Digital printing process

Patent metadata

Field	Value
Publication number	US-10960660-B2
Application number	US-201916432934-A
Country	US
Kind code	B2
Filing date	Jun 6, 2019
Priority date	Mar 5, 2012
Publication date	Mar 30, 2021
Grant date	Mar 30, 2021

Abstract

A printing process is disclosed which comprises directing droplets of an ink onto an intermediate transfer member to form an ink image, the ink including an organic polymeric resin and a coloring agent in an aqueous carrier, and the transfer member having a hydrophobic outer surface so that each ink droplet in the ink image spreads on impinging upon the intermediate transfer member to form an ink film. The ink is dried while the ink image is being transported by the intermediate transfer member by evaporating the aqueous carrier from the ink image to leave a residue film of resin and coloring agent. The residue film is then transferred to a substrate. The chemical compositions of the ink and of the surface of the intermediate transfer member are selected such that attractive intermolecular forces between molecules in the outer skin of each droplet and on the surface of the intermediate transfer member counteract the tendency of the ink film produced by each droplet to bead under the action of the surface tension of the aqueous carrier, without causing each droplet to spread by wetting the surface of the intermediate transfer member.

First claim

The invention claimed is:

1. A printing system comprising:
a. an intermediate transfer member (ITM) comprising an endless flexible belt having upper and lower runs, the belt passing over guide and drive rollers;
b. an image forming station at which droplets of ink are deposited to an outer surface of the ITM to form ink images thereon, the image forming station comprising a plurality of print bars and a plurality of gas-blowers, each gas-blower respectively following a different associated print bar and configured to blow a gas-stream onto the ITM outer surface to only partially dry ink-droplets deposited by the associate print bar; and
c. a main drying station disposed both (i) downstream of the image forming station and (ii) above an upper run of the belt, the main drying station for sufficiently drying the ink images to produce therefrom a residue film of ink solids, sufficient heat being delivered at the main drying station to render the residue film tacky; and
d. an impression station disposed downstream of the main drying station at which the tacky residue film is transferred from the ITM outer surface to substrate, wherein:
(i) a maximum temperature of the ITM outer surface as it passes through the image forming station is defined as an imaging forming station maximum temperature (IFS-Temp MAX );
(ii) as the ITM outer surface passes through the main drying station, the ITM outer surface reaches a temperature exceeding the imaging forming station maximum temperature (IFS-Temp MAX );
(iii) a said gas-blower is present in the image-forming station and downstream of a most downstream print-bar of the image-forming station; and
(iv) each of a plurality of guide rollers disposed at the image-forming station is adjacent to a respective print bar in the image-forming station.

2. The printing system of claim 1 wherein a temperature of the ITM outer surface upon transfer of the tacky residue film therefrom to substrate at the impression station exceeds, by at least 10 degrees Celsius, the imaging forming station maximum temperature (IFS-Temp MAX ).

3. The printing system of claim 2 wherein as the ITM outer surface passes through the image forming station, different ink colors are applied sequentially and respectively to the ITM outer surface, each ink color applied by a different respective one of the print bars.

4. The printing system of claim 3 wherein for first and second of the print bars which respectively apply first and second colors, the gas blower associated with the first print bar blows gas onto the ITM outer surface: (i) after deposition thereon of ink of the first color by the first after and (ii) before reposition on the ITM outer surface of ink of the second color by the second print bars.

5. The printing system of claim 1 , wherein the impression station comprises a pressure cylinder having a compressible outer surface or carrying a compressible blanket and an impression cylinder and wherein the image transfer member comprises an endless belt of greater length than the circumference of the pressure cylinder and passing through a nip between the impression and pressure cylinders and contacting the pressure cylinder over only a portion of the length of the endless belt.

6. The printing system of claim 1 , wherein the intermediate transfer member is an endless blanket incorporating a compressible layer guided over guide rollers or supporting surfaces and having a run or a region thereof that is selectively deflectable by a movable nip roller to be urged against an impression cylinder.

7. The printing system of claim 1 , configured so that the residue film that is formed produced by the drying at the main drying station has a uniform thickness.

8. The printing system of claim 1 , configured so that the residue film that is K formed produced by the drying at the main drying station has a uniform thickness of at most 500 nanometers.

9. The printing system of claim 1 wherein a dilute solution of a charged polymer is applied to the outer surface of the ITM before the droplets of the ink are deposited thereon.

10. The printing system of claim 1 , wherein a treatment solution is applied to the outer surface of the ITM before the droplets of the ink are deposited thereon, and wherein at a time when the ink droplets are deposited on the ITM outer surface, a thickness of the treatment solution on the ITM outer surface is at most a few molecules.

11. The printing system of claim 1 wherein each of the plurality of the guide rollers disposed at the image-forming station is vertically aligned with a respective print bar in the image-forming station or disposed at most a few millimeters downstream therefrom.

12. The printing system of claim 1 wherein the residue film is rendered tacky at a time when the residue film is disposed on the upper run of the belt.

13. The printing system of claim 1 wherein each gas-blower at the image forming station blows a heated gas.

14. The printing system of claim 1 wherein the ink comprises an organic polymeric resin and a coloring agent in an aqueous carrier.

15. The printing system of claim 14 wherein the organic polymeric resin of the ink is the resin which forms the residue film that is rendered tacky.

16. The printing system of claim 14 wherein at the main drying station so that, sufficient liquid carrier is driven off to leave behind only a layer of (i) the organic polymer resin from the ink; and (ii) the coloring agent from ink.

17. The printing system of claim 1 wherein the ink is an aqueous ink, the ITM outer surface is hydrophobic, and gas from the gas-blowers serves both (i) to fix the droplets deposited by each print bar and (ii) to cause the ink droplets to resist contraction when on the hydrophobic ITM outer surface.

18. The printing system of claim 1 wherein the system is configured so that: (i) a pretreatment liquid is applied to the ITM outer surface before the droplets of ink are deposited thereon, (ii) the pretreatment liquid forms a pretreatment film on the ITM outer surface; (iii) therein the pretreatment film is totally dry by the time the pretreatment film reaches print bars of the image forming station; and (iv) the ink interacts with the totally-dry pretreatment film on the ITM outer surface.

19. The printing system of claim 1 wherein the system is configured so that a pretreatment liquid is applied to the ITM outer surface before the droplets of ink are deposited thereon, the pretreatment liquid forming a pretreatment film on the ITM outer surface such that a presence of the pretreatment film on the ITM outer surface assists the ink-droplets to retain their film-like shape after impacting upon the ITM outer surface.

20. A printing system comprising:
a. an intermediate transfer member (ITM) comprising an endless flexible belt having upper and lower runs, the belt passing over guide and drive rollers;
b. an image forming station at which droplets of ink are applied to an outer surface of the ITM to form ink images thereon, the image forming station comprising a plurality of print bars and a plurality of gas-blowers, each gas-blower respectively following a different associated print bar and configured to blow a gas-stream onto the ITM outer surface to only partially dry ink-droplets deposited by the associate print bar; and
c. a main drying station disposed both (i) downstream of the image forming station and (ii) above an upper run of the belt, the main drying station for sufficiently drying the ink images to produce therefrom a residue film of ink solids,

Assignees

• Landa Corp Ltd

Inventors

• Landa Benzion
• Sheinman Yehoshua
• Abramovich Sagi
• Golodetz Galia
• Nakhmanovich Gregory
• Soria Meir

Classifications

• B41N10/00

  Blankets or like coverings; Coverings for wipers for intaglio printing (wipers for intaglio printing B41F9/08) · CPC title

• B41M5/03

  by pressure · CPC title

• B41M5/0256

  the transferable ink pattern being obtained by means of a computer driven printer, e.g. an ink jet or laser printer, or by electrographic means · CPC title

• B41J2/0057 Primary

  where an intermediate transfer member receives the ink before transferring it on the printing material · CPC title