WO1996006384A1

WO1996006384A1 - Imaging method

Info

Publication number: WO1996006384A1
Application number: PCT/NL1994/000204
Authority: WO
Inventors: Peretz Ben-Avraham; Becky Bossidon
Original assignee: Indigo N.V.
Priority date: 1994-08-25
Filing date: 1994-08-25
Publication date: 1996-02-29
Also published as: AU7823694A

Abstract

A printing method including the steps of forming an image on an imaging member, the image comprising colored polymer toner particles and a hydrocarbon liquid carrier and transferring and fusing the developed image to a paper substrate whose surface has been treated with and preferably coated with a compound having a basic functionality. The polymer is preferably an acidic polymer and the coating is preferably an imine compound.

Description

IMAGING METHOD FIELD OF THE INVENTION This application is in the field of printing and more particularly is concerned with the printing of images on coated paper. BACKGROUND OF THE INVENTION In U.S. Patent 5,192,638, the specification of which is incorporated herein in its entirety, Landa et al introduced a new liquid toner comprising a carrier liquid such as a light mineral oil and pigmented toner particles having fibrous extensions. The mineral oils described in the above referenced patent were Isopar L and M ( TM) type saturated hydrocarbon liquids having a high Kauri-Butanol number and a high resistivity. Many other mineral oils such as Marcol 82 or other carrier liquids for liquid toner as are known in the art, are also suitable for the toner type of U.S. Patent 5,192,638, depending on the overall characteristics specified for the toner. A characteristic of these toners is that they solvate the carrier liquid at elevated temperatures but are substantially insoluble in the carrier liquid at room temperature. Other patents and publications which describe preferred embodiments of this toner type and additives useful in the toner are U.S. Patents 5,300,390; 5,286,593; 5,208,130;, 5,266,435; 5,264,313; and 5,225,306 and in PCT publications WO 94/02887 the disclosures of which are incorporated herein by reference. In U.S. Patents 5,289,238; 5,280,326; 5,276,492; ; 5,270776; 5,262,829; 5,255,508; 5,208,637; 5,166,734 and 5,148,222, the disclosures of which are incorporated herein by reference, apparatus which preferably uses these toners is described. In these references a liquid toner image comprising one of the above mentioned toners is formed on an image bearing surface and the image is transferred to a final substrate and fused thereon while it is still wet. It is a characteristic of these toners that they can generally be fused at a relatively low temperature to the paper, since they solvate the carrier liquid and are thereby softened. In a particularly preferred embodiment of the apparatus described, the liquid toner image is transferred to an intermediate transfer member from which it is transferred to the final substrate. The temperature of the intermediate transfer member is elevated, generally to a relatively low temperature of between 85^βC and 125^βC and the image thereon is transferred to and pressure fused to the paper by the pressure of the intermediate transfer member against the paper. Alternatively, the liquid toner image is transferred to the paper and subsequently fused thereto by the application of heat with or without pressure. It has been discovered that the adhesion of the toner to the final substrate, while sufficient for many purposes, is sometimes not sufficient for archival purposes or for security purposes. Raising of the temperature of fusing does not necessarily improve the adhesion to an adequate degree. SUMMARY OF THE INVENTION It is a purpose of the present invention to provide a printing process, generally similar to the processes described in the above patents and applications, for which the adhesion of the image to the final substrate is enhanced. To this end the printing process utilizes acidic toner particles and prints on paper which has a basic surface. In one preferred embodiment of the paper on which the images are fused has been pre-coated with a polymer having an imine functionality such as polyethylene imine (anhydrous or water solution), polyethylene imine epichlorydine (modified), ethoxylated (20%) polyethylene imine or low molecular weight anhydrous polyethylene imine. Alternatively other materials having at least a basic functionality such as polya ides can be employed. Toner images printed on paper, polyester or polypropylene substrates which are coated with the above materials adhere much better than on untreated substrates. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The preferred printing method of the present invention is described in the background of the invention and in the prior art references which are listed therein. As indicated above, the printing process of the present invention is characterized by the use of paper or polymer substrates which have a basic surface functionality and preferably are coated with a basic compound such as an imine compound, preferably a polyethylene imine compound. Such basic surfaces may also be referred to as alkaline surfaces. Preferred coating compounds include 20% ethoxylated polyethylene imine (manufactured by Sigma), anhydrous or water solutions of polyethylene imine (manufactured by BASF, Arsynco or Rhome & Hass under various trade names ) , PRIMAFLOC C-3, a low molecular weight anhydrous polyethylene imine (Rhome & Hass) and epichlorohydrin polyethylene imine (Sigma). Other coating materials having a basic functionality such as polyamides with amine and carboxylic acid functionality (Macromelt 6238, 6239 and 6070 manufactured by Henkel ) have shown improved adhesion, especially on transparencies, however, the preferred coating materials show the superior adhesion enhancement. The paper can be coated using any method known in the art for coating such as dip coating, adding the material during paper making (for example in the final bath), doctor blade coating, spraying or by wire rod coating. In a preferred method, polyethylene imine (50% solution in water) is diluted to l%-2% concentration by the addition of isopropyl alcohol. Wire rod coating is used to coat the paper with the solution. After coating the solvent is evaporated by blowing warm air over the treated paper. Alternatively, solutions of the material only in water or only in alcohol may be used. Almost all types of paper and transparencies treated according to this method show improved adhesion resistance (when measured using an abrasion test similar to ASTM standard for CROKE meter F 1319-90, modified in that the cloth is replaced by a pencil eraser). Papers which showed greatly improved adhesion resistance (at least 50%-150% improvement) include Krome Kote, Star white Vicksberg 110# Index, Lithofect Plus Gloss White (Repap) , Rayprint 110, Lekyam, Neoprint, Arial Top Brilliant #1 and #2, Haπunermill Regalia Cover Alphe White Lustre Finish, Hammermill Lazerprint, Sterling Gloss (Westvaco) and Multifect (Repap). Other papers showed lesser improvement or no improvement. Almost all types of papers showed substantial improvement in a standard peeling test, including Star white Vicksberg 110# Index, Sterling Lithosatin 110#, Lithofect Plus Gloss White, Neoprint, Arial Top Brilliant #2, Hammermill Regalia Cover Alphe White Lustre Finish, Warren Lustrogloss, Sterling Gloss and Multifect (Repap). Other papers showed smaller or no improvement, but many of these already exhibited high peel resistance. The above tests were carried out utilizing pigmented toners based on an ethylene terpolymer which has an acid number of 60 and an ethylene copolymer which has an acid number of 90. Toners based on other polymers such as some Surlyn (DuPont) ionomers (for example Surlyn 8940 and Surlyn 8920) and IOTEK 8030 ionomer (EXXON) also showed generally improved abrasion resistance and/or peel strength improvement even though these polymers had a generally lower acid number than the polymers used in the above tests. Some toner types which are basically unusable on ordinary paper become strongly adhering on paper coated according to the invention. The preferred toners for the printing process of the present invention have the following formulations : Black toner- about 16% Nucrel 925 ( ethylene copolymer by DUPONT ) , about 0 . 4% BT 583D ( blue pigment produced by Cookεon Pigments ) , about 4% Mogul L carbon black ( Cabot ) , approximately 0.45% aluminum tristearate and charge director as described in US patent application 07/915,291 (utilizing lecithin, BBP and ICI G3300B) and in WO 94/02887 in an amount equal to 40 mg/gm of solids and the remainder Isopar L. Magenta toner- about 15.5% Bynell 2002 (ethylene terpoly er by DUPONT), about 2.8% Finess Re F2B magenta pigment ( Toyo Ink), about 0.14% Sico Fast Yellow D1355DD yellow Pigment (BASK) approximately 0.45% aluminum tristearate and charge director as described in US patent application 07/915,291 (utilizing lecithin, BBP and ICI G3300B) and in WO 94/02887 in an amount equal to 40 mg/gm of solids and the remainder Isopar L. Cyan toner has a composition similar to that of the magenta toner except that 2.36% of BT583D pigment (Cookson replaces the magenta pigment and the yellow pigment is reduced to 0.03%. The composition of the yellow toner is similar to that of the black toner except that 3.13% of yellow pigment is substituted for the pigment and carbon black of the black toner. It will be appreciated by persons skilled in the art that the present invention is not limited by the description and example provided hereinabove. Rather, the scope of this invention is defined only by the claims which follow:

Claims

CLAIMS 1. A printing method comprising: forming an image on a imaging member, the image comprising colored polymer toner particles and a hydrocarbon liquid carrier; and transferring and fusing the developed image to a paper substrate whose surface has been treated with a compound having a basic functionality.

2. A printing method comprising: forming an image on a imaging member, the image comprising colored polymer toner particles and an oily liquid carrier; and transferring and fusing the developed image to a paper substrate whose surface has been treated with a compound having a basic functionality.

3. A printing method according to claim 1 or claim 2 wherein the treatment of the surface comprises coating the surface with the compound.

4. A printing method according to any of the preceding claims wherein the compound is a basic compound.

5. A printing method according to any of the preceding claims wherein the colored polymer toner particles are acidic in nature.

6. A printing method according to any of the preceding claims wherein the polymer comprises an ethylene terpolymer.

7. A printing method according to any of claims 1-5 wherein the polymer comprises an ethylene copolymer.

8. A printing method according to any of claims 1-5 wherein the polymer comprises an ionomer. 1

2 9 . A printing method according to any of the preceding

3 claims wherein the compound comprises an imine compound . 4

5 10. A printing method according to cl aim 9 wherein the

6 imine compound comprises a a polyethylene imine compound . 7

8 11 . A printing method according to cl aim 9 wherein the

9 imine compound comprises an ethoxylated polyethylene imine . 10

11 12 . A printing method according to claim 9 where in the

12 imine compound compri ses a epichlorohydrin polyethyl ene

13 imine . 14

15 13. A printing method according to any of the preceding

16 claims wherein the liquid carrier is a saturated

17 hydrocarbon. 18

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