A method is known for adhering to a carrier and providing with an adhering cover foil a sheet of paper provided with a coloured printing, for example a colour copy generated by an ink-jet printer. In order to effect the adhesion between the non-printed side of the paper and the carrier an adhesive substance is applied to the relevant surface.

As a result of the wet printing process the picture quality is found to be adversely affected. Due to the wet printing liquid, such as ink, a toner which is based on liquid or which is temporarily fluid during the heat fixing operation, a certain swelling of the paper can occur depending on the degree of printing and the properties of the paper, while a certain curling of the paper can also occur. This can result in a number of disadvantageous phenomena. Due to the swelling and curling the paper can for instance make contact with the nozzles.

In addition the ink may begin to mix with other colours, whereby the distinctness of separation between differently coloured zones may leave something to be desired. Swelling of the paper can further result in an increased mechanical stress in the paper, particularly when in some circumstances shrinkage occurs or during a laminating operation. It is generally remarked that the concept of "paper* ¹ must be understood in a broad sense in the context of the present patent application. Also suitable in the context of the inventions are laminates which consist partly of plastics such as PVC. The invention is however focussed particularly on paper whereof at least the upper surface for printing has a certain porosity, i.e. paper wherein the said problems occur during wet printing. Such paper may be plain paper, i.e. the untreated, wholly porous paper for instance used for photocopying purposes. It may also be paper embodied as a

laminate of a number of layers, at least the top layer of which has a certain porosity and is suitable for absorbing ink or other liquid intended for forming images. The relevant printing techniques are all printing techniques which operate at any stage of the treatment with a liquid printing. These are for instance ink-jet techniques, off-set techniques, screen-print techniques, techniques with electrostatic printing and dry-copying techniques, wherein for instance in the fixation stage of powder-form toner a heating occurs wherein the toner melts, is therefore temporarily fluid and can cure due to the supplied heat.

The invention has for its object to provide a method to which the above stated problems are not inherent.

The invention has for its particular object to provide a method which can produce a considerably improved picture quality, particularly in cases in which coloured zones are mutually separated by sharp transitions.

With a view to the above the invention provides a method for adhering to a carrier and providing with an adhering cover foil a sheet of paper provided with a coloured printing, for instance a colour copy generated by a dry- copying machine, which method comprises the following steps of:

(1) providing a sheet of paper provided with a coloured printing, which sheet is manufactured by printing a sheet provided beforehand with an adhesive layer, which layer is situated on the side facing away from the printing;

(2) providing an adhering cover foil; and (3) simultaneously transporting the carrier, the printed sheet and the cover foil through an applying station, if necessary after mutual registration, in order to obtain a combination of a carrier, a paper adhered to this carrier and provided with a coloured printing, and a cover foil adhered to that paper.

The method according to the invention integrates the previously separate operation of sticking the information- carrying sheet on a carrier and arranging a protective foil on the sheet.

The adhesive layer can consist of one substance or a mixture of substances, or a laminate of layers with different compositions.

In a specific embodiment the method comprises the steps of:

(4) performing step (1) such that the adhesive layer is of the pressure-sensitive type; and

(5) performing step (3) such that the applying station is adapted to exert pressure. As pressure-sensitive adhesive layer can be considered for instance "Artmount T" and "Art ount V", both obtainable from the Dutch company Sallmetall in Raalte, the Netherlands.

The application of pressure can take place by making use of two rollers urged toward each other and between which the carrier, the printed sheet and the cover foil pass for mutual adhesion.

A pressure-sensitive layer will generally be covered in the factory by a pre-removable protective sheet.

In another embodiment the method comprises the steps of:

(6) performing step (1) such that the adhesive layer is of the heat-activated type; and

(7) performing step (3) such that the applying station is adapted to heat at least the adhesive layer. As heat-activated layer can be considered for instance • ^■ Hotmount", obtainable from the Sallmetall company in Raalte, the Netherlands.

The method can also comprise the step of:

(8) performing step (6) such that the adhesive layer consists at least partially of polyethylene.

Heating of the cover layer must take place to a temperature wherein the cover layer acquires its adhesive properties. The temperature can for instance be increased for this purpose to about 120°C. Use can be made of at least one heated roller which forms part of the applying station. This heated roller will also exert a certain pressure in relation to a counter roller, resulting in a flat laminate consisting of the combination of a carrier, a paper adhered to this

carrier and provided with a coloured printing, and a cover foil adhered to this paper.

Permanent removability is obtained through use of an adhesive layer on the basis of "Artmount P", a registered trademark of and available from Sallmetall in Raalte, the Netherlands.

Substances also exist which provide a temporary removability. The combination can thus remain releasable for some time. The carrier can be of any suitable type, for example a plate of foam material such as polystyrene foam, aluminium, a sandwich panel with two skin plates and a core consisting for instance of foam material, hardboard, or also a relatively flexible plastic plate. The protective foil can be of any desired type. A high- gloss protective foil gives for instance the impression of a sharp picture with an attractive appearance.

In respect of the coloured printing it is noted that for the most frequently occurring applications this is formed on a basis of the basic colours yellow, magenta, cyan and black. These colours, in combination with a white layer for printing on, are generally sufficient.

The invention also provides a combination of a carrier, a paper adhered to this carrier and provided with a coloured printing and a cover foil adhered to this paper.

The invention will now be elucidated with reference to the annexed drawings. Figures 1 and 2 each show a highly schematic perspective view of devices which are adapted to perform the method according to the invention. Figure 1 shows a roll of paper 1 which delivers a strip of paper suitable for printing. The strip of paper 2 passes over a station 3 where a layer of heat-activated copolymer is applied to the underside of the paper strip 2. The thus treated paper strip subsequently passes over a number of deflecting rollers collectively designated with 4 and also serving as loop compensators, whereafter the processed paper strip is rolled onto a roller 5. This roll of paper is then unrolled so that the treated paper strip 6 with adhesive layer is guided through a four-colour printing station 7.

Printing of the substantially white paper takes place here with black and the basic colours yellow, magenta and cyan. Use is made in known manner for this purpose of exactly mutually registered printing units 8, 9, 10, 11. The thus printed paper strip 12 is dried by a drying station 13 and, at any rate in this embodiment, wound onto a roller 14. The roller 14 is guided further by a rotating transport and punching device such that each image detected by unshown means is positioned above a carrier board 16. These carrier boards 16 are fed successively to be combined with the relevant pictures. The combination of a carrier board having lying thereon a sheet with picture is supplied to an applying station 17 where a cover foil 19 is fed to the said combination, also from a roller 18. On the underside is thus situated a carrier board 16, thereon is a sheet 20 with picture, and thereabove the adherable cover foil 19. This combination is carried through rollers 21, 22 pressed toward each other so that a homogeneous pressing takes place. The upper roller 22 is also heated whereby the heat-activated adhesive layer applied in station 3 is activated and the sheet 20 with illustration adheres to the carrier board 16. The foil 19 is also placed in adhering co-action with the exposed top surface. This foil can comprise a thermally- activated adhesive layer or a pressure-sensitive adhesive layer.

Figure 2 shows an embodiment in which use is made of an ink-jet printer.

By means of suction pads 23 one sheet 25 of paper is lifted at a time from a stack 24 and carried as according to arrow 26 to a conveyor 27. Using further suction pads 23 this transports the sheet 25 over a station 28 consisting of a tray with adhesive material which is applied to the underside of sheet 25 via vibrating rollers 47. A sheet 29 thus provided with an adhesive layer is heated by a heating station 30 in order to cause drying of the adhesive layer. Further transport once again takes place by means of suction pads 23 for placing on a stack 31 of protective sheets 43. A reciprocally moving pressure roller 32 serves to press the pressure-sensitive adhesive layer onto the topmost protective

sheet 43 and to prevent inclusion of air as far as possible. Suction pads 23 carry sheets 29, 43 successively to a supply tray 33. This tray 33 is placed in an ink-jet printer 34. This receives from a scanner 35, via a signal processing unit arranged therein, picture information of an original for reproduction 36 in order to form a print 37. An exposed print is the combination 37 of a sheet of printed paper, a pressure-sensitive adhesive layer situated on the underside thereof and a protective sheet situated thereunder. After removal of protective sheet 43 the combination 37 is fed to an applying station 44 which has substantially the same construction as applying station 17 according to figure 1, with the understanding that the upper roller 44 does not have to be heated in this embodiment. If use is indeed made of an unheated roller the adhesive cover foil 46 coming from a roller 45 can if desired be exclusively of the pressure- sensitive type.

The above described two embodiments are not limitative. It will be apparent that another method of applying a printing is also possible, for instance by means of a colour dry-copying machine. In this respect it is emphatically noted that by the word "printing" must be understood any manner of arranging information onto paper.

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