Coating liquid for forming thermo-sensitive recording layer, thermo-sensitive recording medium, and method for manufacturing thermo-sensitive recording medium

Abstract

To provide a thermo-sensitive recording layer formation liquid which enables formation of a thermo-sensitive recording layer that has excellent printability at high speed printing and texture stability, and excellent surface printing physical property.SOLUTION: A coating liquid for forming a thermo-sensitive recording layer contains a leuco dye, a developer containing an electron acceptor for coloring the leuco dye, a binder resin A, a surface active agent, and a solvent, wherein the developer contains a non-phenolic developer, the binder resin A contains an acrylic resin a, the acrylic resin a has an acid value of 120 mgKOH / g or less and Tg of 95°C or lower, and a percentage content of the acrylic resin a is 70 to 100 wt.% with respect to the total binder resin A.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a coating liquid for forming a heat-sensitive recording layer, a heat-sensitive recording medium, and a method for manufacturing the heat-sensitive recording medium.

Background Art

[0002] Generally, a heat-sensitive recording medium is obtained by coating a support such as paper, synthetic paper, or a plastic film with a coating liquid containing a colorless or light-colored leuco dye and a developer, and color development occurs through an instantaneous chemical reaction caused by heating with a thermal head, laser light, etc., to obtain a recorded image. Heat-sensitive recording media are widely used as recording media such as facsimiles, various tickets, measurement recorders, receipts from supermarkets and convenience stores, and label seals. In recent years, in addition to conventional heat-sensitive recording media, there has been an increasing demand for hybrid packaging materials that can be digitally printed in a subsequent process by providing a heat-sensitive recording layer partially on a substrate having a plastic film as a support, such as a label or a packaging package. Furthermore, it is ideal for the packaging material to be manufactured by a process of simultaneously printing a normal design printing layer and a heat-sensitive recording layer using the same printing machine. Normally, the design printing layer of the above-mentioned label or packaging package is often printed at a high speed such as 150 to 300 m / min in the case of gravure printing. Therefore, in the printing of the heat-sensitive recording layer as well, the printing suitability (resistance to plate fogging) of the coating liquid for forming the heat-sensitive recording layer, as well as the substrate stability (resistance to substrate staining) against a drying oven and guide roll friction at high temperatures, are required. Also, it must have physical properties equivalent to those of normal surface printing inks.

[0003] As a technique for providing a heat-sensitive recording layer with high substrate stability partially by a printing process, for example, a heat-sensitive recording layer forming liquid is proposed that contains a leuco dye, an electron-accepting compound as a developer for developing the leuco dye, the solubility of which in 100% ethanol at 20°C is 5.0% by mass or less, and a solvent (Patent Document 1). However, the heat-sensitive recording layer forming liquid described in Patent Document 1 had a problem with the substrate density after printing and winding. In addition, various methods have been proposed for improving the texture stability (for example, Patent Documents 2 and 3). However, the coating liquid for the heat-sensitive recording layer described in Patent Documents 2 and 3 uses a polyvinyl alcohol-based resin as a binder resin, and there are problems in printing suitability and the like.

[0004] On the other hand, phenol-based developers that have been widely used conventionally do not have sufficient storage stability in various printed and non-printed areas and are suspected of being endocrine disruptors. For example, N,N'-diphenylurea derivatives that satisfy the required performance as a heat-sensitive recording material such as the storage stability of the printed area and do not contain phenol compounds that are a concern in environmental hygiene, a method for producing the same, and a heat-sensitive recording material using the same as a developer have been proposed (Patent Document 4).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a heat-sensitive recording layer forming liquid that can form a heat-sensitive recording layer excellent in printing suitability during high-speed printing, texture stability, and surface printing physical properties such as adhesion, rub resistance, and disinfectant resistance.

Means for Solving the Problems

[0007] The present invention relates to the following [1] to

[11] . [1] A coating liquid for forming a heat-sensitive recording layer, comprising a leuco dye, a developer containing an electron acceptor for developing the leuco dye, a binder resin A, a surfactant, and a solvent, wherein the developer contains a non-phenolic developer, wherein the binder resin A contains an acrylic resin a, The acid value of the acrylic resin a is 120 mgKOH / g or less, and the Tg is 95 °C or less, and the content of the acrylic resin a is 70 to 100% by weight based on the total binder resin A. A coating liquid for forming a heat-sensitive recording layer.

[0008] [2] The coating liquid for forming a heat-sensitive recording layer according to [1], wherein the surfactant contains a polyoxyethylene alkyl phenyl ether and / or an acetylene glycol-based nonionic surfactant.

[0009] [3] Furthermore, the coating liquid for forming a heat-sensitive recording layer according to [1] or [2], which contains a extender pigment.

[0010] [4] A leuco dye dispersion liquid for a coating liquid for forming a heat-sensitive recording layer, comprising a leuco dye, a binder resin B, a surfactant, and a solvent, wherein the binder resin B contains an acrylic resin b, The acid value of the acrylic resin b is 120 mgKOH / g or less, and the Tg is 95 °C or less, and the content of the acrylic resin b is 70 to 100% by weight based on the total binder resin B. A leuco dye dispersion liquid for a coating liquid for forming a heat-sensitive recording layer.

[0011] [5] A developer dispersion liquid for a coating liquid for forming a heat-sensitive recording layer, comprising a non-phenolic developer, a binder resin C, a surfactant, and a solvent, wherein the binder resin C contains an acrylic resin c, The acid value of the acrylic resin c is 120 mgKOH / g or less, and the Tg is 95 °C or less, and the content of the acrylic resin c is A developer dispersion for a coating liquid for forming a heat-sensitive recording layer, which is 70 to 100% by weight based on the total amount of the binder resin C.

[0012] [6] A heat-sensitive recording medium comprising a substrate, an ink layer, a heat-sensitive recording layer, and an overcoat layer in this order, The heat-sensitive recording medium, wherein the heat-sensitive recording layer is formed by the coating liquid for forming a heat-sensitive recording layer according to any one of [1] to [3].

[0013] [7] The heat-sensitive recording medium according to [6], wherein the substrate is a polyolefin.

[0014] [8] A method for manufacturing a heat-sensitive recording medium comprising a substrate, an ink layer, a heat-sensitive recording layer, and an overcoat layer in this order, The method for manufacturing a heat-sensitive recording medium, which includes a step of forming the heat-sensitive recording layer using the coating liquid for forming a heat-sensitive recording layer according to any one of [1] to [3] on the ink layer in contact with the substrate.

[0015] [9] Furthermore, the method for manufacturing a heat-sensitive recording medium according to [8], which includes a step of manufacturing a coating liquid for forming a heat-sensitive recording layer using the leuco dye dispersion according to [4] and the developer dispersion according to [5].

[0016]

[10] The method for manufacturing a heat-sensitive recording medium according to [9], wherein the step of manufacturing a coating liquid for forming a heat-sensitive recording layer is a step of using the leuco dye dispersion according to [4], the developer dispersion according to [5], an alcohol-based organic solvent, and / or a glycol ether-based organic solvent.

[0017]

[11] The method for manufacturing a heat-sensitive recording medium according to any one of [8] to

[10] , wherein the step of forming the heat-sensitive recording layer is a step of gravure printing at a speed of 100 m / min or more. [Advantages of the Invention]

[0018] According to the present invention, a heat-sensitive recording layer forming liquid capable of forming a heat-sensitive recording layer excellent in printing suitability and ground texture stability during high-speed printing and excellent in surface printing physical properties such as adhesion, rub resistance, and disinfectant resistance has been provided.

Embodiments for Carrying Out the Invention

[0019] <Coating Liquid for Forming Heat-Sensitive Recording Layer> The coating liquid for forming a heat-sensitive recording layer of the present invention contains a leuco dye, a developer containing an electron acceptor for developing the leuco dye, a binder resin A, a surfactant, and a solvent.

[0020] <Leuco Dye> The leuco dye used in the present invention is not particularly limited and can be appropriately selected according to the purpose from those used in heat-sensitive recording media. For example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes are preferably mentioned. The content of the leuco dye is preferably 5 to 20% by mass based on the total coating liquid for forming the heat-sensitive recording layer.

[0021] <Developer> The developer used in the present invention includes a non-phenol-based developer that is an electron acceptor for developing the leuco dye. The non-phenol-based developer means a developer having no phenol skeleton and is excellent in printing suitability, ground texture stability, environmental harmony, and safety compared with phenol-based developers that have concerns about endocrine disruption.

[0022] Examples of the non-phenol-based developer include compounds represented by the following general formula (1), compounds represented by the following general formula (2), and compounds represented by the following general formula (3). The content of the developer is preferably 10 to 30% by mass based on the total coating liquid for forming the heat-sensitive recording layer.

[0023] General formula (1)

Chemical formula

[0024] (wherein R 1 may be the same or different and each represents an alkyl group or an alkoxy group, and n represents an integer of 0 to 3.)

[0025] General formula (2)

Chemical formula

[0026] (wherein R 2 represents a hydrogen atom or an alkyl group, and R 4 ~R 8 may be the same or different and each represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group, and m represents an integer of 0 to 2.)

[0027] General formula (3)

Chemical formula

[0028] <Sensitizer> In the heat-sensitive recording layer of the heat-sensitive recording medium of the present invention, a sensitizer can be used as needed, and conventionally known sensitizers can be used as the sensitizer. For example, fatty acid amides such as stearic acid amide, bisstearic acid amide, and palmitic acid amide, p-toluenesulfonamide, stearic acid, fatty acid metal salts of calcium, zinc or aluminum such as behenic acid and palmitic acid, p-benzylbiphenyl, diphenyl sulfone, benzyl benzyloxybenzoate, 2-benzyloxynaphthalene, 1,2-bis(p-tolyloxy)ethane, 1,2-bis(phenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,3-bis(phenoxy)propane, dibenzyl oxalate, p-methylbenzyl oxalate, m-terphenyl, 1-hydroxy-2-naphthoic acid can be mentioned.

[0029] <Binder resin A> The binder resin is used to hold the leuco dye and the developer in the heat-sensitive recording layer. The content of the binder resin A is preferably 4 to 20% by mass based on the total coating solution.

[0030] The binder resin A contains an acrylic resin a, and the acrylic resin a has an acid value of 120 mgKOH / g or less and a Tg of 95°C or less. The content of the acrylic resin a is 70 to 100% by weight based on the total binder resin A, preferably 80% by mass or more, and more preferably 90% by mass or more. When the binder resin A contains two or more acrylic resins, the content of the acrylic resin a is the total of the contents of the respective acrylic resins.

[0031] Acrylic resin a is a resin obtained by vinyl polymerization of one or more vinyl monomers containing (meth)acrylic acid ester. Examples of the vinyl monomers include alkyl ester compounds of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, etc.; (meth)acrylamide derivatives containing at least one N-substituted methylol group such as N-methylol (meth)acrylamide; aminoalkyl esters of (meth)acrylic acid such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, dipropylaminopropyl (meth)acrylate; mono- or diesters of (meth)acrylic acid with glycols such as diethylene glycol and dipropylene glycol; styrene derivatives such as styrene and α-methylstyrene; hydroxyalkyl ester compounds of (meth)acrylic acid such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate; and vinyl compounds having acid groups such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid. These may be used alone or in combination. Among them, styrene derivatives are preferred, that is, acrylic resin a is preferably a styrene-acrylic resin.

[0032] Acrylic resin a is preferably a water-soluble acrylic resin that can be used in an aqueous system or an acrylic emulsion. From the viewpoints of the storage stability of the coating liquid and printing suitability, a water-soluble acrylic resin is more preferred. From the viewpoint of the surface printing properties (disinfectant resistance), an acrylic emulsion is more preferred. These may be used alone or in combination.

[0033] The acid value of acrylic resin a is 120 mgKOH / g or less, more preferably 100 mgKOH / g or less, and even more preferably 80 mgKOH / g or less, from the viewpoint of substrate stability (resistance to substrate staining) in the step of printing the heat-sensitive recording layer. Also, the acid value of acrylic resin a is preferably 10 mgKOH / g or more, and more preferably 25 mgKOH / g or more.

[0034] Also, the Tg of acrylic resin a is 95°C or less, more preferably 90°C or less, and even more preferably 80°C or less, from the viewpoint of adhesion (flex resistance) to various substrates including the polyolefin substrate.

[0035] When the binder resin A contains two or more types of acrylic resins, the values of the acid value and Tg of acrylic resin a are the sum of the products of the acid value and Tg of each acrylic resin and the blending ratio.

[0036] <Surfactant> As the surfactant, any of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used. The content of the surfactant is preferably 0.1 to 5% by mass, and more preferably 1 to 4% by mass, based on the total coating liquid.

[0037] Examples of nonionic surfactants include acetylene glycol-based surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, glycerin fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Examples of anionic surfactants include polyoxyethylene alkyl ether carboxylates, linear alkylbenzene sulfonates, and laurates. Examples of cationic surfactants include alkylamine salts, alkyltrimethylammonium salts, dialkyldimethylammonium salts, and benzalkonium chlorides.

[0038] Among them, from the viewpoints of the dispersibility of the leuco dye and the developer and the printability, it is preferable to contain a polyoxyethylene alkyl phenyl ether and / or an acetylene glycol-based nonionic surfactant. These surfactants stabilize the dispersion of the leuco dye and the developer more, and contribute to the improvement of printability such as leveling property and plate wear resistance during gravure printing. The content of the polyoxyethylene alkyl phenyl ether and / or the acetylene glycol-based nonionic surfactant is preferably 0.1 to 5% by mass, more preferably 1 to 4% by mass, based on the whole coating liquid.

[0039] <Solvent> The solvent used in the present invention preferably contains water. The water content is preferably 10 to 80% by mass, more preferably 20 to 60% by mass, based on the whole coating liquid.

[0040] The solvent may contain organic solvents such as alcohol-based, glycol ether-based, ketone-based, and ester-based solvents in addition to water, and preferably contains alcohol-based and glycol ether-based organic solvents among them. Examples of the organic solvent include methanol, ethanol, n-propanol, isopropyl alcohol, 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol, ethylene glycol, propylene glycol, diethylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monopropyl ether. Among them, from the viewpoint of printability such as leveling property and plate wear resistance, one or more selected from the group consisting of isopropyl alcohol, n-propanol, and propylene glycol monomethyl ether are preferable. The content of the organic solvent is preferably 5 to 40% by mass, more preferably 5 to 20% by mass, still more preferably 5 to 13% by mass, based on the whole coating liquid. Also, the content rate of the organic solvent is preferably 5 to 60% by mass, more preferably 5 to 40% by mass, still more preferably 5 to 20% by mass, and particularly preferably 5 to 19% by mass with respect to the whole solvent.

[0041] <Extender pigment> The coating liquid for forming a heat-sensitive recording layer of the present invention preferably further contains an extender pigment. Examples of the extender pigment include inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium oxide, zirconium oxide, aluminum hydroxide, aluminum silicate, zinc hydroxide, barium sulfate, clay, kaolin, talc, and surface-treated silica. These may be used alone or in combination of two or more, but it is preferable to contain calcium carbonate and / or aluminum silicate from the viewpoints of printability and substrate stability. The content rate of the extender pigment is preferably 0.01 to 2 parts by mass with respect to 1 part by mass of the color former.

[0042] <Leuco dye dispersion> The coating liquid for forming a heat-sensitive recording layer of the present invention contains a leuco dye, a color former containing an electron acceptor for developing the leuco dye, a binder resin A, a surfactant, and a solvent. Each component may be charged into the same kettle for production, or a leuco dye dispersion and a color former dispersion may be produced in advance and then mixed together. The leuco dye dispersion of the present invention preferably contains, for example, a leuco dye, a binder resin B, a surfactant, and a solvent. The binder resin B may be the same as or different from the above binder resin A. The binder resin B contains an acrylic resin b, and the acrylic resin b has an acid value of 120 mgKOH / g or less and a Tg of 95°C or less. When the binder resin B contains two or more acrylic resins, the acid value and Tg values of the acrylic resin b are the sum of the products of the acid value and Tg of each acrylic resin and the blending ratio.

[0043] The content of acrylic resin b is 70 to 100% by weight based on the total binder resin B. When the binder resin B contains two or more kinds of acrylic resins, the content of acrylic resin b is the sum of the contents of the respective acrylic resins. The acrylic resin b may be the same as or different from the acrylic resin a.

[0044] <Developer dispersion> The developer dispersion of the present invention preferably contains, for example, a developer, a binder resin C, a surfactant, and a solvent. The binder resin C may be the same as or different from the above binder resin A and / or binder resin B. The binder resin C contains an acrylic resin c, and the acrylic resin c has an acid value of 120 mgKOH / g or less and a Tg of 95°C or less. When the binder resin C contains two or more kinds of acrylic resins, the acid value and Tg values of the acrylic resin c are the sum of the products of the acid value and Tg of each acrylic resin and the blending ratio.

[0045] The content of acrylic resin c is 70 to 100% by weight based on the total binder resin c. When the binder resin C contains two or more kinds of acrylic resins, the content of acrylic resin c is the sum of the contents of the respective acrylic resins. The acrylic resin c may be the same as or different from the acrylic resin a and / or acrylic resin b.

[0046] <Thermosensitive recording medium> The thermosensitive recording medium of the present invention preferably contains, for example, a base material, an ink layer, a thermosensitive recording layer, and an overcoat layer.

[0047] <Base material> The type and thickness of the base material used in the present invention are not particularly limited, but it is preferably in the form of a plastic film. Examples of the type of the base material include a polyolefin base material, a polyolefin base material subjected to an antifogging treatment, a polyester-based base material, a nylon (polyamide) base material, and vapor deposition products of these metal oxides. Among them, from the viewpoint of blocking resistance, a polyolefin substrate is preferable. In the case of a polyolefin substrate, it is more preferable to use a corona discharge-treated polyolefin substrate having a functional group such as a hydroxyl group or a carbonyl group because a good printed matter can be obtained. The plastic substrate is preferably a uniaxially or biaxially stretched substrate.

[0048] <Ink layer> The ink layer used in the present invention is preferably formed by printing and coating an aqueous or oily ink composed of at least a binder resin and a solvent. The aqueous or oily ink may contain a colorant, an aliphatic amide, a hydrocarbon wax, and other additives in addition to the binder resin and the solvent. The binder resin is not particularly limited and can be selected depending on the type and use of the substrate to be printed. As the colorant, organic and inorganic pigments and dyes used in general inks, paints, and recording agents can be used regardless of whether they are colored or colorless. Examples of the organic pigment include pigments such as azo-based, phthalocyanine-based, anthraquinone-based, perylene-based, perinone-based, quinacridone-based, thioindigo-based, dioxazine-based, isoindolinone-based, quinophthalone-based, azomethine azo-based, diketopyrrolopyrrole-based, and isoindoline-based pigments. Examples of the inorganic pigment include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, and mica.

[0049] <Thermal recording layer> The thermal recording layer used in the present invention can be formed using the coating liquid for forming the thermal recording layer of the present invention.

[0050] <Overcoat layer> The overcoat layer used in the present invention is composed of a binder resin, an extender pigment, a lubricant, a crosslinking agent, etc. Examples of the binder resin include acrylic resin and urethane resin. Examples of the lubricant include polyethylene and zinc stearate. Examples of the crosslinking agent include carbodiimide compounds, zirconium carbonate, and isocyanate compounds.

[0051] <Method for manufacturing a thermal recording medium> The method for manufacturing the thermal recording medium of the present invention includes, for example, a step of laminating a base material, an ink layer, a thermal recording layer, and an overcoat layer in this order. Therefore, as a preferred form, A step of forming an ink layer on the base material, A step of forming a thermal recording layer on the ink layer, It is preferable to have a step of forming an overcoat layer on the thermal recording layer.

[0052] The method for manufacturing the thermal recording medium of the present invention preferably further includes a step of manufacturing a coating liquid for forming a thermal recording layer using a leuco dye dispersion liquid and a developer dispersion liquid. The step of manufacturing the coating liquid for forming the thermal recording layer preferably includes, for example, mixing a leuco dye dispersion liquid, a developer dispersion liquid, and, if necessary, a solvent or the like. Also, the step of manufacturing the coating liquid for forming the thermal recording layer is preferably a step of using a leuco dye dispersion liquid, a developer dispersion liquid, an alcohol-based organic solvent, and / or a glycol ether-based organic solvent. When mixing the leuco dye dispersion liquid and the developer dispersion liquid, by mixing both the alcohol-based organic solvent and / or the glycol ether-based organic solvent together, a coating liquid for forming a thermal recording layer with more excellent printing suitability can be obtained. The alcohol-based organic solvent and / or the glycol ether-based organic solvent is preferably at least one selected from the group consisting of isopropyl alcohol, n-propanol, and propylene glycol monomethyl ether.

[0053] The manufacturing method of the thermal recording medium in the present embodiment preferably includes printing on the surface of the winding base material using the above-described ink, the coating liquid for forming the thermal recording layer, and the overcoat varnish. As the printing method, a gravure printing method or a flexographic printing method is preferably used. Both the gravure printing method and the flexographic printing method are of a winding type for printing, enabling high-speed printing and excellent productivity.

[0054] Gravure printing usually uses a gravure plate provided with cells (recesses) for expressing patterns and / or characters on the circumferential surface of a cylindrical cylinder. The cells are filled with printing ink, and the object to be printed (base material) is passed through between the gravure plate and the impression cylinder under pressure contact, so that the printing ink filled in the cells is transferred to the object to be printed, and patterns and / or characters are reproduced on the object to be printed. In flexographic printing, the ink is supplied directly from a container for storing the printing ink or via an ink supply pump or the like to an anilox roller having an uneven shape on its surface. The ink supplied to this anilox roller is transferred to the printing surface by contact with the convex portions of the printing surface, and further transferred to the plastic base material finally by contact between the printing surface and the base material, and patterns and / or characters are formed.

[0055] Since the base material is of a winding type, it is in the form of a roll aligned to a specified width. Therefore, it is different from the sheet paper in which each sheet is pre-separated. The width of the base material is appropriately selected based on the plate width of the printing machine to be used and the width of the image (pattern) portion of the gravure plate. When printing by overlapping a plurality of color printing inks, the order of these inks is not particularly limited.

[0056] Each layer of the present invention is assumed to be formed by surface printing. When performing surface printing, it is common to first print white ink if necessary and then print color ink. When there are a plurality of color inks, for example, they can be printed in the order of yellow, magenta, cyan, and black, but there is no particular limitation. In the present invention, it is preferable to form a white ink and / or a color ink, a heat-sensitive coloring layer, and an overcoat layer for protecting the heat-sensitive coloring layer by surface printing. However, the printing order thereof is not particularly limited except that it is preferable to print the overcoat layer after the heat-sensitive recording layer. From the viewpoint of adhesion to the substrate, it is preferable to print the ink layer as an underlayer thereon, and further from the viewpoint of visibility, it is preferable to print on the white ink or the colorless ink.

[0057] In the step of forming the heat-sensitive recording layer, the coating liquid of the present invention can be gravure-printed at a high speed of 80 m / min or more while maintaining the leveling property and the substrate stability. For example, it can be printed even at a printing speed of 100 m / min.

Examples

[0058] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the present invention, parts and % represent parts by mass and mass % unless otherwise noted.

[0059] (Example 1) (Preparation of coating liquid S1 for forming heat-sensitive recording layer) (Preparation of leuco dye dispersion A1) 50 parts of acrylic resin 1 (manufactured by Starlight PMC Co., Ltd., Hiros-X AW-36H, solid content 20.0% aqueous solvent solution) as a binder resin, 30 parts of black leuco dye (manufactured by Fukui Yamada Chemical Industry Co., Ltd., S-205), 2 parts of acetylene glycol-based surfactant (manufactured by Kawaken Fine Chemical Co., Ltd., Acetylenol E00P), and 18 parts of water were mixed and kneaded with a bead mill until the average particle size reached 0.5 μm to obtain a leuco dye dispersion A1.

[0060] (Preparation of developer dispersion B1) 50 parts of acrylic resin 1 (manufactured by Seiko PMC Co., Ltd., Highros-X AW-36H, 20.0% solid content aqueous solvent solution) as a binder resin, 30 parts of non-phenolic developer 1 (N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea), 2 parts of acetylene glycol-based surfactant (manufactured by Kawaken Fine Chemicals Co., Ltd., Acetylenol E00P), and 18 parts of water were mixed and kneaded with a bead mill until the average particle size reached 0.5 μm to obtain developer dispersion liquid B1.

[0061] Next, 33.3 parts of leuco dye dispersion liquid A1, 66.7 parts of developer dispersion liquid B1, and 25 parts of water were mixed to obtain coating liquid S1 for forming a heat-sensitive recording layer (the ratio of acrylic resin in all binder resins is 100%, the acid value of the acrylic resin is 60 mgKOH / g, and Tg is 53°C).

[0062] <Preparation of Overcoat Varnish> 80 parts of acrylic resin 10 (manufactured by BASF, Joncryl PDX-7667, 40.0% solid content aqueous solvent solution), 2 parts of surfactant (manufactured by Kawaken Fine Chemicals Co., Ltd., Acetylenol E00P), 2 parts of propylene glycol monomethyl ether, 5 parts of lubricant (polyethylene wax, 25.0% solid content aqueous solvent solution), 12 parts of water, and 18 parts of isopropanol were mixed and stirred to prepare overcoat varnish.

[0063] <Production of Heat-Sensitive Recording Media O1 and P1> Using a gravure three-color machine, in the first unit, white ink (manufactured by Toyo Ink Co., Ltd., REAL NEX63 White BOS3) was diluted with a mixed solvent (MCH / n-propyl acetate / n-propanol = 20 / 65 / 15) to a viscosity of 15 seconds (25°C, Zahn cup No. 3), and a white ink layer was printed using a Helio 175L semi-solid plate (plate type Compresso, 100%, semi-solid pattern). In the subsequent second unit, a coating liquid S1 for forming a heat-sensitive recording layer was used to print a heat-sensitive recording layer using a Helio 175L solid plate (plate type Compresso, 100%, solid pattern). In the third unit, overcoat varnish was used to print an overcoat layer using a Helio 200L solid plate (plate type Compresso, 100%, solid pattern) continuously on the corona discharge-treated surface of the following base material (1) or (2) at a printing speed of 100 m / min, and heat-sensitive recording media O1 and P1 were obtained respectively. The printing conditions were carried out at a temperature of 25°C, a humidity of 60%, an oven length of 2 m each, and an oven temperature of 90°C. ·Base material (1) used for printing O1: Biaxially stretched polypropylene (OPP) anti-fogging grade, AF-642S, manufactured by Futamura Chemical Co., Ltd., film thickness 25 μm, wetting index 38 dyne / cm ·Base material (2) used for printing P1: Biaxially stretched polyester (PET), E5100, manufactured by Toyobo Co., Ltd., film thickness 12 μm, wetting index 54 dyne / cm

[0064] (Examples 2 - 26, Comparative Examples 1 - 4, Reference Examples 5 - 6) <Preparation of coating liquids S2 - S26 and T1 - T6 for forming heat-sensitive recording layer> (Preparation of leuco dye dispersion liquids A2 - A22) Leuco dye dispersion liquids A2 - A22 were obtained in the same manner as in Example 1 except that the raw materials shown in Table 1 were used. (Preparation of developer dispersion liquids B2 - B28) Developer dispersion liquids B2 - B28 were obtained in the same manner as in Example 1 except that the raw materials shown in Table 2 were used.

[0065]

Table 1

[0066]

Table 2

[0067] The leuco dye dispersion liquid, the developer dispersion liquid, and the solvent obtained above were mixed so as to have the compositions shown in Table 3, and coating liquids S2 to S26 and T1 to T6 for forming a heat-sensitive recording layer were obtained. In Examples 19 to 22, a mixed solvent (water / isopropanol / propylene glycol monomethyl ether) was used as the solvent, and water was used in the other examples. In addition, the abbreviations in Tables 1 to 3 are as follows. · Acrylic: An acrylic resin obtained by polymerizing only acrylic monomers · Styrene acrylic: Styrene-acrylic resin · sol: Aqueous resin solution · em: Emulsion · AW-36H: Highros-X AW-36H manufactured by Starlight PMC Co., Ltd., Acid value 60 mg KOH / g, Tg 53 °C · NL-1189: Highros-X NL-1189 manufactured by Starlight PMC Co., Ltd., Acid value 90 mg KOH / g, Tg 28 °C · KE-1148: Highros-X KE-1148 manufactured by Starlight PMC Co., Ltd., Acid value 31 mg KOH / g, Tg 21 °C · GL-2439: Highros-X GL-2439 manufactured by Starlight PMC Co., Ltd., Acid value 110 mg KOH / g, Tg 52 °C · TGV-40: Acrys TGV-40 manufactured by Gifu Serac Co., Ltd., Acid value 54 mg KOH / g, Tg 109 °C · VL-1147: Highros-X VL-1147 manufactured by Starlight PMC Co., Ltd., Acid value 150 mg KOH / g, Tg 30 °C · J-140A: Highros-X J-140A manufactured by Starlight PMC Co., Ltd., Acid value 33 mg KOH / g, Tg 6 °C · X-436: Highros-X X-436 manufactured by Starlight PMC Co., Ltd., Acid value 33 mg KOH / g, Tg 21 °C · 352D: Joncryl 352D manufactured by BASF Acid value 51 mg KOH / g, Tg 56 °C · PDX-7667: Joncryl PDX-7667 manufactured by BASF Acid value 82 mg KOH / g, Tg 75 °C · PDX-7780: Joncryl PDX-7780 manufactured by BASF Acid value 46 mg KOH / g, Tg 92 °C · PDX-7692: Joncryl PDX-7692 manufactured by BASF Acid value 147 mg KOH / g, Tg 49 °C · 25-88KL: Poval 25-88KL manufactured by Kuraray · AE-301: Auroren AE-301 manufactured by Nippon Paper Industries · S-205: S-205 manufactured by Fukui Yamada Chemical Industry · E00P: Acetylenol E00P manufactured by Kawaken Fine Chemicals · 780-60: Newcol 780-60 manufactured by Nippon Emulsion · Color former 1: N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea · Color former 2: N-[2-(3-phenylureido)phenyl]benzenesulfonamide · Color former 3: 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenylsulfone · Color former 4: 4,4'-hydroxyisopropoxydiphenylsulfone · Color former 5: 4-hydroxy-4'-isopropoxydiphenylsulfone · Tankal PC: Calcium carbonate Tankal PC manufactured by Shiraishi Kogyo

[0068] <Preparation of thermal recording media O2 to 26, P2 to 26, Q1 to Q6, R1 to R6> Except that the coating liquid S1 for forming a heat-sensitive recording layer was changed to the coating liquids S2 to S26 for forming a heat-sensitive recording layer, heat-sensitive recording media O2 to O26 and P2 to P26 were obtained in the same manner as in Example 1 using the base materials (1) and (2). Further, except that the coating liquid S1 for forming a heat-sensitive recording layer was changed to the coating liquids T1 to T6 for forming a heat-sensitive recording layer, heat-sensitive recording media Q1 to Q6 and R1 to R6 were obtained in the same manner as in Example 1 using the base materials (1) and (2).

[0069] <Evaluation> The following evaluations were performed on the coating liquids for forming a heat-sensitive recording layer and the heat-sensitive recording media of the examples, comparative examples, and reference examples. The results are shown in Table 3.

[0070] <Printing suitability (resistance to plate fogging)> For the coating liquids S1 to S26 and T1 to T6 for forming a heat-sensitive recording layer, the plate fogging property evaluation in gravure printing was performed. The area of the plate fogging portion after 60 minutes of idling of the plate in a gravure printing machine was visually determined and evaluated. (Judgment criteria) ○ The plate fogging area is 0% or more and less than 5%. ○△ The plate fogging area is 5% or more and less than 10%. △ The plate fogging area is 10% or more and less than 15%. △× The plate fogging area is 15% or more and less than 30%. × The plate fogging area is 30% or more. Note that ○, ○△, and △ are within the range where there are no practical problems.

[0071] <Base density after printing and winding> The white ink layer / heat-sensitive recording layer / overcoat layer overprinting portion of the heat-sensitive recording media O1 to O26 and Q1 to 6 after printing and winding was measured with a reflection densitometer (manufactured by X-Rite, X-Rite eXact) and evaluated according to the following criteria. (Judgment criteria) ○ The density K is less than 0.15. ○△ The density K is 0.15 or more and less than 0.20. △ The density K is 0.20 or more and less than 0.25. △× The density K is 0.25 or more and less than 0.35. where the concentration K is 0.35 or more Note that ○, ○△, and △ are within the range where there are no practical problems.

[0072] <Adhesion> After leaving the thermal recording media O1 to O26, P1 to P26, Q1 to Q6, and R1 to R6 at 25°C for 1 day, an adhesive tape (cellophane tape, manufactured by Nichiban Co., Ltd.) with a width of 12 mm was attached to the printing surface, and the appearance state of the printing surface when this was rapidly peeled off in a direction 90° with respect to the base material surface was visually determined. Note that the determination criteria were as follows. (Determination criteria) ○ The ink layer is not removed from the film. ○△ The area where the ink layer has peeled off from the film is less than 5%. △ The area where the ink layer has peeled off from the film is 5% or more and less than 15%. △× The area where the ink layer has peeled off from the film is 15% or more and less than 50%. × The area where the ink layer has peeled off from the film is 50% or more. Note that ○, ○△, and △ are within the range where there are no practical problems.

[0073] <Flex resistance> The thermal recording media O1 to O26, P1 to P26, Q1 to Q6, and R1 to R6 were cut into a size of 10 cm × 10 cm, and the appearance state of the printing surface when both ends were held by both hands and kneaded 50 times was visually determined. Note that the determination criteria were as follows. (Determination criteria) ○ The ink layer is not removed from the film. ○△ The area where the ink layer has peeled off from the film is less than 5%. △ The area where the ink layer has peeled off from the film is 5% or more and less than 15%. △× The area where the ink layer has peeled off from the film is 15% or more and less than 50%. × The area where the ink layer has peeled off from the film is 50% or more. Note that ○, ○△, and △ are within the range where there are no practical problems.

[0074] <Disinfectant Resistance> Thermal recording media O1 - O26, P1 - P26, Q1 - Q6, R1 - R6 were cut into pieces of 2 cm × 20 cm. Alcohol disinfectant solution (70 vol% ethanol aqueous solution) was sprayed onto the printing surface from a height of 30 cm. Immediately after that, a cloth (Kanakin No. 3) was applied, and evaluation was carried out using a Gakushin - type friction fastness tester. The evaluation conditions were friction with a load of 200 g × reciprocating 30 times. The disinfectant resistance was evaluated based on the degree of ink layer peeling from the film after friction. (Judgment Criteria) ○ Those with the area of the ink layer peeled from the film less than 5% ○△ Those with the area of the ink layer peeled from the film being 5% or more and less than 15% △ Those with the area of the ink layer peeled from the film being 15% or more and less than 25% △× Those with the area of the ink layer peeled from the film being 25% or more and less than 50% × Those with the area of the ink layer peeled from the film being 50% or more Note that ○, ○△, and △ are within the range where there are no practical problems.

[0075] <Thermal Color Development Property> The white ink printed parts of thermal recording media O1 - O26, Q1 - 6 were thermocompression - bonded using a heat - sealing tester. The obtained prints were measured with a reflection densitometer (manufactured by X - Rite, X - Rite eXact) and evaluated according to the following criteria. The thermocompression - bonding conditions were thermocompression - bonding at a temperature of 140 °C, a load of 2 kg, and for 1 second. (Judgment Criteria) ○ When the density K is 1.60 or more ○△ When the density K is less than 1.60 and 1.45 or more △ When the density K is less than 1.45 and 1.30 or more △× When the density K is less than 1.30 and 1.15 or more × When the density K is less than 1.15 Note that ○, ○△, and △ are within the range where there are no practical problems.

[0076] <Base Density Stability> After leaving the white ink printed areas of the thermal recording media O1 to O26 and Q1 to Q6 after printing and winding at 50°C / 80% RH for 72 hours, they were measured with a reflection densitometer (X-Rite eXact, manufactured by X-Rite) and evaluated according to the following criteria. For those with a ground density K of 0.35 or more immediately after printing and winding, the evaluation was not carried out. (Judgment Criteria) ○ The density K is less than 0.15 ○△ The density K is 0.15 or more and less than 0.20 △ The density K is 0.20 or more and less than 0.25 △× The density K is 0.25 or more and less than 0.35 × The density K is 0.35 or more Note that ○, ○△, and △ are within the range where there are no practical problems.

[0077]

Table 3

[0078]

Table 3

[0079]

Table 3

Claims

1. A coating liquid for forming a heat-sensitive recording layer, comprising a leuco dye, a developer containing an electron acceptor for developing the leuco dye, a binder resin A, a surfactant, and a solvent, wherein the developer contains a non-phenolic developer, the binder resin A contains an acrylic resin a, the acid value of the acrylic resin a is 120 mgKOH / g or less and the Tg is 95°C or less, and the content of the acrylic resin a is 70 to 100% by weight based on the total binder resin A, the coating liquid for forming a heat-sensitive recording layer.

2. The coating liquid for forming a heat-sensitive recording layer according to claim 1, wherein the surfactant contains a polyoxyethylene alkyl phenyl ether and / or an acetylene glycol-based nonionic surfactant.

3. The coating liquid for forming a heat-sensitive recording layer according to claim 1, further comprising a extender pigment.

4. A leuco dye dispersion for a coating liquid for forming a heat-sensitive recording layer, comprising a leuco dye, a binder resin B, a surfactant, and a solvent, wherein the binder resin B contains an acrylic resin b, the acid value of the acrylic resin b is 120 mgKOH / g or less and the Tg is 95°C or less, and the content of the acrylic resin b is 70 to 100% by weight based on the total binder resin B, the leuco dye dispersion for a coating liquid for forming a heat-sensitive recording layer.

5. A developer dispersion for a coating liquid for forming a heat-sensitive recording layer, comprising a non-phenolic developer, a binder resin C, a surfactant, and a solvent, wherein the binder resin C contains an acrylic resin c, the acid value of the acrylic resin c is 120 mgKOH / g or less and the Tg is 95°C or less, and the content of the acrylic resin c is 70 to 100% by weight based on the total binder resin C, the developer dispersion for a coating liquid for forming a heat-sensitive recording layer.

6. A heat-sensitive recording medium comprising a substrate, an ink layer, a heat-sensitive recording layer, and an overcoat layer in this order, wherein the heat-sensitive recording layer is formed by the coating liquid for forming a heat-sensitive recording layer according to any one of claims 1 to 3, the heat-sensitive recording medium.

7. The heat-sensitive recording medium according to claim 6, wherein the substrate is a polyolefin.

8. A method for manufacturing a heat-sensitive recording medium comprising a substrate, an ink layer, a heat-sensitive recording layer, and an overcoat layer in this order, A method for manufacturing a heat-sensitive recording medium, comprising a step of forming the heat-sensitive recording layer on the ink layer in contact with the base material using the coating liquid for forming the heat-sensitive recording layer according to any one of claims 1 to 3.

9. Furthermore, a method for manufacturing a heat-sensitive recording medium according to claim 8, comprising a step of manufacturing a coating liquid for forming a heat-sensitive recording layer using the leuco dye dispersion liquid according to claim 4 and the developer dispersion liquid according to claim 5.

10. The method for manufacturing a heat-sensitive recording medium according to claim 9, wherein the step of manufacturing the coating liquid for forming the heat-sensitive recording layer is a step of using the leuco dye dispersion liquid according to claim 4, the developer dispersion liquid according to claim 5, and an alcohol-based organic solvent and / or a glycol ether-based organic solvent.

11. The method for manufacturing a heat-sensitive recording medium according to claim 8, wherein the step of forming the heat-sensitive recording layer is a step of gravure printing at a speed of 100 m / min or more.

Images