Heat sensitive recording material

Abstract

Disclosed is a heat-sensitive recording material comprising: a strip-shaped substrate (1) having a front face and a rear face opposite the front face; a heat sensitive recording layer (3) disposed on the front face of the strip-shaped substrate (1), wherein the heat-sensitive recording layer (3) contains at least one dye precursor and at least one (colour) developer that is reactive with the at least one dye precursor; a front-face surface (6) of the heat sensitive recording material, which is designed to be dehesive with respect to adhesive layers (7) which can be applied to the rear face of the strip-shaped substrate (1). The disclosed heat-sensitive recording material is characterised in that, in order to form the dehesive front-face surface (6) thereof, said heat-sensitive recording material has at least one application (5), arranged above the heat-sensitive recording layer (3) and having at least one separating means, and has at least one diffusion layer (4) formed between the application (5) having at least one separating means and the heat-sensitive recording layer (3). Also disclosed are a method for producing such a heat-sensitive recording material and possibilities for the use thereof.

Description

[0001] The present invention relates to a heat-sensitive recording material comprising a web-shaped substrate and a heat-sensitive recording layer arranged on the front side of the web-shaped substrate, wherein this heat-sensitive recording layer contains at least one dye precursor and at least one (color) developer reactive with this dye precursor. Being reactive with a dye precursor, in the context of the present invention in all its proposed embodiments, means that this (color) developer reacts with this dye precursor upon sufficient external heat supply, forming a visually recognizable printed image. By design, the surface of the heat-sensitive recording material is non-adhesive with respect to adhesive layers that can be applied to the reverse side of the web-shaped substrate.

[0002] Heat-sensitive recording materials that react to external heat to form colors have been known for many years and enjoy continued popularity, partly due to the significant advantages they offer businesses issuing tickets, receipts, and admission tickets. Because the color-forming components—dye precursors and the (color) developers that react with heat (also called color acceptors)—are embedded within the recording material itself, thermal printers, which do not require toner or ink cartridges and therefore do not need regular maintenance, can be deployed in large numbers.

[0003] Particularly popular in this context are heat-sensitive recording materials that feature a recording layer on the front (whose functional components have already been discussed above) and an adhesive layer on the back, allowing users to employ them as self-adhesive tickets. This innovative technology has thus become widely established, especially in the retail sector – for example, for labeling self-weighing products – and in public transport – for example, as luggage stickers.

[0004] The adhesive layers on the back can be covered by a separate release paper until use; however, recording materials with front surfaces that are non-adhesive to the adhesive layers on the back are much more popular and practical to handle. In this case, the adhesive layers on the back are covered by the non-adhesive front surfaces of the recording material itself, which is wound onto a roll where the front and back sides meet, until use.

[0005] DE 44 25 737 A1 explains directly in its first paragraph that paper webs with non-adhesive properties can be coated with a silicone layer to produce so-called release papers. To prevent the undesirable penetration of the silicone coating, particularly aqueous and especially solvent-free silicone resins, into the paper, a paper web coated with a water glass layer is proposed for subsequent application of the silicone resins. The water glass coating proposed in this document is unsuitable for heat-sensitive recording materials. Furthermore, after extensive investigations, the inventors realized that even the most effective prevention of silicone penetration into a recording layer beneath the silicone coating is not conducive to the production of self-adhesive, heat-sensitive tickets.

[0006] Also with the aim of preventing the rather undesirable penetration of a silicone coating into a base paper, EP 2 239 368 A1 proposes coating the surface of the base paper followed by smoothing to a surface roughness of < 100 nm. This document also does not concern heat-sensitive recording materials, and its aim of preventing silicone penetration as effectively as possible is contrary to the ideas of the invention proposed here.

[0007] The subject of EP 0 780 241 B1 is a heat-sensitive recording material whose surface is particularly mechanically stable against various printing processes and offers advantages in terms of water and light resistance and graying. A heat-sensitive recording material proposed therein has a protective layer comprising a UV-curing resin and a copolymer resin, including a silicone component as the copolymerizing component. This document does not mention heat-sensitive recording materials for self-adhesive tickets, even though it has proven suitable for this application.

[0008] In this context, EP 1 637 339 B1 proposes a heat-sensitive recording material comprising a substrate, a heat-sensitive recording layer, and a protective layer. The protective layer includes, in addition to a binder resin, filler, and crosslinking agent, a release agent. This release agent is introduced as a spherical and particulate silicone compound with a specific formula. A disadvantage of this known proposal is the complex and expensive manufacturing process involving the substrate, recording layer, and final protective layer. Furthermore, the protective layer, due to its filler and binder components, reduces the dynamic and static sensitivity of the known heat-sensitive recording material to externally applied heat, thus hindering the formation of a visually perceptible printed image.

[0009] Documents also relevant for this registration are WO 2013 / 069581 A1 and DE 198 06 433 A1.

[0010] The object of the present invention is therefore to provide a heat-sensitive recording material with convincing sensitivity to applied external heat for the formation of a visually recognizable printed image, which can be produced at moderate manufacturing costs and designed as a self-adhesive ticket with a back adhesive layer without additional release paper.

[0011] To solve the problem, a heat-sensitive recording material is proposed with the features as defined in claim 1.

[0012] Our own investigations have surprisingly revealed that the diffusion layer (4) makes a significant contribution to the layer adhesion between the release agent-containing substrate (5) and the heat-sensitive recording layer (3). Without the diffusion layer (4), problems arose in the layer adhesion between the release agent-containing substrate (5) and the heat-sensitive recording layer (3), leading to problems in the use of the recording material.

[0013] As a ready-to-use recording material, it preferably has an adhesive layer (7) arranged on the back of the web-shaped substrate (1). Since both the dynamic and static sensitivity of the heat-sensitive recording layer to applied external heat for producing a visually recognizable print image is reduced by the application (5) containing a release agent, although not to the same extent as with a filler-containing protective layer, but still at least clearly noticeable, it is advantageous in the sense of the present invention if the heat-sensitive recording material proposed herein has an intermediate layer (2) comprising hollow body pigments positioned between the web-shaped substrate (1) and the heat-sensitive recording layer (3).

[0014] According to the invention, a method is a method wherein the method includes at least the method steps as defined in claim 12.

[0015] According to the invention, a proportion of 5 wt.% to 50 wt.% of the silicone component, preferably 6 to 45 wt.%, particularly preferably 7 to 4 wt.%, most preferably 8 to 32 wt.%, of the applied third coating composition diffuses into the side of the heat-sensitive recording layer (3) facing the applied third coating composition.

[0016] It can be inferred from the preceding paragraphs that the diffusion layer (4) is formed by the diffusion of at least some of the release agent from the coating (5) into the upper region of the heat-sensitive recording layer (3), which is oriented towards the coating (5) and was applied prior to the coating (5). For this purpose, the heat-sensitive recording layer (3) made from the second coating composition is first applied and dried either on the web-shaped substrate (1) or on the previously applied and fully formed intermediate layer (2) containing hollow pigments. A previously prepared third coating composition is then preferably applied to the fully formed heat-sensitive recording layer (3) using an anilox roller applicator or a five-roller applicator.This third coating composition contains at least one release agent, wherein, according to the invention, the release agent is a silicone component. Most preferably, the formulation for the third coating composition additionally contains the silicone component. at least one adhesion promoter as a component for manipulating the release force effect of the release agent, at least one substance that reacts cross-linking under the influence of high-energy radiation, in particular ultraviolet radiation, and at least one photoinitiator.

[0017] In a preferred embodiment of the present invention, the coating composition and / or the silicone component has a viscosity of 50 to 1,000 mPas, preferably 50 to 100 mPas or 500 to 1,000 mPas. It is particularly preferred that the silicone component is an aqueous emulsion or a UV-curing silicone component, wherein the cross-linking is radical (preferably under a nitrogen protective atmosphere) or cationic. In the case of an aqueous silicone emulsion, the coating (5) can be applied by drying (and optionally cross-linking) the aqueous silicone emulsion, wherein the drying is preferably carried out gently in a temperature range between 40 and 60 °C.In the context of the present invention, it is particularly preferred if the silicone component is a UV-curing component that crosslinks via radical or cationic induced irradiation (after appropriate exposure to high-energy radiation, e.g., UV radiation). In the context of the present invention, it is preferred if the silicone component is not a thermally crosslinking silicone component or a silicone component dissolved in an organic solvent.

[0018] After application of the third coating composition to the fully formed heat-sensitive recording layer (3), a portion of the third coating composition diffuses into the upper region of the formed heat-sensitive recording layer (3), wherein a proportion of 5 to 50 wt.% of the total release agent of the third coating composition, preferably a proportion of 6 to 45 wt.%, particularly preferably a proportion of 7 to 40 wt.%, and most preferably a proportion of 8 to 32 wt.%, diffuses into the upper region of the formed heat-sensitive recording layer (3). By drying orIn the case of a radiation-crosslinking third coating composition, irradiation of the heat-sensitive recording material, including the applied third coating composition, with high-energy radiation results in the formation of the coating (5) containing a release agent. The anchoring of this coating to the underlying heat-sensitive recording layer (3) is ensured by the portion of the third coating composition that diffuses into the recording layer. The upper region of the heat-sensitive recording layer (3), containing the diffused portion of the third coating composition, then forms the diffusion layer (4) through the drying or crosslinking process described above.

[0019] In various investigations carried out in connection with the present invention, the inventors found that for the coating (5) containing the release agent, an area-related mass in the range of 0.5 g / m² to 3 g / m², preferably 0.8 g / m² to 1.85 g / m², and particularly preferably 0.85 g / m² to 1.35 g / m², is particularly suitable, while at the same time the diffusion layer (4) as the upper region in the heat-sensitive recording layer (3) with a preferred thickness of 0.2 µm to 0.8 µm, preferably 0.2 µm to 0.5 µm, in which a portion of the third coating composition has diffused, with a preferred calculated area-related mass for the diffusion layer (4) of 0.15 g / m² to 0.65 g / m², is particularly suitable. 2< , was identified as optimum.

[0020] The binders and pigments that are preferably incorporated into the heat-sensitive recording layer (3) play an important role in influencing the amount of the diffusing portion of the third coating composition into the heat-sensitive recording layer (3). Firstly, it has been found to be very helpful and therefore preferred if the heat-sensitive recording layer (3) contains at least one preferably inorganic pigment selected from the list, comprising: Kaolinite (Kaolin), magnesium silicate hydrate (talc), aluminum hydroxide, calcium carbonate, silicon dioxide (silica).

[0021] It is particularly preferred if the inorganic pigment is platelet-shaped, as is the case, for example, with kaolinite and talc. Kaolinite and talc are therefore particularly preferred as inorganic pigments. It is also particularly preferred if the inorganic, platelet-shaped pigment (especially kaolinite and talc) has an aspect ratio (also called "shape factor") of 5 to 100, preferably 15 to 100, and particularly preferably 20 to 100. In a preferred embodiment, the aspect ratio of the inorganic pigment is greater than 20. The aspect ratio is the quotient between the diameter and the thickness of the platelet of the inorganic pigment before mixing with the other components. An aspect ratio of 20 means that the diameter of the platelet is 20 times larger than its thickness.

[0022] With regard to the amount of pigment in the heat-sensitive recording layer (3), a range of 8 to 18 wt.% (atro) based on the total weight of the heat-sensitive recording layer (3) is considered particularly suitable, which is narrowed downwards by the increasing risk of possible thermal printhead deposits and upwards by an increasing reduction in sensitivity to the heat of the thermal printheads that causes the print image.

[0023] Due to the hydrophobic properties of silicone as a release agent in the third coating composition, which diffuses into the heat-sensitive recording layer (3), the heat-sensitive recording layer (3) contains at least one hydrophilic binder. Particularly preferred are binders selected from the list comprising polyvinyl alcohol, styrene-butadiene latex, styrene-acrylate latex, starch, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, fully saponified polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl alcohol-co-ethylene copolymer, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diaceto group-modified polyvinyl alcohol, silanol group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, epoxy group-modified polyvinyl alcohol, chitosan, polyacrylic acid, polymethacrylic acid, and polyacrylic acid esters.Polymethacrylic acid ester, sodium polyacrylate, polyethylene terephthalate, polybutylene terephthalate, acrylic resin, furan resin, ketone resin, oxybenzoyl polyester, polyacetal, polyether ketone, polyethersulfone, polyamide, polyamide-imide, polyaminobismaleimide, polymethylpentene, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfone, polysulfone, polyallylate, polyallyl sulfone, polybutadiene, polycarbonate, polyethylene, polypropylene, polystyrene, polyvinyl acetate, acrylonitrile / butadiene copolymer, and acrylamide / acrylic acid ester / methacrylic acid terpolymer. Binders selected from the following list are particularly preferred: Ethylene-vinyl acetate copolymer, polyvinyl alcohol, styrene-butadiene latex, styrene-acrylate latex, starch, methylcellulose, polyvinyl alcohol-co-ethylene copolymer.

[0024] It is preferred that the polyvinyl alcohol used as a binder has a degree of saponification of more than 97 mol%, preferably a degree of saponification of 97 mol% to about 99 mol%, or alternatively of more than 99 mol%, and a viscosity of more than 7 mPas, preferably more than 12 mPas, and particularly preferably more than 15 mPas, as measured according to DIN 53015 on an aqueous solution with 4 wt% at 20 °C. Particularly preferred is a polyvinyl alcohol (PVA) 15-99, preferably with a degree of saponification of 99 to 99.8 mol%, or a corresponding PVA with a higher degree of saponification and / or higher viscosity than PVA 15-99.

[0025] In a preferred embodiment of the present invention, the binder is a crosslinking (self- or crosslinking) and / or modified polyvinyl alcohol, wherein the modified polyvinyl alcohol is preferably diacetone-modified polyvinyl alcohol, silanol group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol and / or a polyvinyl alcohol-co-ethylene copolymer, preferably diacetone-modified polyvinyl alcohol or silanol group-modified polyvinyl alcohol and / or a polyvinyl alcohol-co-ethylene copolymer.

[0026] In particular, when a non-self-crosslinking polyvinyl alcohol is used as a binder, it is preferred in a preferred embodiment of the present invention if the heat-sensitive recording layer (3) contains at least one crosslinking agent selected from the list comprising: boric acid, polyamine, epoxy resin, dialdehyde, formaldehyde oligomers, epiochlorohydrin resin, adipic acid dihydrazide, dimethyl urea, melamine formaldehyde, alone or in mixtures with each other.

[0027] In one embodiment of the present invention, ethylene-vinyl acetate copolymer is considered as the sole binder or in combination with polyvinyl alcohol as a particularly preferred binder, which, based on the total weight of the heat-sensitive recording layer (3), is incorporated into the heat-sensitive recording layer (3) in a range of 10 to 20 wt.%.

[0028] The proposed method involves preparing a second coating composition to form a heat-sensitive recording layer (3) arranged on the front side of the web-shaped substrate (1), for which the use of container scales for the precise supply and dosing of bulk components and liquid components is particularly suitable.

[0029] The second coating composition provided for the formation of the heat-sensitive recording layer (3) preferably comprises at least one (color) developer selected from the list, comprising: 4-[(4-(1-methylethoxy)phenyl)sulfonyl]-phenol, N-(p-toluenesulphonyl)-N'-(3p-toluenesulphonyl-oxy-phenyl)-urea, diisopropyldiphenol, 4,4-sulfonyldiphenol and N-[2-(3-phenylureido)phenyl]benzenesulfonamide, of which to a very special degree N-(p-toluenesulphonyl)-N'-(3-p-toluenesulphonyl-oxy-phenyl)-urea and N-[2-(3-phenylureido)phenyl]benzenesulfonamide are preferred. The aforementioned (color) developers ensure, on the one hand, sufficient stability with respect to the components of the adhesive layer (7), the diffusion of which into the heat-sensitive recording layer (3) can never be completely prevented. On the other hand, they also ensure sufficient sensitivity to applied external heat to produce a visually recognizable printed image.

[0030] The heat-sensitive recording material preferably comprises, as dye precursors in the second coating composition for the formation of the heat-sensitive recording layer (3), those selected from the list, comprising 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-( N -Methyl- N -propyl)amino-6-methyl-7-anilinofluoran, 3-(N -Ethyl-N-isoamyl)amino-6-methyl-7-anilinofluoran, 3-( N -Methyl- N -cyclohexyl)amino-6-methyl-7-anilinofluoran, 3-( N -Ethyl- N -tolyl)amino-6-methyl-7-anilinofluoran, 3-( N -Ethyl- N -tetrahydrofuryl)amino-6-methyl-7-anilinofluoran, 3-Di- n -pentyl-amino-6-methyl-7-anilinofluoran, 3-Di- n -butylamino-7-(2-chloranilino)fluoran, 3-Diethylamino-7-(2-chloranilino)fluoran, 3-Diethylamino-6-methyl-7-xylidinofluoran, 3-Diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-( N -Cyclopentyl- N -ethyl)amino-6-methyl-7-anilinofluoran, 3(N-Ethyl-4-toluidino)6-methyl-7-(4-toluidino)fluoran, 3-( N-Methyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluorane), 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-(4-n-butyl-phenylamino)fluorane, and 3-piperidino-6-methyl-7-anilinofluorane. Particularly preferred are those selected from the list comprising 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-( N -Methyl- N -propyl)amino-6-methyl-7-anilinofluoran, 3-( N -Ethyl- N -isoamyl)amino-6-methyl-7-anilinofluoran, 3-( N -Methyl- N -cyclohexyl)amino-6-methyl-7-anilinofluoran, 3-( N -Ethyl- N -tolyl)amino-6-methyl-7-anilinofluorane and 3-( N -Ethyl- N -tetrahydrofuryl)amino-6-methyl-7-anilinofluorane. 3-Dibutylamino-6-methyl-7-anilinofluorane – also known as ODB-2 – is particularly preferred.

[0031] The second coating composition for forming the heat-sensitive recording layer (3) may include at least one sensitizer selected from the list comprising N-hydroxymethylstearic acid amine to increase the thermal response sensitivity. N -Stearylstearic acid amide, ethylenebisstearic acid amide, N -stearylurea, benzyl-2-naphthyl ether, m-Terpenyl, 4-Benzybiphenyl, 1,2-Bis(3-methylphenoxy)ethane, 1,2-Diphenoxyethane, 2,2'-Bis(4-methoxyphenoxy) diethyl ether, α,α'-Diphenoxyxylene, Bis(4-methoxyphenyl) ether, Diphenyl adipate, Dibenzyl oxalate, Bis(4-chlorobenzyl) oxalate ester, Dibenzyl terephthalate, Benzyl paraben, Phenylbenzenesulfonate ester, 4,4'-Diallyloxydiphenyl sulfone, Diphenyl sulfone, 4-Acetylacetophenone, Acetoacetic anilides, Fatty acid anilides, Salicylic anilide, Stearamide, Dimethyl sulfone, 2-(2H-benzotriazol-2-yl)-p-cresol, and Dimethyl terephthalate. Preferably, the second coating composition contains at least one sensitizer selected from the list comprising benzyl-2-naphthyl ether, 1,2-bis(3-methylphenoxy)ethane, and 1,2-diphenoxyethane. According to a first preferred embodiment, these sensitizers are each used alone, that is, not in combination with the other sensitizers mentioned in the preceding list.According to a second, equally preferred embodiment, at least two sensitizers selected from the above list are incorporated into the second coating composition.

[0032] Suitable coating devices for applying the second coating composition to form the heat-sensitive recording layer (3) include, in particular, roller squeegees, knife squeegees, curtain coaters, or air brushes. The mass per unit area of ​​the heat-sensitive recording layer (3), including the preferred calculated mass per unit area for the diffusion layer (4) of 0.15 g / m²< to 0.65 g / m²<, is between 2.4 and 6.2 g / m²<, preferably between 2.5 and 6.2 g / m²<, and even better between 2.5 and 4.9 g / m²<.

[0033] To improve both the dynamic and static sensitivity of the heat-sensitive recording material proposed here, the material preferably includes an intermediate layer (2) containing hollow pigments positioned between the web-shaped substrate (1) and the heat-sensitive recording layer (3), as already described earlier. The importance of the organic hollow pigments in the intermediate layer (2) is due to the fact that such organic pigments are particularly conducive to a high heat reflectivity of the intermediate layer (2). The hollow pigments contain air within them, which acts as a good thermal insulator. The intermediate layer (2), thus optimized as a heat-reflecting layer, specifically enhances the heat sensitivity of the recording layer (3).

[0034] In addition to the organic hollow-body pigments, the intermediate layer (2) particularly preferably also contains inorganic pigments, wherein the inorganic pigments are selected individually or in combination from the list, comprising: natural and calcined kaolin, silicon dioxide, and especially bentonite, calcium carbonate, and aluminum hydroxide, and especially boehmite. The thermal head, which triggers the color-forming reaction of the dye precursors with the (color) developers in the heat-sensitive recording layer (3), causes waxy components in the recording layer (3) to melt. The preferably incorporated inorganic pigments of the intermediate layer (2) also cause absorption of this melt. It is particularly advantageous if the inorganic pigments of the intermediate layer (2) exhibit an oil absorption of at least 80 cm³ / 100 g and even better of 100 cm³ / 100 g, determined according to the Japanese standard JIS K 5101.The inorganic pigments mentioned above meet this requirement.

[0035] The ratio of the total organic hollow-body pigments to the total inorganic pigments within the intermediate layer (2) is a compromise between the effects of the two pigment types, which is particularly advantageous when the pigment mixture consists of 5 to 30 wt.%, or preferably 8 to 20 wt.%, of organic pigment and 95 to 70 wt.%, or preferably 92 to 80 wt.%, of inorganic pigment. Pigment mixtures of different organic and / or different inorganic pigments are conceivable.

[0036] In addition to organic hollow-body pigments and optionally also inorganic pigments, the intermediate layer (2) contains at least one binder, preferably based on a synthetic polymer, with styrene-butadiene latex, for example, yielding particularly good results. The use of a synthetic binder with the addition of at least one natural polymer, such as preferably starch, represents a particularly suitable embodiment. Furthermore, in the course of tests with various organic and inorganic pigments, it was found that a binder-pigment ratio within the intermediate layer of between 3:7 and 1:9, in each case based on wt.%, represents a particularly suitable embodiment.

[0037] Preferably, the first coating composition for forming the intermediate layer (2) is applied using an equalizing coating process selected from the list, including: roller coating, coating knife coating, and (roller) doctor blade coating. Particularly when using one of these coating processes, the intermediate layer (2) can make a positive contribution to equalizing the substrate surface, thereby reducing the amount of the second coating composition required to form the heat-sensitive recording layer (3). The subsequent drying of the coating composition for forming the intermediate layer (2) is usually carried out by applying heat, as is done using hot air drying dryers or contact dryers. A combination of hot air drying dryers and contact dryers has also proven effective.For the area-related mass of the intermediate layer (2), a preferred range between 5 and 20 g / m 2< and even better between 7 and 12 g / m 2< has proven effective.

[0038] In one embodiment of the present invention, instead of the intermediate layer (2) having hollow body pigments, an intermediate layer is used between the web-shaped substrate (1) and the heat-sensitive recording layer (3) which does not have hollow body pigments but inorganic pigments, wherein the inorganic pigments are preferably selected individually or in combination with each other from the list comprising: natural or calcined kaolin, silicon dioxide and here especially bentonite, calcium carbonate and aluminum hydroxide and here especially boehmite.

[0039] Although not limited to paper as a web-like substrate (1), paper, and specifically untreated coated base paper, is the substrate that has become established on the market, also due to its good environmental compatibility and recyclability, and is preferred in the context of the invention. Untreated coated base paper is understood to mean coated base paper that has not been treated in a size press or coating device. For the purposes of the invention, films made of, for example, polypropylene or polyolefin, and papers coated with polyolefin, are equally suitable as web-like substrates (1), without this being an exclusionary characteristic.

[0040] The information given in the description and claims regarding mass per unit area, weight percent (wt%), and parts by weight (wt%) refers to the "atro" weight, i.e., absolutely dry parts by weight. In the descriptions of the organic pigments of the pigment-containing intermediate layer, the corresponding figures are calculated from the "lutro" weight, i.e., air-dried parts by weight, less the weight of water around and within the pigments in their delivered form.

[0041] Another aspect of the present invention is the use of a heat-sensitive recording material according to the invention as a self-adhesive ticket, self-adhesive admission ticket, self-adhesive receipt, self-adhesive label or self-adhesive admission tickets.

[0042] Another aspect described in the present text is a heat-sensitive recording material produced according to a method according to the invention.

[0043] Within the scope of the present invention, several of the aspects designated as preferred above are preferably implemented simultaneously; in particular, the combinations of such aspects and the corresponding features resulting from the attached claims are preferred.

[0044] The invention will be further illustrated by the following examples: Example 1:

[0045] Various heat-sensitive recording materials with different areal masses of 2.4 g / m², 2.5 g / m², 3.0 g / m², 4.0 g / m², 5.0 g / m², and 6.2 g / m² are produced. The carrier paper described in Example 2, with an areal mass of 64 g / m², is used as the web-like substrate (backing paper). The aqueous coatings used for this heat-sensitive recording layer (3) contain the following components according to the formulations shown in Table 1: Table 1: Values ​​in wt.% (atro), based on the total weight of the heat-sensitive recording layer Dye precursor 3-dibutylamino-6-methyl-7-anilinofluorane (ODB-2) 9 9 9 (Color) developer N-(p-toluensulphonyl)-N'-3-(p-toluensulphonyl-oxyphenyl)-urea (Pergafast ® < 201 (BASF)) 20 20 20 sensitizer Benzyl 2-naphthyl ether (BNE) 16 16 1,2-Diphenoxyethane 16 binder Polyvinyl alcohol 15 Polyvinyl alcohol-co-ethylene copolymer (EVOH) 15 15 Cobinder Acrylate copolymers 10 10 Methylcellulose 2 2 pigment Talc (platelet-shaped with an aspect ratio of 25) 16 16 88

[0046] A heat-sensitive recording layer with a mass per unit area of ​​2.5 g / m² is applied to this heat-sensitive recording layer using a roller squeegee applicator. The aqueous coating compound used for this purpose contains the following components according to the formula shown in Table 2. Example 2:

[0047] A paper with a basis weight of 64 g / m² is produced on a Fourdrinier paper machine from bleached and ground hardwood and softwood pulps, with the addition of 0.8 wt% AKD sizing as bulk sizing, based on the total solids content (atro) of the pulp supplied to the paper machine, as well as other usual additives.

[0048] On the front side, a calcined kaolin as pigment, styrene-butadiene latex as binder and, in addition to other additives, starch as a cobinder intermediate layer with a mass per unit area of ​​9 g / m² is applied using a coating knife.

[0049] A heat-sensitive recording layer with a mass per unit area of ​​2.5 g / m² is applied to this pigmented intermediate layer using a roller squeegee. The aqueous coating compound used contains the following components according to the formula shown in Table 2: Table 2: Values ​​in wt.% (atro), based on the total weight of the heat-sensitive recording layer Dye precursor 3-dibutylamino-6-methyl-7-anilinofluorane (ODB-2) 9 (Color) developer N-(p-toluensulphonyl)-N'-3-(p-toluensulphonyl-oxyphenyl)-urea (Pergafast ® < 201 (BASF)) 20 sensitizer Benzyl 2-naphthyl ether (BNE) 16 binder Polyvinyl alcohol-co-ethylene copolymer (EVOH) 15 Cobinder Acrylate copolymers 10 Methylcellulose 2 pigment Talc (platelet-shaped with an aspect ratio of 25) 16 88

[0050] Other components of the heat-sensitive recording layer, not specified as a percentage and based on the total weight in wt.% (atro), include dispersants, defoamers, optical brighteners, thickeners, waxes and crosslinking agents.

[0051] After the application of the heat-sensitive recording layer, it is dried and smoothed, with a value of 500 Bekk / sec (DIN ISO 53107) being measured for the front surface smoothness.

[0052] The manufactured web-shaped substrate with an intermediate layer and a heat-sensitive recording layer is coated on the front side (onto the heat-sensitive recording layer) using an anilox roller applicator with a standard UV-curing, radical-curing silicone system. The solvent-free Evonik standard silicone system used for this purpose contains a formulation shown in Table 3. The silicone application rate is approximately 1.2 g / m². Table 3: RC-711 silicone acrylate 25 parts by weight RC-902 silicone acrylate 50 parts by weight RC-1772 Silicone acrylate (mixture with matting agent) 25 parts by weight TEGO Photoinitiator A-18 2 parts by weight

[0053] The resulting coating containing the release agent is cured with a UV lamp (80 W / cm) under a protective atmosphere of nitrogen.

[0054] The invention yields a heat-sensitive recording material in which the release agent-containing layer does not separate from the heat-sensitive recording layer. Even after storage for 30 days, the release agent-containing layer cannot be separated from the heat-sensitive recording layer. The resulting recording material exhibits good sensitivity. Example 3:

[0055] Example 2 was repeated, except that the composition of the pigmented intermediate layer was changed. The changed composition of the pigmented intermediate layer is given in Table 4. Table 4: Water 100 parts by weight 30% dispersion of fine hollow particles (particle size: 0.45 µm) 300 parts by weight 25% solution of oxidized starch 24 parts by weight 48% latex (glass transition temperature: 0°C) 25 parts by weight

[0056] The invention yields a heat-sensitive recording material in which the release agent-containing layer does not separate from the heat-sensitive recording layer. Even after storage for 30 days, the release agent-containing layer cannot be separated from the heat-sensitive recording layer. The resulting recording material exhibits very good sensitivity. Example 4:

[0057] An adhesive layer was produced on the reverse side of the web-shaped substrate of the heat-sensitive recording layer produced in Example 2 by applying a polyacrylic resin adhesive.

[0058] The web-shaped substrate was then rolled up so that the adhesive layer lay on the release agent-containing layer. Even after storage of 30 days, individual layers of the heat-sensitive recording material can be unrolled without the release agent-containing layer separating from the heat-sensitive recording layer or leaving any adhesive residue on the release agent-containing layer. Example 5:

[0059] An adhesive layer was produced on the reverse side of the web-shaped substrate of the heat-sensitive recording layer produced in Example 3 by applying a polyacrylic resin adhesive.

[0060] The web-shaped substrate was then rolled up so that the adhesive layer lay on the release agent-containing layer. Even after storage of 30 days, individual layers of the heat-sensitive recording material can be unrolled without the release agent-containing layer separating from the heat-sensitive recording layer or leaving any adhesive residue on the release agent-containing layer. Glossary :

[0061] (1) Substrate (2) Intermediate layer containing hollow body pigments (3) Heat-sensitive recording layer (4) Diffusion layer (5) Release agent coating (6) Front surface (7) Adhesive layer

Claims

1. A heat-sensitive recording material - having a web-shaped substrate (1), comprising a front side and a reverse side opposite the front side, - having a heat-sensitive recording layer (3) disposed to the front side of the web-shaped substrate (1), this heat-sensitive recording layer (3) comprising at least one dye precursor and at least one (color) developer which is reactive with this at least one dye precursor, and wherein the heat-sensitive recording layer (3) comprises at least one platelet-shaped pigment and at least one hydrophilic binder, - having a front-side surface (6) of the heat-sensitive recording material that is formed dehesively with respect to layers (7) of adhesive which can be applied to the reverse side of the web-shaped substrate (1), wherein the heat-sensitive recording material, for the formation of its dehesive front-side surface (6), • comprises a furnish (5) which is disposed above the heat-sensitive recording layer (3) and comprises at least one release agent, the furnish (5) comprising, as the at least one release agent, a silicone component, and • a diffusion layer (4), which is formed between the at least one release agent-comprising furnish (5) and the heat-sensitive recording layer (3), the diffusion layer (4) being formed by areal diffusion of parts at least of the release agent from the furnish (5) into the upper region, oriented toward the furnish (5), of the heat-sensitive recording layer (3) applied before the application of the furnish (5), a fraction of the entirety of the release agents of the furnish (5) that diffuses into the upper region of the heat-sensitive recording layer (3) formed being from 5 to 50 wt%.

2. The heat-sensitive recording material as claimed in claim 1, characterized in that a fraction of 6 to 45 wt%, preferably 7 to 40 wt%, more preferably 8 to 31 wt% of the entirety of the release agents of the furnish (5) diffuses into the upper region of the heat-sensitive recording layer (3) formed.

3. The heat-sensitive recording material as claimed in either of claims 1 and 2, characterized in that the platelet-shaped pigment has an aspect ratio of 5 to 100, preferably of 15 to 100, especially preferably of 20 to 100.

4. The heat-sensitive recording material as claimed in any of claims 1 to 3, characterized in that the furnish (5) is UV-crosslinking.

5. The heat-sensitive recording material as claimed in any of claims 1 to 4, characterized in that the heat-sensitive recording material has a layer (7) of adhesive disposed on the reverse side of the web-shaped substrate (1).

6. The heat-sensitive recording material as claimed in any of claims 1 to 5, characterized in that the heat-sensitive recording material has an interlayer (2) comprising hollow pigments and positioned between the web-shaped substrate (1) and the heat-sensitive recording layer (3).

7. The heat-sensitive recording material as claimed in any of claims 1 to 6, characterized in that the heat-sensitive recording layer (3) comprises at least one (color) developer selected from the list encompassing: - 4-[(4-(1-methylethoxy)phenyl)sulfonyl]phenol, - N-(p-toluenesulfonyl)-N'-3-(p-toluenesulfonyloxyphenyl) urea, - diisopropyldiphenol, - 4,4-sulfonyldiphenol, - N-[2-(3-phenylureido)phenyl]benzenesulfonamide.

8. The heat-sensitive recording material as claimed in claim 7, characterized in that the heat-sensitive recording layer (3) comprises at least one (color) developer selected from the list encompassing: - N-(p-toluenesulfonyl)-N'-3-(p-toluenesulfonyloxyphenyl) urea, - N-[2-(3-phenylureido)phenyl]benzenesulfonamide.

9. The heat-sensitive recording material as claimed in any of claims 1 to 8, characterized in that the heat-sensitive recording layer (3) comprises as dye precursor 3-dibutylamino-6-methyl-7-anilinofluoran.

10. The heat-sensitive recording material as claimed in claim 1, characterized in that the heat-sensitive recording layer (3) comprises as binder at least one component selected from the list encompassing: - ethylene-vinyl acetate copolymer - polyvinyl alcohol - styrene-butadiene latex - styrene-acrylate latex - starch - methylcellulose - polyvinyl alcohol-co-ethylene copolymer.

11. The heat-sensitive recording material as claimed in any of claims 1 to 10, characterized in that the heat-sensitive recording layer (3) comprises at least one pigment selected from the list encompassing: - kaolinite (kaolin) - magnesium silicate hydrate (talc) - aluminum hydroxide - calcium carbonate - silicon dioxide (silica).

12. A method for producing a heat-sensitive recording material - having a web-shaped substrate (1), comprising a front side and a reverse side opposite the front side, - having a heat-sensitive recording layer (3) disposed to the front side of the web-shaped substrate (1), this heat-sensitive recording layer (3) comprising at least one dye precursor and at least one (color) developer which is reactive with this at least one dye precursor, - having a front-side surface (6) of the heat-sensitive recording material that is formed dehesively with respect to layers (7) of adhesive which can be applied to the reverse side of the web-shaped substrate (1), wherein the heat-sensitive recording material, for the formation of its dehesive front-side surface (6), • comprises a furnish (5) which is disposed above the heat-sensitive recording layer (3) and comprises at least one release agent, the furnish (5) comprising, as the at least one release agent, a silicone component, and • a diffusion layer (4), which is formed between the at least one release agent-comprising furnish (5) and the heat-sensitive recording layer (3), the diffusion layer (4) being formed by areal diffusion of parts at least of the release agent from the furnish (5) into the upper region, oriented toward the furnish (5), of the heat-sensitive recording layer (3) applied before the application of the furnish (5), a fraction of the entirety of the release agents of the furnish (5) that diffuses into the upper region of the heat-sensitive recording layer (3) formed being from 5 to 50 wt%, the method comprising at least the method steps of: - forming a web-shaped substrate (1), having a front side and a reverse side opposite the front side, - optionally: • providing a first coating composition, this first coating composition comprising at least hollow pigments, • applying the provided first coating composition to form an interlayer (2) comprising hollow pigments, • drying the first coating composition, - providing a second coating composition, this second coating composition comprising at least one dye precursor and at least one (color) developer which is reactive with this at least one dye precursor, - applying the provided second coating composition to form a heat-sensitive recording layer (3) disposed to the front side of the web-shaped substrate (1), - drying the second coating composition, - providing a third coating composition, this third coating composition comprising at least one release agent, - applying the provided third coating composition, - forming a diffusion layer (4) by areal diffusion of parts at least of the release agent from the applied third coating composition into the upper region of the heat-sensitive recording layer (3) formed, wherein an amount of 5 to 50 wt% of the entirety of the release agents of the third coating composition diffuses into the upper region of the heat-sensitive recording layer (3), - drying and / or crosslinking the third coating composition to form the furnish (5) comprising a release agent, - optionally: • providing a fourth coating composition, • applying the provided fourth coating composition to form a layer (7) of adhesive disposed on the reverse side of the web-shaped substrate (1), • drying and / or crosslinking the fourth coating composition.

13. The use of a heat-sensitive recording material as claimed in any of claims 1 to 11 as a self-adhesive ticket.

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