Conventionally, screen printing is used to print such glass panels, but for multicolour images the colours must be printed separately, making the process somewhat expensive, and screen printing is not a commercial proposition for rapid design changes and short production runs. Moreover, adhesion of the image to the glass can be affected by ambient conditions, so that in warmer parts of the world the image may in fact simply fall off the glass.

For these reasons, a process other than screen printing would be preferred.

A photographic process would be suitable. However, no method of using a photographic process has hitherto been found which gives the required density of colour, purity and brilliance such as can be produced by screen printing.

The present invention provides such a method, however, which applies also to other imaging methods such as ink-jet printing.

The invention comprises a method for applying an image to a transparent panel, comprising laminating an image on transparent film to the panel,; applying directly behind the film a backing layer without an intervening adhesive layer and sealing against fluid ingress between the backing layer and the film.

The film may be a photographic emulsion film, and the film is then laminated, preferably emulsion-side to the panels.

The image may, however, be a printed image such as an ink-jet printed image, and may be a computer-generated image.

The film may be laminated to the panel by an optically clear adhesive.

If the image is apertured, as for the viewing windows for the reels of a fruit or slot machine, film material may be removed from the apertured areas after lamination.

The image may be masked to expose apertured areas for chemical removal of the film material. Preferably at least non-curling and antistatic layers of the film material are removed from windowed areas.

The film may be laminated to the panel by transferring adhesive from a release layer on to the panel and then applying the film to the adhesive on the panel and rolling the film to press it to the adhesive.

The backing sheet may comprise a transparent substrate which may be printed to block backlighting in selected panel areas-these will, in a fruit or slot machine panel, of course, be the areas which carry the main part of the image-and the substrate may be printed solid black in those areas. The solid black printing may then, however, be overprinted, e. g. with white, to render the black invisible through the image.

In other selected panel areas the backing sheet may be printed so as to be translucent for back illumination of the image in said other selected panel areas. The backing sheet may be printed translucent white in said other selected areas.

Printing of the backing sheet may be effected by screen printing or otherwise as convenient.

Often, designs call for silvering (or other metallic colouring, here generally referred to as silvering) and this may be carried out in the required areas (usually for edging image features) before application of the image to the panel.

For fruit and slot machines, the panels will usually be of glass (6mm glass being commonly used) but of course other materials, e. g. polycarbonate and acrylic panels can be dealt with in the same fashion.

For production purposes, images may be generated in any suitable fashion but perhaps most easily by a computer-controlled imaging arrangement such as an Eseco Digimatic Universal imaging system which can produce both digital and conventional images (Eseco, Cushing, Oklahoma, USA). Production of the film for lamination to the panel may be on a continuous feed automatic enlarger (such as one produced by Eseco aforementioned). It is found that the image on the film gives best effects in terms of colour density, purity and brilliance in the finished product if the image density on the film is less than would be required to give the correct density of colour in a colour print on to photographic transparency film.

Using the method of the invention, the colour density, purity and brilliance are considerably-surprisingly so-enhanced over screen printing the blacks and whites directly on to a photographic film laminated to a panel or adhesively laminating a printed backing layer to the photographic film.

The sealing may be effected by adhesive applied around the edges of the backing layer, or by adhesive tape applied all around the edge.

Methods for applying an image to a transparent panel according to the invention, and panels with images so applied, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of a panel of a fruit or slot machine; Figure 2 is a cross section of an edge of a finished panel; Figure 3 is a diagrammatic illustration of a method of laminating a film to a panel; Figure 4 is a face-on view of the film laminated to the panel of Figure I; Figure 5 is a view of a first stage in printing a backing sheet for the panel of Figure 1; Figure 6 is a view of a second stage in printing the backing sheet of Figure 4; and Figure 7 is a view of a third stage in printing the backing sheet of Figure 4.

The drawings illustrate a method for applying an image to a transparent panel comprising laminating an image on transparent photographic emulsion film 12 to the panel 11, emulsion-side 12a to the panel 11; applying directly behind the film 12 a backing layer 13 without an intervening adhesive layer and sealing against fluid ingress between the backing layer 13 and the film 12.

The panel 11 as illustrated is a panel of a fruit or slot machine having "windows"14 through which reels (or their electronic equivalent) may be viewed on a prizeline, and back-illuminatable areas 15 which light up to indicate various alphanumeric options, win levels and so forth or transparent portions which serve as infra-red windows. Actually, as illustrated, the panel 11 is composite-usually a reel glass will just have the windows 14, while another panel will have the areas 15, a common feature, however, being that except for the windows 14 and areas 15 the panel is (or panels are) decorated with a design, shown here, simplistically as a design of weapons of war, though in practice thematic designs calculated to attract punters are used. It may be mentioned here that designs are considered very important and machines are changed frequently to avoid becoming jaded reducing takings. It is important, in this particular industry at least, to facilitate an assured supply of new designs of high quality.

The shortcomings of screen printing on to the glass have been discussed above. Attempts to laminate photographic images on to the panels have given disappointing, indeed unacceptable results, however, in terms of the final appearance of the image, which loses brilliancy and depth of colour as well as purity of colour in the process.

However, the method of application according to the present invention provides excellent depth of colour-even though, as will be explained, the colour density of the colour transparency is reduced, as compared to what would be regarded by the expert as appropriate, as well as full purity and brilliance of colour. We are concerned here, of course, with the appearance from the front of the glass, under ambient illumination, of the image applied to the rear of the glass. The transparency of the reel windows 14 is not affected by the application of the image, nor is the appearance of the areas 15.

As it is necessary to use a transparency in order to cater for the windows and backlit areas, it is necessary also to provide a backing to prevent backligthing coming through the image (except where intended) or the workings of the machine to be visible through the image.

Obviously, there is a need for the image and the backing to be applied and held in register affixed to the rear face of the panel and the straightforward way to achieve this would, of course, be for the image and backing to be adhesively laminated together and for them to be laminated in turn, to the rear of the panel. This does not, however, turn out to give a good result. The colours of the image appear washed out when viewed from the front of the panel under ambient light.

It is only when the backing 13 is not adhesively laminated to the photographic film 12 that the image appears in its true colours. This despite the fact that the same optically clear adhesive would be used as is (without any loss of colour) used to laminate the film 12 to the panel 11.

This adhesive 31 is applied as illustrated in Figure 3 by applying it on a release layer 32 to the rear face of the panel 11 and peeling away the release layer 32.

The photographic film 12 bearing the image-which is seen in Figure 4-can then be applied by a roller system 33 pressing it on to the adhesive layer 31.

After the image-bearing film 12 has been laminated to the panel 11, film material in the window areas 14 is removed as by masking the rest of the image and removing film material with a suitable agent. At least the usual non-curling and antistatic layers can be removed in the window areas, although it would also be possible to dissolve them away over the entire image area since the emulsion layers are protected by the film support-this would obviate the need for a mask, of course.

The backing layer 13 can now be prepared. If windows 14 or back illumination of areas 15 are required, the backing layer 13 must be of transparent film material, but must be rendered opaque in the image areas. This is done by screen printing the backing layer, as seen in Figure 5, with solid black over the entire image area 51, leaving unprinted the windows 14 and areas 15. This is then overprinted with a translucent white layer 52 except in the window areas 14, as seen in Figure 6-although it would be possible, of course, just to print the areas 15 with the translucent white.

Finally, an opaque white 53 is printed-Figure 7-to conceal the black, leaving the windows free and the areas 15 printed just with the translucent white. Areas can be left transparent, so that back lighting can illuminate design areas particularly brightly.

The backing layer 13 thus printed is applied in register to the photographic film 12 laminated to the panel 11 and simply pressed or rolled into place to achieve close juxtaposition but without the intermediary of any adhesive. One edge is tacked down with adhesive tape 16, then the backing sheet is roll pressed down on to the photographic image. The other edges are then sealed, as seen in the section of Figure 2. This edge sealing prevents ingress of fluid and essentially maintains a vacuum holding the backing layer 13 on to the film 12. It is important, of course, to similarly seal the edges of any button holes in the panel-holes cut to accommodate operating buttons of the machine.

This can also be done with adhesive tape. Trapped air can, however, be removed by a vacuum pump, the edge then being sealed.

Surprisingly, exposing the photographic film layer 12 to a lesser colour density than would be appropriate for making a regular colour positive print produces, with this attachment regime, a vibrant, densely coloured, true colour appearance of the image area when viewed in ambient light from the front of the panel.

Since it is with viewing of the image area under ambient light conditions that this invention is primarily concerned, rather than with the window or areas 14,15 -which are, of course, not affected one way or the other by the manner of assembly, except insofar as they require the backing layer 13 to be transparent-it is possible to use the method of the invention even for situations where neither windows nor back- illuminated areas are required, even though, without such requirement, wholly different approaches (e. g. simply laminating a non-transparent colour positive to the back of the panel 11) might service.

The correct colour density of the image can, of course, be readily determined through trial and error.

Correction of colour densities can be achieved, however, at the image design stage. Computer generated images or artwork can be electronically manipulated reducing or increasing colour density to give the required results in the various areas of the panel.

By"silvering"as used herein is meant application of any metallic or other special effects directly on to the panel surface, as by conventional silvering (usually aluminium coating) or by decoration of the backing sheet with gold, silver or other metallic effects or holographic effects using hot foil blocking, or cold foil application.

While the method has been specifically described with reference to a photographic image, it is equally applicable to other imaging techniques such for example as ink-jet printing.

The image may be polished, as by buffing with a rotary buffer, or otherwise surface treated to leave it smooth (as by dissolving a water-soluble coating) in order to reduce or eliminate the occurrence of Newton's rings. For example, treatment by anti- Newton sprays or powders may be appropriate.