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 away from the first surface; a heat-sensitive color forming layer disposed on the first side of the carrier substrate, the heat-sensitive color forming layer comprising at least one color former, at least one color developer, and at least one stabilizer; and an adhesive layer disposed on the second side of the carrier substrate, the adhesive layer comprising at least one adhesive. The weight ratio of the stabilizer to the color developing agent in the thermosensitive color forming layer is selected as follows: according to a stability test defined in the description, components in the bonding layer migrate to the thermosensitive color forming layer, so that the stability of an image reserved by the thermosensitive color forming layer after two weeks reaches at least 35%.

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 side and a second side facing away from the first side; a heat-sensitive color-forming layer, arranged on the first side 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, arranged on the second side of the carrier substrate and comprising at least one adhesive.

[0002] Here, the weight ratio of stabilizer to developer in the heat-sensitive color-forming layer is selected so that, according to the stability test defined in the specification, the migration of the components in the adhesive layer to the heat-sensitive color-forming layer results in at least 35% of the image stability retained by the heat-sensitive color-forming layer after two weeks.

[0003] According to a second aspect, the present invention relates to a method for preparing a heat-sensitive recording material, comprising the following method steps: providing a carrier substrate having a first side and a second side facing away from the first side; applying a coating suspension to the first side of the carrier substrate, the coating suspension comprising 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 arranged on the first side of the carrier substrate; 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 that can be prepared by 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 for a thermal recording material, which thermal recording material comprises: a carrier substrate having a first side and a second side facing away from the first side; a thermal color-forming layer arranged on the first side of the carrier substrate and comprising at least one color-forming agent, at least one color developer and at least one stabilizer; and an adhesive layer arranged on the second side of the carrier substrate and comprising at least one adhesive. Background Art

[0006] Thermal recording materials, also known as thermal paper, can be used for a variety of purposes, such as sales receipts in the retail industry.

[0007] Back coating preparations are used in conjunction with heat-sensitive recording materials to obtain adhesive labels or heat-sensitive labels, or to improve various application properties. The back coating preparation can be a self-adhesive layer and / or a coating ("back coating") mainly composed of a polymer binder and a pigment.

[0008] In the existing direct thermal printing technology, a thermal recording material with a self-adhesive layer on the back is disclosed, namely, a so-called thermal label.

[0009] Patent documents JPS 59162087A, US 4370370A and US 4388362A describe thermal labels with release paper.

[0010] Patent document DE 19757589 B4 describes a liner-free ("linerless") heat-sensitive label having a protective layer on the heat-sensitive layer.

[0011] Patent document DE 19806433 B4 discloses a linerless heat-sensitive label whose protective layer does not contain silicon compounds and is cured by actinic radiation.

[0012] Patent documents EP 0600622A1 and DE 19724647C1 describe a linerless thermal label, the back side of which is coated with hot melt adhesive.

[0013] Patent documents EP 1085069 B1 and EP 2474963 B1 disclose linerless heat-sensitive label materials containing heat-activated adhesives, wherein heat-sensitive labels with and without a protective layer are described.

[0014] Patent document EP 3219507A1 claims a linerless heat-sensitive label without an actual protective layer, wherein the surface of the heat-sensitive layer is designed to be debondable from the adhesive.

[0015] The prior art also discloses heat-sensitive recording materials provided with a so-called "back coating" which improves the printability of the back side in conventional printing processes and also minimizes warping of the carrier substrate under adverse humidity conditions.

[0016] Therefore, the back coating can effectively improve the different shrinkage behaviors of the two sides of the carrier substrate of the thermal recording material under different environmental humidity, that is, the different water vapor absorption characteristics of the two sides / coating. For example, patent document US 6667275B2 discloses a multilayer back coating for thermal recording materials, which has a positive effect on the warping tendency of the carrier web.

[0017] Patent document JP 2018167483 discloses that the durability of thermal typefaces on a thermal recording material coated with an oily printing pigment or ink on the back can be improved by applying a coating on the back. The formulation of these back coatings usually contains an aqueous emulsion polymer, such as styrene-butadiene or acrylate latex, as a main component.

[0018] For example, JP 2003175671 claims a back coating of a heat-sensitive recording material prepared with an aqueous latex to form a soft polymer film (glass transition temperature ≥ -30°C). JPH 0720735B2 and JP 2000204123 disclose back coating formulations containing acrylate emulsion polymers for heat-sensitive recording materials.

[0019] Patent documents EP 3957488A1 and WO 2022 / 038242A1 describe a thermosensitive recording layer containing a phenol-free organic developer, a coating composition for preparing the thermosensitive recording layer, and a thermosensitive recording material, especially thermosensitive paper, containing the thermosensitive recording layer. In addition, the use of the thermosensitive recording layer for preparing a thermosensitive recording material, a method for preparing the thermosensitive recording material, and the use of the thermosensitive recording material for thermal paper applications are also described. The thermosensitive recording material has excellent recyclability and high environmental compatibility due to its composition.

[0020] Patent documents US 2021 / 0060994, CA 3149562 A1 and WO 2021 / 041600 A2 also describe thermosensitive recording materials.

[0021] In addition, please refer to patent documents DE 102019126220A1, WO 2021 / 058661A1, KR2022070021A and DE 202020005616U1.

[0022] The color-forming layer of the thermal recording material usually contains a color former and a developer, which react under the action of heat to develop color. Currently, low-cost developers containing phenol groups (bisphenol A, bisphenol S, etc.) are widely used. In some applications, such developers can allow thermal labels to achieve acceptable performance.

[0023] The prior art also discloses heat-sensitive labels containing phenol-free color developers in the heat-sensitive color-forming layer. The purpose of developing such heat-sensitive labels is to improve the durability of the font, especially when the printed heat-sensitive recording material comes into contact with hydrophobic substances such as plasticizers or plasticizing materials or plasticizing oils. In addition to the technical advantages, the public's concern about the potential toxicity of (bis)phenol chemicals has also strongly stimulated people's interest in phenol-free color developers.

[0024] Long-term storage of heat-printed self-adhesive heat-sensitive labels or heat-sensitive recording materials with back coatings, especially at high ambient temperatures and / or air humidity, can impair the application properties. In particular, heat-sensitive recording materials with such back coating preparations can no longer achieve the specified values ​​for the blackness or surface whiteness of the printed matter (e.g. barcodes or fonts) after storage.

[0025] However, low print blackness often results in reduced reading contrast, which is further exacerbated by reduced background whiteness. When applying labels, for example barcodes, readability is particularly important, so low contrast values ​​can negatively impact this important application attribute.

[0026] The cause of this phenomenon is said to be the backside adhesive layer, where substances migrate through the carrier matrix into the chemically reactive heat-sensitive recording layer during storage and interact with it, causing damage to the chromogenic complex. Relatively low molecular weight substances (<10 kDa) have the greatest impact on migration problems. When heat-activated adhesives (i.e. adhesives that are solid at room temperature) are used, performance impairment after storage can also occur.

[0027] Especially compared with the relatively simple (bis)phenol, the more complex chemical developer has a large number of reactive sites in its molecule, just like the developer generally not containing a phenol group, so the developer may interact adversely with the substances released from the thermal recording material equipped with the back coating preparation, thereby being affected.

[0028] In order to ensure the cohesive strength within the PSA adhesive layer and the adhesion strength (adhesion) to the substrate, in addition to the base polymer, a typical PSA formulation also uses non-polymeric viscous resins (such as natural resins or hydrocarbon resins) and / or plasticizers, tackifiers, and other small molecule additives such as crosslinkers, stabilizers, etc., if necessary. If you consider that the base polymer contains residual monomers or oligomers from the synthesis process, and that it will undergo hydrolysis and degradation under the action of high ambient humidity and temperature to form more monomers, it is not difficult to understand the migration potential of small molecules inherent in the adhesive layer.

[0029] In addition to the residual monomers that may be present in the latex mentioned above, typical process-related substances present in the emulsion polymerization process, such as surfactants, soaps, initiators, etc., must also be taken into account when evaluating the migration potential of the back coating polymer components.

[0030] To address this problem of heat-sensitive adhesive labels, the prior art provides a variety of different solutions: as described in patent documents US 4370370A and EP 2474963B1, an additional layer is added between the back of the carrier substrate and the adhesive layer (the so-called back coating layer); or as described in patent document JPS 59162087A, a special substance, such as carboxylated polyvinyl alcohol, is incorporated into the adhesive layer.

[0031] However, the above solutions are not economically viable because they require additional production technology steps, making the label material more complex overall, and the migration problem of the back coating can only be minimized by relying on more expensive low-migration adhesives. Summary of the invention

[0032] The object of the present invention is to optimize the characteristic curve of a hot-printing thermosensitive recording material with an adhesive layer on the back, in particular to minimize the loss of image stability after storage of the thermosensitive recording material, especially when the thermosensitive recording material is to be stored for a long time.

[0033] Image stability can be characterized as the durability of an image after storage of a heat-sensitive recording material, wherein image stability can also be characterized in particular as print contrast.

[0034] In view of the above, an object of the present invention is to improve the minimum durability of a heat-sensitive recording material while maintaining the conventional high requirements for such heat-sensitive recording materials, such as dynamic sensitivity, contrast, and the like.

[0035] Surprisingly, it was found that the above-mentioned defects in the prior art can be overcome by using a developer having at least one group having the ability to form hydrogen bonds (selected from the following group: -NHCO-, -CONH-, -NHCONH-, -CONHNHCO-, -NHCOCONH-, -SO2NH- and -NHSO2) in the heat-sensitive layer of the heat-sensitive recording material in combination with 5-(N-3-methylphenyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide (trade name PF425) as a stabilizer.

[0036] In particular, the use of such a combination of at least one corresponding developer and stabilizer in the heat-sensitive layer of a heat-sensitive recording material can limit the loss of image stability of the heat-sensitive recording material with a back-coating formulation after storage under severe environmental conditions, so that the use of these two components in the heat-sensitive layer can produce a synergistic effect.

[0037] According to a first aspect, the solution of the present invention to achieve the above-mentioned purpose is a thermosensitive recording material, which comprises: a carrier substrate having a first side and a second side facing away from the first side; a thermosensitive color-forming layer arranged on the first side of the carrier substrate, the thermosensitive color-forming layer comprising at least one color former, at least one color developer and at least one stabilizer; and an adhesive layer arranged on the second side of the carrier substrate, the adhesive layer comprising at least one adhesive, wherein the weight ratio of the stabilizer to the color developer in the thermosensitive color-forming layer is selected so that: according to the stability test defined in the specification, the migration of the components in the adhesive layer to the thermosensitive color-forming layer enables the image stability of the thermosensitive color-forming layer to be retained by at least 35% after two weeks.

[0038] According to a first aspect, the stabilizer comprises a compound of formula (I):

[0039]

[0040] Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the following group: C1-C8 alkyl, C5-C6 cycloalkyl; or a compound of formula (II):

[0041]

[0042] wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7 and -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and

[0043] Wherein, Q contains a single bond or a C1-C8 alkylene group, which may be branched or unbranched, wherein when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group contains a main chain with one or more oxygen atoms between two carbon atoms.

[0044] According to a first aspect, at least one developer comprises a compound of formula (NI):

[0045]

[0046] wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the group consisting of hydrogen, phenyl, benzyl and C1-C6 alkyl, wherein R5 is selected from C1-C6 alkyl, wherein n1 and n3 are independently selected from integers ranging from 1 to 5, wherein n2 is an integer ranging from 1 to 4;

[0047] and / or at least one developer comprises a compound of formula (1):

[0048]

[0049] wherein R1 is selected from the group consisting of unsubstituted or substituted phenyl, naphthyl and C1-C 20 wherein X is selected from the group consisting of —C(═NH)—, —C(═S)—, and —C(═O)—, and wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl, and if B is —O—, then R2 is not an alkyl.

[0050] The combination of stabilizer and developer in the thermosensitive color-forming layer advantageously limits the loss of image stability, in particular the loss of relative print contrast, wherein the image stability and / or relative print contrast of the thermosensitive recording material stored according to the stability test (defined below) is always greater than the values ​​obtained with the same thermosensitive recording material without stabilizer. 9.00 mJ / mm2 is common on the market 2 This effect is particularly evident in the critical average current range.

[0051] Without being bound by theory, it is assumed that the stabilizer, due to its functional groups, produces interactions that stabilize the color-developing complex, such as hydrogen bonds, π-π interactions and / or ionic interactions, which, with the synergistic effect of the color developer and the color former, help maintain the stability of the color-developing complex and the font under the influence of unstable factors such as water, chemicals and extreme climatic conditions.

[0052] In particular, at least one stabilizer comprises a compound of formula (I) without a hydroxy-substituted phenyl group, and thus can be referred to as a phenol-free compound.

[0053] In particular, at least one developer comprises a compound of formula (NI) or formula (1) but does not contain a phenyl group substituted with a hydroxyl group, and thus can be referred to as a phenol-free compound.

[0054] The thermal recording material is very suitable for applications where the back of the thermal recording material is provided with an adhesive layer which is thermally printed using a direct thermal process and which guarantees a long storage life even under extreme environmental conditions and meets specified image stability and print contrast values.

[0055] The present invention is not subject to any significant restrictions on how to select the adhesive used on the back side. Adhesives that are viscous at room temperature and adhesives that are viscous only after activation, such as heating, are all applicable. Permanent adhesives and removable adhesives are all applicable. The application technology of the adhesive on the back side of the heat-sensitive recording material does not limit the scope of the present invention in any way. Aqueous dispersions of adhesives or adhesives dissolved or suspended in organic media can be used, and adhesives applied in a molten state, so-called hot melt adhesives, can also be used.

[0056] In summary, surprisingly, the thermosensitive recording material, in particular the thermosensitive label, obtained according to the first aspect of the present invention using at least one developer and a stabilizer can achieve a high image stability and a good printed image contrast value (print contrast) during thermal printing, even after long-term storage under extreme environmental conditions.

[0057] The heat-sensitive recording material according to the present invention relates to the application-related case of a self-adhesive heat-sensitive recording material, ie, 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.

[0058] In the context of the present disclosure, the stability test defined below includes a test at a temperature of 60°C and a pressure of 1350 N / m 2 Store the thermal recording material between two glass slides at a relative humidity of 50% and protected from light for two weeks.

[0059] In the stability test according to the present disclosure, the image stability of the thermal recording material is determined based on the optical density measured once before the thermal recording material is stored and once after the thermal recording material is stored for two weeks. The optical density values ​​measured twice are related to each other as shown in the following formula A, where the deviation of the calculated percentage value is ≤±2 percentage points:

[0060] Image stability (%) = (optical density after storage / optical density before storage) x 100

[0061] (Formula A)

[0062] According to the stability test of the present disclosure, the optical density was measured using a SpectroEye densitometer produced by X-Rite Corporation, wherein the uncertainty of the measurement was estimated to be ≤ 2%.

[0063] Here, according to the stability test, it is preferred to be 9.00 mJ / mm 2 The image stability of the heat-sensitive recording material according to the present invention after storage for two weeks can reach at least 35% under energy stimulation of 100 Å.

[0064] For the stability test, a DIN A4 type heat-sensitive recording material (whose carrier substrate has an adhesive layer on the side facing away from the heat-sensitive color-forming layer) is longitudinally divided into at least two strips 6 cm wide.

[0065] Print and measure one of these strips to determine the optical density before storage. Place the unprinted strip on the printed strip (simulating a hot roller) and then heat at 60°C and 1350 N / m 2 The stacked tape is stored between two glass slides at a relative humidity of 50% and protected from light for two weeks (or four weeks according to some embodiments).

[0066] After storage and adjustment to room temperature, the optical density was measured, the average was taken and related to the optical density value initially measured before storage in order to determine the image stability according to Formula A above.

[0067] In addition to the image stability of the heat-sensitive recording material, the relative print contrast can also be considered as another criterion for the image stability of the heat-sensitive recording material.

[0068] The relative print contrast (DK, in %) is based on the optical density values ​​of the thermally printed area, i.e. the optical density of the printed pattern (oDs) and the optical density of the unprinted area (oDw), and is calculated according to the following formula B, where the deviation of the calculated percentage value is ≤ ±2 percentage points:

[0069] DK(%)=(oDs–oDw / oDs)x 100

[0070] (Formula B)

[0071] Here, according to the stability test, it is preferred to be 9.00 mJ / mm 2 Under the energy stimulation of , the relative printing contrast of the thermal recording material can reach at least 50% after being stored for two weeks.

[0072] According to a first aspect, the stabilizer comprises a compound of formula (I):

[0073]

[0074] Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the following group: C1-C8 alkyl, C5-C6 cycloalkyl; or a compound of formula (II):

[0075]

[0076] wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7, and -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and

[0077] Wherein, Q contains a single bond or a C1-C8 alkylene group, which may be branched or unbranched, wherein when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group contains a main chain with one or more oxygen atoms between two carbon atoms.

[0078] Specifically, the hydrocarbon group having three or four carbon atoms formed together by R2 and R3 and R5 and R6 includes a trimethylene group, a tetramethylene group, a propenylene group, a 2-butenylene group or a 1,3-butadienyl group.

[0079] Preferably, R8 is selected as halogen, more preferably, R8 is selected as chlorine.

[0080] Preferably, Q is selected from: -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-, wherein more preferably, Q is selected from: -CH2-, -CH2-CH2-, -CH2-CH2-O- or -C(Me)H-.

[0081] Preferably, option "C1-C 18 The term "alkyl" includes methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, tert-pentyl (1,1-dimethylpropyl), 1,1,3,3-tetramethylbutyl, n-hexyl, 2-methylpentyl, neopentyl, n-heptyl, 2-ethylhexyl or n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl or n-octadecyl.

[0082] Preferably, the option "C1-C8 alkyl" includes methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, tert-pentyl (1,1-dimethylpropyl), 1,1,3,3-tetramethylbutyl, n-hexyl, 2-methylpentyl, neopentyl, n-heptyl, 2-ethylhexyl or n-octyl or tridecyl, more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-ethylhexyl or tridecyl.

[0083] Preferably, the option "C1-C8 alkoxy" includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, n-pentoxy, n-hexoxy, n-heptyloxy or n-octyloxy. More preferably, the option "C1-C8 alkoxy" includes the option "C1-C6 alkoxy", more preferably methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy or n-hexyloxy.

[0084] Preferably, the option "C1-C8 alkoxy-C1-C8 alkyl" includes methoxymethyl, ethoxymethyl, n-propoxymethyl, isopropoxymethyl, n-butoxymethyl, n-pentyloxymethyl, n-hexyloxymethyl, n-heptyloxymethyl, n-octyloxymethyl, methoxyethyl, ethoxyethyl, n-propoxyethyl, isopropoxyethyl, n-butoxyethyl, 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.

[0085] Preferably, the option "C5-C6 cycloalkyl" includes cyclopentyl or cyclohexyl, more preferably cyclohexyl.

[0086] Preferably, the option "(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.

[0087] Preferably, when R2 and R3 or R4 and R5 or both, or when R3 and R4 or R5 and R6 or both, or when (R2 and R3) and (R5 and R6) together form a hydrocarbon group having three or four carbon atoms, in particular trimethylene, tetramethylene, propenylene, 2-butenylene or 1,3-butadienyl, the option "R2 and R3 together" includes tetramethylene.

[0088] Preferably, the compound of formula (II) is phenyl, benzyl, 3-methylphenyl, 2,6-diethylphenyl, o-isopropylphenyl, p-acetamidophenyl, 1-phenethyl, 2-phenethyl, 2-phenoxyethyl, 1-tetrahydronaphthyl or 2-tetrahydronaphthyl.

[0089] According to one embodiment, the stabilizer comprises a compound of formula (Ia):

[0090]

[0091] Alternatively, the stabilizer comprises a compound of formula (Ib):

[0092]

[0093] Preferably, the compound of formula (Ia) includes at least one of the following compounds: 5-(N-benzyl-sulfonylamino)-(N',N"-dibenzyl)-isophthalamide, 5-(N-3-methylphenyl-sulfonylamino)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-2,6-diethylphenyl-sulfonylamino)-[N',N"-bis(2,6-diethylphenyl)]-isophthalamide, 5-(N-phenyl-sulfonylamino)-(N',N"-diphenyl)-isophthalamide, 5-(N-isopropyl-phenyl-sulfonylamino)-[N',N"-bis(o-isopropylphenyl)]-isophthalamide, 5-(N-p-acetylamino-phenyl-sulfonylamino)-[N',N"-bis(o-isopropylphenyl)]-isophthalamide, ,N"-bis(p-acetylamino-phenyl)]-isophthalamide, 5-(N-1-tetrahydronaphthyl-sulfonamido)-[N',N"-bis(1-tetrahydronaphthyl)]-isophthalamide, 5-(N-3-methylphenyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-1-phenylethyl-sulfonamido)-[N',N"-bis(1-phenylethyl)]-isophthalamide, 5-(N-2-phenylethyl-sulfonamido)-[N',N"-bis(2-phenylethyl)]-isophthalamide, 5-(N-2,6-diethylphenyl-sulfonamido)-[N',N"-bis(2,6-diethylphenyl)]-isophthalamide, 5-(N-butyl isophthalamide, 5-(N-benzyl-sulfonamido)-(N',N"-di-n-butyl)-isophthalamide, 5-(N-2-ethylhexyl-sulfonamido)-(N',N"-di-2-ethylhexyl)-isophthalamide, 5-(N-benzyl-sulfonamido)-(N',N"-diphenyl)-isophthalamide, 5-(N-phenyl-sulfonamido)-(N',N"-dibenzyl)-isophthalamide, 5-(N-benzyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-butyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-1-phenylethyl-sulfonamido)-[N',N"-bis(3-methylphenyl)] ]-isophthalamide, 5-(N-2-phenylethyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-2-methoxyethyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-octyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide, 5-(N-benzyl-sulfonamido)-[N',N"-bis(2,6-diethylphenyl)-isophthalamide, 5-(N-octyl-sulfonamido)-[N',N"-bis(2,6-diethylphenyl)]-isophthalamide and 5-(N-2-phenoxyethyl-sulfonamido)-N',N"-bis(2,6-Diethylphenyl)-isophthalamide.

[0094] In particular, the heat-sensitive recording material comprises a bisamide of formula (Ic):

[0095]

[0096] Preferably, the stabilizer is selected as a compound of formula (Ia), and the heat-sensitive recording material comprises a bisamide of formula (Ic), more preferably, the amount of bisamide (Ic) is 0.01 mol.% to 10 mol.% based on the compound of formula (Ia).

[0097] According to one embodiment, the stabilizer comprises 5-(N-3-methylphenyl-sulfonamido)-[N′,N″-bis(3-methylphenyl)]-isophthalamide.

[0098] Here, the compound 5-(N-3-methylphenyl-sulfonylamino)-[N',N"-bis(3-methylphenyl)]-isophthalamide particularly comprises three different polymorphs, including: an α-form having a melting point of 211.2°C as determined by DSC; a β-form having a melting point of 192.2°C as determined by DSC; and a γ-form having a melting point of 215.6°C as determined by DSC.

[0099] According to a first aspect, at least one developer comprises a compound of formula (NI):

[0100]

[0101] Wherein, R1, R2 and R3 are independently selected from the following groups: hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the following group: hydrogen, phenyl, benzyl and C1-C6 alkyl, wherein R5 is selected as C1-C6 alkyl, wherein n1 and n3 are independently selected as integers from 1 to 5, wherein n2 is an integer from 1 to 4.

[0102] 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 in the compound of formula (NI):

[0103]

[0104]

[0105] Preferably, the compound of formula (NI) is a benzenesulfonamide compound.

[0106] Preferably, R1, R2 and / or R3 are selected from the group consisting of hydrogen, halogen, more preferably fluorine, chlorine, bromine or iodine; nitro; linear, branched or cyclic C1-C6 alkyl, more preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, isohexyl, cyclopropyl, cyclobutyl, 2-methylcyclopropyl, cyclopropylmethyl, cyclopentyl or cyclohexyl; linear, branched or cyclic C1-C6 alkoxy, more preferably methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyl, hexyl, cyclopropyloxy, cyclobutyloxy, 2-methylcyclopropyl, cyclopropylmethyl, cyclopentyl or cyclohexyl; oxy, cyclopropylmethoxy, cyclopentyloxy or cyclohexyloxy; C2-C6 alkenyl, more preferably vinyl, allyl, isopropenyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl or 2-methyl-2-propenyl; C1-C6 fluoroalkyl, more preferably trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluorohexyl or perfluorocyclohexyl; N(R4)2 group, more preferably, R4 is selected from the following group: hydrogen, phenyl, benzyl or C1-C6 alkyl; NHCOR5 group, more preferably, R5 is selected from C1-C6 alkyl; optionally substituted phenyl; and optionally substituted benzyl.

[0107] More preferably, R1, R2 and / or R3 are selected to be hydrogen or a linear C1-C6 alkyl group, wherein most preferably, R1 is hydrogen or methyl, and R2 and R3 are both hydrogen.

[0108] More preferably, the C1-C6 alkyl group selected for R4 or R5 is the same as the C1-C6 alkyl group selected for R1.

[0109] More preferably, the optional substituents of the optionally substituted group are selected from the group consisting of 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-methylpentyl or 2-methylpentyl) and C1-C6 alkoxy (most preferably methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy or tert-butoxy).

[0110] Preferably, the compound of formula (NI) is selected from the group consisting of 4-methyl-N-(2-(3-phenylureido)phenyl)benzenesulfonamide and N-(2-(3-phenylureido)phenyl)benzenesulfonamide, more preferably N-(2-(3-phenylureido)phenyl)benzenesulfonamide.

[0111] According to one embodiment, at least one developer comprises a compound of formula (NI), wherein R1, R2 and R3 are selected to be hydrogen.

[0112] According to one embodiment, at least one developer comprises N-(2-(3-phenylureido)phenyl)benzenesulfonamide, preferably α-crystalline form and / or β-crystalline form of N-(2-(3-phenylureido)phenyl)benzenesulfonamide.

[0113] In particular, the alpha crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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 (onset).

[0114] In particular, the β crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (2θ / CuKa) 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, 31.3 and / or a melting point determined by DSC of 173°C to 174°C (onset).

[0115] Here, X-ray diffraction (XRD) measurements were performed using a Bruker D2 Phaser, copper electrodes, 30 kV voltage, and a Lynxeye detector to obtain the corresponding X-ray diffraction patterns.

[0116] The corresponding melting points determined by DSC were determined using a Netzsch DSC 200F3 Apparatus, aluminum crucible with cold-welded perforated lid, 10 K / min heating rate, 25° C. to 200° C. temperature range for measurements by differential scanning calorimetry (DSC) under N 2 atmosphere.

[0117] The corresponding compound N-(2-(3-phenylureido)phenyl)benzenesulfonamide is sold, inter alia, under the trade name NKK-1304.

[0118] As an alternative or in addition to at least one developer according to formula (N-1), according to a first aspect, at least one developer comprises a compound of formula (1):

[0119]

[0120] wherein R1 is selected from the group consisting of unsubstituted or substituted phenyl, naphthyl and C1-C 20Alkyl, wherein X is selected from the group consisting of —C(═NH)—, —C(═S)— and —C(═O)—, wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12 Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl, and if B is —O—, then R2 is not an alkyl.

[0121] Preferably, R1 is selected to be phenyl or naphthyl, ie phenyl or naphthyl which is unsubstituted or substituted, for example, by C1-C8 alkyl, C1-C8 alkoxy or halogen.

[0122] More preferably, the substituent is selected from the group consisting of: C1-C4 alkyl, most preferably methyl or ethyl; C1-C4 alkoxy, more preferably methoxy or ethoxy; or halogen, more preferably chlorine.

[0123] More preferably, R1 is selected to be unsubstituted naphthyl.

[0124] More preferably, R1 is selected as a substituted phenyl, wherein most preferably, the substituent is selected as one of the above-mentioned alkyl substituents.

[0125] Preferably, R1 is selected from unsubstituted or substituted C1-C 20 Alkyl, more preferably C1-C8 alkoxy or halogen, more preferably C1-C4 alkoxy, most preferably methoxy or ethoxy, or halogen, most preferably chlorine.

[0126] More preferably, R1 is selected from unsubstituted C1-C 20 alkyl.

[0127] More preferably, R1 is an unsubstituted phenyl group or a phenyl group substituted by a C1-C8 alkyl group, a C1-C8 alkoxy group or a halogen group, more preferably a substituted phenyl group, most preferably a phenyl group substituted by a C1-C4 alkyl group, and particularly preferably a methyl group.

[0128] Preferably, X is a group of the formula -C(=S)- or -C(=O)-, more preferably a group of the formula -C(=O)-.

[0129] Preferably, A is unsubstituted phenylene or unsubstituted naphthylene, or substituted phenylene or substituted naphthylene (more preferably 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);

[0130] More preferred are alkyl and alkoxy substituents containing 1 to 4 carbon atoms, and most preferred are C1-C8 alkyl, halogen-substituted C1-C8 alkyl, C1-C8 alkylsulfonyl or halogen.

[0131] More preferably, A is unsubstituted naphthylene.

[0132] Preferably, A is a heterocyclic group, more preferably an unsubstituted pyrimidinylene group or a pyrimidinylene group substituted by a C1-C8 alkyl group (more preferably a C1-C4 alkyl group).

[0133] Preferably, A is C1-C 12 Alkylene, more preferably C1-C8 alkylene, more preferably C1-C4 alkylene.

[0134] More preferably, A is unsubstituted phenylene or substituted phenylene (which is 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), more preferably C1-C8 alkyl, halogen-substituted C1-C8 alkyl, C1-C8 alkylsulfonyl or halogen.

[0135] Most preferably, A is an unsubstituted phenylene group or a phenylene group substituted by a C1-C4 alkyl group or a halogen group, and more preferably an unsubstituted phenylene group.

[0136] Preferably, B is selected from the group consisting of —O—SO2—, —SO2—O—, —SO2—NH—, —S—SO2—, —O—, —O—CO— and —O—CO—NH—, more preferably from the group consisting of —O—SO2—, —SO2—O— and —SO2—NH—, most preferably from the group consisting of —O—SO2— and —O—.

[0137] Preferably, R2 is aryl, more preferably unsubstituted or substituted phenyl or naphthyl (more preferably 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-substituted), most preferably alkyl and alkoxy substituents containing 1 to 4 carbon atoms, more preferably C1-C4 alkyl and halogen substituents.

[0138] Preferably, R2 is naphthyl, more preferably unsubstituted naphthyl.

[0139] Preferably, R2 is benzyl (which is substituted by the substituents mentioned above when R2 is phenyl or naphthyl), more preferably unsubstituted benzyl.

[0140] Preferably, R2 is C1-C 20 Alkyl, more preferably C1-C8 alkyl, more preferably C1-C6 alkyl which is unsubstituted or substituted by, for example, C1-C8 alkoxy, halogen, phenyl or naphthyl, most preferably unsubstituted alkyl, more preferably C1-C4 alkyl.

[0141] 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 substituted phenyl (which is 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 or halogen), naphthyl and benzyl substituted by C1-C4 alkyl or halogen.

[0142] More preferably, R2 is C1-C4 alkyl, halogen-substituted C1-C4 alkyl, phenyl unsubstituted or substituted by C1-C4 alkyl or halogen, naphthyl, and benzyl unsubstituted or substituted by C1-C4 alkyl or halogen, and most preferably phenyl unsubstituted or substituted by C1-C4 alkyl or halogen.

[0143] Preferably, R1 is phenyl substituted by C1-C4 alkyl (more preferably methyl), X is -C(=O)-, A is phenylene unsubstituted or substituted by C1-C8 alkyl or halogen, more preferably unsubstituted phenylene, such as 1,3-phenylene, B is a group of the formula -O-SO2- or -O-, R2 is phenyl, naphthyl or benzyl unsubstituted or substituted by C1-C4 alkyl or halogen, more preferably phenyl substituted by C1-C4 alkyl.

[0144] According to one embodiment, at least one developer of formula (1) includes 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide, preferably α-crystalline and / or β-crystalline of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

[0145] In particular, the alpha crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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, 28.6 and / or a melting point determined by DSC of 161°C to 162°C.

[0146] In particular, the β crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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.

[0147] Here, X-ray diffraction (XRD) measurements were performed using a Bruker D2 Phaser, copper electrodes, 30 kV voltage, and a Lynxeye detector to obtain the corresponding X-ray diffraction patterns.

[0148] The corresponding melting points determined by DSC were determined using a Netzsch DSC 200F3 Apparatus, aluminum crucible with cold-welded perforated lid, 10 K / min heating rate, 25° C. to 200° C. temperature range for measurements by differential scanning calorimetry (DSC) under N 2 atmosphere.

[0149] According to one embodiment, the weight ratio of the stabilizer to the 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.

[0150] In view of the corresponding weight ratio of stabilizer to developer in the heat-sensitive color-forming layer, the stability test defined in the specification showed that the heat-sensitive recording material exhibited very high image stability after two weeks and, in particular, also a highly retained print contrast.

[0151] In particular, the stabilizer is selected as 5-(N-3-methylphenyl-sulfonylamide)-[N',N"-bis(3-methylphenyl)]-isophthalamide (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.

[0152] According to one embodiment, based on the total solid content of the thermosensitive color-forming layer, the weight of the stabilizer is 1 wt.% to 10 wt.%, preferably 2 wt.% to 8 wt.%, more preferably 3 wt.% to 6 wt.%, and most preferably 4 wt.%.

[0153] Taking into account the corresponding weight fractions of stabilizer in the heat-sensitive color-forming layer, a stability test as defined in the specification showed that the heat-sensitive color-forming layer exhibited very highly retained image stability after two weeks and, in particular, also a highly retained print contrast.

[0154] In particular, the stabilizer is selected as 5-(N-3-methylphenyl-sulfonamide)-[N',N"-bis(3-methylphenyl)]-isophthalamide (trade name PF425), and based on the total solid content of the thermosensitive color-forming layer, the weight of the stabilizer is 1wt.% to 10wt.%, preferably 2wt.% to 8wt.%, more preferably 3wt.% to 6wt.%, and most preferably 4wt.%.

[0155] According to one embodiment, based on the total solid content of the thermosensitive color-forming layer, the weight portion of at least one color developer is 6wt.% to 35wt.%, preferably 10wt.% to 30wt.%, more preferably 20wt.% to 30wt.%, and most preferably 24wt.%.

[0156] Taking into account the corresponding weight fractions of at least one color developer in the heat-sensitive color-forming layer, stability tests defined in the specification show that the heat-sensitive color-forming layer exhibits very highly retained image stability after two weeks and in particular also highly retained print contrast.

[0157] In particular, 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, based on the total solid content of the thermosensitive color-forming layer, the weight percentage of at least one color developer is 6wt.% to 35wt.%, preferably 10wt.% to 30wt.%, more preferably 20wt.% to 30wt.%, and most preferably 24wt.%.

[0158] According to one embodiment, the image stability retained by the thermosensitive coloring layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

[0159] The correspondingly high retention of image stability of the thermosensitive color-forming layer after two weeks ensures a high image stability of the thermosensitive recording material.

[0160] According to one embodiment, the adhesive includes a pressure-sensitive adhesive and / or a heat-activated adhesive, wherein the adhesive is preferably a permanent hot melt adhesive based on styrene-isoprene and PVC copolymer, and / or the adhesive is preferably a removable adhesive based on acrylate, and / or the adhesive is preferably a permanent hot melt adhesive based on synthetic rubber.

[0161] The technical advantage achieved in this way is that various types of adhesives can be used in the adhesive layer of the heat-sensitive recording material according to the present invention, while the image stability retained after two weeks can still reach at least 35% according to the stability test.

[0162] For example, a permanent hot melt adhesive based on styrene-isoprene and PVC copolymer is available from Avery Dennison as adhesive type S2200.

[0163] For example, an acrylate-based removable adhesive is R5000N adhesive produced by Avery Dennison.

[0164] An example of a permanent hot melt adhesive based on synthetic rubber is Technomelt PS 8746 adhesive from Henkel.

[0165] According to one embodiment, the adhesive comprises a permanent hot melt adhesive based on styrene-isoprene and PVC copolymer, 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.

[0166] According to one embodiment, the developer comprises the β-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, and / or the developer comprises the α-crystalline form of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

[0167] This provides the technical advantage that when using permanent adhesive hot melts based on styrene-isoprene and PVC copolymers, the β-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide (NKK-1304) and / or the α-crystalline form of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF-201) can achieve excellent results in terms of image stability determined according to stability tests.

[0168] According to one embodiment, the image stability retained by the thermosensitive coloring layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

[0169] According to one embodiment, the adhesive comprises an acrylate-based removable adhesive, wherein the weight ratio of the stabilizer to the 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.

[0170] According to one embodiment, the developer comprises the α-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

[0171] This provides the technical advantage that the α-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide (NKK-1304) is able to achieve excellent results in terms of image stability as determined by stability testing when using acrylate-based removable adhesives.

[0172] According to one embodiment, the image stability retained by the thermosensitive coloring layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

[0173] According to one embodiment, the adhesive comprises a permanent hot melt adhesive based on synthetic rubber, wherein the weight ratio of the stabilizer to the 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.

[0174] According to one embodiment, the developer comprises an α-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, and / or the developer comprises an α-crystalline form of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide.

[0175] The technical advantage provided by this is that when using a permanent adhesive hot melt adhesive based on synthetic rubber, the α-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide (NKK-1304) and / or the α-crystalline form of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF201) can achieve excellent results in terms of image stability determined according to stability tests.

[0176] According to one embodiment, the image stability retained by the thermosensitive coloring layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

[0177] According to one embodiment, image stability is determined by using a printer at 9.00 mJ / mm 2 The printing pattern is thermally printed onto a thermal recording material at an energy level of 100 mm / s and a printing speed of about 100 mm / s, and the optical density of the printed pattern is measured with a densitometer, and the thermal recording material is then stored, and the optical density of the printed pattern is measured again with a densitometer after the thermal recording material has been stored for two weeks, wherein the image stability specifically corresponds to the quotient (unit: %) of the optical density of the printed pattern after the storage period and the optical density of the printed pattern before the storage period.

[0178] Specifically, a temperature of 60° C. and a humidity of 50% were maintained during the two-week storage period.

[0179] The technical advantage achieved in this way is that a unified stability test can be provided according to the present invention.

[0180] According to one embodiment, the weight ratio of the stabilizer to the developer in the thermosensitive color-forming layer is selected so that: the image stability retained by the thermosensitive color-forming layer after two weeks is at least 35%, and the printing contrast retained by the thermosensitive color-forming layer after two weeks is at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably at least 80%.

[0181] This offers the technical advantage that, in addition to image stability, the print contrast is also taken into account, making it a particularly effective way to characterize the quality of thermal recording materials.

[0182] According to one embodiment, the print contrast retained after two weeks is determined by the following formula: DK (%) = (oDs-oDw / oDs) x 100, where the parameter oDs corresponds to the optical density of the printed pattern after two weeks, and the parameter oDw corresponds to the optical density of the unprinted area of ​​the thermal recording material after two weeks.

[0183] This provides the technical advantage that print contrast can be determined efficiently.

[0184] According to one embodiment, at least one color former is a triphenylmethane dye, a fluorane dye, an azaphthalide dye and / or a fluorene dye, preferably a fluorane dye.

[0185] By using a particularly preferred fluoran dye as at least one coupler, it is possible to provide a heat-sensitive recording material having an excellent price-performance ratio due to its availability and application-related balance.

[0186] According to one embodiment, the fluoran dye is selected from the following group: 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-4-toluidine)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2,4-dimethylanilino)fluoran, 3-pyrrolidinyl-6-methyl-7-anilinofluoran, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(3-trifluoromethylanilino)fluoran, 3-N-butylamino 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.

[0187] According to one embodiment, based on the total solid content of the thermosensitive color-forming layer, the weight proportion of the at least one color-forming agent is 3 wt.% to 30 wt.%, preferably 5 wt.% to 20 wt.%, and particularly preferably 8 wt.% to 15 wt.%.

[0188] According to one embodiment, the carrier substrate comprises paper, synthetic paper and / or plastic film.

[0189] However, the carrier substrate is not limited thereto. Preferably, the weight per unit area of ​​the carrier material is 30 g / m 2 Up to 100g / m 2, especially 40g / m 2 Up to 80g / m 2 .

[0190] In particular, the carrier substrate comprises a paper substrate made from hardwood and / or softwood pulp.

[0191] According to one embodiment, the heat-sensitive recording material has at least one intermediate layer disposed between the support substrate and the heat-sensitive color-forming layer. Preferably, the intermediate layer contains at least one pigment, more preferably an organic hollow sphere pigment and / or calcined kaolin.

[0192] Preferably, the organic hollow sphere pigment comprises a styrene-acrylate copolymer. Preferably, the organic hollow sphere pigment 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 an average particle diameter (D50).

[0193] The intermediate layer can not only serve as a heat barrier between the carrier substrate and the thermal-sensitive color-forming layer, but also improve the surface smoothness of the carrier substrate suitable for the thermal-sensitive color-forming layer.

[0194] According to one embodiment, the heat-sensitive recording material has at least one protective layer and / or printing support layer, which is arranged on the side of the heat-sensitive color-forming layer facing away from the adhesive layer. Preferably, the protective layer contains a binder and at least one pigment, more preferably a binder and an inorganic pigment.

[0195] The protective layer and / or printing support layer arranged outside the thermal color-forming layer ensures effective protection or good printability of the thermal color-forming layer.

[0196] According to one embodiment, the binder is selected from the following group: water-soluble starch, starch derivatives, EcoSphere type starch-based bio-latex, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, semi-saponified or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol (such as acetoacetyl, diacetone, carboxyl, silanol-modified polyvinyl alcohol), ethylene-vinyl alcohol copolymer (EVOH) or styrene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylamide-(meth)acrylate copolymer, acrylamide-acrylate-methacrylate terpolymer, polyacrylate, poly(meth)acrylate, acrylate-butadiene copolymer, polyvinyl acetate, acrylonitrile-butadiene copolymer and mixtures thereof, in particular, can be used. A (meth)acrylamide-acrylate-based copolymer, which is preferably in the form of a core-shell structure.

[0197] According to an embodiment, based on the total solid content of the protective layer, the weight of the binder is 30 wt.% to 90 wt.%, preferably, the weight is 40 wt.% to 80 wt.%.

[0198] According to an embodiment, the adhesive is formed as a cross-linking adhesive, preferably, the cross-linking adhesive is formed as a self-cross-linking adhesive, or the protective layer contains a cross-linking agent, which is formed to react with the adhesive to obtain a cross-linking adhesive.

[0199] In order to achieve specific application-related performance characteristics of the thermosensitive recording material, the binder is preferably present in crosslinked form in the protective layer, wherein an optimum degree of crosslinking of the binder is established during the drying step of the coating process, in particular in the presence of a crosslinker.

[0200] According to one embodiment, the self-crosslinking adhesive comprises modified polyvinyl alcohol and / or modified acrylate.

[0201] Regarding self-crosslinking binders (such as special modified polyvinyl alcohol and / or modified acrylate), since the polymer already contains reactive groups, crosslinking can be achieved without adding a crosslinking agent.

[0202] According to one embodiment, the crosslinking agent is selected from the following group: polyvalent aldehydes, preferably glyoxal, dialdehyde starch and / or glutaraldehyde, in particular alone or mixed with boron salts, glyoxylic acid salts or esters, ammonium zirconium carbonate, polyamide amine epichlorohydrin resin, adipic acid dihydrazide, boric acid or its salts, polyamines, epoxy resins, formaldehyde oligomers, cyclic ureas, methylol urea and melamine formaldehyde oligomers and mixtures thereof, more preferably, the crosslinking agent is selected from the following group: ammonium zirconium carbonate and polyamide epichlorohydrin resin.

[0203] According to one embodiment, based on the total solid content of the protective layer, the weight of the crosslinking agent is 0.01 wt.% to 25.0 wt.%, preferably, the weight is 0.05 wt.% to 15 wt.%.

[0204] According to one embodiment, the pigment comprises an inorganic pigment selected from the group consisting of calcium carbonate (preferably synthetic calcium carbonate, natural calcium carbonate or precipitated calcium carbonate), aluminum oxide, aluminum hydroxide, silicic acid, precipitated pyrogenic silicic acid, diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, bentonite and mixtures thereof, or the pigment comprises an organic pigment selected from the group consisting of hollow pigments having a styrene / acrylate copolymer wall, urea / formaldehyde polycondensates and mixtures thereof.

[0205] According to one embodiment, based on the total solid content of the protective layer, the weight of the pigment is 5 wt.% to 50 wt.%, preferably, the weight is 10 wt.% to 45 wt.%.

[0206] According to one embodiment, the protective layer has at least one lubricant, preferably, the lubricant is selected from the following group: fatty acid metal salts (preferably zinc stearate or calcium stearate), behenate or synthetic wax (preferably in the form of fatty acid amide, more preferably stearic acid amide and behenic acid amide), fatty acid alkanolamide (preferably stearic acid formamide), paraffin waxes with different melting points, ester waxes with different molecular weights, polyethylene waxes, polypropylene waxes with different hardness, natural waxes (preferably carnauba wax or montan wax) and mixtures thereof.

[0207] According to an embodiment, based on the total solid content of the protective layer, the weight of the lubricant is 1 wt.% to 30 wt.%, preferably, the weight is 2 wt.% to 20 wt.%.

[0208] According to one embodiment, the protective layer has at least one whitening agent, preferably, the whitening agent is selected from stilbene compounds.

[0209] By using a whitening agent, the surface whiteness of the heat-sensitive color-forming layer can be advantageously adjusted.

[0210] According to one embodiment, the weight per unit area of ​​the protective layer is 0.3 g / m 2 Up to 5.0g / m 2 , preferably 1.0g / m 2 Up to 3.0g / m 2 .

[0211] According to an embodiment, the thickness of the protection layer is 0.3 μm to 6.0 μm, preferably 0.5 μm to 2.0 μm.

[0212] According to an embodiment, the Bekk smoothness of the protective layer is measured according to standard ISO 5267:1995-03 and is 100 seconds to 3000 seconds, preferably 500 seconds to 2000 seconds.

[0213] A correspondingly advantageous Bekk smoothness can be achieved by smoothing.

[0214] According to an embodiment, the surface roughness of the protective layer is 0.5 μm to 2.50 μm, preferably 1.00 μm to 2.00 μm, measured according to standard ISO 8791-4:2008-05.

[0215] In addition to at least one color former, at least one color developer and at least one stabilizer, the heat-sensitive color-forming layer according to an embodiment may further include at least one sensitizer, which has the advantage that it is easier to control the heat pressure sensitivity.

[0216] Generally speaking, the sensitizer is preferably a crystalline material having a melting point between about 90°C and about 150°C and dissolves the color-forming components (including at least one color former and at least one developer) in the molten state without interfering with the formation of the color-forming complex. The sensitizer may be present alone or in a mixture.

[0217] Preferably, at least one sensitizer is selected from the group consisting of fatty acid amides (especially stearic acid amide, behenic acid amide or palmitic acid amide), ethylene bis fatty acid amides (especially N,N'-ethylene bisstearic acid amide or N,N'-ethylene bisoleic acid amide), fatty acid alkanolamides (especially N-(hydroxymethyl) stearic acid amide, N-hydroxymethyl palmitic acid amide or hydroxyethyl stearic acid amide), waxes (especially polyethylene wax or montan wax), carboxylic acid esters (especially dimethyl terephthalate, diisocyan ... benzyl esters, benzyl 4-benzyloxybenzoate, bis(4-methylbenzyl)oxalate, bis(4-chlorobenzyl)oxalate or bis(4-benzyl)oxalate, aromatic ethers (especially 1,2-diphenoxyethane, 1,2-di-(3-methylphenoxy)ethane, 2-benzyloxynaphthalene or 1,4-diethoxynaphthalene), aromatic sulfonic acids (especially diphenyl sulfone), aromatic sulfonamides (especially benzenesulfonanilide or N-benzyl-4-toluenesulfonamide), aromatic hydrocarbons (especially 4-benzylbiphenyl) and mixtures thereof.

[0218] According to one embodiment, based on the total solid content of the thermosensitive color-forming layer, the weight of the sensitizer is 5 wt.% to 40 wt.%, preferably 10 wt.% to 25 wt.%.

[0219] In addition to at least one color former, at least one developer, at least one stabilizer and optionally a sensitizer, according to one embodiment, the thermosensitive color-forming layer may further comprise at least one additional stabilizer.

[0220] Here, the additional stabilizer serves as an anti-aging agent for the color-developing complex in the heat-sensitive color-forming layer.

[0221] Preferably, the additional stabilizer is selected from the following group: sterically hindered phenols, more preferably 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)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, ureaurethane compounds, derivative ethers of 4,4'-dihydroxydiphenyl sulfone, more preferably 4-benzyloxy-4'-(2-methylglycidyloxy)diphenyl sulfone, oligoethers and mixtures thereof.

[0222] Preferably, based on the total amount of the developer in the thermosensitive color-forming layer, the weight portion of the additional stabilizer is 0.2 wt. % to 1.0 wt. %.

[0223] According to one embodiment, the thermosensitive color-forming layer comprises at least one additional binder, preferably, the additional binder is selected from the group consisting of water-soluble starch, starch derivatives, starch-based bio-latex, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, semi-saponified or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer (EVOH) or styrene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylamide-(meth)acrylate copolymer, acrylamide-acrylate-methacrylate terpolymer, polyacrylate, poly(meth)acrylate, acrylate-butadiene copolymer, polyvinyl acetate, acrylonitrile-butadiene copolymer and mixtures thereof, in particular using A (meth)acrylamide-acrylate-based copolymer, which is preferably in the form of a core-shell structure.

[0224] In order to achieve specific application-related performance characteristics of the thermosensitive recording material, preferably a self-adhesive thermosensitive recording material, in particular a self-adhesive label, the binder is preferably present in crosslinked form in the thermosensitive layer, wherein an optimum degree of crosslinking of the binder is established in the presence of the crosslinker during the drying step of the coating process.

[0225] Preferably, the binder is designed as a cross-linking additional binder, preferably, the cross-linking additional binder is formed as a self-cross-linking additional binder, or the thermosensitive color-forming layer contains an additional cross-linking agent, which is designed to react with the additional binder to obtain a cross-linked additional binder.

[0226] The self-crosslinking additional binder also preferably comprises modified polyvinyl alcohol and / or modified acrylate.

[0227] More preferably, the additional crosslinking agent is selected from the group consisting of polyvalent aldehydes, preferably glyoxal, dialdehyde starch and / or glutaraldehyde, in particular borates, glyoxylates or glyoxylates, ammonium zirconium carbonate, polyamide epichlorohydrin resins, adipic acid dihydrazide, boric acid or borates and mixtures thereof, alone or in admixture.

[0228] More preferably, based on the total amount of the crosslinkable additional binder in the thermosensitive color-forming layer, the weight portion of the additional crosslinking agent is 2.5 wt.% to 20 wt.%, preferably 5 wt.% to 15 wt.%.

[0229] According to one embodiment, the carrier substrate, the thermosensitive color-forming layer and / or the adhesive layer are formed as a single layer or multiple layers.

[0230] According to one embodiment, the heat-sensitive color-forming layer has a release agent, preferably, the release agent is selected from the following group: fatty acid metal salts (more preferably zinc stearate or calcium stearate), behenate, synthetic wax (more preferably in the form of fatty acid amide, more preferably stearic acid amide and behenic acid amide), fatty acid alkanolamide (more preferably stearic acid formamide), paraffin waxes with different melting points, ester waxes with different molecular weights, polyethylene waxes, polypropylene waxes with different hardness, natural waxes (more preferably carnauba wax or montan wax) and mixtures thereof.

[0231] According to one embodiment, based on the total solid content of the thermosensitive color-forming layer, the weight portion of the release agent is 1 wt.% to 10 wt.%, preferably, the weight portion is 3 wt.% to 6 wt.%.

[0232] According to one embodiment, the thermal color-forming layer has additional pigments, which have the advantage that these additional pigments can fix the chemical melt produced during the thermal printing process on its surface, and can control the surface whiteness and opacity of the thermal color-forming layer and its printability with traditional printing inks through these additional pigments. In addition, the corresponding additional pigments also have an "increase function", such as being used for relatively high-cost color-imparting functional chemicals.

[0233] Preferably, the additional pigment is selected from the group consisting of inorganic pigments (synthetic and natural origin), precipitated calcium carbonate or natural calcium carbonate, clay, aluminum oxide, aluminum hydroxide, silicic acid, precipitated pyrogenic silicic acid, diatomaceous earth, magnesium carbonate, talc; and organic pigments (more preferably hollow pigments with styrene / acrylate copolymer walls, urea / formaldehyde polycondensates and mixtures thereof).

[0234] Preferably, based on the total solid content of the thermosensitive color-forming layer, the weight portion of the additional pigment is 15 wt.% to 50 wt.%, wherein preferably, the weight portion is 20 wt.% to 35 wt.%.

[0235] According to one embodiment, the heat-sensitive color-forming layer comprises at least one additional whitening agent. Preferably, the additional whitening agent is selected from stilbene compounds.

[0236] By using an additional whitening agent, the surface whiteness of the heat-sensitive recording material can be controlled.

[0237] According to one embodiment, the thermosensitive color-forming layer contains a rheology aid, preferably a thickener and / or a surfactant.

[0238] This has the advantage that certain coating properties of the heat-sensitive color-forming layer can be improved during the preparation process.

[0239] According to one embodiment, the surface application amount of the thermal color-forming layer is 1 g / m 2 Up to 10g / m 2 , preferably 3g / m 2 Up to 5g / m2 .

[0240] According to one embodiment, the Bekk smoothness of the thermosensitive color-forming layer is measured according to standard ISO 5267:1995-03 and is 100 seconds to 1500 seconds, preferably 200 seconds to 750 seconds.

[0241] According to one embodiment, the surface application amount of the adhesive layer is 10 g / m 2 Up to 150g / m 2 , preferably 15g / m 2 Up to 30g / m 2 .

[0242] According to a second aspect, the present invention achieves the above-mentioned object by a method for preparing a heat-sensitive recording material, comprising the following method steps:

[0243] providing a carrier substrate having a first side and a second side facing away from the first side;

[0244] applying a coating suspension to a first side of a carrier substrate, the coating suspension comprising at least one color former, at least one color developer, and at least one stabilizer;

[0245] drying the applied suspension to obtain a thermosensitive color-forming layer disposed on the first side of the carrier substrate;

[0246] applying an adhesive layer to the second side of the carrier substrate,

[0247] The weight ratio of the stabilizer to the developer in the applied suspension is selected so that: according to the stability test defined in the specification, the migration of the components in the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material makes the image stability of the heat-sensitive color-forming layer retained after two weeks reach at least 35%,

[0248] Wherein, the stabilizer comprises a compound of formula (I):

[0249]

[0250] Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the following group: C1-C8 alkyl, C5-C6 cycloalkyl; or a compound of formula (II):

[0251]

[0252] wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7 or -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and

[0253] wherein Q comprises a single bond or a C1-C8 alkylene group, which may be branched or unbranched, and wherein, when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group comprises a main chain having one or more oxygen atoms between two carbon atoms;

[0254] Wherein, at least one developer comprises a compound of formula (NI):

[0255]

[0256] wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the group consisting of hydrogen, phenyl, benzyl or C1-C6 alkyl, wherein R5 is selected from C1-C6 alkyl, wherein n1 and n3 are independently selected from an integer ranging from 1 to 5, and wherein n2 is an integer ranging from 1 to 4; and / or

[0257] Wherein, at least one developer comprises a compound of formula (1):

[0258]

[0259] Wherein, R1 is selected from the following group: unsubstituted or substituted phenyl, naphthyl or C1-C 20 Alkyl, wherein X is selected from the group consisting of —C(═NH)—, —C(═S)— and —C(═O)—, wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl, and if B is —O—, then R2 is not an alkyl.

[0260] By the method according to the second aspect, the thermosensitive recording material can be advantageously obtained.

[0261] According to an embodiment, applying the adhesive layer to the second side of the carrier substrate may include applying, in particular laminating, an adhesive film to the second side of the carrier substrate.

[0262] According to an alternative embodiment, applying the adhesive layer to the second side of the carrier substrate may include applying an adhesive dispersion to the second side of the carrier substrate and subsequently drying the adhesive dispersion to obtain the adhesive layer disposed on the second side of the carrier substrate.

[0263] According to one embodiment, the drying of the adhesive layer is performed at a temperature of 60°C to 80°C, preferably at a temperature of 70°C.

[0264] According to one embodiment, the method comprises the additional method step, which is performed after applying the adhesive layer:

[0265] A release paper is applied onto the adhesive layer, and preferably, the release paper is designed as siliconized release paper.

[0266] According to an embodiment, applying the adhesive layer comprises: applying an adhesive dispersion and subsequently drying the adhesive dispersion, wherein the method comprises an additional method step prior to applying the adhesive dispersion:

[0267] An additional release liner is applied to the second side of the carrier substrate, wherein the adhesive dispersion is applied to the additional release liner.

[0268] According to one embodiment, applying the coating dispersion to the first side of the carrier substrate and drying it is performed before applying the adhesive layer to the second side of the carrier substrate, or applying the adhesive layer to the second side of the carrier substrate is performed before applying the coating dispersion to the first side of the carrier substrate and drying it. Preferably, applying the coating dispersion to the first side of the carrier substrate and drying it is performed before applying the adhesive layer to the second side of the carrier substrate.

[0269] According to one embodiment, the coating dispersion is applied to the first side of the carrier substrate by curtain coating or by a doctor bar on the coated side of the carrier substrate covered with a pre-coated pigment layer, preferably, the pre-coated pigment layer comprises calcined kaolin and a binder based on styrene-butadiene and / or based on polyvinyl alcohol (PVA) and / or starch, or comprises a mixture of organic pigments and inorganic pigments, more preferably, the application amount of the pre-coated pigment layer is 2 g / m 2 Up to 12g / m 2 .

[0270] According to one embodiment, the application amount of the dispersion is 3 g / m 2 Up to 5g / m 2 , preferably 3.6 g / m 2 Up to 4.8g / m 2 , and / or the application amount of adhesive dispersion is 10g / m 2 Up to 30g / m 2 , preferably 20g / m 2 .

[0271] According to one embodiment, the application suspension is obtained in particular by grinding, and its average particle size D (4,3) It is preferably 0.5 μm to 5.0 μm, particularly preferably 0.50 μm to 1.50 μm, and particularly preferably 1.5 μm to 2.50 μm.

[0272] The embodiment of the heat-sensitive recording material according to the first aspect is also applicable to the embodiment of the method for preparing the heat-sensitive recording material according to the second aspect, and vice versa.

[0273] According to a third aspect, the present invention achieves the above object by providing a heat-sensitive recording material prepared according to the method described in the second aspect.

[0274] The embodiment of the heat-sensitive recording material according to the first aspect and the embodiment of the method for preparing the heat-sensitive recording material according to the second aspect are also applicable to the embodiment of preparing the heat-sensitive recording material by the method according to the third aspect.

[0275] According to a fourth aspect, the solution of the present invention to achieve the above-mentioned object is a use of at least one stabilizer and at least one developer for a heat-sensitive recording material, the heat-sensitive recording material comprising: a carrier substrate having a first side and a second side facing away from the first side; a heat-sensitive color-forming layer arranged on the first side of the carrier substrate, the heat-sensitive color-forming layer comprising at least one color-forming agent, at least one color-developing agent and at least one stabilizer; and an adhesive layer arranged on the second side of the carrier substrate, the adhesive layer comprising at least one adhesive, wherein the weight ratio of the stabilizer to the color-developing agent in the heat-sensitive color-forming layer is selected so that: according to the stability test defined in the specification, the migration of the components in the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material makes the image stability retained by the heat-sensitive color-forming layer after two weeks reach at least 35%,

[0276] Wherein, the stabilizer comprises a compound of formula (I):

[0277]

[0278] Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the group consisting of C1-C8 alkyl, C5-C6 cycloalkyl; and compounds of formula (II):

[0279]

[0280] wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7, and -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and

[0281] wherein Q comprises a single bond or a C1-C8 alkylene group, which may be branched or unbranched, and wherein, when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group comprises a main chain having one or more oxygen atoms between two carbon atoms;

[0282] Wherein, at least one developer comprises a compound of formula (NI):

[0283]

[0284] wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the group consisting of hydrogen, phenyl, benzyl and C1-C6 alkyl, wherein R5 is selected from C1-C6 alkyl, wherein n1 and n3 are independently selected from an integer ranging from 1 to 5, and wherein n2 is an integer ranging from 1 to 4;

[0285] And / or wherein at least one developer comprises a compound of formula (1):

[0286]

[0287] Wherein, R1 is selected from the following group: unsubstituted or substituted phenyl, naphthyl or C1-C 20 Alkyl, wherein X is selected from the group consisting of —C(═NH)—, —C(═S)— or —C(═O)—, wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12 Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl, and if B is —O—, then R2 is not an alkyl.

[0288] The embodiment of the heat-sensitive recording material according to the first aspect and the embodiment of the method for preparing the heat-sensitive recording material according to the second aspect are also applicable to the embodiment of using at least one stabilizer and at least one developer for heat-sensitive recording material according to the fourth aspect. DETAILED DESCRIPTION

[0289] In the specific examples described in detail below, various heat-sensitive recording materials or heat-sensitive papers can be prepared by coating an aqueous application suspension and a binder dispersion onto a carrier substrate to form a composite structure.

[0290] Preparation of thermal recording materials

[0291] For example, the adhesive dispersion is applied to the second side of a carrier substrate (especially A4 paper) with a doctor blade, the first side (i.e., the front side) of which carries a thermosensitive color-forming layer, and dried with a hot air gun at a temperature of up to 70° C. to obtain an adhesive layer. In order to protect the adhesive layer from damage during subsequent processing, a siliconized release paper is laminated on the adhesive layer to avoid bubbles and wrinkles.

[0292] If there is an "adhesive liner sandwich structure" consisting of a thin adhesive layer sandwiched between two release papers, after removing one of the release papers, the sticky side of the adhesive layer is pressed to the second side (i.e., the back side) of the carrier substrate to avoid bubbles and wrinkles.

[0293] During the preparation of the heat-sensitive recording material, it is immaterial whether the adhesive layer is first applied to the second side of the carrier substrate and the heat-sensitive recording layer is then applied to the opposite first side of the carrier substrate bearing the adhesive layer, or vice versa.

[0294] On a laboratory scale, the aqueous application suspension was applied by means of a doctor bar to pre-pigmented paper (weight per unit area 65 g / m 2 and 72g / m 2 ), thereby forming a thermosensitive color-forming layer of the thermosensitive recording material.

[0295] The composition of the pigment precoat is not critical. In particular, this coating consists of calcined kaolin and a binder based on styrene-butadiene and / or starch. In particular, it is also possible to precoat with organic (hollow sphere) pigments, possibly mixed with inorganic pigments. The application amount of this pigment layer is about 2 g / m 2 Up to 10g / m 2 .

[0296] After the aqueous application suspension of the heat-sensitive coating material is dried, a heat-sensitive color-forming layer can be obtained. The application amount of the heat-sensitive color-forming layer is 3.8 g / m 2 and 4.3g / m 2 between.

[0297] By applying the adhesive layer to the back side of the substrate opposite to the heat-sensitive layer or to the second side of the carrier substrate, a composite material suitable for use as a heat-sensitive label is obtained. The amount of adhesive applied is about 20 g / m 2 .

[0298] The dispersions for preparing the application suspension are described below (each 1 part by weight).

[0299] Coupler Dispersion A:

[0300] Coupler Dispersion A was prepared by mixing 20 parts by weight of 3-N-n-butylamino-6-methyl-7-anilinofluoran (ODB-2) with 33 parts by weight of 12% GohsenxTM An aqueous solution of L-3266 (sulfonated polyvinyl alcohol produced by Gohsei, Japan) was ground in a bead mill.

[0301] Stabilizer Dispersion B:

[0302] Stabilizer Dispersion B was prepared by mixing 40 parts by weight of (N-3-methylphenyl-sulfonamido)-[N',N"-bis(3-methylphenyl)]-isophthalamide (CAS# 2375645-78-4, referred to as Compound I in the following table) with 66 parts by weight of 12% Gohsenx TM An aqueous solution of L-3266 (sulfonated polyvinyl alcohol produced by Gohsei, Japan) was ground in a bead mill.

[0303] Color developer dispersion C:

[0304] Aqueous developer dispersion C was prepared by mixing 40 parts by weight of the corresponding developer 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (CAS#232938-43-1, α crystal form, hereinafter referred to as compound II), 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (CAS#232938-43-1, β crystal form, hereinafter referred to as compound III), N-(2-(3-phenylureido)phenyl)benzenesulfonamide (CAS#215917-77-4, α crystal form, hereinafter referred to as compound IV) or N-(2-(3-phenylureido)phenyl)benzenesulfonamide (CAS#215917-77-4, β crystal form, hereinafter referred to as compound V) with 66 parts by weight of 12% Gohsenx TM An aqueous solution of L-3266 (sulfonated polyvinyl alcohol produced by Gohsei, Japan) was ground in a bead mill.

[0305] Sensitized dispersion D:

[0306] Sensitized dispersion D was prepared by mixing 40 parts by weight of 1,2-diphenoxyethane with 66 parts by weight of 12% Gohsenx TM It was produced by grinding an aqueous solution of L-3266 (sulfonated polyvinyl alcohol from Gohsei, Japan) in a bead mill.

[0307] The average particle size D of all dispersions A, B, C, D obtained by grinding (4.3) The particle size distribution of the dispersion was measured by laser diffraction using Coulter LS13320 instrument produced by Beckman Coulter.

[0308] Lubricant Dispersion E:

[0309] Lubricant dispersion E is a 20% zinc stearate dispersion comprising 9 parts by weight of zinc stearate, 1 part by weight of Gohsenx TM L-3266 (sulfonated polyvinyl alcohol produced by Gohsei, Japan) and 40 parts by weight of water.

[0310] Pigment P:

[0311] Pigment P is a 72% kaolin coating suspension (produced by BASF S).

[0312] Binder solution:

[0313] The binder solution consisted of a 10% aqueous solution of polyvinyl alcohol (Poval 28-99 from Kuraray Europe).

[0314] The heat-sensitive coating suspension is prepared by mixing 1 part by weight of color former dispersion A, 1 part by weight of stabilizer dispersion B, 1.5 parts by weight of corresponding 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 (added in the order of C, D, B, E, P, A) under stirring, and adjusted to a solid content of about 25% with water. The coating suspension is taken as an example with a developer to stabilizer ratio of 1.5:1.

[0315] The heat-sensitive coating suspension thus obtained is used to prepare a composite structure consisting of a paper support and a heat-sensitive color-forming layer.

[0316] Adhesives:

[0317] To prepare the self-adhesive thermal labels, the following commercial adhesives were used on the side of the paper carrier facing away from the thermal color-forming layer or on the second side of the carrier substrate:

[0318] - R5000N (Avery Dennison): An acrylic-based removable adhesive.

[0319] -S2200 (Avery Dennison): A permanent hot melt adhesive based on styrene-isoprene and PVC copolymer suitable for deep freeze applications.

[0320] - Technomelt PS 8746 (Henkel): a permanent hot melt adhesive based on synthetic rubber.

[0321] The thus obtained heat-sensitive recording material (ie, self-adhesive heat-sensitive label) was tested and evaluated as shown in the following table.

[0322] Optical density measurement:

[0323] A 6 cm wide strip was cut from the correspondingly prepared thermal recording material and printed using a GeBE Printer Lab GPT-10000 test printer (GeBE Elektronik und Feinwerktechnik GmbH, Germany) with a 305 dpi Kyocera print head at an applied voltage of 24 V and an output of 9.00 mJ / mm 2 Thermally printed checkerboard pattern at energy level and print speed of about 100 mm / s. The area of ​​each square in the checkerboard print pattern corresponds to 80 x 80 dots. The optical density (oD) shown in the table below was measured using a SpectroEye densitometer from X-Rite, where the uncertainty of the oD values ​​is estimated to be ≤ 2%. The deviation of the corresponding calculated percentage values ​​is ≤ ± 2 percentage points.

[0324] Relative print contrast determination

[0325] The relative print contrast is calculated based on the optical density value of the printed area (oDs) and the optical density value of the unprinted area (oDw) according to the following formula B, where s represents the black area and w represents the white area:

[0326] DK(%)=(oDs–oDw / oDs)x 100

[0327] (Formula B)

[0328] Thermal label paper adhesion stability test

[0329] According to the above measurement method, a piece of thermal recording material is measured and the optical density (oD) before storage is determined. Subsequently, the thermal recording material is stored between two glass slides at a temperature of 60°C and a pressure of 1350 N / m 2 Store under pressure, 50% relative humidity, and protected from light for two or four weeks.

[0330] After the storage period, the printed area was adjusted to room temperature and the optical density (oDs, at 9.00 mJ / mm 2 The optical density of the printed area (oDw) and the unprinted area (oDw) are averaged and the relative print contrast is calculated according to formula B.

[0331] Use 9.00mJ / mm 2 The optical density before and after storage under energy excitation is used to calculate the retained image stability according to the following formula A:

[0332] Image stability (%) = (optical density after storage / optical density before storage) x 100

[0333] (Formula A)

[0334] Evaluate:

[0335] The following table illustrates the results of image stability and print contrast measurements for a number of different thermal recording materials having a thermal color-forming layer on a first side of a carrier substrate and an adhesive layer on the side of the carrier substrate facing away from the first side.

[0336] The results given in the table are based on an analysis of image stability and print contrast for each thermal recording material, depending on the migration of adhesive layer components into the thermal color-forming layer, after a storage period of two or four weeks, respectively.

[0337] According to this table, the adhesive of the adhesive layer studied was the above-mentioned R5000N adhesive (Avery Dennison), S2200 adhesive (Avery Dennison), and Technomelt PS 8746 adhesive (Henkel).

[0338] According to the table, the compound 5-(N-3-methylphenyl-sulfonylamino)-[N',N"-bis(3-methylphenyl)]-isophthalamide (PF425), i.e., compound I in the table, was studied as a stabilizer for the heat-sensitive color-forming layer.

[0339] According to the table, the developer of the heat-sensitive color-forming layer studied is compound 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF-201), which includes the α crystal form (compound II) and the β crystal form (compound III) in the table.

[0340] According to the table, the developer of the heat-sensitive color-forming layer is also studied as compound N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304), which includes α crystal form (compound IV) and β crystal form (compound V) in the table.

[0341] See the table below. Table:

[0342]

[0343]

[0344]

[0345] As can be seen from the results shown in the table, the thermosensitive recording material according to the present invention exhibits the following advantageous properties.

[0346] First, it should be emphasized that in the comparative experiments for all the tested adhesives (R5000, S2200 and Technomelt), only the stabilizer 5-(N-3-methylphenyl-sulfonamide)-[N',N"-bis(3-methylphenyl)]-isophthalamide (PF425, i.e., compound I in the table) was used without adding the corresponding color developer (see compounds II, III, IV, V in the table). The image stability retained after two weeks was extremely low, which does not meet the requirements of the present invention.

[0347] Similarly, according to comparative experiments for all tested adhesives (R5000, S2200 and Technomelt), only the corresponding developer N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304, i.e., α-form IV and β-form V in the table) and the corresponding developer 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide (PF-201, i.e., α-form II and β-form III in the table) were used without adding the corresponding stabilizer (compound I).

[0348] For example, when adhesive R5000 is used, when only α-crystalline form IV or β-crystalline form V of N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304) is added, the image stability retained after two weeks is extremely low, only 10% or 7%, which is far below the lower limit of at least 35% retained image stability required by the present invention.

[0349] Likewise, in the case of using the adhesive R5000, when only compound II or III is added, the corresponding retained image stability measured after two weeks is also extremely low, at only 26% or 29%.

[0350] It can be seen from the corresponding comparative examples in the table that using only a stabilizer or only a corresponding developer is not sufficient to achieve at least 35% of the retained image stability that meets the requirements of the present invention.

[0351] Secondly, it is important to emphasize that for all tested adhesives (R5000, S2200 and Technomelt), the image stability retained after the two-week study period was significantly improved using a combination of a stabilizer and at least one developer according to the invention compared to stabilizer or developer alone.

[0352] For example, for adhesive R5000, when developer III is combined with stabilizer I, the image stability retained after two weeks can reach 38% to 51%, depending on the weight ratio, which is significantly higher than the corresponding image stability when using only stabilizer (16%) or only compound III (29%).

[0353] As can be seen from the table, all tested binders and developers showed similar effects.

[0354] Third, it is important to highlight that for all tested adhesives (R5000, S2200 and Technomelt), if the weight ratio of stabilizer to developer was increased, the image stability retained after the two-week study period was significantly improved in each case.

[0355] For example, for the adhesive R5000, when the developer IV and the stabilizer I are combined in a weight ratio of 1.5 parts of the developer IV to 1 part of the stabilizer I, the image stability retained after two weeks can reach 72%, which is a very excellent value.

[0356] In the case of using the S2200 binder, when the developer IV and the stabilizer I are combined in a weight ratio of 1.5 parts of the developer IV to 1 part of the stabilizer I, the image stability retained after two weeks can be as high as 75%, which is an extremely excellent value.

[0357] It can be seen from the table that by optimizing the weight ratio of the corresponding developer to the stabilizer, the image stability retained after two weeks for all tested adhesives and all tested developers can be optimized accordingly.

[0358] Thus, by combining a stabilizer with at least one developer in the heat-sensitive color-forming layer, a synergistic effect can be achieved with respect to retention of image stability after two weeks.

[0359] Fourth, it is important to emphasize that by optimizing the weight ratio of the respective developer to stabilizer, it is also possible to optimize the print contrast retained after the two-week study period.

[0360] For example, for adhesive R5000, when developer IV and stabilizer I are combined in a weight ratio of 1.5 parts developer IV to 1 part stabilizer I, the relative print contrast after two weeks can reach 91%, which is a very excellent value.

[0361] Thus, by combining a stabilizer with at least one developer in the heat-sensitive color-forming layer, a synergistic effect can be achieved with respect to retention of print contrast after two weeks.

Claims

1. A thermal recording material comprising: a carrier substrate having a first side and a second side facing away from the first side; a thermosensitive color-forming layer, arranged on the first surface of the carrier substrate, wherein the thermosensitive 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 side of the carrier substrate, wherein the adhesive layer comprises at least one adhesive; Wherein, the weight ratio of the stabilizer to the developer in the thermosensitive color-forming layer is selected so that: according to the stability test defined in the description, the migration of the components in the adhesive layer to the thermosensitive color-forming layer causes the image stability retained by the thermosensitive color-forming layer to reach at least 35% after two weeks; Wherein, the stabilizer comprises a compound of formula (I): Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the following group: C1-C8 alkyl, C5-C6 cycloalkyl; or a compound of formula (II): wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7 and -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and wherein Q comprises a single bond or a C1-C8 alkylene group, which may be branched or unbranched, and wherein, when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group comprises a main chain having one or more oxygen atoms between two carbon atoms; Wherein, the at least one developer comprises a compound of formula (NI): wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the group consisting of hydrogen, phenyl, benzyl and C1-C6 alkyl, wherein R5 is selected from C1-C6 alkyl, wherein n1 and n3 are independently selected from an integer ranging from 1 to 5, and wherein n2 is an integer ranging from 1 to 4; And / or wherein the at least one developer comprises a compound of formula (1): wherein R1 is selected from the group consisting of unsubstituted or substituted phenyl, naphthyl and C1-C 20 wherein X is selected from the group consisting of —C(═NH)—, —C(═S)—, and —C(═O)—, and wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12 Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that: if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl; if B is —O—, then R2 is not an alkyl.

2. The thermal recording material according to claim 1, characterized in that The stabilizer comprises a compound of formula (Ia): Or wherein the stabilizer comprises a compound of formula (Ib):

3. The heat-sensitive recording material according to claim 1 or 2, characterized in that The stabilizer comprises 5-(N-3-methylphenyl-sulfonylamino)-[N',N"-bis(3-methylphenyl)]-isophthalamide.

4. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The at least one developer comprises a compound of formula (NI), and wherein R1, R2 and R3 are selected to be hydrogen.

5. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The at least one developer comprises N-(2-(3-phenylureido)phenyl)benzenesulfonamide, preferably α-crystalline form and / or β-crystalline form of N-(2-(3-phenylureido)phenyl)benzenesulfonamide, in particular wherein the α-crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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, in particular wherein the β crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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, 31.3 and / or a melting point determined by DSC of 173°C to 174°C.

6. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The at least one developer comprises a compound of formula (1), wherein X is selected from —C(═O)—, wherein R1 is selected from substituted or unsubstituted phenyl, preferably C1-C3 alkyl-substituted phenyl, wherein R 2 wherein B is selected as —O—SO2—, and wherein R2 is selected as substituted or unsubstituted aryl, preferably phenyl substituted by a C1-C3 alkyl group.

7. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The at least one developer comprises 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide, preferably α-crystalline form and / or β-crystalline form of 4-methyl-N-(((3-(((4-methylphenyl)sulfonyl)oxy)phenyl)amino)carbonyl)benzenesulfonamide, in particular wherein the α-crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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, 21.6, 23.8, 24.7, 25.9, 26.8, 27.9, 28.1, 29. 0.9, 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, in particular wherein the β crystalline form is characterized by an X-ray diffraction pattern with a Bragg angle (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. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The weight ratio of the stabilizer to the 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.

9. The heat-sensitive recording material according to any one of the preceding claims, characterized in that Based on the total solid content of the thermosensitive color-forming layer, the weight of the stabilizer is 1wt.% to 10wt.%, wherein the weight is preferably 2wt.% to 8wt.%, more preferably 3wt.% to 6wt.%, and most preferably 4wt.%.

10. The heat-sensitive recording material according to any one of the preceding claims, characterized in that Based on the total solid content of the thermosensitive color-forming layer, the weight of the at least one color developer is 6wt.% to 35wt.%, wherein the weight is preferably 10wt.% to 30wt.%, more preferably 20wt.% to 30wt.%, and most preferably 24wt.%.

11. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The image stability retained by the heat-sensitive color-forming layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

12. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The adhesive comprises a pressure-sensitive adhesive and / or a heat-activated adhesive, wherein the adhesive is preferably a permanent hot melt adhesive based on styrene-isoprene and PVC copolymer, and / or wherein the adhesive is preferably a removable adhesive based on acrylate, and / or wherein the adhesive is preferably a permanent hot melt adhesive based on synthetic rubber.

13. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The adhesive comprises a permanent hot melt adhesive based on styrene-isoprene and PVC copolymer, and wherein, The weight ratio of the stabilizer to the 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.

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

15. The heat-sensitive recording material according to claim 13 or 14, characterized in that The image stability retained by the heat-sensitive color-forming layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

16. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The adhesive comprises an acrylate-based removable adhesive, and wherein the weight ratio of the stabilizer to the 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.

17. The heat-sensitive recording material according to claim 16, characterized in that The developer comprises an α-crystalline form of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

18. The heat-sensitive recording material according to claim 16 or 17, characterized in that: The image stability retained by the heat-sensitive color-forming layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

19. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The adhesive comprises a permanent hot melt adhesive based on synthetic rubber, and wherein, The weight ratio of the stabilizer to the 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.

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

21. The heat-sensitive recording material according to claim 19 or 20, characterized in that The image stability retained by the heat-sensitive color-forming layer after two weeks is at least 40%, preferably at least 45%, more preferably at least 50%, more preferably at least 55%, more preferably at least 60%, more preferably at least 65%, more preferably at least 70%, more preferably at least 75%, and most preferably at least 80%.

22. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The image stability was determined by using the printer at 9.00 mJ / mm 2 The printing pattern is thermally printed onto the thermal recording material at an energy level of 0.1% and a printing speed of about 100 mm / s, and the optical density of the printing pattern is measured with a densitometer, and then the thermal recording material is stored, and the optical density of the printing pattern is measured again with a densitometer after the thermal recording material has been stored for two weeks, wherein the image stability specifically corresponds to the quotient of the optical density of the printing pattern after the storage period and the optical density of the printing pattern before the storage period, in the unit of %.

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

24. The heat-sensitive recording material according to claim 23, characterized in that The print contrast retained after two weeks is determined by the following formula: DK (%) = (oDs-oDw / oDs) x 100, wherein the parameter oDs corresponds to the optical density of the printed pattern two weeks later, and wherein the parameter oDw corresponds to the optical density of the unprinted area of ​​the thermal recording material two weeks later.

25. The heat-sensitive recording material according to any one of the preceding claims, characterized in that The at least one color former is a triphenylmethane dye, a fluorane dye, an azaphthalide dye and / or a fluorene dye, preferably a fluorane dye.

26. The heat-sensitive recording material according to claim 25, characterized in that The fluoran dye is selected from the following group: 3-diethylamino-6-methyl-7-anilino fluoran, 3-(N-ethyl-N-4-toluidine)-6-methyl-7-anilino fluoran, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilino fluoran, 3-diethylamino-6-methyl-7-(2,4-dimethylanilino) fluoran, 3-pyrrolidinyl-6-methyl-7-anilino fluoran, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilino fluoran, 3-diethylamino-7-(3-trifluoromethylanilino) fluoran, 3-N-butylamino-6 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. The heat-sensitive recording material according to any one of the preceding claims, characterized in that Based on the total solid content of the thermosensitive color-forming layer, the weight portion of the at least one color-forming agent is 3wt.% to 30wt.%, wherein the weight portion is preferably 5wt.% to 20wt.%, particularly preferably 8wt.% to 15wt.%.

28. A method for preparing a heat-sensitive recording material, comprising the following method steps: providing a carrier substrate having a first side and a second side facing away from the first side; A coating suspension is applied to the first side of the carrier substrate, wherein The application suspension comprises at least one color former, at least one color developer and at least one stabilizer; drying the applied suspension to obtain a thermosensitive color-forming layer disposed on the first surface of the carrier substrate; applying an adhesive layer to the second side of the carrier substrate, The weight ratio of the stabilizer to the developer in the coating suspension is selected so that: according to the stability test defined in the specification, the migration of the components in the adhesive layer of the heat-sensitive recording material to the heat-sensitive color-forming layer of the heat-sensitive recording material makes the image stability of the heat-sensitive color-forming layer retained after two weeks reach at least 35%, Wherein, the stabilizer comprises a compound of formula (I): Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the following group: C1-C8 alkyl, C5-C6 cycloalkyl; or a compound of formula (II): wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7 or -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and wherein Q comprises a single bond or a C1-C8 alkylene group, which may be branched or unbranched, and wherein, when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group comprises a main chain having one or more oxygen atoms between two carbon atoms; Wherein, the at least one developer comprises a compound of formula (NI): wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the group consisting of hydrogen, phenyl, benzyl or C1-C6 alkyl, wherein R5 is selected from C1-C6 alkyl, wherein n1 and n3 are independently selected from an integer ranging from 1 to 5, and wherein n2 is an integer ranging from 1 to 4; And / or wherein the at least one developer comprises a compound of formula (1): Wherein, R1 is selected from the following group: unsubstituted or substituted phenyl, naphthyl or C1-C 20 wherein X is selected from the group consisting of —C(═NH)—, —C(═S)—, and —C(═O)—, and wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12 Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that: if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl; if B is —O—, then R2 is not an alkyl.

29. The method according to claim 28, characterized in that The drying of the adhesive layer is performed at a temperature of 60°C to 80°C, preferably at 70°C.

30. The method according to claim 28 or 29, characterized in that The method further comprises the additional method step after applying the adhesive layer: A release paper is applied to the adhesive layer, wherein the release paper is preferably designed as a siliconized release paper.

31. The method according to any one of claims 28 to 30, characterized in that Applying the adhesive layer comprises applying an adhesive dispersion and subsequently drying the adhesive dispersion, wherein the method further comprises the additional method step of: An additional release liner is applied to the second side of the carrier substrate, wherein the adhesive dispersion is applied to the additional release liner.

32. The method according to any one of claims 28 to 31, characterized in that The application of the coating dispersion to the first side of the carrier substrate and drying is performed before the application of the adhesive layer to the second side of the carrier substrate, or wherein the application of the adhesive layer to the second side of the carrier substrate is performed before the application of the coating dispersion to the first side of the carrier substrate and drying, wherein preferably, the application of the coating dispersion to the first side of the carrier substrate and drying is performed before the application of the adhesive layer to the second side of the carrier substrate.

33. The method according to any one of claims 28 to 32, characterized in that The coating dispersion is applied to the first side of the carrier substrate by curtain coating or by a doctor bar on the coated side of the carrier substrate covered with a pre-coated pigment layer, wherein preferably, the pre-coated pigment layer comprises calcined kaolin and a binder based on styrene-butadiene and / or based on polyvinyl alcohol (PVA) and / or starch, or comprises a mixture of organic pigments and inorganic pigments, wherein more preferably, the application amount of the pre-coated pigment layer is 2 g / m 2 Up to 12g / m 2 .

34. The method according to any one of claims 28 to 33, characterized in that The application amount of the applied dispersion is 3 g / m 2 and 5g / m 2 Between, preferably 3.6g / m 2 and 4.8g / m 2 between, and / or among, The adhesive dispersion was applied in an amount of 10 g / m 2 and 30g / m 2 Between, preferably 20g / m 2 .

35. A heat-sensitive recording material preparable by the method according to any one of claims 28 to 34.

36. Use of at least one stabilizer and at least one developer for a heat-sensitive recording material, the heat-sensitive recording material comprising: a carrier substrate having a first side and a second side facing away from the first side; a thermosensitive color-forming layer disposed on the first side of the carrier substrate, wherein the thermosensitive color-forming layer comprises at least one color former, at least one developer and at least one stabilizer; and an adhesive layer disposed on the second side of the carrier substrate, wherein the adhesive layer comprises at least one adhesive, wherein the weight ratio of the stabilizer to the developer in the thermosensitive color-forming layer is selected such that: according to the stability test defined in the specification, the migration of the components in the adhesive layer of the thermosensitive recording material to the thermosensitive color-forming layer of the thermosensitive recording material enables the image stability of the thermosensitive color-forming layer to be retained by at least 35% after two weeks, Wherein, the stabilizer comprises a compound of formula (I): Wherein, R and R1 are independently selected from the following groups: hydrogen, C1-C 18 Alkyl, C1-C8 alkoxy-C1-C8 alkyl and (R9)2N-C1-C8 alkyl, wherein R9 is selected from the group consisting of C1-C8 alkyl, C5-C6 cycloalkyl; and compounds of formula (II): wherein R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, C1-C8 alkyl, -NH-C(=O)-R7 and -C(=O)-NH-R7, wherein R7 is selected from C1-C8 alkyl or -C(=O)OR8, wherein R8 is selected from C1-C8 alkyl or halogen, or wherein R2 and R3, or R4 and R5 or both, or wherein R3 and R4, or R5 and R6 or both, or wherein R2 and R3 and R5 and R6 together form a hydrocarbon group having three or four carbon atoms, and wherein Q comprises a single bond or a C1-C8 alkylene group, which may be branched or unbranched, and wherein, when the C1-C8 alkylene group has two or more carbon atoms, the C1-C8 alkylene group comprises a main chain having one or more oxygen atoms between two carbon atoms; Wherein, the at least one developer comprises a compound of formula (NI): wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, nitro, C1-C6 alkyl, C1-C6 alkoxy, C2-C6 alkenyl, C1-C6 fluoroalkyl, N(R4)2, NHCOR5, optionally substituted phenyl and optionally substituted benzyl, wherein R4 is selected from the group consisting of hydrogen, phenyl, benzyl and C1-C6 alkyl, wherein R5 is selected from C1-C6 alkyl, wherein n1 and n3 are independently selected from an integer ranging from 1 to 5, and wherein n2 is an integer ranging from 1 to 4; And / or wherein the at least one developer comprises a compound of formula (1): Wherein, R1 is selected from the following group: unsubstituted or substituted phenyl, naphthyl or C1-C 20 Alkyl, wherein X is selected from the group consisting of —C(═NH)—, —C(═S)— or —C(═O)—, wherein A is selected from the group consisting of unsubstituted or substituted phenylene, naphthylene, C1-C 12 Alkylene and unsubstituted or substituted heterocyclic group, wherein B is selected from the group consisting of —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 selected from the group consisting of unsubstituted or substituted aryl, benzyl and C1-C 20 Alkyl, provided that: if B is not an —O—SO2— group, then R2 is unsubstituted or substituted phenyl, naphthyl or C1-C8 alkyl; if B is —O—, then R2 is not an alkyl.

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