer and containing the near-infrared absorbing material.

9. A base material layer, and a near-infrared absorption over-sheet layer containing a near-infrared absorbing material, comprising: the near-infrared absorbing material includes tungsten oxide cesium or lanthanum hexaboride, and by applying laser light to a target portion of the near-infrared absorption over-sheet layer, the near-infrared absorbency of the target portion in at least a predetermined wavelength range is reduced, The base material layer is provided with an opening, and a transparent material having visible light transmittance and near-infrared light transmittance is provided in the opening, and the near-infrared light absorbing over-sheet layer is formed so as to overlap the transparent material. Medium. **Claim 10** A base material layer, A near-infrared light absorbing layer formed using a near-infrared light absorbing ink composition containing a near-infrared light absorbing material, wherein the near-infrared light absorbing material contains cesium tungsten oxide or lanthanum hexaboride, and the near-infrared light absorbing layer A method, characterized in that, in a laminate provided with the above, an opening is provided in the base material layer, a transparent material having visible light transmittance and near-infrared light transmittance is provided in the opening, and the near-infrared light absorbing material is formed so as to overlap the transparent material, and laser light is applied to a target portion of the near-infrared light absorbing layer so as to reduce the near-infrared light absorption of the target portion in at least a predetermined wavelength range. **Claim 11** The method according to claim 10, characterized in that the laminate further comprises an over-sheet layer formed so as to overlap the near-infrared light absorbing layer and having near-infrared light transmittance. **Claim 12** The method according to claim 10 or 11, characterized in that laser light is applied to the target portion so as to increase the reflectance of the target portion to near-infrared light in at least a predetermined wavelength range by 5% or more. **Claim 13** The method according to any one of claims 10 to 12, characterized in that printing using a near-infrared light transmissive colored ink composition or fluorescent ink composition is performed on the base material layer of the laminate so as to at least partially overlap the near-infrared light absorbing layer. **Claim 14** The method according to any one of claims 10 to 13, characterized in that the near-infrared light absorbing ink composition includes a colored ink composition or a fluorescent ink composition containing the near-infrared light absorbing material. **Claim 15** The method according to any one of claims 10 to 14, characterized in that the laminate further comprises a near-infrared light transmissive hologram layer formed so as to at least partially overlap the near-infrared light absorbing layer. **Claim 16** The method according to claim 11, characterized in that a plurality of convex optical element portions are formed in a region of the over-sheet layer of the laminate that overlaps at least a part of the near-infrared light absorbing layer and is on the surface opposite to the near-infrared light absorbing layer. **Claim 17** The method according to any one of claims 10 to 16, wherein the base material layer contains the near-infrared absorbing material.

18. The method according to claim 10, wherein the laminate further comprises a near-infrared absorbing overcoat layer formed so as to overlap the near-infrared absorbing layer and containing the near-infrared absorbing material.

19. A base material layer, A near-infrared absorbing overcoat layer containing a near-infrared absorbing material, wherein the near-infrared absorbing material contains cesium tungsten oxide or lanthanum hexaboride, A method of applying laser light to a target portion of the near-infrared absorbing overcoat layer in a laminate comprising: an opening provided in the base material layer; a transparent material having visible light transmissivity and near-infrared transmissivity provided in the opening; and the near-infrared absorbing overcoat layer formed so as to overlap the transparent material, the laser light being applied so as to reduce the near-infrared absorbency of the target portion at least in a predetermined wavelength range.

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