The present invention relates to a method of printing onto automotive glazing.

Glazing for use in automotive vehicles (referred to herein as "automotive glazing") can be printed for various purposes. For example, a windscreen or window may be printed with a relatively dark region that functions as a sunshade. Printing can also be used to provide an obscuration band. This is often used for aesthetic reasons in order to hide adhesive or other fixing means whereby a piece of glazing is held in place. It can also be used for functional purposes (e.g. in protecting adhesive from UV light). Printing onto automotive glazing can also be used for a plethora of other applications. For example, it may be used to provide security marking, to print a trade mark or a certification mark, to provide opaque regions for privacy reasons, to customise a vehicle (e.g. to print the owner's name), etc.

By far the most widely used method for printing onto automotive glazing is screen printing. This has been used for many years and in various countries. It can be used to print large areas of glazing and is generally reliable. However the screen printing process has various limitations. For example, it is fairly slow, because of the need to hold an item being printed against a screen for a given period during the printing process. Furthermore, it is not particularly suitable for printing to the edge of a piece of glazing, as ink can build up at the edge of the glass, causing defects in the print. When this is attempted using screen printing techniques small gaps are generally left where there is no print close to the edge. This can adversely affect a finished product. For example, if there is a gap between a printed sunshade and the upper edge of a windscreen, this can allow sunlight to dazzle an occupant of the vehicle. If there is a gap between an obscuration band and the edge of a piece of glazing this can allow adhesive to be seen and is not aesthetically desirable. The sunlight may also damage certain adhesives. One solution to printing to the edge of a glazing using screen printing, is to use vacuum equipment, as in EP 0 511 883.

Screen printing can be used however to print fine detailed patterns onto glass, such as trade marks (images and designs indicating compliance with international standards, manufacturer details, details of the glass itself) and logos or designs representing information such as anti- theft device installation and passenger airbags. However, the speed at which such patterns can be printed is limited due to the batch nature of the screen printing process.

However, alternative printing methods are known for printing onto porous substrates, such as ceramic tiles. EP 1 034 905 discloses a roller printing system for applying glaze to ceramic tiles. A roller, comprising an elastically deformable matrix cylinder is disclosed. A plurality of cells, linked by communication channels are etched into the surface of the cylinder. A doctor blade is used to apply a coating of glaze to the cylinder, which is then transferred to the ceramic tile. However, such direct printing onto the smooth glass substrates used in automotive glazings is not known.

Printing using tampon rollers is known for use on glass. EP A 0 338 907 discloses the use of a tampon roller having raised areas for printing onto glass. An ink groove, corresponding to a pattern to be printed onto the glass, is provided on a block roller, which is dipped into ink to fill the groove. The ink is transferred to a tampon roller, which has raised portions corresponding to the ink groove. The block roller and the tampon roller rotate such that the ink groove and raised portions are in rolling contact. Glass passes beneath the tampon roller for printing. However, one disadvantage of using such a roller system is that only relatively crude patterns, such as obscuration bands, can be transferred to the glass.

There is therefore a need to provide an alternative method for printing automotive glazing, which is able to provide fast and accurate printing, including detailed patterns, at the edge as well as the centre of the glazing.

The present invention provides a printing method comprising using a roller to print an image onto a blank of glazing material used to form an automotive glazing, wherein the roller comprises deformable material that is used to hold ink within one or more cavities and wherein the material deforms during printing to transfer ink from the one or more cavities onto the blank.

The advantages of using a roller include enabling printing to the edge of the glazing. Detailed designs, such as logos and trade marks can also be printed easily. There is no requirement to use vacuum equipment to remove the ink from the edges of the glazing as in some screen printing techniques.

Preferably, the deformable material comprises a plurality of spaced cavities. The cavities may be engraved into the deformable material. Preferably, the cavities are laser-engraved.

Preferably, the cavities are channels, grooves or indentations. A single channel, groove or indentation may form a single image. The grooves or channels may be continuous.

The cavities may vary in depth at different regions so that the roller can be used to produce an image that varies in intensity at different regions. The depth of the cavities may gradually change from one part of the roller to another so that the roller can be used to print an image that gradually increases or decreases in intensity from one part of the image to another.

A thermoplastic ink may be used in printing. Preferably, the ink is printed onto a blank at a temperature of greater than 60° C. An electrically conductive ink may be used in printing. Preferably, the electrically conductive ink is used to print a printed circuit, an antenna or a heating element.

The image may be a sunshade, an obscuration band or a logo. The image may be printed up to or close to an edge of the blank.

The deformable material may be an elastomeric material. Preferably, the deformable material is a silicone-containing elastomeric material. The deformable material may be in the form of a cylindrical sheath or another component that is mounted onto a less deformable material.

Preferably, the blank is not stopped whilst it is printed. More preferably, the blank moves during printing at substantially the same velocity as that at which the outer surface of the roller rotates.

The automotive glazing may be formed from the blank using at least one further step of laminating, firing, bending, tempering or toughening the blank following printing.

Preferably, the blank of glazing material is a glass blank. Alternatively, the blank of glazing material is a film or an interlayer for a laminated glazing.

The automotive glazing may be windscreen, a side window, a door window, a backlight or a sunroof.

A blank of glazing material or an automotive glazing formed from a blank of glazing material,

comprising an image printed using the method of the present invention is also provided.

The invention also provides a blank of glazing material used to form an automotive glazing, having an image printed thereon, the image printed using a roller comprising deformable material that is used to hold ink within one or more cavities, wherein the material deforms during printing to transfer ink from the one or more cavities onto the blank.

An automotive glazing may be formed from such a blank. An automotive glazing may be fitted to an automotive vehicle or to a part thereof; wherein the automotive glazing is formed from a blank of glazing material printed by a method according to the invention.

The present invention will now be described by way of example only, and with reference to the accompanying drawings in which

Figure 1 is a schematic cross-sectional view showing a blank for an automotive windscreen being printed according to a method of the present invention; and Figure 2 is a photograph showing a printed shadeband and fadeout band on a glass blank; Figures 3 a and 3b are photographs showing part of a trade mark print on a first glass blank; Figures 4a and 4b are photographs showing part of a trade mark print on a second glass blank; Figures 5a and 5b are photographs showing part of a trade mark print on a third glass blank; Figures 6a and 6b are photographs showing part of a trade mark print on a fourth glass blank; Figures 7a and 7b are photographs showing part of a trade mark print on a fifth glass blank; Figures 8a and 8b are photographs showing part of a trade mark print on a sixth glass blank; Figures 9a and 9b are photographs showing a screen printed trade mark; and Figure 10 shows examples of various blanks for automotive glazing.

Referring to Figure 1, there is shown in schematic form (and not to scale) a roller 100 that can be used to print a desired pattern of dots 170, 180 onto a glass blank 120. The glass blank may be a precursor for an automotive glazing (one used in an automotive vehicle). For ease of printing, the glass blank 120 is in substantially flat form. The blank is cut from flat, float glass and is generally shaped for automotive use, but requires bending in a subsequent procedure, following printing.

The glass blank 120 is moved on a conveyor (not shown) past the roller 100. The roller

contacts the glass blank 120 at a predetermined pressure. The rotational speed of the roller 100 and speed of the conveyor may be varied to increase or decrease the friction between the roller 100 and the glass blank 120. For example, the conveyor may travel at the same speed as the roller 100 rotates. Arrows 110 and 130 show the directions of movement of the conveyor and of the roller respectively.

The roller 100 comprises a cylindrical sheath 102 that is formed of silicone rubber and is resiliently deformable. The cylindrical sheath 102 is mounted upon a relatively rigid metal core 104. The core 104 is itself rotatably mounted upon a central shaft and is driven by a computer-controlled motor (not shown). The cylindrical sheath 102 has a plurality of indentations 140, 150, 160. These have been formed at an earlier stage by laser engraving. For simplicity, only three recesses are shown, although, in practice, many more recesses may of course be present.

An ink loading system (not shown) is used to fill the indentations with ink. This comprises an ink reservoir and a doctor blade that removes excess ink from the surface of the cylindrical sheath.

An ink dot 180 that has been printed at a desired position on the glass blank 120 is shown. The ink printing the dot has previously been released from indentation 160. A further ink dot 170 is shown in the process of being printed. This printing occurs under pressure from the roller 100. The silicone rubber sheath 102 allows the cavity 150 in which the ink is held to deform to a given degree under the pressure applied by the roller 100 so as to aid in depositing ink onto the surface of the glass blank 120. The resilience of the silicone rubber allows the cavity to resume its shape when ink has been deposited and the roller 100 has advanced to a given degree (as can be seen for indentation 160).

Trials were carried out in order to determine whether the quality of a roller printed image would compare favourably with that of a screen printed image.

Laser engraved silicone rollers provided by System S. p. A. were used in a Rotocolor™ printing system to print various images onto glass blanks. The images included a portion of an obscuration band and fadeout band, and a trade mark showing manufacturers name, compliance with ECE R43 and other manufacturing details. The ink comprised an infra-red drying media

and standard automotive frit (14251), and was supplied by Ferro, Inc.. After printing, the ink was dried in an oven, and subsequently toughened in a furnace having an exit temperature of approximately 650 ⁰ C. Glass blanks were also screen printed using a standard automotive frit (14251) in UV media, also available from Ferro, Inc., and toughened in the same furnace, as a comparison.

Figure 2 shows a printed shadeband and fadeout band printed at the edge of a glass blank. The solid print area of the shadeband showed good opacity, and the fadeout dots were well defined. Four samples were printed in the same manner, and their surface roughness R ₃ (μm), R _z (μm), light transmission (%) and fired thickness (μm) measured and compared to the same pattern on a screen printed sample. The values are shown in Table 1 below:

Table 1: Roughness and print thickness measurements for roller printed and screen printed samples.

Although the roughness and print thicknesses of the roller printed samples is higher than that of the screen printed samples, the opacity of the printed band is higher, with all of the roller printed samples showing a lower light transmission than the screen printed samples.

Figures 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a and 8b show printed images of trade marks from six different samples. Figures 3a, 3b and 8a, 9b show images having good definition, where the open areas of the image are free from ink, and the printed text areas solid, with no missing areas or patchiness. Figures 4a, 4b, 5a and 5b show relatively good definition, with clear open areas, but with some text missing and patchiness in the solid text areas. Figures 6a, 6b, 7a and 7b show images where part of the printed text is missing. The skilled person may determine, by simple trial, the conditions required to achieve good definition in any particular case, such as the roller and belt speeds, roller pressure, engraving depth and ink viscosity and density.

Figures 9a and 9b show optical photographs of the same trade mark, but this time screen printed using known techniques. Figures 3 a, 3b, 8a and 8b show a similar and acceptable quality of image to the screen printed samples.

Being able to print onto glass using a silicone roller is surprising. In pad printing techniques, a silicone pad is used to print an image onto glass. However, the release of the ink from the pad is poor, resulting in variations in the thickness of the ink and the opacity of the final printed image. This is in part due to the way in which ink is taken up into the pad (by pressing the pad into a shallow vat of ink) and partly due to the behaviour of the ink on the surface of the glass and the silicone pad. The ink adheres to the silicone pad preferentially, making it difficult to fully release the ink from the pad onto the surface of the glass. In general, the pad needs to be heated, to cause a change in the surface tension of the ink to allow it to be released. Therefore, it would be expected that using a silicone roller would result in similar results to pad printing, and would not be suitable for producing opaque or detailed prints on glass. However, this has been found not to be the case, and both detailed and opaque prints can be achieved on automotive glass.

The roller used in the trials was a silicone roller. However, suitable materials for forming the roller include elastomers. The material may be synthetic or naturally occurring, although a synthetic material is preferred. As in the trials, the material is preferably a silicone rubber. Silicone rubber is a synthetic elastomer made from a cross-linked polymer that is reinforced with silica. The deformable material may, for example, be in the form of a cylindrical sheath that is removably mounted onto a less deformable material (e.g. onto a hard metal core) to form

the roller. The sheath can then be easily replaced when worn or damaged. Such silicone rubber sheaths (hollow cylinders) are known in the art.

The one or more cavities of the roller can be in any appropriate form. For example, they can be in the form of channels, grooves, indentations, etc. The form is not crucial, provided that ink can be held therein during part of the rotation of the roller and can then be transferred onto the piece of automotive glazing or component thereof during printing. The one or more cavities can be provided by any appropriate method, including cutting, moulding, chemical etching, etc.

It is however preferred that the cavities are provided by engraving. Engraving can be performed using an instrument with a sharp blade, but is desirably performed with a laser. Laser engraving technology is well developed and can be used to engrave intricate images in a controlled manner. The engraving instrument can be operably linked with a computer. The computer can be programmed to move the engraving instrument in a controlled manner so as to engrave a desired image into the deformable material. The computer may store an image and/or co-ordinates for the image to be engraved. The computer may be set up to display a map or grid representing a roller surface to be engraved. An operator can then input a desired image onto the map or grid (e.g. by selecting a pattern of pixels). If necessary, the image may then be adjusted (e.g. following a test print). Thus a computer-aided design (CAD) system can be used to store an image of the present invention and can be operably linked to an engraving device for engraving the image.

The engraved image may be continuous. For example, it may be defined by a continuous groove or channel. Alternatively, it may be discontinuous. For example it may be defined by a plurality of spaced cavities, sometimes referred to as "pixels". These may be provided in any desired pattern or arrangement and may combine to provide an image when viewed from a distance. The individual pixels may be generally circular, oval, or polygonal (e.g. square) in outline, or may have any other desired shape. Thus they may be used to print images comprising a plurality of generally circular, oval and/or polygonal markings. A single image or a plurality of images may be engraved.

If desired, the engraving may vary in depth at different regions, allowing an image to be produced that varies in intensity at different regions. Such intensity variation can be used to produce changes in shading (corresponding to different amounts of ink at different locations),

and is particularly useful for printing a sunshade or an obscuration band. For the purposes of the present invention a sunshade is defined as being any printed image suitable for protecting an occupant of a vehicle from dazzle by sunlight. An obscuration band is defined as any printed image that is positioned to obscure adhesive or another vehicle component. The sunshade or obscuration band can be printed, for example, to provide a relatively dark shade at or close to an edge of a piece of automotive glazing, or component thereof, but to provide a relatively light shade further away from the edge. Many other images in addition to sunshades or obscuration bands are also possible.

Laser engraved silicone rollers and roller sheaths, such as used in the Rotocolor™ printing system, may be obtained from System S.p.A., Via Ghiarola Vecchia, 73, 41042 Fiorano (Modena), Italy.

As there is no requirement for vacuum removal of excess ink (as required by certain screen printing techniques), the present invention is useful in printing up to an edge of a glass blank. This can be conveniently performed by the method of the present invention, provided that a roller of sufficient size is used, with the desired image engraved into the roller. As well as printing up to an edge of a glass blank, the present invention allows an image to be printed close to the edge. For example, it may be printed so that the print extends to within 2 mm or within 1 mm of an edge. In preferred embodiments it is used to print to within 0.5 mm or within 0.1 mm of the edge.

If desired, printing up to, or close to, two or more edges may be performed. For example, a large print may even extend up to, or close to all of the edges of a major surface of a piece of automotive glazing. (It may be desired to print a tint over the major surface of a windscreen or window for privacy reasons.) As a further example, it may be desired to print an obscuration band up to, or close to, all of the edges of a windscreen or a window, but to leave a central, relatively clear region.

Alternatively, the image printed may be any other desired marking, tint, pattern, or motif that can be achieved by printing. Thus the term "image" is to be interpreted broadly for the purposes of the present invention. (The image is anything that is a printed representation of the engraving.) The present invention can be used to print an image which is similar in quality and accuracy to screen printed images. It is of course not essential to use the method of the present

invention for printing up to or close to an edge. The technique can be used for printing any desired image at any desired position. For example, a "trade mark" (including manufacturers' trade marks and indications of safety regulations the glazing meets) a certification mark or other logo may be printed in a central position. It may also be desired to print more than one type of image at once, for example, to print both an obscuration band and a trade mark using the same roller on the same printing pass.

It is however important to appreciate that there are many other possibilities apart from using engraved cylindrical sheaths of deformable material or rollers consisting of such material. The deformable material may be in any appropriate form to allow printing according to the method of the present invention. For example, the deformable material may be a raised part of the roller (relative to other parts of a roller). The raised part can be engraved and can be used to apply increased pressure during printing. This is simply one an example of a situation where the deformable material does not cover all of the surface of the roller. Indeed, it is sufficient that a part of the roller used in containing the ink during printing is deformable. The deformable material (in whatever form) is useful in reducing the risk of breaking a piece of automotive glazing or a component thereof during printing. It also assists in allowing ink to be released from an engraved region during printing.

The roller is preferably used to print directly onto the glass blank. Thus it is preferred that the ink from the roller is not transferred onto another part of the printing apparatus (e.g. onto another roller) before printing. Direct printing from the engraved roller is useful in conserving ink and in producing a clear printed image. The roller can be used for continuous printing (where an item being printed is not stopped or stationary during printing). Indeed the piece of automotive glazing or component thereof can move during printing at substantially the same velocity as that at which the outer surface of the roller rotates. This is advantageous in that it allows rapid printing. Print speeds of over 40 linear metres per minute (e.g. over 50, or over 60 linear metres per minute) may be achieved. A single rotation of the roller may be used to print a plurality of pieces of automotive glazing or components thereof. Alternatively, a roller with a single image may rotate several times over a single piece of glazing or component so as to print a plurality of images onto a single item. The size of the roller may be varied to accommodate the size of the glass blank, for example, a smaller roller may be used for smaller glass blanks, such as those used to form sixthlights and quaterlights.

The ink used to print onto the glass blanks must be suitable for printing onto a non-porous substrate. In particular, the release mechanism of the ink from the roller must be compatible with the surface of the glass blank. The viscosity and density of the ink must be such that the ink is released from the cavities, but does not smudges or runs when the roller lifts up from the surface of the glass blank. Preferably, the ink has a low viscosity.

One class of suitable inks is the class of inks that are solid/or at least too viscous to be useful in printing at room temperature, but that "melt" to become fluid and usable at higher temperatures. These inks are sometimes known in the art as "thermoplastic inks" or "hot-melt" inks. Preferred inks melt to become usable at temperature of above 50° C. For example, they may melt above 60° C, or above 70° C. Thus, the inks may be used in printing at high temperatures (e.g. at temperatures of up to 150° C). Without being bound by theory, a temperature range of from 60 to 150° C is likely to be suitable for printing many thermoplastic inks. The printing roller can be heated accordingly to ensure that the ink is released from the cavities in the roller. If desired, the printing process can be thermostatically controlled. The ink may include a ceramic powder. Indeed this is preferred for many applications. For example, frit system 14251 in thermoplastic medium type 74119 can be used and is obtainable from the ink supplier Ferro, Inc.. Other thermoplastic inks suitable for printing onto glazing can be used. Other ink suppliers include Johnson Matthey.

A second class of suitable inks are IR drying inks (inks that dry on exposure to infra-red radiation), which are generally cold, and so do need the roller to be heated to be released from the cavities. Such inks are available from Ferro, Inc., and may contain a standard automotive frit system, such as 14251.

Other suitable inks for printing onto a glass blank are known in the art, and can be used with the present invention. Such inks include standard frit systems for automotive toughening inks in various media having an appropriate viscosity and density to be released from the roller. Indeed the term "ink" is used broadly herein to cover any material that can be printed using the roller of the present invention. Compositions known in the art for use in printing circuits, antennae or heating elements onto glazing can be used and are regarded for the purposes of the present invention as inks. The ink may therefore be electrically and/or thermally conductive, at least when printed. It may comprise a conductive metal, such as silver. If desired, one ink may be printed over another. For example a printed circuit may be printed onto a backing print that

has already been applied to a piece of glazing or component thereof.

Turning now to Figure 10, examples of automotive glazing blanks that can be printed by the method of the present invention are illustrated (not to scale).

A blank for a rear side window 210 (sometimes known as a "vent") is shown in the top left hand corner of the Figure 2. This has a generally triangular form, with rounded corners. It is sometimes referred to in the trade as a "sidelight". A blank for a rear window on the other side of the vehicle will of course also be provided (not shown).

Next to the blank for a rear side window 210, a blank for a front door or side window 220 of the automotive vehicle is shown. This is sometimes referred to in the trade as a "doorlight". A blank for a front door window on the other side of the vehicle will of course also be provided (not shown).

Underneath the blank for a rear side window 210 a blank for a windscreen 230 is shown. Unlike either the blank for the rear side window 210 or the blank for the front door window 220, the blank for the windscreen 230 is generally symmetrical about a central vertical axis. Windscreens of any size or shape can be printed, including, for example, panoramic windscreens (where the side regions of the windscreen wrap around the front of a vehicle to the "A" pillars) and cielo windscreens (where the windscreen extends up into and forms part of the roof of the vehicle.

Next to the blank for a windscreen 230 a blank for a back window 240 is shown. This is sometimes referred to in the trade as a "backlight". Like the blank for a windscreen 230 the blank for a back window 240 is also generally symmetrical about a central vertical axis.

All of the blanks shown are clearly recognisable as being intended for automotive glazing. They have very different shapes from other types of glazing. All have rounded edges and have shapes that are significantly narrower at the top than at the bottom (although many other shapes are possible). The blanks shown are purely illustrative and are not at all limiting. Only a few sample pieces have been shown and many other shapes are possible, depending upon the nature of an automotive vehicle and the position of the glazing. Although the blanks shown are glass blanks, they may be formed of any suitable glazing material used to form automotive glazings,

for example, a plasties material, such as polycarbonate.

The blank may, for example, be a blank for forming a windscreen, a side or door window, a sunroof, a backlight, a cover for a light, etc. It will generally be provided in substantially flat form and require one or more further steps for finishing.

Once a glass blank has been printed using a method of the present invention it may be subject to further processing steps. For example, it may be heated and bent into a desired three- dimensional shape. It may be tempered. During this processing it may be heated to high temperatures. For example it may be heated to over 600° C. Such bending is carefully controlled. Bending can be used to produce a piece of glazing that is slightly curved so as to curve outwardly (in a convex manner) when fitted in an automobile. If tempered glazing is required, tempering is preferably also performed following printing.

The glass blank may be used to form a laminate, having an interlayer of polymeric material. Interlayers are well known in the art and can provide improved safety in reducing the likelihood of glazing shattering into flying fragments when broken by an impact. A polyvinyl butyral (PVB) interlayer is preferred but many alternative interlayers may be used (e.g. polyvinyl acetates, polyvinyl chlorides, polyurethanes, acrylates, etc.) Desirably, the laminate includes two panes of glass, having at least one interlayer located between the panes, although this is not essential.

As an alternative to printing onto a glass blank, a component for a glazing may be printed first and may then be used later on in the production of the glazing. For example, glazing materials such as an interlayer or a film for a laminated glazing may be printed first. The interlayer may then be laminated to one or more other components, for example other glass blanks, or unprinted plies of glasss, in a subsequent procedure. The printing of interlayers is known in the art (see, for example, US 3,868,286), although not by using the roller printing method of the present invention. Inks known for use in printing onto interlayers can be used with the method of the present invention. A further alternative is to first print a piece of glass or another component intended as an outer layer of a glazing laminate. The glazing is then produced by a subsequent lamination procedure.

Components printed by the method of the present invention can be useful intermediates. For

example, a printed component can be sold to a manufacturer of automotive glazing, or it may be stored and/or packaged for subsequent use. A preferred printed component is a printed interlayer for a laminated glazing.

The present invention therefore includes a method of producing an automotive glazing (either a single ply or a laminate) from a glass blank, that has been printed using the method of the present invention, or forming a laminate with a component (e.g. an interlayer) that has been printed, prior to lamination, by a method of the present invention.

An automotive glazing formed from a glass blank or component comprising an image that has been printed by a method of the present invention can be fitted to an automotive vehicle or to a part thereof (e.g. to a door frame, a window frame, or a sunroof frame). The present invention therefore includes not only the printed automotive glazing, but also an automotive vehicle or a part thereof (e.g. a door) to which the piece of automotive glass or glazing has been fitted.

For the purposes of the present invention, the term "automotive vehicle" is used cover any powered mode of transport, but especially to cover a terrestrial powered vehicle, (e.g. a car, truck, motorcycle, moped, scooter, lorry, bus, van, tractor, train, off-road vehicle, farm vehicle, military vehicle, security vehicle, etc.) Preferred automotive vehicles are four-wheeled automotive vehicles.

The part of the automotive vehicle may be a spare part. It is therefore not required that the part be incorporated into an automotive vehicle in order to be within the scope of the present invention.