Security element and security document

Abstract

A security element (10) according to one aspect of the present disclosure is provided with a laminate (12) on a substrate (11). The laminate includes: a phosphor-dispersed layer (14) in which a plurality of phosphor particles (14A) are dispersed; and a light absorption layer (13) that is disposed between the substrate and the phosphor-dispersed layer and is capable of absorbing excitation light for exciting the plurality of phosphor particles.

Description

Security Elements and Security Documents

[0001] The present disclosure relates to security elements and security documents.

[0002] One method proposed for determining the authenticity or identifying an object is to register and verify the distribution of multiple phosphor particles dispersed in a resin as information specific to the object (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-94183

[0004] The distribution of multiple phosphor particles dispersed in a resin can be determined by irradiating the multiple phosphor particles with excitation light and visually observing or capturing the fluorescent light emitted from the multiple phosphor particles. However, when the excitation light contains visible light, the visible light contained in the excitation light acts as noise in the emission distribution formed by the fluorescent light (hereinafter simply referred to as the "emission distribution"), reducing the contrast of the emission distribution. Therefore, it is desirable to provide a security element and a security document that can suppress the reduction in the contrast of the emission distribution.

[0005] A security element according to a first aspect of the present disclosure comprises a laminate on a substrate, the laminate including a phosphor distribution layer in which a plurality of phosphor particles are dispersed, and a light absorption layer disposed between the substrate and the phosphor distribution layer and capable of absorbing excitation light that excites the plurality of phosphor particles.

[0006] A security document according to a second aspect of the present disclosure comprises a first laminate on a card substrate, the first laminate including a security element. The security element is disposed in at least a portion of an area facing the card substrate. The security element has a second laminate on the element substrate. The second laminate includes a phosphor distribution layer in which a plurality of phosphor particles are dispersed, and a light absorption layer disposed between the element substrate and the phosphor distribution layer, the light absorption layer being capable of absorbing excitation light that excites the plurality of phosphor particles.

[0007] In the security element according to the first aspect of the present disclosure, a light-absorbing layer capable of absorbing excitation light that excites the phosphor particles is provided between the substrate and the phosphor distribution layer. This allows components of the excitation light incident on the security element that are not absorbed by the phosphor particles but that pass through the phosphor distribution layer are absorbed by the light-absorbing layer. As a result, the components of the excitation light incident on the security element that are not absorbed by the phosphor distribution layer and the light-absorbing layer and that leak out of the security element due to reflection by the substrate, for example, are less than in a case where the light-absorbing layer is not provided.

[0008] In a security document according to a first aspect of the present disclosure, a light-absorbing layer capable of absorbing excitation light that excites phosphor particles is provided between the element substrate and the phosphor distribution layer. This allows components of the excitation light incident on the security element that are not absorbed by the phosphor particles but that pass through the phosphor distribution layer are absorbed by the light-absorbing layer. As a result, the components of the excitation light incident on the security element that are not absorbed by the phosphor distribution layer and the light-absorbing layer and that leak out of the security element, for example, by being reflected by the element substrate, are less than in a case where the light-absorbing layer is not provided.

[0009] FIG. 1 is a diagram illustrating an example of the cross-sectional configuration of a security element according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the wavelength bands of excitation light, fluorescent light, and excitation light transmitted through a light-absorbing layer, an example of the wavelength dependency of the light transmittance of the light-absorbing layer, and an example of a color-matching function. FIG. 3 is a diagram illustrating an example of the wavelength dependency of the transmittance of the light-absorbing layer of FIG. 1 and an example of the emission intensity distribution of excitation light. FIG. 4 is a diagram illustrating an example of the relationship between the amount of transmitted light and the contrast ratio of the light-absorbing layer of FIG. 1. FIG. 5 is a diagram illustrating an example of the integrated value of visual stimulation by fluorescent light and excitation reflected light. FIG. 6 is a diagram illustrating the state in which excitation incident light is irradiated onto the security element of FIG. 1. FIG. 7 is a diagram illustrating an example of the relationship between the transmittance at 400 nm of the light-absorbing layer of FIG. 1 and the contrast ratio. FIG. 8 is a diagram illustrating a modified cross-sectional configuration of the security element of FIG. 1. FIG. 9 is a diagram illustrating a modified cross-sectional configuration of the security element of FIG. 1. FIG. 10 is a diagram illustrating a modified cross-sectional configuration of the security element of FIG. 8. FIG. 11 is a diagram illustrating an example of the cross-sectional configuration of the image information layer of FIGS. 9 and 10. FIG. 12 is a diagram showing how imaging light is irradiated onto the security element of FIGS. 9 and 10 . FIG. 13 is a diagram showing an example of the wavelength bands of fluorescent light, image light, and imaging light, and an example of the wavelength dependency of the transmittance of a light absorption layer. FIG. 14 is a diagram for explaining an example of a method for deriving feature quantities of a security element. FIG. 15 is a diagram for explaining another example of a method for deriving feature quantities of a security element. FIG. 16 is a diagram showing an example of a perspective configuration of a security document including the security element of FIGS. 1 and 8 to 10 . FIG. 17 is a diagram showing an example of a cross-section of the security document of FIG. 16 taken along line A-A. FIG. 18 is a diagram showing an example of a perspective configuration of a passport including the security document of FIG. 16 . FIG. 19 is a diagram showing a modification of the security document of FIG. 16 . FIG. 20 is a diagram showing an example of a cross-section of the security document of FIG. 19 taken along line A-A. FIG. 21 is a diagram showing an example of a perspective configuration of a passport including the security document of FIG. 19 .

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description is a specific example of the present disclosure, and the present disclosure is not limited to the following aspects.

[0011] 1. Embodiment [Configuration] A security element 10 according to an embodiment of the present disclosure will be described. Fig. 1 shows an example of the cross-sectional configuration of the security element 10 according to the present embodiment. For example, as shown in Fig. 1, the security element 10 includes a laminate 12 on a support substrate 11.

[0012] The support substrate 11 is a support for supporting the laminate 12. The support substrate 11 is preferably made of a material that has excellent heat resistance and dimensional stability in the planar direction. The support substrate 11 may be either optically transparent or non-optically transparent to visible light. When the support substrate 11 is poorly transparent to visible light, the surface color of the support substrate 11 may be, for example, white or a color other than white.

[0013] The support substrate 11 may be, for example, a substrate having high rigidity such as a wafer, or may be flexible thin glass, film, or paper. By using a flexible substrate as the support substrate 11, a flexible (bendable) security element 10 can be realized. Examples of materials constituting the support substrate 11 include inorganic materials, metal materials, and plastics. Examples of inorganic materials include silicon (Si), silicon oxide (SiOx), and silicon nitride (SiN Ｘ ) and aluminum oxide (AlO Ｘ The silicon oxide includes glass and spin-on glass (SOG), etc. The metal material includes at least one selected from the group consisting of aluminum (Al), nickel (Ni), stainless steel, etc.

[0014] The support substrate 11 may include, for example, plastic. The support substrate 11 may include at least one selected from the group consisting of a colorant, an antistatic agent, a flame retardant, a surface modifier, and the like, as necessary. The plastic used for the support substrate 11 includes, for example, at least one selected from the group consisting of an ester-based resin, an amide-based resin, an olefin-based resin, a vinyl-based resin, an acrylic-based resin, an imide-based resin, a styrene-based resin, and an engineering plastic. When the support substrate 11 includes two or more types of resins, the two or more types of resins may be mixed, copolymerized, or laminated.

[0015] As shown in FIG. 1 , the laminate 12 includes a light irradiation surface S1, a light absorption layer 13, and a phosphor distribution layer 14. The light absorption layer 13 is disposed between the support substrate 11 and the phosphor distribution layer 14. The phosphor distribution layer 14 is disposed between the light absorption layer 13 and the light irradiation surface S1. The phosphor distribution layer 14 is a layer in which a plurality of phosphor particles 14A are dispersed in a resin binder 14B. The light irradiation surface S1 is the outermost surface of the laminate 12, and corresponds to the surface onto which excitation light L1 is incident from the outside. FIG. 1 shows an example in which the surface of the phosphor distribution layer 14 serves as the light irradiation surface S1.

[0016] The excitation light L1 is light having optical energy with a wavelength in the near-ultraviolet region that is capable of exciting the plurality of phosphor particles 14A contained in the phosphor distribution layer 14. The excitation light L1 has a peak wavelength λ1 in the near-ultraviolet region, as shown in FIG. 2 . The peak wavelength λ1 is, for example, 385 nm. The light irradiation surface S1 also serves as the surface from which the fluorescent light L2 is emitted to the outside. The fluorescent light L2 is light having optical energy with a wavelength in the visible region that is generated from the plurality of phosphor particles 14A contained in the phosphor distribution layer 14 when the plurality of phosphor particles 14A are excited by the excitation light L1. The fluorescent light L2 has a peak wavelength λ2 in the green wavelength region, as shown in FIG. 2 . The peak wavelength λ2 is, for example, 514 nm. The light irradiation surface S1 also serves as the surface on which the fluorescent light L2 forms a phosphor image IL. The phosphor image IL is an image that reflects the distribution of the plurality of phosphor particles 14A contained in the phosphor distribution layer 14.

[0017] The light absorbing layer 13 is capable of absorbing the excitation light L1. The light absorbing layer 13 is, for example, a layer in which a plurality of near-ultraviolet absorbing particles are dispersed in a resin binder. Each near-ultraviolet absorbing particle is capable of absorbing light energy of a wavelength in the near-ultraviolet region contained in incident external light. Each near-ultraviolet absorbing particle is formed from a material capable of absorbing light energy of a wavelength in the near-ultraviolet region. The component of the excitation light L1 that transmits through the light absorbing layer 13 has a peak wavelength in the near-ultraviolet region, for example, as shown in FIG. 2 .

[0018] The light absorption layer 13 has light absorption characteristics such that the amount of transmitted light of the excitation light L1 is 30% or less, or that the light transmittance at a wavelength of 400 nm, which corresponds to the lower limit of the visible light range, is 70% or less. Assume that the excitation light L1 has a distribution with a peak in the near-ultraviolet range, as shown in FIG. 3 . The excitation light L1 also contains wavelength components of 400 nm or more, which is the visible light range. If light of wavelengths of 400 nm or more, which is the visible light range, leaks from the light irradiation surface S1 due to reflection by the support substrate 11 or the like, it becomes noise in the emission distribution formed by the fluorescent light, reducing the contrast of the emission distribution. However, if the near-ultraviolet components contained in the excitation light L1 that has passed through the phosphor distribution layer 14 are sufficiently absorbed by the light absorption layer 13 having the above-described light absorption characteristics, the amount of visible light components of the excitation light that become noise leaking from the light irradiation surface S1 is reduced, and the reduction in contrast of the emission distribution formed by the fluorescent light is sufficiently suppressed.

[0019] As described above, the phosphor distribution layer 14 is a layer in which a plurality of phosphor particles 14A are dispersed in a resin binder 14B. Each phosphor particle 14A is formed of a phosphor having an excitation wavelength in the near-ultraviolet range. When excitation light L1 is incident on each phosphor particle 14A, each phosphor particle 14A is capable of absorbing the optical energy in the near-ultraviolet range contained in the excitation light L1 and emitting light (fluorescent light L2) with a wavelength longer than the wavelength of the absorbed light. Each phosphor particle 14A is formed of a material capable of absorbing the optical energy in the near-ultraviolet range contained in the excitation light L1 and emitting fluorescent light L2. Each phosphor particle 14A is formed of a phosphor capable of absorbing the excitation light L1 and emitting fluorescent light L2 with a peak in the visible range.

[0020] The diameter of each phosphor particle 14A is preferably 30 μm or more in order to make it easier to grasp the distribution of the multiple phosphor particles. The diameter of each phosphor particle 14A is preferably 100 μm or less in order to prevent the presence of each phosphor particle 14A from being visually recognized by humans. However, the diameter of each phosphor particle 14A is not limited to the above value.

[0021] 4 shows an example of the relationship between the amount of transmitted excitation light and the contrast ratio (Ia / Ib) in the light-absorbing layer 13 of FIG. 1 . This example shows a case in which a phosphor with an external quantum efficiency of 5% and an emission peak at wavelength λ2 in the visible light region is excited by an LED with an emission peak at wavelength λ1, which is shorter than λ2, and an emission spectrum that includes visible light. The transmittance of the light-absorbing layer 13 at λ2 is set to 85%. The contrast ratio (Ia / Ib) is the ratio of the integral value Ia of the visual stimulus of the image generated by the fluorescent light L2 contained in the phosphor image IL to the integral value Ib of the visual stimulus of the image generated by the reflected excitation light L3, as shown in FIG. 5 , for example.

[0022] Here, as shown in FIG. 6 , for example, the phosphor image IL is obtained by visually observing or capturing with a visible light color camera or monochrome camera with spectral sensitivity equivalent to that of the human eye a composite light L4 composed of excitation light L1 irradiated onto the light-irradiated surface S1 in a dark place, resulting in fluorescent light L2 emitted from the phosphor distribution layer 14, and a component of the excitation light L1 incident on the light-irradiated surface S1 that is not absorbed by the phosphor distribution layer 14 or the light-absorbing layer 13 and is reflected by the support substrate 11 and leaks out from the light-irradiated surface S1 (excitation reflected light L3). The phosphor image IL corresponds to a distribution image of multiple phosphor particles 14A generated on the light-irradiated surface S1. The wavelength ranges of the phosphor image IL and composite light L4 are within the visible light range, including the wavelength range of the fluorescent light L2. Furthermore, the visual stimulus is expressed as the integral over the entire wavelength range of the product of the light intensity at each wavelength and a color matching function that indicates the spectral sensitivity of the human eye.

[0023] As shown in Figure 4, when the amount of transmitted light of the excitation light L1 through the light-absorbing layer 13 is 30%, the contrast ratio (Ia / Ib) is 5. It is generally said that when the contrast ratio is 5 or higher, a human can clearly see an image. Therefore, by setting the amount of transmitted light of the excitation light L1 through the light-absorbing layer 13 to 30% or less, the phosphor image IL and the reflected excitation light L3 can be clearly separated by the naked eye. This also applies when using a visible light color camera or monochrome camera with spectral sensitivity equivalent to that of the human eye.

[0024] FIG. 7 shows an example of the relationship between the transmittance of the light-absorbing layer 13 at 400 nm and the contrast ratio (Ia / Ib). This example was created based on a phosphor with an external quantum efficiency of 5% and an emission peak at a wavelength of 514 nm, excited by an LED with an emission peak at a wavelength of 385 nm, very close to the visible light range. As shown in FIG. 7, when the transmittance of the light-absorbing layer 13 at 400 nm is 70%, the contrast ratio (Ia / Ib) is 5. Furthermore, as shown in FIG. 7, when the transmittance of the light-absorbing layer 13 at 400 nm is 70% or less, the contrast ratio (Ia / Ib) is 5 or greater. It is generally believed that a contrast ratio of 5 allows humans to clearly perceive image edges. Therefore, by setting the transmittance of the light-absorbing layer 13 at 400 nm to 70% or less, the fluorescent light L2 and the reflected excitation light L3 can be clearly separated visually. This also applies when using a visible light color camera or monochrome camera with spectral sensitivity equivalent to that of the human eye.

[0025] [Effects] Next, the effects of the security element 10 according to this embodiment will be described.

[0026] In this embodiment, a light absorbing layer 13 is provided between the support substrate 11 and the phosphor distribution layer 14 to absorb the excitation light L1 that excites the phosphor particles 14A. As a result, the component of the excitation light L1 that is incident on the security element 10 and is not absorbed by the plurality of phosphor particles 14A but is transmitted through the phosphor distribution layer 14 is absorbed by the light absorbing layer 13. As a result, the component of the excitation light L1 that is incident on the security element 10 that is not absorbed by the phosphor distribution layer 14 and the light absorbing layer 13 and leaks out of the security element 10 by being reflected by the support substrate 11, for example (excitation reflected light L3), is less than when the light absorbing layer 13 is not provided. Therefore, a decrease in the contrast of the phosphor image IL can be suppressed.

[0027] As described above, in this embodiment, a high-contrast phosphor image IL is obtained. Therefore, authenticity can be reliably determined by a person visually checking for the presence or absence of fluorescent light L2. A high-contrast phosphor image IL can also be obtained by capturing the phosphor image IL with a general color camera that has the same spectral sensitivity as the human eye, or a monochrome camera that captures only the brightness and darkness of the subject. By comparing the fluorescence distribution state of the phosphor image IL with a database created in advance, individual identification can be performed with high accuracy.

[0028] In this embodiment, the light-absorbing layer 13 has light-absorbing properties such that the transmittance in the wavelength range of fluorescent light is 85% or more, while the transmitted light amount of the excitation light L1 is 30% or less. This allows the near-ultraviolet component of the excitation light L1 that is transmitted through the phosphor distribution layer 14 to be sufficiently absorbed by the light-absorbing layer 13. As a result, the reflected excitation light L3 is less than when the light-absorbing layer 13 is not provided. This makes it possible to suppress a decrease in the contrast of the phosphor image IL.

[0029] In this embodiment, each phosphor particle 14A is formed of a phosphor having an excitation wavelength in the near-ultraviolet range. Furthermore, the light-absorbing layer 13 has light-absorbing characteristics such that the light transmittance is 85% or more in the wavelength range of fluorescent light. On the other hand, the light-absorbing layer 13 has light-absorbing characteristics such that the light transmittance is 70% or less at a wavelength of 400 nm, which corresponds to the lower limit of the visible light range. This allows the near-ultraviolet component of the excitation light L1 that passes through the phosphor distribution layer 14 to be sufficiently absorbed by the light-absorbing layer 13. Furthermore, the absorption of the fluorescent light L2 generated by the phosphor distribution layer 14 is sufficiently suppressed. As a result, the excitation reflected light L3 is less than when the light-absorbing layer 13 is not provided. Therefore, a decrease in the contrast of the phosphor image IL can be suppressed.

[0030] In this embodiment, each phosphor particle 14A is formed of a phosphor capable of absorbing excitation light L1 and emitting fluorescent light L2 having a peak in the visible region. This allows the fluorescent light L2 generated from each phosphor particle 14A to produce a phosphor image IL in the visible region. The light absorption layer 13 adequately suppresses the absorption of the fluorescent light L2. This prevents a decrease in the contrast of the phosphor image IL.

[0031] In this embodiment, the phosphor distribution layer 14 is a layer in which a plurality of phosphor particles 14A are dispersed in a resin binder 14B. As a result, by adjusting the content ratio of the plurality of phosphor particles 14A and the viscosity of the resin binder 14B during the manufacturing process, the distribution state of the plurality of phosphor particles 14A (i.e., the object-specific information) can be varied in a variety of ways. This makes it possible to realize a security element 10 with high security.

[0032] In this embodiment, the phosphor image IL may be formed of a phosphor that can absorb excitation light L1 and emit fluorescent light L2 having a peak in the near-infrared or infrared region. In this case, the wavelength range of the phosphor image IL and the combined light L4 is the wavelength range (near-infrared or infrared region) of the fluorescent light L2, and the camera that captures it has sensitivity in the visible light region and the near-infrared or infrared region. Even in this case, the same effects as those of the above embodiment can be obtained.

[0033] 2. Modifications Next, modifications of the security element 10 according to the present embodiment will be described.

[0034] [Variant A] In the above embodiment, the phosphor distribution layer 14 may be composed of, for example, a plurality of phosphor dots 14C made up of a plurality of phosphor particles 14A in contact with the light absorption layer 13, or a plurality of phosphor dots 14C made up of a mixture of a plurality of phosphor particles 14A and a resin material 14D, as shown in Figure 8.

[0035] The fluorescent dots 14C may be, for example, single particles or aggregates of the fluorescent particles 14A. Alternatively, they may be formed by spraying a mixed liquid in which the fluorescent particles 14A are dispersed in a resin liquid before the resin member 14D is cured onto the surface of the light-absorbing layer 13, and then applying energy to cure the mixed liquid sprayed onto the surface of the light-absorbing layer 13. In this modification, a protective layer 15 may be provided to protect the fluorescent dots 14C. The protective layer 15 covers the fluorescent dots 14C and has a flat light irradiation surface S1. The resin member 14D and the protective layer 15 are formed of a resin material such that the difference in refractive index between the resin member 14D and the protective layer 15 is 0.15 or less.

[0036] The resin member 14D is made of, for example, polyurethane with a refractive index of 1.45, acrylic with a refractive index of 1.49, or polycarbonate with a refractive index of 1.58. The protective layer 15 is made of, for example, PVC with a refractive index of 1.53, PET with a refractive index of 1.54, or polycarbonate with a refractive index of 1.58. In any combination of the above-mentioned materials exemplified for the resin member 14D and the above-mentioned materials exemplified for the protective layer 15, the difference in refractive index between the resin member 14D and the protective layer 15 is 0.15 or less.

[0037] In this modification, the phosphor distribution layer 14 is composed of a plurality of phosphor dots 14C. This makes it possible to vary the distribution of the plurality of phosphor particles 14A (i.e., object-specific information) in a variety of ways by adjusting the spraying method of the phosphor particles or the mixed liquid of phosphor particles and resin, the viscosity of the resin liquid, etc., during the manufacturing process. This makes it possible to realize a security element 10 with high security.

[0038] In this modification, the resin member 14D and the protective layer 15 are made of a resin material that results in a difference in refractive index of 0.15 or less between the resin member 14D and the protective layer 15. This makes it possible to make the fluorescent dots 14C less visible to people when the security element 10 is placed in a location where natural light is incident, and also makes it possible to make the fluorescent dots 14C less visible when the light irradiation surface S1 is imaged by a visible light camera.

[0039] [Variation B] In the above-described embodiment and Variation A, the security element 10 may further include an image information layer 16, as shown in Figures 9 and 10, for example. The image information layer 16 is provided between the support substrate 11 and the light absorbing layer 13. The image information layer 16 is a thermosensitive recording layer capable of forming image information in the visible, near-infrared, and infrared regions. The image information layer 16 has one or more photothermal conversion wavelength ranges in the visible region that are different from the wavelength range of the excitation light L1.

[0040] FIG. 11 shows an example of the cross-sectional structure of the image information layer 16 shown in FIGS. 9 and 10 . FIG. 11 shows an example of the cross-sectional structure of the image information layer 16 on which the image information image IX is drawn. "C" in FIG. 11 indicates a portion of the data layer 167 that is colored cyan. "Y" in FIG. 11 indicates a portion of the data layer 165 that is colored yellow. "M" in FIG. 11 indicates a portion of the data layer 163 that is colored magenta. "BK" in FIG. 11 indicates a portion of the data layer 161 that is colored black. The image information layer 16 is, for example, a layer formed on the support substrate 11, as shown in FIG. 11 . The image information layer 16 has, for example, four data layers 161, 163, 165, and 167, three intermediate layers 162, 164, and 166, and one cover layer 168, as shown in FIG. 11 .

[0041] The data layers 161, 163, 165, and 167 are arranged in this order from the support substrate 11 side. The intermediate layer 162 is arranged between the data layers 161 and 163 and is a heat insulating layer capable of suppressing thermal interference between the data layers 161 and 163. The intermediate layer 164 is arranged between the data layers 163 and 165 and is a heat insulating layer capable of suppressing thermal interference between the data layers 163 and 165. The intermediate layer 166 is arranged between the data layers 165 and 167 and is a heat insulating layer capable of suppressing thermal interference between the data layers 165 and 167. The cover layer 168 is a layer for protecting the four data layers 161, 163, 165, and 167. It is preferable that the intermediate layers 162, 164, and 166 and the cover layer 168 are all made of a material that is transparent in the visible range.

[0042] The four data layers 161, 163, 165, and 167 are each configured to include a modulation material capable of modulating optical properties. The modulation material may be, for example, a reversible material capable of transitioning between a colored state and a non-colored state in the visible wavelength range, or an irreversible material capable of transitioning between a colored state and a non-colored state in one direction. The four data layers 161, 163, 165, and 167 are each configured to include, for example, a leuco dye (a reversible thermosensitive color-forming composition) as a reversible material and a photothermal conversion agent that generates heat during writing. The light absorption characteristics of the photothermal conversion agent determine the modulation conditions of the modulation material (leuco dye). The four data layers 161, 163, 165, and 167 are each further configured to include, for example, a color developer and a polymer.

[0043] The leuco dye combines with the developer by heat to develop a color in the visible wavelength range, or separates from the developer to develop a colorless state in the visible wavelength range. The leuco dye contained in the four data layers 161, 163, 165, and 167 develops a predetermined color in the visible wavelength range by, for example, combining with the developer by heat.

[0044] The leuco dye contained in data layer 161 develops a black color, the leuco dye contained in data layer 163 develops a magenta color, the leuco dye contained in data layer 165 develops a yellow color, and the leuco dye contained in data layer 167 develops a cyan color. Furthermore, the four data layers 161, 163, 165, and 167 are transparent in the visible range when in a decolorized state. The photothermal conversion agent absorbs light in the near-infrared range (700 nm to 2500 nm) and generates heat, for example. In this specification, the near-infrared range refers to the wavelength band of 700 nm to 2500 nm.

[0045] The photothermal conversion agent contained in data layer 161 has an absorption peak at wavelength λbk (700 nm≦λbk≦2500 nm), for example. The photothermal conversion agent contained in data layer 163 has an absorption peak at wavelength λm (λm≠λbk, 700 nm≦λm≦2500 nm), for example. The photothermal conversion agent contained in data layer 165 has an absorption peak at wavelength λy (λy≠λbk, λm, 700 nm≦λy≦2500 nm), for example. The photothermal conversion agent contained in data layer 167 has an absorption peak at wavelength λc (λc≠λbk, λm, λy, 700 nm≦λc≦2500 nm), for example. Therefore, the modulation conditions (photothermal conversion wavelength ranges) of the modulation materials (leuco dyes) of the four data layers 161, 163, 165, and 167 are different from each other in wavelength ranges different from the wavelength range of the excitation light L1 among the visible range, near-infrared range, and infrared range.

[0046] The leuco dye may be, for example, a dye used in existing thermal paper. Specific examples include compounds containing an electron-donating group in the molecule, as represented by the following formula (1):

[0047] The color former is not particularly limited and can be appropriately selected depending on the purpose. Specific examples of the color former include the compound represented by formula (1) above, as well as fluoran compounds, triphenylmethanephthalide compounds, azaphthalide compounds, phenothiazine compounds, leucoauramine compounds, and indolinophthalide compounds. Other examples include 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-di(n-butylamino)fluoran, 2-anilino-3-methyl-6-(N-n-propyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-isopropyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-isobutyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-n-amyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-sec-butyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-n-amyl-N-ethylamino)fluoran, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino)fluoran, 2-anilino-3-methyl-6-(N-n-propyl-N-isopropylamino)fluoran, 2-anilino-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran, 2-anilino-3-methyl-6-(N-methyl-p-toluidino)fluoran, 2-(m-trichloromethylanilino)-3-methyl-6-diethylaminofluoran, 2-(m-trifluoromethylanilino)-3-methyl-6-diethylaminofluoran, 2-(m-trichloromethylanilino)-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran, 2-(2,4-dimethylanilino)-3-methyl-6-diethylaminofluoran, 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-ethylanilino)fluoran, 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-propyl-p-toluidino)fluoran, 2-anilino-6-(N-n-hexyl-N-ethylamino)fluoran, 2-(o-chloroanilino)-6-diethylaminofluoran, 2-(o-chloroanilino)-6-dibutylaminofluoran, 2-(m-trifluoromethylanilino)-6-diethylaminofluoran, 2,3-dimethyl-6-dimethylaminofluoran, 3-methyl-6-(N-ethyl-p-toluidino)fluoran, 2-chloro-6 -diethylaminofluoran, 2-bromo-6-diethylaminofluoran, 2-chloro-6-dipropylaminofluoran, 3-chloro-6-cyclohexylaminofluoran, 3-bromo-6-cyclohexylaminofluoran, 2-chloro-6-(N-ethyl-N-isoamylamino)fluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-(o-chloroanilino)-3-chloro-6-cyclohexylaminofluoran, 2-(m-trifluoromethylanilino)-3-chloro-6-diethylaminofluoran, 2-(2,3-dichloroanilino)-3-chloro-6-diethylaminofluoran, 1,2-benzo-6-diethylaminofluoran, 3-diethylamino-6-(m-trifluoromethylanilino)fluoran, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-octyl- 2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-7-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-7-azaphthalide 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-N-n-amyl-N-methylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindol-3-yl)-3-(2-hexyloxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide nyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 2-(p-acetylanilino)-6-(N-n-amyl-N-n-butylamino)fluoran, 2-benzylamino-6-(N-ethyl-p-toluidino)fluoran, 2-benzylamino-6-(N-methyl-2,4-dimethylanilino)fluoran, 2-benzylamino-6-(N-ethyl-2,4-dimethylanilino)fluoran, 2-benzylamino-6-(N-methyl-p-toluidino)fluoran, 2-benzylamino-6-(N-ethyl-p-toluidino)fluoran, 2-(di-p-methylbenzylamino)-6-(N-ethyl-p-toluidino)fluoran, 2-(α-phenylethylamino)-6-(N-ethyl-p-toluidino)fluoran, 2-methylamino-6-(N-methylanilino)fluoran, 2-methylamino-6-(N-ethylanilino)fluoran, 2-methylamino-6-(N-propylanilino)fluoran , 2-ethylamino-6-(N-methyl-p-toluidino)fluoran, 2-methylamino-6-(N-methyl-2,4-dimethylanilino)fluoran, 2-ethylamino-6-(N-ethyl-2,4-dimethylanilino)fluoran, 2-dimethylamino-6-(N-methylanilino)fluoran, 2-dimethylamino-6-(N-ethylanilino)fluoran, 2-diethylamino-6-(N-methyl-p-toluidino)fluoran, 2-diethylamino-6-(N-ethyl-p-toluidino)fluoran, 2-dipropylamino-6-(N-methyl p-toluidino)fluoran, 2-dipropylamino-6-(N-ethylanilino)fluoran, 2-amino-6-(N-methylanilino)fluoran, 2-amino-6-(N-ethylanilino)fluoran, 2-amino-6-(N-propylanilino)fluoran, 2-amino-6-(N-methyl-p-toluidino)fluoran, 2-amino-6-(N-ethyl-p-toluidino)fluoran, 2-amino-6-(N-propyl-p-toluidino)fluoran, 2-amino-6-(N-methyl-p-ethylanilino)fluoran, 2-amino-6-(N-ethylanilino)fluoran 2-amino-6-(N-propyl-p-ethylanilino)fluoran, 2-amino-6-(N-methyl-2,4-dimethylanilino)fluoran, 2-amino-6-(N-ethyl-2,4-dimethylanilino)fluoran, 2-amino-6-(N-propyl-2,4-dimethylanilino)fluoran, 2-amino-6-(N-methyl-p-chloroanilino)fluoran, 2-amino-6-(N-ethyl-p-chloroanilino)fluoran, 2-amino-6-(N-propyl-p-chloroanilino)fluoran, 1,Examples of the color developing compounds include 2-benzo-6-(N-ethyl-N-isoamylamino)fluoran, 1,2-benzo-6-dibutylaminofluoran, 1,2-benzo-6-(N-methyl-N-cyclohexylamino)fluoran, and 1,2-benzo-6-(N-ethyl-N-toluidino)fluoran. Each of the data layers 161, 163, 165, and 167 may contain one of the above color developing compounds alone or two or more of them.

[0048] The developer may contain a compound represented by the following formula (2).

[0049] In formula (2), X 0 is a divalent group containing at least one benzene ring. 01 , Y 02 are each independently a monovalent group. n01 and n02 are each independently an integer of 0 to 5. When n01 is an integer of 2 to 5, Y 01 may be the same or different. When n02 is an integer of 2 to 5, Y 02 may be the same or different. 01 , Z 02 are each independently a hydrogen-bonding group.

[0050] X 0 contains at least one benzene ring, 0 Since the melting point can be made higher than when X is an aliphatic hydrocarbon group (for example, a normal alkyl chain), the color retention properties during storage at high temperature and high humidity (hereinafter referred to as "high temperature and high humidity storage properties") can be improved. 0 Preferably, the compound contains at least two benzene rings. The high-temperature, high-humidity storage characteristics are, for example, storage characteristics under an environment of 80°C and 60% RH. Improved heat resistance improves the resistance of the data layers 161, 163, 165, and 167 to harsh processes (for example, hot pressing or integral molding using molten resin, etc.). 0When contains at least two benzene rings, the at least two benzene rings may be condensed, for example, naphthalene or anthracene.

[0051] Z 01 , Z 02 are each independently a hydrogen-bonding group, the color developers tend to exist in a state of being aggregated together to some extent via hydrogen bonds, thereby improving the stability of the color developers in the data layers 161, 163, 165, and 167. In this specification, a hydrogen-bonding group means a functional group that contains an atom that can form a hydrogen bond with another functional group or an atom present in another compound, etc.

[0052] The developer preferably contains a compound represented by the following formula (3):

[0053] In formula (3), X 1 is a divalent group containing at least one benzene ring. 11 , Y 12 , Y 13 , Y 14 are each independently a monovalent group. 11 , Z 12 are each independently a hydrogen-bonding group.

[0054] X 1 contains at least one benzene ring, 1 In comparison with the case where X is an aliphatic hydrocarbon group (for example, a normal alkyl chain), the melting point can be made higher, and therefore the high-temperature, high-humidity storage properties can be improved. 1 Preferably, X contains at least two benzene rings. 1 When contains at least two benzene rings, the at least two benzene rings may be condensed, for example, naphthalene or anthracene.

[0055] Z 11 , Z 12 are each independently a hydrogen-bonding group, the color developers tend to exist in a state of being solidified to some extent via hydrogen bonds, thereby improving the stability of the color developers in the data layers 161, 163, 165, and 167.

[0056] When formula (2) and formula (3) contain a hydrocarbon group, the hydrocarbon group is a general term for a group composed of carbon (C) and hydrogen (H), and may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. A saturated hydrocarbon group is an aliphatic hydrocarbon group that does not have a carbon-carbon multiple bond, and an unsaturated hydrocarbon group is an aliphatic hydrocarbon group that has a carbon-carbon multiple bond (a carbon-carbon double bond or a carbon-carbon triple bond).

[0057] When formula (2) and formula (3) contain a hydrocarbon group, the hydrocarbon group may be a chain or may contain one or more rings. The chain may be a straight chain or a branched chain having one or more side chains.

[0058] (X containing one benzene ring 0 , X １ ) X in formula (2) 0 and X in formula (3) 1 is, for example, a divalent group containing one benzene ring. The divalent group is, for example, represented by the following formula (4):

[0059] In formula (4), X 21 It doesn't matter if it's there or not, X 21 If there is X 21 is a divalent group. 22 It doesn't matter if it's there or not, X 22 If there is X 22 is a divalent group. 21 is a monovalent group. n21 is an integer of 0 to 4. When n21 is an integer of 2 to 4, R 21 may be the same or different. * indicates a bond.

[0060] In formula (4), X to the benzene ring 21 and X 22 The bonding position of X to the benzene ring is not limited. 21 and X 22 The bonding position may be any of the ortho, meta and para positions.

[0061] The divalent group containing one benzene ring is preferably represented by the following formula (5) from the viewpoint of improving high-temperature, high-humidity storage properties.

[0062] In formula (5), R 22 is a monovalent group. n22 is an integer of 0 to 4. When n22 is an integer of 2 to 4, R 22 may be the same or different. * indicates a bond.

[0063] X in formula (2) 0 is a divalent group containing one benzene ring, in formula (5), Z 01 and Z 02 The bonding position of Z to the benzene ring is not limited. 01 and Z 02 The bonding position may be any of the ortho, meta and para positions.

[0064] X in formula (3) 1 is a divalent group containing one benzene ring, in formula (5), Z 11 and Z 12 The bonding position of Z to the benzene ring is not limited. 11 and Z 12 The bonding position may be any of the ortho, meta and para positions.

[0065] (X 21 , X 22 ) X in formula (4) 21 , X 22 are each independently a divalent group and are not particularly limited, but an example is a hydrocarbon group which may have a substituent. The hydrocarbon group is preferably chain-like. When the hydrocarbon group is chain-like, the melting point of the color developer can be lowered, so that the color developer melts upon irradiation with laser light, making it easier for the color former to develop color. From the viewpoint of lowering the melting point of the color developer, a normal alkyl chain is particularly preferred among chain-like hydrocarbon groups.

[0066] The hydrocarbon group which may have a substituent has, for example, 1 to 15 carbon atoms, 1 to 13 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 3 carbon atoms.

[0067] X in formula (4) 21 , X 22 When is a normal alkyl group, the number of carbon atoms in the normal alkyl group is preferably 8 or less, more preferably 6 or less, even more preferably 5 or less, and particularly preferably 3 or less, from the viewpoint of high-temperature storage stability. When the normal alkyl group has 8 or less carbon atoms, the normal alkyl group is short in length, so that thermal disturbance is unlikely to occur in the color developer during high-temperature storage, and it is thought that the site that interacted with the color former such as a leuco dye during color development is unlikely to be dissociated. Therefore, the color former such as a leuco dye is unlikely to fade during high-temperature storage, improving high-temperature storage stability.

[0068] Examples of the substituent that the hydrocarbon group may have include a halogen group (e.g., a fluorine group) or an alkyl group having a halogen group (e.g., a fluorine group), etc. The hydrocarbon group that may have a substituent may be one in which some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms in the main chain of the hydrocarbon group) have been substituted with an element such as oxygen.

[0069] (R 21 ) R in formula (4) 21 is a monovalent group and is not particularly limited, but examples thereof include a halogen group or an optionally substituted hydrocarbon group. Examples of the halogen group include a fluorine group (-F), a chlorine group (-Cl), a bromine group (-Br), and an iodine group (-I).

[0070] The number of carbon atoms in the hydrocarbon group, which may have a substituent, is, for example, 1 to 15, 1 to 13, 1 to 12, 1 to 10, 1 to 6, or 1 to 3. Examples of the substituent that the hydrocarbon group may have include a halogen group (e.g., a fluorine group) or an alkyl group having a halogen group (e.g., a fluorine group). The hydrocarbon group, which may have a substituent, may be one in which some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms contained in the main chain of the hydrocarbon group) have been substituted with an element such as oxygen.

[0071] (R 22 ) R in formula (5) 22 is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group and a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are respectively represented by R 21 is the same as:

[0072] (X containing two benzene rings 0 , X 1 ) X in formula (2) 0 and X in formula (3) 1 is, for example, a divalent group containing two benzene rings. The divalent group is, for example, represented by the following formula (6):

[0073] In formula (6), X 31 It doesn't matter if it's there or not, X 31 If there is X 31 is a divalent group. 32 It doesn't matter if it's there or not, X 32 If there is X 32 is a divalent group. 33 It doesn't matter if it's there or not, X 33 If there is X 33 is a divalent group. 31 , R 32 are each independently a monovalent group. n31 and n32 are each independently an integer of 0 to 4. When n31 is an integer of 2 to 4, R 31 may be the same or different. When n32 is an integer of 2 to 4, R 32 may be the same or different. * indicates a bond.

[0074] In formula (6), X to the benzene ring 31 and X 32 The bonding position of X to the benzene ring is not limited. 31 and X 32The bonding position of X to the benzene ring in formula (6) may be any of the ortho, meta and para positions. 32 and X 33 The bonding position of X to the benzene ring is not limited. 32 and X 33 The bonding position may be any of the ortho, meta and para positions.

[0075] The divalent group containing two benzene rings is preferably represented by the following formula (7) from the viewpoint of improving high-temperature, high-humidity storage properties.

[0076] In formula (7), X 34 is a divalent group. 33 , R 34 are each independently a monovalent group. n33 and n34 are each independently an integer of 0 to 4. When n33 is an integer of 2 to 4, R 33 may be the same or different. When n34 is an integer of 2 to 4, R 34 may be the same or different. * indicates a bond.

[0077] X in formula (2) 0 is a divalent group containing two benzene rings, Z 01 and X 34 The bonding position of Z to the benzene ring is not limited. 01 and X 34 The bonding position of may be any of the ortho, meta and para positions. 02 and X 34 The bonding position of Z to the benzene ring is not limited. 02 and X 34 The bonding position may be any of the ortho, meta and para positions.

[0078] X in formula (3) 1 is a divalent group containing two benzene rings, Z 11and X 34 The bonding position of Z to the benzene ring is not limited. 11 and X 34 The bonding position of may be any of the ortho, meta and para positions. 12 and X 34 The bonding position of Z to the benzene ring is not limited. 12 and X 34 The bonding position may be any of the ortho, meta and para positions.

[0079] (X 31 , X 32 , X 33 ) X in formula (6) 31 , X 32 , X 33 are each independently a divalent group, and are not particularly limited, but an example thereof is a hydrocarbon group which may have a substituent. 21 , X 22 is the same as:

[0080] (X 34 ) X in formula (7) 34 is not particularly limited as long as it is a divalent group, but an example thereof is a hydrocarbon group which may have a substituent. The hydrocarbon group is the X in the above formula (4). 21 , X 22 is the same as:

[0081] (R 31 , R 32 ) R in formula (6) 31 , R 32 is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group and a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are each represented by R in the above formula (4). 21 is the same as:

[0082] (R 33 , R 34 ) R in formula (7) 33 , R 34is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group and a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are each represented by R in the above formula (4). 21 is the same as:

[0083] (Y 01 , Y 02 ) Y in formula (2) 01 , Y 02 are each independently, for example, a hydrogen group (-H), a hydroxy group (-OH), a halogen group (-X), a carboxy group (-COOH), an ester group (-COOR), or a hydrocarbon group which may have a substituent. Examples of halogen groups include a fluorine group (-F), a chlorine group (-Cl), a bromine group (-Br), or an iodine group (-I).

[0084] The number of carbon atoms in the hydrocarbon group, which may have a substituent, is, for example, 1 to 15, 1 to 13, 1 to 12, 1 to 10, 1 to 6, or 1 to 3. Examples of the substituent that the hydrocarbon group may have include a halogen group (e.g., a fluorine group) or an alkyl group having a halogen group (e.g., a fluorine group). The hydrocarbon group, which may have a substituent, may be one in which some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms contained in the main chain of the hydrocarbon group) have been substituted with an element such as oxygen.

[0085] In formula (2), (Y 01 ) n01 and / or (Y 02 ) n02 It is preferred that one of the groups Y is a hydroxy group (—OH). 01 ) n01 and / or (Y 02 ) n02 When one of the groups is a hydroxy group (—OH), the display quality and light resistance can be improved.

[0086] (Y 11 , Y 12 , Y 13 , Y 14 In formula (3), Y relative to the benzene ring 11 and Y12 The bonding position of Y to the benzene ring is not limited. 11 and Y 12 The bonding position of Y may be any of the ortho, meta and para positions. 13 and Y 14 The bonding position of Y to the benzene ring is not limited. 13 and Y 14 The bonding position of Y to one benzene may be any of the ortho, meta and para positions. 11 and Y 12 and the bonding position of Y to the other benzene 13 and Y 14 may be the same as or different from the binding position of

[0087] Y in formula (3) 11 , Y 12 , Y 13 , Y 14 are each independently, for example, a hydrogen group (-H), a hydroxy group (-OH), a halogen group, a carboxy group (-COOH), an ester group (-COOR), or a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are each represented by Y 01 , Y 02 In formula (3), Y 11 and / or Y 13 is preferably a hydroxy group (—OH). 11 and / or Y 13 When the group is a hydroxy group (—OH), the display quality and light resistance can be improved.

[0088] (Z 01 , Z 02 ) Z in formula (2) 01 , Z 02 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-) or a hydrazide bond (-NHCOCONH-). 01 , Z 02is preferably a urea bond. 01 When Z is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene. 02 is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene.

[0089] (Z 11 , Z 12 ) Z in formula (3) 11 , Z 12 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-) or a hydrazide bond (-NHCOCONH-). 11 , Z 12 is preferably a urea bond. 11 When Z is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene. 12 is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene.

[0090] (Specific examples of color developers) X in formula (2) 0 and X in formula (3) 1 Specifically, the color developer containing one benzene ring includes at least one selected from the group consisting of compounds represented by the following formulas (8-1) to (8-6).

[0091] X in formula (2) 0 and X in formula (3) 1 Specifically, the color developer containing two benzene rings includes at least one selected from the group consisting of compounds represented by the following formulas (9-1) to (9-8).

[0092] The matrix polymer (matrix resin) preferably functions as a binder. The matrix polymer is preferably one in which the color former, color developer, and light-to-heat conversion agent are easily and uniformly dispersed. Examples of the matrix polymer include at least one selected from the group consisting of thermosetting resins and thermoplastic resins. Specific examples include at least one selected from the group consisting of polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins, ethyl cellulose resins, polystyrene resins, styrene copolymer resins, phenoxy resin resins, polyester resins, aromatic polyester resins, polyurethane resins, polycarbonate resins, polyacrylic acid ester resins, polymethacrylic acid ester resins, acrylic acid copolymer resins, maleic acid polymer resins, polyvinyl alcohol resins, modified polyvinyl alcohol resins, hydroxyethyl cellulose resins, carboxymethyl cellulose resins, and starch.

[0093] The matrix polymer preferably contains a polycarbonate-based resin. When the matrix polymer contains a polycarbonate-based resin, the light resistance of the background of the data layers 161, 163, 165, and 167 can be improved. Here, a polycarbonate-based resin is a resin that has at least a carbonate group (—O—(C═O)—O—) as a structural unit in its main chain. Therefore, the main chain may contain other structural units in addition to the carbonate group.

[0094] The photothermal conversion agent used in the data layers 161, 163, 165, and 167 absorbs light in a predetermined wavelength range in the near-infrared region and generates heat, for example. As the photothermal conversion agent, it is preferable to use a near-infrared absorbing dye that has an absorption peak in the wavelength range of 700 nm to 2000 nm and has almost no absorption in the visible region. Specific examples include at least one selected from the group consisting of compounds having a phthalocyanine skeleton (phthalocyanine dyes), compounds having a squarylium skeleton (squarylium dyes), and inorganic compounds. Examples of inorganic compounds include at least one selected from the group consisting of metal complexes such as dithio complexes, diimonium salts, aminium salts, and inorganic compounds. Examples of inorganic compounds include at least one selected from the group consisting of graphite, carbon black, metal powder particles, metal oxides such as tricobalt tetroxide, iron oxide, chromium oxide, copper oxide, titanium black, and ITO (indium tin oxide), metal nitrides such as niobium nitride, metal carbides such as tantalum carbide, metal sulfides, and various magnetic powders. In addition, compounds (cyanine dyes) having a cyanine skeleton with excellent light resistance and heat resistance may also be used. Here, excellent light resistance means that the compound does not decompose under the usage environment, for example, when irradiated with light from a fluorescent lamp. Excellent heat resistance means that the maximum absorption peak value of the absorption spectrum does not change by 20% or more, for example, when the compound is formed into a film together with a polymer material and stored at 150°C for 30 minutes. Examples of such compounds having a cyanine skeleton include compounds containing SbF in the molecule. ６ , P.F. ６ , B.F. ４ , ClO ４ , C.F. ３ SO ３ and (CF ３ SO ３ ) ２and at least one of a counter ion of any of N and a methine chain containing a five-membered ring or a six-membered ring. The compound having a cyanine skeleton used in the recording medium 20 in this embodiment preferably has both one of the counter ions and a cyclic structure such as a five-membered ring or a six-membered ring in the methine chain, but sufficient light resistance and heat resistance are ensured as long as it has at least one of them.

[0095] It is preferable to select a photothermal conversion agent that has a narrow light absorption band, for example, in the wavelength range of 700 nm or more and 2000 nm or less, and whose light absorption bands do not overlap with each other in the data layers 161, 163, 165, and 167. This makes it possible to selectively color a desired layer among the data layers 161, 163, 165, and 167.

[0096] The intermediate layers 162, 164, and 166 may be capable of insulating the layers from one another and suppressing the diffusion of the constituent materials.

[0097] The intermediate layers 162, 164, and 166 include, for example, a general light-transmitting polymer material. Specific examples of the material include at least one selected from the group consisting of acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins, ethyl cellulose resins, polystyrene resins, styrene copolymer resins, phenoxy resin resins, polyester resins, aromatic polyester resins, polyurethane resins, polycarbonate resins, polyacrylic ester resins, polymethacrylic ester resins, acrylic acid copolymer resins, maleic acid polymer resins, polyvinyl alcohol resins, modified polyvinyl alcohol resins, hydroxyethyl cellulose resins, carboxymethyl cellulose resins, and starch. The intermediate layers 22, 24, and 26 may also include various additives, such as ultraviolet absorbers.

[0098] The intermediate layers 162, 164, and 166 may be ultraviolet-curable resin layers. The ultraviolet-curable resin layer includes an ultraviolet-curable resin composition that has undergone a polymerization reaction and solidified. More specifically, for example, the ultraviolet-curable resin layer includes a polymer of a polymerizable compound and a polymer that has undergone a structural change due to the generation of active species by a polymerization initiator upon irradiation with external energy (ultraviolet rays). The ultraviolet-curable resin composition includes, for example, at least one selected from the group consisting of radical polymerization-type ultraviolet-curable resin compositions and cationic polymerization-type ultraviolet-curable resin compositions. The ultraviolet-curable resin composition may optionally include at least one selected from the group consisting of a sensitizer, a filler, a stabilizer, a leveling agent, an antifoaming agent, a viscosity adjuster, and the like. The ultraviolet-curable resin composition may be an ultraviolet-curable resin composition for hard coating. The ultraviolet-curable resin composition may also be an acrylic ultraviolet-curable resin composition.

[0099] The intermediate layers 162, 164, and 166 may contain a translucent inorganic material. For example, porous silica, alumina, titania, carbon, or a composite of these materials is preferable because it has low thermal conductivity and high heat insulating properties. The intermediate layers 162, 164, and 166 can be formed by, for example, a sol-gel method.

[0100] By adjusting the thickness of the intermediate layers 162, 164, and 166, the thickness of the data layers 161, 163, 165, and 167 may be made equal to the thickness of the spacer layer 13, thereby suppressing the occurrence of physical steps. The thickness of the intermediate layers 162, 164, and 166 is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less. When the thickness of the intermediate layers 162, 164, and 166 is 3 μm or more, a sufficient heat insulating effect can be obtained. On the other hand, when the thickness of the intermediate layers 162, 164, and 166 is 100 μm or less, a decrease in light transmittance can be suppressed. In addition, a decrease in the bending resistance of the data layers 161, 163, 165, and 167 can be suppressed, making defects such as cracks less likely to occur.

[0101] The intermediate layers 162, 164, and 166 may contain an adhesive, such as at least one selected from the group consisting of an acrylic resin, a silicone resin, a urethane resin, an epoxy resin, and an elastomer material.

[0102] The cover layer 168 is intended to protect the surfaces of the data layers 161, 163, 165, and 167, and is formed using, for example, at least one of ultraviolet-curing resin, thermoplastic resin, and thermosetting resin. The cover layer 168 may be a hard coat layer. To impart physical resistance, the cover layer 168 may be made of a matrix polymer or a plastic film similar to that of the support substrate 11. To combine protective functions, multiple protective layers may be bonded together using, for example, an adhesive. The thickness of the cover layer 168 is, for example, 0.1 μm or more and 100 μm or less.

[0103] FIG. 12 shows how the imaging light Ld is irradiated onto the security element 10 of FIGS. 9 and 10 . The imaging light Ld includes, for example, four laser beams Lbk, Lm, Ly, and Lc arranged side by side so that their optical axes do not overlap one another. The laser beam Lbk is light for writing to the data layer 161. The laser beam Lm is light for writing to the data layer 163. The laser beam Ly is light for writing to the data layer 165. The laser beam Lc is light for writing to the data layer 167. For example, as shown in FIG. 12 , the imaging light Ld is irradiated onto the light irradiation surface S1, thereby forming an image information image IX on the image information layer 16. At this time, the wavelength region of the imaging light Ld is in the near-infrared region, which does not overlap with the wavelength region of the fluorescent light L2 and the light absorption region (near-ultraviolet region) of the light absorption layer 13, as shown in FIG. 13 .

[0104] In the image information layer 16, the data layer 161 may be omitted as needed. Even in this case, a color image in the visible range is obtained as the image information image IX. Also, in the image information layer 16, the three data layers 163, 165, and 167 may be omitted as needed. In this case, a monochrome image is obtained as the image information image IX.

[0105] The image information layer 16 may be a recording layer on which visible image information (image information image IX) is formed. The recording layer may be, for example, an ink layer printed on the surface of the support substrate 11, a printed matter, a photograph, a laser marking film, or a developed positive film.

[0106] When natural light is irradiated onto the image information image IX formed on the image information layer 16, the resulting image light L5 is light in the visible region R2, as shown in FIG. 13 . The natural light passes through the light absorbing layer 13 and reaches the image information layer 16. The image information layer 16 then absorbs light according to the image information, forming a visible image. The image light L5, generated by reflection of the formed visible image light on the surface of the support substrate 11, passes through the light absorbing layer 13 and is emitted to the outside from the light irradiation surface S1 of the security element 10. The light absorbing layer 13 has light absorption characteristics such that the light transmittance of excitation light L1 at 400 nm is 70% or less, but there is almost no absorption in the wavelength range of visible light above 400 nm. Therefore, the light absorbing layer 13 hardly absorbs natural light or image light L5, and the image light L5 does not have a color bias due to the light absorbing layer 13.

[0107] In this modification, an image information layer 16 is provided between the support substrate 11 and the light absorbing layer 13. In this case, an image information image IX may exist directly below the phosphor distribution layer 14. When the image information image IX exists directly below the phosphor distribution layer 14, for example, as shown in FIG. 6 , assume that excitation light L1 is incident on the light irradiation surface S1. At this time, the light that is not absorbed by the phosphor distribution layer 14 but transmits through is absorbed by the light absorbing layer 13, so the intensity of the visible light components contained in the excitation light L1 that reach the surface containing the image information image IX is extremely low. As a result, the visible light components affected by the image information image IX are hardly observed in the phosphor image IL, resulting in a phosphor image IL that reflects the distribution state of the multiple phosphor particles 14A contained in the phosphor distribution layer 14. Therefore, even if the image information layer 16 is provided between the support substrate 11 and the light absorbing layer 13, a highly secure security element 10 can be realized.

[0108] 3. Authenticity Determination Method Next, an authenticity determination method or individual identification method using the security element 10 according to the present embodiment will be described. First, an example of a method for deriving the feature quantities of the security element 10 will be described, and then an example of a matching method using the feature quantities of the security element 10 will be described.

[0109] (Method of deriving feature quantities) Fig. 14 is a diagram for explaining an example of a method of deriving feature quantities of the security element 10. Fig. 14 shows six bright points P1 to P6 obtained from the phosphor image IL, and distances d1 to d15 between any two bright points selected from the six bright points P1 to P6.

[0110] 6, excitation light L1 is first irradiated onto the light-irradiated surface S1 in a dark place, and as a result, fluorescent light L2 emitted from the phosphor distribution layer 14 and a component of the excitation light L1 incident on the light-irradiated surface S1 that is not absorbed by the phosphor distribution layer 14 or the light-absorbing layer 13 and leaks out from the light-irradiated surface S1 as a result of being reflected by the support substrate 11 or the image information layer 16 (excitation-reflected light L3) are combined and imaged by a visible light camera. Next, in the image (phosphor image IL) obtained by imaging with the visible light camera, bright spots having a brightness greater than a specific threshold value are detected.

[0111] The distances d1 to dn (n = {N × (N - 1)} / 2) between any two bright points selected from the N bright points P1 to PN obtained from the phosphor image IL are derived. The derived n distances d1 to dn become the characteristic quantities of the security element 10.

[0112] Fig. 14 is a diagram illustrating another example of a method for deriving the feature quantities of the security element 10. Fig. 14 shows that the phosphor image IL is divided into an i x j grid, and if a bright spot (a black spot in the figure) exists within a grid, a number "1" is assigned as the number corresponding to that grid, and if no bright spot exists within a grid, a number "0" is assigned as the number corresponding to that grid, and the numbers assigned to each grid are expressed as an i x j matrix M.

[0113] 6, excitation light L1 is first irradiated onto the light-irradiated surface S1 in a dark place, and as a result, fluorescent light L2 emitted from the phosphor distribution layer 14 and a component of the excitation light L1 incident on the light-irradiated surface S1 that is not absorbed by the phosphor distribution layer 14 or the light-absorbing layer 13 and leaks out from the light-irradiated surface S1 as a result of being reflected by the support substrate 11 or the image information layer 16 (excitation-reflected light L3) are combined and imaged by a visible light camera. Next, in the image (phosphor image IL) obtained by imaging with the visible light camera, bright spots having a brightness greater than a specific threshold value are detected.

[0114] The phosphor image IL is divided into an i x j grid, and if a bright spot (a black spot in the figure) exists within a grid, a number "1" is assigned as the number corresponding to that grid, and if no bright spot exists within a grid, a number "0" is assigned as the number corresponding to that grid, and the numbers assigned to each grid are expressed as an i x j matrix M. The i x j matrix M becomes the feature quantity of the security element 10.

[0115] (Matching Method Using Feature Amounts) A plurality of security elements 10 with different feature amounts are prepared. When the security element 10 is used in, for example, a passport, information about the passport owner and the feature amounts of the security element 10 are associated and registered in a database. The security element 10 used in the passport is irradiated with excitation light L1, and the combined light L4 is captured by a visible light camera. When the feature amount of the security element 10 is detected from the image (phosphor image IL) captured by the visible light camera, the detected feature amount is matched with each feature amount registered in the database. As a result, if a feature amount matching the detected feature amount is detected from among the plurality of feature amounts registered in the database, the passport corresponding to the feature amount matching the detected feature amount is deemed to be genuine, and owner information is obtained from the database. The passport owner information obtained from the database is compared with the owner information written on the passport by an authenticity assessor, and the authenticity of the passport is determined accordingly. On the other hand, if no feature amount matching the detected feature amount is found among the plurality of feature amounts registered in the database, information indicating that the passport is a fake is obtained from the database. In this way, the passport is authenticated or individually identified.

[0116] 4. Application Examples [Configuration] Next, application examples of the security element 10 according to the above embodiment and its modifications (hereinafter simply referred to as "security element 10") will be described. Fig. 16 shows an example of the perspective configuration of a security document 1 equipped with the security element 10. Fig. 17 shows an example of the cross-sectional configuration of the security document 1 shown in Fig. 16 taken along line A-A. Fig. 18 shows an example in which the security document 1 is applied to a passport 2.

[0117] 17, the security document 1 comprises a security element 10 on a card substrate 21. The security element 10 is provided only in a part of the area facing the card substrate 21.

[0118] The card substrate 21 includes, for example, plastic. If necessary, the card substrate 21 may include at least one selected from the group consisting of a colorant, an antistatic agent, a flame retardant, a surface modifier, etc. A reflective layer (not shown) may be provided on at least one main surface of the card substrate 21, or the card substrate 21 itself may also function as a reflective layer.

[0119] The plastic used for the card substrate 21 includes at least one selected from the group consisting of, for example, ester resins, amide resins, olefin resins, vinyl resins, acrylic resins, imide resins, styrene resins, engineering plastics, etc. When the base material 11 includes two or more types of resins, the two or more types of resins may be mixed, copolymerized, or laminated.

[0120] The ester-based resin includes, for example, at least one selected from the group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene terephthalate-isophthalate copolymer, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer. The amide-based resin includes, for example, at least one selected from the group consisting of nylon 6, nylon 66, and nylon 610. The olefin-based resin includes, for example, at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP). The vinyl-based resin includes, for example, polyvinyl chloride (PVC).

[0121] The acrylic resin includes, for example, at least one selected from the group consisting of polyacrylate, polymethacrylate, polymethyl methacrylate (PMMA), etc. The imide resin includes, for example, at least one selected from the group consisting of polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), etc. The styrene resin includes, for example, at least one selected from the group consisting of polystyrene (PS), high-impact polystyrene, acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), etc. The engineering plastic includes, for example, at least one selected from the group consisting of polycarbonate (PC), polyarylate (PAR), polysulfone (PSF), polyethersulfone (PES), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyetherketone (PEK), polyether-etherketone (PEEK), polyphenylene oxide (PPO), polyether sulfite, etc.

[0122] 17, the security document 1 may include a background layer 22 and a laser marking layer 23. The background layer 22 is, for example, a recording layer on which an image that forms the background of the security document 1 is recorded. This recording layer is, for example, an ink layer printed on the surface of the card substrate 21, or a developed positive film.

[0123] The laser marking layer 23 may be a known laser marking sheet. The laser marking layer 23 may be configured to be laser markable by at least one of the following methods (1) to (5): (1) A method of foaming a resin material to develop color; (2) A method of adding an additive that absorbs laser light to a resin material to cause the additive itself to develop color; (3) A method of adding an additive that absorbs laser light to a resin material to cause the additive to generate heat and carbonize the surrounding resin material to develop color; (4) A method of etching the surface of a resin layer by irradiating it with a laser to utilize changes in the surface condition; (5) A method of marking by irradiating a black or dark-colored resin material with laser light to sublimate (decompose) the colorant (carbon black) and decolorize it (exposing the base color of the resin material).

[0124] The laser marking layer 23 contains, for example, a light-to-heat conversion agent and a resin material. The resin material used in the laser marking layer contains, for example, a polycarbonate resin. The light-to-heat conversion agent used in the laser marking layer contains, for example, carbon. For example, information (character information) about the passport owner as shown in FIG. 18 is written on the laser marking layer 23. The laser marking layer 23 corresponds to a specific example of a "character information layer" according to an embodiment of the present disclosure.

[0125] As shown in FIG. 17 , the security document 1 further includes an intermediate layer 24 and a protective layer 25. The protective layer 25 corresponds to a specific example of a "protective layer" according to an embodiment of the present disclosure. The intermediate layer 24 is disposed in the same layer as the security element 10. The intermediate layer 24 has a housing portion 24A for housing the security element 10. The housing portion 24A is provided in a portion of the surface of the intermediate layer 24. The housing portion 24A may be a through-hole that penetrates the intermediate layer 24 in the thickness direction. The intermediate layer 24 serves to suppress a step formed by the security element 10 when the security element 10 is sandwiched between the card substrate 21 and the protective layer 25. The intermediate layer 24 has approximately the same thickness as the security element 10 and covers the side surfaces of the security element 10.

[0126] The intermediate layer 24 is in the form of a film. The intermediate layer 24 may be transparent. The intermediate layer 24 includes plastic. Examples of plastic used for the intermediate layer 24 include the same materials as those used for the card substrate 21.

[0127] The protective layer 25 constitutes the outermost surface of the security document 1 and covers the upper surface (light irradiation surface S1) of the security element 10. The protective layer 25 protects the security element 10 and maintains the mechanical reliability of the security element 10. The protective layer 25 is in the form of a film. The protective layer 25 is transparent. The protective layer 25 contains plastic. Examples of plastics used for the protective layer 25 include the same materials as those for the card substrate 21.

[0128] In the security document 1, the security element 10 may be provided over the entire area facing the card substrate 21, or almost the entire area, as shown in, for example, FIGS.

[0129] The security element 10 can be applied to cards other than passports, such as security cards, financial settlement cards (e.g., credit cards, cash cards, etc.), ID cards (e.g., entry / exit passes, employee ID cards, membership cards, student ID cards, etc.), and personal transaction cards (e.g., prepaid cards, point cards, etc.).

[0130] The above provides a specific description of the embodiments, modifications, and application examples of the present disclosure. However, the present disclosure is not limited to the above-described embodiments, modifications, and application examples, and various modifications based on the technical ideas of the present disclosure are possible.

[0131] For example, the configurations, methods, steps, shapes, materials, numerical values, etc. described in the above-described embodiments, modifications, and application examples are merely examples, and different configurations, methods, steps, shapes, materials, numerical values, etc. may be used as necessary. The configurations, methods, steps, shapes, materials, numerical values, etc. of the above-described embodiments, modifications, and application examples can be combined with each other as long as they do not deviate from the spirit of the present disclosure.

[0132] In the numerical ranges described in stages in the above-mentioned embodiments, modifications, and application examples, the upper limit or lower limit of a numerical range of a certain stage may be replaced with the upper limit or lower limit of a numerical range of another stage. Unless otherwise specified, the materials exemplified in the above-mentioned embodiments, modifications, and application examples may be used alone or in combination of two or more.

[0133] Note that the effects described in this specification are merely examples. The effects of the present disclosure are not limited to the effects described in this specification. The present disclosure may have effects other than the effects described in this specification.

[0134] Furthermore, for example, the present disclosure can take the following configurations. (1) A security element comprising a laminate on a substrate, the laminate including: a phosphor distribution layer in which a plurality of phosphor particles are dispersed; and a light absorbing layer disposed between the substrate and the phosphor distribution layer and capable of absorbing excitation light that excites the plurality of phosphor particles. (2) The security element described in (1), in which the laminate further includes a thermosensitive recording layer between the substrate and the light absorbing layer, capable of forming image information in the visible region. (3) The security element described in (2), in which the thermosensitive recording layer has one or more photothermal conversion wavelength ranges in a wavelength range in the visible region that is different from the wavelength range of the excitation light. (4) The security element described in (1), in which the laminate further includes a recording layer between the substrate and the light absorbing layer, in which image information in the visible region is formed. (5) The security element described in any one of (1) to (4), in which the light absorbing layer has light absorption characteristics such that the amount of transmitted light of the excitation light is 30% or less. (6) The security element according to (1), wherein the phosphor particles are formed of a phosphor having an excitation wavelength in the near-ultraviolet region, and the light absorption layer has light absorption characteristics such that the light transmittance at 400 nm is 70% or less. (7) The security element according to (5) or (6), wherein the phosphor particles are formed of a phosphor that is capable of emitting fluorescent light having a peak in the visible region, the near-infrared region, or the infrared region by absorbing the excitation light. (8) The security element according to any one of (1) to (7), wherein the phosphor distribution layer is a layer in which the plurality of phosphor particles are dispersed in a resin binder. (9) The security element according to any one of (1) to (7), wherein the phosphor distribution layer is formed of a plurality of fluorescent dots that are in contact with the light absorption layer or a transparent layer formed on the light absorption layer and are formed of the plurality of phosphor particles or a mixture of the plurality of phosphor particles and a resin member. (10) The security element according to (9), further comprising a protective layer that protects the phosphor distribution layer, wherein the resin member and the protective layer are formed of a resin material such that the difference in refractive index between the resin member and the protective layer is 0.15 or less.(11) A security document comprising a first laminate including a security element on a card substrate, the security element being arranged in at least a part of an area facing the card substrate, the security element having a second laminate on the element substrate, the second laminate including: a phosphor distribution layer in which a plurality of phosphor particles are dispersed; and a light absorption layer arranged between the element substrate and the phosphor distribution layer, capable of absorbing excitation light that excites the plurality of phosphor particles.

[0135] In the security element according to the first aspect of the present disclosure, a light-absorbing layer capable of absorbing excitation light that excites the phosphor particles is provided between the substrate and the phosphor distribution layer. This allows components of the excitation light incident on the security element that are not absorbed by the phosphor particles but that pass through the phosphor distribution layer are absorbed by the light-absorbing layer. As a result, the components of the excitation light incident on the security element that are not absorbed by the phosphor distribution layer and the light-absorbing layer and that leak out of the security element, for example, by being reflected by the substrate, are less than when the light-absorbing layer is not provided. This prevents a decrease in the contrast of the emission distribution formed by the fluorescent light.

[0136] In a security document according to a first aspect of the present disclosure, a light-absorbing layer capable of absorbing excitation light that excites phosphor particles is provided between the element substrate and the phosphor distribution layer. This allows components of the excitation light incident on the security element that are not absorbed by the phosphor particles but that pass through the phosphor distribution layer are absorbed by the light-absorbing layer. As a result, the components of the excitation light incident on the security element that are not absorbed by the phosphor distribution layer and the light-absorbing layer and that leak out of the security element, for example, by being reflected by the element substrate, are less than when the light-absorbing layer is not provided. This prevents a decrease in the contrast of the emission distribution formed by the fluorescent light.

[0137] This application claims priority based on Japanese Patent Application No. 2024-129674, filed on August 6, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0138] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. A security element comprising a laminate on a substrate, the laminate including: a phosphor distribution layer in which a plurality of phosphor particles are dispersed; and a light absorption layer disposed between the substrate and the phosphor distribution layer, the light absorption layer being capable of absorbing excitation light that excites the plurality of phosphor particles.

2. A security element according to claim 1, wherein the laminate further comprises a heat-sensitive recording layer between the substrate and the light-absorbing layer, the heat-sensitive recording layer being capable of forming image information in the visible region.

3. A security element according to claim 2, wherein the heat-sensitive recording layer has one or more photothermal conversion wavelength ranges in a wavelength range different from the wavelength range of the excitation light, selected from the visible range, near-infrared range and infrared range.

4. A security element according to claim 1, wherein the laminate further comprises a recording layer between the substrate and the light absorbing layer, on which image information in the visible region is formed.

5. A security element according to claim 1, wherein the light absorbing layer has a light absorbing property such that the amount of transmitted light of the excitation light is 30% or less.

6. A security element according to claim 1, wherein the phosphor particles are formed from a phosphor having an excitation wavelength in the near ultraviolet region, and the light absorption layer has light absorption characteristics such that the light transmittance at 400 nm is 70% or less.

7. A security element according to claim 5 or claim 6, wherein the phosphor particles are formed from a phosphor capable of absorbing the excitation light and emitting fluorescent light having a peak in the visible range, near-infrared range or infrared range.

8. The security element according to claim 1, wherein the phosphor distribution layer is a layer in which the plurality of phosphor particles are dispersed in a resin binder.

9. The security element according to claim 1, wherein the phosphor distribution layer is formed of a plurality of phosphor dots that are in contact with the light absorption layer or a transparent layer formed on the light absorption layer and are formed of the plurality of phosphor particles or a mixture of the plurality of phosphor particles and a resin material.

10. A security element according to claim 9, further comprising a protective layer for protecting the phosphor distribution layer, wherein the resin member and the protective layer are formed from a resin material such that the difference in refractive index between the resin member and the protective layer is 0.15 or less.

11. A security document comprising a first laminate on a card substrate, the first laminate including a security element, the security element being arranged in at least a part of an area facing the card substrate, the security element having a second laminate on the element substrate, the second laminate including a phosphor distribution layer in which a plurality of phosphor particles are dispersed, and a light absorption layer arranged between the element substrate and the phosphor distribution layer, the light absorption layer being capable of absorbing excitation light that excites the plurality of phosphor particles.

Images