Laser marking information recording medium

Abstract

An object of the present invention is to provide an information recording medium for laser marking, which has an adhesive layer and is excellent in resistance to moisture and heat. The laser marking information recording medium 1 of the present invention is an information recording medium in which a substrate 2, a color-developing layer 4, an intermediate layer 5, and an adhesive layer 6 are laminated in this order. The substrate 2 is a layer that transmits ultraviolet light. The intermediate layer 5 is a layer that contains a resin having a water-soluble portion and / or a crosslinking agent.

Description

Technical Field

[0001] The present invention relates to an information recording medium for laser marking.

Background Art

[0002] Laser marking is a method of printing (marking) with laser light irradiated from a printing device such as a laser marker, and is a type of printing method. Conventionally, techniques for laser marking various objects have been proposed. For example, when the object itself absorbs laser light, the surface of the object is scraped off or altered by the irradiation of the laser light. Thereby, printing can be performed by the difference between the color of the object surface and the color inside the object at the scraped-off location. Also, at the location where the object is altered, printing can be performed by the color change due to the alteration. Further, even for an object with low sensitivity to laser light, by adding an inorganic material or the like that has laser sensitivity and changes color with heat to the object, it is possible to impart or improve the printability (laser marking property) by laser light.

[0003] However, in the above method, there is a problem that the surface of the object or the material exposed on the surface is scraped by the energy of the laser light, and the surface of the object is damaged, that is, the printed portion is missing and the print quality is deteriorated. Also, there is a problem that the density of the drawn characters is low and the color development property and contrast are inferior.

[0004] On the other hand, an information recording medium has been studied in which a dye and a developer are added to a color developing layer to improve color development property and contrast, and further a surface protection layer is laminated on the color developing layer to suppress surface damage during laser marking (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, the laminated recording material of Patent Document 1 substantially requires the addition of an inorganic material or a specific copper phosphonate to enhance the sensitivity to laser light. Further, the laser marking material of Patent Document 2 requires a color former having a melting point of 200°C or higher. Thus, there has been a problem that information recording bodies capable of laser marking and having excellent color developability have only been disclosed for specific ones and have not yet been sufficiently studied.

[0007] Furthermore, even when the color developability could be improved by adding a dye, a color former, etc. to the color developing layer, on the other hand, there was a problem of print storage stability that the color density could decrease during storage due to the influence of external factors such as chemicals. In particular, when the information recording body has a configuration including an adhesive layer, as an external factor, an oil-soluble component (e.g., a monomer component of the adhesive, etc.) in the adhesive layer migrates to the color developing layer, and there has been a problem of moisture and heat resistance that the color density significantly decreases during storage, particularly during storage in a high-temperature and high-humidity environment. For this reason, there has been a problem that a laser marking information recording body having excellent moisture and heat resistance has not yet been specifically provided although it is an information recording body including an adhesive layer.

[0008] Therefore, an object of the present invention is to provide a laser marking information recording body having excellent moisture and heat resistance while being an information recording body including an adhesive layer. [Means for Solving the Problems]

[0009] As a result of intensive studies to achieve the above object, the present inventors have found that a specific information recording medium for laser marking, which is an information recording medium provided with an adhesive layer, is excellent in moisture and heat resistance. The present invention has been completed based on these findings.

[0010] That is, the present invention provides an information recording medium in which a substrate, a color developing layer, an intermediate layer, and an adhesive layer are laminated in this order, wherein the substrate is a layer that transmits ultraviolet rays, and the intermediate layer contains a resin having a water-soluble portion and / or a crosslinking agent, and provides an information recording medium for laser marking.

[0011] The color developing layer preferably contains a leuco dye and a developer.

[0012] The developer preferably contains a non-phenolic developer.

[0013] The non-phenolic developer preferably contains at least a compound represented by the following formula (1) and / or a compound represented by the following formula (2).

Chemical formula

Chemical formula

[0014] The non-phenolic developer more preferably contains at least the compound represented by the above formula (1).

[0015] The intermediate layer preferably contains a resin having a water-soluble portion and a crosslinking agent.

[0016] The resin having the water-soluble portion preferably contains, as the water-soluble portion, at least a core-shell type resin having a carboxy group.

[0017] The crosslinking agent preferably contains an epichlorohydrin resin.

[0018] A separator is preferably provided on the surface of the adhesive layer opposite to the surface on which the intermediate layer is provided.

[0019] The separator is preferably a layer that transmits ultraviolet rays.

[0020] A release layer is preferably provided on the surface of the base material opposite to the surface on which the color developing layer is provided.

[0021] The color developing portion in the color developing layer is preferably visible through the base material.

[0022] The information recording body for laser marking preferably can be colored by irradiation with ultraviolet laser light.

Advantages of the Invention

[0023] According to the information recording body for laser marking of the present invention, it is possible to provide an information recording body having an adhesive layer and excellent in resistance to wet heat for laser marking.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0025] [Information recording body for laser marking] The information recording body for laser marking of the present invention has a laminated structure in which at least a base material, a color developing layer, an intermediate layer, and an adhesive layer are laminated in this order. The above base material is a layer that transmits ultraviolet rays, and the above intermediate layer contains a resin having a water-soluble portion and / or a cross-linking agent.

[0026] The information recording body for laser marking of the present invention preferably further includes an anchor layer. The above anchor layer is a layer provided between the above base material and the above color developing layer. Also, the information recording body for laser marking of the present invention may include other layers other than the above. Examples of the above other layers include a release layer, a separator, a printing layer, an overcoat layer, a heat insulating layer, a protective layer, a light resistance improving layer, and the like.

[0027] Hereinafter, an embodiment of the information recording body for laser marking of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments.

[0028] FIG. 1 is a schematic cross-sectional view showing an embodiment of an information recording body for laser marking according to the present invention. As shown in FIG. 1, the information recording body 1 for laser marking of the present embodiment has a laminated structure in which a color developing layer 4, an intermediate layer 5, and an adhesive layer 6 are laminated in this order on a sheet-like base material 2. Here, the base material 2 is a layer that transmits ultraviolet rays, and the intermediate layer 5 contains a resin having a water-soluble portion and / or a crosslinking agent. The information recording body 1 for laser marking of the present embodiment satisfies such a configuration, and thus is an information recording body capable of laser marking. Even with a configuration including an adhesive layer, excellent moisture and heat resistance can be achieved. Specifically, since the laser light irradiated onto the base material 2 can pass through the base material 2, it is considered that the laser light can act efficiently on the color developing layer 4. And it is considered that the color developing layer 4 can absorb the above laser light and develop color by its energy. Further, since the laser light has high energy, when the color developing layer 4 absorbs the laser light, a phenomenon accompanied by some impact such as foaming, gasification, or chipping may occur. However, since the color developing layer 4 is covered and protected by the base material 2, it is considered that the impact can be contained and laser marking can be performed without causing damage. Furthermore, since the base material 2 is a layer that transmits ultraviolet rays, it is considered that the base material 2 itself can avoid damage such as a large absorption of laser light and the formation of holes. And the information recording body 1 for laser marking of the present embodiment can be used by attaching the adhesive layer 6 to the adherend surface. At this time, since the intermediate layer 5 is located between the color developing layer 4 and the adhesive layer 6 and can protect the color developing layer 4 from at least adverse effects such as a decrease in color density caused by the adhesive layer 6, the information recording body 1 for laser marking can exhibit excellent moisture and heat resistance. Also, when the adhesive layer 6 of the information recording body 1 for laser marking of the present embodiment is attached to the adherend surface, the colored portion (printed portion) in the color developing layer 4 is visually recognized through the base material 2. Therefore, the color developing layer 4 has a laminated structure protected by the base material 2. Here, since the base material is generally superior in strength to a layer (coated layer) formed by coating, the resistance to rubbing and wear can also be improved.

[0029] Figure 2 is a schematic cross-sectional view showing another embodiment of the information recording medium for laser marking of the present invention. As shown in Figure 2, the information recording medium 1 for laser marking of this embodiment has a laminated structure in which an anchor layer 3, a coloring layer 4, an intermediate layer 5, and an adhesive layer 6 are laminated in this order on a sheet-like base material 2. Here, the base material 2 is a layer that transmits ultraviolet rays, and the intermediate layer 6 contains a resin having a water-soluble portion and / or a crosslinking agent. Further, the base material 2 and the anchor layer 3, the anchor layer 3 and the coloring layer 4, the coloring layer 4 and the intermediate layer 5, and the intermediate layer 5 and the adhesive layer 6 are in direct contact with each other, respectively. By providing the anchor layer 3, the adhesion between the base material 2 and the coloring layer 4 is further improved, and delamination between layers can be suppressed, so that it can be more excellent in practicality.

[0030] (Base material) The base material 2 is a layer that transmits ultraviolet rays and can function as a support for the information recording medium 1 for laser marking and protect the coloring layer and the like. From the viewpoint of further improving the transmittance of laser light, specifically, the base material 2 is preferably a layer that transmits at least a part of ultraviolet rays in the wavelength range of 10 to 400 nm, and more preferably a layer that transmits at least a part of ultraviolet rays having a wavelength of more than 351 nm and 400 nm or less. By using such a base material 2, the transmittance of laser light can be further improved, and the laser marking suitability can be further improved. Further, the base material 2 may be a single layer or a multi-layer.

[0031] Examples of the base material 2 include resin films and the like. Examples of the resin constituting the resin film include polyethylene (low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene), polypropylene (random copolymer polypropylene, block copolymer polypropylene, homopolypropylene), polybutene, polymethylpentene, ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate (random, alternating) copolymer, ethylene-vinyl acetate copolymer (EVA), ethylene-propylene copolymer, cyclic olefin polymer, ethylene-butene copolymer, ethylene-hexene copolymer and other polyolefin resins; polyurethane; polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate (PBT) and other polyesters; polystyrene; polycarbonate; polyimide resin; polyetheretherketone; polyetherimide; polyamide such as aramid and wholly aromatic polyamide; polyphenylsulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin such as triacetyl cellulose (TAC); silicone resin; acrylic resin such as polymethyl methacrylate (PMMA); polysulfone; polyarylate; polyvinyl acetate and the like. The above resins can be used alone or in combination of two or more. The resin film may be stretched or not stretched.

[0032] The thickness of the base material 2 is not particularly limited. For example, 5 μm to 150 μm is preferable, and more preferably 10 μm to 100 μm. When the thickness is within the above range, the coatability and supportability can be more excellent.

[0033] From the perspective of further improving the physical strength, the thickness of the base material 2 may be 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, or 50 μm or more. Since the base material 2 is a layer that transmits ultraviolet rays, even if the thickness is within the above range, the laser light can act on the color developing layer 4 efficiently, and the color developability and the physical strength can be compatible.

[0034] The haze of the base material 2 is not particularly limited. However, from the perspective of further improving the visibility and / or the laser marking suitability to ensure the visibility, it is preferably 30% or less, more preferably 20% or less, still more preferably 10% or less, still more preferably 5% or less, and particularly preferably 3% or less. The above haze can be measured by a conventional method. For example, it can be determined by a method in accordance with JIS K7136:2000. When the above haze is within the above range, the transparency of the base material 2 becomes higher, so the visibility when visually recognizing the color developing portion in the color developing layer 4 through the base material 2 can be further improved. Also, when the above haze is within the above range, the transmittance of the laser light can be further improved, so the color developability can be further improved, and the damage to the base material 2 can be further suppressed, so the laser marking suitability can be further improved.

[0035] The total light transmittance of the base material 2 in the wavelength range of 300 nm to 400 nm is not particularly limited, but from the viewpoint of further improving the laser marking suitability, it is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 70% or more. The total light transmittance in the wavelength range of 300 nm to 400 nm can be measured by a conventional method, for example, it can be determined by a method conforming to JIS K7375:2008. When the total light transmittance is within the above range, the transmittance of the laser light can be further improved, so that the color developability can be further improved, and the damage of the base material 2 can be further suppressed, so that the laser marking suitability can be further improved. Further, the total light transmittance in the wavelength range exceeding 351 nm and 400 nm or less is preferably within the above range, the total light transmittance in the wavelength range exceeding 353 nm and 390 nm or less is preferably within the above range, and the total light transmittance in the wavelength range exceeding 353 nm and 360 nm or less is preferably within the above range.

[0036] (Anchor layer) The anchor layer 3 is a layer for the purpose of enhancing the adhesion between the base material 2 and the color developing layer 4. The anchor layer 3 may not be provided if not necessary, and in that case, the color developing layer 4 can be directly laminated on the base material 2. The material for forming the anchor layer 3 is not particularly limited, and for example, it can be formed using a resin. Further, the anchor layer 3 may contain other components. Examples of the above other components include surfactants, preservatives, inorganic pigments, organic pigments, viscosity modifiers, and the like.

[0037] Examples of the above resin include acrylic resins such as acrylic resin, styrene-acrylic resin, acrylic-urethane resin, acrylic-amide resin, vinyl acetate-acrylic resin; maleic acid resins such as maleic acid resin, styrene-maleic acid resin, olefin-maleic acid resin; styrene butadiene latex (SBR) resin, and the like. These resins may be modified resins modified by known methods. Further, these resins can be used alone or in combination of two or more.

[0038] As used herein, the term "acrylic resin" means a resin obtained by homopolymerizing an acrylic monomer (acrylic resin), and / or a resin obtained by copolymerizing an acrylic monomer and another monomer (a monomer other than an acrylic monomer copolymerizable with the acrylic monomer). Here, the above-mentioned other monomer may be one kind or two or more kinds. Further, when simply described as "acrylic", unless otherwise specified, it means (meth)acrylic acid (salt) and / or (meth)acrylate. Here, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid. Further, "(meth)acrylic acid (salt)" means (meth)acrylic acid and / or (meth)acrylate.

[0039] The salt in the above (meth)acrylate is not particularly limited, and examples thereof include ammonium salts such as ammonia; alkanolamine salts such as triethanolamine, diethanolamine, and monoethanolamine; alkylamine salts such as methylamine salt, ethylamine salt, diethylamine salt, and triethylamine salt; polyamine salts such as diethylenetriamine salt and diethylenetriamine salt; alkali metal salts such as lithium, sodium, and potassium; alkaline earth metal salts such as magnesium and calcium; polyvalent metal salts such as zinc and iron. These salts can be used alone or in combination of two or more.

[0040] The composition forming the above resin may be solid, emulsion, or solution. From the viewpoint of excellent handleability and coatability, it is preferably an emulsion or a solution.

[0041] The surfactant includes, for example, anionic surfactants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfate salts; nonionic surfactants such as acetylene glycol and alkylene oxide adducts of acetylene glycol, etc. These surfactants can be used alone or in combination of two or more.

[0042] The coating amount (dry mass) of the anchor layer 3 is, for example, 0.1 g / m 2 ~5.0 g / m 2 is preferable, more preferably 0.3 g / m 2 ~4.0 g / m 2 even more preferably 0.5 g / m 2 ~3.0 g / m 2 When the coating amount is within the above range, the adhesion between layers becomes more appropriate, and delamination between layers can be more effectively suppressed.

[0043] (Color-developing layer) The color-developing layer 4 is a layer that develops color by the energy of laser light and forms a recorded image on the laser marking information recording medium 1. The material for forming the color-developing layer 4 is not particularly limited, and known materials can be appropriately used. For example, from the perspective of performing printing with excellent color-developing property and contrast by laser marking, the color-developing layer 4 preferably contains at least a leuco dye and a developer. The above developer may or may not contain a non-phenol-based developer. From the perspective of environmental protection, etc., the above developer preferably contains a non-phenol-based developer.

[0044] The color-developing layer 4 may further contain other components as needed. Examples of the above other components include binders, fillers, lubricants, dispersants, cross-linking agents, preservatives, sensitizers, surfactants, viscosity modifiers, etc.

[0045] Examples of the above non-phenol-based developer include urea compounds. As the above urea compound, it has one or more sulfonic acid ester structures (-S(=O) 2N, N'- diarylurea derivatives having (-O-) are preferred. Specifically, as the above N, N'- diarylurea derivatives, it is preferable to include a compound represented by the following formula (1) and / or a compound represented by the following formula (2), and it is more preferable to include a compound represented by the following formula (1). In the present specification, the "urea compound" means a compound having one or more urea bonds (-NH-C(=O)-NH-) in the molecule, and the "N, N'- diarylurea derivative" means a compound having an N, N'- diarylurea skeleton.

[0046] [Chemical formula] (In formula (1), R 1 is a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, and a plurality of R 1 may be the same or different. A 1 is a hydrocarbon group having 1 to 4 carbon atoms, and a plurality of A 1 may be the same or different. m represents an integer of 0 to 4, and a plurality of m may be the same or different.) [Chemical formula] (Each symbol in formula (2) is the same as that in formula (1) above.)

[0047] The compound represented by the above formula (1) and / or the compound represented by the above formula (2) can react with, for example, a leuco dye described later by the energy of laser light and develop color.

[0048] In the above formula (1) and the above formula (2), R 1 is a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, and a plurality of R 1 may be the same or different. A 1 is a hydrocarbon group having 1 to 4 carbon atoms, and a plurality of A 1 may be the same or different. m represents an integer of 0 to 4, and when m is 2 or more, a plurality of m may be the same or different.

[0049] In the above formula (1), the plurality of Rs 1 -SO 3 - is directly bonded to the carbon atom constituting the benzene ring. Also, the plurality of Rs 1 -SO 3 - may have the same or different substitution positions. The substitution position of R 1 -SO 3 - is preferably at the 2-position, 3-position, or 4-position, more preferably at the 3-position.

[0050] In the above formula (2), R 1 -SO 3 - is directly bonded to the carbon atom constituting the benzene ring. The substitution position of R 1 -SO 3 - is preferably at the 2-position, 3-position, or 4-position, more preferably at the 3-position.

[0051] In the above formula (1) and the above formula (2), among the "hydrocarbon group having 1 to 12 carbon atoms which may have a substituent" of the above R 1 , examples of the "hydrocarbon group having 1 to 12 carbon atoms" include a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 3 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, and the like. Also, the plurality of "hydrocarbon groups having 1 to 12 carbon atoms which may have a substituent" may be the same or different.

[0052] Examples of the above "linear alkyl group having 1 to 12 carbon atoms, branched alkyl group having 1 to 12 carbon atoms, alicyclic alkyl group having 3 to 12 carbon atoms" include a linear alkyl group having 1 to 12 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a 2-ethylhexyl group, a lauryl group, a branched alkyl group having 1 to 12 carbon atoms, or an alicyclic alkyl group having 3 to 12 carbon atoms. These alkyl groups may further have a substituent described later.

[0053] Examples of the above-mentioned "aralkyl group having 7 to 12 carbon atoms" include unsubstituted aralkyl groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, etc. Further, these aralkyl groups may further have substituents described later. Examples of the "aralkyl group having 7 to 12 carbon atoms and having a substituent" include aralkyl groups having substituents such as p-methylbenzyl group, m-methylbenzyl group, m-ethylbenzyl group, p-ethylbenzyl group, p-i-propylbenzyl group, p-t-butylbenzyl group, p-methoxybenzyl group, m-methoxybenzyl group, o-methoxybenzyl group, m,p-di-methoxybenzyl group, p-ethoxy-m-methoxybenzyl group, p-phenylmethylbenzyl group, p-cumylbenzyl group, p-phenylbenzyl group, o-phenylbenzyl group, m-phenylbenzyl group, p-tolylbenzyl group, m-tolylbenzyl group, o-tolylbenzyl group, p-chlorobenzyl group, etc.

[0054] Examples of the above-mentioned "aryl group having 6 to 12 carbon atoms" include unsubstituted aryl groups such as phenyl group, 1-naphthyl group, 2-naphthyl group, etc. Further, these aryl groups may further have substituents described later. Examples of the "aryl group having 6 to 12 carbon atoms and having a substituent" include aryl groups having substituents such as p-tolyl group, m-tolyl group, o-tolyl group, 2,5-dimethylphenyl group, 2,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,3-dimethylphenyl group, 3,4-dimethylphenyl group, mesitylene group, p-ethylphenyl group, p-i-propylphenyl group, p-t-butylphenyl group, p-methoxyphenyl group, 3,4-dimethoxyphenyl group, p-ethoxyphenyl group, p-chlorophenyl group, t-butylated naphthyl group, etc.

[0055] The above-mentioned "substituent" is not particularly limited. Among the above-mentioned "hydrocarbon group having 1 to 12 carbon atoms which may have a substituent", when the "hydrocarbon group having 1 to 12 carbon atoms" is a "linear alkyl group having 1 to 12 carbon atoms or a branched alkyl group having 1 to 12 carbon atoms", examples of the substituent include a halogen atom, an alkoxy group, and the like. Further, among the above-mentioned "hydrocarbon group having 1 to 12 carbon atoms which may have a substituent", when the "hydrocarbon group having 1 to 12 carbon atoms" is a "cycloalkyl group having 3 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms", examples of the substituent include a halogen atom, an alkyl group, an alkoxy group, an aryl group, and the like. Among them, the substituent is preferably an alkyl group or an alkoxy group. Here, the number of carbon atoms of the alkyl group and the alkoxy group as the substituent is not particularly limited, but among them, 1 to 6 carbon atoms are preferable, and 1 to 4 carbon atoms are more preferable. The above-mentioned "substituent" may be plural or may not be present. Further, the substitution positions of the plural "substituents" may be the same substitution position or different substitution positions. The substitution position of the above-mentioned "substituent" is preferably any one of the 2-position, 3-position, or 4-position of the aralkyl group or the aryl group, and more preferably the 4-position.

[0056] In the above formula (1) and the above formula (2), the above R 1 is preferably an unsubstituted or substituted aryl group having 6 to 12 carbon atoms. More specifically, the above R 1 is preferably a phenyl group, a p-tolyl group, an m-tolyl group, an o-tolyl group, a 2,5-dimethylphenyl group, a 2,4-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2,3-dimethylphenyl group, a 3,4-dimethylphenyl group, and among them, the p-tolyl group is more preferable. When it is such an R 1 the sensitivity becomes more excellent.

[0057] In the above formula (1) and the above formula (2), the above A 1 is a carbon atom constituting the benzene ring, and can be bonded to a carbon atom to which the above R 1 -SO 3 - is not bonded. Further, a plurality of A 1The substitution positions may be the same or different even if they are the same substitution position. The above A 1 For the substitution position of the above A 1 , the 2nd, 3rd, and 4th positions are preferred.

[0058] In the above formula (1) and the above formula (2), the above m is preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and even more preferably 0.

[0059] The above A 1 Examples of the hydrocarbon group having 1 to 4 carbon atoms of the above A 1 include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, and t-butyl group.

[0060] Specific examples of the compound represented by the above formula (1) include, but are not limited to, the following compounds.

[0061] That is, as the compound represented by the above formula (1), N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(p-xylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-xylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N’-di-[3-(benzenesulfonyloxy)-5-methyl-phenyl]urea, N,N’-di-[3-(benzenesulfonyloxy)-4-propyl-phenyl]urea,

[0062] N,N'-Di-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-propylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-isopropylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-t-butylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(m-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-methoxybenzenesulfonyloxy)phenyl]urea,

[0063] N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(m-toluenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(o-toluenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N’-[3-(p-xylenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N’-[3-(mesitylenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N’-[3-(1-naphthalenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N’-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N’-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(ethanesulfonyloxy)phenyl]urea, N-[3-(Benzenesulfonyloxy)phenyl]-N'-[3-(benzenesulfonyloxy)-4-methylphenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N’-[3-(m-toluenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N’-[3-(o-toluenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N'-[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[3-(p-toluenesulfonyloxy)phenyl]-N’-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea,

[0064] N-[3-(p-Toluenesulfonyloxy)phenyl]-N'-[3-(benzylsulfonyloxy)phenyl]urea, N-[3-(p-Toluenesulfonyloxy)phenyl]-N'-[3-(p-methylbenzylsulfonyloxy)phenyl]urea, N-[3-(p-Toluenesulfonyloxy)phenyl]-N'-[3-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0065] N,N'-Di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-Di-[4-(benzenesulfonyloxy)-3-methyl-phenyl]urea, N,N'-Di-[4-(benzenesulfonyloxy)-3-ethyl-phenyl]urea, N,N'-Di-[4-(benzenesulfonyloxy)-3-propyl-phenyl]urea, N,N'-Di-[4-(benzenesulfonyloxy)-3-t-butyl-phenyl]urea,

[0066] N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(p-toluenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(o-toluenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(p-xylenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N'-[4-(mesitylenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N’-[4-(1-naphthalenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N’-[4-(2-naphthalenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N’-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N’-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N’-[4-(benzylsulfonyloxy)phenyl]urea, N-[4-(benzenesulfonyloxy)phenyl]-N’-[4-(ethanesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N’-[4-(m-toluenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N’-[4-(o-toluenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N'-[4-(p-ethylbenzenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N’-[4-(p-methoxybenzenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N’-[4-(2-naphthalenesulfonyloxy)phenyl]urea, N-[4-(p-toluenesulfonyloxy)phenyl]-N’-[4-(benzylsulfonyloxy)phenyl]urea,N-[4-(p-Toluenesulfonyloxy)phenyl]-N’-[4-(p-methylbenzylsulfonyloxy)phenyl]urea, N-[4-(p-Toluenesulfonyloxy)phenyl]-N’-[4-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0067] N,N'-Di-[4-(benzylsulfonyloxy)phenyl]urea, N,N'-Di-[4-(benzylsulfonyloxy)-3-methyl-phenyl]urea, N,N'-Di-[4-(phenylethanesulfonyloxy)phenyl]urea, N,N'-Di-[4-(phenylpropanesulfonyloxy)phenyl]urea, N,N'-Di-[4-(p-methoxybenzylsulfonyloxy)phenyl]urea,

[0068] N,N'-Di-[2-(benzenesulfonyloxy)phenyl]urea, N,N'-Di-[2-(benzenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-Di-[2-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-Di-[2-(benzenesulfonyloxy)-5-methyl-phenyl]urea, N,N'-Di-[2-(benzenesulfonyloxy)-4-propyl-phenyl]urea,

[0069] N,N'-Di-[2-(o-Toluenesulfonyloxy)phenyl]urea, N,N'-Di-[2-(m-Toluenesulfonyloxy)phenyl]urea, N,N'-Di-[2-(p-Toluenesulfonyloxy)phenyl]urea, N,N'-Di-[2-(p-Toluenesulfonyloxy)-4-methyl-phenyl]urea,

[0070] Examples include N,N'-di-[2-(p-xylenesulfonyloxy)phenyl]urea, N,N'-di-[2-(m-xylenesulfonyloxy)phenyl]urea, N,N'-di-[2-(mesitylenesulfonyloxy)phenyl]urea, and the like. Among them, as the compound represented by the above formula (1), from the viewpoint of achieving good color development by laser light and having excellent heat and humidity resistance, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea is particularly preferred.

[0071] In addition, specific examples of the compound represented by the above formula (2) include, but are not limited to, the following compounds.

[0072] That is, as the compound represented by the above formula (2), 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate, 4-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate, 2-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate, 3-[(3-phenylureido)phenyl]-2-methylbenzenesulfonate, 4-[(3-phenylureido)phenyl]-2-methylbenzenesulfonate, 2-[(3-phenylureido)phenyl]-2-methylbenzenesulfonate, 3-[(3-phenylureido)phenyl]-3-methylbenzenesulfonate, 4-[(3-phenylureido)phenyl]-3-methylbenzenesulfonate, 2-[(3-phenylureido)phenyl]-3-methylbenzenesulfonate, 3-[(3-phenylureido)phenyl]-benzenesulfonate, 4-[(3-phenylureido)phenyl]-benzenesulfonate, 2-[(3-phenylureido)phenyl]-benzenesulfonate,

[0073] 3-[3-(4-Methylphenylureido)]phenyl-4-methylbenzenesulfonate, 4-[3-(4-Methylphenylureido)]phenyl-4-methylbenzenesulfonate, 2-[3-(4-Methylphenylureido)]phenyl-4-methylbenzenesulfonate, 3-[3-(4-Methylphenylureido)]phenyl-2-methylbenzenesulfonate, 4-[3-(4-Methylphenylureido)]phenyl-2-methylbenzenesulfonate, 2-[3-(4-Methylphenylureido)]phenyl-2-methylbenzenesulfonate, 3-[3-(4-Methylphenylureido)]phenyl-3-methylbenzenesulfonate, 4-[3-(4-Methylphenylureido)]phenyl-3-methylbenzenesulfonate, 2-[3-(4-Methylphenylureido)]phenyl-3-methylbenzenesulfonate, 3-[3-(4-Methylphenylureido)]phenyl-benzenesulfonate, 4-[3-(4-Methylphenylureido)]phenyl-benzenesulfonate, 2-[3-(4-Methylphenylureido)]phenyl-benzenesulfonate,

[0074] 3-[3-(2-Methylphenylureido)]phenyl-4-methylbenzenesulfonate, 4-[3-(2-methylphenylureido)]phenyl-4-methylbenzenesulfonate, 2-[3-(2-methylphenylureido)]phenyl-4-methylbenzenesulfonate, 3-[3-(2-methylphenylureido)]phenyl-2-methylbenzenesulfonate, 4-[3-(2-methylphenylureido)]phenyl-2-methylbenzenesulfonate, 2-[3-(2-methylphenylureido)]phenyl-2-methylbenzenesulfonate, 3-[3-(2-methylphenylureido)]phenyl-3-methylbenzenesulfonate, 4-[3-(2-methylphenylureido)]phenyl-3-methylbenzenesulfonate, 2-[3-(2-methylphenylureido)]phenyl-3-methylbenzenesulfonate, 3-[3-(2-methylphenylureido)]phenyl-benzenesulfonate, 4-[3-(2-methylphenylureido)]phenyl-benzenesulfonate, 2-[3-(2-methylphenylureido)]phenyl-benzenesulfonate,

[0075] 3-[3-(3-Methylphenylureido)]phenyl-4-methylbenzenesulfonate, 4-[3-(3-methylphenylureido)]phenyl-4-methylbenzenesulfonate, 2-[3-(3-methylphenylureido)]phenyl-4-methylbenzenesulfonate, 3-[3-(3-methylphenylureido)]phenyl-2-methylbenzenesulfonate, 4-[3-(3-methylphenylureido)]phenyl-2-methylbenzenesulfonate, 2-[3-(3-methylphenylureido)]phenyl-2-methylbenzenesulfonate, 3-[3-(3-methylphenylureido)]phenyl-3-methylbenzenesulfonate, 4-[3-(3-methylphenylureido)]phenyl-3-methylbenzenesulfonate, 2-[3-(3-methylphenylureido)]phenyl-3-methylbenzenesulfonate, 3-[3-(3-methylphenylureido)]phenyl-benzenesulfonate, 4-[3-(3-methylphenylureido)]phenyl-benzenesulfonate, 2-[3-(3-methylphenylureido)]phenyl-benzenesulfonate,

[0076] 3-(3-Phenylureido)phenyl-4-propyloxybenzenesulfonate, 4-(3-phenylureido)phenyl-4-propyloxybenzenesulfonate, 2-(3-phenylureido)phenyl-4-propyloxybenzenesulfonate, 3-(3-phenylureido)phenyl-4-phenyloxybenzenesulfonate, 4-(3-phenylureido)phenyl-4-phenyloxybenzenesulfonate, 2-(3-phenylureido)phenyl-4-phenyloxybenzenesulfonate and the like can be mentioned. Among them, as the compound represented by the above formula (2), from the viewpoint that good color developability by laser light can be achieved and excellent moisture and heat resistance can also be obtained, 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate is particularly preferred.

[0077] As the color former, it may contain the compound represented by the above formula (1) alone, or may contain two or more compounds represented by the above formula (1). Similarly, as the color former, it may contain the compound represented by the above formula (2) alone, or may contain two or more compounds represented by the above formula (2). Further, the color former may contain both the compound represented by the above formula (1) and the compound represented by the above formula (2).

[0078] The color former may contain a color former other than the color formers exemplified above (other color formers) as long as the effects of the present invention are not impaired.

[0079] Examples of the other color formers include known non-phenolic color formers such as N-3-[(p-toluenesulfonyl)oxy]phenyl-N'-(p-toluenesulfonyl)-urea (trade name: PF-201), N-[2-(3-phenylureido)phenyl]-benzenesulfonamide (trade name: NKK-1304), 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone (trade name: UU), etc., and known color formers such as 4,4'-isopropylidenediphenol (BPA), 4,4'-dihydroxydiphenylsulfone (BPS), 4-allyloxy-4'-hydroxydiphenylsulfone (trade name: BPS-MAE), 4-allyloxy-4'-hydroxy-diphenylsulfone (trade name: TGSA), 4-hydroxy-4'-propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxysulfone (trade name: D-8), N-(m-tolylaminocarbonyl)-methionine, N-(m-tolylaminocarbonyl)-phenylalanine, and N-(phenylaminocarbonyl)-phenylalanine.

[0080] Furthermore, as other color developers, for example, 1,1-bis(p-hydroxyphenyl)cyclohexane, 1,1-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2'-methylenebis(4-chlorophenol), 2,2-bis(4-hydroxyphenyl)-4-methylpentane, poly(4-hydroxybenzoic acid), benzyl 4-hydroxybenzoate, 2,4-bis(phenylsulfonyl)phenol, α-{4-[(4-hydroxyphenyl)sulfonyl]phenyl}-ω-hydroxy poly(degree of polymerization n = 1 to 7)(oxyethylene oxyethylene oxy-p-phenylene sulfonyl-p-phenylene), 3,5-bis(α-methylbenzyl)salicylic acid, zinc bis[4-(n-octyloxycarbonylamino)salicylate], 4,4'-bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, 4-hydroxybenzenesulfonanilide, N-(2-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, N-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, 4-[4-[4-[4-[[4-(1-methylethoxy)phenyl]sulfonylphenoxy]butoxy]phenyl]sulfonyl]phenol, 4-tert-butylphenol·formaldehyde polycondensate, etc. may be mentioned.

[0081] The content ratio of the above color developer is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more with respect to 100% by mass of the total solid content of the color forming layer 4. When the above content ratio is 10% by mass or more, the sensitivity can be further improved. Also, the content ratio of the above color developer is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less with respect to 100% by mass of the total solid content of the color forming layer 4.

[0082] When the color developing layer 4 contains a non-phenolic color developer, the content ratio of the non-phenolic color developer is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more, based on 100% by mass of the total amount of the color developers in the color developing layer 4. It may also be 100% by mass. When the above content ratio is within the above range, the environmental load can be further suppressed. Also, the total content ratio of the compound represented by the above formula (1) and / or the compound represented by the above formula (2) is preferably within the above range based on 100% by mass of the total amount of the above color developers in the color developing layer 4.

[0083] The melting point of the above color developer is not particularly limited, but for example, it is preferably 130°C or higher, more preferably 140°C or higher, still more preferably 150°C or higher. Also, the melting point of the above color developer is preferably 195°C or lower, more preferably 185°C or lower, for example. Also, the melting point of the above non-phenolic color developer is preferably within the above range. When the above melting point is within the above range, the sensitivity to laser light can be adjusted to a more appropriate range, the laser marking property can be further improved, and the heat resistance and moisture-heat resistance can also be excellent.

[0084] The above leuco dye is not particularly limited. For example, 2'-bromo-6'-(dibutylamino)-3'-methylspiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylamino-2-methylphenyl)-4-azaphthalide, 6-(dimethylamino)-3,3-bis[4-(dimethylamino)phenyl]-1(3H)-isobenzofuranone, 1,2-dihydro-1-ethyl-8-[N-(4-methylphenyl)-N-ethylamino]-2,2,4-trimethylspiro[11H]-chromeno(2,3-g)quinoline-11,3'-phthalide, 2'-[bis(phenylmethyl)amino]-6'-(diethylamino)-spiro[isobenzofuran-1(3H),9'-(9H)xanthene]-3-one, 3-(N-isobutyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-isopentyl-N-ethyl)amino-6-methyl-7-o-chloroanilinofluoran, 3-(N-methyl-N-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethoxypropyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-n-propyl)amino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-p-toluidinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-8-methylfluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-7-chlorofluoran, 3-dibutylamino-6-methyl-7-bromofluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-dimethylamino-5-methyl-7-methylfluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, crystal violet lactone and the like can be mentioned. These leuco dyes can be used alone or in combination of two or more kinds.,

[0085] The average particle size of the above leuco dye is not particularly limited, but is preferably 0.1 μm to 1.0 μm. Generally, since the leuco dye melts and reacts, as the average particle size increases, the reaction becomes sluggish and the sensitivity characteristics decrease. On the other hand, as the average particle size decreases, the risk of unexpected color development due to heat or the like during drying of the coating solution increases. By setting the average particle size of the leuco dye within the above range, the sensitivity characteristics and color development temperature of the leuco dye can be appropriately adjusted. In this specification, the average particle size means the particle size (D50, median diameter) at the integrated value 50% in the particle size distribution measured by the laser diffraction / scattering method. The average particle size by the laser diffraction / scattering method can be measured using a laser diffraction / scattering type particle size distribution measuring device (for example, manufactured by Microtrac Bell Co., Ltd., device name: MT3300EX-II).

[0086] The content ratio of the above leuco dye is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more with respect to 100% by mass of the total solid content of the color developing layer 4. When the above content ratio is 5% by mass or more, the sensitivity can be further improved. Also, the content ratio of the above leuco dye is preferably 40% by mass or less, more preferably 30% by mass or less with respect to 100% by mass of the total solid content of the color developing layer 4.

[0087] The above binder includes, for example, acrylic resins such as acrylic resin, styrene-acrylic resin, acrylic-urethane resin, acrylic-amide resin, vinyl acetate-acrylic resin; maleic acid resins such as maleic acid resin, styrene-maleic acid resin, olefin-maleic acid resin; resins such as styrene butadiene latex (SBR) resin. These resins may be modified resins modified by known methods. Also, starch, casein, gelatin, polyamide, polyacrylamide, modified polyacrylamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl acetate, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methyl vinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinyl pyrrolidone, acrylonitrile, methyl vinyl ether, etc. may be mentioned. These binders can be used alone or in combination of two or more.

[0088] The content ratio of the above binder is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more with respect to 100% by mass of the total solid content of the color developing layer 4. Also, the content ratio of the above binder is preferably 60% by mass or less, more preferably 50% by mass or less with respect to 100% by mass of the total solid content of the color developing layer 4.

[0089] The above lubricants include, for example, hydrocarbon waxes such as paraffin, polyethylene, polystyrene; ester waxes such as carnauba wax; oils such as silicone oil, whale oil; fatty acids such as oleic acid; metal soaps such as zinc stearate. These lubricants can be used alone or in combination of two or more.

[0090] The content ratio of the above lubricant is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more with respect to 100% by mass of the total solid content of the color developing layer 4. Also, the content ratio of the above lubricant is preferably 10% by mass or less, more preferably 5% by mass or less with respect to 100% by mass of the total solid content of the color developing layer 4.

[0091] Examples of the above dispersant include anionic surfactants such as sodium dialkyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfate salts; nonionic surfactants such as acetylene glycol and alkylene oxide adducts of acetylene glycol; polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and sulfonic acid-modified polyvinyl alcohol; and polymer dispersants such as styrene-acrylic copolymers and acrylic resins. These dispersants can be used alone or in combination of two or more.

[0092] The content ratio of the above dispersant is preferably 0.1% by mass or more, more preferably 1% by mass or more, and still more preferably 5% by mass or more with respect to 100% by mass of the total solid content of the color developing layer 4. Also, the content ratio of the above dispersant is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less with respect to 100% by mass of the total solid content of the color developing layer 4.

[0093] Examples of the above filler include inorganic fillers such as aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum silicate, calcium carbonate, magnesium carbonate, barium sulfate, silica gel, activated clay, talc, clay, kaolin, calcined kaolin, diatomaceous earth, white carbon, silicon oxide, silica, colloidal silica, and titanium oxide; and organic fillers such as styrene-acrylic resin particles, polystyrene resin particles, urea-formalin resin particles, and polyolefin resin particles. These fillers can be used alone or in combination of two or more.

[0094] The content ratio of the above-mentioned filler is preferably 0.1% by mass or more, more preferably 1% by mass or more, and still more preferably 5% by mass or more with respect to 100% by mass of the total solid content of the color-forming layer 4. Further, the content ratio of the above-mentioned filler is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less with respect to 100% by mass of the total solid content of the color-forming layer 4.

[0095] Examples of the above-mentioned crosslinking agent include organic crosslinking agents such as cationic crosslinking agents and non-cationic crosslinking agents; and inorganic crosslinking agents such as zirconium carbonate. Examples of the above-mentioned cationic crosslinking agent include epichlorohydrin-based resins such as polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and polyamide polyamine epichlorohydrin resin. Examples of the above-mentioned non-cationic crosslinking agent include oxazoline-based compounds such as oxazoline group-containing polymers and oxazoline group-containing low-molecular substances. These crosslinking agents can be used alone or in combination of two or more.

[0096] The content ratio of the above-mentioned crosslinking agent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more with respect to 100% by mass of the total solid content of the color-forming layer 4. Further, the content ratio of the above-mentioned crosslinking agent is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less with respect to 100% by mass of the total solid content of the color-forming layer 4.

[0097] The color-forming layer 4 may further contain a laser sensitizer. Examples of the above-mentioned laser sensitizer include heavy metal compounds. Specifically, for example, copper compounds such as copper phosphonate; molybdenum compounds such as amine molybdate; zinc compounds such as zinc oxide and zinc borate; cerium compounds such as cerium oxide; nickel compounds such as nickel oxide, etc. In this specification, "heavy metal" means a specific gravity of 5.0 g / cm 3It means the above metal elements. Also, the color developing layer 4 may not contain the above laser sensitizer. According to the information recording body 1 for laser marking of the present embodiment, clear color development can be achieved without using a laser sensitizer, so the environmental load can be further reduced.

[0098] The content ratio of the above laser sensitizer may be 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, or 0.1% by mass or less with respect to 100% by mass of the total solid content of the color developing layer 4.

[0099] The coating amount (dry mass) of the color developing layer 4 is, for example, 0.3 g / m 2 ~10 g / m 2 is preferable, and more preferably 2.5 g / m 2 ~6.5 g / m 2 is. When the coating amount is within the above range, the color developability of the obtained information recording body 1 for laser marking can be made more appropriate.

[0100] (Intermediate layer) The intermediate layer 5 is a layer aimed at suppressing adverse effects such as external factors like chemicals from migrating to the coloring layer 4 and reducing the coloring density, and further improving the print storage property (such as moisture and heat resistance) of the laser marking information recording medium 1. From the perspective of further improving the print storage property such as moisture and heat resistance, the laser marking information recording medium 1 of the present embodiment essentially includes an intermediate layer 5 containing a resin having a water-soluble portion and / or a crosslinking agent. Here, when the intermediate layer 5 contains a resin having a water-soluble portion, the water-soluble portion can more effectively suppress the migration of oil-soluble components and the like. Also, when the intermediate layer 5 contains a crosslinking agent, since a dense crosslinked structure can be formed within the intermediate layer 5, the crosslinked structure portion can more effectively suppress the migration of oil-soluble components and the like. From the perspective of further improving the print storage property such as moisture and heat resistance, it is preferable that the intermediate layer 5 contains both a resin having a water-soluble portion and a crosslinking agent. The intermediate layer 5 may further contain other components as necessary. Examples of the other components include resins, surfactants, preservatives, inorganic pigments, organic pigments, and the like.

[0101] Examples of the resin having a water-soluble portion include, for example, a hydroxy group-containing resin such as polyvinyl alcohol (PVA) resin having a hydroxy group as the water-soluble portion; a carboxy group-containing resin such as an acrylic resin having a carboxy group as the water-soluble portion. Among them, the resin having a water-soluble portion is preferably a carboxy group-containing resin. Since the carboxy group is a highly hydrophilic functional group, it is particularly excellent in the effect of suppressing the migration of oil-soluble components to the coloring layer 4, and is considered to be able to form a crosslinked structure with the crosslinking agent described later.

[0102] The resin having a water-soluble portion is preferably a core-shell type resin. As used herein, the "core-shell type resin" means a resin having a structure in which hydrophobic core particles are coated with a water-soluble shell polymer.

[0103] Among the above core-shell type resins, the core-shell type resin having a carboxy group as the water-soluble part (core-shell type carboxy group-containing resin) is particularly preferable. Here, it is considered that the core-shell type carboxy group-containing resin contains a carboxy group in the structure of at least the water-soluble shell polymer.

[0104] Examples of the core-shell type carboxy group-containing resin include core-shell type acrylic resins such as core-shell type acrylic resins, core-shell type styrene-acrylic resins, core-shell type acrylic-urethane resins, core-shell type acrylic-amide resins, and core-shell type vinyl acetate-acrylic resins; core-shell type maleic acid resins, and the like. As the core-shell type carboxyl group-containing resin, a core-shell type acrylic resin is preferable. Among them, at least one selected from the group consisting of core-shell type acrylic resin, core-shell type styrene-acrylic resin, and core-shell type acrylic-urethane resin is more preferable, and at least one selected from the group consisting of core-shell type acrylic resin and core-shell type styrene-acrylic resin is even more preferable. Examples of the core-shell type acrylic resin include resins commercially available under the name of BARIAS (manufactured by Mitsui Chemicals, Inc.).

[0105] In addition, examples of the above resin include SBR resin.

[0106] The content ratio of the above resin is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more based on 100% by mass of the total solid content of the intermediate layer 5. Also, the content ratio of the above resin may be 99% by mass or less, or may be 95% by mass or less based on 100% by mass of the total solid content of the intermediate layer 5.

[0107] The content ratio of the resin having the above-mentioned water-soluble portion is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more, based on 100% by mass of the total amount of the resin in the intermediate layer 5. It may also be 100% by mass. When the content ratio is within the above range, the barrier property of the intermediate layer 5 can be further improved, and the print storage property such as moisture and heat resistance can be further improved. Also, the content ratio of the core-shell type resin is preferably within the above range with respect to 100% by mass of the total amount of the above resin in the intermediate layer 5.

[0108] Examples of the above crosslinking agent include organic crosslinking agents such as cationic crosslinking agents and non-cationic crosslinking agents; inorganic crosslinking agents such as zirconium carbonate. Examples of the above cationic crosslinking agent include epichlorohydrin-based resins such as polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and polyamide polyamine epichlorohydrin resin. Examples of the above non-cationic crosslinking agent include oxazoline-based compounds such as oxazoline group-containing polymers and oxazoline group-containing low molecules. The above crosslinking agent is preferably a cationic crosslinking agent, and among them, polyamide epichlorohydrin resin is more preferable. These crosslinking agents can be used alone or in combination of two or more.

[0109] The content ratio of the above crosslinking agent is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, based on 100% by mass of the total solid content of the intermediate layer 5. Also, the content ratio of the above crosslinking agent is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less, based on 100% by mass of the total solid content of the intermediate layer 5. When the content ratio is within the above range, a proper crosslinked structure can be formed, the barrier property of the intermediate layer 5 can be further improved, and the print storage property such as moisture and heat resistance can be further improved.

[0110] The coating amount (dry mass) of the intermediate layer 5 is, for example, 0.3 g / m 2 ~10 g / m 2 is preferable, and more preferably 1.0 g / m 2 ~4.0 g / m2 It is so. When the coating amount is within the above range, the barrier property of the obtained information recording body 1 for laser marking can be made more appropriate, and the print storage property such as moisture and heat resistance can be further improved.

[0111] (Adhesive layer) Since the information recording body 1 for laser marking of the present embodiment includes the adhesive layer 6, it can be suitably used, for example, for label (seal) applications. The material for forming the adhesive layer 6 is not particularly limited, and known or commonly used adhesives can be used. Further, the adhesive layer 6 may contain other components.

[0112] Examples of the above adhesive include acrylic adhesives, rubber adhesives (natural rubber-based, synthetic rubber-based, mixed systems thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, fluorine adhesives, and the like. The above adhesives can be used alone or in combination of two or more. Further, the composition for forming the above adhesive is not particularly limited, and it may be an emulsion type, a solvent type, or a solventless type.

[0113] The coating amount (dry mass) of the adhesive layer 6 is, for example, 0.3 g / m 2 ~50 g / m 2 is preferable, and more preferably 5 g / m 2 ~40 g / m 2 It is so. When the coating amount is within the above range, the adhesive force becomes a more suitable range.

[0114] (Other layers) The release layer is a layer that exhibits releasability with respect to the adhesive layer. The information recording body 1 for laser marking of the present embodiment can include the release layer so as to be in direct contact with the adhesive layer 6. Thereby, the adhesive layer 6 is protected until it is adhered, and is easily peeled off from the release layer during adhesion, so that the information recording body 1 for laser marking can be suitably used for label applications.

[0115] The release layer can be provided on the surface of the base material 2 opposite to the surface where the color developing layer 4 is provided. In this case, it is preferable that the laser marking information recording medium 1 includes an adhesive layer 6 on one end face and a release layer on the other end face. With such a configuration, for example, in the wound state, since the adhesive layer 6 contacts the release layer on the inner side of one layer, the adhesion between the laser marking information recording media 1 is suppressed. The laser marking information recording medium 1 having such a configuration can be suitably used as an adhesive label (separator-less label) that does not require a separator described later.

[0116] The material for forming the release layer is not particularly limited, and known or commonly used release agents can be used. Examples of the release agent include silicone release agents and fluorine release agents. Further, the release agent may be any of ultraviolet curable type, thermosetting type, solventless type, and solvent type. The release agent can be used alone or in combination of two or more. Further, the release layer may contain other components.

[0117] The coating amount (dry mass) of the release layer is, for example, 0.1 g / m 2 ~10 g / m 2 is preferable, and more preferably 0.2 g / m 2 ~2 g / m 2 When the coating amount is within the above range, the peelability becomes more suitable.

[0118] The separator is a layer that exhibits peelability with respect to the adhesive layer, and since it contains a core material, it is a layer that can exhibit the function as a support and the function of protecting the adhesive layer and the like. Examples of the separator include those in which the release layer is formed on the surface of a core material such as a resin film or paper. The separator is used as a protective material by being bonded to the adhesive layer 6 of the laser marking information recording medium 1. Note that the separator is peeled off when the laser marking information recording medium 1 is adhered.

[0119] The separator is preferably laminated on the surface opposite to the surface provided with the intermediate layer 5 of the adhesive layer 6 such that the release layer and the adhesive layer 6 are in direct contact. The information recording body 1 for laser marking having such a configuration can be suitably used as an adhesive label (label with separator) provided with a separator.

[0120] The separator is preferably a layer that transmits ultraviolet rays. In the case of an information recording body for laser marking having such a configuration, by irradiating the separator with laser light, color development can be caused in the color developing layer 4. Therefore, it can be suitably used as a label with a separator capable of laser printing from the separator side.

[0121] The thickness of the separator is not particularly limited, and for example, 5 μm to 150 μm is preferable, and more preferably 10 μm to 100 μm. When the thickness is within the above range, the supportability and / or protectiveness can be more excellent.

[0122] From the viewpoint of further improving the physical strength, the thickness of the separator may be 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, or 50 μm or more. When irradiating the separator with laser light, even if the thickness is within the above range, the laser light can act on the color developing layer 4 efficiently, and color developability and physical strength can be compatible.

[0123] The haze of the separator is not particularly limited, and may be 30% or less, 20% or less, 10% or less, 5% or less, or 3% or less. The haze is required in the same manner as the base material 2.

[0124] The total light transmittance of the separator in the wavelength range of 300 nm to 400 nm is not particularly limited, but it may be 40% or more, preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more. The total light transmittance is determined in the same manner as for the base material 2. Further, the total light transmittance in the wavelength range exceeding 351 nm and not exceeding 400 nm is preferably within the above range, the total light transmittance in the wavelength range exceeding 353 nm and not exceeding 390 nm is preferably within the above range, and the total light transmittance in the wavelength range exceeding 353 nm and not exceeding 360 nm is preferably within the above range.

[0125] [Laser Marking Method] The information recording body 1 for laser marking of the present embodiment can be colored by irradiation with laser light. The laser light is not particularly limited. For example, infrared laser light such as carbon dioxide laser light, YAG laser light, YVO 4 Infrared laser light such as laser light; visible light laser light such as green laser light; ultraviolet laser light such as excimer laser light, THG laser light, etc. Among them, the laser light is preferably ultraviolet laser light having a wavelength exceeding 351 nm and not exceeding 400 nm, more preferably ultraviolet laser light having a wavelength exceeding 353 nm and not exceeding 390 nm, still more preferably ultraviolet laser light having a wavelength exceeding 353 nm and not exceeding 360 nm, and particularly preferably THG laser light. When such laser light is used as a light source, better color development properties can be obtained.

[0126] The information recording body 1 for laser marking of the present embodiment is colored, for example, based on the reaction between the leuco dye contained in the color developing layer 4 and the developer. Therefore, compared with the coloring based on phenomena such as scraping, gasifying, and carbonizing the object in conventional laser marking, printing can be performed more clearly. Further, in the case of the laminated structure of the present embodiment, since the base material 2 protects the coating layer such as the color developing layer, dust generation during laser light irradiation can be suppressed, and pollution of the working environment can be further suppressed.

[0127] [Manufacturing Method of Information Recording Body for Laser Marking] The manufacturing method of the information recording medium for laser marking of the present invention is not particularly limited and can be manufactured by known or conventional methods. For example, a coating liquid for the color-developing layer is prepared by dispersing the materials contained in the color-developing layer 4 in a solvent such as water. Similarly, a coating liquid for the intermediate layer is prepared by dispersing the materials contained in the intermediate layer 5 in a solvent such as water. Next, the coating liquid for the color-developing layer is applied onto the substrate 2 and dried to form the color-developing layer 4, and then the intermediate layer 5 is formed on the color-developing layer 4 by the same procedure. Next, a known adhesive composition is applied onto the intermediate layer 5 and dried to form the adhesive layer 6, and the information recording medium 1 for laser marking shown in FIG. 1 can be obtained. Alternatively, a known adhesive composition is applied onto the release paper and dried to form the adhesive layer 6, and the intermediate layer 5 and the adhesive layer 6 are bonded together to obtain the information recording medium 1 for laser marking shown in FIG. 1.

[0128] (Preparation step) The method for preparing the coating liquid for the color-developing layer and the coating liquid for the intermediate layer is not particularly limited. For example, it can be prepared by previously dispersing all the materials in the same solvent. Also, in the preparation of the coating liquid for the color-developing layer, a dye and a developer that react with each other may be prepared as separate dispersion liquids and then mixed to obtain the coating liquid for the color-developing layer. At that time, other components may be added to either the dispersion liquid containing the dye or the dispersion liquid containing the developer, or to both. Examples of the method for preparing the coating liquid for the color-developing layer include crushing treatments using stirring, ultrasonic treatment, ball mill, bead mill, sand mill, high-pressure homogenizer, etc. These methods can be used alone or in combination of two or more.

[0129] (Coating step) The method of applying the coating liquid for the color developing layer is not particularly limited, and examples thereof include a method of directly applying it to a substrate, a method of applying it to a release liner or the like and then transferring it to a substrate. Examples of the coating method include air knife coating, bar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, gravure coating, and the like. Further, manual coating using a wire bar may also be used. These methods can be used alone or in combination of two or more. The method of applying the coating liquid for the intermediate layer is also not particularly limited, and the methods described above can be adopted.

[0130] (Drying step) The method of drying the coating liquid for the color developing layer is not particularly limited, and examples thereof include heat drying, room temperature drying, vacuum drying, and the like. These methods can be used alone or in combination of two or more. The color developing layer 4 can be formed by these methods. The method of drying the coating liquid for the intermediate layer is also not particularly limited, and the methods described above can be adopted.

[0131] When the information recording body for laser marking of the present invention includes a layer other than the substrate, the color developing layer, the intermediate layer, and the adhesive layer, the manufacturing method of the information recording body for laser marking can incorporate the above content.

[0132] As a manufacturing method of the information recording body for laser marking according to an embodiment of the present invention, it is exemplified below with reference to FIG. 2. First, a coating liquid for an anchor layer is applied onto a substrate 2 and dried to form an anchor layer 3. Then, a coating liquid for a color developing layer is applied onto the anchor layer 3 and dried to form a color developing layer 4. Next, a coating liquid for an intermediate layer is applied onto the color developing layer 4 and dried to form an intermediate layer 5. Then, a known adhesive composition is applied and dried to form an adhesive layer 6, whereby the information recording body 1 for laser marking in FIG. 2 can be obtained. Here, the method for preparing the coating liquid for the anchor layer, the coating method, and the drying method can all adopt the same methods as those exemplified in the items of the coating liquid for the color developing layer.

[0133] As another embodiment, in the laser marking information recording medium 1 of FIG. 1 or FIG. 2, a known release agent composition is applied and dried on the surface opposite to the surface on which the color developing layer 4 of the base material 2 is formed, whereby a release layer can be formed on the surface of the base material 2 (separatorless label).

[0134] As another embodiment, a separator can be produced by applying a known release agent composition to the surface of a known resin film and drying it. The separator can be laminated with the adhesive layer 6 of the laser marking information recording medium 1 of FIG. 1 or FIG. 2 (label with separator).

[0135] The method for forming each of the above layers is not particularly limited. For example, multilayer simultaneous coating may be performed using a curtain coater or the like, or individual sequential formation may be performed. Also, some layers may be simultaneously coated and some layers may be individually and sequentially formed.

Examples

[0136] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples in any way.

[0137] Example 1 (Production of Laser Marking Information Recording Medium) <Anchor layer> Using water as a solvent, a styrene acrylic resin with a solid content concentration of 38% by mass was applied and dried on the surface of a resin film (material: polypropylene, thickness: 30 μm) as a base material by a conventional method, whereby an anchor layer with a coating amount of 0.9 g / m 2 (dry mass) was formed.

[0138] <Color developing layer> As a dye, 17.4% by mass of 3-dibutylamino-6-methyl-7-anilinofluoran, as a developer, 26.8% by mass of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, as a filler, 10.0% by mass of kaolin (aqueous dispersion), as a binder, 33.1% by mass of styrene-butadiene latex (SBR), as a lubricant, 1.5% by mass of polystyrene, as a dispersant, 9.1% by mass of an acrylic resin, as a crosslinking agent, 2.0% by mass of a polyamide epichlorohydrin resin, and water as a solvent, were used to prepare a coating liquid for a color-forming layer (solid content concentration: 21% by mass) by a conventional method. The coating liquid for the color-forming layer was applied to the surface of the anchor layer by a conventional method and dried to form a color-forming layer with a coating amount of 4.5 g / m 2 (dry mass). Note that the numerical values of the above materials indicate the mass ratio of each material to 100% by mass of the color-forming layer (dry state).

[0139] <Intermediate layer> As a resin, 85.0% by mass of a core-shell type acrylic resin, as a crosslinking agent, 15.0% by mass of a polyamide epichlorohydrin resin, and water as a solvent, were used to prepare a coating liquid for an intermediate layer (solid content concentration: 18.5% by mass) by a conventional method. The coating liquid for the intermediate layer was applied to the surface of the color-forming layer by a conventional method and dried to form an intermediate layer with a coating amount of 1.9 g / m 2 (dry mass). Note that the numerical values of the above materials indicate the mass ratio of each material to 100% by mass of the intermediate layer (dry state).

[0140] <Adhesive layer> An acrylic adhesive was applied to the surface of the intermediate layer by a conventional method and dried to form an adhesive layer with a coating amount of 14 g / m 2 (dry mass). In this way, an information recording body for laser marking of Example 1 having a laminated structure of [substrate / anchor layer / color-forming layer / intermediate layer / adhesive layer] was produced.

[0141] Comparative Example 1 (Production of information recording body for laser marking) A laser marking information recording medium of Comparative Example 1 consisting of [substrate / anchor layer / coloring layer / adhesive layer] was produced in the same manner as in Example 1 except that an intermediate layer was not formed.

[0142] <Evaluation> The following evaluations were performed on the laser marking information recording media produced in the examples and comparative examples. The results are shown in Table 1.

[0143] (1) Printability with THG laser Using a UV laser printer manufactured by Keyence Corporation with the operating speed set to 1300 mm / sec, laser light was irradiated onto the surface of the substrate side of the laser marking information recording medium to perform printing. When dust generation was observed during printing or damage was confirmed by visually observing the surface of the substrate after printing, the printability with the THG laser was evaluated as "×", and when no dust generation and surface damage were confirmed, the printability with the THG laser was evaluated as "○". In this measurement, the frequency of the UV laser printer was 55 Hz and the laser power was 50%. The above UV laser printer has a laser light wavelength of 355 nm and is a printing device using a THG laser as a light source.

[0144] (2) Optical density of the colored part before and after the damp heat resistance test Using a thermal gradient plate (manufactured by Toyo Seiki Seisakusho Co., Ltd., device name: HG-100-2) set at 170 °C, a pressure of 1 kg / cm 2 , and a time of 1 second, the laser marking information recording medium was colored to achieve the maximum coloring density. The optical density of the colored part was measured with a spectrophotometer (manufactured by Videojet X-Rite Co., Ltd., device name: X-rite eXact), and the optical density at this time was defined as the optical density before the damp heat resistance test. Next, after leaving the laser marking information recording medium in an environment of 50 °C and 100% humidity for 1 day, the optical density of the colored part was measured again in the same manner, and the optical density at this time was defined as the optical density after the damp heat resistance test. The residual rate of the colored part was determined by dividing the value of the optical density after the test by the value of the optical density before the test.

[0145]

Table 1

[0146] As shown in Table 1, the information recording body for laser marking capable of irradiating a laser beam onto the color developing layer through a base material was confirmed to be excellent in printing suitability by a THG laser (UV laser printer) because printing was possible without generating dust or damaging the base material (Examples 1 and Comparative Example 1).

[0147] Also, as shown in Table 1, in the damp heat resistance test, when the intermediate layer was provided, no decrease in color density was observed (Example 1). This is presumably because the intermediate layer has a crosslinked structure derived from a resin having a water-soluble portion and a crosslinking agent, suppressing the migration of oil-soluble components in the adhesive layer to the color developing layer, and as a result, the damp heat resistance was improved. On the other hand, when the intermediate layer was not provided, a significant decrease in color density was observed (Comparative Example 1). This is presumably because the color developing layer was in direct contact with the adhesive layer, causing the migration of oil-soluble components to the color developing layer and resulting in fading of the printed portion.

[0148] Hereinafter, variations of the invention according to the present disclosure will be described. [Appendix 1] An information recording body in which a base material, a color developing layer, an intermediate layer, and an adhesive layer are laminated in this order, The base material is a layer that transmits ultraviolet rays, The intermediate layer contains a resin having a water-soluble portion and / or a crosslinking agent, an information recording body for laser marking. [Appendix 2] The information recording body for laser marking according to Appendix 1, wherein the color developing layer contains a leuco dye and a developer. [Appendix 3] The information recording body for laser marking according to Appendix 2, wherein the developer contains a non-phenolic developer. [Appendix 4] The information recording body for laser marking according to Appendix 3, wherein the non-phenolic developer contains at least the compound represented by the above formula (1) and / or the compound represented by the above formula (2). [Appendix 5] The non-phenolic color former-containing laser marking information recording medium according to Appendix 3 or 4, which contains at least the compound represented by the above formula (1). [Appendix 6] The laser marking information recording medium according to any one of Appendices 1 to 5, wherein the intermediate layer contains a resin having a water-soluble portion and a crosslinking agent. [Appendix 7] The laser marking information recording medium according to Appendix 6, wherein the resin having a water-soluble portion contains at least a core-shell type resin having a carboxy group as the water-soluble portion. [Appendix 8] The laser marking information recording medium according to Appendix 6 or 7, wherein the crosslinking agent contains an epichlorohydrin resin. [Appendix 9] The laser marking information recording medium according to any one of Appendices 1 to 8, wherein a separator is provided on the surface of the pressure-sensitive adhesive layer opposite to the surface on which the intermediate layer is provided. [Appendix 10] The laser marking information recording medium according to Appendix 9, wherein the separator is a layer that transmits ultraviolet light. [Appendix 11] The laser marking information recording medium according to any one of Appendices 1 to 10, wherein a release layer is provided on the surface of the base material opposite to the surface on which the color-forming layer is provided. [Appendix 12] The laser marking information recording medium according to any one of Appendices 1 to 11, wherein the color-forming portion in the color-forming layer is visible through the base material. [Appendix 13] The laser marking information recording medium according to any one of Appendices 1 to 12, wherein the haze of the base material is 30% or less. [Appendix 14] The laser marking information recording medium according to any one of Appendices 1 to 13, which can be colored by irradiation with ultraviolet laser light. [Appendix 15] The laser marking information recording medium according to any one of Appendices 1 to 14, wherein the base material is a resin film. [Appendix 16] The laser marking information recording medium according to any one of Appendices 1 to 15, wherein the thickness of the base material is 15 μm or more. [Appended Note 17] The base material is a laser marking information recording body according to any one of Appended Notes 1 to 16, which is located on one end face of the laser marking information recording body. [Appended Note 18] The laser marking information recording body may include a separator in direct contact with the adhesive layer on the surface opposite to the surface provided with the intermediate layer of the adhesive layer. When the laser marking information recording body includes the separator, the separator is located on the other end face of the laser marking information recording body. When the laser marking information recording body does not include the separator, the adhesive layer is located on the other end face of the laser marking information recording body. The laser marking information recording body according to Appended Note 17.

Explanation of Signs

[0149] 1 Laser marking information recording body 2 Base material 3 Anchor layer 4 Color-developing layer 5 Intermediate layer 6 Adhesive layer

Claims

1. This is an information recording material in which a base material, a color-developing layer, an intermediate layer, and an adhesive layer are laminated in this order. The aforementioned substrate is a layer that transmits ultraviolet light, The color-developing layer comprises a leuco dye and a color developer. The intermediate layer comprises a resin having a water-soluble portion and / or a crosslinking agent, and is an information recording body for laser marking.

2. The information recording body for laser marking according to claim 1, wherein the color developer comprises a non-phenolic color developer.

3. The laser marking information recorder according to claim 2, wherein the non-phenolic color developer comprises at least a compound represented by the following formula (1) and / or a compound represented by the following formula (2). 【Chemistry 1】 (In formula (1), R １ is a hydrocarbon group having 1 to 12 carbon atoms, which may have substituents, and a plurality of R １ They may be the same or different. A １ It is a hydrocarbon group having 1 to 4 carbon atoms, and multiple A １ (m may be the same or different. m represents an integer from 0 to 4, and multiple m values ​​may be the same or different.) 【Chemistry 2】 (Each symbol in formula (2) is the same as in formula (1) above.)

4. The information recording body for laser marking according to claim 3, wherein the non-phenolic color developer comprises at least a compound represented by formula (1).

5. The information recording body for laser marking according to any one of claims 1 to 4, wherein the intermediate layer comprises a resin having a water-soluble portion and a crosslinking agent.

6. The information recording body for laser marking according to claim 5, wherein the resin having the water-soluble portion includes a core-shell type resin having at least a carboxyl group as the water-soluble portion.

7. The information recording body for laser marking according to claim 5, wherein the crosslinking agent comprises an epichlorohydrin resin.

8. A separator is provided on the side of the adhesive layer opposite to the side on which the intermediate layer is provided, according to any one of claims 1 to 4.

9. The information recording body for laser marking according to claim 8, wherein the separator is a layer that transmits ultraviolet light.

10. The laser marking information recording body according to any one of claims 1 to 4, wherein a release layer is provided on the surface of the substrate opposite to the surface on which the color-developing layer is provided.

11. The colored portion in the colored layer is visible through the substrate, as described in any one of claims 1 to 4, for use as a laser marking information recording body.

12. An information recording body for laser marking according to any one of claims 1 to 4, which can produce color by irradiation with ultraviolet laser light.

Images