This invention relates to scratch-off cards and, more specifically, to a process for producing scratch-off cards and to a release material particularly intended for use in such production. Scratch-off cards are well-known in having an opaque layer that can be scratched off to reveal "secret" printed matter which, typically, can be redeemable for cash or some other prize.

The conventional process for producing scratch-off cards, utilises a form of rotary-screen printing in which aromatic solvent-based inks and a rubber/latex-based so- called "silver" coating are applied through a polypropylene mesh screen. However, this known process has the disadvantages of being relatively slow and, usually also, environmentally unfriendly as the extracted solvents may subsequently be discharged into the atmosphere.

It is one object of the present invention to provide a process for producing scratch-off cards, in which the above disadvantages are at least reduced - usually at less expense than that involved with the conventional process.

According to the present invention, a process for

the production of scratch-off cards is based on offset- lithographic printing and comprises applying printed- matter to a base by means of at least one set of rollers, then applying a wax-like release layer of oleoresinous resin varnish onto at least one area of said printed matter by means of at least one other set of rollers, and then applying an opaque coating over said release layer by means of at least one further set of rollers.

Preferably, the release layer is transparent and comprises oleamide wax and a polyethylene wax which provide a surface-active ingredient to induce release of the opaque coating. The printed matter may be derived from conventional grey-text offset-litho ink, and the opaque coating may be an aluminium-containing coater "silver" ink applied by means of a coating unit and then dried and cured by UV light.

The invention also provides a wax-like release material, particularly intended for use in the production of scratch-off cards, and comprising an oleoresinous varnish which provides a surface-active ingredient to induce release of an over-coating layer.

Preferably, the oleoresinous varnish includes an oleamide wax and a propylene wax.

An embodiment of the present invention will now be

described, by way of example, with reference to the accompanying drawings in which:

Fig. 1 is a cross-sectional view illustrating, on an exaggerated scale, the basic structure of a scratch-off card according to the invention;

Fig. 2 is a plan view illustrating the (printed) base part of the card; and,

Fig. 3 is a diagrammatic side elevation showing a printing press for producing the scratch-off cards.

Referring to Figs. 1 and 2 of the drawings, a scratch-off card comprises a base (10) formed of conventional material such as paper or card and carrying printed matter (11) on its upper face, a wax-like release layer (12) adhering firmly to the base, and an opaque coating (13) removably adhering to the release layer (12). As with known scratch-off cards, the opaque coating conceals completely an area of "secret" text (14) within the printed matter on the base, but can be removed - using for example the edge of a coin - to reveal the secret text which may comprise numbers or other symbols that can occasionally form a combination to attract a prize.

The scratch-off cards are produced, in sheets, on an offset-litho printing press such as illustrated in Fig.

3, and which can comprise a modified version of the Roland 600 series produced by MAN Roland Drukmaschinen AG, Germany.

In the printing operation, blank sheets (15) are fed from a stack (16) by means of a feeder separator (17), and passed through first, second and third banks of double printing units (18,19,20). The six units are more or less standard, and each comprises first and second printing plate cylinders (21,22), offset blanket cylinders (23,24) and an impression cylinder (25). Promotional and instructional material is printed on each sheet (15) by means of the first and second printing units (18 and 19) in a conventional manner. In the third unit (20) the secret text (14) is applied to an area of the sheet by means of printing plate cylinder (21A), and a release layer of oxidation wax (12) is applied over that area by means of a relief plate mounted on cylinder (22A). From the printing unit (20) the sheets are fed to a coating unit (26) which has a printing plate cylinder (27) and an impression cylinder (28), and which applied an opaque scratch-off coating (13) over the wax layer by means of a Cyrel relief plate; the coating is then dried and cured by UV radiation in a Spectral UV light system (29). More specifically, in the drying/curing process,

the "silver" coating is cured by the UV radiation whereas the transparent release layer dries by oxidation.

The finished sheets are fed to a collection bay (30), again by means of gripper bars (31), and subsequently guillotined or punched into individual or blocks of scratch-off cards.

The printing of the secret text (14) may employ a conventional grey-text ink such as Coates Lorilleux V0727, although other colours may be employed, and the opaque coating may comprise an aluminium-containing coater "silver" ink such as Coates Lorilleux Ultra-Violet UX 7024 which is a combination of finely-divided aluminium blended into mixed molecular weight acrylates, photoinitiators and stabilisers; it is printed from photopolymer plates and dried immediately by the end-of- press UV lamps in the light system (29). The product is printed wet-on-wet over the wax release varnish so that, when UV-cured, it withstands general handling and subsequently, when scratched off, both coater "silver" (13) and wax release varnish (12) are removed from inks beneath.

The release layer (12) is preferably an oleoresinous release varnish which will be referred to as VO 730 and which comprises an oleamide wax and a polyethylene wax

that provide a surface-active ingredient to induce release of the overprinted ink. The oleamide and polyethylene waxes are semi-oxidative and are dispersed into a base varnish which is used as the carrier for the wax through the printing machine, so enabling transfer of the image and binding of the wax to the substrate or base

(10). The base varnish consists of rosin maleic resin and vinyl toluidine alkyl dissolved in a mixture of soya alkyd, vegetable oil and petroleum distillate to impart hardness, flexibility and chemical resistance of the printed film, with the metallic drier used to accelerate the speed by which this is achieved. The release varnish layer (12) is applied dry-offset in the last printing unit (20) over any other inks on the particular design required, and is immediately over-printed by the coater silver. VO 730 has the following analysis (%):

Oleamide Wax 28 - 30

Polyethylene Wax 8 - 10

Rosin Maleic Resin 15 - 17

Vinyl Toluidine Alkyd 4 - 6

Soya Alkyd 4 - 6

Vegetable Oil 11 - 13

Petroleum Distillate 21 - 23

Metallic (Co) Driers 0.3 - 0.5

The above-defined release material is novel and it has been found that, with the use of release and coating materials as described above, in combination, scratch-off

cards can be readily produced relatively quickly; the opaque silver coating (13) can be cured in a short period of time and, after just a few hours or even less, the opaque coating can be removed to leave the grey-type text (14) clearly visible through any residual (transparent) wax layer (12) .

It will be appreciated to one skilled in the art that at least the above-mentioned Vegetable Oil may be substituted by a suitable equivalent material.

The release material may be employed in other processes for producing scratch-off cards, preferably using off-set lithographic rather than rotary-screen printing, and the adhesive properties of the material can find applications other than in the production of scratch-off cards.

Although the printing machine described above is generally conventional, the normal use of the coating unit (26) is for the application of transparent lacquers, and of course the UV drying/curing unit (29) is an additional feature of the machine. If necessary for increased security, an additional printing unit may be incorporated. It will also be appreciated that scratch- off cards according to the present invention can be produced by a reel-fed system as an alternative to a sheet-fed system.