EP2325010B1 - Method for determining characteristics of a printed material - Google Patents

Description

The invention relates to a method for determining properties of a printed substrate according to the preamble of claim 1.

From practice it is known, for controlling a printing process, for example for color control, to measure substrates printed in a printing machine with the aid of a measuring device and thus metrologically to detect properties of the printed substrate, based on the metrologically recorded properties of the printed substrate to regulate the printing process. Among the properties of the printed substrate to understand the interaction of the substrate with the ink applied to the same, with the interaction of the substrate with the ink applied to the same many printing conditions of the printing process influence.

In this case, the measuring device which is used for measuring the printed substrate, be integrated into the printing press to measure the printed substrate inline to the printing process in printing press speed. Alternatively, it is possible that the measuring device is installed on the printing press in order to measure the printed substrate online for the printing process but not in printing press speed. Regardless of whether the printed substrate is not measured in line with the printing process at press speed or online during the printing process at press speed, the metrologically recorded properties are made accessible to the printing process.

From the EP 2 033 789 A2 is a method for determining colorimetric properties of a printed substrate known, said after this Method using an inaccurate, designed as a colorimeter measuring device relative color readings and an accurate, also designed as a colorimeter measuring device absolute color readings are detected, and wherein by means of the measured values of the accurate colorimeter calibration of the inaccurate colorimeter can be made. Since both the exact colorimeter and the inaccurate colorimeter can provide colorimetric color readings, both colorimeters are based on the same measurement principle.

From the DE 10 2006 014 657 B4 a method for color control of a printing press is known in which two measuring devices are used, which are based on different measuring principles. By means of a density measurement-providing measuring device designed as a densitometer, the setting of inking units takes place in a set-up phase of the printing press. For color control, the printed substrate is measured in the continuous printing operation of the printing press by means of a measuring device designed as a camera, which provides colorimetric measured values. Based on the camera's colorimetric readings, the inking settings made on the density readings of the densitometer can be adjusted to improve color control.

Out EP 0 408 507 A1 A method for determining the chromaticity differences between two printed by a printing press grids and a method for color control or color control of the printing of a printing press is known. In this case, grids, preferably gray balance fields, are scanned with the aid of a densitometer. The grid density differences resulting from comparative measurements are transformed by means of an experimentally determined transformation matrix into colorimetric differences of an equidistant graded color space, so that on the one hand the advantages resulting from a quality assessment in a true color measurement system instead of a densitometric measurement system can be utilized Use of control strategies is possible, which is a color measurement system, such as the L * a * b * system or the LUV system. The transformation matrix is determined experimentally by generating a reference gauge pressure as well as several additional gauge prints, each having a gray balance field and three solid tone fields. At each additional calibration pressure, the layer thickness of another solid field is increased. By detecting color metric differences and halftone density differences and inserting them into a system of equations indicating the relationship between the halftone density differences and the color metric differences, the elements of the transformation matrix describing the relationship between halftone density changes and associated colorimetric changes can be determined.

Out US 5,182,721 A is a method for inking control in a printing press, a suitably equipped printing system and a measuring device for such printing plants known. To improve the color control of an offset printing machine provided on the sheet color fields are not evaluated as previously densitometric, but colorimetric by spectral measurement. To adjust the color, spectral reflections are used or color coordinates are calculated and compared with corresponding target reflections or desired color coordinates. The resulting color differences are used to control the color guide. For the stabilization of the output, the spectral reflectances are converted into filter color densities, and the color guide is conventionally based on these color densities.

Out EP 0 143 744 A1 For example, there is known a method and apparatus for evaluating the print quality and / or control of ink guide in an offset printing machine and an offset printing machine equipped with a corresponding apparatus. The scanning of the signatures takes place immediately after the last printing unit. The signatures are scanned pixel by pixel with one or more measuring heads. On each pixel, the reflectance is measured in four spectral regions (infrared for black, red for cyan, green for magenta, and blue for yellow). The measured remission values are based on the Neugebauer equations in area coverings converted (unmasked) and fed to a computer for evaluation. Both the setpoint values (OK arc) and the actual values (continuous pressure) are measured with the same measuring device. The computer compares the measured data, weighting them according to the area coverage, foreign color content and environment of the respective picture element and provides per zone and color a control signal for controlling the color guide. From the area coverage values of the four colors, the color coordinates (X, Y, Z) can be determined for each picture element in a parallel calculation process. With this method, it is possible to control on-line color guide of a multicolor printing machine without using a colorimeter by direct measurement in the printed image.

On this basis, the present invention is based on the problem to provide a novel method for determining properties of a printed substrate.

This problem is solved by a method for determining properties of a printed substrate according to claim 1.

According to the invention, at least one second property of the printed substrate is determined on the basis of the or each metrologically detected by the measuring device first property under access to a database, which is not metrologically detectable with the measuring device to the or each second property as well as the or each first Property to the printing process.

With the method according to the invention, it is possible, on the basis of the measured values of a measuring device based on a defined measuring principle, to determine properties of the measured printed substrate by accessing a database, which metrologically measures the measuring device based on the measuring principle of the measuring device can not be recorded. This makes it possible to reduce the number of measuring devices used in the printing process.

Fig. 1

eine Bogendruckmaschine zur Verdeutlichung des erfindungsgemäßen Verfahrens zur Bestimmung von Eigenschaften eines bedruckten Bedruckstoffs.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

Fig. 1

a sheet-fed printing machine to illustrate the method according to the invention for determining properties of a printed substrate.

The invention relates to a method for determining the properties of a printed substrate in a printing press. With reference to Fig. 1 the method according to the invention is described by way of example on a sheet-fed printing press in which sheet-shaped substrates are printed. However, the invention can also be used in web-fed printing presses in which a web-shaped printing material is printed.

Characteristics of the printed substrate to understand the interaction of the substrate with the ink applied to the same, wherein the interaction of the substrate with the ink applied to the same, the printing conditions of the printing process influence.

Fig. 1 schematically shows a sheet-fed press 10, a feeder 11, a boom 12, a plurality of positioned between the feeder 11 and the boom 12 printing units 13 and 14 and two coating units 15 includes. The printing units 13 are used for printing a first side of a printing material to be printed and the printing units 14 for printing a second side of the printing material to be printed, wherein between the printing units 13 and the printing units 14, a turning device 16 is positioned. According to Fig. 1 the sheet-fed press 10 is associated with a measuring device 17, by means of which in the illustrated embodiment, a printed substrate between the printing units 14 and the coating units 15 can be measured.

The measuring device 17 is based on a defined measurement principle and based on this measurement principle, at least a first property of the printed substrate metrologically capture and make the printing process accessible, such as displaying the or each first property on a control station 18 of the printing machine 10th

For the purposes of the present invention, it is proposed to ascertain at least one second property of the printed substrate on the basis of the or each measurement property detected by means of the measuring device 17, wherein the or each second access to the database 19 is determined Property with the measuring device 17 can not be detected metrologically.

The or each property detected based on the database 19 and the or each first property may be made accessible to the printing process along with the or each first property, such as for display on the control station 18 of the printing press.

Accordingly, it is within the meaning of the present invention to measure printed substrates printed by means of a measuring device 17 based on a defined measuring principle and thus to metrologically determine at least one first property of the printed printing material. Furthermore, on the basis of the or each metrologically determined first property, access to the database 19 is used to determine at least one second property of the printed printing material which can not be measured by the measuring device 17 on the basis of its measuring principle. The or each first property, as well as the or each second property, are made accessible to the printing process, such as displaying the properties on the control room 18 and / or storing the properties in the control room 18 or other storage medium not shown and / or for control and / or regulation of the printing process.

In the database 19 are with another, in Fig. 1 stored or used measured values not shown, based on a second measuring principle based on which then or by means of the or each detected by the first measuring device 17 first property or each second property is determined.

Accordingly, the measuring device 17, by means of which the or each first property is determined metrologically, and the second measuring device, whose measured values are incorporated into the database 19, are based on different measuring principles.

Based on the or each property detected by means of the measuring device 17, at least one second characteristic for the printed product can be determined with reference to the database 19 in which or in which measured values recorded with the further measuring device based on the second different measuring principle are stored which can not be measured by measuring device 17.

According to a first development of the invention, the measuring device 17 based on the first measuring principle, by means of which the or each first characteristic of the printed product is detected metrologically, is a colorimetric and / or spectral measuring values-providing color measuring device. In this case, the measuring device based on the second measuring principle, whose measured values flow into the database 19, is then designed as a densitometer providing density readings, which records the density measured values either with a polarizer or without a polarizer.

According to a second, alternative development of the invention, it is also possible that the measuring device based on the first measuring principle, by means of which the or each first characteristic of the printed product is detected metrologically, is a densitometer-providing densitometer which operates with polarizing filter or without polarizing filter. In this case, the measuring device based on the second measuring principle, the measured values of which flow into the database 19, is listed as a colorimetric and / or spectral measuring value-providing measuring device.

The measuring device 17, which is based on the first measuring principle and metrologically detects the printing material during the printing operation of the printing machine, is integrated in the printing machine 10 in such a way that it records the or each first characteristic of the printed printing material inline to the printing process in printing press speed and the printing process.

In this case, the or each on the basis of the or each metrologically detected first property under access to the database 19 determined second property is then determined inline to the printing process in press speed and made accessible to the printing process.

Alternatively, however, it is also possible for the measuring device 17, which is based on the first measuring principle and serves for the metrological detection of the or each first property of the printing material, to be installed on the printing machine, but not the same or any first characteristic online with the printing process captured at press speed and made accessible to the printing process.

In this case, the or each on the basis of the or each metrologically detected first property under access to the database 19 determined second property is not determined online for printing process in press speed and made accessible to the printing process.

Then, if a database 19 is accessed in order to determine the or each second property, which can not be measured by the measuring device 17, based on the or each metrologically detected first property, reference data of printed substrates are stored in the database 19.

In this case, both reference measured values are stored in the database 19, which are recorded using a measuring device 17 based on the first measuring principle, and reference measured values which are recorded on the same printing substrate with a further measuring device (not shown) based on the second, different measuring principle.

When determining the reference measured values, it is not necessary to use the measuring devices of the printing press exactly; instead, identical measuring devices based on the respective measuring principles can be used.

In doing so, the reference measured values, which are recorded with the measuring devices based on different measuring principles, as well as any variables derived therefrom, are correlated with each other. Preferably, the database 19 is then continuously updated, namely continuously expanded and / or changed.

The reference measured values stored in the database are reference measured values which are stored for different types of printing materials and / or different printing inks and / or different printing ink types.

It is thus possible to store corresponding reference measured values in the database 19 for substrates of different thicknesses and different quality. It is likewise possible to store corresponding reference measured values in the database 19 for the process colors of the autotypic compression, ie for the process colors cyan, magenta, yellow and black.

Furthermore, corresponding reference measured values can be stored in the database for process colors from different manufacturers, that is to say for different types of printing inks.

Furthermore, corresponding reference measured values can also be stored in the database 19 for the unprinted printing material.

Then, when accessing a known per se model 20, which is not part of the present invention, to determine based on the or each metrologically determined first property at least a second property for the printed substrate, are via the model 20 from the metrological acquired first properties, the second properties calculated or derived. In this case, in contrast to the procedure with the database 19, no reference measurements with both measuring devices based on different measuring principles of the identical printed substrate are required.

Rather, using a model 20, it is possible to proceed in such a way that when, for example, a density is measured as the first characteristic with a measuring device 17 designed as a densitometer, the associated reflectance spectrum is determined for a particular printing substrate / ink combination. The determination of the reflectance spectrum corresponding to the density value can take place, for example, by physical modeling of the layer thickness, the layer thickness being iteratively changed in infinitesimal steps until the measured density is reached. Alternatively, the layer thickness can also be determined in mathematically closed form. From the remission spectrum thus determined, the calculation of color values can be carried out, whereby the standard color values and, therefrom, other color values (such as CIELAB or DIN99) can be calculated from a remission spectrum on the one hand via the standard spectral value curves. This applies to other spectral value curves in the same way for other color values.

In addition, on the basis of the model 20, a conversion of remission spectra into spectra with polarizing filters or vice versa can be carried out, if densities are to be determined or are given, which are measured with polarizing filters. The conversion of spectra measured with polarizing filters into spectra measured without polarizing filters can be done by empirical methods or techniques, such as in DE 10 2004 040 621 described, done.

Similarly, by accessing a model 20 as second properties, density values may be determined from a color value measured as a first property, since the filter characteristics as well as the standard spectral value curves are standardized. The remission spectrum can be used to establish a relationship between density values and colorimetric values. A color value is thus clearly associated with a specific substrate-ink combination on the remission spectrum a density and vice versa.

As already stated, if a model 20 is accessed in order to determine at least one second property for the printed substrate based on the or each first characteristic measured, the or each second property is calculated via the model from the metrologically recorded first properties or derived. The model 20 has parameters which are theoretically derived on the basis of system-dynamic or system-theoretical modeling and / or determined on the basis of measured values. The measured values are obtained using a measuring device based on a different measuring principle to the measuring device 17 based on the first measuring principle. However, these are not the reference measured values on the identical printed substrate needed for the database solution.

The parameters of the model 20 are determined for different types of substrates and / or different inks and / or different types of ink in advance once per print job or once per substrate type ink-type combination and can, for. B. be deposited in a memory on the same then if necessary to access.

LIST OF REFERENCE NUMBERS

10

Sheetfed

11

investor

12

boom

13

printing unit

14

printing unit

15

coating unit

16

turning device

17

measuring device

18

control station

19

Database

20

model

Claims (9)

1. A method for determining characteristics of a printed material, wherein a printed material is either measured by means of a measuring device, which is based on a first measuring principle, inline to the printing process in printing press speed or online to the printing process not in printing press speed, to detect at least a first characteristic of a printed printing material by measurement and to make it accessible to the printing process, characterized in that, based on the or each first characteristic detected with the help of the measuring device by measurement with access to a database, at least a second characteristic of the printed printing material is determined, which cannot be detected by means of the measuring device by measurement, in order to make the or each second characteristic as well as the or each first characteristic accessible to the printing process, and
   that measuring values detected by means of a further measuring device, which is based on a second measuring principle, are stored in the database, based on which the or each second characteristic is determined with the help of the or each first characteristic,
   wherein reference measuring values of printed printing materials are stored in the database, namely both reference measuring values, which are detected by means of a measuring device, which is based on the first measuring principle, and reference measuring values, which are detected on the same printing material by means of a further measuring device, which is based on the second measuring principle.
2. The method according to claim 1,
   characterized in
   that the measuring device, which is based on the first measuring principle, with the help of which the or each first characteristic is detected by measurement, is a measuring device, which provides colorimetric and/or spectral measuring values, and that the measuring device, which is based on the second measuring principle, the measuring values of which are stored in the database, is a densitometer, which provides density measuring values with or without pole filter.
3. The method according to claim 1,
   characterized in
   that the measuring device, which is based on the first measuring principle, with the help of which the or each first characteristic are detected by measurement, is a densitometer, which provides density measuring values with or without pole filter, and that the measuring device, which is based on the second measuring principle, the measuring values of which are stored in the database, is a measuring device, which provides colorimetric and/or spectral measuring values.
4. The method according to one of claims 1 to 3,
   characterized in
   that the measuring device, which is based on the first measuring principle, is integrated into the printing press in such a way that the or each first characteristic is detected inline to the printing process in printing press speed and is made accessible to the printing process with said printing press, wherein the or each second characteristic is then also determined in printing press speed and is made accessible to the printing process based on the or each first characteristic detected by measurement.
5. The method according to one of claims 1 to 3,
   characterized in
   that the measuring device, which is based on the first measuring principle, is installed on the printing press in such a way that the or each first characteristic is detected by means of said measuring device online to the printing process not in printing press speed and is made accessible to the printing process, wherein the or each second characteristic is then also not determined in printing press speed by accessing the database and is made accessible to the printing process.
6. The method according to one of claims 1 to 5,
   characterized in
   that the reference measuring values, which are detected by means of the measuring device, which is based on the first measuring principle, and the reference measuring values, which are detected by means of the further measuring device, which is based on the second measuring principle, as well as variables, which are possibly derived therefrom, are correlated with one another.
7. The method according to claim 6,
   characterized in
   that the database is updated continuously.
8. The method according to one of claims 6 or 7,
   characterized in
   that reference measuring values for different printing material types and/or different printing inks and/or different printing ink types are stored in the database.
9. The method according to one of claims 1 to 8,
   characterized in
   that the or each first characteristic, together with the or each second characteristic, is made available to the printing process in such a way that the or each first characteristic and/or the or each second characteristic is in particular displayed and/or stored and/or used to control and/or regulate the printing process at a control station.

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