METHOD FOR INK CONTROL IN A PRINTING PRESS

Abstract

The ink in a printing press is controlled during a printing process in which an opaque ink is printed onto a substrate in a first printing unit and a transparent ink is printed onto the opaque ink in a second printing unit. An optical density value of the transparent ink is ascertained by a detection device for the transparent ink printed onto the previously printed opaque ink. A film thickness of the transparent ink is set at the second printing unit by a control unit that detects the optical density value of the transparent ink as a function of the film thickness of the opaque ink, or as a function of an optical density value of the opaque ink, so that the optical density value of the transparent ink corresponds to a target value set at the control unit for the transparent ink, and considering a transparent ink tolerance range.

Claims

1-13. (canceled)

14. A method for ink control in a printing press, comprising, during an ongoing printing process, an opaque ink (02) being printed onto a print substrate (01) in a first printing unit (06), and subsequently a transparent printing ink (03) being printed onto the opaque ink (02) in a second printing unit (07), a. at least one actual value of the optical density of the opaque ink (02) being ascertained by a first detection device (08), configured as a densitometer, for the opaque ink (02) printed onto the print substrate (01); b. a film thickness of the opaque ink (02) to be applied onto the print substrate (01) being set at the relevant printing unit (06) by a control unit (11) detecting the at least one actual value of the optical density of the opaque ink (02), as a function of a previously ascertained value of the optical density of the surface of the unprinted print substrate (01), in such a way that the at least one actual value of the optical density of the opaque ink (02) detected by the first detection device (08) corresponds to a target value set at the control unit (11) for the opaque ink (02), taking a tolerance range defined in the control unit (11) for the opaque ink (02) into consideration; c. at least one actual value of the optical density of the printing ink (03) being ascertained by a second detection device (09), configured as a densitometer, for the printing ink (03) printed onto the previously printed opaque ink (02); and d. a film thickness of the printing ink (03) to be applied onto the opaque ink (02) being set at the printing unit (07) printing the printing ink (03) by the control unit (11) which also detects the at least one actual value of the optical density of the printing ink (03), as a function of the film thickness of the opaque ink (02) previously applied onto the print substrate (01) or as a function of the actual value of the optical density of the opaque ink (02), in such a way that the at least one actual value of the optical density of the printing ink (03) detected by the second detection device (09) corresponds to a target value set at the control unit (11) for the printing ink (03), taking a tolerance range defined in the control unit (11) for the printing ink (03) into consideration.

15. The method according to claim 14, characterized in that the dependence of the film thickness of the printing ink (03) to be applied onto the opaque ink (02) on the film thickness of the opaque ink (02) previously applied onto the print substrate (01), or the dependence of the film thickness of the printing ink (03) to be applied onto the opaque ink (02) on the actual value of the optical density of the opaque ink (02), in each case consists of a relationship between the target value of the film thickness of the printing ink (02) to be applied and the actual value of the film thickness of the opaque ink (02), or of a defined relationship between the target value of the optical density of the printing ink (03) and the actual value of the optical density of the previously applied opaque ink (02).

16. The method according to claim 14, characterized in that opaque white or a non-transparent ink in one of the color shades encompassing gold or silver is used as the opaque ink (02), and that a process ink in one of the color shades encompassing cyan or magenta or yellow or black is used as the printing ink (03) or that a Pantone ink or another transparent specialty ink is used as the printing ink (03).

17. The method according to claim 14, characterized in that at least two, and up to four, opaque inks (02) and/or at least two, and up to ten, printing inks (03) are applied onto the print substrate (01) by different printing units (06; 07), each of these printing units (06; 07) in each case applying a single one of the opaque inks (02) onto the print substrate (01) and/or in each case applying a single one of the printing inks (03) onto one of the opaque inks (02).

18. The method according to claim 14, characterized in that an opaque ink (02) is used that is lighter than the surface of the print substrate (01) to be printed, and lighter than the printing ink (03) to be applied onto the opaque ink (02).

19. The method according to claim 14, characterized in that the ink control of the opaque ink (02) and the ink control of the printing ink (03) are in each case carried out in conjunction with a control, carried out by the control unit (11), of at least one zone opening in an inking unit associated with the printing unit (06) of the opaque ink (02), or an inking unit associated with the printing unit (07) of the printing ink (03).

20. The method according to claim 14, characterized in that printing units (06; 07) that print according to an offset printing method are used.

21. The method according to claim 14, characterized in that a sheet-format print substrate (01) or a web-format print substrate (01) is used and/or that a print substrate (01) made of paper or a plastic material or metal is used.

22. The method according to claim 14, characterized in that a control console comprising an operating unit (12) and a display device (13) is used as the control unit (11).

23. The method according to claim 14, characterized in that the method is activated at the control unit (11) by selecting the print substrate (01) to be printed during an upcoming printing process from a set of print substrates (01) stored in the control unit (11).

24. The method according to claim 14, characterized in that a printing press comprising a turning device for the print substrate (01) is used as the printing press, the method being activated at the control unit (11) by selecting the relevant print substrate (01) in each case individually from a set of print substrates (01) that are stored in the control unit (11) for the two sides of the print substrate (01) to be printed in the upcoming printing process.

25. The method according to claim 14, characterized in that the tolerance range defined in the control unit (11) for the target value of the optical density of the respective opaque ink (02) or the respective printing ink (03) is in each case defined based on the printing unit and across print jobs.

26. The method according to claim 14, characterized in that the at least one opaque ink (02) is applied in the same printing operation together with the at least one printing ink (03) in a printing press comprising a plurality of printing units (06; 07), or that the at least one opaque ink (02) is applied in the relevant printing press in a printing pass preceding the printing operation applying the at least one printing ink (03), or that the at least one opaque ink (02) is applied onto the print substrate (01) in a printing press that differs from the printing press applying the at least one printing ink (03).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] An exemplary embodiment of the invention is illustrated in the drawings and will be described in greater detail below. The drawings show:

[0015] FIG. 1 a layer structure of a printing ink applied onto an opaque ink; and

[0016] FIG. 2 a schematic representation of the ink control.

DETAILED DESCRIPTION

[0017] FIG. 1, by way of example, shows a layer structure of a printing ink 03 applied onto an opaque ink 02 in a drastically enlarged sectional illustration, wherein the opaque ink 02 is applied onto a print substrate 01. In reality, at least the respective ink films of the opaque ink 02 and printing ink 03 applied onto the print substrate 01 in general are less than 0.1 mm, wherein the film thicknesses of the different inks can differ and are subject to fluctuations during the printing process. The print substrate 01 used is a sheet-format print substrate 01 or a web-format print substrate 01, made in each case of any material, e.g., made of paper or a plastic material or metal. The sheet-format print substrate 01 is in particular configured as a foil. The print substrate 01 can also be configured to be transparent. Opaque white or another non-transparent opaque color, i.e., thoroughly covering the backing, in particular the print substrate 01, for example in one of the color shades encompassing gold or silver is preferably used as the opaque ink 02. Preferably, opaque inks 02 without optical brighteners are used. The printing ink 03 used is preferably a process ink in one of the color shades encompassing cyan or magenta or yellow or black. These process inks are generally in each case embodied as a transparent printing ink 03, i.e., as a printing ink 03 forming, in contrast to an opaque ink 02, a translucent ink film, wherein the respective color shade of the applied ink film is not created until a color filter-like effect that is translucent to impinging light is achieved. It is also possible, e.g., to use a Pantone ink or another transparent specialty ink, i.e., a printing ink 03 having a color shade deviating from the process colors, as the printing ink 03. Daylight inks or luminous inks or fluorescent inks or mica inks or gloss finishes or matte varnishes or textured inks are not used as printing inks 03 in the method described here. The at least one opaque ink 02 can be applied onto the relevant print substrate 01 in the same printing operation together with the at least one printing ink 03 in a printing press comprising multiple printing units, e.g., in an inline configuration, or in the relevant printing press in a printing pass preceding the printing operation applying the at least one printing ink 03, or even in a printing press that differs from the printing press applying the at least one printing ink 03.

[0018] In the proposed method for controlling the color in a printing press, an opaque ink 02 is printed onto the print substrate 01 in a first printing unit, and subsequently a transparent printing ink 03 is printed onto the opaque ink 02 in a second printing unit, during an ongoing printing process. In the process, an opaque ink 02 is used that is lighter than the surface of the print substrate 01 to be printed, and lighter than the printing ink 03 to be applied onto this opaque ink 02. It may be provided that at least two, and up to four, opaque inks 02 and/or at least two, and up to ten, printing inks 03 are applied onto the relevant print substrate 01, e.g., in the same printing press by its printing units, or by the relevant printing units if different printing presses are used, wherein each of these printing units in each case applies a single one of the opaque inks 02 and/or in each case applies a single one of the printing inks 03 onto the print substrate 01. Preferably, printing units that print according to an offset printing method are used. The printing press applying the at least one transparent printing ink 03 onto the surface of the print substrate 01 comprises a control unit, wherein in particular a control console of this printing press comprising an operating unit and a display device is used as the control unit. The color control of the printing ink 03, if necessary also the color control of the opaque ink 02, are in each case carried out in conjunction with a control, e.g., carried out by the control unit, of at least one zone opening in an inking unit associated with the printing unit of the relevant printing ink 03, or an inking unit associated with the printing unit of the relevant opaque ink 02. The measurement and control of printing inks 03 on opaque inks 02 are preferably carried out inline and online.

[0019] For the opaque ink 02 printed by one of the printing units onto the print substrate 01, at least one actual value of the optical density of this opaque ink 02 is preferably ascertained inline, i.e., in the relevant printing press, by a first detection device. The optical density of the opaque ink 02 can be detected as needed or periodically or continuously. The first detection device can also, e.g., detect a sequence of actual values of the optical density of this opaque ink 02, wherein, e.g., a mean value is calculated from this set of actual values by the control unit, and the color control is carried out using this mean value. The first detection device arranged in the relevant printing press is, e.g., configured as a densitometer or is at least suitable for carrying out a densitometric measurement. A definition range of the value of the optical density of the opaque ink 02, e.g., of opaque white, applied onto the print substrate 01 preferably ranges from zero to 3, wherein a possible number of places after the decimal point following the nominal value is generally two. A typical normal value is 2.00, e.g., a maximum, e.g., being 2.50 (very white), and a minimum, e.g., being 0.00. The higher the nominal value of the optical density of the opaque ink 02, the lighter or whiter it appears, in particular in relation to the surface of the print substrate 01 to be printed.

[0020] A film thickness of the opaque ink 02 to be applied onto the relevant print substrate 01 during the further course of the printing process is set at the relevant printing unit by a control unit detecting the at least one actual value of the optical density of this opaque ink 02, as a function of a previously ascertained value of the optical density of the surface of the unprinted print substrate 01, in such a way that the at least one actual value of the optical density of this opaque ink 02 detected by the first detection device corresponds to a target value set at this control unit for this opaque ink 02, taking a tolerance range defined in the control unit for this opaque ink 02 into consideration.

[0021] For the printing ink 03 printed onto the previously printed opaque ink 02, at least one actual value of the optical density of this printing ink 03 is preferably ascertained inline, i.e., in the relevant printing press, by a second detection device. The optical density of the printing ink 03 can be detected as needed or periodically or continuously. The second detection device can also, e.g., detect a sequence of actual values of the optical density of this printing ink 03, wherein, e.g., a mean value is calculated from this set of actual values by the control unit, and the color control is carried out using this mean value. The second detection device arranged in the relevant printing press is, e.g., configured as a densitometer or is at least suitable for carrying out a densitometric measurement. A definition range of the value of the optical density of the printing ink 03 applied onto the opaque ink 02 preferably ranges from zero to 3, wherein a possible number of places after the decimal point following the nominal value is generally two. A typical normal value is 1.50, e.g., a maximum, e.g., being 2.50 (very dark), and a minimum, e.g., being 0.00. The higher the nominal value of the optical density of the printing ink 03, the darker or more color-intensive it appears in relation to the previously applied opaque ink 02.

[0022] A film thickness of this printing ink 03 to be applied onto the opaque ink 02 during the further course of the printing process is set at the printing unit printing this printing ink 03 by the control unit that also detects the at least one actual value of the optical density of this printing ink 03, as a function of the film thickness of the opaque ink 02 previously applied onto the print substrate 01 or as a function of the actual value of the optical density of the opaque ink 02, in such a way that the at least one actual value of the optical density of this printing ink 03 detected by the second detection device corresponds to a target value set at the control unit for this printing ink 03, taking a tolerance range defined in the control unit for this printing ink 03 into consideration.

[0023] The dependence of the film thickness of the printing ink 03 to be applied onto the opaque ink 02 on the film thickness of the opaque ink 02 previously applied onto the print substrate 01, or the dependence of the film thickness of the printing ink 03 to be applied onto the opaque ink 02 on the actual value of the optical density of the opaque ink 02, in each case in particular consists of a relationship, previously defined in the control unit, between the target value of the film thickness of the printing ink 03 to be applied and the actual value of the film thickness of the opaque ink 02, or of a defined relationship between the target value of the optical density of the printing ink 03 and the actual value of the optical density of the previously applied opaque ink 02. This definition can, e.g., consist in that the color control, carried out by the control unit during an ongoing printing process in the relevant printing press, is aimed at maintaining the actual value of the optical density of the opaque ink 02 at 2.00, taking into consideration a permissible tolerance range previously defined for this opaque ink 02 in the control unit, and at maintaining the actual value of the optical density of the printing ink 03 at 1.50, taking into consideration a permissible tolerance range previously defined for this printing ink 03 in the control unit, so that the actual value of the optical density of the printing ink 03 is always, e.g., 75% of the actual value of the optical density of the opaque ink 02, despite permissible fluctuations, which are inevitable during the printing process, in the respective ink film thicknesses applied onto the print substrate 01, and thus also in the detected actual values of the optical densities. As a result of such a definition, the dependence of the optical effect of the printing ink on the film thickness of the opaque ink 02 previously applied onto the print substrate 01 is taken into consideration during a color control of the printing ink 03 carried out during an ongoing printing process in the relevant printing press.

[0024] The tolerance range defined in the control unit for the target value of the optical density of the respective opaque ink 02 or of the respective printing ink 03 is preferably in each case defined based on the printing unit and across print jobs. The control unit is provided with LAB values, but not with optical densities for each job. The control unit converts the job-based LAB values into values of the optical densities.

[0025] This method is activated at the control unit, e.g., by selecting the print substrate 01 to be printed during an upcoming printing process from a set of print substrates 01 stored in the control unit. When a printing press comprising a turning device for the print substrate 01 is used as the relevant printing press, this method is activated at the control unit, e.g., by selecting the relevant print substrate 01 in each case individually from a set of print substrates 01 that are stored in the control unit for the two sides of the print substrate 01 to be printed in the upcoming printing process.

[0026] The color of the respective opaque ink 02 or the respective printing ink 03 can in each case be controlled, e.g., using a color measurement strip printed onto the print substrate 01.

[0027] FIG. 2 shows a color control, e.g., in a printing press comprising several printing units, e.g., in a printing press printing a print substrate 01 in the form of a material web, i.e., a web-fed printing press, in a drastically simplified schematic representation. An opaque ink 02 is printed onto the print substrate 01 in a first printing unit 06, and a transparent printing ink 03 is printed thereon in a second printing unit 07, in the transport direction T through this printing press. The printing units 06; 07 are, e.g., each configured as an offset printing unit. In the transport direction T of the print substrate 01, a first detection device 08, e.g., in the form of a first inline densitometer, is arranged downstream from the first printing unit 06, and a second detection device 09, e.g., in the form of a second inline densitometer, is arranged downstream from the second printing unit 07. The first detection device 08 transmits the at least one value, detected thereby, of an optical density of the opaque ink 02 applied onto the print substrate 01 to a control unit 11. Likewise, the second detection device 09 transmits the at least one value, detected thereby, of an optical density of the printing ink 03 applied onto the print substrate 01 to the control unit 11. The control unit 11 is equipped with an operating unit 12 and a display device 13. The control unit 11 is also provided with order-based LAB values, which the control unit converts into values of optical densities. The control unit 11 is preferably a control console of this printing press. The control unit 11 activates the first printing unit 06 and the second printing unit 07 in such a way that the above-described method for color control is carried out in a printing press. Even though a bidirectional data exchange is possible between most components of the color control system, the directional arrows in FIG. 2 indicate the signal direction that is primarily required for carrying out the color control.

[0028] Although the disclosure herein has been described in language specific to examples of structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described in the examples. Rather, the specific features and acts are disclosed merely as example forms of implementing the claims.