Projection slides are well known in the art, and are used for example in slide shows to illustrate presentations. The slides are magnified and projected onto a screen by a slide projector comprising a light source and lens system.

A typical slide comprises a cut piece of developed 35 mm photographic film held in a slide mount. The mount typically comprises a pair of half frame elements, each having a corresponding aperture therein, which are riveted or clipped together with the photographic film clamped between.

The slide mount protects the film from damage, and allows it to be easily handled and for example to be mounted in the feed magazine of a slide projector.

Besides photographic film, it is also known to produce slides by using a print from a dye thermal transfer printing process. In dye thermal transfer printing, selected regions of a dye donor sheet are heated to cause dye to pass from the heated regions of the donor sheet to corresponding regions of a dye receiver sheet to form an image therein. The heating may be carried out in a number of ways, for example by a thermal head comprising a number of heatable elements, or by a scanning laser beam which is modulated as it is scanned. Transfer of dye may be by a diffusion process (in which the donor and receiver sheets contact one another), or by a sublimation process (in which the dye crosses a gap of a few microns between the donor and receiver sheets) In the prior art, a receiver sheet so printed is generally cut and mounted in a slide mount as for

photographic film.

Other methods of providing slides of images produced using dye thermal transfer printing are also known. For example, US-A-5450117 discloses a device for producing a slide in which an image is printed onto a record carrier that is already held in a slide mount by passing a ribbon-type ink carrier through the slide mount itself. US-A-5234886 discloses an integral one- piece moulded polymeric slide element comprising a central dye-receiving section and a frame section, and US-A-5422230 discloses a laminated slide element comprised of a mask layer, a transparent support and an image layer.

The present invention aims to provide a new slide mount and slide which have a number of advantages and which are able to facilitate dye transfer printing. The invention also relates to a new printing process and to apparatus for producing slides using such mounts.

Viewed from one aspect, the present invention provides a system for printing a slide, wherein dye from a dye donor sheet is thermally transferred to a dye receiver sheet mounted between a pair of apertured slide mount halves, one of said mount halves having a larger aperture than the other, and dye being transferred to the side of the receiver sheet exposed by the larger aperture.

The invention also provides a method of printing a slide wherein a receiver sheet is printed to after it has been mounted in a slide mount, and wherein a slide mount is used which has apertures of different sizes, the smaller aperture defining the possible projection area of the slide, and the larger aperture receiving a dye donor sheet for printing purposes.

The invention further provides a slide mount comprising a pair of opposed mount halves for mounting a dye receiver sheet therebetween, one of the halves having an aperture larger than the other, the smaller aperture defining the projection area of a mounted

receiver sheet, and the larger aperture facilitating the application of a dye donor sheet to a mounted receiver sheet for printing purposes (enabling for example access by a print head).

The invention also provides a slide comprising a dye receiver sheet which has not yet had an image for projection printed thereon, mounted between a pair of slide mount halves, one mount half having a larger aperture than the other, the smaller aperture defining the area of the receiver sheet which is viewed on projection, and the larger aperture facilitating the application of a dye donor sheet to the receiver sheet for printing purposes (enabling for example access by a print head).

Viewed from a further aspect, the present invention provides a process for printing slides, comprising the step of mounting an unprinted dye receiver sheet between a pair of apertured slide mount halves, one of which has a larger aperture than the other, and the step of printing an image on the receiver sheet, by dye transfer printing, on the side of the receiver sheet exposed by the larger aperture.

The invention also extends to slide dye transfer printing apparatus for carrying out such a process, the apparatus comprising means for mounting an unprinted slide as above at a print station and means for printing to the slide.

Still further, the invention extends to printed slides produced by the above process.

The invention can be seen to reside in the printing of a slide after it has been mounted in a slide mount rather than before, together with the use of a slide mount which has apertures of different sizes, the smaller aperture defining the projection area of the slide, and the larger aperture facilitating access to the receiver sheet by a dye donor sheet for printing purposes. The larger aperture thus allows a dye donor sheet to contact the receiver sheet, and also may allow

access to the sheets by a suitable print head, such as a thermal head, platen roller, and/or laser optics, in order for example for the head to bring the donor and receiver sheets into contact and to heat the donor sheet for dye transfer.

A number of advantages flow from the present invention.

Firstly, the invention provides a simple and quick system for producing professional high quality slides for presentations. An easy to handle pre-produced unprinted slide may simply be placed by the user in a suitable print engine (which may be a stand-alone printer unit or for example a printer unit connected to e.g. a personal computer) . The user need then only initiate the print process, and remove a finished printed slide which is ready for use. There is no need for the user to become involved in the awkward and time- consuming process of having to handle and print to a flimsy receiver sheet, and then to mount the printed receiver sheet in a slide mount.

The differently sized apertures allow the dye sheet to be larger than the projection area of the receiver sheet (as defined by the smaller aperture), so that the size of the dye sheet and its location is not critical.

Also, dye sheets wider than the print area may be used without creasing their edges and causing feed problems, etc. The use of the large aperture and a larger size of dye sheet allows printing right to the edges of the projected area of the receiver sheet.

A further advantage of the invention is that factory-mounting of the receiver sheet is able to achieve better flatness of the receiver sheet than mounting at point-of-use, and so thinner receiver sheets, which tend to be more difficult to keep flat, may be used.

Preferred thicknesses of the receiver sheet are between about 50 ym and about 200 ym.

The mounting of the receiver sheet within the two

slide mount halves helps to protect the receiver sheet from damage or marking during use and handling, and for example when the slide is placed on a work surface.

The slide also permits projection of well-defined borders, as only one aperture, the smaller aperture, forms the image frame.

The invention has the added benefit that the portion of the receiver sheet which is exposed by the larger aperture but not by the smaller one may be printed on with macroscopic information (e.g. data that may be read with the naked eye). This may include for example information as to the content of the slide, the correct orientation of the slide, as well as copyright information, such as the producer's name and the date on which the slide was made. Such information can therefore easily be added during the printing process, whilst remaining unobtrusive, as it is not projected onto the projection screen. As the macroscopic information is located within the larger aperture, it too is protected from damage.

Having regard to this feature, the invention further extends to a printed slide having apertured mount halves between which a receiver sheet is mounted, the apertures being of differing size, with macroscopic information printed on the region of the receiver sheet which is exposed by the larger aperture but not by the smaller aperture.

Printing to the slide can be quickly and easily achieved using any suitable dye transfer printing method. As these tend to be dry processes, requiring no chemicals, they are quick and simple to use. A thermal head, laser, or other means for causing the dye transfer, may be controlled to print a suitable slide using information downloaded from for example a personal computer.

Preferably, the slide is printed using laser dye thermal transfer printing, as this provides for a particularly high quality, controllable and flexible

system.

The donor and receiver sheets may be brought into contact with one another in any suitable manner using any suitable means, and may be heated from either the smaller or the larger aperture side of the slide.

Heating through the larger aperture side is preferable, as printing may then be carried out up to and past the edges of the projection area defined by the smaller aperture.

In one embodiment, the dye donor sheet may be brought into contact with the receiver sheet by a roller.

The means for bringing the donor and receiver elements together may be transparent to a laser beam, so that the beam may be incident on the donor sheet through such means. For example, a transparent roller may be used. The transparent means may also focus the beam, and may take the form of a cylindrical lens or rod lens.

The larger aperture size ensures that the roller, rod lens, etc., is able to lie on the receiver sheet fully over the smaller aperture area, and can print fully over it in both the length and width directions.

A support is preferably provided on the smaller aperture side of the slide for supporting the receiver sheet against for example a transparent roller or rod lens.

The support may take any suitable form, and could, for example, comprise a roller element. In a preferred form, the support comprises a rectangular block of material with appropriate compliance and surface finish, such as DelrinTM. The support may function to help accurately locate the slide in place in the print engine.

A particularly useful method and apparatus for laser dye transfer printing which uses a rod lens is described in EP 96305216.2 filed on 16 July 1996 by the present applicants (USSN 08/682905 filed on the same date is the corresponding US application), the contents

of which are incorporated herein by reference. In this method, the rod lens focuses the laser beam onto the donor sheet at a position offset from the point at which the donor and receiver sheets touch, i.e. along a line parallel to but offset from the nip of the rod lens and support. This system provides a particularly advantageous way of obtaining a constant gap between the elements for sublimation transfer printing. In this method also, the dye donor sheet may be slightly spaced from the rod lens at the point of dye transfer, so as to minimise optical interference effects, etc., at the interface between the two. Alternatively or also, the dye donor and/or receiver sheets could be coated in an anti-reflective or anti-Newton ring material.

The present invention is particularly suited to the above printing method of EP 96305216.2, in that the larger aperture ensures that the whole of the receiver sheet's viewed print area (as defined by the smaller aperture) can be printed on.

After printing, it may be necessary to fix the dye into the receiver sheet. This may be carried out by any suitable known method. In one particularly preferred form, the dye is fixed in the receiver sheet by a flash rich in infra-red light, e.g. from a xenon flash tube as are used in photographic flash guns. Such a method is disclosed in WO 97/38863, the contents of which are incorporated herein by reference.

The slide mount halves may be made of any suitable materials, e.g. moulded plastics, and may be held together in any suitable manner, e.g. by rivets, glue, clips, tongue and groove arrangements, or welding, and could, for example, be hinged together.

The receiver sheet may be held in place in any suitable manner, e.g. by adhesive or merely by being clamped in place between the mount halves.

Preferably, at least one of the mount halves has a recess to accept the receiver sheet. The recess may be primed with adhesive before the receiver sheet is

inserted. The adhesive can hold the receiver sheet stationary for good registration, whilst allowing for controlled thermal expansion and flexing of the sheet without distortion of the image.

One or both of the mount halves may have a recess therein to contain adhesive for gluing the receiver sheet in place. This recess may extend about the whole of the periphery of the aperture. By using a recess for the adhesive, the adhesive is able to deform in the recess, so as not to have any influence on the position of the receiver sheet.

As a further possibility, strips of adhesive may be provided on the surface of one or both of the mount halves for holding the receiver sheet.

The slide is preferably printed to so that, for viewing, it is mounted between a light source and a screen with the smaller aperture facing the light source. In this case, the projection light passes through the body of the receiver sheet before, and not after, illumination of the print on the surface of the sheet. An advantage of this is that the body of the receiver sheet is able to absorb W light from the projection light, which might otherwise fade the colours of the slide over time. A further advantage is that distortions in the projected image which might otherwise be produced by the projection light passing through the receiver body after imaging the print are reduced.

The apertures may be of any suitable dimensions.

Typically, to enable use of the present slides in standard projectors, the slides themselves should have an overall size in the region of about 50 mm x about 50 mm. The smaller aperture which defines the area of the receiver sheet which is projected should preferably be of the same size as standard slide apertures, in order to be used in standard equipment, for example the smaller aperture may have dimensions of about 34 mm to about 38 mm x about 22 mm to about 30 mm. The larger aperture need only be larger than the smaller aperture

to the extent required to facilitate the application of a dye sheet to the receiver sheet, and preferably to allow a thermal head, roller or rod lens, etc., to have access to the receiver sheet and to be able to print over the full extent of the projected area. For a preferred size of rod lens of about 34 mm in length, a suitable size for the larger aperture in the direction in which the length of the rod lens is received would be about 36 mm. A typical size for the larger aperture would be e.g. about 38 mm to about 44 mm x about 33 mm to about 39 mm.

In one embodiment, margins may be printed onto the receiver sheet about the edges of the smaller aperture.

This then effectively reduces the size of the picture area of the receiver sheet, with the margins simulating the edges of the smaller aperture, and with the central area of the receiver sheet forming the projected image.

The margins may for example be printed black, and to have a high optical density. In such a system, the margins may be of any suitable widths to produce any suitable image sizes and shapes, with the dimensions of the smaller aperture defining the maximum possible area of the receiver sheet which may be imaged. The use of such margins provides a good deal of flexibility in the use of the slide. For example, by printing suitable margins on the receiver sheet, an image may be produced on the slide in either a standard 35 mm format or, for example, in formats corresponding to the shape (i.e.

length to width ratio) of an A4 or US "A" sheet. If the apertures are further extended to a square format (e.g.

a smaller aperture of about 34 mm square to about 38 mm square and a corresponding larger aperture of about 38 mm square to about 44 mm square), then it is possible to print a portrait, landscape or square form, without changing the orientation of the slide.

Means may be provided to indicate the correct orientation of the slide. For example, one or more notches may be provided at an edge or edges of the slide

to indicate its top and/or its left or right orientation. The above-mentioned printing of dark margins is especially useful when e.g. orientation notches are provided, as the slide is able to retain the same edge as the top edge, irrespective of whether it holds an image in a portrait or landscape orientation.

Therefore, only one type of slide with one notch configuration is needed.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram of printing apparatus in accordance with the present invention, showing a slide in accordance with the present invention in cross- section; and Fig. 2 is a schematic perspective view of a slide and associated printing apparatus adjacent thereto of a system such as that shown in Fig. 1.

Referring to Figs. 1 and 2, a moulded plastics slide mount 1 comprises a top half 2 having an aperture 3, and a bottom half 4 having an aperture 5. The bottom aperture 5 is smaller in both the length and width than the top aperture 3. For example the smaller aperture 5 may have dimensions of 35.5 mm x 28 mm, and the larger aperture 3 may have dimensions of 41 mm x 36 mm.

The lower mount half 4 has a recess 6 extending about its aperture 5 for locating a receiver sheet 7 therein. This recess is e.g. about 43 mm square by 100 ym deep and is primed with adhesive before the receiver sheet 7 (42 mm square by 100 ym deep) is inserted. The receiver sheet 7 may be of any standard type well known in the art. If a flash fixing process is used to fix the dye, as discussed in WO 97/38863, then the receiver sheet may comprise a mixture of polyester resin, infrared absorbing dye and other coloured dyes. The infrared absorbing dye is used to help fix the dye in the receiver sheet on being flash fixed by a burst of light rich in infrared light, whilst the other coloured

dyes neutralise the colouring effect of the infrared absorbing dye.

The two mount halves 2 and 4 are held together by plastic rivets 8 in a manner well-known in the art.

A printed slide is produced by mounting the unprinted slide in a suitable print engine for dye thermal transfer printing.

The print system shown in Fig. 1 is a laser dye transfer printing system.

<BR> <BR> TM<BR> A support member 9, such as Delrin>, is provided on the side of the slide 1 having the smaller aperture 5.

On the opposite side, a dye sheet 10, only shown in Fig.

2, is pressed against the receiver sheet 7 by a rod lens 11. The dye sheet 10 may be of any suitable type as well known in the art, and may comprise a substrate supporting an infrared absorbing layer (such as one including carbon black), and a dye donor layer (e.g.

comprising a thermally-transferable dye held in a polymeric binder).

A laser beam 12 from e.g. a multimode laser diode 13, which produces a beam having a high divergence axis and a low divergence axis, is collimated by suitable optics 14, and focused onto the donor sheet 10 in its high divergence axis by an fO cylindrical lens 15, and in its low divergence axis by the rod lens 11.

A rotating polygon mirror or a galvanometer mirror 16 is used to scan the beam 12 along the length of the rod lens 11 across the dye sheet 10. The system is actually configured so that the lens 11 focuses the beam along a scan line offset slightly from the nip of the lens 11 and support member 10, so as to heat the dye sheet 10 along a line which is out of contact with the receiver sheet 7 to cause dye sublimation transfer across the gap between the two sheets 7,10 to form an image in the receiver sheet 7. To avoid interference effects at the interface between the dye sheet 10 and rod lens 11, the dye sheet 10 may be spaced slightly from the surface of the rod lens 11 in the region in

which dye transfer takes place. Alternatively, the donor sheet and/or receiver sheet may include an anti- reflective or anti-Newton ring coating. Reference is made to EP 96305216.2 mentioned previously for further details of this apparatus and method.

A driver circuit of the laser diode 13 is controlled so as to modulate the laser beam 12 as it is scanned across the dye sheet 10, so as to heat selected pixel regions of the dye sheet 10 in accordance with the image to be produced on the receiver sheet 7. The driver circuit may for example receive instructions from a personal computer.

The rod lens 11 and focusing system, and the slide mount 1 are moved relative to one another in the plane perpendicular to the paper, as shown in Fig. 1, to allow for 2D scanning over the whole of the receiver sheet.

Colour printing can be achieved by printing to the receiver sheet 7 three times, using successive magenta, cyan and yellow dyes. In this regard, the dye sheet 10 may comprise a ribbon having alternate magenta, cyan and yellow dye areas along its length.

The difference in the aperture sizes exposes a stepped portion 7a of the receiver sheet 7 about the smaller aperture 5 which is not projected. This area of the receiver sheet 7 may be printed to with information that may be viewed with the naked eye, e.g. a title of the slide, copyright information, or information as to which way around the slide should be, etc. This information will then be available to the user, but will not be projected onto the viewing screen. Such information may simply be printed on the receiver sheet at the same time as the main image.

The image should be printed onto the slide so that during projection the smaller aperture of the slide faces the light source and the larger aperture faces the screen. The projection light passes through the body of the receiver sheet before, and not after, illumination of the print on the surface of the sheet. This has the

advantage that the body of the receiver sheet is able to absorb ultraviolet light from the projection light, which might otherwise fade the colours of the image on the slide.

As the projected image is defined by only the small aperture, it is possible to provide sharp edge projection.

After the slide has been printed to, it may be necessary to fix the dye into the receiver sheet. An advantageous way of doing this would be through the flash fixing method as disclosed in WO 97/38863, in which the receiver sheet is exposed to a flash of light rich in infra-red, e.g. from a xenon flash tube as are used in photographic flash guns. Reference should be had to WO 97/38863 for further details of this method.

It should be realised that the term "sheet", as used in e.g. "dye sheet" or "receiver sheet", should be taken to cover ribbons, films, and any other suitable donor and receiver media.

The above is only one embodiment of the present invention, and various alternatives are of course possible. For example, the rod lens could be replaced by a cylindrical lens or a transparent roller with focusing optics upstream thereof. Further, any other suitable method of dye transfer could be used, such as by a thermal head comprising a number of heatable elements, flash printing or ultrasonic means. Also, the slide could include a recess for the adhesive. The receiver sheet may have margins of high optical density printed at the edges of the smaller aperture, in order to vary the size and shape of the image which is projected, the dark margins simulating the edges of a slide.