Laser marking information recording medium

Abstract

An object of the present invention is to provide an information recording medium for laser marking which is capable of printing with excellent color development even when marking is performed at high speed. The laser marking information recording medium 1 of the present invention is an information recording medium in which a first substrate, a color-developing layer, and a metal layer are laminated in this order. The first substrate 2 is a layer that transmits ultraviolet light.

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, at the scraped portion, printing can be performed by the difference between the color of the object surface and the color inside the object. Also, at the portion where the surface of the object is altered, printing can be performed by the color change due to the alteration. Furthermore, 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 becomes possible to impart or improve the printability (laser marking suitability) by laser light.

[0003] By the way, in various scenes such as a manufacturing site, improvement of manufacturing efficiency is strongly demanded. For this reason, as laser marking progresses toward practical use, the demand for printing a large number of objects at high speed is increasing. However, when performing laser marking at high speed, there has been a problem that the energy of the laser light does not sufficiently act on the object, the density of the drawn characters becomes thin, and the color development property deteriorates.

[0004] On the other hand, a laser marking label provided with a reflective layer capable of reflecting laser light on the back side of a photosensitizing layer containing a photosensitizing ink has been proposed (see, for example, Patent Document 1). With such a configuration, when laser light is irradiated from the front side of the photosensitizing layer, the laser light that has not been able to act on the photosensitizing layer and has passed through is reflected by the reflective layer and can act on the photosensitizing layer. Therefore, since the laser light can act on the photosensitizing layer more efficiently, laser marking at a higher speed becomes possible.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, in the laser marking label of the above Patent Document 1, a photosensitizing ink mainly containing an inorganic material such as kaolin reacts with laser light to form voids, thereby performing marking. However, in such a marking method, since marking is performed using the shadow due to the voids, there is a problem that the color development property is insufficient. For this reason, there has been a problem that a laser marking information recording medium capable of printing with excellent color development even when marking is performed at high speed has not yet been specifically provided.

[0007] The present invention has been conceived under such circumstances, and an object thereof is to provide a laser marking information recording medium capable of printing with excellent color development even when marking is performed at high speed.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the present inventors have found that by adopting a laminated structure in which a color developing layer is sandwiched between a first base material and a metal layer, it is possible to perform printing with excellent color development even when marking is performed at high speed. The present invention has been completed based on these findings.

[0009] That is, the present invention provides an information recording medium in which a first base material, a color developing layer, and a metal layer are laminated in this order, wherein the first base material is a layer that transmits ultraviolet rays, for a laser marking information recording medium.

[0010] The coloring layer preferably contains a leuco dye and a developer.

[0011] The developer preferably contains a non-phenolic developer.

[0012] 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

[0013] The non-phenolic developer more preferably contains at least the compound represented by formula (1) above.

[0014] The coloring part in the coloring layer is preferably visible through the first base material.

[0015] The information recording body for laser marking preferably can be colored by irradiation with ultraviolet laser light.

[0016] The metal layer preferably contains aluminum and / or aluminum oxide.

[0017] The 60° glossiness of the metal layer is preferably 200% or more.

[0018] The total reflectance of the metal layer is preferably 30% or more.

Advantages of the Invention

[0019] According to the information recording body for laser marking of the present invention, printing can be performed with excellent coloring properties even when marking is performed at high speed.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0021] [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 first base material, a coloring layer, and a metal layer are laminated in this order. The first base material is a layer that transmits ultraviolet rays.

[0022] The information recording medium for laser marking of the present invention preferably further includes an anchor layer. The above anchor layer is a layer provided between the above first base material and the above color developing layer. Further, the information recording medium for laser marking of the present invention preferably further includes an intermediate layer. The above intermediate layer is a layer provided between the above color developing layer and the above metal layer. Further, the information recording medium for laser marking of the present invention preferably further includes a laminate layer. The above laminate layer is a layer provided between the above color developing layer and the above metal layer when there is no intermediate layer, and is a layer provided between the above intermediate layer and the above metal layer when there is an intermediate layer. Further, the information recording medium for laser marking of the present invention preferably further includes a second base material. The above second base material is a layer provided on the surface of the above metal layer opposite to the surface on which the above color developing layer is provided. Further, the information recording medium for laser marking of the present invention may include other layers other than the above. Examples of the above other layers include a printing layer, an overcoat layer, a heat insulating layer, a protective layer, a light resistance improving layer, an adhesive layer, a release layer, a separator, and the like.

[0023] Hereinafter, an embodiment of the information recording medium 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.

[0024] FIG. 1 is a schematic cross-sectional view showing an embodiment of the information recording medium for laser marking of the present invention. As shown in FIG. 1, in the information recording medium 1 for laser marking of the present embodiment, a color developing layer 4 and a metal layer 7 are laminated in this order on a sheet-like first base material 2, so that the color developing layer 4 is sandwiched between the first base material 2 and the metal layer 7 to have a laminated structure. Further, at least the first base material 2 is a layer that transmits ultraviolet rays. For example, since the laser light irradiated onto the first base material 2 can pass through the first base material 2, it is considered that the laser light can act on the color developing layer 4 efficiently. And it is considered that the color developing layer 4 can absorb the above laser light and exhibit color development by its energy. Furthermore, a part of the above laser light passes through without acting on the color developing layer 4, but is reflected by the metal layer 7 and returns to the color developing layer 4 to act. Therefore, it is considered that good color development can be achieved even when marking is performed at high speed. Also, since laser light generally has high energy, when the color developing layer 4 absorbs the laser light, a phenomenon accompanied by some impact such as foaming, gasification, or shaving may occur. However, since the color developing layer 4 is sandwiched and protected by the first base material 2 and the metal layer 7, it is considered that laser marking can be performed without causing damage. Furthermore, since the first base material 2 is a layer that transmits ultraviolet rays, it is considered that the first base material 2 itself absorbs a lot of laser light and damage such as holes being opened can be avoided.

[0025] FIG. 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 FIG. 2, the information recording medium 1 for laser marking of the present embodiment has a laminated structure in which an anchor layer 3, a color developing layer 4, an intermediate layer 5, a laminate layer 6, a metal layer 7, and a second substrate 8 are laminated in this order on a sheet-like first substrate 2. Here, the first substrate 2 is a layer that transmits ultraviolet rays. Further, the first substrate 2 and the anchor layer 3, the anchor layer 3 and the color developing layer 4, the color developing layer 4 and the intermediate layer 5, the intermediate layer 5 and the laminate layer 6, the laminate layer 6 and the metal layer 7, and the metal layer 7 and the second substrate 8 are in direct contact with each other. In this specification, a laminate including the first substrate 2, the anchor layer 3, the color developing layer 4, the intermediate layer 5, and the laminate layer 6 may be referred to as a "first laminate", and a laminate including the metal layer 7 and the second substrate 8 may be referred to as a "second laminate".

[0026] (First Substrate) The first substrate 2 is a layer that transmits ultraviolet rays and can function as a support of the information recording medium 1 for laser marking or a layer that protects the color developing layer and the like. From the viewpoint of further improving the transparency of the laser beam, specifically, the first substrate 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 with a wavelength exceeding 351 nm and not exceeding 400 nm. By using such a first substrate 2, the transparency of the laser beam can be further improved, and the laser marking suitability can be further improved. Further, the first substrate 2 may be a single layer or a multilayer.

[0027] Examples of the first substrate 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; polyether ether ketone; polyether imide; polyamide such as aramid and wholly aromatic polyamide; polyphenyl sulfide; 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.

[0028] The thickness of the first substrate 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.

[0029] The thickness of the first substrate 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 from the viewpoint of further improving the physical strength. Since the first substrate 2 is a layer that transmits ultraviolet rays, even if the thickness is within the above range, the laser light can act on the coloring layer 4 efficiently, and both color developability and physical strength can be achieved.

[0030] The haze of the first substrate 2 is not particularly limited, but from the viewpoint of further improving transparency and / or laser marking suitability, 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, by a method based on JIS K7136:2000. When the above haze is within the above range, the transparency of the first substrate 2 becomes higher, so the visibility when visually recognizing the colored portion in the coloring layer 4 through the first substrate 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 first substrate 2 can be further suppressed, so the laser marking suitability can be further improved.

[0031] The total light transmittance of the first substrate 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 in accordance with 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 development property can be further improved and the damage of the first substrate 2 can be further suppressed, and thus 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.

[0032] (Anchor layer) The anchor layer 3 is a layer for the purpose of enhancing the adhesion between the first substrate 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 first substrate 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 other components include surfactants, preservatives, inorganic pigments, organic pigments, viscosity modifiers, and the like.

[0033] Examples of the 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.

[0034] As used herein, the "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 salt.

[0035] 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 diethyleneamine 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.

[0036] The composition for 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.

[0037] The above 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. These surfactants can be used alone or in combination of two or more.

[0038] As the coating amount (dry mass) of the anchor layer 3, 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 and 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.

[0039] (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 compatibility, etc., the above developer preferably contains a non-phenol-based developer.

[0040] The color-developing layer 4 may further contain other components as needed. Examples of the above other components include a binder, a filler, a lubricant, a dispersant, a crosslinking agent, a preservative, a sensitizer, a surfactant, a viscosity modifier, etc.

[0041] 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 the compounds represented by the following formula (1) and / or the compounds represented by the following formula (2), and it is more preferable to include the compounds represented by the following formula (1). In this 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.

[0042] [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.)

[0043] The compounds represented by the above formula (1) and / or the compounds 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.

[0044] 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.

[0045] In the above formula (1), a plurality of Rs 1 -SO 3 - is directly bonded to a carbon atom constituting the benzene ring. Also, a plurality of Rs 1 -SO 3 - may have the same or different substitution positions. R 1 -SO 3 - preferably has a substitution position at the 2nd, 3rd, or 4th position, more preferably at the 3rd position.

[0046] In the above formula (2), R 1 -SO 3 - is directly bonded to a carbon atom constituting the benzene ring. R 1 -SO 3 - preferably has a substitution position at the 2nd, 3rd, or 4th position, more preferably at the 3rd position.

[0047] 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, a plurality of "hydrocarbon groups having 1 to 12 carbon atoms which may have a substituent" may be the same or different.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 The substitution positions of are preferably the 2nd, 3rd, and 4th positions.

[0054] 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.

[0055] The above A 1 Examples of the hydrocarbon group having 1 to 4 carbon atoms of include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, and t-butyl group.

[0056] Specific examples of the compound represented by the above formula (1) include, but are not limited to, the following compounds.

[0057] 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,

[0058] 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,

[0059] 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,

[0060] 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,

[0061] 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,

[0062] 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,

[0063] 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,

[0064] 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,

[0065] 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,

[0066] 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 can be mentioned. Among them, as the compound represented by the above formula (1), from the viewpoint that good color developability by laser light can be achieved and excellent moisture and heat resistance can also be obtained, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea is particularly preferable.

[0067] Further, as specific compounds of the compound represented by the above formula (2), for example, the following compounds can be mentioned, but it is not limited to these compounds.

[0068] 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,

[0069] 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,

[0070] 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,

[0071] 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,

[0072] 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 heat and humidity resistance can also be obtained, 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate is particularly preferable.

[0073] 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).

[0074] The color former may contain a color former other than the color formers exemplified above (other color formers) within a range that does not impair the effects of the present invention.

[0075] 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.

[0076] 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, bis[zinc 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.

[0077] The content ratio of the above color developer is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, based on 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, still more preferably 40% by mass or less, based on 100% by mass of the total solid content of the color forming layer 4.

[0078] 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. Also, it may 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.

[0079] The melting point of the above color developer is not particularly limited. 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 suitability can be further improved, and the heat resistance and humidity heat resistance can also be excellent.

[0080] 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.,

[0081] The average particle size of the above-mentioned 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 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 of 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).

[0082] The content ratio of the above-mentioned 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-mentioned 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.

[0083] 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 included are 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. These binders can be used alone or in combination of two or more.

[0084] 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, based on 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, based on 100% by mass of the total solid content of the color developing layer 4.

[0085] 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.

[0086] 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 forming 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 forming layer 4.

[0087] 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 completely 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.

[0088] 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 forming 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 forming layer 4.

[0089] 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.

[0090] 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, based on 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, based on 100% by mass of the total solid content of the color-forming layer 4.

[0091] Examples of the above-mentioned 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-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.

[0092] 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, based on 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, based on 100% by mass of the total solid content of the color-forming layer 4.

[0093] 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. In this specification, "heavy metal" refers to 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, since distinct color development can be achieved without using a laser sensitizer, the environmental load can be further reduced.

[0094] 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.

[0095] 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 When the coating amount is within the above range, the color - developing property of the obtained information recording body 1 for laser marking can be made more appropriate.

[0096] (Intermediate layer) The intermediate layer 5 is a layer whose purpose is to further improve the print storage property (such as moisture - and heat - resistance) of the information recording body 1 for laser marking by suppressing the adverse effect that external factors such as chemicals migrate to the color - developing layer 4 and the color - developing density decreases. Among them, when the information recording body 1 for laser marking of the present embodiment includes the laminate layer 6, the metal layer 7, and the second base material 8, due to the migration of oil - soluble components and the like in the laminate layer 6, the metal layer 7, and the second base material 8 to the color - developing layer 4, problems such as the decrease in color - developing density during storage, especially during storage in a high - temperature and high - humidity environment, may occur in terms of print storage properties such as moisture - and heat - resistance. In such a case, by providing the intermediate layer 5 between the color - developing layer 4 and the laminate layer 6, it has the function of suppressing the migration of the above - mentioned oil - soluble components and the like to the color - developing layer 4 and improving the print storage properties such as the above - mentioned moisture - and heat - resistance.

[0097] The information recording medium 1 for laser marking according to this embodiment may or may not include an intermediate layer 5. From the viewpoint of further improving the print retention property, it is preferable to include the intermediate layer 5. The intermediate layer 5 can be mainly formed of a resin. The resin is not particularly limited, but preferably includes a resin having a water-soluble portion. The intermediate layer 5 may further contain other components as necessary. Examples of the other components include a crosslinking agent, a surfactant, a preservative, an inorganic pigment, an organic pigment, and the like. Among them, the intermediate layer 5 preferably contains a crosslinking agent. When the intermediate layer 5 contains a resin having a water-soluble portion, the water-soluble portion can more effectively suppress the migration of the oil-soluble component and the like. Further, when the intermediate layer 5 contains a crosslinking agent, a dense crosslinked structure can be formed in the intermediate layer 5, so that the crosslinked structure portion can more effectively suppress the migration of the oil-soluble component and the like.

[0098] Examples of the resin having a water-soluble portion include 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 the oil-soluble component to the color developing layer 4, and is considered to be able to form a crosslinked structure with the crosslinking agent described later.

[0099] 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.

[0100] Among the core-shell type resins, a core-shell type resin having a carboxy group as the water-soluble portion (core-shell type carboxy group-containing resin) is preferable. Here, it is considered that the core-shell type carboxy group-containing resin contains a carboxy group in at least the structure of the water-soluble shell polymer.

[0101] Examples of the core-shell type carboxyl 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; and core-shell type maleic acid resins. Among them, core-shell type acrylic resins are preferred, and at least one selected from the group consisting of core-shell type acrylic resins, core-shell type styrene-acrylic resins, and core-shell type acrylic-urethane resins is more preferred, and at least one selected from the group consisting of core-shell type acrylic resins and core-shell type styrene-acrylic resins is even more preferred. Examples of the core-shell type acrylic resin include resins commercially available under the name of BARIAS (manufactured by Mitsui Chemicals, Inc.).

[0102] In addition, examples of the resin include SBR resins.

[0103] 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 with respect to 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 95% by mass or less with respect to 100% by mass of the total solid content of the intermediate layer 5.

[0104] The content ratio of the resin having the above water-soluble portion is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more with respect to 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 heat and humidity resistance can be 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.

[0105] The above crosslinking agent includes, for example, organic crosslinking agents such as cationic crosslinking agents and non-cationic crosslinking agents; inorganic crosslinking agents such as zirconium carbonate. Examples of the cationic crosslinking agent include epichlorohydrin-based resins such as polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and polyamide polyamine epichlorohydrin resin. Examples of the non-cationic crosslinking agent include oxazoline-based compounds such as oxazoline group-containing polymers and oxazoline group-containing low-molecular-weight compounds. 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.

[0106] The content ratio of the above crosslinking agent is preferably 1% by mass or more, more preferably 5% by mass or more, and 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, and 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 above content ratio is within the above range, an appropriate crosslinked structure can be formed, the barrier property of the intermediate layer 5 is further improved, and the print storage property such as heat and humidity resistance can be further improved.

[0107] 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 / m 2 When the above 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 heat and humidity resistance can be further improved.

[0108] (Laminated layer) The laminate layer 6 is a layer aimed at enhancing the adhesion between the intermediate layer 5 and the metal layer 7. Further, when the laser marking information recording body 1 does not include the intermediate layer 5, it also functions as a layer for enhancing the adhesion between the color developing layer 4 and the metal layer 7 (drawing omitted). The laminate layer 6 may not be provided if not necessary. In that case, for example, after coating the color developing layer 4 on the first base material 2, the metal layer 7 may be laminated by bonding it before the color developing layer 4 is completely dried and then completely drying the color developing layer 4. The material for forming the laminate layer 6 is not particularly limited, and for example, known or commonly used laminate adhesives, adhesives, thermoplastic resins, hot melts, aqueous adhesives, etc. can be used. Further, the laminate layer 6 may contain other components.

[0109] Examples of the above laminate adhesive include dry laminate adhesives such as urethane type, ether type, ester type, and epoxy type; non-solvent laminate adhesives such as urethane type, ether type, ester type, epoxy type, and isocyanate type. The above laminate adhesive may be a one-component type or a two-component type. The above laminate adhesive may be an aliphatic type or an aromatic type. Among them, from the viewpoint of excellent adhesion strength, a urethane type laminate adhesive is preferable, a urethane type dry laminate adhesive is more preferable, and a two-component type urethane type dry laminate adhesive is even more preferable. Further, from the viewpoint of environmental compatibility, an isocyanate type non-solvent laminate adhesive is preferable. The above two-component type laminate adhesive is used by mixing a main agent and a curing agent, and as the curing agent, for example, known or commonly used curing agents such as isocyanate type curing agents can be used. The above laminate adhesive can be used alone or in combination of two or more.

[0110] Examples of the above-mentioned 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. Among them, acrylic adhesives are preferred from the viewpoints of excellent adhesion and transparency. The above-mentioned adhesive can be used alone or in combination of two or more kinds.

[0111] The coating amount (dry mass) of the laminate layer 6 is, for example, 0.3 g / m 2 ~50 g / m 2 is preferable, and more preferably 0.5 g / m 2 ~40 g / m 2 is. When the coating amount is within the above range, the adhesion between layers becomes more appropriate, and delamination between layers can be more suppressed.

[0112] (Metal layer) The metal layer 7 is a layer for the purpose of reflecting laser light and improving the coloring efficiency. Also, the metal layer 7 may be a single layer or a multilayer.

[0113] The material constituting the metal layer 7 is not particularly limited, and for example, it can mainly be made of metal. Examples of the metal constituting the metal layer 7 include aluminum (alloy), silver (alloy), copper (alloy), gold (alloy), magnesium (alloy), nickel (alloy), palladium (alloy), zinc (alloy), titanium (alloy), chromium (alloy), tin (alloy), silicon (alloy), etc. Also, a part and / or all of the above metals may be oxidized, and examples of the metal constituting the metal layer 7 include aluminum oxide (alloy), silver oxide (alloy), copper oxide (alloy), gold oxide (alloy), magnesium oxide (alloy), nickel oxide (alloy), palladium oxide (alloy), zinc oxide (alloy), titanium oxide (alloy), chromium oxide (alloy), tin oxide (alloy), silicon oxide (alloy), etc. Among them, from the viewpoint of improving the reflectivity of laser light, the metal layer 7 preferably contains at least aluminum (alloy) and / or aluminum oxide (alloy), and more preferably contains aluminum and / or aluminum oxide. The above metals can be used alone or in combination of two or more. In this specification, for example, "aluminum (alloy)" means aluminum and / or an aluminum alloy. The same applies to other metals. The metal layer 7 may further contain other components as required.

[0114] The form of the metal layer 7 is not particularly limited and can take a known form. Examples of the form of the metal layer 7 include a vapor deposition layer, a sheet (foil), a plate, etc. Among them, from the viewpoints of flexibility and adhesion to an adjacent layer, a vapor deposition layer is preferred. Further, as the vapor deposition layer, an aluminum (alloy) vapor deposition layer and / or an aluminum oxide (alloy) vapor deposition layer are preferred, and an aluminum vapor deposition layer and / or an aluminum oxide vapor deposition layer are more preferred. The above vapor deposition layer is formed, for example, by performing a known or conventional vapor deposition method such as a vacuum vapor deposition method or a plasma-activated chemical reaction vapor deposition method on the second substrate 8 described later.

[0115] The 60° glossiness of the metal layer 7 is not particularly limited, but is preferably 200% or more, more preferably 300% or more, still more preferably 400% or more, still more preferably 500% or more, and particularly preferably 550% or more. When the 60° glossiness is within the above range, the reflectivity of the laser light is further improved and the coloring efficiency is further improved, so that sufficient color development can be achieved even during high-speed marking.

[0116] The 20° glossiness of the metal layer 7 is not particularly limited, but is preferably 200% or more, more preferably 400% or more, still more preferably 600% or more, still more preferably 800% or more, and particularly preferably 900% or more. When the 20° glossiness is within the above range, the reflectivity of the laser light is further improved and the coloring efficiency is further improved, so that sufficient color development can be achieved even during high-speed marking.

[0117] Let the 60° glossiness of the metal layer 7 be G 60 and the 20° glossiness of the metal layer 7 be G 20 When it is set, G 20 >G 60 is preferably the case. With such a relationship, the glossiness of the metal layer becomes higher, and more sufficient coloring efficiency can be imparted. Also, let the 60° glossiness when measuring the information recording medium 1 for laser marking from the first base material 2 side be G’ 60 and the 20° glossiness when measuring the information recording medium 1 for laser marking from the first base material 2 side be G’ 20 When it is set, G’ 20 >G’ 60 is preferably the case.

[0118] The above glossiness can be measured by a conventional method. For example, it can be obtained by a method conforming to JIS Z8741:1997. Such glossiness can be controlled by the type of metal constituting the metal layer, the surface smoothness and thickness of the metal layer, etc.

[0119] The total reflectance of the metal layer 7 is not particularly limited, but is preferably 30% or more, more preferably 50% or more, still more preferably 70% or more, and particularly preferably 90% or more. Also, the total reflectance in the wavelength range exceeding 351 nm and 400 nm or less is preferably within the above range, the total reflectance in the wavelength range exceeding 353 nm and 390 nm or less is preferably within the above range, and the total reflectance in the wavelength range exceeding 353 nm and 360 nm or less is preferably within the above range. The above total reflectance can be measured by a conventional method using a spectrophotometer equipped with an integrating sphere. When the above total reflectance is within the above range, the reflectance of the laser light is further improved and the coloring efficiency is further improved, so that sufficient color development can be achieved even during high-speed marking. Such total reflectance can be controlled by the type of metal constituting the metal layer, the surface smoothness and thickness of the metal layer, etc.

[0120] The thickness of the metal layer 7 is not particularly limited, and for example, 1 nm to 200 μm is preferable, and more preferably 10 nm to 100 μm. When the above thickness is within the above range, the flexibility and the like can be in a more appropriate range.

[0121] (Second substrate) The second substrate 8 can function as a support of the laser marking information recording body 1 or a layer that can protect the coloring layer and the like. Also, the second substrate 8 may be a single layer or a multilayer.

[0122] The second substrate 8 is not particularly limited, and examples thereof include resin films, fine paper, art paper, coated paper, kraft paper, papers such as laminated papers obtained by laminating a thermoplastic resin such as polyethylene on these paper substrates, synthetic papers, and porous materials such as non-woven fabrics. Examples of the resin constituting the above resin film are the same as those exemplified in the item of the first substrate 2. The above resins can be used alone or in combination of two or more. The above resin film may be stretched or not stretched.

[0123] The thickness of the second substrate 8 is not particularly limited. For example, it is preferably 5 μm to 200 μm, more preferably 10 μm to 150 μm. When the thickness is within the above range, the supportability and physical strength can be in a more appropriate range.

[0124] As the material including the metal layer 7 and the second substrate 8, for example, commercially available aluminum (alloy) vapor deposition paper, aluminum (alloy) vapor deposition film, aluminum (alloy) foil paper, aluminum (alloy) foil film, silver (alloy) vapor deposition paper, silver (alloy) vapor deposition film, silver (alloy) foil paper, silver (alloy) foil film, gold (alloy) vapor deposition paper, gold (alloy) vapor deposition film, gold (alloy) foil paper, gold (alloy) foil film, etc. can be used. These materials may include layers other than the metal layer 7 and the second substrate 8. For example, a known primer layer for enhancing the adhesion between the metal layer 7 and the second substrate 8, or a known coat layer etc. may be provided on the surface of the metal layer 7 opposite to the surface provided with the second substrate 8. Also, the above coat layer may or may not be colored. When the metal layer 7 is provided with the above coat layer, from the viewpoint of further improving the transmittance of the laser light, it is preferable that the above coat layer is not colored.

[0125] The 60° glossiness of the laser marking information recording body 1 is not particularly limited, but as the value measured from the first substrate side, it is preferably 50% or more, more preferably 100% or more, still more preferably 200% or more, still more preferably 400% or more, and particularly preferably 500% or more. The above 60° glossiness is obtained by the same method as that for the metal layer 7. Such glossiness can be controlled by the glossiness of the metal layer, and the materials, transparency, haze, etc. of the coating layers such as the color developing layer, the intermediate layer, and the laminate layer.

[0126] The glossiness at 20° of the information recording medium 1 for laser marking is not particularly limited, but as a value measured from the first substrate side, 100% or more is preferable, more preferably 200% or more, still more preferably 400% or more, still more preferably 600% or more, and particularly preferably 800% or more. The above-mentioned glossiness at 20° is determined by the same method as for the metal layer 7. Such glossiness can be controlled by the glossiness of the metal layer, and the materials, transparency, haze, etc. of coating layers such as the color developing layer, intermediate layer, and laminate layer.

[0127] The total reflectance of the information recording medium 1 for laser marking is not particularly limited, but as a value measured from the first substrate side, 30% or more is preferable, more preferably 60% or more, and still more preferably 90% or more. Also, the total reflectance in the wavelength range exceeding 351 nm and 400 nm or less is preferably within the above range, the total reflectance in the wavelength range exceeding 353 nm and 390 nm or less is preferably within the above range, and the total reflectance in the wavelength range exceeding 353 nm and 360 nm or less is preferably within the above range. The above-mentioned total reflectance is determined by the same method as for the metal layer 7. Such total reflectance can be controlled by the total reflectance of the metal layer, and the materials, transparency, haze, etc. of coating layers such as the color developing layer, intermediate layer, and laminate layer.

[0128] [Laser Marking Method] The information recording medium 1 for laser marking of the present embodiment can be colored by irradiation with laser light. The above-mentioned laser light is not particularly limited, and examples thereof include infrared laser light such as carbon dioxide laser light, YAG laser light, YVO 4 laser light; visible light laser light such as green laser light; ultraviolet laser light such as excimer laser light and THG laser light. Among them, the above-mentioned laser light is preferably ultraviolet laser light with a wavelength exceeding 351 nm and 400 nm or less, more preferably ultraviolet laser light with a wavelength exceeding 353 nm and 390 nm or less, still more preferably ultraviolet laser light with a wavelength exceeding 353 nm and 360 nm or less, and particularly preferably THG laser light. When such laser light is used as a light source, better color development properties and color development efficiency can be obtained.

[0129] The information recording medium 1 for laser marking according to this embodiment develops color based on the reaction between, for example, a leuco dye contained in the color developing layer 4 and a developer. Therefore, it is possible to print more clearly as compared with color development based on phenomena such as scraping, gasifying, and carbonizing an object in conventional laser marking. Further, in the case of the laminated structure of this embodiment, since the first base material 2 protects the coating layer such as the color developing layer 4, it is possible to suppress the generation of dust during laser light irradiation and further suppress the contamination of the working environment.

[0130] [Method for manufacturing an information recording medium for laser marking] The method for manufacturing the information recording medium for laser marking of the present invention is not particularly limited, and it can be manufactured by a known or conventional method. 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, this is applied onto the first base material 2, and before the coating liquid is completely dried, the metal layer 7 is bonded and laminated to obtain the information recording medium 1 for laser marking shown in FIG. 1.

[0131] (Preparation step) The method for preparing the coating liquid for the color developing layer is not particularly limited, and for example, it can be prepared by previously dispersing all the materials in the same solvent. Further, a dye and a developer that react with each other may be prepared as separate dispersion liquids and then mixed to obtain a 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 may be added to both. Examples of the method for preparing the coating liquid for the color developing layer include crushing treatment 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.

[0132] (Coating step) The method of applying the coating liquid for the color developing layer is not particularly limited. For example, there are methods of directly applying it to the first substrate, or applying it to a release liner or the like and then transferring it to the first 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, etc. Also, manual coating using a wire bar may be used. These methods can be used alone or in combination of two or more kinds.

[0133] (Drying process) The method of drying the coating liquid for the color developing layer is not particularly limited. For example, there are heating drying, normal temperature drying, vacuum drying, etc. These methods can be used alone or in combination of two or more kinds. The color developing layer 4 can be formed by these methods.

[0134] When the information recording body for laser marking of the present invention includes layers other than the first substrate, the color developing layer, and the second substrate, the manufacturing method of the information recording body for laser marking can incorporate the above content. Also, when a laminate layer is provided, it can be laminated by known or conventional methods such as dry lamination method, non-solvent lamination method, extrusion lamination method, hot melt lamination method, etc.

[0135] As a method for manufacturing an information recording medium 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 first substrate 2 and dried to form an anchor layer 3. Next, 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 laminate layer 6 is formed on the intermediate layer 5 to produce a first laminate. Then, a second laminate is produced by forming a metal layer 7 on a second substrate 8. Next, the laminate layer 6 and the metal layer 7 are laminated via the laminate layer 6 so that they are in contact with each other, thereby obtaining the information recording medium 1 for laser marking. Here, the coating liquid for the anchor layer and the coating liquid for the intermediate layer can be prepared by the same method as the method for preparing the coating liquid for the color developing layer. Also, the preparation method, the coating method, and the drying method are not particularly limited, and the methods listed above can be used. Also, the method of laminating via the laminate layer 6 is not particularly limited, and a known or commonly used method can be applied according to the material of the laminate layer 6. For example, bonding by a dry lamination method using a dry lamination adhesive, bonding by a non-solvent lamination method using a non-solvent lamination adhesive, bonding by a hot melt lamination method using a hot melt adhesive, and bonding by an extrusion lamination method using a thermoplastic resin can be applied. When using the above extrusion lamination method, a known or commonly used anchor coating agent for extrusion lamination can also be used as an auxiliary agent. Also, when using an adhesive as the material of the laminate layer 6, the first laminate and the second laminate can be bonded by applying pressure with or without heating.

[0136] The method for forming each of the above layers is not particularly limited. For example, multi-layer simultaneous coating may be performed using a curtain coater or the like, or they may be formed individually and sequentially. Also, some layers may be simultaneously coated and some layers may be individually and sequentially formed.

Example

[0137] Examples are given below to explain the present invention in more detail, but the present invention is not limited to these examples at all.

[0138] Example 1 (Production of Information Recording Medium for Laser Marking) <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 the first substrate by a conventional method, whereby an anchor layer with a coating amount of 0.9 g / m 2 (dry mass) was formed.

[0139] <Color-forming 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 (water-dispersed product), 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 contained to prepare a coating liquid for the color-forming layer (solid content concentration: 21% by mass) by a conventional method. The above coating liquid for the color-forming layer was applied and dried on the surface of the above anchor layer by a conventional method, whereby a color-forming layer with a coating amount of 4.5 g / m 2 (dry mass) was formed. Note that the numerical values of the above respective materials indicate the mass ratio of each material with respect to 100% by mass of the color-forming layer (dry state).

[0140] <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 contained to prepare a coating liquid for the intermediate layer (solid content concentration: 18.5% by mass) by a conventional method. The above coating liquid for the intermediate layer was applied and dried on the surface of the above color-forming layer by a conventional method, whereby a coating amount of 1.9 g / m 2An intermediate layer of (dry mass) was formed. The numerical values of the above materials indicate the mass ratio of each material with respect to 100% by mass of the intermediate layer (dry state).

[0141] <Laminate layer> A urethane-type adhesive for dry lamination containing ethyl acetate as a solvent and having a solid content concentration of 22% by mass (main agent: 93.7% by mass, curing agent: 6.3% by mass) was applied to the surface of the above intermediate layer by a conventional method to form a laminate layer, and a first laminate was obtained. The numerical values of the above materials indicate the mass ratio of each material with respect to 100% by mass of the laminate layer (dry state).

[0142] <Metal layer> As the second base material provided with a metal layer, silver aluminum vapor deposition paper (60° glossiness: 620%, 20° glossiness: 913%) having an aluminum vapor deposition layer formed on a paper base material was used. By dry laminating the above silver aluminum vapor deposition paper and the above first laminate, an information recording body for laser marking of Example 1 having the above resin film at one end face and the above paper base material at the other end face was produced. The glossiness of the above silver aluminum vapor deposition paper was measured by a method according to JIS Z8741:1997 using a handy gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd., device name: PG-1M). The above glossiness was measured from the side opposite to the paper base material of the aluminum vapor deposition layer.

[0143] Example 2 (Production of information recording body for laser marking) An information recording body for laser marking of Example 2 was produced in the same manner as in Example 1, except that gold aluminum vapor deposition paper (60° glossiness: 530%, 20° glossiness: 913%) was used instead of silver aluminum vapor deposition paper. The above gold aluminum vapor deposition paper has an aluminum vapor deposition layer and a colored coating layer colored yellow formed on a paper base material in this order, and due to this configuration, the aluminum vapor deposition layer appears gold through the above coating layer. The above glossiness is the value measured when the colored coating layer is laminated on the aluminum vapor deposition layer, and was measured from the colored coating layer side.

[0144] Comparative Example 1 (Preparation of Information Recording Medium for Laser Marking) A laser marking information recording medium of Comparative Example 1 was prepared in the same manner as in Example 1, except that a resin film (material: polyethylene terephthalate, thickness: 12 μm, 60° glossiness: 121%, 20° glossiness: 104%) was used instead of the silver aluminum vapor deposition paper.

[0145] <Evaluation> The following evaluations were performed on the laser marking information recording media prepared in the examples and comparative examples. The results are shown in Table 1.

[0146] (1) Optical Density of Printed Portion by THG Laser Printing was performed on the information recording medium for laser marking using a UV laser printer manufactured by Keyence Corporation with the operating speed set to any one of 1000 mm / sec, 1300 mm / sec, 1600 mm / sec, 1900 mm / sec, 2200 mm / sec, or 2500 mm / sec. Subsequently, the optical density (OD value) of the developed printed portion was measured from the first substrate side using a spectrophotometer (manufactured by Videojet Exalite Co., Ltd., device name: X-rite eXact). The results are shown in Table 1. In this measurement, the frequency of the UV laser printer was 55 Hz and the laser power was 50%. During printing, the laser light was irradiated onto the first substrate side of the above information recording medium for printing. The above UV laser printer is a printing device using a THG laser as a light source with a laser light wavelength of 355 nm.

[0147]

Table 1

[0148] As shown in Table 1, the information recording body for laser marking having a metal layer was able to print with excellent color development because even when marking was performed at a high speed with an operation speed of 2500 mm / sec, the optical density exceeded 1 (Examples 1 to 2). This is presumably because although part of the irradiated laser light passed through without acting on the color developing layer, it was able to act on the color developing layer by being reflected by the metal layer. At this time, no dust generation or damage to the first substrate was observed, and it was also confirmed that all of them were excellent in printing suitability by a THG laser (UV laser printer). Further, Example 1 using silver aluminum vapor deposition paper tended to show a higher optical density than Example 2 using gold aluminum vapor deposition paper. The reason for this is presumably that, for example, when silver aluminum vapor deposition paper was used, there was no colored coating layer between the color developing layer and the metal layer, and since attenuation of the laser light was more suppressed, the laser light was able to act on the color developing layer more efficiently. On the other hand, it was confirmed that in the information recording body for laser marking not having a metal layer, the optical density tended to decrease as the operation speed increased (Comparative Example 1). In particular, since the optical density was less than 1 when the operation speed was 2200 mm / sec or more, satisfactory color development could not be maintained when marking was performed at high speed.

[0149] Hereinafter, variations of the invention according to the present disclosure will be described. [Appendix 1] An information recording body in which a first substrate, a color developing layer, and a metal layer are laminated in this order, The information recording body for laser marking, wherein the first substrate is a layer that transmits ultraviolet rays. [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 color-developing portion in the color-developing layer is visible through the first base material. [Appendix 7] The laser marking information recording medium according to any one of Appendices 1 to 6, which can be colored by irradiation with ultraviolet laser light. [Appendix 8] The laser marking information recording medium according to any one of Appendices 1 to 7, wherein the metal layer contains aluminum and / or aluminum oxide. [Appendix 9] The laser marking information recording medium according to any one of Appendices 1 to 8, wherein the 60° glossiness of the metal layer is 200% or more. [Appendix 10] The laser marking information recording medium according to any one of Appendices 1 to 9, wherein the total reflectance of the metal layer is 30% or more. [Appendix 11] A thermal recording medium in which an intermediate layer is further provided between the color-developing layer and the metal layer, and the intermediate layer contains a resin having a water-soluble portion and / or a cross-linking agent. The laser marking information recording medium according to any one of Appendices 1 to 10. [Appendix 12] The laser marking information recording medium according to Appendix 11, wherein the intermediate layer contains a resin having a water-soluble portion and a cross-linking agent. [Appendix 13] The laser marking information recording medium according to Appendix 11 or 12, wherein the resin having a water-soluble portion is a core-shell type resin having at least a carboxy group as the water-soluble portion. [Appendix 14] The laser marking information recording medium according to any one of Appendices 11 to 13, wherein a laminate layer is further provided between the intermediate layer and the metal layer. [Appendix 15] The laser marking information recording medium according to any one of Appendices 1 to 14, wherein the first 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 first base material is 15 μm or more. [Appended Note 17] The first base material is the 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 second base material in direct contact with the metal layer on the surface opposite to the surface provided with the color developing layer of the metal layer. When the laser marking information recording body includes the second base material, the second base material 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 second base material, the metal 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 Reference Numerals

[0150] 1 Laser marking information recording body 2 First base material 3 Anchor layer 4 Color developing layer 5 Intermediate layer 6 Laminating layer 7 Metal layer 8 Second base material

Claims

1. This is an information recording body in which a first substrate, a color-developing layer, and a metal layer are stacked in this order. The first substrate is a layer that transmits ultraviolet light, The color-developing layer comprises a leuco dye and a urea compound, which is a non-phenolic color developer, and is used as an information recording medium for laser marking.

2. The laser marking information recorder according to claim 1, wherein the urea compound 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.)

3. The laser marking information recording body according to claim 2, wherein the urea compound comprises at least a compound represented by formula (1).

4. The colored portion in the colored layer is visible through the first substrate, as described in any one of claims 1 to 3, for use as a laser marking information recording body.

5. An information recording body for laser marking according to any one of claims 1 to 3, which can produce color by irradiation with ultraviolet laser light.

6. The information recording body for laser marking according to any one of claims 1 to 3, wherein the metal layer comprises aluminum and / or aluminum oxide.

7. The laser marking information recording body according to any one of claims 1 to 3, wherein the 60° gloss of the metal layer is 200% or more.

8. The laser marking information recording body according to any one of claims 1 to 3, wherein the total reflectance of the metal layer is 30% or more.

Images