WO2018024760A1

WO2018024760A1 - Method for producing an optically variable printed image

Info

Publication number: WO2018024760A1
Application number: PCT/EP2017/069497
Authority: WO
Inventors: Peter Clauter; Klaus RODENHAEUSER
Original assignee: Merck Patent Gmbh
Priority date: 2016-08-04
Filing date: 2017-08-02
Publication date: 2018-02-08
Also published as: CN109562629B; CN109562629A; DE112017003883A5

Abstract

The present invention relates to a method for printing optically variable images in the RGB mode. According to said method, interference pigments are used in conjunction with absorption pigments or combination pigments for the color pigmentation of the printing inks. The invention also relates to the printed products produced by this method and to their use in decorative or artistic products or security products.

Description

Method for producing an optically variable printed image

The present invention relates to a method for printing optically variable printed images in the RGB mode, in which for the colored pigmentation of the printing inks interference pigments in conjunction with

Absorbent pigments or combination pigments may be used on printed products produced by such a process and their use in decorative, artistic or security products.

In conventional printing processes such as offset printing, gravure printing or screen printing, multicolor printed images are printed on the usually white or light-colored printing substrate by printing dots or printing surfaces lying side by side and on top of the primary colors cyan, magenta, yellow and optionally also black (CMYK) customary for analog printing methods. Each of the inks is pigmented with classic absorption colors that subtly blend in visual perception. From suitable combinations of the primary colors can be produced as many desired shades of the color wheel. However, if equivalent quantities of cyan, magenta and yellow pigmented printing inks are applied to one another on a single surface unit, the color perceived by the observer is black. In addition, in practical printing applications black areas or lettering are additionally reinforced with black pigmented printing ink. Modern digital processes such as inkjet printing or toner based electrophotography are also based on the proven CMYK system because the printing of the images is still linked to the presence of colored absorption pigments or dyes in the inks, although the digital images themselves are not in the CMYK system, but to be stored in RGB mode. Digital displays of various kinds of screens (LCD, LED, OLED, plasma) use light beams of the primary colors red, green and blue, which are combined in various combinations with one another to form light points that can assume any desired color position of the color wheel. In contrast to the CMYK color system, colored light rays mix in RGB mode in an additive way, ie superimposed RGB light rays of adequate intensity mix in the visual perception to white. Digital recordings of photo or film cameras are also made in RGB mode, so that they can be played back on digital displays without major adjustment problems, while the printing of digital recordings in common printers, for example in inkjet printers, a computer-aided conversion of In the RGB mode, image data obtained in data for a mechanically printable image in the CMYK system requires.

In addition to the use of absorption pigments or dyes, interference pigments with different optical properties (pure interference colors, interference colors combined with absorption colors, gloss and glitter effects, optically variable effects) have also been used more frequently in recent years in CMYK-based printing processes, which emphasize them of details, obtaining a special extra gloss or glitter, or altogether for optically improving the overall impression of the printed products. However, such printed products are not favorable in the production and achieve only moderate effects due to the small amounts of possible use of interference pigments.

In addition, it is becoming increasingly difficult to find interference pigments that can achieve very special, attention-generating effects even in the art.

The optical effect of interference pigments is based on the refractive index difference of materials which are thinner in the pigments Layers are arranged one above the other and reflected light depending on the refractive index of the respective layer and the medium surrounding the interference pigment in different ways, transmit and optionally also absorb. Differences in refractive index between adjacent layers lead to differences in the path of the reflected light beams, so that the former is superimposed and wavelength-selective light of specific wavelengths is amplified or attenuated. The reflected light beams in the thus-amplified visible wavelength range are perceived by the viewer under suitable conditions as a visible interference color. If all layers of the interference pigments are composed of transparent, colorless materials, only interference colors but no body colors of the interference pigments are perceptible. Visually, the interference colors of interference pigments, which have no absorption colors, such as colored light rays, thus combine with each other additively. For example, a bed of transparent interference pigments which are colorless as individual pigments and have a suitable mixing ratio of red, blue and green interference pigments (ie interference pigments which show a red, green or blue interference color in the application medium) should theoretically have a visually perceptible white overall impression However, in practice often deviates from it, so that a whitish, light gray hue is perceived.

Individual interference pigments usually consist of a platelet-shaped carrier material and of one or more, more or less transparent layers, with which the platelet-shaped carriers are coated. However, the uniform layer thickness of the support and the individual layers, the homogeneity of the composition of the individual layers and the surface properties of the support and individual layers as well as the size and size distribution of the pigments determine Among other things, to what extent the optical behavior of the respective interference pigments deviates from the ideal behavior of the currently used materials. Thus, the production conditions of interference pigments have a great influence on their optical behavior. This explains the large differences in the optical behavior, expressed for example by saturation, brightness or color angle, of interference pigments of the same formal hue (eg red) and a formally identical layer structure (eg titanium dioxide layer on mica platelets), depending on the manufacturer and the manufacturer used manufacturing process, sometimes even depending on the batch.

Therefore, until recently, it has not yet been possible to develop analogue printing methods which make it possible to produce colorful printed images whose coloration is based exclusively on the optical effect of pure interference colors which are produced by interference pigments.

Interference pigments, which in addition to interference colors also have absorption colors, are referred to as combination pigments. The optical effect of such pigments is composed of the respective interference color (s) and the absorption color, wherein the absorption color, which is also referred to as body color, generates the main color impression of the pigment, which is either intensified or supplementarily superimposed by the interference effects. Because colorful colors are very often used as absorption colors in combination pigments in order to complement the relatively weakly colored interference effects attractively

Combination pigments in printing inks either with body colors in the range cyan, magenta or yellow or with different colorful body colors used to obtain special optical effects. However, the use of combination pigments in conventional printing processes is limited to the achievement of special effects and always takes place only in admixture with the usual colored absorption pigments in the colors cyan, magenta and yellow instead.

In contrast, combination pigments which show a black body color and at the same time weak interference colors are always used in the application medium as a substitute for, or as a supplement to, classic black pigments.

As an alternative printing method to the classical CMYK printing process, a theoretical concept was proposed in US 2006/0082844 A1 with the aid of which interference pigments should be able to be used for printing multicolor printed images. This R'G'B'Y 'concept is based on the use of four printing inks, each containing red, green, blue and yellow (gold) interference pigments, whereby four so-called bytes are required to produce a printing dot (pixel). This concept is based on the recognition or assumption that red and green interference pigments, unlike red and green light, do not mix too yellow, but rather gray. In order to obtain a yellow color of the pixels, therefore, a separate yellow or golden color trace must be created in this concept. It also follows that to produce a white color impression, a red, green, blue and yellow printing ink is required, which is pigmented with interference pigments of the respective interference color. However, the concept described here remains theoretical. Thus, neither practically usable information about the interference pigments to be used is contained nor can be found in the disclosure

Printing modalities that would allow a practical implementation of this concept.

However, the Applicant has recently succeeded in developing a viable printing process that has received much attention in the art, based on the use of only three colored inks exclusively pigmented with interference pigments (PCT / EP2016 / 000120). This is a printing method in RGB mode, with the help of which brilliant colorful print images in all colors of the color wheel can be produced from printing inks, which are each color-pigmented exclusively with red, green or blue interference pigments. However, the method is most effective on black or dark colored substrates, as these provide sufficient contrast to the interference colors of the interference pigments, which are known to be much weaker in optical

Perception are as common colored absorption pigments.

However, there is still a need for visually exceptional, attention-creating printed products which can be produced on the white, light or even transparent colorless substrates of various kinds which are commonly used for printing processes and have hitherto unknown optical effects.

The object of the present invention is to provide a printing method which can be implemented in the RGB mode in practice, with the aid of which optically attractive printed images can be produced on variable, preferably colorless, transparent, white or light substrates, the printing inks having interference pigments not but pigmented with colored absorption pigments and wherein with the smallest possible number of different printing inks a printed image can be produced which has hues in the entire color space, and wherein the printing process can be variably adapted to the usual analog and digital printing methods.

Another object of the invention is to provide printed products which have colorful printed images with additional special optical effects and to show their use. The object of the present invention is achieved by a method for printing an optically variable print image in the RGB mode, wherein three colored inks are successively applied and solidified in the form of printing surface units on a substrate, and wherein the

Printing inks each consist of an ink vehicle, which

a) is pigmented with in each case red interference pigments, green interference pigments or blue interference pigments as well as a black absorption pigment, the printing ink vehicle additionally containing no further coloring pigments, or

b) is pigmented in color exclusively with combination pigments, one printing ink each having red, green or blue combination pigments which have a red interference color, a green interference color or a blue interference color and in each case additionally a black absorption color,

and wherein from the three colored printing inks side by side and / or superimposed printing unit units are formed, which give at least at a first viewing angle a colorful total print image, which is different from a second total printed image, which appears under at least a second viewing angle.

The object of the present invention is also solved by

Printed matter produced by the process described above, and their use in decorative or artistic products or in security products.

The printing method according to the invention is based on the RGB mode which is known per se, but which, as described above, with the exception of the still unpublished method shown in PCT / EP2016 / 000120, hitherto only for the combination of differently colored light beams in

Displays or similar technical devices practical application has found. However, the present inventors can surprisingly now provide a further printing process in which the successive printing of only three inks pigmented exclusively with interference pigments or combination pigments is sufficient to be able to obtain optically variable printed images which, while maintaining the illumination angle, are at least one viewing angle show a colorful overall print image with hues that can extend across the entire color space, while at least a second viewing angle, a total print image is visible, which differs significantly in its color from the first complete print image and is preferably not colorful or colored.

Red, green or blue printing inks are understood below to mean printing inks which are pigmented exclusively with interference pigments or with combination pigments which each have a red, green or blue interference color.

The presence of the interference color is determined as is customary on the basis of the reflection of interference pigments in a transparent, colorless medium, usually a coating on a substrate.

The black absorption pigments added according to the invention to the red, green and blue interference pigments in the respective printing ink, which have no interference colors in addition to the black absorption color, are not regarded as colored pigments or pigment pigments according to the invention and according to the general perception of traffic, because "black" in the color theory, as well as "white", does not apply as color. In the present invention, all measurements are carried out with the aid of the samples described below with a multi-angle color spectrophotometer MA 68/11 from X-Rite, Inc., USA. To determine the interference color of the interference pigments, the directional reflection at the sample and the spectrally resolved analysis of the reflected light are used here. The measurement conditions for all data used in the present description are at an illumination angle of 45 ° and a viewing angle of as 25 ° (aspecular 25 °, the distance of the viewing angle to the glancing angle).

In any case, the red interference pigments have a reinforced

Reflection in the wavelength range of 600 to 750 nm, the green

Interference pigments enhanced reflection in the wavelength range from 490 to 550 nm and the blue interference pigments a reinforced

Reflection in the wavelength range of 400 to 490 nm. The more pronounced and narrow the corresponding reflection maximum, the more clearly a monochrome and saturated interference color is visually perceptible. The specified wavelength ranges for the corresponding reflection maxima also apply to combination pigments which, in addition to the respective red, green or blue interference color, also have a black absorption color. The latter represents the visible body color of these pigments, the corresponding pigment powder thus looks black or dark gray and not colorless or whitish, as is the case with the red, green and blue interference pigments, which have no absorption color.

The production of a colorful overall print image which is visible under at least one viewing angle as a result of the method according to the invention and which one over the entire color space Under the conditions according to the invention, it is only possible to carry out a range of colors by means of three-color printing inks if yellow printing surface units are contained on a substrate by successively applying a printing ink containing red interference pigments and a printing ink containing green interference pigments to be obtained on the same printing unit area.

For this, the red ink and the green ink must contain red or green interference pigments that meet certain conditions. Thus, according to the present invention, it is yellow for production

Pressure area units requires that the red interference pigments in the red ink in the CIELUV (1976) color space system have a hue in the range of 0 ° to 25 °, in particular 0 ° to 20 °, and more particularly in the range of 0 ° to 10 °, and the green interference pigments in the green printing ink have a hue angle h _u v in the range from 100 ° to 180 °, in particular from 100 ° to 150 °, and particularly preferably in the range from 100 ° to 130 °, the hue angle of the red Interference pigments are not 0 ° when the hue angle of the green interference pigments is 180 ° and vice versa (see Figure 1; hue angle determined in a separate, full-area coating of the respective color ink on a black substrate in the CIELUV (1976)) color space system at 45 as 25 °, for a more detailed description see below).

(For the meaning and determination of the hue angle see: Richter, M., Introduction to Colorimetry, 2nd edition, de Gruyter, 1981, pp.118-122.)

The application-related color properties of interference pigments, irrespective of which color space system, can only be determined in one application form, but not on the individual particle. For this reason, all used in the present invention

Color data on a coating consisting of a commercial liquid ink vehicle and the respective interference pigment in one Concentration of 23 wt.%, Based on the finished coating composition, consists and applied over the entire surface of a black substrate by gravure and solidified.

(30 parts by weight of pigment and 70 parts by weight of gravure binder (eg Siegwerk 5036 Verge NC TOF) are intimately mixed and before printing the viscosity is adjusted to 30 parts by weight of a mixture of ethanol / ethyl acetate (3: 1) ready for printing , blue or green interference pigments, are then each individually applied to a black-colored substrate (eg Fedrigoni SPX Black) with a gravure printing device (60 L / cm, 120 °, E-Engraving) and dried The resulting printed substrate is cut into pieces of suitable size divided and visually measured, see below)

The measurement of the color data is carried out with a Multiangle Color Spectrophotometer MA 68 / II from X-Rite, Inc., USA. From the obtained spectral data, the respective color coordinates ΙΑ, ν 'for the CIELUV (1976) color space system for given boundary conditions (2 ° or 10 ° normal observer and D65 light source) are calculated.

The method according to the invention can be carried out particularly advantageously if the distance of the hue angle h _u v of the red interference pigment from the hue angle h _u v of the green interference pigment is 90 to 160 degrees of angle (grd) and preferably in the range of 105 to 140 degrees of angle and in particular in the range of 1 is 10 to 130 angular degrees. In the same way, this also applies to the respective distances between the hue angles between the green and the blue interference pigments and between the blue and the red interference pigments. This means that also the distance of the hue angle h _u v of the green

Interference to hue h _u v of the blue interference pigment and the distance of the hue h _u v of the blue interference hue to hue h _u v of the red interference pigment advantageously each in the range of 90 to 160 degrees, preferably from 105 to 140 degrees and in particular in the range of 1 Should be 10 to 130 degrees. In compliance with these conditions, in particular with respect to the red and green interference pigment, it is possible that a unit area on a substrate, which is successively printed overlapping with a red ink and a green ink according to the previous definition, under certain proportions of the inks and at a defined Pigment content may even have a visually perceptible yellow color. In this case, each of the applied print layers can be separately solidified or the composite of a print layer of red ink and a first layer overlapping print layer of green ink is solidified together.

The hue angle h _u v of the blue interference pigments can be chosen to be relatively free, but is preferably determined by the ranges given above for the distances between the hue angles and is advantageously in the range from 210 ° to 280 °.

Adhering to the conditions described above, in particular for the red and green interference pigments, makes it possible for a printing process with only three inks pigmented with interference pigments to be sufficient to obtain multicolored printed images in the color diversity of the entire color space under at least one viewing angle , Of course, the color intensity and the brilliance of the printed images depends on further conditions.

These include in particular high color saturation and high chroma. According to the invention, therefore, an embodiment of the present invention is advantageous in which the interference pigments used in each case have the highest possible color saturation, that is to say are particularly strong in color, and exhibit high chroma. Corresponding details and particularly suitable interference pigments are explained in more detail in the already mentioned patent application PCT / EP2016 / 000120. On the mentioned patent application is insofar expressly incorporated herein by reference.

If, however, no yellow printing surfaces are provided or required for the optically variable printed image which is to be produced by the method according to the invention, and if it is acceptable to compromise on the scope of the color space to be achieved (gamut), the red, green or blue interference pigments used can be used for the respective printing inks also deviate in terms of their hue angle from the above-mentioned hue angle ranges, so that other red, green and blue interference colors can be used, which can even be produced individually from mixtures of different interference pigments. With respect to the saturation and the chroma of the interference pigments, however, it is also very advantageous if for the inventive

Method the interference pigments are selected with the highest available values.

The interference pigments used for the printing process according to the invention show either a red or a blue or a green interference color in the application medium. They consist of platelet-shaped carriers which are coated with one or more layers of materials which have a refractive index different from carrier material, which applies at least to the material of the first carrier layer, and, if several layers are present on the carrier are, have different refractive indices between directly superimposed layers.

According to the present invention, the red, blue and green interference pigments used are those each consisting of transparent, colorless, platelet-shaped supports which are coated with one or more layers of transparent, colorless materials. The interference pigments themselves are also platelet-shaped.

Although in the printing process according to the invention in principle red, green and blue interference pigments can be used in all available particle sizes, which are usually in the range of 1 to 250 μιτι for length or

Width of the pigment platelets and values of 0.1 to 5 μιτι thickness, it is to obtain a high coverage of the printed substrates and thus to achieve a high color intensity of the colorful printed images very advantageous if the particle size of the present invention used red, green and blue interference pigments in the range of 1 to 45 μιτι with a dgo value of <40 μιτι, in particular of <35 μιτι, is. Preferably, interference pigments are used whose dso value is <20 μm, in particular <18 μm, and whose dio value is preferably <12 μm. The particle size refers in each case to the main axis of the pigments, i. the longest extent of the respective pigment particle.

In order to obtain absolute values for the particle size, which are based on a broad statistical evaluation, the particle size data in the present invention are based on a single evaluation in a light microscope with automated image analysis. Since interference pigments have a platelet shape and can be oriented with their main surface parallel to the light source, in each case the concrete particle surface and the shape factors can be measured with this method. The number-weighted distribution of the major axis length is expressed by the d io, dso, dgo and optionally dgs values (corresponding to the percentage of particles smaller than the specified value). In each case more than 1000 pigment particles are evaluated. The evaluation is performed in accordance with [a] ISO 13322-1: 2014 -Particle size analysis-image analysis methods-Part 1: Static image analysis methods; [b] ASTM E1617 -09 (2014) Standard Practice for reporting Particle size characterization data; or [c] Powder sampling and particle size determination, T. Allen, Elsevier 2003. The values obtained by means of this individual evaluation in the light microscope allow an extremely realistic overview of the particle sizes and the particle size distribution of platelet-shaped pigments. However, other common methods of determining the

Particle size of interference pigments are used.

The interference pigments used according to the invention generally have an aspect ratio (ratio of the mean diameter to the mean particle thickness) of 3: 1 to 1000: 1 and in particular from 6: 1 to 250: 1.

It can be seen from the above-mentioned values that the red, blue and green interference pigments preferably used according to the invention advantageously have an extremely small proportion of coarse grain. Moreover, it is particularly preferred if they also have a high mean fine grain content, in which up to 40% of the pigment particles have a particle size in the range of 12 to 20 μιτι.

As red, blue and green interference pigments, interference pigments of various manufacturers can be used in the printing process according to the invention, for example the commercially available interference pigments which are known under the names Iriodin®, Colorstream®, Xirallic®, Pyrisma®, Spectraval ™, Miraval®, Lustrepak® , Colorcrypt®, Colorcode® and Securalic® from Merck KGaA, pigments of the name Mearlin® and pigments of the Lumina®Royal series from BASF SE and also other commercially available interference pigments from other manufacturers. If these pigments meet the requirements described above with regard to color angle, saturation, chroma and particle size, the printing method according to the invention at least one viewing angle high-quality, colorful printed images are available, which, if desired, can have a photorealistic visual impression. Especially suitable have been interference pigments which are marketed under the names Iriodin®, Pyrisma® and Spectraval ™, in particular the interference pigments of the Pyrisma® and Spectraval ™ series.

These interference pigments are inventively in a first

Embodiment of the present invention in the respective printing inks used together with a black absorption pigment. In the black absorbing pigment may be particulate Fe3O ₄ to based particulate Fe3O ₄ pigments to act particulate graphite, particulate carbon black, or even the combination pigments described below with black absorption color.

In the case of particulate Fe 3 O ₄ , particulate Fe 3 O ₄ -based pigments, particulate graphite or particulate carbon black, corresponding materials are commercially available in various particle sizes and, for example, under the names Cl Pigment Black 7, Cl Pigment Black 11, Cl Pigment Black 28 , Cl Pigment Black 30 or Cl Pigment Black 33 known. The particular particle size depends on the printing method used, since different

Printing process also generally very different requirements on the particle size of the particulate contained in the printing inks

Put materials. In particular, particulate material must not clog the cups of the printing plates whose emptying does not obstruct or hinder or lead to deposits on the printing form. In general, the black absorption pigments have a particle size in the range of 0.01 to 100 μιτι, in particular from 0.01 to 20 μιτι. The abovementioned black absorption pigments can be used individually or as a mixture in the respective printing ink. However, it is particularly advantageous to use carbon black, in particular finely divided carbon black, which is generally used in ordinary CMYK printing processes under the name Cl Pigment Black 7. The proportion by weight of these black absorption pigments in the respective printing ink is according to the invention 0.001 to 1, 5 wt .-%, in particular 0.02 to 0.75 wt .-% and particularly preferably 0.03 to 0.40 wt .-%, based on the total weight of the ink.

However, according to the invention, the combination pigments with black absorption color described below can also be used as black absorption pigments. These have, in addition to the black absorption color, a red, green or blue interference color and are correspondingly used correlatively with the red, green or blue interference pigments. This intensifies the interference effects in the respective printing ink. Since the combination pigments with black absorption paint have a platelet shape and a particle size which is similar to the particle size of the interference pigments, it comes in ready-made pigment mixtures of both

Ingredients or in the finished inks to a lesser extent settling or segregation of both components, as may occur with particulate components of different shape and size.

When the combination pigments having black absorption color are used as black absorption pigments according to the first embodiment of the present invention, their proportion in the respective ink is 5 to 30% by weight, especially 10 to 25% by weight, based on the total weight of interference pigment and combination pigment , ie based on the total pigment content in the respective printing ink.

Corresponding commercially available products are described below. The proportion of the respective red, green or blue interference pigment in the respective printing ink is generally between 1 and 40 percent by weight and preferably between 5 and 35 percent by weight, in particular between 10 and 30 percent by weight, based on the total weight of the respective printing ink. It goes without saying that the pigment concentration is chosen in each case so that the printing process according to the invention can be carried out without problems with the apparatuses available in each case. In addition, depending on the printing apparatus used, the pigment concentration in the printing ink is selected such that preferably the highest possible, processable pigment content is selected in order to obtain the required surface coverage of the printing surface units to be printed. If necessary, the pigment concentrations in the red, blue and green printing inks can be chosen differently from each other. Equally preferred, however, is the same pigment concentration in each of the three printing inks when using the same printing apparatuses for each printing step.

In a second embodiment of the present invention, the red, green and blue printing ink are pigmented in color exclusively with red, green or blue combination pigments which have a red, green or blue interference color in addition to a black absorption fab.

Such combination pigments are based on platelet-shaped supports and have at least one interference layer on the support, either the support or the at least one interference layer or both consisting of Fe 3 O ₄ or graphite or containing Fe 3 O ₄ , graphite or carbon black either singly or in admixture.

Pigments which are based for example on graphite flakes and at the same time have interference colors are commercially available as well as the so-called carbon inclusion pigments which have incorporated carbon in the carrier material and / or in a carrier layer. In addition, further interference layers, which usually consist of metal oxides, may be present.

Preferably, the red, green or blue

Combination pigments containing platelet-shaped pigments having a flake-form support made of natural or synthetic mica, S1O2, AI2O3 or glass, and an interference layer located on the carrier, the Fe3O. ₄ Optionally, one or more further interference layers may be included.

As a non-limiting example of suitable combination pigments, mention may be made of the combination pigments of the Rona Colorona® Blackstar series offered by Merck KGaA, namely Rona Colorona® Blackstar Red, Rona Colorona® Blackstar Green and Rona Colorona® Blackstar Blue. These are based on mica flakes that are on the

platelet-shaped carrier have a layer containing Fe3O ₄ .

The particle size of the combination pigments used is 1 -250 μιτι, in particular 5-100 μιτι and preferably 10-60 μιτι, with a thickness of the pigment platelets in the range of 0.1 to 5 μιτι. A particularly fine particle size distribution as in the interference pigments used in the first embodiment does not lead to improved printing results in the second embodiment of the present invention, but may be advantageous in the use of the combination pigments as a black absorption pigment in the first embodiment of the invention.

According to the second embodiment of the present invention, the red, green and blue printing ink are each color-pigmented exclusively with said combination pigments, the color being obtained here only by the corresponding interference colors. The concentration of the combination pigments in the respective printing ink is between 1 and 40 percent by weight and preferably between 5 and 35 percent by weight, in particular between 10 and 20 percent by weight, based on the total weight of the respective printing ink. The concentration of the combination pigments can be the same in each of the three printing inks or, if necessary, can also be set to different values.

Since the combination pigments partly a very strong black

Absorption and thus body color, in some cases, concentrations are required which do not exceed 15 wt .-% and advantageously in the range of 1 to 10 wt .-%, based on the total weight of the ink, are. Both in the first and in the second embodiment of the method according to the invention, the application of the three printing inks on the corresponding substrate (the substrate) takes place successively.

Each of the three printing inks consists of one

Ink vehicle, the corresponding interference pigment and a black absorption pigment (first embodiment) or from a printing ink vehicle and the corresponding combination pigment (second embodiment) together. Commercially available or generally customary printing ink vehicles which comprise at least one binder or binder system and frequently also solvents, if they are not radiation-curing binder systems, can be used as printing ink vehicles. Binders which can be used are the binders or binder systems customarily used for printing processes, for example aqueous or solvent-containing binders based on nitrocellulose, Polyamide-based, acrylic-based, polyvinyl butyral-based, PVC-based, PUR-based or suitable mixtures of these. It is important for the success of the printing process according to the invention that the corresponding binders or binder systems cure in a transparent and colorless manner so as not to obstruct or distort the optical effect of the interference pigments in interaction with the black absorption pigments or the combination pigments.

In addition to water, organic solvents may also be used, for example branched or unbranched alcohols, aromatics or alkyl esters, such as ethanol, 1-methoxy-propanol, 1-ethoxy-2-propanol, ethyl acetate, butyl acetate, toluene or mixtures containing them. However, the respective colored printing ink can also be poor or completely free from solvents when radiation-curing binder systems, such. As UV-curing binder systems can be used.

In addition to the binder or binder system and, if appropriate, the solvent (s), the ink vehicle may additionally contain various auxiliaries and / or additives in addition to the respective interference pigments mixed with black absorption pigments or the combination pigments.

UV stabilizers, inhibitors, flame retardants, lubricants, dispersants, redispersants, defoamers, leveling agents, film formers, adhesion promoters, drying accelerators,

Drying retardants, photoinitiators, etc. in question. Preferably, the respective ink vehicle contains all the necessary auxiliaries in liquid form, so that the optical effect of the interference pigments by

additional solids are not mitigated or otherwise impaired. For this reason, preferably in the finished colored inks neither (soluble) dyes nor other coloring

Pigments or solid fillers other than those necessary according to the invention red, blue or green interference pigments in combination with black absorption pigments or the red, green and blue combination pigments. The red, blue and green interference pigments described above are present individually or as a mixture of two or more in the colored printing inks used according to the invention. This means that, for example, a red printing ink either contains only a single type of red interference pigments or can also contain several different red interference pigments (several types), which have a formally identical, a similar or a mutually different layer structure on the same substrate or even may have on different substrates, but as a mixture meet the requirements described _{above in} terms of color angle h _u v and preferably also in terms of saturation value and chroma. As long as the conditions mentioned are adhered to and the interference pigments used have a high transparency as particles and are preferably colorless, the process according to the invention can be carried out successfully.

The described composition of the interference pigments in the respective colored printing ink of course applies in the same way as for the above-described red printing ink also for the blue or the green printing ink. In the printing method according to the invention, a red, a blue and a green printing ink, each with red, blue or green

Interference pigments in the mixture with black absorption pigments or with red, green or blue combination pigments are pigmented in color, applied successively in the form of printing surface units on a substrate and solidified. In this case, a printing surface unit is composed of a printing layer of one or more printing layers composed of two or three printing inks. Each of the individual Colored print layers may be separately solidified or the two or three print layers on a print area unit may be sequentially applied and consolidated together in a single process step.

According to the invention, the substrate can be virtually all

Substrates that can be printed by ordinary printing processes, ie to paper of various composition, cardboard, wallpaper, plastic films, plastic body, metal foils, metal body, textiles, ceramics and glass of various forms, wood or composites, which at least one of the aforementioned

Materials included. In this case, according to the invention, in addition to substrates having an opaque surface, even colorless transparent substrates, such as, for example, colorless, transparent plastic films, can be printed.

As such, the opaque substrates may have a light or white coloration, or may have primer or satinization layers that are light or white in color. Such bright or precoated substrates, in contrast to the method described in PCT / EP2016 / 000120, are particularly suitable for the method of the present invention because they provide sufficient contrast to the gray levels formed by the black absorption pigments or the black absorption color of the combination pigments hereinafter be explained. They are commercially available in great variety because these are usually in common printing processes

used printing materials is.

Preferably, the opaque substrates have a white or light color with an L ^* value (CIELUV) in the range of 60 to 100. These

Coloring of the substrate can, depending on the substrate material used and the intended use of the finished product, either by mass coloring of the substrate material, for example at Plastic films, or be obtained by coating the substrate with a white or light coating. The latter can be applied in addition or as an alternative to priming or satinizing layers. You can by the addition of conventional colorants to appropriate coating compositions, such as the addition of

White pigments such as ΤΊΟ2, BaSO ₄ or ZnO can be obtained.

Preferably, the entire surface of the opaque substrate to be printed is white or light or with such white or light

Coating may be provided, but white or light and transparent surface portions may also be present on the substrate or the substrate may be completely transparent.

Effects on the color design of the achievable print image also has the order of the order of the individual colored inks. Thus, it is particularly preferred according to the invention if the order of the printing inks to be applied to the substrate is as follows:

first printing layer: red printing ink with red interference pigments or red combination pigments,

second printing layer: green printing ink with green interference pigments or green combination pigments and

third printing layer: blue printing ink with blue interference pigments or blue combination pigments

(Order RGB). In the printing method according to the invention, the three colored printing inks are applied in the form of printing surface units on the substrate to be printed, wherein the printing surface units respectively printed with the individual colored inks next to each other or completely or partially, ie overlapping, are arranged. Only in the case of completely or partially overlapping printing surface units for the individual printing inks does the resulting printed image produce mixed colors which are composed of the red, blue and green interference pigments in combination with the black absorption pigments or from the red, green and blue combination pigments are formed in different compositions. Under pressure surface units are depending on the printing form to be used

Pressure points or printing surfaces understood that can take on different sizes and shapes, depending on whether it is a screen printing process or a printing process in which larger area units can be printed directly.

The printing method according to the invention can generally be applied to a wide variety of common printing methods and therefore also be carried out with conventional printing tools. Thus, it may be carried out as a conventional analog printing method such as a planographic printing method, a gravure printing method, a high-pressure printing method or a through-printing method, or as a digital printing method.

Under planographic printing process are in particular conventional or UV-curing offset printing process or dry offset printing process to understand that are performed without dampening solution. Gravure printing methods are, for example, packaging gravure printing, illustration gravure printing, decorative gravure printing or intaglio printing processes (intaglio printing). High-pressure processes are understood to mean a letterpress printing process, an indirect high-pressure process such as letterpress printing or the frequently used flexographic printing process. A well-known printing process is screen printing. Digital processes include inkjet printing, toner-based electrophotography or thermal transfer printing. All of these popular printing processes usually work in four-color printing according to CMYK color separation. Instead, the inventive The printing process can be applied to all mentioned printing processes in such a way that, instead of the customary cyan, magenta, yellow and black pigmented printing inks, the red, blue, green inks pigmented exclusively with interference pigments and black absorption pigments or with the said combination pigments are subsequently printed one after the other.

These result in the different color combinations, in particular when the pure interference pigments are used in admixture with black absorption pigments, namely likewise a yellow, cyan or magenta-colored printed image, in the combinations red / green-yellow, green / blue - Cyan and Blue / Red - Magenta.

Each of the printing methods described above permits in each case a maximum layer thickness of the resulting dry printing layer in a single printing operation. This is very different from printing process to printing process. Accordingly, the layer thicknesses of the individual printed layers in the printing process according to the invention 0.2 to 250 μιτι. However, it is understandable that with very low layer thicknesses of the individual printing layer only very few pigments are applied to the respective printing surface unit. Therefore, in these cases, to set a high area coverage, the printing step of transferring a single color ink to the substrate may optionally be repeated one or more times. The print layer thicknesses (dry layer thicknesses) for the individual printing inks are therefore preferably in the range from 0.4 to 80 μm, more preferably in the range from 0.6 to 10 μm, and in particular in the range from 1.0 to 5.0 μm.

A high area coverage of the individual printing surface units with the coloring pigments used according to the invention can additionally be achieved by the selection of the printing tools, for example by the screening of the printing rollers and / or the scooping volume of the cells be favored on the printing plates. However, such measures belong to the expertise of the printing expert and therefore need not be explained in detail here. The printing method according to the invention is preferably carried out such that each of the different printing inks is applied by means of the respectively same printing method, ie by means of similar printing tools. Although it is basically possible to use different printing tools for each of the different printing steps, this would unnecessarily complicate and increase the cost of the printing process.

The printing method according to the invention can be adapted to the most common analog and digital printing methods and can therefore be carried out with conventional printing tools. With only three colored inks, which are pigmented exclusively with interference pigments mixed with black absorption pigments or with combination pigments which have a black absorption color, in RGB mode it is possible to create optically variable printed images which, under at least one viewing angle, produce a color palette over the entire available range Color space can cover and give a completely different from the first print image in its color effect second printed image under a different viewing angle.

In addition, the printing method according to the invention can also be combined with conventional printing methods in CMYK mode, so that certain surface or print motif parts in the usual CMYK color division mode and parts of these or different other surface or print motif parts in the RGB substrate according to the invention on the same substrate. Mode can be printed. For the color design of surfaces in printing processes, this offers new, previously unattainable possibilities and effects. The present invention also provides a printed product which represents an optically variable printed image on a preferably white, light or colorless transparent substrate and is produced by the method described above.

Print products are referred to as optically variable if they have a markedly different color and / or gloss behavior at different viewing and / or illumination angles. The printed image according to the invention and thus the printed product containing the printed image shows at constant illumination angle, at a steep viewing angle (for example, in normal observation) either a very weakly colored appearance on a dark background or preferably a non-colored appearance in halftone quality, ie in different shades of gray.

At a viewing angle which is within the range of the gloss angle ± 30 degrees of angle (grd) (the glancing angle corresponds to the angle of incidence of the light beam reflected at an imaginary 90 ° line), however, the corresponding printed image has markedly improved color in rich, dark shades with increased gloss (second embodiment) or an impressively clear, opaque, bright colorfulness including possible yellow surface portions and a strong gloss (first embodiment) on. Since the optical effects in the first embodiment are surprisingly clear and spectacular, this embodiment of the method according to the invention is clearly preferred. The appearing in the glancing angle and in the range around the glancing angle colorful printed image according to the first embodiment of the present invention behaves optically as a printed with bright gloss, opaque platelet-like effect pigments (for example, with colored metal effect pigments) printed image, but has a far greater color variety than the latter, if this also just three different printing inks would have been produced. In addition, such a comparative printing image would also be colored when viewed in the normal, while the printed image according to the present invention has an extremely distinct color and gloss difference between the different viewing angles and each printed as with different inks, namely as exclusively with halftone-quality black pigments under at least one (preferably steep) viewing angle and with colorful luster pigments in a wide variety of colors and with high hiding power in the glancing angle and its surroundings.

In addition, the use of the above-described printed products in decorative or artistic products and in particular also in security products is the subject of the present invention. The above-described optical properties of the printed products according to the invention predestinate their use in decorative

Products of all kinds, which either themselves consist of the printed products according to the invention, such as advertising and commercial printing, or contain these, such as packaging for a variety of products and in a variety of designs. Since the printed products according to the present invention over hitherto in

Printing methods have not available optical properties, they are also suitable for use in the artistic field, for example for wallpapers, advertising prints, collages, calendars, textile coatings and much more.

In particular, the use of the invention provides

However, printed products in safety products of various kinds, since the novel process leads to optically variable printed images, which are commonly used in security documents in the previously known forms that show different bright colors under at least two viewing angles, in the but can not be faked here practically unknown and therefore difficult or impossible to fake.

Security products in which the optically variable printed products according to the present invention can be applied are, for example, banknotes, checks, passports, conditional documents, certificates, stock certificates, tax stamps, credit cards and other payment media, tickets, lottery tickets, gift certificates, stamps, tokens or brand logos just to name a few.

The printed products produced according to the invention have attractive optical properties which are not available on the market in this way and therefore make a valuable contribution to the expansion of the range of decorative and artistic products as well as the possible security features for security products.

Figure 1: shows the CIELUV color space (1976) with the neutral or

Anchor point E and the structure for determining color angles in this color space

The invention will be explained below by means of examples, but not limited to these. Example 1 :

1 a:

There will be a red, a green and a blue ink from a commercial printing ink vehicle for screen printing (Follmann

Aquascreen FS 10-931) was prepared by comparing the interference pigments mentioned below in the respective concentration with in each case 0.1 parts by weight of a black printing ink (Follmann Aquascreen FS-801; about 0.025 wt.% of Cl Pigment Black 7 in the ink)

Add ink vehicle and mix all ingredients intimately: Pyrisma® T30-21 Red 15 parts by weight

Pyrisma® T30-24 Green 12 parts by weight

Pyrisma® T30-23 Blue 9 parts by weight

(all figures refer to 100 parts by weight of the finished printing ink in each case)

On a white cardboard coated on both sides (Invercoat Creato from Iggesund), a standard screen (90 L / cm, 40 PW, mesh size 68 μιτι) is successively printed in this order in a motif dissected into the red-green-blue printing inks.

It is obtained a printed image, which at the same illumination angle at a steep viewing angle, a non-colored appearance (in gray halftone) with good contrast and tilting in the glancing angle a brightly colored, opaque, shiny colorful appearance in a variety of colors, which includes yellow pressure surfaces ,

1 b:

Example 1 a is repeated with the change that the respective

Printing inks, the black ink in a proportion of 0.5

Parts by weight (equivalent to about 0.125% by weight of C.I. Pigment Black 7 in the printing ink).

A printed image is obtained, which at a constant illumination angle at a steep viewing angle is a non-colored

Appearance (in gray halftone values) with very high contrast and when tilted in the glancing angle a high-contrast, brightly colored, opaque, colorful appearance in rich colors, with high gloss and in many colors, including yellow pressure surfaces. Example 2:

Aquascreen FS 10-931) by adding the combination pigments mentioned below in the respective concentration to the ink vehicle and intimately mixing all the constituents:

Colorona® Blackstar Red: 15 parts by weight

Colorona® Blackstar Green: 15 parts by weight

Colorona® Blackstar Blue: 15 parts by weight

On a white cardboard coated on both sides (Invercoat Creato of Iggesund) is successively with a conventional sieve (90L / cm, 40 PW, mesh 68 μιτι) in the printing inks red-green-blue decomposed motive of Examples 1 a and 1 b in printed in this order.

A printed image is obtained which, with the illumination angle remaining the same at a steep viewing angle, has a faintly colored appearance on a dark background with good contrast and when tilted in the gloss angle a clearly colored, opaque, slightly glossy appearance in colorful, dark colors. Yellow print areas can not be observed.

Claims

claims

Method for producing an optically variable printed image in RGB mode, wherein three colored printing inks are successively applied and solidified in the form of printing surface units on a substrate, characterized in that the printing inks each consist of an ink vehicle, which

a) each with red interference pigments, green

Pigments or blue interference pigments and a black absorption pigment is pigmented, wherein the ink vehicle further contains no further coloring pigments,

or

b) is pigmented in color only with combination pigments, wherein a printing ink in each case has red, green or blue combination pigments which have a red interference color, a green interference color or a blue interference color and in each case additionally a black absorption color, and wherein of the three colored printing colors side by side and or superimposed pressure surface units are formed which give at least at a first viewing angle a colorful total pressure image, which is different from a second total pressure image, which appears under at least a second viewing angle.

A method according to claim 1, characterized in that the overall color printed image comprises yellow printing area units formed by successively applying the printing ink containing red interference pigments and the printing ink containing green interference pigments to the substrate. A method according to claim 1 or 2, characterized in that the red, green or blue combination pigments are in each case platelet-shaped pigments which have a

platelet-shaped carrier and at least one on the carrier located interference layer, wherein either the carrier or the at least one interference layer or both consist of Fe3O ₄ or graphite or Fe3O ₄ , graphite or carbon black either individually or in a mixture.

A method according to claim 3, characterized in that the red, green or blue combination pigments are platelet-shaped pigments comprising a platelet-shaped support of natural or synthetic mica, S1O2, Al2O3 or glass and an interference layer on the support, the Fe3O ₄ contains.

Process according to Claim 1 or 2, characterized in that the black absorption pigment is particulate Fe 3 O ₄ , particulate Fe 3 O ₄ -based pigments, particulate graphite, particulate carbon black or a combination pigment with a black absorption color.

A method according to claim 5, characterized in that the particulate carbon black is carbon black.

Method according to one or more of claims 1 to 6, characterized in that it is the black

Absorption pigment to particulate Fe3O ₄ , based on particulate Fe3O ₄ pigments, particulate graphite or particulate carbon black and the weight fraction of the black absorption pigment in the with red, green or blue interference pigments

pigmented colored printing ink each 0.001 to 1, 5 wt.%, Based on the weight of the respective printing ink is.

8. The method according to one or more of claims 1 to 5, characterized in that it is the black

Absorption pigment to a combination pigment with a

is black absorption color and the proportion by weight of the black absorption pigment in the colored with red, green or blue interference pigments colored ink each 5 to 30 wt.%, Based on the total weight of interference pigment and combination pigment.

9. The method according to one or more of claims 1 to 8,

characterized in that the red, green or blue

Interference pigments each of transparent, colorless,

platelet-shaped supports coated with one or more layers of transparent, colorless materials.

10. The method according to one or more of claims 1 to 9,

characterized in that the red, blue and green

Interference pigments have a particle size in the range of 1 to 45 μιτι and a dgo value of <40 μιτι.

Method according to one or more of Claims 1 to 10, characterized in that the substrate is a transparent colorless substrate or an opaque substrate having a surface which has an L ^* value (CIELUV) in the range of 60 to 100 , acts.

A method according to claim 1 1, characterized in that it is the substrate to a plastic film, a plastic body, glass, ceramics, a paper, a cardboard, a wallpaper, a

Metal foil, a textile, wood or a composite material containing at least one of said materials.

13. The method according to one or more of claims 1 to 12, characterized in that it is the non-colored halftone printed image at the appearing under at least a second viewing angle total print image.

14. The method according to one or more of claims 1 to 13, characterized in that it is in the first

Viewing angle by an angle in the range of gloss angle ± 30 angular degrees (grd) acts.

Comprises 15. Process according to one or more of claims 1 to 14, characterized in that the red interference pigments have a hue angle h _and v, which to a hue angle h _u v green interference pigments a distance in the range from 90 to 160 degrees of angle (degree) , Wherein the hue angle is determined in each case from a separate, full-area coating on a black substrate under the measurement condition 45 as 25 ° of a printing ink, which is exclusively with the respective

Interference pigment is pigmented. 16. The method according to one or more of claims 1 to 15, characterized in that it is a planographic printing method, a gravure printing method, a high-pressure method, a through-printing method or a digital printing method. 17. The method according to one or more of claims 1 to 16, characterized in that each of the printing inks with a

Dry film thickness in the range of 0.2 to 250 μιτι is applied.

18. Printed product, produced by a process according to one or more of claims 1 to 17. Use of a printed product according to claim 18 decorative or artistic products or in

Security products.