EP2546066B2 - Pressure-sensitive recording material and its' method of preparation - Google Patents

Description

• ■ ein bahnförmiges Substrat,
  aufweisend eine Vorderseite als die erste der beiden Substratseiten und eine Rückseite als die zweite der beiden Substratseiten,
• ■ eine auf mindestens einer der beiden Substratseiten ausgebildete Beschichtung, aufweisend ein Zink-Salicylat als mindestens ein Farbakzeptor.

The invention relates to a recording material for the pressure-induced formation of a typeface. More particularly, the present invention relates to a recording material for the pressure-induced formation of a typeface, comprising at least:

• ■ a web-shaped substrate,
  comprising a front side as the first of the two substrate sides and a back side as the second of the two substrate sides,
• A coating formed on at least one of the two substrate sides, comprising a zinc salicylate as at least one color acceptor.

The invention also relates to a method for producing a recording material for the pressure-induced formation of a typeface to the same extent.

In general, zinc benzoates are generally known as color acceptors in color-reactive recording materials. Thus, for example, the non-generic EP 1 375 182 A1 the zinc 4-nitrobenzoate, which is not identical to zinc salicylate, as a developer component in heat-sensitive recording materials. In the EP 2 161 255 A1 Among others, zinc benzoates, and also those color developers, which include the zinc salicylate proposed here, are generally disclosed as components of color-reactive recording materials, without being concerned with possible concentrations in the color reaction layers.

Subject of the US 4,257,935 A is a color-developing coating composition which, according to introductory passages, is to be used preferably for pressure-sensitive recording systems. By way of example only and in comparison with a commercially available transfer sheet, such a coating composition contains, in addition to zinc salicylate as the color acceptor and starch and latex as binder, a clay pigment whose possible inclusion in the description of the coating composition proposed there is not mentioned.

To the same extent is from the EP 0 485 064 A1 a SC (selfcontained) coating composition for forming a carbonless paper, are disclosed for the zinc-salicylate as a color acceptor, a variety of possible components such as starch and polyvinyl alcohol as a binder and optionally also various pigments as possible fillers.

Finally, the beats too EP 0 360 522 A2 a developer composition containing as a possible color acceptor zinc salicylate. While mention is made of the possible incorporation of binders into the developer composition, there is a vain search for possible indications of incorporation of pigments into such a developer composition.

• □ das über eine hervorragende Kurzzeit-Farbentwicklung sowie über eine sehr gute Farbintensität der durch lokale Druckeinwirkung bewirkten Schriftbilder verfügt, weil die bekannten druckempfindlichen Aufzeichnungsmaterialien hier mitunter am Markt nicht vollends überzeugende Ergebnisse zu bringen in der Lage sind,
• □ das hinsichtlich der für die Herstellung von Formularsätzen besonders wichtigen Selbsttrennverleimbarkeit vorteilhaft ausgebildet ist,
• □ das über eine gute Offset-Bedruckbarkeit insbesondere auf der Seite mit der Beschichtung, aufweisend ein Zink-Salicylat als mindestens ein Farbakzeptor, verfügt, weil Kundenanforderungen inzwischen häufig eine Offsetbedruckung der druckempfindlichen Aufzeichnungsmaterialien vorsehen und
• □ das im Rahmen seiner Herstellung einen problemlosen und stabilen Maschinenlauf auch bei höheren Maschinenlaufgeschwindigkeiten gewährleistet.

Based on the prior art outlined above, the inventors have faced the task of making available to the public a new recording material for the pressure-induced formation of typefaces,

• □ has an excellent short-term color development and a very good color intensity of the caused by local pressure typefaces, because the known pressure-sensitive recording materials sometimes here in the situation are not able to bring completely convincing results
• □ which is advantageously designed with regard to the self-releasing ability which is particularly important for the production of form sets,
• □ has a good offset printability especially on the side with the coating, comprising a zinc salicylate as at least one color acceptor, because customer requirements nowadays often provide an offset printing of the pressure-sensitive recording materials, and
• □ ensures trouble-free and stable machine operation as part of its production, even at higher machine speeds.

The object is achieved according to the findings of the inventors by means of a recording material for the pressure-induced formation of a typeface according to the appended claims.

According to the development and production work on which this invention is based, there has been a particular preference of the inventors for the use of zinc salicylate ER-054 manufactured by Sanko Co., Ltd., Japan.

In the context of a first embodiment variant, the recording material proposed here is formed from a web-shaped substrate, on the front side of which a first coating composition is applied for forming a so-called CF layer as a possibility of a color reaction layer . CF layers (coated front) are understood as meaning layers having color developers (colorants or color acceptors) which can be formed as color developer pigment or, as in the case according to the invention, as oil-soluble acidic organic substances and which are admixed with suitable dye precursors, preferably leuco dyes a color reaction, in which a color complex is formed. Examples of organic color acceptors well known in the art include phenolic substances such as phenol, resorcinol, naphthols and salicylic acid, which may also be alkyl substituted and may be present as monomers, oligomers or polymers (resins).

In the context of a second embodiment, the recording material proposed here is formed from a web-shaped substrate, on the front side of which a coating composition is applied for forming a so-called SC layer as a further possibility of a color reaction layer . Self-contained SC layers are understood as meaning layers which contain a zinc salicylate as well as at least one color acceptor as well as encapsulated dye precursors for the purposes of the present invention.

• ein anorganisches Pigment,
• ein Bindemittel,
• Mittel zur Hydrophobierung dieser pigmentierten Beschichtung auf der Rückseite des Substrats.

If the recording material proposed here for the pressure-induced formation of a typeface is carried out either according to its first embodiment or according to its second embodiment according to the two preceding paragraphs, it represents a preferred embodiment, when the substrate carries on its back a coating of a second coating composition which most preferably at least comprises:

• an inorganic pigment,
• a binder,
• Means for hydrophobing this pigmented coating on the back of the substrate.

Silica, kaolin, aluminum (hydr) oxide and, in particular, natural calcium carbonate are suitable as inorganic pigment within this backside coating, and it is also conceivable to mix these inorganic pigments with one another or with other inorganic pigments. If, in addition to the previously disclosed pigments, other pigments are also to be used within the backcoat coating, it is preferred if these other inorganic pigments have a mixing ratio, relative to wt.%, Of silica, aluminum (hydr) oxide or, in particular, natural calcium carbonate 1: 4 and 1:25 are incorporated within the second coating composition.

Styrene-acrylate latex, starch, polyvinyl alcohol and very particularly preferably styrene-butadiene latex are suitable as binders within this backside coating. Wax and / or AKD glue are used in particular as a means of hydrophobing the pigmented coating.

In the context of a third and most preferred embodiment, the proposed here Recording material formed from a web-shaped substrate, on the front side as a first coating composition, the composition for forming the coating with zinc salicylate as at least one color acceptor is applied to form a CF layer, while on the back of the substrate, a so-called CB layer (coated back) is formed. In this case, recording materials which have on the front side a CF layer with color acceptors or color acceptors and on the backside a CB layer are referred to as so-called CFB materials, sheets or sheets. The CB layer contains microcapsules containing dye precursors in a suitable solvent. In principle, the application of a localized pressure to the CB coating, for example by writing by means of a pen or a typewriter, causes the microcapsules to break up, resulting in a release of the previously encapsulated dye precursors. Then come dye precursors from the microcapsules of the CB or SC layer in contact with the zinc salicylate as at least one color acceptor within the CF or SC layer, it leads to the formation of a color reaction, which takes place exactly where previously by the Pressure exerted the microcapsules are broken: usually this happens along a script line, which is formed by inscription using a pen or typewriter.

In particular with CFB sheets, there is a risk that the dye precursor solution will also spread within the CFB sheet and spread to the front side, i.e. to the CFB sheet. H. the CF layer breaks through, causing an undesirable color reaction here. To avoid the corresponding substrates, if they are made of paper, fully sized in the mass. Alternatively, especially for CFB sheets, without being limited to the purposes of the present invention, the CF coatings and / or the CB coatings are underlaminated with barrier-forming intermediate coatings, which means that the barrier-forming intermediate coatings between substrate and CF coating and / or are formed between the substrate and the CB coating.

In the case of the recording material proposed here for the pressure-induced formation of a typeface having a coating on at least one of the two substrate sides which comprises a zinc salicylate as at least one color acceptor, the dye precursors are encapsulated in microcapsules having the size and leuco dyes preferably used therein are largely not restricted. However, those microcapsules which have a wall material of melamine-formaldehyde resin with a preferred average capsule size in a range in particular of 4 to 6 μm are particularly well-proven. Diisopropylnaphthalene oil (KMC oil from Rütgers Novares GmbH, Duisburg, Germany) is preferably used as the capsule content, containing as dye precursor leuco dyes in a range from 4 to 7.5% by weight.

• natürliches Kaolin, kalziniertes Kaolin, Kieselsäure, Talkum, natürliches Kalziumkarbonat, gefälltes Kalziumkarbonat sowie Aluminium(hydr)oxid.

Ganz besonders bevorzugt sind die zwei stofflich verschiedenen anorganischen Pigmente jeweils ausgesucht sind aus der Liste, umfassend:

• natürliches Kaolin, kalziniertes Kaolin, Talkum, gefälltes Kalziumkarbonat sowie Aluminium(hydr)oxid.

Dabei ist es unerheblich, ob die Beschichtung mit dem Zink-Salicylat auf einem bahnförmigen Substrat ausgebildet ist, bei dem Substrat und Beschichtung mit dem Zink-Salicylat zu einem hier vorgeschlagenen Aufzeichnungsmaterial gemäß erster Ausführungsvariante, eine CF-Beschichtung betreffend, zweiter Ausführungsvariante, eine SC-Beschichtung betreffend, oder dritter Ausführungsvariante, ein CFB-Aufzeichnungsmaterial betreffend, zu zählen ist. Im Rahmen einer ganz besonders bevorzugten Ausführung enthält die Beschichtung mit dem Zink-Salicylat eine Pigmentmischung ausschließlich aus natürlichem Kaolin und gefälltem Kalziumkarbonat. In einem solchen Fall zeigten die der Erfindung voraus gegangenen Versuche und Versuchsanfertigungen, dass eine besondere Präferenz seitens der Erfinderschaft auf eine Beschichtung mit dem Zink-Salicylat als mindestens ein Farbakzeptor gelegt wird, bei dem als Pigment eine Pigmentmischung aus natürlichem Kaolin und gefälltem Kalziumkarbonat enthalten ist, wobei das auf Gew.-% bezogene Mischungsverhältnis von natürlichem Kaolin und gefälltem Kalziumkarbonat in einem Bereich von 2 : 1 bis 1 : 2 liegt.According to the invention, the coating with the zinc salicylate as inorganic pigment has a pigment mixture of exactly two materially different inorganic pigments, the two materially different inorganic pigments each selected from the list, comprising:

• natural kaolin, calcined kaolin, silicic acid, talc, natural calcium carbonate, precipitated calcium carbonate and aluminum (hydr) oxide.

Most preferably, the two materially different inorganic pigments are each selected from the list, comprising:

• natural kaolin, calcined kaolin, talc, precipitated calcium carbonate and aluminum (hydr) oxide.

It is irrelevant whether the coating with the zinc salicylate is formed on a web-like substrate, in the substrate and coating with the zinc salicylate to a recording material according to the first embodiment proposed here, concerning a CF coating, second embodiment, a SC Coating, or third embodiment, concerning a CFB recording material. In a most preferred embodiment, the zinc salicylate coating contains a pigment mixture exclusively of natural kaolin and precipitated calcium carbonate. In such a case, the experiments and trial preparations preceding the invention showed that the Inventor places a particular preference on a coating with the zinc salicylate as at least one color acceptor containing as pigment a pigment mixture of natural kaolin and precipitated calcium carbonate wherein the weight percent mixing ratio of natural kaolin and precipitated calcium carbonate ranges from 2: 1 to 1: 2.

• ■ 25,0 - 32,0 cm (Messgeschwindigkeit 1,60 mm/s),
• ■ 31,0 - 37,0 cm (Messgeschwindigkeit 3,45 mm/s),
• ■ 37,0 - 45,0 cm (Messgeschwindigkeit 8,55 mm/s)

notieren. Nicht zuletzt, um solche bevorzugten Messwerte zu erreichen, gelten genauso Pigmentmischungen aus kalziniertem Kaolin und Aluminiumhydroxid insbesondere mit einem Mischungsverhältnis in einem Bereich von 1 : 1,8 bis 1 : 2,8 sowie aus kalziniertem Kaolin und Talkum insbesondere mit einem Mischungsverhältnis in einem Bereich von 1 : 3,5 bis 1 : 6,5 als besonders bevorzugt.The essential feature of such a pigment mixture characterizing the invention is the setting of the porosity of the coating with zinc salicylate in a decisive manner via exactly two materially different inorganic pigments within the pigment mixture, of which one pigment tends to increase the porosity of the coating preferred pigment mixture of the previous paragraph, this task is performed by the precipitated calcium carbonate, while the other pigment has a tendency to ensure lower porosity of the coating, given in the preferred pigment mixture by the natural kaolin. In the context of the present invention, it has been recognized that both the offset printability and the self-releasability of the paper can be optimized by means of the porosity. The inventors could in this regard particularly convincing samples comprising a substrate with back starch preparation and a front coat application as a CF coating of a first coating composition according to the benchmark data of Table 1. Bristow readings (test liquid: Levacell violet 6 BG, diluted 1: 500, ink amount: 40 μm; narrow gap) in a preferred range of:

• ■ 25.0 - 32.0 cm (measuring speed 1.60 mm / s),
• ■ 31.0 - 37.0 cm (measuring speed 3.45 mm / s),
• ■ 37,0 - 45,0 cm (measuring speed 8,55 mm / s)

note. Last but not least, in order to achieve such preferred measured values, pigment mixtures of calcined kaolin and aluminum hydroxide, in particular having a mixing ratio in the range of 1: 1.8 to 1: 2.8, and of calcined kaolin and talcum, in particular with a mixing ratio in one range, also apply from 1: 3.5 to 1: 6.5 is particularly preferred.

In addition to the invention characterizing pigment mixture of exactly two materially different inorganic pigments, the coating with the zinc salicylate preferably contains at least one binder selected from the list, comprising: styrene-butadiene latex, styrene-acrylate latex, starch, polyvinyl alcohol. The preference of the inventors is styrene-butadiene latex, which is used in particular together with starch.

• Zink-Salicylat_gesamt: anorganisches Pigment_gesamt
• in einem Bereich von 1 : 6,5 bis 1 : 14,0,
• ganz besonders bevorzugt in einem Bereich von 1 : 7,5 bis 1 : 12,5 liegt.

Within the coating with the zinc salicylate, it is moreover particularly preferred if the zinc salicylate in a range of 5.5 to 11.0 wt .-% - based on the total weight of the coating with the zinc salicylate - in this coating is integrated. At the same time, it has been found to be particularly advantageous and is considered to be preferred when the ratio based on wt .-% within the coating with the zinc salicylate

• Zinc salicylate _general: inorganic pigment _Total
• in a range of 1: 6.5 to 1: 14.0,
• most preferably in a range of 1: 7.5 to 1: 12.5.

• in Form eines Musters oder
• in Form geometrischer Figuren, wie Quadrat, Rechteck, Ellipse oder
• in Form alphanumerischer Zeichen

aufgetragen sein. In diesem Fall, aber nicht beschränkt auf diesen Fall, gilt es als bevorzugt, wenn die Vorderseite des Substrates zwischen dem Substrat selbst und der Schicht mit dem Zink-Salicylat

1. (a.) eine Stärke-Präparation gegebenenfalls mit Oberflächen leimenden Zusätzen und/oder
2. (b.) einen pigmentierten Überzug aufweist. Dieser pigmentierte Überzug weist dann bevorzugt mindestens ein anorganisches Pigment auf, wofür sich insbesondere kalziniertes Kaolin anbietet. Jedoch auch folgende anorganische Pigmente sind als Bestandteile des pigmentierten Überzugs sehr gut geeignet: Siliziumoxid, Bentonit, Kalziumkarbonat sowie Aluminiumoxid. Auch Mischungen aus mehreren verschiedenartigen anorganischen Pigmenten sind vorstellbar. Neben den anorganischen Pigmenten enthält der pigmentierte Überzug mindestens ein Bindemittel bevorzugt auf Basis eines synthetischen Polymers, wobei beispielsweise Styrol-Butadien-Latex besonders gute Ergebnisse liefert. Die Verwendung eines synthetischen Bindemittels unter Beimischung mindestens eines natürlichen Polymers, wie besonders bevorzugt Stärke, stellt eine besonders geeignete Ausführungsform dar.

In the context of a possible embodiment, which can be combined with all embodiments and variants proposed here, the coating with the zinc salicylate can only partially

• in the form of a pattern or
• in the form of geometric figures, such as square, rectangle, ellipse or
• in the form of alphanumeric characters

be applied. In this case, but not limited to this case, it is considered preferable if the front side of the substrate between the substrate itself and the zinc salicylate layer

1. (a.) a starch preparation optionally with surface sizing additives and / or
2. (b.) Having a pigmented coating. This pigmented coating then preferably has at least one inorganic pigment, for which in particular calcined kaolin is offered. However, the following inorganic pigments are also very suitable as constituents of the pigmented coating: silicon oxide, bentonite, calcium carbonate and aluminum oxide. Also mixtures of several different types of inorganic pigments are conceivable. In addition to the inorganic pigments, the pigmented coating contains at least one binder preferably based on a synthetic polymer, for example, styrene-butadiene latex gives particularly good results. The use of a synthetic binder with the admixture of at least one natural polymer, such as particularly preferred starch, represents a particularly suitable embodiment.

• ■ als nicht oberflächenbehandeltes, in der Masse geleimtes Papier,
• ■ als ungeleimtes, aber zumindest vorderseitig und/oder rückseitig präpariertes Papier - wobei als Mittel zur Präparation bevorzugt eine Stärkelösung gegebenenfalls mit Oberflächen leimenden Zusätzen zum Einsatz kommt,
• ■ als zumindest vorderseitig mit einer Polyolefinbeschichtung versehenes Papier.

Genauso vorstellbar als bahnförmiges Substrat ist beispielsweise eine Folie, insbesondere eine Corona-behandelte Folie.As a web-shaped substrate is paper as preferred, which is used in particular

• ■ as non-surface-treated, mass-glued paper,
• As unprimed paper, but at least on the front side and / or on the back prepared paper - preferably using a starch solution optionally with surface-sizing additives as the preparation for preparation,
• ■ as at least the front side provided with a polyolefin coating paper.

Also conceivable as a web-shaped substrate is, for example, a film, in particular a corona-treated film.

The invention also relates, to the same extent, to a method for producing a recording material for the pressure-induced formation of a typeface in all the embodiments and variants already proposed here.

In this case, such a method comprises the method steps defined in claim 12.

The formation of the web-like substrate is done for example on a paper machine, in which at least one upstream Mischbütte a paper pulp of different pulp, optionally groundwood, fillers and water is applied and where to this paper pulp before being fed to the paper machine preferably further ingredients such as resin glue for engine sizing and other customary additives, such as pigments, shading dyes and / or optical brighteners are added. After a possible smoothing of the paper web as a web-shaped substrate, this can be rolled up as a semi-finished product on a spool at the end of the paper machine.

After an optionally necessary upstream unrolling of the web-shaped substrate as a semi-finished product of a drum, the first coating composition is preferably applied to the front of the substrate using a coater, the coater preferably selected from the list comprising: roller coater, roller blade coater, knife coater, air brush and all particularly preferred curtain coater. Especially in the use of a curtain coater both in its design as Schlitzgießer with downwardly open color head from which immediately forms the color curtain, as well as in its design as Gleitflächenbeschichter, in which the paint head is the coating mass on an inclined flow sheet, from where forming the color curtain, particularly convincing product and especially machine running properties within the coating process could be observed, eventually leading to a particularly homogeneous appearance of the color reaction layer from the first coating composition. The first coating composition used to form a color reaction layer is preferably aqueous. The subsequent drying of the first coating composition is usually carried out by a method in which heat is supplied, as is done by hot-air floatation dryer or contact dryer. Proven is also a combination of the listed dry processes. After drying the first coating composition, the color reaction layer thus formed is preferably at least slightly frosted. The basis weight of the color reaction layer of the first coating composition is preferably from 3.2 to 7.2 g / m ^2, and more preferably from 3.4 to 4.8 g / m ² .

In an embodiment of the color reaction layer of the first coating composition as a CF layer particularly convincing results could be achieved if a recipe was used according to the key data of the following Table 1 , which are considered to be very particularly preferred <u> Table 1: </ u> component amount Precipitated calcium carbonate Together 60-80% by weight with a ratio of calcium carbonate: kaolin in a range of 2: 1 to 1: 2 kaolin Strength Together 8-18 wt% with a starch: styrene-butadiene latex ratio in the range of 1: 1 to 1: 2.5 Styrene-butadiene latex Zinc salicylate 4-14% by weight, most preferably 5.5 to 11% by weight

• □ Ausbilden eines bahnförmigen Substrats,
  aufweisend eine Vorderseite als die erste der beiden Substratseiten und eine Rückseite als die zweite der beiden Substratseiten;
• □ Vorbereiten einer ersten Beschichtungszusammensetzung, wobei diese erste Beschichtungszusammensetzung mindestens umfasst:
  • als anorganisches Pigment eine Pigmentmischung aus genau zwei stofflich verschiedenen anorganischen Pigmenten, jeweils ausgesucht aus der Liste, umfassend: natürliches Kaolin, kalziniertes Kaolin, Rieselsäure, Talkum, natürliches Kalziumkarbonat, gefälltes Kalziumkarbonat sowie Aluminium(hydr)oxid,
  • ein Bindemittel,
  • Zink-Salicylat;
• □ Aufbringen der vorbereiteten ersten Beschichtungszusammensetzung auf der Vorderseite des Substrates zur Ausbildung einer Farb-Reaktionsschicht;
• □ Trocknen der ersten Beschichtungszusammensetzung;
• □ Vorbereiten einer zweiten Beschichtungszusammensetzung, wobei diese zweite Beschichtungszusammensetzung mindestens umfasst:
  • ein anorganisches Pigment,
  • ein Bindemittel
  • und bevorzugt zusätzlich Mittel zur Hydrophobierung;
• □ Aufbringen der vorbereiteten zweiten Beschichtungszusammensetzung zur Ausbildung einer pigmentierten und bevorzugt hydrophoben Beschichtung auf der Rückseite des Substrats;
• □ Trocknen der zweiten Beschichtungszusammensetzung;
• □ Aufrollen des bahnförmigen Substrats mit der pigmentierten Rückseitenbeschichtung und der Farb-Reaktionsschicht.

If the recording material proposed for this purpose for the pressure-induced formation of a typeface should have a pigmented backside coating, a process for producing such a recording material preferably comprises at least the following process steps:

• □ forming a web-shaped substrate,
  having a front side as the first of the two substrate sides and a back side as the second of the two substrate sides;
• □ preparing a first coating composition, said first coating composition comprising at least
  • inorganic pigment as a pigment mixture of exactly two materially different inorganic pigments, each selected from the list, comprising: natural kaolin, calcined kaolin, Rieselsäure, talc, natural calcium carbonate, precipitated calcium carbonate and aluminum (hydr) oxide,
  • a binder,
  • Zinc salicylate;
• Applying the prepared first coating composition to the front side of the substrate to form a color reaction layer;
• □ drying the first coating composition;
• □ preparing a second coating composition, said second coating composition comprising at least
  • an inorganic pigment,
  • a binder
  • and preferably additionally hydrophobing agents;
• Applying the prepared second coating composition to form a pigmented and preferably hydrophobic coating on the back side of the substrate;
• □ drying the second coating composition;
• Rolling up the web-like substrate with the pigmented backcoat and the color reaction layer.

The application of the second coating composition to form a pigmented and preferably hydrophobic coating on the back side of the substrate is preferably accomplished by means of a coater selected from the list comprising: roller coater, curtain coater, doctor blade and doctor roll coater. The second coating composition used to form this pigmented backside coating is also preferably aqueous. The subsequent drying after application of the second Again, coating composition is usually done by a process of adding heat, such as by hot-air floatation dryers or contact dryers. Proven is also a combination of the listed dry processes. The basis weight of the pigmented backcoat of the second coating composition is preferably between 2.5 and 4.2 g / m ^2, and more preferably between 2.7 and 3.7 g / m ² .

• □ Ausbilden eines bahnförmigen Substrats,
  aufweisend eine Vorderseite als die erste der beiden Substratseiten und eine Rückseite als die zweite der beiden Substratseiten;
• □ Vorbereiten einer ersten Beschichtungszusammensetzung, wobei diese erste Beschichtungszusammensetzung mindestens umfasst:
  • als anorganisches Pigment eine Pigmentmischung aus genau zwei stofflich verschiedenen anorganischen Pigmenten, jeweils ausgesucht aus der Liste, umfassend: natürliches Kaolin, kalziniertes Kaolin, Kieselsäure, Talkum, natürliches Kalziumkarbonat, gefälltes Kalziumkarbonat sowie Aluminium(hydr)oxid,
  • ein Bindemittel,
  • Zink-Salicylat;
• □ Aufbringen der vorbereiteten ersten Beschichtungszusammensetzung auf der Vorderseite des Substrates zur Ausbildung einer CF-Schicht;
• □ Trocknen der ersten Beschichtungszusammensetzung;
• □ Vorbereiten einer dritten Beschichtungszusammensetzung mit eingekapselten Farb-stoffvorläufern,
• □ Aufbringen der vorbereiteten dritten Beschichtungszusammensetzung zur Ausbildung einer CB-Schicht auf der Rückseite des Substrats;
• □ Trocknen der dritten Beschichtungszusammensetzung;
• □ Aufrollen des bahnförmigen Substrats mit der vorderseitigen CF-Schicht und der rückseitigen CB-Schicht.

If the recording material proposed for this purpose for the pressure-induced formation of a typeface in addition to the front-side coating with the zinc salicylate as CF layer should have a backside coating with encapsulated dye precursors as CB layer, a process for producing such a recording material preferably comprises at least the following process steps :

• □ forming a web-shaped substrate,
  having a front side as the first of the two substrate sides and a back side as the second of the two substrate sides;
• □ preparing a first coating composition, said first coating composition comprising at least
  • inorganic pigment as a pigment mixture of exactly two materially different inorganic pigments, each selected from the list, comprising: natural kaolin, calcined kaolin, silica, talc, natural calcium carbonate, precipitated calcium carbonate and aluminum (hydr) oxide,
  • a binder,
  • Zinc salicylate;
• Applying the prepared first coating composition to the front surface of the substrate to form a CF layer;
• □ drying the first coating composition;
• □ preparing a third coating composition with encapsulated dye precursors,
• Applying the prepared third coating composition to form a CB layer on the back side of the substrate;
• □ drying the third coating composition;
• Rolling up the web-shaped substrate with the front CF layer and the backside CB layer.

The application of the third coating composition to form a CB layer on the back surface of the substrate is preferably accomplished by means of a coater selected from the list comprising: roller coater, curtain coater, doctor blade and doctor blade coater. Especially in the use of a curtain coater both in its design as Schlitzgießer with downwardly open color head from which immediately forms the color curtain, as well as in its design as Gleitflächenbeschichter, in which the paint head is the coating mass on an inclined flow sheet, from where forming the color curtain, excellent product and especially machine running properties could be observed within the coating process, eventually leading to a particularly homogeneous appearance of the CB coating from the third coating composition. Also, the third coating composition used to form the CB layer is preferably aqueous. The subsequent drying of the second coating composition after the application is again usually carried out by a method in which heat is supplied, as is done by hot-air floatation dryer or contact dryer. Proven is also a combination of the listed dry processes. The basis weight of a CB layer of the third coating composition is preferably between 2.2 and 6.2 g / m ^2, and more preferably between 2.4 and 3.8 g / m ² .

It represents a most preferred embodiment of the presently proposed method of forming a recording material for the pressure-induced formation of a typeface having a front face zinc salicylate color acceptor CF layer and backside CB layer when both the CF layer and the CB layer Layer can be formed with a curtain coater. The process implemented here is characterized in particular by the preferred fact that both layers are within a single pass be applied by a coater, this coater has characteristically for the proposed method two curtain coater, each with downstream drying areas. Such a method is not restrictive to be integrated into a paper machine as well.

The following examples, together with the following comparative examples, will further clarify the invention:

On a fourdrinier paper machine, a paper web of bleached and ground deciduous and softwood pulps having a basis weight of 67 g / m ² with conventional additives and in particular with the addition of resin size for engine sizing is produced as a web-shaped substrate and at the end of the paper machine as a semi-finished product rolled up on a spool.

Within a coater, after the necessary unwinding of the web-shaped substrate as semi-finished product from the spool, a color reaction layer is applied on the front side using a curtain coater in its slitter coater design, and a second coater composition for forming a pigmented and hydrophobic coater is applied using a further curtain coater as slot coater , The second coating composition contains as main constituents natural calcium carbonate as pigment, styrene-acrylate latex and starch as binder mixture and AKD glue as a means for hydrophobizing the pigmented backcoat. While the back coating is applied at a basis weight of 3.0 g / m ² , the basis weight for the color reaction layer is 4.0 g / m ² .

Within the three examples of the invention and the four comparative examples, the color reaction layer is alternatively formed from seven different first coating compositions, these coating compositions differing as shown in Table 2 below.

• (i.-1) Kurzzeit-Farbentwicklung,
• (i.-2) Farbintensität,
• (ii.) Selbsttrennverleimbarkeit,
• (iii.) Offset-Bedruckbarkeit und
• (iv.) Runnability

schnell klar. Es ergeben sich Beurteilungen gemäß Tabelle 3:

When looking at finished samples on the one hand of Examples 1 to 3 according to the invention and on the other hand of Comparative Examples 1 to 4, the superiority of the examples according to the invention with regard to the task aspects defined above

• (i.-1) short-term color development,
• (i.-2) color intensity,
• (ii.) self-releasability,
• (iii.) offset printability and
• (iv.) runnability

quickly clear. There are judgments according to Table 3:

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

Claims (13)

1. Recording material for the pressure-induced formation of a text image, comprising at least:

   ▪ a web-form substrate,
   having a front side as the first of the two substrate sides and a rear side as the second of the two substrate sides,

   ▪ a coating formed on at least one of the two substrate sides, having:

   - a zinc salicylate as at least one colour acceptor,

   - an inorganic pigment,

   having the features that

   ▪ the zinc salicylate is incorporated in the coating containing the zinc salicylate as colour acceptor in a range of from 4 to 14 % by weight - based on the total weight of that coating,

   ▪ as inorganic pigment, a pigment mixture composed of just two chemically different inorganic pigments is incorporated in that coating,

   characterised in that

   a) the coating containing the zinc salicylate contains as inorganic pigment a pigment mixture composed of natural kaolin and precipitated calcium carbonate and the mixing ratio of natural kaolin and precipitated calcium carbonate lies in a range of from 2 : 1 to 1 : 2, based on % by weight
   or

   b) the coating containing the zinc salicylate contains as inorganic pigment a pigment mixture composed of calcined kaolin and aluminium hydroxide
   or

   c) the coating containing the zinc salicylate contains as inorganic pigment a pigment mixture composed of calcined kaolin and talcum.
2. Recording material according to patent claim 1, characterised in that the recording material comprises at least:

   ▪ a web-form substrate,

   ▪ a coating containing the zinc salicylate on the front side of the substrate,

   ▪ a pigmented coating on the rear side of the substrate.
3. Recording material according to either one of patent claims 1 and 2, characterised in that the coating containing the zinc salicylate additionally contains encapsulated dye precursors.
4. Recording material according to patent claim 1, characterised in that the recording material comprises at least:

   ▪ a web-form substrate,

   ▪ a coating containing the zinc salicylate on the front side of the substrate,

   ▪ a coating containing encapsulated dye precursors on the rear side of the substrate.
5. Recording material according to any one of patent claims 1 to 4, characterised in that the zinc salicylate is incorporated in the coating containing the zinc salicylate in a range of from 5.5 to 11.0 % by weight, based on the total weight of that coating.
6. Recording material according to any one of patent claims 1 to 5, characterised in that the ratio
   zinc salicylate_total : inorganic pigment_total
   lies in a range of from 1 : 6.5 to 1 : 14.0, based on % by weight in the coating containing the zinc salicylate.
7. Recording material according to any one of patent claims 1 to 6, characterised in that the mixing ratio of calcined kaolin and aluminium hydroxide lies in a range of from 1 : 1.8 to 1 : 2.8, based on % by weight.
8. Recording material according to any one of patent claims 1 to 6, characterised in that the mixing ratio of calcined kaolin and talcum lies in a range of from 1 : 3.5 to 1 : 6.5, based on % by weight.
9. Recording material according to any one of patent claims 1 to 8, characterised in that the coating containing the zinc salicylate additionally contains at least one binder selected from the list comprising: styrenebutadiene latex, styrene-acrylate latex, starch, polyvinyl alcohol.
10. Web-form recording material according to any one of patent claims 1 to 9, characterised in that the coating containing the zinc salicylate is applied to only part of the substrate.
11. Web-form recording material according to any one of patent claims 2, 3 and 5 to 10, characterised in that the pigmented coating on the rear side of the substrate comprises at least:

    ▪ an inorganic pigment,

    ▪ a binder,

    ▪ means for hydrophobising this pigmented coating on the rear side of the substrate.
12. Process for the production of a recording material for the pressure-induced formation of a text image, the process comprising at least the following process steps:

    □ forming a web-form substrate, having a front side as the first of the two substrate sides and a rear side as the second of the two substrate sides;

    □ preparing a first coating composition, this first coating composition comprising at least:

    - as inorganic pigment, a pigment mixture composed of natural kaolin and precipitated calcium carbonate, the mixing ratio of natural kaolin and precipitated calcium carbonate lying in a range of from 2 : 1 to 1 : 2, based on % by weight.

    - a binder,

    - zinc salicylate, the zinc salicylate being present in a range of from 4 to 14 % by weight, based on the total weight of the coating;

    □ applying the prepared first coating composition to the front side of the substrate to form a colour reaction layer;

    □ drying the first coating composition;

    □ rolling up the web-form substrate having the colour reaction layer.
13. Process for the production of a recording material according to patent claim 12, characterised in that the first coating composition is applied by means of a coating unit selected from the list comprising: roller coating device, doctor roller coating device, blade coating device, curtain coater and airbrush.