Lithographic Printing Plates and Processes for Making them

• US 20090123741A1
• Filed: 05/08/2007
• Published: 05/14/2009
• Est. Priority Date: 05/10/2006
• Status: Abandoned Application

• Current Assignee: Technova Imaging Systems (P) Limited
• Original Assignee: Technova Imaging Systems (P) Limited
• Inventors: Thyagarajan, Anantaraman Iyer, Bhatt, Jivan Gulabrai, Kurian, Manelal Chirayil Jacob, Aniruddha, Shreekant Damle
• Application Number:
  US12/227,122
• Publication Number:
  US 20090123741A1
• Time in Patent Office: Days
• US Class Current: 428/337
• CPC Class Codes: B41C 1/1066 by spraying with powders, by using a nozzle, e.g. an ink jet system, by fusing a previously coated powder, e.g. with a laser
• CPC Class Codes: B41N 1/08 for lithographic printing B41N1/003, B41N3/03 take precedence; compositions of the image-forming layer B41C1/10
• CPC Class Codes: B41N 1/14 Lithographic printing foils B41N1/003, B41N3/03 take precedence; compositions of the image-forming layer B41C1/10
• CPC Class Codes: B41N 3/036 characterised by the presence of a polymeric hydrophilic coating
• CPC Class Codes: Y10T 428/266 of base or substrate
• CPC Class Codes: Y10T 428/31507 Of polycarbonate
• CPC Class Codes: Y10T 428/31721 Of polyimide
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

Abstract

A novel lithographic printing plate suitable for use with inkjet printers as image forming devices and a method for making such a plate is disclosed. The novel lithographic printing plate according to this invention comprises: (a) a substrate; (b) at least one base coat provided on the substrate, said base coat obtained from a composition comprising, in a first solvent (i) at least one first hydrophilic binder, (ii) a mixture of pigments comprising at least one porous hydrophilic pigment and at least one non-porous hydrophilic pigment, (iii) at least one first cross-linking agent, and (iv) at least one first catalyst; and (c) at least one top coat provided on the base coat, said top coat obtained from a composition comprising, in a second solvent (i) at least one second hydrophilic binder, (ii) at least one hydrophilic pigment in particulate form, wherein at least 10% of the pigment particles have particle size of about 3-15 micron (iii) at least one second cross-linking agent, and (iv) at least one second catalyst.

Claims

1. A lithographic printing plate suitable for use with inkjet printers as an image forming device, said plate comprising:

(a) a substrate;

(b) at least one base coat provided on the substrate, said base coat obtained from a composition comprising, in a first solvent (i) at least one first hydrophilic binder, (ii) a mixture of pigments comprising at least one porous hydrophilic pigment and at least one non-porous hydrophilic pigment, (iii) at least one first cross-linking agent, and (iv) at least one first catalyst; and

(c) at least one top coat provided on the base coat, said top coat obtained from a composition comprising, in a second solvent (i) at least one second hydrophilic binder, (ii) at least one hydrophilic pigment in particulate form, wherein at least 10% of the pigment particles have particle size of about 3-15 micron (iii) at least one second cross-linking agent, and (iv) at least one second catalyst.

2. A lithographic printing plate as claimed in claim 1, wherein the substrate has one operative surface and one inoperative surface, said operative surface being provided with at least one base coat and at least one top coat.

3. A lithographic printing plate as claimed in claim 1, wherein the substrate has two operative surfaces and each of said operative surfaces is provided with at least one base coat and at least one top coat.

4. A lithographic printing plate as claimed in claim 1, wherein the substrate is a treated substrate.

5. A lithographic printing plate as claimed in claim 1, wherein the substrate comprises at least one material selected from a group consisting of metal, polymer paper and their laminates.

6. A lithographic printing plate as claimed in claim 1, wherein the substrate comprises at least one polymer selected from a group of polymers consisting of a polyester, polycarbonate, polyamide, polyimide, polyolefin and Teflon.

7. A lithographic printing plate as claimed in claim 1, wherein the substrate is a multi-layered laminate.

8. A lithographic printing plate as claimed in claim 1, wherein the thickness of the substrate is about 50 to about 400 microns.

9. A lithographic printing plate as claimed in claim 1, wherein the first solvent and the second solvent is independently selected from a group of solvents consisting of hydrophilic solvents.

10. A lithographic printing plate as claimed in claim 1, wherein the first solvent and the second solvent is independently selected from a group of solvents consisting of water, (C₁-C₆) alcohol or a mixture thereof.

11. A lithographic printing plate as claimed in claim 1, wherein the first hydrophilic binder and the second hydrophilic binder is independently at least one binder selected from a group of binders consisting of a polymer or a copolymer derived from vinyl monomers, acrylic monomers, anhydride monomers, caprolactam monomers and urethane monomers.

12. A lithographic printing plate as claimed in claim 1, wherein the first hydrophilic binder and the second hydrophilic binder is independently at least one binder selected from a group of binders consisting of a polyester, polyamide, polyimide, polyurethane, polyvinyl alcohol, polyvinyl pyrolidone, polyacrylate, starch, starch derivatives, gelatin, polysaccharide, resins derived from formaldehyde and polyethers.

13. A lithographic printing plate as claimed in claim 1, wherein the hydrophilic pigment is a metal oxide.

14. A lithographic printing plate as claimed in claim 1, wherein the hydrophilic pigment is at least one pigment selected from a group of pigments consisting of silicon dioxide, alumina, zinc oxide, magnesium oxide, titanium oxide, silica, calcium carbonate, kaolin, talc, mica, dolomite, zeolite, gypsum, calcium sulfate and barium sulfate.

15. A lithographic printing plate as claimed in claim 1, wherein the first cross-linking agent and the second cross-linking agent is independently at least one cross-linking agent selected from a group of cross-linking agents consisting of formaldehyde, polyols, glyoxal, aziridine and its derivatives, zirconium ammonium carbonate, alkylated melamine, phenolic resins, boric acid, derivatives of orthosilicate and epoxides.

16. A lithographic printing plate as claimed in claim 1, wherein the first catalyst and the second catalyst is independently at least one catalyst selected from a group of catalysts consisting of organic acid, inorganic acid, organic anhydride, salts of organic acids and derivatives of organic acid.

17. A lithographic printing plate as claimed in claim 1, wherein not more than 90% by mass of the total hydrophilic pigment in the top coat has a particle size less than about 400 nanometers.

18. A lithographic printing plate as claimed in claim 1, wherein thickness of the base coat is about 1 micron to about 25 micron.

19. A lithographic printing plate as claimed in claim 1, wherein thickness of the top coat is about 1 micron to about 25 micron.

20. A lithographic printing plate as claimed in claim 1, wherein the total pigment content in base coat is less than 90% by mass of the total base coat composition excluding solvent.

21. A lithographic printing plate as claimed in claim 1, wherein the non-porous pigment in the base coat is present in an amount from about 50 to 95% by mass of the total pigment content.

22. A lithographic printing plate as claimed in claim 1, wherein the first hydrophilic binder is present in an amount from about 10 to about 40% by mass of the total base coat composition excluding solvent.

23. A lithographic printing plate as claimed in claim 1, wherein the first cross-linking agent is present in an amount from about 0.5 to about 4% by mass of the total base coat composition excluding solvent.

24. A lithographic printing plate as claimed in claim 1, wherein the first catalyst is present in an amount from about 0.4 to about 4% by mass of the total base coat composition excluding solvent.

25. A lithographic printing plate as claimed in claim 1, wherein the total pigment content in the top coat is in the range of about 50 to about 90% by mass of the total top coat composition excluding solvent.

26. A lithographic printing plate as claimed in claim 1, wherein the second hydrophilic binder is present in an amount from about 10 to about 40% by mass of the total top coat composition excluding solvent.

27. A lithographic printing plate as claimed in claim 1, wherein the second cross-linking agent is present in an amount from about 0.5 to about 4% by mass of the total top coat composition excluding solvent.

28. A lithographic printing plate as claimed in claim 1, wherein the second catalyst is present in an amount from about 0.4 to about 4% by mass of the total top coat composition excluding solvent.

29. A lithographic printing plate ac claimed in claim 1, wherein the base coat and the top coat are provided on both the sides of the substrate.

30. A process for preparing a lithographic plate as claimed in claim 1 comprising:

(a) Selecting a substrate;

(b) Optionally pre-treating the substrate,

(c) Providing a base coat composition on the substrate;

(d) Curing the base coat;

(e) Providing a top coat composition on base coat; and

(f) Curing the top coat.

31. A process as claimed in claim 30, wherein the pre-treatment of the substrate in step (b) includes treatment with at least substance selected from a group of substances comprising mineral acid, chlorinated phenol, organic acids, polymeric resins, C₁-C₆ alcohol.

32. A process as claimed in claim 30, wherein the pre-treatment of a substrate in step (b) includes at least one process selected from a group comprising subbing, corona treatment or plasma flame treatment.

33. A process as claimed in claim 30, wherein the base coat is provided on the substrate by means of at least one process selected from a group comprising Meir process, air knife process, reverse role coating process, comma doctor process, gravure coating process and cast coating process.

34. A process as claimed in claim 30, wherein the top coat is provided on the base coat by means of at least one process selected from a group comprising Meir process, air knife process, reverse role coating process, comma doctor process, gravure coating process and cast coating process.

35. A process as claimed in claim 30, wherein the curing in step (d) and (f) is achieved at a surface temperature of less than about 180°

C.

36. A process as claimed in claim 30, wherein the curing in step (d) and (f) is achieved by means of hot air or infrared radiation.

37. A process as claimed in claim 30, wherein the base coat is partially cured in step (d).

38. A process as claimed in claim 30, including the steps of forming a base coat composition, providing the base coat composition on substrate, forming a top coat composition and providing the top coat composition on the base coat.

39. A process as claimed in claim 38, wherein the step of forming a base coat composition includes mixing at least one first hydrophilic binder, at least one porous hydrophilic pigment, at least one non-porous hydrophilic pigment, at least one first cross-linking agent and at least one first catalyst in a first solvent.

40. A process as claimed in claim 38, wherein the step of forming a top coat composition includes mixing at least one second hydrophilic binder, at least one hydrophilic pigment having particle size of about 3 to about 5 microns, at least one second cross-linking agent and at least one second catalyst in a second solvent.

41. A process as claimed in claim 39-40, wherein formation of the coat composition comprises:

(a) Dispersing at least one pigment in a solvent, and

(b) Adding at least one binder, at least one cross-linking agent and at least one catalyst to the dispersion obtained in step (a).

42. A process as claimed in claim 30, wherein the steps (a) to (f) are carried out on each side of the substrate.

43. A process as claimed in claim 30 wherein the steps (a) to (f) are carried out in a sequence:

(a) Optionally, pre-treating the first surface,

(b) Optionally pre-treating the second surface,

(c) Providing a base coat on the first surface and optionally curing it,

(d) Providing a base coat on the second surface and optionally curing it,

(e) Providing a top coat on the first surface and optionally curing it, and

(f) Providing a top coat on the second surface and optionally curing it.

44. A process as claimed in claim 43, including the steps of providing a base coat on first surface of the substrate, providing a base coat on the second surface of substrate and simultaneously curing the base coat on each surface.

45. A process as claimed in claim 43, including the steps of providing a top coat on the base coat of the first surface of the substrate, providing a top coat on the base coat of the second surface of substrate and simultaneously curing the top coat on each surface.