EP0037477A2 - Copying system and method for its manufacture, and offset or printing dyes useful in this system - Google Patents

Abstract

The invention relates to a process for the production of pressure-sensitive, carbon-free copying systems, in which a coating composition is applied to a surface of the paper substrate in part or over the full surface using the technique of wet or dry offset printing or letterpress printing, which contains microcapsules containing dye precursors; the copying systems produced by this process; an offset printing or letterpress ink, which consists of reactive resins, dye precursors containing microcapsules, spacers and other auxiliaries and additives; and the use of these offset printing or letterpress inks for the production of pressure-sensitive, carbon-free copy systems on offset printing or letterpress machines.

Description

• - ein Verfahren zur Herstellung von druckempfindlichen, kohlefreien Durchschreibesystemen, bei welchem auf einer Oberfläche des Papiersubstrates partiell oder vollflächig mit der Technik des Naß- oder Trockenoffsetdruckes oder des Buchdruckes eine Beschichtungskomposition aufgebracht wird, die Farbstoffvorläufer enthaltende Mikrokapseln enthält;
• - die nach diesem Verfahren hergestellten Durchschreibesysteme;
• - eine Offsetdruck- bzw. Buchdruckfarbe, die aus Reaktionsharzen, Farbstoffvorläufer enthaltenden Mikrokapseln, Abstandhaltern, sowie weiteren Hilfs- und Zusatzstoffen besteht;
• - die Verwendung dieser Offsetdruck- bzw. Buchdruckfarben zur Herstellung druckempfindlicher, kohlefreier Durchschreibesysteme auf Offsetdruck- bzw. Buchdruckmaschinen.

The invention relates

• - A process for the production of pressure-sensitive, carbon-free copy systems, in which a coating composition which contains dye precursors containing microcapsules is applied to a surface of the paper substrate in part or over the full surface using the technique of wet or dry offset printing or letterpress printing;
• - the copying systems produced by this method;
• - An offset printing or letterpress ink, which consists of reactive resins, dye precursors containing microcapsules, spacers, and other auxiliaries and additives;
• - The use of these offset printing or letterpress inks for the production of pressure-sensitive, carbon-free copy systems on offset printing or letterpress machines.

Reaction copy papers are known (see M. Gutcho, Capsule Technology and Microencapsulation, Noyes Data Corporation, 1972, pages 242-277; G. Baxter in Microencapsulation, Processes and Applications, edited by JE Vandegaer, Plenum Press, New York, London, pages 127-143).

Reaction copy papers preferably consist of two or more sheets of paper loosely placed one on top of the other, the top one on the back
a donor layer and the lower one on the front contains a slave layer. In other words, a donor layer and a receiver layer are in contact with each other. The donor layer contains microcapsules, the core of which is a solution of a color former in an organic solvent, and the receiver layer contains a material that develops the dye former into a dye. When writing, the capsules are destroyed under the high pressure of the writing utensil and the leaking core material hits the slave layer, so that a copy is produced.

The receiver layer usually contains binders and pigments, e.g. active absorbents such as kaolin, attapulgite, montmorillonite, bentonite, acidic bleaching earth or phenolic resins. You can e.g. Use acid-activated dyes on the donor layer and acid-reacting components in the receiver layer.

A further development of these reaction copy papers are the "one-component" reaction copy papers. In these, one side of a single breading sheet carries the dye precursor, generally in the form of microcapsules, and at the same time the color developer. If pressure is now applied, e.g. using a typewriter or other writing tool, the capsule containing the color precursor is torn open and the color precursor reacts with the color developer surrounding it (see US Pat. No. 2,730,456).

The coating of the paper substrate for the production of the carbon-free copying systems is generally carried out over the entire area with an aqueous coating composition, such as e.g. in German Offenlegungsschriften 1 934 457 and 1 955 542.

The disadvantage of the methods described is that after the coating composition has been applied, the water evaporates, which requires a considerable amount of energy. The need to dry further requires the use of complex and costly equipment to continuously dry a substrate that has been coated with an aqueous coating compound. Another but related problem relates to the removal of contaminated water resulting from the manufacture and cleaning of the aqueous coating composition.

If volatile organic solvents are used in the production of the coatings, the excess solvent must also be evaporated in order to dry the coating. In this way, solvent vapors are produced which pose particular risks.

Full-surface coatings are inefficient because in most cases only parts of the carbonless system are used.

Numerous methods have therefore become known for partially applying coating compositions to a paper substrate. Thus, according to the prior art, aqueous or solvent-containing coatings can be partially applied to a paper support by means of gravure printing or flexographic printing (see, for example, DE-OS 2 541 001, US Patents 3,016,308 and 3,914,511). These processes also have the disadvantage of having to dry the coatings subsequently. For these reasons, it has been proposed, for example, in US Pat. Nos. 3,016,308, 3,079,351 and 3,684,549, as well as in German Offenlegungsschriften 2,719,914 and 2,719,935. to take up the microcapsules in waxes and to coat the paper carrier with such hot-melt systems.

Although these proposed measures prevent the removal of the solvents, the wax-like coating changes the character of the paper, since relatively large amounts of the waxes have to be applied.

In addition, the melting systems are applied to hot carbon printing machines, which, although they allow printing, coating with wax materials and finishing to be combined in an online system, always require a separate system for each process step.

Processes to print microcapsules in coating compositions on offset printing machines or even letterpress machines were not feasible in this prior art, since it was generally assumed that both in the manufacture of the printing ink and in the distributor rollers of the printing machines and during the printing process, the shear and Pressure forces that would largely destroy the microcapsules.

This invention is based on the finding that microcapsules incorporated in printing inks can be applied largely undamaged on a paper support on offset and letterpress machines.

The invention accordingly relates to a method for producing pressure-sensitive, carbon-free copying systems, which is characterized in that on a surface of the paper substrate partially or fully covered with the technique of wet or Trockenoffsetdruc ^kes or of printing a coating is applied _un t gskomposition containing dye precursor-containing microcapsules.

The invention further relates to the copying systems produced by the method according to the invention.

This invention is also based on the knowledge that a coating composition comprising reactive resins, dye precursors containing microcapsules and spacers, and, if appropriate, further auxiliaries and additives can be applied to a paper web using offset printing machines or letterpress machines.

The invention accordingly also relates to an offset printing or letterpress ink which consists of reactive resins (preferably 90-20% by weight of the ink), microcapsules containing dye precursors (preferably 10-40% by weight of the ink), spacers (preferably 2- 20 wt .-% of the color), as well as other auxiliaries and additives (up to 50 wt .-% of the color).

The invention further relates to the use of these printing inks for the production of pressure-sensitive, carbon-free copy systems on offset printing or letterpress machines.

A large number of the microcapsules to be used to carry out the process according to the invention and processes for their production are known. Thus, the long-known microcapsules can be used, which can be produced by coacervation or complex coacervation from gelatin and acacia, as well as gelatin and other inorganic and organic polyanions. Various such methods have become known, inter alia, in M. Gutcho, Capsule Technology and Microencapsulation, Noyes Data Corporation 1972.

In particular, microcapsules are used in the method according to the invention, the walls of which consist of polymers, polycondensation and polyaddition products.

The following overview is G. Baxter, Microencapsulation, Processes and Applications, edited by J. _E. Vandegaer, taken and shows a compilation of the capsule wall polymers known according to the prior art.

Microcapsules with walls made of special polyacrylates, such as e.g. described in DE-OS 2 237 545 and DE-OS 2 119 933 can be used.

Furthermore, phenol or urea-formaldehyde condensates can be used as wall material, optionally also in combination with the capsule wall polymers mentioned above.

Microcapsules are preferably used in the process according to the invention, the shells of which consist of polyadducts of polyisocyanates and polyamines.

Isocyanates to be used for the production of such microcapsules are diisocyanates such as xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, Ethylidene diisocyanate, cyclo-hexyl-1,2-diisocyanate, cyclohexyl-1,4-diisocyanate, polyisocyanate prepolymers, e.g. Addition product of hexamethylene diisocyanate and hexanetriol, adduct of 2,4-tolylene diisocyanate with pyrocatechol, adduct of tolylene diisocyanate with hexanetriol, adduct of tolylene diisocyanate with trimethylolpropane, adduct of xylylene diisocyanate with trimethylolpropane, or the polyethyl compounds indicated above, or the polyethyl compounds corresponding to those described above or with trimethylolpropane.

Other modified aliphatic isocyanates are those based on hexamethylene-1,6-diisocyanate, m-xylylene diisocyanate, 4,4'-diisocyanatodicyclohexylmethane or isophorone diisocyanate, which have at least two functional isocyanate groups per molecule.

Other suitable compounds are polyisocyanates based on derivatives of hexamethylene-1,6-diisocyanate with a biuret structure, the preparation of which can be found in DE-AS 11 01 394 and 15 43 178, and in DE-OS 15 68 017 and 19 31 055.

The polyisocyanates that can be used can additionally be modified before use for microencapsulation by reaction with di- and trifunctional chain extenders, e.g. Water, with polyfunctional alcohols such as ethanediol, glycerol or trimethylolpropane or carboxylic acids such as succinic acid, adipic acid, sebacic acid in proportions of 0.01 to 0.5 mol per isocyanate equivalent.

Instead of the isocyanate groups, carbodiimide, uretdione, uretonimine, uretidinedione diimine, 4-imino-oxazolidinone (2), β-alkylene-propiolactone or cyclobutanedione (1,3) groups can also be present as reactive groups .

For example, polyisocyanato-polyuretonimines, such as those formed by carbodiimidization of hexamethylene-1,6-diisocyanate containing biuret groups with phosphorus-organic catalysts, can be used by further reaction of primarily formed carbodiimide groups with isocyanate groups to form uretonimine groups. Furthermore, these isocyanates can be used in a mixture with one another and other aliphatic and aromatic isocyanates.

Depending on the reaction conditions, the resulting modified polyisocyanate can contain considerable proportions of oxadiazinetrione, triisocyanurate or sym. Triazinedioneimine as the structural element. Such products are also suitable as shell formers.

n = 3-6.Diisocyanates of the formula I are particularly suitable

n = 3-6.

• Ethylendiamin-(1,2), Bis(3-aminopropyl)-amin, Hydrazin, Hydrazin-ethanol.-(2), Bis-(2-methylaminoethyl)-methylamin, 1,4-Diaminocyclohexan, 3-Amino-1-methyl-amino- propan, N-Hydroxy-ethylethylendiamin., N-Methyl-bis-(3-aminopropyl)-amin, 1,4-Diamino-n-butan, 1,6-Diamino-n-hexan, Ethylen-(1,2)-diamin-N-Ethyl-sulfonsäure (als AlkaliSälz), N-Aminoethylethylendiamin-(1,2) (Diethylentriamin),Bis-(N,N'-aminoethyl)-ethylendiamin-(1,2) (Triethylentetramin). Hydrazin und seine Salze werden im vorliegenden Zusammenhang ebenfalls als Diamine angesprochen.

For reaction with the isocyanates mentioned suitable diamines are primary or secondary aliphatic i- _D and polyamines, such as:

• Ethylenediamine (1,2), bis (3-aminopropyl) amine, hydrazine, hydrazine ethanol .- (2), bis (2-methylaminoethyl) methylamine, 1,4-diaminocyclohexane, 3-amino-1- methylamino propane, N-hydroxyethylethylene diamine., N-methyl-bis- (3-aminopropyl) amine, 1,4-diamino-n-butane, 1,6-diamino-n-hexane, ethylene- ( 1,2) -Diamine-N-ethyl-sulfonic acid (as alkali salt), N-aminoethylethylenediamine- (1,2) (diethylenetriamine), bis- (N, N'-aminoethyl) -ethylenediamine- (1,2) (triethylenetetramine ). Hydrazine and its salts are also referred to as diamines in the present context.

Examples of the color formers are triphenylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds or the like.

• Beispiele für eine Triphenylmethanverbindung sind 3,3-Bis-(p-dimethylaminophenyl)-6-dimethylaminophthalid (nämlich Kristallviolettlacton, nachstehend als C.V.L. bezeichnet) und 3,3-Bis-(p-dimethylaminophenyl)-phthalid (nämlich Malachitgrünlacton).

Examples of the groups listed above are as follows:

• Examples of a triphenylmethane compound are 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (namely crystal violet lactone, hereinafter referred to as CVL) and 3,3-bis (p-dimethylaminophenyl) phthalide (namely malachite green lactone).

Examples of a diphenylmethane compound are 4,4'-bisdimethylaminobenzhydrylbenzylether, N-halophenylleucolamine, N-ß-naphthylleucolamine, N-2,4,5-trichlorophenylleucolamine, N-2,4-dichlorophenylleucolamine or the like.

Examples of a xanthene compound are rhodamine-β-anilinolactam, rhodamine-β- (p-nitroaniline) -lactam, rhodamine-β- (p-chloroaniline) -lactam, 7-dimethylamine-2-methoxy-fluorane, 7-diethylamine-3 -methoxyfluorane, 7-diethylamine-3-methylfluorane, 7-diethylamine-3-chlorofluorane, 7-diethylamine-3-chloro-2-methylfluorane, 7-diethylamine-2,4-dimethylfluorane, 7-diethylamine-2,3-dimethylfluorane , 7-diethylamine- (3-acetylmethylamine) -fluorane, 7-diethylamine-3-methylfluorane, 3,7-diethylaminefluoroane, 7-diethylamino-3- (dibenzylamine) -fluoroane, 7-diethylamine-3- (methylbenzylamine) -fluorane, 7-diethylamine-3- (chloroethylmethylamino) -fluorane, 7-diethylamine-3- (dichloroethyl-amine) -fluorane, 7-diethylamine-3- (diethylamine) -fluorane or the like.

Examples of a thiazine compound are ^- N-benzoyl-leucomethylene blue, o-chlorobenzoylleucomethylene blue, p-nitrolbenzoylleucomethylene blue or the like.

Examples of a spiro compound are 3-methyl-2,2'-spirobis (benzo (f) chromium) or the like.

Solvents that dissolve these color formers are e.g. chlorinated diphenyl, chlorinated paraffin, cottonseed oil, peanut oil, silicone oil, phthalate esters, phosphate esters, sulfonate esters, monochlorobenzene, furthermore partially hydrogenated terphenyls, alkylated diphenyls, alkylated naphthalenes, aryl ethers, aryl alkyl ethers, higher alkylated benzene and others which can be used alone or in combination.

Diluents are often added to the solvents, e.g. Kerosene, n-paraffins, isoparaffins.

To produce the microcapsules by the polyaddition process, the colorants and the isocyanate are first mentioned in the

Solvents and emulsified this organic phase in the continuous aqueous phase, which may contain protective colloid and optionally emulsifiers. An aqueous polyamine solution is added to the emulsion in a stoichiometric amount to the polyisocyanate in the organic phase.

Protective colloids and emulsifying aids are added to the aqueous phase to emulsify and stabilize the emulsion formed. Examples of such products acting as protective colloids are carboxymethyl cellulose, gelatin and polyvinyl alcohol.

Examples of emulsifiers are ethoxylated 3-benzylhydroxybiphenyl, reaction products of nonylphenol with different amounts of ethylene oxide and sorbitan fatty acid ester.

The microcapsules can be produced continuously or batchwise. Dispersing devices which generate a shear gradient are generally used. Examples include blade, basket, high-speed stirrers, colloid mills, homogenizers, ultrasonic dispersers, nozzles, steel nozzles, and Supraton machines. The strength of the turbulence during mixing is primarily decisive for the diameter of the microcapsules obtained. Capsules ranging from 1 to 2000 _µm can be made. Capsules are preferred, with diameters from 2 to 20 _/ um. The capsules do not agglomerate and have a narrow particle size distribution. The weight ratio of core material to shell material is 50-90 to 50-10.

The microcapsules are taken up in suitable resinous binders for application to the paper support by the process according to the invention and in one for the wet. or dry offset printing or printing ink suitable for letterpress printing.

This can be done, for example, by stirring the aqueous microcapsule dispersions into the binder and then removing the water in vacuo. Such processes have also become known for incorporating pigments into printing inks as the so-called flush process.

Another method is, for example, that the aqueous capsule dispersions are spray dried into agglomerate-free capsule powder and then incorporated into the printing inks by known methods.

Spray drying microcapsules is already known in the art. Other known drying techniques can also be used to manufacture the capsule powder.

The microcapsule powders are incorporated into binders by the processes according to the invention, which are used according to the known prior art for producing a printing ink which can be processed in wet or dry offset printing or letterpress printing.

Offset printing inks and letterpress inks are known.They contain a reaction resin, i.e. an organic resin, which can be hardened by a chemical reaction (e.g. with atmospheric oxygen or peroxide, or UV radiation or electron radiation).

Combinations of different viscous stand oils with air-drying alkyd resins, hard resins or resin varnishes are primarily used as binders for book and offset printing inks. The latter are made by dissolving natural or synthetic resins in mineral oil.

Other suitable starting materials for the production of binders include in the "Lackrohstoffabellen" by E. Karsten 6th edition 1976, Curt R. Vincentz Verlag Hannover and in "Printing and Litho Inks" by Herbert Jay Wolfe, 6th edition 1967 McNair Donald Company, New York City.

• 1. Ausreichende Verträglichkeit mit den üblichen Standölen und Mineralölen möglichst schon bei Raumtemperatur, sowie weitgehende Kombinierbarkeit mit anderen Bindemitteln, Hartharzen oder Harz-Öl-Verkochungen.
• 2. Gutes Benetzungsvermögen für die Mikrokapseln, um den Anreibeprozeß zu vereinfachen.
• 3. Hohe Aufnahmefähigkeit für die Mikrokapseln zur Erzielung farbstarker Durchschriften.
• 4. Kurze Trocknungszeiten.
• 5. Hohe Glanzgebung.
• 6. Voll ausreichende Haft- und Scheuerfestigkeit auf Papier, Kunststoff- und Metallfolien.
• 7. Gutes rheologisches Verhalten, das zusammen mit dem der Mikrokapseln den einwandfreien Transport der Druckfarbe innerhalb der Maschine gewährleistet und auch auf schnellaufenden Druckmaschinen kein Spritzen oder Rupfen der Druckfarbe verursacht.

The requirements placed on the printing ink binder for the process according to the invention are as follows:

• 1. Sufficient compatibility with the usual stand oils and mineral oils, if possible at room temperature, as well as extensive combinability with other binders, hard resins or resin-oil boilings.
• 2. Good wetting ability for the microcapsules to simplify the rubbing process.
• 3. High absorption capacity for the microcapsules to achieve strong color copies.
• 4. Short drying times.
• 5. High gloss.
• 6. Fully adequate adhesion and abrasion resistance on paper, plastic and metal foils.
• 7. Good rheological behavior which, together with that of the microcapsules, ensures that the printing ink is transported properly within the machine and that it does not cause the printing ink to splash or crack, even on high-speed printing machines.

This short list already shows that a binder alone can scarcely combine all of the desired properties and one generally works with binder combinations.

For example, monomers containing vinyl groups or else acrylates and methacrylates can be added to the binders which may be used, in particular also radiation-curing resins.

Book and offset printing inks also contain - in small quantities - various aids, e.g. B. siccatives and skin contraceptives, as well as printing oils and printing pastes (see W. Wacenski in "Der Polygraph" issue 12, 1980, p.1016-1021).

Desiccants (= drying accelerators) are oil and gasoline-soluble metal compounds predominantly of cobalt, lead and manganese with organic acids such as fatty, resin or naphthenic acid.

Depending on the content of drying constituents in the ink (oils, alkyd resins, desmalkyd types), small amounts of siccative (by 2%) can be used to shorten the drying time of the ink. Too large quantities can cause the ink to dry too hard (there are many difficulties, especially when printing several colors together) or even delay drying.

Skin contraceptives are intended to prevent the drying of the book and offset printing inks in the can or the drying on the rollers of the printing machine - possibly with a temporary machine standstill. Skin contraceptives are volatile (oximic) or non-volatile (phenolic) in nature. Their effect is opposite to that of siccatives. They are also added to the printing ink in only small amounts ( _1-5 %). Printing aids such as printing oils or printing pastes allow the capsule-containing coating composition to be further adapted to the prevailing processing conditions.

Pressure oil, a mixture of spindle oil (mineral oil) and linseed oil, reduces the consistency of the composition and improves its striking away. Printing pastes make the color "shorter"; these pastes are usually obtained by melting waxes, petroleum jelly or wool fat in mineral oils. They have no drying properties and are strictly different from dry pastes (siccatives).

To prevent agglomeration of the microcapsules, dispersing aids, preferably from the group of the cationic surfactants, can be added to the printing ink.

In order to prevent destruction of the microcapsules when rubbing the printing ink and during the printing process itself, in a preferred embodiment, so-called spacers are added to the printing ink in amounts of 10-30% by weight, based on the amount of microcapsules. According to the known prior art, these spacers are also used in the production of the conventional carbonless carbonless papers. They can consist, for example, of cellulose fiber particles or starch granules, the diameter of which is usually 1.5-2 times the microcapsule diameter.

Pigments and auxiliaries which have a favorable effect on the opacity of the coating can be added as further additives.

The amount of microcapsules that is incorporated into the binder formulation depends on the requirements that must be placed on the finished printing ink. The amount of capsules is set so high by the method according to the invention that it is justifiable taking into account the rheology and "speed" of the finished printing ink, on the other hand to apply an optimal amount of microcapsules with the lowest possible coating weight.

To formulate the printing ink, for example, the binder formulation can be presented and the dry capsules and other additives can be introduced using a planetary mixer.

The binder formulation thus produced is then rubbed in several passages on the three-roll mill.

As already stated, it is also a method which has long been known for the production of printing inks, to stir aqueous capsule dispersions into the binder formulation and then to evaporate the water in vacuo (flush process).

The binder formulation thus produced can be printed on commercially available offset printing machines using the wet or dry offset process.

Wet offset printing - or more often just referred to as offset printing - is the classic flat printing process, in which printing and non-printing areas are located on almost one level. Printing is made possible by the mutual repulsion of fat and water. The printing areas are prepared so that they repel water and thereby accept the oleophilic printing ink, while the non-printing areas are hydrophilic and repel printing ink.

Offset machines therefore have ink and dampening roller systems that wet the printing plate on a plate cylinder and place the print image on the paper web via a rubber cylinder.

"Dry offset" uses the same printing press, but works without a dampening system. This printing process is therefore often referred to as "indirect letterpress".

In the way of working, a distinction is made between sheetfed and web offset. While trimmed sheets are printed in sheetfed offset, web offset is printed on a paper web that is unwound from rolls.

Offset printing is therefore part of the long-known state of the art, and suitable printing machines with which the method according to the invention can be carried out are therefore commercially available.

Printing is preferably carried out in succession in a web offset printing press with a plurality of printing units. Such printing machines are already commercially available for multi-color offset printing.

It is a particular advantage of the method according to the invention that multi-color offset printing machines of this type can be printed in one operation and the carbonless paper according to the invention can be produced.

The binder formulation can also be printed on commercially available letterpress machines.

Letterpress is therefore part of the long-known state of the art, and suitable printing machines with which the method according to the invention can be carried out are therefore commercially available.

It is possible to integrate additional devices into the printing machines for better and faster drying of the papers produced in this way, for example warm air blowers, which dry the coatings quickly or, if radiation-curable binders are used, to attach an appropriate radiation source.

A particular advantage of the method according to the invention is that no special requirements are placed on the paper carrier. For example, commercially available CF papers can be used as paper supports, the front of which are already coated with a color developer and which can be printed on the back with the printing inks according to the invention.

However, normal, uncoated papers can also be used and the developer composition can also be applied in the printing press.

In a particular embodiment of the present invention, the color-developing substances can be incorporated directly into the microcapsule-containing printing inks.

So-called one-component reaction papers can be produced by printing printing inks, which also contain microcapsules containing dye precursors and color developers, on the top of the paper carrier web.

Color developing substances are known. They are usually acidic clays, such as montmorillonites, bentonites and smectites or phenolic compounds.

Further explanations can be found in the examples below.

example 1

An offset printing ink was produced as follows:

200 g of microcapsule powder were stirred into 440 g of printing varnish (brilliant gloss overprint varnish 10754 from the printing ink factory Gebr. Schmidt GmbH, Frankfurt). The microcapsule powder was largely free of agglomerates and consisted of capsules with an average particle size of 5 _μm . The capsules were further characterized in that the walls consisted of a polyaddition product from the oxadiazinetrione of hexamethylene diisocyanate and diethylene triamine. The content of the capsules was a 2.7% solution of crystal violet lactone in diisopropylnaphthalene. The core / wall ratio of the capsules was 85:15.

After stirring the microcapsules in the overprint varnish 55 g of cellulose fibers small fraction of an average size of 50 _/ um were added. 85 g of printing oil (printing oil special from the printing ink factory Gebr. Schmidt GmbH, Frankfurt) were also added.

The mixture was rubbed 5 times on a three-roll mill. The coating composition formulated in this way was applied as dry offset printing with an offset printing machine (Heidelberg offset printing press factory, format 64 x 46) to paper with a basis weight of 40 g / m ² .

The application weight of the coating was 4.2 gjm ² . The paper was then placed with the printed side on a commercially available CF paper, which was coated with color-developing substances. When using a normal writing pressure, legible Copies can be obtained on the CF sheet.

In a test, a further 7 base papers were placed on a combination of the printed CB paper and a CF paper, and a square of the area 4 x 4 cm was inscribed as narrowly as possible with the letter small "w" using a typewriter with a constant velocity .

The 8th copy appearing on the CF paper was examined with a reflectance measuring device (Elrephomat from Zeiss) for the loss of reflection compared to unlabelled paper and the corresponding value was determined.

wobei

• I = gemessener Remissionswert
• I_o = Remissionswert des unbeschrifteten Papiers.

The remission value is defined by

in which

• I = measured reflectance value
• I _o = reflectance value of the unlabelled paper.

A remission value of 17.9% was measured.

Example 2

The procedure was as described in Example 1, with the difference that a coating weight of 9 g / m ^{2 was} applied to the paper.

In the remission measurement of the 8th copy according to the method described in Example 1, a remission value of 33% was measured.

Example 3

A 30% aqueous microcapsule dispersion was produced, the microcapsule walls of which consisted of a polyaddition product of the oxadiazinetrione of hexamethylene diisocyanate and a polyamine. The capsule contents were a solution of 2.7% crystal violet lactone and 0.9% N-benzoylieukomethylene blue in di-isopropyl-diphenyl. The core / wall ratio of the microcapsules was 83:17.

The 30% capsule dispersion was converted into a largely agglomerate-free capsule powder by spray drying. The mean capsule diameter was found to be 7.3 _/ µm.

300 parts by weight of urethane-modified alkyd resin (Desmalkyd L 181 from Bayer AG) were placed in a planetary mixer and 125 parts by weight of the microcapsule powder prepared were stirred in. 75 parts by weight of linseed oil-stand oil were added.

The mixture thus mixed was rubbed three times over a three-roll mill and the ink thus pasted was deaerated in a vacuum chamber. The printing ink thus produced, containing 25% by weight of microcapsules, was subjected to a wet offset process using a web offset press with a Dahlgren dampening system (manufacturer: Muller Martini) On the back of a commercial CF paper (Giroset - CF from Feldmühle) a square with a side length of 5 cm is printed.

The coating weight of the coating was _{5, 5} g / m ² after drying, and a spot-coated carbonless copy paper was obtained.

When writing on several superimposed papers produced in this way, a clearly legible copy could be created within the printed squares.

The following example describes the production of the printing ink according to the invention by the so-called flush process known in the printing ink industry.

Example 4

300 parts by weight of urethane-modified alkyd resin (Desmalkyd L 181 from Bayer AG) and 75 parts by weight of linseed oil-base oil were placed in a vacuum kneader. With constant stirring, 125 parts by weight of a 30% microcapsule dispersion according to Example 3 Herge _- is slowly added. The vacuum kneader was evacuated with continued constant stirring and heated to a temperature of about 60 ° C until all the water had evaporated.

A printing ink containing 25% of microcapsules was obtained, which was printed with a sheet-fed offset printing machine (Heidelberger Offsetdruckmaschinenfabrik) on the front of a commercially available CF paper (Giroset CF from Feldmühle) in the form of a square with a side length of 5 cm. The coating weight was 5 g / m 2 and a spot-coated one-component reaction paper was produced by the process described, which gave good copy results when superimposed within the square-shaped imprint.

Example 5

A 30% aqueous microcapsule dispersion was prepared, the microcapsule walls of which consisted of a polyaddition product of the oxadiazinetrione of hexamethylene diisocyanate and a polyamine. The capsule content was a solution of 2.7% crystal violet lactone and 0.9 7 N-benzoyl leukomethylene blue in di-isopropyl-diphenyl. The core / wall ratio of the microcapsules was 83:17.

The 30% capsule dispersion was converted into a largely agglomerate-free capsule powder by spray drying, the mean capsule diameter of which was determined to be 7.3 _/ μm.

30 parts by weight of urethane-modified alkyd resin (Desmalkyd ( ^R ) L 181 from Bayer AG) were placed in a planetary mixer and 125 parts by weight of the microcapsule powder prepared were stirred in. 75 parts by weight of linseed oil stand oil were added.

The mixture thus mixed was rubbed three times on a three-roll mill and the paint thus pasted was deaerated in a vacuum chamber. The printing ink containing 25% by weight of microcapsules produced in this way was printed with a letterpress machine (manufacturer: Heidelberger Maschinenfabrik) using the letterpress method on the back of a commercially available CF paper (Giroset - CF from Feldmühle) of the capital letter W in a 10 cm size.

The application weight of the coating was 5.5 g / m ² and after drying a spot-coated, carbon-free carbonless paper was obtained.

When writing on several superimposed papers produced in this way, a clearly legible copy could be created within the printed letter.

Example 6

A letterpress ink was made as follows:

200 g of microcapsule powder were stirred into 275 g of printing varnish (brilliant gloss overprint varnish 10754 from Druckfarbenfabrik Gebr. Schmidt GmbH, Frankfurt / M.). The microcapsule powder was largely free of agglomerates and consisted of capsules with an average particle size of 5 μm. The capsules were further characterized in that the walls consisted of a polyaddition product from the oxadiazinetrione of hexamethylene diisocyanate and diethylene triamine. The content of the capsules was a 2.7% solution of crystal violet lactone in diisopropylnaphthalene. The core / wall ratio of the capsules was 85:15.

The mixture was rubbed 5 times on a three-roll mill. The coating composition thus formulated was applied as a letterpress using a letterpress machine (Heidelberger Maschinenfabrik) to paper with a basis weight of 40 g / m.

The application weight of the coating was 5.5 g / m ² . The paper was then placed with the printed side on a commercially available CF paper, which was coated with color-developing substances. When using a normal writing print, easily legible copies could be achieved.

Claims (4)

1. A process for producing pressure-sensitive, carbon-free transmission systems, characterized in that a non-aqueous, essentially solvent-free coating which contains dye precursors is applied to at least one surface of a paper substrate partially or over the entire surface using the technique of _wet or dry offset printing or letterpress printing . 2. Pressure-sensitive, carbon-free copy systems, produced according to claim 1. 3. Offset printing or letterpress ink, consisting of 1.) reaction resins, 2 ..) microcapsules containing dye precursors, 3.) spacers with a grain size of 1.5 to 5 times the microcapsule diameter, 4.) auxiliaries and additives. 4. Use of the offset printing or letterpress inks according to claim 3 for the production of pressure-sensitive, carbon-free copy systems on offset or letterpress machines.