SCREEN PRINTING, IN PARTICULAR ROTARY SCREEN PRINTING OF TEXTILE MATERIALS

Abstract

A method of screen printing an image on a substrate, such as rotary screen printing, includes using a printing screen having a surface structure at its printing side and attached imaged lacquer layer having open areas defining the image to be printed, where the image includes pixel based design elements, the printing screen has a parallelogram pattern, preferably an orthogonal pattern, of screen openings and the open areas of the imaged lacquer layer representing the pixel based design elements are arranged in an orthogonal raster.

Claims

1. A method of screen printing an image on a substrate (14) comprising the steps of: providing a printing screen having a printing side and a squeegee side opposite the printing side, and having a pattern of screen openings delimited by bridges and crossing points; providing an imaged lacquer layer having open areas defining the image to be printed on the printing side of the printing screen; and forcing ink paste through the printing screen and the imaged lacquer layer from the squeegee side of the printing screen to the printing side thereof onto the substrate wherein: the image to be printed comprises pixel based design elements; the printing screen has a pattern of screen openings that are oriented in a parallelogram raster; and the open areas of the imaged lacquer layer representing the pixel based design elements are arranged in an orthogonal raster.

2. The method according to claim 1, wherein the pattern of screen openings is an orthogonal pattern.

3. The method according to claim 1, wherein the printing screen is a cylindrical screen with a longitudinal axis for rotary screen printing.

4. The method according to claim 3, wherein the orthogonal pattern of the screen openings has axes that are arranged at an angle to the longitudinal axis of the rotary printing screen.

5. The method according to claim 1, wherein the substrate is a textile material, in particular a textile material having an orthogonal orientation.

6. The method according to claim 1, wherein the pixel based design elements comprise a halftone raster and/or a geometrical design.

7. The method according to claim 1, wherein the orthogonal raster of the imaged lacquer layer is arranged at an angle to the axes of the pattern of the screen openings.

8. The method according to claim 1, wherein the printing screen is an electroformed printing screen.

9. The method according to claim 1, wherein the printing screen has a surface structure of the bridges and the crossing points at the printing side of the printing screen, wherein the crossing points have a higher thickness than the bridges.

10. The method according to claim 1, wherein the screen openings have a square cross-section with rounded corners.

11. The method according to claim 1, wherein the size of the screen openings have a size that increases from the squeegee side to the printing side.

12. An assembly of a printing screen having a printing side and a squeegee side opposite from the printing side, and having a pattern of screen openings delimited by bridges and crossing points, the screen openings being oriented in a parallelogram pattern, and an imaged lacquer layer having open areas defining an image to be printed, wherein the image to be printed comprises pixel based design elements and the open areas of the imaged lacquer layer representing the pixel based design image elements are arranged in an orthogonal raster.

13. The assembly according to claim 12, wherein the pattern of screen openings is an orthogonal pattern.

14. The assembly according to claim 12, wherein the printing screen is a cylindrical printing screen with a longitudinal axis for rotary screen printing.

15. The assembly according to claim 14, wherein the axes of the orthogonal pattern of the screen openings are arranged at an angle to the longitudinal axis of the rotary printing screen.

16. The assembly according to claim 13, wherein the orthogonal raster of the imaged lacquer layer is arranged at an angle to the orthogonal pattern of the screen openings.

17. The assembly according to claim 12, wherein the printing screen is an electroformed screen.

18. The assembly according to claim 12, wherein the printing screen has a surface structure of the bridges and the crossing points at the printing side of the printing screen, wherein the crossing points have a higher thickness than the bridges.

19. The assembly according to claim 12, wherein the screen openings have a square cross-section with rounded corners.

20. The assembly according to claim 12, wherein the size of the screen openings have a size that increases from the squeegee side to the printing side of the printing screen.

21. The assembly according to claim 12, wherein the pixel based design elements comprise a halftone raster and/or a geometrical design.

22.-23. (canceled)

24. A screen printing device, in particular a rotary screen printing device, having a conveyor for conveying a substrate to be printed, at least one printing station having an ink paste supply and squeegee, typically a supply unit for supplying the substrate to be printed to the conveyor and a discharge unit for discharging the printed substrate, wherein the printing station is provided with an assembly of a printing screen and imaged lacquer layer according to any one of the claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention is illustrated by the attached drawings, wherein:

[0030] FIG. 1 is a diagrammatic representation of an embodiment of a rotary screen printing device;

[0031] FIG. 2 is an embodiment of a printing screen having an orthogonal pattern of screen openings according to the invention;

[0032] FIG. 3 is an embodiment of an imaged lacquer layer used in the invention;

[0033] FIG. 4 represents diagrams illustrating an effect of the invention (FIG. 4a) compared to prior art (FIG. 4b);

[0034] FIGS. 5 and 6 show examples of printed images on textile, which images have been printed according to the invention (FIG. 5a; FIG. 6a) and according to the prior art (FIG. 5b;

[0035] FIG. 6b); and

[0036] FIGS. 7 and 8 show further examples of printed images on textile, that have been printed according to the invention and according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

[0037] FIG. 1 diagrammatically shows an embodiment of a textile rotary screen printing device which in its entirety is indicated by reference numeral 10. In this embodiment the printing device 10 comprises a feed section 12, in this case a controlled reel for unwinding the textile substrate 14 to be printed, which is conveyed, typically supported on a blanket 16, through the printing stations 18 of the printing section 20, where the process colours are applied onto the substrate 14 from the inside of a rotary printing screen 22 by means of a squeegee or roll 24 through the screen openings (see also FIG. 2) onto the substrate 14. The printing paste is supplied by a print paste feed 26 to the interior of the rotary printing screen 22 and the squeegee 24 that contacts the squeegee side of the printing screen 22, forces the ink paste through the screen openings. Only four printing stations 18 are shown in this representation. However, more printing stations could be added for additional process colours. After drying in corresponding drying station 28 the printed textile substrate 14 exits the printing device 10 at the discharge section 30, e.g. wound on a reel 32.

[0038] FIG. 2 shows an embodiment of a printing screen according to the invention in top view. The printing side 40 of the printing screen 22 has a 3D surface structure, consisting of crossing points 42 that each connect four bridges 44, defining a screen opening 46. The squeegee side opposite the printing side is configured for smooth sliding contact with the squeegee. As indicated the crossing points 42 have a higher thickness than the bridges 44.

[0039] FIG. 3 is an embodiment of a halftone imaged lacquer layer showing an orthogonal raster of circular open areas 50.

[0040] FIG. 4a shows the superposition of the textile substrate, the printing screen and the imaged lacquer layer. The axes 14 representing the orthogonal orientation of the textile substrate are drawn as solid lines, those axes 22 representing the orthogonal pattern of the printing screen in dotted lines, and the axes 48 of the orthogonal pattern of the imaged lacquer layer in broken lines. Similarly FIG. 4b shows the same superposition, but for a printing screen 22′ having a hexagonal pattern of screen openings, and thus 3 axes 22′ are present. As is apparent for an orthogonal pattern of screen openings in the printing screen as shown in FIG. 4a the available range of angles (indicated by arrows) for arranging the imaged lacquer layer orientation with respect to the pattern of the printing screen is larger than the range for a hexagonal pattern (FIG. 4b).

[0041] FIG. 5a shows part of a geometric design, in this case a zigzag structure of fine lines, screen printed with a 195 mesh rotary printing screen having an orthogonal pattern of screen openings according to the invention and FIG. 5b shows the same design that has been screen printed with a proprietary rotary printing screen (Novascreen™) of the same mesh and open area, but having a hexagonal pattern of screen openings.

[0042] FIG. 6a represents a printed line image using 195 mesh rotary printing screen having an orthogonal pattern of screen openings according to the invention, while FIG. 6b shows the same printed line image using the proprietary printing screen having a hexagonal pattern of screen openings.

[0043] As is apparent the orthogonal image elements of the images have a significant higher print quality when printed according to the invention. The printed image of FIG. 5a shows fine solid lines having a high edge definition, while these lines in FIG. 5b are sometimes broken and show a serrated edge. Comparing the printed images of FIGS. 6a and 6b, in particular the parts at the left hand lower corner, it appears that the example according to the invention allows to print extreme fine lines with high precision, while the prior art screen does not print at all.

[0044] FIGS. 7 and 8 are pictures of printed images that are printed using the same screen according to the invention (upper part) and the same prior art screen (lower part) as in the examples of FIGS. 5 and 6. It appears that the printed image according to the invention does not show any Moire defects, while the Moire interference is clearly visible with the naked eye in the lower parts.