DE102023104323A1 - Coating for an environmentally friendly heat-sensitive recording material - Google Patents

Abstract

The present invention relates to a coating for an environmentally friendly, heat-sensitive recording material, which forms a visually recognizable typeface by means of a heat-induced phase change, consisting of or comprising a layer (A), consisting of or comprising i) one, two or more colored or black colorants, ii ) one, two or more fusible compounds of the general formula (I), where the compound of the general formula (I) has a melting point in the range from 60 to 160 ° C, the sum of the components ii) in the range from ≥ 3 to ≤ 80 Percentage by mass is based on the dry mass of layer (A) and iii) one, two or more polymeric organic binders, layer (A) containing no organic dye precursors, no hollow body pigments and no nanocellulose. The present invention also relates to a method for producing a coating for an environmentally friendly heat-sensitive recording material and the use of this as a heat-sensitive recording material. Furthermore, the present invention relates to a heat-sensitive recording material comprising a coating according to the invention.

Description

wobei die Verbindung der allgemeinen Formel (I) einen Schmelzpunkt im Bereich von 60 bis 160 °C aufweisen, wobei die Summe der Komponenten ii) im Bereich von ≥ 3 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (A) und iii) ein, zwei oder mehrere polymere organische Bindemittel, wobei die Schicht (A) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält. Die vorliegende Erfindung betrifft zudem ein Verfahren zur Herstellung einer Beschichtung für ein umweltfreundliches wärmeempfindliches Aufzeichnungsmaterial, sowie die Verwendung dieser als wärmeempfindliches Aufzeichnungsmaterial. Des Weiteren betrifft die vorliegende Erfindung ein wärmeempfindliches Aufzeichnungsmaterial umfassend eine erfindungsgemäße Beschichtung.The present invention relates to a coating for an environmentally friendly, heat-sensitive recording material, which forms a visually recognizable typeface by means of a heat-induced phase change, consisting of or comprising a layer (A), consisting of or comprising i) one, two or more colored or black colorants, ii ) one, two or more fusible compounds of general formula (I)

where the compound of the general formula (I) has a melting point in the range from 60 to 160° C., the sum of components ii) being in the range from ≧3 to ≦80 percent by mass, based on the dry mass of layer (A) and iii ) one, two or more polymeric organic binders, the layer (A) containing no organic dye precursors, no hollow body pigments and no nanocellulose. The present invention also relates to a method for producing a coating for an environmentally friendly heat-sensitive recording material and the use of this as a heat-sensitive recording material. Furthermore, the present invention relates to a heat-sensitive recording material comprising a coating according to the invention.

Thermal paper (often also referred to as “heat-sensitive recording materials”) is paper that can be written on with text, symbols or graphics by exposure to small amounts of heat (e.g. in the range of 2 to 16 mJ/mm ² ). Two different mechanisms of action of thermal papers are currently being described, which lead to the conversion of a coating through the action of heat, usually with the formation of a discoloration, and thus lead to a typeface.

The classic thermal papers contain an organic dye precursor, which is usually a colorless or less intensely colored compound that reacts through a chemical reaction to form an intensely colored dye. The chemical reaction here takes place between the organic dye precursor and a developer and is induced by the action of heat. In the past, bisphenol A (BPA) and bisphenol S (BPS) were commonly used as color developers. Due to health concerns about BPA, BPS and other developers containing phenol, these are often replaced by the alternative phenol-free substitutes Pergafast® 201 (equivalent to N-(4-methylphenylsulfonyl)-N-(3-(4-methylphenylsulfonyloxy)phenyl)urea), “D8” (corresponds to 4-Hydroxy-4'-isopropoxydiphenylsulfone), N-[2-(3-Phenylureido)phenyl]benzenesulfonamide or N-{2-[(Phenylcarbamoyl)amino]phenylbenzenesulfonamide.

With these classic thermal papers, there are concerns as to whether they can be disposed of as waste paper. The color developers used can be distributed as ingredients in the waste paper and can be returned to the consumer or the environment as recycling products. As a precaution, the German Federal Environment Agency recommends that thermal papers continue to be disposed of as residual waste, even if they do not contain BPA, BPS or other developers containing phenol.

Classic thermal papers are used, for example, in DE 10 2004 004 204 A1 or DE 10 2015 104 306 A1 described. In the DE 10 2004 004 204 A1 proposes 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.

In the U.S. 2014/0176652 A1 no classic thermal paper is described, but a white ink that can be used in inkjet printers. The white ink comprises white pigments, a branched triamide and a polymeric binder. A color change of the ink by heating is not described. Optionally, a UV dye can be added to the white ink, which emits light when exposed to UV light.

US 2012/0236091 A1 describes a magnetic ink comprising magnetic pigments and a vehicle that is mono- or tetra-amides. The ink can also contain a dye and a polymeric binder. After printing with the ink, it can be recorded with a magnetic reader (Magnetic Ink Character Recognition (MICR)). A color change of the ink due to heat is not described.

In the document DE 10 2015 104 306 A1 describes a heat-sensitive recording material which comprises a carrier substrate and a heat-sensitive color-forming layer containing at least one dye precursor and at least one phenol-free color developer, N-phenyl-N'[(phenylamino)sulfonyl]-urea, N-(4- methylphenyl)-N'[(4-ethylphenylamino)sulfonyl]urea, N-(4-ethoxycarbonylphenyl)-N'[(4-ethoxycarbonylphenylamino)sulfonyl]urea or structurally similar compounds can be used.

Thermal papers that contain no dye precursors and developers have been known for a number of years. With these papers, the base paper is coated over the entire surface with a dye (usually black) and a polymer layer comprising hollow microspheres is applied to this colored layer. The hollow microspheres collapse under the effect of heat and the initially opaque polymer layer becomes transparent, so that the dye underneath becomes visible.

In the WO 2012/145456 A1 a corresponding thermal paper is described, which a) a carrier with at least one colored surface and, arranged thereon, b) a layer which contains certain polymer particles with a core/shell structure, ie hollow microspheres, described, wherein the polymer particles, if they are dry, comprise at least one cavity.

In the WO2019183471A1 describes a thermal paper without dye precursor and developer, which contains two different types of scattering particles, wherein a first type of scattering particles changes its state from solid to liquid when heated. This first type of particle, upon melting, fills the spaces between a second type of particle (alumina particles or hollow microspheres), thereby eliminating or substantially reducing light scattering, revealing an underlying colorant at selected pressure points. In order to form a colored typeface, it is necessary for there to be a colored layer on which the particle-containing layer is applied.

These dye-precursor and developer-free thermal papers have several disadvantages. The use of hollow microspheres, but also aluminum hydroxide particles, is questionable since the former are microplastics and this can pose risks for the environment and water if these hollow microspheres are released. Pollution of the environment by micro- or nanoparticles poses a problem for ecosystems and the latest research results suggest that such particles can pose risks for smaller organisms as well as for humans. The recycling of thermal papers that contain microplastics is also problematic, since the microplastics cannot be separated efficiently and can be distributed as an ingredient in the waste paper and can return to the consumer or the environment as recycling products. In addition, the thermal papers containing microspheres have the disadvantage that they are sensitive to touch, since high pressure can also lead to the microspheres collapsing or the polymer layer can simply be scratched off. Aluminum hydroxide is often used in medicine as a phosphate former in dialysis or as an adjuvant for vaccines and has been criticized in the past because prolonged use in dialysis can cause cerebral toxicity (dementia), as well as bone toxicity, or in vaccines a can cause an allergic reaction. Even if the use of aluminum hydroxide is discussed in the medical literature and studies speak for or against the use of aluminum hydroxide, the use of aluminum hydroxide should be avoided as a precaution.

In addition, it has been shown that thermal papers contain organic materials that cannot be obtained from renewable raw materials, or only with great effort. It is therefore not possible or very expensive to obtain this thermal paper from renewable raw materials.

It was now a primary object of the present invention to provide a coating for a heat-sensitive recording material which has particularly good recyclability and high environmental compatibility while at the same time having excellent printability.

A further object was to provide a coating that can be obtained entirely or at least to a large extent from renewable raw materials.

A further object of the present invention is to design the coating in such a way that it is suitable for direct contact with people and/or food.

A further object of the present invention was to provide a heat-sensitive recording material which, in the printed state, has high resistance to environmental influences such as moisture, heat and/or chemicals.

• i) ein, zwei oder mehrere bunte oder schwarze Farbmittel,
• ii) eine, zwei oder mehrere schmelzbare Verbindungen der allgemeinen Formel (I)
  
  wobei R₁ ein substituierter oder unsubstituierter, verzweigter oder unverzweigter Alkyl- oder Alkylenrest mit acht bis 28 Kohlenstoffatomen ist oder ein Rest der allgemeinen Formel (II) ist
  
  wobei m eine ganze Zahl von 1 bis 21 ist und R₃ ein substituierter oder unsubstituierter, verzweigter oder unverzweigter Alkyl- oder Alkylenrest mit acht bis 28 Kohlenstoffatomen ist, und R₂ Wasserstoff, ein substituierter oder unsubstituierter, verzweigter oder unverzweigter Alkyl- oder Alkylenrest mit acht bis 28 Kohlenstoffatomen ist oder ein Rest der allgemeinen Formel (III) ist,
  
  wobei n eine ganze Zahl von 1 bis 21 ist und R₄ ein substituierter oder unsubstituierter, verzweigter oder unverzweigter Alkylrest mit acht bis 28 Kohlenstoffatomen ist, wobei die Verbindung der allgemeinen Formel (I) einen Schmelzpunkt im Bereich von 60 bis 160 °C aufweisen, wobei die Summe der Komponenten ii) im Bereich von ≥ 3 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (A)

und

• iii) ein, zwei oder mehrere polymere organische Bindemittel,

wobei die Schicht (A) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält.Surprisingly, it has now been found that the primary object and other objects and/or sub-objects of the present invention are achieved by a coating for a heat-sensitive recording material consisting of or comprising a layer (A) consisting of or comprising

• i) one, two or more colored or black colorants,
• ii) one, two or more fusible compounds of general formula (I)
  
  where R ₁ is a substituted or unsubstituted, branched or unbranched alkyl or alkylene radical having eight to 28 carbon atoms or a radical of the general formula (II).
  
  where m is an integer from 1 to 21 and R ₃ is a substituted or unsubstituted, branched or unbranched alkyl or alkylene group having eight to 28 carbon atoms, and R ₂ is hydrogen, a substituted or unsubstituted, branched or unbranched alkyl or alkylene group with is eight to 28 carbon atoms or is a radical of the general formula (III),
  
  where n is an integer from 1 to 21 and R ₄ is a substituted or unsubstituted, branched or unbranched alkyl radical having eight to 28 carbon atoms, the compound of general formula (I) having a melting point in the range from 60 to 160 °C, where the sum of components ii) is in the range from ≥ 3 to ≤ 80 percent by mass, based on the dry mass of layer (A)

and

• iii) one, two or more polymeric organic binders,

where layer (A) contains no organic dye precursors, no hollow body pigments and no nanocellulose.

The fusible compounds of the general formula (I) of component ii) with a melting point in the range from 60 to 160° C. are referred to below as fusible compounds, as a compound of the general formula (I) or as a fusible compound of the general formula (I).

The dotted line in the general formulas (II) and (III) indicates the point of connection (a CC single bond) of the residues on the compound of the general formula (I).

A coating is preferred according to the invention, wherein when R ₁ is an alkenyl radical, R 1 is an alkenyl radical with one double bond or two double bonds, preferably with one double bond.

A coating is preferred according to the invention, wherein when R ₁ is substituted, R 1 is substituted with a hydroxy group, preferably substituted with a hydroxy group.

A coating is particularly preferred according to the invention, where R ₁ is selected from the group consisting of nonyl, undecanyl, pentadecanyl, heptadecanyl, octadecyl, heneicosyl, heptadec-8-enyl, octadec-9-enyl, 11-hydroxyheptadecanyl and heneicos-12-enyl .

A coating is preferred according to the invention, wherein when R ₂ is an alkenyl radical, R ₂ is an alkenyl radical with one double bond or two double bonds, preferably with one double bond.

A coating is preferred according to the invention, wherein when R ₂ is substituted, R ₂ is substituted with a hydroxy group, preferably is substituted with a hydroxy group.

A coating is particularly preferred according to the invention, where R ₂ is selected from the group consisting of nonyl, undecanyl, pentadecanyl, heptadecanyl, octadecyl, heneicosyl, heptadec-8-enyl, octadec-9-enyl, 11-hydroxyheptadecanyl and heneicos-12-enyl .

A coating is preferred according to the invention, wherein when R ₃ is an alkenyl radical, R ₃ is an alkenyl radical with one double bond or two double bonds, preferably with one double bond.

A coating is preferred according to the invention, wherein when R ₃ is substituted, R ₃ is substituted with a hydroxy group, preferably substituted with a hydroxy group.

A coating is particularly preferred according to the invention, where R ₃ is selected from the group consisting of nonyl, undecanyl, pentadecanyl, heptadecanyl, octadecyl, heneicosyl, heptadec-8-enyl, octadec-9-enyl, 11-hydroxyheptadecanyl and heneicos-12-enyl .

A coating is preferred according to the invention, wherein when R ₄ is an alkenyl radical, R ₄ is an alkenyl radical with one double bond or two double bonds, preferably with one double bond.

A coating is preferred according to the invention, wherein when R ₄ is substituted, R ₄ is substituted with a hydroxy group, preferably substituted with a hydroxy group.

A coating is particularly preferred according to the invention, where R ₄ is selected from the group consisting of nonyl, undecanyl, pentadecanyl, heptadecanyl, octadecyl, heneicosyl, heptadec-8-enyl, octadec-9-enyl, 11-hydroxyheptadecanyl and heneicos-12-enyl .

A coating is particularly preferred according to the invention, where when R ₃ and R ₂ are each a substituted or unsubstituted, branched or unbranched alkyl or alkylene radical, both are identical.

A coating is particularly preferred according to the invention, where when R ₁ and R ₄ are each a substituted or unsubstituted, branched or unbranched alkyl or alkylene radical, both are identical.

A coating is preferred according to the invention, where n is an integer from 1 to 10, preferably an integer from 1 to 8, more preferably an integer is an integer from 1 to 6. In particular it is preferred if n is 1, 2, 3, 4, 5 or 6.

A coating is preferred according to the invention, where m is an integer from 1 to 10, preferably an integer from 1 to 8, more preferably an integer is an integer from 1 to 6. In particular, it is preferred when m is 1, 2, 3, 4, 5 or 6.

A coating is preferred according to the invention, the compound of the general formula (I) being selected from the group consisting of stearic acid amide (CAS number 124-26-5), N-(hydroxymethyl)stearamide (CAS number 3370-35-2) , Lauramide (CAS number 1120-16-7), Palmitamide (CAS number 629-54-9), 12-Hydroxystearamide (CAS number 7059-49-6), Oleamide (CAS number 301-02-0), Erucamide (CAS number 112-84-5), N-Stearyl stearamide (CAS number 13276-08-9), N-Stearyl oleamide (CAS number 6592-63-2; melting point 67°C), N-Oleyl stearamide (CAS number 6592-63-2), N-stearyl erucamide (CAS number 10094-45-8), ethylenebis oleamide (CAS number 110-31-6), hexamethylenebis oleamide (CAS number 6283-37- 0), N,N'-Dioleyl adipamide (CAS number 85888-37-5), Methylenebis stearamide (CAS number 109-23-9), Ethylenebis capramide (CAS number 51139-08-3), Ethylenebis lauramide ( CAS number 7003-56-7), ethylenebis stearamide (CAS number 110-30-5), ethylenebis 12-hydroxystearamide (CAS number 123-26-2), ethylene-bis-behenamide (CAS number 7445-68). -3), hexamethylenebis stearamide (CAS number 4112-25-8), hexamethylenebis behenamide (CAS number 96548-58-2), N,N'-distearyl adipamide (CAS number 25151-31-9) and hexamethylenebis 12 -hydroxystearamides (CAS number 55349-01-4). These compounds are hereinafter referred to as preferred fusible compounds.

Surprisingly, it has been shown in our own investigations that coatings according to the invention which contain a mixture of a) at least one colored or black colorant and b) at least one of the abovementioned compounds with the general formula (I) and in particular the preferred fusible compounds are suitable for forming a typeface without the need for an additional underlying colored layer. Depending on the dye used, the coatings according to the invention initially have a slight coloration and heating the coating causes it to become more intensively colored at certain points. The fusible compounds all have in common that they are organic compounds that melt in a temperature range of 60 to 160 °C. Without wishing to be bound by any particular theory, it is assumed that in the non-described state of the coating, the fusible compounds are present as domains which form an opaque layer. This opaque layer is hardly or very little permeable to light. These domains mean that the chromatic or black colorants contained in layer (A) do not show through to the outside, if at all. Upon melting, the fusible links coalesce into a predominantly continuous phase that has substantially reduced opacity and is nearly transparent. As a result, colored or black colorants become visible and a typeface is created. During the melting of the fusible compounds, it can also happen that the colored or black colorants separate from the molten phase, resulting in an accumulation of the colorants, e.g. in the background of the layer.

During the production of layer (A), the one, two or more fusible compounds of the general formula (I) described above are present as an aqueous dispersion. Without wanting to be bound by any particular theory, it is assumed that during the drying of the coating composition used to produce layer (A), individual particles of the fusible compounds are formed from the particles present in finely divided form in the aqueous dispersion. These domains are partially fixed by the polymeric organic binder or separated by the colorant. However, the individual domains can also border one another and form boundaries between the domains. Local heating of the layer above the melting point of the fusible compounds leads to a local melting of the domains, whereby a melting region is formed by deformation of the domains, which has a higher transparency, since the light is no longer refracted at the boundaries between the domains.

According to the invention, it is possible for the coatings to be produced entirely or predominantly from renewable raw materials, and the coatings can be composted and recycled since they contain neither organic dye precursors nor hollow body pigments or other nanoplastics. Our own investigations have shown that at least 90% of the coating is decomposed within 90 days in an industrial composting plant. This is possible in particular if one or more compounds produced from fatty acids, for example fatty acid amides such as stearic acid amide, are used as the fusible compound. These compounds are easily made from fats from renewable plants and are biodegradable.

Our own investigations have also shown that coatings according to the invention or heat-sensitive recording materials which contain coatings according to the invention can be recycled without removing the printing ink (also referred to as deinking) and can be processed, for example, into environmental paper/environmental protection paper. Initial studies also indicate that point out that coatings according to the invention or heat-sensitive recording materials which contain coatings according to the invention can also be used for ink removal during paper recycling. Without wishing to be bound to a fixed theory, it is assumed that the high hydrophobicity of the fusible compounds can improve or enable the removal of printing ink (deinking).

It has also been shown that the coatings can be in direct contact with people, animals and/or food.

In the context of this invention, a colorant is understood as meaning a coloring substance. This includes inorganic as well as organic colorants. Colorants are usually divided into pigments and dyes according to their solubility, pigments being insoluble in the application medium, i.e. in the coating or in the coating composition used to make the coating. The person skilled in the art distinguishes between chromatic and achromatic pigments, chromatic pigments meaning red, violet, blue, green, yellow, orange and brown pigments and achromatic meaning white and black pigments. In the context of the present invention, colored or black colorants are understood as meaning all colorants that are not white colorants.

In the context of the present connection, nanocellulose is understood to mean the following types of cellulose, namely cellulose nanocrystals, cellulose nanofibers, also referred to as nanofibrillated cellulose, or bacterial nanocellulose, which refers to nanostructured cellulose produced by bacteria.

In a preferred embodiment, one, two, at least one of the several or all black colorants are selected from the group consisting of aniline black, bone black, graphite, charcoal, vegetable charcoal, carbon black, copper dichromate, iron oxide black, vine black, spinel black, chrome iron brown hematite, Iron Manganese Black Oxide, Pigment Black, Manganese Black, Slate Black, Carbon Black and Frankfurt Black.

Our own investigations have surprisingly shown that these black color pigments lead to a particularly high contrast between printed and unprinted areas of the coating and are also compatible with the fusible compounds of component ii).

According to the invention, preference is given to a coating in which the layer (A) additionally comprises iv) one, two or more white colorants. Our own investigations have surprisingly shown that this can improve the contrast between printed and unprinted areas of the coating according to the invention if a white colorant is present in addition to a colored or black colorant.

A white colorant means organic or inorganic colorants that are white or nearly white. Depending on the origin and storage location of the white colorants, they can contain different concentrations of impurities or admixtures that affect the degree of whiteness of the minerals. The term white colorants includes both naturally occurring white minerals and synthetically produced white pigments and white dyes. The use of inorganic white colorants is preferred. The use of white minerals as white colorants is particularly preferred according to the invention.

In a preferred embodiment, one, two, at least one of the several or all of the white colorants are selected from the group consisting of calcined kaolin, natural kaolin, kaolinite, magnesium silicate hydrate, silicon dioxide, bentonite, calcium carbonate, calcium silicate hydrate, calcium aluminate sulfate, aluminum oxide, mica (MICA ) and boehmite. The white substance is particularly preferably kaolin and calcium carbonate.

Our own investigations have shown that it is advantageous if coatings according to the invention do not contain any aluminum hydroxide.

According to the invention, the form of the white colorant is preferably in the form of flakes or, if several white colorants are used, at least one white colorant or all of the colors are white medium flaky. It is therefore preferred if one, two, at least one of the plurality or all of the white colorants are in the form of flakes.

• Beispielsweise kann die Trockenmasse einer Probe (insbesondere einer Probe einer Schicht) für die Zwecke der vorliegenden Erfindung bestimmt werden, indem man eine Probe definierter Masse vor Trocknung (z.B. 1,5 g der Probe vor Trocknung) fünf Stunden lang bei 105 °C im Trockenofen trocknet und anschließend auf an sich bekannte Weise nach dem Abkühlen auf Raumtemperatur (im Zweifel auf 23 °C) auf Gewichtskonstanz prüft (z. B. durch nochmaliges Erhitzen und erneute Massebestimmung), wobei natürlich eine Wiederaufnahme von Wasser beim Abkühlvorgang vermieden werden muss (Exsikkator).

“Dry mass” in the context of the present invention is preferably understood to mean the water- and moisture-free mass of a sample (here: a layer) measured (under laboratory conditions at 23° C. and 50% RH). For the purposes of the present invention, the dry matter is determined--as is customary in the art--on the sample to be examined, which had been dried at 105.degree. C. to constant weight prior to the determination. Methods for determining the dry matter of a sample are known to those skilled in the art:

• For example, the dry mass of a sample (in particular a sample of a layer) can be determined for the purposes of the present invention by drying a sample of defined mass (eg 1.5 g of the sample before drying) for five hours at 105° C. in a drying oven dries and then, after cooling to room temperature (in case of doubt, to 23 °C), checks for constant weight (e.g. by heating it up again and determining the mass again) in a manner known per se, whereby re-absorption of water during the cooling process must of course be avoided (desiccator ).

Likewise, for the purposes of the present invention, the dry mass of a sample (in particular a sample of a layer) can be determined in a manner known per se using a moisture determination device, for example a halogen moisture determination device known per se, under the conditions specified above (105 °C, heating up to to constant weight) are determined.

In order to improve the mechanical resistance of the coating, layer (A) comprises one, two or more polymeric organic binders. A coating is preferred according to the invention, wherein the one, two, at least one of the several or all polymeric binders in layer (A) are selected from the group consisting of starch, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination of polyvinyl alcohol and ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, silanol-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, modified polyethylene glycol, unmodified polyethylene glycol, α-isodecyl-cu-hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene latex, styrene acrylate polymers, acrylic copolymers and blends thereof.

According to the invention, preference is given to a coating in which the one, two, at least one of the plurality or all of the polymeric binders in layer (A) are present in a total amount in the range from ≧1 to ≦30 percent by mass, preferably from ≧2 to ≦20 percent by mass preferably from ≧4 to ≦16.5 percent by mass, based on the dry mass of layer (A).

It is preferred according to the invention that the layer (A) (in the unprinted state) has an opacity according to ISO 2471 of at least 50%, preferably at least 60%, particularly preferably at least 70%. The layers (A) in recording materials according to the invention usually have an opacity of more than 75%, more than 80% or even more than 85%.

The opacity of layer (A) is determined according to ISO 2471:2008-12, with the isolated layer being measured. For this purpose, for example, a layer (A) with the same composition and thickness can be applied to a completely transparent carrier (eg quartz glass) and measured.

A coating is preferred according to the invention, wherein the fusible compound in layer (A) is present in a total amount in the range from ≧3 to ≦80 percent by mass, preferably from ≧4 to ≦75 percent by mass, more preferably from ≧5 to ≦70 percent by mass, based on the dry mass of layer (A).

A coating is particularly preferred according to the invention, wherein the fusible compound in layer (A) is present in a total amount in the range from ≧20 to ≦80 percent by mass, preferably from ≧25 to ≦75 percent by mass, more preferably from ≧40 to ≦75 percent by mass are present, based on the dry matter of layer (A).

Our own investigations have shown that with higher amounts of the fusible compound in layer (A), the formation of the typeface takes place particularly well if the coating is heated during printing in a thermal printer. If more than 80% by mass of the fusible compound In layer (A), however, this effect no longer increases. The optimum range is between 40 and 75% by mass of the fusible compound in layer (A).

According to the invention, preference is given to a coating in which component ii) in layer (A) comprises stearic acid amide or a mixture of stearic acid amide with a stearic acid salt and/or N-(hydroxymethyl)stearamide as the meltable compound.

Surprisingly, our own investigations have shown that stearic acid amide has particularly good properties and can also be obtained from renewable raw materials. The properties of the coatings can be further improved by adding stearic acid salt and/or N-(hydroxymethyl)stearamide to the stearic acid amide. Our own investigations have surprisingly shown that the addition of a stearic acid salt improves the whiteness of the coating. In addition, this has the advantage that the friction of the scratch-sensitive surface is reduced during the manufacturing process.

A coating is preferred according to the invention, the stearic acid salt being present in layer (A) in a total amount in the range from ≧0.05 to ≦3.0 percent by mass, preferably from ≧0.1 to ≦2.5 percent by mass from ≧0.2 to ≦2.0 percent by mass, based on the dry mass of layer (A).

The stearic acid salt is particularly preferably zinc stearate or calcium stearate.

A coating is preferred according to the invention, wherein the N-(hydroxymethyl)stearamide in layer (A) is present in a total amount in the range from ≧3 to ≦80 percent by mass, preferably from ≧4 to ≦75 percent by mass, more preferably from ≧5 to ≦ 70 percent by mass, based on the dry mass of layer (A).

• i) ein buntes oder schwarzes Farbmittel, vorzugsweise in einer Menge im Bereich von ≥ 3 bis ≤ 20 Massenprozent,
  • ii a) Stearinsäureamid, in einer Menge im Bereich von ≥ 3 bis ≤ 80 Massenprozent,
  • ii b) optional N-(Hydroxymethyl)stearamid, vorzugsweise in einer Menge im Bereich von ≥ 3 bis ≤ 80 Massenprozent,
  • ii c) optional Zinkstearat und/oder Calciumstearat, vorzugsweise in einer (Gesamt-)Menge im Bereich von ≥ 0,05 bis ≤ 4,0 Massenprozent,
• iii) ein, zwei oder mehrere polymere organische Bindemittel, vorzugsweise in einer Menge im Bereich von ≥ 4 bis ≤ 16,5 Massenprozent,
• iv) optional ein, zwei oder mehrere weiße Farbmittel, vorzugsweise in einer Menge im Bereich von ≥ 5 bis ≤ 80 Massenprozent,

jeweils bezogen auf die Trockenmasse der Schicht,
wobei die Schicht (A) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält.According to the invention, preference is given to a coating consisting of or comprising a layer (A) consisting of or comprising

• i) a colored or black colorant, preferably in an amount ranging from ≥ 3 to ≤ 20 percent by mass,
  • ii a) stearic acid amide, in an amount ranging from ≥ 3 to ≤ 80 percent by mass,
  • ii b) optionally N-(hydroxymethyl)stearamide, preferably in an amount ranging from ≥ 3 to ≤ 80 percent by mass,
  • ii c) optionally zinc stearate and/or calcium stearate, preferably in a (total) amount in the range from ≧0.05 to ≦4.0 percent by mass,
• iii) one, two or more polymeric organic binders, preferably in an amount in the range from ≧4 to ≦16.5 percent by mass,
• iv) optionally one, two or more white colorants, preferably in an amount ranging from ≥ 5 to ≤ 80 percent by mass,

in each case based on the dry mass of the layer,
where layer (A) contains no organic dye precursors, no hollow body pigments and no nanocellulose.

According to the invention, preference is given to a coating in which the dry mass per unit area of layer (A) is in the range from ≧2.0 g/m2 to ≦15.0 g/m ² , preferably in the range from ≧2.5 g/m2 to ≦12 0 g/m ² , particularly preferably in the range from ≧3.0 g/m ² to ≦10.0 g/m ² .

• Bi) ein, zwei oder mehrere Farbmittel,
• Bii) eine, zwei oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus Verbindungen der allgemeinen Formel (I) mit einem Schmelzpunkt im Bereich von 60 bis 160 °C (vorzugsweise bevorzugten schmelzbare Verbindungen), Dimethylterephthalat, β-Naphthylbenzylether, 1,2-Diphenoxyethan und 1,2-Bis(3-methylphenoxy)ethan, wobei die Summe der Komponenten Bii) im Bereich von ≥ 40 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (B)

und

• Biii) ein, zwei oder mehrere polymere organische Bindemittel,

wobei die Schicht (B) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält.In an embodiment of the present invention that is preferred according to the invention, the coating additionally comprises a layer (B) arranged on the layer (A), consisting of or comprising

• Bi) one, two or more colorants,
• Bii) one, two or more compounds selected from the group consisting of compounds of general formula (I) with a melting point in the range from 60 to 160°C (preferably preferred fusible compounds), dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis(3-methylphenoxy)ethane, where the sum of components Bii) is in the range from ≥ 40 to ≤ 80 percent by mass, based on the dry mass of layer (B)

and

• Biii) one, two or more polymeric organic binders,

where layer (B) contains no organic dye precursors, no hollow body pigments and no nanocellulose.

If it is stated that a layer is arranged on layer (A), this means that after the coating has been applied to a carrier substrate, the layer arranged on layer (A) (in this case the layer (B)) is not between the carrier substrate and the layer (A).

If a layer (B) is arranged on layer (A), it is preferred according to the invention that the sum of components Bii) in layer (B) is in the range from ≧40 to ≦80 percent by mass, based on the dry mass of the layer (B).

Our own investigations have shown that this arrangement has the advantage that the whiteness of the coating can be improved and a better contrast between printed and unprinted areas of the coating is obtained.

According to the invention, particular preference is given to a coating in which one, two, at least one of the plurality or all of the colorants of component Bi) in layer (B) are white colorants.

An alternative embodiment of the coating according to the invention is preferred, where one, two, at least one of the several or all of the colorants of component Bi) in layer (B) are colored or black colorants.

• a) weißen Farbmittel
• und/oder
• b) bunten und/oder schwarzen Farbmitteln sind.

According to the invention, preference is given to a coating in which the one, two, at least one or more or all of the colorants of component Bi) in layer (B) are a mixture of

• a) white colorant
• and or
• b) colored and/or black colorants.

In order to improve the mechanical resistance of the coating, layer (B) comprises one, two or more polymeric organic binders. A coating is preferred according to the invention, wherein the one, two, at least one of the several or all polymeric binders in layer (B) are selected from the group consisting of starch, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination of polyvinyl alcohol and ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, silanol-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, modified polyethylene glycol, unmodified polyethylene glycol, α-isodecyl-cu-hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene latex, styrene acrylate polymers, acrylic copolymers and mixtures of these binders.

According to the invention, preference is given to a coating in which the one, two, at least one of the plurality or all of the polymeric binders in layer (B) are present in a total amount in the range from ≧1 to ≦30 percent by mass, preferably from ≧2 to ≦20 percent by mass preferably from ≧4 to ≦16.5 percent by mass, based on the dry mass of layer (B).

According to the invention, preference is given to a coating in which component Bii) in layer (B) comprises stearic acid amide or a mixture of stearic acid amide with a stearic acid salt and/or N-(hydroxymethyl)stearamide as the meltable compound.

1. A) eine Schicht (A) bestehend aus oder umfassend
   1. i) ein, zwei oder mehrere bunte oder schwarze Farbmittel,
   2. ii) eine, zwei oder mehrere schmelzbare Verbindungen der allgemeinen Formel (I), vorzugsweise eine, zwei oder mehrere bevorzugte schmelzbare Verbindungen, wobei die Summe der Komponenten ii) im Bereich von ≥ 3 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (A),
   3. iii) ein, zwei oder mehrere polymere organische Bindemittel
   und
   • iv) optional ein, zwei oder mehrere weiße Farbmittel, vorzugsweise im Bereich von ≥ 5 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (A)
   und
2. B) eine auf der Schicht (A) angeordnete Schicht (B) bestehend aus oder umfassend
   • Bi) ein, zwei oder mehrere weiße Farbmittel,
   • Bii) eine, zwei oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus Verbindungen der allgemeinen Formel (I) mit einem Schmelzpunkt im Bereich von 60 bis 160 °C (vorzugsweise bevorzugten schmelzbare Verbindungen), Dimethylterephthalat, β-Naphthylbenzylether, 1,2-Diphenoxyethan und 1,2-Bis(3-methylphenoxy)ethan, wobei die Summe der Komponenten ii) im Bereich von ≥ 40 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (B)
   und
   • Biii) ein, zwei oder mehrere polymere organische Bindemittel,
   wobei die Schicht (A) und die Schicht (B) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthalten.

A coating is preferred according to the invention, consisting of or comprising

1. A) a layer (A) consisting of or comprising
   1. i) one, two or more colored or black colorants,
   2. ii) one, two or more fusible compounds of the general formula (I), preferably one, two or more preferred fusible compounds, the sum of components ii) being in the range from ≧3 to ≦80 percent by mass, based on the dry mass of the layer (A),
   3. iii) one, two or more polymeric organic binders
   and
   • iv) optionally one, two or more white colorants, preferably in the range from ≥ 5 to ≤ 80 percent by mass, based on the dry mass of layer (A)
   and
2. B) a layer (B) arranged on the layer (A) consisting of or comprising
   • Bi) one, two or more white colorants,
   • Bii) one, two or more compounds selected from the group consisting of compounds of general formula (I) with a melting point in the range from 60 to 160°C (preferably preferred fusible compounds), dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis(3-methylphenoxy)ethane, the sum of components ii) being in the range from ≧40 to ≦80 percent by mass, based on the dry mass of layer (B)
   and
   • Biii) one, two or more polymeric organic binders,
   wherein the layer (A) and the layer (B) contain no organic dye precursors, no hollow body pigments and no nanocellulose.

1. A) eine Schicht (A) bestehend aus oder umfassend
   • i) ein buntes oder schwarzes Farbmittel, vorzugsweise in einer Menge im Bereich von ≥ 3 bis ≤ 20 Massenprozent,
     • ii a) Stearinsäureamid, in einer Menge im Bereich von ≥ 3 bis ≤ 80 Massenprozent,
     • ii b) optional N-(Hydroxymethyl)stearamid, vorzugsweise in einer Menge im Bereich von ≥ 3 bis ≤ 80 Massenprozent,
     • ii c) optional Zinkstearat und/oder Calciumstearat, vorzugsweise in einer (Gesamt-)Menge im Bereich von ≥ 0,05 bis ≤ 4,0 Massenprozent,
   • iii) ein, zwei oder mehrere polymere organische Bindemittel, vorzugsweise in einer Menge im Bereich von ≥ 4 bis ≤ 16,5 Massenprozent,
   jeweils bezogen auf die Trockenmasse der Schicht (A),

und

• B) eine auf der Schicht (A) angeordnete Schicht (B) bestehend aus oder umfassend
  • Bi) ein, zwei oder mehrere weiße Farbmittel, vorzugsweise in einer Menge im Bereich von ≥ 10 bis ≤ 60 Massenprozent,
    • Bii a) Stearinsäureamid, in einer Menge im Bereich von ≥ 40 bis ≤ 80 Massenprozent,
    • Bii b) optional N-(Hydroxymethyl)stearamid, vorzugsweise in einer Menge im Bereich von ≥ 40 bis ≤ 80 Massenprozent,
    • Bii c) optional Zinkstearat und/oder Calciumstearat, vorzugsweise in einer (Gesamt-)Menge im Bereich von ≥ 0,05 bis ≤ 4,0 Massenprozent,
  • Biii) ein, zwei oder mehrere polymere organische Bindemittel, vorzugsweise in einer Menge im Bereich von ≥ 4 bis ≤ 16,5 Massenprozent,
  • Biv) optional ein buntes oder schwarzes Farbmittel, vorzugsweise in einer Menge im Bereich von ≥ 3 bis ≤ 20 Massenprozent,
  jeweils bezogen auf die Trockenmasse der Schicht (B),

wobei die Schicht (A) und die Schicht (B) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthalten.A coating is particularly preferred according to the invention, consisting of or comprising

1. A) a layer (A) consisting of or comprising
   • i) a colored or black colorant, preferably in an amount ranging from ≥ 3 to ≤ 20 percent by mass,
     • ii a) stearic acid amide, in an amount ranging from ≥ 3 to ≤ 80 percent by mass,
     • ii b) optionally N-(hydroxymethyl)stearamide, preferably in an amount ranging from ≥ 3 to ≤ 80 percent by mass,
     • ii c) optionally zinc stearate and/or calcium stearate, preferably in a (total) amount in the range from ≧0.05 to ≦4.0 percent by mass,
   • iii) one, two or more polymeric organic binders, preferably in an amount in the range from ≧4 to ≦16.5 percent by mass,
   in each case based on the dry mass of layer (A),

and

• B) a layer (B) arranged on the layer (A) consisting of or comprising
  • Bi) one, two or more white colorants, preferably in an amount ranging from ≥ 10 to ≤ 60 percent by mass,
    • Bii a) stearic acid amide, in an amount in the range from ≥ 40 to ≤ 80 percent by mass,
    • Bii b) optionally N-(hydroxymethyl)stearamide, preferably in an amount in the range from ≧40 to ≦80 percent by mass,
    • Bii c) optionally zinc stearate and/or calcium stearate, preferably in a (total) amount in the range from ≧0.05 to ≦4.0 percent by mass,
  • Biii) one, two or more polymeric organic binders, preferably in an amount in the range from ≧4 to ≦16.5 percent by mass,
  • Biv) optionally a colored or black colorant, preferably in an amount ranging from ≥ 3 to ≤ 20 percent by mass,
  in each case based on the dry matter of layer (B),

wherein the layer (A) and the layer (B) contain no organic dye precursors, no hollow body pigments and no nanocellulose.

In our own investigations, this preferred embodiment shows a particularly high degree of whiteness, a higher contrast between printed and unprinted areas and a sharper printed image.

In one embodiment of the present invention, the composition of layer (B) is identical to the composition of layer (A). To this end, a coating composition can be applied twice in succession to a carrier. This configuration has the advantage that the coat application of the individual layers can be reduced and the production speed can thereby be increased.

It is preferred according to the invention that the layer (B) (in the unprinted state) has an opacity according to ISO 2471:2008-12 of at least 50%, preferably at least 60%, particularly preferably at least 70%. The layers (B) in recording materials according to the invention usually have an opacity of more than 75%, more than 80% or even more than 85%.

The opacity of layer (B) is determined according to ISO ISO 2471:2008-12, with the isolated layer being measured. For this purpose, for example, a layer (B) with the same composition and thickness can be applied to a completely transparent substrate (e.g. quartz glass) and measured.

• Ci) optional ein, zwei oder mehrere bunte oder schwarze Farbmittel,
• Cii) ein, zwei oder mehrere weiße Farbmittel, und
• Ciii) ein, zwei oder mehr polymere organische Bindemittel,

wobei die Schicht (C) vorzugsweise keine organischen Farbstoffvorläufer, keine Nanocellulose und auch keine Hohlkörperpigmente enthält.In an embodiment of the present invention that is preferred according to the invention, the coating additionally comprises a layer (C) arranged below the layer (A), consisting of or comprising

• Ci) optionally one, two or more colored or black colorants,
• Cii) one, two or more white colorants, and
• Ciii) one, two or more polymeric organic binders,

the layer (C) preferably containing no organic dye precursors, no nanocellulose and also no hollow body pigments.

If it is stated that a layer is arranged under layer (A), this means that after the coating has been applied to a carrier substrate, the layer arranged under layer (A) (here the layer (C)) between the carrier substrate and of layer (A).

In order to improve the mechanical resistance of the coating, layer (C) comprises one, two or more polymeric organic binders. A coating is preferred according to the invention, wherein the one, two, at least one of the several or all polymeric binders in layer (C) are selected from the group consisting of starch, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination of polyvinyl alcohol and ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, silanol-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, modified polyethylene glycol, unmodified polyethylene glycol, α-isodecyl-cu-hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene Latex, styrene-acrylate polymers, acrylic copolymers and mixtures of the aforementioned binders.

According to the invention, preference is given to a coating in which the one, two, at least one of the plurality or all of the polymeric binders in layer (C) are present in a total amount in the range from ≧5 to ≦30 percent by mass, preferably from ≧7 to ≦20 percent by mass preferably from ≧8 to ≦18 percent by mass, based on the dry mass of layer (C).

It is preferred according to the invention that layer (C) (in the unprinted state) has an opacity according to ISO 2471:2008-12 of at least 50%, preferably at least 60%, particularly preferably at least 70%. The layers (C) in recording materials according to the invention usually have an opacity of more than 75%, more than 80% or even more than 85%.

The opacity of the layer (C) is determined according to ISO 2471:2008-12, with the isolated layer being measured. For this purpose, for example, a layer (C) with the same composition and thickness can be applied to a completely transparent carrier (eg quartz glass) and measured.

According to the invention, preference is given to a coating in which the dry mass per unit area of layer (C) is in the range from ≧2.0 g/m2 to ≦15.0 g/m ² , preferably in the range from ≧3.0 g/m2 to ≦12. 0 g/m ² , particularly preferably in the range from ≧4.0 g/m ² to ≦10.0 g/m ² .

• C) eine Schicht (C), bestehend aus oder umfassend
  • Ci) optional ein, zwei oder mehrere bunte oder schwarze Farbmittel,
  • Cii) ein, zwei oder mehrere weiße Farbmittel, und
  • Ciii) ein, zwei oder mehrere polymere organische Bindemittel
  und
• A) eine auf der Schicht (C) angeordnete Schicht (A) bestehend aus oder umfassend
  • i) ein, zwei oder mehrere bunte oder schwarze Farbmittel,
  • ii) eine, zwei oder mehrere schmelzbare Verbindungen der allgemeinen Formel (I), vorzugsweise eine, zwei oder mehrere bevorzugte schmelzbare Verbindungen, wobei die Summe der Komponenten ii) im Bereich von ≥ 3 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (A),
  • iii) ein, zwei oder mehrere polymere organische Bindemittel
  und
  • iv) optional ein, zwei oder mehrere weiße Farbmittel, vorzugsweise in einer Menge im Bereich von ≥ 5 bis ≤ 80 Massenprozent,
  und
• B) optional eine auf der Schicht (A) angeordnete Schicht (B) bestehend aus oder umfassend
  • Bi) ein, zwei oder mehrere weiße Farbmittel,
  • Bii) eine, zwei oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus Verbindungen der allgemeinen Formel (I) mit einem Schmelzpunkt im Bereich von 60 bis 160 °C (vorzugsweise bevorzugten schmelzbare Verbindungen), Dimethylterephthalat, β-Naphthylbenzylether, 1,2-Diphenoxyethan und 1,2-Bis(3-methylphenoxy)ethan, wobei die Summe der Komponenten ii) im Bereich von ≥ 40 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Schicht (B)
  und
  • Biii) ein, zwei oder mehrere polymere organische Bindemittel,

wobei die Schicht (A) und (sofern vorhanden) die Schicht (B) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält und die Schicht (C) keine organischen Farbstoffvorläufer, keine Nanocellulose und vorzugsweise auch keine Hohlkörperpigmente enthält.A coating is preferred according to the invention, consisting of or comprising

• C) a layer (C) consisting of or comprising
  • Ci) optionally one, two or more colored or black colorants,
  • Cii) one, two or more white colorants, and
  • Ciii) one, two or more polymeric organic binders
  and
• A) a layer (A) arranged on the layer (C) consisting of or comprising
  • i) one, two or more colored or black colorants,
  • ii) one, two or more fusible compounds of the general formula (I), preferably one, two or more preferred fusible compounds, the sum of components ii) being in the range from ≧3 to ≦80 percent by mass, based on the dry mass of the layer (A),
  • iii) one, two or more polymeric organic binders
  and
  • iv) optionally one, two or more white colorants, preferably in an amount ranging from ≥ 5 to ≤ 80 percent by mass,
  and
• B) optionally a layer (B) arranged on the layer (A) consisting of or comprising
  • Bi) one, two or more white colorants,
  • Bii) one, two or more compounds selected from the group consisting of compounds of general formula (I) with a melting point in the range from 60 to 160°C (preferably preferred fusible compounds), dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis(3-methylphenoxy)ethane, the sum of components ii) being in the range from ≧40 to ≦80 percent by mass, based on the dry mass of layer (B)
  and
  • Biii) one, two or more polymeric organic binders,

wherein layer (A) and (if present) layer (B) contain no organic dye precursors, no hollow body pigments and no nanocellulose and layer (C) contains no organic dye precursors, no nanocellulose and preferably also no hollow body pigments.

Preference is given to an above-mentioned coating for a heat-sensitive recording material additionally comprising one or more processing aids in layer (A) and/or (if present) in layer (B) and/or (if present) in layer (C). , preferably selected from the group consisting of defoamers, biocides, dispersants, and wetting agents, preferably in a total amount of ≤ 5 percent by mass, more preferably in a total amount in the range of ≥ 0.1 to ≤ 3 percent by mass and more preferably in the range of ≥ 0 .1 to ≤ 2 percent by mass, based on the dry mass of the respective layer.

The one or more processing aids preferably serve to facilitate or enable the processing of a coating according to the invention (or a coating composition for producing a layer of a coating according to the invention) in the industrial manufacturing process, in particular in the industrial process of papermaking.

• - einem Trägersubstrat, vorzugsweise einem Papiersubstrat, aufweisend eine Vorderseite und eine der Vorderseite gegenüberliegende Rückseite

und

• - einer vorstehend beschriebenen, erfindungsgemäßen Beschichtung welche auf zumindest einer der Seiten des Trägersubstrats angeordnet ist.

The combination of a carrier substrate and a coating according to the invention applied to the carrier substrate is referred to as a heat-sensitive recording material on which a visually perceptible image can be generated by means of heat-induced phase change. A further aspect of the present invention relates to such a heat-sensitive recording material comprising or consisting of

• - A carrier substrate, preferably a paper substrate, having a front side and a back side opposite the front side

and

• - A coating according to the invention as described above which is arranged on at least one of the sides of the carrier substrate.

A recording material according to the invention is preferred in which the carrier substrate is paper, cardboard or a film. Coating base paper is particularly preferred as the carrier substrate, since it has good recyclability and good environmental compatibility. Coating base paper is understood to be paper that has been treated in a size press or in a coating device. Films made of polypropylene or other polyolefins are preferred as plastic films.

In a particularly preferred embodiment, the carrier is a paper substrate. It is preferred here if the paper substrate contains a proportion of ≧80 percent by mass of recycled fibers, based on the total mass of the air-dried paper substrate.

A recording material according to the invention is preferred according to the invention, wherein the paper substrate contains a proportion of ≦25 percent by mass of fresh fibers, based on the total mass of the air-dried paper substrate.

For the purposes of the present invention, the mass of an "air dry" paper substrate given above is determined under standard ambient conditions (23°C, 50% RH, 1013 hPa). A water content of the paper substrate of 10 percent by mass is assumed for an air-dried paper substrate--as is customary in the technical field.

In an alternative embodiment of the recording material according to the invention, a high proportion of more than 80 percent by mass of fresh fibers can also be used, or only fresh fibers are used. This has the advantage that the resulting material has fewer impurities and substrates with low grammages (eg less than or equal to 42 or 30 g/m ² ) can also be used.

Coatings according to the invention exhibit high adhesion to the supports described above.

In one embodiment of the recording materials according to the invention, the coating according to the invention is completely or partially covered with a protective layer (T). Due to the arrangement of a protective layer (T) covering the coating, the coating is also shielded from the outside or from the carrier substrate of the next layer within a roll, so that protection from external influences takes place.

In such cases, such a protective layer (T) often has the additional positive effect of improving the printability of the heat-sensitive recording material according to the invention, particularly in indigo offset and flexographic printing, in addition to protecting the coating arranged under the protective layer (T) from environmental influences. It has also been shown that the chemical resistance and in particular the resistance to fat and oil can be improved by the presence of a protective layer (T).

The protective layer (T) of the recording material according to the invention preferably contains one or more crosslinked or uncrosslinked binders selected from the group consisting of with carboxyl group-modified polyvinyl alcohols, polyvinyl alcohols modified with silanol groups, diacetone-modified polyvinyl alcohols, partially and fully hydrolyzed polyvinyl alcohols, ethylene-acrylic acid copolymer waxes and film-forming acrylic copolymers.

If present, the coating composition for forming the protective layer (T) of the recording material according to the invention preferably contains one or more crosslinking agents for the binder or binders in addition to one or more binders. The crosslinking agent is then preferably selected from the group consisting of polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, adipic acid dihydrazide, melamine formaldehyde, urea, glyoxal, methylolurea, ammonium zirconium carbonate, polyamideepichlorohydrin resins and dihydroxybis(ammonium lactato)titanium(IV) ^Tyzor® LA (CAS- No. 65104-06-5).

A recording material according to the invention whose protective layer (T) 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 (T) one or more binders crosslinked by reaction with one or more crosslinking agents , wherein the crosslinking agent(s) are selected from the group consisting of polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, adipic acid dihydrazide, melamine formaldehyde, urea, glyoxal, methylolurea, ammonium zirconium carbonate, polyamideepichlorohydrin resins and dihydroxybis(ammonium lactato)titanium(IV) Tyzor ^® LA (CAS -No. 65104-06-5). “Crosslinked binder” is understood to mean the reaction product formed by reacting a binder with one or more crosslinking agents.

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

It is preferred that the protective layer (T) according to this embodiment variant has a mass per unit area in a range from 0.5 g/m ² to 6 g/m ² and particularly preferably from 0.75 g/m ² to 3.8 g/m m ² , more preferably in the range from 0.95 to 3.0 g/m ² . The protective layer (T) is preferably formed in one layer.

It is preferred according to the invention if layer (T) contains one or more processing aids, preferably selected from the group consisting of defoamers, biocides, dispersants and wetting agents, preferably in a total amount of ≦5 percent by mass, particularly preferably in one Total amount in the range from ≥ 0.1 to ≤ 3 percent by mass and more preferably in the range from ≥ 0.1 to ≤ 2 percent by mass, based on the dry mass of the layer (T).

The one or more processing aids preferably serve to facilitate or enable the processing of a coating according to the invention (or a coating composition for producing a layer of a coating according to the invention) in the industrial manufacturing process, in particular in the industrial process of papermaking.

According to the invention, preference is given to a coating in which a) the layer (A) does not include any ferromagnets, b) the layer (B) (if present) does not include any ferromagnets, c) the layer (C) (if present) does not include any ferromagnets, and/ or d) the protective layer (T) (if any) does not comprise ferromagnets.

A coating is particularly preferred according to the invention, wherein the coating does not include any ferromagnets. In the context of the present invention, a ferromagnet is understood to mean a substance which itself generates a magnetic field or is attracted by a pole of an external magnetic field. For example, surface-coated magnetic nanoparticles are understood as ferrous magnets that have, for example, a core made of iron, cobalt, nickel, an alloy of one or more of these metals or another magnetic or magnetizable alloy or another magnetic or magnetizable metal.

A coating is preferred according to the invention, the coating not comprising any ferromagnets.

The explanations given above for the coating according to the invention and/or for the coating composition according to the invention apply accordingly, and vice versa.

Another aspect of the present invention relates to the use of a coating according to the invention or a recording material according to the invention that can be changed by heat-induced phase change as a temperature indicator, security paper, admission ticket, receipt, self-adhesive label, ticket, TITO ticket (ticket-in, ticket-out), thermal photo, flight -, train, boat or bus ticket, parking ticket, label, gambling receipt, sales receipt, bank statement, medical and/or technical chart paper or fax paper.

A further aspect of the present invention relates to the use of a coating according to the invention or of a heat-sensitive recording material according to the invention for the formation of a printed image by heating. The printed image can be text, symbols or graphics. Here, it is preferable that the heating is performed by a warm pen, a thermal head, or laser heating.

A use is preferred according to the invention in which an amount of heat in the range from 1 to 20 mJ/mm ² , preferably 2 to 16 mJ/mm ² acts on the coating according to the invention or the heat-sensitive recording material according to the invention.

According to the invention, it is particularly preferred if the print image is formed in a thermal printer, preferably a direct thermal printer with a thermal print head or thermal strip. Correspondingly, the use of a coating according to the invention or of heat-sensitive recording materials according to the invention in thermal printers is particularly preferred. Thermal printers are well known to those skilled in the art.

1. i. Bereitstellen oder Herstellen eines Trägersubstrats;
2. ii. Bereitstellen oder Herstellen einer Beschichtungszusammensetzung (A) zur Herstellung einer Schicht (A), wobei die Beschichtungszusammensetzung (A) folgende Bestandteile umfasst
   • Ai) ein buntes oder schwarzes Farbmittel,
   • Aii) eine, zwei oder mehrere schmelzbare Verbindungen der allgemeinen Formel (I), vorzugsweise eine, zwei oder mehrere bevorzugte schmelzbare Verbindungen, wobei die Summe der Komponenten ii) im Bereich von ≥ 3 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Beschichtungszusammensetzung (A)
   und
   • Aiii) ein, zwei oder mehrere polymere organische Bindemittel,
   wobei die Beschichtungszusammensetzung (A) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält,
3. iii. Aufbringen der in Schritt ii) bereitgestellten oder hergestellten Beschichtungszusammensetzung (A) auf eine Seite des in Schritt i) bereitgestellten oder hergestellten Trägersubstrats;
4. iv. Trocknen der in Schritt ii) aufgebrachten Beschichtungszusammensetzung (A) unter Ausbildung einer Schicht (A).

A further aspect of the present invention relates to a method for producing a coating that can be changed by means of a heat-induced phase change or an environmentally friendly recording material that can be changed by heating a heat-induced phase change, comprising the following steps:

1. i. Providing or producing a carrier substrate;
2. ii. Providing or producing a coating composition (A) for producing a layer (A), the coating composition (A) comprising the following components
   • Ai) a colored or black colorant,
   • Aii) one, two or more fusible compounds of the general formula (I), preferably one, two or more preferred fusible compounds, where the sum of components ii) is in the range from ≧3 to ≦80 percent by mass, based on the dry mass of the coating composition (A)
   and
   • Aiii) one, two or more polymeric organic binders,
   wherein the coating composition (A) contains no organic dye precursors, no hollow body pigments and no nanocellulose,
3. iii. applying the coating composition (A) provided or produced in step ii) to one side of the carrier substrate provided or produced in step i);
4. IV. Drying the coating composition (A) applied in step ii) to form a layer (A).

• v. Bereitstellen oder Herstellen einer Beschichtungszusammensetzung (B) zur Herstellung einer Schicht (B), wobei die Beschichtungszusammensetzung (B) folgende Bestandteile umfasst
  • Bi) ein, zwei oder mehrere weiße Farbmittel,
  • Bii) eine, zwei oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus Verbindungen der allgemeinen Formel (I) mit einem Schmelzpunkt im Bereich von 60 bis 160 °C (vorzugsweise bevorzugten schmelzbare Verbindungen), Dimethylterephthalat, β-Naphthylbenzylether, 1,2-Diphenoxyethan und 1,2-Bis(3-methylphenoxy)ethan, wobei die Summe der Komponenten Bii) im Bereich von ≥ 40 bis ≤ 80 Massenprozent liegt, bezogen auf die Trockenmasse der Beschichtungszusammensetzung (B)
  und
  • Biii) ein, zwei oder mehrere polymere organische Bindemittel,
  und wobei die Beschichtungszusammensetzung (B) keine organischen Farbstoffvorläufer, keine Hohlkörperpigmente und keine Nanocellulose enthält,
• vi. Aufbringen der in Schritt v) bereitgestellten oder hergestellten Beschichtungszusammensetzung (B) auf die in Schritt iv) ausgebildete Schicht (A);
• vii. Trocknen der in Schritt vi) aufgebrachten Beschichtungszusammensetzung (B) unter Ausbildung einer Schicht (B).

A method according to the invention is preferably additionally comprising the steps

• v. Providing or producing a coating composition (B) for producing a layer (B), the coating composition (B) comprising the following components
  • Bi) one, two or more white colorants,
  • Bii) one, two or more compounds selected from the group consisting of compounds of general formula (I) with a melting point in the range from 60 to 160°C (preferably preferred fusible compounds), dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis(3-methylphenoxy)ethane, the sum of components Bii) being in the range from ≧40 to ≦80 percent by mass, based on the dry mass of the coating composition (B)
  and
  • Biii) one, two or more polymeric organic binders,
  and wherein the coating composition (B) contains no organic dye precursors, no hollow body pigments and no nanocellulose,
• vi. applying the coating composition (B) provided or produced in step v) to the layer (A) formed in step iv);
• vii. Drying the coating composition (B) applied in step vi) to form a layer (B).

• viii. Bereitstellen oder Herstellen einer Beschichtungszusammensetzung (C) zur Herstellung einer Schicht (C), wobei die Beschichtungszusammensetzung (C) folgende Bestandteile umfasst
  • Ci) optional ein Farbpigment,
  • Cii) ein, zwei oder mehr Weißstoffe,
  und
  • Ciii) ein, zwei oder mehr polymere organische Bindemittel.
  und wobei die Beschichtungszusammensetzung (C) keine organischen Farbstoffvorläufer und keine Nanocellulose enthält,
• ix. Aufbringen der in Schritt viii) bereitgestellten oder hergestellten Beschichtungszusammensetzung (C) auf eine Seite des in Schritt i) bereitgestellten oder hergestellten Trägersubstrats;
• x. Trocknen der in Schritt ix) aufgebrachten Beschichtungszusammensetzung (C) unter Ausbildung einer Schicht (C).

In one embodiment of the present invention, the following steps are carried out after step i).

• viii. Providing or producing a coating composition (C) for producing a layer (C), the coating composition (C) comprising the following components
  • Ci) optionally a color pigment,
  • Cii) one, two or more white fabrics,
  and
  • Ciii) one, two or more polymeric organic binders.
  and wherein the coating composition (C) contains no organic dye precursors and no nanocellulose,
• ix. applying the coating composition (C) provided or produced in step viii) to one side of the carrier substrate provided or produced in step i);
• x. drying of the coating composition (C) applied in step ix) to form a layer (C).

In this embodiment, the coating composition (A) provided or produced in step ii) is not applied to one side of the carrier substrate provided or produced in step i), but to the layer (C) formed in step x.).

The layers (A), (B) and (C) of coatings according to the invention are preferably produced by applying an appropriate aqueous coating composition in which the fusible compounds are present as a dispersion.

• 1 bis 8 schematisch mögliche Schichtaufbauten von erfindungsgemäßen Beschichtungen auf einem Trägersubstrat.

Further embodiments result from the exemplary embodiments explained in more detail in the figures and the example. In the figures show:

• 1 until 8th schematic of possible layer structures of coatings according to the invention on a carrier substrate.

1 shows a recording material according to the invention that can be changed by heat-induced phase change and consists of a carrier substrate (2), which is preferably a paper substrate, and a layer (A) applied to the carrier substrate (2). The layer (A) comprises i) one, two or more colored or black colorants, which are preferably carbon black or activated carbon, carbon black, ii) one, two or more fusible compounds, the sum of components ii) in the range from ≧3 to ≦80 percent by mass, based on the dry mass of layer (A), and iii) one, two or more polymeric organic binders. Layer (A) corresponds to a coating according to the invention for a heat-sensitive recording material.

2 shows a recording material 1 , in which the layer (A) is additionally coated with a protective layer (T) in order to protect the layer (A) from unwanted environmental influences. Layer (A) corresponds to a coating according to the invention for a heat-sensitive recording material.

3 shows a recording material according to the invention that can be changed by heat-induced phase change and consists of a carrier substrate (2), which is preferably a paper substrate, a layer (A) applied to the carrier substrate (2) and a layer (A) applied to the layer (A). B) acts. The layer (A) comprises i) one, two or more colored or black colorants, which are preferably carbon black or activated carbon, ii) one, two or more fusible compounds, the sum of the components ii) being in the range of ≥ 3 up to ≤80 percent by mass, based on the dry mass of layer (A), and iii) one, two or more polymeric organic binders. The layer (B) comprises Bi) one, two or more colorants, Bii) one, two or more compounds selected from the group consisting of compounds of the general formula (I) with a melting point in the range from 60 to 160 ° C (preferably preferred fusible compounds), dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis(3-methylphenoxy)ethane, the sum of components Bii) being in the range from ≧40 to ≦80 percent by mass, based on the dry matter of layer (B) and Biii) one, two or more polymeric organic binders. The layers (A) and (B) correspond to a coating according to the invention for a heat-sensitive recording material.

4 shows a recording material 3 , in which the layer (B) is additionally coated with a protective layer (T) in order to protect the layer (B) from unwanted environmental influences. The layers (A) and (B) correspond to a coating according to the invention for a heat-sensitive recording material.

5 shows a recording material according to the invention that can be changed by heat-induced phase change and consists of a carrier substrate (2), which is preferably a paper substrate, a layer (C) applied to the carrier substrate (2) and a layer (C) applied to the layer (C). A) acts. Layer (C) comprises Ci) one, two or more chromatic or black colorants, Cii) one, two or more white colorants, and Ciii) one, two or more polymeric organic binders. The layer (A) comprises i) one, two or more colored or black colorants, which are preferably carbon black or activated carbon, ii) one, two or more fusible compounds, the sum of the components ii) being in the range of ≥ 3 up to ≤80 percent by mass, based on the dry mass of layer (A), and iii) one, two or more polymeric organic binders. The layers (A) and (C) correspond to a coating according to the invention for a heat-sensitive recording material.

6 shows a recording material 5 , in which the layer (A) is additionally coated with a protective layer (T) in order to protect the layer (A) from unwanted environmental influences. The layers (A) and (C) correspond to a coating according to the invention for a heat-sensitive recording material.

7 shows a recording material according to the invention that can be changed by heat-induced phase change and consists of a carrier substrate (2), which is preferably a paper substrate, a layer (C) applied to the carrier substrate (2), a layer (C) applied to the layer (C) A) and a layer (B) applied to the layer (A). Layer (C) comprises Ci) one, two or more chromatic or black colorants, Cii) one, two or more white colorants, and Ciii) one, two or more polymeric organic binders. The layer (A) comprises i) one, two or more colored or black colorants, which are preferably carbon black or activated carbon, ii) one, two or more fusible compounds, the sum of the components ii) being in the range of ≥ 3 up to ≤80 percent by mass, based on the dry mass of layer (A), and iii) one, two or more polymeric organic binders. The layer (B) comprises Bi) one, two or more colorants, Bii one, two or more compounds selected from the group consisting of compounds of the general formula (I) with a melting point in the range from 60 to 160 ° C (preferably preferred fusible Compounds), dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis (3-methylphenoxy) ethane, the sum of the components Bii) in the range of ≥ 40 to ≤ 80 percent by mass, based on the dry matter Layer (B) and Biii) one, two or more polymeric organic binders. The layers (A), (B) and (C) correspond to a coating according to the invention for a heat-sensitive recording material.

8th shows a recording material 7 , in which the layer (B) is additionally coated with a protective layer (T) in order to protect the layer (B) from unwanted environmental influences. The layers (A), (B) and (C) correspond to a coating according to the invention for a heat-sensitive recording material.

Examples:

The examples given below are intended to describe and explain the invention in more detail without restricting its scope.

In paper manufacture and in the following examples, a distinction is made between three grades for the dryness of paper and pulp: "atro" (absolutely dry), "air-dry" (air-dry) and "otro" (oven-dry). The information is given in "% atro", "% lutro" and "% otro". "atro" stands for paper or pulp with 0% water content. For "lutro" a "normal" (essentially necessary for the paper) moisture content is used as the basis for the calculation. In the case of cellulose and groundwood, the calculation mass usually refers to 90:10, i.e. 90 parts of pulp and 10 parts of water. The state of paper or pulp after drying under specified, defined conditions is referred to as "otro".

Examples:

Preparation of an achromatic black dye dispersion:

An aqueous achromatic black dye dispersion was prepared by mixing the components listed in Table 1. Table 1: Composition of the achromatic black dye dispersion Achromatic Black Dye Suspension: component Otro amount [%] Air [g] Water - 307.15 Nurosperse FA 196 (dispersant) 1.0 4.75 Carbon Black powder (achromatic black colorant) 99.0 188.10 total 100 192.85

Preparation of a first achromatic white dye dispersion:

A first aqueous achromatic white dye dispersion was prepared by mixing the components listed in Table 2. Table 2: Composition of the first achromatic white dye dispersion First achromatic white dye dispersion: component Otro amount [%] Air [g] Water - 248.51 Maredis 507 (dispersant) 0.3984 2.49 CaCO ₃ (achromatic white colorant) 99.6016 249.00 total 100.00 251.49

Preparation of a second achromatic white dye dispersion:

A second aqueous achromatic white dye dispersion was prepared by mixing the ingredients listed in Table 3. Table 3: Composition of the second achromatic white dye dispersion Second achromatic white dye dispersion: component Otro amount [%] Air [g] Water - 248.51 Maredis 507 (dispersant) 0.3984 2.49 Ansilex 93 B (calcined kaolin) 99.6016 249.00 total 100.00 251.49

Preparation of a stearamide dispersion:

A stearamide dispersion was prepared by blending the ingredients listed in Table 4. Table : Composition of the stearamide dispersion Stearamide dispersion: component Otro amount [%] Air [g] Water - 87.76 PVA GOSENX L 3266 - solution 9.9800 52.69 Envirogem AD 01 (wetting agent / defoamer) 0.1996 0.26 Finnawax S (Stearamide) 89.8204 59.28 total 100.00 112.24

Preparation of an N,N'-ethylene-bis-stearamide dispersion:

A N,N'-ethylene-bis-stearamide dispersion was prepared by blending the ingredients listed in Table 4. Table 5: Composition of the N,N'-ethylene-bis-stearamide dispersion N,N'-Ethylene-bis-stearamide dispersion: component Otro amount [%] Air [g] Water - 101.37 PVA GOSENX 3266 - solution 9.9800 46.31 Envirogem AD 01 (wetting agent / defoamer) 0.1996 0.23 N,N'-Ethylene-bis-stearamides 89.8204 52.10 total 100.00 98.63

Preparation of an n-(hydroxymethyl)stearamide dispersion:

An n-(hydroxymethyl)stearamide dispersion was prepared by blending the ingredients listed in Table 4. Table 5: Composition of the n-(hydroxymethyl)stearamide dispersion n-(Hydroxymethyl)stearamide dispersion: component Otro amount [%] Air [g] Water - 101.37 PVA GOSENX L 3266 - solution 9.9800 46.31 Envirogem AD 01 (wetting agent / defoamer) 0.1996 0.23 N,N'-Ethylene-bis-stearamides 89.8204 52.10 total 100.00 98.63

Examples 1 to 5:

A paper web made of bleached and ground hardwood and softwood pulps with a mass per unit area of 42 g/m ² is produced as the carrier substrate on a fourdrinier paper machine with the addition of customary additives in customary quantities.

To prepare a coating composition required for the preparation of layer (A), two dispersions (dispersion 1 and dispersion 2) are prepared using the dispersions described above and then mixed in the ratios given in Table 3. The components of the dispersions are given in Tables 1 and 2 below: Table 1: Composition of dispersion 1 Dispersion 1: component Otro amount [%] Air [g] Water - 0.85 Achromatic black dye dispersion 10.2041 29.54 First achromatic white dye dispersion 81.6327 124.72 PVA dispersion (20% by weight dry matter) 8.1633 44.90 total 100.00 199.15 Table 2: Composition of dispersion 2 Dispersion 2: component Otro amount [%] Air [g] Water - 5.82 PVA dispersion (12.50% by weight dry matter) 6.1033 80.56 First achromatic white dye dispersion 32.8638 108.45 stearamide dispersion 61.0329 305.16 total 100.00 250.00 Table 3: Composition of the coating composition Preparation of the coating composition from both prepared dispersions examples Proportion of dispersion 1 Proportion of dispersion 2 example 1 90% 10% example 2 80% 20% Example 3 70% 30% example 4 60% 40% Example 5 50% 50%

Using a coating machine, a coating composition for producing a layer (A) with a mass per unit area of 5.0 g/m ² is applied to the felt side of the paper web produced (paper substrate) by means of a doctor blade and dried conventionally after application.

Examples 6 to 10:

The previous Examples 1 to 5 were repeated, except that the dispersion specified in Table 4 was used as dispersion 2. Table 4: Composition of dispersion 2 Dispersion 2: component Otro amount [%] Air [g] Water - 12.48 PVA dispersion (12.50% by weight dry matter) 5.9798 78.93 First achromatic white dye dispersion 32.1987 106.26 stearamide dispersion 59.7976 298.99 zinc stearate 2.0239 3.34 total 100.00 487.52

Examples 11 to 15:

The previous Examples 1 to 5 were repeated, except that the dispersion specified in Table 5 was used as dispersion 2. Table 5: Composition of dispersion 2 Dispersion 2: component Otro amount [%] Air [g] Water - 5.82 PVA dispersion (12.50% by weight dry matter) 6.1033 80.56 First achromatic white dye dispersion 32.8638 108.45 N,N'-Ethylene-bis-stearamide dispersion 61.0329 305.16 total 100.00 494.18

Examples 16 to 20:

The previous Examples 1 to 5 were repeated, except that the dispersion specified in Table 5 was used as dispersion 2. Table 5: Composition of dispersion 2 Dispersion 2: component Otro amount [%] Air [g] Water - 5.82 PVA dispersion (12.50% by weight dry matter) 6.1033 80.56 First achromatic white dye dispersion 32.8638 108.45 n-(Hydroxymethyl)stearamide dispersion 61.0329 305.16 total 100.00 494.18

Examples 21 to 40:

Examples 1 to 20 were repeated and an additional layer (B) was applied to the layers (A) produced.

The coating composition required to produce layer (B) has the composition given in Table 10: Table 10: Composition of the coating composition for producing layer (B) Coating composition for making layer (B): component Otro amount [%] Air [g] Water - 5.82 Ansilex dispersion 32.8638 108.45 N-(Hydroxymethyl)stearamide 61.0329 305.16 PVA dispersion 6.1033 80.56 total 100 250

Using a coating machine, a coating composition for producing a layer (B) with a mass per unit area of 5.0 g/m ² is applied to the layers (A) produced in Examples 1 to 20 by means of a doctor blade and dried conventionally after application .

Examples 41 to 80:

Examples 1 to 40 were repeated, in each case before applying layer (A) to the paper web (paper substrate) produced, first using a roller doctor coater, a coating composition to produce a layer (C) with a basis weight of 5.0 g / m ² applied and dried conventionally after application. The layer (A) was then applied to the conventionally dried layer (C).

The coating composition required to produce layer (C) has the composition given in Table 11: Table 11: Composition of the coating composition for producing layer (C) Coating composition for producing layer (C): component Otro amount [%] Air [g] Water - 202.91 Dispersant (40% by weight dry matter) 0.3293 1.89 Calcium carbonate slurry (72% by weight dry matter) 16.4745 52.63 Starch solution (21% by weight dry matter) 4.1186 45:11 Calcined kaolin 65.8980 60.63 Binder (50 wt% dry matter) 13.1796 60.63 total 100.00 311.82

Examples 81 to 120:

Examples 41 to 80 were repeated, except that the coating composition given in Table 12 was used to produce layer (C). Table 12: Composition of the coating composition for producing layer (C) Coating composition for producing layer (C): component Otro amount [%] Air [g] Water - 202.91 Dispersant (40% by weight dry matter) 0.3293 1.89 Starch solution (21% by weight dry matter) 4.1186 45:11 Calcined kaolin 82.3725 189.46 Binder (50 wt% dry matter) 13.1796 60.63 total 100.00 297.09

Examples 121 to 240:

Examples 1 to 120 were repeated, but the coating composition given in Table 13 was used to produce the protective layer (T) and applied to the last layer (A) or (B) with a weight per unit area of 3.0 g/m ² and conventionally dried after application. The result is a recording material with an additional protective layer (T)

The ingredients shown in Table 13 are mixed to prepare the coating composition. Table 13: Composition of the coating composition for the production of the protective layer (T) component component Mass fractions w(x) (atro) pigment Kaolin (trade name: ASP 179) 0.30 to 0.40 pigment Silicic acid (trade name: Sipernat 22S) 0.020 to 0.040 polyvinyl alcohol Acetoacetyl Modified PVA (Trade Name: Gohsenx Z-410) 0.05 to 0.15 polyvinyl alcohol Acetoacetyl Modified PVA (Trade Name: Gohsenx Z-200) 0.20 to 0.50 additive Zinc stearate (trade name: Hidorin Z-7-30) 0.05 to 0.07 crosslinker Polyamideamine epichlorohydrin resin (trade name: Giluton 20XP) 0.015 to 0.035 Alkylene/(meth)acrylic acid copolymer Ethylene-acrylic acid copolymer (trade name: Aquacer 1061) 0.015 to 0.040 crosslinker Sodium/Calcium Glyoxylate (Trade Name: SPM-01/SPM-02) 0.005 to 0.020

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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

• DE 102004004204 A1 [0005]
• DE 102015104306 A1 [0005, 0008]
• US 2014/0176652 A1 [0006]
• US 2012/0236091 A1 [0007]
• WO 2012/145456 A1 [0010]
• WO 2019183471 A1 [0011]

Claims (10)

Coating irreversibly convertible by heating, consisting of or comprising a layer (A), consisting of or comprising i) one, two or more colored or black colorants, ii) one, two or more fusible compounds of general formula (I)

where R ₁ is a substituted or unsubstituted, branched or unbranched alkyl or alkylene radical having eight to 28 carbon atoms or a radical of the general formula (II).

where m is an integer from 1 to 21 and R ₃ is a substituted or unsubstituted, branched or unbranched alkyl or alkylene group having eight to 28 carbon atoms, and R ₂ is hydrogen, a substituted or unsubstituted, branched or unbranched alkyl or alkylene group with is eight to 28 carbon atoms or is a radical of the general formula (III),

where n is an integer from 1 to 21 and R ₄ is a substituted or unsubstituted, branched or unbranched alkyl radical having eight to 28 carbon atoms, the compound of general formula (I) having a melting point in the range from 60 to 160 °C, where the sum of components ii) is in the range from ≥ 3 to ≤ 80 percent by mass, based on the dry mass of layer (A) and iii) one, two or more polymeric organic binders, where layer (A) has no organic dye precursors, none Contains hollow body pigments and no nanocellulose. coating claim 1 , wherein the compound of general formula (I) is selected from the group consisting of stearic acid amide (CAS number 124-26-5), N-(hydroxymethyl)stearamide (CAS number 3370-35-2), lauramide (CAS number 1120-16-7), palmitamides (CAS number 629-54-9), 12-hydroxystearamides (CAS number 7059-49-6), oleamides (CAS number 301-02-0), erucamides (CAS number 112-84-5), N-Stearyl stearamide (CAS number 13276-08-9), N-Stearyl oleamide (CAS number 6592-63-2; melting point 67°C), N-Oleyl stearamide (CAS number 6592-63-2), N-Stearyl erucamide (CAS number 10094-45-8), Ethylenebis oleamide (CAS number 110-31-6), Hexamethylenebis oleamide (CAS number 6283-37-0), N ,N'-Dioleyl adipamide (CAS number 85888-37-5), Methylenebis stearamide (CAS number 109-23-9), Ethylenebis capramide (CAS number 51139-08-3), Ethylenebis lauramide (CAS number 7003 -56-7), ethylenebis stearamide (CAS number 110-30-5), ethylenebis 12-hydroxystearamide (CAS number 123-26-2), ethylene-bis-behenamide (CAS number 7445-68-3), Hexamethylenebis stearamide (CAS number 4112-25-8), hexamethylenebis behenamide (CAS number 96548-58-2), N,N'-Distearyl adipamide (CAS number 25151-31-9) and hexamethylenebis 12-hydroxystearamide (CAS number 55349-01-4). coating claim 1 or 2 wherein layer (A) additionally comprises iv) one, two or more white colorants. Coating according to one of the preceding claims, wherein the sum of components ii) is in the range from ≥ 20 to ≤ 80 percent by mass, preferably in the range from ≥ 25 to ≤ 75 percent by mass, more preferably in the range from ≥ 40 to ≤ 75 percent by mass, based on the dry mass of layer (A). Coating according to one of the preceding claims, wherein component ii) in layer (A) comprises stearic acid amide or a mixture of stearic acid amide with a stearic acid salt and/or N-(hydroxymethyl)stearamide as the fusible compound. Coating according to one of the preceding claims, additionally comprising a layer (B) arranged on the layer (A), consisting of or comprising Bi) one, two or more colorants, Bii) one, two or more compounds selected from the group consisting of compounds of general formula (I) with a melting point in the range from 60 to 160°C, dimethyl terephthalate, β-naphthyl benzyl ether, 1,2-diphenoxyethane and 1,2-bis (3-methylphenoxy), where the sum of components Bii) is in the range from ≧40 to ≦80 percent by mass, based on the dry mass of layer (B) and Biii) one, two or more polymeric organic binders, where layer (B) contains no organic dye precursors, no hollow body pigments and no nanocellulose. Coating according to one of the preceding claims, additionally comprising a layer (C) arranged under the layer (A), consisting of or comprising Ci) one, two or more colored or black colorants, Cii) one, two or more white colorants, and Ciii) one, two or more polymeric organic binders, where layer (C) contains no organic dye precursors, no nanocellulose and preferably no hollow body pigments. Heat-sensitive recording material, comprising or consisting of - a carrier substrate, preferably a paper substrate, having a front side and a back side opposite the front side and - a coating according to one of Claims 1 until 7 which is arranged on at least one of the sides of the carrier substrate. Use coating according to one of Claims 1 until 7 in or in a recording material that can be irreversibly converted by heating as a temperature indicator, security paper, admission ticket, receipt, self-adhesive label, ticket, TITO ticket (ticket-in, ticket-out), thermal photo, flight, train, ship or bus ticket, parking ticket, Label, gambling receipt, sales receipt, bank statement, medical and/or technical chart paper or fax paper. Method for producing a coating which can be irreversibly transformed by heating, comprising the following steps: i. Providing or producing a carrier substrate; ii. Providing or producing a coating composition (A) for producing a layer (A), the coating composition (A) comprising the following components i) a colored or black colorant, ii) one, two or more fusible compounds of the general formula (I) as in claim 1 defined with a melting point in the range from 60 to 160 ° C, the sum of the components ii) in the range from ≥ 3 to ≤ 80 percent by mass, based on the dry mass of the coating composition (A) and iii) one, two or more polymeric organic binders, and wherein the coating composition (A) contains no organic dye precursors, no hollow body pigments and no nanocellulose, iii. applying the coating composition (A) provided or produced in step ii) to one side of the carrier substrate provided or produced in step i); IV. Drying the coating composition (A) applied in step ii to form a layer (A).

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