heat-sensitive recording material

Abstract

The present invention relates to a heat-sensitive recording material comprising: a carrier substrate having a first surface and a second surface facing opposite to the first surface; a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate, wherein the heat-sensitive color-forming layer comprises at least one color former, at least one color developer, and at least one stabilizer; and an adhesive layer disposed on the second surface of the carrier substrate, wherein the adhesive layer comprises at least one adhesive. The weight ratio of stabilizer to developer in the thermosensitive color-forming layer is selected so that migration of components from the adhesive layer to the thermosensitive color-forming layer results in at least 35% remaining image stability in the thermosensitive color-forming layer after a two-week period, according to the stability test defined herein.

Description

[Technical Field]

[0001] According to a first aspect, the present invention relates to a heat-sensitive recording material comprising: a carrier substrate having a first surface and a second surface facing opposite to the first surface; a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate and including at least one color former, at least one developer, and at least one stabilizer; and an adhesive layer disposed on the second surface of the carrier substrate and including at least one adhesive.

[0002] The weight ratio of stabilizer to developer in the thermosensitive color-forming layer is selected so that migration of components from the adhesive layer to the thermosensitive color-forming layer results in at least 35% remaining image stability in the thermosensitive color-forming layer after a two-week period, according to the stability test defined herein.

[0003] According to a second aspect, the present invention relates to a method for producing a heat-sensitive recording material, comprising the following method steps: providing a carrier substrate having a first side and a second side facing opposite to the first side; applying a coating suspension to the first side of the carrier substrate, wherein the coating suspension comprises at least one color former, at least one color developer, and at least one stabilizer; drying the coating suspension to obtain a heat-sensitive color-forming layer disposed on the first side of the carrier substrate; and applying an adhesive layer to the second side of the carrier substrate.

[0004] According to a third aspect, the present invention relates to a heat-sensitive recording material producible according to the method according to the second aspect.

[0005] According to a fourth aspect, the present invention relates to the use of at least one stabilizer and at least one color developer in a heat-sensitive recording material comprising a carrier substrate having a first surface and a second surface facing opposite to the first surface, a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate and comprising at least one color former, at least one color developer, and at least one stabilizer, and an adhesive layer disposed on the second surface of the carrier substrate and comprising at least one adhesive, wherein the adhesive layer comprises at least one adhesive. [Background technology]

[0006] Heat-sensitive recording materials, also known as thermal paper, are used in a variety of applications, such as sales receipts in retail stores.

[0007] Backside preparations are used with heat-sensitive recording materials to obtain adhesive or heat-sensitive labels or to improve various application properties. The backside preparations can be self-adhesive layers and / or coatings ("back coats") consisting essentially of polymer binders and pigments.

[0008] Heat-sensitive recording materials, so-called heat-sensitive labels for thermal direct printing, which are provided with a self-adhesive layer on the back side, are known from the prior art.

[0009] Japanese Patent Application Laid-Open No. 59-162087, US Pat. No. 4,370,370 and US Pat. No. 4,388,362 describe heat-sensitive labels with release paper.

[0010] DE 19757589 describes a release-free ("linerless") heat-sensitive label having a protective layer on top of the heat-sensitive layer.

[0011] DE 19806433 discloses a linerless heat-sensitive label cured using actinic radiation, which is provided with a protective layer that does not contain silicon compounds.

[0012] EP 0 600 622 A1 and DE 197 24 647 A1 describe linerless heat-sensitive labels with a protective layer coated with a hot melt on the backside.

[0013] EP 1085069 and EP 2474963 disclose heat sensitive label materials in a linerless design with a heat activated adhesive, whereby the heat sensitive label may be written with or without a protective layer.

[0014] EP 3219507 A1 claims a linerless heat-sensitive label that has no actual protective layer, and the surface of the heat-sensitive layer is designed to avoid adhesion to adhesives.

[0015] Heat-sensitive recording materials that have been provided with a so-called "back coat" coating to improve the printability of the reverse side by conventional printing processes or to minimize the tendency of the carrier substrate to curl under adverse humidity conditions are also known from the prior art.

[0016] The different shrinkage behavior of the two sides of the carrier substrate of a heat-sensitive recording material at different ambient humidities, i.e., the different water vapor absorption of both sides / both coats, can be effectively improved by back coating. For example, U.S. Patent No. 6,667,275 discloses a multi-layer back coating for a heat-sensitive recording material that favorably influences the curl tendency of the carrier material web.

[0017] JP 2018-167483 A discloses, inter alia, a method for improving the stability of the thermally generated type surface in a heat-sensitive recording material coated on the back with an oil-based printing ink or ink, by applying a coating to the backside. The formulations of these backside coatings often contain aqueous emulsion polymers such as styrene-butadiene or acrylate latex as an essential component.

[0018] For example, JP 2003-175671 A claims a back coating for a heat-sensitive recording material prepared using an aqueous latex, which forms a soft polymer film (glass transition temperature ≧−30° C.). JP 7-20735 B and JP 2000-204123 A disclose back coating formulations using acrylate emulsion polymers for heat-sensitive recording materials.

[0019] European Patent Application Publication No. 3957488, as well as International Publication No. WO 2022 / 038242, describe a heat-sensitive recording layer having an organic color developer that does not contain a phenol group, a coating composition for producing the heat-sensitive recording layer, and a heat-sensitive recording material, particularly heat-sensitive paper, that includes the heat-sensitive recording layer. The use of the heat-sensitive recording layer for producing a heat-sensitive recording material, a method for producing the heat-sensitive recording material, and the use of the heat-sensitive recording material in heat-sensitive paper applications are also described. Due to their composition, heat-sensitive recording materials are particularly recyclable and environmentally friendly.

[0020] Heat-sensitive recording materials are also described in US Patent Application Publication No. 2021 / 0060994, Canadian Patent Application Publication No. 3149562 and International Patent Application Publication No. WO 2021 / 041600.

[0021] Reference is also made to the following documents: German Patent Application Publication No. 102019126220, International Publication No. 2021 / 058661, Korean Patent Publication No. 2022-070021, and German Utility Model No. 202020005616.

[0022] The color-forming layer of a heat-sensitive recording material typically contains a color former and a color developer, which react with each other under the influence of heat, resulting in color development. Inexpensive color developers containing phenolic groups (such as bisphenol A and bisphenol S) are widely used. These can be used to produce heat-sensitive labels with performance profiles acceptable for specific applications.

[0023] Heat-sensitive labels containing a color developer that does not contain a phenol group in the heat-sensitive color-forming layer are also known in the prior art. These have been developed, inter alia, to improve the durability of the typeface when the printed heat-sensitive recording material comes into contact with a substance or material that contains a hydrophobic substance, such as a plasticizer or oil. In addition to technical advantages, public debate, especially regarding the toxicity of (bis)phenolic chemicals, has greatly stimulated interest in color developers that do not contain phenol groups.

[0024] Storage of thermally printed self-adhesive heat-sensitive labels or back-coated heat-sensitive recording materials for extended periods, especially at high ambient temperatures and / or air humidities, can impair their application properties, in particular such back-coated heat-sensitive recording materials may no longer achieve the specified blackness or surface whiteness of the print (e.g., barcodes or typefaces) after storage.

[0025] However, low print blackness generally leads to reduced reading contrast, which is further exacerbated by a reduced background whiteness. For example, particularly in label applications, where barcode readability is important, low contrast values ​​have a negative impact on this important application property.

[0026] The cause of this phenomenon is said to be the adhesive layer on the backside, from which substances migrate through the carrier substrate during storage into the chemically reactive heat-sensitive recording layer and interact with it in a way that is detrimental to the color composite. Substances with relatively low molecular weights (<10 kDa) contribute most significantly to the migration problem. Also, the use of heat-activated adhesives, i.e., adhesives that are solid at room temperature, can also cause performance degradation after storage.

[0027] In particular, developers with more complex chemical structures than the relatively simple (bis)phenols having multiple reactive sites in the molecule, as is often the case with developers that do not contain phenolic groups, may suffer from the problem of undesirable interactions with substances that may be released from a heat-sensitive recording material that has been treated with a backside formulation.

[0028] To ensure the cohesive strength within the adhesive layer of the pressure-sensitive adhesive and the adhesive strength (adhesion) to the substrate, a typical pressure-sensitive adhesive formulation uses, in addition to a base polymer, a non-polymeric tackifying resin (e.g., natural resin or carbon resin) and / or a plasticizer, a tackifier, and possibly other small molecule additives, such as crosslinkers, stabilizers, etc. Considering that the base polymer contains residual monomers or oligomers from the synthesis process and that further monomers may be formed by hydrolysis promoted by high ambient humidity and temperature, the possibility of migration of small molecule substances inherent in the adhesive layer can be easily recognized.

[0029] In addition to the above-mentioned possibility of residual monomers being present in the latex, the presence of typical process-related materials such as surfactants, soaps, initiators, etc. during emulsion polymerization must be considered when assessing the migration potential of the polymeric components of the backcoat coating.

[0030] The prior art has proposed various solutions to this problem for adhesive heat-sensitive labels: applying an additional layer (a so-called back coat) between the backside of the carrier substrate and the adhesive layer, as in U.S. Pat. No. 4,370,370 and EP 2,474,963, or incorporating special substances, such as carboxylated polyvinyl alcohol, into the adhesive layer, as described in JP 59-162087 A1.

[0031] However, these solutions are economically disadvantageous because they require additional manufacturing steps and make the overall label material more complex, and can only minimize backcoating migration problems if more expensive low-migration binders are used. Summary of the Invention

[0032] The object of the present invention is to optimize the property profile of a thermally printed heat-sensitive recording material having an adhesive layer on the back side, in particular when the heat-sensitive recording material is stored for long periods of time, and in particular to limit as much as possible the loss of image stability after storage of the heat-sensitive recording material.

[0033] Image stability is characterized by the durability of the image after storage of the heat-sensitive recording material, whereby image stability can also be characterized in particular by print contrast.

[0034] The present invention therefore aims to improve the minimum shelf life of heat-sensitive recording materials while at the same time maintaining the usual high requirements for such heat-sensitive recording materials, such as dynamic sensitivity, contrast, etc.

[0035] Surprisingly, it has thus been found that the above-mentioned drawbacks of the prior art can be improved by using a combination of at least one colour developer having a group capable of forming a hydrogen bond selected from the group consisting of -NHCO-, -CONH-, -NHCONH-, -CONHNHCO-, -NHCOCONH-, -SONH- and -NHSO-, and 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide (trade name PF425) as a stabilizer in the heat-sensitive layer of a heat-sensitive recording material.

[0036] In particular, the use of this combination of at least one corresponding colour developer and stabilizer in the heat-sensitive layer of a heat-sensitive recording material limits the loss of image stability after storage under harsh environmental conditions of the heat-sensitive recording material provided with the backside preparation, and thus the use of both components in the heat-sensitive layer provides a synergistic effect.

[0037] The above-mentioned object is solved by a first aspect of a heat-sensitive recording material comprising: a carrier substrate having a first surface and a second surface facing opposite to the first surface; a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate, wherein the heat-sensitive color-forming layer comprises at least one color former, at least one color developer, and at least one stabilizer; and an adhesive layer disposed on the second surface of the carrier substrate, wherein the adhesive layer comprises at least one adhesive; wherein the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is selected such that migration of components from the adhesive layer to the heat-sensitive color-forming layer results in a remaining image stability of at least 35% after a period of two weeks, according to the stability test defined herein.

[0038] According to a first embodiment, the stabilizer has formula (I): [ka] The compound where R and R are independently hydrogen, C1-C 18 -alkyl, C1-C8-alkoxy-C1-C8-alkyl, and (R9)2N—C1-C8-alkyl, where R9 is selected from the group comprising C1-C8-alkyl, C5-C6-cycloalkyl; or a group of formula (II) [ka] Compounds of wherein R2, R3, R4, R5 and R6 are independently selected from the group comprising hydrogen, C1-C8-alkyl, -NH-C(=O)-R7 and -C(=O)-NH-R7, where R7 is selected as C1-C8-alkyl or -C(=O)OR8, where R8 is selected as C1-C8-alkyl or halogen, or R2 and R3, or R4 and R5, or both, or R3 and R4, or R5 and R6, or both, or R2 and R3 and R5 and R6 together form a hydrocarbon group having 3 or 4 carbon atoms, wherein Q comprises a single bond or C1-C8-alkylene, which may be branched or unbranched, and wherein C1-C8-alkylene, when it has more than two carbon atoms, comprises a main chain having one or more oxygen atoms between the two carbon atoms.

[0039] According to a first embodiment, the at least one colour developer has the formula (NI): [ka] Compounds of wherein R1, R2, and R3 are independently selected from the group comprising hydrogen, halogen, nitro, C1-C6-alkyl, C1-C6-alkoxyl, C2-C6-alkenyl, C1-C6-fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl, and optionally substituted benzyl, where R4 is selected from the group comprising hydrogen, phenyl, benzyl, and C1-C6-alkyl, where R5 is selected as C1-C6-alkyl, where n1 and n3 are independently selected as integers from 1 to 5, and where n2 is an integer from 1 to 4; and / or at least one developer is represented by formula (1): [ka] Compounds of where R1 is unsubstituted or substituted phenyl, naphthyl and C1-C 20 -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C1-C 12-alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is selected from the group comprising -O-SO2-, -SO2-O-, -NH-SO2-, -SO2-NH-, -S-SO2-, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO2-, -O-CO-NH-SO2-, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO2-NH-CO-, -O-CO-O- and -O-PO-(OR2)2, wherein R2 is unsubstituted or substituted aryl, benzyl and C1-C 20 -alkyl, with the proviso that if B is not a group of the formula -O-SO-, then R is unsubstituted or substituted phenyl, naphthyl or C-C-alkyl, and if B is -O-, then R is not alkyl.

[0040] The combination of stabilizer and developer in the thermosensitive color-forming layer advantageously results in limiting the loss of image stability, and in particular also the loss of relative print contrast, so that the image stability and / or relative print contrast of a thermosensitive recording material stored according to the stability test (defined below) is always greater than the value obtained using the same thermosensitive recording material without stabilizer. This effect is evident in the commercially available critical average current range of 9.00 mJ / mm 2 This is particularly evident in

[0041] Without being bound by theory, it is hypothesized that the stabilizer contributes to maintaining the color complex in its interaction with the developer and color coupler and under the influence of destabilizing influences such as water, chemicals and critical climatic conditions by color complex stabilizing interactions resulting from its functional groups, such as hydrogen bonding, π-π interactions and / or ionic interactions, maintaining the typeface.

[0042] In particular, at least one stabilizer comprises a compound of formula (I) that does not contain a hydroxy-substituted phenyl substituent, and therefore can also be referred to as a phenol-free compound.

[0043] In particular, at least one colour developer comprises a compound of formula (NI) or (1) which does not contain a hydroxy-substituted phenyl group and therefore can also be referred to as a compound which does not contain a phenol group.

[0044] The heat-sensitive recording material is well suited for applications in which an adhesive layer is provided on the back of the heat-sensitive recording material, which is printed using a thermal direct process, and in which a long shelf life must be guaranteed even under harsh environmental conditions with specified image stability and print contrast values.

[0045] The present invention is not subject to any significant restrictions regarding the choice of adhesive applied to the backside. Both adhesives that are tacky at room temperature and adhesives that only become tacky after activation, for example by heat, are possible. Both permanent and removable adhesives can be used. The technique for applying the adhesive to the backside of the heat-sensitive recording material also does not limit the scope of the present invention. Both aqueous dispersions of adhesive or adhesives dissolved or suspended in an organic medium and adhesives that are applied in the molten state, so-called hot-melt adhesives, can be used.

[0046] In summary, it can be said that it has surprisingly been shown that by using at least one developer and stabilizer according to the first aspect of the present invention it is possible to obtain heat-sensitive recording materials, in particular heat-sensitive labels, which are characterized by high image stability of the printed image and good contrast values ​​(print contrast) in the thermal print after long-term storage under harsh environmental conditions.

[0047] The heat-sensitive recording material according to the present invention relates to the application-related case of a self-adhesive heat-sensitive recording material, i.e. a heat-sensitive recording material having an adhesive layer on the side of the carrier substrate facing away from the heat-sensitive color-forming layer.

[0048] In the context of this disclosure, the stability test as defined below is carried out by subjecting the heat-sensitive recording material to a temperature of 60°C, 1350 N / m 2 The test involves storing the sample between two glass plates at a pressure of 0.05 psi, a relative humidity of 50% and in the dark for a period of two weeks.

[0049] As part of the stability testing according to the present disclosure, the image stability of the heat-sensitive recording material is determined based on the optical density twice: before storing the heat-sensitive recording material and after storing the heat-sensitive recording material for two weeks. The two determined values ​​of optical density are related to each other as shown in the following formula A, and the calculated % value has a variation of ≦±2 percentage points: Image Stability (%)=(Optical Density After Storage / Optical Density Before Storage)×100 (Formula A) As part of the stability testing according to the present disclosure, the optical density was measured with an X-Rite SpectroEye densitometer, and the measurement uncertainty of the measurements was estimated to be ≦2%.

[0050] Preferably 9.00 mJ / mm 2 The image stability of the heat-sensitive recording material according to the present invention, tested according to the stability test at an irradiation energy of 1000 kJ / cm, is at least 35% after a storage period of 2 weeks.

[0051] To carry out the stability test, a DIN A4 heat-sensitive recording material having an adhesive layer on the side of the carrier substrate facing away from the heat-sensitive color-forming layer is divided longitudinally into at least two 6 cm wide strips.

[0052] One of these strips is printed and measured to determine the optical density before storage. An unprinted strip is placed on the printed strip (simulating a thermal roll), and the stack is then stored between two glass plates for 2 weeks (or 4 weeks according to some embodiments) at 60°C and 1350 N / m 2 Store at 50% relative humidity and protected from light.

[0053] After storage and conditioning at room temperature, the optical density is measured, averaged, and related to the optical density value originally determined before storage to determine image stability according to Equation A above.

[0054] With regard to the image stability of a heat-sensitive recording material, in addition to image stability, relative print contrast can also be considered as a further criterion for the image stability of a heat-sensitive recording material.

[0055] The relative print contrast (DK%) is calculated based on the optical density of the thermally printed area, i.e., the optical density of the printed pattern (oDs) and the optical density of the non-printed area (oDw), according to the following formula B, whereby the variation of the calculated % value is ≦±2 percentage points: DK(%)=(oDs-oDw / oDs)×100 (Formula B), preferably 9.00 mJ / mm 2 The relative print contrast of the heat-sensitive recording material tested according to the stability test at an irradiation energy of 1000 uV is at least 50% after a storage period of 2 weeks.

[0056] According to a first embodiment, the stabilizer has formula (I): [ka] The compound where R and R are independently hydrogen, C1-C 18 -alkyl, C1-C8-alkoxy-C1-C8-alkyl, and (R9)2N—C1-C8-alkyl, where R9 is selected from the group comprising C1-C8-alkyl, C5-C6-cycloalkyl; or a group of formula (II) [ka] Compounds of wherein R2, R3, R4, R5 and R6 are independently selected from the group comprising hydrogen, C1-C8-alkyl, -NH-C(=O)-R7 and -C(=O)-NH-R7, where R7 is selected as C1-C8-alkyl or -C(=O)OR8, where R8 is selected as C1-C8-alkyl or halogen, or R2 and R3, or R4 and R5, or both, or R3 and R4, or R5 and R6, or both, or R2 and R3 and R5 and R6 together form a hydrocarbon group having 3 or 4 carbon atoms, wherein Q comprises a single bond or C1-C8-alkylene, which may be branched or unbranched, and wherein C1-C8-alkylene, when it has more than two carbon atoms, comprises a main chain having one or more oxygen atoms between the two carbon atoms.

[0057] Preferably, the hydrocarbon group formed by R2 and R3 and R5 and R6 together with three or four carbon atoms includes trimethylene, tetramethylene, propenylene, 2-butenylene or 1,3-butadienylene.

[0058] Preferably, R8 is selected as halogen, and more preferably R8 is selected as chlorine.

[0059] Preferably, Q is selected as -CH2-, -CH2-CH2-, -CH2-O-, -CH2-CH2-O-, -CH2-CH2-CH2-, -CH2-CH2-CH2-CH2-, -C(Me)H-, -C(Et)H-, -C(n-Pr)H-, -C(i-Pr)H-, -C(n-Bu)H-, -C(i-Bu)H-, -C(sec-Bu)H-, -C(tert-Bu)H-, -C(Me)HCH2-, -CMe2CH2-, where Q is more preferably selected as -CH2-, -CH2-CH2-, -CH2-CH2-O- or -C(Me)H-.

[0060] Preferably, "C1 to C 18 The selection of "alkyl" includes methyl, ethyl, propyl, isopropyl, N-butyl, isobutyl, sec-butyl, tert-butyl, amyl, tert-amyl (1,1-dimethylpropyl), 1,1,3,3-tetramethylbutyl, N-hexyl, 2-methylpentyl, neopentyl, N-heptyl, 2-ethyl-hexyl or N-octyl, N-nonyl, N-decyl, N-undecyl, N-dodecyl, N-tridecyl, N-tetradecyl, N-pentadecyl, N-hexadecyl, N-heptadecyl, or N-octadecyl.

[0061] The selection "C1-C8 alkyl" preferably includes methyl, ethyl, propyl, isopropyl, N-butyl, isobutyl, sec-butyl, tert-butyl, amyl, tert-amyl (1,1-dimethylpropyl), 1,1,3,3-tetramethylbutyl, N-hexyl, 2-methylpentyl, neopentyl, N-heptyl, 2-ethyl-hexyl or N-octyl, or tridecyl, more preferably methyl, ethyl, N-propyl, isopropyl, N-butyl, isobutyl, sec-butyl, tert-butyl, 2-ethyl-hexyl or tridecyl.

[0062] Preferably, the selection "C1-C8 alkoxy" includes methoxy, ethoxy, N-propoxy, isopropoxy, N-butyloxy, N-pentyloxy, N-hexyloxy, N-heptyloxy, or N-octyloxy. More preferably, the selection "C1-C8-alkoxy" includes the selection "C1-C6-alkoxy", and even more preferably includes methoxy, ethoxy, N-propoxy, isopropoxy, N-butyloxy, or N-hexyloxy.

[0063] The selection "C1-C8-alkoxy-C1-C8-alkyl" preferably comprises methoxymethyl, ethoxymethyl, N-propoxymethyl, isopropoxymethyl, N-butyloxymethyl, N-pentyloxymethyl, N-hexyloxymethyl, N-heptyloxymethyl, N-octyloxymethyl, methoxyethyl, ethoxyethyl, N-propoxyethyl, isopropoxyethyl, N-butyloxyethyl, N-pentyloxyethyl, N-hexyloxyethyl, N-heptyloxyethyl, N-octyloxyethyl, methoxymethyl, 1-methoxyethyl, 2-methoxyethyl, 3-methoxy-n-propyl, 1-methoxy-2-propyl, 4-methoxy-n-butyl, 5-methoxy-n-pentyl, 6-methoxy-n-hexyl, 7-methoxy-n-heptyl, 8-methoxy or N-octyl, more preferably 2-methoxyethyl.

[0064] Preferably, the selection "C5-C6-cycloalkyl" includes cyclopentyl or cyclohexyl, more preferably cyclohexyl.

[0065] Preferably, the selection "(R9)2N-C1-C8-alkyl" includes 2-(dimethylamino)methyl, 2-(dimethylamino)ethyl, 2-(diethylamino)ethyl, 2-(diisopropylamino)ethyl, 2-(n-propylamino)ethyl, 3-(dimethylamino)propyl, or 3-(cyclohexylamino)propyl.

[0066] Preferably, the selection "R2 and R3 together" includes tetramethylene when R2 and R3, or R4 and R5, or both, or R3 and R4, or R5 and R6, or both, or (R2 and R3) and (R5 and R6) together form a hydrocarbon group having 3 or 4 carbon atoms, such as, in particular, trimethylene, tetramethylene, propenylene, 2-butenylene, or 1,3-butadienylene.

[0067] Preferably, the compound of formula (II) is phenyl, benzyl, 3-methylphenyl, 2,6-diethylphenyl, o-isopropylphenyl, p-acetamidophenyl, 1-phenylethyl, 2-phenylethyl, 2-phenoxyethyl, 1-tetralino, or 2-tetralino.

[0068] According to one embodiment, the stabilizer has formula (Ia): [ka] or Alternatively, the stabilizer may be a compound of formula (Ib): [ka] This includes compounds of the formula:

[0069] Preferably, the compound of formula (Ia) comprises at least one of the following compounds: 5-(N-benzyl-sulfonylamido)-(N',N''-dibenzyl)-isophthalic acid diamide, 5-(N-3-methylphenyl-sulfonylamido)-(N',N''-bis(3-methylphenyl)-isophthalic acid diamide, 5-(N-2,6-diethylphenyl-sulfonylamido)-(N',N''-bis(2,6-diethylphenyl)-isophthalic acid diamide, 5-(N-phenyl-sulfonylamido)-(N',N''-bisf phenyl)-isophthalic acid diamide, 5-(No-isopropyl-phenyl-sulfonylamido)-(N',N''-bis-(o-isopropylphenyl)-isophthalic acid diamide, 5-(Np-acetamido-phenyl-sulfonylamido)-(N',N''-bis(p-acetylaminophenyl)-isophthalic acid diamide, 5-(N-1-tetralino-sulfonylamido)-(N',N''-bis(1-tetralino)-isophthalic acid diamide, 5-(N-3-methylphenyl-sulfonylamido)-(N',N''-bis(3 -methylphenyl)-isophthalic acid diamide, 5-(N-1-phenylethyl-sulfonylamido)-(N',N''-bis(1-phenylethyl)-isophthalic acid diamide, 5-(N-2-phenylethyl-sulfonylamido)-(N',N''-bis-(2-phenylethyl)-isophthalic acid diamide, 5-(N-2,6-diethylphenyl-sulfonylamido)-(N',N''-bis-(2,6-diethylphenyl)-isophthalic acid diamide, 5-(Nn-butyl-sulfonylamido)-(N',N''-di-n-butyl 1-isophthalic acid diamide, 5-(N-2-ethylhexyl-sulfonylamido)-(N',N''-di-2-ethylhexyl)-isophthalic acid diamide, 5-(N-benzyl-sulfonylamido)-(N',N''-diphenyl)-isophthalic acid diamide, 5-(N-phenylsulfonylamido)-(N',N''-dibenzyl)-isophthalic acid diamide, 5-(N-benzylsulfonylamido)-(N',N''-bis(3-methyl-phenyl)-isophthalic acid diamide, 5-(N-butyl-sulfonylamido)-(N',N''-bis-(3-methyl-phenyl)-isophthalic acid diamide, 5-(N-1-phenyl-ethyl-sulfonylamido)-(N',N''-bis-(3-methyl-phenyl)-isophthalic acid diamide, 5-(N-2-phenyl-ethyl-sulfonylamido)-(N',N''-bis-(3-methyl-phenyl)-isophthalic acid diamide, 5-(N-2-methoxy-ethyl-sulfonylamido)-(N',N''-bis-(3-methyl-phenyl)-isophthalic acid diamide, 5-(Nn-octyl-sulfonylamido)-(N',N''-bis-(3-methyl-phenyl)-isophthalic acid diamide 5-(N-benzyl-sulfonylamido)-(N',N''-bis-(3-methyl-phenyl)-isophthalic acid diamide, 5-(N-benzyl-sulfonylamido)-(N',N''-bis-(2,6-diethyl-phenyl)-isophthalic acid diamide, 5-(Nn-octyl-sulfonylamido)-(N',N''-bis-(2,6-diethyl-phenyl)-isophthalic acid diamide, and 5-(N-2-phenoxy-ethyl-sulfonylamido)-(N',N''-bis-(2,6-diethyl-phenyl)-isophthalic acid diamide.

[0070] In particular, the heat-sensitive recording material has the formula (Ic): [ka] Preferably, the stabilizer is selected as a compound of formula (Ia), and the heat-sensitive recording material comprises a bisamide of formula (Ic), and more preferably, the amount of bisamide (Ic) is 0.01 mol % to 10 mol % relative to the compound of formula (Ia).

[0071] According to one embodiment, the stabilizer comprises 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-{3-methylphenyl)-isophthalic acid diamide.

[0072] In this case, the compound 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-{3-methylphenyl)-isophthalic acid diamide includes in particular three different polymorphs, including an α-polymorph with a melting point of 211.2°C as determined by DSC, an α,β-polymorph with a melting point of 192.2°C as determined by DSC, and a γ-polymorph with a melting point of 215.6°C as determined by DSC.

[0073] According to a first embodiment, the at least one colour developer has the formula (NI): [ka] Compounds of wherein R1, R2, and R3 are independently selected from the group comprising hydrogen, halogen, nitro, C1-C6-alkyl, C1-C6-alkoxyl, C2-C6-alkenyl, C1-C6-fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl, and optionally substituted benzyl, wherein R4 is selected from the group comprising hydrogen, phenyl, benzyl, and C1-C6-alkyl, and wherein R5 is selected as C1-C6-alkyl, and wherein n1 and n3 are independently selected as integers from 1 to 5, and wherein n2 is an integer from 1 to 4.

[0074] Preferably, the compound of formula (NI) is a compound of formula (IV) or a compound of formula (V), wherein R1 and R3 are as defined for compounds of formula (NI): [ka] [ka]

[0075] Preferably, the compound of formula (NI) is a benzenesulfonamide compound.

[0076] Preferably, R1, R2 and / or R3 are hydrogen, halogen, more preferably fluorine, chlorine, bromine or iodine, nitro, a linear, branched or cyclic C1-C6-alkyl group, more preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, isohexyl, cyclopropyl, cyclobutyl, 2-methylcyclopropyl, cyclopropylmethyl, cyclopentyl or cyclohexyl, a linear, branched or cyclic C1-C6-alkoxy group, more preferably methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentyloxy, isopentyloxy, hexyloxy, cyclopropoxy, cyclobutoxy, 2-methylcyclopropoxy, cyclopropylmethoxy, cyclopropylmethyl. pentyloxy, or cyclohexyloxy; C2-C6-alkenyl groups, more preferably vinyl, allyl, isopropenyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl, or 2-methyl-2-propenyl groups; C1-C6-fluoroalkyl groups, more preferably trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluorohexyl, or perfluorocyclohexyl groups; N(R4)2 groups, where R4 is more preferably selected as hydrogen, phenyl, benzyl, or C1-C6-alkyl; NHCOR5 groups, where R5 is more preferably selected as C1-C6-alkyl, optionally substituted phenyl; and optionally substituted benzyl groups.

[0077] Even more preferably, R1, R2 and / or R3 are selected as hydrogen or a linear C1-C6 alkyl group, and most preferably, R1 is hydrogen or methyl, and R2 and R3 are each hydrogen.

[0078] Even more preferably, the selection of C1-C6 alkyl groups selected according to R4 or R5 is the same as the selection of C1-C6 alkyl groups selected according to R1.

[0079] Even more preferably, the optional substituents of the optionally substituted group are selected from hydroxy, halogen, most preferably fluorine, chlorine, bromine or iodine, C1-C6-alkyl, most preferably methyl, ethyl, N-propyl, isopropyl, N-butyl, sec-butyl, tert-butyl, N-pentyl, isopentyl, neopentyl, tert-pentyl, N-hexyl, isohexyl, 1-methyl-pentyl or 2-methyl-pentyl, and C1-C6-alkoxy, most preferably methoxy, ethoxy, N-propoxy, isopropoxy, N-butoxy, sec-butoxy or tert-butoxy.

[0080] Preferably, the compound of formula (NI) is selected from 4-methyl-N-(2-(3-phenylureido)phenyl)benzenesulfonamide and N-(2-(3-phenylureido)phenyl)benzenesulfonamide, more preferably N-(2-(3-phenylureido)phenyl)benzenesulfonamide.

[0081] According to one embodiment, the at least one developer comprises a compound of formula (NI), wherein R1, R2, and R3 are selected as hydrogen.

[0082] According to one embodiment, the at least one colour developer comprises N-(2-(3-phenylureido)phenyl)benzenesulfonamide, preferably the α- and / or β-polymorph of N-(2-(3-phenylureido)phenyl)benzenesulfonamide.

[0083] In particular, the α-polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 5.8, 9.3, 13.2, 15.7, 17.3, 18.3, 18.7, 19.5, 20.3, 21.1, 21.9, 22.8, 23.3, 23.6, 24.4, 24.9, 25.6, 26.7, 27.8, 28.1, 29.3, 29.6, 30.2, 31.6, 32.3, and 32.8 and / or a melting point (onset temperature) of 158°C-159°C as determined by DSC.

[0084] In particular, the β-polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 10.0, 11.0, 12.3, 12.7, 13.8, 14.9, 15.6, 16.8, 17.7, 18.5, 20.1, 20.9, 21.6, 22.0, 22.8, 23.0, 23.6, 24.3, 25.5, 26.7, 27.8, 28.4, 29.0, 29.8, 30.5, 31.1, and 31.3 and / or a melting point of 173°C-174°C (onset temperature) as determined by DSC.

[0085] The corresponding X-ray diffraction patterns were obtained by X-ray diffraction (XRD) measurements using a Bruker D2 Phaser, Cu electrodes, a voltage of 30 kV, and a Lynxeye detector.

[0086] The corresponding melting points determined by DSC were measured by dynamic differential calorimetry in a Netzsch DSC 200 F3 Maia® apparatus, Al crucibles with cold-welded perforated lids, at a heating rate of 10 K / min and in a N2 atmosphere in the temperature range 25 °C to 200 °C.

[0087] The corresponding compound, N-(2-(3-phenylureido)phenyl)benzenesulfonamide, is also sold under the name NKK-1304.

[0088] Instead of or in addition to the at least one colour developer according to formula (N-1), according to a first embodiment, the at least one colour developer is of formula (1): [ka] Compounds of where R1 is unsubstituted or substituted phenyl, naphthyl and C1-C 20 -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C1-C 12 -alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is selected from the group comprising -O-SO2-, -SO2-O-, -NH-SO2-, -SO2-NH-, -S-SO2-, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO2-, -O-CO-NH-SO2-, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO2-NH-CO-, -O-CO-O- and -O-PO-(OR2)2, wherein R2 is unsubstituted or substituted aryl, benzyl and C1-C 20 alkyl, with the proviso that when B is not a group of formula -O-SO-, then R is unsubstituted or substituted phenyl, naphthyl or C-C alkyl, and when B is -O-, then R is not alkyl.

[0089] Preferably, R1 is selected as phenyl or naphthyl, which may be unsubstituted or substituted, for example, with C1-C8 alkyl, C1-C8 alkoxy or halogen.

[0090] More preferably, the substituents are selected as C1-C4 alkyl, most preferably methyl or ethyl, C1-C4 alkoxy, more preferably methoxy or ethoxy, or halogen, more preferably chlorine.

[0091] More preferably, R1 is selected as unsubstituted naphthyl.

[0092] More preferably, R1 is selected as a substituted phenyl, and most preferably the substituent is selected as one of the alkyl substituents mentioned above.

[0093] Preferably, R1 is an unsubstituted or substituted C1-C 20 -alkyl, more preferably C1-C8-alkoxy or halogen, even more preferably C1-C4-alkoxy, most preferably methoxy or ethoxy, or halogen, most preferably chlorine.

[0094] More preferably, R1 is an unsubstituted C1-C 20 - alkyl is selected.

[0095] Even more preferably, R1 is unsubstituted phenyl or phenyl substituted with C1-C8-alkyl, C1-C8-alkoxy or halogen, with substituted phenyl being even more preferred. Most preferred is phenyl substituted with C1-C4-alkyl, even more preferably methyl.

[0096] Preferably, X is a group of formula -C(=S)- or -C(=O)-, more preferably a group of formula -C(=O)-.

[0097] Preferably, A is an unsubstituted phenylene group or an unsubstituted naphthylene group, or more preferably a phenylene or naphthylene group substituted by C1-C8-alkyl, halogen-substituted C1-C8-alkyl, C1-C8-alkoxy-substituted C1-C8-alkyl, C1-C8-alkoxy, halogen-substituted C1-C8-alkoxy, C1-C8-alkylsulfonyl, halogen, phenyl, phenoxy or phenoxycarbonyl.

[0098] Even more preferred are alkyl and alkoxy substituents containing 1 to 4 carbon atoms, with C1-C8-alkyl, halogen-substituted C1-C8-alkyl, C1-C8-alkylsulfonyl or halogen being most preferred.

[0099] More preferably, A is an unsubstituted naphthylene group.

[0100] A is preferably a heterocyclic group, which more preferably includes unsubstituted pyrimidylene or pyrimidylene substituted with C1-C8 alkyl, even more preferably C1-C4 alkyl.

[0101] A is preferably C1 to C 12 -alkylene group, more preferably C1-C8-alkylene, even more preferably C1-C4-alkylene.

[0102] More preferably, A is unsubstituted phenylene or phenylene substituted with C1-C8-alkyl, halogen-substituted C1-C8-alkyl, C1-C8-alkoxy-substituted C1-C8-alkyl, C1-C8-alkoxy, halogen-substituted C1-C8-alkoxy, C1-C8-alkylsulfonyl, halogen, phenyl, phenoxy or phenoxycarbonyl, even more preferably C1-C8-alkyl, halogen-substituted C1-C8-alkyl, C1-C8-alkylsulfonyl or halogen.

[0103] Most preferably, A is unsubstituted phenylene or phenylene substituted with C1-C4-alkyl or halogen, even more preferably unsubstituted phenylene.

[0104] Preferably, B is selected as -O-SO2-, -SO2-O-, -SO2-NH-, -S-SO2-, -O-, -O-CO- and -O-CO-NH-, more preferably -O-SO2-, -SO2-O- and -SO2-NH-, most preferably -O-SO2- and -O-.

[0105] Preferably, R2 is aryl, more preferably phenyl or naphthyl, which is unsubstituted or substituted, even more preferably substituted with C1-C8-alkyl, halogen-substituted C1-C8-alkyl, C1-C8-alkoxy-substituted C1-C8-alkyl, C1-C8-alkoxy, halogen-substituted C1-C8-alkoxy or halogen, most preferably the alkyl and alkoxy substituents contain 1 to 4 carbon atoms, where C1-C4-alkyl and halogen are even more preferred substituents.

[0106] Preferably, R2 is naphthyl, which is even more preferably unsubstituted.

[0107] Preferably, R2 is benzyl, which is substituted with the substituents previously mentioned for selecting R2 as phenyl or naphthyl, with unsubstituted benzyl being even more preferred.

[0108] Preferably, R2 is C1 to C 20 Alkyl, more preferably C1-C8 alkyl, even more preferably C1-C6 alkyl, which is unsubstituted or substituted, for example, by C1-C8 alkoxy, halogen, phenyl or naphthyl, most preferably an unsubstituted alkyl group, even more preferably C1-C4 alkyl.

[0109] More preferably, R2 is C1-C6-alkyl, halogen-substituted C1-C6-alkyl, phenyl-substituted C1-C6-alkyl, naphthyl-substituted C1-C6-alkyl, unsubstituted phenyl, or phenyl substituted with C1-C8-alkyl, halogen-substituted C1-C8-alkyl, C1-C8-alkoxy-substituted C1-C8-alkyl, C1-C8-alkoxy, halogen-substituted C1-C8-alkoxy or halogen, naphthyl substituted with C1-C4-alkyl or halogen and benzyl.

[0110] Even more preferably, R2 is C1-C4 alkyl, halogen-substituted C1-C4 alkyl, phenyl unsubstituted or substituted with C1-C4 alkyl or halogen, naphthyl and benzyl unsubstituted or substituted with C1-C4 alkyl or halogen, most preferably phenyl unsubstituted or substituted with C1-C4 alkyl or halogen.

[0111] Preferably, R1 is phenyl substituted with C1-C4-alkyl, more preferably methyl; X is -C(=O)-; A is phenylene which is unsubstituted or substituted with C1-C8-alkyl or halogen, with unsubstituted phenylene, such as 1,3-phenylene, being more preferred; B is a group of formula -O-SO2- or -O-; R2 is phenyl, naphthyl or benzyl which is unsubstituted or substituted with C1-C4-alkyl or halogen, with phenyl substituted with C1-C4-alkyl being more preferred.

[0112] According to one embodiment, the at least one colour developer of formula (1) comprises 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide, preferably the α- and / or β-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

[0113] In particular, the α polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 8.5, 9.5, 11.8, 12.1, 12.2, 13.7, 14.1, 16.6, 17.1, 18.3, 18.6, 19.1, 19.3, 20.1, 20.4, 20.9, 21.3, 23.1, 24.2, 24.6, 25.0, 27.9, and 28.6 and / or a melting point determined by DSC of 161°C-162°C.

[0114] In particular, the β polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 10.3, 11.0, 12.9, 13.2, 15.4, 17.1, 18.0, 18.2, 19.4, 20.0, 20.7, 21.2, 23.0, 24.9, 25.3, 26.5, 26.8, 27.5, 30.7, and 32.7 and / or a melting point of 166°C-167°C as determined by DSC.

[0115] The corresponding X-ray diffraction patterns were obtained by X-ray diffraction (XRD) measurements using a Bruker D2 Phaser, Cu electrodes, a voltage of 30 kV and a Lynxeye detector.

[0116] The corresponding melting points determined by DSC were measured by dynamic differential calorimetry in a Netzsch DSC 200 F3 Maia® apparatus, Al crucibles with cold-welded perforated lids, at a heating rate of 10 K / min and in a N2 atmosphere in the temperature range 25 °C to 200 °C.

[0117] According to one embodiment, the weight ratio of the stabilizer to the color developer in the thermosensitive color-forming layer is 1:11 to 1:1, preferably 1:8 to 1:4, more preferably 1:7 to 1:5, and most preferably 1:6.

[0118] Due to the corresponding weight ratio of stabilizer to developer in the heat-sensitive color-forming layer, the heat-sensitive marking material also exhibits particularly high image stability, especially high remaining print contrast, after a two-week period in the stability test defined herein.

[0119] In particular, the stabilizer is selected as 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-{3-methylphenyl)isophthalic acid diamide (trade name PF425), and at least one color developer is selected as N-(2-(3-phenylureido)phenyl)benzenesulfonamide (trade name NKK-1304) and / or 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (trade name PF-201), wherein the weight ratio of the stabilizer to the color developer in the thermosensitive color-forming layer is 1:11 to 1:1, preferably 1:8 to 1:4, more preferably 1:7 to 1:5, and most preferably 1:6.

[0120] According to one embodiment, the stabilizer has a weight proportion of 1% to 10% by weight based on the total solid content of the thermosensitive color-forming layer, preferably 2% to 8% by weight, more preferably 3% to 6% by weight, and most preferably 4% by weight.

[0121] With the corresponding weight percentage of stabilizer in the thermosensitive color forming layer, particularly high remaining image stability, especially high remaining print contrast of the thermosensitive color forming layer is also exhibited after a two week period in the stability test defined herein.

[0122] In particular, the stabilizer is selected as 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-{3-methylphenyl)-isophthalic acid diamide (trade name PF425), and the stabilizer has a weight proportion of 1 wt % to 10 wt % based on the total solid content of the thermosensitive color-forming layer, where the weight proportion is preferably 2 wt % to 8 wt %, more preferably 3 wt % to 6 wt %, and most preferably 4 wt %.

[0123] According to one embodiment, the at least one color developer has a weight percentage of 6% to 35% by weight based on the total solid content of the thermosensitive color-forming layer, wherein the weight percentage is preferably 10% to 30% by weight, more preferably 20% to 30% by weight, and most preferably 24% by weight.

[0124] With the corresponding weight proportion of at least one color developer in the thermosensitive color forming layer, particularly high remaining image stability, especially high remaining print contrast of the thermosensitive color forming layer was also demonstrated after a period of two weeks in the stability test defined herein.

[0125] In particular, the at least one color developer is selected as N-(2-(3-phenylureido)phenyl)benzenesulfonamide (trade name NKK-1304), and / or 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (trade name PF-201), wherein the at least one color developer has a weight proportion of 6% to 35% by weight based on the total solid content of the thermosensitive color-forming layer, wherein the weight proportion is preferably 10% to 30% by weight, more preferably 20% to 30% by weight, and most preferably 24% by weight.

[0126] According to one embodiment, the image stability of the remaining thermosensitive color forming layer after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, and most preferably at least 80%.

[0127] The correspondingly high image stability of the heat-sensitive color-forming layer remaining after a two-week period ensures high image stability of the heat-sensitive recording material.

[0128] According to one embodiment, the adhesive comprises a pressure-sensitive adhesive and / or a heat-activatable adhesive, the adhesive is preferably a permanent hot melt adhesive based on styrene-isoprene and PVC copolymers, and / or the adhesive is preferably a removable adhesive based on acrylates, and / or the adhesive is preferably a permanent hot melt adhesive based on synthetic rubber.

[0129] This provides the technical advantage that a large number of different adhesive types can be used in the adhesive layer of the heat-sensitive recording material according to the present invention, while still providing an image stability of at least 35% remaining after a period of two weeks according to a stability test.

[0130] For example, a permanent hot melt adhesive based on a copolymer of styrene-isoprene and PVC is Avery Dennison's S2200 adhesive.

[0131] For example, an acrylate-based removable adhesive is Avery Dennison Adhesive R5000N.

[0132] For example, a synthetic rubber-based permanent hot melt adhesive is Technomelt PS 8746 adhesive from Henkel.

[0133] According to one embodiment, the adhesive comprises a permanent hot melt adhesive based on styrene-isoprene and PVC copolymer, wherein the weight ratio of stabilizer to developer in the heat-sensitive color-forming layer is 1:11 to 1:1, preferably 1:8 to 1:4, more preferably 1:7 to 1:5, and most preferably 1:6.

[0134] According to one embodiment, the colour developer comprises the β-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide and / or the α-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

[0135] This offers the technical advantage that when permanent hot melt adhesives based on styrene-isoprene and PVC copolymers are used, when the β-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide (NKK-1304) is used and / or when the α-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF-201) is used, particularly favorable results are obtained when determining image stability according to stability tests.

[0136] According to one embodiment, the image stability of the thermosensitive color forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, and most preferably at least 80%.

[0137] According to one embodiment, the adhesive comprises a removable acrylate adhesive, wherein the weight ratio of the stabilizer to the color developer in the thermosensitive color-forming layer is 1:11 to 1:1, preferably 1:8 to 1:4, more preferably 1:7 to 1:5, and most preferably 1:6.

[0138] According to one embodiment, the developer comprises the α-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

[0139] This offers the technical advantage that when using removable acrylate adhesives, particularly advantageous results are obtained in determining image stability according to stability tests when using the α-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide (NKK-1304).

[0140] According to one embodiment, the image stability of the thermosensitive color forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, and most preferably at least 80%.

[0141] According to one embodiment, the adhesive comprises a synthetic rubber-based permanent hot melt adhesive, and the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is 1:11 to 1:1, preferably 1:8 to 1:4, more preferably 1:7 to 1:5, and most preferably 1:6.

[0142] According to one embodiment, the developer comprises the α-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide and / or the developer comprises the α-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide. This offers the technical advantage that when using synthetic rubber-based permanent hot melt adhesives, the use of the α-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide (NKK-1304) and / or the use of the α-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF201) provides particularly advantageous results when determining image stability according to stability tests.

[0143] According to one embodiment, the image stability of the thermosensitive color forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, and most preferably at least 80%.

[0144] According to one embodiment, image stability is 9.00 mJ / mm using a printer. 2 and a printing speed of about 100 mm / sec, and then measuring the optical density of the printed pattern with a densitometer before storing the heat-sensitive recording material, and measuring the optical density of the printed pattern with a densitometer after a two-week storage period of the heat-sensitive recording material, wherein the image stability particularly corresponds to the quotient (%) of the optical density of the printed pattern after the storage period and the optical density of the printed pattern before storage.

[0145] In particular, a temperature of 60°C and humidity of 50% is maintained during the two week storage period.

[0146] This provides the technical advantage that the present invention provides uniform stability testing.

[0147] According to one embodiment, the weight ratio of stabilizer to developer in the thermosensitive color-forming layer is selected so that the image stability of the thermosensitive color-forming layer remaining after a two-week period is at least 35%, and the print contrast of the thermosensitive color-forming layer remaining after a two-week period is at least 50%, preferably at least 60%, preferably at least 60%, more preferably at least 70%, and most preferably at least 80%.

[0148] This offers the technical advantage that it makes it possible to characterise the quality of a heat-sensitive recording material particularly effectively by taking into account print contrast in addition to taking into account image stability.

[0149] According to one embodiment, the print contrast remaining after two weeks is determined using the following formula: DK(%)=(oDs-oDw / oDs)×100, where the parameter oDs corresponds to the optical density of the printed pattern after a period of two weeks, and the parameter oDw corresponds to the optical density of the non-printed areas of the thermosensitive recording material after a period of two weeks.

[0150] This provides the technical advantage of allowing for effective determination of print contrast.

[0151] According to one embodiment, the at least one color former is a dye based on triphenylmethane, fluoran, azaphthalide and / or fluorene, preferably a dye based on fluoran.

[0152] The use of a particularly preferred fluoran-based dye as at least one color former makes it possible to provide a heat-sensitive recording material with an advantageous cost-performance ratio due to its ready availability and well-balanced application-related properties.

[0153] According to one embodiment, the fluoran-based dye is 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-4-toluidineamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2,4-dimethylanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(3-trifluoromethylanilino)fluoran, 3-Nn-dibutylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino ...(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(2,4-dimethylanilino)fluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(2,4-dimethylanilino)fluoran, 3-diethylamino-7-(2,4 and mixtures thereof.

[0154] According to one embodiment, the at least one color former has a weight proportion of 3% to 30% by weight, based on the total solids content of the thermosensitive color former layer, whereby the weight proportion is preferably 5% to 20% by weight, particularly preferably 8% to 15% by weight.

[0155] According to one embodiment, the carrier substrate comprises paper, synthetic paper and / or plastic film.

[0156] The carrier substrate is not limited here. The carrier material preferably has a density of 30 g / m 2 ~100g / m 2 , especially 40g / m 2 ~80g / m 2 The sheet has a basis weight of .

[0157] In particular, the carrier substrate includes a paper substrate made from hardwood and / or softwood pulp.

[0158] According to one embodiment, the heat-sensitive recording material has at least one intermediate layer disposed between the carrier substrate and the heat-sensitive color-forming layer, wherein the intermediate layer preferably comprises at least one pigment, more preferably an organic hollow sphere pigment and / or calcined kaolin.

[0159] The organic hollow sphere pigment preferably comprises a styrene-acrylate copolymer. The organic hollow sphere pigment preferably has a glass transition temperature of 40°C to 80°C and / or an average particle size of 0.1 μm to 2.5 μm. In particular, the average particle size includes the average particle size (D50).

[0160] The intermediate layer functions as a thermal barrier between the carrier substrate and the heat-sensitive color-forming layer, and also makes it possible to improve the surface smoothness of the carrier substrate relative to the heat-sensitive color-forming layer.

[0161] According to one embodiment, the heat-sensitive recording material has at least one protective layer and / or pressure-supporting layer arranged on the side of the heat-sensitive color-forming layer facing away from the adhesive layer, wherein the protective layer preferably comprises a binder and at least one pigment, more preferably a binder and an inorganic pigment.

[0162] The protective layer and / or printing support layer arranged outside the heat-sensitive color-forming layer ensures effective protection of the heat-sensitive color-forming layer or advantageous printability.

[0163] According to one embodiment, the binder is selected from the group comprising water-soluble starch, starch derivatives, starch-based biolattices of the EcoSphere type, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohols such as acetoacetyl-, diacetone-, carboxy- or silanol-modified polyvinyl alcohols, ethylene-vinyl alcohol copolymers (EVOH) or styrene-maleic anhydride copolymers, styrene-butadiene copolymers, acrylamide-(meth)acrylate copolymers, acrylamide-acrylate-methacrylate terpolymers, polyacrylates, poly(meth)acrylic acid esters, acrylate-butadiene copolymers, polyvinyl acetate, acrylonitrile-butadiene copolymers and mixtures thereof, in particular (meth)acrylamide-acrylic acid ester copolymers of the Bariastar® type may be used, preferably in the form of a core-shell structure.

[0164] According to one embodiment, the binder has a weight proportion of 30% to 90% by weight, based on the total solid content of the protective layer, and the weight proportion is preferably 40% to 80% by weight.

[0165] According to one embodiment, the binder is designed as a cross-linked binder, which is preferably designed as a self-cross-linking binder, or the protective layer comprises a cross-linking agent which is designed to react with the binder to obtain a cross-linked binder.

[0166] In order to achieve specific application-relevant performance properties of the heat-sensitive recording material, the binder is preferably present in crosslinked form in the protective layer, the optimum degree of crosslinking of the binder being established during the drying stage of the coating process, particularly in the presence of a crosslinking agent.

[0167] According to one embodiment, the self-crosslinking binder comprises a modified polyvinyl alcohol and / or a modified acrylate.

[0168] Self-crosslinking binders, such as specially modified polyvinyl alcohols and / or modified acrylates, allow crosslinking without the addition of a crosslinking agent due to reactive groups that are already part of the polymer of the self-crosslinking binder.

[0169] According to one embodiment, the crosslinking agent is selected from the group comprising polyhydric aldehydes, preferably glyoxal, dialdehyde starch, and / or glutaraldehyde, in particular alone or in mixture with boron salts, salts or esters of glyoxylic acid, ammonium zirconium carbonate, polyamidoamine epichlorohydrin resins, adipic acid dihydrazide, boric acid or its salts, polyamines, epoxy resins, formaldehyde oligomers, cyclic ureas, methylol ureas, and melamine formaldehyde oligomers and mixtures thereof, wherein the crosslinking agent is further preferably selected from the group comprising ammonium zirconium carbonate and polyamidoamine epichlorohydrin resins.

[0170] According to one embodiment, the crosslinking agent has a weight proportion of 0.01% to 25.0% by weight, based on the total solid content of the protective layer, and the weight proportion is preferably 0.05% to 15% by weight.

[0171] According to one embodiment, the pigment comprises an inorganic pigment selected from the group comprising calcium carbonate, preferably synthetic, natural or precipitated calcium carbonate, aluminium oxide, aluminium hydroxide, silica, precipitated and pyrogenic silica, diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, bentonite and mixtures thereof, or the pigment comprises an organic pigment selected from the group comprising hollow pigments with styrene / acrylate copolymer walls, urea / formaldehyde condensation polymers, and mixtures thereof.

[0172] According to one embodiment, the pigment has a weight proportion of 5% to 50% by weight, based on the total solid content of the protective layer, and the weight proportion is preferably 10% to 45% by weight.

[0173] According to one embodiment, the protective layer comprises at least one lubricant, preferably selected from the group comprising fatty acid metal salts, preferably zinc stearate or calcium stearate, behenates or synthetic waxes, preferably fatty acid amides, more preferably in the form of stearic acid amide and behenic acid amide, fatty acid alkanolamides, preferably stearic acid methylolamide, paraffin waxes of various melting points, ester waxes of different molecular weights, polyethylene waxes, polypropylene waxes of different hardness, natural waxes, preferably carnauba wax or montan wax, and mixtures thereof.

[0174] According to one embodiment, the lubricant has a weight proportion of 1% to 30% by weight, based on the total solid content of the protective layer, where the weight proportion is preferably 2% to 20% by weight.

[0175] According to one embodiment, the protective layer comprises at least one whitening agent, which is preferably selected as a stilbene.

[0176] The whitening agent can advantageously adjust the whiteness of the surface of the heat-sensitive color-forming layer.

[0177] According to one embodiment, the protective layer has a coating weight of 0.3 g / m 2 ~5.0g / m 2 , preferably 1.0 g / m 2 ~3.0g / m 2 The sheet has a basis weight of .

[0178] According to one embodiment, the protective layer has a thickness of 0.3 μm to 6.0 μm, preferably 0.5 μm to 2.0 μm.

[0179] According to one embodiment, the protective layer has a Beck smoothness measured according to the ISO 5267:1995-03 standard of 100 seconds to 3000 seconds, preferably 500 seconds to 2000 seconds.

[0180] A correspondingly advantageous Beck smoothness can be achieved by a smoothing process.

[0181] According to one embodiment, the protective layer has a surface roughness measured according to the ISO 8791-4:2008-05 standard of 0.5 μm to 2.50 μm, preferably 1.00 μm to 2.00 μm.

[0182] In addition to at least one color former, at least one color developer and at least one stabilizer, the heat-sensitive color former layer may also have at least one sensitizer according to one embodiment, which has the advantage that the heat pressure sensitivity can be more easily controlled.

[0183] Generally, crystalline substances having a melting point between about 90° C. and about 150° C., which in the molten state dissolve the color-forming components, including at least one color former and at least one color developer, without interfering with the formation of a color complex, are advantageously considered as sensitizers. The sensitizers can be present either alone or as a mixture.

[0184] The at least one sensitizer is preferably a fatty acid amide, in particular stearic acid amide, behenamide or palmitic acid amide, an ethylene bis fatty acid amide, in particular N,N'-ethylene bis stearic acid amide or N,N'-ethylene bis oleic acid amide, a fatty acid alkanolamide, in particular N-(hydroxymethyl) stearic acid amide, N-hydroxymethyl palmitic acid amide or hydroxyethyl stearic acid amide, a wax, in particular polyethylene wax or montan wax, a carboxylic acid ester, in particular dimethyl terephthalate, dibenzyl terephthalate, 4 benzyl benzyloxybenzoate, di-(4-methylbenzyl) oxalate, di-(4-chlorobenzyl) oxalate or di-(4-benzyl) oxalate, aromatic ethers, in particular 1,2-diphenoxyethane, 1,2-di(3-methylphenoxy)ethane, 2-benzyloxynaphthalene or 1,4-diethoxynaphthalene, aromatic sulfones, in particular diphenyl sulfone, aromatic sulfonamides, in particular benzenesulfonanilide or N-benzyl-4-toluenesulfonamide, aromatic hydrocarbons, in particular 4-benzylbiphenyl and mixtures thereof.

[0185] According to one embodiment, the sensitizer has a weight proportion of 5% to 40% by weight based on the total solid content of the thermosensitive color-forming layer, and the weight proportion is preferably 10% to 25% by weight.

[0186] In addition to at least one color former, in addition to at least one color developer, in addition to at least one stabilizer, and in addition to the optionally present sensitizer, the thermosensitive color former layer may also, according to one embodiment, have at least one further stabilizer.

[0187] The additional stabilizer acts as an anti-aging agent for the color complex in the heat-sensitive color forming layer.

[0188] The additional stabilizer is preferably selected from the group comprising sterically hindered phenols, more preferably 1,1,3-tris-(2-methyl-4-hydroxy-5-cyclohexyl-phenyl)butane, 1,1,3-tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, and / or 1,1-bis-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, urea-urethane compounds, ethers derived from 4,4'-dihydroxydiphenylsulfone, more preferably 4-benzyloxy-4'-(2-methylglycidyloxy)-diphenylsulfone, oligomeric ethers and mixtures thereof.

[0189] The additional stabilizer preferably has a weight proportion of 0.2% to 1.0% by weight based on the total proportion of the color developer in the heat-sensitive color-forming layer.

[0190] According to one embodiment, the thermosensitive color-forming layer comprises at least one further binder, which is preferably selected from the group comprising water-soluble starch, starch derivatives, starch-based biolattices of the EcoSphere type, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene-vinyl alcohol copolymers (EVOH) or styrene-maleic anhydride copolymers, styrene-butadiene copolymers, acrylamide-(meth)acrylate copolymers, acrylamide-acrylate-methacrylate terpolymers, polyacrylates, poly(meth)acrylic acid esters, acrylate-butadiene copolymers, polyvinyl acetate, acrylonitrile-butadiene copolymers, and mixtures thereof, whereby in particular (meth)acrylamide-acrylic acid ester copolymers of the Bariastar® type are used, which are preferably in the form of a core-shell structure.

[0191] In order to achieve specific application-relevant performance properties of the heat-sensitive recording material, preferably the self-adhesive heat-sensitive recording material, in particular the self-adhesive label, the binder is preferably present in the heat-sensitive layer in crosslinked form, whereby an optimum degree of crosslinking of the binder is established during the drying stage of the coating process in the presence of a crosslinking agent.

[0192] The binder is preferably designed as an additional cross-linking binder, wherein the additional cross-linking binder is preferably designed as an additional self-cross-linking binder, or the thermosensitive color-forming layer comprises a further cross-linking agent that is designed to react with the additional binder to obtain an additional cross-linking binder.

[0193] The additional self-crosslinking binder even more preferably comprises a modified polyvinyl alcohol and / or a modified acrylate.

[0194] The further crosslinking agent is further preferably selected from the group comprising polyhydric aldehydes, preferably glyoxal, dialdehyde starch, and / or glutaraldehyde, in particular alone or in mixture with boron salts, salts or esters of glyoxylic acid, ammonium zirconium carbonate, polyamidoamine epichlorohydrin resins, adipic acid dihydrazide, boric acid or its salts, and mixtures thereof.

[0195] More preferably, the further crosslinking agent has a weight proportion of 2.5% to 20% by weight, based on the total proportion of the crosslinkable further binder in the thermosensitive color-forming layer, and the weight proportion is preferably 5% to 15% by weight.

[0196] According to one embodiment, the carrier substrate, the thermosensitive color-forming layer, and / or the adhesive layer are formed in one layer or multiple layers.

[0197] According to one embodiment, the thermosensitive color-forming layer preferably comprises a release agent selected from the group comprising fatty acid metal salts, more preferably zinc stearate or calcium stearate, behenates or synthetic waxes, in particular fatty acid amides, more preferably in the form of stearic acid amide and behenic acid amide, fatty acid alkanolamides, more preferably stearic acid methylolamide, paraffin waxes of various melting points, ester waxes of different molecular weights, polyethylene waxes, polypropylene waxes of different hardness, natural waxes, more preferably carnauba wax or montan wax, and mixtures thereof.

[0198] According to one embodiment, the release agent has a weight percentage of 1% to 10% by weight based on the total solid content in the thermosensitive color forming layer, and the weight percentage is preferably 3% to 6% by weight.

[0199] According to one embodiment, the thermosensitive color-forming layer has additional pigments, which have the advantage that these additional pigments can fix the chemical melts produced in the thermal printing process to its surface, and the whiteness and opacity of the surface of the thermosensitive color-forming layer and its printability with conventional printing inks can be controlled via the additional pigments. Furthermore, the corresponding additional pigments have, for example, an "extender function" for the relatively expensive color-forming functional chemicals.

[0200] The additional pigments are preferably selected from the group comprising inorganic pigments, both synthetic and natural, precipitated or natural calcium carbonate, clay, aluminum oxide, aluminum hydroxide, silica, precipitated and pyrogenic silica, diatomaceous earth, magnesium carbonate, talc, as well as organic pigments, more preferably hollow pigments with styrene / acrylate copolymer walls, urea / formaldehyde condensation polymers and mixtures thereof.

[0201] The additional pigment preferably has a weight proportion of 15% to 50% by weight, based on the total solid content in the thermosensitive color-forming layer, and the weight proportion is preferably 20% to 35% by weight.

[0202] According to one embodiment, the thermosensitive color forming layer comprises at least one additional whitening agent, which is preferably selected as a stilbene.

[0203] Additional whitening agents can be used to control the whiteness of the surface of the heat-sensitive recording material.

[0204] According to one embodiment, the heat-sensitive color-forming layer comprises a rheological aid, preferably a thickener and / or a surfactant.

[0205] This provides the advantage that certain coating properties of the heat-sensitive color forming layer can be improved during the manufacturing process.

[0206] According to one embodiment, the surface coating weight of the heat-sensitive color forming layer is 1 g / m 2 ~10g / m 2 , preferably 3 g / m 2 ~5g / m 2 is.

[0207] According to one embodiment, the heat-sensitive color forming layer has a Beck smoothness of 100 seconds to 1500 seconds, preferably 200 seconds to 750 seconds, measured according to the ISO 5267:1995-03 standard.

[0208] According to one embodiment, the surface coating weight of the adhesive layer is 10 g / m 2 ~150g / m 2 , preferably 15 g / m 2 ~30g / m 2 is.

[0209] The above mentioned object is achieved according to a second aspect by a method for producing a heat-sensitive recording material, comprising the following method steps:

[0210] providing a carrier substrate having a first surface and a second surface facing opposite the first surface; applying a coating suspension to a first surface of a carrier substrate, wherein the coating suspension comprises at least one color former, at least one color developer, and at least one stabilizer; drying the coating suspension to obtain a heat-sensitive color-forming layer disposed on the first side of the carrier substrate; applying an adhesive layer to a second surface of the carrier substrate; wherein the weight ratio of stabilizer to developer in the coating suspension is selected such that, after a period of two weeks, migration of components of the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material results in a remaining image stability of at least 35% in the heat-sensitive color-forming layer, according to the stability test defined herein; wherein the stabilizer has the formula (I): [ka] The compound where R and R are independently hydrogen, C1-C 18 -alkyl, C1-C8-alkoxy-C1-C8-alkyl, and (R9)2N—C1-C8-alkyl, where R9 is selected from the group comprising C1-C8-alkyl, C5-C6-cycloalkyl; or a group of formula (II) [ka] Compounds of wherein R2, R3, R4, R5 and R6 are independently selected from the group comprising hydrogen, C1-C8-alkyl, -NH-C(=O)-R7 or -C(=O)-NH-R7, where R7 is selected as C1-C8-alkyl or -C(=O)OR8, where R8 is selected as C1-C8-alkyl or halogen, or R2 and R3, or R4 and R5, or both, or R3 and R4, or R5 and R6, or both, or R2 and R3 and R5 and R6 together form a hydrocarbon group having 3 or 4 carbon atoms, wherein Q comprises a single bond or C1-C8-alkylene, which may be branched or unbranched, and wherein C1-C8-alkylene, when it has more than two carbon atoms, comprises a main chain having one or more oxygen atoms between the two carbon atoms; wherein at least one developer has the formula (NI): [ka] Compounds of wherein R1, R2, and R3 are independently selected from the group comprising hydrogen, halogen, nitro, C1-C6-alkyl, C1-C6-alkoxyl, C2-C6-alkenyl, C1-C6-fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl, and optionally substituted benzyl, where R4 is selected from the group comprising hydrogen, phenyl, benzyl, and C1-C6-alkyl, where R5 is selected as C1-C6-alkyl, where n1 and n3 are independently selected as integers from 1 to 5, and where n2 is an integer from 1 to 4; and / or At least one developer has the formula (1): [ka] Compounds of where R1 is unsubstituted or substituted phenyl, naphthyl or C1-C 20 -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C1-C 12-alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is selected from the group comprising -O-SO2-, -SO2-O-, -NH-SO2-, -SO2-NH-, -S-SO2-, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO2-, -O-CO-NH-SO2-, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO2-NH-CO-, -O-CO-O- and -O-PO-(OR2)2, wherein R2 is unsubstituted or substituted aryl, benzyl and C1-C 20 -alkyl, with the proviso that if B is not a group of the formula -O-SO-, then R is unsubstituted or substituted phenyl, naphthyl or C-C-alkyl, and if B is -O-, then R is not alkyl.

[0211] The heat-sensitive recording material is advantageously obtainable by the process according to the second aspect.

[0212] According to one embodiment, applying an adhesive layer to the second side of the carrier substrate may comprise applying, in particular laminating, an adhesive film to the second side of the carrier substrate.

[0213] According to an alternative embodiment, applying the adhesive layer to the second side of the carrier substrate can include applying an adhesive dispersion to the second side of the carrier substrate and subsequently drying the adhesive dispersion to obtain an adhesive layer disposed on the second side of the carrier substrate.

[0214] According to one embodiment, drying of the adhesive layer is carried out at a temperature between 60°C and 80°C, preferably at a temperature of 70°C.

[0215] According to one embodiment, the method comprises further method steps that are carried out after the application of the adhesive layer:

[0216] Applying a release paper to the adhesive layer, wherein the release paper is preferably designed as a siliconized release paper.

[0217] According to one embodiment, applying the adhesive layer comprises applying an adhesive dispersion and then drying the adhesive dispersion, the method comprising further method steps carried out before applying the adhesive dispersion.

[0218] Applying an additional release paper to the second side of the carrier substrate, wherein the adhesive dispersion is further applied to the release paper.

[0219] According to one embodiment, the application and drying of the coating dispersion to the first side of the carrier substrate is performed before the application of the adhesive layer to the second side of the carrier substrate, or the application of the adhesive layer to the second side of the carrier substrate is performed before the application and drying of the coating dispersion to the first side of the carrier substrate, wherein the application and drying of the coating dispersion to the first side of the carrier substrate is preferably performed before the application of the adhesive layer to the second side of the carrier substrate.

[0220] According to one embodiment, the application of the coating dispersion to the first side of the carrier substrate is carried out by curtain coating or by bar doctoring onto the coated side of a carrier substrate precoated with a pigmented coating, wherein the pigmented precoat preferably comprises calcined kaolin and a binder based on styrene-butadiene and / or polyvinyl alcohol (PVA) and / or starch, or an organic pigment in a mixture with an inorganic pigment, and wherein the application weight of the pigmented precoat is more preferably 2 g / m 2 ~12g / m 2 is.

[0221] According to one embodiment, the coating amount of the coating dispersion is 3 g / m 2 and 5 g / m 2 between 3.6g / m and 5.6g / m 2 and 4.8 g / m 2 and / or the coating weight of the adhesive dispersion is between 10 g / m 2 and 30 g / m 2 between 20 g / m and 20 g / m 2 is.

[0222] According to one embodiment, the coating suspension is produced, in particular by milling, preferably to an average particle size D of 0.5 μm to 5.0 μm, particularly preferably 0.50 μm to 1.50 μm, very particularly preferably 1.5 μm to 2.50 μm. (4,3) It has.

[0223] The embodiments given for the heat-sensitive recording material according to the first aspect are also embodiments for the method of manufacturing the heat-sensitive recording material according to the second aspect and vice versa.

[0224] The above object is achieved according to a third aspect by a heat-sensitive recording material producible by the method according to the second aspect.

[0225] The embodiments given for the heat-sensitive recording material according to the first aspect and for the method for producing a heat-sensitive recording material according to the second aspect are also embodiments of a heat-sensitive recording material producible by the method according to the third aspect.

[0226] The above-mentioned object is achieved, according to a fourth aspect, by the use of at least one stabilizer and at least one color developer in a heat-sensitive recording material comprising: a carrier substrate having a first surface and a second surface facing opposite to the first surface; a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate, wherein the heat-sensitive color-forming layer comprises at least one color former, at least one color developer, and at least one stabilizer; and an adhesive layer disposed on the second surface of the carrier substrate, wherein the adhesive layer comprises at least one adhesive, wherein the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is selected such that migration of components from the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material results in a remaining image stability of at least 35% within a period of two weeks according to a stability test defined herein; wherein the stabilizer has the formula (I): [ka] The compound where R and R are independently hydrogen, C1-C18 -alkyl, C1-C8-alkoxy-C1-C8-alkyl, and (R9)2N—C1-C8-alkyl, where R9 is selected from the group comprising C1-C8-alkyl, C5-C6-cycloalkyl; or a group of formula (II) [ka] Compounds of wherein R2, R3, R4, R5 and R6 are independently selected from the group comprising hydrogen, C1-C8-alkyl, -NH-C(=O)-R7 and -C(=O)-NH-R7, where R7 is selected as C1-C8-alkyl or -C(=O)OR8, where R8 is selected as C1-C8-alkyl or halogen, or R2 and R3, or R4 and R5, or both, or R3 and R4, or R5 and R6, or both, or R2 and R3 and R5 and R6 together form a hydrocarbon group having 3 or 4 carbon atoms, wherein Q comprises a single bond or C1-C8-alkylene, which may be branched or unbranched, and wherein C1-C8-alkylene, when it has more than two carbon atoms, comprises a main chain having one or more oxygen atoms between the two carbon atoms; wherein at least one developer has the formula (NI): [ka] Compounds of wherein R1, R2, and R3 are independently selected from the group comprising hydrogen, halogen, nitro, C1-C6-alkyl, C1-C6-alkoxyl, C2-C6-alkenyl, C1-C6-fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl, and optionally substituted benzyl, where R4 is selected from the group comprising hydrogen, phenyl, benzyl, and C1-C6-alkyl, where R5 is selected as C1-C6-alkyl, where n1 and n3 are independently selected as integers from 1 to 5, and where n2 is an integer from 1 to 4; and / or At least one developer has the formula (1): [ka] Compounds of where R1 is unsubstituted or substituted phenyl, naphthyl and C1-C 20 -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C1-C 12 -alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is selected from the group comprising -O-SO2-, -SO2-O-, -NH-SO2-, -SO2-NH-, -S-SO2-, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO2-, -O-CO-NH-SO2-, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO2-NH-CO-, -O-CO-O- and -O-PO-(OR2)2, wherein R2 is unsubstituted or substituted aryl, benzyl and C1-C 20 -alkyl, with the proviso that if B is not a group of the formula -O-SO-, then R is unsubstituted or substituted phenyl, naphthyl or C-C-alkyl, and if B is -O-, then R is not alkyl.

[0227] The embodiments given for the heat-sensitive recording material according to the first aspect and for the method for producing a heat-sensitive recording material according to the second aspect are also embodiments of the use of at least one stabilizer and at least one developer in a heat-sensitive recording material according to the fourth aspect. DETAILED DESCRIPTION OF THE INVENTION

[0228] In the detailed embodiments below, a number of heat-sensitive recording materials or papers were produced by coating an aqueous coating suspension and adhesive dispersion onto a carrier substrate to form a composite structure.

[0229] Manufacture of heat-sensitive recording materials For example, a carrier substrate carrying a color-developing thermosensitive layer on its first side, particularly the front side of an A4 sheet of paper, is coated with an adhesive dispersion using a doctor blade, and the second side is dried at up to 70°C in a hot air oven to obtain an adhesive layer. To protect the adhesive layer during further processing, a siliconized release paper is laminated onto the adhesive layer to prevent air entrapment and wrinkles.

[0230] In the case of an "adhesive liner sandwich" where there is a thin adhesive layer between two sheets of release paper, after removing one of the two liner papers, the sticky side of the adhesive layer is laminated to the second side, which is the backside of the carrier substrate, while avoiding air pockets and creases.

[0231] In producing the heat-sensitive recording material, it does not matter whether the adhesive layer is first applied to the second side of the carrier substrate and then the heat-sensitive recording layer is applied to the first side opposite the carrier substrate carrying the adhesive layer, or vice versa.

[0232] The application of the aqueous coating suspension for forming the heat-sensitive color-forming layer of the heat-sensitive recording material is carried out at a rate of 65 g / m, particularly on a laboratory scale. 2 and 72 g / m 2 The coating is applied using a doctor blade to the coated side of a paper precoated with a pigment coating having a basis weight of 1000 ppm.

[0233] The composition of the pigmented precoat is not critical. In particular, this coating consists of calcined kaolin and a binder based on styrene-butadiene and / or starch. In particular, precoats with organic (hollow sphere) pigments, possibly mixed with inorganic pigments, are also possible. The application weight of this pigmented layer is approximately 2 and 10 g / m. 2 There is a gap between

[0234] After the aqueous coating suspension of the heat-sensitive coating layer has dried, a heat-sensitive color-forming layer is obtained. The coating amount of the heat-sensitive color-forming layer is 3.8 g / m 2 and 4.3 g / m 2It is between.

[0235] An adhesive layer is applied to the backside of the substrate carrying the heat-sensitive layer, or to the second side of the carrier substrate, to provide a composite suitable for use as a heat-sensitive label. The adhesive coating weight is approximately 20 g / m 2 is.

[0236] The preparation of the dispersion liquid (1 part by weight each) of the suspension for coating will be described below.

[0237] Color former dispersion A:

[0238] Color former dispersion A was prepared by grinding 20 parts by weight of 3-Nn-dibutylamino-6-methyl-7-anilinofluoran (ODB-2) with 33 parts by weight of a 12% aqueous solution of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) in a bead mill.

[0239] Stabilizer dispersion B:

[0240] Stabilizer dispersion B was prepared by grinding 40 parts by weight of (N-3-methylphenylsulfonylamido)-(N′,N″-bis{3-methylphenyl)-isophthalic acid diamide (CAS number 2375645-78-4, referred to as Compound I in the tables below) with 66 parts by weight of a 12% aqueous solution of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) in a pearl mill.

[0241] Developer dispersion C:

[0242] The aqueous color developer dispersion C contained 40 parts by weight of each of the color developers 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (CAS No. 232938-43-1, α-polymorph, referred to as Compound II in the tables below), 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (CAS No. 232938-43-1, β-polymorph, referred to as Compound III in the tables below). N-(2-(3-phenylureido)phenyl)benzenesulfonamide (CAS No. 215917-77-4, α-polymorph, referred to as Compound IV in the tables below), or N-(2-(3-phenylureido)phenyl)benzenesulfonamide (CAS No. 215917-77-4, β-polymorph, referred to as Compound V in the tables below) was prepared by grinding in a bead mill with 66 parts by weight of a 12% aqueous solution of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic).

[0243] Sensitized Dispersion D:

[0244] Sensitized Dispersion D was prepared by milling 40 parts by weight of 1,2-diphenoxyethane with 66 parts by weight of a 12% aqueous solution of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) in a pearl mill.

[0245] Dispersions A, B, C, and D produced by milling all had an average particle size D between 0.7 μm and 1.3 μm. (4,3) The particle size distribution of the dispersion was measured by laser diffraction using a Beckman Coulter Coulter LS13320 instrument.

[0246] Lubricant dispersion E:

[0247] Lubricant Dispersion E is a 20% zinc stearate dispersion containing 9 parts by weight zinc stearate, 1 part by weight Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) and 40 parts by weight water.

[0248] Pigment P:

[0249] Pigment P is a 72% coated kaolin suspension (Lustra® S, BASF).

[0250] Binder solution:

[0251] The binder solution consisted of a 10% aqueous solution of polyvinyl alcohol (Poval 28-99, Kuraray Europe).

[0252] The heat-sensitive coating suspension was prepared by mixing, under stirring, 1 part by weight of color former dispersion A, 1 part by weight of stabilizer dispersion B, 1.5 parts by weight of each developer dispersion C, 2.5 parts by weight of sensitizer dispersion D, 1 part by weight of lubricant dispersion E, 2.1 parts by weight of pigment P and 2.5 parts by weight of binder solution, taking into account the addition order C, D, B, E, P, A, with water to a solids content of about 25%. The coating suspension is presented as an example for a developer-stabilizer ratio of 1.5:1.

[0253] The heat-sensitive coating suspension thus obtained was used to produce a composite structure made of a paper carrier and a heat-sensitive color-forming layer.

[0254] glue To prepare the self-adhesive heat-sensitive labels, the following commercially available adhesives were used on the side of the paper carrier facing away from the heat-sensitive color-forming layer, or second side of the carrier substrate:

[0255] - R5000N (Avery Dennison) is an acrylate-based removable adhesive.

[0256] - S2200 (Avery Dennison) is a permanent hot melt adhesive for refrigeration applications based on styrene-isoprene and PVC copolymers.

[0257] - Technomelt PS 8746 (Henkel) is a permanent hot melt adhesive based on synthetic rubber.

[0258] The heat-sensitive recording materials thus obtained were incorporated into self-adhesive heat-sensitive labels and were tested and evaluated as shown in the table below.

[0259] Optical density measurement:

[0260] From the heat-sensitive recording material thus produced, a 6 cm wide strip was obtained, which was printed using a GE-BE PrinterLab GPT-10000 test printer (GE-BE Elektronik and Feinwerktechnik GmbH, Germany) with a 305 dpi Kyocera print bar at a print density of 9.00 mJ / mm using an applied voltage of 24 V and a checkerboard pattern. 2 The thermal printing was performed at an energy level of 1000 kJ / s and a printing speed of approximately 100 mm / s. The area of ​​one square of the printed pattern corresponds to 80 x 80 points. The optical densities (oD) shown in the table below were measured using an X-Rite SpectroEye densitometer, whereby the measurement uncertainty of the oD values ​​is estimated to be ≤2%. The variation of the corresponding calculated % values ​​is ≤±2% percentage points.

[0261] Measuring relative print contrast Relative print contrast is the optical density (oD) of the thermally printed area. S ) and the optical density (oD) of the unprinted area W ) is used as a reference and is calculated according to the following formula B, where s represents the black area and w represents the white area: DK(%)=(oDs-oDw / oDs)×100 (Formula B) Adhesive stability test for thermal label paper The strip of heat-sensitive recording material was measured according to the above measurement method to determine the optical density (oD) before storage. The heat-sensitive recording material was then placed between two glass plates at 60°C and 1350 N / m 2 The samples were stored at 100°C, 50% relative humidity and in the dark for 2 or 4 weeks.

[0262] After the storage period and after conditioning to room temperature, the printed area (oDs, 9.00 mJ / mm 2 The optical density of the printed area (oDw) and the unprinted area (oDw) was measured, averaged, and used to determine the relative print contrast according to Equation B.

[0263] 9.00mJ / mm 2 The optical densities before and after storage at irradiation energies of 100 s were used to determine the remaining image stability according to the following formula A: Image stability (%) = (optical density after storage / optical density before storage) x 100 (Formula A). evaluation The following table lists the results of the image stability and print contrast measurements described for a variety of different heat-sensitive recording materials having a heat-sensitive color on a first side of the carrier substrate and an adhesive layer on the side of the carrier substrate facing away from the first side.

[0264] The results given in the table are based on an analysis of the image stability and print contrast of each heat-sensitive recording material as a function of the migration of components from the adhesive layer to the heat-sensitive color-forming layer after corresponding periods of 2 or 4 weeks.

[0265] According to the table, the adhesive layers tested were Avery Dennison R5000N, Avery Dennison S2200, and Henkel Technomelt PS8746, as previously mentioned.

[0266] According to the table, the compound 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-{3-methylphenyl)isophthalic acid diamide (PF425) was investigated as a stabilizer for the heat-sensitive color-forming layer, which is designated as Compound I in the table.

[0267] According to the table, the compound 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF-201) was investigated as a color developer for a thermosensitive color forming layer containing the α-polymorph, designated as Compound II in the table, and the β-polymorph, designated as Compound III.

[0268] According to the table, the compound N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304) was investigated as a color developer for a thermosensitive color layer containing the α-polymorph as compound IV and the β-polymorph as compound V.

[0269] The table is shown below.

[0270] table: [Table 1-1] [Table 1-2] [Table 1-3] From the results shown in the table it can be seen that the heat-sensitive recording material according to the invention exhibits the following advantageous properties:

[0271] Firstly, it is emphasized that for all adhesives considered in the corresponding comparative experiments (R5000, S2200 and Technomelt), the exclusive use of the stabilizer 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis{3-methylphenyl)-isophthalic acid diamide (PF425) according to compound I shown in the table, without the addition of the corresponding developer (see compounds II, III, IV, V in the table), only leads to a very low corresponding residual image stability after 2 weeks and is therefore not in accordance with the present invention.

[0272] Corresponding comparative experiments also show that for all adhesives considered (R5000, S2200 and Technomelt) the same is true when the corresponding stabilizer of compound I is not added but only the corresponding developer N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304) according to the α-polymorph IV and β-polymorph V shown in the table, and the corresponding developer 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF-201) according to the α-polymorph II and β-polymorph III shown in the table are used.

[0273] For example, when only the α-polymorph IV or β-polymorph V of N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304) was added, a correspondingly very low residual image stability of only 10% was obtained after 2 weeks, or 7% when adhesive R5000 was used, which is significantly below the limit of at least 35% residual image stability considered sufficient according to the present invention.

[0274] The same is true when compounds II or III are added alone, which results in very low image stability with a corresponding remaining 26% or 29% after the corresponding period of 2 weeks when using R5000 adhesive.

[0275] The corresponding comparative examples in the table show that the use of the stabilizer alone or the exclusive use of each developer alone is not sufficient to achieve a residual image stability of at least 35% which is considered to be in accordance with the present invention.

[0276] Secondly, it is highlighted that for all adhesives considered (R5000, S2200, and Technomelt), the inventive combination of a stabilizer and at least one developer significantly increases the remaining image stability after the two-week consideration period compared to the use of either the stabilizer or the developer alone.

[0277] For example, in the case of adhesive R5000, when developer III was combined with stabilizer I, the remaining image stability after 2 weeks was between 38% and 51% by weight depending on the weight ratio, which is significantly higher than the corresponding image stability when stabilizer alone (16%) or compound III alone (29%) was used.

[0278] The corresponding effect can be seen from the table for all adhesives tested and for all developers tested.

[0279] Thirdly, it is emphasized that for all adhesives tested (R5000, S2200, and Techno-melt), an increase in the weight ratio of stabilizer to developer was found to significantly increase the remaining image stability after the two-week test period in all cases.

[0280] For example, in the case of R5000 adhesive, when Developer IV and Stabilizer I are combined in a weight ratio of 1.5 parts by weight of Developer IV to 1 part by weight of Stabilizer I, a remaining image stability of 72% can be obtained after a corresponding period of 2 weeks, which corresponds to an excellent value.

[0281] When using S2200 adhesive, when Developer IV and Stabilizer I are combined in a weight ratio of 1.5 parts by weight of Developer IV to 1 part by weight of Stabilizer I, a remaining image stability of 75% can be obtained after a corresponding period of 2 weeks, which corresponds to an extremely good value.

[0282] The corresponding optimization of the remaining image stability after a period of two weeks based on the optimization of the weight ratio between the respective developer and stabilizer can be read from the table for all adhesives tested and for all developers tested.

[0283] Therefore, the combination of a stabilizer and at least one color developer in the heat-sensitive color forming layer can provide a synergistic effect with respect to remaining image stability after a two week period.

[0284] Fourth, it is emphasized that by optimizing the weight ratio between the respective color developers and stabilizers, the remaining print contrast after the two-week test period is also optimized.

[0285] For example, in the case of adhesive R5000, when developer IV and stabilizer I are combined in a weight ratio of 1.5 parts by weight of developer IV to 1 part by weight of stabilizer I, a remaining relative print contrast of 91% can be obtained after a corresponding period of 2 weeks, which corresponds to an excellent value.

[0286] Thus, by combining a stabilizer and at least one color developer in a heat-sensitive color-forming layer, a synergistic effect can be demonstrated regarding remaining print contrast after a two week period.

Claims

1. a carrier substrate having a first surface and a second surface facing opposite the first surface; a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate, wherein the heat-sensitive color-forming layer comprises at least one color former, at least one color developer, and at least one stabilizer; and an adhesive layer disposed on the second surface of the carrier substrate, wherein the adhesive layer comprises at least one adhesive; Equipped with wherein the weight ratio of stabilizer to developer in said heat-sensitive color-forming layer is selected such that migration of components from said adhesive layer to said heat-sensitive color-forming layer after a two week period results in a remaining image stability of at least 35% according to the stability test defined herein; wherein the stabilizer has the formula (I): 【Chemical 1】 The compound where R and R １ are independently hydrogen, C １ ~C １８ -Alkyl, C １ ~C ８ -alkoxy-C １ ~C ８ -alkyl, and (R ９ ) ２ N-C １ ~C ８ - alkyl, where R ９ is C １ ~C ８ -Alkyl, C ５ ~C ６ -cycloalkyl: or formula (II) 【Chemistry 2】 Compounds of Here, R ２ , R ３ , R ４ , R ５ , and R ６ are independently hydrogen, C １ ~C ８ -Alkyl, -NH-C(=O)-R ７ and —C(═O)—NH—R ７ where R ７ is C １ ~C ８ -alkyl or -C(=O)OR ８ where R ８ is C １ ~C ８ - selected as alkyl or halogen, or R ２ and R ３ , or R ４ and R ５ , or both, or R ３ and R ４ , or R ５ and R ６ , or both, or R ２ and R ３ and R ５ and R ６ together form a hydrocarbon group having 3 or 4 carbon atoms, where Q is a single bond or C １ ~C ８ - alkylene, which may be branched or unbranched, where C １ ~C ８ -Alkylene is the C １ ~C ８ - when alkylene has more than two carbon atoms, it contains a backbone with one or more oxygen atoms between two carbon atoms; wherein at least one developer has formula (NI): 【Chemistry 3】 Compounds of Here, R １ , R ２ , and R ３ are independently hydrogen, halogen, nitro, C １ ~C ６ -Alkyl, C １ ~C ６ -alkoxyl, C ２ ~C ６ -alkenyl, C １ ~C ６ -fluoroalkyl, N(R ４ ) ２ , NHCOR ５ , optionally substituted phenyl, and optionally substituted benzyl, wherein R ４ is hydrogen, phenyl, benzyl, and C １ ~C ６ - alkyl, where R ５ is C １ ~C ６ -alkyl, where n1 and n3 are independently selected as integers from 1 to 5, and where n2 is an integer from 1 to 4; and / or at least one developer is represented by formula (1): 【Chemistry 4】 Compounds of Here, R １ represents unsubstituted or substituted phenyl, naphthyl and C １ ~C ２０ -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C １ ~C １２ -alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is -O-SO ２ -, -SO ２ -O-, -NH-SO ２ -, -SO ２ -NH-, -S-SO ２ -, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO ２ -, -O-CO-NH-SO ２ -, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO ２ -NH-CO-, -O-CO-O- and -O-PO-(OR ２ ) ２ where R ２ is unsubstituted or substituted aryl, benzyl and C １ ~C ２０ -alkyl, provided that B is of the formula -O-SO ２ If it is not a - group, R ２ is unsubstituted or substituted phenyl, naphthyl or C １ ~C ８ -alkyl and B is -O-, then R ２ is not alkyl, including Heat-sensitive recording material.

2. The stabilizer is represented by formula (Ia): 【Chemistry 5】 ； Compounds include Or the stabilizer has the formula (Ib): 【Chemistry 6】 including the compound 2. The heat-sensitive recording material according to claim 1.

3. 2. The heat-sensitive recording material of claim 1, wherein the stabilizer comprises 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-{3-methylphenyl)isophthalic acid diamide.

4. The at least one color developer comprises a compound of formula (NI), wherein R １ , R ２ , and R ３ 2. The heat-sensitive recording material according to claim 1, wherein is selected as hydrogen.

5. the at least one colour developer comprises N-(2-(3-phenylureido)phenyl)benzenesulfonamide, preferably the α-polymorph and / or the β-polymorph of N-(2-(3-phenylureido)phenyl)benzenesulfonamide, In particular, the α-polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 5.8, 9.3, 13.2, 15.7, 17.3, 18.3, 18.7, 19.5, 20.3, 21.1, 21.9, 22.8, 23.3, 23.6, 24.4, 24.9, 25.6, 26.7, 27.8, 28.1, 29.3, 29.6, 30.2, 31.6, 32.3, 32.8 and / or a melting point determined by DSC of 158° C. to 159° C., and in particular the β-polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 5.8, 9.3, 13.2, 15.7, 17.3, 18.3, 18.7, 19.5, 20.3, 21.1, 21.9, 22.8, 23.3, 23.6, 24.4, 24.9, 25.6, 26.7, 27.8, 28.1, 29.3, 29.6, 30.2, 31.6, 32.3, 32.8 and / or a melting point determined by DSC of 158° C. to 159° C. 20.9, 21.6, 22.0, 22.8, 23.0, 23.6, 24.3, 25.5, 26.7, 27.8, 28.4, 29.0, 29.8, 30.5, 31.1, 31.3 and / or a melting point of 173°C to 174°C as determined by DSC.

6. The at least one developer comprises a compound of formula (1), wherein X is selected as —C(═O)—, and wherein R １ is unsubstituted or substituted phenyl, preferably C １ ~C ３ -alkyl-substituted phenyl, where R ２ is selected as unsubstituted or substituted aryl, preferably as unsubstituted phenyl, where B is —O—SO ２ -, where R ２ is unsubstituted or substituted aryl, preferably C １ ~C ３ 2. The heat-sensitive recording material according to claim 1, wherein the aryl group is selected as a -alkyl substituted phenyl.

7. The at least one colour developer comprises 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide, preferably the α-polymorph and / or the β-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide, wherein in particular the α-polymorph has Bragg angle (2θ / CuKα) values ​​of 8.5, 9.5, 11.8, 12.1, 12.2, 13.7, 14.1, 16.6, 17.1, 18.3, 18.6, 19.1, 19.3, 20.1, 20.4, 20.9, 21.3, 23.1, 24.2, 24.6, 25.0, 27.9, 28.6 and / or a melting point determined by DSC of 161°C to 162°C, wherein in particular the β-polymorph is characterized by an X-ray diffraction pattern with Bragg angles (2θ / CuKα) of 10.3, 11.0, 12.9, 13.2, 15.4, 17.1, 18.0, 18.2, 19.4, 20.0, 20.7, 21.2, 23.0, 24.9, 25.3, 26.5, 26.8, 27.5, 30.7, 32.7 and / or a melting point determined by DSC of 166°C to 167°C.

8. 2. The heat-sensitive recording material according to claim 1, wherein the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is from 1:11 to 1:1, preferably from 1:8 to 1:4, more preferably from 1:7 to 1:5, and most preferably 1:

6.

9. 2. The heat-sensitive recording material according to claim 1, wherein the stabilizer has a weight percentage of 1 to 10% by weight, based on the total solid content of the heat-sensitive color-forming layer, wherein the weight percentage is preferably 2 to 8% by weight, more preferably 3 to 6% by weight, and most preferably 4% by weight.

10. 2. The heat-sensitive recording material according to claim 1, wherein the at least one color developer has a weight percentage of 6% to 35% by weight, based on the total solid content of the heat-sensitive color forming layer, wherein the weight percentage is preferably 10% to 30% by weight, more preferably 20% to 30% by weight, and most preferably 24% by weight.

11. 2. The heat-sensitive recording material according to claim 1, wherein the image stability of the heat-sensitive color-forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, and most preferably at least 80%.

12. 2. The heat-sensitive recording material according to claim 1, wherein the adhesive comprises a pressure-sensitive adhesive and / or a heat-activatable adhesive, wherein the adhesive is a permanent hot-melt adhesive, preferably based on styrene-isoprene and PVC copolymer, and / or the adhesive is a removable adhesive, preferably based on acrylate, and / or the adhesive is a permanent hot-melt adhesive, preferably based on synthetic rubber.

13. 2. The heat-sensitive recording material according to claim 1, wherein the adhesive comprises a permanent hot-melt adhesive based on styrene-isoprene and PVC copolymer, and the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is from 1:11 to 1:1, preferably from 1:8 to 1:4, more preferably from 1:7 to 1:5, and most preferably 1:

6.

14. 14. The heat-sensitive recording material according to claim 13, wherein the colour developer comprises the β-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide and / or the colour developer comprises the α-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

15. 14. The heat-sensitive recording material according to claim 13, wherein the image stability of the heat-sensitive color-forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75% and most preferably at least 80%.

16. 2. The heat-sensitive recording material according to claim 1, wherein the adhesive comprises a removable acrylate adhesive, and the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is from 1:11 to 1:1, preferably from 1:8 to 1:4, more preferably from 1:7 to 1:5, and most preferably 1:

6.

17. The developer comprises the β-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

17. The heat-sensitive recording material according to claim 16.

18. 17. The heat-sensitive recording material according to claim 16, wherein the image stability of the heat-sensitive color-forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75% and most preferably at least 80%.

19. 2. The heat-sensitive recording material according to claim 1, wherein the adhesive comprises a synthetic rubber-based permanent hot-melt adhesive, and the weight ratio of the stabilizer to the color developer in the heat-sensitive color-forming layer is from 1:11 to 1:1, preferably from 1:8 to 1:4, more preferably from 1:7 to 1:5, and most preferably 1:

6.

20. 20. The heat-sensitive recording material according to claim 19, wherein the colour developer comprises the α-polymorph of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, and / or the colour developer comprises the α-polymorph of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

21. 20. The heat-sensitive recording material according to claim 19, wherein the image stability of the heat-sensitive color-forming layer remaining after a period of two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75% and most preferably at least 80%.

22. The image stability was measured using a printer at 9.00 mJ / mm ２ and a printing speed of about 100 mm / sec, and then measuring the optical density of the printed pattern with a densitometer before storing the heat-sensitive recording material, and measuring the optical density of the printed pattern with the densitometer after a storage period of two weeks of the heat-sensitive recording material, wherein the image stability corresponds, in particular, to the quotient (%) of the optical density of the printed pattern after the storage period and the optical density of the printed pattern before storage.

23. 23. The heat-sensitive recording material according to claim 22, wherein the weight ratio of stabilizer to developer in said heat-sensitive color-forming layer is selected so that the image stability of said heat-sensitive color-forming layer remaining after a period of two weeks is at least 35% and the print contrast of said heat-sensitive color-forming layer remaining after a period of two weeks is at least 50%, preferably at least 60%, preferably at least 60%, more preferably at least 70%, and most preferably at least 80%.

24. 24. The heat-sensitive recording material according to claim 23, wherein the print contrast remaining after two weeks is determined by the following formula: DK(%)=(oDs-oDw / oDs)×100, where the parameter oDs corresponds to the optical density of the printed pattern after a period of two weeks, and the parameter oDw corresponds to the optical density of the non-printed areas of the heat-sensitive recording material after a period of two weeks.

25. 2. The heat-sensitive recording material according to claim 1, wherein said at least one color former is a triphenylmethane-based, fluoran-based, azaphthalide-based and / or fluorene-based dye, preferably a fluoran-based dye.

26. Fluoran dyes include 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-4-toluidineamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2,4-dimethylanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(3-trifluoromethylanilino)fluoran, 3-N-n-dibutylamino ...anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3 26. The heat-sensitive recording material according to claim 25, wherein the compound is selected from the group comprising: 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-N-n-dibutylamino-7-(2-chloroanilino)fluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran and mixtures thereof.

27. 2. The heat-sensitive recording material according to claim 1, wherein the at least one color former has a weight proportion of 3 to 30% by weight, based on the total solids content of the heat-sensitive color forming layer, wherein the weight proportion is preferably 5 to 20% by weight, particularly preferably 8 to 15% by weight.

28. 1. A method for producing a heat-sensitive recording material, comprising the following method steps: providing a carrier substrate having a first surface and a second surface facing opposite the first surface; applying a coating suspension to the first side of the carrier substrate, wherein the coating suspension includes at least one color former, at least one color developer, and at least one stabilizer; drying the coating suspension to obtain a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate; applying an adhesive layer to the second surface of the carrier substrate; Equipped with wherein the weight ratio of stabilizer to developer in the coating suspension is selected such that, after a period of two weeks, migration of components of the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material results in a remaining image stability of at least 35% in the heat-sensitive color-forming layer according to the stability test defined herein; wherein the stabilizer has the formula (I): 【Chemical 1】 The compound where R and R １ are independently hydrogen, C １ ~C １８ -Alkyl, C １ ~C ８ -alkoxy-C １ ~C ８ -alkyl, and (R ９ ) ２ N-C １ ~C ８ - alkyl, where R ９ is C １ ~C ８ -Alkyl, C ５ ~C ６ -cycloalkyl: or formula (II) 【Chemistry 2】 Compounds of Here, R ２ , R ３ , R ４ , R ５ , and R ６ are independently hydrogen, C １ ~C ８ -Alkyl, -NH-C(=O)-R ７ or —C(═O)—NH—R ７ where R ７ is C １ ~C ８ -Alkyl or -C(=O)OR ８ where R ８ is C １ ~C ８ - selected as alkyl or halogen, or R ２ and R ３ , or R ４ and R ５ , or both, or R ３ and R ４ , or R ５ and R ６ , or both, or R ２ and R ３ and R ５ and R ６ together form a hydrocarbon group having 3 or 4 carbon atoms, where Q is a single bond or C １ ~C ８ - alkylene, which may be branched or unbranched, where C １ ~C ８ -Alkylene is the C １ ~C ８ - when alkylene has more than two carbon atoms, it contains a backbone with one or more oxygen atoms between two carbon atoms; wherein at least one developer has the formula (NI): 【Chemistry 3】 Compounds of Here, R １ , R ２ , and R ３ are independently hydrogen, halogen, nitro, C １ ~C ６ Alkyl, C １ ~C ６ Alkoxyl, C ２ ~C ６ Alkenyl, C １ ~C ６ Fluoroalkyl, N(R ４ ) ２ , NHCOR ５ , optionally substituted phenyl, and optionally substituted benzyl, wherein R ４ is hydrogen, phenyl, benzyl, or C １ ~C ６ - alkyl, where R ５ is C １ ~C ６ -alkyl, where n1 and n3 are independently selected as integers from 1 to 5, and where n2 is an integer from 1 to 4; and / or At least one colour developer is represented by formula (1): 【Chemistry 4】 Compounds of Here, R １ is unsubstituted or substituted phenyl, naphthyl or C １ ~C ２０ -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C １ ~C １２ -alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is -O-SO ２ -, -SO ２ -O-, -NH-SO ２ -, -SO ２ -NH-, -S-SO ２ -, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO ２ -, -O-CO-NH-SO ２ -, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO ２ -NH-CO-, -O-CO-O- and -O-PO-(OR ２ ) ２ where R ２ is unsubstituted or substituted aryl, benzyl and C １ ~C ２０ alkyl, provided that B is of the formula -O-SO ２ If it is not a - group, R ２ is unsubstituted or substituted phenyl, naphthyl or C １ ~C ８ -alkyl and B is -O-, then R ２ is not alkyl, including method.

29. 29. The method of claim 28, wherein drying of the adhesive layer is carried out at a temperature between 60°C and 80°C, preferably at 70°C.

30. The method comprises further method steps carried out after application of the adhesive layer: - applying a release paper to the adhesive layer, said release paper being preferably designed as a siliconized release paper; 29. The method of claim 28, comprising:

31. The application of the adhesive layer comprises applying an adhesive dispersion followed by drying the adhesive dispersion, wherein the method comprises further method steps carried out before the application of the adhesive dispersion: applying an additional release paper to the second side of the carrier substrate, wherein the adhesive dispersion is applied to the additional release paper; 29. The method of claim 28, comprising:

32. 29. The method of claim 28, wherein the application and drying of the coating dispersion to the first side of the carrier substrate occurs before the application of the adhesive layer to the second side of the carrier substrate, or the application of the adhesive layer to the second side of the carrier substrate occurs before the application and drying of the coating dispersion to the first side of the carrier substrate, preferably wherein the application and drying of the coating dispersion to the first side of the carrier substrate occurs before the application of the adhesive layer to the second side of the carrier substrate.

33. The application of the coating dispersion to the first side of the carrier substrate is carried out by curtain coating or by doctor blade onto a coated side of a carrier substrate precoated with a pigmented coating, wherein the pigmented precoat preferably comprises calcined kaolin and a binder based on styrene-butadiene and / or polyvinyl alcohol (PVA) and / or starch, or an organic pigment in a mixture with an inorganic pigment, and wherein the coating weight of the pigmented precoat is more preferably 2 g / m ２ ~12g / m ２ 29. The method of claim 28, wherein:

34. The coating amount of the coating dispersion is 3 g / m ２ and 5 g / m ２ between 3.6 g / m and 5.6 g / m ２ and 4.8 g / m ２ and / or the coating amount of the adhesive dispersion is between 10 g / m ２ and 30 g / m ２ between 20 g / m and 20 g / m ２ 29. The method of claim 28, wherein:

35. A heat-sensitive recording material that can be produced by the method according to any one of claims 28 to 34.

36. 1. Use of at least one stabilizer and at least one color developer in a heat-sensitive recording material, comprising: a carrier substrate having a first surface and a second surface facing opposite to the first surface; a heat-sensitive color-forming layer disposed on the first surface of the carrier substrate, wherein the heat-sensitive color-forming layer comprises at least one color former, at least one color developer, and at least one stabilizer; and an adhesive layer disposed on the second surface of the carrier substrate, wherein the adhesive layer comprises at least one adhesive, wherein a weight ratio of stabilizer to color developer in the heat-sensitive color-forming layer is selected such that after a period of two weeks, the remaining image stability of the heat-sensitive color-forming layer is at least 35% due to migration of components from the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material according to a stability test defined herein; wherein the stabilizer has the formula (I): 【Chemical 1】 The compound where R and R １ are independently hydrogen, C １ ~C １８ -Alkyl, C １ ~C ８ -alkoxy-C １ ~C ８ -alkyl, and (R ９ ) ２ N-C １ ~C ８ - alkyl, where R ９ is C １ ~C ８ -Alkyl, C ５ ~C ６ -cycloalkyl: or formula (II) 【Chemistry 2】 Compounds of Here, R ２ , R ３ , R ４ , R ５ , and R ６ are independently hydrogen, C １ ~C ８ -Alkyl, -NH-C(=O)-R ７ and —C(═O)—NH—R ７ where R ７ is C １ ~C ８ -alkyl or -C(=O)OR ８ where R ８ is C １ ~C ８ alkyl or halogen, or R ２ and R ３ , or R ４ and R ５ , or both, or R ３ and R ４ , or R ５ and R ６ , or both, or R ２ and R ３ and R ５ and R ６ together form a hydrocarbon group having 3 or 4 carbon atoms, where Q is a single bond or C １ ~C ８ - alkylene, which may be branched or unbranched, where C １ ~C ８ -Alkylene is the C １ ~C ８ - when alkylene has more than two carbon atoms, it contains a backbone with one or more oxygen atoms between two carbon atoms; wherein at least one developer has formula (NI): 【Chemistry 3】 Compounds of Here, R １ , R ２ , and R ３ are independently hydrogen, halogen, nitro, C １ ~C ６ -Alkyl, C １ ~C ６ -alkoxyl, C ２ ~C ６ -alkenyl, C １ ~C ６ -fluoroalkyl, N(R ４ ) ２ , NHCOR ５ , optionally substituted phenyl, and optionally substituted benzyl, wherein R ４ is hydrogen, phenyl, benzyl, and C １ ~C ６ - alkyl, where R ５ is C １ ~C ６ -alkyl, where n1 and n3 are independently selected as integers from 1 to 5, and where n2 is an integer from 1 to 4; and / or At least one colour developer is represented by formula (1): 【Chemistry 4】 Compounds of Here, R １ represents unsubstituted or substituted phenyl, naphthyl and C １ ~C ２０ -alkyl, where X is selected from the group comprising -C(=NH)-, -C(=S)- and -C(=O)-, where A is unsubstituted or substituted phenylene, naphthylene, C １ ~C １２ -alkylene, and unsubstituted or substituted heterocyclic groups, wherein B is -O-SO ２ -, -SO ２ -O-, -NH-SO ２ -, -SO ２ -NH-, -S-SO ２ -, -O-CO-, -O-CO-NH-, -NH-CO-, -NH-CO-O-, -S-CO-NH-, -S-CS-NH-, -CO-NH-SO ２ -, -O-CO-NH-SO ２ -, -NH=CH-, -CO-NH-CO-, -S-, -CO-, -O-, -SO ２ -NH-CO-, -O-CO-O- and -O-PO-(OR ２ ) ２ where R ２ is unsubstituted or substituted aryl, benzyl and C １ ~C ２０ -alkyl, provided that B is of the formula -O-SO ２ If it is not a - group, R ２ is unsubstituted or substituted phenyl, naphthyl or C １ ~C ８ -alkyl and B is -O-, then R ２ is not alkyl, including use.

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