GB2210327A - Colouring xerographically produced images - Google Patents

Abstract

Toner images may be coloured simply by tackifying the image with a suitable solvent and bringing the tackified image into contact under pressure with a transferable colour layer carried on a foil. The solvent may be applied by bringing the foil itself, solvent-wetted, into contact with the toner image, or by means of a brush or felt-tip direct on to the toner image, or by wiping over the image surface. If the image-carrying substrate is porous the solvent may be applied from the reverse side. The process does not require heat, and can be carried out using very simple equipment.

Description

COLOURING XEROGRAPHICALLY PRODUCED IMAGES This invention relates to the colouring of toner images and in particular to colouring the toner images on xerographically produced copies.

In the creation of artwork, graphic designers often wish to obtain coloured images rather than simple black and white images of their designs. One way of obtaining colour copies is to photograph the black and white image, produce a negative and from this produce, with one of the known colour films, a colour image of the design.

Alternatively one of the coloured toner xerographic copiers can be used to obtain a colour copy of the design.

Another way is selectively to apply colour to the toner image of a xerographic copy. Several such processes exist. However, these processes require the sandwiching together of a toner image carrying substrate and a colour-carrying foil, with the toner and colour juxtaposed, require heat and pressure to be applied, to the sandwich, in order to render the toner tacky and the colour from the foil to adhere to the tacky toner more strongly then it is held on the foil so that on peeling substrate and foil apart, the colour remains on the toner images. EP-A-0191592 gives more details, including details of applying metallic coated foils, which require a layer of adhesive on the metallised colour to adhere the metallised colour to the toner.

The present invention provides a method for applying colour to toner images comprising: applying a suitable solvent to the toner image to render the toner tacky, applying a coloured foil to the tacky toner, consolidating by pressing the foil into contact with the tacky toner removing the foil leaving colour adhered to the tacky toner.

Accordingly no heat is required in order to transfer colour to toner images. This makes the transferring of colour to toner images far simpler. Also, less equipment is required in a graphic art studio to produce colour images. Another advantage to the designer is that he can apply the solvent only in those image areas to which he wishes colour to be transferred.

Thus the present invention not only allows the designer to colour toner images selectively but also allows him to colour only those parts of the toner image which he wishes to colour.

Multicolour images can thus be produced by selectively applying different colours to different toner areas.

Preferably, the toner images are xerographically produced. The toner particles on such copies are generally of the type containing a resin and/or wax. The solvent used in carrying out the invention may accordingly be of a type which will swell the resin and/or wax and so render the toner image tacky. The solvent should not dissolve the toner. The substrate on which the toner image is carried may be paper, film or other desired substrate, but should be one which is not adversely damaged by the application of the solvent used for making the toner image thereon tacky. Thus the solvent used can be applied to the toner image without the image becoming smeared.

The solvent needs to be chosen carefully to fulfil such requirements. Mixtures of solvents and non-solvents may be used to advantage, the precise nature of the mixed solvent being easily controlled by varying the mixing ratio. A useful system is to mix an aromatic hydrocarbon solvent (which has an affinity for or will attack toner base materials) with an aliphatic hydrocarbon or alcohol (which generally does not interact with toner base materials) in a ratio appropriate to give a solvent mix which tackifies adequately, but does not dissolve, the toner image.

One preferred solvent for use in the method of the invention comprises a mixture of xylene and alcohol.

Preferably, the mixture comprises xylene and ethanol in proportions of around 25% and 75% by weight respectively.

Xylene is readily absorbed by toner resin and the ethanol acts as a diluent to reduce the toner swelling power of the mixture.

The solvent can be applied either to the toner image (xerographic copy) by wiping it directly onto the surface of the toner image, or by applying it to the surface of the coloured foil and then applying the foil itself to the toner image. With certain imaged substrates, e.g. of paper, the solvent can be applied to the non-imaged side and allowed to soak through to the toner side there to render the toner image tacky. Solvent applied to image areas with no toner particles will simply evaporate and the non-toner image areas will not become tacky. This method avoids any mechanical action on the toner image which could cause smudging.

The solvent can be stored for use and applied in any convenient fashion. One preferred approach is to use the solvent in a felt tip pen such as a nylon fibre tip pen, the pen acting both as storage container and as a convenient applicator. Brush pen types can be used in similar fashion.

The coloured foil is applied to the toner image carrying surface and where the toner particles are tacky, the colour will adhere to the tacky toner areas and remain on those areas when the foil is peeled away. Metallic and pigmented colour foils can be used. The colour material on the foil should be of adequate opacity to mask the toner itself. The colour is usually in the form of a layer having suitable shearing and adhesive and cohesive properties. The colour layer should shear easily exactly around the edges of the tacky toner areas resulting in a high definition coloured image. The foil may have more than one layer which will transfer in this way, the outermost layer (which need not be coloured) being chosen to be very easily adhereable to the tackified toner.

The following examples will show how the invention may be practised.

EXAMPLE 1 A design produced by a graphic artist is xerographically copied using a standard office copier.

The copy shows the design as a black toner image on a white paper ground.

Solvent comprising 25% by weight xylene and 75% by weight ethyl alcohol is applied to the image bearing surface of the copy by means of a nylon fibre tipped pen.

The toner swells due to the partial dissolving of the components and becomes tacky.

A matt yellow blocking foil is applied to the tacky toner image-bearing surface of the copy, the toner being sandwiched between the white paper and the colour layer of the foil. Pressure is applied to consolidate the contact between the colour layer and the tacky toner.

The foil is then peeled away from the paper. This can be done anything from a few seconds after consolidation to hours or even days afterwards. The yellow coloured layer remains fixed to the paper in the areas of toner, and is retained by the foil in the regions where no tackified toner was present. The result is a black and yellow design on a white ground.

EXAMPLE 2 A xerographically produced copy in black toner on solvent porous white paper is placed image side down on top of a red coated foil.

A mixture of 20 parts by weight zylene and 80 parts by weight hexane is applied to the back of the paper. The mixture seeps through the paper to the toner layer which becomes tacky, and adheres to the red coating. The solvent is allowed to evaporate and the paper and foil are peeled apart. The black toner images which had been tackified by the solvent are covered in an adherent red layer. The resulting coloured design is black and red on white.

EXAMPLE 3 A solvent saturated pad is located in a foil strip dispenser in such a way that foil may be uncoiled from a reel thereof, passed over the pad, and emerge from the dispenser with its coated side wetted with solvent. The dispenser has a roller over' which the non-wetted side of the strip passes as it exits the dispenser. The dispenser is rolled along a line of type in a xerographically produced copy, the roller pressing the solvent wetted coating into contact with the toner image. After a strip is dispensed and pressed onto the page this way, the strip is cut (leaving a tab for pulling the next section from the dispenser) and the cut section then peeled from the page to leave a line of the text coloured due to adhesion of the colour coating to the underlying toner images of letters.

Claims (8)

1. A method of applying colour to a toner image comprising: applying a suitable solvent to the toner image to render the toner tacky, applying a coloured foil to the tacky toner, consolidating by pressing the foil into contact with the tacky toner, and removing the foil to leave colour from the foil adhered to the toner image.

2. A method according to claim 1 wherein the solvent is applied to the colour coating on the coloured foil which is then in turn applied to the toner image, left in contact therewith for a short while, and then removed.

3. A method according to claim 1 wherein the solvent is applied to the toner image via a solvent porous substrate bearing the image.

4. A method according to claim 3 wherein the coloured foil is applied to the toner image before the solvent is applied to the non-imaged side of the image carrying solvent porous substrate.

5. A method according to any one of claims 1 to 4 wherein the solvent is applied by means of a fibre tip or brush applicator.

6. A method according to any one of claims 1 to 5 wherein the solvent comprises a mixture of ethanol and xylene.

7. A method of applying colour to a toner image substantially as hereinbefore described with reference to any one of the foregoing Examples.

8. A coloured toner image produced by the method of any one of the preceding claims.