WO2005053963A1

WO2005053963A1 - Printing method

Info

Publication number: WO2005053963A1
Application number: PCT/GB2004/005115
Authority: WO
Inventors: Brian John Howard Hughes
Original assignee: Digital Glass Limited
Priority date: 2003-12-05
Filing date: 2004-12-06
Publication date: 2005-06-16
Also published as: GB0328302D0

Abstract

A method of producing an image on an optically transparent material, which method includes: a) providing an optically transparent substrate; b) providing a first digital image; c) removing a selected portion of the image to leave a print image, whereby the portion of the image removed results in substantially optically clear areas of the digital image; d) optionally creating a mask of the print image; and e) printing the mask and the print image onto a first side of the substrate.

Description

PRINTING METHOD

The present invention is concerned with an optically transparent substrate, such as an acetate film or the like, having printed thereon a digital image .

Window films are becoming more and more popular, not only for the benefit of rejecting up to 77% of the sun's solar energy and also blocking out 98% of harmful and damaging UV light, but also for aesthetic purposes and to provide a uniform appearance to a building, factory, school or the like. Further benefits associated with the installation of window films include reduced heat gain/heat loss (therefore reduced energy costs) , improved occupant comfort, reduced glare, increased privacy, visual security, increased fade protection and protection from accidents, burglars and explosives etc.

Window films are typically transparent layers of high quality polyester which may be metalised, laminated and coated using special adhesives, ultra violet inhibitors and protective scratch coatings.

It has been known to print onto clear overhead projector (OHP) type film. However, although such film is a polyester film, it is not necessarily optically clear.

Furthermore, OHP film is coated via first side with a clear ink receptive coating having minor matting so as to identify the ink receptive side. The second side of the film has a special stabiliser coating to prevent curling on hot overhead projectors. Such film would not be considered optically transparent. Furthermore, the printing technology utilised involves an electrostatically charged revolving drum which transfers the image to the substrate and then fuses the colour to the film using heat . A disadvantage of this technology is that it can only be used for sizes up to A3.

Prior art window films have been utilised in the past which are often dyed or 'frosted' during manufacture to produce a decorative coloured film. However, use of such dyed decorative film is disadvantageous because the coloured film has to be manufactured in large quantities. Furthermore, frosted window films involve the removal of unwanted elements of the design by hand, which is typically a time-consuming process.

Digital printing to optically clear transparent films has not been able to be achieved in the past as the printing processes used in traditional digital printers, such as Inkjet printers, piezo, and related ink technologies have not allowed images/designs to be consistently transmitted or transferred to optically clear substrates. This has been due to the inability of the printing machines to 'read' the presence of an optically clear substrate and the difficulty of the ink in adhering/curing to the substrate and forming an adequate bond.

It is therefore an aim of the present invention to alleviate at least some of the disadvantages identified above .

It is yet a further aim of the present invention to provide an optically clear substrate having printed thereon an image, or design which contains visual elements within the image or design, which are completely optically clear. Therefore, according to a first aspect of the present invention, there is provided a method of producing an image on an optically transparent material, which method includes : a) providing an optically transparent substrate; b) providing a first digital image; c) removing a selected portion of the image to leave a subject image, whereby the portion of the image removed results in substantially optically clear areas of the digital image; and d) printing the subject image onto a first side of the substrate.

It is particularly preferred that a mask of the subject image is created.. The mask and the subject image are preferably printed onto a first side of the substrate.

Further preferably the mask and the subject image are combined such that they are printed on the first side of the substrate in a single print operation.

Accordingly, there is further provided a method of producing an image on an optically transparent material, which method includes : a) providing an optically transparent substrate; b) providing a first digital image; c) removing a selected portion of the image to leave a subject image, whereby the portion of the image removed results in substantially optically clear areas of the digital image; d) creating a mask of the subject image; e) printing the mask and the subject image onto a first side of the substrate.

The present invention advantageously provides an effective method for the management of clear spaces (such as optically clear spaces) during printing, typically by digital means .

Advantageously, the subject image is removed from a background of the image such that when the subject image is printed to the substrate, the background is optically clear, and substantially clear from digital printing. Preferably, substantially all stray pixels are removed from the selected portion of the first image.

Preferably, the mask and the subject image are printed on the first side of the substrate in a single print operation..

The print image and the mask are preferably digitally printed onto the first side of the substrate.

It is particularly preferred that the mask is a silhouette of the subject image. The mask is preferably designated as a further print layer to which the subject image is merged. Advantageously, the mask acts as a base layer for the subject image to strengthen its visual appearance and/or qualities .

The mask may be printed as a white or as a tone of the subject image (preferably the lightest tone) . Although it is envisaged that the user can decide on the 'colour' in which the mask is printed. It is particularly preferred that the subj ect image and the mask are merged prior to printing.

The subject image and/or the mask are typically printed onto the first surface of the substrate using an ink jet printer, such as a piezoelectric ink jet printer; however it is, of course, envisaged that any suitable printer may be used .

A typical digital image has a dpi of about 300 to 420 (such as 360) however more course or finer pictures may also be printed according to the method of the present invention.

Advantageously, the present invention permits the simulation of frosted film in many different colours and/or designs overcoming the limitations of designs cut from frosted films. A further advantage is that the method does not necessarily need to be carried out in clean room conditions .

It is further envisaged that a fill layer is provided, the fill layer is obtained by converting the subject image to greyscale and subsequently inverting to a negative. The fill layer is typically white. Preferably, the fill layer is merged with the subject image and/or mask. The fill layer typically strengthens the image and enables the image to be 'read' from the other side of the substrate when applied.

Furthermore, the present invention permits full colour designs to be printed, on demand, directly to an optically clear substrate, whilst retaining the optical clarity of the unprinted substrate.

The optically transparent substrate is preferably a flexible film, such as an acetate-based film. The film is typically of high quality polyester which may be laminated or coated using special adhesives, ultraviolet inhibitors and/or protective scratch resistant coatings.

The substrate typically has a thickness of about 1mm to 18mm, preferably 2mm to 14mm. According to a first embodiment, the substrate may have an adhesive coating (which is also preferably optically transparent) applied to a second surface of the substrate. The adhesive coating preferably has high cohesive and peel strength, and is environmentally stable. Suitable optically clear adhesives are sold by Bekaert Speciality Films and others .

It is envisaged that the adhesive may be applied prior to printing the subject image onto the first surface. Alternatively, the adhesive may be applied after the subject image has been printed. However, if adhesive is applied after the image has been printed, the adhesive is preferably applied in 'clean room conditions'.

According to an alternative embodiment, an adhesive coating (which, is also preferably optically transparent) is applied to the first surface of the substrate after the subject image has been printed thereon (thereby effectively creating a sandwich-type structure of substrate, image and then adhesive) .

The adhesive is particularly advantageous for fixing the substrate in its final position. The final position may be a glass or rigid plastics surface. It is envisaged that the glass or rigid plastics surface is also optically transparent .

Preferably, the adhesive has a protective film thereon to protect the adhesive from the atmosphere and foreign bodies. However, the protective film is removed prior to installing the printed film in its final position.

It is envisaged that the substrate is a safety window film such as the window film sold (under the trade mark ARMORCOAT) by Bekaert Speciality Films. (AMROCOAT) Safety window films advantageously include a pressure-sensitive mounting adhesive which helps hold glass in place when natural disasters, vandalism, explosions, bomb blasts and other incidents result in glass breakage. Typically, such window films have a thickness of between about 50 micron and 350 micron.

The subject image is preferably printed using a piezo inkjet direct to substrate printer.

Therefore, the present invention extends to an optically transparent substrate having printed thereon a digital image. The digital image being applied by the method according to the first aspect of the present invention.

The optically clear substrate is substantially as described hereinbefore with reference to the first aspect of the present invention.

The image may include images and designs that can be printed by the four colour processes known as CMYK and/or RGB.

The image, once applied to the substrate, may advantageously be coated or protected with a protective coating which is preferably digitally applied. The protective coating typically adheres to the image, thereby providing a protective seal over the printed image. The protective coating may include any suitable material. The protective coating is typically digitally applied substantially over the image only, thereby retaining the optically clear qualities of the substrate. However, it is envisaged that the coating may also be substantially transparent .

The protective coating is arranged to substantially prolong the life of the image on the substrate. This is achieved by preventing the image being scratched or scraped off the surface of the substrate to which it is applied.

The present invention will now be described, by way of example only.

The digital image is created, enhanced and applied using standard software available. A Flatbet Printing System with Piezo-electric Inkjet using UV curing pigmented inks (CMYK) direct to substrate was used.

A roll of optically clear polyester material having an optically clear adhesive fixed to a first side, the adhesive being protected by a removable film (essentially the adhesive is sandwiched between the polyester and the protective film) .

The digital image is printed onto the sheet of polyester material on a second side which does not currently have adhesive applied thereto. Following printing of the digital image a protective coating may be applied to the image printed on the polyester sheet. A protective coating is printed in exact dot to dot registration onto the image using the same printer used for printing the image, however one or more of the printer heads has been replaced by a head containing a protective seal.

The digital image is also printed to an optically clear polyester substrate and then the surface to which the printed image is attached, is coated with an optically clear adhesive and release liner. When applied to glass the printed image is then sandwiched between the glass and the optically clear substrate.

The present invention can now further excemplified, with reference the accompanying figures which are given by way of example only, wherein:

Figures la to le are a schematic representation of the steps in a method according to present invention.

Figures la to le, where like numerals are used to represent like parts, there is provided a first image 1 comprising a subject image 2 and a coloured background 3. The background 3 is selected and digitally removed from the first image so as to provide a subject image 4 on its own (figure lb) . As shown in figure lc, a silhouette of the image is created. The silhouette 5 is digitally combined the subject image 4 (figure Id) . The combined image 6 (which comprises the silhouette 5 and subject image 2) is then printed onto an optically clear substrate so as to provide an image having an optically clear background 7.

Claims

1. A method of producing an image on an optically transparent material, which method includes: a) providing an optically transparent substrate; b) providing a first digital image; c) removing a selected portion of the image to leave a subject image, whereby the portion of the image removed results in substantially optically clear areas of the digital image; and d) printing the sbuject image onto a first side of the substrate .

2. A method according to clam 1, wherein a mask is created of the subject image.

3. A method according to claim 2, wherein the mask and the subject image are combined such that they are printed on the first side of the substrate in a single print operation.

4. A method of producing an image on an optically transparent material, which method includes: a) providing an optically transparent substrate; b) providing a first digital image; c) removing a selected portion of the image to leave a subject image, whereby the portion of the image removed results in substantially optically clear areas of the digital image; d) creating a mask of the print image; e) printing the mask and the subject image onto a first side of the substrate.

5. A method according to any preceding claim, wherein the subject image is removed from a background of the image such that when the subject image is printed to the substrate, the background is optically clear, and substantially clear from digital printing.

6. A method according to any of claims 2 to 5, wherein the mask and the subject image are printed on the first side of the substrate in a single print operation.

7. A method according to any of claims 2 to 6, wherein the subject image and the mask are digitally printed onto the first side of the substrate.

8. A method according to any of claims 2 to 7, wherein the mask is a silhouette of the subject image.

9. A method according to any of claims 2 to 8 , wherein the mask is designated as a further print channel to which the subject image is merged.

10. A method according to any of claims 2 to 9, wherein the mask is printed as a white or as a tone of the subject image (preferably the lightest tone) .

11. A method according to any of claims 2 to 10, wherein the print image and/or the mask are printed onto the first surface of the substrate using an ink jet printer, such as a piezoelectric ink jet printer.

12. A method according to any preceding claim, wherein a fill layer is obtained after step c) , the fill layer being obtained by converting the subject image to greyscale and subsequently inverting to a negative.

13. A method according to claim 12, wherein the fill layer is white .

14. A method according to claims 13, wherein the fill layer is merged with the subject image and/or mask.

15. A method according to any preceding claim, wherein the optically transparent substrate is a flexible film, such as an acetate-based film.

16. A method according to claim 15, wherein the film is a high quality polyester which may be laminated or coated using special adhesives, ultraviolet inhibitors and/or protective scratch resistant coatings.

17. A method according to any preceding claim, wherein the substrate has a thickness of about 1mm to 18mm, preferably 2mm to 14mm.

18. A method according to any preceding claim, wherein the substrate has an adhesive coating (which is also preferably optically transparent) applied to a second surface of the substrate.

19. A method according to claim 18, wherein the adhesive is applied prior to printing the image onto the first surface .

20. A method according to claim 18, wherein the adhesive is applied after the subject image has been printed.

21. A method according to any of claims 1 to 17, wherein the adhesive coating (which is also preferably optically transparent) is applied to the first surface of the substrate after the subject image has been printed thereon.

22. A method according to any preceding claim, wherein the substrate is a safety window film such as the window film sold (under the trade mark ARMORCOAT) by Bekaert Speciality Films.

23. An optically transparent substrate having printed thereon a digital image having been applied by the method defined in any of claims 1 to 22.