Method for setting the layer thickness of a covering coating material to be applied to a substrate by an application device

Abstract

A method is provided for setting a layer thickness of a covering coating material to be applied to a substrate by an application device. The coating material is applied to the substrate in a printing machine or in a paper-processing machine. The coating material is applied at various points on the substrate by the use of the application device in a machine process. At each of at least one first point on the substrate, the coating material is applied in a grid having a plurality of grid points, and at each of at least one other second point on the substrate, the coating material is applied over the full area. Each first point on the substrate forms a grid zone and each second point on the substrate forms a solid zone. A control unit connected to a sensing device determines respective values of the optical density of the layer of the coating material applied on the points on the substrate using data captured by the sensing device at the first and second points on the substrate. The control unit defines the layer thickness of the coating material currently applied to the substrate by the application device in an ongoing machine process. At the defined thickness, the value of the optical density determined in a grid zone corresponds to the value of the optical density determined in a solid zone, as the layer thickness of the coating material having an opacity of 100%.

Claims

1. A method for setting a layer thickness of a covering coating material to be applied to a substrate by an application device including: applying the covering coating material to the substrate one of in a printing machine and in a paper-processing machine; the covering coating material being applied at least to first and second points on the substrate using the application device in a machine process; applying the covering coating material at at least one of the first points on the substrate, the covering coating material being applied to the at least one first point in a grid having a plurality of grid points; applying the covering coating material at at least one of the second points on the substrate, the coating material being applied to the at least one of the second points over a full area of the at least one of the second points, wherein each first point on the substrate forms a grid zone and each second point on the substrate forms a solid zone; using a control unit and a connected sensing device for determining a value for an optical density of the layer of the covering coating material applied at the first and second points on the substrate using data captured by the sensing device at the first and second points on the substrate and provided to the control unit; using at least one covering printing ink as the covering coating material, and wherein the covering printing ink is formed as one of a primary color and as an opaque white and as a metallic color; using the sensing device for continually collecting the measured values of the covering coating material applied to subsequent ones of the substrate during an ongoing operation of the one of the printing machine and the paper-processing machine, wherein the application of the covering coating material onto subsequent ones of the substrate using the application device during the ongoing operation of the one of the printing machine and the paper-processing machine is monitored continually with the sensing device during the ongoing production, and wherein the control unit stipulates and controls a layer thickness of the covering coating material applied to the subsequent ones of the substrate by the application device in the ongoing operation, at which stipulated and controlled layer thickness a value (DR) for an optical density determined in a grid zone corresponds to a value (DV) for an optical density determined in a solid zone, as a layer thickness of the covering coating material having an opacity of 100%.

2. The method according to claim 1, wherein the control unit sets the layer thickness of the coating material, which is to be applied to at least one further substrate by the application device in the ongoing operation, such that the layer of the coating material to be applied to the at least one subsequent substrate, with the application device, has the opacity of 100% in the further ongoing operation of the one of the printing machine and the paper-processing machine.

3. The method according to claim 1, wherein, for defining the layer thickness of the covering coating material having the opacity of 100%, the control unit stores one of currently provided operating data and control data of the application device in a storage device in association with the opacity of 100% for the layer thickness of the coating material.

4. The method according to claim 1, characterized in that wherein the control unit sets the respective value (DR) for the optical density determined from a grid zone in relation to the respective value (DV) for the optical density determined from a solid zone, and defines the layer thickness of the covering coating material currently being applied to the substrate by the application device in the ongoing operation, as the particular layer thickness of the covering coating material having the opacity of 100% when the control unit determines a significant change in one of a course and a behavior of this relationship in a series of several sequential collections of the optical densities.

5. The method according to claim 1, further including providing a measuring strip having several measuring fields on the substrate and wherein at least a first measuring field, which is formed as the grid zone on said measuring strip, and wherein at least a second measuring field, which is formed as the solid zone on said measuring strip, are used as the at least first and second points on the substrate.

6. The method according to claim 1, wherein a printing substrate is used as the substrate, wherein the printing substrate one of consists of one of paper and paperboard and sheet metal and textiles, and glass and ceramics, and consists of one of a film comprising one of metal and plastic and wherein the printing substrate is formed as one of a hollow object and as a sheet and as a material web.

7. The method according to claim 1, wherein one of a liquid and a paste and a powder coating material is used as the covering coating material.

8. The method according to claim 1, wherein a colorant is used as the covering coating material, wherein the colorant is formed as one of a color-providing inorganic and as an organic substance, wherein the colorant is one of natural and synthetic origin and wherein the colorant has one of pigments and at least one dye.

9. The method according to claim 1, wherein the sensing device functions without contact and with an optoelectronic measuring method and densitometrically and spectrophotometrically.

10. The method according to claim 1, further including providing the application device has having a metering device which is one of controlled and regulated by the control unit, wherein the metering device influences a quantity of the covering coating material to be applied to the substrate by one of setting a width of at least one discharge opening of a reservoir supplying the covering coating material and by setting a cycle of a lifter transferring the covering coating material and by setting a rotational speed of a roller one of applying and transferring the covering coating material to be applied to the substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are shown in the figures and described in greater detail in the following.

(2) The following is shown:

(3) FIG. 1 a machine unit of a printing machine with an application device;

(4) FIG. 2 a sheet with at least one print image and with one measuring strip.

(5) The invention is explained without limitation in the following using the example of a printing machine, preferably a rotary printing machine, particularly a sheet-fed rotary printing machine. The printing machine can execute its printing process, e.g., in an offset printing process or in a flexographic printing process or in a screenprinting process or in an inkjet printing process.

(6) FIG. 1 shows, in a simplified and schematic manner, a machine unit 01, in a section from the printing machine, having a transport device arranged in a frame 03 for the transport of at least one substrate (FIG. 2), for example, formed respectively as a sheet 13 to be processed in this printing machine, particularly to be printed, wherein this transport device has, e.g., at least one transport cylinder 02, or preferably several successive, e.g. three or more successive, transport cylinders 02, in the preferred embodiment in the transport direction T of the at least one substrate. The respective rotational direction of the transport cylinder 02 is respectively indicated by a directional arrow. Holding elements which are formed, e.g., as grippers or as suction devices on the respective transport cylinders 02 fix the respective substrate in position during its transport from one transport cylinder 02 to the next transport cylinder 02 on the particular casing surface of the respective transport cylinder 02. The respective transport cylinders 02 are formed, e.g., in multiple sizes such that two or three or even more substrates are arranged or at least can be arranged successively on the respective outer circumference of the transport cylinders.

(7) The machine unit 01 shown in FIG. 1 has an application device 04, in interaction with one of the transport cylinders 02, for applying a covering coating material to the respective substrate transported by the transport cylinder 02 in question during its rotation. This covering coating material, for example, is a covering printing ink, which is formed, for example, as a primary color or as an opaque white or as a metallic color. A layer thickness of the coating material applied to the substrate with the application device 04 is, for example, in the micrometer range or nanometer range. In one printing machine, the application device 04 is formed, for example, as a metering device controlled or regulated by a control unit 06, wherein this metering device influences a respective quantity of the coating material to be applied to the substrate due to the setting of a width of at least one discharge opening of a reservoir supplying the coating material, e.g. an ink duct or doctor blade system 09, and/or of a cycle of a lifter transferring the coating material and/or of a rotational speed of a roller, e.g. a ductor roller 07 and/or forme roller 08, applying or transferring the coating material. The application device 04 may be arranged in the printing machine, in the transport direction T of the at least one substrate, e.g. upstream of a printing unit belonging to the printing machine, in order, for example, to initially apply an opaque white to the respective substrate, before the layer formed from the opaque white is printed over, at least partially, with at least one other printing ink. On the other hand, the application device 04 may also be arranged in the printing machine, in the transport direction T of the at least one substrate, downstream of a printing unit belonging to the printing machine in order to print over, at least partially, at least one printing ink already applied to the respective substrate and thus to create, for example, a printing result which can be backlit with a special effect. The applying of the covering coating material to the respective substrate can be carried out over the complete surface or partially or in halftone. The layer of the covering coating material applied to the respective substrate with the application device 04 in the printing machine may also have or be a primer coat for improved adherence. If necessary, an application of the covering coating material in the printing machine can also take place multiple times on the same substrate, wherein, for example, more than one single machine unit 01 is arranged with a respective application device 04 in the transport direction T of the substrate in question. Furthermore, a device for physical drying and/or for chemical curing may be provided in the printing machine, in the transport direction T of the at least one substrate, downstream of the application device 04, wherein the device for physical drying is formed, for example, as a hot air dryer 11 and/or as an infrared dryer 11, and the device for chemical curing is formed, for example, as a UV dryer 11.

(8) The layer thickness of the coating material applied to the substrate with the application device 04 is monitored with a sensing device 12, wherein the sensing device 12 collects measured values inline, i.e. during production, from the covering coating material applied to the respective substrate during an ongoing operation of the printing machine. The sensing device 12, which is arranged within the printing machine, is connected to the respective control unit 06, wherein the control unit 06 determines a value for the opacity of the layer of the coating material applied to the substrate from the measured values previously recorded by the sensing device 12. The signal paths and signal directions from the sensing device 12, via the control unit 06, to the application device 04 are indicated by directional arrows in FIG. 1. In particular, operating data and/or control data may also be provided bidirectionally between the control unit 06 and the application device 04. It is provided that, following the determination of the current value for the opacity of the layer of the coating material already applied to the substrate, the control unit 06 sets the layer thickness of this coating material to be applied to at least one further substrate by the application device 04 such that the layer of the coating material to be applied to the at least one further substrate with the application device 04 achieves a value, which was previously specified in the control unit 06, e.g. by means of a manual or automated entry, preferably a freely selectable value, for the opacity which is normally within the scope of permissible tolerances and/or the control unit retains the value normally within the scope of the aforementioned tolerances in ongoing operation of the printing machine. In the preferred embodiment, the control unit 06 sets the application device 04 such that the layer of the coating material to be applied to the at least one further substrate with application device 04 achieves a value for the opacity and/or retains it during ongoing operation of the printing machine in a range of at least 95% to 100%.

(9) The sensing device 12 preferably functions without contact and/or with an optoelectronic measuring method and/or densitometrically or spectrophotometrically. In an especially preferred embodiment, the sensing device 12 is formed as a camera, e.g. as a grayscale camera or as an RGB camera or as a CMYK colorimeter camera, wherein the control unit 06 determines the current value for the opacity of the layer of the coating material applied to the substrate, for example, by means of an evaluation of one or more images of the substrate taken by the camera, i.e. from at least one photographic depiction and/or from the underlying image data. In a further design variant, the sensing device 12 is formed as a reflection light sensor. The control unit 06 sets the layer thickness of the coating material applied to the substrate by the application device 04, particularly starting from at least a value of the opacity determined during an accumulating layer structure, e.g. in a start-up of the printing machine or in a different operating phase of the printing machine, in which the translucency of the layer of the coating material applied to the substrate decreases continually to the point of opacity.

(10) FIG. 2 shows a substrate formed as a sheet 13 with at least one print image 14 and with a measuring strip 16 extending transversely as relates to the transport direction T of the substrate in question, particularly over the width of the print image 14. The measuring strip 16 has several measuring fields 17 in a row, wherein individual measuring fields 17 are coated with a respective coating material with the described application device 04, e.g. over the entire surface or in halftone, e.g. in the printing machine according to FIG. 1 in an industrial process. In the preferred embodiment, the sensing device 12 described by means of FIG. 1 is directed onto at least one measuring field 17 in the measuring strip 16 of the sheet 13, wherein the control unit 06 connected to the sensing device 12 determines the respective value of the opacity of the layer of the coating material applied in the at least one measuring field 17 in the measuring strip 16 of the sheet 13. It may be provided that the control unit 06 determines the respective value of the opacity of the respectively applied layer of the coating material from several or all measuring fields 17 in the measuring strip 16 of the sheet 13 and, depending on the determined value for the opacity of the respectively applied layer of the coating material, sets the layer thickness to be applied to at least one subsequent sheet 13 by the application device 04 individually, i.e. as needed, for several or each of the zones 18 extending in the transport direction T of the sheet 13 in question and corresponding to at least one measuring field 17. A further design variant provides that the respective value of the opacity of the respectively applied layer of the coating material is to be detected, instead of or in addition to the detection in at least one of the measuring fields 17 of the measuring strip 16, at at least one preferably selectable position in the at least one print image 14 printed onto the sheet 13.

(11) Furthermore, it may be provided to apply the coating material at various points on the sheet 13 in question normally simultaneously in the same printing process by means of the application device 04. The points on the sheet 13 in question, which are different from one another, are, for example, at least two measuring fields 17 different from one another of the same measuring strip 16 or at least two different elements in the same print image 14. It is provided in this case that the coating material is applied at at least one first point on the sheet 13 in question in a grid respectively having several grid points, and the coating material is applied at at least one other second point on the sheet 13 in question over the entire surface. Specifically, this means, for example, that the coating material is applied particularly in at least one of the measuring fields 17 of the measuring strip 16 in question in a grid respectively having several grid points, and the coating material is applied in at least one other measuring field 17 of this measuring strip 16 over the entire surface in the same printing process by means of the application device 04. A first point formed, e.g., as a measuring field 17 on the sheet 13 in question, at which point the coating material is respectively applied in halftone, is also designated as a grid zone, while a second point formed, e.g., as a measuring field 17 on the sheet 13 in question, at which point the coating material is respectively applied over the entire surface, is also designated as a solid zone. The control unit 06 determines a respective value for the optical density of the layer of the coating material applied to the sheet 13 at the points in question from data, e.g. image data, recorded by the sensing device 12 at the respective first and second point on the sheet 13 in question.

(12) The control unit 06 also preferably places the value DR for the optical density, determined from a grid zone, in relation to the respective value DV for the optical density, determined from a solid zone, e.g., by the formation of a ratio DR/DV. Because the optical density is proportional to the quantity of the coating material applied per unit of surface area to the sheet 13 at the points in question on the sheet 13, e.g. in the respective measuring fields 17 of the measuring strip 16, the value DR for the optical density determined in a grid zone in a printing process is less than the value DV for the optical density determined in a solid zone, at least at the start. As the layer thickness of the coating material applied in a grid zone increases, there is an increase in the optical density determined in the grid zone in question, e.g. due to a spreading of the grid points therein and/or optical effects, and the ratio formed from value DR for the optical density determined from a respective grid zone and value DV for the optical density determined from the respective solid zone changes significantly. The control unit 06 then stipulates, particularly when it determines a significant change in the ratio formed from the optical densities, i.e. as a function of this determination, the particularly layer thickness of the coating material currently being applied to the sheet 13 in question by the application device 04, at which layer thickness the value DR for the optical density determined in a grid zone corresponds to the value DV for the optical density determined in a solid zone, as the particular layer thickness of the coating material having an opacity of 100%. The significant change in the ratio formed from the optical densities may be because of the fact that, for example, the value of a ratio formed from these optical densities approximates initially the value 1 in a series of several successive data collections, i.e. determinations of these optical densities, but then stays at least practically unchanged at the value 1 for a preferably previously stipulated number of successive data collections. Thus, the control unit 06 monitors a course or a behavior of this relationship for a significant change, i.e. a change exceeding the permissible tolerance limits, in a series of several successive collections of the optical densities in question. The stipulation relating to the layer thickness of the coating material with an opacity of 100% takes place, for example, in that the control unit 06 stores the currently provided operating data and/or control data of the application device 04 in a storage device 19 in association with the opacity of 100% for the layer thickness of the coating material. Following the determination made, the control unit 06 sets the layer thickness of the coating material, which is to be applied to at least one further substrate, i.e. particularly at least one further sheet 13, by the application device 04, such that the layer of the coating material to be applied to the at least one further substrate with the application device 04 has the opacity of 100% and thus retains it in the subsequent printing process, particularly during ongoing operation of the printing machine or the paper-processing machine.

(13) Well preferred embodiments of a method for setting a layer thickness of a covering coating material to be applied to a substrate by an application device, in accordance with the present invention, have been set forth fully and completely herein above, it will be apparent to one of skill in the art that various changes could be made thereto, without departing from the true spirit and scope of the present invention, which is to be limited only by the appended claims.