DE102016219569A1 - Heat-sensitive recording material - Google Patents

Abstract

The present invention relates to a heat-sensitive recording material comprising i) a support substrate and ii) a heat-sensitive recording layer, wherein the heat-sensitive recording layer comprises a color former and a color developer mixture and the color developer mixture a) N- [2- (3-phenylureido) phenyl] benzenesulfonamide (Compound of Formula (I)), wherein the compound of formula (I) is present in a crystalline form having an absorption band at 3401 ± 20 cm ^-1 in the IR spectrum, and b) N- (4-methylphenylsulfonyl) -N ' - (3- (4-methylphenylsulfonyloxy) phenyl) urea (compound of formula (II)), wherein the mass ratio between the compound of formula (I) and the compound of formula (II) 99.5: 0.5 to 65 : 35 is.

Description

The present invention relates to a thermosensitive recording material comprising a) a compound of the formula (I) and b) a compound of the formula (II), a use of the thermosensitive recording material and a process for producing a thermosensitive recording material.

Heat-sensitive recording materials have been known for many years and enjoy a high level of popularity. This popularity is due, among other things, to the fact that their use has the advantage that the color-forming components are contained in the recording material itself and therefore toner and color cartridge-free printers can be used. It is therefore no longer necessary to purchase or replenish toner or ink cartridges. Thus, this innovative technology has largely prevailed, especially in public transport and retail.

• – Bisphenol-A, das ist 2,2 bis (4-hydroxyphenyl)-Propan, und
• – Bisphenol-S, das ist 4,4'-Dihydroxydiphenylsulfon,

In the recent past, however, increased concerns about the environmental compatibility of particular (color) developers, also known as color acceptors, sometimes even of dye precursors with which react the (color) developers with heat to form a visually recognizable color, come up, which can not be ignored by industry and especially by trade. For example, the (color) developers have recently become well-known and scientifically well-studied components, known as

• Bisphenol A, that is 2,2 bis (4-hydroxyphenyl) propane, and
• Bisphenol-S, which is 4,4'-dihydroxydiphenylsulfone,

• – Pergafast^® 201, das ist N-(4-Methylphenylsulfonyl)-N'-(3-(4-methylphenylsulfonyloxy)phenyl)harnstoff, der Firma BASF SE,
• – D8, das ist 4-Hydroxy-4'-isopropoxydiphenylsulfon,
• – N-[2-(3-Phenylureido)phenyl]benzolsulfonamid und
• – N-{2-[(Phenylcarbamoyl)amino]phenyl}benzolsulfonamid.

reinforced in the center of public criticism and are therefore sometimes replaced by

• - Pergafast ^® 201, which is N- (4-methylphenylsulfonyl) -N '- (3- (4-methylphenylsulfonyloxy) phenyl) urea, BASF SE,
• D8, which is 4-hydroxy-4'-isopropoxydiphenyl sulfone,
• N- [2- (3-phenylureido) phenyl] benzenesulfonamide and
• - N - {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide.

With the aim of improving heat-sensitive recording materials, particularly in their use as tickets or lottery tickets, in terms of their resistance to environmental influences such as heat, moisture and chemicals, the underlying chemistry and the production technique for producing such recording materials has been further developed.

To increase the durability of a thermo-print (heat-induced recording) available on a heat-sensitive recording material against water, aqueous alcohol solutions and plasticizers, US Pat DE 10 2004 044 204 A1 a heat-sensitive recording material whose heat-sensitive recording layer has conventional dye precursors and the combination of a phenolic color developer and a urea-urethane-based color developer.

Subject of the US 2005/0148467 A1 is a thermosensitive recording material containing at least the components of two color-forming systems to form an irreversible printed image, one being a chelate-type system and the other being a conventional leuco-dye system.

However, there is a continuing need for other heat-sensitive recording materials for a variety of uses, which can be produced due to high sales volumes in a fiercely competitive market at low production costs and therefore must have a simple structure. Another challenge is that a printed thermosensitive recording material may be used in its typical uses as a ticket, ticket, ticket, parking ticket, and the like. a variety of different environmental influences, such as moisture, heat or chemicals exposed.

Thus, during normal use, thermosensitive recording materials may come into contact with a variety of different substances which may affect the resistance of the thermal term. In addition to water and organic solvents, these also include fats and oils, which are contained, for example, in hand care products and can be transferred to them when the heat-sensitive recording material is touched. In particular, the resistance to fats and oils is therefore very relevant.

In addition to the resistance to chemicals which may come into contact with the heat-sensitive recording materials, heat-sensitive recording materials must also have a high resistance to thermal influences. On the one hand, the heat-sensitive recording material should be energy-saving and easy to print, for example, to consume low energy in mobile applications. On the other hand, the printed image should remain after printing, and when exposed to heat, the printed image should not fade, nor should the unprinted background be discolored, which would make the print no longer legible. For example, in the case of parking tickets, which are stored behind the windshield after printing and are exposed to high temperatures and direct sunlight in summer, the thermal resistance is extremely relevant.

Also, for tickets such as concert tickets or air tickets, which are often made a long time in advance, or for receipts required as proof of purchase over a long warranty period, the long-term durability of the heat-sensitive recording material is very important. In particular, if it has to be assumed that the heat-sensitive recording materials can come into contact with moisture, for example by keeping the recording materials used as a concert ticket, plane ticket or proof of purchase close to the body (eg in the trouser pocket) and thereby be able to come into contact with perspiration To ensure that the recording materials remain legible even after contact with moisture.

Although it has been found that recording materials containing N- [2- (3-phenylureido) phenyl] benzenesulfonamide as (color) developers have good resistance to heat, especially at high humidity, they have unsatisfactory resistance to fats and oils exhibit.

There is therefore a continuing need to improve the resistance of the thermal term to various environmental conditions. The object of the present invention is thus to provide a heat-sensitive recording material which has a good resistance to greases and oils when printed, while at the same time having a high long-term resistance to environmental influences, such as moisture and, heat or chemicals.

The improved thermosensitive recording materials should have a low long-term aging even at high temperatures (40 to 60 ° C) and high humidity and thereby have improved over the prior art improved resistance to fat.

• i) ein Trägersubstrat und
• ii) eine wärmeempfindliche Aufzeichnungsschicht,

This problem is solved by a heat-sensitive recording material comprising

• i) a carrier substrate and
• ii) a heat-sensitive recording layer,

• a) eine Verbindung der Formel (I)
  
  enthält, wobei die Verbindung der Formel (I) in einer kristallinen Form vorliegt, die im IR-Spektrum eine Absorptionsbande bei 3401 ± 20 cm^–1 aufweist,

und

• b) eine Verbindung der Formel (II)
  
  enthält, wobei das Massenverhältnis zwischen der Verbindung der Formel (I) und der Verbindung der Formel (II) 99,5:0,5 bis 65:35 beträgt.

wherein the heat-sensitive recording layer comprises a color former and a color developer mixture and the color developer mixture

• a) a compound of the formula (I)
  
  wherein the compound of formula (I) is in a crystalline form having an absorption band at 3401 ± 20 cm ^-1 in the IR spectrum,

and

• b) a compound of the formula (II)
  
  wherein the mass ratio between the compound of formula (I) and the compound of formula (II) is 99.5: 0.5 to 65:35.

The compound of the formula (II) is the already known compound N- (4-methylphenylsulfonyl) -N '- (3- (4-methylphenylsulfonyloxy) phenyl) urea, which is sold under the name Pergafast 201 and, for example in the EP 1 140 515 B1 is described. Pergafast 201 is the most widely used phenol-free color developer.

The compound of the formula (I) is likewise already known and is described, for example, in US Pat EP 2 923 851 A1 described. It is sold under the name NKK. However, it has been found that the compound of formula (I) can exist in two different crystalline forms. Both crystalline forms have different physical properties that may affect the thermosensitive recording material.

A crystalline form of the compounds of formula (I) has a melting point of about 158 ° C, while the second used in the invention crystalline form of the compounds of formula (I) has a melting point of 175 ° C. In connection with heat-sensitive recording materials, only the compound of the formula (I) which is the crystalline form having a melting point of about 158 ° C. has been described in the literature so far (cf., for example, US Pat EP 2 923 851 A1 Paragraph [0084]). Neither the preparation nor the use of the crystalline form of the compounds of the formula (I) having a melting point of about 175 ° C. used according to the invention are described in the literature. Accordingly, it is to be understood that the crystalline form of the compound of the formula (I) having a melting point of about 158 ° C has always been used, although the melting point is not explicitly mentioned in the corresponding document. The crystalline form of the compound of the formula (I) having a melting point of 175 ° C. used according to the invention has recently become commercially available as well.

According to the invention, preference is therefore given to a heat-sensitive recording material, the crystalline form of the compound of the formula (I) having a (preferably endothermic) transition at a temperature between 170 ° C and 178 ° C, preferably between 173 ° C and 177 ° C, more preferably between 174 ° C and 176 ° C as determined by differential scanning calorimetry (DKK) at a heating rate of 10 K / min.

Both crystalline forms of the compounds of the formula (I) can also be distinguished from one another in the IR absorption spectrum. Particularly characteristic in the crystalline form of the compounds of the formula (I) used according to the invention is an absorption band in the IR spectrum at 3401 ± 20 cm ^-1 . In the crystalline form of the compounds of the formula (I), which has a melting point of about 158 ° C, this band is not present, but in each case a band at 3322 and 3229 cm ^-1 .

According to the invention, preference is given to a thermosensitive recording material, wherein the crystalline form of the compound of the formula (I) in the IR spectrum has absorption bands at 689 ± 10 cm ^-1 , 731 ± 10 cm ^-1 , 1653 ± 10 cm ^-1 3364 ± 20 cm ^-1 and 3401 ± 20 cm ^-1 .

According to the invention, preference is given to a heat-sensitive recording material, wherein the IR absorption spectrum of the crystalline form of the compound of the formula (I) is substantially identical to that in 1a) . 2a) and or 3a) mapped IR absorption spectrum.

Both crystalline forms of the compounds of the formula (I) can likewise be distinguished from one another in the X-ray powder diffractogram. According to the invention, preference is given to a heat-sensitive recording material, the crystalline form of the compound of the formula (I) having an X-ray powder diffractogram with diffraction reflections at ° 2θ values of 10.00 ± 0.20, 11.00 ± 0.20, 12.40 ± 0, 20, 13.80 ± 0.20 and 15.00 ± 0.20.

According to the invention, preference is given to a heat-sensitive recording material, wherein the crystalline form of the compound of the formula (I) has an X-ray powder diffractogram which substantially corresponds to that in FIG 4b) corresponds to the X-ray powder diffraction pattern.

For the purposes of this text, a compound of the formula (I) is always described as being the crystalline form which has an absorption band at 3401 ± 20 cm ^-1 in the IR spectrum or has a melting point of 175 ° C. or a transition at one temperature between 170 ° C. and 178 ° C. (determined by means of differential scanning calorimetry (DKK) at a heating rate of 10 K / min) or in the X-ray powder diffractogram with diffraction reflections at ° 2θ values of at least 10.00 ± 0.20, 11.00 ± 0.20, 12.40 ± 0.20, 13.80 ± 0.20, and 15.00 ± 0.20, unless the existence of the other crystal structure is explicitly described.

It has surprisingly been found that the addition of small amounts of the compound of the formula (II) to the compound of the formula (I) significantly improves the resistance to fats and oils, while the already good moisture resistance is maintained over longer periods.

Especially with regard to the resistance at high temperatures (60 ° C), it has been found that the printed image less decreases even after storage for 24 hours at 60 ° C than in heat-sensitive recording materials, in which the color developer mixture in equal parts by weight by a compound of formula (I) has been replaced. In part, the printed image of heat-sensitive recording materials according to the invention has a higher print density after storage for 24 hours at 60 ° C. than in heat-sensitive recording materials in which the color developer mixture has been replaced in equal parts by weight by a compound of formula (I) or (II). The combination of a compound of the formula (I) used according to the invention with a compound of the formula (II) thus has a synergistic effect which was unpredictable and therefore completely surprising.

According to the invention, a heat-sensitive recording material is preferred, wherein the aging of the heat-sensitive recording material when stored for 24 hours at 40 ° C and 90% relative humidity is less than the aging of a heat-sensitive recording material in which the color developer mixture in equal parts by weight by a compound of formula (II ) has been replaced.

Also preferred according to the invention is a heat-sensitive recording material, wherein the aging of the heat-sensitive recording material when stored for 24 hours at 60 ° C is less than the aging of a heat-sensitive recording material, wherein the color developer mixture in equal parts by weight of a compound of formula (I) or preferably a compound of formula (II) has been replaced.

The aging of the thermosensitive recording material is considered to be lower if the printing density of a printed area decreases less than that of the comparative sample.

Also preferred in the invention is a thermosensitive recording material, wherein the durability of the thermosensitive recording material to lanolin is higher than or equal to 14 days, than the resistance of a thermosensitive recording material in which the color developing agent in equal parts by weight has been replaced by a compound of formula (II).

The durability of the thermosensitive recording material to lanolin is considered to be higher if the printing density of a printed area decreases less than that of the comparative sample.

It is known to the person skilled in the art that the combination of different developers, such as compounds of the formula (I) or (II), usually leads to a deterioration of the properties of the heat-sensitive recording material. Usually, the combination of two or more developers leads to an undesirable change in the color of the thermosensitive recording material, so that the thermosensitive recording material, for example, gray effect, without thereby improving the other properties. Accordingly, when attempting to solve the above-described problem, the person skilled in the art would not have considered combining different developers with one another and did not carry out corresponding tests. For this reason too, the solution according to the invention shown here is surprising, since the skilled person first had to overcome the technical prejudice that two developers should not be combined with one another in order to achieve the object.

Surprisingly, it has been found that no graying of the unprinted recording material can be observed in the heat-sensitive recording material according to the invention. In particular, at a mass ratio between the compound of formula (I) and the compound of formula (II) 1:99 to 25:75 no relevant graying of the unprinted recording material takes place. This mixing ratio is therefore preferred.

According to the invention, preference is given to a heat-sensitive recording material, the mass ratio between the compound of the formula (I) and the compound of the formula (II) being 97: 3 to 85:15, preferably 95: 5 to 90:10.

It has been shown in our own investigations that mixtures with a mass ratio between the compound of the formula (I) and the compound of the formula (II) of about 93: 7 or in the above-defined ranges from 97: 3 to 85:15 is preferably 95: 5 to 90:10, particularly good in terms of resistance for at least 24 hours at 60 ° C and improved resistance to grease (especially lanolin). Heat-sensitive recording materials having mixtures of these proportions as a color developer mixture exhibit better properties (moisture resistance or grease resistance) than heat-sensitive recording materials in which the color developer mixture has been replaced in equal parts by only one compound of formula (II) or (I).

According to the invention, a heat-sensitive recording material is preferred, wherein the carrier substrate is a paper, synthetic paper or a plastic film. As a carrier substrate, a non-surface treated base paper is particularly preferred because it has good recyclability and good environmental compatibility. 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 coater. As plastic films, films of polypropylene or other polyolefins are preferred. Also preferred according to the invention are papers coated with one or more polyolefins (in particular polypropylene).

In a very particularly preferred embodiment, the carrier substrate is a paper with a fraction of recycled fibers of at least 70% by weight, based on the total pulp content in the paper.

According to the invention, preference is given to a heat-sensitive recording material, additionally comprising an intermediate layer located between the carrier substrate and the heat-sensitive recording layer, the intermediate layer preferably containing pigments. The pigments can be organic pigments, inorganic pigments or a mixture of organic pigments and inorganic pigments.

It is inventively preferred if the basis weight of the intermediate layer in the range of 5 to 20 g / m ² , preferably in the range of 7 to 12 g / m ² .

In the case where the intermediate layer contains pigments, it is preferred in one embodiment of the invention if the pigments are organic pigments, preferably organic hollow-body pigments.

Our own investigations have shown that the incorporation of organic pigments into the intermediate layer is advantageous, since organic pigments have a high heat reflectivity. Increased heat reflection of the intermediate layer formed with organic pigments increases the response of the heat-sensitive recording layer to heat because the radiated heat is at least partially reflected in the heat-sensitive recording layer instead of being conducted to the support substrate. This significantly increases the sensitivity and resolving power of the thermosensitive recording material, and further increases the printing speed in the thermal printer. In addition, the energy consumption during the printing process can be reduced, which is particularly advantageous for mobile devices. Hollow body pigments have air in their interior, whereby they usually have even higher heat reflection, and the sensitivity and resolving power of the thermosensitive recording material can be further increased.

In the case that the intermediate layer contains pigments, it is preferred in an alternative embodiment of the invention, when the pigments are inorganic pigments, preferably selected from the list consisting of calcined kaolin, silica, bentonite, calcium carbonate, alumina and boehmite.

When inorganic pigments are incorporated in the intermediate layer sandwiched between the recording layer and the substrate, these pigments can absorb the components (e.g., waxes) of the thermosensitive recording layer liquefied by heat from the thermal head in the typeface formation, thus promoting even safer and faster operation of the heat-induced recording.

It is particularly advantageous if the inorganic 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 which is Japanese standard JIS K 5101 , exhibit. Calcined kaolin has proven particularly useful due to its large absorption reservoir in the cavities. Also mixtures of several different types of inorganic pigments are conceivable.

The ratio between organic and inorganic pigment is a combination of the two types of pigments caused effects, 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.% Of inorganic pigment. Pigment mixtures of different organic pigments and / or inorganic pigments are conceivable.

According to the invention, preference is given to a heat-sensitive recording material, the intermediate layer optionally containing, in addition to the inorganic and / or organic pigments, at least one binder, preferably based on a synthetic polymer, with styrene-butadiene latex giving particularly good results. The use of a synthetic binder with the admixture of at least one natural polymer, particularly preferably starch, is a particularly suitable embodiment. In the context of experiments with inorganic pigments, it was further found that a binder-to-pigment ratio within the intermediate layer of between 3: 7 and 1: 9, in each case based on wt .-% in the intermediate layer, represents a particularly suitable embodiment.

According to the invention, preference is given to a heat-sensitive recording material, wherein the color former is selected from derivatives of compounds from the group consisting of fluoran, phthalide, lactam, triphenylmethane, phenothiazine and spiropyran.

Our own investigations have shown that these color formers have particularly good properties in combination with the color developer mixture used according to the invention.

A preferred heat-sensitive recording material according to the invention preferably comprises, as color formers, fluoran-type compounds selected from the group consisting of 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3'-methylphenylamino) fluoran ( 6 '- (diethylamino) -3'-methyl-2' - (m-tolylamino) -3H-spiro [isobenzofuran-1,9'-xanthene] -3-one; ODB-7), 3-di-n- pentylamino-6-methyl-7-anilinofluoran, 3- (diethylamino) -6-methyl-7- (3-methylphenylamino) fluoran, 3-di-n-butylamino-7- (2-chloroanilino) fluoran, 3 Diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7- (2-carbomethoxyphenylamino) fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3 Pyrrolidino-6-methyl-7- (4-n-butylphenylamino) fluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-Nn-dibutylamine-6-methyl-7-anilinofluoran (ODB-2), 3- (N -methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3- (N -methyl-N-propyl) amino-6-methyl-7-anilinofluoran, 3- (N -methyl-N -tetrahydr ofurfuryl) amino-6-methyl-7-anilinofluoran), 3- (N-ethyl-N-isoamyl) 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- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 3- (N Ethyl-4-toluidino) 6-methyl-7- (4-toluidino) fluoran and 3- (N-cyclopentyl-N-ethyl) amino-6-methyl-7-anilinofluoran.

Likewise preferred are heat-sensitive recording materials according to the invention which, as color formers, are those described in paragraphs [0049] to [0052] of the EP2923851A1 contained compounds.

Particularly preferred according to the invention is a heat-sensitive recording material, wherein the color former is selected from the group consisting of 3-N-di-n-butylamine-6-methyl-7-anilinofluoran (ODB-2) and 3- (N-ethyl-N- isopentylamino) -6-methyl-7-anilinofluoran.

Preferred in the invention is a heat-sensitive recording material, wherein the heat-sensitive recording layer contains a sensitizer.

When a sensitizer is used, the sensitizer is first melted during the application of heat during printing, and the molten sensitizer dissolves the color formers and color developers coexisting in the thermosensitive recording layer and / or lowers the melting temperature of the color formers and color developers to cause a color development reaction. The sensitizer does not participate in the color-winding reaction itself.

A sensitizer is therefore understood to mean substances which serve to adjust the melting temperature of the heat-sensitive recording layer and with which preferably a melting temperature of about 70 to 80 ° C. can be set without the sensitizers themselves being involved in the color-winding reaction.

As sensitizers, for example, fatty acid salts, fatty acid esters and fatty acid amides (e.g., zinc stearate, stearic acid amide, palmitic acid amide, oleic acid amide, lauric acid amide, ethylene and methylenebisstearic acid amide, methylolstearic acid amide), naphthalene derivatives, biphenyl derivatives, phthalates and terephthalates can be used in the present invention.

Particularly preferred according to the invention is a heat-sensitive recording material, wherein the sensitizer is selected from the group consisting of 1,2-bis (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1,2-di (m-methylphenoxy) ethane, 2 (2H-Benzotriazol-2-yl) -p-cresol, 2,2'-bis (4-methoxyphenoxy) diethyl ether, 4,4'-diallyloxydiphenylsulfone, 4-acetylacetophenone, 4-benzylbiphenyl, acetoacetic anilides, benzyl 2-naphthyl ether, Benzyl naphthyl ether, benzyl 4- (benzyloxy) benzoate, benzyl paraben, bis (4-chlorobenzyl) oxalate ester, bis (4-methoxyphenyl) ether, dibenzyl oxalate, dibenzyl terephthalate, dimethyl terephthalate, dimethyl sulfone, diphenyl adipate, diphenyl sulfone, ethylenebisstearic acid amine, fatty acid anilides, m-terpenyl , N-hydroxymethylstearic acid amine, N-methylolstearamide, N-stearylurea, N-stearylstearic acid amide, p-benzylbiphenyl, phenylbenzenesulfonate ester, salicylic anilide, stearamide and α, α'-diphenoxyxylene, wherein benzylnaphthyl ether, diphenylsulfone, 1,2-di (m-methylphe noxy) ethane and 1,2-diphenoxyethane are particularly preferred.

Also preferred are heat-sensitive recording materials according to the invention which act as sensitizers in paragraphs [0059] to [0061] of the EP2923851A1 contained compounds.

According to a first preferred embodiment, these sensitizers are each used alone, that is, not in combination with the other sensitisers mentioned above. According to a second, almost preferred embodiment, at least two sensitisers selected from the above list are incorporated in the heat-sensitive recording layer.

According to the invention, a heat-sensitive recording material is preferred, wherein the sensitizer has a melting point of 60 ° C to 180 ° C, preferably a melting point of 80 ° C to 140 ° C.

Further, in the heat-sensitive recording materials of the present invention, the use of 4,4'-diaminodiphenylsulfone (4,4'-DDS, dapsone) as an additional additive in the heat-sensitive recording layer may prove useful as appropriate. The use of 4,4'-diaminodiphenyl sulfone in thermal papers is for example in the WO 2014/143174 A1 described. The invention may then in this case relate to a heat-sensitive recording material, 4,4'-diaminodiphenylsulfone in the heat-sensitive recording layer, in particular additionally as an additive, is included.

If desired, heat-sensitive recording materials are preferred, the heat-sensitive recording layer containing a binder, preferably a crosslinked or uncrosslinked binder selected from the group consisting of polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination of polyvinyl alcohol and ethylene-vinyl alcohol copolymer, silanol group-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acrylate copolymer and film-forming acrylic copolymers.

Preferably, the coating composition for forming the heat-sensitive recording layer of the heat-sensitive recording material according to the present invention contains one or more crosslinking agents for the binder (s) in addition to one or more binders. Preferably, the crosslinking agent is selected from the group consisting of zirconium carbonate, polyamidoamine-epichlorohydrin resins, Boric acid, glyoxal, dihydroxy bis (ammonium lactato) titanium (IV) (CAS = 65104-06-5; Tyzor LA) and glyoxal derivatives.

A heat-sensitive recording material of the present invention whose heat-sensitive recording layer is formed from such a coating composition containing one or more binders and one or more crosslinking agents for the binder or binders contains one or more binders crosslinked by reacting with one or more crosslinking agents in the heat-sensitive recording layer. wherein the crosslinking agent (s) are selected from the group consisting of zirconium carbonate, polyamidoamine-epichlorohydrin resins, boric acid, glyoxal, dihydroxy bis (ammonium lactato) titanium (IV) (CAS = 65104-06-5, Tyzor LA) and glyoxal derivatives. By "crosslinked binder" is meant the reaction product formed by reaction of a binder with one or more crosslinking agents.

According to the invention, a heat-sensitive recording material is preferred, wherein the basis weight of the heat-sensitive recording layer is in the range of 1.5 to 6 g / m ² , preferably in the range of 2.0 to 5.5 g / m ² , particularly preferably in the range of 2.0 to 4.8 g / m ² .

Also preferred according to the invention is a heat-sensitive recording material, the proportion of the color developer mixture in the heat-sensitive recording layer being 35 to 15% by weight, preferably 31 to 19% by weight, particularly preferably 28 to 22% by weight, based on the total solids content the heat-sensitive recording layer.

In recording materials according to the invention may additionally image stabilizers, dispersants, antioxidants, release agents, defoamers, light stabilizers, brighteners, as are known in the art, can be used. Each of the components is usually used in an amount of 0.01 to 15 wt .-%, in particular - with the exception of defoamers - 0.1 to 15 wt .-%, preferably 1 to 10 wt .-%, based on the total Solid content of the heat-sensitive recording layer. When defoamers are used in the relevant formulations, the antifoaming agent may be present in amounts of from 0.03 to 0.05% by weight in the recording materials according to the invention, based on the total solids content of the heat-sensitive recording layer.

In one embodiment of the heat-sensitive recording materials according to the invention, the heat-sensitive recording layer is completely or partially covered with a protective layer. By disposing a protective layer covering the heat-sensitive recording layer, the heat-sensitive recording layer is also shielded to the outside or the supporting substrate of the next layer within a roll, so that it is protected from external influences.

Such a protective layer in such cases, in addition to the protection of the heat-sensitive recording layer arranged under the protective layer against environmental influences, often has the additional positive effect of being able to print the heat-sensitive recording material according to the invention, in particular in the indigo range. Improve offset and flexo printing. For this reason, it may be desirable for certain applications that the heat-sensitive recording material of the present invention has a protective layer although the presence of a color developing agent as defined above in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention selects the resistance of a thermal printable on a heat-sensitive recording material of the present invention to cloths from the group consisting of water, alcohols, fats, oils and their mixtures, even without a protective layer is already sufficient.

The protective layer of the heat-sensitive recording material according to the invention preferably comprises one or more crosslinked or uncrosslinked binders selected from the group consisting of carboxyl-modified polyvinyl alcohols, silanol-modified polyvinyl alcohols, diacetone-modified polyvinyl alcohols, partially and fully hydrolyzed polyvinyl alcohols and film-forming acrylic copolymers.

Preferably, if present, the coating composition for forming the protective layer of the heat-sensitive recording material according to the invention contains, in addition to one or more binders, one or more crosslinking agents for the binder (s). Preferably, the crosslinking agent is then selected from the group consisting of boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, adipic dihydrazide, melamine formaldehyde, urea, methylol urea, ammonium zirconium carbonate, polyamide epichlorohydrin resins and Tyzor LA.

A heat-sensitive recording material according to the invention, the protective layer of which is formed from such a coating composition comprising one or more binders and one or more crosslinking agents for the binder or binders, contains in the protective layer one or more binders crosslinked by reaction with one or more crosslinking agents, wherein the one or more Crosslinking agents are selected from the group consisting of boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, adipic dihydrazide melamine formaldehyde, urea, methylol urea, ammonium zirconium carbonate and polyamide epichlorohydrin resins. By "crosslinked binder" is meant the reaction product formed by reaction of a binder with one or more crosslinking agents.

In a first embodiment variant, the protective layer wholly or partly covering the heat-sensitive recording layer is obtainable from a coating composition comprising one or more polyvinyl alcohols and one or more crosslinking agents. It is preferred that the polyvinyl alcohol of the protective layer is modified with carboxyl or in particular silanol groups. It is also possible to use mixtures of different carboxyl-group- or silanol-modified polyvinyl alcohols. Such a protective layer has a high affinity with respect to the preferably UV-crosslinking printing ink used in the offset printing process. This critically supports meeting the demand for excellent printability within offset printing.

The one or more crosslinking agents for the protective layer according to this embodiment are preferably selected from the group consisting of boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, polyamine epichlorohydrin resin, adipic dihydrazide, melamine formaldehyde and Tyzor LA. It is also possible to use mixtures of different crosslinking agents.

Preferably, in the coating composition for forming the protective layer according to this embodiment, the weight ratio of the modified polyvinyl alcohol to the crosslinking agent is in a range of 20: 1 to 5: 1, and more preferably in a range of 12: 1 to 7: 1. Particularly preferred is a ratio of the modified polyvinyl alcohol to the crosslinking agent in the range of 100 parts by weight to 8 to 11 parts by weight.

Particularly good results have been achieved when the protective layer according to this embodiment additionally contains an inorganic pigment. In this case, the inorganic pigment is preferably selected from the group consisting of silicon dioxide, bentonite, aluminum hydroxide, calcium carbonate, kaolin and mixtures of said inorganic pigments.

It is preferred to apply the protective layer according to this embodiment with a basis weight in a range from 1.0 g / m ² to 6 g / m ² and more preferably from 1.2 g / m ² to 3.8 g / m ² , In this case, the protective layer is preferably formed in one layer.

In a second embodiment, the coating composition for forming the protective layer comprises a water-insoluble, self-crosslinking acrylic polymer as a binder, a crosslinking agent and a pigment component, wherein the pigment component of the protective layer consists of one or more inorganic pigments and at least 80 wt .-% of a highly purified alkaline treated Bentonite are formed, the binder of the protective layer of one or more water-insoluble, self-crosslinking acrylic polymers and the binder / pigment ratio is in a range of 7: 1 to 9: 1.

A self-crosslinking acrylic polymer within the protective layer according to the second embodiment described herein is preferably selected from the group consisting of styrene-acrylic acid ester copolymers, acrylamide-containing copolymers of styrene and acrylic acid esters and copolymers based on acrylonitrile, methacrylamide and acrylic esters. The latter are preferred. As a pigment alkaline bentonite, natural or precipitated calcium carbonate, kaolin, silica or aluminum hydroxide may be incorporated into the protective layer. Preferred crosslinking agents are selected from the group consisting of cyclic urea, methylol urea, ammonium zirconium carbonate and polyamide-epichlorohydrin resins.

The choice of a water-insoluble, self-crosslinking acrylic polymer as a binder and its weight ratio (i) to pigment in a range of 7: 1 to 9: 1 and (ii) to crosslinking agent greater than 5: 1 is already a protective layer with a relatively low surface mass a high Environmental resistance of the heat-sensitive recording material according to the invention given. Such weight ratios are thus preferred.

The protective layer itself can be applied by means of conventional brushing, for which inter alia a coating color is usable, preferably with a surface-related mass in a range from 1.0 to 4.5 g / m ² . In an alternative variant, the protective layer is printed. Processing technology and particularly suitable in terms of their technological properties are those protective layers which are curable by means of actinic radiation. The term "actinic radiation" UV or ionizing radiation, such as electron beams to understand.

The appearance of the protective layer is significantly determined by the type of smoothing and the friction in the calender and calender influencing roll surfaces and their materials. In particular, due to existing market requirements, a roughness (Parker Print Surf roughness) of the protective layer of less than 1.5 microns (determined according to the ISO standard 8791, part 4 ) are considered preferred. In the context of the experimental work preceding this invention, the use of calendering tools in which NipcoFlex ^™ or zone controlled Nipco P ^™ rolls are used has proven particularly useful; however, the invention is not limited thereto.

A further aspect of the present invention relates to the use of a heat-sensitive recording material according to the invention as entrance tickets, air tickets, rail tickets, bus tickets, gambling papers, parking tickets, labels, receipts, bank statements, self-adhesive labels, medical chart paper, fax paper, security paper or barcode labels.

A further aspect of the present invention relates to products, preferably tickets, air, rail, boat or bus ticket, gambling document, parking ticket, label, receipt, bank statements, self-adhesive label, medical chart paper, fax paper, security paper or bar code labels, comprising a heat-sensitive according to the invention recording material.

zur Verbesserung der Fettbeständigkeit, insbesondere der Beständigkeit gegenüber Lanolin, eines Druckbildes eines wärmeempfindlichen Aufzeichnungsmaterials, bei dem eine Verbindung der Formel (I)

wobei die Verbindung der Formel (I) in einer kristallinen Form vorliegt, die im IR-Spektrum eine Absorptionsbande bei 3401 ± 20 cm^–1 aufweist, als Farbentwickler enthalten ist, wobei das Massenverhältnis zwischen der Verbindung der Formel (I) und der Verbindung der Formel (II) 99,5:0,5 bis 65:35 beträgt, vorzugsweise 97:3 bis 85:15 beträgt, besonders bevorzugt 95:5 bis 90:10 beträgt. A further aspect of the present invention relates to a use of a compound of the formula (II)

for improving the grease resistance, in particular the resistance to lanolin, of a printed image of a thermosensitive recording material in which a compound of the formula (I)

wherein the compound of the formula (I) is in a crystalline form having an absorption band at 3401 ± 20 cm ^-1 in the IR spectrum, contained as a color developer, wherein the mass ratio between the compound of the formula (I) and the compound of the Formula (II) is 99.5: 0.5 to 65:35, preferably 97: 3 to 85:15, more preferably 95: 5 to 90:10.

• i. Bereitstellen oder Herstellen eines Trägersubstrates;
• ii. Bereitstellen oder Herstellen einer Beschichtungszusammensetzung, umfassend eine Verbindung der Formel (I) wie in einem erfindungsgemäßen wärmeempfindlichen Aufzeichnungsmaterial eingesetzt und eine Verbindung der Formel (II) wie in einem erfindungsgemäßen wärmeempfindlichen Aufzeichnungsmaterial eingesetzt;
• iii. Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung auf das bereitgestellte oder hergestellte Trägersubstrat;
• iv. Trocknen der aufgebrachten Beschichtungszusammensetzung unter Ausbildung einer wärmeempfindlichen Aufzeichnungsschicht.

A further aspect of the present invention relates to a process for producing a heat-sensitive recording material, at least comprising the following process steps:

• i. Providing or producing a carrier substrate;
• ii. Providing or preparing a coating composition comprising a compound of the formula (I) as used in a heat-sensitive recording material of the invention and a compound of the formula (II) as used in a heat-sensitive recording material of the invention;
• iii. Applying the provided or prepared coating composition to the provided or prepared carrier substrate;
• iv. Drying the applied coating composition to form a heat-sensitive recording layer.

• a) Bereitstellen oder Herstellen einer Beschichtungszusammensetzung umfassend Pigmente;
• b) Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung auf dem Trägersubstrat;
• c) Trocknen der aufgebrachten Beschichtungszusammensetzung unter Ausbildung einer Zwischenschicht;

wobei die Verfahrensschritte a) bis c) vor dem Verfahrensschritt ii. durchgeführt werden und die Zwischenschicht zwischen dem Trägersubstrat und der wärmeempfindlichen Aufzeichnungsschicht angeordnet ist. Sofern eine Zwischenschicht ausgebildet wird, erfolgt das Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung in Schritt iii. des erfindungsgemäßen Verfahrens auf die ausgebildete Zwischenschicht und nicht direkt auf das bereitgestellte oder hergestellte Trägersubstrat. According to the invention, a method additionally comprising the method steps is preferred

• a) providing or preparing a coating composition comprising pigments;
• b) applying the provided or prepared coating composition to the carrier substrate;
• c) drying the applied coating composition to form an intermediate layer;

wherein the method steps a) to c) before the method step ii. and the intermediate layer is disposed between the support substrate and the heat-sensitive recording layer. If an intermediate layer is formed, the coating composition provided or prepared is applied in step iii. of the inventive method on the formed intermediate layer and not directly on the provided or prepared carrier substrate.

• A) Bereitstellen oder Herstellen einer Beschichtungszusammensetzung;
• B) Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung auf der wärmeempfindlichen Aufzeichnungsschicht;
• C) Trocknen der aufgebrachten Beschichtungszusammensetzung unter Ausbildung einer Schutzschicht;

wobei die Verfahrensschritte A) bis C) nach dem Verfahrensschritt iv. durchgeführt werden und die Schutzschicht auf der wärmeempfindlichen Aufzeichnungsschicht angeordnet ist. Also preferred according to the invention is a method additionally comprising the method steps

• A) providing or preparing a coating composition;
• B) applying the provided or prepared coating composition to the heat-sensitive recording layer;
• C) drying the applied coating composition to form a protective layer;

wherein the method steps A) to C) after the method step iv. and the protective layer is disposed on the heat-sensitive recording layer.

1 shows a comparison of IR spectra in the wavenumber range of about 4000 to 2000 cm ^{-1 of} the two crystalline forms of the compound of formula (I). Shown in the upper part and denoted by a) is the IR spectrum of the crystalline form used according to the invention of the compound of formula (I) with a melting point of 175 ° C. Shown in the lower part and labeled b) is the IR spectrum of the crystalline form of the compound of the formula (I) having a melting point of about 158 ° C.

2 shows a comparison of IR spectra in the wavenumber range of about 2400 to 400 cm ^{-1 of} the two crystalline forms of the compound of formula (I). Shown in the upper part and denoted by a) is the IR spectrum of the crystalline form used according to the invention of the compound of formula (I) with a melting point of 175 ° C. Shown in the lower part and labeled b) is the IR spectrum of the crystalline form of the compound of the formula (I) having a melting point of about 158 ° C.

3 shows a comparison of IR spectra of the two crystalline forms of the compound of formula (I). Shown in the upper part and denoted by a) is the IR spectrum of the crystalline form used according to the invention of the compound of formula (I) with a melting point of 175 ° C. Shown in the lower part and labeled b) is the IR spectrum of the crystalline form of the compound of the formula (I) having a melting point of about 158 ° C.

4 shows a comparison of X-ray powder diffraction patterns of the two crystalline forms of the compound of formula (I). Shown in the upper part and denoted by a) is the X-ray powder diffractogram of the crystalline form of the compound of formula (I) with a melting point of about 158 ° C. Shown in the lower part and denoted by b) is the X-ray powder diffractogram of the crystalline form of the compound of the formula (I) having a melting point of 175 ° C. used according to the invention.

5 shows the results of determination of long-term climatic resistance of heat-sensitive recording materials (at 40 ° C and 90% RH). In the diagram shown, the resistance of the printed image in% is shown as a function of the ratio of the compounds of the formulas (I) and (II).

6 shows the results of determination of the resistance of thermosensitive recording materials to lanolin. In the diagram shown, the resistance of the printed image in% is shown as a function of the ratio of the compounds of the formulas (I) and (II).

The following examples and comparative examples will further illustrate the invention:

Examples 1 to 5 and Comparative Examples 1 to 12:

On a fourdrinier paper machine, a paper web of bleached and ground hardwood and softwood pulps with a basis weight of 67 g / m ² is prepared as the carrier substrate with the addition of customary additives in conventional amounts. On the front side, an intermediate layer comprising hollow-shell pigments and calcined kaolin as pigment, styrene-butadiene latex as binder and starch as cobinder with a mass per unit area of 9 g / m ^{2 is} applied using a roller-blade coating unit and dried conventionally.

Using a coater, a heat-sensitive recording layer with a basis weight of 6.0 g / m ^{2 is} applied to the intermediate layer by means of a roller blade coating unit and dried conventionally after the application.

For the heat-sensitive recording layer, there is used a formulation containing as a binder a mixture comprising polyvinyl alcohol, 3-N-di-n-butylamine-6-methyl-7-anilinofluoran (50 parts by dry weight) as a color former and an acrylate copolymer and as pigment comprises calcium carbonate. Further constituents of the heat-sensitive recording layers of the individual exemplary embodiments are given in Table 1 below: Compound of the formula (I) Compound of the formula (II) Comparative Example 1 (not according to the invention) 100 atro parts by weight 0 atro parts by weight Comparative Example 2 (not according to the invention) 0 atro parts by weight 100 atro parts by weight Example 1 (according to the invention) 99 atro parts by weight 1 atro parts by weight Example 2 (according to the invention) 97 atro parts by weight 3 atro parts by weight Example 3 (according to the invention) 95 atro parts by weight 5 atro parts by weight Example 4 (according to the invention) 93 atro parts by weight 7 atro parts by weight Example 5 (according to the invention) 90 atro parts by weight 10 atro parts by weight Example 6 (according to the invention) 80 atro parts by weight 20 atro parts by weight Example 7 (according to the invention) 70 atro parts by weight 30 atro parts by weight Comparative Example 3 (not according to the invention) 60 atro parts by weight 40 atro parts by weight Comparative Example 4 (not according to the invention) 50 atro parts by weight 50 atro parts by weight Comparative Example 5 (not according to the invention) 40 atro parts by weight 60 atro parts by weight Comparative Example 6 (not according to the invention) 30 atro parts by weight 70 atro parts by weight Comparative Example 7 (not according to the invention) 20 atro parts by weight 80 atro parts by weight Comparative Example 8 (not according to the invention) 10 atro parts by weight 90 atro parts by weight Comparative Example 9 (not according to the invention) 5 atro parts by weight 95 atro parts by weight Comparative Example 10 (not according to the invention) 3 atro parts by weight 97 atro parts by weight Table 1

Examples 8 to 14:

Examples 8 to 14 were carried out analogously to Examples 1 to 7. However, the intermediate layer is not applied with a roller blade coating unit, but a contour line is drawn with a blade as an intermediate layer.

The heat-sensitive recording layer is applied by curtain coating, the basis weight being from 1.5 to 6.0 g / m 2, preferably from 2 to 5.5 g / m 2. The 3-N-di-n-butylamine-6-methyl-7-anilinofluoran (color former) is added in an amount of 40-60 parts by weight.

Determination of the climatic resistance of thermosensitive recording materials (at 40 ° C and 90% RH for 24 hours);

To measure the climatic resistance of a thermal print on the thermosensitive recording materials of Inventive Examples 1 to 5 and Comparative Examples 1 to 12, black-and-white checkered thermoprinting prints were each printed on the thermosensitive recording materials to be tested with an Atlantek 400 instrument from Printrex (USA ) using a thermal head with a resolution of 300 dpi and an energy per unit area of 16 mJ / mm ² .

After the preparation of the black and white plaid thermoprobing print, after a rest period of more than 5 minutes, a determination of the print density was carried out on three spots each of the black colored areas and the uncolored areas of the thermoprobing print using a Gretag Macbeth Model RD - 1152 "B" densitometer , From the respective measured values of the black-colored areas and the uncoloured areas, the average value was formed in each case.

A thermoprobing print was hung in a climatic cabinet at 40 ° C and 90% relative humidity. After 24 hours, the thermal paper printout was taken out, cooled to room temperature, and a print density determination was again carried out on three spots each of the black colored areas and the uncolored areas of the thermal printout by means of a Gretag Macbeth Model RD-1152 "B" densitometer. From the respective measured values black colored areas and the uncoloured areas the mean value was formed in each case.

The consistency of the printed image in% corresponds to the quotient of the average value of the print density of the colored areas before and after storage in the climate chamber multiplied by 100.

The measurement results thus obtained are listed in Table 2 and in 5 displayed: example Resistance of the printed image in% example Resistance of the printed image in% Example 1 (according to the invention) 97.3 Comparative Example 5 (not according to the invention) 87.6 Example 2 (according to the invention) 95.5 Comparative Example 6 (not according to the invention) 85.3 Example 3 (according to the invention) 96.4 Comparative Example 7 (not according to the invention) 80.8 Example 4 (according to the invention) 95.5 Comparative Example 8 (not according to the invention) 75.5 Example 5 (according to the invention) 95.4 Comparative Example 9 (not according to the invention) 74.0 Example 6 (according to the invention) 95.5 Comparative Example 10 (not according to the invention) 71.9 Example 7 (according to the invention) 93.6 Comparative Example 1 (not according to the invention) 96.4 Comparative Example 3 (not according to the invention) 92.5 Comparative Example 2 (not according to the invention) 70.8 Comparative Example 4 (not according to the invention) 89.4 Table 2

The measurement results shown in Table 2 show that the climatic resistance of thermosensitive recording materials (at 40 ° C and 90% RH for 24 hours) of Inventive Examples 1 to 7 remains approximately unchanged. In spite of adding a compound of the formula (II) which has poor climatic resistance (see Comparative Example 2), the climatic resistance of the heat-sensitive recording materials of the present invention is not deteriorated, which is very surprising.

Determination of resistance of thermosensitive recording materials to lanolin (10 minutes):

For measuring the resistance of a thermal expression on the heat-sensitive recording materials of Examples 1, 2 and 3 and Comparative Examples 1 and 2 to lanolin were on each of the thermosensitive recording materials to be tested black / white checkered designed Thermoprobeausdrucke with a device of the type Atlantek 400 of Company Printrex (USA), using a thermal head with a resolution of 300 dpi and an energy per unit area of 16 mJ / mm ² .

After making the black / white plaid thermoprobograph prints, after a rest time of more than 5 minutes at three points of the black colored areas and the unstained areas of the thermoprobograph prints, a print density determination was made by means of a Gretag MacBeth TYPE D19C densitometer. From the respective measured values of the black-colored areas and the uncoloured areas, the average value was formed in each case.

Subsequently, the prepared Thermoprobeausdruck the test thermosensitive recording material was coated with lanolin. After a reaction time of 10 minutes, the lanolin is carefully wiped off. A determination of the print density was again carried out on three spots of the black-colored areas and on the undyed areas of the thermoprobeable prints using a Gretag MacBeth TYPE D19C densitometer. From the respective measured values of the black-colored areas and the uncoloured areas, the average value was formed in each case.

The resistance to lanolin in% corresponds to the quotient of the formed average of the print density before the lanolin treatment and after the lanolin treatment multiplied by 100.

The measurement results thus obtained are listed in Table 3 and in 6 displayed: example Resistance to lanolin in% example Resistance to lanolin in% Example 1 (according to the invention) 14.3 Comparative Example 5 (not according to the invention) 64.9 Example 2 (according to the invention) 16.2 Comparative Example 6 (not according to the invention) 63.0 Example 3 (according to the invention) 23.3 Comparative Example 7 (not according to the invention) 62.9 Example 4 (according to the invention) 33.3 Comparative Example 8 (not according to the invention) 61.0 Example 5 (according to the invention) 45.1 Comparative Example 9 (not according to the invention) 63.4 Example 6 (according to the invention) 61.7 Comparative Example 10 (not according to the invention) 62.7 Example 7 (according to the invention) 65.8 Comparative Example 1 (not according to the invention) 13.0 Comparative Example 3 (not according to the invention) 63.4 Comparative Example 2 (not according to the invention) 62.7 Comparative Example 4 (not according to the invention) 64.2 Table 3.

The measurement results shown in Table 3 show that the resistance of the printed image to lanolin in Examples 1 to 7 of the invention is better than the durability of a printed image in which the color developer mixture was replaced in equal parts by weight with a compound of Formula (I) (Comparative Example 1) ). By adding even small amounts of the compound of formula (II) to the compound of formula (I), the resistance to lanolin can be significantly improved become. Surprisingly, the improvement in the resistance of the printed image to lanolin in the case of recording materials according to the invention is exponential.

Resistance to water and aqueous ethanol solutions (23 ° C, 50% rh, 24h):

By means of these tests, the resistance of the image formed on the recording layer to water and aqueous solutions is evaluated. To the printed areas produced by the TEC printer 572 at maximum pressure energy (level +1) is applied a drop of distilled water or the chosen aqueous 25% ethanol solution. The excess test liquid is dabbed after 20 minutes exposure time with a filter paper or cotton cloth and the test sheet then stored for 24 hours at room temperature (23 ° C, 50% relative humidity). Before application of the respective test liquid and after expiry of the storage time, the Macbeth Densitometer 1150 determines the optical density of the printed areas and their difference.

The resistance to water or aqueous ethanol solutions corresponds to the quotient of the average value of the print density formed before and after the treatment with the respective test fluid multiplied by 100.

The measurement results thus obtained are listed in Tables 4 and 5 below: Example Nr .: See 6 See 7 See Fig. 8 See 9 See 10 See 1 See 2 1 2 Water resistance (23 ° C, 50% rh, 24h): resistance 83.5 83.5 82.8 82.7 83.3 86.8 82.4 85.7 87.2 Resistance to 25% aqueous ethanol solution (23 ° C, 50% RH, 24 h): resistance 81.7 81.1 78.8 79.6 78.4 81.7 79.2 79.7 80.3 Tables 4: Results of Water and Aqueous Ethane Solution Resistance Tests (Part 1) (See Comparative Example) Example Nr .: 3 4 5 6 7 See 3 See 4 See Fig. 5 Water resistance (23 ° C, 50% RH, 24h): resistance 87.2 87.7 88.6 84.3 87 90.3 83.6 83.8 Resistance to 25% aqueous ethanol solution (23 ° C, 50% RH, 24h): resistance 82.1 82.6 84.2 85.2 84.3 85 83.6 81.1 Tables 5: Results of Resistance Testing against Water and Aqueous Ethanol Solutions (Part 2) (See Comparative Example)

The reproduced measurement results show that the resistance of the printed image to water and aqueous ethanol solution in Inventive Examples 1 to 7 did not deteriorate as compared with Comparative Examples 1 to 10.

Preparation of the crystalline form of the compound of the formula (I) used according to the invention:

The commercially available compound of formula (I) having a melting point of about 158 ° C is recrystallized from ethanol. The compound of the formula (I) according to the invention having a melting point of about 175 ° C. is obtained. The compound of the formula (I) according to the invention has an absorption band at 3401 ± 20 cm ^-1 in the IR spectrum.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004044204 A1 [0006]
• US 2005/0148467 A1 [0007]
• EP 1140515 B1 [0017]
• EP 2923851 A1 [0018, 0019, 0052, 0059]
• WO 2014/143174 A1 [0062]

Cited non-patent literature

• Japanese Standard JIS K 5101 [0046]
• ISO standard 8791, part 4 [0083]

Claims (10)

A heat-sensitive recording material comprising i) a support substrate and ii) a heat-sensitive recording layer, the heat-sensitive recording layer comprising a color former and a color developer mixture and the color developer mixture a) a compound of the formula (I)

in which the compound of the formula (I) is in a crystalline form which has an absorption band at 3401 ± 20 cm ^-1 in the IR spectrum, and b) a compound of the formula (II)

wherein the mass ratio between the compound of formula (I) and the compound of formula (II) is 99.5: 0.5 to 65:35. A heat-sensitive recording material according to claim 1, wherein the mass ratio between the compound of the formula (I) and the compound of the formula (II) is 97: 3 to 85:15, preferably 95: 5 to 90:10.  Heat-sensitive recording material according to one of the preceding claims, wherein the proportion of the color developer mixture in the heat-sensitive recording layer 35 to 15 wt .-%, preferably 31 to 19 wt .-%, particularly preferably 28 to 22 wt .-%, based on the total solids content the heat-sensitive recording layer. A heat-sensitive recording material according to any one of the preceding claims, wherein the basis weight of the heat-sensitive recording layer is in the range of 1.5 to 6 g / m ² , preferably in the range of 2.0 to 5.5 g / m ² .  A heat-sensitive recording material according to any one of the preceding claims, further comprising an intermediate layer located between the support substrate and the heat-sensitive recording layer, the intermediate layer preferably containing pigments.  A heat-sensitive recording material according to claim 5, wherein the pigments are a) organic pigments, preferably organic hollow body pigments and or b) is inorganic pigments, preferably selected from the list consisting of calcined kaolin, silica, bentonite, calcium carbonate, alumina and boehmite.  A heat-sensitive recording material according to any one of the preceding claims, wherein the heat-sensitive recording layer is completely or partially covered with a protective layer.  Use of a heat-sensitive recording material according to one of claims 1 to 7 as a flight, train, ship or bus ticket, gambling document, parking ticket, label, receipt, self-adhesive label, medical chart paper, fax paper or barcode labels. Use of a compound of the formula (II) as defined in any one of the preceding claims for improving the lanolin resistance of a printed image of a thermosensitive recording material comprising a compound of the formula (I) as defined in any one of the preceding claims as a color developer, the mass ratio being between the compound of formula (I) and the compound of formula (II) is 99.5: 0.5 to 65:35, preferably 97: 3 to 85:15, more preferably 95: 5 to 90:10.  Process for the preparation of a heat-sensitive recording material, comprising at least the following process steps: i. Providing or producing a carrier substrate; ii. Providing or preparing a coating composition comprising a compound of formula (I) as defined in any one of claims 1 to 7 and a compound of formula (II) as defined in any one of claims 1 to 7; iii. Applying the provided or prepared coating composition; iv. Drying the applied coating composition to form a heat-sensitive recording layer.

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