Recording medium, card, booklet, image recognition system, and image recognition method

Abstract

Provided is a recording medium that allows authenticity determination.　The recording medium comprises a substrate and a recording layer. The recording layer has an uneven surface having random unevenness and comprises a coloring compound having electron donating properties, a developer having electron accepting properties, and a matrix resin.

Description

[Technical Field]

[0001] This disclosure relates to recording media, cards, booklets, image recognition systems, and image recognition methods. [Background technology]

[0002] A recording medium has been proposed that features a recording layer capable of displaying images and other data using laser light. In recent years, the incorporation of such recording media into cards such as financial settlement cards and ID cards, as well as booklets such as passports, has been under consideration. For such cards and booklets, improved security is desirable.

[0003] Patent Document 1 discloses a multilayer thermal label characterized by having an upper substrate and a lower substrate laminated so that they are the front and back surfaces, adhesive layers 1 and 2 laminated adjacent to each other on the inside of each substrate, at least two thermal recording layers laminated between adhesive layer 1 and adhesive layer 2, and a release layer provided between two adjacent thermal recording layers. It also discloses that when the multilayer thermal label having the above configuration is attached to an object as a sealing label and then opened, the label peels off from the release layer, separating into two parts, which remain on the envelope body and flap, thus providing high security. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-268380 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] For financial payment cards, ID cards, and other cards, as well as passports and other booklets, it is desirable to be able to determine the authenticity of the recording medium from the standpoint of improving security. However, Patent Document 1 mentioned above does not describe any technology that enables the determination of the authenticity of a recording medium (multilayer thermal label).

[0006] The purpose of this disclosure is to provide a recording medium, card, booklet, image authentication system, and image authentication method capable of determining authenticity. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the recording medium of this disclosure is It comprises a substrate and a recording layer, The recording layer has an uneven surface composed of random bumps and contains an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. fruit, The aforementioned irregularities are formed by Bénard cells. .

[0008] The card disclosed herein comprises the recording medium disclosed herein.

[0009] The booklet of this disclosure comprises the recording medium of this disclosure.

[0010] The image authentication system disclosed herein is: The system comprises a first terminal device, a second terminal device, and an image authentication device. The first terminal device, after drawing an image on a first recording medium having a recording layer with an uneven surface composed of random bumps and dips using an image drawing device, focuses on the recording layer of the first recording medium and images a portion of the first recording medium with a first imaging device to acquire a first image, which is then sent to an image authentication device. The second terminal device focuses on a recording layer having an uneven surface composed of random bumps and dips, and captures a portion of the second recording medium having the recording layer using the second imaging device to acquire a second image, which is then sent to the image authentication device. The image authentication device compares the first image received from the first terminal device with the second image received from the second terminal device, and notifies the second terminal device of the result of the comparison. death, The recording layer of the first recording medium and the recording layer of the second recording medium each comprise an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. The irregularities of the first recording medium and the irregularities of the second recording medium are formed by Bénard cells. .

[0011] The image authentication method disclosed herein is: The first terminal device draws an image on a first recording medium having a recording layer with an uneven surface composed of random bumps and dips using an image drawing device, then focuses on the recording layer of the first recording medium and captures a portion of the first recording medium using a first imaging device to acquire a first image, and transmits it to an image authentication device. The second terminal device focuses on a recording layer having an uneven surface composed of random bumps and dips, captures a portion of the second recording medium having the recording layer using the second imaging device, acquires a second image, and transmits it to the image authentication device. The image authentication device compares the first image received from the first terminal device with the second image received from the second terminal device and notifies the second terminal device of the result of the comparison. Equipped with 、 The recording layer of the first recording medium and the recording layer of the second recording medium each comprise an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. The irregularities of the first recording medium and the irregularities of the second recording medium are formed by Bénard cells. . [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a plan view showing an example of the external appearance of a recording medium according to the first embodiment. [Figure 2] Figure 2 is a cross-sectional view showing an example of the configuration of a recording medium according to the first embodiment. [Figure 3] Figure 3 is a plan view showing an example of the surface shape of the recording layer in an unrecorded state. [Figure 4] Figure 4 shows the test apparatus for the 90-degree peel test. [Figure 5] Figure 5 is a cross-sectional view showing the configuration of a recording medium according to a reference example. [Figure 6]Figure 6 shows an example of an observed image when the recording layer of the recording medium according to the first embodiment is in focus. [Figure 7] Figure 7A is a cross-sectional view showing a first example of the recording medium configuration according to Modification 1. Figure 7B is a cross-sectional view showing a second example of the recording medium configuration according to Modification 1. Figure 7C is a cross-sectional view showing a third example of the recording medium configuration according to Modification 1. [Figure 8] Figure 8A is a cross-sectional view showing a fourth example of the recording medium configuration according to Modification 1. Figure 8B is a cross-sectional view showing a fifth example of the recording medium configuration according to Modification 1. Figure 8C is a cross-sectional view showing a sixth example of the recording medium configuration according to Modification 1. [Figure 9] Figure 9 is a cross-sectional view showing an example of the configuration of a recording medium according to Modification 2. [Figure 10] Figure 10A is a plan view showing an example of the appearance of a card according to the second embodiment. Figure 10B is a cross-sectional view along the line XB-XB in Figure 10A. [Figure 11] Figure 11 is a cross-sectional view showing an example of the card configuration according to Modification Example 1. [Figure 12] Figure 12 is a cross-sectional view showing an example of the configuration of a card according to the third embodiment. [Figure 13] Figure 13 is a perspective view showing an example of the appearance of a booklet according to the fourth embodiment. [Figure 14] Figure 14 shows an example of the configuration of an image authentication system according to the fifth embodiment. [Figure 15] Figure 15 is a diagram illustrating an example of the image registration operation of the image authentication system according to the fifth embodiment. [Figure 16] Figure 16 is a diagram illustrating an example of the image authentication operation of the image authentication system according to the fifth embodiment. [Modes for carrying out the invention]

[0013] Embodiments of this disclosure will be described in the following order with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts will be denoted by the same reference numerals. 1. First Embodiment (Example of Recording Medium) 1.1 Recording medium configuration 1.2 Image characteristics of recording media 1.3 Method for manufacturing recording media 1.4 Recording method for recording media 1.5 Effects 1.6 Variations 2. Second Embodiment (Example of a Card) 2.1 Card Composition 2.2 Card Manufacturing Method 2.3 Effects 2.4 Variations 3. Third Embodiment (Example of a Card) 3.1 Card Composition 3.2 Card Manufacturing Method 3.3 Effects 3.4 Variations 4. Fourth Embodiment (Example of a Booklet) 4.1 Booklet structure 4.2 Effects 4.3 Variations 5. Fifth Embodiment (Example of an Image Recognition System) 5.1 Configuration of the Image Recognition System 5.2 Image Registration Operation 5.3 How image authentication works 5.4 Effects 5.5 Variations

[0014] <1 First Embodiment> [1.1 Recording medium configuration] Figure 1 is a plan view showing an example of the external appearance of the recording medium 10 according to the first embodiment. The recording medium 10 is, for example, a recording medium for a card or passport, and a facial photograph is drawn on the recording medium 10. The recording medium 10 is configured to change its coloring state by irradiation with laser light (external stimulus). By changing this coloring state, an image can be drawn on the recording medium 10. In the first embodiment, an example in which the image is a facial photograph is described, but the image may be a photograph other than a facial photograph. The image is not limited to a photograph, but may be a pattern or color pattern, or text such as letters or symbols. The image may be composed of a combination of two or more types: a photograph, a pattern, a color pattern, and text.

[0015] The laser light is preferably near-infrared laser light. In this specification, near-infrared laser light refers to laser light having a peak wavelength in the wavelength range of 780 nm and 2.5 μm or less. The change in color state may be reversible or irreversible. That is, the recording medium 10 may be rewritable, allowing images to be rewritten, or it may be write-once, allowing images to be written only once. From the viewpoint of preventing tampering, it is preferable that the change in color state is irreversible.

[0016] Figure 2 is a cross-sectional view showing an example of the configuration of a recording medium 10 according to the first embodiment. The recording medium 10 comprises, in order, a substrate 11, an intermediate layer 12A, a recording layer 13A, an intermediate layer 12B, a recording layer 13B, an intermediate layer 12C, a recording layer 13C, an intermediate layer 12D, a UV-cut layer 14, and a cover layer 15. The intermediate layer 12D, the UV-cut layer 14, and the cover layer 15 are provided as needed. For example, the UV-cut layer 14 may not be provided, and the intermediate layer 12D, the UV-cut layer 14, and the cover layer 15 may not be provided. In this specification, when the intermediate layers 12A, 12B, 12C, and 12D are not particularly distinguished and are referred to collectively as intermediate layer 12, they may be referred to as recording layer 13. Similarly, when the recording layers 13A, 13B, and 13C are not particularly distinguished and are referred to collectively as recording layer 13, they may be referred to as recording layer 13. Recording layers 13A, 13B, and 13C are examples of the first, second, and third recording layers, respectively.

[0017] (Base material 11) The substrate 11 supports the intermediate layer 12A, the recording layer 13A, the intermediate layer 12B, the recording layer 13B, the intermediate layer 12C, the recording layer 13C, the intermediate layer 12D, the UV cut layer 14, and the cover layer 15. Preferably, the substrate 11 is made of a material that has excellent heat resistance and excellent dimensional stability in the planar direction. The substrate 11 may have either transmittance or opacity to visible light. In this specification, visible light refers to light in the wavelength range of 360 nm to 780 nm. The substrate 11 may have a predetermined color, such as white. The substrate 11 may be, for example, in the form of a plate or a film. In this disclosure, film is defined to include sheets.

[0018] The substrate 11 may be rigid or flexible. If the substrate 11 is flexible, a flexible recording medium 10 can be realized. Examples of a rigid substrate 11 include a wafer or a glass substrate. Examples of a flexible substrate 11 include flexible glass, film, or paper.

[0019] The substrate 11 includes, for example, at least one selected from the group consisting of inorganic materials, metallic materials, and polymer materials. Examples of inorganic materials include silicon (Si) and silicon dioxide (SiO₂). X ), silicon nitride (SiN X ) and aluminum oxide (AlO X The materials include at least one selected from the group consisting of, for example, glass and spin-on glass (SOG). The silicon dioxide includes at least one selected from the group consisting of, for example, aluminum (Al), nickel (Ni), and stainless steel. The polymer materials include at least one selected from the group consisting of, for example, polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethyl ether ketone (PEEK), and polyvinyl chloride (PVC).

[0020] Furthermore, a reflective layer (not shown) may be provided on at least one of the first and second surfaces of the substrate 11, or the substrate 11 itself may also function as a reflective layer. Having such a configuration in the substrate 11 enables clearer color display.

[0021] (Recording layers 13A, 13B, 13C) Recording layers 13A, 13B, and 13C in a recorded state are in a colored state, while recording layers 13A, 13B, and 13C in an unrecorded state are in a decolorized state. Recording layers 13A, 13B, and 13C can change from a decolorized state to a colored state by irradiation with laser light. The decolorized state may be a state in which the laser light and visible light can pass through.

[0022] Recording layers 13A, 13B, and 13C are each capable of exhibiting different hues in their colored state. Specifically, recording layer 13A is capable of exhibiting magenta in its colored state. Recording layer 13B is capable of exhibiting cyan in its colored state. Recording layer 13C is capable of exhibiting yellow in its colored state. Magenta, cyan, and yellow are examples of the first, second, and third primary colors, respectively. The first, second, and third primary colors may also be the three primary colors of pigment. The first, second, and third primary colors may also be colors other than magenta, cyan, and yellow. The laser light capable of changing recording layer 13A to a colored state, the laser light capable of changing recording layer 13B to a colored state, and the laser light capable of changing recording layer 13C to a colored state each have different peak wavelengths.

[0023] Figure 3 is a plan view showing an example of the surface of the recording layer 13A in an unrecorded state (uncolored state). The recording layer 13A has an uneven surface 13AS on its front side. The front side of the recording layer 13A refers to the side on which the image recorded on the recording layer 13A is observed. The front sides of the recording layers 13B and 13C are considered to have the same characteristics as the front side of the recording layer 13A. The presence of the uneven surface 13AS on the recording layer 13A increases the peel strength of the interface between the recording layer 13A and the intermediate layer 12B.

[0024] The recording layer 13B has an uneven surface 13BS on its front side. The presence of the uneven surface 13BS on the recording layer 13B increases the peel strength of the interface between the recording layer 13B and the intermediate layer 12C.

[0025] The recording layer 13C has an uneven surface 13CS on its front side. The presence of the uneven surface 13CS on the recording layer 13C increases the peel strength of the interface between the recording layer 13C and the intermediate layer 12C.

[0026] The uneven surfaces 13AS, 13BS, and 13CS are composed of random bumps and ridges. These random bumps and ridges are formed, for example, by Bénard cells. The random bumps and ridges formed by Bénard cells, etc., are unique to each recording medium 10 and have a structure that is difficult to counterfeit. In this specification, when the uneven surfaces 13AS, 13BS, and 13CS are not specifically distinguished and are referred to collectively as uneven surface 13S.

[0027] The size of the random irregularities on surface 13AS, surface 13BS, and surface 13CS is, for example, between 50 μm and 100 μm. The height of the random irregularities on surface 13AS, surface 13BS, and surface 13CS is, for example, between 2 μm and 3 μm.

[0028] The size of the random bumps and dips can be determined by one of the following methods (1) to (3). (1) Using a microscope equipped with a high-resolution camera, depth composite of the surface irregularities of the recording layer is performed in the height direction to acquire image data. The length in the width direction of the acquired irregularities is measured to determine the size of the irregularities. (2) A cross-section is obtained using a microtome or similar device, and the size of the surface irregularities of the recording layer 13 is measured using a Scanning Electron Microscope (SEM). (3) After drawing, a patchy image is obtained by observing the area that has been colored to a uniform shade under a microscope. The size of the patches is due to the unevenness of the recording layer 13, and can therefore be considered to represent the size of the unevenness.

[0029] The height of the random bumps can be determined by either of the following methods (4) or (5). (4) Using a microscope equipped with a high-resolution camera, the surface irregularities of the recording layer are depth composited in the height direction to acquire image data. The height of the irregularities is determined by measuring the difference in height between the peaks and valleys of the acquired irregularities. (5) A cross-section is obtained using a microtome or similar device, and the height of the surface irregularities of the recording layer 13 is measured using a Scanning Electron Microscope (SEM).

[0030] In the recording state, the recording layer 13A has a first pixel that constitutes an image such as a facial photograph. The first pixel is composed of a dot-shaped first color-producing portion. The first pixel of the recording layer 13A, i.e., the first color-producing portion, has a magenta color.

[0031] In the recording state, the recording layer 13B has a second pixel that constitutes an image such as a facial photograph. The second pixel is composed of a dot-shaped second color-producing portion. The second pixel of the recording layer 13B, i.e., the second color-producing portion, has a cyan color.

[0032] In the recording state, the recording layer 13C has a third pixel that constitutes an image such as a facial photograph. The third pixel is composed of a dot-shaped third color-emitting portion. The third pixel of the recording layer 13C, i.e., the third color-emitting portion, has a yellow color.

[0033] The thickness of each recording layer 13A, 13B, and 13C is preferably 1 μm to 20 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 7 μm, for example, about 5 μm. If the thickness of the recording layers 13A, 13B, and 13C is 1 μm or more, the color density can be improved. On the other hand, if the thickness of the recording layers 13A, 13B, and 13C is 20 μm or less, the increase in the amount of heat used by the recording layers 13A, 13B, and 13C can be suppressed, and the deterioration of color development can be suppressed.

[0034] The recording layer 13A comprises a first color-developing compound having electron-donating properties, a first color developer having electron-accepting properties, and a first photothermal converter. Preferably, the recording layer 13A further comprises a first matrix resin.

[0035] The recording layer 13B comprises a second color-developing compound having electron-donating properties, a second color developer having electron-accepting properties, and a second photothermal converter. Preferably, the recording layer 13B further comprises a second matrix resin.

[0036] The recording layer 13C comprises a third color-developing compound having electron-donating properties, a third color developer having electron-accepting properties, and a third photothermal converter. Preferably, the recording layer 13C further comprises a third matrix resin.

[0037] (The first, second, and third color-producing compounds) The first, second, and third color-developing compounds can each develop color by reacting with the first, second, and third color developers, respectively. The first, second, and third color-developing compounds can exhibit different hues in their developed state. Specifically, the first color-developing compound can exhibit magenta in its developed state. The second color-developing compound can exhibit cyan in its developed state. The third color-developing compound can exhibit yellow in its developed state.

[0038] The first, second, and third color-developing compounds are, for example, leuco dyes. When the lactone ring in a leuco dye reacts with an acid, the lactone ring opens and develops color. When the open lactone ring in a leuco dye reacts with a base, it closes and becomes colorless. The leuco dye may be, for example, an existing dye for thermal paper.

[0039] The first, second, and third color-developing compounds are not particularly limited and can be appropriately selected depending on the purpose. The first, second, and third color-developing compounds include, for example, at least one selected from the group consisting of fluorane compounds, triphenylmethanephthalide compounds, azaphthalide compounds, phenothiazine compounds, leucoauramine compounds, and indolinophthalide compounds. In addition, the first, second, and third chromogenic compounds include, for example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-di(n-butylamino)fluorane, 2-anilino-3-methyl-6-(Nn-propyl-N-methylamino)fluorane, 2-anilino-3-methyl-6-(N-isopropyl-N-methylamino)fluorane, 2-anilino-3-methyl-6-(N-isobutyl-N-methylamino)fluorane, 2-anilino-3-methyl-6-(Nn-amyl-N-methylamino)fluorane, 2-anilino-3-methyl-6-(N-sec-butyl-N-methylamino)fluorane, 2-anilino- 3-methyl-6-(N-iso-amyl-N-ethylamino)fluorane, 2-anilino-3-methyl-6-(Nn-propyl-N-isopropylamino)fluorane, 2-anilino-3-methyl-6-(N-cyclohexyl-N-methylamino)fluorane, 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluorane, 2-anilino-3-methyl-6-(N-methyl-p-toluidino)fluorane, 2-(m-trichloromethylanilino)-3-methyl-6-diethylaminofluorane, 2-(m-trifluoromethylanilino)-3-methyl-6-diethylaminofluorane, 2-(m-trichloromethylanilino)-3-methyl-6-(N-cyclohexyl-N-methylamino)fluorane, 2-(2,4-dimethylanilino)-3-methyl-6-diethylaminofluorane, 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-ethylanilino)fluorane, 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-propyl-p-toluidino)fluorane, 2-anilino-6-(Nn-hexyl-N-ethylamino)fluorane, 2-(o-chloroanilino)-6-diethylaminofluorane, 2-(o-chloroanilino)-6-dibutylaminofluorane, 2-(m-trifluoromethylanilino)-6-diethylaminofluorane, 2,3-dimethyl-6-dimethylaminofluorane, 3-methyl-6-(N-ethyl-p-toluidino)fluorane, 2-chloro-6 -Diethylaminofluorane, 2-bromo-6-diethylaminofluorane, 2-chloro-6-dipropylaminofluorane, 3-chloro-6-cyclohexylaminofluorane, 3-bromo-6-cyclohexylaminofluorane, 2-chloro-6-(N-ethyl-N-isoamylamino)fluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-(o-chloroanilino)-3-chloro-6-cyclohexylaminofluorane, 2-(m-trifluoromethylanilino)-3-chloro-6-diethylaminofluorane, 2-(2,3-dichloroanilino)-3-chloro-6-diethylaminofluorane, 1,2-Benzo-6-diethylaminofluorane, 3-diethylamino-6-(m-trifluoromethylanilino)fluorane, 3-(1-ethyl-2-methylindole-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindole-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-octyl- 2-methylindole-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindole-3-yl)-3-(2-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindole-3-yl)-3-(2-methyl-4-diethylaminophenyl)-7-azaphthalide, 3-(1-ethyl-2-methylin Dol-3-yl)-3-(4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindole-3-yl)-3-(4-Nn-amyl-N-methylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindole-3-yl)-3-(2-hexyloxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl) Phenyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 2-(p-acetylanilino)-6-(Nn-amyl-Nn-butylamino)fluorane, 2-benzylamino-6-(N-ethyl-p-toluidino)fluorane, 2-benzylamino-6-(N-methyl-2,4-dimethylanilino)fluorane, 2-benzylamino-6-(N-ethyl-2,4-dimethylanilino)fluorane, 2-benzylamino-6-(N-methyl-p-toluidino)fluorane, 2-benzylamino-6-(N-ethyl-p-toluidino)fluorane, 2-(di-p-methylbenzylamino)-6-(N-ethyl-p-toluidino)fluorane, 2-(α-phenylethylamino)-6-(N-ethyl-p-toluidino)fluorane, 2-methylamino-6-(N-methylanilino)fluorane, 2-methylamino-6-(N-ethylanilino)fluorane, 2-methylamino-6-(N-propylanilino)fluorane , 2-ethylamino-6-(N-methyl-p-toluidino)fluorane, 2-methylamino-6-(N-methyl-2,4-dimethylanilino)fluorane, 2-ethylamino-6-(N-ethyl-2,4-dimethylanilino)fluorane, 2-dimethylamino-6-(N-methylanilino)fluorane, 2-dimethylamino-6-(N-ethylanilino)fluorane, 2-diethylamino-6-(N-methyl-p-toluidino)fluorane, 2-diethylamino-6-(N-ethyl-p-toluidino)fluorane, 2-dipropylamino-6-(N-methyl Fluoranilino)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 (Tyl-p-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,It may contain at least one selected from the group consisting of 2 - benzo - 6-(N - ethyl - N - isoamylamino) fluoran, 1,2 - benzo - 6 - dibutylamino fluoran, 1,2 - benzo - 6-(N - methyl - N - cyclohexylamino) fluoran, 1,2 - benzo - 6-(N - ethyl - N - toluidino) fluoran, etc.,

[0040] (First, second, and third developers) The first, second, and third developers can each cause the first, second, and third color - forming compounds in the decolorized state to develop color. The types of the first, second, and third developers may be the same, or the types of the first, second, and third developers may be different from each other. The first, second, and third developers are compounds containing a group having an electron - accepting property in the molecule. The electron - accepting parts of the first, second, and third developers react with the lactone rings of the first, second, and third color - forming compounds respectively, and the lactone rings open, causing the first, second, and third color - forming compounds to develop color. The first, second, and third developers include, for example, at least one selected from the group consisting of phenol derivatives, salicylic acid derivatives, and urea derivatives, etc.,

[0041] Specifically, for example, the developer contains a compound represented by the following formula (1). [Chemical formula] (However, in formula (1), X 0 is a divalent group containing at least one benzene ring. Y 01 , Y 02 are each independently a monovalent group. n01 and n02 are each independently an integer from 0 to 5. When n01 is an integer from 2 to 5, Y 01 may be the same as or different from each other. When n02 is an integer from 2 to 5, Y 02 may be the same as or different from each other. Z 01 , Z 02 are each independently a hydrogen - bonding group.)

[0042] X0 X contains at least one benzene ring. 0 Since the melting point can be made higher compared to when it is an aliphatic hydrocarbon group (e.g., a normal alkyl chain), the color retention characteristics during high-temperature, high-humidity storage (hereinafter referred to as "high-temperature, high-humidity storage characteristics") can be improved. From the viewpoint of improving high-temperature, high-humidity storage characteristics and heat resistance, X 0 However, it is preferable that it contains at least two benzene rings. High-temperature, high-humidity storage characteristics refer to, for example, storage characteristics under conditions of 80°C and 60%RH. Improved heat resistance enhances the resistance of the recording medium 10 to harsh processes (e.g., heated pressing or integral molding using molten resin, etc.). 0 If it contains at least two benzene rings, at least two benzene rings may be fused together. For example, it may be naphthalene or anthracene, etc.

[0043] Z 01 , Z 02 Because each of these groups is independently a hydrogen bonding group, the color developers tend to remain somewhat cohesive through hydrogen bonding, thereby improving the stability of the color developers within the recording layer 13. In this specification, a hydrogen bonding group means a functional group that contains an atom capable of forming hydrogen bonds with other functional groups or atoms present in other compounds.

[0044] The color developer preferably contains a compound represented by the following formula (2). [ka] (However, in equation (2), X 1 Y is a divalent group containing at least one benzene ring. 11 , Y 12 , Y 13 , Y 14 Each of them is an independent, undivided base. Z 11 , Z 12 Each of these is an independent hydrogen bonding group.

[0045] X 1 X contains at least one benzene ring.1 Since the melting point can be increased compared to when it is an aliphatic hydrocarbon group (e.g., a normal alkyl chain), the high-temperature, high-humidity storage characteristics can be improved. From the viewpoint of improving high-temperature, high-humidity storage characteristics and heat resistance, X 1 However, it is preferable that it contains at least two benzene rings. 1 If it contains at least two benzene rings, at least two benzene rings may be fused together. For example, it may be naphthalene or anthracene, etc.

[0046] Z 11 , Z 12 Because each of these groups is independently a hydrogen bonding group, the color developers tend to remain somewhat cohesive through hydrogen bonding, thus improving the stability of the color developers within the recording layer 13.

[0047] When formulas (1) and (2) contain hydrocarbon groups, these hydrocarbon groups are a general term for groups composed of carbon (C) and hydrogen (H), and may be saturated hydrocarbon groups or unsaturated hydrocarbon groups. Saturated hydrocarbon groups are aliphatic hydrocarbon groups that do not have multiple carbon-carbon bonds, and unsaturated hydrocarbon groups are aliphatic hydrocarbon groups that have multiple carbon-carbon bonds (carbon-carbon double bonds or carbon-carbon triple bonds).

[0048] If formulas (1) and (2) contain a hydrocarbon group, the hydrocarbon group may be in the form of a chain or may contain one or more rings. The chain may be linear or branched with one or more side chains, etc.

[0049] (X containing one benzene ring) 0 , X 1 ) X in equation (1) 0 and X in equation (2) 1 This is, for example, a divalent group containing one benzene ring. This divalent group can be represented, for example, by the following formula (3). [ka] (However, in equation (3), X21 It can be there or not, X 21 If X 21 X is a divalent group. 22 It can be there or not, X 22 If X 22 R is a divalent group. 21 is a single-valued base. n21 is an integer from 0 to 4. If n21 is an integer from 2 to 4, then R 21 These elements may be identical or different. (* indicates a connection point.)

[0050] In equation (3), X relative to the benzene ring 21 and X 22 The bonding position of X is not limited. That is, X relative to the benzene ring. 21 and X 22 The bond position may be the ortho, meta, or para position.

[0051] The above divalent group containing one benzene ring is preferably represented by the following formula (4) from the viewpoint of improving high-temperature and high-humidity storage characteristics. [ka] (However, in equation (4), R 22 is a single-valued base. n²² is an integer from 0 to 4. If n²² is an integer from 2 to 4, then R 22 These elements may be identical or different. (* indicates a connection point.)

[0052] X in equation (1) 0 If is a divalent group containing one benzene ring, then in formula (4), Z relative to the benzene ring 01 and Z 02 The bonding position is not limited. That is, Z relative to the benzene ring. 01 and Z 02 The bond position may be the ortho, meta, or para position.

[0053] X in equation (2) 1If is a divalent group containing one benzene ring, then in formula (4), Z relative to the benzene ring 11 and Z 12 The bonding position is not limited. That is, Z relative to the benzene ring. 11 and Z 12 The bond position may be the ortho, meta, or para position.

[0054] (X 21 , X 22 ) X in equation (3) 21 , X 22 Each of these groups can be independently a divalent group and is not particularly limited, but examples include hydrocarbon groups which may have substituents. The hydrocarbon groups are preferably in a chain form. When the hydrocarbon groups are in a chain form, the melting point of the color developer can be reduced, so that the color developer dissolves upon irradiation with laser light and the color-developing compound becomes easier to color. From the viewpoint of reducing the melting point of the color developer, among the chain-like hydrocarbon groups, a n-alkyl chain is particularly preferred.

[0055] The number of carbon atoms in the hydrocarbon group, which may have substituents, is, for example, 1 to 15, 1 to 13, 1 to 12, 1 to 10, 1 to 6, or 1 to 3.

[0056] X in equation (3) 21 , X 22 When the normal alkyl group 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 number of carbon atoms in the normal alkyl group is 8 or less, the length of the normal alkyl group is short, so thermal disturbance is less likely to occur in the color developer during high-temperature storage, and the site that interacted with the color-developing compound such as leuco dye during color development is less likely to detach. Therefore, the color-developing compound such as leuco dye is less likely to lose its color during high-temperature storage, thus improving high-temperature storage stability.

[0057] Examples of substituents that a hydrocarbon group may have include halogen groups (e.g., fluorine groups) or alkyl groups having halogen groups (e.g., fluorine groups). A hydrocarbon group that may have substituents 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) are substituted with an element such as oxygen.

[0058] (R 21 ) R in equation (3) 21 This can be any monovalent group and is not particularly limited, but examples include a halogen group or a hydrocarbon group which may have substituents.

[0059] Halogen groups include, for example, fluorine (-F), chlorine (-Cl), bromine (-Br), or iodine (-I).

[0060] The number of carbon atoms in the hydrocarbon group, which may have substituents, is, for example, 1 to 15, 1 to 13, 1 to 12, 1 to 10, 1 to 6, or 1 to 3.

[0061] Examples of substituents that a hydrocarbon group may have include halogen groups (e.g., fluorine groups) or alkyl groups having halogen groups (e.g., fluorine groups). A hydrocarbon group that may have substituents 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) are substituted with an element such as oxygen.

[0062] (R 22 ) R in equation (4) 22 R can be any monovalent group and is not particularly limited, but examples include a halogen group or a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are R in formula (3) above, respectively. 21 It is similar to that.

[0063] (X containing two benzene rings) 0 , X 1 ) X in formula (1) 0 and X in formula (2) 1 is a divalent group containing, for example, two benzene rings. The divalent group is represented by, for example, the following formula (5). [Chemical formula] (However, in formula (5), X 31 may or may not be present. When X 31 is present, X 31 is a divalent group. X 32 may or may not be present. When X 32 is present, X 32 is a divalent group. X 33 may or may not be present. When X 33 is present, X 33 is a divalent group. R 31 , R 32 are each independently a monovalent group. n31 and n thirty-two are each independently an integer between 0 and 4. When n31 is an integer between 2 and 4, R 31 may be the same as or different from each other. When n32 is an integer between 2 and 4, R 32 may be the same as or different from each other. The * mark represents a bonding site.)

[0064] In formula (5), the bonding positions of X 31 and X 32 to the benzene ring are not limited. That is, the bonding positions of X 31 and X 32 to the benzene ring may be any of the ortho, meta, and para positions. Similarly, in formula (5), the bonding positions of X 32 and X 33 to the benzene ring are not limited. That is, the bonding positions of X 32 and X 33 to the benzene ring may be any of the ortho, meta, and para positions.

[0065] The divalent group containing two benzene rings is preferably represented by the following formula (6) from the viewpoint of improving the high-temperature and high-humidity storage characteristics.

Chemical formula

[0066] When X 0 in formula (1) is a divalent group containing two benzene rings, in formula (6), the bonding positions of Z 01 and X 34 to the benzene ring are not limited. That is, the bonding positions of Z 01 and X 34 to the benzene ring may be any of the ortho position, meta position, and para position. Similarly, in formula (6), the bonding positions of Z [[ID=三十二]] 02 and X 34 to the benzene ring are not limited. That is, the bonding positions of Z 02 and X 34 to the benzene ring may be any of the ortho position, meta position, and para position.

[0067] When X 1 in formula (2) is a divalent group containing two benzene rings, in formula (6), the bonding positions of Z 11 and X 34 to the benzene ring are not limited. That is, the bonding positions of Z 11 and X 34 to the benzene ring may be any of the ortho position, meta position, and para position. Similarly, in formula (6), the bonding positions of Z 12 and X34 The bonding position is not limited. That is, Z relative to the benzene ring. 12 and X 34 The bond position may be the ortho, meta, or para position.

[0068] (X 31 , X 32 , X 33 ) X in equation (5) 31 , X 32 , X 33 Each of these can be a divalent group, and is not particularly limited, but an example would be a hydrocarbon group which may have substituents. The hydrocarbon group is X in formula (3) above. 21 , X 22 It is similar to that.

[0069] (X 34 ) X in equation (6) 34 X in formula (3) above is not particularly limited, but any divalent group is acceptable. For example, a hydrocarbon group which may have substituents is acceptable. 21 , X 22 It is similar to that.

[0070] (R 31 , R 32 ) R in equation (5) 31 , R 32 R can be any monovalent group and is not particularly limited, but examples include a halogen group or a hydrocarbon group which may have substituents. The halogen group and the hydrocarbon group which may have substituents are R in formula (3) above, respectively. 21 It is similar to that.

[0071] (R 33 , R 34 ) R in equation (6) 33 , R 34R can be any monovalent group and is not particularly limited, but examples include a halogen group or a hydrocarbon group which may have substituents. The halogen group and the hydrocarbon group which may have substituents are R in formula (3) above, respectively. 21 It is similar to that.

[0072] (Y 01 , Y 02 ) Y in equation (1) 01 , Y 02 Each of these is independently, for example, a hydrogen group (-H), a hydroxyl group (-OH), a halogen group (-X), a carboxyl group (-COOH), an ester group (-COOR), or a hydrocarbon group which may have substituents.

[0073] Halogen groups include, for example, fluorine (-F), chlorine (-Cl), bromine (-Br), or iodine (-I).

[0074] The number of carbon atoms in the hydrocarbon group, which may have substituents, is, for example, 1 to 15, 1 to 13, 1 to 12, 1 to 10, 1 to 6, or 1 to 3.

[0075] Examples of substituents that a hydrocarbon group may have include halogen groups (e.g., fluorine groups) or alkyl groups having halogen groups (e.g., fluorine groups). A hydrocarbon group that may have substituents 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) are substituted with an element such as oxygen.

[0076] In equation (1), (Y 01 ) n01 one of the following, and / or (Y 02 ) n02 It is preferable that one of them is a hydroxyl group (-OH). (Y 01 ) n01 one of the following, and / or (Y 02 ) n02 One of these groups is a hydroxyl group (-OH), which improves label quality and lightfastness.

[0077] (Y 11 , Y 12 , Y 13 , Y 14 ) In equation (2), Y relative to the benzene ring 11 and Y 12 The bonding position is not limited. That is, Y relative to the benzene ring. 11 and Y 12 The bond position of can be any of the ortho, meta, or para positions. Similarly, in formula (2), Y relative to the benzene ring 13 and Y 14 The bonding position is not limited. That is, Y relative to the benzene ring. 13 and Y 14 The bond position may be any of the ortho, meta, or para positions. In formula (2), Y for one of the benzenes 11 and Y 12 The bond position of and Y relative to the other benzene 13 and Y 14 The bonding position may be the same as or different from that position.

[0078] Y in equation (2) 11 , Y 12 , Y 13 , Y 14 Each of these is independently, for example, a hydrogen group (-H), a hydroxyl group (-OH), a halogen group, a carboxyl 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, respectively, Y in formula (1) above. 01 , Y 02 It is similar to that.

[0079] In equation (2), Y 11 and / or Y 13 It is preferable that it is a hydroxyl group (-OH). 11 and / or Y 13 The presence of a hydroxyl group (-OH) improves both label quality and lightfastness.

[0080] (Z 01 , Z 02 ) Z in equation (1) 01 , Z 02 These are, independently of each other, for example, urea bonds (-NHCONH-), amide bonds (-NHCO-, -OCHN-), or hydrazide bonds (-NHCOCONH-). From the viewpoint of improving high temperature and high humidity storage characteristics, Z 01 , Z 02 It is preferable that it is a urea bond. 01 If it 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 If the bond 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.

[0081] (Z 11 , Z 12 ) Z in equation (2) 11 , Z 12 These are, independently of each other, for example, urea bonds (-NHCONH-), amide bonds (-NHCO-, -OCHN-), or hydrazide bonds (-NHCOCONH-). From the viewpoint of improving high temperature and high humidity storage characteristics, Z 11 , Z 12 It is preferable that it is a urea bond. 11 If it 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 If the bond 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.

[0082] (Specific examples of color developers) X in equation (1) 0 and X in equation (2) 1A color developer containing one benzene ring specifically includes, for example, at least one selected from the group consisting of compounds represented by the following formulas (7-1) to (7-6). [ka]

[0083] X in equation (1) 0 and X in equation (2) 1 A color developer containing two benzene rings specifically includes, for example, at least one selected from the group consisting of compounds represented by the following formulas (8-1) to (8-8). [ka]

[0084] (First, second, and third photothermal converters) The first, second, and third photothermal converters are capable of absorbing light in a predetermined wavelength range, such as the near-infrared region, and generating heat. The first, second, and third photothermal converters have different absorption wavelength peaks. Specifically, the first photothermal converter has an absorption wavelength peak at wavelength λ1. The second photothermal converter has an absorption wavelength peak at wavelength λ2. The third photothermal converter has an absorption wavelength peak at wavelength λ3. Wavelengths λ1, λ2, and λ3 are different from each other. It is preferable that the absorption wavelength peaks are in the near-infrared region. The near-infrared region is, for example, the range of wavelengths from 700 nm to 2000 nm. As described above, by having different absorption wavelength peaks for the first, second, and third photothermal converters, it is possible to selectively color a desired layer among the recording layers 13A, 13B, and 13C by irradiation with laser light. It is preferable that the first, second, and third photothermal converters use near-infrared absorbing dyes that have almost no absorption in the visible region.

[0085] The first, second, and third photothermal converters each include, for example, at least one selected from the group consisting of compounds having a phthalocyanine skeleton (phthalocyanine dyes), compounds having a squarylium skeleton (squirlium dyes), and inorganic compounds.

[0086] The inorganic compound includes, for example, at least one selected from the group consisting of metal complexes such as dithio complexes, diimonium salts, aminium salts, graphite, carbon black, metal powder particles, cobalt tetroxide, iron oxide, chromium oxide, copper oxide, titanium black, metal oxides such as ITO (Indium Tin Oxide), metal nitrides such as niobium nitride, metal carbides such as tantalum carbide, metal sulfides, and various magnetic powders. In addition, the inorganic compound may include compounds having a cyanine skeleton (cyanine dyes) that have excellent lightfastness and heat resistance. Here, excellent lightfastness means that it does not decompose under the usage environment, for example, when exposed to light from a fluorescent lamp. Excellent heat resistance means that, for example, when formed into a film with a polymer material and stored at, for example, 150°C for 30 minutes, there is no change of more than 20% in the maximum absorption peak value of the absorption spectrum. Examples of compounds having such a cyanine skeleton include those having at least one of the following counterions in the molecule: SbF6, PF6, BF4, ClO4, CF3SO3, and (CF3SO3)2N, and a methine chain containing a five-membered ring or a six-membered ring. In the first embodiment, it is preferable that the cyanine skeleton compound used in the recording medium 10 has both one of the above counterions 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 can be ensured if at least one of them is present.

[0087] (First, second, and third matrix resins) The first, second, and third matrix resins preferably function as binders. The first matrix resin is preferably one in which the first color-developing compound, the first color developer, and the first photothermal converter can be homogeneously dispersed. The second matrix resin is preferably one in which the second color-developing compound, the second color developer, and the second photothermal converter can be homogeneously dispersed. The third matrix resin is preferably one in which the third color-developing compound, the third color developer, and the third photothermal converter can be homogeneously dispersed. The first, second, and third matrix resins may be the same type, or they may be different types.

[0088] The first, second, and third matrix resins each include at least one selected from the group consisting of, for example, thermosetting resins and thermoplastic resins. Preferably, the first, second, and third matrix resins include polycarbonate resins. By including polycarbonate resins in the first, second, and third matrix resins, the light resistance of the surface of the recording medium 10 can be improved. Here, a polycarbonate resin is a resin having at least a carbonate group (-O-(C=O)-O-) as a structural unit in its main chain. Therefore, it may have other structural units in addition to carbonate groups in its main chain.

[0089] The first, second, and third matrix resins may, in place of or in combination with polycarbonate resins, contain at least one selected from the group consisting of polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylcellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid polymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethylcellulose, carboxymethylcellulose, and starch.

[0090] (Additives) The recording layers 13A, 13B, and 13C may further contain at least one additive selected from the group consisting of sensitizers and ultraviolet absorbers, etc., as needed. From the viewpoint of suppressing scalp discoloration, it is preferable that the recording layers 13A, 13B, and 13C contain amine compounds.

[0091] When recording layers 13A, 13B, and 13C contain an amine-based compound, it is preferable that recording layers 13A, 13B, and 13C also contain at least one compound selected from the group consisting of epoxy-based compounds and carbodiimide-based compounds, along with the amine-based compound. If recording layers 13A, 13B, and 13C contain an amine-based compound, the reliability of the color-developing portion during high-temperature, high-humidity storage may decrease. However, if recording layers 13A, 13B, and 13C also contain at least one compound selected from the group consisting of epoxy-based compounds and carbodiimide-based compounds, along with the amine-based compound, the decrease in the reliability of the color-developing portion during high-temperature, high-humidity storage caused by the amine-based compound can be suppressed.

[0092] (Middle layer 12A, 12B, 12C, 12D) Intermediate layer 12A is provided between the substrate 11 and the recording layer 13A. Intermediate layer 12A can insulate the space between the substrate 11 and the recording layer 13A and can suppress the diffusion of the constituent material between the substrate 11 and the recording layer 13A. Intermediate layer 12B is provided between the recording layer 13A and the recording layer 13B. Intermediate layer 12B can insulate the space between the recording layer 13A and the recording layer 13B and can suppress the diffusion of the constituent material between the recording layer 13A and the recording layer 13B. Intermediate layer 12C is provided between the recording layer 13B and the recording layer 13C. Intermediate layer 12C can insulate the space between the recording layer 13B and the recording layer 13C and can suppress the diffusion of the constituent material between the recording layer 13B and the recording layer 13C. Intermediate layer 12D is provided between the recording layer 13C and the UV cut layer 14. The intermediate layer 12D can insulate the space between the recording layer 13C and the UV-cut layer 14, and can also suppress the diffusion of the constituent materials between the recording layer 13C and the UV-cut layer 14.

[0093] The intermediate layer 12A may be transparent to or opaque to the laser light and visible light used for writing on the recording medium 10. The intermediate layers 12B, 12C, and 12D are transparent to the laser light and visible light used for writing on the recording medium 10.

[0094] The thickness of each intermediate layer 12A, 12B, 12C, and 12D is preferably 3 μm to 100 μm, more preferably 5 μm to 50 μm, and even more preferably 7 μm to 15 μm, for example, about 10 μm. If the thickness of the intermediate layers 12A, 12B, 12C, and 12D is 3 μm or more, a sufficient heat insulation effect and a sufficient diffusion suppression effect can be obtained. On the other hand, if the thickness of the intermediate layers 12A, 12B, 12C, and 12D is 50 μm or less, a decrease in light transmittance can be suppressed. Furthermore, a decrease in the bending resistance of the recording medium 10 can be suppressed, and defects such as cracks can be made less likely to occur. The thicknesses of the intermediate layers 12A, 12B, 12C, and 12D may be the same or may be different from each other.

[0095] The intermediate layer 12A comprises an adhesive layer 12A1 and an ultraviolet-curable resin layer 12A2 in that order on the substrate 11. The adhesive layer 12A1 bonds the substrate 11 and the ultraviolet-curable resin layer 12A2. The adhesive layer 12A1 may also provide insulation between the substrate 11 and the recording layer 13A. The ultraviolet-curable resin layer 12A2 can provide insulation between the substrate 11 and the recording layer 13A and can suppress the diffusion of the constituent material (e.g., the first color-developing compound) between the substrate 11 and the recording layer 13A. The intermediate layer 12A may further include a film (not shown). This film is provided, for example, between the adhesive layer 12A1 and the ultraviolet-curable resin layer 12A2. Examples of the material of the film include materials similar to the polymer material of the substrate 11.

[0096] The intermediate layer 12B comprises an adhesive layer 12B1 and an ultraviolet-curable resin layer 12B2 in that order on the recording layer 13A. The adhesive layer 12B1 bonds the recording layer 13A and the ultraviolet-curable resin layer 12B2. The adhesive layer 12B1 is adjacent to the uneven surface 13AS. The adhesive layer 12B1 may also provide insulation between the recording layer 13A and the recording layer 13B. The ultraviolet-curable resin layer 12B2 can provide insulation between the recording layer 13A and the recording layer 13B and can suppress the diffusion of constituent materials (e.g., first and second color-developing compounds, etc.) between the recording layer 13A and the recording layer 13B. The intermediate layer 12B may further comprise a film (not shown). This film is provided, for example, between the adhesive layer 12B1 and the ultraviolet-curable resin layer 12B2. Examples of the material of the film include materials similar to the polymer material of the substrate 11.

[0097] The intermediate layer 12C comprises an adhesive layer 12C1 and an ultraviolet-curable resin layer 12C2 in that order on the recording layer 13B. The adhesive layer 12C1 bonds the recording layer 13B and the ultraviolet-curable resin layer 12C2. The adhesive layer 12C1 is adjacent to the uneven surface 13BS. The adhesive layer 12C1 may also provide insulation between the recording layer 13B and the recording layer 13C. The ultraviolet-curable resin layer 12C2 can provide insulation between the recording layer 13B and the recording layer 13C, and can also suppress the diffusion of constituent materials (e.g., second and third color-developing compounds, etc.) between the recording layer 13B and the recording layer 13C. The intermediate layer 12C may further comprise a film (not shown). This film is provided, for example, between the adhesive layer 12C1 and the ultraviolet-curable resin layer 12C2. Examples of the material of the film include materials similar to the polymer material of the substrate 11.

[0098] The intermediate layer 12D comprises an adhesive layer 12D1 and an ultraviolet-curable resin layer 12D2 in that order on the recording layer 13C. The adhesive layer 12D1 bonds the recording layer 13C and the ultraviolet-curable resin layer 12D2. The adhesive layer 12D1 is adjacent to the uneven surface 13CS. The adhesive layer 12D1 may also provide insulation between the recording layer 13C and the UV-cut layer 14. The ultraviolet-curable resin layer 12D2 can provide insulation between the recording layer 13C and the UV-cut layer 14 and can suppress the diffusion of constituent materials (e.g., a third color-developing compound) between the recording layer 13C and the UV-cut layer 14.

[0099] The adhesive layers 12A1, 12B1, 12C1, and 12D1 are, for example, double-sided adhesive films such as OCA (Optical Clear Adhesive).

[0100] The UV-curable resin layers 12A2, 12B2, 12C2, and 12D2 contain UV-curable resins that have undergone polymerization and solidified. More specifically, for example, the UV-curable resin layers 12A2, 12B2, 12C2, and 12D2 contain polymers of polymerizable compounds and polymers obtained when a polymerization initiator generates active species and undergoes a structural change upon irradiation with external energy (ultraviolet light). The UV-curable resin composition includes, for example, at least one selected from the group consisting of radical polymerization type UV-curable resin compositions and cationic polymerization type UV-curable resin compositions. The UV-curable resin composition may optionally include at least one selected from the group consisting of sensitizers, fillers, stabilizers, leveling agents, defoamers, and viscosity modifiers.

[0101] (Average peel strength) The average peel strength at the interface between the recording layer 13A and the intermediate layer 12B, the average peel strength at the interface between the recording layer 13B and the intermediate layer 12C, and the average peel strength at the interface between the recording layer 13C and the intermediate layer 12D are preferably 3.5 N / cm or more, more preferably 4.0 N / cm or more, and even more preferably 5.0 N / cm or more. When the average peel strength at each of the above interfaces is 3.5 N / cm or more, peeling at each of the above interfaces can be suppressed. Therefore, tampering with the recording medium 10 can be prevented.

[0102] The average peel strength at the interface between the recording layer 13A and the intermediate layer 12B is determined by performing a 90-degree peel test. The 90-degree peel test will be described below with reference to Figure 4.

[0103] First, the recording medium 10 is cut into a strip 10 mm wide and 100 mm long to prepare a test piece 60, which is left in a standard atmosphere of 23 ± 1 °C and 50 ± 5% relative humidity for 24 hours or more. Hereinafter, the laminate below the interface between the recording layer 13A and the intermediate layer 12B of the test piece 60 will be referred to as the adherend 60A, and the laminate above the interface will be referred to as the adherend 60B. Next, at one end of the test piece 60 in the longitudinal direction, a notch is made between the adherend 60A and adherend 60B using a sharp blade such as a cutter, and the adherend 60B is peeled off by a length of 20 mm in the longitudinal direction to create a gripping area. Then, the side of the test piece 60 on the adherend 60A side is fixed to the test stand 71 with a strong adhesive. As an adhesive, one with sufficiently high adhesive strength is selected to prevent the test piece 60 from peeling off the test stand 71 when measuring the peel strength between the recording layer 13A and the intermediate layer 12B, such as 3M's Scotch® strong adhesive tape.

[0104] Next, one end of the tension member 61 is attached to the surface of the adherend 60B on the intermediate layer 12B side. The tension member 61 is a strip-shaped film with sufficient strength so that it does not elongate or break during the measurement of peel strength. In addition, one end of the tension member 61 is attached to the adherend 60B with sufficiently high adhesive force so that the tension member 61 does not peel off from the adherend 60A during the measurement of peel strength. Figure 4 shows an example in which the tension member 61 is used as a gripping space, but if there is sufficient stroke before the adherend 60B is clamped by the clamping device (metal plate) 62, the adherend 60B may be clamped directly without using the tension member 61.

[0105] Next, the gripping portion of the tensile member 61 is passed between a pair of movable rolls 73A and 73B of the jig 72, and then the gripping portion is clamped and fixed by 10 mm or more using the clamping device (metal plate) 62 of the tensile and compression testing machine SV-55C 2H manufactured by Imada Seisakusho Co., Ltd. The movable rolls 73A and 73B serve as the fulcrum for peeling during the 90-degree peel test. Next, the 90-degree peel test is performed using the tensile and compression testing machine, and the test force [N / cm] and stroke [mm] are monitored as voltage values, for example, using a data logger manufactured by Keyence Corporation, converted to force, and stored in memory as CSV output data. The above 90-degree peel test is performed at a tensile speed of 5 mm / sec. under standard conditions of a temperature of 23 ± 1°C and a relative humidity of 50 ± 5%. The stroke is set to 50 mm or more.

[0106] The above 90-degree peel test is performed a total of three times. The point where the peel strength is stable (where the force rises gradually) is used as the starting point (0 mm), and the CSV output data from that point to a relative distance of 50 mm is arithmetic mean to calculate the average value. This allows the average peel strength between the recording layer 13A and the intermediate layer 12B to be determined. However, if there are points (spikes) in the CSV output data where the peel force is suddenly low, these points (spikes) are excluded from the CSV output data before calculating the average peel strength.

[0107] The delamination strength of the interface between the recording layer 13B and the intermediate layer 12C, and the delamination strength of the interface between the recording layer 13C and the intermediate layer 12D, are determined using the same procedure as for the delamination strength of the interface between the recording layer 13A and the intermediate layer 12B.

[0108] [1.2 Image Characteristics of Recording Media] The following describes the differences in enlarged images between the recording medium 10 according to the first embodiment and the recording medium 110 according to the reference example. The recording medium 110 according to the reference example differs from the recording medium 10 according to the first embodiment in that the recording layers 113A, 113B, and 113C do not have uneven surfaces 13AS, 13BS, and 13CS (see Figure 2) on their front surface, but rather have flat surfaces 113AS, 113BS, and 113CS, as shown in Figure 5.

[0109] Figure 6 schematically shows an example of an image 10P (hereinafter referred to as "internal image 10P") taken at high magnification by focusing an optical microscope on the recording layer 13B of the recording medium 10, as shown by the light ray L in Figure 2. In Figure 6, the shaded areas indicate areas where color has developed. In the internal image 10P of the recording medium 10, the colored areas are observed as spots. On the other hand, in the internal image of the recording medium 110, spot-like colored areas like those in the internal image 10P of the recording medium 10 are not observed.

[0110] As described above, the recording medium 10 according to the first embodiment is configured to acquire a spotted image (internal image 10P) caused by the uneven surface 13S by imaging the recording medium 10 with focus on the recording layer 13. In the internal image 10P of the recording medium 10 according to the first embodiment, the colored areas are observed as spots. These spots are unique to each recording medium 10. Therefore, these spots can be used to determine the authenticity of the recording medium 10, or the authenticity of a card or booklet containing the recording medium 10.

[0111] [1.3 Method for manufacturing recording media] The following describes an example of a method for manufacturing the recording medium 10 according to the first embodiment. Here, we will describe an example in which the recording medium 10 includes films between the adhesive layer 12A1 and the ultraviolet curing resin layer 12A2, between the adhesive layer 12B1 and the ultraviolet curing resin layer 12B2, and between the adhesive layer 12C1 and the ultraviolet curing resin layer 12C2. Note that the film is not shown in Figure 2.

[0112] (First layered film formation process) First, the first matrix resin is dissolved in a solvent (e.g., methyl ethyl ketone). Next, the first color-developing compound in a decolorized state, the first color developer, and the first photothermal converter are added to this solution and dispersed. This prepares the first recording layer forming coating. Subsequently, the UV-curable resin is applied to a film such as a PET film, and then the UV-curable resin is cured by irradiating it with ultraviolet light to form a UV-curable resin layer 12A2. Next, the first recording layer forming coating is applied to the UV-curable resin layer 12A2 and dried to form a recording layer 13A having an uneven surface 13AS. This yields a first laminated film consisting of a film, a UV-curable resin layer 12A2, and a recording layer 13A having an uneven surface 13AS on its surface.

[0113] The uneven surface 13AS of the recording layer 13A is formed, for example, by adjusting the application and drying conditions of the first recording layer forming coating to generate Benard cells in the coating film. An example of the application and drying conditions of the first recording layer forming coating is shown below. Application method: Gravure application method Coating thickness: 30 μm or more and 40 μm or less (coating thickness when the thickness of the recording layer 13A after drying is 5 μm or more and 6 μm or less) Drying temperature: 80℃ or higher and 110℃ or lower

[0114] The uneven surface 13AS of the recording layer 13A can also be formed by generating Benard cells by adjusting the additive formulation to the first recording layer forming coating, selecting the type of color developer, selecting the type of dispersion medium, selecting the type of matrix resin, adjusting the particle size distribution of the color developer, or adjusting the viscosity of the dispersion. It is also possible to combine two or more of the above methods for forming the uneven surface 13AS (adjustment of coating and drying conditions, formulation of additives, selection of type of color developer, selection of type of dispersion medium, selection of type of matrix resin, adjustment of particle size distribution of the color developer, adjustment of viscosity of the dispersion).

[0115] (Second laminated film formation process) A second laminated film is obtained in the same manner as the first laminated film formation process, except that a second matrix resin, a second coloring compound, a second color developer, and a second photothermal converter are used instead of the first matrix resin, a first coloring compound, a first color developer, and a first photothermal converter. The second laminated film consists of a film, an ultraviolet curing resin layer 12B2, and a recording layer 13B having an uneven surface 13BS.

[0116] (Third layered film formation process) A third laminated film is obtained in the same manner as the first laminated film formation process, except that a third matrix resin, a third coloring compound, a third coloring agent, and a third photothermal converter are used instead of the first matrix resin, a first coloring compound, a first color developer, and a first photothermal converter. The third laminated film consists of a film, an ultraviolet curing resin layer 12C2, and a recording layer 13C having an uneven surface 13CS.

[0117] (Lamination process) First, a fourth laminated film is prepared, which is provided in order with a cover layer 15, a UV-cut layer 14, and an ultraviolet-curing resin layer 12D2. Next, an adhesive layer 12D1 is formed on the ultraviolet-curing resin layer 12D2 of the fourth laminated film, and then the third laminated film is bonded onto the adhesive layer 12D1 so that the adhesive layer 12D1 and the recording layer 13C are in contact.

[0118] Next, an adhesive layer 12C1 is formed on the ultraviolet-curing resin layer 12C2, and then a second laminated film is bonded onto the adhesive layer 12C1 so that the adhesive layer 12C1 and the recording layer 13B are in contact.

[0119] Next, an adhesive layer 12B1 is formed on the ultraviolet curing resin layer 12B2, and then the first laminated film is bonded onto the adhesive layer 12B1 so that the adhesive layer 12B1 and the recording layer 13A are in contact.

[0120] Next, an adhesive layer 12A1 is formed on the ultraviolet-curable resin layer 12A2, and then the substrate 11 is bonded onto the adhesive layer 12A1. This completes the process to obtain the recording medium 10 shown in Figure 2.

[0121] [1.4 Recording Method for Recording Media] The following describes an example of a recording method for the recording medium 10 according to the first embodiment.

[0122] The recording layer 13A is colored magenta in the following manner. When near-infrared laser light with a peak wavelength λ1 is irradiated onto a predetermined location on the recording layer 13A, the first photothermal converter contained in the laser-irradiated area absorbs the near-infrared laser light and generates heat. This heat melts the first color developer, and a color reaction (color development reaction) occurs between the first color developer and the first color-developing compound, causing the laser-irradiated area to turn magenta.

[0123] The recording layer 13B is colored cyan as follows: When near-infrared laser light with a peak wavelength λ2 is irradiated onto a predetermined location on the recording layer 13B, the irradiated area of ​​the laser light is colored cyan by the same reaction as described above for the recording layer 13A.

[0124] The recording layer 13C is colored yellow as follows: When near-infrared laser light with a peak wavelength λ3 is irradiated onto a predetermined location on the recording layer 13B, the irradiated area of ​​the recording layer 13A is colored yellow by the same reaction as described above.

[0125] As described above, the desired full-color image is drawn on the recording medium 10 by the development of magenta, cyan, and yellow colors at predetermined positions on the recording layers 13A, 13B, and 13C, respectively.

[0126] [1.5 Effects] As described above, in the recording medium 10 according to the first embodiment, the recording layers 13A, 13B, and 13C each have uneven surfaces 13AS, 13BS, and 13CS on their front side. The uneven surfaces 13AS, 13BS, and 13CS are composed of random bumps and dips. These random bumps and dips are unique to each recording medium 10 and have a structure that is difficult to counterfeit. Therefore, it is possible to determine the authenticity of the recording medium 10 using the uneven surfaces 13AS, 13BS, 13CS or patterns (spotted images) caused by their shape.

[0127] Since the recording layers 13A, 13B, and 13C each have uneven surfaces 13AS, 13BS, and 13CS on their front sides, the peel strength of the interfaces between the recording layer 13A and the intermediate layer 12B, between the recording layer 13B and the intermediate layer 12C, and between the recording layer 13C and the intermediate layer 12D can be increased. Therefore, tamper resistance can be improved.

[0128] In the recording medium 10 according to the first embodiment, the recording layers 13A, 13B, and 13C are capable of exhibiting magenta, cyan, and yellow colors, respectively, in their colored state. Therefore, a desired image can be drawn in full color.

[0129] [1.6 Variant] (Variation 1) In the first embodiment, an example was described in which all three recording layers 13 have an uneven surface 13S on the front side. However, one or two of the three recording layers 13 may have an uneven surface 13S on the front side.

[0130] For example, as shown in Figure 7A, among the recording layers 13A, 13B, and 13C, the recording layer 13C closest to the cover layer 15 has an uneven surface 13CS on its front side, while the other recording layers 13A and 13B may each have flat surfaces 113AS and 113BS on their front sides.

[0131] For example, as shown in Figure 7B, among the recording layers 13A, 13B, and 13C, the recording layer 13B, which is the second closest to the cover layer 15, has an uneven surface 13BS on its front side, while the other recording layers 13A and 13C may each have flat surfaces 113AS and 113CS on their front sides.

[0132] For example, as shown in Figure 7C, among the recording layers 13A, 13B, and 13C, the recording layer 13A, which is furthest from the cover layer 15, has an uneven surface 13AS on its front side, while the other recording layers 13B and 13C may each have flat surfaces 113BS and 113CS on their front sides.

[0133] For example, as shown in Figure 8A, among the recording layers 13A, 13B, and 13C, the recording layer 13C closest to the cover layer 15 and the recording layer 13B second closest to the cover layer 15 have uneven surfaces 13CS and 13BS on their front sides, respectively, while the recording layer 13A furthest from the cover layer 15 may have a flat surface 113AS on its front side.

[0134] For example, as shown in Figure 8B, among the recording layers 13A, 13B, and 13C, the recording layer 13C closest to the cover layer 15 and the recording layer 13A furthest from the cover layer 15 have uneven surfaces 13CS and 13AS on their front sides, respectively, while the recording layer 13B, the second closest to the cover layer 15, may have a flat surface 113BS on its front side.

[0135] For example, as shown in Figure 8C, among the recording layers 13A, 13B, and 13C, the recording layer 13B, which is second closest to the cover layer 15, and the recording layer 13A, which is furthest from the cover layer 15, have uneven surfaces 13BS and 13AS on their front sides, respectively, while the recording layer 13C, which is closest to the cover layer 15, may have a flat surface 113CS on its front side.

[0136] (Modification 2) In the first embodiment, an example was described in which the recording medium 10 has three recording layers 13, but the recording medium 10 may also have one recording layer 13.

[0137] Figure 9 is a cross-sectional view showing an example of the configuration of a recording medium 10 having one recording layer 13D. The recording medium 10 may also comprise, in order, a substrate 11, an intermediate layer 12A, a recording layer 13D, an intermediate layer 12D, a UV-cut layer 14, and a cover layer 15.

[0138] The recording layer 13D has an uneven surface 13DS on its front side. The uneven surface 13DS is the same as the uneven surface 13AS of the recording layer 13A in the first embodiment. The recording layer 13D is capable of exhibiting a predetermined color in the color development state. Examples of predetermined colors include, but are not limited to, black, cyan, magenta, yellow, red, green, or blue. The recording layer 13D is the same as the recording layer 13A in the first embodiment, except that it is capable of exhibiting a predetermined color in the color development state. That is, the recording layer 13D is the same as the recording layer 13A in the first embodiment, except that it contains a color-developing compound that is capable of exhibiting a predetermined color in the color development state.

[0139] (Variation 3) In the first embodiment, an example was described in which the recording medium 10 comprises three recording layers 13. However, the recording medium 10 may also comprise multiple recording layers 13 other than three (i.e., two or more recording layers 13). In this case as well, an intermediate layer 12 may be provided between the stacked recording layers 13. Each of the multiple recording layers 13 may exhibit a different hue in the colored state. That is, the color-producing compounds contained in each of the multiple recording layers 13 may exhibit a different hue in the colored state. The photothermal converters contained in each of the multiple recording layers 13 may have different absorption wavelength peaks.

[0140] At least one of the multiple recording layers 13 may have an uneven surface on its front side. Specifically, for example, all of the multiple recording layers 13 may have an uneven surface on their front side, or a specific layer among the multiple recording layers 13 may have an uneven surface on its front side, while the other layers may not have an uneven surface on their front side. The layers other than the specific layer may, for example, have a flat surface on their front side. The number of specific layers may be one or two or more. The uneven surface is the same as the uneven surface 13AS of the recording layer 13A in the first embodiment.

[0141] <2 Second Embodiment> In the second embodiment, an example of a card equipped with the recording medium 10 according to the first embodiment will be described.

[0142] [2.1 Card composition] Hereinafter, an example of the configuration of the card 30 according to the second embodiment will be described with reference to Figures 10A and 10B. The card 30 comprises, in order, a base material (card base material) 31, an adhesive layer 32, an intermediate layer 33, an adhesive layer 34, and an overlay layer 35. The intermediate layer 33 includes a recording medium 10.

[0143] Card 30 is an ID card (e.g., employee ID, membership card, student ID, etc.). An ID card is an example of a card-type identification document. In the second embodiment, an example in which card 30 is an ID card is described, but the type of card on which the recording medium 10 is provided is not limited to this. The card on which the recording medium 10 is provided may be, for example, a security card, a financial settlement card (e.g., a credit card, cash card, etc.), a driver's license, a health insurance card, a basic resident register card, a My Number card (individual number card), or a personal transaction card (e.g., a prepaid card, a point card, etc.). Card 30 may also be a contactless IC card.

[0144] (Base material 31) The base material 31 is a support that supports the intermediate layer 33. The base material 31 has a rectangular, thin plate shape. The base material 31 has a first surface (front) on which the adhesive layer 32, intermediate layer 33, adhesive layer 34, and overlay layer 35 are laminated, and a second surface (back) opposite to the first surface. The base material 31 may have a color such as white. A design, picture, photograph, text, or a combination of two or more of these (hereinafter referred to as "design, etc.") may be printed on the first surface of the base material 31. The base material 31 may have an IC (integrated circuit) chip and an antenna coil, etc., on the first surface.

[0145] The base material 31 includes, for example, plastic. The base material 31 may optionally include at least one selected from the group consisting of colorants, antistatic agents, flame retardants, and surface modifiers.

[0146] The plastic includes, for example, at least one selected from the group consisting of ester resins, amide resins, olefin resins, vinyl resins, acrylic resins, imide resins, styrene resins, and engineering plastics. If the base material 31 contains two or more resins, these two or more resins may be mixed, copolymerized, or laminated.

[0147] Ester resins include, 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. Amide resins include, for example, at least one selected from the group consisting of nylon 6, nylon 66, and nylon 610. Olefin resins include, for example, at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP). Vinyl resins include, for example, polyvinyl chloride (PVC).

[0148] Acrylic resins include, for example, at least one selected from the group consisting of polyacrylate, polymethacrylate, and polymethyl methacrylate (PMMA). Imide resins include, for example, at least one selected from the group consisting of polyimide (PI), polyamideimide (PAI), and polyetherimide (PEI). Styrene resins include, for example, at least one selected from the group consisting of polystyrene (PS), high-impact polystyrene, acrylonitrile-styrene resin (AS resin), and acrylonitrile-butadiene-styrene resin (ABS resin). Engineering plastics include, 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), and polyethersulfite.

[0149] (Middle class 33) The intermediate layer 33 is provided between the base material 31 and the overlay layer 35. More specifically, the intermediate layer 33 is provided on the first surface of the base material 31, and an adhesive layer 32 is sandwiched between the base material 31 and the intermediate layer 33. The intermediate layer 33 has a housing portion 33A for housing the recording medium 10. The housing portion 33A is provided in a part of the surface of the intermediate layer 33. The housing portion 33A may be a through hole that penetrates in the thickness direction of the intermediate layer 33. The intermediate layer 33 is intended to suppress the step difference formed by the recording medium 10 when the recording medium 10 is sandwiched between the base material 31 and the overlay layer 35. The intermediate layer 33 has approximately the same thickness as the recording medium 10 and covers the area of ​​the first surface of the base material 31 other than the area on which the recording medium 10 is provided.

[0150] The intermediate layer 33 has a film-like structure. The intermediate layer 33 may be transparent to visible light. The intermediate layer 33 contains plastic. Examples of plastic materials include those similar to those used for the base material 31.

[0151] (Overlay layer 35) The overlay layer 35 is provided on the intermediate layer 33 and the recording medium 10, and covers the intermediate layer 33 and the recording medium 10. An adhesive layer 34 is sandwiched between the intermediate layer 33, the recording medium 10 and the overlay layer 35. The overlay layer 35 protects the internal components of the card 30 (i.e., the recording medium 10 and the intermediate layer 33) and maintains the mechanical reliability of the card 30.

[0152] The overlay layer 35 has a film-like structure. The overlay layer 35 is transparent to visible light. The overlay layer 35 contains plastic. Examples of plastic materials include those similar to those used for the base material 31. A design or pattern may be printed on at least one surface of the overlay layer 35.

[0153] (Adhesive layer 32, 34) Adhesive layer 32 is provided between the substrate 31 and the intermediate layer 33, and adheres the substrate 31 and the intermediate layer 33. Adhesive layer 34 is provided between the intermediate layer 33 and the overlay layer 35, and adheres the intermediate layer 33 and the overlay layer 35. Adhesive layers 32 and 34 contain a thermosetting adhesive. The thermosetting adhesive contains a thermosetting resin. The thermosetting resin includes, for example, at least one selected from the group consisting of epoxy resins and urethane resins. The curing temperature of the thermosetting adhesive is preferably in the temperature range of 100°C to 120°C from the viewpoint of reducing damage to the recording medium 10.

[0154] (Recording medium 10) The recording medium 10 is placed between the base material 31 and the overlay layer 35. The recording medium 10 is housed in the housing section 33A such that the base material 11 of the recording medium 10 faces the base material 31. A facial photograph or the like is drawn on the recording medium 10. However, the information drawn on the recording medium 10 is not limited to a facial photograph, but may also be security ID information or the like.

[0155] The recording medium 10 has a first surface facing the overlay layer 35 and a second surface facing the substrate 31. From the viewpoint of improving adhesion, it is preferable that the first surface and / or the second surface of the recording medium 10 be subjected to an easy-adhesion treatment such as plasma treatment. In this specification, "and / or" means at least one of the three possibilities, for example, "X and / or Y" means X only, Y only, or X and Y.

[0156] [2.2 Method for manufacturing cards] The following describes an example of a method for manufacturing the card 30 according to the second embodiment.

[0157] First, a thermosetting resin is applied to the first surface of the base material 31 as a thermosetting adhesive to form an adhesive layer 32. Next, an intermediate layer 33 is placed on the adhesive layer 32, and then the recording medium 10 is fitted into the housing portion 33A of the intermediate layer 33. Alternatively, the intermediate layer 33 with the recording medium 10 already fitted into the housing portion 33A may be placed on the adhesive layer 32. The adhesive layer 32 may also be formed by applying a thermosetting resin to the intermediate layer 33 with the recording medium 10 already fitted into the housing portion 33A, and then placing the intermediate layer 33 on the first surface of the base material 31 with the coating film sandwiched in between. Alternatively, the adhesive layer 32 may be formed by bonding a sheet, which has been formed in advance by applying a thermosetting resin to a separator, to the first surface of the base material 31 or to the intermediate layer 33 with the recording medium 10 already fitted into the housing portion 33A by means of thermal lamination or the like.

[0158] Next, a thermosetting resin is applied to the intermediate layer 33 as a thermosetting adhesive to form an adhesive layer 34, and then an overlay layer 35 is placed on the adhesive layer 34. Next, the resulting laminate is sandwiched between metal plates and heated and pressurized to thermoset the adhesive layer 32 and adhesive layer 34. The temperature applied to the laminate during thermosetting is preferably 100°C to 120°C from the viewpoint of reducing damage to the recording medium 10. This yields the desired card 30. The adhesive layer 34 may also be formed by applying a thermosetting resin to the overlay layer 35 and then placing the overlay layer 35 on the intermediate layer 33 with the coating film in between. Alternatively, the adhesive layer 34 may be formed by bonding a sheet, which has been formed in advance by applying a thermosetting resin to a separator, to the overlay layer 35 or the intermediate layer 33 by means of thermal lamination or the like.

[0159] [2.3 Effects] As described above, the card 30 according to the second embodiment includes the recording medium 10 according to the first embodiment. Therefore, the authenticity of the card 30 can be determined using the uneven surfaces 13AS, 13BS, 13CS of the recording medium 10 or patterns (spotted images) resulting from their shape.

[0160] In the card 30 according to the second embodiment, the base material 31 and the intermediate layer 33 are bonded together by an adhesive layer 32 containing a thermosetting adhesive, and the intermediate layer 33 and the overlay layer 35 are also bonded together by an adhesive layer 32 containing a thermosetting adhesive. This allows for strong bonding between the base material 31 and the intermediate layer 33, and between the intermediate layer 33 and the overlay layer 35. Therefore, tamper resistance can be improved.

[0161] Since the recording medium 10 is fitted into the housing portion 33A of the intermediate layer 33, it is possible to make it difficult to see the boundary between the recording medium 10 and the intermediate layer 33 in the in-plane direction of the card 30. Therefore, it becomes difficult to identify where on the plane of the card 30 the recording medium 10 is located. Thus, the tamper-proof properties can be improved. Since the recording medium 10 is enclosed inside the card 30, the effect of moisture on the recording medium 10 can be reduced.

[0162] [2.4 Variant] (Variation 1) In the second embodiment, an example was described in which the card 30 has the recording medium 10 in a portion of the first surface of the base material 31. However, as shown in Figure 11, the card 30 may have the recording medium 10 in substantially the entire area of ​​the first surface of the base material 31. Specifically, the card 30 may have a recording medium 10 that is substantially the same size as the base material 31 between the adhesive layer 32 and the adhesive layer 34.

[0163] (Modification 2) In the second embodiment, an example was described in which the card 30 comprises the recording medium 10 according to the first embodiment, but the card 30 may also comprise a recording medium 10 according to a modified example of the first embodiment.

[0164] <3 Third Embodiment> In the third embodiment, an example of a card having a different configuration from that of the second embodiment will be described.

[0165] [3.1 Card Composition] Hereinafter, with reference to Figure 12, an example of the configuration of card 30A according to the third embodiment will be described. Card 30A differs from card 30 according to the second embodiment in that it does not have adhesive layers 32 and 34, and the base material 31 and the intermediate layer 33 and the intermediate layer 33 and the overlay layer 35 are bonded together by fusion.

[0166] In the third embodiment, it is preferable that the base material 31, the intermediate layer 33, and the overlay layer 35 contain a thermoplastic resin as the plastic. By including a thermoplastic resin in the base material 31, the intermediate layer 33, and the overlay layer 35, the interlayer adhesion strength due to fusion can be increased. From the viewpoint of reducing damage to the recording medium 10, it is preferable that the thermoplastic resin is capable of heat-sealing the layers of the card 30A in a temperature range of 130°C to 200°C.

[0167] The base material 31, the intermediate layer 33, and the overlay layer 35 may contain the same type of thermoplastic resin, or the base material 31, the intermediate layer 33, and the overlay layer 35 may not contain the same type of thermoplastic resin. When the base material 31, the intermediate layer 33, and the overlay layer 35 do not contain the same type of thermoplastic resin, one of the base material 31, the intermediate layer 33, and the overlay layer 35 may contain a different type of thermoplastic resin from the other two layers, or the base material 31, the intermediate layer 33, and the overlay layer 35 may each contain a different type of thermoplastic resin.

[0168] When the base material 31, the intermediate layer 33, and the overlay layer 35 contain the same type of thermoplastic resin, the base material 31, the intermediate layer 33, and the overlay layer 35 preferably contain at least one selected from the group consisting of semi-crystalline thermoplastic resins and amorphous thermoplastic resins from the viewpoint of improving the interlayer adhesion strength by fusion. The semi-crystalline thermoplastic resin includes, for example, at least one selected from the group consisting of polypropylene (PP), polyethylene (PE), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK).

[0169] The amorphous thermoplastic resin includes, for example, at least one selected from the group consisting of ABS resin, polycarbonate (PC), a polymer alloy of ABS resin and PC (hereinafter referred to as "ABS / PC polymer alloy"), AS resin, polystyrene (PS), polymethyl methacrylate (PMMA), polyphenylene oxide (PPO), polysulfone (PSU), polyvinyl chloride (PVC), polyether imide (PEI), and polyether sulfone (PES).

[0170] If the base material 31, intermediate layer 33, and overlay layer 35 do not contain the same type of thermoplastic resin, it is preferable that the base material 31, intermediate layer 33, and overlay layer 35 contain an amorphous thermoplastic resin from the viewpoint of improving interlayer adhesion strength through fusion.

[0171] The following combinations of amorphous thermoplastic resins are preferred for the two adjacent layers of card 30A. If one of the two adjacent layers of card 30A contains ABS resin, it is preferable that the other layer contains at least one selected from the group consisting of ABS / PC polymer alloy, polycarbonate (PC), AS resin, polystyrene (PS), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC).

[0172] If one of the two adjacent layers of card 30A contains an ABS / PC polymer alloy, it is preferable that the other layer contains at least one selected from the group consisting of ABS resin, polycarbonate (PC), and polymethyl methacrylate (PMMA). If one of the two adjacent layers of card 30A contains polycarbonate (PC), it is preferable that the other layer contains at least one selected from the group consisting of ABS resin, ABS / PC polymer alloy, and polymethyl methacrylate (PMMA).

[0173] If one of the two adjacent layers of card 30A contains AS resin, it is preferable that the other layer contains at least one selected from the group consisting of ABS resin, polystyrene (PS), polymethyl methacrylate (PMMA), and polyphenylene oxide (PPO).

[0174] If one of the two adjacent layers of card 30A contains polymethyl methacrylate (PMMA), it is preferable that the other layer contains at least one selected from the group consisting of ABS resin, ABS / PC polymer alloy, AS resin, and polyphenylene oxide (PPO). If one of the two adjacent layers of card 30A contains polyphenylene oxide (PPO), it is preferable that the other layer contains at least one selected from the group consisting of polycarbonate (PC), AS resin, polystyrene (PS), and polymethyl methacrylate (PMMA).

[0175] If one of the two adjacent layers of card 30A contains polysulfone (PSU), it is preferable that the other layer contains polycarbonate (PC). If one of the two adjacent layers of card 30A contains polyvinyl chloride (PVC), it is preferable that the other layer contains ABS resin.

[0176] [3.2 Method for manufacturing cards] The following describes an example of a manufacturing method for card 30A according to the third embodiment.

[0177] First, an intermediate layer 33 is placed on the first surface of the base material 31, and then the recording medium 10 is fitted into the housing portion 33A of the intermediate layer 33. Alternatively, the intermediate layer 33 with the recording medium 10 already fitted into the housing portion 33A may be placed on the first surface of the base material 31. Next, an overlay layer 35 is placed on the intermediate layer 33. Then, the resulting laminate is sandwiched between metal plates and heat-fused with pressure while being heated, thereby thermally fusing the base material 31 and the intermediate layer 33, and the intermediate layer 33 and the overlay layer 35. The temperature applied to the laminate during thermal fusion is preferably between 110°C and 200°C, from the viewpoint of reducing damage to the recording medium 10 and achieving sufficient fusion strength. This yields the desired card 30A.

[0178] [3.3 Effects] As described above, in the card 30A according to the third embodiment, the base material 31 and the intermediate layer 33, and the intermediate layer 33 and the overlay layer 35 are fused together. This allows for a strong bond between the base material 31 and the intermediate layer 33, and between the intermediate layer 33 and the overlay layer 35. Therefore, the tamper-proof properties can be improved.

[0179] [3.4 Variant Example] (Variation 1) In the second embodiment, an example was described in which the card 30 has a recording medium 10 in a portion of the first surface of the base material 31, but the card 30A may have a recording medium 36 in substantially the entire area of ​​the first surface of the base material 31. Specifically, the card 30A may have a recording medium 36 that is substantially the same size as the base material 31 between the base material 31 and the overlay layer 35.

[0180] (Modification 2) In the third embodiment, an example was described in which the card 30 comprises the recording medium 10 according to the first embodiment, but the card 30 may also comprise a recording medium 10 according to a modified example of the first embodiment.

[0181] <4. Fourth Embodiment> In the second and third embodiments, examples of cards 30 and 30A equipped with the recording medium 10 according to the first embodiment were described, but the recording medium 10 may also be provided in a booklet.

[0182] [4.1 Booklet Structure] Figure 13 is a perspective view showing an example of the configuration of a booklet 40 according to the fourth embodiment. The booklet 40 is a passport. A passport is an example of a booklet-type identification document. The booklet 40 comprises a plurality of sheets 41. The plurality of sheets 41 are saddle-stitched. A recording medium 10 is provided on at least one or both sides of a sheet 41. A photograph or the like is drawn on the recording medium 10. The sheet 41 may have a layered structure similar to the card 30 according to the third embodiment or the card 30A according to the fourth embodiment. In this case, the base material may be paper or the like.

[0183] [4.2 Effects] As described above, the booklet 40 according to the fourth embodiment includes the recording medium 10 according to the first embodiment. Therefore, it is possible to determine the authenticity of the booklet 40 by using the uneven surfaces 13AS, 13BS, 13CS of the recording medium 10 or patterns (spot images) etc. resulting from their shapes.

[0184] [4.3 Variations] (Variation 1) In the third embodiment, an example where the booklet 40 includes the recording medium 10 in a partial area of the main surface of the sheet 41 has been described, but the booklet 40 may include the recording medium 10 in substantially the entire area of the main surface of the sheet 41. Specifically, the booklet 40 may include a recording medium 10 having substantially the same size as the sheet 41.

[0185] (Variation 2) In the third embodiment, an example where the booklet 40 includes the recording medium 10 according to the first embodiment has been described, but the booklet 40 may include the recording medium 10 according to a variation of the first embodiment.

[0186] <5 The Fifth Embodiment> [5.1 Configuration of the Image Authentication System] Hereinafter, an example of the configuration of the image authentication system according to the fifth embodiment will be described with reference to FIG. 14. The image authentication system includes a first terminal device 51, a second terminal device 52, and an image authentication device 53.

[0187] (The First Terminal Device 51) The first terminal device 51 can transmit information such as images to the image authentication device 53 via a network such as the Internet, and can also receive information from the image authentication device 53.

[0188] The drawing device 51A and the imaging device 51B are connected to the first terminal device 51. The first terminal device 51 can control the drawing device 51A to draw an image on the recording medium 10. The first terminal device 51 can control the imaging device 51B to capture the entire image drawn on the recording medium 10. The first terminal device 51 can control the imaging device 51B to focus on a specified recording layer 13 among the recording layers 13A, 13B, and 13C of the recording medium 10, thereby causing the imaging device 51B to capture an enlarged image of a specified area (i.e., a part of the entire image) of the entire image drawn on the recording medium 10. This makes it possible to obtain a spotted image (first image (see Figure 6)) caused by the unevenness of the uneven surface 13S of the specified recording layer 13. The acquisition of the enlarged image of the specified area may be performed using positional information of the entire image, etc. The first terminal device 51 can transmit the overall image and spotted image acquired by the imaging device 51B to the image authentication device 53.

[0189] The first terminal device 51 includes a storage device 51C. The storage device 51C is, for example, a hard disk drive. The first terminal device 51 can store the overall image and spotted images acquired by the imaging device 51B in the storage device 51C.

[0190] The first terminal device 51 may be a general-purpose terminal device such as a personal computer, or it may be a dedicated terminal device for controlling the drawing device 51A and the imaging device 51B.

[0191] (Drawing device 51A) The drawing device 51A can draw an image by irradiating the recording layers 13A, 13B, and 13C of the recording medium 10 from the cover layer 15 side with first, second, and third laser beams, respectively, based on the control of the first terminal device 51. The first, second, and third laser beams are preferably near-infrared laser beams. The first, second, and third laser beams are preferably each other and have different peak wavelengths. This allows for selective drawing of an image on the desired recording layer 13 of the recording layers 13A, 13B, and 13C.

[0192] Specifically, the writing device 51A can color the recording layer 13A magenta by irradiating it with a first laser beam having a peak wavelength at wavelength λ1. The writing device 51A can color the recording layer 13B cyan by irradiating it with a second laser beam having a peak wavelength at wavelength λ2. The writing device 51A can color the recording layer 13C yellow by irradiating it with a third laser beam having a peak wavelength at wavelength λ3. The focal points of the first, second, and third laser beams are aligned with the recording layers 13A, 13B, and 13C, respectively.

[0193] (Imaging device 51B) The imaging device 51B, based on the control of the first terminal device 51, captures images of the entire image drawn on the recording medium 10 and a magnified image of a specified area (i.e., a part of the entire image) within the entire image, and transmits them to the first terminal device 51. The imaging device 51B is, for example, a camera. The magnified image of the specified area is captured by focusing on a specified recording layer 13 among the recording layers 13A, 13B, and 13C. By adjusting the focal position in this way and capturing the magnified image, it is possible to obtain a spotted image caused by the unevenness of the uneven surface 13S of the specified recording layer 13.

[0194] (Second terminal device 52) The second terminal device 52 can transmit information such as images to the image authentication device 53 via a network such as the Internet, and can also receive information such as authentication results from the image authentication device 53.

[0195] The imaging device 52B is connected to the second terminal device 52. The second terminal device 52 can control the imaging device 52B and cause it to capture the entire image drawn on the recording medium 10. The second terminal device 52 can control the imaging device 52B and, by focusing on a specified recording layer 13 among the recording layers 13A, 13B, and 13C of the recording medium 10, cause the imaging device 52B to capture an enlarged image of a specified area (i.e., a part of the entire image) of the entire image drawn on the recording medium 10. This makes it possible to acquire a spotted image (second image (see Figure 6)) caused by the unevenness of the uneven surface 13S of the specified recording layer 13. The acquisition of the enlarged image of the specified area may be performed using positional information of the entire image, etc. The second terminal device 52 can transmit the entire image and the spotted image acquired by the imaging device 52B to the image authentication device 53.

[0196] The second terminal device 52 may be a general-purpose terminal device such as a personal computer, or it may be a dedicated terminal device for controlling the imaging device 52B.

[0197] (Imaging device 52B) The imaging device 52B, based on the control of the second terminal device 52, captures images of the entire image drawn on the recording medium 10 and magnified images of a specified area (i.e., a part of the entire image) within the entire image, and transmits them to the second terminal device 52. The imaging device 52B is, for example, a camera. The magnified image of the specified area is captured by focusing on a specified recording layer 13 among the recording layers 13A, 13B, and 13C. By adjusting the focal position in this way and capturing the magnified image, it is possible to obtain a spotted image caused by the unevenness of the uneven surface 13S of the specified recording layer 13.

[0198] (Image authentication device 53) The image authentication device 53 can receive information such as images from the first terminal device 51 and the second terminal device 52 via a network such as the Internet, and can also transmit information such as authentication results to the first terminal device 51 and the second terminal device 52.

[0199] The image authentication device 53 includes a storage device 53A. The storage device 53A is, for example, a hard disk drive. The image authentication device 53 can store the overall image and spotted image (magnified image) received from the first terminal device 51 in the storage device 53A.

[0200] The image authentication device 53 can compare the spotted image received from the second terminal device 52 with the spotted image stored in the storage device 53A and notify the second terminal device 52 of the result of the comparison. Specifically, the image authentication device 53 compares the spotted image received from the second terminal device 52 with the spotted image stored in the storage device 53A, and if a match is found, it notifies the second terminal device 52 that the recording medium 10 is genuine. On the other hand, if a match is not found, it notifies the second terminal device 52 that the recording medium 10 is fake. The image authentication device 53 may be a server such as a cloud server.

[0201] [5.2 Image Registration Operation] Hereinafter, with reference to Figure 15, an example of the image registration operation of the image authentication system according to the fifth embodiment will be described.

[0202] First, in step S1, the first terminal device 51 controls the drawing device 51A to draw an image onto the recording medium 10. Next, in step S2, the first terminal device 51 controls the imaging device 51B to capture the entire image drawn on the recording medium 10. Then, the first terminal device 51 stores the entire image captured by the imaging device 51B in the storage device 511C.

[0203] Next, in step S3, the first terminal device 51 controls the imaging device 51B and focuses on a specified recording layer 13 among the recording layers 13A, 13B, and 13C of the recording medium 10, causing the imaging device 51B to capture an enlarged image of a specified area (i.e., a part of the whole image) of the entire image drawn on the recording medium 10. As a result, a spotted image caused by the unevenness of the uneven surface 13S of the specified recording layer 13 is acquired. Next, the first terminal device 51 stores the spotted image acquired in step S3 in the storage device 51C. Next, in step S4, the first terminal device 51 transmits the overall image and the spotted image acquired in steps S2 and S3 to the image authentication device 53. Next, the image authentication device 53 stores the overall image and the spotted image received from the first terminal device 51 in the storage device 53A.

[0204] [5.3 Image Recognition Operation] Hereinafter, with reference to Figure 16, an example of the image authentication operation of the image authentication system according to the fifth embodiment will be described.

[0205] First, in step S11, the second terminal device 52 controls the imaging device 52B to cause the imaging device 51B to capture the entire image drawn on the recording medium 10. Next, in step S12, the second terminal device 52 controls the imaging device 52B and focuses on a specified recording layer 13 among the recording layers 13A, 13B, and 13C of the recording medium 10, causing the imaging device 52B to capture an enlarged image of a specified area (i.e., a part of the whole image) of the entire image drawn on the recording medium 10. As a result, a spotted image caused by the unevenness of the uneven surface 13S of the specified recording layer 13 is obtained.

[0206] Next, in step S13, the second terminal device 52 transmits the overall image and spotted image acquired in steps S11 and S12 to the image authentication device 53. The image authentication device 53 then compares the spotted image received from the second terminal device 52 with the spotted image stored in the storage device 53A and notifies the second terminal device 52 of the result of the comparison.

[0207] [5.4 Effects] As described above, in the image authentication system according to the fifth embodiment, the first terminal device 51 draws an image on the recording medium 10 having a recording layer 13 having an uneven surface 13S composed of random bumps and dips using a drawing device 51A, then focuses on the recording layer 13 and images a portion of the recording medium 10 (a defined area) using an imaging device 51B to acquire a spotted image as the first image and transmits it to the image authentication device 53. The second terminal device 52 focuses on the recording layer 13 having an uneven surface 13S composed of random bumps and dips and images a portion of the recording medium 10 having the recording layer 13 (a defined area) using an imaging device 52B to acquire a spotted image as the second image and transmits it to the image authentication device 53. The image authentication device 53 compares the spotted image as the first image received from the first terminal device 51 with the spotted image as the second image received from the second terminal device 52 and notifies the second terminal device 52 of the result of the comparison. Therefore, the authenticity of a recording medium 10 on which an image such as a facial photograph is drawn can be determined via a network such as the Internet.

[0208] [5.5 Variant] (Variation 1) After an image such as a facial photograph is drawn onto the recording medium 10 by the imaging device 51B, the recording medium 10 may be placed on a card 30, card 30A, or booklet 40. Alternatively, an image such as a facial photograph may be directly drawn onto the recording medium 10 that is already placed on card 30, card 30A, or booklet 40 by the imaging device 51B.

[0209] The recording medium 10 provided on card 30, card 30A, or booklet 40 may be imaged by imaging devices 51B, 52B. In this case, the authenticity of card 30, card 30A, or booklet 40 containing the recording medium 10 can be determined via a network such as the Internet.

[0210] (Modification 2) The first terminal device 51 may, after acquiring a two-dimensional spotted image as an enlarged image (hereinafter referred to as "2D spotted image"), convert the 2D spotted image into a three-dimensional spotted image (hereinafter referred to as "3D spotted image"), store it in the storage device 51C, and transmit it to the image authentication device 53. The second terminal device 52 may, after acquiring a 2D spotted image as an enlarged image, convert the 2D spotted image into a 3D spotted image and transmit it to the image authentication device 53.

[0211] The image authentication device 53 may store the 3D spotted image received from the first terminal device 51 in the storage device 53A. The image authentication device 53 may compare the 3D spotted image received from the second terminal device 52 with the 3D spotted image stored in the storage device 53A and notify the second terminal device 52 of the result of the comparison.

[0212] Alternatively, the image authentication device 53 may receive a 2D spotted image from the first terminal device 51, convert the 2D spotted image into a 3D spotted image, and then store it in the storage device 53A. Or, the image authentication device 53 may receive a 2D spotted image from the second terminal device 52, convert the 2D spotted image into a 3D spotted image, compare the converted 3D spotted image with the 3D spotted image stored in the storage device 53A, and notify the second terminal device 52 of the result of the comparison.

[0213] The image authentication device 53 can obtain spot height information from a 3D spot image. The image authentication device 53 may obtain spot location information and height information from a 3D spot image received from a first terminal device 51, and may also obtain spot location information and height information from a 3D spot image received from a second terminal device 52. The image authentication device 53 may also compare the obtained location information and height information. By comparing the location information and height information in this way, the image authentication device 53 can improve security.

[0214] (Variation 3) In the fifth embodiment, an example was described in which the image authentication device 53 compares a spotted image received from the second terminal device 52 with a spotted image stored in the storage device 53A and notifies the second terminal device 52 of the result of the comparison. However, the image authentication method is not limited to this. For example, the image authentication device 53 may compare a spotted image received from the first terminal device 51 with a spotted image stored in the storage device 53A and notify the first terminal device 51 of the result of the comparison. Alternatively, the first terminal device 51 may compare a spotted image acquired by the imaging device 51B with a spotted image previously stored in the storage device 51C and display the result of the comparison on the display device of the first terminal device 51.

[0215] (Modification 4) In the fifth embodiment, an example was described in which the first terminal device 51 and the second terminal device 52 each acquire one spotted image and transmit it to the image authentication device 53. However, the first terminal device 51 and the second terminal device 52 may each acquire multiple spotted images and transmit them to the image authentication device 53. In this case, the image authentication device 53 may compare the multiple spotted images received from the first terminal device 51 with the multiple spotted images received from the second terminal device 52 and notify the second terminal device of the result of the comparison. Note that in the first terminal device 51 and the second terminal device 52, each spotted image is acquired at approximately the same location. As described above, the image authentication device 53 can improve security by matching multiple spotted images. [Examples]

[0216] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples.

[0217] [Example 1] (First layered film formation process) First, polycarbonate (PC) was dissolved in methyl ethyl ketone (MEK) as a matrix resin, and then a color developer was added and dispersed using a rocking mill. A bis(hydroxybenzoic acid) type compound was used as the color developer. Next, a leuco dye that exhibits a magenta color in the colored state was added, and the final mixture was prepared in a ratio (mass ratio) of leuco dye:color developer:polycarbonate = 1:2:4. Furthermore, a photothermal conversion material having an absorption wavelength peak at wavelength λ1 and a phthalocyanine skeleton was added to prepare the first recording layer forming coating. The amount of photothermal conversion material added was set so that the absorbance of the coated film was approximately 0.32.

[0218] Next, a UV-curable resin was applied to the PET film, which served as the first film, and then cured by irradiating the UV-curable resin with ultraviolet light to form a first UV-curable resin layer with a thickness of 3 μm. Then, a first recording layer-forming coating was applied to the first UV-curable resin layer by gravure coating and dried to form a first recording layer with a thickness of 5 μm having an uneven surface. This uneven surface was formed by adjusting the coating and drying conditions to generate Benard cells in the coating film of the first recording layer-forming coating, thereby creating random irregularities on the coating film surface. Thus, a first laminated film consisting of a first film, a first UV-curable resin layer (PET film), and a first recording layer was obtained.

[0219] (Second laminated film formation process) As the leuco dye, a leuco dye that exhibits a cyan color in the colored state was used, and as the photothermal conversion agent, a photothermal conversion material having an absorption wavelength peak at wavelength λ2 and having a phthalocyanine skeleton was used. Apart from these, the process was the same as that for forming the first laminated film, to obtain a second laminated film consisting of a second film (PET film), a second UV-curable resin layer, and a second recording layer.

[0220] (Third layered film formation process) As the leuco dye, a leuco dye that exhibits a yellow color in the colored state was used, and as the photothermal conversion agent, a photothermal conversion material having an absorption wavelength peak at wavelength λ3 and a phthalocyanine skeleton was used. Aside from these, the process was the same as that for forming the first laminated film, to obtain a third laminated film consisting of a third film (PET film), a third UV-curable resin layer, and a third recording layer. The wavelengths λ1, λ2, and λ3 were selected to be different values ​​from each other.

[0221] (Lamination process) First, a fourth laminated film was prepared, comprising, in order, a 23 μm thick cover layer (PET film), a 10 μm thick UV-cut layer, and a 3 μm thick fourth UV-curing resin layer. Next, a 5 μm thick fourth adhesive layer (OCA) was formed on the UV-curing resin layer of the fourth laminated film, and then the third laminated film was laminated onto the fourth adhesive layer so that the fourth adhesive layer and the third recording layer were in contact.

[0222] Next, a third adhesive layer was formed on the third UV-curing resin layer, and then the second laminated film was bonded onto the third adhesive layer so that the third adhesive layer and the second recording layer were in contact.

[0223] Next, a second adhesive layer was formed on the second ultraviolet-curing resin layer, and then the first laminated film was bonded onto the second adhesive layer so that the second adhesive layer and the first recording layer were in contact.

[0224] Next, a first adhesive layer was formed on the first UV-curing resin layer, and then a 23 μm thick base film (PET film) was laminated onto the first adhesive layer. As a result, a recording medium was obtained in which a first intermediate layer, a first recording layer, a second intermediate layer, a second recording layer, a third intermediate layer, a third recording layer, a fourth intermediate layer, a UV-cut layer, and a cover layer were sequentially laminated on the base film.

[0225] [Comparative Example 1] In the first laminated film formation step, a first recording layer with a thickness of 5 μm and a flat surface was formed. In the second laminated film formation step, a second recording layer with a thickness of 5 μm and a flat surface was formed. In the third laminated film formation step, a third recording layer with a thickness of 5 μm and a flat surface was formed. The surfaces (flat surfaces) of the first, second, and third recording layers were formed by adjusting the coating and drying conditions so that random irregularities caused by Bénard cells were not formed on the coating film. A recording medium was obtained in the same manner as in Example 1, except for these conditions.

[0226] [evaluation] The recording media of Example 1 and Comparative Example 1, obtained as described above, were evaluated as follows.

[0227] (Surface unevenness) The surface irregularities were measured using the surface irregularity measurement method described in the first embodiment. The results are shown in Table 1.

[0228] (Irregularity diameter) The diameter of the unevenness was measured using the method for measuring the diameter of the unevenness described in the first embodiment. The results are shown in Table 1.

[0229] (Average peel strength) The average peel strength at the interface between the first recording layer and the second intermediate layer was measured using the average peel strength measurement method described in the first embodiment. The results are shown in Table 1.

[0230] (Enlarged image) First, laser light with wavelengths λ1, λ2, and λ3 was irradiated onto the first, second, and third recording layers, respectively, to create an image on the recording medium. Next, by focusing on the second recording layer, an enlarged image of a portion of the recording medium was obtained. The results are shown in Table 1. Figure 6 also shows a schematic diagram of an enlarged image of Example 1.

[0231] [Table 1]

[0232] Table 1 shows that recording media in which the surface of the recording layer is an uneven surface formed by Bénard cells (an uneven surface composed of random irregularities) can have higher peel strength compared to recording media in which the surface of the recording layer is flat. Table 1 and Figure 6 show that in recording media where the surface of the recording layer is an uneven surface formed by Bénard cells, spots are observed in the magnified image, whereas in recording media where the surface of the recording layer is flat, no spots are observed in the magnified image.

[0233] While embodiments and modifications of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments and modifications described above, and various modifications based on the technical idea of ​​the present disclosure are possible.

[0234] For example, the configurations, methods, processes, shapes, materials, and numerical values ​​listed in the above embodiments and modifications are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as needed.

[0235] The configurations, methods, processes, shapes, materials, and numerical values ​​of the above embodiments and modified examples can be combined with each other without departing from the spirit of this disclosure.

[0236] In the numerical ranges described stepwise in the above embodiments and modifications, the upper or lower limit of a numerical range in one step may be replaced with the upper or lower limit of a numerical range in another step.

[0237] Unless otherwise specified, the materials illustrated in the above embodiments and modifications can be used individually or in combination of two or more.

[0238] Furthermore, this disclosure may also adopt the following configuration. (1) It comprises a substrate and a recording layer, The recording layer has an uneven surface composed of random irregularities and is a recording medium comprising an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. (2) The recording medium according to (1), wherein the aforementioned irregularities are formed by a Benard cell. (3) The recording medium according to (1) or (2), wherein the recording layer is provided in multiple locations. (4) The recording medium according to (3), wherein the multiple recording layers are capable of exhibiting different hues in the color development state. (5) The plurality of recording layers include a first recording layer, a second recording layer, and a third recording layer. The first recording layer is capable of exhibiting a first primary color. The second recording layer is capable of exhibiting a second primary color. The recording medium according to (3) or (4), wherein the third recording layer is capable of exhibiting a third primary color. (6) Multiple recording layers include a photothermal conversion agent, The recording medium according to any one of (3) to (5), wherein each of the plurality of recording layers contains a photothermal converter having different absorption wavelength peaks. (7) With multiple intermediate layers, The recording medium according to any one of (3) to (6), wherein the intermediate layer is provided between adjacent recording layers. (8) The recording medium according to (7), wherein the intermediate layer comprises an adhesive layer and an ultraviolet curing resin layer. (9) The adhesive layer is adjacent to the uneven surface, The recording medium according to (8), wherein the average peel strength of the interface between the recording layer and the intermediate layer is 3.5 N / cm or more. (10) A recording medium according to any one of (1) to (9), wherein a spot image caused by the unevenness can be obtained by imaging the recording medium with the recording layer in focus. (11) A card having a recording medium as described in any one of items (1) to (10). (12) A booklet comprising a recording medium as described in any one of items (1) to (10). (13) The system comprises a first terminal device, a second terminal device, and an image authentication device. The first terminal device, after drawing an image on a first recording medium having a recording layer having an uneven surface composed of random bumps and dips using an image drawing device, captures a portion of the first recording medium with a first imaging device, focusing on the recording layer of the first recording medium, acquires a first image, and sends it to the image authentication device. The second terminal device focuses on a recording layer having an uneven surface composed of random bumps and depressions, captures a portion of the second recording medium having the recording layer using the second imaging device, acquires a second image, and sends it to the image authentication device. The image authentication device is an image authentication system that compares the first image received from the first terminal device with the second image received from the second terminal device and notifies the second terminal device of the result of the comparison. (14) The image authentication system according to (13), wherein the recording layer of the first recording medium and the recording layer of the second recording medium each comprise an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. (15) The first image is a first spot image resulting from the unevenness of the recording layer of the first recording medium, The image authentication system according to (13) or (14), wherein the second image is a second spotted image resulting from the unevenness of the recording layer of the second recording medium. (16) The first terminal device draws an image on a first recording medium having a recording layer with an uneven surface composed of random bumps and dips using an image drawing device, then focuses on the recording layer of the first recording medium and captures a portion of the first recording medium using a first imaging device to acquire a first image, and transmits it to an image authentication device. The second terminal device focuses on a recording layer having an uneven surface composed of random bumps and dips, captures a portion of the second recording medium having the recording layer using the second imaging device, acquires a second image, and transmits it to the image authentication device. The image authentication device compares the first image received from the first terminal device with the second image received from the second terminal device, and notifies the second terminal device of the result of the comparison. An image authentication method comprising the following features. [Explanation of symbols]

[0239] 10, 110 recording media 10P Image 11, 31 Base material 12A, 12B, 12C, 12D intermediate layer 12A1, 12B1, 12C1, 12D1 adhesive layer 12A2, 12B2, 12C2, 12D2 UV curing resin layer 13A, 13B, 13C, 13D, 113A, 113B, 113C Recording Layer 13AS, 13BS, 13CS uneven surface 13AR color range 113AS, 113BS, 113CS plane 14 UV-cut layer 15. Cover layer 30, 30A card 32, 34 Adhesive layer 33 Middle Class 33A Storage area 35 Overlay Layers 40 booklets 41 sheets 51 First terminal 52 Second terminal 51A Drawing device 51B, 52B Imaging device 51C, 53C storage device 53 Image Recognition Device

Claims

1. It comprises a substrate and a recording layer, The recording layer has an uneven surface composed of random irregularities and comprises an electron-donating color-producing compound, an electron-accepting color developer, and a matrix resin. The aforementioned irregularities are formed by a recording medium made of Bénard cells.

2. The recording medium according to claim 1, wherein a plurality of the recording layers are provided.

3. The recording medium according to claim 2, wherein the plurality of recording layers are capable of exhibiting different hues from each other in the color development state.

4. The plurality of recording layers include a first recording layer, a second recording layer, and a third recording layer. The first recording layer is capable of exhibiting a first primary color. The second recording layer is capable of exhibiting a second primary color. The recording medium according to claim 2, wherein the third recording layer is capable of exhibiting a third primary color.

5. Multiple recording layers include a photothermal conversion agent, The recording medium according to claim 2, wherein each of the plurality of recording layers contains a photothermal converter having different absorption wavelength peaks.

6. With multiple intermediate layers, The recording medium according to claim 2, wherein the intermediate layer is provided between adjacent recording layers.

7. The recording medium according to claim 6, wherein the intermediate layer comprises an adhesive layer and an ultraviolet curing resin layer.

8. The adhesive layer is adjacent to the uneven surface, The recording medium according to claim 7, wherein the average peel strength of the interface between the recording layer and the intermediate layer is 3.5 N / cm or more.

9. The recording medium according to claim 1, wherein a spot image caused by the unevenness can be obtained by imaging the recording medium with the recording layer in focus.

10. A card comprising the recording medium described in claim 1.

11. A booklet comprising the recording medium described in claim 1.

12. The system comprises a first terminal device, a second terminal device, and an image authentication device. The first terminal device, after drawing an image on a first recording medium having a recording layer having an uneven surface composed of random bumps and dips using an image drawing device, captures a portion of the first recording medium with a first imaging device, focusing on the recording layer of the first recording medium, acquires a first image, and sends it to the image authentication device. The second terminal device focuses on a recording layer having an uneven surface composed of random bumps and depressions, captures a portion of the second recording medium having the recording layer using the second imaging device, acquires a second image, and sends it to the image authentication device. The image authentication device compares the first image received from the first terminal device with the second image received from the second terminal device, and notifies the second terminal device of the result of the comparison. The recording layer of the first recording medium and the recording layer of the second recording medium each comprise an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. An image recognition system in which the irregularities of the first recording medium and the irregularities of the second recording medium are formed by Bénard cells.

13. The first image is a first spot image resulting from the unevenness of the recording layer of the first recording medium, The image authentication system according to claim 12, wherein the second image is a second spotted image resulting from the unevenness of the recording layer of the second recording medium.

14. The first terminal device draws an image on a first recording medium having a recording layer with an uneven surface composed of random bumps and dips using an image drawing device, then focuses on the recording layer of the first recording medium and images a portion of the first recording medium with a first imaging device to acquire a first image, and transmits it to an image authentication device. The second terminal device focuses on a recording layer having an uneven surface composed of random bumps and dips, captures a portion of the second recording medium having the recording layer using the second imaging device, acquires a second image, and transmits it to the image authentication device. The image authentication device compares the first image received from the first terminal device with the second image received from the second terminal device, and notifies the second terminal device of the result of the comparison. Equipped with, The recording layer of the first recording medium and the recording layer of the second recording medium each comprise an electron-donating color-developing compound, an electron-accepting color developer, and a matrix resin. An image authentication method in which the irregularities of the first recording medium and the irregularities of the second recording medium are formed by Bénard cells.

Images