Thermal recording linerless label

Abstract

To provide a thermosensitive recording linerless label having excellent sensitivity, heat resistant ground fogging properties and plasticizer resistance in which an addition polymerization type silicone layer provided on a printing surface side has good curing properties.SOLUTION: There is provided a thermosensitive recording linerless label which has a support, a thermosensitive recording layer containing a dye precursor and a developing agent, a protective layer containing an adhesive, and a release layer on one surface of the support from a side nearest to the support and has an adhesive layer on the other surface of the support, wherein the amount of adipic acid dihydrazide detected from the thermosensitive recording linerless label is 15 to 450 mg / m2 and the release layer is an addition polymerization type silicone release layer containing a platinum catalyst.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a linerless thermal recording label that utilizes a color-developing reaction between a dye precursor and a color developer. [Background technology]

[0002] Thermosensitive recording media, which produce a recorded image by contacting an electron donor compound with an electron acceptor compound using thermal energy, are well known. Such thermosensitive recording media are relatively inexpensive, require compact recording equipment, and are easy to maintain, and are therefore used as recording media for facsimiles, various computers, and the like.

[0003] In particular, in recent years, there has been an increasing demand for thermally printed barcodes on financial-related recording paper such as receipts for gas, water, and electricity bills, ATM usage statements from financial institutions, and various receipts, as well as thermally printed labels or tags for POS systems, and there is a demand for thermal recording media that are suitable for printing barcodes.

[0004] Such a thermosensitive recording medium for label use has an adhesive layer on the backside of the thermosensitive recording layer, and a release paper attached to the adhesive layer, and is loaded in a rolled state into a recording device. Because the thickness of such a thermosensitive recording adhesive sheet is increased by the composition of the adhesive layer and the release paper, the length of the thermosensitive recording adhesive sheet that can be loaded into a recording device is also limited, and disposal of the release paper generated during lamination after recording is also a problem from the viewpoint of resource conservation.

[0005] Various adhesive sheets for thermal recording that do not use release paper have been proposed, and are used in a rolled state with a release layer containing a silicone resin or the like on the thermal recording medium and an adhesive layer on the backside. However, various problems arise when the release layer and adhesive layer are superimposed on the thermal recording layer.

[0006] That is, unlike conventional labels with release paper, linerless thermal recording labels have the problem that the release layer on the recording surface is scraped off, or the adhesive layer transferred to the surface of the release layer when stored in a rolled state and the front and back are in close contact, peeling off, resulting in the formation of head residue. Head residue can cause scratches on the recording surface and, if accumulated, can inhibit heat transfer to the recording surface, causing print smearing.

[0007] Patent Document 1 reports a linerless thermal recording label comprising a support, one side of which has at least a heat-retaining layer, a thermosensitive coloring layer, a barrier layer, and a release layer, in that order, and the other side of which has an adhesive layer, the release layer containing a cured silicone resin, and the barrier layer containing a cured product of a water-soluble resin and a crosslinking agent, an inorganic filler, and crosslinked polymethyl methacrylate particles having a volume average particle diameter of 1.0 μm to 8.0 μm, wherein the adhesive strength between the release layer and the barrier layer is greater than the adhesive strength between the adhesive layer and the release layer. It also describes that, particularly when the linerless thermal recording label is rolled, the release layer on the front side of the linerless thermal recording label can be smoothly peeled off from the adhesive layer on the back side without bonding, even without a release paper, and that sticking of the material forming the release layer can be prevented even when printing with a thermal printer.

[0008] Currently, there is a strong demand for a linerless thermal recording label that has excellent resistance to plasticizers, good hardening properties of the release layer, and little head residue. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5906864 Summary of the Invention [Problem to be solved by the invention]

[0010] The main object of the present invention is to provide a linerless thermal recording label which has excellent sensitivity, heat resistance to background fogging and resistance to plasticizers, and in which the addition polymerization type silicone release layer provided on the printing surface side has good curing properties. [Means for solving the problem]

[0011] As a result of extensive research to achieve the above object, the present inventors have discovered that the release layer is an addition polymerization type silicone release layer containing a platinum catalyst, and the amount of adipic acid dihydrazide detected from a linerless thermal recording label is 15 to 450 mg / m 2 The inventors have found that the above problems can be solved by the above, and have thus achieved the present invention. That is, the present invention relates to the following thermal recording linerless label.

[0012] Item 1: A linerless thermal recording label having a support, a thermal recording layer containing a dye precursor and a color developer on one side of the support, a protective layer containing an adhesive, and a release layer from the side closest to the support, and an adhesive layer on the other side of the support, The amount of adipic acid dihydrazide detected from the thermal recording linerless label is 15 to 450 mg / m 2 and The release layer is an addition polymerization type silicone release layer containing a platinum catalyst. Thermal recording linerless label. Item 2: The amount of adipic acid dihydrazide is 50 to 250 mg / m 2 Item 2. The linerless thermal recording label according to Item 1, Item 3: The linerless thermal recording label according to Item 1 or 2, wherein the adhesive contained in the protective layer is at least one selected from acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol. Item 4: The linerless thermosensitive recording label according to any one of Items 1 to 3, which has an undercoat layer between the support and the thermosensitive recording layer. Item 5: The thermal recording linerless label according to Item 4, wherein the undercoat layer contains hollow particles, the hollow particles having a maximum particle size (D100) of 10 to 30 μm, an average particle size (D50) of 4.0 to 15 μm, a ratio D100 / D50 of the maximum particle size (D100) to the average particle size (D50) of 1.8 to 3.0, a hollowness of 80 to 98%, and a volume percentage of particles having a particle size of 2.0 μm or less of 1% or less. Item 6: The linerless thermal recording label according to any one of Items 1 to 5, wherein the undercoat layer contains a styrene-butadiene latex having a Tg of -30°C to -50°C. Item 7: The linerless thermal recording label according to any one of Items 1 to 6, wherein the developer has a melting point of 150° C. or higher. Item 8: The linerless thermal recording label according to any one of Items 1 to 7, wherein the developer is 2-phenylsulfonylamino-N,N'-diphenylurea. Item 9: The thermosensitive recording layer contains, as a storage stabilizer, a compound of the following general formula (1):

[0013] [ka]

[0014] Item 9. A linerless thermal recording label according to any one of items 1 to 8, containing a urea-urethane compound represented by the formula: [Effects of the Invention]

[0015] The linerless thermal recording label of the present invention is excellent in sensitivity, heat resistance to background fogging, and resistance to plasticizers, and the addition polymerization type silicone release layer provided on the printing surface side has good curing properties. DETAILED DESCRIPTION OF THE INVENTION

[0016] In this specification, the expression "comprise" includes the concepts of "comprise," "consist essentially of," and "consist only of."

[0017] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0018] The latex in the present invention includes a gel or a dried film formed by drying a dispersion medium.

[0019] In the present invention, the "average particle size" refers to the volume-based median size measured by laser diffraction. More simply, particle sizes may be measured from particle images (SEM images) using an electron microscope, and the average value of 10 particles may be used.

[0020] The present invention provides a linerless thermal recording label having a support, a thermal recording layer containing a dye precursor and a color developer on one surface of the support, a protective layer containing an adhesive, and a release layer from the side closest to the support, and a pressure-sensitive adhesive layer on the other surface of the support, The amount of adipic acid dihydrazide detected from the thermal recording linerless label is 15 to 450 mg / m 2 and The release layer is an addition polymerization type silicone release layer containing a platinum catalyst. It is characterized by:

[0021] In the present invention, adipic acid dihydrazide is contained in at least one of the undercoat layer, the thermosensitive recording layer, and the protective layer, which promotes crosslinking of the adhesive in the protective layer, improves the barrier properties, and prevents the penetration of plasticizers into the thermosensitive recording layer.

[0022] In the present invention, the amount of adipic acid dihydrazide detected from the thermal recording linerless label is 15 to 450 g / m 2 15g / m 2 By adjusting the thickness to 450 g / m or more, the plasticizer resistance can be improved. 2 By adjusting the amount of adipic acid dihydrazide to the range of 50 to 250 g / m, the curing property of the addition polymerization type silicone release layer can be enhanced, and as a result, the head scum resistance can be improved.2 The preferred thickness is 130 to 220 g / m 2 A degree is more preferable.

[0023] The amount of adipic acid dihydrazide detected from the linerless thermal recording label is measured by the method described in the examples.

[0024] The amounts of adipic acid dihydrazide blended in the undercoat layer, the thermosensitive recording layer and the protective layer may be appropriately selected so that the above amount can be detected from the thermosensitive recording linerless label.

[0025] [Support] The support used in the present invention is not particularly limited, but examples thereof include neutral or acidic wood-free paper, synthetic paper, transparent or translucent plastic film, white plastic film, etc. The thickness of the support is not particularly limited, but is usually about 20 to 200 μm. The density of the support is not particularly limited, but is 0.60 to 0.95 g / cm. 3 The degree is preferable.

[0026] [Undercoat layer] The linerless thermosensitive recording label of the present invention may optionally include an undercoat layer between the support and the thermosensitive recording layer. This can further improve recording sensitivity and recording runnability. The undercoat layer preferably contains hollow particles and an adhesive.

[0027] (hollow particles) The hollow particles are preferably made of an organic resin from the viewpoint of improving cushioning properties. The undercoat layer, which has high heat insulating properties due to the inclusion of hollow particles, can prevent the diffusion of heat applied to the thermosensitive recording layer and enhance the sensitivity of the thermosensitive recording linerless label.

[0028] Hollow particles made of organic resins can be divided into expanded and non-expanded types depending on their manufacturing method. Of these two types, expanded hollow particles generally have a larger average particle diameter and a higher hollowness than non-expanded hollow particles. Therefore, expanded hollow particles can achieve better sensitivity and image quality than non-expanded hollow particles.

[0029] Non-expanded hollow particles can be produced by polymerizing seeds in a solution, polymerizing another resin so that the seeds are wrapped around the seeds, and then swelling and dissolving the seeds to remove them, thereby forming internal cavities. An alkaline aqueous solution or the like is used to swell and dissolve the seeds to remove them. Non-expanded hollow particles with a relatively large average particle size can also be obtained by subjecting core-shell particles, in which alkali-swellable core particles are coated with a shell layer that is not alkali-swellable, to an alkali swelling treatment.

[0030] Expanded hollow particles can be produced by preparing particles in which a volatile liquid is enclosed inside a resin, and then softening the resin by heating, thereby vaporizing and expanding the liquid inside the particles.

[0031] Expanded hollow particles have a high hollow ratio and high thermal insulation properties due to the thermal expansion of the liquid inside during the manufacturing process, which can increase the sensitivity of the thermal recording linerless label and improve recording density. Improved sensitivity is particularly important when coloring a mid-tone region where the thermal energy applied to the thermal recording layer is small. Furthermore, forming a thermal recording layer via a highly insulating undercoat layer can prevent the diffusion of heat applied to the thermal recording layer, resulting in excellent image uniformity and improved image quality. Therefore, in this embodiment, it is preferable to use expanded hollow particles, which are excellent at improving the thermal insulation properties of the undercoat layer.

[0032] Resins that can be used for the expanded hollow particles include thermoplastic resins such as styrene-acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, polyvinyl chloride resin, polyvinylidene chloride resin, acrylic resin (e.g., acrylic resin containing acrylonitrile as a constituent component), styrene resin, vinylidene chloride resin, and copolymer resins mainly composed of polyvinylidene chloride and acrylonitrile. Typical gases contained inside the expanded hollow particles include propane, butane, isobutane, and air. Among the various resins listed above, acrylonitrile resin and copolymer resins mainly composed of polyvinylidene chloride and acrylonitrile are preferred for the resins used for the hollow particles in terms of the strength required to maintain the shape of the expanded particles.

[0033] The maximum particle diameter of the hollow particles in the present invention is preferably 10 to 30 μm, more preferably 10 to 25 μm. The maximum particle diameter is also referred to as D100. When the maximum particle diameter of the hollow particles is 10 μm or more, the cushioning properties of the undercoat layer are improved, thereby improving the adhesion of the linerless thermal recording label to the thermal head during printing, resulting in a linerless thermal recording label with high image quality. This high image quality can result in improved recording density in halftones that are developed with lower energy than that required to achieve the maximum recording density (Dmax). On the other hand, when the maximum particle diameter of the hollow particles is 30 μm or less, the smoothness of the undercoat layer is improved, allowing the thermal recording layer provided via the undercoat layer to be uniform, resulting in a linerless thermal recording label with less white gaps in the image.

[0034] The average particle diameter of the hollow particles in the present invention is preferably 4.0 to 15 μm, more preferably 4.5 to 12 μm. Here, the average particle diameter is the diameter at which the larger and smaller particles occupy equal volumes when divided into two groups based on particle diameter, i.e., the median particle diameter, also referred to as D50, which is the particle diameter at 50% volume frequency. When the average particle diameter of the hollow particles is 4.0 μm or greater, the cushioning properties of the undercoat layer are improved, thereby improving the adhesion of the linerless thermal recording label to the thermal head during printing, resulting in a linerless thermal recording label with high image quality. This high image quality can result in improved recording density in halftones that are developed with lower energy than the maximum recording density (Dmax). On the other hand, when the average particle diameter of the hollow particles is 15 μm or less, the smoothness of the undercoat layer is improved, allowing the thermal recording layer provided through the undercoat layer to be uniform, resulting in a linerless thermal recording label with less white gaps in the image.

[0035] The maximum particle size (D100) and average particle size (D50) of the hollow particles can be measured using a laser diffraction particle size distribution analyzer.

[0036] The ratio D100 / D50 of the maximum particle diameter (D100) to the average particle diameter (D50) of hollow particles is an index showing the degree of particle size distribution. This ratio D100 / D50 is preferably 1.8 to 3.0, more preferably 1.8 to 2.8. When the D100 / D50 of the hollow particles is 1.8 or more, the hollow particles are sufficiently expanded, the maximum particle diameter is sufficiently large, the hollow ratio is high, and the heat insulating properties of the primer layer can be improved. On the other hand, when the D100 / D50 of the hollow particles is 3.0 or less, the hollow particles are uniform in size, which improves the smoothness of the primer layer and reduces white spots in the image.

[0037] In the particle size distribution determined by a laser diffraction particle size analyzer, the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is preferably 1% or less. Furthermore, the volume percentage of hollow particles with a particle diameter of 2.0 μm or less is preferably 0.5%, and more preferably none. Hollow particles with a particle diameter of 2 μm or less are too small to provide sufficient hollow regions, and therefore are thought to contribute very little to heat insulation. By keeping the volume percentage of hollow particles with a particle diameter of 2 μm or less in the undercoat layer to 1% or less, it is possible to improve recording density, image quality, etc.

[0038] The hollow particles preferably have a void ratio of 80 to 98%, more preferably 90 to 98%. When the hollow particles have a void ratio of 80% or more, the primer layer containing the hollow particles can be imparted with high heat insulating properties. On the other hand, when the hollow particles have a void ratio of 98% or less, the strength of the film surrounding the hollow portion is improved, and the hollow particles can be made to be resistant to crushing during the formation of the primer layer.

[0039] The hollowness of hollow particles can be determined by measuring the true specific gravity using the IPA method and then calculating the hollowness from the true specific gravity value as follows. (1) Sample pretreatment Dry the sample at 60°C overnight to prepare the sample. (2) Reagents Isopropyl alcohol (IPA: first-grade reagent) (3) Measurement method ·Weigh the volumetric flask accurately (W1). ·Place approximately 0.5 g of the dried sample in a measuring flask and weigh it out accurately (W2). Add approximately 50 mg of IPA and shake thoroughly to completely remove any air from the capsule. Add IPA up to the mark and measure (W3). As a blank, add only IPA to the volumetric flask up to the mark and measure carefully (W4). (4) Calculation of true specific gravity True specific gravity = {(W2-W1)×((W4-W1) / 100)} / {(W4-W1)-(W3-W2)} (5) Calculation of hollow ratio Hollowness ratio (%)={1-1 / (1.1 / true specific gravity)}×100

[0040] The hollow ratio is calculated by the following formula (d 3 / D 3 ) × 100. In this formula, d represents the inner diameter of the hollow particle, and D represents the outer diameter of the hollow particle.

[0041] The hollow particles in the present invention have a relatively large particle diameter, so their content in the undercoat layer can be reduced. The hollow particle content is preferably 5 to 40 mass % of the total solid content of the undercoat layer, and more preferably 5 to 35 mass %. When the hollow particle content is 5 mass % or more, the heat insulating properties of the undercoat layer can be improved. On the other hand, when the hollow particle content is 40 mass % or less, problems are less likely to occur in terms of coatability, etc., a uniform undercoat layer can be easily formed, and recording density can be improved. In addition, the coating strength of the undercoat layer can be increased.

[0042] (glue) Examples of adhesives include polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, and ethyl cellulose, water-soluble polymer materials such as sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymers, acrylamide-acrylic acid ester-methacrylic acid ester copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, casein, gelatin, and their derivatives, as well as emulsions of polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid esters, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, and ethylene-vinyl acetate copolymers, and latexes of water-insoluble polymers such as styrene-butadiene copolymers and styrene-butadiene-acrylic copolymers. These can be used alone or in combination of two or more.

[0043] The adhesive of the undercoat layer preferably contains a latex that has excellent surface strength. The latex is not particularly limited, and examples include latexes of water-insoluble polymers such as styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, and acrylonitrile-butadiene copolymer. Among these latexes, styrene-butadiene-based latex (SBR) is preferred because of its high water-resistant surface strength. Among styrene-butadiene-based latexes, styrene-butadiene-based latexes with a glass transition temperature (Tg) of -10°C or lower are preferred. A glass transition temperature of -10°C or lower can improve image quality and increase the density of halftone prints. The glass transition temperature of styrene-butadiene-based latex is more preferably -30°C or lower, as this can further increase the density of halftone prints. Furthermore, the glass transition temperature is preferably -50°C or higher.

[0044] The content of the adhesive in the undercoat layer can be selected from a wide range, but is generally preferably about 10 to 70 mass % of the total solid content of the undercoat layer, and more preferably about 15 to 60 mass %.

[0045] The undercoat layer may contain an oil-absorbing pigment having an oil absorption of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g, where the oil absorption is determined according to the method of JIS K 5101.

[0046] Various oil-absorbing pigments can be used, and specific examples include inorganic pigments such as calcined kaolin, amorphous silica, precipitated calcium carbonate, and talc. The average primary particle size of these oil-absorbing pigments is preferably about 0.01 to 5 μm, and particularly about 0.02 to 3 μm. The amount of oil-absorbing pigment used can be selected from a wide range, but is generally preferably about 20 to 60 mass % of the total solids content of the undercoat layer, and more preferably about 25 to 55 mass %.

[0047] The undercoat layer is generally prepared by mixing water as a dispersion medium with an adhesive, and optionally hollow particles, adipic acid dihydrazide, an oil-absorbing pigment, a crosslinking agent, various auxiliaries, etc., and applying the coating liquid for the undercoat layer onto the support to a dry mass of preferably 3 to 20 g / m. 2 Approximately, more preferably 4 to 12 g / m 2 The coating is applied and dried to a thickness of approximately 1000 μm.

[0048] Examples of auxiliaries contained in the coating liquid for the undercoat layer include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts; waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax; water-resistant agents such as hydrazide compounds, boric acid, dialdehyde starch, glyoxylates, and epoxy compounds; antifoaming agents; coloring dyes; and fluorescent dyes.

[0049] [Thermal recording layer] The heat-sensitive recording layer in the present invention contains a dye precursor and a color developer. A combination of a leuco dye as a dye precursor and a color developer is preferably used because it provides excellent color density.

[0050] As the leuco dye and the color developer, various known ones can be used.Specific examples of the leuco dye include, for example, 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-methylanilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluoran, 3-di(n-butyl)amino-6-methyl-7-anilinofluoran, and 3-di(n-pentyl)amino-6-methyl-7-anilinofluoran. , 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran, 3-di(n-butyl)amino-6-chloro-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3-p-(p-dimethylaminoanilino)anilino-6-methyl-7-chlorofluoran, 3-p-(p-chloroanilino)anilino-6-methyl-7-chlorofluoran, 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, and the like.

[0051] Of course, the present invention is not limited to these, and two or more types can be used in combination. The content of the leuco dye can be appropriately selected depending on the color developer used, and is not particularly limited, but is preferably about 3 to 50% by mass, and more preferably about 5 to 40% by mass, of the total solid content of the thermosensitive recording layer.

[0052] Specific examples of the developer include 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidene diphenyl, 1,1-bis(4-hydroxyphenyl)-ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxyphenyl(4'-n-propoxyphenyl)sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 2,2'-bis[4-(4-hydroxyphenyl)phenoxy]diethyl ether, Np-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone, 4-Hydroxybenzoic acid benzyl ester, N,N'-di-m-chlorophenylthiourea, Np-tolylsulfonyl-N'-phenylurea, 4,4'-bis(p-tolylsulfonylaminocarbonylamino)diphenylmethane, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, 5-(N-3-methylphenyl-sulfonamido)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, 3-[(phenyl

[0033] 4-[(2-(p-methoxyphenoxy)ethyloxy)amino]phenyl-4-methylbenzenesulfonate, 2-phenylsulfonylamino-N,N'-diphenylurea, 4-[2-(p-methoxyphenoxy)ethyloxy]zinc salicylate, 4-{3-(p-tolylsulfonyl)propyloxy]zinc salicylate, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]zinc salicylate, and diphenyl sulfone-bridged compounds represented by the following general formula (2).

[0053] [ka] (In the formula, n represents an integer of 1 to 6.)

[0054] The color developer preferably has a melting point of 140°C or higher. A melting point of 140°C or higher can improve heat resistance to background fogging. The melting point of the color developer is more preferably 150°C or higher. Specific examples of color developers having a melting point of 140°C or higher include 2-phenylsulfonylamino-N,N'-diphenylurea (melting point 152°C) and 4-allyloxy-4'-hydroxydiphenylsulfone (melting point 180°C).

[0055] The content of the color developer may be appropriately selected depending on the leuco dye used and is not particularly limited. However, it is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 1.2 parts by mass or more, and particularly preferably 1.5 parts by mass or more, per 1 part by mass of the leuco dye. Furthermore, the content of the color developer is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less, per 1 part by mass of the leuco dye. By using an amount of 0.5 parts by mass or more, recording performance can be improved. On the other hand, by using an amount of 10 parts by mass or less, background fogging (heat-resistant background fogging) in high-temperature environments can be effectively suppressed.

[0056] The heat-sensitive recording layer may contain a storage stabilizer, thereby improving the storage stability of the recording portion. Specific examples of such storage stabilizers include hindered stabilizers such as 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, and 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane. phenol compounds, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenyl sulfone, diglycidyl terephthalate, epoxy compounds such as cresol novolac epoxy resins, phenol novolac epoxy resins, and bisphenol A epoxy resins, N,N'-di-2-naphthyl-p-phenylenediamine, bis(4-ethyleneiminocarbonylaminophenyl)methane, and compounds represented by the following general formula (1):

[0057] [ka] Examples of the storage stabilizer include urea urethane derivative urea urethane compounds such as 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone, 4,4'-bis[(2-methyl-5-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone, and 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureidodiphenyl sulfone, represented by the following formula: Preferred as the storage stabilizer are urea urethane derivative urea urethane compounds represented by the following formula (1), and among these, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone is preferred.

[0058] The content of the storage stabilizer may be an amount effective for improving storage stability, and is usually preferably about 1 to 30% by mass, more preferably about 5 to 20% by mass, of the total solid content of the thermosensitive recording layer.

[0059] The heat-sensitive recording layer may contain a sensitizer, thereby increasing the recording sensitivity. Specific examples of such sensitizers include stearic acid amide, methylenebisstearic acid amide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, 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 1-(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, di(β-biphenylethoxy)benzene, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, oxalic acid dibenzyl ester, and the like.

[0060] The content of the sensitizer may be an amount effective for sensitization, and is usually preferably about 2 to 40% by mass, more preferably about 5 to 25% by mass, of the total solid amount of the thermosensitive recording layer.

[0061] Various resins are typically used as adhesives in coating solutions for thermosensitive recording layers. Examples of such adhesives include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, diisobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, styrene-butadiene copolymer, urea resin, melamine resin, amide resin, and polyurethane resin. At least one of these is preferably blended in an amount of about 5 to 50% by mass, more preferably about 9 to 40% by mass, of the total solid content of the thermosensitive recording layer. When the medium for the coating solution for thermosensitive recording layers is water, the hydrophobic resin may be used in the form of a latex.

[0062] Furthermore, various auxiliary agents can be added to the coating liquid for the thermosensitive recording layer as needed. Examples of such auxiliary agents include pigments such as kaolin, light (heavy) calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, amorphous silica, and urea-formaldehyde resin fillers; dispersants such as dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts; waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax; water-resistant agents such as hydrazine compounds, boric acid, dialdehyde starch, glyoxylates, and epoxy compounds; antifoaming agents; coloring dyes; and fluorescent dyes.

[0063] A crosslinking agent that cures the adhesive in at least one of the coating layers of the thermosensitive recording layer and the protective layer can be contained in the undercoat layer, the thermosensitive recording layer, and at least one of the coating layers. By incorporating a crosslinking agent, the water resistance of at least one of the coating layers of the thermosensitive recording layer and the protective layer can be improved. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate, boric acid, boric acid triesters, boron-based polymers, hydrazide compounds, and glyoxylates. These agents may be used alone or in combination of two or more. The amount of crosslinking agent used is preferably about 1 to 10 parts by weight per 100 parts by weight of the total solids content of the thermosensitive recording layer. This can improve the water resistance of the heat-sensitive recording layer.

[0064] The thermosensitive recording layer is formed by coating a coating liquid for the thermosensitive recording layer on the undercoat layer and drying it. The coating amount of the thermosensitive recording layer is preferably 2 to 12 g / m2 in dry mass. The coating amount of the thermosensitive recording layer is preferably 2 to 12 g / m2. 2 Approximately, more preferably 2 to 6 g / m 2 The coating is applied to the undercoat layer and dried to form a coating having a thickness of about 1000 μm.

[0065] [Protective layer] The protective layer in the present invention contains an adhesive. The adhesive is not particularly limited, but from the viewpoint of enhancing the barrier property, a water-soluble or water-dispersible aqueous adhesive is preferred. In particular, at least one water-soluble adhesive selected from acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol is preferably used.

[0066] Acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol are produced by copolymerizing a vinyl ester with a monomer having an acetoacetyl group or a diacetone group, respectively, and saponifying the resulting resin.

[0067] The degree of saponification is preferably about 85 mol% to about 100 mol% (complete saponification), more preferably about 90 to 100 mol%. The average degree of polymerization is preferably about 300 to 3000, more preferably about 400 to 2000. 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 degree of saponification, the better the water resistance, but it is necessary to select them depending on the situation, taking into account the coating concentration, viscosity, coatability, and drying properties.

[0068] The amount of at least one selected from the group consisting of acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol used in the protective layer is preferably about 10 to 90% by mass, more preferably about 15 to 50% by mass, of the total solid content of the protective layer.

[0069] Other adhesives can also be used in combination as long as the effects of the present invention are not impaired. Examples of such adhesives include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, starch, oxidized starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, diisobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, urea resin, melamine resin, amide resin, acrylic resin latex, and urethane resin latex.

[0070] 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 preferred because they cause little deterioration in barrier properties against chemicals such as plasticizers and oils, and also cause little deterioration in recording density.

[0071] Examples of auxiliary agents that can be contained in the protective layer include lubricants such as zinc stearate, calcium stearate, carnauba wax, paraffin wax, and ester wax; surfactants such as sodium alkylbenzenesulfonate, sodium dioctyl sulfosuccinate, sulfone-modified polyvinyl alcohol, and sodium polyacrylate; water-resistant agents such as dialdehyde starch, glyoxylates, epoxy compounds, and hydrazine compounds; ultraviolet absorbers, fluorescent dyes, coloring dyes, release agents, and antioxidants.

[0072] The protective layer is formed by, for example, mixing and stirring a protective layer coating solution prepared by using water as a dispersion medium, preferably a specific adhesive, and optionally adipic acid dihydrazide, a pigment, a crosslinking agent, an auxiliary agent, etc., in a coating amount of preferably 0.1 to 8 g / m2 in terms of dry mass. 2 About 0.5 to 5 g / m 2 More preferably, 1 to 4 g / m 2 The coating is applied to the thermosensitive recording layer and dried to form a layer having a thickness of about 1000 nm.

[0073] [Peeling layer] The linerless thermal recording label has a release layer on a protective layer, which is an addition polymerization type silicone release layer containing a platinum catalyst.

[0074] The release silicones used in the release layer can be broadly classified into solvent-based, solventless, and emulsion-based types. Addition polymerization silicones include those consisting of an alkenyl group-containing polyorganosiloxane as a base polymer, a hydrogen group-containing polyorganosiloxane as a crosslinking agent, and a platinum compound as a curing catalyst.

[0075] The functional groups other than the alkenyl group in the alkenyl group-containing polyorganosiloxane are monovalent substituted or unsubstituted hydrocarbon groups, such as alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; and substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Generally, methyl and phenyl groups are preferred because of their ease of synthesis.

[0076] The hydrogen group-containing polyorganosiloxane is a component that serves as a crosslinking agent. The amount of hydrogen group-containing polyorganosiloxane is preferably an amount that provides 0.5 to 20 hydrogen atoms per alkenyl group of the base polymer, and if a composition with good curability and release properties is desired, the range of 0.5 to 10 is preferred. By using 0.5 or more hydrogen atoms, curing can proceed sufficiently, and by using 20 or less hydrogen atoms, good release properties can be obtained.

[0077] The inclusion of a platinum catalyst enables a crosslinking reaction during the thermal drying process. The platinum catalyst is a curing catalyst that reacts the alkenyl groups of the base polymer with the hydrogen groups of the hydrogen group-containing polyorganosiloxane to obtain a cured product. Examples of platinum compounds include chloroplatinic acid, platinum olefin complexes, platinum vinylsiloxane complexes, platinum phosphorus complexes, platinum alcohol complexes, and platinum black. The amount of platinum compound added is preferably 1 to 1,000 ppm relative to the alkenyl group-containing polysiloxane base polymer.

[0078] Furthermore, an auxiliary agent can be added to the release agent as needed. Examples of the auxiliary agent include dyes, pigments, wetting agents, antifoaming agents, dispersants, antistatic agents, leveling agents, lubricants, and the like.

[0079] The release layer is prepared by, for example, mixing and stirring a release silicone, a platinum catalyst, and, if necessary, an auxiliary agent in an organic solvent as a dispersion medium, and applying a coating solution for the release layer in an amount of preferably 0.05 to 3 g / m in terms of dry mass. 2 approximately, more preferably 0.1 to 2 g / m 2 about 0.5 to 1.5 g / m 2 The coating is applied to the protective layer and dried to form a layer having a thickness of about 1000 nm.

[0080] [Adhesive layer] The thermosensitive recording linerless label has an adhesive layer on the other side of the support (the side opposite to the side with the thermosensitive recording layer). Examples of adhesives that can be used in the present invention include those primarily composed of rubber-based materials such as natural rubber, styrene-butadiene rubber, polyisobutylene rubber, and isoprene rubber; those primarily composed of vinyl ether-based materials; those primarily composed of copolymers with 2-ethylhexyl acrylate as the main monomer; those consisting of reaction products of active hydrogen group-containing compounds such as polyols with isocyanate compounds; and those primarily composed of rubbery siloxanes and resinous siloxanes. These rubber-based, acrylic-based, urethane-based, and silicone-based adhesives can be used as emulsions or various solvent- or solvent-free adhesives. The coating amount of the adhesive layer is not particularly limited, and is 5 to 50 g / m2 in dry mass. 2 It is preferable to adjust it within a certain range.

[0081] [Thermal recording linerless label] The method for forming each layer on the support may be any of known coating methods such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, a curtain method, a slot die method, a slide die method, and an extrusion method, or a method using a printing machine.

[0082] After the formation of each layer, smoothing treatment such as supercalendering may be carried out, and various known techniques in the field of thermosensitive recording media production may be used as needed. Furthermore, the film may be subjected to processing such as printing and die-cutting to form a label.

[0083] In the present invention, in order to further increase the added value of the product, a multicolor thermosensitive recording linerless label can also be produced. Generally, multicolor thermosensitive recording media are attempts to utilize differences in heating temperature or thermal energy, and are generally constructed by laminating a high-temperature coloring layer and a low-temperature coloring layer, which develop different color tones, on a support. These can be broadly classified into two types: a decolorizing type and an additive coloring type. There are methods using microcapsules and a method for producing a multicolor thermosensitive recording linerless label using composite particles consisting of an organic polymer and a leuco dye. [Example]

[0084] The present invention will be explained in more detail with reference to examples, but is not limited thereto. Unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass," respectively. Particle sizes such as average particle size and maximum particle size were measured using a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation). The average particle size here refers to the median diameter (D50).

[0085] The hollow particles used in the examples and comparative examples are as follows. Hollow particle A: Average particle size (D50) 5.0 μm, maximum particle size (D100) 13.5 μm, hollow rate 90%, percentage of particles 2 μm or less 0.2% by volume, solid content 15.0%, foam type Hollow particle B: Trade name "Ropeake SN-1055" (manufactured by Dow Chemical Company), average particle size (D50) 1.0 μm, maximum particle size (D100) 1.8 μm, hollow rate 55%, percentage of particles 2 μm or less 100% by volume, solid content 26.5%, non-foaming type The average particle size (D50) and maximum particle size (D100) of each hollow particle were measured using a laser diffraction particle size distribution analyzer SALD2200 (Shimadzu Corporation) at a refractive index of 1.70-0.01i.

[0086] The latexes used in the examples and comparative examples are as follows: Latex A: Styrene-butadiene copolymer latex (Tg: -35°C, particle size: 300 nm, solid content: 48%) Latex B: Styrene-butadiene copolymer latex (product name L-1571, manufactured by Asahi Kasei Corporation, Tg: -3°C, particle size 190 nm, solid content 48%)

[0087] Example 1 (1) Preparation of coating liquid for undercoat layer 133.3 parts of hollow particles A, 35.0 parts of Ansilex 93, 84.6 parts of latex A, 4.4 parts of adipic acid dihydrazide (solids concentration 100%, manufactured by Otsuka Chemical Co., Ltd.) and 75.0 parts of water were mixed and stirred to obtain a coating liquid for an undercoat layer.

[0088] (2) Preparation of leuco dye dispersion (liquid A) 40 parts of 3-di-(n-butyl)amino-6-methyl-7-anilinofluoran, 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%), and 20 parts of water were mixed, and the mixture was ground using a sand mill (sand grinder, manufactured by Imex Co., Ltd.) until the median diameter measured with a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) reached 0.5 μm, thereby obtaining a leuco dye dispersion liquid (Liquid A).

[0089] (3) Preparation of developer dispersion liquid (liquid B) 40 parts of 2-phenylsulfonylamino-N,N'-diphenylurea (NKK-1304, melting point 152°C, 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 ground using a sand mill (sand grinder, manufactured by Imex Co., Ltd.) until the median diameter measured with a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) reached 1.0 μm, to obtain a developer dispersion (Liquid B).

[0090] (4) Preparation of shelf life improver dispersion (liquid C) 40 parts of 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone (manufactured by Chemipro Chemical Co., Ltd., UU), 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%), and 20 parts of water were mixed, and the mixture was ground using a sand mill (sand grinder manufactured by Imex Co., Ltd.) until the median diameter measured with a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) reached 1.0 μm, thereby obtaining a storage stability improver dispersion (Liquid C).

[0091] (5) Preparation of coating solution for thermosensitive recording layer A coating liquid for a thermosensitive recording layer was obtained by mixing and stirring 36.4 parts of solution A, 63.6 parts of solution B, 22.7 parts of solution C, 36.0 parts of 1,2-di(3-methylphenoxy)ethane (trade name: KS232S, manufactured by Sankosha, solids concentration 50%), 18.0 parts of light calcium carbonate (trade name: Brilliant-15, manufactured by Shiraishi Kogyo Co., Ltd., solids concentration 100%), 50 parts of a 10% aqueous solution of fully saponified polyvinyl alcohol (trade name: Kuraray Poval 11-98, manufactured by Kuraray Co., Ltd.), 10.4 parts of latex B, and 120 parts of water.

[0092] (6) Preparation of protective layer coating solution A coating liquid for the protective layer was obtained by mixing and stirring a composition consisting of 300 parts of a 12% aqueous solution of diacetone-modified polyvinyl alcohol (trade name: DF-10, manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.), 60 parts of aluminum hydroxide (trade name: KH-101, manufactured by KC Corporation), 4 parts of silica (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Industries, Ltd.), and 114.5 parts of water.

[0093] (7) Preparation of thermal recording medium Basis weight 60g / m 2 On one side of a sheet of high-quality paper, the coating liquid for the undercoat layer, the coating liquid for the thermosensitive recording layer, and the coating liquid for the protective layer were applied in a dry amount of 4.5 g / m 2 , 3.0 g / m 2 , 2.0 g / m 2 The coating was then dried to form an undercoat layer, a thermosensitive recording layer, and a protective layer in that order, and the surface was smoothed by a supercalender to obtain a thermosensitive recording medium.

[0094] (8) Formation of peeling layer On the protective layer of the obtained thermal recording medium, a coating liquid for a release layer, prepared by mixing and stirring 100 parts of an addition polymerization type curable silicone compound (trade name: LTC-310, manufactured by Dow Chemical Company), 1.6 parts of a platinum catalyst (trade name: SRX212, manufactured by Dow Chemical Company), and 293.4 parts of hexane, was applied in an amount of 0.35 g / m. 2 After drying and applying the coating, the peel layer was cured at 40°C for a maximum of 10 days until it was sufficiently hardened.

[0095] (9) Formation of adhesive layer Furthermore, on the other side of the support of the thermosensitive recording medium on which the release layer had been formed and cured, a water-based acrylic emulsion adhesive (trade name: L-145, manufactured by Nippon Carbide Industries Co., Ltd.) was applied as a coating liquid for the adhesive layer in a coating amount of 25 g / m after drying. 2 After forming an adhesive layer by applying the adhesive by a roll coater method so that the adhesive layer satisfies the following formula and drying, a roll-up linerless thermal recording label was obtained.

[0096] Example 2 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 80.9 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 6.2 parts.

[0097] Example 3 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 78.9 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 7.3 parts.

[0098] Example 4 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 88.3 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 2.6 parts.

[0099] Example 5 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 90.5 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 1.5 parts.

[0100] Example 6 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 73.1 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 9.9 parts.

[0101] Example 7 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer of Example 1, 75.5 parts of hollow particles B were used instead of 133.3 parts of hollow particles A.

[0102] Example 8 A thermal recording linerless label was obtained in the same manner as in Example 1, except that in preparing solution B in Example 1, 40 parts of 2-phenylsulfonylamino-N,N'-diphenylurea (manufactured by Nippon Soda Co., Ltd., NKK-1304, melting point 152°C) were replaced with 40 parts of 4-allyloxy-4'-hydroxydiphenyl sulfone (manufactured by Nicca Chemical Co., Ltd., BPS-MAE, melting point 180°C).

[0103] Example 9 A thermal recording linerless label was obtained in the same manner as in Example 1, except that in preparing solution B in Example 1, 40 parts of 2-phenylsulfonylamino-N,N'-diphenylurea (manufactured by Nippon Soda Co., Ltd., NKK-1304, melting point 152°C) were replaced with 40 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone (manufactured by Nippon Soda Co., Ltd., D-8, melting point 128°C).

[0104] Example 10 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the thermal recording layer in Example 1, the amount of liquid C was changed from 45.5 parts to 0 parts, and the amount of light calcium carbonate (product name: Brilliant-15, manufactured by Shiraishi Kogyo Co., Ltd., solid content concentration 100%) was changed from 18.0 to 28.0 parts.

[0105] Example 11 A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, 84.6 parts of latex B was used instead of 84.6 parts of latex A.

[0106] (Comparative Example 1) A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 92.4 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 0.7 parts.

[0107] (Comparative Example 2) A linerless thermal recording label was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the undercoat layer in Example 1, the amount of Latex A was changed from 84.6 parts to 69.5 parts, and the amount of adipic acid dihydrazide was changed from 4.4 parts to 11.8 parts.

[0108] (Comparative Example 3) In the preparation of the coating liquid for the undercoat layer of Example 1, the amount of hollow particles A was changed to 0 parts instead of 133.3 parts, the amount of Ancilex 93 was changed to 55.0 parts instead of 35.0 parts, the amount of latex A was changed to 69.5 parts instead of 84.6 parts, and the amount of adipic dihydrazide was changed to 11.8 parts instead of 4.4 parts. Otherwise, a thermal recording linerless label was obtained in the same manner as in Example 1.

[0109] Regarding the above Examples and Comparative Examples, evaluation was carried out by the following method. The results were as shown in Table 1.

[0110] 〔ADH detection amount〕 A 8 cm × 8 cm square of the thermal recording linerless label was measured and further cut into 5 mm squares. The cut samples were placed in sample bottles and ultrasonic treatment was performed for 10 minutes together with 5 ml of water. Then, filtration was carried out with a membrane filter having a pore size of 0.2 μm, and the obtained solution was analyzed by HPLC-CAD. Quantitative analysis was performed by the one-point calibration curve method. The details of the HPLC conditions are shown below. <HPLC condition details> Apparatus: HPLC Waters alliance2690 Detector: CAD Column: Waters XBridge length × inner diameter = 250 × 4.6 mm particle size = 5 μm Column temperature: 30 °C Eluent: 0.1% IPCC-MS-3 aqueous solution (85%) + acetonitrile (15%) 1 mL of IPCC-MS-3 was diluted to 1000 mL with pure water. 850 mL of the diluted IPCC-MS-3 aqueous solution and 150 mL of acetonitrile were mixed to obtain the eluent. Flow rate: 1.0 mL / min (isocratic) Injection volume: 2 μL

[0111] 〔Intermediate tone recording density〕 Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), recording was performed on each thermal recording linerless label in the halftone energy region with applied energy of 0.16 mJ / dot, and the resulting printed area was measured in visual mode with a Macbeth densitometer (RD-914, manufactured by Macbeth Co., Ltd.). The larger the value, the higher the print density. For practical purposes, a recording density of 1.30 or higher is required, and 1.50 or higher is more preferable.

[0112] [Plasticizer resistance] A polycarbonate pipe (40 mm diameter) was wrapped in three layers of cling film (product name: Hi-Wrap KMA-W, manufactured by Mitsui Chemicals), and the thermal recording linerless label after recording for measuring the recording density was placed on top of that. Another three layers of cling film were wrapped around that, and after leaving it at 40°C for 24 hours, the printed area was measured in visual mode with a Macbeth densitometer (described above). A retention rate of 80% or more of the recording density after processing is acceptable for use, but 90% or more is more preferable.

[0113] [Curing property of silicone layer] The hardening property of the release layer was evaluated according to the following criteria. ◎: The peeling layer was sufficiently hardened after 3 days of curing at 40°C. ○: The peeling layer was sufficiently hardened after 4 to 7 days of curing at 40°C. △: The peeling layer was sufficiently hardened after 8 to 10 days of curing at 40°C. ×: The peel layer was not sufficiently hardened after 10 days of curing at 40°C. *Criteria for determining whether the product has hardened sufficiently: The peeling layer should not peel off even when rubbed with a finger 10 times in succession.

[0114] [Heat resistance evaluation] Each thermal recording linerless label was left at 90°C for 1 hour, and the blank area was measured with a Macbeth densitometer. A value of 0.20 or less after processing is acceptable for use, but a value of 0.15 or less is more preferable.

[0115] [Table 1]

Claims

1. A linerless thermal recording label having a support, an undercoat layer on one side of the support, a thermal recording layer containing a dye precursor and a color developer, a protective layer containing an adhesive, and a release layer from the side closest to the support, and an adhesive layer on the other side of the support, The amount of adipic acid dihydrazide detected from the thermal recording linerless label, as measured by the method described below, is 50 to 250 mg / m ２ and A thermal recording linerless label is measured to an 8cm x 8cm square and then cut into 5mm squares. The cut sample is placed in a sample bottle and ultrasonicated with 5ml of water for 10 minutes. It is then filtered through a membrane filter with a pore size of 0.2µm, and the resulting solution is analyzed by HPLC-CAD. Quantitative analysis is performed using the single-point calibration method. Detailed HPLC conditions are shown below. <HPLC condition details> Apparatus: HPLC Waters Alliance 2690 Detector: CAD Column: Waters XBridge length x inner diameter = 250 x 4.6 mm particle size = 5 μm Column temperature: 30°C Eluent: 0.1% IPCC-MS-3 aqueous solution (85%) + acetonitrile (15%). Dilute 1 mL of IPCC-MS-3 with pure water to 1000 mL. Mix 850 mL of the diluted IPCC-MS-3 aqueous solution with 150 mL of acetonitrile to make the eluent. Flow rate: 1.0 mL / min (isocratic) Injection volume: 2 μL” the release layer is an addition polymerization type silicone release layer containing a platinum catalyst, the undercoat layer contains adipic acid dihydrazide, The protective layer contains at least one adhesive selected from acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol, The developer contains 2-phenylsulfonylamino-N,N'-diphenylurea, The coating amounts of the undercoat layer, the thermosensitive recording layer, the protective layer and the release layer are 3 to 20 g / m 2 , 2 to 12 g / m 2 , 0.1 to 8 g / m 2 and 0.05 to 3 g / m 2 , respectively, in terms of dry mass; Thermal recording linerless label.

2. 2. The linerless thermal recording label according to claim 1, wherein the undercoat layer contains hollow particles, the hollow particles having a maximum particle size (D100) of 10 to 30 μm, an average particle size (D50) of 4.0 to 15 μm, a ratio D100 / D50 of the maximum particle size (D100) to the average particle size (D50) of 1.8 to 3.0, a hollowness of 80 to 98%, and a volume percentage of particles having a particle size of 2.0 μm or less of 1% or less.

3. A linerless thermal recording label according to claim 1, wherein the undercoat layer contains a styrene-butadiene latex having a Tg of -30°C to -50°C.

4. 3. The linerless thermal recording label according to claim 1, wherein the developer has a melting point of 150[deg.] C. or higher.

5. The heat-sensitive recording layer contains a storage stabilizer represented by the following formula (1): 【Chemistry 1】 3. The linerless thermal recording label according to claim 1, further comprising a urea-urethane compound represented by the formula:

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