LAMINATES

FIELD OF THE INVENTION

This invention relates to laminates, and more particularly laminates for use in the production of display systems and a process for the production of such laminates.

BACKGROUND OF THE INVENTION

Display systems of the type used, for example, in signs and placards, posters, pictures, stickers, illuminated and reflective signs, are produced by a wide variety of techniques. A typical display system comprises a laminate of an optically transparent protective cover surface and a sheet of paper carrying the required information printed thereon. In general the printing process is expensive, particularly where colour printing is required, and for outdoor applications the paper must be protected against ingress of water.

It is known to laminate the printed paper sheet to the optically transparent cover surface using an optically transparent adhesive, and if necessary to apply a protective backing surface which may also be adhered to the paper.

Such laminates are widely used for advertising and display purposes, but because of the printing process are relatively expensive, particularly when only small numbers of prints are required.

Attempts have been made to produce laminates for advertising and display purposes by the use of heat transfer processes, but these are also relatively expensive and of limited application. Photographic processes have also been used, but only to a limited extent again because of the high costs involved.

Further difficulties have been introduced by prior art lamination processes which often require elevated temperatures and specialised lamination equipment unsuitable for single jobs or small customised runs.

There is therefore a need for a laminate comprising a protective optically transparent cover surface and a sheet carrying information to be displayed, which is both versatile and can be inexpensively produced in small or large quantities on relatively inexpensive equipment.

BRIEF DESCRIPTION OF THE INVENTION

In the present invention there is provided a laminate, suitable for use as a display system, which comprises a polymeric film material having an image electrostatically deposited thereon, and a process for the production of such a laminate.

According to one aspect of the present invention there is provided a laminate comprising:

a first layer of polymeric film material having an image deposited thereon by an electrostatic deposition process, a second layer of optically transparent or translucent material, the first layer being bonded to the second layer by a layer of optically transparent adhesive material, the arrangement being such that the image on the first layer can be viewed through the second layer and the layer of optically transparent adhesive material.

In a second aspect the invention further provides a method of making a laminate which comprises: depositing an image on a first layer of polymeric film material by an electrostatic deposition process, and bonding a second layer of optically transparent or translucent material to the first layer using an optically transparent adhesive material, such that the image on the first layer can be viewed through the second layer and the optically transparent adhesive material.

In a further aspect the invention provides a method of making an adhesive laminate which comprises: depositing an image on a first surface of the first layer of polymeric film material by an electrostatic deposition process,

removing adhesion inhibitingmaterials associatedwith the electrostatic deposition process from the film material surface whilst leaving the image undisturbed, and applying a layer of optically transparent adhesive material to the first surface film material carrying the deposited image.

DETAILED DESCRIPTION OF THE INVENTION

The first layer of polymeric film material preferably comprises a biaxially orientated polymeric film which may be formed from any suitable polymeric material such as, for example, a polyester, for example a polyacrylate, and more particularly a polyethylene terephthalate; or a methyl methacrylate or ethyl methacrylate polymer or copolymer; an olefin polymer, copolymer or block copolymer, for example polymers, copolymers and block copolymers of ethylene, propylene, butylene and other olefins with, if desired, other vinyl monomers; a polycarbonate; a polyethersulphone; a polyether ether ketone; or a polyurethane. A preferred polymer is polyethylene terephthalate and a suitable polyethylene terephthalate biaxially orientated film is produced by ICI under the trade mark Melinex, of which the particular grades preferred for use in the present invention are Melinex 542 and Melinex 054. These grades are pre-treated to improve the adhesion thereto by print and lacquer. Melinex S is also suitable, but this is an untreated grade which may need to be treated to improve its image adhesion characteristics. The

treatment may, for example, comprise coating with an organic polymer layer having improved image adhesion characteristics. Typical coatings which may be applied to a base film material to improve image adhesion are acrylic or cellulosic materials, which may also desirably contain a slip agent.

It is important that the first layer of polymeric film material should be thermally and dimensionally stable under the conditions used in electrostatic deposition processes. For example the temperature of an electrostatic copier roller is normally greater than 150°C, and can be from 160°C to 190°C. Although the first layer of polymeric film material is exposed to the heat of the roller for only a short time, it can become degraded, twisted and buckled, or even melt, if a polymer of too low a thermal and dimensional stability is chosen. Acetate films, for example, are not normally suitable for this reason. In general, the first layer of polymeric film material should be capable of withstanding a temperature of at least 150°C and preferably at least 190°C without substantial instantaneous degradation, structural change, dimensional change, or colour change. Most preferably the film material should be such that it is thermally and dimensionally stable when exposed to a temperature of 200°C for at least 0.5 seconds.

The above preferred grades of film are normally transparent, but for many purposes an opaque, and especially a white opaque, film is preferred. Such white opaque films can be produced by applying to the polymeric film a coating layer

comprising a filler such as silica or titanium dioxide dispersed in a suitable binder. Suitable white opaque coated polymeric films are produced by Imperial Graphic Products pic, Cel a AG, Renka, 3M and Image Data (division of ICI) . These companies also produce films in colours other than white for example by applying to the film coating layers comprising suitable colourants. These films may also be used in the present invention.

Even where an opaque grade of polymeric film is used, for example because an opaque filler has been included during manufacture, the film will usually still require a surface coating for image adhesion purposes, as previously discussed.

Although the inventionwill subsequently be described with reference to the use of polyester films, it is to be understood that it is not limited thereto, and any other suitable polymeric film having the appropriate surface characteristics and stability for electrostatic copying can also be used.

The image is deposited on the first polymeric film layer by an electrostatic and particularly a xerographic process, preferably by passing the polymeric film layer through a xerographic photocopier, especially a colour photocopier. Any ^■ suitable colour photocopier can be used in the process of the present invention, for example a laser copier, digital copier or the like and the invention is not limited to any particular colour photocopying method or electrostatic technique for the

production of the deposited image. Good results have been achieved using a Xerox model 5775 and Canon CLC, and these are the preferred machines, although other machines, using other electrostatic deposition techniques, may also be suitable.

Xerographic processes deposit the image onto the film as a powder or toner layer which is subsequently fixed by heating and treatment with a stabilizer containing a silicone material, for example a silicone oil.

I have discovered that the silicone-containing stabilizer remains on the surface of the xerographic electrostatically deposited image and inhibits adhesion to the polymeric film surface, such that conventional adhesives, particularly those that are active at ambient or relatively low elevated temperatures, cannot be used to form a laminate.

I have now discovered, surprisingly, that the silicone containing stabilizer material can be removed from the film sufficiently to obtain a substantial improvement in adhesion by gentle washing or wiping with a cleaning liquid or solution without harming the image, and this is an important aspect of the method of the present invention. Clearly such a process could not be applied to normal xerographic paper, because it would soon absorb the cleaning liquid or solution and ultimately disintegrate, but it has been found that washing or wiping the film in accordance with the process of the invention enables the undesirable adhesion-inhibiting components of the

xerographic image surface to be removed whilst leaving the image itself substantially unaffected.

In general any aqueous or non-aqueous liquid or solution capable of removing the adhesion-inhibiting materials from the film surface can be used, provided that the xerographic image is not disturbed and the film is not discoloured or degraded, but it is convenient and preferred to use an aqueous soap or detergent solution. In one method of carrying out this process of the invention, the film carrying the deposited image can be dipped or immersed in a bath of the cleaning liquid or solution, which can, for example, comprise a detergent solution containing several drops of a commercial liquid detergent such as Fairy Liquid or Sunlight Liquid per litre of water. The process can be carried out at ambient temperature, at a temperature that is "hand warm" or at any temperature that will not affect the film or the image, for example up to about 60°C or even more. More concentrated detergent solutions can also be used but this is not normally necessary.

For applications where the use of a washing process is inconvenient, for example if the method of the invention is to be used in areas with limited working space, the adhesion- inhibiting materials can still be removed to a satisfactory extent by the application of a suitable cleaning liquid or solution which can, for example, be an aqueous or non-aqueous solution containing a detergent or some other chemical compound capable of removing oily or silicone deposits from the surface

of the deposited image. The solution can, for example, be applied as a spray. Such a spray can, for example, be hand¬ held, and may have a hand pump trigger action. Suitable liquids and solutions are those that do not scratch or damage the surface of the image, are smear-free and stain-free, are non-toxic, and do not give off unpleasant or hazardous vapours and fumes.

The spray solution can, for example, be a solution of a detergent in a mixture of water and a suitable organic solvent, which may be, for example, an alcohol such as isopropyl alcohol, or an ether such as ethyl glycol mono butyl ether (also known as EGB) . A variety of commercially available cleaning liquids and solutions can be used, but it is important that any liquid or solution should first be subjected to a trial to ensure that it does not contain any components likely to damage the image or the film.

A fine spray of the solution can be directed onto the surface of the image and the liquid then wiped away and the surface thoroughly dried using a clean, soft, lint free cloth. It is found that, with suitable treatment, which may be repeated if necessary, the deposits of adhesion-inhibiting materials may be satisfactorily removed.

It is also possible, with suitable cleaning liquids and solutions, to apply a few drops of the liquid or solution to

a damp cloth and use this to wipe away the adhesion-inhibiting materials from the surface of the deposited image.

The second layer of optically transparent or translucent material comprises the protective cover surface for the image, and may comprise a biaxially orientated sheet or film of a suitable polymeric material, for example a polyester, an acrylicpolymer, apolyethylene terephthalate, or polycarbonate or similar material. The invention is not, however, limited to such materials _r and other transparent or translucent sheet materials such as glass may also be used in certain applications. The sheet can be rigid or flexible depending on the application, and may be of any desired thickness. Where the second layer is translucent, that is to say not optically clear, the light transmission must still be sufficient for the image to be viewed through it, if necessary with illumination from the back of the laminate.

The optically transparent adhesive material should be capable of forming a permanent bond, and of adhering without leaving bubbles (pockets of air) in the laminate. It should of course be capable of adhering to the xerographic image comprising the toner used in the xerographic process. Suitable adhesives include acrylic-based resins such as methyl methacrylate and ethyl methacrylate, synthetic rubber-based adhesives, ethylene-propylene copolymers, propylene polymers, and ionomer resins and suitable grades are made by several manufacturers. Particularly good results have been obtained

using an adhesive supplied as a film, which may have a protective overlay on one or both surfaces. Such adhesives are sold, for example, by Mactac under the trade marks Macbond (acrylic and rubber-based adhesives) , Macmount (acrylic and rubber-based adhesives) , and Macfilm (acrylic adhesives) , all of which may be provided with protective overlays of polymeric film or paper. Good results have been obtained using Mactac UV protective acrylic adhesive reference No. F2010.

Curing acrylic films such as Mactac are preferred for certain applications because they permit the possibility of repositioning the components of the laminate within a few minutes of application, for example if the components have not been lined up correctly.

The adhesive is preferably one that will achieve a satisfactory bonding at ambient temperatures, that is to say room temperature, or at only slightly elevated temperatures, for example below about 60° C.

Some protective cover films are supplied ready-coated with adhesive, for example Mactac, lOOμ vinyl polymer film with Macal 8199 acrylic adhesive, Mactac PG7036, 36μ and Mactac 7075, 75μ, polyester polymer films with acrylic adhesive, and PF-6000, a 420μ matt finish translucent polycarbonate film coated with adhesive.

The components of the laminate may be assembled by any suitable method, and in any order. In one preferred method the optically transparent adhesive material is applied to the second layer of optically transparent or translucent material in a first stage, and then the adhesive coated optically transparent or translucent material laminated to the polymeric film material carrying the image in the second stage. If the polymeric film material carrying the image is to have a backing applied thereto, this is preferably applied to the polymeric film material first, to avoid the possibility of the laminate curling. Lamination can be achieved by passing the materials through a pair of laminating rollers, or by any other convenient process. Suitable laminating rollers are produced by Sallmetall BV.

The laminates of the invention may be provided with a wide variety of backing surfaces, either for protection, or for adhering to a substrate, or to achieve special effects. For example, the laminate may be adhered to a substrate such as a metal, plastic, cardboard or woodblock backing sheet layer by the use of a double-sided adhesive film such as, for example, Stera-Tape. Preferably the double-sided adhesive film is provided with a protective overlay, whereby it is possible to produce self-adhesive stickers using the laminates of the present invention. Many other types of acrylic or rubber-based adhesive can of course be used for this application, and of course the adhesive may be applied as a coating from a solvent based system, or by any other convenient means. Good results

have, however, been obtained using Sera-Tape 4051 cross linked acrylic adhesive, Sera-Tape 1091 modified acrylic adhesive and Sera-Tape 4151 modified acrylic adhesive; and Sera-Tape rubber adhesives 4471 and 3471. In some cases it is possible to obtain the backing sheet with the adhesive already adhered thereto and ready for use once its protective overlay is removed. In such cases a preferred lamination method comprises first depositing the image on a first surface of the film, then laminating a second surface of the film to the backing sheet, removing the adhesion inhibiting materials from the film surface, and finally laminating the second layer of optically transparent or translucent material to the first surface of the film.

An important use of the present invention is in the production of illuminated and reflective signs. In the case of illuminated signs, the first layer of polymeric film material may be a transparent or translucent material, such that the image is illuminated when a light is positioned behind the laminate, and the image can thus be viewed through the second layer of optically transparent material. In an alternative construction, the image is deposited on a first layer of transparent polymeric film material and this is laminated to a protective cover sheet and/or a backing sheet of translucent material through which the image can be illuminated.

Reflective signs can be produced by depositing the image on a first layer of transparent polymeric film material and providing a backing layer of a reflective material. Suitable reflective film materials for use as the reflective backing layer are produced by Mactac under the trade marks Macmark and Maclite 1010, by 3M under the name 3M Reflective, by Ciba-Geigy under the trade mark Cibalite, and by other manufacturers.

Other types of backing which may be used include magnetic sheet materials which can be used to attach the laminate to metallic iron or steel surfaces, for example to form a magnetic sign or display.

The deposited image may be a composite produced by a combination of different processes. For example characters or letters may be applied by pressure transfer, such as by the

Letraset technique, or alternatively a black xerographic image may be produced on a transparent film and a metallic coating applied thereto using a heat transfer foil and passing the foil and film through a heated roller. This transfers the metallic material from the foil to the black areas of the xerographic image. This film can then be laminated, together with a film carrying a colour image, between protective surface and backing sheets, so that when viewed the metallic image, characters or letters stand out in front of the colour image (which may for example be a picture) .

Compositions can be made using a computer screen, and transmitted to a xerographic colour copier using the appropriate software to produce the desired image.

An important advantage of the process of the present invention is that by the appropriate selection of materials the entire process can be carried out at room temperature with the use of very simple equipment.

Using the laminates and the process of the present invention, a wide variety of display systems, decorative and artistic pictures and designs can be quickly and economically manufactured in large or small numbers. Even individual items such as estate agents boards and other advertising signs can be readily produced. The invention may also be applied to produce decorative laminated articles and decorative laminates, and may also be used to replace photographic enlargements and reduce the usage of silver in the photo printing industry. Lampshades and other diffuser lights and displays can readily be produced.

The invention can also be used to produce signs adapted to adhere to, and be viewed through, glass such as shop windows and the like. For example the optically transparent material comprising the protective cover surface for the image may itself have a surface which can adhere to a glass surface when pressed thereon. Alternatively, the protective cover surface in the laminate can comprise a release layer which can be

removed to reveal the adhesive layer below. This can then be applied to the glass surface so that the glass surface becomes the protective cover surface for the laminate.

The invention is illustrated by the following Examples:

EXAMPLE 1

This Example describes the production of a laminate according to the invention.

An opaque sheet of coated biaxially oriented polyethylene terephthalate Melinex film having good toner acceptance is placed in a Canon colour photocopier and an image xerographically deposited thereon. The film is then washed in a warm aqueous solution of detergent . The film is dried with a soft lint-free cloth.

The film is then placed face down on a clean surface, the protective overlay is removed from one side of a film of Sera- Tape 4051 cross-linked acrylic adhesive and the adhesive surface applied to the back of the film. The remaining protective carrier layer of the adhesive film is left in place.

A sheet of clear acrylic plastic is provided with a layer of Mactac UV F2010 acrylic adhesive by removing one of the protective overlays from the adhesive and pressing the surfaces together.

The adhesive-backed Melinex film is laid face up on a table and an edge of the acrylic sheet applied thereto with 2.5 cms of the adhesive on the sheet exposed at the contact edge region. The laminate is then passed through a pair of laminating rollers, spaced so as to apply gentle pressure to the laminate, gently removing the protective overlay between the acrylic sheet adhesive and the film carrying the image as the laminate passes into and through the rollers. Surplus film is trimmed with a sharp knife.

There is produced a laminate having a self-adhesive backing useful for many display purposes. The laminate can be applied to a substrate by passing the substrate, together with the laminate, through a pair of laminating rollers and removing the protective overlay on the self-adhesive backing as the laminate passes through the rollers. In this way signs having aluminium or plastic backing, or a magnetic sheet backing may be produced.

EXAMPLE 2

The process of example 1 is repeated except: that the image is xerographically deposited on clear transparent coated plastic film. When the laminate has been produced the protective overlay is removed from the backing adhesive and the laminate is applied to a reflective material having a foil backing, thereby producing a reflective sign.

EXAMPLE 3

The process of example 1 is repeated except that there is interposed between the polymeric film carrying the image and the transparent protective surface layer a further transparent coated film layer. The further layer is passed through a black and white photocopier to deposit a black image thereon and is then passed through a pair of heated rollers together with a metallic heat transfer material, to transfer the metallic material to the black portions of the image. The transparent film carrying the metallic image is then sandwiched between the transparent protective surface and the film carrying the xerographic colour image and laminated with further layers of optically clear adhesive. In this way metallic lettering or other characters can be viewed together with the colour image to achieve special effects.

EXAMPLE 4

The process of Example 1 is repeated except that the image is again produced on a clear transparent coated plastic film. When used with a reflective backing such as Maclite 1010, Cibalite or 3M Reflective, this can produce a sign having all reflective colours except black.

EXAMPLE 5

The process of Example 2 is repeated except that the reflective material is replaced with a translucent backing material. The resultant laminate can be illuminated from behind (backlit) to produce an illuminated sign or display.

EXAMPLE 6

The process of Example 1 is repeated except that the washing step is omitted and the adhesion-inhibiting silicone materials are removed from the image by wiping with a damp cloth to which a few drops of Fairy Liquid detergent have been applied. The film is then dried and treated as before to form a laminate.

The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All the features disclosed in this specification

(including any accompanying claims, abstract and drawings) , and/or all of the steps or any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.