DE102019103679A1 - Heat-sensitive recording material with color developers made from renewable raw materials - Google Patents

Abstract

The present invention relates to a heat-sensitive recording material comprising i) a carrier substrate and ii) a heat-sensitive recording layer, the heat-sensitive recording layer comprising at least one color former and at least one color developer and the color developer or at least one of the color developers being selected from the group consisting of natural tanning agents and alkali - Or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethylcelluloses, resin acids, phytosterols, coumarins, monomeric phenolic compounds, lignins, lignans, fatty acids, extracts from delignification processes and / or, at least, from condensation products from delignification processes and from polycondensation products Mandelic acid as monomeric units.

Description

The present invention relates to a heat-sensitive recording material comprising i) a carrier substrate and ii) a heat-sensitive recording layer, the heat-sensitive recording layer comprising at least one color former and at least one color developer and the color developer or at least one of the color developers being selected from the group consisting of natural tanning agents, alkali - Or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethyl celluloses, resin acids, phytosterols, coumarins, monomeric phenolic compounds, lignins, lignans, fatty acids, extracts from delignification processes and / or, at least, from catechoresin products and from polycondensation products Mandelic acid as monomeric units.

Heat-sensitive recording materials have been known for many years and enjoy great popularity. This popularity is due, among other things, to the fact that their use is associated with the advantage that the color-forming components are contained in the recording material itself and therefore printers that do not require toner or ink cartridges can be used. It is therefore no longer necessary to purchase, store, change or refill toner or color cartridges. This innovative technology has largely established itself across the board, particularly in public transport and retail.

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

verstärkt im Zentrum öffentlicher Kritik und werden deshalb mitunter ersetzt durch

• ■ 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.

In the recent past, however, there have been increasing concerns about the environmental compatibility, in particular of certain (color) developers, also referred to as color acceptors, and in some cases also of dye precursors with which the (color) developers react when heated to form a visually recognizable color that cannot be ignored by industry and especially by trade. Recently, for example, the (color) developers have been using the well-known and scientifically excellently investigated components, known as

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

increasingly at the center of public criticism and are therefore sometimes replaced by

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

However, the alternatives used often have the disadvantage that they have to be synthesized in numerous steps due to their chemically complex structure. This leads to the fact that a lot of waste materials, such as solvents, by-products or auxiliary materials used during the synthesis, are generated and that a lot of energy has to be used for production. In addition, at least some of the starting materials or auxiliary materials used for the synthesis are non-renewable raw materials, i.e. Raw materials whose consumption is faster than their regeneration, such as petroleum.

The object of the present invention was to identify color developers for use in heat-sensitive recording materials which can be obtained partially or completely from renewable raw materials and thus lead to an improvement in the life cycle assessments (LCA) of the heat-sensitive recording material.

1. i) ein Trägersubstrat und
2. ii) eine wärmeempfindliche Aufzeichnungsschicht,

wobei die wärmeempfindliche Aufzeichnungsschicht mindestens einen Farbbildner und mindestens einen Farbentwickler umfasst und der Farbentwickler oder mindestens einer der Farbenwickler ausgewählt ist aus der Gruppe bestehend aus natürlichen Gerbstoffen, Alkali- oder Erdalkalimetallsalze von Tanninen, oligomere Proanthocyanidinen, Flavonoiden, Carbonsäuren, Saccharide, Saccharidderivate, Carboxymethylcellulosen, Harzsäuren, Phytosterinen, Cumarinen, monomere Phenolverbindungen, Ligninen, Lignanen, Fettsäuren, Extrakten aus Delignifizierungsprozessen und Polykondensationsprodukten hergestellt zumindest aus Pinoresinol, Catechin, Bernsteinsäure und/oder Mandelsäure als monomere Einheiten.Comprising thermosensitive recording material

1. i) a carrier substrate and
2. ii) a thermosensitive recording layer,

wherein the heat-sensitive recording layer comprises at least one color former and at least one color developer and the color developer or at least one of the color developers is selected from the group consisting of natural tanning agents, alkali or alkaline earth metal salts of tannins, oligomers Proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethyl celluloses, resin acids, phytosterols, coumarins, monomeric phenolic compounds, lignins, lignans, fatty acids, extracts from delignification processes and polycondensation products made at least from pinoresinol, catechol as monomeric units, and mandelic acid.

It has surprisingly been found that the above-mentioned groups of substances can be used as color developers.

In the present invention, two, three, four or more of the color developers to be used in the present invention can also be used; h, mixtures comprising two, three, four or more of the color developers selected from the group consisting of natural tanning agents, alkali or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethyl celluloses, resin acids, phytosterols, coumarins, monomeric phenol compounds , Lignins, lignans, fatty acids, extracts from delignification processes and polycondensation products made at least from pinoresinol, catechin, succinic acid and / or mandelic acid as monomeric units.

Tanning agents are chemical substances that are commonly used to tan animal hides. It was therefore surprising that tanning agents react with color formers to form a color when heated. Natural tannins are often found in plants, for example in leaves, woods, bark, fruits and roots of chestnuts, bananas, oaks, spruces, mimosas, quebracho, tea and coffee. According to the invention, both hydrolyzable tannins and condensed tannins can be used. According to the invention, the natural tanning agents are preferably a compound selected from the group consisting of tannin, catechu, chestnut extract, mimosa extract, tare and tannic acid (CAS number: 1401-55-4).

Tannins are polyhydroxyphenols that are found in dicotyledonous shrubs, shrubs and tree leaves and other parts of plants, especially in plants from the tropics and subtropics. According to the invention, hydrolyzable tannins (gallotannins) and condensed tannins (catechin tannins), also known as condensed proanthocyanidins, can be used. Catechu is a resin obtained from the hardwood of the gerber acacia (Senegalia catechu).

Our own studies have shown that alkali or alkaline earth metal salts of tannins can also be used as color developers. Alkaline earth metal salts of tannins and here in particular calcium and magnesium salts of tannins are particularly preferred. Magnesium salts of tannins, in particular magnesium salts of tannins, are very particularly preferred.

Oligomeric proanthocyanidins, also oligomeric procyanidins, OPC or PCO (oligomeric proanthocyanidins), are naturally occurring substances in plants that belong to the group of flavanols and can be assigned to the higher-level polyphenols. OPC are mostly dimers or trimers of catechins. Together with the polymeric proanthocyanidins they form the group of condensed proanthocyanides (tannins). According to the invention, it is preferred if the color developer is an oligomeric proanthocyanidin from grape seed extract.

The flavonoids are a group of secondary plant substances, to which a large part of the flower pigments belong. Like oligomeric proanthocyanidins and condensed proanthocyanides (tannins), the basic body is formally derived from flavan (2-phenylchroman): two aromatic rings connected by a tetrahydropyran ring.

According to the invention, the flavonoids are preferably a compound selected from the group consisting of quercitrin, quercetin, sparingly soluble catechin, (+) - catechin, (-) - catechin, guarana catechin, acacia catechin, (-) - epicatechin and (+) - epicatechin, particularly preferably a compound selected from the group consisting of (+) - catechin, (-) - catechin, (-) - epicatechin and (+) - epicatechin.

Guarana catechin, acacia catechin and sparingly soluble catechin are extracts from natural catechin sources, which in addition to catechin as a main component can also include other compounds. Due to the compounds that are present in addition to catechin, these catechins differ from pure catechins, for example in terms of melting point and color.

According to the invention, the carboxylic acids are preferably a compound selected from the group consisting of citric acid, L - (+) - ascorbic acid, ascorbic acid, salicylic acid, mandelic acid, 6-palmitoyl-L-ascorbic acid, succinic acid and 2,5-furandicarboxylic acid.

Our own studies have shown that these carboxylic acids are particularly suitable as color developers. It is also advantageous that these compounds have already been very well investigated and do not show any toxicity.

According to the invention, the saccharides are preferably compounds selected from the group consisting of cellobiose, glucose, sucrose and maltose. According to the invention, the saccharide is particularly preferably maltose.

According to the invention, the saccharide derivatives are preferably uronic acids or oxidized saccharides. It is preferred according to the invention if the uronic acid is a compound selected from the group consisting of D-glucuronic acid, mucic acid and D-saccharolactone. According to the invention, the oxidized saccharides are preferably oxidized cellobiose.

In the context of the present invention, resin acids are understood to mean diterpenic acids, which form the main components of the balsams (resins) of various conifers. According to the invention, the resin acids are preferably colophony, a mixture of different resin acids, and abietic acid.

According to the invention, the phytosterols are preferably β-sitosterol and the coumarins are umbelliferone.

According to the invention, the monomeric phenol compounds are preferably a compound selected from the group consisting of vanillin, vanillic acid, syringaldehyde, syringic acid, resorcinol and phloroglucinol.

According to the invention, the lignins are preferably pyrolysis lignin, precipitated lignin from delignification processes, straw lignin (preferably straw lignin produced using hydrothermal carbonization (HTC straw lignin)), sulfate lignin or organosolvlignin, preferably pyrolysis lignin made from beech wood, spruce wood or fir wood.

According to the invention, the lignans are preferably pinoresinol, ((+) - pinoresinol, (-) - pinoresinol or a mixture thereof) or raw pinoresinol.

Delignification processes are understood to mean processes, in particular chemical digestion processes for pulp and cellulose production with the aim of removing lignin and other accompanying substances (polyoses, resins) from the cellulose. For the purposes of this document, these processes are used to obtain extracts, lignin, for example as precipitated lignin, and the like.

According to the invention, the fatty acids are preferably stearic acid, myristic acid or lauric acid.

According to the invention, the extracts from delignification processes are preferably hydrophobic extracts from beech organosolva liquor, hydrophobic extracts from beech sulphate waste liquor or hydrophobic extracts from pine sulphate waste liquor. The extracts from delignification processes comprise complex mixtures of monomeric and higher molecular weight phenols.

According to the invention, the extracts from delignification processes can also be present in methylated form. For this purpose, the extracts are reacted with a methylating agent, for example tetramethylammonium hydroxide.

In the context of the present invention, carboxymethyl celluloses (CMC) are understood to mean cellulose ethers, derivatives of cellulose, in which at least some of the hydroxyl groups of the cellulose are linked as ethers to a carboxymethyl group (-CH ₂ -COOH). The carboxymethyl group can be modified, for example as a salt or ether. According to the invention, the carboxymethyl celluloses are (partially) hydrolyzed carboxymethyl cellulose, sodium carboxymethyl cellulose, methyl ether carboxymethyl cellulose or the acid form of carboxymethyl celluloses.

1. a) ein Polymer hergestellt aus Pinoresinol, Mandelsäure und Stearinsäure als Monomere,
2. b) ein Polymer hergestellt aus Catechin (vorzugsweise D-Catechin), Bernsteinsäure und Triethanolamin als Monomere,
3. c) ein Polymer hergestellt aus Catechin (vorzugsweise D-Catechin) und Zitronensäure als Monomere,
4. d) ein Polymer hergestellt aus Bernsteinsäure und Glycerin als Monomere oder
5. e) ein Polymer hergestellt aus Mandelsäure und Glycerin als Monomere.

For the purposes of the present invention, polycondensation products are polymers which have been produced by polycondensation of monomers. According to the invention, pinoresinol, catechin, succinic acid and / or mandelic acid are used as monomers, it also being possible to use other monomers (such as triethanolamine, stearic acid and glycerol). According to the invention, the polycondensation product is particularly preferably

1. a) a polymer made from pinoresinol, mandelic acid and stearic acid as monomers,
2. b) a polymer made from catechin (preferably D-catechin), succinic acid and triethanolamine as monomers,
3. c) a polymer made from catechin (preferably D-catechin) and citric acid as monomers,
4. d) a polymer made from succinic acid and glycerol as monomers or
5. e) a polymer made from mandelic acid and glycerin as monomers.

According to the invention, the compounds used as developers, namely color developers selected from the group consisting of natural tannins, alkali or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethyl celluloses, resin acids, phytosterols, coumarins, monomeric phenol compounds, can be used , Lignans, fatty acids, extracts from delignification processes and polycondensation products made at least from pinoresinol, catechin, succinic acid and / or mandelic acid are present as monomeric units, single, double, triple or more than triple alkylated. They are then alkyl derivatives of the corresponding compound.

Our own studies have surprisingly shown that the properties as color developers can be improved by alkylating the compounds. Without wishing to be bound by a specific theory, it is assumed that the alkyl groups contribute to stabilizing the color former.

According to the invention, the alkyl groups are preferably alkyl groups having 1 to 18 carbon atoms. The alkyl groups are particularly preferably methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, Octyl, nonyl, decyl, dodecyl, tetradecyl, hesadecyl or octadecyl groups. The alkyl groups are particularly preferably methyl groups.

An alkylated compound is understood to mean derivatives of the compound in which one, two, three or more than three alkyl groups are introduced into the compound. Usually, the carbon atoms of the compound are alkylated, and alkylation of heteroatoms is also possible if the compounds contain heteroatoms.

According to the invention it is also possible that the alkylation, i. at least one alkyl group is introduced by esterification or formation of an ether.

According to the invention, a heat-sensitive recording material is preferred, the carrier substrate being a paper, synthetic paper or a plastic film. A non-surface-treated base paper is particularly preferred as the carrier substrate, since it has good recyclability and good environmental compatibility. A base paper that has not been surface-treated is to be understood as meaning a base paper that has not been treated in a size press or in a coating device. As plastic films, films made of polypropylene or other polyolefins are preferred. Papers coated with one or more polyolefins (in particular polypropylene) are also preferred according to the invention.

According to the invention, a heat-sensitive recording material is preferred which additionally contains 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 preferred according to the invention if the mass per unit area of the intermediate layer is in the range from 5 to 20 g / m ² , preferably in the range from 7 to 12 g / m ² .

In the event that 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 studies have shown that the integration of organic pigments in the intermediate layer is advantageous, since organic pigments have a high heat reflectivity. Increased heat reflection of the intermediate layer designed with organic pigments increases the response of the heat-sensitive recording layer to heat, since the radiated heat is at least partially reflected into the heat-sensitive recording layer instead of being conducted to the carrier substrate. As a result, the sensitivity and the resolving power of the heat-sensitive recording material are markedly increased, and the printing speed in the thermal printer is also increased. In addition, the energy consumption can be reduced during the printing process, which is particularly advantageous for mobile devices. Hollow body pigments have air in their interior, as a result of which they usually have an even higher heat reflection and the sensitivity and the resolving power of the heat-sensitive recording material can be increased even further.

In the event that the intermediate layer contains pigments, it is preferred in an alternative embodiment of the invention if the pigments are inorganic pigments, preferably selected from the list consisting of calcined kaolin, silicon oxide, bentonite, calcium carbonate, aluminum oxide and boehmite .

If inorganic pigments are incorporated into the intermediate layer between the recording layer and the substrate, these pigments can absorb the components (e.g. waxes) of the heat-sensitive recording layer that are liquefied by the action of heat from the thermal head during the formation of the typeface and thus promote an even more reliable and faster functioning of the heat-induced recording.

It is particularly advantageous if the inorganic pigments of the intermediate layer ^cm3 / 100 g, and more preferably 100 ^cm3 / 100 g, an oil absorption of at least 80, determined according to the Japanese standard JIS K 5101, have. Calcined kaolin has proven particularly useful due to its large absorption reservoir in the cavities. Mixtures of several different types of inorganic pigments are also conceivable.

The quantitative ratio between organic and inorganic pigment is a combination of the effects brought about by the two types of pigment, which is achieved particularly advantageously when the pigment mixture has a mass fraction of 5 to 30% or, better still, 8 to 20% of organic and a mass fraction of 95 to 70% or better 92 to 80% of inorganic pigment. Pigment mixtures of different organic pigments and / or inorganic pigments are conceivable.

According to the invention, a heat-sensitive recording material is preferred, 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 admixture of at least one natural polymer, such as particularly preferably starch, is a particularly suitable embodiment. In the context of tests with inorganic pigments, it was also found that a binder-pigment ratio within the intermediate layer between 3: 7 and 1: 9, based in each case on the percentage mass fraction in the intermediate layer, represents a particularly suitable embodiment.

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

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

A preferred heat-sensitive recording material according to the invention preferably has compounds of the fluorine type as color formers, selected from the group consisting of 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3'-methylphenylamino) fluorane (6 '- (diethylamino) -3'-methyl-2' - (m-tolylamino) -3H-spiro [isobenzofuran-1,9'-xanthene] -3-one; ODB-7), 3-di- n-pentyl-amino-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-butyl-phenylamino) 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-tetrahydrofurfuryl) 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.

Also preferred are heat-sensitive recording materials according to the invention which, as color formers, are those in paragraphs [0049] to [0052] of EP 2 923 851 A1 contain compounds mentioned.

According to the invention, a heat-sensitive recording material is particularly preferred, the color former being 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.

According to the invention, a heat-sensitive recording material is preferred, the heat-sensitive layer, in addition to the color developers used according to the invention, additionally containing color developers selected from the group consisting of N- (4-methylphenylsulfonyl) -N '- (3- (4-methylphenylsulfonyloxy) phenyl) urea (Pergafast ® 201), 4-hydroxy-4'-isopropoxydiphenylsulfone (D8), N- [2- (3-phenylureido) phenyl] benzenesulfonamide, N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide and N- {2- [(Phenylcarbamoyl) amino] phenyl} benzenesulfonamide. N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide can have a melting point of about 158 or about 175 ° C., depending on the crystal structure of the compound used. According to the invention, N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide with a melting point of 175 ° C. is preferred.

A heat-sensitive recording material is preferred according to the invention, the heat-sensitive recording layer containing a sensitizer.

When using a sensitizer, the sensitizer is first melted during the application of heat during the printing process, and the melted sensitizer dissolves the color formers and color developers present next to one another in the heat-sensitive recording layer and / or lowers the melting temperature of the color formers and color developers to cause a color development reaction. The sensitizer itself does not take part in the color development reaction.

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

According to the invention, 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, methylol stearic acid amide), naphthalene derivatives, biphenyl derivatives and phthalates can be used as sensitizers.

According to the invention, a heat-sensitive recording material is particularly preferred, the sensitizer being 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) diethylether, 4,4'-diallyloxydiphenylsulfone, 4-acetylacetophenone, 4-benzybiphenyl, acetoacetic anilide, benzyl-2-naphthylether, Benzyl naphthyl ether, benzyl 4- (benzyloxy) benzoate, benzyl paraben, bis (4-chlorobenzyl) o-xalate ester, bis (4-methoxyphenyl) ether, dibenzyl oxalate, dibenzyl terephthalate, fatty acid, methyl acid, ethylenic acid, dimethyl sulfone, diphenyl adipsulfonate, diphenyl adipsulfonate -Terpenyl, N-hydroxymethylstearic acid amine, N-methylol stearamide, N-stearylurea, N-stearyl stearic acid amide, p-benzylbiphenyl, phenylbenzenesulphonate ester, salicylic anilide, stearamide and α, α'-diphenoxyxulphon, 1,2-methylphenylsulphon, where benzylnaphylnaphyl (m, 1,2-methylphenylsulphon-diphenoxythylsulphon, 1,2-methylphenylsulphon,) ) ethane and 1, 2-diphenoxyethane are particularly preferred.

Also preferred are heat-sensitive recording materials according to the invention which, as sensitizers, are those described in paragraphs [0059] to [0061] of EP2923851A1 contain compounds mentioned.

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

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

Preference is given to heat-sensitive recording materials in which the heat-sensitive recording layer contains 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, and silanol groups -modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acrylate copolymer and film-forming acrylic copolymers.

In addition to one or more binders, the coating composition for forming the heat-sensitive recording layer of the heat-sensitive recording material according to the invention preferably contains one or more crosslinking agents for the binder or binders. Preferably, the crosslinking agent is selected from the group consisting of zirconium, Polyamidaminepichlorhydrinharzen, boric acid, glyoxal, dihydroxy bis (ammonium lactato) titanium (IV) (CAS No. 65104-06-5;. Tyzor ^® LA) and glyoxal derivatives.

A heat-sensitive recording material according to the invention, the heat-sensitive recording layer of which is formed from such a coating composition containing one or more binders and one or more crosslinking agents for the binder or binders, contains in the heat-sensitive recording layer one or more binders crosslinked by reaction with one or more crosslinking agents, wherein the crosslinking agent or agents are selected from the group consisting of zirconium carbonate, polyamidamine epichlorohydrin resins, boric acid, glyoxal, dihydroxy bis (ammonium lactato) titanium (IV) (CAS No. 65104-06-5; Tyzor ^® LA) and glyoxal derivatives. “Crosslinked binder” is understood to mean the reaction product formed by the reaction of a binder with one or more crosslinking agents.

According to the invention, a heat-sensitive recording material is preferred, the weight per unit area of the heat-sensitive recording layer being in the range from 1.5 to 6 g / m ² , preferably in the range from 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 mass fraction of the color developer mixture in the heat-sensitive recording layer being 35 to 15%, preferably 31 to 19%, particularly preferably 28 to 22%, based on the total solids content of the heat-sensitive recording layer.

Image stabilizers, dispersants, antioxidants, release agents, defoamers, light stabilizers, brighteners, as are known in the prior art, can additionally be used in the recording materials according to the invention. Each of the components is usually used in a mass fraction of 0.01 to 15%, in particular - with the exception of defoamer - 0.1 to 15%, preferably 1 to 10%, based on the total solids mass fraction of the heat-sensitive recording layer. If defoamers are used in the relevant formulations, the defoamer can be present in the recording materials according to the invention in a mass fraction of 0.03 to 0.05%, 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 arranging a protective layer covering the heat-sensitive recording layer, the heat-sensitive recording layer is also shielded from the outside or from the carrier substrate of the next layer within a roll, so that protection against external influences takes place.

In such cases, such a protective layer, in addition to protecting the heat-sensitive recording layer arranged under the protective layer, from environmental influences often has the additional positive effect of making the heat-sensitive recording material according to the invention printable, especially in indigo. Improve offset and flexographic printing. Because of this, it can be for certain Applications may be desired that the heat-sensitive recording material according to the invention has a protective layer, although the presence of a color developer mixture as defined above in the heat-sensitive recording layer of the heat-sensitive recording material according to the invention, the resistance of a thermal print available on a heat-sensitive recording material according to the invention to substances selected from the group consisting of water, Alcohols, fats, oils and their mixtures is sufficient even without a protective layer.

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

If present, the coating composition for forming the protective layer of the heat-sensitive recording material according to the invention preferably contains, in addition to one or more binders, one or more crosslinking agents for the binder or binders. The crosslinking agent is then preferably selected from the group consisting of boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, sodium glyoxylate, calcium glyoxylate, sodium / calcium glyoxylate, adipic acid dihydrazide, melamine formaldehyde, lactic acid (lactic acid) oxybenziramate (ammonium-epichloride) urea, and IV) Tyzor ^® LA (CAS no. 65104-06-5).

A heat-sensitive recording material according to the invention, the protective layer of which is formed from such a coating composition containing 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, the or the crosslinking agents are selected from the group consisting of boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, sodium glyoxylate, calcium glyoxylate, sodium / calcium glyoxylate, adipic acid dihydrazide, melamine formaldehyde, urea, methylolurea, ammonium-epichlorohydrazide, urea, methylolurea, ammonium-hydrocarbonate, dihydric acid, urea, methylolurea, ammonium-hydrocarbonate-dihydric, urea, methylolurea (ammonium-hydrochloride). Tyzor ^® LA (CAS No. 65104-06-5). “Crosslinked binder” is understood to mean the reaction product formed by the reaction of a binder with one or more crosslinking agents.

In a first embodiment variant, the protective layer which completely or partially covering the heat-sensitive recording layer can be obtained from a coating compound 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. Mixtures of different polyvinyl alcohols modified with carboxyl groups or silanols can also be used with preference. Such a protective layer has a high affinity for the preferably UV-crosslinking printing ink used in the offset printing process. This makes a decisive contribution to meeting the requirement for excellent printability within offset printing.

The crosslinking agent or 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, polyaminepichlorohydrin resin, adipic acid dihydrazide, melamine formaldehyde and dihydroxybis (ammonium lactato) titanium (IV) Tyzor ^® LA (CAS no . 65104-06-5). Mixtures of different crosslinking agents are also possible.

The weight ratio of the modified polyvinyl alcohol to the crosslinking agent in the coating composition for forming the protective layer according to this variant is preferably in a range from 20: 1 to 5: 1 and particularly preferably in a range from 12: 1 to 7: 1 The ratio of the modified polyvinyl alcohol to the crosslinking agent in the range of 100 parts by mass to 8 to 11 parts by mass.

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

It is preferred to apply the protective layer according to this embodiment variant with a mass per unit area in a range from 1.0 g / m ² to 6 g / m ² and particularly preferably from 1.2 g / m ² to 3.8 g / m ² . The protective layer is preferably formed in one layer.

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

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

By choosing a water-insoluble, self-crosslinking acrylic polymer as a binder and its mass ratio (i) to pigment in a range from 7: 1 to 9: 1 and (ii) to crosslinking agent greater than 5: 1, even with a protective layer with a relatively low mass per unit area given a high environmental resistance of the heat-sensitive recording material according to the invention. Such mass ratios are therefore preferred.

The protective layer itself can be applied with the help of conventional coating devices, for which a coating color, among other things, can be used, preferably with a mass per unit area in a range from 1.0 to 4.5 g / m ² . In an alternative variant, the protective layer is printed on. Particularly suitable in terms of processing technology and with regard to their technological properties are those protective layers which can be cured with the aid of actinic radiation. The term “actinic radiation” means UV or ionizing radiation, such as electron beams.

The appearance of the protective layer is largely determined by the type of smoothing and the roller surfaces and their materials that influence the friction in the smoothing unit and calender. In particular because of existing market requirements, a roughness (Parker Print Surf roughness) of the protective layer of less than 1.5 μm (determined in accordance with ISO standard 8791, part 4) is considered to be preferred. The use of calendering units in which NipcoFlex ™ or zone-regulated Nipco-P ™ rolls are used has proven particularly useful in the experimental work preceding this invention; however, the invention is not limited to this.

Another aspect of the present invention relates to the use of a paint curler selected from the group consisting of natural tanning agents, alkali or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethylcelluloses, resin acids, phytosterols, coumarins, monomeric phenol compounds, ligninol compounds , Lignans, fatty acids, extracts from delignification processes and polycondensation products made at least from pinoresinol, catechin, succinic acid and / or mandelic acid as monomeric units in heat-sensitive recording materials.

Another aspect of the present invention relates to the use of a heat-sensitive recording material according to the invention as admission tickets, flight, train, ship or bus tickets, gambling receipts, parking tickets, labels, receipts, bank statements, self-adhesive labels, medical chart paper, fax paper, security paper or barcode labels.

Another aspect of the present invention relates to products, preferably admission tickets, flight, train, ship or bus tickets, gambling receipts, parking tickets, labels, receipts, bank statements, self-adhesive labels, medical chart paper, fax paper, security paper or barcode labels, comprising a heat-sensitive label according to the invention Recording material.

1. i. Bereitstellen oder Herstellen eines Trägersubstrates;
2. ii. Bereitstellen oder Herstellen einer Beschichtungszusammensetzung, umfassend einen Farbbildner und einen Farbenwickler ausgewählt aus der Gruppe bestehend aus natürlichen Gerbstoffen, Alkali- oder Erdalkalimetallsalze von Tanninen, oligomere Proanthocyanidinen, Flavonoiden, Carbonsäuren, Saccharide, Saccharidderivate, Carboxymethylcellulosen, Harzsäuren, Phytosterinen, Cumarinen, monomere Phenolverbindungen, Ligninen, Lignanen, Fettsäuren, Extrakten aus Delignifizierungsprozessen und Polykondensationsprodukten hergestellt zumindest aus Pinoresinol, Catechin, Bernsteinsäure und/oder Mandelsäure als monomere Einheiten,
3. iii. Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung auf das bereitgestellte oder hergestellte Trägersubstrat;
4. iv. Trocknen der aufgebrachten Beschichtungszusammensetzung unter Ausbildung einer wärmeempfindlichen Aufzeichnungsschicht.

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

1. i. Providing or producing a carrier substrate;
2. ii. Providing or producing a coating composition comprising a color former and a color developer selected from the group consisting of natural tannins, alkali or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethylcelluloses, resin acids, phytosterols, coumarins, Lignins, lignans, fatty acids, extracts from delignification processes and polycondensation products made at least from pinoresinol, catechin, succinic acid and / or mandelic acid as monomeric units,
3. iii. Applying the provided or produced coating composition to the provided or produced carrier substrate;
4. iv. Drying the applied coating composition to form a thermosensitive recording layer.

1. a) Bereitstellen oder Herstellen einer Beschichtungszusammensetzung umfassend Pigmente;
2. b) Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung auf dem Trägersubstrat;
3. 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 is also preferably comprising the method steps

1. a) providing or producing a coating composition comprising pigments;
2. b) applying the provided or produced coating composition to the carrier substrate;
3. c) drying the applied coating composition to form an intermediate layer;

process steps a) to c) before process step ii. and the intermediate layer is disposed between the support substrate and the thermosensitive recording layer. If an intermediate layer is formed, the coating composition provided or produced is applied in step iii. of the method according to the invention on the intermediate layer formed and not directly on the prepared or produced carrier substrate.

1. A) Bereitstellen oder Herstellen einer Beschichtungszusammensetzung;
2. B) Aufbringen der bereitgestellten oder hergestellten Beschichtungszusammensetzung auf der wärmeempfindlichen Aufzeichnungsschicht;
3. 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

1. A) providing or producing a coating composition;
2. B) applying the coating composition provided or prepared to the heat-sensitive recording layer;
3. C) drying the applied coating composition to form a protective layer;

process steps A) to C) after process step iv. and the protective layer is disposed on the thermosensitive recording layer.

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

Example:

The individual compounds were screened for their suitability as potential developers. The screening of potential developers was carried out in a melting point apparatus according to Thiele. The substance to be tested as a developer is mixed in a mass ratio of 1: 1 or 4: 1 with 3-Nn-dibutylamine-6-methyl-7-anilinofluoran (ODB-2) as a color former and then in a melting capillary in a melting point apparatus according to Thiele heated up to a temperature of 230 ° C. Possible melting points or color change temperatures are noted. The melt capillaries are filled with the sample mixture about 3 mm high. If the sample mixtures are liquid or pasty, they are introduced into the enamel capillaries using syringes with long syringe tips. The results are given in the table below: substance Melting point [° C] Own color Color of the heated mixture Discoloration temp. the mixture [° C] Catechu - light brown black 175-230 Tannin - light beige black 150-179 Chestnut extract - medium brown black 190-225 Mimosa extract - beige black 190-230 Tare - light beige black 120-180 Grape seed extract - light brown black 130-230 Quercetin - yellow black 180-230 Quercitrin 172 yellow grey black 158 poorly soluble catechin 142 beige dark brown / black 130-137 D-catechin 140 beige black 134 Guarana catechin 200 beige grey black 138 Acacia catechin 198 beige black 140 L-epicatechin 237 light beige black 170-217 D-epicatechin 228 light beige black 165-185 citric acid 150 White black 142 L - (+) - ascorbic acid 189 White black 175 Salicylic acid 158 White black 115 Ascorbic acid 189 White black 178 D-glucuronic acid 165 White black 160-172 β-sitosterol 140 light beige white black 150 Umbelliferone 230 light beige black 155-180 Vanillin 82 White black 81-82 Vanillic acid 212 light beige grey black 168-195 Syringaldehyde 113 beige-white dark green 113-118 Syringic acid 207 beige black 179-205 Pyrolysis lignin (beech) - medium brown black 135-170 Pyrolysis lignin (spruce / fir) - medium brown black 130-150 Pyrolysis lignin - medium brown black 130-230 Organosolvlignin - medium brown dark brown / black 150-179 Sulphate lignin (beech) - dark brown black 140-162 Sulphate lignin (pine) - dark brown black 170-179 dI-pinoresinol 150 White black 143 Pinoresinol 151 White black 135 Organosolv extract - Orange red black 55 Sulphate extract (beech) - black black 120 Sulfate extract (pine) - red black 100

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• EP 2923851 A1 [0049, 0057]

Claims (10)

Comprising thermosensitive recording material i) a carrier substrate and ii) a heat-sensitive recording layer, wherein the heat-sensitive recording layer comprises at least one color former and at least one color developer and the color developer or at least one of the color developers is selected from the group consisting of natural tanning agents, alkali or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, Saccharides, saccharide derivatives, carboxymethyl celluloses, resin acids, phytosterols, coumarins, monomeric phenolic compounds, lignins, lignans, fatty acids, extracts from delignification processes and polycondensation products made at least from pinoresinol, catechin, succinic acid and / or mandelic acid as monomeric units. Heat-sensitive recording material according to Claim 1 , the natural tanning agents being a compound selected from the group consisting of tannin, catechu, chestnut extract, mimosa extract, tare and tannic acid (CAS number: 1401-55-4). Heat-sensitive recording material according to Claim 1 , wherein the color developer is an oligomeric proanthocyanidin from grape seed extract. Heat-sensitive recording material according to Claim 1 , the flavonoids being a compound selected from the group consisting of quercitrin, quercetin, sparingly soluble catechin, (+) - catechin, (-) - catechin, guarana catechin, acacia catechin, (-) - Epicatechin and (+) - epicatechin. Heat-sensitive recording material according to Claim 1 , the carboxylic acids being a compound selected from the group consisting of citric acid, L - (+) - ascorbic acid, salicylic acid, ascorbic acid, mandelic acid, 6-palmitoyl-L-ascorbic acid, succinic acid and 2,5-furandicarboxylic acid. Heat-sensitive recording material according to Claim 1 , the saccharide derivatives being a compound selected from the group consisting of oxidized cellobiose, D-glucuronic acid, mucic acid and D-saccharolactone. Heat-sensitive recording material according to Claim 1 , the phytosterols being β-sitosterol and the coumarins being umbelliferone. Heat-sensitive recording material according to Claim 1 , the monomeric phenolic compounds being a compound selected from the group consisting of vanillin, vanillic acid, syringaldehyde, syringic acid, resorcinol and phloroglucinol. Heat-sensitive recording material according to Claim 1 , whereby the lignins are precipitated lignin from delignin infection processes, straw lignin, sulphate lignin or organosolvlignin and the extracts from delignin infection processes are hydrophobic extracts from beech organosolve liquor, hydrophobic extracts from beech sulphate waste liquor or hydrophobic extracts from pine sulphate. Use of a compound selected from the group consisting of natural tanning agents, alkali or alkaline earth metal salts of tannins, oligomeric proanthocyanidins, flavonoids, carboxylic acids, saccharides, saccharide derivatives, carboxymethyl celluloses, resin acids, phytosterols, coumarins, monomeric phenolic compounds, lignins, lignans, extracts produced at least from pinoresinol, catechin, succinic acid and / or mandelic acid as monomeric units in heat-sensitive recording materials, preferably as color developers.