Information recording medium for laser marking

Abstract

An object of the present invention is to provide an information recording medium that enables laser marking and has excellent color-developing properties. The information recording medium 1 for laser marking of the present invention is an information recording medium in which a first base material 2, a color-developing layer 4, and a second base material 7 are laminated in this order. The first base material 2 is a layer that transmits ultraviolet rays. The color-developing layer 4 is a layer containing a leuco dye and a developer.

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 kind 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. Further, at the portion where the object surface is altered, printing can be performed by the color change due to the alteration. Also, even for an object with low sensitivity to laser light, by adding an inorganic material or the like that has laser sensitivity and changes color with heat to the object, it is possible to impart or improve the printability (laser marking suitability) by laser light.

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

[0004] On the other hand, by adding a dye and a developer to the color developing layer, the contrast is improved, the color development is excellent, and by laminating a surface protective layer on the above color developing layer, an information recording medium capable of suppressing surface damage during laser marking has been studied (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

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

[0007] Furthermore, in the laminated recording materials and laser marking materials of Patent Documents 1 and 2, a developer having a phenol skeleton, that is, a phenolic developer, is used as the developer. Although phenolic developers are conventionally used components, in recent years, their use has tended to be avoided from the viewpoint of environmental compatibility. For this reason, there has been an increasing demand for a laser marking information recording body that enables laser marking, has excellent color developability, and uses a non-phenolic developer as the developer, but such an information recording body has not yet been specifically provided.

[0008] In general, when the color developing layer contains a developer, there has been a problem of print storage stability that the color density decreases during storage due to the influence of external factors such as chemicals. In particular, when the information recording body includes a base material or a laminate layer, components in the base material or laminate layer (for example, oil-soluble components such as monomer components and plasticizers) migrate into the color developing layer, resulting in a problem of moisture and heat resistance that the color density decreases during storage, particularly during storage in a high-temperature and high-humidity environment. For this reason, there has been a problem that a laser marking information recording body that enables laser marking and has excellent color developability and moisture and heat resistance has not yet been specifically provided.

[0009] In addition, the printing device that irradiates laser light has different wavelengths of the laser light irradiated depending on the type of device, such as carbon dioxide laser light, YAG laser light, YVO 4 Laser marking information recording media capable of printing with infrared laser light such as laser light have been conventionally known. However, there has been a problem that a laser marking information recording medium capable of printing with ultraviolet laser light having a wavelength exceeding 351 nm and 400 nm or less, such as THG (Third Harmonic Generation) laser light, and having excellent color development properties has not yet been specifically provided.

[0010] Therefore, an object of the present invention is to provide an information recording medium capable of laser marking and having excellent color development properties. In particular, as a first object of the present invention, it is to provide a laser marking information recording medium capable of laser marking, having excellent color development properties, and further containing a non-phenolic developer as a developer. Further, a second object of the present invention is to provide a laser marking information recording medium capable of laser marking and having excellent color development and moisture and heat resistance. Further, a third object of the present invention is to provide an ultraviolet laser marking information recording medium capable of laser marking using ultraviolet laser light having a wavelength exceeding 351 nm and 400 nm or less as a light source and having excellent color development properties.

Means for Solving the Problems

[0011] As a result of intensive studies to achieve the above object, the present inventors have found that by sandwiching a color developing layer between a first substrate and a second substrate and further adding a developer to the color developing layer, laser marking can be performed without damage to the surface during laser light irradiation, and an information recording medium having excellent color development properties can be obtained.

[0012] Among them, it has been found that an information recording medium containing a specific non-phenolic developer as a developer can provide an information recording medium capable of laser marking and having excellent color developability.

[0013] Also, it has been found that by providing a specific intermediate layer, it is possible to provide an information recording medium for laser marking that is capable of laser marking, has excellent color developability, and is even more excellent in heat and humidity resistance.

[0014] Further, by adopting the above laminated structure, even when ultraviolet laser light having a wavelength exceeding 351 nm and not exceeding 400 nm is used as a light source, it is possible to provide an information recording medium for laser marking that can be laser marked without suffering surface damage and has excellent color developability. The present invention has been completed based on these findings.

[0015] That is, the present invention provides an information recording medium in which a first substrate, a color developing layer, and a second substrate are laminated in this order, wherein the first substrate is a layer that transmits ultraviolet light, the color developing layer contains a leuco dye and a developer, and the developer contains a non-phenolic developer, and provides an information recording medium for laser marking.

[0016] 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

[0017] It is preferable that a laminate layer is further provided between the color - developing layer and the second base material.

[0018] The present invention also provides an information recording medium in which a first base material, a color - developing layer, an intermediate layer, and a second base material are laminated in this order. The first base material is a layer that transmits ultraviolet rays. The color - developing layer contains a leuco dye and a developer. The intermediate layer contains a resin having a water - soluble portion and / or a cross - linking agent, and provides an information recording medium for laser marking.

[0019] It is preferable that the intermediate layer contains a resin having a water - soluble portion and a cross - linking agent.

[0020] The resin having a water - soluble portion is preferably a core - shell type resin having at least a carboxy group as the water - soluble portion.

[0021] It is preferable that a laminate layer is further provided between the intermediate layer and the second base material.

[0022] The present invention also provides an information recording medium in which a first base material, a color - developing layer, and a second base material are laminated in this order. The first base material is a layer that transmits ultraviolet rays. The color - developing layer contains a leuco dye and a developer. It provides an information recording medium for ultraviolet laser marking that can be colored by irradiation with ultraviolet laser light having a wavelength exceeding 351 nm and not exceeding 400 nm.

[0023] The ultraviolet laser light is preferably THG laser light.

[0024] It is preferable that a laminate layer is further provided between the color-developing layer and the second base material.

[0025] It is preferable that an anchor layer is further provided between the first base material and the color-developing layer.

[0026] The second base material is preferably a layer that transmits ultraviolet rays.

Effects of the Invention

[0027] According to the information recording body for laser marking of the present invention, it is possible to provide an information recording body for laser marking that enables laser marking, has excellent color-developing properties, and further contains a non-phenolic developer as a developer. In addition, it is possible to provide an information recording body for laser marking that enables laser marking, has excellent color-developing properties, and is even more excellent in heat and humidity resistance. Further, it is possible to provide an information recording body for laser marking that enables printing by irradiation with ultraviolet laser light having a wavelength exceeding 351 nm and 400 nm or less and has excellent color-developing properties.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0029] [Information Recording Body for Laser Marking] The information recording body for laser marking according to the first aspect of the present invention has a laminated structure in which at least a first base material, a color-developing layer, and a second base material are laminated in this order. The first base material is a layer that transmits ultraviolet rays. The color-developing layer contains at least a leuco dye and a developer, and the developer contains at least a non-phenolic developer.

[0030] The information recording body for laser marking according to the second aspect of the present invention has a laminated structure in which at least a first base material, a color developing layer, an intermediate layer, and a second base material are laminated in this order. The above first base material is a layer that transmits ultraviolet rays. The above color developing layer contains at least a leuco dye and a developer. The above intermediate layer contains at least a resin having a water-soluble portion and / or a crosslinking agent.

[0031] The information recording body for laser marking according to the third aspect of the present invention has a laminated structure in which at least a first base material, a color developing layer, and a second base material are laminated in this order. The above first base material is a layer that transmits ultraviolet rays. The above color developing layer contains at least a leuco dye and a developer. The above information recording body for laser marking can be colored by irradiation with ultraviolet laser light having a wavelength exceeding 351 nm and 400 nm or less.

[0032] As used herein, the "information recording body for laser marking of the present invention" means a general term encompassing the information recording body for laser marking of the above first aspect, the information recording body for laser marking of the above second aspect, and the information recording body for laser marking of the above third aspect.

[0033] The information recording body for laser marking of the present invention preferably further includes an anchor layer, and also preferably further includes a laminate layer. Further, it is more preferable to further include an anchor layer and a laminate layer. The above anchor layer is a layer provided between the first base material and the color developing layer. The above laminate layer is a layer provided between the color developing layer and the second base material when there is no intermediate layer, and is a layer provided between the intermediate layer and the second base material when there is an intermediate layer. Also, other layers other than the above may be provided. Examples of the above other layers include a printing layer, an adhesive layer, a back coat layer, an overcoat layer, a heat insulating layer, a protective layer, and the like.

[0034] Hereinafter, an embodiment of the information recording body for laser marking of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments.

[0035] 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 second base material 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 second base material 7 to have a laminated structure. Further, at least the first base material 2 is a layer that transmits ultraviolet rays. By satisfying such a configuration, the information recording medium 1 for laser marking of the present embodiment can be laser marked and can achieve good color development properties. 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 containing a leuco dye and a developer can absorb the above laser light and exhibit a distinct color development by its energy. Further, 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, and scraping may occur. However, since the color developing layer 4 is protected by the first base material 2 and the second base material 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 can avoid absorbing a large amount of laser light and damage such as the formation of holes. Also, according to the laminated structure in which the color developing layer 4 is sandwiched between the base materials, generally, the base material tends to be superior in strength to the layer formed by coating (coating layer), so the resistance to rubbing and wear can also be improved.

[0036] FIG. 2 is a schematic cross-sectional view showing another embodiment of the information recording body for laser marking of the present invention. As shown in FIG. 2, the information recording body 1 for laser marking of the present embodiment has an anchor layer 3, a color developing layer 4, an intermediate layer 5, a laminate layer 6, and a second substrate 7 laminated in this order on a sheet-like first substrate 2, and the color developing layer 4 is sandwiched between the first substrate 2 and the second substrate 7. 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, and the laminate layer 6 and the second substrate 7 are in direct contact with each other. In this specification, the laminate including the first substrate 2, the anchor layer 3, the color developing layer 4, and the intermediate layer 5 may be referred to as the "first laminate", and the laminate including the laminate layer 6 and the second substrate 7 may be referred to as the "second laminate". By providing the anchor layer 3, the adhesion between the first substrate 2 and the color developing layer 4 is further improved, and delamination between layers can be suppressed. Further, by providing the laminate layer 6, the adhesion between the intermediate layer 5 and the second substrate 7 is further improved, and delamination between layers can be suppressed. Further, in the manufacturing method described later, since the first laminate and the second laminate can be laminated by various lamination methods or the like, the information recording body 1 for laser marking can be efficiently manufactured.

[0037] (First substrate) The first substrate 2 is a layer that transmits ultraviolet rays and can function as a support for the information recording body 1 for laser marking and protect 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 having 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 multi-layer.

[0038] Examples of the first base material 2 include resin films and the like. Examples of the resin constituting the resin film include polyethylene (low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene), polypropylene (random copolymer polypropylene, block copolymer polypropylene, homopolypropylene), polybutene, polymethylpentene, ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate (random, alternating) copolymer, ethylene-vinyl acetate copolymer (EVA), ethylene-propylene copolymer, cyclic olefin-based polymer, ethylene-butene copolymer, ethylene-hexene copolymer and other polyolefin resins; polyurethane; polyester such as polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate (PBT); polystyrene; polycarbonate; polyimide-based 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 non-stretched.

[0039] The thickness of the first base material 2 is not particularly limited, and for example, 5 μm to 150 μm is preferable, and more preferably 10 μm to 100 μm. When the thickness is within the above range, the coatability and supportability can be more excellent.

[0040] 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. When irradiating the first substrate 2 with laser light, since the first substrate 2 is a layer that transmits ultraviolet light, even if the thickness is within the above range, the laser light can act on the coloring layer 4 efficiently, and the color developability and the physical strength can be compatible.

[0041] The haze of the first substrate 2 is not particularly limited, but from the viewpoint of further improving the visibility and / or the 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 conforming to JIS K7136:2000. When the above haze is within the above range, the transparency of the first substrate 2 becomes higher, so that the visibility when visually recognizing the coloring portion in the coloring layer 4 through the first substrate 2 can be further improved. Further, when the above haze is within the above range, the transmittance of the laser light can be further improved, so that the color developability can be further improved, and the damage to the first substrate 2 can be further suppressed, and thus the laser marking suitability can be further improved.

[0042] The total light transmittance of the first substrate 2 in the wavelength range of 300 nm to 400 nm is not particularly limited. However, 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 to the first substrate 2 can be further suppressed. Therefore, the laser marking suitability can be further improved. In addition, 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.

[0043] (Second substrate) The second substrate 7 is a layer that can function as a support for the laser marking information recording body 1 and can protect the color developing layer and the like. The second substrate 7 may be a single layer or a multilayer.

[0044] The second substrate 7 is not particularly limited. For example, it includes resin films, high-quality 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 resin film include the same ones as those exemplified in the item of the first substrate. The resins can be used alone or in combination of two or more. The resin film may be stretched or non-stretched.

[0045] The second substrate 7 may be a layer that transmits ultraviolet rays. In this case, since laser light can also be irradiated from the side of the second substrate 7 to cause the laser marking information recording body to develop color, the degree of freedom in design is further improved. From such a viewpoint, it is preferable that the second substrate 7 is a resin film.

[0046] The thickness of the second substrate 7 is not particularly limited. For example, 5 μm to 200 μm is preferable, and more preferably 10 μm to 150 μm. When the above thickness is within the above range, the coatability and supportability can be more excellent. Also, from the viewpoint of further improving the physical strength, the thickness of the second substrate 7 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, 60 μm or more, 80 μm or more, 100 μm or more. Among them, when the second substrate 7 is a layer that transmits ultraviolet rays, even if the above thickness is within the above range, the laser light can act on the coloring layer 4 efficiently, so that the color developability and the physical strength can be compatible.

[0047] The haze of the second substrate 7 is not particularly limited. However, when the second substrate 7 is a resin film, from the viewpoint of further improving the transparency and / or the 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 is required in the same manner as the first substrate 2.

[0048] The total light transmittance of the second substrate 7 in the wavelength range of 300 nm to 400 nm is not particularly limited. However, from the perspective 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 is determined in the same manner as for the first substrate 2. Further, the total light transmittance in the wavelength range exceeding 351 nm and not exceeding 400 nm is preferably within the above range, the total light transmittance in the wavelength range exceeding 353 nm and not exceeding 390 nm is preferably within the above range, and the total light transmittance in the wavelength range exceeding 353 nm and not exceeding 360 nm is preferably within the above range.

[0049] (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 above other components include surfactants, preservatives, inorganic pigments, organic pigments, viscosity modifiers, and the like.

[0050] Examples of the above resin include acrylic resins such as acrylic resin, styrene-acrylic resin, acrylic-urethane resin, acrylic-amide resin, vinyl acetate-acrylic resin; maleic acid resins such as maleic acid resin, styrene-maleic acid resin, olefin-maleic acid resin; styrene butadiene latex (SBR) resin, and the like. These resins may be modified resins modified by known methods. Further, these resins can be used alone or in combination of two or more.

[0051] As used herein, the term "acrylic resin" means a resin obtained by homopolymerizing an acrylic monomer (acrylic resin), and / or a resin obtained by copolymerizing an acrylic monomer and another monomer (a monomer other than an acrylic monomer copolymerizable with the acrylic monomer). Here, the above-mentioned other monomer may be one kind or two or more kinds. Further, when simply described as "acrylic", unless otherwise specified, it means (meth)acrylic acid (salt) and / or (meth)acrylate. Here, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid, and "(meth)acrylic acid (salt)" means (meth)acrylic acid and / or (meth)acrylate salt.

[0052] 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.

[0053] 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.

[0054] Examples of the above surfactant include anionic surfactants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfate ester 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.

[0055] The coating amount (dry mass) of the anchor layer 3 is, for example, 0.1 g / m 2 ~5.0 g / m 2 is preferable, and 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 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.

[0056] (Color-developing layer) The color-developing layer 4 is a layer that forms a recorded image on the laser marking information recording medium 1 by causing a chemical reaction to proceed between a leuco dye and a developer by the energy of laser light.

[0057] Here, the color-developing layer 4 included in the laser marking information recording medium 1 of the first aspect of the present invention contains at least a leuco dye and a developer, and the developer contains at least a non-phenolic developer. In the first aspect of the present invention, by satisfying all such configurations for the color-developing layer 4, it is possible to provide the laser marking information recording medium 1 that is excellent in laser marking suitability and more suppresses the load on the environment. The above leuco dye can be used alone or in combination of two or more, and the above non-phenolic developer can be used alone or in combination of two or more.

[0058] In addition, the color - developing layer 4 included in the information recording body 1 for laser marking according to the second and third aspects of the present invention contains at least a leuco dye and a developer. In the second and third aspects of the present invention, by satisfying all such configurations for the color - developing layer 4, it is possible to provide an information recording body 1 for laser marking with excellent laser - marking suitability. The above developer may not contain a non - phenolic developer, but from the perspective of environmental response and the like, it is preferably included. The above leuco dye can be used alone or in combination of two or more, and the above developer can be used alone or in combination of two or more.

[0059] The color - developing layer 4 may further contain other components as necessary. Examples of the above other components include a binder, a filler, a lubricant, a dispersant, a cross - linking agent, a preservative, a sensitizer, a surfactant, a viscosity modifier, and the like.

[0060] Examples of the above non - phenolic developer include urea compounds. As the above urea compound, an N,N'- diarylurea derivative having one or more sulfonic acid ester structures (-S(=O) 2 -O-) in the molecule is preferable. Specifically, as the above N,N'- diarylurea derivative, it is preferably included a compound represented by the following formula (1) and / or a compound represented by the following formula (2). 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.

[0061]

Chemical formula

[0062] The compound represented by the above Formula (1) and / or the compound represented by the above Formula (2) can be colored by contacting, for example, a leuco dye described later, with the energy of laser light.)

[0063] 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 from 0 to 4, and when m is 2 or more, a plurality of m's may be the same or different.)

[0064] In the above Formula (1), a plurality of R 1 -SO 3 - is directly bonded to the carbon atom constituting the benzene ring. Also, the substitution positions of a plurality of R 1 -SO 3 - may be the same substitution position or different substitution positions. The substitution position of R 1 -SO 3 - is preferably at the 2-position, 3-position, or 4-position, more preferably at the 3-position.)

[0065] In the above Formula (2), R 1 -SO 3 - is directly bonded to the carbon atom constituting the benzene ring. The substitution position of R 1 -SO 3 - is preferably at the 2-position, 3-position, or 4-position, more preferably at the 3-position.)

[0066] In the above Formula (1) and the above Formula (2), the above R 1Among the "optionally substituted hydrocarbon groups having 1 to 12 carbon atoms", examples of the "hydrocarbon groups having 1 to 12 carbon atoms" include linear alkyl groups having 1 to 12 carbon atoms, branched alkyl groups having 1 to 12 carbon atoms, alicyclic alkyl groups having 3 to 12 carbon atoms, aralkyl groups having 7 to 12 carbon atoms, aryl groups having 6 to 12 carbon atoms, and the like. Also, a plurality of the "optionally substituted hydrocarbon groups having 1 to 12 carbon atoms" may be the same or different.

[0067] Examples of the above "linear alkyl groups having 1 to 12 carbon atoms, branched alkyl groups having 1 to 12 carbon atoms, and alicyclic alkyl groups having 3 to 12 carbon atoms" include linear alkyl groups having 1 to 12 carbon atoms such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, cyclopentyl group, hexyl group, cyclohexyl group, 2-ethylhexyl group, lauryl group, branched alkyl groups having 1 to 12 carbon atoms, or alicyclic alkyl groups having 3 to 12 carbon atoms. These alkyl groups may further have substituents described later.

[0068] Examples of the above "aralkyl groups having 7 to 12 carbon atoms" include unsubstituted aralkyl groups such as benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, and the like. Also, these aralkyl groups may further have substituents described later. Examples of the "aralkyl groups having 7 to 12 carbon atoms and having substituents" 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, and the like.

[0069] Examples of the above-mentioned "aryl group having 6 to 12 carbon atoms" include unsubstituted aryl groups such as a phenyl group, a 1-naphthyl group, and a 2-naphthyl group. 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 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, a mesitylene group, a p-ethylphenyl group, a p-i-propylphenyl group, a p-t-butylphenyl group, a p-methoxyphenyl group, a 3,4-dimethoxyphenyl group, a p-ethoxyphenyl group, a p-chlorophenyl group, and a t-butylated naphthyl group.

[0070] 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 and an alkoxy group. 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, and an aryl group. 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 or different. 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.

[0071] In the above formula (1) and the above formula (2), the above R 1is preferably an aryl group having 6 to 12 carbon atoms which is unsubstituted or has substituents. More specifically, the above R 1 is preferably a phenyl group, 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, and among them, p-tolyl group is more preferable. When such R 1 is the case, the sensitivity becomes more excellent.

[0072] 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. Also, the substitution positions of a plurality of A 1 may be the same substitution position or different substitution positions. The substitution position of the above A 1 is preferably the 2-position, 3-position, or 4-position.

[0073] 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 still more preferably 0.

[0074] Examples of the hydrocarbon group having 1 to 4 carbon atoms of the above A 1 include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, and t-butyl group.

[0075] Specific compounds represented by the above formula (1) include, for example, the following compounds, but are not limited to these compounds.

[0076] 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,

[0077] 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,

[0078] 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,

[0079] 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,

[0080] 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,

[0081] 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,

[0082] 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,

[0083] 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,

[0084] 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,

[0085] Examples include N,N'-di-[2-(p-xylenesulfonyloxy)phenyl]urea, N,N'-di-[2-(m-xylenesulfonyloxy)phenyl]urea, N,N'-di-[2-(mesitylenesulfonyloxy)phenyl]urea, and the like. Among them, as the compound represented by the above formula (1), from the viewpoint of achieving good color development by laser light and excellent wet heat resistance, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea is particularly preferred.

[0086] In addition, specific examples of the compound represented by the above formula (2) include, but are not limited to, the following compounds.

[0087] 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,

[0088] 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,

[0089] 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,

[0090] 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,

[0091] 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 wet heat resistance can also be obtained, 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate is particularly preferable.

[0092] 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).

[0093] The color former may contain a color former other than the color formers exemplified above (other color formers) as long as the effects of the present invention are not impaired.

[0094] Examples of the other color formers include known non-phenol 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., 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 and other known color formers.

[0095] 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[4-(n-octyloxycarbonylamino)salicylic acid zinc], 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.

[0096] 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.

[0097] When the color forming layer 4 contains a non-phenolic color former, the content ratio of the non-phenolic color former 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 formers in the color forming layer 4. It may also be 100% by mass. When the above content ratio is within the above range, the environmental load can be further suppressed. Also, the total content ratio of the compound represented by the above formula (1) and / or the compound represented by the above formula (2) is preferably within the above range based on 100% by mass of the total amount of the above color formers in the color forming layer 4.

[0098] The melting point of the above color former is not particularly limited, but for example, it is preferably 130°C or higher, more preferably 140°C or higher, still more preferably 150°C or higher. Also, the melting point of the above color former is preferably 195°C or lower, more preferably 185°C or lower, for example. Further, the melting point of the above non-phenolic color former 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 moisture and heat resistance can also be excellent.

[0099] The above-mentioned 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.,

[0100] The average particle diameter 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 diameter increases, the reaction becomes sluggish and the sensitivity characteristics decrease. On the other hand, as the average particle diameter decreases, the risk of unexpected color development due to heat during drying of the coating solution increases. By setting the average particle diameter 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 diameter means the particle diameter (D50, median diameter) at the integrated value of 50% in the particle size distribution measured by the laser diffraction / scattering method. The average particle diameter 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).

[0101] 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.

[0102] 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, etc.; maleic acid resins such as maleic acid resin, styrene-maleic acid resin, olefin-maleic acid resin, etc.; resins such as styrene butadiene latex (SBR) resin, etc. These resins may be modified resins modified by known methods. Also, starch, casein, gelatin, polyamide, polyacrylamide, modified polyacrylamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl acetate, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methyl vinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinyl pyrrolidone, acrylonitrile, methyl vinyl ether, etc. may be mentioned. These binders can be used alone or in combination of two or more kinds.

[0103] The content ratio of the above binder is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more with respect to 100% by mass of the total solid content of the color forming layer 4. Also, the content ratio of the above binder is preferably 60% by mass or less, more preferably 50% by mass or less with respect to 100% by mass of the total solid content of the color forming layer 4.

[0104] The above lubricants include, for example, hydrocarbon waxes such as paraffin, polyethylene, polystyrene, etc.; ester waxes such as carnauba wax, etc.; oils such as silicone oil, whale oil, etc.; fatty acids such as oleic acid, etc.; metal soaps such as zinc stearate, etc. These lubricants can be used alone or in combination of two or more kinds.

[0105] 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. Further, 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.

[0106] Examples of the above dispersant include anionic surfactants such as sodium dialkyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, and alkyl ether sulfate salts; nonionic surfactants such as acetylene glycol and alkylene oxide adducts of acetylene glycol; polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and sulfonic acid-modified polyvinyl alcohol; and polymer dispersants such as styrene-acrylic copolymers and acrylic resins. These dispersants can be used alone or in combination of two or more.

[0107] 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. Further, 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.

[0108] 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.

[0109] The content ratio of the above filler is preferably 0.1% by mass or more, more preferably 1% by mass or more, and still more preferably 5% by mass or more with respect to 100% by mass of the total solid content of the color - forming layer 4. Further, the content ratio of the above filler is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less with respect to 100% by mass of the total solid content of the color - forming layer 4.

[0110] Examples of the above cross - linking agent include organic cross - linking agents such as cationic cross - linking agents and non - cationic cross - linking agents; inorganic cross - linking agents such as zirconium carbonate. Examples of the above cationic cross - linking agent include epichlorohydrin - based resins such as polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and polyamide polyamine epichlorohydrin resin. Examples of the above non - cationic cross - linking agent include oxazoline - based compounds such as oxazoline - group - containing polymers and oxazoline - group - containing low - molecular substances. These cross - linking agents can be used alone or in combination of two or more.

[0111] The content ratio of the above cross - linking agent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more with respect to 100% by mass of the total solid content of the color - forming layer 4. Further, the content ratio of the above cross - linking agent is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less with respect to 100% by mass of the total solid content of the color - forming layer 4.

[0112] The color - forming layer 4 may further contain a laser sensitizer. Examples of the above 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" means a specific gravity of 5.0 g / cm 3It means the above metal elements. Further, 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.

[0113] 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.

[0114] 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.

[0115] (Intermediate layer) The intermediate layer 5 is a layer whose purpose is to suppress adverse effects such as external factors such as chemicals migrating to the color - developing layer 4 and causing a decrease in color - developing density, and to further improve the print storage property (such as moisture and heat resistance) of the information recording body 1 for laser marking. Among them, when the information recording body 1 for laser marking of the present embodiment includes the second base material 7 and the laminate layer 6, oil - soluble components in the second base material 7 and the laminate layer 6 may migrate to the color - developing layer 4, resulting in a problem of moisture and heat resistance that the color - developing density decreases during storage, especially during storage in a high - temperature and high - humidity environment. In such a case, by providing the intermediate layer 5 between the color - developing layer 4 and the second base material 7 or the laminate layer 6, migration of oil - soluble components in the second base material 7 and the laminate layer 6 to the color - developing layer 4 can be suppressed, and the above - mentioned moisture and heat resistance can be improved.

[0116] Here, the information recording medium 1 for laser marking according to the second aspect of the present invention essentially includes an intermediate layer 5 containing a resin having a water-soluble portion and / or a crosslinking agent. In the second aspect of the present invention, by providing such an intermediate layer 5, it is possible to further suppress the transfer of external factors such as chemicals to the color developing layer 4. Among them, when the intermediate layer 5 contains a resin having a water-soluble portion, the water-soluble portion can more effectively suppress the transfer of oil-soluble components in the second base material 7 and the laminate layer 6. Further, when the intermediate layer 5 contains a crosslinking agent, since a dense crosslinked structure can be formed within the intermediate layer 5, the crosslinked structure portion can more effectively suppress the transfer of oil-soluble components in the second base material 7 and the laminate layer 6. The intermediate layer 5 may further contain other components as required. Examples of the other components include resins, surfactants, preservatives, and the like.

[0117] Further, the information recording medium 1 for laser marking according to the first and third aspects of the present invention may or may not include the intermediate layer 5. From the viewpoint of further improving the print storage properties such as moisture and heat resistance, it is preferable to provide the intermediate layer 5. In the first and third aspects of the present invention, 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, similar to the second aspect. The intermediate layer 5 may further contain other components as required. Examples of the other components include crosslinking agents, surfactants, preservatives, inorganic pigments, organic pigments, and the like. Among them, similar to the second aspect, it is preferable to contain a crosslinking agent.

[0118] 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 transfer of oil-soluble components to the color developing layer 4 and is considered to be able to form a crosslinked structure with the crosslinking agent described below.

[0119] The resin having the above-mentioned water-soluble portion is preferably a core-shell type resin. In the present specification, the "core-shell type resin" means a resin having a structure in which hydrophobic core particles are coated with a water-soluble shell polymer.

[0120] Among the above core-shell type resins, a core-shell type resin having a carboxy group as the above water-soluble portion (core-shell type carboxy group-containing resin) is particularly preferable. Here, it is considered that the above core-shell type carboxy group-containing resin contains a carboxy group in at least the structure of the water-soluble shell polymer.

[0121] Examples of the above core-shell type carboxy group-containing resin include core-shell type acrylic resins such as core-shell type acrylic resins, core-shell type styrene-acrylic resins, core-shell type acrylic-urethane resins, core-shell type acrylic-amide resins, and core-shell type vinyl acetate-acrylic resins; core-shell type maleic acid resins, and the like. As the above core-shell type carboxyl group-containing resin, a core-shell type acrylic resin is preferable, and among them, at least one selected from the group consisting of core-shell type acrylic resin, core-shell type styrene-acrylic resin, and core-shell type acrylic-urethane resin is more preferable, and at least one selected from the group consisting of core-shell type acrylic resin and core-shell type styrene-acrylic resin is even more preferable. Examples of the above core-shell type acrylic resin include resins commercially available under the name of BARIAS (manufactured by Mitsui Chemicals, Inc.).

[0122] In addition, examples of the above resin include SBR resin.

[0123] The content ratio of the above resin is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the total solid content of the intermediate layer 5. Further, the content ratio of the above resin may be 99% by mass or less, or may be 95% by mass or less, based on 100% by mass of the total solid content of the intermediate layer 5.

[0124] 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, still more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more, based on 100% by mass of the total amount of the resin in the intermediate layer 5. It may also be 100% by mass. When the content ratio is within the above range, the barrier property of the intermediate layer 5 can be further improved, and the print storage property such as moisture and heat resistance can be further improved. Also, the content ratio of the core-shell type resin is preferably within the above range with respect to 100% by mass of the total amount of the above resin in the intermediate layer 5.

[0125] Examples of the above crosslinking agent include organic crosslinking agents such as cationic crosslinking agents and non-cationic crosslinking agents; inorganic crosslinking agents such as zirconium carbonate. Examples of the above cationic crosslinking agent include epichlorohydrin-based resins such as polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and polyamide polyamine epichlorohydrin resin. Examples of the above non-cationic crosslinking agent include oxazoline-based compounds such as oxazoline group-containing polymers and oxazoline group-containing low molecules. The above crosslinking agent is preferably a cationic crosslinking agent, and among them, polyamide epichlorohydrin resin is more preferable. These crosslinking agents can be used alone or in combination of two or more.

[0126] The content ratio of the above crosslinking agent is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, based on 100% by mass of the total solid content of the intermediate layer 5. Also, the content ratio of the above crosslinking agent is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less, based on 100% by mass of the total solid content of the intermediate layer 5. When the content ratio is within the above range, an appropriate crosslinked structure can be formed, the barrier property of the intermediate layer 5 can be further improved, and the print storage property such as moisture and heat resistance can be further improved.

[0127] 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 / m2 ~4.0 g / m 2 When the coating amount is within the above range, the barrier property of the obtained information recording body 1 for laser marking can be made more appropriate, and the print storage properties such as moisture and heat resistance can be further improved.

[0128] (Laminating layer) The laminating layer 6 is a layer for the purpose of enhancing the adhesion between the intermediate layer 5 and the second base material 7. Further, when the information recording body 1 for laser marking does not include the intermediate layer 5, it can also function as a layer for enhancing the adhesion between the coloring layer 4 and the second base material 7 (drawing omitted). The laminating layer 6 may not be provided if not necessary. For example, when the first base material 2 and / or the second base material 7 is a resin film having heat sealability, an information recording body for laser marking can be obtained by heat sealing. Alternatively, after applying the coloring layer 4 to the first base material 2, the second base material 7 may be bonded before the coloring layer 4 is completely dried, and the coloring layer 4 may be completely dried. The material for forming the laminating layer 6 is not particularly limited, and for example, known or commonly used laminating adhesives, adhesives, thermoplastic resins, hot melts, aqueous adhesives, etc. can be used. Further, the laminating layer 6 may contain other components.

[0129] The above laminate adhesive includes, for example, 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 adhesive 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. Also, 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, 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.

[0130] The above adhesive includes, for example, 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, etc. Among them, from the viewpoint of excellent adhesion and transparency, an acrylic adhesive is preferable. The above adhesive can be used alone or in combination of two or more.

[0131] 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 above coating amount is within the above range, the adhesion between layers becomes more appropriate, and delamination between layers can be more suppressed.

[0132] (Other layers) The above printing layer can be provided at an appropriate position according to the intended use of the information recording body for laser marking of the present invention. For example, when the first base material is a transparent or translucent layer and printing is to be visually recognized from the first base material side, the printing layer can be provided on the surface opposite to the surface on which the first base material is located, when taking the color-developing layer as a reference. As the position where the printing layer is provided, for example, it may be between the color-developing layer and the intermediate layer, between the intermediate layer and the laminate layer, between the laminate layer and the second base material, or it may be the surface of the second base material opposite to the surface on which the laminate layer is provided. Also, when the second base material is a transparent or translucent layer and printing is to be visually recognized from the second base material side, the printing layer can be provided on the surface opposite to the surface on which the second base material is located, when taking the color-developing layer as a reference. As the position where the printing layer is provided, for example, it may be between the color-developing layer and the anchor layer, between the anchor layer and the first base material, or it may be the surface of the first base material opposite to the surface on which the anchor layer is provided. By providing such a printing layer, the printed portion of the color-developing layer can be visually recognized with the printing layer as a background, so that the contrast of the printed portion is improved and the visibility and decorative properties can be improved. The above printing layer can be mainly formed of a known or commonly used white ink such as titanium oxide or a colored ink. The above printing layer may further contain other components as required.

[0133] [Laser Marking Method] The information recording bodies for laser marking according to the first and second aspects of the present invention can be colored by irradiation with laser light. The above laser light is not particularly limited. For example, carbon dioxide laser light, YAG laser light, YVO 4Examples of the laser light include infrared laser light such as laser light, visible light laser light such as green laser light, and ultraviolet laser light such as excimer laser light and THG laser light. Among them, the laser light is preferably ultraviolet laser light with a wavelength exceeding 351 nm and not exceeding 400 nm, more preferably ultraviolet laser light with a wavelength exceeding 353 nm and not exceeding 390 nm, still more preferably ultraviolet laser light with a wavelength exceeding 353 nm and not exceeding 360 nm, and particularly preferably THG laser light. When such laser light is used as a light source, better color development properties can be obtained.

[0134] The information recording medium for laser marking according to the third aspect of the present invention can be colored by irradiation with ultraviolet laser light having a wavelength exceeding 351 nm and not exceeding 400 nm. Among them, the ultraviolet laser light is preferably ultraviolet laser light with a wavelength exceeding 353 nm and not exceeding 390 nm, more preferably ultraviolet laser light with a wavelength exceeding 353 nm and not exceeding 360 nm, and still more preferably THG laser light. When such laser light is used as a light source, better color development properties can be obtained.

[0135] The information recording medium for laser marking of the present invention develops color based on the reaction between the leuco dye mainly contained in the color developing layer and the developer. Therefore, compared with the color development based on phenomena such as scraping, gasifying, and carbonizing the object in conventional laser marking, printing can be performed more clearly. Further, in the laminated structure of the present invention, since the first substrate and / or the second substrate protects the coating layer such as the color developing layer, dust generation during laser light irradiation can be suppressed, and pollution of the working environment can be further suppressed.

[0136] [Method for manufacturing 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 material contained in the color developing layer 4 in a solvent such as water, this is coated on the first substrate 2, and further, the second substrate 7 is bonded and laminated to obtain the information recording medium 1 for laser marking shown in FIG. 1.

[0137] (Preparation Process) The method for preparing the coating liquid for the color developing layer is not particularly limited. For example, it can be prepared by previously dispersing all the materials in the same solvent. Also, a dye and a developer that react with each other can be prepared as separate dispersions and then mixed to obtain the coating liquid for the color developing layer. At that time, other components can be added to either the dispersion containing the dye or the dispersion containing the developer, or 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 kinds.

[0138] (Coating Process) The method for coating the coating liquid for the color developing layer is not particularly limited. For example, it includes a method of directly coating on a substrate, or a method of coating on a release liner or the like and then transferring it to a substrate. Examples of the coating method include air knife coating, bar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, gravure coating, 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.

[0139] (Drying Process) The method for drying the coating liquid for the color developing layer is not particularly limited. For example, it includes heat 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.

[0140] When the information recording medium for laser marking of the present invention includes layers other than the first base material, the color developing layer, and the second base material, the manufacturing method of the information recording medium for laser marking can incorporate the above content. Further, 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.

[0141] As a manufacturing method of the 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 the first base material 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. Then, a coating liquid for an intermediate layer is applied onto the color developing layer 4 and dried to form an intermediate layer 5, thereby producing a first laminate. Then, a second laminate is produced by forming a laminate layer 6 on the second base material 7. Next, the laser marking information recording medium 1 can be obtained by laminating through the laminate layer 6 such that the intermediate layer 5 of the first laminate and the laminate layer 6 are in contact. 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 preparation method of the coating liquid for the color developing layer. Further, the preparation method, coating method, and drying method are not particularly limited, and the methods listed above can be used. Also, the method of laminating through the laminate layer 6 is not particularly limited, and known or conventional methods can be applied according to the material of the laminate layer 6. For example, bonding by the dry lamination method using a dry lamination adhesive, bonding by the non-solvent lamination method using a non-solvent lamination adhesive, bonding by the hot melt lamination method using a hot melt adhesive, and bonding by the extrusion lamination method using a thermoplastic resin can be applied. When the above extrusion lamination method is used, a known or conventional anchor coating agent for extrusion lamination can also be used as an auxiliary agent. Further, when an adhesive is used 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.

[0142] As another embodiment, when the laser marking information recording medium 1 includes the intermediate layer 5, the laminate layer 6 may be formed on the intermediate layer 5 (drawing omitted).

[0143] As another embodiment, when the laser marking information recording medium 1 does not include the intermediate layer 5, the laminate layer 6 may be formed on the color developing layer 4 (drawing omitted).

[0144] The method for forming each of the above layers is not particularly limited. For example, they may be simultaneously coated in multiple layers by a curtain coater or the like, or may be sequentially formed individually. Also, some layers may be simultaneously coated and some layers may be sequentially formed individually.

Examples

[0145] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples at all.

[0146] A first laminate in which an anchor layer, a color developing layer, and an intermediate layer were laminated in this order on a first base material was produced by the following steps. Further, a second laminate in which a laminate layer was laminated on a second base material was produced by the following steps. By laminating such that the intermediate layer of the first laminate is in contact with the laminate layer of the second laminate, a laser marking information recording medium was produced and evaluated using it in each of the following tests.

[0147] Example 1 (Production of Laser Marking Information Recording Medium) <Anchor Layer> Using water as a solvent, a styrene acrylic resin having a solid content concentration of 38% by mass was applied and dried on the surface of a resin film A (material: polypropylene, thickness: 30 μm) as the first base material by a conventional method, whereby an anchor layer having a coating amount of 0.9 g / m 2 (dry mass) was formed.

[0148] <Color Developing Layer> As the dye, 17.4% by mass of 3-dibutylamino-6-methyl-7-anilinofluoran, as the developer, 26.8% by mass of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, as the filler, 10.0% by mass of kaolin (aqueous dispersion), as the binder, 33.1% by mass of styrene-butadiene latex (SBR), as the lubricant, 1.5% by mass of polystyrene, as the dispersant, 9.1% by mass of an acrylic resin, as the crosslinking agent, 2.0% by mass of a polyamide epichlorohydrin resin, and water as the solvent were used to prepare a coating liquid for the color-forming layer (solid content concentration: 21% by mass) by a conventional method. The coating liquid for the color-forming layer was applied to the surface of the anchor layer by a conventional method and dried to form a color-forming layer A with a coating amount of 4.5 g / m 2 (dry mass). The numerical values of the above materials represent the mass ratios of the respective materials with respect to 100% by mass of the color-forming layer (dry state).

[0149] <Intermediate layer> As the resin, 85.0% by mass of a core-shell type acrylic resin, as the crosslinking agent, 15.0% by mass of a polyamide epichlorohydrin resin, and water as the solvent were used to prepare a coating liquid for the intermediate layer (solid content concentration: 18.5% by mass) by a conventional method. The coating liquid for the intermediate layer was applied to the surface of the color-forming layer by a conventional method and dried to form an intermediate layer A with a coating amount of 1.9 g / m 2 (dry mass), and a first laminate was obtained. The numerical values of the above materials represent the mass ratios of the respective materials with respect to 100% by mass of the intermediate layer (dry state).

[0150] <Laminating layer> A urethane type adhesive A for dry lamination containing ethyl acetate as the solvent and having a solid content concentration of 22% by mass (main component: 93.7% by mass, curing agent: 6.3% by mass) was applied to the surface of a resin film B (material: polyethylene terephthalate, thickness: 50 μm) as the second substrate by a conventional method to form a laminating layer A, and a second laminate was obtained. The numerical values of the above materials represent the mass ratios of the respective materials with respect to 100% by mass of the laminating layer (dry state).

[0151] Next, the laminate layer A of the second laminate and the intermediate layer of the first laminate were laminated by dry lamination so that they were in direct contact (dry lamination method). In this way, an information recording body for laser marking of Example 1 composed of [resin film A / anchor layer / color developing layer A / intermediate layer A / laminate layer A / resin film B] was produced.

[0152] 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 a resin film C (material: polyethylene terephthalate, thickness: 12 μm) was used instead of the resin film B as the second base material.

[0153] Example 3 (Production of Information Recording Body for Laser Marking) An information recording body for laser marking of Example 3 was produced in the same manner as in Example 1, except that a resin film C (material: polyethylene terephthalate, thickness: 12 μm) was used instead of the resin film B as the second base material, a laminate layer B was used instead of the laminate layer A, and it was laminated by bonding instead of the dry lamination method. The laminate layer B was formed by coating an acrylic adhesive B on the surface of the second base material by a conventional method and heating and drying. At this time, since the laminate layer B has adhesiveness, it can be laminated by bonding so as to be in direct contact with the intermediate layer A of the first information recording body.

[0154] Example 4 (Production of Information Recording Body for Laser Marking) An information recording body for laser marking of Example 4 was produced in the same manner as in Example 1, except that a resin film D (material: biaxially oriented polypropylene, thickness: 40 μm) was used instead of the resin film B as the second base material.

[0155] Example 5 (Production of Information Recording Body for Laser Marking) A laser marking information recording medium of Example 5 was produced in the same manner as in Example 1, except that laminate layer C was used instead of laminate layer A and the layers were laminated by a non-solvent lamination method instead of a dry lamination method. The above laminate layer C was formed by applying an isocyanate type adhesive C for non-solvent lamination to the surface of the second substrate.

[0156] Example 6 (Production of Laser Marking Information Recording Medium) A laser marking information recording medium of Example 6 was produced in the same manner as in Example 1, except that intermediate layer A was not formed.

[0157] Example 7 (Production of Laser Marking Information Recording Medium) A laser marking information recording medium of Example 7 was produced in the same manner as in Example 1, except that color developing layer B was used instead of color developing layer A. The above color developing layer B is the same as color developing layer A, except that the developer is 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate instead of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0158] Example 8 (Production of Laser Marking Information Recording Medium) A laser marking information recording medium of Example 8 was produced in the same manner as in Example 1, except that color developing layer C was used instead of color developing layer A. The above color developing layer C is the same as color developing layer A, except that the developer is 4-hydroxy-4'-propoxydiphenyl sulfone instead of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0159] Comparative Example 1 (Production of Laser Marking Information Recording Medium) A laser marking information recording medium of Comparative Example 1 consisting of [resin film A / anchor layer / color developing layer A / intermediate layer A] was produced in the same manner as in Example 1, except that the laminate layer and the second substrate were not laminated.

[0160] Comparative Example 2 (Preparation of Information Recording Medium for Laser Marking) A laser marking information recording medium of Comparative Example 2 was prepared in the same manner as in Example 1, except that Color Developing Layer B was used instead of Color Developing Layer A, and the laminate layer and the second base material were not laminated.

[0161] Comparative Example 3 (Preparation of Information Recording Medium for Laser Marking) A laser marking information recording medium of Comparative Example 3 was prepared in the same manner as in Example 1, except that Color Developing Layer C was used instead of Color Developing Layer A, and the laminate layer and the second base material were not laminated.

[0162] (Evaluation) The following evaluations were performed on the information recording media for laser marking prepared in the examples and comparative examples. The results are shown in Tables 1 and 2.

[0163] (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, or 1600 mm / sec. Subsequently, the optical density (OD value) of the developed printed portion was measured using a spectrophotometer (manufactured by Videojet X-Rite Co., Ltd., device name: X-rite eXact). Also, when dust generation was observed during printing at the setting of 1300 mm / sec operating speed, or when damage was confirmed by visual observation of the surface of the printed portion after printing, the appearance was evaluated as "×", and when neither dust generation nor surface damage was confirmed, the appearance was evaluated as "○". In this measurement, the frequency of the UV laser printer was 55 Hz and the laser power was 50%. During printing, the laser marking information recording medium of the example was irradiated with laser light on the side of the second base material, which is one end face, and the laser marking information recording medium of the comparative example was irradiated with laser light on the side of the intermediate layer, which is one end face. Note that 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.

[0164]

Table 1

[0165] (2) Optical density of the colored part before and after the damp heat resistance test For the information recording body for laser marking, a thermal gradient plate set at 170 °C with a 10 °C gradient was used to cause color development to achieve the maximum color density. The optical density of the colored part was measured with a spectrophotometer (manufactured by Videojet X-Rite Co., Ltd., device name: X-rite eXact), and the optical density at this time was taken as the optical density before the damp heat resistance test. Next, after leaving the information recording body for laser marking stationary in an environment of 50 °C and 100% humidity for 1 day, the optical density of the colored part was measured again in the same manner, and the optical density at this time was taken as the optical density after the damp heat resistance test. By dividing the value of the optical density after the test by the value of the optical density before the test, the residual ratio of the colored part (optical density after the damp heat resistance test / optical density before the damp heat resistance test) was obtained.

[0166]

Table 2

[0167] As shown in Table 1, for the information recording body for laser marking provided with the second substrate, no dust generation was confirmed during laser light irradiation, and no damage was confirmed from the second substrate after printing. Therefore, it was confirmed that it is suitable for printing by a UV laser printer (Examples 1 to 8). Furthermore, it was also confirmed that in all cases, the optical density exceeded 1, and high contrast and good color development properties could be achieved (Examples 1 to 8).

[0168] Also, at this time, the thickness and material of the second substrate, and the material of the laminate layer were not limited at all and were widely applicable. Among them, from the comparison between Example 1 and Example 2, when using substrates composed of a common resin, Example 1 with a larger thickness tended to show a higher optical density. Specifically, in Example 1, printing was performed by irradiating a laser beam onto Resin Film B (thickness: 50 μm), and the optical density at that time was 1.52. On the other hand, in Example 2, Resin Film C (thickness: 12 μm) was used, and the optical density at that time was 1.46. The reason for this is not clear, but for example, it is conceivable that as the thickness of the first substrate increases, the physical strength is further improved, so the protection for the color-developing layer 4 is further improved, defects in the printed area during laser beam irradiation are more suppressed, and the color-developing property is also further improved.

[0169] On the other hand, for the laser marking information recording body without the second substrate, dust generation and damage to the surface on the intermediate layer side were confirmed during laser beam irradiation, and a decrease in optical density was also observed. Therefore, it was confirmed that it was not suitable for printing by a UV laser printer (Comparative Examples 1 to 3).

[0170] Here, the information recording body for laser marking in the examples has a laminated structure in which the color-developing layer is sandwiched between a first base material and a second base material that are resin films transmitting ultraviolet rays. Therefore, as in the above examples, the laser light irradiated onto the second base material can pass through the second base material and act efficiently on the color-developing layer. Thus, it is considered that the color-developing layer absorbed the laser light and could exhibit good color development due to its energy. Further, since laser light generally has high energy, when the color-developing layer absorbs the laser light, a phenomenon accompanied by some impact such as foaming or gasification may occur. However, since the above color-developing layer is protected by being sandwiched between the base materials, it is considered that laser marking was possible without causing damage. As a result, it is considered that all of the information recording bodies for laser marking in the examples were capable of laser marking and could achieve good color-developing properties. On the other hand, since the information recording body for laser marking in the comparative example has a laminated structure without the second base material, laser light is irradiated onto the intermediate layer which is the coating layer. And, for example, since the intermediate layer which is the coating layer is inferior in physical strength to the base material, it may not withstand the above impact when the color-developing layer absorbs the laser light and may be damaged, or there is a possibility that the intermediate layer itself absorbs the laser light and is damaged by its energy. In addition, since the information recording bodies for laser marking in the above Examples 1 to 8 are resin films transmitting ultraviolet rays for both the first base material and the second base material, printing was possible even when laser light was irradiated from the first base material side.

[0171] Also, as shown in Table 2, in the damp heat resistance test, when the intermediate layer is provided (Example 1), the residual rate of the coloring portion is higher than when the intermediate layer is not provided (Example 6). Thus, it was confirmed that providing the intermediate layer improves the damp heat resistance. This is because the intermediate layer has a crosslinked structure derived from a resin having a water-soluble portion and a crosslinking agent, and the water-soluble portion and the crosslinked structure suppress the migration of the oil-soluble components in the second base material and the laminate layer to the coloring layer. As a result, it is considered that the damp heat resistance has been improved. Furthermore, it was confirmed that the absolute value of the optical density before the damp heat resistance test was also larger when the intermediate layer was provided (Example 1) than when the intermediate layer was not provided (Example 6). This is considered to be because when the intermediate layer is not provided as in Example 6, even after the information recording body for laser marking is produced and before it is used in the damp heat resistance test, the coloring portion is affected by the laminate layer, and the optical density of the coloring portion decreases. That is, even in a room temperature environment with a lower load rather than in an environment subjected to a high load such as the damp heat resistance test, the optical density of the coloring portion can decrease due to the influence of the laminate layer, but by providing the intermediate layer of the present invention, such a decrease in the optical density can be more suppressed.

[0172] Also, as shown in Table 2, in the test using 3-[(3-phenylureido)phenyl]-4-methylbenzenesulfonate, which is a non-phenolic developer, when the second base material and the laminate layer are provided (Example 7), it was confirmed that the damp heat resistance was significantly improved compared to when the second base material and the laminate layer were not provided (Comparative Example 2). From this result, it was found that even a developer that is relatively easily affected by a high temperature and high humidity environment has improved damp heat resistance by adopting the laminated structure of the present invention. This is considered to be because since the coloring layer is protected by the second base material and the laminate layer, it becomes difficult for water (moisture) in the environment to reach the developer contained in the coloring layer, and as a result, the discoloration reaction caused by the water is more suppressed.

[0173] Hereinafter, variations of the invention according to the present disclosure will be described. [Supplementary Note 1] An information recording medium in which a first substrate, a color developing layer, and a second substrate are laminated in this order, wherein the first substrate is a layer that transmits ultraviolet rays, the color developing layer contains a leuco dye and a developer, and the developer contains a non-phenolic developer, an information recording medium for laser marking. [Supplementary Note 2] The information recording medium for laser marking according to Supplementary Note 1, 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). [Supplementary Note 3] The information recording medium for laser marking according to Supplementary Note 1 or 2, wherein the non-phenolic developer contains at least the compound represented by the above formula (1). [Supplementary Note 4] The information recording medium for laser marking according to any one of Supplementary Notes 1 to 3, wherein a laminate layer is further provided between the color developing layer and the second substrate. [Supplementary Note 5] A thermal recording medium in which an intermediate layer is further provided between the color developing layer and the second substrate, and the intermediate layer contains a resin having a water-soluble portion and / or a cross-linking agent, the information recording medium for laser marking according to any one of Supplementary Notes 1 to 3. [Supplementary Note 6] The information recording medium for laser marking according to Supplementary Note 5, wherein the intermediate layer contains a resin having a water-soluble portion and a cross-linking agent. [Supplementary Note 7] The information recording medium for laser marking according to Supplementary Note 5 or 6, 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. [Supplementary Note 8] The information recording medium for laser marking according to any one of Supplementary Notes 5 to 7, wherein a laminate layer is further provided between the intermediate layer and the second substrate. [Supplementary Note 9] An information recording medium in which a first substrate, a color developing layer, an intermediate layer, and a second substrate are laminated in this order, wherein the first substrate is a layer that transmits ultraviolet rays, the color developing layer contains a leuco dye and a developer, and the intermediate layer contains a resin having a water-soluble portion and / or a cross-linking agent, an information recording medium for laser marking. [Appendix 10] The information recording medium for laser marking according to Appendix 9, wherein the intermediate layer contains a resin having a water-soluble portion and a crosslinking agent. [Appendix 11] The information recording medium for laser marking according to Appendix 10, 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 12] The information recording medium for laser marking according to any one of Appendices 9 to 11, wherein a laminate layer is further provided between the intermediate layer and the second base material. [Appendix 13] An information recording medium in which a first base material, a coloring layer, and a second base material are laminated in this order, wherein the first base material is a layer that transmits ultraviolet rays, the coloring layer contains a leuco dye and a developer, and is an information recording medium for ultraviolet laser marking that can be colored by irradiation with ultraviolet laser light having a wavelength exceeding 351 nm and 400 nm or less. [Appendix 14] The information recording medium for laser marking according to Appendix 13, wherein the ultraviolet laser light is THG laser light. [Appendix 15] The information recording medium for laser marking according to Appendix 13 or 14, wherein a laminate layer is further provided between the coloring layer and the second base material. [Appendix 16] The information recording medium for laser marking according to any one of Appendices 1 to 15, wherein an anchor layer is further provided between the first base material and the coloring layer. [Appendix 17] The information recording medium for laser marking according to any one of Appendices 1 to 16, wherein the second base material is a layer that transmits ultraviolet rays. [Appendix 18] The information recording medium for laser marking according to any one of Appendices 1 to 17, wherein the first base material is a resin film. [Appendix 19] The information recording medium for laser marking according to any one of Appendices 1 to 18, wherein the thickness of the first base material is 15 μm or more. [Appendix 20] The information recording medium for laser marking according to any one of Appendices 1 to 19, wherein the second base material is a resin film. [Appendix 21] The laser marking information recording medium according to any one of Appendices 1 to 20, wherein the thickness of the second base material is 15 μm or more. [Appendix 22] The laser marking information recording medium according to any one of Appendices 1 to 21, wherein the first base material is located on one end face of the laser marking information recording medium, and the second base material is located on the other end face of the laser marking information recording medium.

Explanation of Reference Numerals

[0174] 1 Laser marking information recording medium 2 First base material 3 Anchor layer 4 Color-developing layer 5 Intermediate layer 6 Laminating layer 7 Second base material

Claims

1. This is an information recording body in which a first substrate, a color-developing layer, an intermediate layer, a laminate layer, and a second substrate 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 color developer. The aforementioned color developer includes a non-phenolic color developer having a melting point of 195°C or lower. The color-developing layer may contain a laser sensitizer. If the color-developing layer contains the laser sensitizer, the content of the laser sensitizer is 20% by mass or less with respect to 100% by mass of the total solid content of the color-developing layer, in an information recording body for laser marking.

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

3. This is an information recording body in which a first substrate, a color-developing layer, an intermediate layer, and a second substrate 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 color developer. The aforementioned intermediate layer is an information recording medium for laser marking, comprising a core-shell type resin.

4. The information recording body for laser marking according to claim 3, wherein the intermediate layer comprises the core-shell type resin and a crosslinking agent.

5. The information recording body for laser marking according to claim 4, wherein the core-shell type resin is a core-shell type resin having at least a carboxyl group as a water-soluble portion.

6. The laser marking information recording body according to claim 5, wherein a laminate layer is further provided between the intermediate layer and the second substrate.

7. This is an information recording body in which a first substrate, a color-developing layer, and a second substrate 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 color developer having a melting point of 195°C or lower. The color-developing layer may contain a laser sensitizer. If the color-developing layer contains the laser sensitizer, the content of the laser sensitizer is 20% by mass or less with respect to 100% by mass of the total solid content of the color-developing layer. An information recording medium for ultraviolet laser marking that can produce color when irradiated with ultraviolet laser light with a wavelength between 351 nm and 400 nm.

8. The information recording body for laser marking according to claim 7, wherein the ultraviolet laser light is THG laser light.

9. The laser marking information recording body according to claim 8, wherein a laminate layer is further provided between the color-developing layer and the second substrate.

10. The laser marking information recording body according to any one of claims 1 to 9, wherein an anchor layer is further provided between the first substrate and the color-developing layer.

11. The laser marking information recording body according to any one of claims 1 to 9, wherein the second substrate is a layer that transmits ultraviolet light.

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