EP1925459A2 - Heat-sensitive recording material with authentification feature - Google Patents

Abstract

Heat sensitive recording material with authentication, comprises a substrate and a color former and color acceptors containing heat sensitive recording layer, where the recording material exhibits an additional layer with not colored as authentication, in water and/or in alcohol soluble solid particles, and the solid particles are reactive in an strong alkaline aqueous solution.

Description

The present invention relates to a thermosensitive recording material having an authenticating feature comprising a substrate, optionally a pigmented intermediate layer applied to the substrate, and a thermosensitive recording layer containing color formers and color acceptors.

Recording materials of this kind determine daily life in society and in professional life. For the use of recording materials, the authorized use of which is generally to be demonstrated by a specific marking of the material approved for this purpose, various solutions of authenticity-proofing security features have already been proposed in the past.

• echten Wasserzeichen, die durch Verdrängung (so genannte Licht-Wasserzeichen) oder durch Anreicherung (so genannte Schatten-Wasserzeichen) der Fasermasse beispielsweise unter Verwendung eines Egoutteurs in der Siebpartie einer Papiermaschine hergestellt werden,
• halbechten, so genannten Moletten-Wasserzeichen, die durch die Prägung des noch nassen Papiers in der Pressenpartie einer Papiermaschine erzeugt werden, wobei die Ausbildung solcher wie auch echter Wasserzeichen in den Substraten wärmeempfindlicher Aufzeichnungsmaterialien unter anderem in der EP 0 611 664 B1 beschrieben wird,
• und schließlich unechten Wasserzeichen, wobei letztere gewöhnlich außerhalb der Papiermaschine entweder durch das Prägen oder durch das Bedrucken des fertig gestellten Papiers mit einem farblosen, gerne auch unter UV-Licht fluoreszierenden Lack erstellt werden, wie es unter anderem in der EP-A-0 844 097 beschrieben wird. Im zuletzt beschriebenen Beispiel für ein unechtes Wasserzeichen wird selbstverständlich keine unterschiedliche Papierdicke mehr durch die Zeichnung im Papier hervorgerufen.

Authenticates for documents in the form of passive examinations, for example, are made possible by the greatest popularity of pleasing watermarks, ie drawings in the paper, which are usually caused by different paper thickness. It is differentiated between

• genuine watermarks produced by displacement (so-called light watermarks) or by enrichment (so-called shadow watermarks) of the fiber mass, for example using a dandy cutter in the wire section of a paper machine,
• Halbchten, so-called Moletten watermark, which are produced by the embossing of the still wet paper in the press section of a paper machine, the formation of such as real watermarks in the substrates of heat-sensitive recording materials, inter alia in the EP 0 611 664 B1 is described
• and finally spurious watermarks, the latter usually being located outside the paper machine either by embossing or by printing the finished paper with a colorless, even UV light fluorescent paint can be created as it is in the EP-A-0 844 097 is described. Of course, in the example of a fake watermark described last, no different paper thickness is caused by the drawing in the paper.

Based on the known spurious watermarks, it has been recognized as a disadvantage for certain applications that this authenticity-proofing security feature is recognizable at all times. The present invention was then based on the object of providing an authentication feature for a recording material which should not be visible at all times and immediately, but only from a desired point in time at which the authenticity of the recording material carrying the feature should be visible.

The specified object is achieved by a heat-sensitive recording material having an authentication feature comprising a substrate and a thermosensitive recording layer containing a color former and color acceptors, color formers and color acceptors reacting with each other in a color-forming manner under the action of heat. The proposed recording material has as an authentication feature an additional layer of non-colored, water-soluble and / or alcohol-soluble solid particles, the solid particles being strongly alkaline-reactive in an aqueous solution.

For the purposes of the present invention, color in connection with the solid particles does not mean that they appear whitish or whitish in the dry state, while a water or alcohol solution with these solid particles is transparent.

In an aqueous solution, the solid particles are highly alkaline reactive, which means that such an aqueous solution has a pH above 9.0, preferably above 10.0, and more preferably above 11.0.

• eines Musters,
• von Logos bzw. von fortlaufenden Nummerierungen
• eines diagonalen Streifengittermusters

und/oder in Formen, wie sie aus zyklisch wiederkehrenden Wasserzeichen bekannt sind, aufgebracht. Es ist möglich, die wärmeempfindliche Aufzeichnungsschicht mit der zusätzlichen Schicht zu unterlegen, so dass sie zwischen Substrat und Aufzeichnungsschicht bzw., sofern im Rahmen einer bevorzugten Ausführungsform gegeben, zwischen pigmentierter Zwischenschicht und Aufzeichnungsschicht gelegen ist. Als besonders bevorzugt gilt eine Ausführungsvariante, bei der die zusätzliche Schicht mit den nicht farbigen, in Wasser und/oder in Alkohol löslichen Feststoffpartikeln direkt auf die wärmeempfindliche Aufzeichnungsschicht aufgebracht ist.The additional layer is preferably in the form

• a pattern,
• logos or consecutive numbering
• a diagonal stripe grid pattern

and / or in forms known from cyclically recurring watermarks. It is possible to underlay the heat-sensitive recording layer with the additional layer so as to be located between the substrate and the recording layer or, if given in a preferred embodiment, between the pigmented intermediate layer and the recording layer. Particularly preferred is a variant in which the additional layer with the non-colored, water-soluble and / or alcohol-soluble solid particles is applied directly to the heat-sensitive recording layer.

As possible methods for applying the additional layer to the heat-sensitive recording layer, stamping and, in general, all analog printing methods, in particular offset printing, have proven to be useful without being limited in any way. Also, the application of the additional layer by means of inkjet printing is suitable. However, heat-sensitive recording materials having an additional layer stamped on the heat-sensitive recording layer are particularly preferred.

A good example of the solid particles of the additional layer is guanidine carbonate. A 15% aqueous Guanidincarbonat solution with a pH of 11.5, in a preferred embodiment with an addition of, based on the aqueous guanidine carbonate solution, 5% ethanol provided, can be excellent as an authentication feature on the heat-sensitive recording layer Apply, with a layer formed in this way also quickly absorbs and dries.

Guanidine carbonate is outstandingly capable of blocking the color-forming reaction of color formers and color acceptors when heat is given by the formation of a strongly alkaline environment, wherein this blocking is essentially sharply defined in the invention and takes place in the form of the intended pattern. A disadvantage of Guanidincarbonat is its low stability, which is characterized by a shows gray to yellowish discoloration. If, however, the recording material according to the invention is used only for a comparatively short period of a few hours up to a few days, guanidine carbonate is very easy to use owing to low procurement prices.

Another example of the solid particles of the additional layer is arginine satisfying the following formula (1):

Arginine does not have the disadvantages of low stability and at the same time is able to ensure very sharp-edged blockages of the color-forming reaction of color former and dye acceptors when heat is applied. For this purpose, a 3 to 5% aqueous arginine solution is preferably used for application to the heat-sensitive recording layer. In this solution, in addition, a wetting agent, in particular olefin, and, based on the arginine solution, to 1 to 3.5%, for example, 12% polyvinylalcohol solution and 4 to 8% ethanol are added.

Another example of the solid particles of the additional layer is lysine.

The heat-sensitive recording material according to the invention may comprise as color former at least one substance selected from the group of phthalide, xanthene, fluoran, triarylmethane, diphenylmethane, fluorene, oxazine, thiazine or spiropyran compounds known from the prior art where xanthene compounds are considered preferred.

Typical compounds of this type are, for example:

Xanthene compounds:

Rhodamine-B-anilinolactam, rhodamine-Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6- chloro-7-methylfluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N Ethyl, N-tolyl) amino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilino-fluoran, 3- (N-ethyl, N-tolyl) amino-6-methyl-7- phenylethylfluoran, 3-diethylamino-7- (4-nitroanilino) fluoran, 3- (N -methyl, N-propyl) amino-6-methyl-7-anilinofluoran, 3- (N -methyl, N-cyclohexyl) amino-6 methyl 7-anilino-fluoran, 3- (N-ethyl, N-tetrahydrofuryl) amino-6-methyl-7-anilinofluoran, etc.

Triarylmethane compounds:

3,3-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (Crystal Violet Lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindole-3 -yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3.3 Bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylamino-phthalide, 3,3-bis (9-ethylcarbazole 3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenyl-indol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3 (1-methylpyrrol-2-yl) -6- dimethylaminophthalide, etc.

Diphenylmethane compounds:

4,4'-bis-dimethylaminophenyl benzhydryl benzyl ether, N-halophenyl leucoauramines, N-2,4,5-trichlorophenyl leucoauramine, and the like.

Thiazine compounds:

Benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc.

Spiropyran compounds:

3-methylspiro-dinaphthopyran, 3-ethylspiro-dinaphthopyran, 3,3-dichlorospiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho (3-methoxy-benzo) spiropyran, 3-propyl-spiro-benzopyran, etc ,

Furthermore, the recording layer can also contain, for example, one or more of the following near infrared absorbing compounds:

3,6-Bis (dimethylamino) fluorene-9-spiro-3 '- (6'-dimethylaminophthalide), 3-diethylamino-6-dimethylaminofluorene-9-spiro-3' - (6'-dimethylaminophthalide), 3.6- Bis (diethylamino) -fluorene-9-spiro-3 '- (6'-dimethylaminophthalide), 3-dibutylamino-6-dimethylaminofluorene-9-spiro-3' - (6'-dimethylaminophthalide), 3-dibutylamino-6-diethylaminofluorene -9-spiro-3 '- (6'-dimethylaminophthalide), 3,6-bis (dimethylamino) fluorene-9-spiro-3' - (6'-diethylamino-phthalide), 3-diethylamino-6-dimethylaminofluorene-9 -spiro-3 '- (6'-diethylaminophthalide), 3-dibutylamino-6-dimethylaminofluorene-9-spiro-3' - (6'-diethylaminophthalide), 3,6-bis (diethylamino) fluorene-9-spiro 3 '- (6'-diethylaminophthalide), 3,6-bis (dimethylamino) -fluorene-9-spiro-3' - (6'-dibutylaminophthalide), 3-dibutylamino-6-di-ethylaminofluorene-9-spiro 3 '- (6'-diethylaminophthalide), 3-diethylamino-6-dimethylaminofluorene-9-spiro-3' - (6'-dibutylaminophthalide), 3,3-bis [2- (4-dimethylamino-phenyl) -2- (4-methoxyphenyl) -ethenyl] -4,5,6,7-tetrachlorophthalide, etc.

Very particularly preferred color formers in the heat-sensitive recording layer in the context of the present invention are those substances selected from the list comprising: 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 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 and 3- (N-ethyl-N-tetrahydrofuryl) -amino-6-methyl -7-anilinofluoran.

auf.The recording layer of the heat-sensitive recording material of the present invention can be basically any of those mentioned above, and in particular to the preferred color formers listed in the individual suitable Farbakzeptoren, in particular organic Farbakzeptoren include. Preferably, the heat-sensitive recording layer has, as a color acceptor, N- (p-toluenesulphonyl) -N'-3- (p-toluenesulphonyl-oxy-phenyl) -urea according to the formula (2)

on.

The recording layer of the heat-sensitive recording material of the present invention may also preferably contain sensitisers having a melting point of preferably from 60 ° C to 180 ° C, more preferably having a melting point of from 80 ° C to 140 ° C, to increase the thermal responsiveness. Such sensitizers are, for example: benzyl p-benzyloxybenzoate, stearamide, N-methylol stearamide, p-benzylbiphenyl, 1,2-di (phenoxy) ethane, 1,2-di (m-methylphenoxy) ethane, m-terphenyl, Dibenzyl oxalate, benzyl naphthyl ether, diphenyl sulfone, etc., with benzyl naphthyl ether, diphenyl sulfone, 1,2-di (m-methylphenoxy) ethane and 1,2-di (phenoxy) ethane being preferred.

Suitable binders for incorporation into the heat-sensitive recording layer are, for example, water-soluble binders such as starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohols, modified polyvinyl alcohols, sodium polyacrylates, acrylamide-acrylate copolymers, acrylamide-acrylate-methacrylate terpolymers, alkali metal salts of styrene. Maleic anhydride copolymers or ethylene-maleic anhydride copolymers, etc., which may be used alone or in combination with each other; also water-insoluble latex binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, methyl acrylate-butadiene copolymers, etc. are suitable as binders for incorporation into the heat-sensitive recording layer. For the purposes of the present invention are polyvinyl alcohol alone and / or in conjunction with acrylate copolymers and / or in conjunction with methyl cellulose as particularly preferred binders which together, based on the total weight (atro) of the recording layer, in a range of 12 to 25 wt % (atro), preferably in a range of 18 to 22% by weight (atro), are incorporated in the thermosensitive recording layer.

In order to prevent sticking to a thermal head and to avoid excessive wear of the thermal head, the heat-sensitive recording layer may further contain lubricants and release agents such as metal salts of higher fatty acids, for example, zinc stearate, calcium stearate, etc .; Waxes, for example paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearamides, castor wax, etc. Further constituents of the recording layer are, for example, pigments, preferably inorganic pigments such as, for example, aluminum (hydr) oxide, silicic acid and calcium carbonate, in which case calcium carbonate, which is preferred in from 10 to 18% by weight, based on the total weight of the recording layer, of being incorporated in the recording layer is considered preferable.

Roller coater, knife coater, curtain coater or air brush are particularly suitable as coating apparatus for applying the heat-sensitive recording layer. According to a preferred embodiment, the coating composition used to form the recording layer is aqueous. The subsequent drying of the coating composition is usually done by a method in which heat is supplied, as is done by hot-air floating dryer or contact dryer. Proven is also a combination of the listed dry processes. The basis weight of the heat-sensitive recording layer is preferably from 2 to 6 g / m ^2, and more preferably from 2.3 to 5.8 g / m ² .

Between the recording layer and the substrate of the heat-sensitive recording material according to the invention, a pigmented intermediate layer is expediently arranged. If the intermediate layer is applied in a preferred embodiment with leveling coating devices, such as, for example, roller coater, doctor blade or doctor blade coaters, the intermediate layer can also make a positive contribution to equalization of the substrate surface, thus increasing the amount of coating material necessarily to be applied to the substrate heat-sensitive recording layer reduced. For the basis weight of the intermediate layer, a preferred range between 5 and 20 g / m ² and even better between 7 and 11 g / m ^{2 has} proven.

When inorganic oil-absorbing pigments are incorporated in the intermediate layer sandwiched between the recording layer and the substrate, these pigments can absorb the thermoset liquefied wax components of the thermosensitive recording layer in print image formation, thereby promoting still safer and faster operation of the thermally-induced recording, thus such an embodiment preferably applies.

It is particularly advantageous if the pigments of the intermediate layer has an oil absorption of at least 80 ^cm3 / 100 g, and more preferably 100 ^cm3 / 100 g, determined according to the Japanese standard JIS K 5101, is having. Calcined kaolin has proven particularly useful due to its large absorption reservoir in the cavities. However, the following inorganic pigments are also very well suited as constituents of the intermediate layer: silicon oxide, bentonite, calcium carbonate and aluminum oxide and, in particular, boehmite here. Also mixtures of several different types of inorganic pigments are conceivable.

Experiments have shown that the incorporation of organic pigments into the pigmented intermediate layer can also be very advantageous, which is justified by the fact that such organic pigments in a particular extent contribute to a high heat reflectivity of the intermediate layer are. The arranged in an intermediate layer of a heat-sensitive recording material organic, so-called hollow body pigments have in their interior air, which is a good heat insulator. The intermediate layer thus optimized as the heat reflection layer increases the response of the recording layer to heat, which remarkably increases the resolving power of the thermosensitive recording material and further raises the printing speed in the thermal printer.

The ratio between organic and inorganic pigment is a compromise of the effects caused by the two types of pigments, which is particularly advantageously solved when the pigment mixture to 5 to 30 wt .-% or better to 8 to 20 wt .-% of organic and 95 to 70 wt .-% or better to 92 to 80 wt .-% consists of inorganic pigment. Pigment mixtures of different organic pigments are conceivable.

In addition to the inorganic and optionally also organic pigments, the pigmented intermediate layer contains at least one binder, preferably based on a synthetic polymer, wherein, for example, styrene-butadiene latex gives particularly good results. The use of a synthetic binder with the addition of at least one natural polymer, particularly preferably starch, is a particularly suitable embodiment. In the context of inorganic pigment experiments, it has also been found that with a binder-pigment ratio within the pigmented intermediate layer between 3: 7 and 1: 9, in each case based on wt .-%, a particularly suitable embodiment is present.

In particular, when the additional layer containing the non-colored, water-soluble and / or alcohol-soluble solid particles is stamped onto the heat-sensitive recording layer, the proposed recording material preferably has a protective layer, including any indication of a possible authentication feature or its shape to prevent.

To form such a protective layer, for example, coating colors, as they are used in the EP-B-0 909 242 and secondly in the EP-B-1 333 991 be proposed. In both cases, the protective layer combines high environmental resistance with recyclability and good printability in the wet offset process. The protective layers mentioned are both relatively cheap to produce and apply in one layer.

As inorganic pigments, natural or precipitated calcium carbonate, kaolin or titanium oxide are possible for the protective layer. Crosslinking agents for the protective layer are, in particular, cyclic urea, methylolurea, polyamide-epichlorohydrin resin, ammonium zirconium carbonate.

It is preferred to apply the protective layer with a basis weight in a range of 1.5 to 6 g / m ² and especially between 1.8 and 4 g / m ² , in particular roller coater, doctor blade or (roll) doctor blade coater , but also offer curtain coaters and airbrush application units as coating units for application of the protective layer.

To a particular extent, the printing technology application of a protective layer is preferred. Processing technology and in terms of their technological properties are particularly suitable such protective layers which are curable by means of actinic radiation. The term "actinic radiation" UV or ionizing radiation, such as electron beams to understand.

Although not limited to paper as a substrate, paper and especially a non-surface treated base paper preferred in a range for the basis weight between 45 and 130 g / m ^2, the substrate, which is also in the market with regard to the good environmental performance because of Good recycling ability has prevailed and is preferred for the purposes of the invention. A non-surface treated base paper is to be understood as meaning a base paper which has not been treated in a size press or in a coating device. For the purposes of the present invention is in particular a non-surface treated, mass-sized base paper with an inorganic pigment, in particular calcium carbonate, considered suitable in the mass. For the invention, films of, for example, polyolefin and polyolefin-coated papers as a substrate are possible to the same extent, without such an embodiment having an exclusive character.

The basis weight,% by weight (% by weight) given in the specification and in the claims refer to the "atro" weight, respectively. absolutely dry parts by weight.

The invention will be further clarified by the following example :

The substrate used on a fourdrinier paper machine made of bleached and ground hardwood and softwood pulps with the addition of, based on the total solids content (atro) of the pulp fed to the paper machine, 0.6 wt .-% (atro) Harzleim as engine sizing and other conventional admixtures a support paper having a basis weight of 53 g / m ^{2 was} produced. On the front side, a calcined kaolin pigment, styrene-butadiene latex as a binder and, in addition to other aids, starch as cobinder-containing intermediate layer having a basis weight of 9 g / m ^{2 is} applied using a doctor blade.

Onto this pigmented intermediate layer, a heat-sensitive recording layer having a basis weight of 5.4 g / m ^{2 is} applied by means of a roller doctor coater. The aqueous coating used for this purpose contains the following components according to the formulation shown in Table 1: <u> Table 1: </ u> Data in wt .-% (atro), based on the total weight of the heat-sensitive recording layer color formers 3-dibutylamino-6-methyl-7-anilinofluoran (ODB-2) 9 color acceptor N- (p-toluensulphonyl) -N'-3- (p-toluensulphonyl-oxyphenyl) -urea according to formula (2), which is Pergafast ^® 201 (CIBA) 22 sensitizer Benzylnaphthyl ether (BNE) 22 binder Polyvinyl alcohol (PVA) 7 co-binder Acrylate copolymers 12 methylcellulose 2 pigment calcium carbonate 16 90

Other components of the heat-sensitive recording layer which are not stated in percent and based on the total weight in% by weight (atro) include dispersants, defoamers, optical brighteners, thickeners, waxes and crosslinkers.

After drying the thermosensitive recording layer and smoothing the recording material, here a value of 150 Bekk sec is measured, carried out with the aid of a stamp, the application of an aqueous solution to the heat-sensitive recording layer, wherein for the solution, the following components according to the reproduced in Table 2 recipe be used: <u> Table 2: </ u> In wt .-% (atro), based on the total weight of the aqueous arginine solution Solid particles Arginine according to formula (1) 4 wetting agent Olfin 0.5 binder polyvinyl alcohol 1

Finally, 7 parts of ethanol are added based on 100 parts of the finished arginine solution.

To identify the thus formed authentication feature, the heat-sensitive recording material is placed for 2 min in a drying oven at 120 ° C heat. The heat causes blackening of the heat-sensitive recording layer as a result of the color-forming reaction of color former and color acceptor, but this blackening does not occur in sharp-edged places where the aqueous arginine solution had previously been applied.

The experiment very clearly shows that the proposed invention has convincingly succeeded in providing an authentication feature for a recording material which is not directly but only from a desired point in time at which the authenticity of the recording material carrying the feature is to be demonstrated. can be made visible. In the case described, this point in time is the formation of the heat-induced blackening of the recording layer, which, of course, can not only be applied nationwide, but also with the aid of a thermal printer according to a printed image. It is equally possible to apply a solvent tincture to the recording layer with the additional layer as an authentication feature in the context of a rapid test, for example with a correspondingly prepared felt-tip pen. In this case, the solvent would cause blackening of the recording layer, but this blackening does not occur in sharp-edged places where the aqueous arginine solution had previously been applied.

Claims (9)

A heat-sensitive recording material having an authentication feature, comprising a substrate and a heat-sensitive recording layer containing a color former and color acceptors, characterized in that the recording material has as an authentication feature an additional layer of non-colored, water-soluble and / or alcohol-soluble solid particles, the solid particles being in an aqueous Solution are strongly alkaline reactive. Heat-sensitive recording material according to claim 1, characterized in that the additional layer is applied in the form of a pattern. Heat-sensitive recording material according to one of the claims 1 and 2, characterized in that the additional layer is stamped on the recording layer. Heat-sensitive recording material according to one of the claims 1 and 2, characterized in that the additional layer is printed on the recording layer. Heat-sensitive recording material according to one of the claims 1 and 4, characterized in that the solid particles form a substance which satisfies the following formula (1):

Heat-sensitive recording material according to one of claims 3 and 4, characterized in that the recording material has a protective layer covering the recording layer with an applied additional layer. A heat-sensitive recording material according to any one of claims 1 to 6, characterized in that the thermosensitive recording layer comprises a color former selected from the list comprising: 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7 Anilinofluoran, 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 and 3- (N-ethyl-N-tetrahydrofuryl) amino-6 methyl-7-anilinofluoran. Heat-sensitive recording material according to one of claims 1 to 7, characterized in that the heat-sensitive recording layer as color acceptor N- (p-toluenesulphonyl) -N'-3- (p-toluenesulphonyl-oxy-phenyl) -urea according to the formula (2)

having. Heat-sensitive recording material according to one of the claims 1 to 8, characterized in that a pigmented intermediate layer is formed between the substrate and the heat-sensitive recording layer.