Method and printing device for aligning printed pattern on printing medium

Abstract

A method for aligning a printed pattern on a print medium (30) in a printing device (10) having at least a first printing unit (16) and a second printing unit (18), where each printing unit (16, 18) comprises a printing roller (24, 25), and where the second printing unit (18) comprises an optical detection unit (26), wherein the print 5 medium (30) comprises a first side edge region (35) and a second side edge region (37) opposite the first side edge region (35), and travels from the first printing unit (16) to the second printing unit (18) in the longitudinal direction. One method step comprises printing, by a first printing unit (16), a first registration mark (38) on a first side edge region (35) of a printing medium (30) and a second registration mark (40) on a second side edge region 10 (37) opposite the first side edge region (35). Another method step comprises determining the horizontal and vertical position of the first registration mark (38) at the first side edge region (35) using the detection unit (26) and adjusting the vertical and / or horizontal registration based on the position of the first registration mark (38). Another method step 15 comprises printing a third registration mark (46) on the first side edge region (35) of the printing medium (30) and printing a fourth registration mark (48) on the second side edge region (37) of the printing medium (30) by means of the second printing unit (18) after setting the vertical and / or horizontal registration on the basis of the position of the first registration mark (38). The maximum width of the second and fourth registration marks (40, 48) on the second side edge 20 region (37) is smaller than the maximum width of the first and third registration marks (38, 46) on the first side edge region (35). Furthermore, a printing device (10) is provided.

Description

Technical Field

[0001] The present invention relates to a method for aligning a plurality of printed patterns on a printing medium in a printing device, and to a printing device having at least two printing units. In particular, the present invention relates to a rotogravure printing press, a flexographic printing press or an offset printing press. Background Art

[0002] The printing unit usually has a plurality of printing units for printing different color planes. The print medium then passes through the various printing units.

[0003] The alignment of the color planes must be very precise. In particular, a color misalignment of more than 50 microns can significantly affect the print quality. Therefore, it is necessary to control the registration of the printing units with regard to horizontal and vertical alignment as well as tilt.

[0004] It is known to print registration marks in the side edge areas of the print medium, which helps with registration control. However, the area with the registration marks does not contribute to the finished print and must be cut off at the end of the printing process. Summary of the invention

[0005] It is therefore an object of the present invention to achieve adequate registration of a printed pattern on a print medium in a printing device while reducing the generation of waste.

[0006] The object is achieved by a method for aligning a printed pattern on a print medium in a printing device having at least a first printing unit and a second printing unit, wherein each printing unit comprises a printing roller, and wherein the second printing unit comprises an optical detection unit, wherein the print medium comprises a first side edge region and a second side edge region opposite to the first side edge region, and travels from the first printing unit to the second printing unit along a longitudinal direction. One method step comprises printing a first registration mark on the first side edge region and printing a second registration mark on the second side edge using the first printing unit. A further method step comprises determining the horizontal and vertical position of the first registration mark at the first side edge region using the detection unit and adjusting the vertical and / or horizontal registration based on the position of the first registration mark. Another method step comprises, after adjusting the vertical and / or horizontal registration based on the position of the first registration mark, printing a third registration mark on the first side edge region of the print medium and printing a fourth registration mark on the second side edge region by the second printing unit. The maximum width of the second and fourth registration marks on the second side edge region is less than the maximum width of the first and third registration marks on the first side edge region.

[0007] Since the width of the registration mark on the second side edge region is smaller than the width of the registration mark on the first side edge region, space can be obtained on the print medium, thereby reducing waste. Specifically, the width of the registration mark on the second side edge region can be reduced because the horizontal registration is adjusted based on the position of the first registration mark printed by the first printing unit on the first side edge region, so that the horizontal position of the registration mark printed by the second printing unit has been clearly defined. Therefore, it is ensured that the registration mark printed by the second printing unit on the second side edge region still passes through the sensitive area of ​​the optical detection unit despite its reduced size. However, the method of the present invention still allows highly accurate alignment.

[0008] The width of the register mark on the second side edge region is, for example, one third to two thirds of the width of the register mark on the first side edge region.

[0009] The vertical register can be adjusted by temporarily changing the rotation speed of the printing roller of the second printing unit.

[0010] The horizontal register can be adjusted by moving the printing roller of the second printing unit along its axis of rotation, in particular using a special moving device.

[0011] According to one aspect, the registration mark on the first side edge region is a two-dimensional registration mark, and the registration mark on the second side edge region is a one-dimensional registration mark or a two-dimensional registration mark. A two-dimensional registration mark is a mark that allows two positions (particularly the horizontal and vertical position of the mark) to be measured using a single point sensor (e.g. an optical photocell). A one-dimensional registration mark is a mark that allows only one position (particularly the vertical position) to be measured.

[0012] For example, the register mark on the first side edge region has a horizontal edge and an edge inclined to the horizontal edge. The horizontal edge allows the vertical position of the register mark to be detected, while the inclined edge allows the horizontal position to be measured. Due to the inclined edge, the length of the detected register mark is different depending on the horizontal position of the register mark.

[0013] For example, a first printing unit prints a trigger code on a first side edge region, wherein a first registration mark printed by the first printing unit on the first side edge region is printed after the trigger code relative to the travel direction of the print medium. The trigger code allows the mark to be measured without prior knowledge of the longitudinal position of the mark. In particular, the trigger code is used to set the zero position of the registration system.

[0014] Preferably, the first printing unit prints the trigger code on the second side edge region, and the second registration mark printed by the first printing unit on the second side edge region is printed after the trigger code relative to the travel direction of the print medium. In addition to the advantages already mentioned with respect to the trigger code on the first side edge region, the trigger code on the second side edge region allows the registration mark on the second side edge region to be placed in any vertical position relative to the registration mark on the first side edge region. Therefore, the printing pattern of the registration mark is more flexible.

[0015] It is possible to measure the vertical distance from the third reference mark printed on the first side edge region by the second printing unit to the reference point, and measure the vertical distance from the fourth reference mark printed on the second side edge region by the second printing unit to the reference point, and detect the tilt between the first printing unit and the second printing unit based on the measured distances. This allows tilt misalignment to be detected in a simple manner.

[0016] The reference point may be a trigger code, a register mark printed by the first printing unit or another mark at a defined distance from the third register mark or the fourth register mark.

[0017] According to one embodiment, the vertical distance between the registration marks printed by the first printing unit and the second printing unit on the first side edge area is measured, and the vertical distance between the registration marks printed by the first printing unit and the second printing unit on the second side edge area is measured, and the vertical distances between the registration marks can be compared to detect the tilt between the first printing unit and the second printing unit. Specifically, the tilt can be detected based on the comparison of the two measured vertical distances. If the two detected vertical distances are equal, there is no tilt, but if the two measured vertical distances are different from each other, the printing units must be adjusted for the tilt.

[0018] For example, the degree of tilt between the first printing unit and the second printing unit is determined, and the tilt is adjusted by pivoting a tilt roller between the printing roller of the first printing unit and the printing roller of the second printing unit. Thus, the tilt misalignment is corrected.

[0019] The horizontal position of the second registration mark printed by the first printing unit on the second side edge area can be measured, and the horizontal registration can be adjusted again based on the position of the second registration mark on the second side edge area. Thereby, the alignment of the color plane can be more accurate. Specifically, the horizontal adjustment can be improved by averaging the measurement results of the first registration mark and the second registration mark.

[0020] The object of the present invention is also solved by a printing device configured to perform the method and tilt adjustment of the present invention, wherein at least two printing units are arranged successively to each other, wherein each printing unit includes a printing roller and a tilting roller, and the second printing unit arranged after the first printing unit includes an optical detection unit, the optical detection unit preferably includes a first phototube and a second phototube arranged downstream of the printing roller, so that the first phototube can detect the registration mark in the first side edge area of ​​the printing medium, and the second phototube can detect the registration mark in the second side edge area of ​​the printing medium.

[0021] The second photocell preferably has a sensitive area that is smaller in width than the first photocell.The second photocell may be of the same type and model as the first photocell, but oriented differently.

[0022] The axis of rotation of the tilted roller is, for example, movable on one side and fixed on the opposite side. Thus, the tilting parameters can be adjusted.

[0023] As an alternative embodiment, the inclined rollers may be movable on both sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features and advantages become clear from the following description and the accompanying drawings. In the drawings:

[0025] - Figure 1 The printing device of the present invention is schematically shown,

[0026] - Figure 2 Shows Figure 1 a printing unit of a printing device,

[0027] - Figure 3 shows the printed pattern,

[0028] - Figure 4 shows the registration marks, and

[0029] - Figure 5 The sensor paths are shown. DETAILED DESCRIPTION

[0030] Figure 1 A printing device 10 is shown schematically.

[0031] The printing apparatus includes an unwinder 12, a preheating unit 14, a first printing unit 16, and a second printing unit 18 disposed after the first printing unit 16. However, the printing apparatus 10 may include more than two printing units.

[0032] For example, the printing apparatus 10 is a seven-color printing apparatus having seven printing units.

[0033] Please note that the first printing unit 16 is not necessarily the first printing unit of the printing device. There may be a printing unit that does not require precise registration before the first printing unit 16. In addition, the second printing unit 18 can be any printing unit arranged after the first printing unit, but not necessarily adjacent to the first printing unit 16.

[0034] A dryer 20 is arranged downstream of each printing unit 16 , 18 .

[0035] Each printing unit 16 , 18 comprises an inclined roller 21 , 22 and a printing roller 24 , 25 .

[0036] The second printing unit 18 (also Figure 2 (as can be seen in the figure) also includes an optical detection unit 26 arranged downstream of the printing roller 25.

[0037] The detection unit 26 may include two photoelectric tubes 28 , 29 .

[0038] The photoelectric tubes 28 and 29 are, for example, monochrome photoelectric tubes.

[0039] As an alternative, the optical detection unit 26 may consist of two cameras 28 , 29 .

[0040] The print medium 30 travels in the printing device 10 along a travel direction indicated by arrow 32 .

[0041] In order to ensure a high printing quality, the printing units 16 , 18 must be aligned with high precision in the horizontal and vertical directions as well as in terms of tilt.

[0042] The vertical direction corresponds to the traveling direction of the print medium 30 .

[0043] The horizontal direction is transverse to the travel direction of the print medium 30 .

[0044] In order to adjust the horizontal offset of the printing units 16 , 18 , the printing rollers 24 , 25 are moved along their axes of rotation.

[0045] To adjust the vertical misalignment of the printing units 16, 18, the angular position of the printing rollers 24, 25 is adjusted by adjusting the printing roller stage before printing, i.e. before the printing rollers 24, 25 are brought into contact with the print medium 30. This can be achieved by temporarily changing the rotation speed of the printing roller 24.

[0046] By pivoting the inclined rollers 21, 22, for example by Figure 2 The tilt is corrected by moving one side of the tilted rollers 21, 22 in the direction indicated by the middle arrow 23 while keeping the other side fixed.

[0047] refer to Figures 3 to 5 , a method for detecting misalignment of different color planes is described.

[0048] The color plane is a pattern printed by a single printing unit 16 , 18 .

[0049] First, the first printing unit 16 prints the trigger code 34 on the first side edge 35 area of ​​the printing medium 30. In the figure, the first side edge area 35 is located on the left side of the printing medium 30.

[0050] In addition, the first printing unit 16 prints the trigger code 36 on a second side edge region 37 opposite to the first side edge region 35 of the printing medium 30 , and the second side edge region 37 is located on the right side of the printing medium 30 in the figure.

[0051] The trigger codes 34, 36 are codes that have different distinct features in the vertical direction and include markings with horizontal edges.

[0052] The trigger codes 34 , 36 on the first and second side edge regions 35 , 37 are positioned at a vertical distance relative to each other with respect to the travel direction 32 of the print medium 30 .

[0053] In the figure, the marks printed by one printing unit are represented by the same shading. In fact, the marks printed by one printing unit have the same color.

[0054] The first printing unit 16 also prints a first registration mark 38 on the first side edge region 35 and a second registration mark 40 on the second side edge region 37 .

[0055] The first and second registration marks 38, 40 are printed after the trigger codes 34, 36. Therefore, the registration marks 38, 40 are located at a vertical distance relative to the trigger codes 34, 36.

[0056] The distances between the first and second registration marks 38, 40 and the corresponding trigger codes 34, 36 are defined.

[0057] Figure 4 A first registration mark 38 printed on the first side edge region 35 is shown in an enlarged view.

[0058] The first registration mark 38 has a horizontal edge 42 and an edge 44 that is inclined toward the horizontal edge 42. In the illustrated embodiment, the first registration mark 38 is in the shape of a right triangle.

[0059] In addition, the sensor path of the corresponding photoelectric tube 28 is Figure 4 The dashed line shows in the figure.

[0060] The width of the first registration mark 38 printed on the first side edge region 35 is such that it covers the maximum lateral error in the position of the print medium 30 .

[0061] For example, the width w of the first registration mark 38 is 6 mm.

[0062] In this embodiment, the second registration mark 40 on the second side edge region 37 has the same shape as the first registration mark 38 on the first side edge region 35 .

[0063] The first registration mark 38 and the second registration mark 40 are both two-dimensional registration marks.

[0064] However, the second registration mark 40 on the second side edge region 35 may also be a one-dimensional registration mark, such as a square or a rectangle.

[0065] When the print medium 30 travels in the travel direction and the portion with the trigger codes 34 , 36 enters the second printing unit 18 , the detection unit 26 reads the trigger codes 34 , 36 when the second printing unit 18 is not printing (ie, the printing roller 24 is not in contact with the print medium 30 ).

[0066] By reading the trigger code 34 , 36 , the alignment process is started.

[0067] After reading the trigger code 34 , the detection unit 26 detects the first registration mark 38 on the first side edge area 35 .

[0068] As the first registration mark 38 travels along the corresponding photoelectric cell 28 , the vertical position of the first registration mark 38 may be determined by detecting the position of the horizontal edge 42 .

[0069] like Figure 4 As shown, the horizontal position of the first registration mark 38 can be determined by detecting the length l of the first registration mark 38. Since the edge 44 is inclined toward the horizontal edge 42, the detected length l is specific to the horizontal position of the first registration mark 38. Preferably, the edge 44 is inclined toward the horizontal edge 42 at an angle between 40° and 50°, in particular 45°. Angles within this range can ensure high accuracy.

[0070] After determining the horizontal and vertical positions of the first registration mark 38 on the first side edge region 35 , the vertical and / or horizontal registration is adjusted based on the position of the first registration mark 38 .

[0071] After adjusting the vertical and / or horizontal registration based on the position of the first registration mark 38 , the second printing unit 18 prints a third registration mark 46 on the first side edge area 35 and prints a fourth registration mark 48 on the second side edge 37 area of ​​the print medium 30 .

[0072] The shapes of the third and fourth registration marks 46 and 48 printed by the second printing unit 18 correspond to the shapes of the first and second registration marks 38 and 40 printed by the first printing unit 16. However, they may also be of different shapes.

[0073] Due to the previous adjustments, the horizontal and vertical positions of the third and fourth registration marks 46, 48 printed by the second printing unit 18 are already well defined.

[0074] Due to the clearly defined position, the monochrome photocell can determine from its position which printing unit created the register mark.

[0075] In the next step, the vertical distance v1 between the first registration mark 38 and the third registration mark 46 printed by the first and second printing units 16, 18 on the first side edge area 35 is measured, and the vertical distance v2 between the second registration mark 40 and the fourth registration mark 48 printed by the first and second printing units 16, 18 on the second side edge area 37 is measured. The vertical distances v1 and v2 between the registration marks are compared. 2， To detect the tilt between the first and second printing units 16 , 18 .

[0076] Specifically, if the distances v1 and v2 are different from each other, tilt correction is required.

[0077] The degree of inclination between the first printing unit 16 and the second printing unit 18 is determined and adjusted by pivoting the inclination roller 22 between the printing roller 24 of the first printing unit 16 and the printing roller 25 of the second printing unit 18 .

[0078] In an alternative embodiment, the vertical distance of the registration marks 46, 48 may be measured relative to the trigger codes 34, 36, respectively, or relative to other reference points to detect tilt.

[0079] In an optional method step, the horizontal and / or vertical position of the second registration mark 40 printed by the first printing unit 16 on the second side edge area 37 is measured, and the vertical and / or horizontal registration is adjusted again based on the position of the second registration mark 40 on the second side edge area 37. As a result, the alignment of the color planes can be more accurate.

[0080] The method steps described for the first printing unit 16 and the second printing unit 18 can be repeated for subsequent printing units of the printing device.

[0081] The maximum width of the second and fourth registration marks 40 , 48 on the second side edge region 37 is smaller than the maximum width of the first and third registration marks 38 , 46 on the first side edge region 35 , and is specifically one third to two thirds of the width of the first and third registration marks 38 , 46 on the first side edge region 35 .

[0082] For example, when the same photocells 28, 29 with the same orientation are used on both sides 35, 37 of the medium, the maximum width of the registration marks 40, 48 on the second side edge region 37 is 4 mm. In another example, when a photocell 29 with a narrower sensitive area in the transverse direction is used, the maximum width of the registration marks 40, 48 on the second side edge region 37 is 2 mm.

[0083] Smaller width is possible because the maximum lateral error is reduced after the first alignment. In addition, the vertical position of the registration marks 40, 48 on the second side edge region 37 is measured, but it is not necessary to measure its horizontal position. This also helps to make the width of the registration marks 40, 48 on the second side edge region 37 as small as possible.

[0084] Thus, the waste generated during the printing process is reduced.

[0085] In particular, the side edge regions 35 , 37 carrying the register marks do not participate in the finished print product and are cut after the printing process.

[0086] Figure 5 The sensor paths of the photoelectric cells 28 , 29 of the detection unit 26 , in particular the paths of the sensitive areas of the photoelectric cells 28 , 29 , are shown.

[0087] The sensitive areas of the photoelectric cells 28, 29 are rectangular.

[0088] For example, a photocell has a sensitive area of ​​2mm x 1mm.

[0089] Figure 5 It is shown that the width of the second photoelectric tube 29 is smaller than that of the first photoelectric tube 28 .

[0090] For example, the photocells 28, 29 are identical, but the second photocell 29 is rotated about 90° relative to the first photocell 28. Specifically, the photocell 28 is used horizontally for the larger registration marks 38, 46 on the first side edge region, while the second photocell 29 is used vertically for the smaller marks 40, 48 on the second side edge region.

[0091] In another example, the photocells 28 , 29 are different, wherein the second photocell 29 has a smaller sensitive area than the first photocell 28 .

[0092] Due to the lateral error in the position of the print medium 30, the width of the registration marks 38, 46 on the first side 35 of the medium 30 added to the width of the sensitive area of ​​the photocell 28 must be at least slightly larger than the initial lateral position error tolerance to ensure that the marks pass through the sensitive area of ​​the photocell 28. The width of the registration marks 38, 46 is preferably at least as large as the width of the sensitive area of ​​the photocell 28 to ensure that the registration marks 38, 46 completely pass through the sensitive area of ​​the photocell 28. Therefore, the width of the registration marks 38, 46 is preferably slightly larger than the width of the sensitive area of ​​the photocell 28. The same is true for the second side 37 of the medium (i.e., for the registration marks 40, 48) and the photocell 29. However, since the lateral error tolerance on the second side 37 is smaller (because it is applied after the initial lateral alignment based on the marks on the first side 35 of the medium), the size of the marks on the second side 37 of the medium can be made smaller.

[0093] Since the horizontal positions of the second and fourth registration marks 40, 48 have been set according to the positions of the first and third registration marks 38, 46 on the first side edge region 35, the error of the horizontal position is within the range of 1 mm.

Claims

1. A method for aligning a print pattern on a print medium (30) in a printing device (10) having at least a first print unit (16) and a second print unit (18), wherein each print unit (16, 18) comprises a print roller (24, 25), and wherein the second print unit (18) comprises an optical detection unit (26), wherein the print medium (30) comprises a first side edge region (35) and a second side edge region (37) opposite to the first side edge region (35), and travels from the first print unit (16) to the second print unit (18) in a longitudinal direction, the method comprising: - printing a first register mark (38) on the first side edge region (35) and a second register mark (40) on the second side edge region (37) by means of the first printing unit (16), - printing a third registration mark (46) on the first side edge region (35) and a fourth registration mark (48) on the second side edge region (37) of the print medium (30) by the second printing unit (18), - using the detection unit (26) to determine the horizontal and vertical position of the first registration mark (38) in the first side edge area (35), - using the detection unit (26) to determine the horizontal position of the third registration mark (46) in the first side edge area (35), - adjusting the horizontal registration of the second printing unit (18) according to the relative horizontal positions of the first registration mark (38) and the third registration mark (46), - wherein the maximum width of the second and fourth registration marks (40, 48) in the region of the second side edge (37) is smaller than the maximum width of the first and third registration marks (38, 46) in the region of the first side edge.

2. The method according to claim 1, wherein the method comprises: - determining the vertical position of the first registration mark (38) at the first side edge region (35) using the detection unit (26), - using the detection unit (26) to determine the vertical position of the third registration mark (46) at the first side edge region (35), - adjusting the vertical registration of the second printing unit (18) based on the relative vertical positions of the first registration mark (38) and the third registration mark (46).

3. A method according to claim 1 or 2, wherein the registration mark (38, 46) on the first side edge area (35) is a two-dimensional registration mark, and the registration mark (40, 48) on the second side edge area (37) is a one-dimensional or two-dimensional registration mark.

4. The method according to any of the preceding claims, wherein the register mark (38, 46) on the first side edge region (35) has a horizontal edge (42) and an edge (44) inclined toward the horizontal edge (42).

5. A method according to any one of the preceding claims, wherein a trigger code (34) is printed on the first side edge area (35) by the first printing unit (16), and wherein the first registration mark (38) printed on the first side edge area (35) by the first printing unit (16) is printed after the trigger code (34) relative to the travel direction of the print medium (30).

6. A method according to any one of the preceding claims, wherein a trigger code (36) is printed on the second side edge area (37) by the first printing unit (16), and the second registration mark (40) printed by the first printing unit (18) on the second side edge area (37) is printed after the trigger code (36) relative to the travel direction of the print medium (30).

7. A method according to any one of the preceding claims, wherein: The vertical distance between a third reference mark (46) printed by the second printing unit (18) on the first side edge area (35) and a reference point is measured, and the vertical distance between a fourth reference mark (48) printed by the second printing unit (18) on the second side edge area (37) is measured, and based on the measured distances, when the measured distances are different, the tilt between the first and second printing units (16, 18) is detected.

8. A method according to claim 7, wherein a vertical distance (v1) between registration marks (38, 46) printed by the first and second printing units (16, 18) on the first side edge area (35) is measured, and a vertical distance (v2) between registration marks (40, 48) printed by the first and second printing units (16, 18) on the second side edge area (37) is measured, and wherein the vertical distances (v1, v2) between the registration marks (38, 40, 46, 48) are compared to detect the tilt between the first and second printing units (16, 18).

9. The method according to claim 7 or 8, wherein: The degree of inclination between the first printing unit (16) and the second printing unit (18) is determined, and the inclination is adjusted by pivoting an inclination roller (22) between the printing roller (24) of the first printing unit (16) and the printing roller (25) of the second printing unit (18).

10. A method according to any one of the preceding claims, wherein the horizontal positions of the second registration mark (40) and the fourth registration mark (48) on the second side edge area (37) are measured, and based on the positions of the second registration mark (40) and the fourth registration mark (48) on the second side edge area (37), the horizontal registration is adjusted again.

11. A printing device (10) configured to perform a method according to any of the preceding claims and additionally according to claim 8, wherein at least two printing units (16, 18) are arranged successively to each other, wherein each printing unit (16, 18) comprises a printing roller (24, 25) and an inclined roller (21, 22), and the second printing unit (18) arranged after the first printing unit (16) comprises an optical detection unit (26), the optical detection unit (26) comprising a first and a second phototube (28, 29), which are arranged downstream of the printing roller (25) so that the first phototube (28) can detect a registration mark (38, 46) in the first side edge area (35) of the printing medium (30), and the second phototube (29) can detect a registration mark (40, 48) in the second side edge area (37) of the printing medium (30).

12. The printing device according to claim 11, wherein: The width of the second photoelectric tube (29) is smaller than that of the first photoelectric tube (28).

Images