WO1991006042A1

WO1991006042A1 - Transferring images on to artwork

Info

Publication number: WO1991006042A1
Application number: PCT/GB1990/001625
Authority: WO
Inventors: Peter Mckie
Original assignee: Esselte Letraset Limited
Priority date: 1989-10-23
Filing date: 1990-10-23
Publication date: 1991-05-02
Also published as: GB8923830D0; AU6633590A

Abstract

Toner images formed on transparent or translucent sheets may be transferred to artwork by covering them with adhesive in order to stick the toner image to the artwork more strongly than it adheres to the transparent or translucent sheet and then peeling the transparent or translucent sheet away. In accordance with the invention the toner image is adhered by selective transfer of a low tack pressure sensitive adhesive from a layer of such adhesive on a release surface. Transfer is effected by bringing the toner image into intimate contact with the layer of adhesive and then lifting away the transparent or translucent sheet which can thereafter be used in the manner of a dry transfer sheet to transfer the toner image to the desired artwork. The toner image may be covered prior to the application of adhesive by the selective application of a further layer, e.g. from a blocking foil of known type.

Description

TRANSFERRING IMAGES ON TO ARTWORK

This invention relates to transferring images on to artwork.

British Patent Specification 1602937 discloses methods of forming a xerographic toner image on an abhesive sheet of material to enable subsequent transfer of the image on to artwork or the like, and the application of adhesive from an adhesive donor sheet to the toner image such that, on contact between the toner image and the donor sheet under special conditions, the adhesive transfers from the donor sheet to the toner image. When the adhesed toner image is brought into contact with the material to which the image is to be applied, then the adhesion between the toner image and the material is the greater than that between the abhesive sheet and the toner image and the toner image is transferred. The initial creation of the toner image may either be by means of repeated passes of the abhesive sheet through the xerographic copier unit whereby an image sufficiently robust for transfer is built up, or by means of using a special toner in the xerographic copier which would provide, in a single pass an image robust enough for transfer.

The need for multiple passes is unsatisfactory as, for successful results, accurate registration is needed between the successively laid down toner images. This is difficult to achieve reliably. In addition, successive passes result in the build up not only of the desired image but also of the background contamination around the image. The alternative approach requires the provision of a special toner which, in a xerographic copying machine not dedicated to making images of this nature, is both costly and inconvenient. The methods of application of the adhesive to the toner image are both time consuming and require the use of specialised apparatus.

In accordance with the present invention, the need to use special toner is avoided while retaining the ability to transfer the image produced in a single pass through the apparatus by applying from a coated carrier sheet a layer of adhesive using pressure alone selectively to transfer adhesive to the toner image, which adhesive is capable of removing the image bodily and adhering it to the artwork.

Thus, the present invention provides a method of transferring images on to artwork which comprises forming a toner image of the desired image using a xerographic imaging apparatus and using as receptor sheet for the xerographically formed image a sheet having a release surface, applying adhesive selectively to the toner image on the release surface and subsequently adhering the toner image by means of the applied adhesive to the artwork in the desired position more strongly than the toner image adheres to the release surface, wherein the application of adhesive to the toner image while it is residing on the release surface is effected by bringing the imaged but unadhesed sheet into contact with a carrier sheet bearing a layer of releasable adhesive thereon, applying pressure to urge the toner image into intimate contact with the layer of adhesive and pulling the two sheets apart. The xerographic imaging apparatus may be a xerographic copier or laser printer or like apparatus for depositing a toner image on to a substrate.

If desired, the toner image may be treated before the application of adhesive by the selective application thereto of a further layer of material, e.g. applied from a commercially available blocking foil. This has the advantage of increasing the optical density of the toner image, and can provide a less fragile transferable unit.

The nature of the adhesive and the nature of the surface of the carrier sheet on which the adhesive layer is carried should be chosen such that the adhesive is transferred to the imaged sheet only where pressure has been applied to provide the intimate contact and not in other areas.

The imaged sheet, now carrying adhesive substantially only over the image, can then be used as before by placing it adhesive side down on top of the artwork, and rubbing from the back of the sheet to transfer the image to the artwork and leave it adhered there when the sheet on to which the image was originally deposited is peeled away.

By suitable choice of adhesive composition and of the surface of the sheet on to which the image is deposited, the adhesive may be caused to adhere only to the toner areas, thus leaving the surrounding areas free of adhesive.

This selective application of adhesive to the toner image may be effected by application of finger pressure in the image area when the two sheets are placed together if appropriate formulations are used. The bringing together of the imaged sheet and the adhesive coated carrier sheet preferably takes place such that the adhesive carrier sheet is placed on top of the image sheet such that the adhesive contacts the toner image and the back of the adhesive sheet is uppermost. Light finger pressure only needs to be applied over the appropriately formulated adhesive sheet to effect transfer of the adhesive to the toner image. If too much pressure is applied then adhesive transfers in the surrounding areas of the image, which can ultimately result in adhesive contamination. However, with familiarity and careful use, good results can be achieved whereby little or no background adhesive contamination is experienced.

The invention may be practised with a variety of materials, simple experiment being desirable to optimise adhesive composition and coating weight for use with any given toner imaging system. The surface of the sheet on to which the toner image is deposited by the photocopier or laser printer may be varied also, and needs to be chosen dependent upon the type of thermoplastic toner and the fusing conditions used in order that the toner image adheres satisfactorily thereto such that it is not transferred from the sheet on to which it has been placed in the photocopier or laser printer during the application of adhesive thereto, but can be easily transferred on to artwork under the action of the applied adhesive.

A particular advantage of the method of operation of the present invention is that it enables the production on artwork of coloured image areas when used in conjunction with a toner imaging colouring system of known type. A specific advantage is that using sequential toner transfer (on to the artwork) and colouring the transferred images, multicolour artwork images can be built up without difficulty. Toner image colouring systems using blocking foils and reliance upon the thermoplastic properties of toner images have recently become widely used and commercialised. Specific mention may be made of the systems commercialised under the Trade Marks OMNICROM and COLOR TAG. In these systems, a blocking foil is placed over a toner image and heat and pressure applied, either using a heated nip between two rollers or, e.g. using a small hand-held heated platen. Under the action of heat and pressure, coloured material transfers selectively from the blocking foil to the toner image but not to the surrounding areas. In practising the method of the present invention, a first toner image may be laid down and then coloured by the use of heat and a blocking foil as just noted whereafter, if desired, a second further toner image may be laid down wholly or partly on top of the first coloured toner image. The blocking foil treatment may then be repeated, e.g. using a different colour, and again the transfer of colour from the blocking foil will only be in the areas where thermoplastic toner is still exposed, i.e. the second toner image applied, not the first which is, by this time, already covered with a non-adhesive coloured layer.

In this way, colour overlay effects may be obtained rapidly and effectively.

The following Examples will serve to illustrate the invention:

Example 1

Sheets of polyethylene terephthalate film of thickness 75 to 100 microns were coated with a silicone release layer.

The silicone release layer was made by mixing together the following ingredients in the following proportions by weight :

Cellulose derivative solution (2% parts by weight by weight in water of a non-ionic cellulose derivative, Natrosol HHR-P, ex National Starch) 38.630

Silicone premix 3.213 Vinylidene chloride aqueous copolymer emulsion (Polydene 33-041, ex Scott Bader) 1.033

Polyalkylene oxide modified dimethylpoly- siloxanes (Silvet L77, ex Union Carbide) 0.2

Water to 100.0

The silicone premix was an equal weight mixture of two grades of 40 percent by weight solids emulsion of a reactive organo-functional siloxane, one grade being without and the other including a dispersed catalyst, these being standard proprietary grades (Q2-7198 and Q2-7199, ex Dow Corning).

The release coat formulation was coated on to the polyethylene terephthalate sheets at a coating weight of 0.5 grams per square metre. Immediately after coating, the sheets were dried at 120°C for 30 to 60 seconds to cure the silicone coating thereon.

These sheets were then imaged using a conventional thermoplastic toner xerographic system on a commercial photocopier (type Konica U-Bix 550Z).

Sheets of release paper were separately coated with a coating of a low tack pressure sensitive adhesive at a coating weight of 1.0 gram per square metre. A variety dry transfer adhesive compositions could be used, for example those described in British Patent Specifications 959670, 1577617 and 2005598.

The imaged polyethylene terephthalate sheet was then brought into contact with its imaged side towards the adhesive coating on the release paper and the area of th desired image worked over, e.g. with a burnisher or stylus. On peeling the release paper and polyethylene terephthalate sheets apart, adhesive transferred to the toner image.

The sheet bearing the toner image was then laid on to a piece of artwork, adjusted to the desired position and t toner image urged into intimate contact with the artwork by rubbing over the back of the polyethylene terephthala sheet with a stylus. On peeling the polyethylene terephthalate sheet away, the toner image was adhered preferentially to the artwork by means of the adhesive a peeled cleanly from the release coating on the polyethylene terephthalate sheet.

Example 2

Sheets of polyethylene terephthalate film of thickness 7 to 100 microns were coated with a surface coating of polyvinyl octadecyl carbamate. The coating was applied from a 2% by weight solution of this polymer in toluene and at a coating weight such that the dried down coating weight was around 0.5 grams per square metre. These sheets were imaged using a conventional thermoplastic toner xerographic system on a commercial photocopier (typ Konica U-Bix 550Z). These sheets were then used with release paper sheets coated with low tack pressure-sensitive adhesive as noted in Example_. 1. Similar, though not quite as good, results were obtained.

Example 3

Example 1 was repeated but with the addition, between the making of the toner image and adhesing it, of a strengthening treatment: the polyethylene terephthalate sheet was imaged, then assembled, image side touching with a blocking foil (OMNICROM, black, ex Esselte Letraset Limited) and the assembly passed through a heated up (OMNICROM CT 100, speed setting 3, temperature setting 4). The Omnicron foil was then peeled off the black coating thereon was firmly adherent to the toner images, and could be selectively adhesed as described above.

The images were then transferred on to artwork. Transfer was easier than in Example 1 as the images were more robust. They also had a higher optical density.

Claims

1. A method of transferring images on to artwork which comprises forming a toner image of the desired image using a xerographic imaging apparatus and using as receptor sheet for the xerographically formed image a sheet having a release surface, applying adhesive selectively to the toner image on the release surface and subsequently adhering the toner image by means of the applied adhesive to the artwork in the desired position more strongly than the toner image adheres to the release surface, characterised in that the application of adhesive to the toner image while it is residing on the release surface is effected by bringing the toner images located on the release surface into contact with a carrier sheet bearing a layer of releasable adhesive thereon, applying pressure to urge the toner image into a contact with the layer of releasable adhesive and pulling the two sheets apart.

2. A method according to Claim 1, wherein after formation of the toner image and prior to the selective application of the adhesive to the toner image, a further layer is applied to the toner image from a blocking foil.

3. A method according to Claim 2, wherein the further layer is a coloured layer.