Recording medium, card, and booklet

Abstract

Provided is a recording medium that can suppress coloration of nonrecording regions and that can exhibit improved color retention characteristics when subjected to high-temperature, high-humidity storage.　The recording medium comprises a recording layer that contains: a color-forming compound having an electron-donating behavior, and a developer having an electron-accepting behavior. The developer contains a compound given by formula (1). (In formula (1), X1 is a divalent group that contains at least one benzene ring. Y11, Y12, Y13, and Y14 are each independently a monovalent group. Z11 and Z12 are each independently a hydrogen-bonding group.)

Description

Recording media, cards and booklets

[0001] The present disclosure relates to a recording medium, and a card and booklet including the same.

[0002] In recent years, development of recording media containing a color former having electron donating properties and a color developer having electron accepting properties has been progressing as an alternative to printed matter. Patent Document 1 describes the use of a bis(hydroxybenzoic acid)-type compound (bis-urea compound) represented by a specific formula as the color developer.

[0003] Japanese Patent Application Publication No. 8-244355

[0004] In recent years, it has been desired that recording media containing a color former and a color developer have improved color retention properties under high-temperature, high-humidity environments and that coloring of unrecorded areas (hereinafter sometimes referred to as "background") be suppressed. However, Patent Document 1 does not consider color retention properties under high-temperature, high-humidity environments.

[0005] An object of the present disclosure is to provide a recording medium that can improve color retention properties during storage at high temperature and high humidity and can suppress background color development, as well as a card and booklet that include the same.

[0006] In order to solve the above-mentioned problems, the first disclosure is a recording medium having a recording layer containing a color former having electron donating properties and a color developer having electron accepting properties, wherein the color developer contains a compound represented by the following formula (1): (However, in formula (1), X 1 is a divalent group containing at least one benzene ring. 11 , Y 12 , Y 13 , Y 14 are each independently a monovalent group. 11 , Z 12 are each independently a hydrogen-bonding group.

[0007] The second disclosure is a recording medium having a recording layer containing a color former having electron donating properties and a color developer having electron accepting properties, wherein the color developer contains a compound represented by the following formula (a): (However, in formula (a), X0 is a divalent group containing at least one benzene ring. 01 , Y 02 are each independently a monovalent group. n01 and n02 are each independently an integer of 0 to 5. When n01 is an integer of 2 to 5, Y 01 may be the same or different. When n02 is an integer of 2 to 5, Y 02 may be the same or different. 01 , Z 02 are each independently a hydrogen-bonding group.

[0008] A third disclosure is a card including the recording medium of the first or second disclosure.

[0009] A fourth disclosure is a booklet including the recording medium of the first or second disclosure.

[0010] FIG. 1 is a cross-sectional view showing an example of the configuration of a recording medium according to a first embodiment. FIG. 2 is a cross-sectional view showing an example of the configuration of a recording medium according to a second embodiment. FIG. 3 is a cross-sectional view showing an example of the configuration of a recording medium according to a third embodiment. FIG. 4 is a perspective view showing an example of the configuration of a laminate according to a fourth embodiment. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. FIG. 6 is a cross-sectional view showing an example of the configuration of a laminate according to a fifth embodiment. FIG. 7A is a plan view showing an example of the appearance of Application Example 1. FIG. 7B is a cross-sectional view taken along line VIIB-VIIB in FIG. 7A. FIG. 8 is a perspective view showing an example of the appearance of Application Example 2. FIG. 9A is a plan view showing an example of the appearance (front side) of Application Example 3. FIG. 9B is a plan view showing an example of the appearance (rear side) of Application Example 3. FIG. 10A is a plan view showing an example of the appearance (front side) of Application Example 4. FIG. 10B is a plan view showing an example of the appearance (rear side) of Application Example 4. FIG. 11A is a perspective view showing an example of the appearance (front side) of Application Example 5. FIG. 11B is a perspective view illustrating an example of the appearance (rear side) of Application Example 5. FIG. 12A is a plan view illustrating an example of the appearance (first surface side) of Application Example 6. FIG. 12B is a plan view illustrating an example of the appearance (second surface side) of Application Example 6. FIG. 13A is a plan view illustrating an example of the appearance (top surface side) of Application Example 7. FIG. 13B is a plan view illustrating an example of the appearance (side surface side) of Application Example 7. FIG. 14 is a plan view illustrating an example of the appearance of Application Example 8. FIG. 15 is a perspective view illustrating an example of the appearance of Application Example 9. FIG. 16A is a plan view illustrating an example of the appearance of Application Example 10. FIG. 16B is a cross-sectional view taken along line XVIB-XVIB in FIG. 16A.

[0011] Embodiments of the present disclosure will be described in the following order. Note that in all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals. 1 First embodiment (example of recording medium) 1.1 Configuration of recording medium 1.2 Recording method for recording medium 1.3 Method for manufacturing recording medium 1.4 Functions and effects 2 Second embodiment (example of recording medium) 2.1 Configuration of recording medium 2.2 Recording method for recording medium 2.3 Functions and effects 3 Third embodiment (example of recording medium) 3.1 Configuration of recording medium 3.2 Recording method for recording medium 3.3 Functions and effects 4 Fourth embodiment (example of laminate) 4.1 Configuration of recording medium 4.2 Method for manufacturing recording medium 4.3 Functions and effects 5 Fifth embodiment (example of laminate) 5.1 Configuration of recording medium 5.2 Method for manufacturing recording medium 5.3 Functions and effects 6 Modification 7 Application example 8 Example

[0012] In this specification, "and / or" means at least one of the two. For example, "X and / or Y" means X only, Y only, or X and Y.

[0013] <1 First Embodiment> [1.1 Configuration of Recording Medium] An example of the configuration of a recording medium 10 according to the first embodiment will be described below with reference to Fig. 1. The recording medium 10 is configured so that its coloring state can be changed by irradiation with laser light (external stimulus). This change in coloring state makes it possible to draw, for example, an image on the recording medium 10. Here, the image is not limited to images such as designs, color patterns, and photographs, but also includes text such as letters and symbols.

[0014] The laser light is preferably near-infrared laser light. The change in color state may be a reversible change or an irreversible change. That is, the recording medium 10 may be rewritable, in which an image or the like can be rewritten, or may be write-once, in which an image or the like can be written only once. From the viewpoint of preventing tampering, it is preferable that the change in color state be an irreversible change.

[0015] The recording medium 10 includes a substrate 11 and a recording layer 12 provided on the substrate 11. The recording medium 10 may further include a protective layer 13 provided on the recording layer 12. The substrate 11, the recording layer 12, and the protective layer 13 will be described below in order.

[0016] (Substrate) The substrate 11 is a support for supporting the recording layer 12. The substrate 11 is preferably made of a material that has excellent heat resistance and dimensional stability in the planar direction. The substrate 11 may be either light-transmitting or non-light-transmitting. The substrate 11 may have a predetermined color such as white. The substrate 11 has, for example, a plate or film shape. In the present disclosure, the term "film" is defined to include a sheet.

[0017] The substrate 11 may be, for example, rigid or flexible. When a flexible substrate 11 is used, a flexible recording medium 10 can be realized. Examples of the rigid substrate 11 include a wafer or a glass substrate. Examples of the flexible substrate 11 include flexible glass, a film, or paper.

[0018] Examples of the constituent material of the substrate 11 include inorganic materials, metal materials, polymer materials, etc. Two or more of these inorganic materials, metal materials, polymer materials, etc. may be combined. When two or more constituent materials are combined, the two or more constituent materials may be laminated. When an inorganic material and a polymer material are combined, inorganic material particles may be dispersed in the polymer film. Similarly, when a metal material and a polymer material are combined, metal material particles may be dispersed in the polymer film.

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

[0020] A reflective layer (not shown) may be provided on at least one of the main surfaces of the substrate 11, or the substrate 11 itself may also function as a reflective layer. When the substrate 11 has such a configuration, a clearer color display is possible.

[0021] (Recording Layer) The recording layer 12 in an unrecorded state (initial state) is in a decolorized state. The recording layer 12 can be changed from the decolorized state to a colored state by irradiation with laser light. The recording layer 12 can exhibit a predetermined color in the colored state. Examples of the predetermined color include, but are not limited to, black, cyan, magenta, yellow, red, green, and blue.

[0022] The thickness of the recording layer 12 is preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 15 μm or less. When the thickness of the recording layer 12 is 1 μm or more, sufficient color density can be obtained. On the other hand, when the thickness of the recording layer 12 is 20 μm or less, excessive heat utilization of the recording layer 12 can be prevented. Therefore, deterioration of color development can be prevented.

[0023] The recording layer 12 contains a color former having electron donating properties and a color developer having electron accepting properties. The recording layer 12 preferably further contains at least one material selected from the group consisting of a photothermal conversion agent and a matrix resin.

[0024] (Color-forming compound) The color-forming compound can develop color by reacting with a color developer. An example of the color-forming compound is a leuco dye. When a lactone ring in the leuco dye molecule reacts with an electron-accepting compound such as an acid, the lactone ring opens and develops color. When the open lactone ring in the leuco dye reacts with a base, it closes and the leuco dye may lose its color. The leuco dye may be, for example, an existing dye for thermal paper. The leuco dye may be, for example, an existing dye for thermal paper. A specific example of a leuco dye is a compound represented by the following formula (2) that contains an electron-donating group in the molecule.

[0025]

[0026] The color former is not particularly limited and can be appropriately selected depending on the purpose. Specific examples of the color former include fluoran compounds, triphenylmethanephthalide compounds, azaphthalide compounds, phenothiazine compounds, leucoauramine compounds, and indolinophthalide compounds. Other examples include 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-di(n-butylamino)fluoran, 2-anilino-3-methyl-6-(N-n-propyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-isopropyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-isobutyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-n-amyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-sec-butyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-n-amyl-N-ethylamino)fluoran, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino)fluoran, 2-anilino-3-methyl-6-(N-n-propyl-N-isopropylamino)fluoran, 2-anilino-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran, 2-anilino-3-methyl-6-(N-methyl-p-toluidino)fluoran, 2-(m-trichloromethylanilino)-3-methyl-6-diethylaminofluoran, 2-(m-trifluoromethylanilino)-3-methyl-6-diethylaminofluoran, 2-(m-trichloromethylanilino)-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran, 2-(2,4-dimethylanilino)-3-methyl-6-diethylaminofluoran, 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-ethylanilino)fluoran, 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-propyl-p-toluidino)fluoran, 2-anilino-6-(N-n-hexyl-N-ethylamino)fluoran, 2-(o-chloroanilino)-6-diethylaminofluoran, 2-(o-chloroanilino)-6-dibutylaminofluoran, 2-(m-trifluoromethylanilino)-6-diethylaminofluoran, 2,3-dimethyl-6-dimethylaminofluoran, 3-methyl-6-(N-ethyl-p-toluidino)fluoran, 2-chloro-6 -diethylaminofluoran, 2-bromo-6-diethylaminofluoran, 2-chloro-6-dipropylaminofluoran, 3-chloro-6-cyclohexylaminofluoran, 3-bromo-6-cyclohexylaminofluoran, 2-chloro-6-(N-ethyl-N-isoamylamino)fluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-(o-chloroanilino)-3-chloro-6-cyclohexylaminofluoran, 2-(m-trifluoromethylanilino)-3-chloro-6-diethylaminofluoran, 2-(2,3-dichloroanilino)-3-chloro-6-diethylaminofluoran, 1,2-benzo-6-diethylaminofluoran, 3-diethylamino-6-(m-trifluoromethylanilino)fluoran, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-octyl- 2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-7-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-7-azaphthalide 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-N-n-amyl-N-methylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindol-3-yl)-3-(2-hexyloxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide nyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 2-(p-acetylanilino)-6-(N-n-amyl-N-n-butylamino)fluoran, 2-benzylamino-6-(N-ethyl-p-toluidino)fluoran, 2-benzylamino-6-(N-methyl-2,4-dimethylanilino)fluoran, 2-benzylamino-6-(N-ethyl-2,4-dimethylanilino)fluoran, 2-benzylamino-6-(N-methyl-p-toluidino)fluoran, 2-benzylamino-6-(N-ethyl-p-toluidino)fluoran, 2-(di-p-methylbenzylamino)-6-(N-ethyl-p-toluidino)fluoran, 2-(α-phenylethylamino)-6-(N-ethyl-p-toluidino)fluoran, 2-methylamino-6-(N-methylanilino)fluoran, 2-methylamino-6-(N-ethylanilino)fluoran, 2-methylamino-6-(N-propylanilino)fluoran , 2-ethylamino-6-(N-methyl-p-toluidino)fluoran, 2-methylamino-6-(N-methyl-2,4-dimethylanilino)fluoran, 2-ethylamino-6-(N-ethyl-2,4-dimethylanilino)fluoran, 2-dimethylamino-6-(N-methylanilino)fluoran, 2-dimethylamino-6-(N-ethylanilino)fluoran, 2-diethylamino-6-(N-methyl-p-toluidino)fluoran, 2-diethylamino-6-(N-ethyl-p-toluidino)fluoran, 2-dipropylamino-6-(N-methyl p-toluidino)fluoran, 2-dipropylamino-6-(N-ethylanilino)fluoran, 2-amino-6-(N-methylanilino)fluoran, 2-amino-6-(N-ethylanilino)fluoran, 2-amino-6-(N-propylanilino)fluoran, 2-amino-6-(N-methyl-p-toluidino)fluoran, 2-amino-6-(N-ethyl-p-toluidino)fluoran, 2-amino-6-(N-propyl-p-toluidino)fluoran, 2-amino-6-(N-methyl-p-ethylanilino)fluoran, 2-amino-6-(N-ethylanilino)fluoran 2-amino-6-(N-propyl-p-ethylanilino)fluoran, 2-amino-6-(N-methyl-2,4-dimethylanilino)fluoran, 2-amino-6-(N-ethyl-2,4-dimethylanilino)fluoran, 2-amino-6-(N-propyl-2,4-dimethylanilino)fluoran, 2-amino-6-(N-methyl-p-chloroanilino)fluoran, 2-amino-6-(N-ethyl-p-chloroanilino)fluoran, 2-amino-6-(N-propyl-p-chloroanilino)fluoran, 1,Examples of suitable leuco dyes include 2-benzo-6-(N-ethyl-N-isoamylamino)fluoran, 1,2-benzo-6-dibutylaminofluoran, 1,2-benzo-6-(N-methyl-N-cyclohexylamino)fluoran, and 1,2-benzo-6-(N-ethyl-N-toluidino)fluoran. Each recording layer 12 may contain one of the above leuco dyes alone, or two or more of them.

[0027] (Color Developer) The color developer can, for example, cause a colorless color former to develop a color. The color developer is a compound containing an electron-accepting group in the molecule. The electron-accepting moiety of the color developer reacts with the lactone ring of the color former, opening the lactone ring and causing the color former to develop a color.

[0028] The color developer includes a compound represented by the following formula (a): (However, in formula (a), X 0 is a divalent group containing at least one benzene ring. 01 , Y 02 are each independently a monovalent group. n01 and n02 are each independently an integer of 0 to 5. When n01 is an integer of 2 to 5, Y 01 may be the same or different. When n02 is an integer of 2 to 5, Y 02 may be the same or different. 01 , Z 02 are each independently a hydrogen-bonding group.

[0029] X 0 contains at least one benzene ring, 0 Since the melting point can be made higher than when X is an aliphatic hydrocarbon group (for example, a normal alkyl chain), the color retention properties during storage at high temperature and high humidity (hereinafter referred to as "high temperature and high humidity storage properties") can be improved. 0Preferably, the compound has at least two benzene rings. The high-temperature, high-humidity storage characteristics are, for example, storage characteristics under an environment of 80°C and 60% RH. Improved heat resistance improves the resistance of the recording medium 10 to harsh processes (for example, hot pressing or integral molding using molten resin, etc.). 0 When contains at least two benzene rings, the at least two benzene rings may be condensed, for example, naphthalene or anthracene.

[0030] Z 01 , Z 02 are each independently a hydrogen-bonding group, the color developers tend to exist in a state of being aggregated together to some extent via hydrogen bonds, thereby improving the stability of the color developer in the recording layer 12. In this specification, a hydrogen-bonding group means a functional group that contains an atom that can form a hydrogen bond with another functional group or an atom present in another compound, etc.

[0031] The color developer preferably contains a compound represented by the following formula (1): (However, in formula (1), X 1 is a divalent group containing at least one benzene ring. 11 , Y 12 , Y 13 , Y 14 are each independently a monovalent group. 11 , Z 12 are each independently a hydrogen-bonding group.

[0032] X 1 contains at least one benzene ring, 1 In comparison with the case where X is an aliphatic hydrocarbon group (for example, a normal alkyl chain), the melting point can be made higher, and therefore the high-temperature, high-humidity storage properties can be improved. 1 Preferably, X contains at least two benzene rings. 1 When contains at least two benzene rings, the at least two benzene rings may be condensed, for example, naphthalene or anthracene.

[0033] Z 11, Z 12 are each independently a hydrogen-bonding group, the color developer tends to exist in a state of being solidified to some extent via hydrogen bonds, and the stability of the color developer in the recording layer 12 is improved.

[0034] When Formula (a) and Formula (1) contain a hydrocarbon group, the hydrocarbon group is a general term for a group composed of carbon (C) and hydrogen (H), and may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. A saturated hydrocarbon group is an aliphatic hydrocarbon group that does not have a carbon-carbon multiple bond, and an unsaturated hydrocarbon group is an aliphatic hydrocarbon group that has a carbon-carbon multiple bond (a carbon-carbon double bond or a carbon-carbon triple bond).

[0035] When Formula (a) and Formula (1) contain a hydrocarbon group, the hydrocarbon group may be a chain or may contain one or more rings. The chain may be a straight chain or a branched chain having one or more side chains.

[0036] (X containing one benzene ring 0 , X １ ) X in formula (a) 0 and X in formula (1) 1 is, for example, a divalent group containing one benzene ring. The divalent group is, for example, represented by the following formula (3): (However, in formula (3), X 21 It doesn't matter if it's there or not, X 21 If there is X 21 is a divalent group. 22 It doesn't matter if it's there or not, X 22 If there is X 22 is a divalent group. 21 is a monovalent group. n21 is an integer of 0 to 4. When n21 is an integer of 2 to 4, R 21 may be the same or different. * indicates a bond.)

[0037] In formula (3), X to the benzene ring 21 and X 22 The bonding position of X to the benzene ring is not limited. 21 and X22 The bonding position may be any of the ortho, meta and para positions.

[0038] The divalent group containing one benzene ring is preferably represented by the following formula (4) from the viewpoint of improving high-temperature, high-humidity storage properties. (However, in formula (4), R 22 is a monovalent group. n22 is an integer of 0 to 4. When n22 is an integer of 2 to 4, R 22 may be the same or different. * indicates a bond.)

[0039] X in formula (a) 0 is a divalent group containing one benzene ring, in formula (4), Z 01 and Z 02 The bonding position of Z to the benzene ring is not limited. 01 and Z 02 The bonding position may be any of the ortho, meta and para positions.

[0040] X in formula (1) 1 is a divalent group containing one benzene ring, in formula (4), Z 11 and Z 12 The bonding position of Z to the benzene ring is not limited. 11 and Z 12 The bonding position may be any of the ortho, meta and para positions.

[0041] (X 21 , X 22 ) X in formula (3) 21 , X 22 are each independently a divalent group and are not particularly limited, but an example is a hydrocarbon group which may have a substituent. The hydrocarbon group is preferably chain-like. When the hydrocarbon group is chain-like, the melting point of the color developer can be lowered, so that the color developer melts upon irradiation with laser light, making it easier for the color former to develop color. From the viewpoint of lowering the melting point of the color developer, a normal alkyl chain is particularly preferred among chain-like hydrocarbon groups.

[0042] The hydrocarbon group which may have a substituent has, for example, 1 to 15 carbon atoms, 1 to 13 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 3 carbon atoms.

[0043] X in formula (3) 21 , X 22 When is a normal alkyl group, the number of carbon atoms in the normal alkyl group is preferably 8 or less, more preferably 6 or less, even more preferably 5 or less, and particularly preferably 3 or less, from the viewpoint of high-temperature storage stability. When the normal alkyl group has 8 or less carbon atoms, the normal alkyl group is short in length, so that thermal disturbance is unlikely to occur in the color developer during high-temperature storage, and it is thought that the site that interacted with the color former such as a leuco dye during color development is unlikely to be dissociated. Therefore, the color former such as a leuco dye is unlikely to fade during high-temperature storage, improving high-temperature storage stability.

[0044] Examples of the substituent that the hydrocarbon group may have include a halogen group (e.g., a fluorine group) or an alkyl group having a halogen group (e.g., a fluorine group), etc. The hydrocarbon group that may have a substituent may be one in which some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms in the main chain of the hydrocarbon group) have been substituted with an element such as oxygen.

[0045] (R 21 ) R in formula (3) 21 is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group or a hydrocarbon group which may have a substituent.

[0046] The halogen group is, for example, a fluorine group (--F), a chlorine group (--Cl), a bromine group (--Br), or an iodine group (--I).

[0047] The hydrocarbon group which may have a substituent has, for example, 1 to 15 carbon atoms, 1 to 13 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 3 carbon atoms.

[0048] Examples of the substituent that the hydrocarbon group may have include a halogen group (e.g., a fluorine group) or an alkyl group having a halogen group (e.g., a fluorine group), etc. The hydrocarbon group that may have a substituent may be one in which some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms in the main chain of the hydrocarbon group) have been substituted with an element such as oxygen.

[0049] (R 22 ) R in formula (4) 22 is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group and a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are respectively represented by R 21 is the same as:

[0050] (X containing two benzene rings 0 , X 1 ) X in formula (a) 0 and X in formula (1) 1 is, for example, a divalent group containing two benzene rings. The divalent group is, for example, represented by the following formula (5): (However, in formula (5), X 31 It doesn't matter if it's there or not, X 31 If there is X 31 is a divalent group. 32 It doesn't matter if it's there or not, X 32 If there is X 32 is a divalent group. 33 It doesn't matter if it's there or not, X 33 If there is X 33 is a divalent group. 31 , R 32 are each independently a monovalent group. n31 and n32 are each independently an integer of 0 to 4. When n31 is an integer of 2 to 4, R 31 may be the same or different. When n32 is an integer of 2 to 4, R 32 may be the same or different. * indicates a bond.)

[0051] In formula (5), X to the benzene ring31 and X 32 The bonding position of X to the benzene ring is not limited. 31 and X 32 The bonding position of X to the benzene ring in formula (5) may be any of the ortho, meta and para positions. 32 and X 33 The bonding position of X to the benzene ring is not limited. 32 and X 33 The bonding position may be any of the ortho, meta and para positions.

[0052] The divalent group containing two benzene rings is preferably represented by the following formula (6) from the viewpoint of improving high-temperature, high-humidity storage properties. (However, in formula (6), X 34 is a divalent group. 33 , R 34 are each independently a monovalent group. n33 and n34 are each independently an integer of 0 to 4. When n33 is an integer of 2 to 4, R 33 may be the same or different. When n34 is an integer of 2 to 4, R 34 may be the same or different. * indicates a bond.)

[0053] X in formula (a) 0 is a divalent group containing two benzene rings, Z 01 and X 34 The bonding position of Z to the benzene ring is not limited. 01 and X 34 The bonding position of may be any of the ortho, meta and para positions. 02 and X 34 The bonding position of Z to the benzene ring is not limited. 02 and X 34 The bonding position may be any of the ortho, meta and para positions.

[0054] X in formula (1)1 is a divalent group containing two benzene rings, Z 11 and X 34 The bonding position of Z to the benzene ring is not limited. 11 and X 34 The bonding position of may be any of the ortho, meta and para positions. 12 and X 34 The bonding position of Z to the benzene ring is not limited. 12 and X 34 The bonding position may be any of the ortho, meta and para positions.

[0055] (X 31 , X 32 , X 33 ) X in formula (5) 31 , X 32 , X 33 are each independently a divalent group, and are not particularly limited, but an example thereof is a hydrocarbon group which may have a substituent. 21 , X 22 is the same as:

[0056] (X 34 ) X in formula (6) 34 is not particularly limited as long as it is a divalent group, but an example thereof is a hydrocarbon group which may have a substituent. The hydrocarbon group is the X in the above formula (3). 21 , X 22 is the same as:

[0057] (R 31 , R 32 ) R in formula (5) 31 , R 32 is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group and a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are each represented by R in the above formula (3). 21 is the same as:

[0058] (R 33 , R34 ) R in formula (6) 33 , R 34 is not particularly limited as long as it is a monovalent group, but examples thereof include a halogen group and a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are each represented by R in the above formula (3). 21 is the same as:

[0059] (Y 01 , Y 02 ) Y in formula (a) 01 , Y 02 are each independently, for example, a hydrogen group (-H), a hydroxy group (-OH), a halogen group (-X), a carboxy group (-COOH), an ester group (-COOR), or a hydrocarbon group which may have a substituent.

[0060] The halogen group is, for example, a fluorine group (--F), a chlorine group (--Cl), a bromine group (--Br), or an iodine group (--I).

[0061] The hydrocarbon group which may have a substituent has, for example, 1 to 15 carbon atoms, 1 to 13 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 3 carbon atoms.

[0062] Examples of the substituent that the hydrocarbon group may have include a halogen group (e.g., a fluorine group) or an alkyl group having a halogen group (e.g., a fluorine group), etc. The hydrocarbon group that may have a substituent may be one in which some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms in the main chain of the hydrocarbon group) have been substituted with an element such as oxygen.

[0063] In formula (a), (Y 01 ) n01 and / or (Y 02 ) n02 Preferably, one of the groups Y is a hydroxy group (—OH). 01 ) n01 and / or (Y 02 ) n02 When one of the groups is a hydroxy group (—OH), the display quality and light resistance can be improved.

[0064] (Y 11 , Y 12 , Y 13 , Y 14 In formula (1), Y relative to the benzene ring 11 and Y 12 The bonding position of Y to the benzene ring is not limited. 11 and Y 12 The bonding position of Y may be any of the ortho, meta and para positions. 13 and Y 14 The bonding position of Y to the benzene ring is not limited. 13 and Y 14 The bonding position of Y to one benzene may be any of the ortho, meta and para positions. 11 and Y 12 and the bonding position of Y to the other benzene 13 and Y 14 may be the same as or different from the binding position of

[0065] Y in formula (1) 11 , Y 12 , Y 13 , Y 14 are each independently, for example, a hydrogen group (-H), a hydroxy group (-OH), a halogen group, a carboxy group (-COOH), an ester group (-COOR), or a hydrocarbon group which may have a substituent. The halogen group and the hydrocarbon group which may have a substituent are each represented by Y 01 , Y 02 is the same as:

[0066] In formula (1), Y 11 and / or Y 13 is preferably a hydroxy group (—OH). 11 and / or Y 13 When the group is a hydroxy group (—OH), the display quality and light resistance can be improved.

[0067] (Z 01 , Z 02 ) Z in formula (1) 01 , Z02 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-) or a hydrazide bond (-NHCOCONH-). 01 , Z 02 is preferably a urea bond. 01 When Z is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene. 02 is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene.

[0068] (Z 11 , Z 12 ) Z in formula (1) 11 , Z 12 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-) or a hydrazide bond (-NHCOCONH-). 11 , Z 12 is preferably a urea bond. 11 When Z is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene. 12 is an amide bond, the nitrogen contained in the amide bond may be bonded to benzene, or the carbon contained in the amide bond may be bonded to benzene.

[0069] (Specific examples of color developers) X in formula (a) 0 and X in formula (1) 1 Specifically, the color developer containing one benzene ring includes at least one selected from the group consisting of compounds represented by the following formulas (3-1) to (3-6).

[0070] X in formula (a) 0 and X in formula (1) 1Specifically, the color developer containing two benzene rings includes at least one selected from the group consisting of compounds represented by the following formulas (5-1) to (5-8).

[0071] (Photothermal conversion agent) The photothermal conversion agent can absorb light in a predetermined wavelength range, such as the near-infrared region, and generate heat. As the photothermal conversion agent, it is preferable to use a near-infrared absorbing dye that has an absorption peak in a wavelength range of 700 nm to 2000 nm and has almost no absorption in the visible region. Specific examples include at least one selected from the group consisting of compounds having a phthalocyanine skeleton (phthalocyanine dyes), compounds having a squarylium skeleton (squarylium dyes), and inorganic compounds.

[0072] Examples of inorganic compounds include 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, metal oxides such as tricobalt tetroxide, iron oxide, chromium oxide, copper oxide, titanium black, and ITO (indium tin oxide), metal nitrides such as niobium nitride, metal carbides such as tantalum carbide, metal sulfides, and various magnetic powders. In addition, compounds (cyanine dyes) having a cyanine skeleton with excellent light resistance and heat resistance may also be used. Here, excellent light resistance means that the compound does not decompose under the usage environment, for example, when irradiated with light from a fluorescent lamp. Excellent heat resistance means that the maximum absorption peak value of the absorption spectrum does not change by 20% or more, for example, when the compound is formed into a film together with a polymer material and stored at 150°C for 30 minutes. Examples of such compounds having a cyanine skeleton include compounds containing SbF in the molecule. ６ , P.F. ６ , B.F. ４ , ClO ４ , C.F. ３ SO ３ and (CF ３ SO ３ ) ２and at least one of a counter ion of any of N and a methine chain containing a five-membered ring or a six-membered ring. The compound having a cyanine skeleton used in the recording medium 10 in the first embodiment preferably has both one of the counter ions and a cyclic structure such as a five-membered ring or a six-membered ring in the methine chain, but sufficient light resistance and heat resistance are ensured as long as it has at least one of them.

[0073] (Matrix Resin) The matrix resin preferably functions as a binder. The matrix resin preferably allows the color former, developer, and photothermal conversion agent to be easily and homogeneously dispersed. The matrix resin preferably contains at least one resin selected from the group consisting of thermosetting resins and thermoplastic resins. The matrix resin preferably contains a polycarbonate-based resin. By including a polycarbonate-based resin in the matrix resin, the light resistance of the background of the recording medium 10 can be improved. Here, a polycarbonate-based resin is a resin having at least a carbonate group (—O—(C═O)—O—) as a structural unit in the main chain. Therefore, the main chain may contain other structural units in addition to the carbonate group.

[0074] The matrix resin may contain, instead of or in addition to the polycarbonate-based resin, at least one selected from the group consisting of polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene-based copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid-based copolymer, maleic acid-based polymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, starch, and the like.

[0075] (Additives) If necessary, the recording layer 12 may further contain at least one additive selected from the group consisting of antioxidants, sensitizers, UV absorbers, light stabilizers, hydrolysis inhibitors, etc. From the viewpoint of suppressing coloration of the background, the recording layer 12 preferably contains an amine compound.

[0076] When the recording layer 12 contains an amine compound, it is preferable that the recording layer 12 contains, together with the amine compound, at least one compound selected from the group consisting of epoxy compounds and carbodiimide compounds. If the recording layer 12 contains an amine compound, there is a risk that the reliability of the color-forming portion will decrease during storage at high temperature and high humidity. However, if the recording layer 12 contains, together with the amine compound, at least one compound selected from the group consisting of epoxy compounds and carbodiimide compounds, it is possible to suppress the decrease in reliability of the color-forming portion during storage at high temperature and high humidity caused by the amine compound.

[0077] (Protective Layer) The protective layer 13 protects the surface of the recording layer 12. The protective layer 13 may have either a single-layer structure or a multilayer structure. A single-layer protective layer 13 may be a coating layer such as a hard coating layer. The coating layer may contain, for example, at least one cured product selected from the group consisting of ultraviolet-curable resins and thermosetting resins. The coating layer may contain fine particles, etc. A multilayer protective layer may include a resin layer and an adhesive layer provided on one side of the resin layer. The configuration of the multilayer heat-insulating layer is not limited to the above configuration. The number of layers in the multilayer structure is also not limited to the above two layers, and a structure of three or more layers may be adopted. The resin layer may be a polymer film or a coating layer such as an ultraviolet-curable resin layer. The adhesive layer may be, for example, an adhesive layer or a pressure-sensitive adhesive layer. The thickness of the protective layer 13 is, for example, 0.1 μm or more and 20 μm or less.

[0078] [1.2 Recording Method of Recording Medium] An example of a recording method of the recording medium according to the first embodiment will be described below. For example, when a laser beam is irradiated onto a predetermined position of the recording layer 12 using a semiconductor laser, a photothermal conversion agent contained in the laser beam-irradiated portion of the recording layer 12 absorbs the laser beam and generates heat. This heat causes the color developer to melt, and a color reaction (color-forming reaction) occurs between the color developer and the color-forming compound. Specifically, the color developer dissolves and reacts with the lactone ring of the color-forming compound (e.g., a leuco dye), opening the lactone ring and causing the color-forming compound to develop color. As a result, the laser beam-irradiated portion develops color, and a desired image is drawn on the recording layer 12. It is preferable to use near-infrared laser light as the laser beam.

[0079] [1.3 Method for Manufacturing Recording Medium] An example of a method for manufacturing the recording medium 10 according to the first embodiment will be described below. Here, an example of manufacturing the recording medium 10 using a coating method will be described.

[0080] First, a matrix resin is dissolved in a solvent (e.g., methyl ethyl ketone). Next, a color former in a decolorized state, a color developer, and a photothermal conversion agent are added to this solution and dispersed. This results in a coating material for forming a recording layer. Next, this coating material for forming a recording layer is applied to the substrate 11 and dried to form the recording layer 12. Next, if necessary, the substrate 11 and the recording layer 12 may be integrated by heat pressing. Next, if necessary, a coating material for forming a protective layer is applied to the recording layer 12 and cured. The coating material for forming the protective layer contains, for example, at least one resin selected from the group consisting of ultraviolet-curable resins and thermosetting resins. This results in the recording medium 10 shown in FIG. 1 being obtained.

[0081] [1.4 Effects] In the recording medium 10 according to the first embodiment, the color developer contains a compound represented by the above formula (a). Once the compound represented by the above formula (a) reacts with the color developer, it is difficult to separate. Furthermore, because the color developer tends to exist in a state of solidification to some extent through hydrogen bonds, the stability of the color developer in the recording layer 12 is improved. Therefore, the high-temperature, high-humidity storage characteristics of the recording medium 10 can be improved. Furthermore, because the compound represented by the above formula (a) does not readily interact with the color developer, background coloring can be suppressed. The reasons why the compound represented by the above formula (a) does not readily interact with the color developer are thought to be the compound's high melting point, the high aggregation ability of the compounds, the type of functional group at the compound's terminal, and steric hindrance due to the arrangement of the functional groups possessed by the compound. Furthermore, when the color developer contains the compound represented by the above formula (a), the energy required to dissolve the color developer in the recording layer 12 increases, allowing the recording medium 10 to withstand high-temperature pressing (e.g., high-temperature pressing at 150°C). Here, "able to withstand" means that color change due to high-temperature pressing can be suppressed.

[0082] In formula (a), X 0 is a divalent group containing at least one benzene ring, and Z 11 , Z 12 When the bond is a urea bond (-NHCONH-), the melting point of the entire color developer can be increased, thereby improving the heat resistance of the recording medium 10. This improves the resistance of the recording medium 10 to harsh processes (for example, heat pressing or integral molding using molten resin, etc.). This allows the recording medium 10 to be used in a variety of products (identification cards, cards, clothing (including wearable devices), electronic devices, etc.).

[0083] When the recording layer 12 contains a polycarbonate resin as the matrix resin (matrix polymer), the matrix resin is less likely to generate acid through photodecomposition, and the generated acid can be prevented from reacting with the color-forming compound. This prevents the background (unrecorded areas) of the recording medium 10 from developing a color. This improves the light resistance of the background of the recording medium 10.

[0084] The matrix resin of the recording layer 12 contains a transparent polycarbonate-based resin. In addition to the excellent transparency of the polycarbonate-based resin itself, the compounds represented by the above formulas (a) and (1) have benzene rings and other elements in addition to hydrogen-bonding groups within their molecules, making them highly compatible with the matrix resin. Therefore, it is easy to achieve small particle sizes (e.g., 1 μm or less) during dispersion, and they are difficult to see during film formation. This allows for improved transparency of the recording layer 12.

[0085] <2 Second Embodiment> In the above first embodiment, an example in which the recording medium has one recording layer is described, whereas in the second embodiment, an example in which the recording medium has three recording layers, each of which has a different color hue in the colored state, is described.

[0086] [2.1 Configuration of Recording Medium] An example of the configuration of a recording medium 10A according to the second embodiment will be described below with reference to Fig. 2. The recording medium 10A includes a substrate 11, three recording layers 12A, 12B, and 12C, and two intermediate layers 14A and 14B. The three recording layers 12A, 12B, and 12C and the two intermediate layers 14A and 14B are stacked on the substrate 11 in the following order: recording layer 12A, intermediate layer 14A, recording layer 12B, intermediate layer 14B, and recording layer 12C. The recording medium 10A may further include a protective layer 13 on recording layer 12C.

[0087] (Recording Layers) In an unrecorded state (initial state), the recording layers 12A, 12B, and 12C are in a decolorized state. The recording layers 12A, 12B, and 12C can be changed from the decolorized state to a colored state by irradiation with laser light. The recording layers 12A, 12B, and 12C can each exhibit a different hue in the colored state. Specifically, the recording layer 12A can exhibit magenta in the colored state. The recording layer 12B can exhibit cyan in the colored state. The recording layer 12C can exhibit yellow in the colored state. The magenta, cyan, and yellow colors are examples of the first color, the second color, and the third color, respectively. The first color, the second color, and the third color may be colors other than magenta, cyan, and yellow. The laser light capable of changing the recording layer 12A into a color-developing state, the laser light capable of changing the recording layer 12B into a color-developing state, and the laser light capable of changing the recording layer 12C into a color-developing state each have a different peak wavelength.

[0088] The thickness of each of the recording layers 12A, 12B, and 12C is preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 15 μm or less. When the thickness of each of the recording layers 12A, 12B, and 12C is 1 μm or more, the color density can be improved. On the other hand, when the thickness of each of the recording layers 12A, 12B, and 12C is 20 μm or less, an increase in the amount of heat utilized by the recording layers 12A, 12B, and 12C can be suppressed, and deterioration of color development can be suppressed.

[0089] The recording layer 12A contains a first color former having electron donating properties, a first color developer having electron accepting properties, and a first photothermal conversion agent. The recording layer 12A preferably further contains a first matrix resin.

[0090] The recording layer 12B contains a second color former having electron donating properties, a second color developer having electron accepting properties, and a second photothermal conversion agent. The recording layer 12B preferably further contains a second matrix resin.

[0091] The recording layer 12C includes a third color former having electron donating properties, a third color developer having electron accepting properties, and a third photothermal conversion agent. The recording layer 12C preferably further includes a third matrix resin.

[0092] (First, second, and third color formers) The first, second, and third color formers can exhibit different hues in a color-developed state. Specifically, the first color former can exhibit magenta in a color-developed state. The second color former can exhibit cyan in a color-developed state. The third color former can exhibit yellow in a color-developed state. Magenta, cyan, and yellow are examples of the first color, second color, and third color, respectively. The first color, second color, and third color may be colors other than magenta, cyan, and yellow.

[0093] (First, second, and third color developers) The first color developer is used to cause the first color former compound in a decolorized state to develop a color. The second color developer is used to cause the second color former compound in a decolorized state to develop a color. The third color developer is used to cause the third color former compound in a decolorized state to develop a color. The first, second, and third color developers may be the same as the color developer contained in the recording layer 12 of the first embodiment. The first, second, and third color developers may be of the same type, or may be different types from each other.

[0094] (First, second, and third photothermal conversion agents) The first, second, and third photothermal conversion agents absorb light in a predetermined wavelength range, such as the near-infrared region, and generate heat. The first, second, and third photothermal conversion agents have different absorption wavelength peaks. Specifically, the first photothermal conversion agent absorbs light in a wavelength λ １ The second photothermal conversion agent has an absorption wavelength peak at wavelength λ ２ The third photothermal conversion agent has an absorption wavelength peak at wavelength λ ３ It has an absorption wavelength peak at wavelength λ １ , λ ２ , λ ３are different. The absorption wavelength peak is preferably in the near-infrared region. The near-infrared region is, for example, a wavelength range of 700 nm or more and 2000 nm or less. As described above, the first, second, and third photothermal conversion agents have different absorption wavelength peaks, so that a desired layer among the recording layers 12A, 12B, and 12C can be selectively colored by irradiation with laser light. Examples of the first, second, and third photothermal conversion agents include the same photothermal conversion agents as those contained in the recording layer 12 of the first embodiment.

[0095] (First, second, and third matrix resins) Examples of the first, second, and third matrix resins include those similar to the matrix resin contained in the recording layer 12 of the first embodiment. The first, second, and third matrix resins may be of the same type, or may be of different types.

[0096] (Additives) The recording layers 12A, 12B, and 12C may contain the same additives as the recording layer 12, if necessary.

[0097] (Intermediate Layer) The intermediate layer 14A is provided between the recording layer 12A and the recording layer 12B. The intermediate layer 14A is a heat insulating layer that can provide heat insulation between the recording layer 12A and the recording layer 12B. The intermediate layer 14B is provided between the recording layer 12B and the recording layer 12C. The intermediate layer 14B is a heat insulating layer that can provide heat insulation between the recording layer 12B and the recording layer 12C.

[0098] The intermediate layers 14A and 14B are made of, for example, a general light-transmitting polymer material. Specific examples of the material include at least one selected from the group consisting of polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid polymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, silicone, polyethylene, polypropylene, and starch. The intermediate layers 14A and 14B may also contain various additives, such as ultraviolet absorbers.

[0099] The intermediate layers 14A and 14B may also be made of a translucent inorganic material. For example, porous silica, alumina, titania, carbon, or a composite of these materials is preferable because it has low thermal conductivity and high heat insulating properties. The intermediate layers 14A and 14B can be formed, for example, by a sol-gel method.

[0100] The thickness of the intermediate layers 14A, 14B is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less. If the thickness of the intermediate layers 14A, 14B is too thin, there is a risk that sufficient heat insulating effect will not be obtained. On the other hand, if the thickness of the intermediate layers 14A, 14B is too thick, there is a risk that the light transmittance will decrease. Furthermore, there is a risk that the bending resistance of the recording medium 10B will decrease, making it more susceptible to defects such as cracks.

[0101] [2.2 Recording Method on Recording Medium] Hereinafter, an example of a recording method on the recording medium 10A according to the second embodiment will be described.

[0102] The recording layer 12A is colored magenta as follows: When a peak wavelength λ is applied to a predetermined position on the recording layer 12A, １When the near-infrared laser beam is irradiated onto the surface of the substrate, the first photothermal conversion agent contained in the irradiated area absorbs the near-infrared laser beam and generates heat. This heat melts the first color developer, causing a color reaction (color-forming reaction) between the first color developer and the first color former, causing the irradiated area to develop a magenta color.

[0103] The recording layer 12B is colored cyan as follows: When a peak wavelength λ is applied to a predetermined position on the recording layer 12B, ２ When the near-infrared laser beam is irradiated, the portion irradiated with the laser beam develops a cyan color due to the same reaction as in the recording layer 12A.

[0104] The recording layer 12C is colored yellow as follows: When a peak wavelength λ 1 is applied to a predetermined position of the recording layer 12B, ３ When the near-infrared laser beam is irradiated, the portion irradiated with the laser beam develops yellow color due to the same reaction as that of the recording layer 12A.

[0105] As described above, predetermined positions of the recording layers 12A, 12B, and 12C are colored magenta, cyan, and yellow, respectively, thereby forming a desired full-color image on the recording medium 10A.

[0106] [2.3 Effects] The recording medium 10A according to the second embodiment can provide the same effects as the recording medium 10 according to the first embodiment.

[0107] Furthermore, in the recording medium 10A according to the second embodiment, the recording layers 12A, 12B, and 12C can exhibit magenta, cyan, and yellow colors, respectively, in a color-developing state, allowing a desired image to be drawn in full color.

[0108] <3 Third embodiment> In the above second embodiment, an example was described in which the recording medium has three recording layers and is capable of drawing a full-color image, whereas in the third embodiment, an example is described in which the recording medium has a recording layer containing three types of microcapsules and is capable of drawing a full-color image.

[0109] [3.1 Configuration of Recording Medium] An example of the configuration of a recording medium 10B according to the third embodiment will be described below with reference to Fig. 3. The recording medium 10B includes a substrate 11 and a recording layer 15 provided on the substrate 11. The recording medium 10B may further include a protective layer 13 provided on the recording layer 15. Note that in the third embodiment, parts that are the same as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0110] (Recording Layer) The recording layer 15 includes three types of microcapsules 15A, 15B, and 15C and a matrix resin. The colored state of the microcapsules 15A, 15B, and 15C can be changed by irradiation with laser light. The microcapsules 15A, 15B, and 15C can each exhibit a different hue in the colored state. Specifically, the microcapsule 15A can exhibit magenta in the colored state. The microcapsule 15B can exhibit cyan in the colored state. The microcapsule 15C can exhibit yellow in the colored state. The magenta, cyan, and yellow colors are examples of the first color, the second color, and the third color, respectively. The first color, the second color, and the third color may be colors other than magenta, cyan, and yellow. The laser light capable of changing the microcapsule 15A into a colored state, the laser light capable of changing the microcapsule 15B into a colored state, and the laser light capable of changing the microcapsule 15C into a colored state each have a different peak wavelength.

[0111] The microcapsules 15A contain a first microcapsule wall, a first color former having electron donating properties, a first color developer having electron accepting properties, and a first photothermal conversion agent. The microcapsules 15A may further contain a first matrix resin. The first microcapsule wall encapsulates the above-mentioned various materials.

[0112] The microcapsules 15B contain a second microcapsule wall, a second color former having electron donating properties, a second color developer having electron accepting properties, and a second photothermal conversion agent. The microcapsules 15B may further contain a second matrix resin. The second microcapsule wall encapsulates the various materials described above.

[0113] Microcapsule 15C includes a third microcapsule wall, a third color former having electron donating properties, a third color developer having electron accepting properties, and a third photothermal conversion agent. Microcapsule 15C may further include a third matrix resin. The third microcapsule wall encapsulates the various materials described above.

[0114] (Microcapsule Wall) The first, second, and third microcapsule walls are made of, for example, a light-transmitting polymeric material. Specific materials for the microcapsule walls include at least one selected from the group consisting of polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid polymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, and starch. The materials for the first, second, and third microcapsule walls may be the same, or may be different from each other.

[0115] (First, second and third electron-donating dyes) The first, second and third electron-donating dyes are the same as those in the second embodiment.

[0116] (First, second and third color developers) The first, second and third color developers are the same as those in the second embodiment.

[0117] (First, second and third photothermal conversion agents) The first, second and third photothermal conversion agents are the same as those in the second embodiment.

[0118] (First, second and third matrix resins) The first, second and third matrix resins are the same as those in the second embodiment.

[0119] (Additives) The microcapsules 15A, 15B, and 15C may contain, if necessary, the same additives as those in the recording layer 12. In this case, the additives may be encapsulated in the first, second, and third microcapsule walls.

[0120] [3.2 Recording Method on Recording Medium] Hereinafter, an example of a recording method on the recording medium 10B according to the third embodiment will be described.

[0121] The recording layer 15 is colored magenta as follows: When a peak wavelength λ 1 is applied to a predetermined position of the recording layer 15, １ The microcapsules 15A contained in the area irradiated with the laser light develop a magenta color. As a result, the area irradiated with the laser light develops a magenta color.

[0122] The recording layer 15 is colored cyan in the following manner. ２ The microcapsules 15B contained in the area irradiated with the laser light develop a cyan color. As a result, the area irradiated with the laser light develops a cyan color.

[0123] The recording layer 15 is colored yellow as follows: When a peak wavelength λ 1 is applied to a predetermined position of the recording layer 15, ３ The microcapsules 15C contained in the area irradiated with the laser light develop a yellow color. As a result, the area irradiated with the laser light develops a yellow color.

[0124] As described above, predetermined positions of the recording layer 15 are colored in magenta, cyan, and yellow, respectively, thereby forming a desired full-color image on the recording medium 10B.

[0125] [3.3 Effects] The recording medium 10B according to the third embodiment can provide the same effects as the recording medium 10 according to the first embodiment.

[0126] Furthermore, in the recording medium 10B according to the third embodiment, the recording layer 15 contains three types of microcapsules 15A, 15B, and 15C. The microcapsules 15A, 15B, and 15C can exhibit magenta, cyan, and yellow colors, respectively, in a color-developed state. Therefore, a desired image can be drawn in full color.

[0127] 4. Fourth Embodiment In the fourth embodiment, an example of a laminate including the recording medium 10 according to the first embodiment, the recording medium 10A according to the second embodiment, or the recording medium 10B according to the third embodiment will be described.

[0128] [4.1 Configuration of Laminate] Fig. 4 is a perspective view showing an example of the configuration of a laminate 20 according to a fourth embodiment. Fig. 5 is a cross-sectional view taken along line V-V in Fig. 4. The laminate 20 includes a substrate 21, an adhesive layer 22, an intermediate layer 23, an adhesive layer 24, an overlay layer 25, and a recording medium 26. The laminate 20 may be a card (hereinafter referred to as a "security card or the like") such as a security card, a financial settlement card (e.g., a credit card, a cash card, etc.), an ID card (e.g., an employee ID card, a membership card, a student ID card, etc.), or a personal transaction card (e.g., a prepaid card, a point card, etc.).

[0129] (Substrate) The substrate 21 is a support that supports the recording medium 26 and the intermediate layer 23. The substrate 21 may be a card. The substrate 21 may have a color such as white. The substrate 21 may have a design, a picture, a photograph, text, or a combination of two or more of these (hereinafter referred to as a "design, etc.") printed on one main surface on which the intermediate layer 23, the recording medium 26, etc. are provided.

[0130] The substrate 21 includes, for example, plastic. The substrate 21 may include at least one selected from the group consisting of a colorant, an antistatic agent, a flame retardant, a surface modifier, and the like, as needed.

[0131] The plastic includes at least one selected from the group consisting of, for example, ester-based resins, amide-based resins, olefin-based resins, vinyl-based resins, acrylic-based resins, imide-based resins, styrene-based resins, engineering plastics, etc. When the substrate 21 includes two or more types of resins, the two or more types of resins may be mixed, copolymerized, or laminated.

[0132] Examples of the ester resin include 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. Examples of the amide resin include at least one selected from the group consisting of nylon 6, nylon 66, and nylon 610. Examples of the olefin resin include at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP). Examples of the vinyl resin include polyvinyl chloride (PVC).

[0133] The acrylic resin includes, for example, at least one selected from the group consisting of polyacrylate, polymethacrylate, polymethyl methacrylate (PMMA), etc. The imide resin includes, for example, at least one selected from the group consisting of polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), etc. The styrene resin includes, for example, at least one selected from the group consisting of polystyrene (PS), high-impact polystyrene, acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), etc. The engineering plastic includes, for example, at least one selected from the group consisting of polycarbonate (PC), polyarylate (PAR), polysulfone (PSF), polyethersulfone (PES), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyetherketone (PEK), polyether-etherketone (PEEK), polyphenylene oxide (PPO), polyether sulfite, etc.

[0134] (Intermediate Layer) The intermediate layer 23 is provided on one main surface of the substrate 21, and the adhesive layer 22 is sandwiched between the substrate 21 and the intermediate layer 23. The intermediate layer 23 has a storage section 23A for storing the recording medium 26. The storage section 23A is provided in a portion of the surface of the intermediate layer 23. The storage section 23A may be a through-hole that penetrates the intermediate layer 23 in the thickness direction. The intermediate layer 23 is intended to suppress steps formed by the recording medium 26 when the recording medium 26 is sandwiched between the substrate 21 and the overlay layer 25. The intermediate layer 23 has approximately the same thickness as the recording medium 26, and covers one main surface of the substrate 21 except for the area where the recording medium 26 is provided.

[0135] The intermediate layer 23 has a film shape. The intermediate layer 23 may be transparent. The intermediate layer 23 includes a plastic. Examples of the plastic include the same materials as those of the base material 21.

[0136] (Overlay Layer) The overlay layer 25 is provided on the intermediate layer 23 and the recording medium 26, and covers the intermediate layer 23 and the recording medium 26. An adhesive layer 24 is sandwiched between the intermediate layer 23, the recording medium 26, and the overlay layer 25. The overlay layer 25 protects the internal members of the laminate 20 (i.e., the recording medium 26 and intermediate layer 23) and maintains the mechanical reliability of the laminate 20.

[0137] The overlay layer 25 has a film shape. The overlay layer 25 is transparent. The overlay layer 25 includes a plastic. Examples of the plastic include the same materials as those of the substrate 21. A pattern or the like may be printed on at least one main surface of the overlay layer 25.

[0138] (Adhesive Layer) The adhesive layer 22 is provided between the substrate 21 and the intermediate layer 23, bonding the substrate 21 and the intermediate layer 23 together. The adhesive layer 24 is provided between the intermediate layer 23 and the overlay layer 25, bonding the intermediate layer 23 and the overlay layer 25 together. The adhesive layers 22 and 24 contain a thermal adhesive. The thermal adhesive contains a thermosetting resin. The thermosetting resin includes at least one selected from the group consisting of, for example, epoxy resins and urethane resins. The curing temperature of the thermal adhesive is preferably in the range of 100°C or higher and 120°C or lower, from the viewpoint of reducing damage to the recording medium 26.

[0139] (Recording Medium) The recording medium 26 is the recording medium 10 according to the first embodiment, the recording medium 10A according to the second embodiment, or the recording medium 10B according to the third embodiment.

[0140] [4.2 Manufacturing Method of Laminate] Hereinafter, an example of a manufacturing method of the laminate 20 according to the fourth embodiment will be described.

[0141] First, a thermosetting resin is applied as a thermal adhesive to one main surface of the substrate 21 to form an adhesive layer 22. Next, the intermediate layer 23 is placed on the adhesive layer 22, and then the recording medium 26 is fitted into the storage section 23A of the intermediate layer 23. Note that the intermediate layer 23, with the recording medium 26 already fitted into the storage section 23A, may be placed on the adhesive layer 22. Alternatively, the adhesive layer 22 may be formed by applying a thermosetting resin to the intermediate layer 23, with the recording medium 26 already fitted into the storage section 23A, and then placing the intermediate layer 23 on the main surface of the substrate 21 so that the coating is sandwiched between them. Alternatively, the adhesive layer 22 may be formed by bonding a sheet, which has been previously formed by applying a thermosetting resin to a separator, to the main surface of the substrate 21 or to the intermediate layer 23, with the recording medium 26 already fitted into the storage section 23A, by means of thermal lamination or the like.

[0142] Next, a thermosetting resin is applied as a thermal adhesive to the intermediate layer 23 to form an adhesive layer 24, and then the overlay layer 25 is placed on the adhesive layer 24. The resulting laminate is then sandwiched between metal plates and heated and pressurized to thermally cure the adhesive layers 22 and 24. The temperature applied to the laminate during thermal curing is preferably 100°C or higher and 120°C or lower, in order to reduce damage to the recording medium 26. This results in the desired laminate 20. The adhesive layer 24 may be formed by applying a thermosetting resin to the overlay layer 25 and then placing the overlay layer 25 on the intermediate layer 23 with the coating sandwiched between them. Alternatively, the adhesive layer 24 may be formed by bonding a sheet, previously formed by applying a thermosetting resin to a separator, to the overlay layer 25 or the intermediate layer 23 by means of thermal lamination or the like.

[0143] [4.3 Effects] As described above, in the laminate 20 according to the fourth embodiment, the substrate 21 and the intermediate layer 23 are bonded together by the adhesive layer 22 containing a thermal adhesive, and the intermediate layer 23 and the overlay layer 25 are bonded together by the adhesive layer 22 containing a thermal adhesive. This allows the substrate 21 and the intermediate layer 23, and the intermediate layer 23 and the overlay layer 25, to be firmly bonded together. This improves tamper resistance.

[0144] Because the recording medium 26 is fitted into the housing portion 23A of the intermediate layer 23, it is possible to make it difficult to visually recognize the boundary between the recording medium 26 and the intermediate layer 23 in the in-plane direction of the laminate 20. Therefore, it is difficult to identify which part of the laminate 20 in the plane in which the recording medium 26 is provided. This improves tamper resistance. Because the recording medium 26 is sealed inside the laminate 20, it is possible to reduce the effects of exposure to moisture, chemicals, etc. on the recording medium 26.

[0145] 5. Fifth Embodiment In the fifth embodiment, an example of a laminate having a different configuration from that of the fourth embodiment will be described.

[0146] 6 is a cross-sectional view showing an example of the configuration of a laminate 20A according to the fifth embodiment. The laminate 20A differs from the laminate 20 according to the fourth embodiment in that the laminate 20A does not include the adhesive layer 22 and the adhesive layer 24, and the substrate 21 and the intermediate layer 23, and the intermediate layer 23 and the overlay layer 25 are bonded together by fusion bonding.

[0147] In the fifth embodiment, the substrate 21, the intermediate layer 23, and the overlay layer 25 preferably contain a thermoplastic resin as the plastic. By containing a thermoplastic resin in the substrate 21, the intermediate layer 23, and the overlay layer 25, the interlayer adhesion strength due to fusion can be increased. From the viewpoint of reducing damage to the recording medium 26, the thermoplastic resin is preferably one that can heat-seal the layers of the laminate 20A at a temperature range of 130°C to 200°C.

[0148] The substrate 21, the intermediate layer 23, and the overlay layer 25 may contain the same type of thermoplastic resin, or they may not contain the same type of thermoplastic resin. If the substrate 21, the intermediate layer 23, and the overlay layer 25 do not contain the same type of thermoplastic resin, one of the substrate 21, the intermediate layer 23, and the overlay layer 25 may contain a different type of thermoplastic resin from the other two layers, or the substrate 21, the intermediate layer 23, and the overlay layer 25 may each contain a different type of thermoplastic resin.

[0149] When the substrate 21, the intermediate layer 23, and the overlay layer 25 contain the same type of thermoplastic resin, it is preferable that the substrate 21, the intermediate layer 23, and the overlay layer 25 contain at least one type 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.

[0150] The semi-crystalline thermoplastic resin includes at least one selected from the group consisting of, for example, polypropylene (PP), polyethylene (PE), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK).

[0151] 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), polyetherimide (PEI), and polyethersulfone (PES).

[0152] When the substrate 21, the intermediate layer 23, and the overlay layer 25 do not contain the same type of thermoplastic resin, it is preferable that the substrate 21, the intermediate layer 23, and the overlay layer 25 contain a non-crystalline thermoplastic resin from the viewpoint of improving the interlayer adhesion strength by fusion.

[0153] The following combinations of amorphous thermoplastic resins are preferred for the two adjacent layers of the laminate 20A: When one of the two adjacent layers of the laminate 20A contains an ABS resin, the other layer preferably contains at least one selected from the group consisting of an ABS / PC polymer alloy, polycarbonate (PC), AS resin, polystyrene (PS), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC).

[0154] When one of the two adjacent layers of the laminate 20A contains an ABS / PC polymer alloy, the other layer preferably contains at least one selected from the group consisting of ABS resin, polycarbonate (PC), and polymethyl methacrylate (PMMA).When one of the two adjacent layers of the laminate 20A contains polycarbonate (PC), the other layer preferably contains at least one selected from the group consisting of ABS resin, ABS / PC polymer alloy, and polymethyl methacrylate (PMMA).

[0155] When one of the two adjacent layers of the laminate 20A contains an AS resin, the other layer preferably contains at least one selected from the group consisting of an ABS resin, polystyrene (PS), polymethyl methacrylate (PMMA), and polyphenylene oxide (PPO).When one of the two adjacent layers of the laminate 20A contains polystyrene (PS), the other layer preferably contains at least one selected from the group consisting of an AS resin and polyphenylene oxide (PPO).

[0156] When one of two adjacent layers of laminate 20A contains polymethyl methacrylate (PMMA), the other layer preferably contains at least one selected from the group consisting of ABS resin, ABS / PC polymer alloy, AS resin, and polyphenylene oxide (PPO).When one of two adjacent layers of laminate 20A contains polyphenylene oxide (PPO), the other layer preferably contains at least one selected from the group consisting of polycarbonate (PC), AS resin, polystyrene (PS), and polymethyl methacrylate (PMMA).

[0157] When one of the two adjacent layers of the laminate 20A contains polysulfone (PSU), the other layer preferably contains polycarbonate (PC).When one of the two adjacent layers of the laminate 20A contains polyvinyl chloride (PVC), the other layer preferably contains ABS resin.

[0158] [5.2 Manufacturing Method of Laminate] Hereinafter, an example of a manufacturing method of the laminate 20 according to the fifth embodiment will be described.

[0159] First, the intermediate layer 23 is placed on one main surface of the substrate 21, and then the recording medium 26 is fitted into the accommodation portion 23A of the intermediate layer 23. Alternatively, the intermediate layer 23, with the recording medium 26 already fitted into the accommodation portion 23A, may be placed on one main surface of the substrate 21. Next, the overlay layer 25 is placed on the intermediate layer 23. The resulting laminate is then sandwiched between metal plates and heated and pressurized to heat-seal the substrate 21 and the intermediate layer 23, and the intermediate layer 23 and the overlay layer 25. The temperature applied to the laminate during heat-sealing is preferably 130°C or higher and 200°C or lower, from the viewpoints of reducing damage to the recording medium 26 and achieving sufficient fusion strength. This results in the desired laminate 20A.

[0160] [5.3 Effects] As described above, in the laminate 20A according to the fifth embodiment, the substrate 21 and the intermediate layer 23, and the intermediate layer 23 and the overlay layer 25 are fused together. This allows the substrate 21 and the intermediate layer 23, and the intermediate layer 23 and the overlay layer 25 to be firmly bonded together. This improves the tamper resistance.

[0161] <6. Modifications> (Modification 1) In the second embodiment, an example was described in which the intermediate layers 14A, 14B were insulation layers having a single-layer structure. However, the intermediate layers 14A, 14B may also be insulation layers having a multilayer structure. The insulation layer having a multilayer structure may include a resin layer and an adhesive layer provided on one side of the resin layer, or may include a resin layer and adhesive layers provided on both sides of the resin layer. Note that the configuration of the insulation layer having a multilayer structure is not limited to the above configuration. Furthermore, the number of layers in the multilayer structure is not limited to the above two or three layers, and a structure of four or more layers may be adopted.

[0162] The resin layer may be a polymer film or a coating layer such as an ultraviolet-curable resin layer. The attachment layer may be, for example, an adhesive layer or a bonding layer. The attachment layer may be a double-sided adhesive film such as OCA (Optical Clear Adhesive). The double-sided adhesive film may be composed of only an adhesive layer, or may be composed of a film as a substrate, a first adhesive layer provided on a first surface of the film, and a second adhesive layer provided on a second surface of the film.

[0163] (Variation 2) In the second embodiment, an example was described in which the recording medium 10A includes three recording layers 12A, 12B, and 12C and two intermediate layers 14A and 14B. However, the recording medium 10A may include a plurality of recording layers other than three and a plurality of intermediate layers other than two. The plurality of recording layers and the plurality of intermediate layers may be stacked so that the recording layers and the intermediate layers are alternately positioned. The plurality of recording layers may each be capable of exhibiting a different hue in a color-developed state. In other words, the color-developing compounds contained in the plurality of recording layers may each be capable of exhibiting a different hue in a color-developed state. The photothermal conversion agents contained in the plurality of recording layers may each have a different absorption wavelength peak.

[0164] (Variation 3) In the third embodiment, an example was described in which the recording layer 15 includes three types of microcapsules 15A, 15B, and 15C, but the recording layer 15 may include multiple types of microcapsules other than these. The multiple types of microcapsules may each be capable of exhibiting a different hue when colored. That is, the color-forming compounds contained in the multiple types of microcapsules may each be capable of exhibiting a different hue when colored. The photothermal conversion agents contained in the multiple types of microcapsules may each have a different absorption wavelength peak.

[0165] (Modification 4) In the first to third embodiments, examples have been described in which the recording media 10, 10A, and 10B include the substrate 11, but the recording media 10, 10A, and 10B do not necessarily have to include the substrate 11.

[0166] (Variation 5) In the first embodiment, an example in which the protective layer 13 is provided on the recording layer 12 has been described, but a UV-cutting layer may be provided between the recording layer 12 and the protective layer 13. By providing the UV-cutting layer, UV light incident on the recording layer 12 can be blocked, thereby suppressing deterioration of the recording layer 12 due to UV light. Similarly, in the second embodiment, a UV-cutting layer may be provided between the recording layer 12C and the protective layer 13. Similarly, in the third embodiment, a UV-cutting layer may be provided between the recording layer 12C and the protective layer 13.

[0167] (Other Modifications) Although the embodiments and modifications of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and modifications, and various modifications based on the technical ideas of the present disclosure are possible.

[0168] For example, the configurations, methods, steps, shapes, materials, and numerical values, etc., described in the above embodiments and variations are merely examples, and different configurations, methods, steps, shapes, materials, and numerical values, etc., may be used as necessary.

[0169] The configurations, methods, steps, shapes, materials, numerical values, etc. of the above-described embodiments and modified examples can be combined with each other without departing from the spirit of the present disclosure.

[0170] In the above embodiments and modified examples, in the numerical ranges described in stages, the upper limit or lower limit of a numerical range in one stage may be replaced with the upper limit or lower limit of a numerical range in another stage.

[0171] Unless otherwise specified, the materials exemplified in the above-described embodiments and modifications can be used singly or in combination of two or more.

[0172] The present disclosure may also employ the following configuration: (1) A recording medium comprising a recording layer containing a color former having electron donating properties and a color developer having electron accepting properties, wherein the color developer contains a compound represented by the following formula (1): (However, in formula (1), X 1 is a divalent group containing at least one benzene ring. 11 , Y 12 , Y 13 , Y 14 are each independently a monovalent group. 11 , Z 12 (2) The recording medium according to (1), wherein the recording layer further contains a polycarbonate resin. (3) Z in the formula (1) 11 , Z 12 (4) The recording medium according to (1) or (2), wherein Z in the formula (1) is independently a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-), or a hydrazide bond (-NHCOCONH-). 11 , Z 12 (5) The recording medium according to (1) or (2), wherein Y in the formula (1) is a urea bond (—NHCONH—). 11 and Y 13 (6) The recording medium according to any one of (1) to (4), wherein X in the formula (1) is a hydroxy group (—OH). 1 (7) The recording medium according to any one of (1) to (5), wherein Y is a divalent group containing at least two benzene rings. 11 , Y 12 and / or a benzene ring having Y12 , Y 13 (8) The recording medium according to any one of (1) to (6), wherein the benzene ring having the formula (1) is a weak acid. 1 The recording medium according to any one of (1) to (7), wherein: is a divalent group represented by the following formula (3): (However, in formula (3), X 21 It doesn't matter if it's there or not, X 21 If there is X 21 is a divalent group. 22 It doesn't matter if it's there or not, X 22 If there is X 22 is a divalent group. 21 is a monovalent group. n21 is an integer of 0 to 4. When n21 is an integer of 2 to 4, R 21 may be the same or different. * denotes a bond.) (9) X in the formula (1) 1 The recording medium according to any one of (1) to (7), wherein: is a divalent group represented by the following formula (4): (However, in formula (4), R 22 is a monovalent group. n22 is an integer of 0 to 4. When n22 is an integer of 2 to 4, R 22 may be the same or different. * denotes a bond.) (10) X in the formula (1) 1 The recording medium according to any one of (1) to (7), wherein: is a divalent group represented by the following formula (5): (However, in formula (5), X 31 It doesn't matter if it's there or not, X 31 If there is X 31 is a divalent group. 32 It doesn't matter if it's there or not, X 32 If there is X 32 is a divalent group. 33 It doesn't matter if it's there or not, X 33 If there is X 33 is a divalent group. 31 , R 32are each independently a monovalent group. n31 and n32 are each independently an integer of 0 to 4. When n31 is an integer of 2 to 4, R 31 may be the same or different. When n32 is an integer of 2 to 4, R 32 may be the same or different. * indicates a bond.) (11) X in the formula (1) 1 The recording medium according to any one of (1) to (7), wherein: is a divalent group represented by the following formula (6): (However, in formula (6), X 34 is a divalent group. 33 , R 34 are each independently a monovalent group. n33 and n34 are each independently an integer of 0 to 4. When n33 is an integer of 2 to 4, R 33 may be the same or different. When n34 is an integer of 2 to 4, R 34may be the same or different. * denotes a connecting portion.) (12) The recording medium according to any one of (1) to (11), wherein a plurality of the recording layers are provided, and the color former compounds contained in the plurality of recording layers are capable of exhibiting different hues in a color-developed state. (13) The recording medium according to (12), wherein the plurality of recording layers contain a photothermal conversion agent, and the photothermal conversion agents contained in the plurality of recording layers have different absorption wavelength peaks. (14) The recording medium according to any one of (1) to (11), wherein the recording layer contains multiple types of capsules, and the multiple types of capsules contain the color former and the color developer, and the color former compounds contained in the plurality of types of capsules are capable of exhibiting different hues in a color-developed state. (15) The recording medium according to (14), wherein the multiple types of capsules contain a photothermal conversion agent, and the photothermal conversion agents contained in the plurality of types of capsules have different absorption wavelength peaks. (16) A recording medium comprising a recording layer containing a color former having electron donating properties and a color developer having electron accepting properties, wherein the color developer contains a compound represented by the following formula (a): (However, in formula (a), X 0 is a divalent group containing at least one benzene ring. 01 , Y 02 are each independently a monovalent group. n01 and n02 are each independently an integer of 0 to 5. When n01 is an integer of 2 to 5, Y 01 may be the same or different. When n02 is an integer of 2 to 5, Y 02 may be the same or different. 01 , Z 02 are each independently a hydrogen-bonding group. (17) A card comprising the recording medium according to any one of (1) to (16). (18) A booklet comprising the recording medium according to any one of (1) to (16).

[0173] <7 Application Examples> Next, application examples of the recording media 10, 10A, and 10B according to the first, second, and third embodiments and their modifications will be described. However, the configurations of the electronic devices and the like described below are merely examples, and the configurations can be modified as appropriate. The recording media 10, 10A, and 10B can be applied to various electronic devices and parts of clothing, and the types of electronic devices and clothing are not particularly limited. Specifically, for example, the recording media 10, 10A, and 10B can be applied to parts of clothing such as watches, bags, clothes, hats, glasses, and shoes as wearable devices. Furthermore, the recording media 10, 10A, and 10B can be applied not only to electronic devices and clothing but also to exterior components of interior or exterior walls of buildings and exterior components of furniture such as desks.

[0174] In the following application examples 1 to 10, examples will be described in which recording medium 10 is applied to identification cards, cards, electronic devices, etc., but it is also possible to apply either recording medium 10A or 10B instead of recording medium 10 to identification cards, cards, electronic devices, etc., or to combine two or more of recording media 10, 10A, and 10B to identification cards, cards, electronic devices, etc. Furthermore, in the following application examples 1 to 10, an example will be described in which a predetermined image is drawn on recording medium 10 and recorded portions and unrecorded portions are formed in recording layer 12.

[0175] (Application Example 1) Fig. 7A shows the appearance of a card-type identification card. Fig. 7B is a cross-sectional view taken along line VIIB-VIIB in Fig. 7A. The card-type identification card is an example of a card or an identification card. The card-type identification card sequentially comprises a substrate 31, an adhesive layer 32, a recording medium 33, an adhesive layer 34, and an overlay layer 35. Here, an example in which the recording medium 33 is provided on one side of the substrate 31 will be described, but the recording medium 33 may also be provided on both sides of the substrate 31.

[0176] The substrate 31 is a supporting substrate that supports the recording medium 33. The substrate 31 is, for example, a plastic substrate. The recording medium 33 is the recording medium 10. The bonding layer 32 bonds the substrate 31 and the recording medium 33 together. The bonding layer 34 bonds the recording medium 33 and the overlay layer 35 together. The overlay layer 35 protects the recording medium 33. The overlay layer 35 covers one side of the recording medium 33.

[0177] Specific examples of card-type identification cards include a driver's license, a health insurance card, a resident registration card, or a personal identification number card (My Number card).

[0178] (Application Example 2) Fig. 8 shows the appearance of a booklet-type identification card. A booklet-type identification card is an example of a booklet. The booklet-type identification card comprises a plurality of sheets 41. The plurality of sheets 41 are saddle-stitched. A recording medium 10 is provided on at least one side of the sheets 41. Letters, numbers, a photograph, etc. are drawn on the recording medium 10. A specific example of a booklet-type identification card is a passport, for example.

[0179] 9A and 9B show the appearance of an integrated circuit (IC) card with a rewritable function. In this IC card, the surface of the card is a print surface 110, and a sheet-like recording medium 10 is provided on the print surface 110. By providing the recording medium 10 on the print surface 110 of the IC card, it becomes possible to draw a desired image or the like on the print surface 110, as shown in FIGS. 9A and 9B.

[0180] (Application Example 4) Figures 10A and 10B show the appearance of a credit card with an IC chip. A credit card with an IC chip is another example of an IC card. The credit card has an IC chip 121 on the front (first side) 120B and a facial photograph 122 on the back (second side) 120A. By placing recording medium 10 on front 120B and back 120A of the credit card, it becomes possible to draw on front 120B and back 120A of the credit card, as shown in Figures 10A and 10B.

[0181] (Application Example 5) Fig. 11A shows the external configuration of the front of a smartphone. Fig. 11B shows the external configuration of the back of the smartphone shown in Fig. 11A. This smartphone includes, for example, a display unit 210, a non-display unit 220, and a housing 230. For example, a recording medium 10 is provided as an exterior member of the housing 230 on, for example, one surface of the rear side of the housing 230, thereby making it possible to display various colors and patterns as shown in Fig. 11B. Note that while a smartphone is used as an example here, the present invention is not limited to this, and can also be applied to, for example, a notebook personal computer (PC), a tablet PC, etc.

[0182] (Application Example 6) Figures 12A and 12B show the external appearance of a bag. This bag has, for example, a storage section 310 and a handle 320, and a recording medium 10 is provided in the storage section 310. This makes it possible to display various characters, designs, etc. on the storage section 310. Furthermore, by attaching the recording medium 10 to the handle 320, it is possible to display various colors and patterns. As shown in the examples of Figures 12A and 12B, the design of the storage section 310 can be changed. This makes it possible to realize an electronic device that is also useful for fashion purposes.

[0183] (Application Example 7) Fig. 13A shows the appearance of the top surface of an automobile, and Fig. 13B shows the appearance of the side surface of the automobile. By attaching the recording medium 10 to parts of the automobile body, such as a hood 411, a bumper 412, a roof 413, a trunk cover 414, a front door 415, a rear door 416, and a rear bumper 417, it is possible to display various information and colors and patterns on each part. Furthermore, by attaching the recording medium 10 to the interior of the automobile, such as the steering wheel or dashboard, it is possible to display various colors and patterns.

[0184] (Application Example 8) Fig. 14 shows the external appearance of a cosmetic container. This cosmetic container has a storage section 510 and a lid 520 that covers the storage section 510, and a recording medium 10 is attached to the lid 520. The lid 520 is decorated with the recording medium 10, for example, with a design, color pattern, or text as shown in Fig. 14. The design, color pattern, or text on the lid 520 can be written using a predetermined drawing device. Note that the recording medium 10 can be attached not only to the front surface (lid 520) of the cosmetic container, but also to the back surface (storage section 510), etc.

[0185] (Application Example 9) Figure 15 shows the appearance of nail tips. Nail tips are an example of an exterior member. The nail tips have a recording medium 10 on their surface. By providing the recording medium 10 on the surface of the nail tips in this way, various colors and patterns can be displayed. In the above example, a configuration in which the nail tips have a recording medium 10 on their surface has been described, but the configuration of the nail tips is not limited to this, and the recording medium 10 itself may be the nail tip. In this case, the base material 11 is shaped like a nail.

[0186] (Application Example 10) Fig. 16A shows the appearance of a nail sticker. Fig. 16B shows a cross section taken along line XVIB-XVIB in Fig. 16A. The nail sticker is an example of an exterior member. The nail sticker includes a recording medium 610 with an adhesive layer and a release sheet 620. The recording medium 610 with an adhesive layer includes a recording medium 10 and an adhesive layer 611. By including the recording medium 10 in the recording medium 610 with an adhesive layer in this manner, it is possible to display various colors and patterns. The adhesive layer 611 is provided on the surface of the recording medium 10 facing the substrate 11. The recording medium 10 may further include a protective layer 13 on the recording layer 12.

[0187] The recording medium 10 etc. has a plurality of nail seal parts 612 to be attached to the nails of the fingers of both hands. The nail seal parts 612 are held in a cut or semi-cut state relative to the nail seal and are configured to be peelable at the interface between the adhesive layer 611 and the release sheet 620.

[0188] In Application Examples 9 and 10, examples in which the present disclosure is applied to nail tips and nail stickers have been described, but application examples of the present disclosure to nails are not limited to these. For example, the recording layer 12 may be formed directly on a natural nail (human nail) as a supporting substrate. The recording layer 12 may be formed by applying paint to the natural nail and curing it, or a self-supporting recording layer 12 may be formed separately and then attached to the natural nail.

[0189] 8. Examples Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to these examples.

[0190] Examples 1 to 9 (Preparation of Coating for Forming a Recording Layer) First, polycarbonate (PC) was dissolved as a matrix resin in methyl ethyl ketone (MEK), and a color developer was added and dispersed using a rocking mill. As shown in Table 1, a different color developer (a compound represented by formulas (2A) to (10A)) was used in Examples 1 to 9. Next, a leuco dye represented by formula (2) above, which exhibits a magenta color in the developed state, was added, resulting in a final ratio (mass ratio) of leuco dye:color developer:polycarbonate = 1:2:4. A photothermal conversion material having a phthalocyanine skeleton was then added to prepare a coating for forming a recording layer. The amount of photothermal conversion material was adjusted so that the absorbance of the coated film was 0.32.

[0191] (Recording layer forming process) Next, the recording layer forming paint was applied to a 50 μm thick PET (support substrate) using a wire bar and dried at 110° C. for 5 minutes to obtain a recording layer. At this time, the application conditions for the recording layer forming paint were adjusted so that the film thickness of the recording layer after drying would be the value shown in Table 1. Next, a laser beam was irradiated onto the recording layer to form colored areas and uncolored areas (background). As a result, the desired recording medium was obtained.

[0192] Example 10 A recording medium was obtained in the same manner as in Example 2, except that a leuco dye that exhibits a yellow color in a colored state was blended as the leuco dye in the step of preparing the coating material for forming the recording layer.

[0193] Example 11 A recording medium was obtained in the same manner as in Example 2, except that a leuco dye that exhibits a cyan color in a color-developed state was blended as the leuco dye in the step of preparing the coating material for forming the recording layer.

[0194] Example 12 A recording medium was obtained in the same manner as in Example 11, except that a light stabilizer (Hostavin N-30, manufactured by Clariant) was further blended into the recording layer-forming paint in the preparation step of the recording layer-forming paint. The blending amount of the light stabilizer was set to 1.4 parts by mass per 100 parts by mass of the total amount of the leuco dye, developer, polycarbonate, photothermal conversion material, and light stabilizer.

[0195] [Example 13] A recording medium was obtained in the same manner as in Example 2, except that in the preparation process of the coating material for forming the recording layer, polyvinyl chloride-vinyl acetate copolymer (PVC) was used as the matrix resin instead of polycarbonate (PC).

[0196] [Comparative Examples 1 to 4] In the preparation process of the coating material for forming a recording layer, a different color developer (a compound represented by formulas (1B) to (4B) respectively) was used in each of Comparative Examples 1 to 4, as shown in Table 1. In addition, in the coating process of the coating material for forming a recording layer, the coating conditions for the coating material for forming a recording layer were adjusted so that the film thickness of the recording layer after drying would be the value shown in Table 1. Aside from the above, recording media were obtained in the same manner as in Example 1.

[0197] [Evaluation] The recording media obtained as described above were evaluated as follows.

[0198] (Evaluation of OD in a standard environment) The OD of the colored portion of the recording medium was measured three times at the same location in a standard environment (23°C, 50% RH), and the measured values ​​were simply averaged (arithmetic mean) to determine the average OD of the colored portion. The OD of each of C (cyan), M (magenta), and Y (yellow), corresponding to the visually recognized color, was taken as the OD of each color. The average OD of the uncolored portion (background) of the recording medium was determined in the same manner as the average OD of the colored portion of the recording medium. The OD measurement conditions were as follows: Measurement device: Spectrophotometer (Xrite eXact, manufactured by Xrite Corporation) Measurement diameter: 2.0 mm Illuminant: D50 Standard observer: 2° Measurement conditions: No filter (M0)

[0199] Next, the average OD of the colored portion and the average OD of the uncolored portion were converted to the average OD of the colored portion in a 5 μm-thick recording layer and the average OD of the uncolored portion in a 5 μm-thick recording layer, respectively. Table 1 shows the average OD of the colored portion before and after conversion, and the average OD of the uncolored portion before and after conversion.

[0200] Next, the average OD of the uncolored portions (unrecorded portions) after conversion was evaluated using the following two-level evaluation. The evaluation results are shown in Table 1. Evaluation 2: The average OD of the uncolored portions (unrecorded portions) after conversion is 0.30 or less. Evaluation 1: The average OD of the uncolored portions (unrecorded portions) after conversion exceeds 0.30. When the average OD of the uncolored portions (unrecorded portions) after conversion exceeds 0.30, this is generally a level at which color development is noticeable to anyone, so an average OD of the uncolored portions (unrecorded portions) after conversion of 0.30 was used as the reference value for the two-level evaluation.

[0201] (Evaluation of Storage Stability in a High-Temperature, Low-Humidity Environment) First, a storage test was conducted by storing the recording medium under high-temperature, low-humidity conditions of 80°C and 30% RH for 200 hours. The 80°C storage test temperature is the highest temperature used in storage tests of all components, and if good results are obtained in storage tests at this temperature, it is believed that the recording medium can withstand storage in a variety of environments. Next, the average OD of the colored portion of the 5 μm-thick recording layer was calculated in the same manner as in the "Evaluation of OD in a Standard Environment" above. Next, the OD retention rate of the colored portion before and after the storage test was calculated using the following formula: (OD retention rate of the colored portion before and after the storage test) [%] = ((average OD of the colored portion after the storage test) / (average OD of the colored portion before the storage test)) × 100. Note that the average OD of the colored portion of the 5 μm-thick recording layer calculated in the "Evaluation of OD in a Standard Environment" above was used as the average OD of the colored portion before the storage test.

[0202] Next, the OD retention rate of the colored portion before and after the storage test was evaluated using the following two-level evaluation. The evaluation results are shown in Table 1. Evaluation 2: The OD retention rate of the colored portion before and after the storage test was 85% or more. Evaluation 1: The OD retention rate of the colored portion before and after the storage test was less than 85%. If the OD retention rate of the colored portion before and after the storage test is less than 85%, generally anyone would notice a change from the original color, so an OD retention rate of 85% was used as the reference value for the two-level evaluation.

[0203] (Evaluation of storage stability under high temperature and high humidity environment) The OD maintenance rate of the colored portion before and after the storage test was determined in the same manner as in the above "Evaluation of storage stability under high temperature and low humidity environment" except that the storage test was performed by storing the recording medium under high temperature and high humidity conditions of 80°C and 60% RH for 200 hours. Subsequently, the storage stability was evaluated on a two-level scale in the same manner as in the above "Evaluation of storage stability under high temperature and low humidity environment". The evaluation results are shown in Table 1.

[0204] (Evaluation of Heat Resistance (1)) First, an unheated recording medium was prepared, and this was designated as Sample A. Next, the L of the uncolored portion of Sample A was measured in a standard environment (23° C., 50% RH). ＊ , a ＊ , b ＊ Each measurement was made three times at the same location, and the measured values ​​were simply averaged (arithmetic mean) to obtain the average L ＊ , average a ＊ , average b ＊ (Hereinafter referred to as “L ０ ＊ , a ０ ＊ , b ０ ＊ Next, the unheated recording medium was placed in an oven (As One Corporation, ETTAS vacuum dryer AVO-250V) preheated to 150°C for 30 minutes, and this was designated as Sample B. Next, the L ＊ , a ＊ , b ＊ is measured three times at the same location, and the measured values ​​are simply averaged (arithmetic mean) to obtain the average L ＊ , average a ＊ , average b ＊ (Hereinafter referred to as “L １ ＊ , a１ ＊ , b １ ＊ ") was sought. ＊ , a ＊ , b ＊ The measurement conditions are as follows: Measurement device: spectrophotometer (Xrite eXact, manufactured by Xrite) Measurement diameter: 2.0 mm Illuminant: D50 Standard observer: 2° Measurement conditions: no filter (M0)

[0205] Next, using the following formula, ΔE of the uncolored portion relative to sample A is calculated. ａｂ ＊ was calculated.

[0206] Next, ΔE ａｂ ＊ The results are shown in Table 1. ａｂ ＊ <3.2 Rating 2: 3.2≦ΔE ａｂ ＊ <6.5 Rating 1: 6.5≦ΔE ａｂ ＊ ΔE ａｂ ＊ <3.2 is ΔE ａｂ ＊ This means that the tolerance is at or below Class A. Class A tolerance means a color difference level that is barely noticeable when comparing colors side by side, i.e., a level at which the colors are generally considered to be the same. ａｂ ＊ <6.5 is ΔE ａｂ ＊ This means that the tolerance is Class B. Note that Class B tolerance means the range in which the colors can be treated as the same at the impression level. 6.5≦ΔE ａｂ ＊ is ΔE ａｂ ＊ This means that the tolerance is equal to or greater than Class C. Class C tolerance means a color difference equivalent to one degree on a JIS standard color chart, a Munsell color chart, or the like.

[0207] (Evaluation of Heat Resistance (2)) An unheated recording medium was placed in an oven (As One Corporation, ETTAS Vacuum Dryer AVO-250V) preheated to 180°C for 5 minutes, and this was designated as Sample B. Other than this, the same procedure as in "Evaluation of Heat Resistance (1)" was followed, and ΔE ａｂ ＊ Next, ΔE ａｂ ＊ The results of the evaluation are shown in Table 1.

[0208] (Lightfastness Evaluation) The following lightfastness evaluation was carried out on the recording media of Examples 2 and 13. First, a UV-cut barrier was formed on the recording layer of the recording media of Examples 2 and 13 obtained as described above, and then the average OD of each of the colored and uncolored areas was determined. Next, the recording media were subjected to an accelerated lightfastness test (test conditions: irradiance 60 W / m ) using a xenon arc tester (Q-SUN Xe-1, manufactured by Q-Lab). ２ After the lightfastness test, the average OD of each of the colored and uncolored portions of the recording medium was determined again. Next, the OD maintenance rate before and after the lightfastness test was determined for each of the colored and uncolored portions using the following formula: (OD maintenance rate before and after lightfastness test) [%] = ((average OD after lightfastness test) / (average OD before lightfastness test)) x 100. The average OD before and after the lightfastness test were determined using the same procedure as in the "Evaluation of OD in a standard environment" above.

[0209] Next, the OD retention rate of the colored portion before and after the lightfastness test was evaluated using the following two-stage evaluation. The evaluation results are shown in Table 2. Evaluation 2: The OD retention rate of the colored portion before and after the lightfastness test was 85% or more. Evaluation 1: The OD retention rate of the colored portion before and after the lightfastness test was less than 85%. If the OD retention rate of the colored portion before and after the lightfastness test was less than 85%, generally anyone would notice a change from the original color, so an OD retention rate of 85% was used as the reference value for the two-stage evaluation.

[0210] Next, the OD retention rate of the uncolored portion before and after the lightfastness test was evaluated using the following two-level evaluation. The evaluation results are shown in Table 2. Evaluation 2: The OD retention rate of the colored portion before and after the lightfastness test was 115% or less. Evaluation 1: The OD retention rate of the colored portion before and after the lightfastness test was greater than 115%. If the OD retention rate of the uncolored portion before and after the lightfastness test was greater than 115%, generally anyone would be able to see a change from the initial color, and therefore an OD retention rate of 115% was used as the reference value for the two-level evaluation.

[0211]

[0212]

[0213] In Table 1, Z 11 , Z 12 and X 1 indicates the symbol in formula (1) above. In Table 1, in the column for the evaluation result of OD maintenance rate, ">95", ">85", and "<50" indicate the following evaluation results: >95: The evaluation result of the OD maintenance rate is greater than 95%. >85: The evaluation result of the OD maintenance rate is greater than 85% and equal to or less than 95%. >50: The evaluation result of the OD maintenance rate is less than 50%. In Table 2, in the column for the evaluation result of OD maintenance rate, ">120" and ">95" indicate the following evaluation results: >120: The evaluation result of the OD maintenance rate is greater than 120%. >95: The evaluation result of the OD maintenance rate is greater than 95% and equal to or less than 120.

[0214] In Table 1, the compounds of formulae (2A) to (10A) and (1B) to (4B) are as follows.

[0215]

[0216] The following can be seen from Table 1: When the recording layer contains the compound represented by formula (1) as a color developer, it is possible to improve both high-temperature, low-humidity storage properties and high-temperature, high-humidity storage properties, and to suppress background coloration. It is also possible to improve heat resistance.

[0217] The following can be seen from Table 2: When the recording layer contains polycarbonate as the matrix resin, the light resistance of the background of the recording medium can be improved.

[0218] 10, 10A, 10B, 26, 33 Recording medium 11, 21, 31 Substrate 12, 12A, 12B, 12C, 15 Recording layer 13 Protective layer 14A, 14B Heat insulating layer 15A, 15B, 15C Microcapsules 20, 20A Laminate 22, 24 Adhesive layer 23 Intermediate layer 23A Storage section 25, 35 Overlay layer 32, 34 Bonding layer 41 Sheet 110 Printed surface 120A Back surface 120B Front surface 121 IC chip 122 Face photo 210 Display section 220 Non-display section 230 Housing 310 Storage section 320 Handle 411 Hood 412 Bumper 413 Roof 414 Trunk cover 415 Front door 416 Rear door 417 Rear bumper 510 Storage section 520 Lid 610 Recording medium with adhesive layer 620 Release sheet 611 Adhesive layer 612 Nail seal section

Claims

1. A recording medium comprising a recording layer containing a color-developing compound having electron-donating properties and a color-developing agent having electron-accepting properties, wherein the color-developing agent contains a compound represented by the following formula (1): (In the formula (1), X 1 is a divalent group containing at least one benzene ring. 11 , Y 12 , Y 13 , Y 14 are each independently a monovalent group. 11 , Z 12 are each independently a hydrogen bonding group.

2. The recording medium according to claim 1, wherein the recording layer further contains a polycarbonate resin.

3. Z in the formula (1) 11 , Z 12 The recording medium according to claim 1, wherein each of the groups independently represents a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-) or a hydrazide bond (-NHCOCONH-).

4. Z in the formula (1) 11 , Z 12 2. The recording medium according to claim 1, wherein: is a urea bond (-NHCONH-).

5. Y in the formula (1) 11 and Y 13 2. The recording medium according to claim 1, wherein: is a hydroxy group (-OH).

6. X in the above formula (1) 1 2. The recording medium according to claim 1, wherein: is a divalent group containing at least two benzene rings.

7. In the formula (1), Y 11 , Y 12 and / or a benzene ring having Y 12 , Y 13 2. The recording medium according to claim 1, wherein the benzene ring having the formula: is a weak acid.

8. X in the above formula (1) 1 2. The recording medium according to claim 1, wherein: (In the formula (3), X 21 It doesn't matter if it's there or not, X 21 If there is X 21 is a divalent group. 22 It doesn't matter if it's there or not, X 22 If there is X 22 is a divalent group. 21 is a monovalent group. n21 is an integer of 0 to 4. When n21 is an integer of 2 to 4, R 21 may be the same or different. * indicates a bond.) 9. X in the above formula (1) 1 2. The recording medium according to claim 1, wherein: (In the formula (4), R 22 is a monovalent group. n22 is an integer of 0 to 4. When n22 is an integer of 2 to 4, R 22 may be the same or different. * indicates a bond.) 10. X in the above formula (1) 1 2. The recording medium according to claim 1, wherein: (In the formula (5), X 31 It doesn't matter if it's there or not, X 31 If there is X 31 is a divalent group. 32 It doesn't matter if it's there or not, X 32 If there is X 32 is a divalent group. 33 It doesn't matter if it's there or not, X 33 If there is X 33 is a divalent group. 31 , R 32 are each independently a monovalent group. n31 and n32 are each independently an integer of 0 to 4. When n31 is an integer of 2 to 4, R 31 may be the same or different. When n32 is an integer of 2 to 4, R 32 may be the same or different. * indicates a bond.) 11. X in the above formula (1) 1 2. The recording medium according to claim 1, wherein: (In the formula (6), X 34 is a divalent group. 33 , R 34 are each independently a monovalent group. n33 and n34 are each independently an integer of 0 to 4. When n33 is an integer of 2 to 4, R 33 may be the same or different. When n34 is an integer of 2 to 4, R 34 may be the same or different. * indicates a bond.) 12. The recording medium according to claim 1, wherein a plurality of said recording layers are provided, and the color formers contained in the plurality of said recording layers are capable of exhibiting different hues in a colored state.

13. The recording medium according to claim 12, wherein the plurality of recording layers contain a light-to-heat conversion agent, and the light-to-heat conversion agent contained in each of the plurality of recording layers has a mutually different absorption wavelength peak.

14. The recording medium according to claim 1, wherein the recording layer contains a plurality of types of capsules, the plurality of types of capsules each containing the color-forming compound and the color developer, and the color-forming compounds contained in the plurality of types of capsules are capable of exhibiting different hues when in a colored state.

15. The recording medium according to claim 14, wherein the plurality of types of capsules contain a photothermal conversion agent, and the photothermal conversion agent contained in each of the plurality of types of capsules has a mutually different absorption wavelength peak.

16. A recording medium comprising a recording layer containing a color former having electron donating properties and a color developer having electron accepting properties, the color developer containing a compound represented by the following formula (a): (In the formula (a), X 0 is a divalent group containing at least one benzene ring. 01 , Y 02 Each of n01 and n02 is independently an integer of 0 to 5. When n01 is an integer of 2 to 5, Y 01 may be the same or different. When n02 is an integer of 2 to 5, Y 02 may be the same or different. 01 , Z 02 are each independently a hydrogen bonding group.

17. A card comprising the recording medium according to claim 1.

18. A booklet comprising the recording medium according to claim 1.

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