EP0542190B1 - Relief printing and application therefore - Google Patents

Abstract

In a process for applying binder systems, in particular printing ink, to web material by the relief printing technique, a solvent-free binder system is applied to the relief printing form of an applicator roll by means of an engraved roller which has engraved cells of a cell depth of </= 15 mu m. The applicator device has an impression cylinder and one or more applicator rolls which are each supplied with a binder system, preferably printing ink, via a binder application system with an engraved roller, which has engraved cells of a cell depth of </= 15 mu m.

Description

The invention relates to a method for applying binder systems, especially printing ink on web material according to the high pressure technology according to the preamble of claim 1 and an application device the preamble of claim 7 and an anilox roller for implementation of the procedure.

When printing web-shaped printing material, e.g. Paper, plastic or the like, this runs over an impression cylinder and is printed by means of a printing roller with a inking unit Ink is colored. The cliché is high in the high-pressure process the printing roller is raised, in the case of the flexographic printing process the cliché made of a plastic material with elastomeric properties consists. For high pressure, especially flexographic printing only solvent-based printing inks with a solid content of about 30% by weight and a solvent content of about 70% by weight. Organic solvents serve as solvents (diluents) Solvent and / or water. GB-A-1307166 is a flexographic printing unit known with an anilox roller with cup grid, in which 250 to 800 wells are arranged per linear inch, the depth of which is 12 Micrometer should not exceed.

Surprisingly, it has now been found that the high pressure process with solvent-free (i.e. 100% solid content) printing inks or binder systems can be carried out if a specially designed Anilox roller for inking or coating the printing or application roller is used.

The invention thus relates to a method for applying Binder systems, especially printing inks (with the characteristics of Claim 1. Advantageous embodiments of this method are in the Claims 2 to 6 indicated.

The invention also relates to an application device with the features of claim 7 for performing the aforementioned method. Appropriate developments of the application device according to the invention are listed in claims 8 to 18.

An embodiment of an anilox roller according to the invention for implementation of the method according to the invention is defined in claim 19.

Basically come to carry out the method of the invention all solvent-free binder systems in question, according to their application properties e.g. referred to as printing inks, varnishes or adhesives will.

Solvent-free printing inks are, for example, radiation-curing printing inks, where UV-curing printing inks based on acrylate or methacrylate or based on epoxy resin are preferred. Such inks are under the Name UVAFLEX (Zeller & Gmelin GmbH, Eislingen), UVA temp (Hostmann-Steinberg, Celle) or SUNCURE (Sun Chemical, Brussels) im Available commercially.

Examples of suitable solvent-free adhesives are radiation-curable Hot melt adhesive based on acrylate or methacrylate or on epoxy resin. These serve e.g. for the production of composite films.

Compared to the known flexographic printing process that uses solvent-based Working with printing inks with a solvent content of 70% by weight the method of the invention has various advantages. Because the conventional The inks release the solvent as part of the drying process complex changes such as shrinkage, Porosity, pigment changes or "knocking away" of the binders. In contrast, solvent-free systems are much more stable over time from application to hardening. Only the shrinkage behavior is currently known of radiation-curable systems; can be here by a suitable Molecular weight distribution to minimize shrinkage when curing. There the ink does not contain any solvents, there is no drying out, i.e. the thickness of the wet film is equal to the thickness of the dry film. There no solvents escape, no special effort is required for the suction and, if necessary, the recovery of solvents. The solvent-free inks are largely odorless; both means an improvement in occupational hygiene. Due to the lack of solvent evaporation special fire protection measures are also unnecessary, and finally, the inks contain no raw materials that are on a Negative list of the Federal Health Office or the Federal Drug Administration stand what for the printing of food packaging from Meaning is. The Draize value is below 1, i.e. the skin irritation factor corresponds to conventional solvent-based printing inks.

As a result of the use of solvent-free inks with a solid content 100% gives an excellent expression. Here the grid points are optimal, i.e. with correct design of the pressure cylinder parameters, such as cliché material or substructure, and in particular the Anilox roller configuration, good tonal value increase conditions are observed. During solvent-based printing inks according to solvent evaporation show a strong increase in viscosity, they are according to the invention used printing inks or binders viscosity stable, the Viscosity can be regulated in a defined range via the temperature can. In contrast to solvent-based printing inks, it also happens not to dry in the machine, even after a long standstill, e.g. on the weekend. It goes without saying with UV curing systems make sure that all UV exposure is kept away.

The processing of the solvent-free used according to the invention Binder systems, e.g. Printing inks or hot melt glue can be used Room temperature, i.e. 20 - 25 ° C. However, this can be easy problems arise because the viscosity of the binder is too high, and certain binders can be put into practice at room temperature do not process at all. It is therefore preferable to the Processing temperatures of common solvent-based inks with around 5 - 60 ° C elevated temperatures worked. Based on the above At room temperature this means a processing range of 25 - 85 ° C, preferably 30-65 ° C. Temperatures of 35-45 are preferred ° C, with temperatures in the practical implementation around 40 ° C have proven particularly effective.

According to the selected working temperature, it is to be guaranteed a uniform printing process required, a tempering over the entire application work of an application device, e.g. Printing device, to perform, where appropriate also the impression cylinder and the High pressure rollers are to be heated.

In general, binder systems can be processed which have viscosities (at shear rates of 25-400 s ^-1 ) of 0.01-2 Pa · s. At processing temperatures of around 40 ° C. for printing inks, the printing ink viscosities are generally in the range from 0.02 to 0.5, preferably 0.05 to 0.15, with viscosities from 0.08 to 0.12 being particularly preferred. In the case of printing inks, the pigment content generally bears 20-50% by weight. In the case of adhesives, the processing temperatures and the viscosities are generally higher.

A particular advantage of the radiation-curable binder systems is that that - due to the lack of solvents - no drying is necessary and moreover the curing (crosslinking) of the binder so quickly it is done that the multi-color overprinting work without problems can. Here it is used in the known methods Solvent-based systems sometimes cause difficulties because of incomplete ones Drying and / or incomplete cross-linking occur.

The cleaning of cylinders, clichés, cleaning cloths, dirty clothes etc. can e.g. with aqueous surfactant-containing alkaline solutions or using solvents. The UV-hardened printing inks are also exceptionally stable, with chemicals, Resistance to temperature, scratching, creasing and adhesion are to be mentioned.

Overall, this results in a much more problem-free manner according to the invention Printability than in the known methods using solvent-based Systems. UV-curing solvent-free printing inks are indeed considerably more expensive than the known solvent-based printing inks. Based on the solids content or the amount of printed products is the However, comparison is cost-neutral, whereby when working with solvent-free Printing inks additionally the above Advantages.

Numerous substrates, e.g. made of polyethylene, polypropylene, polyamides, polyesters, paper or steel / aluminum (varnished or unpainted) with good adhesion and authenticity. With conventional printing inks, different color systems are often required be used. There is a for printed plastic sheets particular advantage of UV-curable printing inks is that they can be used without Discoloration are sealable and laminable. Finally there is another Advantage in the fact that when using UV-curing printing inks due to UV exposure, the printed material (possibly also from the inside!) is sterile, which has advantages when used for medical purposes.

In one embodiment of the method of the invention is called solvent free Binder system a radiation-curable laminating adhesive on a first web material applied and a second web material fed and concealed. Depending on the adhesive system, this can trigger a reaction (hardening) by the influence of radiation (UV light or electron beams) both before can also be used after lamination. An advantage of this procedure consists in the fact that the adhesive is applied immediately after the lamination process is cured so that the composite material is immediately cutable while the hardening in processes according to the prior art 3 - 10 days lasts.

In a further embodiment of the method of the invention, the Glue application only in the area of the benefit, so that after punching out the Use the adhesive-free film residues can be reused. A important application for this is the recovery of composite film waste, e.g. B. leadframe recycling.

The method according to the invention is carried out with a Application device with a counter-pressure cylinder and one or more Application rollers, each with a binder application unit with a Anilox roller with the binder system, preferably the printing ink, be supplied, the anilox roller a cup grid with one opposite conventional anilox rollers (40 µm) significantly reduced well depth of ≤ 15 µm. The depth of the cells is in the range of 1 - 10 µm, preferably in the range of 5-8 µm. The cups are geometric designed as a cylinder, dome or truncated pyramid. Furthermore have well geometries with high loss of skin, i.e., it comes when printing only to a small well emptying, as special proven advantageous.

An important parameter for anilox rollers is the so-called halftone screen (L / cm), which indicates the number of cells measured in a line of 1 cm. A screen size of 100 L / cm (a screen size customary for conventional screen rollers) means, for example, that there are 100 cells per cm or 10,000 cells per cm ² . The screen rollers according to the invention have considerably larger screen widths, generally in the range from 170-280, preferably 180-240 and in particular 190-200 L / cm, the screen width of 200 L / cm corresponding to 40,000 cells / cm ² .

Another important parameter of anilox rollers is the well / web ratio (N / S ratio), whereby, as with the screen ruling, in the Line is measured (see Fig. 2). According to the invention, the N / S ratios are 8: 1 to 1: 1, preferably 5: 1 to 2: 1 and in particular 3: 1 to 2: 1. The measurement in the line at the N / S ratio entails that with the same N / S ratio, the area of the webs in relation to the area the well openings are larger for round wells than for square ones. This difference would have to be taken into account if necessary, since it is always based on area is printed or laminated.

In a special embodiment of a grid, the web surfaces are partially deepened between the wells, but the depths are less than in the wells, e.g. only 5 µm deep at a well depth of 10 µm. The partial deepening of the web surfaces may refer to the entire web area, only go so far that there is still enough contact area for the squeegee is available, otherwise the anilox roller will no longer work properly can be supplied with printing ink or binder. The partial deepening of the web surfaces offers an advantage in the full surface Pressure, because here the better area filling means better area filling and thus better print products are obtained.

In one embodiment of the application device are located on the outer circumference the impression cylinder one or more devices for Release of high-energy radiation to the printed web material. Preferably these radiation devices are designed as UV lamps. Because of The high energy density of the UV lamps (about 150 W / cm) are the lamps water-cooled, whereby a water-cooled housing has proven itself. Here are movable in a further embodiment inside the housing attached, water-cooled reflectors provided, which in the event of malfunctions, especially at standstill, automatically between the radiation source and push the impression cylinder so that the substrate overheats and system parts is avoided. At the same time, the radiator output increases a minimum of e.g. reduced about 40 W / cm. When changing the substrate throughput speed is a constant adjustment of the radiator output operated.

The application unit advantageously supplies the anilox roller Binder system or printing ink a chambered doctor blade with binder level regulator on, the chamber doctor blade being fed and emptied by a Binder container, which is via a fore / return pump via a single line is connected to the doctor blade. The line ends in the chambered doctor blade at the lowest point of the binder filling, so that the fresh Binder is fed from below.

In one embodiment, the chambered doctor blade is a heatable doctor blade elastic sealing profiles on both sides as well as inlets and outlets educated. In contrast to solvent-based printing inks in the case of solvent-free printing inks, the viscosity is controlled via the Solvent content not possible. A desired reduction in viscosity can therefore only be achieved by increasing the temperature. To reach the higher temperature and keeping the desired temperature constant is the heated chamber doctor blade. The adjustment and fixing the doctor arm can e.g. done via steel springs. The side Sealing profiles are made of an elastomeric material, e.g. from swell-resistant Rubber. By pulling off the side sealing profiles the doctor blade can be easily cleaned.

The chambered doctor blade advantageously contains at a distance from the lateral sealing profiles one or more additional sealing profiles, the resulting chambers formed its own ink supply and one Own level control. This makes it possible to use the individual chambers to feed different printing inks, so that at the same time printed multicolored can be.

In the application device of the invention, the impression cylinder and / or the binder application unit in the axial direction in several thermal Zones can be divided, the individually controllable temperature control devices exhibit. This makes it possible for solvent-free binders the viscosity of which is temperature-dependent, specific changes or measurements the amount of binder or paint applied.

The anilox roller according to the invention consists e.g. made of steel and has one Ceramic or titanium nitride surface. The engraving (generation of the grid geometry) can be done using laser beams.

Figur 1

eine perspektivische Darstellung einer erfindungsgemäßen Auftragsvorrichtung,

Figur 2A-E

stark vergrößerte Teildarstellungen (II der Rasterwalze 13 von Fig. 1) verschiedener Oberflächenstrukturen einer erfindungsgemäßen Rasterwalze,

Figur 3

eine perspektivische Darstellung eines beheizbaren Kammerrakels,

Figur 4

einen Schnitt durch ein Kammerrakel mit Farbbehälter und Pumpe

Figur 5

eine schematische Darstellung einer Auftragsvorrichtung im Zusammenhang mit einer Kaschiereinrichtung, und

Figur 6

einen Schnitt durch einen UV-Strahler mit beweglichen Reflektoren.

The invention is described below with reference to the drawings. Show it:

Figure 1

a perspective view of an application device according to the invention,

Figure 2A-E

greatly enlarged partial representations (II of the anilox roller 13 of FIG. 1) of various surface structures of an anilox roller according to the invention,

Figure 3

a perspective view of a heatable doctor blade,

Figure 4

a section through a doctor blade with ink tank and pump

Figure 5

a schematic representation of an application device in connection with a laminating device, and

Figure 6

a section through a UV lamp with movable reflectors.

In the application device shown in FIG. 1, a web material (polyethylene film 20 μm thick) runs at a web speed of 300 m / min over an impression cylinder 11 and is printed on by means of a high-pressure roller 12. The high-pressure roller 12 is supplied via an inking unit 17, which comprises an anilox roller 13 with a doctor blade 14 and an inking roller 15 with an ink pan 16. The anilox roller 13 has a well depth t of 6 ± 1 μm (see FIG. 2). The anilox roller 13 has a geometry according to FIG. 2A with a raster width of 180 L / cm corresponding to 32,400 cells / cm ² , and an N / S ratio of approximately 2: 1. A solvent-free (100% solid) UV-curable acrylate printing ink with a pigment content of 20% by weight is used. This has a viscosity of 0.1 Pa · s at 40 ° C. The high-pressure roller 12 is a conventional high-pressure cliché. It is printed with an application thickness of 1.5 µm, whereby there is practically no difference between wet and dry film thickness. Immediately after the printing ink has been applied to the web material 10 by means of a high-pressure roller 12, the curing of the printing ink takes place by means of two UV lamps (see the description of FIG. 6 for details on the outer circumference of the impression cylinder).

FIG. 2 shows details of the surface condition of the anilox roller 13 2A, 2B, 2C and 2D show in the said Order of cup geometries in the form of domes, stump pyramids, pyramids and cylinders, the cell-bridge ratio being approximately 2: 1 (FIG. 2A) to is about 3: 1 (Figure 2D). 2E shows (in plan view) a variant of FIG. 2B with partial bar recess. At a depth t of the well N of 10 μm there are partial depressions P of 5 μm in the web surfaces S. Depth, so that on the one hand the well N through the partial recesses P are connected to each other, but on the other hand still enough web area S as Contact surface for the ink squeegee is available. With the embodiment according to FIG. 2E, a better surface profile and thus achieve a better area filling, which increases the print quality means.

FIG. 3 shows a perspective illustration of a heatable doctor blade 52, which is closed on both sides by elastic sealing profiles 32, 32 '. By the sealing doctor is another sealing profile 32 '', 32 '' 'attached inside 52 divided into three separate chambers 35, 35 ', 35' ', each with its own Ink supply 56, 56 ', 56' 'and its own color level controller 53, 53', 53 '' have. The subdivision of the chambered doctor blade enables the separate chambers to feed with different inks, so that at the same time multicolored can be printed. Due to different temperature control in the axial direction by means of individually controllable temperature control devices (not shown) the viscosities of the individual printing inks are influenced, so that targeted Changes or measurements of the paint application quantities are made can. Squeegee arms 36, 36 'are adjusted and fixed by Steel springs (not shown). The side and inner sealing profiles are made of swell-resistant rubber. By pulling off the side sealing profiles 32, 32 'or moving the middle sealing profiles 32' ', 32' '' can do that Clean the doctor blade easily.

FIG. 4 shows a section through the chambered doctor blade 52 from FIG. 3, fed via an ink tank 58, which via a fore / back pump 57 via a single Ink line 56 is connected to the doctor blade 52. The ink line 56 opens into the chambered doctor blade 52 at the lowest point of the ink filling 65 ', so that the fresh printing ink is always updated from below. The supply of the ink container 58 takes place via a feed line 59 Agitator 60 maintains the homogeneity of the ink 65. The Chamber squeegee 52 has ventilation devices 66 to avoid blistering in the ink filling 65 '. Both the ink tank 58 and the chambered doctor blade 52 can be heated by means of temperature control devices 69 and 67, keeping the temperature constant via control devices 70 and 68.

5 shows a schematic representation of an application device according to the invention in connection with a laminating device. A web material 10 (polyethylene, 20 .mu.m) is drawn off from a roll 21 and fed to an impression cylinder 11 via a deflection roll 22. A UV-curable laminating adhesive is applied to the web material 10 by means of a high-pressure roller 12. The supply of the high-pressure roller 12 with laminating adhesive takes place by means of an anilox roller 13 with a heatable doctor blade 52. A further web material 20 (polyamide, 60 μm) is then applied to the web material 10 coated with the reaction laminating adhesive, which is pulled off a roller 23 and by means of a Laminating roller 24 is applied to the adhesive-coated web material 10. The laminated composite material is then taken up on a roller 26 via a deflection roller 25. UV lamps 18, 18 'are provided on the outer circumference of the impression cylinder 11 for curing the reaction laminating adhesive. Before the second material web 20 is applied, the UV lamp 18 pre-hardens the reaction adhesive, care being taken to ensure that sufficient tack is still available when the second web material 20 is applied to achieve adhesive lamination. After the second web material 20 has been fed in, post-curing is then carried out by means of the UV lamp 18 '. It works with a web speed of the impression cylinder 11 of 150 m / min. A solvent-free UV-curable laminating adhesive based on epoxy resin with a viscosity at the working temperature of 60 ° C of 0.6 Pa · s is used. The application takes place over the entire area in an amount of 3 g / m ² , which corresponds to an application thickness of approximately 3 µm. An anilox roller 13 with a geometry according to FIG. 2E is used, with a raster width of 170 and an N / S ratio of 3: 1 (here the web depressions are calculated as a web). The entire system is kept at a working temperature of 60 ° C by appropriate temperature control devices.

6 shows details of such a UV lamp. Such one UV lamp 61 has a UV radiation source 63 with an energy density of 150 W / cm (axial), which is housed in a water-cooled housing 62. in the Inside the housing are movable, also water-cooled reflectors 64, 64 ' provided that automatically in the event of faults, especially when the system is at a standstill between the radiation source 63 and the impression cylinder 11 (see FIG 5) so that overheating of the web material 10 or 10 and 20 (cf. Figure 5) is avoided. In addition, a control device (not shown) provided when the web speed of the counterpressure cylinder changes 11 causes an automatic adjustment of the radiation power.

Claims (19)

1. Method of applying bonding agent systems, more especially printing ink on web material according to high-pressure technique, wherein the bonding agent system is applied to the high-pressure form of a coating roller by means of a screen roller, characterised in that a solvent-free bonding agent system is coated by means of a screen roller which has a cup-type screen with a cup depth of ≤ 15 µm.
2. Method according to claim 1, characterised in that a radiation-hardenable printing ink is used.
3. Method according to claim 1, characterised in that a UV-hardenable printing ink is used.
4. Method according to claim 3, characterised in that a printing ink based on acrylate or methylacrylate is used.
5. Method according to claim 4, characterised in that a printing ink is used, having a pigment content of between 20 and 50 % by wt. and a viscosity at 40° C of between 0.08 and 0.12 Pa.s, and said printing ink is processed at a temperature of 40 - 60° C.
6. Method according to claim 1, characterised in that a radiation-hardenable bonding adhesive is used as the solvent-free bonding agent, a second material web being bonded onto the web material provided with the adhesive coating, and the radiation-hardening of the adhesive being achieved before and/or after the bonding process.
7. Coating apparatus for the high-pressure technique, having a counter-pressure cylinder (11) and one or more coating rollers (12), which are each respectively supplied with a solvent-free bonding agent system via a bonding agent coating mechanism (17) having a screen roller (13), characterised in that the screen roller (13) has a cup-type screen with a cup depth (t) of 1 - 10 µm, in that the screen roller (13) has a cup:web ratio of between 8:1 and 1:1, and in that the screen width of the screen roller (13) is between 170 and 280 L/cm.
8. Coating apparatus according to claim 7, characterised in that the cup depth (t) of the screen roller (13) is 5 - 8 µm.
9. Coating apparatus according to one of claims 7 to 8, characterised in that the screen width of the screen roller (13) is between 180 and 240 L/cm.
10. Coating apparatus according to one of claims 7 to 9, characterised in that one or more arrangements (18) for transmitting energy-rich radiation to a web material (10) are mounted on the external circumference of the counter-pressure cylinder (11).
11. Coating apparatus according to claim 10, characterised in that the arrangements (18) are configured as UV radiators (61).
12. Coating apparatus according to claim 11, characterised in that the UV radiators (61) are cooled.
13. Coating apparatus according to claim 12, characterised in that the UV radiators (61) are provided with a water-cooled housing (62) and displaceable, water-cooled reflectors (64, 64').
14. Coating apparatus according to one of claims 7 to 13, characterised in that the coating mechanism (17) for supplying the screen roller (13) with bonding agent has a chamber wiper (52) with a means (53) for regulating the bonding agent level and is fed and emptied by a container (58) which is connected to the chamber wiper (52) by a front/back pump (57) via a single bonding agent line (56).
15. Coating apparatus according to claim 14, characterised in that the bonding agent line (56) in the chamber wiper (52) terminates at the lowest point of the bonding agent filling.
16. Coating apparatus according to claim 14 or 15, characterised in that the chamber wiper is configured as a heatable wiper with bilateral, resilient sealing profiles (32, 32') as well as supply means and discharge means (56).
17. Coating apparatus according to claim 16, characterised in that the chamber wiper (52) has, at a spacing from the lateral sealing profiles (32, 32'), one or more additional sealing profiles (32'', 32'''), the chambers (35, 35', 35'') formed thereby each having their own bonding agent supply means (56, 56', 56''), and their own level regulating means (53, 53', 53'').
18. Coating apparatus according to one of claims 14 to 17, characterised in that the chamber wiper (52) has air-removing means (66, 66', 66'') to prevent bubbles from forming in the bonding agent.
19. Screen roller with a cup-type screen for carrying out the method according to one of claims 1 to 6, characterised in that the screen roller (13) has a cup-type screen with a cup depth (t) of 1 - 10 µm, in that the screen roller (13) has a cup:web ratio of between 8:1 and 1:1, and in that the screen width of the screen roller (13) is between 170 and 280 L/cm.

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