JP7363886B2 - Thermal recording linerless label - Google Patents

Description

The present invention relates to a heat-sensitive recording linerless label that utilizes a color-forming reaction between an electron-donating compound and an electron-accepting compound, and in particular, a recorded image can be obtained by a color-forming reaction caused by thermal energy.

2. Description of the Related Art Thermosensitive recording materials in which a recorded image is obtained by bringing an electron-donating compound and an electron-accepting compound into contact with each other using thermal energy are well known. Such heat-sensitive recording media are relatively inexpensive, have compact recording devices, and are easy to maintain, so they are used as recording media for facsimile machines, various types of computers, and the like.

Particularly in recent years, receipts for gas, water, and electricity bills, ATM usage statements from financial institutions, various receipts, financial recording papers (for so-called handy terminals), thermal recording labels for POS systems, and thermal recording Opportunities for thermal recording printing of various barcodes on tags, etc. are increasing, and there is a demand for thermal recording media that is suitable for barcode printing, and there is a need for high-speed printing, high storage stability, etc. of thermal recording media. quality requirements are required.

A conventional heat-sensitive recording material for label use has an adhesive layer provided on the back side of a heat-sensitive recording layer and a release paper having a release layer attached thereto, and is loaded into a recording device in a wound state. The paper thickness of such adhesive sheets for thermal recording increases depending on the composition of the adhesive layer and release paper, which limits the length of the adhesive sheet for thermal recording that can be loaded into recording equipment. Processing is also an issue from the perspective of resource conservation.

Various heat-sensitive recording adhesive sheets that do not use release paper, that is, heat-sensitive recording linerless labels, have been proposed. It is used in the open state (see Patent Documents 1 to 4). However, various problems occur when the release layer and the adhesive layer are superimposed on the heat-sensitive recording layer.

Generally, a heat-sensitive recording linerless label has a heat-sensitive recording layer on one side of a support, a protective layer on the heat-sensitive recording layer, and a release layer on the protective layer. Furthermore, if necessary, an intermediate layer is provided between the heat-sensitive recording layer and the protective layer, which increases the number of coated layers and lowers the sensitivity of the heat-sensitive recording layer. There is a strong demand for achieving both of the following, compared to conventional heat-sensitive recording labels that use release paper.

In addition, printing problems such as desensitization caused by adhesives and release agents have not been sufficiently solved for thermal recording linerless labels, and the quality requirements are much stricter than for conventional labels using release paper. has been done. In particular, for applications that are used under harsh conditions in distribution management, thermal recording linerless labels with excellent shelf life, which do not lose their coloring ability even when stored in high temperature and high humidity environments for long periods of time, are used. It is strongly required.

Japanese Unexamined Patent Publication No. 60-54842 Japanese Patent Application Publication No. 5-8541 Japanese Patent Application Publication No. 6-222717 Japanese Patent Application Publication No. 2013-195889

The main object of the present invention is to provide a heat-sensitive recording linerless label that is excellent in heat-resistant background fogging and blank paper storage stability.

As a result of extensive studies, the inventors of the present invention have solved the above-mentioned problems by incorporating a specific color developer into the heat-sensitive recording layer. That is, the present invention relates to the following heat-sensitive recording linerless label.

Item 1: A support, having a heat-sensitive recording layer containing a dye precursor and a color developer, a protective layer containing an adhesive, and a release layer on one side of the support from the side closer to the support; A heat-sensitive recording linerless label having an adhesive layer on the other side of the support, containing at least one diphenylsulfone derivative represented by the following general formula (1) as a color developer, and further comprising a color developer. A heat-sensitive recording liner comprising at least one member selected from the group consisting of a diphenylsulfone crosslinked compound represented by the following general formula (2) and a urea urethane compound represented by the following general formula (3). Res label.

Item 2: The thermal recording linerless label according to item 1, wherein the diphenylsulfone derivative is 4-hydroxy-4'-n-propoxydiphenylsulfone.

Item 3: The heat-sensitive recording linerless label according to Item 1 or 2, wherein the diphenylsulfone crosslinked compound is contained in an amount of 0.05 to 4 parts by weight per 1 part by weight of the diphenylsulfone derivative.

Item 4: The heat-sensitive recording linerless label according to any one of Items 1 to 3, wherein the urea urethane compound is contained in 0.05 to 4 parts by weight per 1 part by weight of the diphenylsulfone derivative.

Item 5: The method according to any one of Items 1 to 4, wherein the diphenylsulfone crosslinked compound and the urea urethane compound are contained in a total of 0.1 to 4 parts by weight per 1 part by weight of the diphenylsulfone derivative. Thermal recording linerless label.

Item 6: The heat-sensitive recording linerless label according to any one of Items 1 to 5, wherein the urea urethane compound is contained in an amount of 0.2 to 3 parts by weight per 1 part by weight of the diphenylsulfone crosslinked compound.

The heat-sensitive recording linerless label of the present invention has excellent heat-resistant background fogging properties and blank paper storage stability.

The heat-sensitive recording linerless label of the present invention has a heat-sensitive recording layer containing a dye precursor and a color developer, a protective layer containing an adhesive, and a release layer on one side of the support from the side closer to the support. and has an adhesive layer on the other side of the support. Conventional thermal recording labels that generally use release paper have a protective layer as the top layer. On the other hand, the heat-sensitive recording linerless label has an increased thickness due to the release layer, and variations in the thickness of the coating layer including the protective layer and the release layer may cause a decrease in the sensitivity of the heat-sensitive recording layer. Normally, the production line for heat-sensitive recording materials, in which a heat-sensitive recording layer and a protective layer are formed on a support, is different from the label processing line, in which a release layer and an adhesive layer are formed in the post-process, so it is difficult to predict a decrease in sensitivity. It is. On the other hand, the heat-sensitive recording layer of the present invention has a coloring ability sufficient to compensate for variations in the thickness of the coating layer, and can obtain a desired recording density. In addition, in conventional thermal recording labels, the release paper acts as a heat insulator, and at the same time, when printing is performed by passing between the printer's thermal head and the platen roll by the thickness of the release paper, the thermal head is pressed against and in close contact with the recording surface, and the heat from the thermal head is effectively used to increase the sensitivity of the heat-sensitive recording layer. On the other hand, since the present invention does not use a release paper, this heat is not used effectively and tends to escape from the thermal head to the platen roll, and the adhesion is also likely to decrease. You can obtain complementary coloring ability.

The release layer in the present invention is not particularly limited as long as it exhibits releasability, but may include, for example, release silicone. Release silicones are broadly classified into solvent-based, solvent-free, and emulsion-based types, and also into thermosetting, ultraviolet, or electron beam-curing types based on curing methods, but environmental issues and heat-sensitive recording layers are important. Since it is required that no color develops, it is preferable to use a coating liquid for a release layer containing an ultraviolet or electron beam curable silicone compound as a main component.

Specific examples of these silicone compounds include mixed compositions of mercapto group-containing organosiloxanes and vinyl group-containing organopolysiloxanes, organopolysiloxane compositions containing acrylic, methacrylic, or cinnamoyl groups, and maleimide or phenomaleimide groups. containing arganopolysiloxane composition, mixed composition of azide group-containing organopolysiloxane and vinyl group-containing organopolysiloxane, organopolysiloxane composition containing thioacrylic group, thiomethacrylic group or thiocinnamoyl group, acrylamide group, methacrylamide group Alternatively, a cinnamoylamide group-containing organopolysiloxane composition may be mentioned, and a mixed composition of an epoxy group-containing organopolysiloxane using UV-initiated cationic polymerization and a diazonium Lewis acid salt as a photodegradable initiator may also be used. be able to.

In the case of ultraviolet curing, a photopolymerization initiator is required, and specific examples include benzoyl alkyl ether and its derivatives, acetophenone and its derivatives, thioxanthone and its derivatives, and boron-based cation derivatives.

Such release silicone contains various chemicals such as solvents, dispersants, and surfactants in addition to the silicone component, so the protective layer is required to have excellent barrier properties. From the viewpoint of improving barrier properties, the protective layer is preferably a resin layer, and may also contain a pigment. As the adhesive (binder) contained in the protective layer, an adhesive having film-forming properties is preferably used. Such an adhesive is not particularly limited, but a water-based adhesive that is water-soluble or water-dispersible is preferred from the viewpoint of improving barrier properties. In particular, it is preferable to contain at least one water-soluble adhesive selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol.

Acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are produced by copolymerizing a vinyl ester with a monomer having an acetoacetyl group, a diacetone group, a carboxyl group, and a silyl group, respectively. It is produced by saponifying the resin obtained.

The degree of saponification is not particularly limited, but is preferably about 85 mol% to about 100 mol%, which is complete saponification, and more preferably about 90 to 100 mol%. The average degree of polymerization is preferably about 300 to 3,000, more preferably about 400 to 2,000. The degree of modification is preferably about 0.5 to 10 mol%, more preferably about 1 to 9 mol%, from the viewpoint of improving water resistance. The higher the degree of polymerization and saponification, the better the water resistance, but it is necessary to select depending on the situation from the viewpoint of coating concentration, viscosity, coating properties, or drying properties.

The content ratio of at least one selected from the group consisting of acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol used in the protective layer is not particularly limited; It is preferably about 10 to 90% by mass, more preferably about 15 to 50% by mass of the total solid amount.

Other adhesives can also be used in combination without impairing the effects of the present invention. Examples of such adhesives include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, starch and its derivatives such as oxidized starch, cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, and carboxymethyl cellulose, gelatin, casein, gum arabic, diisobutylene-maleic anhydride, etc. Water-soluble adhesives such as acid copolymer salts, styrene-maleic anhydride copolymer salts, ethylene-acrylic acid copolymer salts, styrene-acrylic acid copolymer salts, urea resins, melamine resins, amide resins, styrene - Water-dispersible adhesives such as butadiene copolymer, acrylic resin latex, urethane resin latex, etc.

The protective layer in the present invention may contain a pigment. Examples of the pigment include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, aluminum hydroxide, barium sulfate, talc, kaolin, and calcined kaolin. Among these, kaolin and aluminum hydroxide are particularly preferably used because they cause less deterioration in barrier properties against chemicals such as plasticizers and oil, and also cause less deterioration in recording density.

Examples of auxiliary agents that can be included in the protective layer include lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, sodium alkylbenzene sulfonate, sodium dioctyl sulfosuccinate, sulfone-modified polyvinyl alcohol, Surfactants such as sodium polyacrylate, water resistance agents such as dialdehyde starch, methylol urea, glyoxylates, epoxy compounds, hydrazine compounds, ultraviolet absorbers, fluorescent dyes, colored dyes, mold release agents, oxidation Examples include inhibitors.

The protective layer is prepared by mixing and stirring, for example, an adhesive, pigments, auxiliary agents, etc., using water as a dispersion medium, and the coating amount is preferably 0.1 to 8 g on a dry weight basis. It is formed by coating and drying on the heat-sensitive recording layer so that the amount is ^about 0.5 to 5 g/m ² , more preferably about 1 to 4 g/m ² .

The heat-sensitive recording layer in the present invention is a layer formed on one side of the support, and contains a dye precursor as an electron-donating compound and a color developer as an electron-accepting compound. As the dye precursor, it is preferable to use a leuco dye because it exhibits excellent color development when combined with a color developer.

Specific examples of leuco dyes include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl) )-6-dimethylaminophthalide, 3-(N-ethyl-Np-tolyl)amino-7-N-methylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6 -Methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluorane, 3-di(n-butyl) ) Amino-6-methyl-7-anilinofluorane, 3-di(n-pentyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl -7-anilinofluorane, 3-di(n-butyl)amino-6-chloro-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6- Methyl-7-anilinofluorane, 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachloro Phthalide, 3-p-(p-dimethylaminoanilino)anilino-6-methyl-7-chlorofluorane, 3-p-(p-chloroanilino)anilino-6-methyl-7-chlorofluorane, 3, Examples include 6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide.

Of course, it is not limited to these, and two or more types can also be used in combination. Furthermore, the content of the leuco dye may be adjusted appropriately depending on the color developer used, and is not particularly limited, but it is preferably about 3 to 50% by mass, and about 5 to 40% by mass, based on the total solid amount of the heat-sensitive recording layer. is more preferable.

The present invention contains at least one diphenylsulfone derivative represented by the general formula (1) (hereinafter also simply referred to as a diphenylsulfone derivative) as a color developer, and further contains the diphenylsulfone derivative represented by the general formula (2) as a color developer. ) (hereinafter also simply referred to as a diphenylsulfone crosslinked compound) and a urea urethane compound represented by the general formula (3) (hereinafter also simply referred to as a urea urethane compound). Contains at least one selected from the group. This results in excellent heat-resistant background fogging and blank paper storage stability. Among the diphenylsulfone derivatives, 4-hydroxy-4'-n-propoxydiphenylsulfone is preferred. The content ratio of the diphenylsulfone derivative is not particularly limited, and is preferably about 5 to 40% by mass, more preferably about 10 to 35% by mass, based on the total solid amount of the heat-sensitive recording layer.

R ¹ in the general formula (1) represents a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group. The alkyl group may be linear or branched, preferably having 1 to 6 carbon atoms, and more preferably having 1 to 3 carbon atoms. The alkyl group here also includes the alkyl portion of an aralkyl group. The alkenyl group may be linear or branched, preferably having 2 to 6 carbon atoms, more preferably having 2 to 3 carbon atoms. The aryl group means a monocyclic or polycyclic group consisting of a 5- or 6-membered aromatic hydrocarbon ring. The aryl group herein also includes the aryl portion of an aralkyl group. Aralkyl group means arylalkyl group.

The diphenylsulfone crosslinked compound may be used alone or as a mixture of compounds in which n represents an integer of 1 to 6. The content ratio of the diphenylsulfone crosslinked compound is not particularly limited, but it is preferably contained in 0.05 to 4 parts by mass, and preferably 0.1 to 1.5 parts by mass, per 1 part by mass of the diphenylsulfone derivative. It is more preferable that Thereby, oil resistance and plasticizer resistance can be improved.

Specific examples of the urea urethane compound include 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4,4'-bis[(2-methyl-5- Examples include phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureidodiphenylsulfone, and the like. These urea urethane compounds can be used alone or in combination of two or more. The content ratio of the urea urethane compound is not particularly limited, but it is preferably contained in 0.05 to 4 parts by mass, and preferably 0.1 to 1.5 parts by mass, per 1 part by mass of the diphenylsulfone derivative. It is more preferable. This makes it possible to improve recording density, heat resistance to background fog, and resistance to plasticizers.

Preferably, the diphenylsulfone crosslinked compound and the urea urethane compound are contained in a total of 0.1 to 4 parts by mass, and preferably 0.2 to 2.5 parts by mass, per 1 part by mass of the diphenylsulfone derivative. It is more preferable. Thereby, recording density, heat resistance to background fog, and resistance to plasticizers can be simultaneously increased while maintaining excellent blank paper storage stability.

The urea urethane compound is preferably contained in an amount of 0.2 to 3 parts by weight, more preferably 0.5 to 3 parts by weight, per 1 part by weight of the diphenylsulfone crosslinked compound. This makes it possible to further improve heat-resistant skin fogging properties.

Other color developers may be included as long as they do not impair the effects of the present invention. Other color developers include, for example, 4,4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4- Hydroxyphenyl)-1-phenylethane, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 3,3'-diallyl-4,4' -dihydroxydiphenylsulfone, 2,2'-bis[4-(4-hydroxyphenyl)phenoxy]diethyl ether, N-p-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea, 4-hydroxy Benzoic acid benzyl ester, N,N'-di-m-chlorophenylthiourea, N-p-tolylsulfonyl-N'-phenylurea, 4,4'-bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, 4- [2-(p-methoxyphenoxy)ethyloxy]zinc salicylate, 4-{3-(p-tolylsulfonyl)propyloxy]zinc salicylate, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]zinc salicylate, etc. can be mentioned. These may be added in amounts that do not impede the quality of the present invention. Although its content is not particularly limited, it is usually preferably less than 50% by mass based on the total amount of the specific color developer in the present invention.

The heat-sensitive recording layer may contain a preservability improver. Thereby, the storage stability of the recording section can be improved. Specific examples of such storage improvers include 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 1 , 1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 2,2 -Hindered phenol compounds such as bis(4-hydroxy-3,5-dimethylphenyl)propane, 4,4'-diglycidyloxydiphenylsulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenylsulfone , diglycidyl terephthalate, cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, etc., N,N'-di-2-naphthyl-p-phenylenediamine, bis(4-ethyleneiminocarbonyl) (aminophenyl)methane, etc. The content of the storage improver is not particularly limited, but is preferably about 1 to 30% by weight, more preferably about 5 to 20% by weight based on the total solid amount of the heat-sensitive recording layer.

The heat-sensitive recording layer may contain a sensitizer. Thereby, recording sensitivity can be increased. Specific examples of such sensitizers include stearamide, methoxycarbonyl-N-benzamide stearate, N-benzoylstearamide, N-eicosanoic acid amide, ethylene bis stearamide, behenic acid amide, methylene bis stearin. Acid amide, N-methylolstearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthyl benzyl ether, m -terphenyl, p-benzylbiphenyl, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, dibenzyl oxalate, p-tolylbiphenyl ether, di(p-methoxyphenoxyethyl) ether , 1,2-di(3-methylphenoxy)ethane, 1,2-di(4-methylphenoxy)ethane, 1,2-di(4-methoxyphenoxy)ethane, 1,2-di(4-chlorophenoxy) ) Ethane, 1,2-diphenoxyethane, 1-(4-methoxyphenoxy)-2-(3-methylphenoxy)ethane, p-methylthiophenylbenzyl ether, 1,4-di(phenylthio)butane, p-acetotoluidide , p-acetophenetidide, N-acetoacetyl-p-toluidine, 1,2-diphenoxymethylbenzene, di(β-biphenylethoxy)benzene, p-di(vinyloxyethoxy)benzene, 1-isopropylphenyl- Examples include 2-phenylethane, di-o-chlorobenzyl adipate, 1,2-bis(3,4-dimethylphenyl)ethane, 1,3-bis(2-naphthoxy)propane, diphenyl, and benzophenone. These can be used together as long as there is no problem. The content of the sensitizer may be an effective amount for sensitization, and is usually preferably about 2 to 40% by mass, more preferably about 5 to 25% by mass, based on the total solid amount of the heat-sensitive recording layer. preferable.

Furthermore, various auxiliary agents can be contained in the heat-sensitive recording layer as required. Examples of auxiliary agents include kaolin, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, amorphous silica, pigments such as urea/formalin resin filler, sodium dioctyl sulfosuccinate, and dodecylbenzene. Dispersants such as sodium sulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, zinc stearate, calcium stearate, waxes such as polyethylene wax, carnauba wax, paraffin wax, and ester wax, hydrazine compounds such as adipic acid dihydrazide, glyoxal , boric acid, dialdehyde starch, methylol urea, glyoxylate, water resistance agents such as epoxy compounds, antifoaming agents, colored dyes, and fluorescent dyes.

The heat-sensitive recording layer is prepared by dispersing water as a dispersion medium, and dispersing dye precursors, color developers, and if necessary, storage improvers, sensitizers, etc. together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill. It is formed by finely dispersing the particles so that the particle size is 2 μm or less, then applying a coating liquid for a heat-sensitive recording layer prepared by adding a water-based adhesive, an auxiliary agent, etc. to one side of the support and drying it. . The heat-sensitive recording layer is formed by coating and drying on the support so that the dry weight is preferably about 2 to 12 g/m ² , more preferably about 2 to 6 g/m ² .

As the adhesive used in the heat-sensitive recording layer, for example, any water-based adhesive, such as a water-soluble adhesive or a water-dispersible adhesive, can be used. Examples of water-soluble adhesives include modified polyvinyl alcohols such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, starch and its derivatives, methoxy cellulose, carboxymethyl cellulose, hydroxy Cellulose derivatives such as methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, polyamide, diisobutylene-maleic anhydride copolymer salt, styrene-acrylic acid copolymer salt, styrene-anhydride Maleic acid copolymer salt, ethylene-maleic anhydride copolymer salt, acrylic amide-acrylic ester copolymer, acrylic amide-acrylic ester-methacrylic acid copolymer, polyacrylamide, sodium alginate, gelatin, Examples include casein and gum arabic. Water-dispersible adhesives include polyvinyl acetate, polyurethane, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride-acetic acid. Water in vinyl copolymers, polybutyl methacrylate, ethylene-vinyl acetate copolymers, silylated urethanes, acrylic-silicon composites, acrylic-silicon-urethane composites, urea resins, melamine resins, amide resins, polyurethane resins, etc. Examples include insoluble polymer latex. These can be used alone or in combination of two or more. At least one of these is preferably blended in an amount of about 5 to 50% by mass, more preferably about 5 to 30% by mass, based on the total solid amount of the heat-sensitive recording layer.

The type and form of the adhesive used in the adhesive layer in the present invention is not particularly limited as long as it can be attached to an adherend as a label, and can be appropriately selected from various known types. Most of them are water-based adhesives obtained by emulsion polymerization, or hot melt types that contain almost no emulsifier. The hot-melt type is a method in which the base polymer is heated and melted and then applied to the substrate.There is no need for a drying process and the space required to accommodate the equipment can be reduced, but since the raw material is a special polymer, the adhesive There are problems such as the high cost, the need to introduce nitrogen gas into the melting and coating processes, and the difficulty in modifying by crosslinking. Water-based adhesives obtained by emulsion polymerization require a drying process, but if equipment is designed exclusively for water-based adhesives from the beginning, they are economically advantageous and are increasingly being used in Japan. However, because adhesives are essentially manufactured by emulsion polymerization, they contain surfactants, and when they come into contact with films such as flexible polyvinyl chloride, the problem is that the plasticizers contained in the films transfer to the adhesive. This may affect adhesive performance. In the case of heat-sensitive recording linerless labels, there is a problem that common color developers, sensitizers, etc. contained in the heat-sensitive recording layer migrate to the adhesive layer when they come into contact with the plasticizer of the film such as soft polyvinyl chloride. In particular, there is a strong tendency to migrate under high temperature and high humidity environments. In the present invention, color development ability can be maintained by containing a specific color developer.

As a specific example of a water-based adhesive obtained by emulsion polymerization, acrylic adhesives are mainly used. The base monomers are combined and copolymerized, generally designed so that the glass transition point is -30°C or lower. Generally, an alkylphenol type nonion is mainly used as a surfactant, and a small amount of an anion type is often used in combination. In addition, as a polymerization initiator, a water-soluble peroxide catalyst such as ammonium persulfate is used, but in order to improve emulsion stability during polymerization, it is preferable to polymerize at a relatively low temperature. A redox polymerization method using a combination of agents is often used. These are used in the form of emulsions.

The support used in the thermal recording medium of the present invention is not particularly limited, but includes, for example, a paper support such as neutral paper such as high-quality paper or acidic paper, synthetic paper, transparent or translucent plastic film, white paper support, etc. Examples include plastic films. Note that the thickness of the support is not particularly limited, but is usually about 20 to 200 μm.

In the present invention, an undercoat layer may be provided between the support and the heat-sensitive recording layer, if necessary. Thereby, recording sensitivity and recording running performance can be further improved. The undercoat layer has an oil absorption amount of 70 ml/100 g or more, particularly about 80 to 150 ml/100 g, of an oil-absorbing pigment and/or organic hollow particles and/or thermally expandable particles, and an undercoat layer coating liquid whose main components are an adhesive. It is formed by coating and drying on a support. Here, the above-mentioned oil absorption amount is a value determined according to the method of JIS K 5101.

Various kinds of oil-absorbing pigments can be used, and specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle diameter of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, more preferably about 0.02 to 3 μm. The amount of the oil-absorbing pigment to be used can be selected from a wide range, but is generally preferably about 2 to 95% by weight, more preferably about 5 to 90% by weight based on the total solid amount of the undercoat layer.

In the present invention, a back layer containing a pigment and a binder as main components can be provided on the surface of the support opposite to the heat-sensitive recording layer, if necessary. This makes it possible to further improve storage stability, curl suitability, and printer runnability.

Examples of methods for forming each layer on the support include air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, curtain method, slot die method, slide die method, extrusion method, etc. Any of the known coating methods or printing press methods may be used.

Smoothing treatment using a supercalender or the like may be performed after forming each layer or at any time after forming all layers. Various known techniques in the field of manufacturing heat-sensitive recording materials can be added as necessary.

The present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. Note that unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass," respectively.

Example 1
・Preparation of coating liquid for undercoat layer Micro hollow particles (product name: Lowpeke SN-1055) are added to a dispersion obtained by dispersing 60 parts of calcined kaolin (product name: Ancilex 93, manufactured by BASF) in 80 parts of water. , manufactured by Dow Chemical Company, solid content concentration 26.5%) 75 parts, 31 parts of styrene-butadiene copolymer latex (trade name: L-1571, manufactured by Asahi Kasei Chemicals Company, solid content concentration 48%), and carboxymethyl cellulose (Product name: Celogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.5 parts, similarly carboxymethyl cellulose (Product name: Celogen AG Gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1 part, and 95.5 parts of water were mixed and stirred. A coating liquid for an undercoat layer was obtained.

・Preparation of leuco dye dispersion 40 parts of 3-di-(n-butyl)amino-6-methyl-7-anilinofluorane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water were mixed and ground using a sand mill (manufactured by Imex Corporation, sand grinder) until the median diameter was 0.5 μm using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation) to obtain the leuco dye. A dispersion was obtained. The obtained leuco dye dispersion is also referred to as liquid A hereinafter.

・Preparation of color developer dispersion I
4-hydroxy-4'-n-propoxydiphenylsulfone (trade name: Tomilac KN, manufactured by Mitsubishi Chemical Corporation) 40 parts, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%), and 20 parts of water. The developer dispersion liquid ( Solution B) was obtained. The obtained color developer dispersion liquid will be hereinafter also referred to as B liquid.

・Preparation of color developer dispersion II
40 parts of the compound represented by the general formula (2) (a mixture containing 2,2-[4-(4-hydroxyphenylsulfone)phenoxy]diethyl ether as a main component, trade name: D90, manufactured by Nippon Soda Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%) and 20 parts of water were mixed, and a laser diffraction particle size distribution analyzer SALD2200 (Shimadzu (manufactured by Seisakusho Co., Ltd.) until the median diameter was 1.0 μm to obtain a color developer dispersion. The obtained developer dispersion liquid is also referred to as C liquid hereinafter.

・Preparation of color developer dispersion III
40 parts of 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone (trade name: UU, manufactured by Asahi Kasei Corporation), 10 parts of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%) % aqueous solution and 20 parts of water, and using a sand mill (manufactured by Imex Corporation, sand grinder) until the median diameter becomes 1.0 μm as measured by a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation). It was pulverized to obtain a color developer dispersion. The obtained developer dispersion liquid is also referred to as D liquid hereinafter.

・Preparation of sensitizer dispersion 40 parts of di-p-methylbenzyl oxalate (trade name: HS-3520, manufactured by DIC), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization 500, degree of saponification 88%) , and 20 parts of water were mixed and pulverized using a sand mill (manufactured by Imex Corporation, sand grinder) until the median diameter was 1.0 μm using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation). A sensitizer dispersion was obtained. The obtained sensitizer dispersion is hereinafter also referred to as liquid E.

・Preparation of coating liquid for heat-sensitive recording layer 29.5 parts of liquid A, 65.0 parts of liquid B, 25.0 parts of liquid C, 20.0 parts of liquid D, 45.5 parts of liquid E, fully saponified polyvinyl alcohol (product 12.9 parts of a 10% aqueous solution of PVA110, saponification degree: 99 mol%, average degree of polymerization: 1000, manufactured by Kuraray Co., Ltd., styrene-butadiene copolymer latex (trade name: L-1571, manufactured by Asahi Kasei Co., Ltd.) 22.5 parts of light calcium carbonate (product name: Brilliant-15, manufactured by Shiroishi Kogyo Co., Ltd.), 17.1 parts of paraffin wax (product name: Hydrin L-700, manufactured by Chukyo Yushi Co., Ltd., solid content) A coating liquid for a heat-sensitive recording layer was obtained by mixing and stirring 6.7 parts of dihydrazide adipic acid (30% concentration), 4.0 parts of adipic acid dihydrazide (manufactured by Otsuka Chemical Co., Ltd.), and 100 parts of water.

・Preparation of coating liquid for protective layer Acetoacetyl-modified polyvinyl alcohol (trade name: Gosenex Z-200, degree of saponification: 99.4 mol%, average degree of polymerization: 1000, degree of modification: 5 mol%, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) 300 parts of a 12% aqueous solution of 35 parts of aluminum oxide (product name: Higilite H-42M, manufactured by Showa Denko Co., Ltd.), 4 parts of amorphous silica (product name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.), polyethylene wax (product name: Chemipearl W-400) (manufactured by Mitsui Chemicals, solid content concentration 40%) and 114.5 parts of water were mixed and stirred to obtain a coating liquid for a protective layer.

・Preparation of heat-sensitive recording material On one side of high-quality paper with a basis weight of 60 g/m ² as a support, the coating liquid for the undercoat layer, the coating liquid for the heat-sensitive recording layer, and the coating liquid for the protective layer were applied in the respective amounts after drying. After coating and drying to form an undercoat layer, a heat-sensitive recording layer, and a protective layer in order to give a weight of 6.0 g/m ² , 4.0 g/m ² and 2.5 g/m ² , the surface was coated with a super calendar. A thermosensitive recording material was obtained by smoothing.

・Formation of release layer On the protective layer of the obtained heat-sensitive recording material, 100 parts of a solvent-free ultraviolet curable silicone compound (trade name: UV-271, manufactured by Arakawa Chemical Co., Ltd.) and a photopolymerization initiator (trade name: CATA211, boron-based cationic curing catalyst, manufactured by Arakawa Chemical Co., Ltd.) was mixed and stirred to form a release layer coating solution, which was then applied using a printing machine so that the coating amount after drying was 0.35 g/m ² , and then irradiated with ultraviolet rays. A release layer was formed.

・Formation of adhesive layer: Apply an acrylic emulsion adhesive (trade name: L-145, Nippon Car Co., Ltd.), which is a water-based adhesive, as a coating liquid for the adhesive layer to the other side of the support of the heat-sensitive recording material on which a release layer has been formed. (manufactured by Baito Kogyo Co., Ltd.) by a roll coater method so that the coated amount after drying was 25 g/m ² and dried to form an adhesive layer, and then a rolled-up heat-sensitive recording linerless label was obtained.

Example 2
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of C liquid was changed to 45.0 parts instead of 25.0 parts, and the amount of D liquid was changed to 0 parts instead of 20.0 parts. A heat-sensitive recording linerless label was obtained in the same manner as in Example 1.

Example 3
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, except that the amount of liquid C was changed to 0 parts instead of 25.0 parts, and the amount of liquid D was changed to 45.0 parts instead of 20.0 parts. A heat-sensitive recording linerless label was obtained in the same manner as in Example 1.

Example 4
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of liquid B was changed to 32.5 parts instead of 65.0 parts, the amount of liquid C was changed to 40.0 parts instead of 25.0 parts, A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that the amount of liquid D was changed to 37.5 parts instead of 20.0 parts.

Example 5
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of liquid B was changed to 87.5 parts instead of 65.0 parts, the amount of liquid C was changed to 10.0 parts instead of 25.0 parts, A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that the amount of liquid D was changed to 10.0 parts instead of 20.0 parts.

Example 6
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of liquid C was changed to 12.5 parts instead of 25.0 parts, and the amount of liquid D was changed to 32.5 parts instead of 20.0 parts. A heat-sensitive recording linerless label was obtained in the same manner as in Example 1 except for this.

Example 7
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of liquid B was changed to 100.0 parts instead of 65.0 parts, the amount of liquid C was changed to 5.0 parts instead of 25.0 parts, A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that the amount of liquid D was changed to 5.0 parts instead of 20.0 parts.

Example 8
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of liquid B was changed to 25.0 parts instead of 65.0 parts, the amount of liquid C was changed to 42.5 parts instead of 25.0 parts, A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that the amount of liquid D was changed to 42.5 parts instead of 20.0 parts.

Example 9
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of liquid B was changed to 25.0 parts instead of 65.0 parts, the amount of liquid C was changed to 85.0 parts instead of 25.0 parts, A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that the amount of liquid D was changed to 0 parts instead of 20.0 parts.

Example 10
In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, the amount of B liquid was changed to 25.0 parts instead of 65.0 parts, the amount of C liquid was changed to 0 parts instead of 25.0 parts, and D liquid A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that the amount was changed from 20.0 to 85.0 parts.

Comparative example 1
In the preparation of Solution B in Example 1, Np-tolylsulfonyl-N'-3(p-tolylsulfonyloxy)phenylurea (trade name: A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that PF-201 (manufactured by BASF) was used.

Comparative example 2
In the preparation of Solution B in Example 1, 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone (trade name: TGSH, Nippon Kayaku) was used instead of 4-hydroxy-4'-n-propoxydiphenylsulfone. A heat-sensitive recording linerless label was obtained in the same manner as in Example 1, except that a heat-sensitive recording linerless label was used.

The heat-sensitive recording linerless label thus obtained was left for 24 hours at 40° C. and 50% RH, and then evaluated as follows. The results were as shown in Table 1.

・Recording density Using a thermal recording evaluation device (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording linerless label was recorded at an applied energy of 0.24 mJ/dot, and the reflection of the resulting printed area was recorded. The concentration was measured using the visual mode of a Macbeth densitometer (RD-914, manufactured by Macbeth). The larger the measured value, the higher the density of the print, which is better. The recording density is preferably 1.30 or higher in practical terms. The density of the blank area was also measured.

・Blank storage stability After storing each heat-sensitive recording linerless label at 40°C and 90% RH for 7 days, it was recorded under the above recording density conditions, and the reflection density of the printed area was measured using the Macbeth densitometer. did. The larger the measured value is, the better it is because it indicates that there is no deterioration of the heat-sensitive recording layer (decrease in coloring ability). The recording density is preferably 1.20 or more. The storage rate is obtained by dividing the density obtained in the blank paper storage evaluation by the recording density obtained in the above-mentioned recording density evaluation.

- Heat Resistance to Background Fogging Each heat-sensitive recording linerless label was left at 90° C. for 1 hour, and the reflection density of the blank area was measured using the Macbeth densitometer. If the measured value is 0.20 or less, there is no problem in use, and if it is 0.10 or less, it is more preferable.

・Plasticizer resistance A wrap film (product name: Hi-Lap KMA-W, manufactured by Mitsui Chemicals, Inc.) was wrapped three times around a polycarbonate pipe (40 mm diameter), and the thermal sensitivity recorded in the above recording density evaluation was A recording linerless label was placed, and a cling film was further wrapped three times over it. This was left for 24 hours at 40°C. Thereafter, the density of the printed area was measured using the visual mode of the Macbeth densitometer. The preservation rate is calculated by dividing the recording density after processing by the recording density before processing (recording density obtained from the above recording density evaluation).If it is 85% or more, there is no problem in use, and if it is 95% or more, it is acceptable. It is more preferable if there is.

Claims (5)

a support, a heat-sensitive recording layer containing a dye precursor and a color developer, a protective layer containing an adhesive, and a release layer on one side of the support from the side closer to the support; A heat-sensitive recording linerless label having an adhesive layer on the other side, containing at least one diphenylsulfone derivative represented by the following general formula (1) as a color developer, and further containing the following general formula (1) as a color developer. The diphenylsulfone derivative contains at least one selected from the group consisting of a diphenylsulfone crosslinked compound represented by formula (2) and a urea urethane compound represented by the following general formula (3), and the diphenylsulfone derivative is 4-hydroxy-4 A heat-sensitive recording linerless label characterized by being made of '-n-propoxydiphenyl sulfone .

The heat-sensitive recording linerless label according to claim 1, wherein the diphenylsulfone crosslinked compound is contained in an amount of 0.05 to 4 parts by mass per 1 part by mass of the diphenylsulfone derivative. The heat-sensitive recording linerless label according to claim 1 or 2, wherein the urea urethane compound is contained in an amount of 0.05 to 4 parts by mass per 1 part by mass of the diphenylsulfone derivative. The thermosensitive recording according to any one of claims 1 to 3 , wherein the diphenylsulfone crosslinked compound and the urea urethane compound are contained in a total of 0.1 to 4 parts by mass with respect to 1 part by mass of the diphenylsulfone derivative. Linerless label. The heat-sensitive recording linerless label according to any one of claims 1 to 4 , wherein the urea urethane compound is contained in an amount of 0.2 to 3 parts by mass per 1 part by mass of the diphenylsulfone crosslinked compound.