WO1996030811A2 - Single-layer paper product - Google Patents

Abstract

In order to make it more difficult to forge single-layer paper products printed on with toner by a laser printer, the invention proposes that a thin, uniform coating of a primer compound is applied to at least parts of one side, the primer compound including a thermoplastic material which, at elevated temperatures, forms a join which cannot be separated by mechanical means between the toner, which is sintered at the elevated temperature used, and the paper.

Description

 Single-ply paper product

The invention relates to a single-layer paper product for printing with laser printer toner materials.

Laser printing as a machine-made printout of computer systems is being used more and more, also in areas in which the creation of originals and in particular also originals with security-relevant data is concerned. Originals, in particular originals with security-relevant data, mean, for example, notifications from insurance companies regarding the guarantee of certain insurance benefits, computer-generated check printouts, computer-generated official certificates, etc., in which the machine or computer -Printed printout is regarded as the original document and immediately grants rights of any kind to the owner and / or owner of this publication or confirms any operations.

On the one hand, with the more and more practiced computerization of administrative tasks, at least with the current printing technology, the multitude of originals can no longer be created differently than by machine printing, which is usually done by so-called laser printers in high-performance printers. in which toner materials are applied as a typeface on a paper product and sintered thereon.

The large number of such security-relevant documents also does not allow an additional process to identify such originals separately, and typically forms produced in this way are prepared for dispatch immediately after printing, ie as so-called single-sheet mailers either directly sealed or automatically pushed into envelopes and sealed in them and sent to the recipient.

The problem with this is that the laser printing technology with the sintering of toner images on the paper product uses an identical technology as is also used in the copying technology that is now widespread. This means that the copy is essentially no longer distinguishable from the original, and the printout on colored paper or the color printout itself no longer offers any guarantee, since the color copy technology that has become available in the meantime can be used to produce copies which are in In many cases the original can hardly be distinguished, especially if the original and the copy are not available at the same time.

A particular problem with the security-relevant original documents that are created with laser printer technology is that the sintered toner material is often made using relatively simple means, such as, for example, sharp-edged objects, can be removed relatively easily from the paper product, without a noticeable change in the paper surface necessarily taking place and the paper product thus directly providing information about the attempted manipulation. This is due in particular to the fact that the times and temperatures available during the sintering of the toner material and the available toner materials themselves cannot offer any guarantee that a permanent connection will be made with the underlying paper layer of the paper product.

The possibility of counterfeiting is opened in the simplest way with such documents or original pieces. For example, this problem illuminates the message that machine-generated receipts authorizing disbursement lead to disbursement rates of significantly more than 100%. The object of the present invention is to improve a single-ply paper product of the type described at the outset in such a way that, after printing with a laser printer toner material, counterfeiting is made much more difficult and, in particular, attempts at manipulation can be clearly recognized.

This object is achieved according to the invention in that the single-ply paper product is provided with a flat, uniform coating applied to at least some areas on a surface with a primer composition which comprises a thermoplastic material which is produced at elevated temperature forms a mechanically inseparable bond between the toner material sintered at the elevated temperature and the paper layer of the paper product.

Because the single-layer paper product, at least in the safety-relevant surface areas, is provided with the above-mentioned coating with a primer mass, when printing in these areas such a close bond between the sintered toner material and the paper layer is created that a me Mechanical removal of the print can only take place with destruction of the paper surface of the paper layer. However, the original laser print-out immediately recognizes that manipulation has taken place here, and the changed original can no longer, or at least not easily, be provided with a partially modified print.

Surprisingly, it has been found that when using the primer coating, in particular with full-area application, cheaper paper than paper layer can be used, which was previously excluded from use in laser printing because of the lack of quality in the printout.

The thermoplastic material of the primer composition can be selected so that it liquefies at the elevated temperature which is required for the sintering of the toner material and forms a dissolving phase for the toner material, which is partially dissolved and thus forms a firm bond with the thermoplastic material and the underlying paper layer during curing.

Alternatively, the thermoplastic material can be selected such that the toner material at the elevated temperature and the thermoplastic material at the common interface, at least partially, form a common phase and thus merge into one another without a phase boundary. This also creates the possibility of a very strong bond between the sintered toner material and the paper layer, which can no longer be separated mechanically without damaging the paper surface.

In the case of a particularly preferred thermoplastic material, at the elevated temperature required for sintering the toner material, liquefaction takes place to such an extent that it partially penetrates into the paper fiber composite of the paper layer and thus leads to a further improved adhesion with the Paper layer leads.

The toner components, which enable the sintering process and produce the bond with the paper to be printed, are binders, which are usually selected from polystyrene acrylates, polyesters and polybutadiene, which have proven particularly useful in toners which are exposed to heat and pressure, ie so be fixed on contact.

The composition of the primer composition according to the invention must, of course, take into account the toner binder in some respects, and here a primer composition with a thermoplastic material based on it has become particularly useful for toners containing polystyrene acrylates as binders recommended by vinyl acetate or acrylate or methacrylate polymers. This is surprising, since polyvinyl acetates in particular are generally recommended as release agents as toner additives and ensure that the toner can be adequately cleaned from the fixing roller.

In addition, long-term tests have shown that the improved toner adhesion to the paper due to the coating allows the fixing or sintering of the toner material to release agents, such as e.g. Silicon oils to be avoided. This ultimately leads to a further improvement in toner adhesion.

Particularly preferred thermoplastic materials are vinyl acetate polymers, copolymers of vinyl acetate with vinyl laurate and / or vinyl chloride and / or ethylene as well as acrylate polymers and methyl acrylate polymers and copolymers with styrene thereof.

The aforementioned thermoplastic materials are preferably used in the primer composition in the form of 40 to 60% by weight. % aqueous dispersions.

The primer composition can comprise fillers, in particular particulate, granular fillers, with fractions of up to 80% by weight, based on the total primer composition, the fillers predominantly comprising pigments and materials which modify the primer composition include.

In order to prevent the coated paper product from having a plastic-like gloss and / or a plastic-like handle, a filler content of the primer mass of at least approx. 20% by weight is recommended.

If the paper product is used for the production of one-sheet mailers, that is to say letters which after printing have been folded, they are then folded and then sealed and made ready for dispatch If, without using separate envelopes for this purpose, the primer can optionally be used to serve as an adhesive for gluing two layers of paper of the paper product together. This seal sets limits to the filler content, since from a filler content of approx. 50% by weight the quality of the seal decreases significantly or significantly higher temperatures are required for good sealing of the one-sheet mailers.

The coating weights with which the primer mass is applied to the paper product are normally in the range from 2 to 10 g / m 2, preferably from 4 to 7 g / m 2 and most preferably from 5 to 6 g / tv. These coating weights are understood in each case for the coated, ready-to-use paper product.

With these coating weights, an outstanding adhesion of the toner materials to the paper layer is achieved, and in the higher range of the coating weights an excellent sealing of one-sheet mailers with the primer mass can also be achieved.

The pigment portions of the filler, which have been mentioned above, can on the one hand serve to improve the grip of the paper, and on the other hand can of course also be used for coloring the same and for emphasizing the coated paper surfaces, here in particular the safety-relevant surface areas to be printed.

In addition, it has been found that the use of pearlescent pigments gives very special color effects which also serve as an original printout to prevent counterfeiting of the paper product, since these pearlescent effects cannot be reproduced with color copiers. The invention also relates to a single-layer, machine-printable paper product which, through a different type of treatment of the surface to be printed, leads to an increase in the protection against forgery of the machine-printed originals.

A problem with machine-made originals printed with laser toner materials is that certain solvents, such as e.g. Isopropyl alcohol, methyl ethyl ketone, acetone and toluene, easily allow the toner material to peel off the paper surface. The imprints which have been chemically removed in this way can then be printed with other information without the paper product itself providing proof thereof without the counterfeit original being able to be distinguished from the original.

This problem is remedied by a machine-printable single-ply paper product which is characterized by a flat, uniform coating applied to a surface to be printed, at least in some areas, which is carried out with a coating composition comprising a color component, the color component being in contact with a Solvent shows a color reaction.

The mentioned color reaction can occur in many configurations and consist, for example, in the bleeding out of a color component, which produces typical and non-removable color contours on the original paper product.

In addition, it can also be provided that the color component comprises a leuco dye and a so-called color developer, which are present alongside one another in the coating composition, often at least one of the reactants, ie the leuco dye or the color developer, being present in encapsulated form in microcapsules. If solvent now meets the color component, the leuco dye is as the color developer is offered a reaction medium in which the color reaction takes place and the dye can be formed, which is noticeable in a discoloration of the correspondingly coated areas of the paper product. In addition, transport processes relating to the dye are associated with the spreading of a solvent drop, so that a strikingly different coloration on the paper surface is inevitably obtained. This also causes an irreversible change in the printed original and indicates the attempted manipulation of the original document.

The inclusion of a color component that can undergo a color reaction with solvents also includes a further safety aspect. In addition to the possibility of being able to detect attempts at forgery on the original, there is also the possibility to check very easily whether the printout presented is an original or a simple color copy, in which, of course, this bleeding effect or the color formation reaction or in general the color reaction of the color component does not take place.

Bis-phenol A is frequently used as the color developer in this connection, and the leuco base or the leuco dye is regularly introduced in encapsulated form in the coating composition. The microcapsule walls can then be adjusted so that when they come into contact with solvents which also detach the toner material, they soften or break through and in any case release the leuco dye so that it can initiate the color development reaction with the color developer.

In a particularly preferred embodiment of the invention, the abovementioned coating composition comprises a primer composition as described at the outset, so that the single-ply, machine-printable paper product can be both counterfeit-proof with regard to mechanical attempts at counterfeiting and chemical attacks. The fact that the single-ply paper product is a paper product which can produce counterfeit-proof origins cannot be seen in the paper product if this is not desired. On the other hand, however, a conscious color design of the security-relevant and machine-to-print fields can be carried out, in which case slightly bleeding dyes or dye combinations can also be used in the color-designed printing areas, which are under the actual printing ink for this section can be mixed in.

These and other advantages of the invention are explained in more detail below with the aid of the examples.

In the following, some exemplary recipes for a coating composition are first presented which serve to improve the security against forgery with regard to mechanical attacks, in particular the attempt to detach them with adhesive films, etc., the quantities being given in parts by weight unless otherwise stated is defined:

example 1

200 parts of water are mixed with three parts of WALCOCEL CRT 30

(available from Wolf, Walsrode), three parts caustic soda,

75 parts of microtalkum with a particle size> 10 μm and 125 parts of chemically precipitated calcium carbonate mixed. This mixture is added as a thermoplastic material with primer action Mowilith LDM 7410 in the quantities 750 parts, 1000 parts and 1520 parts (the product Mowilith LDM 7410 is available from Hoechst AG).

The proportions of caustic soda make the coating material slightly alkaline, so that even with somewhat acidic paper a uniform coating can be achieved. The shares in microtalkum and Calcium carbonate serve to improve the grip of the paper or to push back the plastic-finished handle.

While the addition of Mowilith LDM 7410 with 750 parts offers a first significant improvement in the toner adhesion compared to the uncoated paper, 1000 parts and especially the 1520 parts are able to produce a very good adhesion of the toner material with the underlying paper layer. The toner adhesion was checked on prints from a Siemens printer NDX No. 2140 with an average printing performance of 8000 sheets / hour (12-inch format) and a fixing temperature of approx. 230 ° C.

In a coating having 5 to 6 g / m ^Λ of the aforementioned Be¬ schichtemasse (in dry state) is in each of the Rezeptu¬ ren a sealing ability of the paper product given, so that from this one-sheet mailer can be produced without additional measures with respect to the coating .

Even the addition of 750 parts of the thermoplastic material allows a significant improvement in the adhesion of the sintered toner material on the paper surface, while already 1000 parts and especially 1520 parts completely effectively prevent mechanical attempts at removal, and only a complete detachment enable by serious injury to the paper surface.

Example 2

Here, with otherwise the same composition of the primer composition as the thermoplastic material, Vinnapas EP 400 from Wacker Chemie is added in 750 parts, 1000 parts and 1520 parts, and after coating as described above, results comparable to Example 1 with regard to toner adhesion on the paper layer and its further processing to single-sheet mailers.

Example 3

With the same composition of the primer mass as in Example, a Vinnapas oil version T53 / 22 VL from Wacker Chemie was used instead of the Mowilith LDM 7410, in proportions of 750, 1000 and 1520 parts and with the same quantitative ratios applied as previously described.

Attempts to mechanically remove the toner print again gave the same results as previously reported, as did the sealability tests.

Example 4

Instead of the material mentioned there, the recipe in Example 1 was added as a thermoplastic material Vinnapas dispersion EP 11 from Wacker Chemie, in 750 parts, 1000 parts and 1520 parts, the same positive after an application as described above Result regarding the connection of the sintered toner material with the underlying paper layer.

In the above examples, the addition of the 75 parts of microtalkum with a grain size> 10 μ and the chemically precipitated calcium carbonate ensures that the proportions of the thermoplastic material in the coating lead to a plastic-ready grip on the paper.

Example 5

270 parts of water are mixed with 50 parts of a pearlescent dye, for example Iriodin 111 or Iriodin 103 from the company Merck was added and 950 parts of Mowilith LDM 7410 (Hoechst AG) were then added to this mixture. The coating of a paper with 5 to 6 g / πr ¹ results in a paper with a paper handle, ie the proportions of iriodin already reduce the plastic handle of the paper to a sufficient extent and, moreover, ensure a pearlescent appearance of the paper, which is the same as usual Color copiers are not reproducible. Here, not only does the sintered toner material adhere perfectly to the underlying paper layer, but it also makes it possible to produce printed originals that cannot be reproduced using the available copying options. Processing to single-sheet mailers also delivers satisfactory results.

The following examples provide simple recipes for improving counterfeit protection using color components that show a color reaction in contact with solvents:

Example 6

The coating composition is made from 20 g transparent white 12D 0380-LDS (Gebr. Schmid GmbH, Druckfarbenfabrik, Cologne) a typical transparent lacquer for wet offset, which serves as a binder here (oxidative drying lacquer based on linseed oil). 1 g of crystal violet lactone in finely ground form and 1 g bisphenol A, likewise in finely ground form, are added to this binder. The crystal violet lactone is a leuco dye, but bisphenol A is the associated color developer. The leuco dye and the color developer can be present side by side in the transparent white binder without any problem, without the development of color. After sufficient homogenization, the coating composition is applied to the paper with an application weight of approx. 2.5 g / m 2. In an alternative formulation, in addition to the crystal violet lactone and bisphenol A, 1 g of Pergascript Red I-6B (leuco base from Ciba-Geigy) and 1 g of salicylic acid can be added as a further color developer. The Per gascript red and the salicylic acid are also present in finely ground form, all substances were homogenized in the mixture with one another.

This mixture was also applied to the paper to be coated with an application weight of approximately 2.5 g / m ² . In contact with a solvent, such as, for example, isopropyl alcohol, toluene, acetone, methyl ethyl ketone, etc., which are able to detach sintered toner materials from the paper, bleeding effects have been achieved which are initially preceded by the formation of a red-violet color complex, which migrates with the liquid front in the paper and thus produces clearly visible color spots or color fronts on the paper.

With this type of coating, as in Examples 7 to 9 below, there is no improved toner adhesion (but also no impairment). Furthermore, these coated papers cannot be sealed.

Example 7

In this formulation, the transparent white used above is homogenized in an amount of 20 g with 1 g of finely ground RODAMIN 6G DN dye and applied with a coating weight of approx. 2.5 g / m ² . The RODAMIN 6G DN is already the dye form, so that this coating gives the paper a red-orange color. In contact with the abovementioned solvents, a bleeding effect occurs immediately, ie a front with concentrated dye in the paper migrates from the application point of the droplet of solvent, which does not remove again even through increased application of solvent leaves. Thus, as in the above, the attempted manipulation or forgery is visibly preserved.

Other alternatives are given below.

Example 8

800 parts of water, 8 parts of caustic soda, 30 parts of Solvicol as binder (starch product from AVEBE), 200 parts of microtalum, 50 parts of fulacolor (calcined clay with the function of a color developer (available from Laporte)), 250 parts chemically precipitated calcium carbonate, 10 parts of Pergascript 12R (leuco base from the company Ciba-Geigy) as well as further binding agents, 150 parts of M76 polymer, which acts as a styrene-butadiene-based binder, and 50 parts of Licomer M36 (acrylate binder, available from Hoechst AG) and finally 10 parts of Mowiol 5-88, a polyvinyl alcohol, which prevents a blue color from developing prematurely (available from Hoechst AG). A fine color dispersion was prepared from the above-mentioned mixture components in a homogenizer and applied to 80 g / m ² paper with a doctor blade with 6 g / m ² . The coating weight refers to the dried product.

When applying solvents, as mentioned above, there is currently blue bleeding, which cannot be removed again by increased application of solvent.

Example 9

A mixture of 800 parts of water, 200 parts of microtalkum, 200 parts of calcium carbonate in freshly precipitated form, 30 parts of Lupasol FF3231 (ground bisphenol A as a color developer (available from BASF AG)), 20 parts of Pergascript 1-2R as a leuco base (from Ciba -Geigy), 100 parts Synthomer M76 as Binder component based on styrene butadiene and 50 parts of Licomer M36 as an acrylate polymer from Hoechst AG were processed in a homogenizer to form a fine color dispersion. The application was carried out with a doctor blade, so that after the

Drying 6 g / m ² coating weight were obtained.

The dropwise addition of isopropyl alcohol, toluene, acetone or methyl ethyl ketone gives rise to a momentary intensive and stable deep blue bleeding, which cannot be removed even by increased application of solvent.

The above-mentioned recipes for the production of a compound of the toner materials with the underlying paper layer as well as the recipes for the production of a bleeding color material resulting in a color reaction can be combined with one another without any problems, so that separate examples of these can be dispensed with. In particular, a combination of the formulations of Examples 1 to 5 with those given in Examples 6 to 9, which illustrate the bleeding effect, bring optimal results in terms of security against counterfeiting, since this is already visible to the naked eye The original can be distinguished from the counterfeit because, for example, the copy lacks the pearlescent effect and, moreover, attempts to counterfeit become immediately visible in the original, either by damaging the surface of the paper or by bleeding.

In addition, the papers coated with combined formulations, as explained for Examples 1 to 5, can be sealed into single-sheet mailers on account of the proportion of primer they contain.

Claims

PATENT CLAIMS 1. Single-ply paper product for printing with laser printer toner materials, characterized by a flat, uniform coating applied to a surface, at least in some areas, with a primer composition which comprises a thermoplastic material which, under elevated temperature, no longer mechanically forms separable bond of the toner material sintered at the elevated temperature with the paper layer of the paper product. 2. Paper product according to claim 1, characterized in that the thermoplastic material partially dissolves the toner material at the elevated temperature. 3. Paper product according to claim 1, characterized in that the thermoplastic material and the toner material at the elevated temperature at their interface, at least partially, without transition into one another. 4. Paper product according to one of claims 1 to 3, characterized in that the thermoplastic material is liquefiable at the elevated temperature to such an extent that it penetrates partially into the paper fiber composite of the paper layer. 5. Paper product according to one of the preceding claims, characterized in that the primer composition comprises a thermoplastic material based on vinyl acetate or acrylate or methyl acrylate. 6. Paper product according to claim 5, characterized in that the thermoplastic material is selected from vinyl acetate polymers, copolymers of vinyl acetate with vinyl laurate and / or vinyl chloride and / or ethylene as well as acrylate polymers and methacrylate polymers and copolymers of acrylate and methyl acrylate. 7. Paper product according to claim 5 or 6, characterized gekenn¬ characterized in that the thermoplastic material in the form of a 40 to 60 wt. % aqueous dispersion is used. 8. Paper product according to one of claims 1 to 7, characterized in that the primer composition comprises up to 80% by weight of a filler. 9. Paper product according to claim 8, characterized in that the filler content is at least about 20% by weight. 10. Paper product according to claim 8 or 9, characterized gekenn¬ characterized in that the filler content is at most about 50 wt.%. 11. Paper product according to one of the preceding claims, characterized in that the coating weight of the Pri¬ mer mass about 2 to 10 g / m ² , preferably 4 to 7 g / m ² , most preferably 5 to 6 g / m2, is. 12. Paper product according to one of claims 8 to 11, characterized in that the filler comprises a pigment portion. 13. Paper product according to claim 12, characterized in that the pigment portion comprises pearlescent pigments. 14. Machine-printable, single-ply paper product, characterized by a flat, uniform coating applied to a surface to be printed on at least in some areas from a coating composition comprising a color component, the color component being subject to a color reaction in contact with a solvent . 15. Paper product according to claim 14, characterized in that the color component comprises a leuco base and a color developer, of which the leuco base and / or the color developer is in encapsulated form and can be released by means of the solvent. 16. Paper product according to claim 14, characterized in that the color component comprises a readily soluble, bleeding dye or such a dye combination. 17. Paper product according to one of claims 14 to 16, characterized in that the coating composition comprises a primer composition according to one of claims 1 to 13. 18. Paper product according to one of claims 1 to 17, characterized in that the regionally coating is limited to fields to be printed mechanically.