ES2290263T3 - PROCEDURE TO CONTROL A PRINTING PROCESS IN HUECOGRABADO. - Google Patents

Abstract

Color jump pick-up procedure for the control and / or control of monochrome or polychrome printing of a gravure printing process with a control strip or a control block containing an arrangement of control fields, characterized in that the control strip or the control block contains a control field (10) of color evolution in the form of a weft field (11) as a strip of a primary color, reproducing the control field (10) of the evolution of the color, in all its longitudinal extension, an evolution of the tone values that constantly increases or decreases according to nominal values, and means for indicating the nominal values (12) of the tone values, and because the nominal value of the tone value corresponding to the degree of surface coverage when a plot field flood (11) occurs is determined with the aid of the indicating means n.

Description

Procedure to control a process of gravure printing.

The present invention concerns a method according to the preamble of claim 1.

In gravure printing concentration color (relative composition of printing inks based on ink concentrate, mixture and solvent) is one of the parameters most important to be controlled. It influences so decisive in the process color supply, as well as in the quality of color and tone of the printing product. The color concentration in turn depends on the nature of the substrate to print on which a sensation should be generated of certain color. Quality is valued today in a way practically exclusive through sight and with the help of densitometers

The quality check is carried out with help of control strips or control blocks that are made up each of them from an arrangement of control fields.

The layout of several control fields is called control strips or control blocks. Per control strip It is understood according to DIN 16527, part 1, March 1993, a One-dimensional juxtaposition of control fields. Analogously to this, a control block is a two-dimensional arrangement of control fields There are control strips printed on a single color or intended for printing in a single color, as well as control blocks printed in various colors or intended for multicolor print. The control strips that are intended exclusively to the control, command or regulation of printing, especially called print control strips, and the strips of control that serve exclusively to monitor the copying is They are especially called copy control strips, while the strips that can serve both purposes are called only control strips

The control field is defined according to DIN 16527, part 1, a surface on which they are arranged for testing purposes one or more image elements; these last they can be, for example, plot points, lines or full tones. The term control field refers to DIN 16527, part 1, a a test surface that has been transferred to a material flat carrier (for example, a sheet) directly in shape visible, regardless of whether the information was presented previously stored in analog form (for example, movie) or digital (for example, magnetic memory, optical disk).

The control strips and the control blocks are used for visual control or for the metrotechnical control of copying and printing processes, for example for printing test or print run on printing machines according to Early flat printing, gravure printing, the Embossed printing or transpress.

Another application of such control means is the command or regulation of printing during production. The first application can be done both after an assessment visual as after a metrotechnical assessment of one or more control fields, and the last application can only be made after a metrotechnical evaluation. To this end, according to the state of the technique, densitometers or measuring devices of color, such as spectral photometers. Both devices capture the optical energy reflected by a printed control field.

The control fields planned for the metrotechnical and / or visual evaluation consist of a pitch field complete, that is, a printed surface in its entirety or intended for full-length printing, or a field hatched, that is, a surface resolved at points or lines of printed plot or intended for printing. Both tones complete as raster tones can be applied in a single Color or in various colors. It is said that a control field is applied in several colors on the substrate to be printed when has obtained him for the superimposed printing of several inks of Print. Overlay printing here means an impression on the that different color printing inks have been applied on the same surface. How printing inks are understood here layers of pigment that are transferred, for example as suspensions, by means of a printing machine, to the substrate to be to print.

The printing inks whose segments generate the primary colors used for multicolored printing, by example black (K), cyano (C), magenta (M), yellow (Y) in the four-color printing, they are called printing inks of scale.

A first category of control fields includes the control fields applied in various colors for the visual assessment or measurement, such as, for example, the fields of full tone of the secondary colors blue, green, red and the tertiary black color, which have been generated by printing superimposed of the chromatic primary colors (CMY), as well as the gray balance fields.

The gray balance fields are according to DIN 16527, part 1, weft fields applied in various colors in the that the color densities of the printing inks involved they are in a numerical relationship such that an impression produced in unaltered average printing conditions appears as achromatic for the eye, that is to say that it appears in neutral gray. From one minimum observation distance, fields cannot be distinguished from printed gray balance with achromatic appearance regarding raster fields that are printed only with the color of achromatic print black (K).

Another category of control fields is formed the monochromatically applied control fields of the inks of scale printing (CMYK), as well as eventually the inks of special printing. These control fields make possible the control of the optical density and color place of the inks of cited scale printing or printing inks special, for example by means of densitometers.

The geometry of the control fields is in general such that its form is adapted to the usual form of measuring spots of deintometers and other reflectometers. By therefore, they are rectangular in the case of measuring devices with elliptical and square, circular or hexagonal measuring spot in the case of circular measuring spots.

The state of the art reveals numerous procedures already matured for the verification of results of printing using control strips or control blocks before mentioned. However, these procedures refer to predominantly to offset printing procedures, as well as to paper printing, which are subdivided for them in classes according to specific guidelines.

However, in the packaging sector faces one with a large number of packaging materials that They have very different surfaces to print. Such surfaces they can be, for example, paper, plastic, metal or coatings ceramic

However, the different surfaces of substrate decisively influence color transmission from the printing form to the substrate.

In gravure printing the sites of impression are located deeper in the form of impression that sites with no printing. The ink of impression to apply is then located in the depressions of impression, the so-called plot wells. Plot wells are mutually delimited by the so-called partitions or partition walls that are located higher and, by consequently, they do not carry printing ink. In halftone images raster wells arranged in a hatched manner have a step size. In the printing process the ink is transferred in the printing area from the plot wells to the substrate to be printed.

It is known that in printing images plotted by the gravure procedure the elements of color, from a certain tone value, also called degree of color coverage or color coverage value, tend to flow on the substrate to be printed and to flood the surface of the substrate, thereby adjusting a higher pitch value than the which is planned according to the nominal value. The sharp increase in tone value caused by surface flooding of impression should not be confused with the so-called increase in value of tone. The increase in the tone value certainly indicates the magnitude which has the surface coverage on the substrate printed with with respect to the nominal value, for example based on a model, but based on increasing the size of the color elements on the printed substrate compared to the model and you can present in all degrees of surface coverage without abrupt variations

If a plot plot with magnification is considered Continuous tone values according to the nominal value, is presented then at a given tone value a so-called color jump, that is, a sharp increase in the degree of surface coverage. He color jump can be attributed to the aforementioned flood of the raster surface, that is to say that the color elements applied begin to flow into each other and join with each other, the intermediate spaces produced are filled with printing ink by partitions or partition surfaces.

When the hatched model is constituted, by example, for points, applications at points begin to merge with one another from a degree of coverage surface determined and color prints are formed between points, so that the intermediate spaces of color are covered completely with printing ink, producing at the same time a sharp increase in the degree of surface coverage. Therefore,  an additional increase in tone values above the range flooding acts only still on the color density, as it increases the thickness of the ink layer.

As a consequence, tone values prefixed and transposed to the printing form, called values Nominals in this text are difficult to achieve in the range of a Color break of this class. For this reason, it is desirable to capture and locate the color jump to be able to influence so corresponding about the printing process. Given that the appearance of the color jump depends very strongly on the nature of the substrate to be printed and the printing ink as well as of different process parameters, the problem of the jump of color can only be attacked individually for each process of Print.

Control strips or control blocks of the prior art also offer the disadvantage that the verification of the optical density (color density) of the different primary colors are only possible by calibrating the fields Monochrome control (full tone field) of colors primary by means of densitometers. Consequently, for reasons cost, color densities cannot be monitored continuously in print run by the method of Measure mentioned above. However, it is desirable to continuously monitor the color densities of the primary colors with the most cost reduced possible, so that, in case of discrepancies, they can calibrate immediately, with a view to error determination, Monochrome control fields of primary colors (CMY)

They are known by the documents DE-A 43 38 976 and US-A-4 310 248 procedures of control and / or command of polychrome printing of a procedure gravure printing with a control strip or a block of control that contains an arrangement of control fields.

The invention is based on the problem of improve the arrangement of control fields of a strip of control or a control block for a printing procedure in gravure with respect to materials or substrates to be printed very different, making this provision possible to capture a color jump in the range of the tone value. In a development further of the problem a field arrangement will also be proposed  of control that allows the control of the density values of the primary colors.

According to the invention, the problem is solved by means of a procedure with the characteristics of the claim 1.

The nominal value of a tone value is adjusted here to the plot field effectively engraved on the cylinder of Print.

The means to indicate the nominal values of tone values in the frame field preferably comprise a scale of tone values assigned to the frame field at the edge longitudinal lateral of the control field of the evolution of the color.

The evolution of the nominal values of the degrees of surface coverage is preferably linearly increasing or decreasing. The plot field preferably presents a plot of points.

The evolution of the nominal values of the Pitch values in the frame field are preferably reproduced for the range of 0% to 100%. Since the critical tone value, in which the cited color jump is presented, it may be located in a respective similar range of tone values for a class of substrates to be printed, you have to, for this kind of Substrates, can also be printed as a control field only a certain segment of the range of tone values from 0-100%.

For this reason, the reproduction of evolution of the nominal values of the tone values in the field of frame may be limited especially to the range of values of tone of 50% to 100% and advantageously at the range of 70% to 100%.

The color evolution control field allows to continuously determine or control the color jump in the section field visually or with the help of a device measure and assign this jump to a specific tone value (value nominal) by means of the scale of tone values laterally ready. In knowledge of this critical tone value, you can deliberately remove a range of tone values beforehand  in the print model, for example during the preparation of the Print.

The nominal value of the tone values obtained with the method according to the invention, in which the control jump, can be transferred to a treatment process image to make corresponding corrections.

The control strip or the control block it also contains, in a preferred embodiment variant, fields Multi-zone control, each with a first and a second partial control fields, where

(to)

the first partial control fields are chromatic fields of gray balance resulting from the superimposed printing of the primary colors cyano (C), magenta (M) and yellow (Y) in values stepped tone from 0 to 100% and

(b)

the second partial control fields are achromatic plot fields black (K) in staggered tone values from 0 to 100%,

and the pitch values of the fields first and second partial control of a control field of multiple zones have been chosen so that the control field of multiple zones appear as a unit tone surface and the two partial control fields of a multiple control field areas are directly contiguous and splicing one with other.

Therefore, monitoring the densities of Primary color (CMY) color is done through fields of gray balance control, verifying the constancy of these not in a calibrated way densitometrically, but visually by the comparison with the adjacent plot fields of black color achromatic. Therefore, the constancy of the fields of gray balance and not the way they behave separately different primary printing colors (CMY).

Partial control fields first and second of a multi-zone control field present preferably matching color values, that is, a matching color feeling.

The multi-zone control fields substantially represent the gray axis structure of, by on the one hand, CMY primary colors and, on the other hand, black (K)

The multi-zone control fields are preferably divided into two parts. They are willing too contiguous preferably in the order of tone values increasing or decreasing, preferably directly and splicing with each other, the balance fields being arranged gray so that they are contiguous to each other on an axis and the achromatic black weft fields being arranged so that are contiguous to each other on an axis.

The multi-zone control field is preferably rectangular or square. However, it can also appear in a circle or ellipse form or have a polygonal structure, for example hexagonal.

The subdivision of the multiple control field zones in a first and a second partial control fields can be done in any desired way. However, the subdivision should be such that a direct visual comparison is possible of the first partial control field with the second control field partial multi-zone control field.

The multi-zone control field can be subdivided, for example, into a core zone and a zone of edge as partial fields, being sized preferably the core zone such that it can be calibrated with a color measuring device. In the core zone gray balance fields may be arranged, for example and preferably the achromatic black raster fields.

The multi-zone control field is preferably presents in a rectangular or square shape and is subdivided into two rectangular partial control fields of, to If possible, the same size.

In a preferred embodiment the control strip or the control block also contains an arrangement of fields control in the form of monochrome weft fields of colors CMY primaries with stepped tone values of preference evenly from 0 to 100%. That is to say that for each primary color set a control field for a given number of values of tone in the range of 0 to 100%.

The multi-zone control fields and / or the Monochrome raster fields of primary colors (CMY) contain preferably each of them a multiple control field zones or a control field as a full tone field (100%)

The monochrome control fields mentioned above of the primary colors (CMY), as well as the fields of gray balance and therefore black raster fields achromatic, are advantageously set for tone values 5%, 20%, 40%, 60%, 80% and 100%, 100% corresponding to a field of full tone

The control fields of the different colors Primary (CMY) are preferably arranged in the order of degree of increasing or decreasing surface coverage of preference contiguous directly and splicing with each other.

The gray axis set from black (K) it is considered as a reference for the CMY gray axis (fields of gray balance) with respect to color density at certain tone values (taking into account the increase in the tone value). When the visual comparison of the two partial control fields throws marked differences, that is to say that the balance fields of Gray contain a tint of color, it can be deduced that there is a divergence in color densities of colors primary (CMY). This divergence may be based, by for example, in an altered acceptance of one or more inks of printing (CMY).

When such divergences arise, you can compare in a next step, by means of a densitometer, the Color densities of full tone control fields (100%) of the primary colors (CMY) and you can compare these densities with nominal values.

Consequently, the provision of fields of control allows continuous (visual) density monitoring CMY primary color color during printing runs, without having to re-measure permanently individually the color densities of CMY primary colors.

Through continuous verification of the fields gray balance can ensure a timely readjustment of the inking or ink supply cylinders.

The substrate to be printed is preferably a sheet, especially a flexible packaging sheet. The sheet of Packaging can be transparent or opaque translucent and / or it can be dyed superficially or dyed from part to part. The sheets of Packaging may contain colored, spectral surface layers or metallized and may have surfaces with optical effect of color, mirror and / or metallization.

Printable packaging sheets can be monolamines or composite sheets. Packing sheets can contain or comprise layers or sheets of plastic, such as polyolefins, polyesters, polypropylenes, polyamides or metals, such as aluminum, iron, steel or alloys thereof, or of celluloses, such as paper, parchment or cellophane.

The surfaces to be printed may consist, by example, in one of the papers, plastics or metals mentioned above. Also, the surface to be printed can be a coating ceramic.

The thickness of the packing material can be, for example, 5 to 1000 µm, especially 7 to 200 \ mum.

The color densities of the different colors primary (CMY) of the gray balance fields are preferably adapted to the optical and / or mechanical properties of the substrate to be printed. For this reason, the Color densities of primary colors (CMY) must be set in advance to establish the balance fields of Gray.

In a first step an impression of testing of a test form, for example an IT test form 8.7 / 3 according to ISO 300. The test print is made on the same substrate class as subsequent print run. TO then the test form is measured by means of a photometer spectral. On the basis of the measured test form, it is established a so-called ICC (International Color Consortium) entry profile. This means that the measured device values are converted in the color space L * a * b independent of the device.

Based on the measured test form, it then determine the L * a * b values of the gray values of achromatic black. Then, based on the profile of ICC input CMY gray values are calculated for values corresponding gray of achromatic black. The values obtained they are taken as the basis for subsequent printing of runs.

Next, the invention is explained with more detail by way of example and with reference to the drawings attached. They show:

Figure 1, color control fields Primary (CMYK) with integrated gray balance fields;

Figure 2, a field of evolution control of the color with continuous evolution of the tone value from 0 to 100%; Y

Figure 3, multiple control fields areas with partial control fields of the primary black color achromatic (K) and gray balance.

Figure 1 reproduces an arrangement Especially advantageous of control fields of a control strip.  Control fields with reference symbols 1 to 4 represent monochrome weft fields of the primary colors CMYK with different color tones. Reference symbols 1 are refer to control fields of the cyano primary color (C), the reference symbols 2 refer to color control fields magenta primary (M), reference symbols 3 refer to Control fields of the yellow primary color (Y) and the symbols of reference 4 refer to partial fields of color control primary achromatic black (K). The letters a to f represent values of different tone, representing a tone value of 100%, b of 80%, c of 60%, d of 40%, e of 20% and f of 5%. Therefore, the reference number 2e refers to the number 2 and the letter e a a magenta primary color control field (M) with a degree of 20% surface coverage. The control fields described are arranged adjoining and splicing with each other.

Control fields 4 of the primary black color correspond in this embodiment to half of a field of control 6 of multiple zones, which corresponds in size to the Control fields 1, 2, 3 of the primary colors (CMY). He second partial control field is occupied by the fields 5 chromatic gray balance. Partial control fields are arranged so that a gray balance field 5 is always faces a plot field 4 of achromatic black color with The same feeling of color. For the sake of clarity, it has included in figure 1, by way of example, only the symbol of reference of the control field 6f formed by the fields of partial control 4f and 5f.

This arrangement allows visual control of the gray balance fields in direct comparison with the fields of achromatic black weft, which represent the values of reference. When the printing process runs correctly and color reproduction is not altered, the two fields of opposite control should always leave the same behind feeling of color However, when the balance fields of gray deviate from the achromatically black plot fields, they you have to continue measuring by means of a densitometer the color density of primary colors in control fields 1st, 2nd, 3rd full tone to detect possible divergences of color densities.

Of course, it can also be done any other desired staggering of the tone values. Also, the staggering of the tone values can be varied with additional control fields or by deletion of control fields. In addition, the magnitude and the nature of the subdivision of the two control fields parts However, it has been seen that it is advantageous that the fields of control of multiple zones correspond to the size of the fields of primary color control (CMY).

Figure 3 reproduces the control fields 6 of multiple zones with partial control fields 4 and 5 according to the description of figure 1.

Figure 2 shows a control field 10 of the color evolution with a weft field 11 of strip form. He weft field 11 of strip form reproduces linear evolution - constant according to nominal values - of the tone values from 0 to 100% For reasons of space, Figure 2 represents only one fragment of such control field 10 of the color evolution.

Next to the strip-shaped weft field 11 a scale of values 12 is arranged with the corresponding nominal values of the tone values in percentages. He staggering or resolution of the scale of values can be arbitrary. In the present embodiment it has been found to be advantageous set pitch values in pitch widths of 3% each of they.

The arrangement allows to visually detect or with a measuring device the color jump in frame field 11 strip shape and assign the color jump to the tone value corresponding on the basis of the corresponding data of tone value indicated to the side.

The control strip or the control block can also contain other control fields, such as control for secondary colors red, gray, blue, resulting of the overlay printing of the primary colors (CMY) and the black (K), achromatic weft fields with a tone value of 50% with different patterns, such as plot of points and plot of lines, a Siemens star to verify the resolution and / or a field of record to verify the record offset.

Claims (3)

1. Color jump pick-up procedure for the control and / or control of monochrome or polychrome printing of a gravure printing procedure with a control strip or a control block containing an arrangement of control fields, characterized because the control strip or the control block contains a control field (10) of color evolution in the form of a weft field (11) as a strip of a primary color, reproducing the control field (10) of the evolution of the color, in all its longitudinal extension, an evolution of the tone values that constantly increases or decreases according to nominal values, and means for indicating the nominal values (12) are assigned to the field of strip form (11). ) of the tone values, and because the nominal value of the tone value corresponding to the degree of surface coverage when a plot field flood (11) occurs is determined with the aid of the indicating means ion. Method according to claim 1, characterized in that the means for indicating the nominal values (12) of the tone values comprise a scale of tone values associated with the weft field (11) on a lateral longitudinal edge of the control field (10) of the evolution of color. Method according to claim 1 or 2, characterized in that the nominal value obtained (12) of the tone value is transferred to an image processing process to make corresponding corrections.