WO2002100644A1

WO2002100644A1 - Method for selecting printed materials

Info

Publication number: WO2002100644A1
Application number: PCT/EP2001/006580
Authority: WO
Inventors: Bernhard J. Lattner
Original assignee: Gutjahr, Alexander
Priority date: 2001-06-11
Filing date: 2001-06-11
Publication date: 2002-12-19

Abstract

The invention relates to a method for representing and selecting printed materials and the technical printing properties thereof, in addition to a method for selecting the various printing methods for printing in colour printing machines. Prior to the actual printing in the colour printing machines, a computer (1) stores information relating to the types of printed materials and the printing properties thereof and displays said information on a monitor (2) which cooperates with said computer (1). The graphic colour image to be printed is digitally entered according to the various printing methods and colours and the properties thereof, and displayed on the monitor (2). By means of an input keyboard (3), which is connected to the computer (1) and the monitor (2), the type of printed material and the printing method are selected in order to represent a simulated proof on the monitor (2).

Description

Process for the selection of substrates

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

Many customers of printed products are surprised when they see their printed product on the substrate, preferably paper, because the color of the printing ink changes dramatically on certain papers. The surprise also extends to the color brilliance, which comes into play differently for certain papers, for example if these papers have not been surface-treated, i. H. if they have not been finished and the screen dot cannot be fully occupied due to the surface quality.

From DE-A1-196 27 459 a method for controlling a printing press is known, in which the printed image carrier web printed after passing through a four-color printing device with four colors (C, M, Y, K) is scanned by a scanner for generating image signals is converted into color measurement values in a control device and then compared with target values. Adjustment signals resulting from this comparison then set color adjustment devices of the printing device to correct the print image and, if necessary, display on a monitor whether the correction can lead to the desired print image result at all.

In this known method, a specific, selected print image carrier web is inserted into the printing press. If it turns out that the desired print image cannot be reached with the inserted web, another web must be inserted and a new proof must be made, and so on. Such a trial procedure is very time consuming and costly. DE-C2-44 31 270 discloses a method for measuring the color density of a print image grid point for controlling the color guidance of a printing press. With this method, too, the measured values are obtained from real proofs.

DE-A1-43 35 143 discloses a method and a device for converting color values, in which an image is processed using tables and the processed image can be output on a color monitor and a proof recorder. In this document, the method for transporting color values is taken up, but the method does not take into account the color space of the substrate, which was selected by a graphic artist well in advance of printing, but which has a decisive influence on the printing process and the printing result compared to the layout on the monitor.

EP-A2-0 063 286 A2 describes a method for the representation of

Color values in CMYK colors (cyan, magenta, yellow, black) after conversion from the monitor display RGB (red, green, blue).

It takes into account the color space of an image document in RGB as well as in CMYK for conventional printing, but not the color space of the substrate.

A method (apparatus) in the scanning process, namely redigitizing offset films, is described in US Pat. No. 4,393,398.

EP-B1-0 255 128 describes a method for an instant camera.

The documents EP-A3-0 392 814, DE-A1-197 24 171 and DE-C2-44 31 270 describe methods for color control in rotary machines.

The document DE-A1-196 27 459 describes a method for color control in digital printing machines. US 5 212 546 describes a method for calibrating a DTP workflow. Here, a reference picture is taken and compared using the method or rather adapted to the circumstances.

US 5 606 432 discloses a method for simulating a halftone print on a monitor and for output as a simulation on a printer. This is a common proofing process.

The US 5 333 069 describes a calibration method for proofers, since some output devices work in RGB color space and others again in CMYK and thus due to the differently used colors, such as. B. Ink for inkjet printers and printing ink in offset, different color impressions arise. Here, too, a neutral (white) background is assumed, which is very rarely the case in conventional printing. The substrate is not taken into account here for display on the monitor either.

The method for determining the color appearance disclosed by DE-A1-197 01 967 ensures that certain color values can be embedded in an ICC profile and the database can thus be optimized. However, the color space of the substrate is not taken into account.

In all known methods, only the transport of the color values in closed workflows is dealt with and the implementation on the output devices is always based on a white background.

The US Pat. No. 5,606,432 mentioned attempts to simulate a print on a monitor, but only by taking a print into account. However, the display and visualization on a monitor can only be promising be, even if the paper to be printed is not only shown in its color, but also in its structure.

The idea of the substrate on the monitor with its properties (color, structure,

Color behavior etc.) and the overlying print image and its effects on the substrate is not taken into account in these known publications.

DE-A1-97 01 967 mentioned takes into account, among other things, the printing density and the latents of a printing ink, but only in connection with a raster print and according to the calculation basis of Neugebauer. However, no solution to a calculation in surface pressure is proposed here either.

The object is to create a method according to the preamble of claim 1, which enables the definition of various printing parameters in advance of the later, real printing and thereby avoids real proofs and their costs.

This object is achieved with the feature of claim 1.

This creates a possibility to show the effects on a specific printing material, in particular paper, and to prepare them in consideration of the respective printing process, for example an offset, gravure, screen or flexo printing, for example with regard to the printing characteristic, gradation and Glazing behavior of printing inks that an optimal printing result is achieved. On the other hand, the user can also be shown that it is not feasible to produce the printed product according to his ideas using the selected printing material. It is important for the present invention that any printing material is also digitally recorded in advance and that a test print must be carried out. Only then can densitometry be evaluated and the character trait taken into account. The best example is reflected in the finest papers. 111

The basic idea of the invention is essentially to enable a color comparison in advance of the subsequent, real print on a monitor, since a red, green and blue (RGB) display on the monitor has different results than the conventional CMYK print, for example in offset -, gravure or screen printing, reproduces (the abbreviation CMYK stands for the basic colors cyan, magenta, yellow and the contrast color black). This is related, among other things, to the color emission (additive color mixing and subtractive color mixing).

The invention makes it possible to display different printing materials, such as different types of paper, plastics, textiles, wood, stone, metal or coatings, and their printing properties, which have been determined by printing, on the monitor, in order to achieve a preselection of the different printing processes, and at the same time to create a real representation on the monitor that simulates the later printed product.

A further, expedient development of the method provides that the types of printing material are recorded photographically and slides are created therefrom and that the slides are then scanned by means of a scanner and the digitized sample values are entered into the computer. Here they are available to the user to select substrate types for a print product on the computer

According to a further embodiment of the method, a conventional printing of a test form on a specific printing material carries out densitometric evaluation of the color image on the printing material to be simulated for the later ICC profile. This evaluation can thus advantageously be used further. According to a further embodiment of the method, the input keyboard and the monitor are used to carry out a visual color comparison of the monitor display with the conventional pressure, with the incorporation of the densitometric evaluation. A simple correction of the color image is therefore possible.

According to a further embodiment of the method, an ICC profile is created after the color matching and stored on a storage medium. You can always use these ICC profiles.

According to a further advantageous embodiment of the method, the ICC profile stored on the storage means can be integrated into the graphic color image and can be displayed on the monitor. As a result, the user's database is optimally prepared for printing using the substrate-specific ICC profile.

The invention will now be explained in more detail on the basis of a schematic diagram for the method.

In the middle of the figure, a computer 1 is connected to a 21 ^" monitor 2 and an input keyboard 3. This monitor and this input keyboard are shown again at the bottom right of the figure.

Digitized data about the types of printing material and their printing properties are entered into the computer 1 in the following way: The paper types a indicated by a box 4 are recorded photographically in accordance with arrow 5 in a conventional manner and created as slides b in box 6. The slides b are scanned by means of a scanner 7, and the scanned values are digitized in accordance with arrow 8 and stored as paper image ac in box 9 and fed from there to computer 1 in accordance with arrow 10, in which they are stored. This image document ac can be displayed on the monitor 2 using the input keyboard 3.

On the other hand, a box 11 symbolizes digital, graphic color image documents f according to printing processes and thus according to printing inks and their properties. Shafts according to the arrow 12 fed to the computer 1 and displayed together with the image documents ac on the monitor 3.

A specific representation ac + f on the monitor 2 can then be selected by means of the input keyboard 3 and used to represent a simulated pressure g on the monitor 3. This simulated proof refers, for example, to a conventional offset printing on paper type a indicated by the arrow 13 and a printing press 14. With conventional pressure g, a sitometric evaluation is carried out according to standard values from FOGRA. Conventional pressure g and densitometric evaluation are indicated by a box 15. The pressure g is required in order to be able to carry out a visual comparison on monitor 2. Furthermore, the density range of the pressure g is measured with the aid of a densitometer, in order to be able to create a pressure characteristic curve, which in turn is required to create an ICC profile, as will be explained.

After viewing the color image of the proof g on the monitor 2 using the input keyboard 3, a color comparison can now be carried out in accordance with the arrow 16, the densitometric evaluation being incorporated and then an ICC profile S being produced on the selected paper a. Color matching and ICC profile creation are indicated by a box 17. Then, according to arrow 18, a CD can be produced using a corresponding device 19, which embeds the substrate profiles in the existing ICC__ workflow.

From box 17, an ICC profile i can also be integrated into a graphical color image document according to arrow 20 and displayed on monitor 2. The integration takes place by means of a programmed tool.

The term ICC profile is generally known in specialist circles. The name ICC stands for the "international Color Consortium", a committee made up of representatives of leading hardware and Software vendors. This committee has drawn up a platform-independent ICC device profile format which contains the information about colorimetric characterization values

te of the respective devices. These ICC profiles are independent of their creation program, so that they can be used on any ICC-compatible device. According to arrow 21 coming from monitor 2 and arrow 22 coming from box 15, a softproofing method S and a representation g simulated on monitor 2 are therefore created, as indicated by box 23, with which a selection of printing methods and their properties, printing colors and their properties and substrates and their properties are possible before the real proof.

The advantages of the presented method are summarized again:

- optimization of the individual printing processes,

- pre-selection for printing implementation on the monitor,

- Selection of specific printing processes that allow the optimum quality (color behavior) to be achieved on the selected substrate and

- Optimization of the database with regard to the selected substrate using ICC profiles.

Claims

Expectations:

1. A method for the selection of substrates and their properties and for optimizing the printing method for printing in color printing presses, characterized in that, before being printed on the color printing machine, the types of the printing substrate and its printing properties are stored in a computer (1) and on a monitor (2) and, on the other hand, the graphic color image to be printed is entered digitally according to various printing processes and thus according to printing inks and their properties and is displayed on the monitor (2) and that the type of substrate is used by means of an input keyboard (3) connected to the computer and the monitor and the printing method for displaying a simulated proof (15) on the monitor (2) is selected.

2. The method according to claim 1, characterized in that the substrate types are photographically recorded (4) and slides (6) are created therefrom and that the slides are then scanned by means of a scanner (7) and the digitized samples are entered into the computer (1) ,

3. The method according to claim 1 or 2, characterized in that with the conventional pressure of a test form on a specific printing material, a densitometric evaluation of the color image on the printing material to be simulated is carried out for the later ICC profile (15).

4. The method according to claim 3, characterized in that by means of the input keyboard (3) and the monitor (2) a visual color matching of the conventional proof (15) takes place with the incorporation of the densitometric evaluation. Method according to Claim 4, characterized in that an ICC profile is created after the color matching and is stored on a storage means (19).

A method according to claim 5, characterized in that the ICC profile stored on the storage means (19) can be integrated into the graphic color image and can be displayed on the monitor (2).