GB2355959A

GB2355959A - Improvement in or relating to printing on leather

Info

Publication number: GB2355959A
Application number: GB9926142A
Authority: GB
Inventors: Eric Charles Gilham
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-11-05
Filing date: 1999-11-05
Publication date: 2001-05-09
Also published as: AU1160901A; WO2001032434A1; GB9926142D0; JP2003512958A; EP1152900A1

Abstract

A process for printing on leather includes the steps of generating a digital monochromatic or polychromatic image, printing the image on inkjet transfer paper, pressing the image onto a leather piece, removing the backing layer of the transfer paper, and heat treating the leather to refix the print image in the leather.

Description

2355959 IMPROVEMENTS IN OR RELATING TO PRINTING ON LEATHER This invention

concerns improvements in or relating to printing on leather. 5 An object of the present invention is to provide an improved process for the printing of leather which obviates the undesirable aspects of known techniques.

Accordingly, a process for printing on leather includes the steps of preparing an image of monochromatic or polychromatic character, printing the image using one or more inks or dyes onto a sheet of transfer paper having a backing layer, pressing the transfer paper onto a piece or strip of tanned leather to transfer the said image, removing the backing layer of the transfer paper using a solvent, and heat treating the leather piece or strip carrying the image to fix the inks or dyes into the body of the leather piece.

The image may conveniently be digitally generated and stored.

The transfer paper may be inkjet transfer paper obtained from a commercial source.

The inks or dyes employed in the method of the invention are preferably those produced from naturally occurring sources, such as plants. The inks or dyes may be pigmented dyes.

The leather to which the application of the present invention is particularly suited is one which preferably has no mineral salt content and is one produced using naturally occurring dyes and tanning materials. However, 2 the invention is applicable to leathers having a very light mineral salt content which advantageously does not exceed 5%. It is believed that a leather having a salt content greater than the stated upper limit will not be receptive to the printing process of the instant invention, since the salt will resist the acceptance by the leather of the ink or dye.

The leather may be provided with a surface coating with the printing being effected on the surface carrying said coatin The surface coating may be 9 a water-based paint. 10 The removal of the backing layer of the inkjet transfer sheet is an important step in terms of restoring the surface, of the leather piece to a natural texture both in tactile and visual senses. The solvent used for this removal step is conveniently one which is capable of removing water- based paints. The solvent may be one marketed under the trade mark NITROMORSO which is conventionally used for removing water-based textured paint, and in such use intrusive damage to the substrate is avoided by gently lifting off the backing layer. 'Fhe backing layer may be removed by careful wiping or by washing with a harmless liquid such as water.

The heating step following the removal of the backing layer of the inkjet transfer paper is intended to fix the inks or dyes in the leather piece, and is preferably effected by the use of a sheet of non-stick material, for example that sold under the trade mark TEFLON191, which diffuses the heat evenly across the leather piece or strip. The heat may be provided by a conventional heating platen under pressure.

The duration of the heating step and the temperature at which the heat transfer occurs is dictated by the nature and physical characteristics of the 3 leather piece being printed, eg its thickness. For example, the heating step may last for a period of 15 seconds at a temperature of 180'C, but variations both temporally and in temperature level may be made according to the leather piece or strip being processed.

The leather piece or strip may be further treated following the heating step in order to restore its drop characteristics, ie its ability to fall easily from the point of suspension, or in essence its pliancy. Such treatment involves a physical massaging of the leather and may be achieved by conventional means used in the leather making industry.

A still further treatment of the leather may involve the application of a stain-resistant medium, such as that sold under the trademark SCOTCHGUARD9.

By way of example only, one process for printing on leather according to the present invention is described below.

A polychromatic image is generated digitally on a computer and is printed using a large format inkjet printer, for example an Encad Nova-Jet Pro 600e, provided with reactive inks or dyes which lay the image on inkjet transfer paper.

The sheet bearing the printed image is then pressed onto a piece of leather which has been tanned.

The next step in the process involves the removal of the backing sheet by means of the application of a solvent which is a textured water-based paint remover, for example a remover sold under the trade name NITROMORS9.

The action of this remover is to soften the backing layer to an extent that it 4 can easily be wiped gently off the surface of the leather. In an alternative, the softened backing layer thus produced may be washed off the surface of the leather.

The removal of the backing layer restores the tactile and visual characteristics of the leather, but it is necessary to apply heat to the leathE!r in order to refix the inks or dyes.

In this example, a sheet of non-stick material, such as that sold under the trade mark TEFLONO, is placed over the leather piece and heat and pressure are applied to the non-stick material which evenly diffuses the heat, thereby to refix and press the inks or dyes back into the body of the leather piece.

The resulting leather piece has the normal appearance and tactile qualities of unprinted leather but carries the print image generated digitally by computer, the image being fixed in the fabric of the leather.

The printed leather may be further protected by the use of a product such as SCOTCHGUARD 0.

lt will be understood that the printing of leather may be carried out in a continuous process with the leather being in lengths which could fotexample be worked over rollers with suitable treatment stations being provided for the printing, image application to the leather, backing layer removal, and heat treatment.

Claims

CLAIMS:

I. A process for printing on leather including the steps of preparing an image of monochromatic or polychromatic character, printing the image using one or more natural inks or dyes onto a sheet of transfer paper having a backing layer, pressing the transfer paper onto a piece or strip of tanned leather, removing the backing layer of the transfer paper using a solvent, and heat treating the leather piece or strip carrying the image to fix the inks or dyes into the body of the leather piece.
2. A process according to Claim I in which the image is generated and stored digitally.
3. A process according to Claim I in which the transfer paper is inkjet transfer paper.
4. A process according to any one of the preceding claims in which the inks or dyes are those produced from naturally occurring sources.
5. A process according to Claim 4 in which the inks or dyes are plant dyes.
6. A process according to Claim 4 in which the inks or dyes are pigmented.
7. A process according to any one of the preceding claims 1 to 3 in which the inks or dyes are synthetic.

6
8. A process according to any one of the preceding claims in which the dyes are reactive dyes.
9. A process according to any one of the preceding claims in which the inks or dyes are water-based.
10. A process according to any one of the preceding claims in which the leather of which the strip or piece is made is one which has been tanned using a natural tanning process.
11. A process according to Claim 10 in which the leather no mineral content.
12, A process according to Claim 10 in which the leather has a chromium salt content of up to 5%.
13. A process according to Claim 10 in which the leather has an alum salt content of up to 5%.
14. A process according to any one of the preceding claims in which the solvent used for the removal of the backing layer is one which I'S capable of removing water-based paints.
15. A process according to any one of the preceding claims in which the solvent softens the backing layer which is thereby rendered removable.
16. A process according to any one of the preceding claims in which the heating step is effected by employing a heat source in combination with a non-stick pressing sheet in contact with the leather piece or strip.
17. A process according to any one of the preceding claims in which a further treatment step following the heat treatment step involves the restitution of the drop characteristics of the leather.
18. A process according to any one of the preceding claims in which a stain-resistant medium is applied to the leather piece following the heat treatment step.
19. A process for printing on leather substantially as hereinbefore described.