WO2013178325A2

WO2013178325A2 - Method for producing a value document

Info

Publication number: WO2013178325A2
Application number: PCT/EP2013/001421
Authority: WO
Inventors: Alexander Bornschlegl; Christoph Mengel; Andreas BAADER; Günter OLSCHEWSKI
Original assignee: Giesecke & Devrient Gmbh
Priority date: 2012-05-29
Filing date: 2013-05-14
Publication date: 2013-12-05
Also published as: CA2870463A1; HK1201234A1; CN104321199A; WO2013178325A3; EP2888112B1; EP2888112A2; CN104321199B; DE102012010534A1; ZA201408152B; MX359340B; CA2870463C; BR112014029183A2; MX2014014369A

Abstract

The invention relates to a method for producing a value document, comprising the steps of: a) printing a value document substrate with an oxidatively drying ink; b) treating the printed value document substrate with UV radiation or with ozone; and c) drying the printed valuable document substrate, which has been treated with UV radiation, at room temperature or at an elevated temperature.

Description

Method for producing a value document

The invention relates to a method for producing a value document, such as a banknote, a document or a document of identification.

In the production of value documents, the printing process is usually carried out in several printing steps, with a variety of successive printing and finishing processes can be used. One of the first steps here is usually a monochrome or multicolor background printing in the offset and / or letter set method. The printing equipment used for this can vary greatly and depends on the following parameters:

- the safety colors or safety pigments used;

the type of value document substrate used (e.g., cotton fiber based substrates; mixed fiber based substrates; substrates)

Base of plastic films);

the provision of substrates to be printed having a nonhomogeneous structure (for example paper substrates provided with a film element, partially pre-printed substrates);

- The provision of substrates to be printed, which have at different locations a different pH and / or a different paper moisture.

While production errors, which lead to a visible deterioration of the printing result, can already be detected and compensated on the printing press (eg the ink guide), there is a risk that production delays affecting the substrate drying and / or the substrate dimensions will greatly delay the further production process and also increase the waste volume. The different printing equipment required for the printing also have a strong influence on the behavior of the signatures in the others Printing steps. Pressure steps that introduce heat lead to substrate shrinkage. In printing steps that take place under high mechanical pressure, dimensional changes (in particular dimensional enlargements) on the substrate are evident. In particular, intaglio printing, which is widespread in securities and security printing, places particular stress on the substrate and ink layers, so that sufficient drying is essential.

If the dimensional changes on the substrate exceed certain tolerance limits, often only the reprint with changed printing equipment remains. Alternatively, the printing equipment of the following

Pressure steps are adjusted, which is associated with high costs and high costs.

The lack of drying of a printed value document substrate due to a problematic colorant formulation or due to a non-repulsive substrate can be accelerated in part by the supply of heat. However, the heating of printed products often leads to a poorly controllable change in the dimensions of the printed substrate. This is the case, in particular, in the case of cellulose, cotton and other paper substrates, in which the heat input leads to loss of moisture. As a result, the register can often not be complied with during the subsequent printing steps. The effect also occurs when using plastic substrates or hybrid substrates (eg multilayer film / paper / film substrates, as are known from WO 2004/028825 A2). A further disadvantage is that the deposition of ink within a stack of value documents can not be significantly improved in this way. The laying down of printing ink here denotes the phenomenon that the still wet printing ink forms on the next printed sheet and disturbs the printing result there. The drying of a printed value document substrate can be further accelerated by the addition of metal-containing driers. Oxidatively drying inks (ie inks that are not UV inks or UV inks) usually contain a drier or siccative. Dry substances are, in particular, organic salts of certain metals such as cobalt (eg cobalt octoate, cobalt naphthenate), manganese, calcium (eg calcium octoate), zirconium or cerium. Metal-containing driers develop their effect only in the presence of oxygen. Provided that storage and transport take place largely under exclusion of air, a dry matter can already be incorporated into the paint ex works. However, the disadvantage of these driers is that the use of (heavy) metal compounds for reasons of work-related safety and health hazards are problematic. A low use concentration would therefore be desirable, but this leads to long drying times.

Moreover, the drying of a printed value-added substrate can be accelerated by the addition of peroxide-containing substances, such as inorganic or organic peroxides. These decompose free radical oxygen and thus accelerate the oxidative drying of the ink layer. This also works in places where air or oxygen deficiency prevails, consequently also in non-impacting substrates and in high or large value document stacks. The disadvantage, however, is that peroxide-containing substances of color may be added relatively shortly before printing, because the color can not be stored for a longer period of time by the onset of the addition of the peroxide chemical reaction. The drying of a printed value document substrate can also be accelerated by the use of UV-drying undercoats or hybrid UV systems instead of oxidative drying systems. However, such paints are considerably more expensive, often have sensitizing properties and may have poor overprintability. In addition, they have only a limited durability as finished paint. The same applies to novel hybrid color formulations which contain both conventional, oxidatively drying paint components and UV-curing paint components.

It is therefore an object of the present invention to provide a process improved with regard to the drying of printed value document substrates. In particular, the method should produce one or more of the following technical effects:

- the adaptation of the shrinkage of the sheet to the needs of the subsequent printing steps;

the recoverability of problems with the color formulation (for example the content of dry substances), preferably also after the printing has taken place;

- Shortening the drying time to allow shorter production time and reduction of storage space. This object is achieved by the feature combinations according to the independent claims. The dependent claims represent preferred embodiments. Summary of the invention

A first aspect of the invention relates to a method for producing a value document, comprising:

a) printing a value document substrate with an oxidatively drying ink;

b) treating the printed value document substrate with UV radiation; and

c) drying the UV-treated, printed value-added substrate at room temperature or at elevated temperature.

It is preferred that in step b) the treatment of the value document substrate with UV radiation and additionally with ozone takes place. The additional treatment with ozone is preferably carried out by pressurizing the value document substrate with ozone in room air at a concentration in the range from 1 to 15 ppm.

Furthermore, it is preferred that in step b) the treatment with UV radiation is carried out by a (simul- tan) printing machine equipped with a UV drying system, wherein preferably a UV dose rate of 10 mj / cm ² to 200 mj / cm ² per page is selected. A UV dose rate of 15 mj / cm ² to 80 mj / cm ² per side is particularly preferred. The UV dose can be measured by means of a photochromatic film, for example by means of a 70 mm × 19 mm measuring strip "tesa® UV Strip" from Dr. Hönle AG.

In step c) drying is preferably carried out at room temperature. Furthermore, it is preferred to carry out the drying of the value documents in the form of a document of value document, wherein the document of value documents in particular special 200 to 10,000 sheets, preferably 5000 to 7000 sheets, has.

A second aspect of the invention relates to a method for producing a value document, comprising:

a) printing a value document substrate with an oxidatively drying ink;

b) treating the printed value document substrate with ozone; and

c) drying the ozone treated printed value document substrate at room temperature or at elevated temperature.

Detailed Description of the Invention The first aspect of the invention will now be described by way of preferred embodiments.

The inventive method is applicable to all standard value document substrates, in particular paper substrates, polymer substrates and so-called hybrid substrates, which are to be understood composite film substrates, either a paper-based core and polymer-based outer layers or a core of a plastic material and outer layers on a paper basis. It is preferred to use substrates based on cotton fibers.

The substrate may have certain coatings, impregnations or imprints and / or security elements or film elements. In the case of a polymer substrate or composite substrate having a core of paper and polymer-based outer layers, it is convenient to use moderate, apply to the polymeric material one or more coatings that ensure the adhesion of the applied to the respective substrate imprint. This layer applied to the polymeric material is commonly referred to as the ink accepting layer. In the case of a paper substrate, ink receiving layers are generally dispensable, but the paper substrate can be completely or partially coated in order to provide it with certain properties, for example luminescent properties, due to luminescent substances applied. Oxidatively drying inks include (or consist of the following components): oxidatively drying film formers, (color) pigments, fillers, solvents, and additives. According to DIN 55 945, the film former is the constituent of the binder which is essential for the formation of the film (see also: Thomas Brock: "Lehrbuch der Lacktechnik", 2nd edition, Curt R. Vincentz Verlag, 2000, page 190) Film formers are in particular macromolecular organic substances and according to this standard, the term "non-volatile content" of a coating material without pigment and filler but including plasticizers, driers and other non-volatile auxiliaries To understand 4618.

With respect to the oxidatively drying film former which can be used for the oxidatively drying printing ink, film former molecules which can be linked to aliphatic double bonds by the action of atmospheric oxygen via oxygen bridges are preferred. In particular, oxidatively drying alkyd resins, Urethanalkyde, epoxy resin esters with unsaturated fatty acids, oil-modified phenolic resins, and natural or synthetic Triglycerides with at least partially unsaturated fatty acid residues as film formers preferred.

The oxidatively drying ink may preferably comprise driers or siccatives, especially organic salts of certain metals such as cobalt (e.g., cobalt octoate, cobalt naphthenate), manganese, calcium (e.g., calcium octoate), zirconium, cerium, zinc, lead, or iron. Organic acids, especially higher fatty acids such as linseed oil fatty acid or tall oil fatty acid, rosin acids, naphthenic acid or 2-ethylhexanoic acid can be used to form the organic salts. In the case of oxidatively drying film formers, the dry substances catalyze the oxygen transfer from the air by redox reactions and accelerate film formation by polymerization. The oxidatively drying printing ink is in particular a background printing ink.

The step of treating the printed value document substrate with UV radiation is expediently carried out by using UV drying systems which can be based, in particular, on medium-pressure mercury UV lamps or iron or gallium-doped medium-pressure mercury UV lamps. The emitter power per lamp is in the range of 120 W / cm to 250 W / cm, preferably 180 W / cm. A suitable emitter system, for example, offered by the company IST METZ GmbH units BLK-5 or BLK-2.

In the case of a (simultaneous) printing machine equipped with a UV drying system, the method expediently takes place at a printing speed of 8000 to 12000 sheets / h, in particular 10,000 sheets / h, and a setting of a single-jet dose rate within a range of 4 mj / cm ² to 100 mj / cm ² . With regard to avoiding the shrinkage of the printing sheet, it is preferable to set the radiator power within a range of 4 mj / cm ² to 60 mj / cm ² , with the range of 10 mj / cm ² to 40 mj / cm ^{2 being} particularly preferred becomes.

The step of drying the UV-treated printed value-added substrate is at room temperature or elevated temperature. Room temperature is understood herein to mean a temperature of 20 ° C. The drying at elevated temperature can be carried out in particular at a temperature in a range of 35 ° C to 40 ° C.

In order to avoid the shrinkage of the value document substrate, it is preferred to carry out the step of drying the value documents in the form of a value document stack. The value document stack may in particular have 200 to 10,000 signatures, preferably 5000 to 7000 signatures. A value document stack with approximately 6000 signatures is particularly preferred for drying. Furthermore, it is preferred that the stack core temperature does not exceed a temperature of 40 ° C. The drying of the value documents in the form of a document of value document is preferably carried out at room temperature.

The second aspect of the invention will be described below with reference to preferred embodiments.

With reference to steps a) and c) of the method according to the second aspect of the invention, reference is made to the preferred embodiments described in connection with the first aspect of the invention. The step b) of treating the printed value-document substrate with ozone is expediently carried out by subjecting the value-document substrate to ozone in room air with a concentration in the range from 1 to 15 ppm, a concentration of about 10 ppm being particularly preferred. Furthermore, it is preferred to carry out the production of the ozone directly in the immediate vicinity of the paper surface, for example by the UV radiation emitted by the UV lamps in the presence of (air t) oxygen. Further embodiments and advantages of the invention are explained below in conjunction with the figures.

1 shows the results of the test series according to embodiment D, which were obtained on the basis of a carbon black pigment without dry matter;

2 shows the results of the test series according to embodiment E, which were obtained on the basis of a carbon black pigment with dry matter;

Fig. 3 shows the results of the test series according to embodiment F, which were obtained on the basis of an organic colored pigment with dry matter.

In the embodiments, a suitable for printing with conventionally drying inks suitable simultaneous printing machine with retrofitted UV drying system of IST Metz ("BLK-5", two spotlights per side with a radiator output of 180 W / cm) was used.

Embodiment A: Cotton velor paper was printed on both sides in a simultaneous sheetfed press with one offset and two letter set inks. The paints contained 3% by weight cobalt / manganese salt drier. The printing speed was 8000 sheets / h. The signatures were dried at room temperature in stacks of 6000 sheets each and could be further processed by intaglio printing after 48 hours at the earliest. After connecting two UV aggregates (IST Metz, model "BLK-5") on each side at 40% of the maximum output and subsequent drying at room temperature in stacks of 6000 sheets each, further processability by intaglio printing was achieved within 20 hours ,

It could be shown that the paper substrate is not appreciably changed in its dimension or spatial dimension due to the UV doses required to reduce the drying time to less than 20 hours, while a higher heat input by hot air very well to a higher shrinkage of the Substrate leads. In the event that increased shrinkage is desired, the power of the UV lamps can be increased.

Embodiment B:

Cotton velor paper was printed on both sides in a simultaneous sheetfed press with three letter set colors each. The paints contained 3% by weight cobalt / manganese salt drier. The printing speed was 10,000 sheets / h. The signatures were dried at room temperature in batches of 6000 sheets each until further processing. Five sheets each from the stack top, the stack center and the bottom of the stack were taken from the stack after one hour, measured and the average of the measured values determined.

At a radiant power of 90% of the maximum power, an average shrinkage of the substrate was found in a range of 1.5 mm to 1.9 mm. Further processing after 20 hours in intaglio printing was possible without problems. The dimensional enlargement of the substrate caused by intaglio printing was of the same order of magnitude, so that with the described method a substantial dimensional neutrality could be achieved.

Embodiment C:

Cotton velvet paper with film elements applied in subregions was printed on both sides in each case with one offset and three letter set inks in a simultaneous sheetfed press. The paints contained 3% by weight cobalt / manganese salt drier. The printing speed was 8000 sheets / h. In particular, the film areas that were printed with the wet offset ink were not sufficiently dried in the arrangement of the printed sheets in the stack, so that strong deposition was observed in the stack on the respective next sheet back page. After connecting two UV aggregates (IST Metz, model "BLK-5") on each side at 50% of the maximum power, the problem of depositing did not occur, as a result of which the UV radiation already caused a pronounced hardening of the paint surface within a few minutes ,

The further embodiments D, E and F were carried out on laboratory pressure units. The basic procedure was as follows: On a sample printing equipment from IGT Metz, a trial print with an application quantity of the printing ink of 1 g / m ^{2 was} carried out on cotton velvet paper. After drying under the conditions indicated, the printed side was placed on an unprinted piece of paper of the same size and this combination was pressed together. The amount of ink transferred to the previously unprinted paper was used as a measure of drying. This method reflects the real production conditions well, because here too the printed sheets in the next processing step have to withstand a similar load.

Provision of reference samples:

The print strips were dried open in the room air at a temperature of 20 ° C for four hours.

Carrying out the drying by means of UV radiation:

The print strips were exposed immediately after printing in a continuous UV belt dryer at the indicated UV dose rate. The UV lamps used were both normal mercury UV medium-pressure lamps (company IST, spectra type CK) and iron-doped mercury UV medium-pressure lamps (company IST, spectra type CK-II). The print strips were also fixed on a metal support for rapid heat dissipation. The temperature of the printing strips reached room temperature again after only 5 to 10 seconds after the dryer had been run through. The strips were then dried next to the reference strips for four hours.

Carrying out the drying by means of heat: The printing strips were dried in a drying oven at 35 ° C. for one, two or three hours immediately after printing. After each time, the strips were removed from the oven and further dried at room temperature for the remaining time to the total drying time of four hours, in addition to the reference stiffeners.

Carrying out the drying by means of ozone: The pressure strips were gassed immediately after the pressure in a chamber with a mixture of atmospheric air and ozone under the specified conditions at room pressure. At the end of the indicated time, the strips were removed from the chamber and further dried at room temperature for the remaining time to the total drying time of four hours, in addition to the reference stiffeners. The connected ozone generator was operated with dried room air and worked with a corona discharge.

Exemplary embodiment D (test series):

A black letter set ink based on a carbon black pigment without dry matter was applied to cotton veline substrate with an application rate of ¹ g / m ² and dried in various ways: Reference: Drying for ⁴ hours at room temperature.

UV 1: irradiation with a UV dose rate of 70 mj / cm ² , followed by four hours of drying at room temperature. UV 2: irradiation with the double UV dose rate of UV 1, followed by four hours of drying at room temperature.

UV 3: irradiation with three times the UV dose rate of UV 1, followed by four hours of drying at room temperature.

Heat 1: drying for one hour at 35 ° C followed by drying for three hours at room temperature. Heat 2: drying for two hours at 35 ° C followed by further drying at room temperature for two hours.

Heat 3: drying for two hours at 35 ° C followed by one-hour drying at room temperature.

FIG. 1 shows the amount of ink transferred by the pressing onto the unprinted substrate. The larger this is, the worse the color was dried at the time of the knock-off. Usually, a dry-free paint at room temperature has to dry for at least a week or more until the signatures can be further processed. So there is no industrial production possible. The drying in the oven also requires a relatively long drying time and also changes the dimension of the paper substrate. Thus, also in the exemplary embodiment D, it can be seen that a three-hour heat input can not achieve a significant effect compared to the reference. By contrast, UV radiation already achieves a measurable effect.

Exemplary embodiment E (test series): A black paint composition based on a carbon black pigment containing 3% by weight of a cobalt salt-based dry substance was applied to a cotton wool substrate at an application rate of ¹ g / m ² and dried in various ways:

Reference: four hours drying at room temperature.

Irradiation with a UV dose rate of 70 mj / cm ² followed by four hours of drying at room temperature.

UV 2: irradiation with the double UV dose rate of UV 1 followed by four hours of drying at room temperature. UV 3: irradiation with the triple UV dose rate of UV 1 followed by four hours of drying at room temperature. one hour drying at 35 ° C followed by further drying at room temperature for 3 hours. drying for two hours at 35 ° C followed by further drying at room temperature for two hours.

FIG. 2 shows the quantity of ink transferred by the pressing onto the unprinted substrate. The larger this is, the worse the paint was dried. It is thus clear that the UV radiation compared to the reference can achieve effects in the order of magnitude that otherwise can only be caused by heat.

Exemplary embodiment F (test series):

A red letter set paint based on an organic colored pigment was applied to a cotton wool substrate at an application rate of ¹ g / m ² and dried in various manners. The paint contained 3% by weight of dry matter:

Reference: four hours drying at room temperature.

UV 2: irradiation with the double UV dose rate of UV 1 followed by four hours of drying at room temperature.

UV 3: irradiation with the triple UV dose rate of UV 1 followed by four hours of drying at room temperature.

Heat 1: Drying for one hour at 40 ° C followed by three-hour drying at room temperature.

Heat 2: drying at 40 ° C for two hours followed by further drying at room temperature for two hours. Heat 3: drying for two hours at 40 ° C followed by one hour of further drying at room temperature.

Ozone 1: one-minute exposure to ozone in room air with one

Concentration of approx. 10 ppm followed by four hours

Further drying at room temperature.

FIG. 3 shows the quantity of ink transferred by the pressing onto the unprinted substrate. The larger it is, the worse the paint has dried.

It is thus clear that the UV radiation compared to the reference can achieve effects in the order of magnitude that otherwise can only be caused by heat. Ozone also shows a beneficial effect.

Combination experiments have shown that ozone enhances the effect of UV radiation even further. The effect of UV treatment of less than one second followed by further drying for 4 hours at room temperature has e.g. for a tested paint containing a normal siccative, the effect is similar to the four hour drying at a temperature of 35 ° C. Particularly interesting is the additional observation that the UV irradiation also shows an effect for colors without siccative, while the application of heat within the observed period has caused no appreciable drying.

Claims

Patent claims

A method for producing a value document, comprising:

a) printing a value document substrate with an oxidatively drying ink;

b) treating the printed value document substrate with UV radiation; and

c) drying the UV-treated printed value document substrate at room temperature or at elevated temperature.

2. A method of producing a value document, comprising:

a) printing a value document substrate with an oxidatively drying ink;

b) treating the printed value document substrate with ozone; and

3. The method of claim 1, wherein in step b) the treatment of the value document substrate is carried out with UV radiation and additionally with ozone.

4. The method according to any one of claims 1 or 3, wherein in step b) the treatment with UV radiation by a equipped with a UV drying system (simultaneous) printing machine takes place in the at a printing speed of 10,000 sheets / h a UV dose rate of 10 mj / cm ² to 40 mj / cm ² per radiator is selected.

5. The method according to any one of claims 1 to 4, wherein in step c) the drying is carried out at room temperature, in particular in a stack.

6. The method according to claim 5, wherein the drying of the value documents is carried out in the form of a value-document stack and the value-document stack in particular from 1000 to 10,000 sheets, preferably 5000 to 7000 sheets.

The method of claim 2 wherein step b) of treating the printed value document substrate with ozone is performed by exposing the value document substrate to ozone in ambient air at a concentration in the range of 1 to 15 ppm.