Recording media, cards and booklets

Abstract

The present invention provides a recording medium that makes it possible to suppress background coloration.　The recording medium comprises a recording layer including: an electron-donating coloring compound; an electron-accepting developer; an amine compound; at least one compound from among epoxy compounds and carbodiimide compounds; and a polycarbonate resin. The developer includes at least one compound from among compounds represented by formula (1A) and formula (1B).

Description

[Technical Field]

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

[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 a recording medium to replace 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-244355 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a bis(hydroxybenzoic acid) type compound is used as a color developer, the non-recording area (hereinafter sometimes referred to as "background") may become colored.

[0005] An object of the present disclosure is to provide a recording medium capable of suppressing coloring of the background, and a card and booklet including the same. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the first disclosure provides: a recording layer containing a color former having electron donating properties, a color developer having electron accepting properties, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, and a polycarbonate resin; The color developer is a recording medium containing at least one of the compounds represented by the following formula (1A) and formula (1B). [ka] (In formula (1A), Z1 and Z2 each independently represent Urea bond (-NHCONH-) or amide bond (-NHCO-, -OCHN-) Y1 is a divalent group. [ka] (In the formula (1B), Z3 and Z4 each independently represent Urea bond (-NHCONH-) or amide bond (-NHCO-, -OCHN-) )

[0007] The second disclosure is: a recording layer including a color former having electron donating properties, a color developer having electron accepting properties, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, and a matrix resin; The color developer is a recording medium containing at least one of the compounds represented by the following formula (1A) and formula (1B). [ka] (In formula (1A), Z1 and Z2 each independently represent Urea bond (-NHCONH-) or amide bond (-NHCO-, -OCHN-) Y1 is a divalent group. [ka] (In the formula (1B), Z3 and Z4 each independently represent Urea bond (-NHCONH-) or amide bond (-NHCO-, -OCHN-) )

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

[0009] The fourth disclosure is a booklet comprising the recording medium of the first or second disclosure. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the configuration of a recording medium according to the first embodiment. [Figure 2]FIG. 2 is a cross-sectional view showing an example of the configuration of a recording medium according to the second embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the configuration of a recording medium according to the third embodiment. [Figure 4] Fig. 4A is a plan view showing an example of the appearance of Application Example 1. Fig. 4B is a cross-sectional view taken along line IVB-IVB in Fig. 4A. [Figure 5] FIG. 5 is a perspective view showing an example of the appearance of Application Example 2. As shown in FIG. [Figure 6] Fig. 6A is a plan view illustrating an example of the appearance (front surface side) of Application Example 3. Fig. 6B is a plan view illustrating an example of the appearance (rear surface side) of Application Example 3. [Figure 7] Fig. 7A is a plan view illustrating an example of the appearance (front surface side) of Application Example 4. Fig. 7B is a plan view illustrating an example of the appearance (rear surface side) of Application Example 4. [Figure 8] Fig. 8A is a perspective view illustrating an example of the appearance (front side) of Application Example 5. Fig. 8B is a perspective view illustrating an example of the appearance (rear side) of Application Example 5. [Figure 9] Fig. 9A is a plan view illustrating an example of the appearance (first surface side) of Application Example 6. Fig. 9B is a plan view illustrating an example of the appearance (second surface side) of Application Example 6. [Figure 10] Fig. 10A is a plan view illustrating an example of the appearance (top surface side) of Application Example 7. Fig. 10B is a plan view illustrating an example of the appearance (side surface side) of Application Example 7. [Figure 11] FIG. 11 is a plan view illustrating an example of the appearance of Application Example 8. As shown in FIG. [Figure 12] FIG. 12 is a perspective view illustrating an example of the appearance of Application Example 9. As shown in FIG. [Figure 13] Fig. 13A is a plan view illustrating an example of the appearance of Application Example 10. Fig. 13B is a cross-sectional view taken along line XIIIB-XIIIB in Fig. 13A. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the present disclosure will be described in the following order: In all 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 Recording medium configuration 1.2 Recording method for recording media 1.3 Recording medium manufacturing method 1.4 Effects 2. Second embodiment (example of recording medium) 2.1 Recording medium configuration 2.2 Recording method for recording media 2.3 Effects 3. Third embodiment (example of recording medium) 3.1 Recording medium configuration 3.2 Recording method for recording media 3.3 Effects 4. Variations 5. Application Examples 6. Working Example

[0012] <1 First Embodiment> [1.1 Recording medium configuration] 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.

[0013] 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, which allows images and the like to be rewritten, or may be write-once, which allows images and the like to be written only once. From the viewpoint of anti-counterfeiting, it is preferable that the change in color state be an irreversible change.

[0014] 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. Below, the substrate 11, the recording layer 12, and the protective layer 13 will be described in order.

[0015] (base material) 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.

[0016] 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.

[0017] Examples of the constituent material of the substrate 11 include inorganic materials, metal materials, and polymeric materials. Examples of the inorganic materials include 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.

[0018] 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, it becomes possible to display clearer colors.

[0019] (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 a 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.

[0020] 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.

[0021] The recording layer 12 contains an electron-donating color former, an electron-accepting color developer, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, a photothermal conversion agent, and a matrix resin. In addition to the above materials, the recording layer 12 may also contain at least one additive selected from the group consisting of a sensitizer, an ultraviolet absorber, and the like, as needed.

[0022] (color-forming compound) The color former can develop color by reacting with a color developer. The color former is, for example, a leuco dye. When the lactone ring in the leuco dye molecule reacts with an acid, the lactone ring opens, and the leuco dye develops color. When the open lactone ring reacts with a base, the leuco dye closes and loses color. The leuco dye may be, for example, an existing dye for thermal paper.

[0023] The leuco dye is not particularly limited and can be appropriately selected depending on the purpose. Specific examples of the leuco dye include fluoran-based compounds, triphenylmethanephthalide-based compounds, azaphthalide-based compounds, phenothiazine-based compounds, leucoauramine-based compounds, and indolinophthalide-based compounds. Other examples include 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-di(n-butylamino)fluoran, 2-anilino-3-methyl-6-(Nn-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-(Nn-amyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(N-sec-butyl-N-methylamino)fluoran, 2-anilino-3-methyl-6-(Nn-amyl-N-ethylamino)fluoran, 2-anilino-3-methyl-6-( N-iso-amyl-N-ethylamino)fluoran, 2-anilino-3-methyl-6-(Nn-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-(Nn-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-Nn-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 phenyl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 2-(p-acetylanilino)-6-(Nn-amyl-Nn-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 2-amino-6-(N-propylanilino)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.

[0024] (developer) The color developer is used to cause, for example, a colorless color former to develop a color. The color developer includes a bis(hydroxybenzoic acid) type compound containing an electron-accepting group in the molecule. The bis(hydroxybenzoic acid) type compound includes at least one of the compounds represented by the following formula (1A) and formula (1B). The acidic group (hydroxybenzoic acid) of the bis(hydroxybenzoic acid) type compound reacts with the lactone ring of the color former (e.g., a leuco dye), opening the lactone ring and causing the color former to develop a color.

[0025] [ka] (In formula (1A), Z1 and Z2 each independently represent a hydrogen-bonding group, and Y1 represents a divalent group.)

[0026] [ka] (In formula (1B), Z3 and Z4 are each independently a hydrogen-bonding group.)

[0027] In formulas (1A) and (1B), the bonding positions of the hydroxy group (-OH) and the carboxyl group (-COOH) to the benzene are not limited. That is, the bonding positions of the hydroxy group and the carboxyl group to the benzene may be any of the ortho, meta, and para positions. In formulas (1A) and (1B), the bonding positions of the hydroxy group and the carboxyl group to one benzene may be the same as or different from the bonding positions of the hydroxy group and the carboxyl group to the other benzene.

[0028] In formula (1A), Z1 and Z2 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-), or a hydrazide bond (-NHCOCONH-). When Z1 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. When Z2 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.

[0029] In formula (1B), Z3 and Z4 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-), or a hydrazide bond (-NHCOCONH-). When Z3 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. When Z4 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.

[0030] Y1 may be any divalent group, and is not particularly limited. For example, it may be a hydrocarbon group which may have a substituent. Some of the carbon atoms of the hydrocarbon group (e.g., some of the carbon atoms contained in the main chain of the hydrocarbon group) may be substituted with an element such as oxygen. The hydrocarbon group is a general term for a group composed of carbon (C) and hydrogen (H), and may be a saturated or unsaturated hydrocarbon group. Here, a saturated hydrocarbon group is an aliphatic hydrocarbon group without a carbon-carbon multiple bond, and an unsaturated hydrocarbon group is an aliphatic hydrocarbon group with a carbon-carbon multiple bond (a carbon-carbon double bond or a carbon-carbon triple bond). The hydrocarbon group may be chain-like or may contain one or more rings, with a chain-like structure being preferred. The chain-like structure may be linear or branched with one or more side chains. A chain-like hydrocarbon group can lower the melting point of the color developer, thereby allowing the color developer to melt upon irradiation with laser light, facilitating the color development of the color former. From the viewpoint of lowering the melting point of the color developer, among the chain hydrocarbon groups, normal alkyl chains are particularly preferred.

[0031] The hydrocarbon group may have, 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.

[0032] When Y1 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 interacts 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.

[0033] Furthermore, when Y1 is a normal alkyl group, taking into consideration the different behavior depending on whether the carbon number is even or odd (whether the carbon number is odd or odd), the melting point of a color developer having an odd-numbered carbon atom in the normal alkyl group is generally likely to be lower than that of a color developer having an even-numbered carbon atom in the normal alkyl group. Therefore, in order to improve color development, it is preferable that the normal alkyl group has an odd number of carbon atoms. From the viewpoint of improving both high-temperature storage properties and color development properties, the normal alkyl group preferably has an odd number of carbon atoms of 7 or less, more preferably an odd number of 5 or less, and even more preferably an odd number of 3 or less.

[0034] Examples of the substituent that the hydrocarbon group may have include a halogen group (for example, a fluorine group) and an alkyl group having a halogen group (for example, a fluorine group).

[0035] More specifically, the bis(hydroxybenzoic acid) type developer may contain at least one selected from the group consisting of compounds represented by the following formulas (1-1) to (1-19).

[0036] [ka]

[0037] [ka]

[0038] (amine compounds) When the recording layer 12 contains an amine compound, the amine compound caps the acidic group (hydroxybenzoic acid) of the color developer (a bis(hydroxybenzoic acid)-type compound). This prevents the acidic group of the color developer from reacting with the color-forming compound (e.g., the lactone ring of a leuco dye), thereby suppressing background coloration. This improves the color expression of the recording medium 10. For example, if the substrate 11 is white, the white expression of the recording medium 10 can be improved.

[0039] An amine compound is a compound containing at least one amine in one molecule. When an amine compound contains two or more amines in one molecule, the two or more amines may be the same or different. The amine functions as an adsorption group. The amine may be, for example, a primary amine (-NH2), a secondary amine (-NHR), or a tertiary amine (-NRR'). The amine may have a salt structure.

[0040] The amine compound preferably has a branched structure. The branched structure of the amine compound enhances the steric hindrance effect of the amine compound when it caps the acidic group (hydroxybenzoic acid) of the developer (bis(hydroxybenzoic acid)-type compound). This prevents the acidic group of the developer from reacting with the color-forming compound (e.g., the lactone ring of a leuco dye), further suppressing background discoloration.

[0041] The branched structure may be, for example, a comb-shaped molecular structure, a star-shaped molecular structure, or a dendritic molecular structure. The amine compound may be a comb-shaped molecule having an amino group, a star-shaped molecule having an amino group, or a dendritic molecule having an amino group. The recording layer 12 may contain two or more amine compounds having different branched structures. The amine compound having a branched structure may be an amine dispersant. The amine compound may be an amine polymer. In this specification, a polymer refers to one having a number average molecular weight (Mn) of 1000 or more.

[0042] The amine compound may be a hindered amine compound, which is represented by, for example, the following formula (2): [ka] However, in formula (2), it is bonded to an atom such as a hydrogen atom or another structure at the position represented by *. The hindered amine compound may be a polymer containing the above structure in one or both of the main chain and the side chain.

[0043] The greater the content of the amine compound in the recording layer 12, the more the background coloring tends to be suppressed, but the greater the content of the amine compound in the recording layer 12, the more the reliability of the colored portion during storage at high temperature and high humidity tends to decrease. From the viewpoint of achieving both the suppression of background coloring and the suppression of a decrease in the reliability of the colored portion during storage at high temperature and high humidity, the content of the amine compound in the recording layer 12 is preferably 3 to 25 parts by mass per 100 parts by mass of the color developer, more preferably 5 to 20 parts by mass per 100 parts by mass of the color developer, even more preferably 8 to 15 parts by mass per 100 parts by mass of the color developer, and most preferably about 10 parts by mass per 100 parts by mass of the color developer.

[0044] The content of the amine compound in the recording layer 12 is measured as follows. First, the recording medium 10 is decomposed to expose the recording layer 12. Next, the exposed recording layer 12 is immersed in an organic solvent to extract the material that constitutes the recording layer 12. Methanol is particularly preferred as the organic solvent. However, if methanol is insufficient to extract the material, organic solvents such as acetone, methyl ethyl ketone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, chloroform, and acetonitrile can also be used.

[0045] The extract is then analyzed by liquid chromatography / mass spectrometry (LC / MS) to identify and quantify the components contained in the extract. If it is difficult to identify and quantify the components using LC / MS alone, organic analytical methods such as infrared spectroscopy, pyrolysis gas chromatography / mass spectrometry (GC / MS), and nuclear magnetic resonance (NMR) may be used in combination. Methanol or acetonitrile is particularly preferred as the mobile phase for LC / MS analysis, but organic solvents such as 2-propanol, ethanol, or acetone can also be used.

[0046] (epoxy compounds, carbodiimide compounds) If the recording layer 12 contains an amine compound, there is a risk that the reliability of the color-forming portion may decrease during storage at high temperature and humidity. This decrease in reliability is presumably due to the amine compound acting on the color developer bonded to the color former, which causes a neutralization reaction and dissociation between the color former and the color developer.

[0047] When the recording layer 12 contains at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound in addition to an amine compound, it is possible to prevent the deterioration of the reliability of the color-developing portion during storage at high temperature and humidity. The following four actions are presumed to be the causes of this inhibitory effect. (1) The compound reacts with moisture that has penetrated into the recording layer 12, thereby suppressing decolorization caused by moisture. (2) The compound reacts with the color former and the color developer to form a crosslinked structure, which inhibits the transfer of materials in the recording layer 12 and suppresses the dissociation of the color former and the color developer. (3) The compound reacts with the color-forming compound, stabilizing the color-forming structure. (4) The acidic groups of the color developer act as catalysts in the decolorization of the color former, and the above compounds react with the acid sites of the color developer to deactivate it, thereby suppressing decolorization.

[0048] An epoxy compound is a compound containing at least one epoxy group in one molecule. The epoxy compound may be an epoxy resin. An example of an epoxy compound is an alicyclic epoxy compound. An alicyclic epoxy compound is a compound having at least one epoxy group bonded to an alicyclic ring in one molecule. An example of an alicyclic epoxy compound is a compound containing a structure represented by the following formula (3) (wherein, in formula (3), n represents the number of repeating units). [ka]

[0049] A specific example of a compound containing a structure represented by formula (3) is 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol (manufactured by Daicel Corporation, EHPE3150).

[0050] A carbodiimide compound is a compound containing at least one carbodiimide group (-N=C=N-) in one molecule. The carbodiimide compound may be a polymer.

[0051] The lower limit of the content of at least one compound selected from the epoxy compounds and carbodiimide compounds in the recording layer 12 is preferably 10 parts by mass or more per 100 parts by mass of the color developer, more preferably 50 parts by mass or more per 100 parts by mass of the color developer, from the viewpoint of preventing a decrease in the reliability of the color-developing portion during storage at high temperature and high humidity. The upper limit of the content of at least one compound selected from the epoxy compounds and carbodiimide compounds in the recording layer 12 is preferably 150 parts by mass or less, more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less, from the viewpoint of ensuring the uniformity of the coating film when the coating material for forming the recording layer is applied.

[0052] The content of at least one compound selected from the group consisting of epoxy compounds and carbodiimide compounds in the recording layer 12 is measured in the same manner as the content of the amine compounds in the recording layer 12 described above.

[0053] (Photothermal conversion agent) The photothermal conversion agent absorbs light in a predetermined wavelength range, such as the near-infrared region, and generates heat. As the photothermal conversion agent, it is preferable to use a near-infrared absorbing dye that has an absorption peak in the wavelength range of 700 nm to 2000 nm and has almost no absorption in the visible region. Specific examples include at least one selected from the group consisting of compounds having a phthalocyanine skeleton (phthalocyanine dyes), compounds having a squarylium skeleton (squarylium dyes), and inorganic compounds.

[0054] 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 having a cyanine skeleton (cyanine dyes) with excellent light resistance and heat resistance may also be used. Here, excellent light resistance refers to the absence of decomposition under the usage environment, for example, by irradiation with fluorescent light. Excellent heat resistance refers to the absence of a change of 20% or more in the maximum absorption peak value of the absorption spectrum, for example, when 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 those having, in the molecule, at least one of a counter ion selected from SbF6, PF6, BF4, ClO4, CF3SO3, and (CF3SO3)2N, and a methine chain containing a five- or six-membered ring. Note that, although 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- or six-membered ring in the methine chain, sufficient light resistance and heat resistance are ensured as long as it has at least one of the counter ions.

[0055] (matrix resin) The matrix resin preferably functions as a binder. The matrix resin is preferably one that allows the color former, developer, amine compound, epoxy compound, carbodiimide compound, and photothermal conversion agent to be uniformly 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 resin. Here, a polycarbonate 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.

[0056] The matrix resin may contain, instead of or in addition to a 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.

[0057] (protective layer) The protective layer 13 is intended to protect the surface of the recording layer 12. The protective layer 13 contains, for example, at least one cured product selected from the group consisting of ultraviolet curable resins and thermosetting resins. The protective layer 13 may contain fine particles and the like. The thickness of the protective layer 13 is, for example, 0.1 μm or more and 20 μm or less.

[0058] [1.2 Recording method for recording media] An example of a recording method for a 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, resulting in a color reaction (color-forming reaction) between the color developer and the color former. Specifically, a bis(hydroxybenzoic acid)-type compound serving as the color developer melts, and the hydroxybenzoic acid in the bis(hydroxybenzoic acid)-type compound reacts with a lactone ring in the color former (e.g., a leuco dye), opening the lactone ring and causing the color former to develop color. This causes the laser beam-irradiated portion to develop 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.

[0059] [1.3 Recording medium manufacturing method] 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.

[0060] First, a matrix resin is dissolved in a solvent (e.g., methyl ethyl ketone). Next, a color-developing compound in a decolorized state, a color developer, at least one compound selected from epoxy compounds and carbodiimide compounds, and a photothermal conversion agent are added to and dispersed in this solution. 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 a protective layer contains, for example, at least one resin selected from the group consisting of ultraviolet-curable resins and thermosetting resins. This results in a recording medium 10 shown in FIG. 1.

[0061] [1.4 Action and Effects] The recording medium 10 according to the first embodiment has a recording layer 12 containing a color-forming compound having electron-donating properties, a color developer having electron-accepting properties, an amine-based compound, at least one compound selected from the group consisting of an epoxy-based compound and a carbodiimide-based compound, and a matrix resin.

[0062] When the recording layer 12 contains an amine compound, the amine compound caps the acidic group (hydroxybenzoic acid) of the color developer (a bis(hydroxybenzoic acid)-type compound). This prevents the acidic group of the color developer from reacting with the color former (e.g., the lactone ring of a leuco dye), thereby suppressing background coloration. This improves the color expression of the recording medium 10.

[0063] If the recording layer 12 contains an amine-based compound, there is a risk that the reliability of the color-forming portion will decrease when stored at high temperature and humidity. However, if the recording layer 12 contains an amine-based compound as well as at least one compound selected from epoxy-based compounds and carbodiimide-based compounds, the decrease in the reliability of the color-forming portion when stored at high temperature and humidity due to the amine-based compound can be suppressed.

[0064] The color developer contains at least one of the compounds represented by the above formula (1A) and formula (1B). Because the above compounds are highly acidic, they are difficult to separate once they react with the color former. Furthermore, the above compounds tend to exist in a state of solidification to some extent via hydrogen bonds, which improves the stability of the color developer in the recording layer 12. Therefore, the storage stability of the recording medium 10 can be improved. Furthermore, since the energy required to dissolve the color developer in the recording layer 12 increases, the recording medium 10 can withstand high-temperature pressing (e.g., high-temperature pressing at 150°C). Here, "withstanding high-temperature pressing" means that color changes (changes in transmittance) due to high-temperature pressing can be suppressed.

[0065] When the matrix resin contains a polycarbonate-based resin, the polycarbonate-based resin is less likely to generate acid through photodecomposition, and therefore the acid generated from the matrix resin can be prevented from reacting with the color-forming compound. This can prevent the background (unrecorded area) of the recording medium 10 from developing color. This can improve the light resistance of the background of the recording medium 10.

[0066] The compounds represented by the above formulas (1A) and (1B) have alkyl chains and benzene rings in addition to hydrogen-bonding groups within their molecules, making them highly compatible with polycarbonate-based resins. Therefore, the compounds represented by the above formulas (1A) and (1B) can be easily dispersed to particle sizes of 1 μm or less, making them difficult to see in transparent polycarbonate-based resins. This improves the transparency of the recording layer 12.

[0067] <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 with a different color hue in the colored state, is described.

[0068] [2.1 Recording medium configuration] 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.

[0069] (recording layer) The recording layers 12A, 12B, and 12C are in a decolored state in an unrecorded state (initial state). The recording layers 12A, 12B, and 12C can change from a decolored 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 recording layer 12A to a color-developing state, the laser light capable of changing recording layer 12B to a color-developing state, and the laser light capable of changing recording layer 12C to a color-developing state each have a different peak wavelength.

[0070] 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 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 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.

[0071] The recording layer 12A includes a first color-developing compound having electron-donating properties, a first color developer having electron-accepting properties, a first amine-based compound, at least one compound selected from a first epoxy-based compound and a first carbodiimide-based compound, a first photothermal conversion agent, and a first matrix resin.

[0072] The recording layer 12B includes a second color-forming compound having electron-donating properties, a second color developer having electron-accepting properties, a second amine-based compound, at least one compound selected from a second epoxy-based compound and a second carbodiimide-based compound, a second photothermal conversion agent, and a second matrix resin.

[0073] The recording layer 12C includes a third color-developing compound having electron-donating properties, a third color developer having electron-accepting properties, a third amine-based compound, at least one compound selected from a third epoxy-based compound and a third carbodiimide-based compound, a third photothermal conversion agent, and a third matrix resin.

[0074] Like the recording layer 12, the recording layers 12A, 12B, and 12C may contain, in addition to the above materials, at least one additive selected from the group consisting of a sensitizer, an ultraviolet absorber, and the like.

[0075] (First, second, and third color-forming compounds) 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, 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.

[0076] (First, second, and third developers) The first color developer is for causing the first color former compound in a decolorized state to develop a color. The second color developer is for causing the second color former compound in a decolorized state to develop a color. The third color developer is for causing the third color former compound in a decolorized state to develop a color. Examples of the first, second, and third color developers include those similar to the color developers 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 of different types.

[0077] (First, second, and third amine compounds) The first, second, and third amine compounds are the same as the matrix resin contained in the recording layer 12 of the first embodiment. The first, second, and third amine compounds may be the same in type, or may be different in type from each other.

[0078] (First, second, and third epoxy compounds) The first, second, and third epoxy compounds are the same as the epoxy compounds contained in the recording layer 12 of the first embodiment. The first, second, and third epoxy compounds may be the same type, or the first, second, and third epoxy compounds may be different types.

[0079] (First, second, and third carbodiimide compounds) The first, second, and third carbodiimide compounds are the same as the carbodiimide compounds contained in the recording layer 12 of the first embodiment. The first, second, and third carbodiimide compounds may be the same in type, or may be different in type.

[0080] (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 has an absorption wavelength peak at wavelength λ1. The second photothermal conversion agent has an absorption wavelength peak at wavelength λ2. The third photothermal conversion agent has an absorption wavelength peak at wavelength λ3. The wavelengths λ1, λ2, and λ3 are different. The absorption wavelength peaks are preferably in the near-infrared region. The near-infrared region is, for example, a wavelength range of 700 nm or more to 2000 nm or less. As described above, since the first, second, and third photothermal conversion agents have different absorption wavelength peaks, 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 photothermal conversion agents contained in the recording layer 12 of the first embodiment.

[0081] (First, second, and third matrix resins) The first, second, and third matrix resins are the same as the matrix resin contained in the recording layer 12 of the first embodiment. The first, second, and third matrix resins may be the same type, or may be different types from each other.

[0082] (middle class) 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.

[0083] 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, and starch. The intermediate layers 14A and 14B may also contain various additives, such as ultraviolet absorbers.

[0084] Alternatively, the intermediate layers 14A and 14B may 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.

[0085] The thickness of the intermediate layers 14A and 14B is preferably 3 to 100 μm, more preferably 5 to 50 μm. If the thickness of the intermediate layers 14A and 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 and 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.

[0086] [2.2 Recording method for recording media] An example of a recording method for the recording medium 10A according to the second embodiment will be described below.

[0087] The recording layer 12A develops a magenta color as follows: When a near-infrared laser beam with a peak wavelength λ1 is irradiated onto a predetermined position of the recording layer 12A, the photothermal conversion agent contained in the irradiated portion of the laser beam absorbs the near-infrared laser beam and generates heat. This heat melts the color developer, causing a color reaction (color-forming reaction) between the color developer and the color-forming compound, causing the irradiated portion to develop a magenta color.

[0088] The recording layer 12B develops a cyan color as follows: When a predetermined position on the recording layer 12B is irradiated with near-infrared laser light having a peak wavelength λ2, the portion irradiated with the laser light develops a cyan color due to the same reaction as that of the recording layer 12A described above.

[0089] The recording layer 12C develops a yellow color as follows: When a predetermined position on the recording layer 12B is irradiated with near-infrared laser light having a peak wavelength λ3, the portion irradiated with the laser light develops a yellow color due to the same reaction as that of the recording layer 12A.

[0090] As described above, predetermined positions of the recording layers 12A, 12B, and 12C develop magenta, cyan, and yellow colors, respectively, thereby forming a desired full-color image on the recording medium 10A.

[0091] [2.3 Action and 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.

[0092] 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.

[0093] <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 full-color images, 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 full-color images.

[0094] [3.1 Recording medium configuration] 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. In the third embodiment, parts that are the same as those in the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted.

[0095] (recording layer) The recording layer 15 includes three types of microcapsules 15A, 15B, and 15C and a matrix resin. The color 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 a colored state. Specifically, the microcapsule 15A can exhibit magenta in a colored state. The microcapsule 15B can exhibit cyan in a colored state. The microcapsule 15C can exhibit yellow in a 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 microcapsule 15A to a colored state, the laser light capable of changing microcapsule 15B to a colored state, and the laser light capable of changing microcapsule 15C to a colored state each have a different peak wavelength.

[0096] The microcapsules 15A each contain a first microcapsule wall, a first color-developing compound having electron-donating properties, a first color developer having electron-accepting properties, a first amine-based compound, at least one compound selected from a first epoxy-based compound and a first carbodiimide-based compound, a first photothermal conversion agent, and a first matrix resin. The first microcapsule wall encapsulates the above-mentioned various materials.

[0097] Microcapsule 15B includes a second microcapsule wall, a second color-developing compound having electron-donating properties, a second color developer having electron-accepting properties, a second amine compound, at least one compound selected from a second epoxy compound and a second carbodiimide compound, a second photothermal conversion agent, and a second matrix resin. The second microcapsule wall encapsulates the above-mentioned various materials.

[0098] Microcapsule 15C includes a third microcapsule wall, a third color former having electron donating properties, a third color developer having electron accepting properties, a third amine compound, at least one compound selected from a third epoxy compound and a third carbodiimide compound, a third photothermal conversion agent, and a third matrix resin. The third microcapsule wall encapsulates the above-mentioned various materials.

[0099] (microcapsule wall) The first, second, and third microcapsule walls are made of, for example, a light-transmitting polymer material. Specific examples of the material 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.

[0100] (First, second, and third electron donor dyes) The first, second and third electron-donating dyes are the same as those in the second embodiment.

[0101] (First, second, and third developers) The first, second and third color developers are the same as those in the second embodiment.

[0102] (First, second, and third amine compounds) The first, second and third amine compounds are the same as those in the second embodiment.

[0103] (First, second, and third epoxy compounds) The first, second, and third epoxy compounds are the same as those in the second embodiment.

[0104] (First, second, and third carbodiimide compounds) The first, second, and third carbodiimide compounds are the same as those in the second embodiment.

[0105] (First, second, and third photothermal conversion agents) The first, second and third photothermal conversion agents are the same as those in the second embodiment.

[0106] (First, second, and third matrix resins) The first, second and third matrix resins are the same as those in the second embodiment.

[0107] [3.2 Recording method for recording media] An example of a recording method for the recording medium 10B according to the third embodiment will be described below.

[0108] The recording layer 15 is colored magenta as follows: Near-infrared laser light with a peak wavelength λ1 is irradiated onto a predetermined position on the recording layer 15. 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.

[0109] The recording layer 15 is colored cyan as follows: A predetermined position on the recording layer 15 is irradiated with near-infrared laser light having a peak wavelength λ2. 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.

[0110] The recording layer 15 is colored yellow as follows: Near-infrared laser light with a peak wavelength λ3 is irradiated onto a predetermined position on the recording layer 15. 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.

[0111] As described above, predetermined positions of the recording layer 15 develop magenta, cyan, and yellow colors, respectively, thereby forming a desired full-color image on the recording medium 10B.

[0112] [3.3 Action and 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.

[0113] 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 colored state. Therefore, a desired image can be drawn in full color.

[0114] <4 Variations> (Variation 1) In the second embodiment, an example in which the intermediate layers 14A and 14B are heat insulating layers has been described, but the intermediate layers 14A and 14B may be a laminate including a heat insulating layer and an attachment layer provided on one side of the heat insulating layer, or a laminate including a heat insulating layer and attachment layers provided on both sides of the heat insulating layer. The attachment layer is, for example, an adhesive layer or a pressure-sensitive adhesive layer.

[0115] (Variation 2) In the second embodiment, an example has been 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 12 other than three and a plurality of intermediate layers 14 other than two. The plurality of recording layers 12 and the plurality of intermediate layers 14 may be stacked so that the recording layers 12 and the intermediate layers 14 are alternately positioned. The plurality of recording layers 12 may each be capable of exhibiting a different hue when colored. That is, the color-developing compounds contained in the plurality of recording layers 12 may each be capable of exhibiting a different hue when colored. The photothermal conversion agents contained in the plurality of recording layers 12 may each have a different absorption wavelength peak.

[0116] (Variation 3) In the third embodiment, an example has been 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.

[0117] (Variation 4) In the third embodiment, an example was described in which microcapsules 15A, 15B, and 15C contain a first matrix resin, a second matrix resin, and a third matrix resin, respectively, but microcapsules 15A, 15B, and 15C may not contain a matrix resin.

[0118] (Variation 5) 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.

[0119] (Variation 6) In the first, second, and third embodiments, examples have been described in which the bis(hydroxybenzoic acid) type developer contains at least one of the compounds represented by the above formulas (1A) and (1B), but the bis(hydroxybenzoic acid) type developer may also contain at least one of the compounds represented by the following formulas (1C) and (1D). Alternatively, the bis(hydroxybenzoic acid) type developer may also contain at least one of the compounds represented by formulas (1A), (1B), (1C), and (1D).

[0120] [ka] (In formula (1C), Z5 and Z6 each independently represent a hydrogen-bonding group. Y2 represents a divalent group. R1 and R2 each independently represent a divalent group.)

[0121] [ka] (In formula (1D), Z7 is a hydrogen-bonding group, and R3 and R4 are each independently a divalent group.)

[0122] In formula (1C), Z5 and Z6 are each independently, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-), or a hydrazide bond (-NHCOCONH-). When Z5 is an amide bond, the nitrogen contained in the amide bond may be bonded to R1, or the carbon contained in the amide bond may be bonded to R1. When Z6 is an amide bond, the nitrogen contained in the amide bond may be bonded to R2, or the carbon contained in the amide bond may be bonded to R2.

[0123] Z7 in formula (1D) is, for example, a urea bond (-NHCONH-), an amide bond (-NHCO-, -OCHN-) or a hydrazide bond (-NHCOCONH-).

[0124] Y2 in formula (1C) is the same as Y1 in formula (1A).

[0125] R1 and R2 in formula (1C) may be divalent groups and are not particularly limited. For example, they may be hydrocarbon groups which may have a substituent. Some of the carbon atoms in the hydrocarbon group (e.g., some of the carbon atoms in the main chain of the hydrocarbon group) may be substituted with elements such as oxygen (O), sulfur (S), or nitrogen (N). The term "hydrocarbon group" refers to a group composed of carbon (C) and hydrogen (H), and may be a saturated or unsaturated hydrocarbon group. Here, a saturated hydrocarbon group is an aliphatic hydrocarbon group without a carbon-carbon multiple bond, and an unsaturated hydrocarbon group is an aliphatic hydrocarbon group with a carbon-carbon multiple bond (a carbon-carbon double bond or a carbon-carbon triple bond). The hydrocarbon group may be linear or contain one or more rings. The linear structure may be linear or branched with one or more side chains. An example of a saturated hydrocarbon group containing one ring is a phenylene group.

[0126] When R1 and R2 have a hydrocarbon group, the hydrocarbon group may have, 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.

[0127] R3 and R4 in formula (1D) may be divalent groups and are not particularly limited. For example, they may be hydrocarbon groups which may have a substituent. Some of the carbon atoms in the hydrocarbon group (e.g., some of the carbon atoms in the main chain of the hydrocarbon group) may be substituted with elements such as oxygen (O), sulfur (S), or nitrogen (N). The term "hydrocarbon group" refers to a group composed of carbon (C) and hydrogen (H), and may be either a saturated or unsaturated hydrocarbon group. Here, a saturated hydrocarbon group is an aliphatic hydrocarbon group without a carbon-carbon multiple bond, and an unsaturated hydrocarbon group is an aliphatic hydrocarbon group with a carbon-carbon multiple bond (a carbon-carbon double bond or a carbon-carbon triple bond). The hydrocarbon group may be linear or contain one or more rings. The linear structure may be linear or branched with one or more side chains.

[0128] When R3 and R4 have a hydrocarbon group, the hydrocarbon group may have, 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.

[0129] More specifically, the bis(hydroxybenzoic acid) type developer may contain at least one selected from the group consisting of compounds represented by the following formula (1-20) and formula (1-21).

[0130] [ka]

[0131] (Other variations) The above describes the embodiments and modifications of the present disclosure in detail, but the present disclosure is not limited to the above embodiments and modifications, and various modifications based on the technical ideas of the present disclosure are possible.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] Unless otherwise specified, the materials exemplified in the above-described embodiments and modifications can be used singly or in combination of two or more.

[0136] The present disclosure may also employ the following configuration. (1) a recording layer containing a color former having electron donating properties, a color developer having electron accepting properties, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, and a polycarbonate resin; The color developer comprises at least one of compounds represented by the following formula (1A) and formula (1B): [ka] (In formula (1A), Z1 and Z2 each independently represent a hydrogen-bonding group, and Y1 represents a divalent group.) [ka] (In formula (1B), Z3 and Z4 are each independently a hydrogen-bonding group.) (2) The recording medium according to (1), wherein the amine compound has a branched structure. (3) The recording medium according to (1), wherein the amine compound is a comb-shaped molecule having an amino group. (4) The recording medium according to any one of (1) to (3), wherein the amine compound is a hindered amine compound. (5) The recording medium according to any one of (1) to (4), wherein the epoxy compound is an epoxy resin. (6) The recording medium according to any one of (1) to (5), wherein the content of the amine compound in the recording layer is 3 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the developer. (7) The recording medium according to any one of (1) to (6), wherein the content of the at least one compound in the recording layer is 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the developer. (8) The recording layer is provided in plurality, The recording medium according to any one of (1) to (7), wherein the color formers contained in the plurality of recording layers are capable of exhibiting different hues in a colored state. (9) the plurality of recording layers contain a light-to-heat conversion agent; The recording medium according to (8), wherein the light-to-heat conversion agents contained in the plurality of recording layers have different absorption wavelength peaks. (10) the recording layer includes a plurality of types of capsules, the plurality of types of capsules each contain the color former, the color developer, the amine compound, the at least one compound, and the polycarbonate resin; The recording medium according to any one of (1) to (7), wherein the color formers contained in the plurality of types of capsules are capable of exhibiting different hues in a colored state. (11) the plurality of types of capsules contain a photothermal conversion agent; The recording medium according to (10), wherein the photothermal conversion agents contained in the capsules of each of the plurality of types have different absorption wavelength peaks. (12) Further comprising a substrate; The recording medium according to any one of (1) to (11), wherein the recording layer is provided on the substrate. (13) a recording layer including a color former having electron donating properties, a color developer having electron accepting properties, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, and a matrix resin; The color developer comprises at least one of compounds represented by the following formula (1A) and formula (1B): [ka] (In formula (1A), Z1 and Z2 each independently represent a hydrogen-bonding group, and Y1 represents a divalent group.) [ka] (In formula (1B), Z3 and Z4 are each independently a hydrogen-bonding group.) (14) A card equipped with a recording medium according to any one of (1) to (13). (15) A booklet comprising a recording medium according to any one of (1) to (13).

[0137] <5 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, they can be applied to parts of clothing such as watches (wristwatches), bags, clothes, hats, glasses, and shoes as wearable devices. Furthermore, they 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, for example.

[0138] 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 to identification cards, cards, electronic devices, etc. instead of recording medium 10, 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.

[0139] (Application example 1) FIG. 4A shows the appearance of a card-type identification card. FIG. 4B is a cross-sectional view taken along line IVB-IVB in FIG. 4A. The card-type identification card is an example of a card or an identification card. The card-type identification card sequentially comprises a substrate 21, an adhesive layer 22, a recording medium 23, an adhesive layer 24, and an overlay layer 25. Here, an example in which the recording medium 23 is provided on one side of the substrate 21 will be described, but the recording medium 23 may also be provided on both sides of the substrate 21.

[0140] The substrate 21 is a supporting substrate that supports the recording medium 23. The substrate 21 is, for example, a plastic substrate. The recording medium 23 is the recording medium 10. The bonding layer 22 bonds the substrate 21 and the recording medium 23 together. The bonding layer 24 bonds the recording medium 23 and the overlay layer 25 together. The overlay layer 25 protects the recording medium 23. The overlay layer 25 covers one side of the recording medium 23.

[0141] Specific examples of card-type identification cards include a driver's license, a health insurance card, a basic resident register card, and a personal identification number card (My Number card).

[0142] (Application example 2) FIG. 5 shows the appearance of a booklet-type identification card. A booklet-type identification card is an example of a booklet. A booklet-type identification card has a plurality of sheets 31. The plurality of sheets 31 are saddle-stitched. A recording medium 10 is provided on at least one side of the sheets 31. Letters, numbers, a photograph, etc. are drawn on the recording medium 10. A specific example of a booklet-type identification card is a passport.

[0143] (Application example 3) 6A and 6B 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. 6A and 6B.

[0144] (Application example 4) 7A and 7B 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 a recording medium 10 on the front 120B and back 120A of the credit card, it becomes possible to draw on the front 120B and back 120A of the credit card, as shown in FIGS. 7A and 7B.

[0145] (Application example 5) FIG. 8A shows the external configuration of the front of a smartphone. FIG. 8B shows the external configuration of the back of the smartphone shown in FIG. 8A. 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, which allows various colors and patterns to be displayed, as shown in FIG. 8B. Note that, although a smartphone is given 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.

[0146] (Application Example 6) 9A and 9B show the exterior of a bag. This bag has, for example, a storage section 310 and a handle 320, with a recording medium 10 provided in the storage section 310. This makes it possible to display various characters, designs, etc. on the storage section 310. Also, 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 FIGS. 9A and 9B, 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.

[0147] (Application Example 7) Fig. 10A shows the appearance of the top of an automobile, and Fig. 10B shows the appearance of the side of the automobile. By attaching recording medium 10 to the body of the automobile, for example, hood 411, bumper 412, roof 413, trunk cover 414, front door 415, rear door 416, and rear bumper 417, various information and colors and patterns can be displayed on each part. Furthermore, by attaching recording medium 10 to the interior of the automobile, for example, the steering wheel or dashboard, various colors and patterns can be displayed.

[0148] (Application Example 8) FIG. 11 shows the 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. 11. The design, color pattern, or text on the lid 520 can be written using a predetermined drawing device. 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.

[0149] (Application Example 9) FIG. 12 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 was 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.

[0150] (Application Example 10) FIG. 13A shows the appearance of a nail sticker. FIG. 13B shows a cross section taken along line XIIIB-XIIIB in FIG. 13A. The nail sticker is an example of an exterior member. The nail sticker comprises a recording medium 610 with an adhesive layer and a release sheet 620. The recording medium 610 with an adhesive layer comprises a recording medium 10 and an adhesive layer 611. By providing the recording medium 10 on the recording medium 610 with an adhesive layer in this manner, it is possible to display a variety of color 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 comprise a protective layer 13 on the recording layer 12.

[0151] The recording medium 10 etc. has a plurality of nail seal parts 612 to be attached to the nails of each finger 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.

[0152] 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 the 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.

[0153] <6 Working Examples> The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0154] In the following embodiments and comparative examples, the contents of the amine-based compounds, epoxy-based compounds, and carbodiimide-based compounds in the recording layer of the completed recording medium are values ​​determined by the measurement method described in the first embodiment.

[0155] <Study on recording layer containing amine-based compound and epoxy-based compound or carbodiimide-based compound> [Examples 1 to 7] (Preparation process of coating material for forming recording layer) First, polycarbonate (PC) was dissolved in methyl ethyl ketone (MEK), and a developer was added. The mixture was dispersed using a rocking mill to obtain a solution. The compound represented by the above formula (1A) was used as the developer. Next, a leuco dye was added to the solution, and the final ratio (mass ratio) of leuco dye:developer:polycarbonate was adjusted to 1:2:4. Furthermore, a photothermal conversion agent having a phthalocyanine skeleton was added to the solution. The amount of the photothermal conversion agent was adjusted so that the absorbance of the coated film was 0.2. An amine compound and an epoxy compound were then added to the solution to prepare a coating material for forming a recording layer.

[0156] The amount of the amine compound was adjusted so that the content of the amine compound in the recording layer of the finished recording medium was 10 parts by mass per 100 parts by mass of the developer, and the amount of the epoxy compound was adjusted so that the content of the epoxy compound in the recording layer of the finished recording medium was 100 parts by mass per 100 parts by mass of the developer.

[0157] The following materials were used as the leuco dye, amine compound, and epoxy compound, as shown in Table 1. (leuco dye) Leuco dye capable of producing magenta color (amine compounds) Amine compounds having a comb-shaped molecular structure: SOLSPERSE 24000GR (Example 1), SOLSPERSE 35000 (Example 2), SOLSPERSE 71000 (Example 3), SOLSPERSE 72700 (Example 4), SOLSPERSE 76700 (Example 5), SOLSPERSE M387 (Example 6), SOLSPERSE X300 (Examples 7, 16, and 18) (all manufactured by Lubrizol Corporation) (epoxy compounds) Epoxy resin: EHPE3150 (1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol) (manufactured by Daicel Corporation, epoxy equivalent: 170-190 g / mol)

[0158] (Recording layer formation process) Next, the coating material for forming the recording layer was applied to a 50 μm thick PET film (support substrate) using a wire bar to a thickness of 5 μm, and then dried at 110°C for 5 minutes to obtain a recording layer. Next, a laser beam was irradiated onto the recording layer to form colored areas and uncolored areas (background). The output of the laser beam was adjusted so that the OD (Optical Density) during color development was 1.1. As a result, the desired recording medium was obtained.

[0159] [Examples 8 to 12] A recording medium was obtained in the same manner as in Example 1, except that the following amine compound was used. (amine compounds) DISPERBYK-145 (Example 8), DISPERBYK-161 (Example 9), DISPERBYK-166 (Example 10), DISPERBYK-2155 (Example 11), BYK-9076 (Example 12) (all manufactured by BYK Japan Co., Ltd.)

[0160] [Example 13] A recording medium was obtained in the same manner as in Example 1, except that the following amine compound was used. (amine compounds) Amine compound with a comb-shaped molecular structure: Hinoact T9100 (Kawaken Fine Chemicals Co., Ltd.)

[0161] [Example 14] A recording medium was obtained in the same manner as in Example 1, except that the following amine compound was used. (amine compounds) Hindered amine compound: Hostavin N 30 (Clariant Chemicals)

[0162] [Example 15] A recording medium was obtained in the same manner as in Example 7, except that the following carbodiimide-based compound was used instead of the epoxy-based compound. The amount of the carbodiimide-based compound was adjusted so that the content of the carbodiimide-based compound in the recording layer of the completed recording medium was 100 parts by mass per 100 parts by mass of the color developer. (Carbodiimide compounds) Carbodiimide oligomer (Nisshinbo Chemical Co., Ltd., Carbodilite V-09GB, carbodiimide equivalent weight 200 g / mol)

[0163] [Example 16] A recording medium was obtained in the same manner as in Example 7, except that the following leuco dye was used. (leuco dye) Leuco dye capable of producing a cyan color

[0164] [Example 17] A recording medium was obtained in the same manner as in Example 16, except that the following carbodiimide compound was used instead of the epoxy compound. (Carbodiimide compounds) Carbodiimide oligomer (Nisshinbo Chemical Co., Ltd., Carbodilite V-09GB, carbodiimide equivalent weight 200 g / mol)

[0165] [Example 18] A recording medium was obtained in the same manner as in Example 7, except that the following leuco dye was used. (leuco dye) Leuco dye capable of producing yellow color

[0166] [Example 19] A recording medium was obtained in the same manner as in Example 18, except that the following carbodiimide compound was used instead of the epoxy compound. (Carbodiimide compounds) Carbodiimide oligomer (Nisshinbo Chemical Co., Ltd., Carbodilite V-09GB, carbodiimide equivalent weight 200 g / mol)

[0167] [Comparative Example 1] A recording medium was obtained in the same manner as in Example 7, except that in the step of preparing the coating material for forming a recording layer, the coating material for forming a recording layer was prepared without adding an epoxy compound.

[0168] Comparative Example 2 A recording medium was obtained in the same manner as in Example 7, except that the coating material for forming a recording layer was prepared without adding an amine compound in the step of preparing the coating material for forming a recording layer.

[0169] Comparative Example 3 A recording medium was obtained in the same manner as in Example 7, except that in the step of preparing the coating material for forming a recording layer, the coating material for forming a recording layer was prepared without adding the amine compound and the epoxy compound.

[0170] Comparative Example 4 A recording medium was obtained in the same manner as in Example 16, except that in the step of preparing the coating material for forming a recording layer, the coating material for forming a recording layer was prepared without adding the amine compound and the epoxy compound.

[0171] Comparative Example 5 A recording medium was obtained in the same manner as in Example 18, except that in the step of preparing the coating material for forming a recording layer, the coating material for forming a recording layer was prepared without adding the amine compound and the epoxy compound.

[0172] [Evaluation of uncolored areas] The OD of the uncolored portions of the recording media obtained as described above was measured. Samples with an OD of 0.25 or less in the uncolored portions were rated "good," while samples with an OD change rate of more than 0.25% before and after the storage test were rated "bad." It is generally believed that an OD of more than 0.25 is a level at which the color of the color-forming dye can be discerned by anyone, so 0.25 was used as the standard value for determining whether a sample is good or bad. The evaluation results for the uncolored portions are shown in Table 1.

[0173] [Evaluation of storage stability] First, the OD of the colored portion of the recording medium obtained as described above was measured. Next, a storage test was conducted by storing the recording medium under high-temperature, high-humidity conditions of 80°C and 60% RH for 24 hours. The 80°C storage test temperature is the highest temperature used for storage tests of any component, and if good results are obtained in a storage test at this temperature, it is believed that the recording medium can withstand storage in a variety of environments. Next, the OD change rate of the colored portion before and after the storage test was calculated using the following formula. (OD change rate before and after storage test) [%] = 100 - ((OD after storage test) / (OD before storage test)) x 100)

[0174] Samples with an OD change rate of 20% or less before and after the storage test were rated "good," while samples with an OD change rate of more than 20% before and after the storage test were rated "poor." When the OD change rate before and after the storage test exceeds 20%, it is generally said that anyone can see the change from the original color, so a 20% OD change rate was set as the standard value for judging good / poor. The storage stability evaluation results are shown in Table 1.

[0175] [Table 1]

[0176] Table 1 reveals the following: By including an amine-based compound and an epoxy-based compound or a carbodiimide-based compound in the recording layer, coloring of the background can be suppressed, and a decrease in the reliability of the color-developing area during storage at high temperature and humidity can be suppressed (see Examples 1 to 19). When the recording layer contains an amine-based compound but does not contain an epoxy-based compound or a carbodiimide-based compound, coloring of the background can be suppressed, but the reliability of the color-developing area when stored at high temperature and humidity decreases (see Comparative Example 1). When the recording layer does not contain an amine compound but does contain an epoxy compound, the reliability of the colored portion does not decrease during storage at high temperature and humidity, but the background becomes colored (see Comparative Example 2). When the recording layer does not contain an amine-based compound, an epoxy-based compound, or a carbodiimide-based compound, the reliability of the color-developing area does not decrease or decreases very little when stored at high temperature and humidity, but the background becomes colored (see Comparative Examples 3 to 5).

[0177] <Study on the content of amine compounds in the recording layer> [Examples 20 to 22] As shown in Table 2, recording media were obtained in the same manner as in Example 7, except that the amount of the amine compound was adjusted so that the content of the amine compound in the recording layer of the finished recording medium was 5 parts by mass, 20 parts by mass, or 30 parts by mass per 100 parts by mass of the developer.

[0178] [Evaluation of uncolored areas] The recording medium obtained as described above was evaluated for the uncolored portion in the same manner as in the evaluation of the uncolored portion described above. The results are shown in Table 2.

[0179] [Evaluation of storage stability] The storage stability of the recording medium obtained as described above was evaluated in the same manner as in the evaluation of storage stability described above. The results are shown in Table 2.

[0180] [Table 2]

[0181] Table 2 reveals the following: The greater the content of the amine compound in the recording layer, the more the background coloration tends to be suppressed, but the greater the content of the amine compound in the recording layer, the more the reliability of the color-developed area tends to decrease when stored at high temperature and humidity. From the viewpoint of achieving both suppression of background coloration and suppression of deterioration in the reliability of the color-developing portion during storage at high temperature and high humidity, the content of the amine-based compound in the recording layer is preferably 3 to 25 parts by mass per 100 parts by mass of developer, more preferably 5 to 20 parts by mass per 100 parts by mass of developer, and even more preferably 8 to 15 parts by mass per 100 parts by mass of developer.

[0182] <Study on the content of epoxy compounds in the recording layer> [Examples 23 and 24] As shown in Table 3, a recording medium was obtained in the same manner as in Example 7, except that the amount of epoxy compound was adjusted so that the content of the epoxy compound in the recording layer of the finished recording medium was 50 parts by mass or 150 parts by mass per 100 parts by mass of developer.

[0183] [Evaluation of uncolored areas] The recording medium obtained as described above was evaluated for the uncolored portion in the same manner as in the evaluation of the uncolored portion described above. The results are shown in Table 3.

[0184] [Evaluation of storage stability] The storage stability of the recording medium obtained as described above was evaluated in the same manner as in the evaluation of storage stability described above. The results are shown in Table 3.

[0185] [Table 3]

[0186] Table 3 reveals the following: When the recording layer contains an epoxy compound, it is possible to prevent the reliability of the color-developing portion from decreasing during storage at high temperature and humidity. The content of the epoxy compound in the recording layer is preferably 10 parts by mass or more per 100 parts by mass of the developer, and more preferably 50 parts by mass or more per 100 parts by mass of the developer, from the viewpoint of preventing a decrease in the reliability of the color-developing portion during storage at high temperature and high humidity. [Explanation of symbols]

[0187] 10, 10A, 10B Recording medium 11, 21 Base material 12, 12A, 12B, 12C, 15 recording layers 13 Protective layer 14A, 14B insulation layer 15A, 15B, 15C Microcapsules 22, 24 Laminating layer 25 Overlay Layers 31 seats 110 Printing surface 120A back side 120B surface 121 IC chip 122 Face photo 210 Display section 220 Hidden part 230 cabinet 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 unit 520 Lid 610 Recording media with adhesive layer 620 Peel-off sheet 611 Adhesive layer 612 Nail seal section

Claims

1. a recording layer containing a color former having electron donating properties, a color developer having electron accepting properties, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, and a polycarbonate resin; The color developer comprises at least one of compounds represented by the following formula (1A) and formula (1B): 【Chemistry 1】 (However, in formula (1A), Z １ , Z ２ are each independently a urea bond (-NHCONH-) or an amide bond (-NHCO-, -OCHN-). １ is a divalent group. 【Chemistry 2】 (However, in formula (1B), Z ３ , Z ４ are each independently a urea bond (-NHCONH-) or an amide bond (-NHCO-, -OCHN-).

2. The recording medium according to claim 1 , wherein the amine compound has a branched structure.

3. 2. The recording medium according to claim 1, wherein the amine compound is a comb-shaped molecule having an amino group.

4. 2. The recording medium according to claim 1, wherein the amine compound is a hindered amine compound.

5. 2. The recording medium according to claim 1, wherein the epoxy compound is an epoxy resin.

6. 2. The recording medium according to claim 1, wherein the content of the amine compound in the recording layer is 3 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the developer.

7. 2. The recording medium according to claim 1, wherein the content of the at least one compound in the recording layer is 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the color developer.

8. The recording layer is provided in plurality, 2. The recording medium according to claim 1, wherein the color formers contained in the plurality of recording layers are capable of exhibiting different hues in a colored state.

9. the plurality of recording layers contain a light-to-heat conversion agent; The recording medium according to claim 8 , wherein the light-to-heat conversion agents contained in the plurality of recording layers have mutually different absorption wavelength peaks.

10. the recording layer includes a plurality of types of capsules, the plurality of types of capsules each containing the color former, the color developer, the amine compound, the at least one compound, and the polycarbonate resin; 2. The recording medium according to claim 1, wherein the color formers contained in the plurality of types of capsules are capable of exhibiting different hues when in a colored state.

11. the plurality of types of capsules contain a photothermal conversion agent; The recording medium according to claim 10 , wherein the photothermal conversion agents contained in the plurality of types of capsules have different absorption wavelength peaks.

12. Further comprising a substrate; 2. The recording medium according to claim 1, wherein the recording layer is provided on the substrate.

13. a recording layer including a color former having electron donating properties, a color developer having electron accepting properties, an amine compound, at least one compound selected from the group consisting of an epoxy compound and a carbodiimide compound, and a matrix resin; The color developer comprises at least one of compounds represented by the following formula (1A) and formula (1B): 【Transformation 3】 (However, in formula (1A), Z １ , Z ２ are each independently a urea bond (-NHCONH-) or an amide bond (-NHCO-, -OCHN-). １ is a divalent group. 【Chemistry 4】 (However, in formula (1B), Z ３ , Z ４ are each independently a urea bond (-NHCONH-) or an amide bond (-NHCO-, -OCHN-).

14. A card comprising the recording medium according to any one of claims 1 to 13.

15. A booklet comprising the recording medium according to any one of claims 1 to 13.

Images