GB2300384A

GB2300384A - Method and apparatus for forming laminated articles

Info

Publication number: GB2300384A
Application number: GB9607506A
Authority: GB
Inventors: Bock Jan Julien Irma De; Schamphelaere Lucien Amede De
Original assignee: Xeikon NV
Current assignee: Xeikon NV
Priority date: 1995-05-04
Filing date: 1996-04-11
Publication date: 1996-11-06
Also published as: GB9607506D0

Abstract

A printed article (44), such as a bank card or identity card, is formed by applying a mirrored toner image onto a web (12) of transparent material and thereafter laminating the transparent material with a relatively opaque substrate (51), with the substrate in contact with the image-carrying face of the transparent material, thereby to form a printed article in which the image is visible through the transparent material. The method is particularly useful where passing the substrate through an electrostatographic printer is to be avoided. It is preferably used with multi-coloured toner images with the 4 colours being produced at the 4 printers (A, B, C, and D), the speed of the web (12) through the printers being controlled by rollers (22a, 22b) which are driven by controllable motors (23a, 23b) so that proper registration of the images occurs. The speed of substrate (51) is also controlled by motor (48) on roller (47) so that, when the substrate (51) contains an image, it is properly registered with the toner image.

Description

DESCRIPTION Field of the 1 Invention This invention relates to a method and apparatus for forming a printed article, particularly such an article carrying a toner image.

Backaron to the Invention It is well known to print toner images onto a substrate, such as paper, for example by electrostatographic means.

Indeed this technique is the basis of photocopying and many printing processes.

In European patent application EP 629924-A (Xeikon NV), there is described an electrostatographic single-pass multiple station (for example multi-colour) printer, in particular such a printer as is capable of printing colour images for professional purposes as a cost effective alternative to conventional printing of short to medium sized runs. The printer is designed for printing images onto a paper web, either in simplex (i.e.

single-sided) or duplex (double-sided) format. The web is fed through the printer, past a number of printing stations where toner images are applied. These images are then fixed onto the web which may then be cut into LAMINATE sheets as desired.

It is sometimes required to print images onto substrates, which differ from paper in one or more respects and which therefor means that the use of the printer of EP 629924-A is less than ideal. For example, the substrate may have a high gloss surface so that the toner does not adhere well thereto. The substrate may have a thickness and/or a stiffness which is too great to be properly fed through the printer, for example a thickness of more than 300cm.

Alternatively, the substrate may have a strength which is too low to withstand the necessary web tensions in the printer without deformation or damage. The substrate may be unsuitable for toner transfer for electrical reasons, e.g. because the substrate is electrically conductive.

With a web-fed machine, some wastage of the web tends to be inevitable at the beginning and end of the print run.

With a short run, this wastage becomes significant, especially if the substrate is formed of a costly material. Further, the substrate may be of such a shape that it is not suitable for passing through the printer.

Nevertheless, it is still desirable to use toner printing for such substrates, because of the quality thereof compared with other cost-effective printing techniques.

LAMINATE summary of the invention It is an object of the present invention to provide a method and apparatus in which the aforesaid difficulties of printing onto certain substrates can be overcome.

We have discovered that this and other useful objectives can be achieved without the need to pass the substrate through the printer and in particular by applying the toner to a transparent material which is then laminated to the substrate.

Thus, according to a first aspect of the invention there is provided a method of forming a printed article comprising the steps of: (i) applying a mirrored toner image onto a web of transparent material; and thereafter (ii) laminating the transparent material with a relatively opaque substrate, with the substrate in contact with the image-carrying face of the transparent material, thereby to form a printed article in which the image is visible through the transparent material.

According to a second aspect of the invention, there is provided an apparatus for forming a printed article, LAMINATE comprising: (a) electrostatographic printing means for applying a mirrored toner image onto a web of transparent material; (b) laminating means for laminating the transparent material with a relatively opaque substrate, with the substrate in contact with the image-carrying face of the transparent material, thereby to form a printed article in which the image is visible through the transparent material.

Toner image printing can be carried out by methods well known in the art, such as electrostatographic printing and magnetographic printing. Electrostatographic printing operates according to the principles and embodiments of non-impact printing as described, eg, in "Principles of Non-Impact Printing" by Jerome L Johnson (1986) - Palatino Press - Irvine CA, 92715 USA). As used herein, the term "electrostatographic" also includes the direct image-wise application of electrostatic charges on an insulating support, for example by ionography and electrophotography.

The printing step (i) may include forming a charged image on a rotatable endless surface, applying toner to the charged image to form a toner image, and transferring the LAMINATE toner image to the web of transparent material.

Preferably, the toner image is applied to one face only of the transparent material, referred to herein as the "inside" face. The other, or "outside" face of the transparent material will normally not carry any image.

However, it is within the scope of this invention to provide the other face with an image, either a toner image or an image in some other form. This image may be applied before or after lamination as desired.

Optionally a protective additional transparent layer may be laminated over the printed transparent material.

The toner image applied to the inside face of the transparent material is a mirrored image, since in the final product the image is to be viewed through the transparent material to which it has been applied.

The toner image may be at least partly fixed on the transparent material before the laminating step (ii).

Several techniques are known for fixing a toner image onto its receiving member. One such method is to fix the toner image on the transparent material using a noncontact radiant heated fixing device. The fixing device is preferably controlled to generate a temperature on the surface of the transparent material which is sufficient to partially but not completely fix the toner particles LAMINATE thereto. The purpose of this pre-fixing is to ensure that the toner image does not become removed from the transparent material during further processing. The selection of this pre-fixing temperature will depend upon the nature of the toner and the transparent material and the linear speed of the web through the fixing device.

The laminating step (ii) may include cold or hot lamination, hot lamination serving to complete the fixing of the toner image. By fixing the toner image in two stages in this manner, we have found that better saturation of the image is achieved, with less light scattering. This can be very beneficial where the substrate has a very flat e.g. glossy surface where toner images are known to exhibit light scattering leading to poor colour saturation. The hot laminating means may comprise a heated roller pair through which the transparent material and the substrate pass, this arrangement being particular applicable where the transparent material web is to be cut downstream of the laminating means. The transparent material may pass directly from the pre-fixing to a hot lamination step, without significant loss of temperature. Alternatively, the transparent material may be allowed to cool before the lamination step. Even in that case, advantages can be gained from pre-heating the transparent material and/or the substrate prior to lamination. Other hot LAMINATE laminating means may also be used however, such as the application of a hot iron or a heated mould. These alternative laminating means are most applicable where the transparent material web is cut before lamination.

Cold lamination is possible if the first image fixing is a complete fixing.

The transparent material ideally has a thickness of at least lym, preferably from 5ym to 100yam, such as from 20m to 50cm. The transparent material preferably has a light transmissivity of at least 50% at the viewing wavelength, most preferably at least 90%. The transparent material is suitably selected from transparent material film such as polyester and PVC. Not only does the transparent material act as a carrier enabling the superposition of the toner image on the substrate, it also acts as a protective film for the product, since in those embodiments where no toner image is present on the outside face of the material, the toner image is not on the exposed face of the product.

For successful lamination, it is advisable for either the transparent material or the substrate to have a heatsoftenable thermoplastic surface. This property may be inherent in the transparent material as such, or may be derived from a layer of suitable material applied to the transparent material or to the substrate. Thus, for LAMINATE example, the transparent material may be polyester carrying a coating of polyethylene, or may be polyester carrying a layer of hot melt adhesive.

The relatively opaque substrate will usually have a thickness of more than 50cm, preferably from 200m to lmm, and, depending upon the nature of the material, may conveniently be in the form of a web. The substrate material preferably has a light reflectivity of more than 50%, most preferably more than 90% at the viewing wavelength. The viewing wavelength need not necessarily be within the visible spectrum. Some product applications may require that the image should be discernable only, or additionally, under ultra violet light for example.

The substrate is suitably selected from plastics materials, paper, card, textiles, wood, vitreous materials, ceramics, and metals. The invention is particularly useful where the surface of the substrate does not allow good adherence of the toner particles.

The invention is also particularly useful where the substrate is of an irregular shape, for example where the surface to be laminated is not flat.

Where electrostatographic printing is used the apparatus preferably comprises a plurality of toner image-producing LAMINATE electrostatographic stations each having rotatable endless surface means onto which a toner image can be formed, means for conveying the transparent material past the stations, and transfer means for transferring the toner image on each rotatable surface means onto the transparent material. Magnetographic printing can be similarly structured.

Preferably, the apparatus includes means for conveying the transparent material web in succession past the stations, means for controlling the speed and tension of the transparent material web while it is running past the stations, and guiding means which determine for the transparent material web wrapping angles about the rotatable surface means.

In order to transfer a plurality of toner images in succession, that is in a single pass through the printer, directly onto the transparent material web, accurate registration of the images with each other is required, ideally to an accuracy of about 40cm, or better. In order to achieve this registration accuracy, it is essential that there should be no slippage, i.e. there should be synchronism between the transparent material web and the image bearing surface. This may be achieved by ensuring that adherent contact of the transparent material web with the rotatable endless surface means is LAMINATE such that the movement of the transparent material web controls the peripheral speed of the surface means in synchronism with the movement of the transparent material web.The adherent contact results also from a mechanical contact obtained by guiding and tensioning the transparent material web over a certain wrapping angle in contact with the rotatable endless surface means.

While the toner image on the endless surface means may be transferred to the transparent material web by other means, such as an opposed hot roller or pressure roller, we prefer to use a corona discharge device as the transfer means. This has the advantage that, at least partly, the adherent contact between the transparent material web and the endless surface means comes from the transfer corona discharge device providing electrostatic adhesion between the transparent material web and the endless surface means. With most transparent plastics materials it is found that the efficiency of transfer by this method is usually better than with conventional paper materials.

Usually, the rotatable endless surface means comprises a belt or the circumferential surface of a drum. In the following general description, reference is made to a drum, but it is to be understood that such references are also applicable to endless belts or to any other form of LAMINATE endless surface means. The drum preferably has a photoconductive surface and each toner image-producing electrostatographic station preferably comprises means for charging the surface of the drum, and usually the surface of the drums at all the image-producing stations are charged to the same polarity. Using photoconductors of the organic type, it is most convenient to charge the surface of the drums to a negative polarity and to develop the latent image formed thereon in reversal development mode by the use of a negatively charged toner.

The means for image-wise exposing the charged surface of the drum or belt may comprise an array of image-wise modulated light-emitting diodes or take the form of a scanning laser beam.

The toner will usually be in dry particulate form, but the invention is equally applicable where the toner particles are present as a dispersion in a liquid carrier medium or in a gas medium in the form of an aerosol.

In one embodiment of the invention, the transparent material web is unwound from a roll and the printer may further comprise a roll stand for unwinding a roll of transparent material web. The drive means for the transparent material web may comprise one or more drive LAMINATE rollers, preferably at least one drive roller being positioned downstream of the image-producing stations and a brake or at least one drive roller being positioned upstream of the image forming stations. The speed of the transparent material web through the printer and the tension therein is dependent upon the speed and the torque applied to these drive rollers. For example, one may provide two motor driven drive rollers, one driven at a constant speed defining the transparent material web speed and the other driven at constant torque defining the transparent material web tension. Preferably the transparent material web is conveyed through the printer at a speed of from 5 cm/sec to 50 cm/sec and the tension in the transparent material web at each image-producing station preferably lies within the range of 0.1 to 2.0 N/cm transparent material web width.

The transfer means is preferably in the form of a corona discharge device which sprays charged particles having a charge opposite to that of the toner particles. The supply current fed to the corona discharge device is preferably within the range of 1 to 10 yA/cm transparent material web width, most preferably from 2 to 5 yA/cm transparent material web width, depending upon the characteristics of the transparent material and will be positioned at a distance of from 3 mm to 10 mm from the path of the transparent material web.

LAMINATE The present invention can be used to produce a wide range of printed articles. In particular, we have found it useful for the preparation of identity cards, credit and debit cards, cards for use in automatic cash dispensers of banks and the like and other documents of a laminated form which include a relatively stiff substrate material and require the printing of high quality images thereon, especially personal photographs.

Preferred embodiments of the Invention The invention will now be further described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 shows schematically an electrostatographic single-pass multiple station printer according to the invention; and Figure 2 shows in detail a cross-section of one of the print stations of the printer shown in Figure 1.

The apparatus shown in Figure 1 comprises 4 printing stations A, B, C and D which are arranged to print yellow, magenta, cyan and black images respectively and a laminating station L. The printing stations A, B, C and D are arranged in a substantially vertical configuration, LAMINATE although it is of course possible to arrange the stations in a horizontal or other configuration. A web of transparent material 12, for example formed of polyethylene-coated polyester having a thickness of 20cm, is unwound from a supply roller 14, which holds for example sufficient quantity to print, say, up to 5,000 "A3" images (16.5" by 11.7"). The web 12 is conveyed in an upwards direction past the printing stations in turn.

After passing the last printing station D, the web of transparent material 12, now carrying toner images on one face thereof, passes through an image-fixing station 16, an optional cooling zone 18, an optional radiant or hotshoe pre-heater 19, the laminating station L and thence to a cutting station 20 to cut the laminated product 44 into sheets. The transparent material web 12 is conveyed through the printer by two drive rollers 22a, 22b, one positioned between the supply station 13 and the first printing station A, and the second positioned between the image-fixing station 16 and the laminating station L.

The drive rollers 22a, 22b, are driven by controllable motors, 23a, 23b. One of the motors 23a, 23b is speed controlled at such a rotational speed as to convey the transparent material web through the printer at the required speed, which may for example be about 125mm/sec.

The other motor is torque controlled in such a way as to generate a transparent material web tension of, for example, about 1 N/cm transparent material web width.

LAMINATE As shown in Figure 2, each printing station comprises a cylindrical drum 24 having a photoconductive outer surface 26. Circumferentially arranged around the drum 24 there is a main corotron or scorotron charging device 28 capable of uniformly charging the drum surface 26, for example to a potential of about -600V, an exposure station 30 which may, for example, be in the form of a scanning laser beam or an LED array, which will imagewise and line-wise expose the photoconductive drum surface 26 causing the charge on the latter to be selectively reduced, for example to a potential of about -250V, leaving an image-wise distribution of electric charge to remain on the drum surface 26. This so-called "latent image?1 is rendered visible by a developing station 32 which by means known in the art will bring a developer in contact with the drum surface 26.The developing station 32 includes a developer drum 33.

According to one embodiment, the developer contains (i) toner particles containing a mixture of a resin, a dye or pigment of the appropriate colour and normally a chargecontrolling compound giving triboelectric charge to the toner, and (ii) carrier particles charging the toner particles by frictional contact therewith. The carrier particles may be made of a magnetizable material, such as iron or iron oxide. In a typical construction of a developer station, the developer drum 33 contains magnets carried within a rotating sleeve causing the mixture of LAMINATE toner and magnetizable material to rotate therewith, to contact the surface 26 of the drum 24 in a brush-like manner.Negatively charged toner particles, triboelectrically charged to a level of, for example 9 are are attracted to the photo-exposed areas on the drum surface 26 by the electric field between these areas and the negatively electrically biased developer so that the latent image becomes visible.

After development, the toner image adhering to the drum surface 26 is transferred to the moving transparent material web 12 by a transfer corona device 34. The moving transparent material web 12 is in face-to-face contact with the drum surface 26 over a wrapping angle X of about 150 determined by the position of guide rollers 36. The charge sprayed by the transfer corona device, being on the opposite side of the transparent material web to the drum, and having a polarity opposite in sign to that of the charge on the toner particles, attracts the toner particles away from the drum surface 26 and onto the surface of the transparent material web 12. The transfer corona device typically has its corona wire positioned about 7 mm from the housing which surrounds it and 7 mm from the transparent material web.A typical transfer corona current is about 3mA/cm transparent material web width. The transfer corona device 34 also serves to generate a strong adherent force between the LAMINATE transparent material web 12 and the drum surface 26, causing the latter to be rotated in synchronism with the movement of the transparent material web 12 and urging the toner particles into firm contact with the surface of the transparent material web 12.The transparent material web, however, should not tend to wrap around the drum beyond the point dictated by the positioning of a guide roller 36 and there is therefore provided circumferentially beyond the transfer corona device 34 a transparent material web discharge corona device 38 driven by alternating current and serving to discharge the transparent material web 12 and thereby allow the transparent material web to become released from the drum surface 26. The transparent material web discharge corona device 38 also serves to eliminate sparking as the transparent material web leaves the surface 26 of the drum.

Thereafter, the drum surface 26 is pre-charged to a level of, for example -580V, by a pre-charging corotron or scorotron device 40. The pre-charging makes the final charging by the corona 28 easier. Thereby, any residual toner which might still cling to the drum surface may be more easily removed by a cleaning unit 42 known in the art. Final traces of the preceding electrostatic image are erased by the corona 28. The cleaning unit 42 includes an adjustably mounted cleaning brush 43, the LAMINATE position of which can be adjusted towards or away from the drum surface 26 to ensure optimum cleaning. The cleaning brush 43 is earthed or subject to such a potential with respect to the drum as to attract the residual toner particles away from the drum surface.

After cleaning, the drum surface is ready for another recording cycle.

The rotatable cleaning brush 43 is driven to rotate in a sense the same as to that of the drum 24 while the brushlike developer drum 33 rotates in a sense opposite to that of the drum 24.

Referring back to Figure 1, after passing the first printing station A, as described above, the transparent material web passes successively to printing stations B, C and D, where images in other colours are transferred to the transparent material web. It is critical that the images produced in successive stations be in register with each other. In order to achieve this, the start of the imaging process at each station has to be critically timed and there must be no slip between the transparent material web 12 and the drum surface 26.

The fixing station 16 is of the type comprising one or more radiant heat sources such as described in European Patent Application 629930-A (Xeikon NV). The fixing LAMINATE device is controlled to generate a temperature of about 1200C on the surface of the transparent material, sufficient to partially but not completely fix the toner particles thereto.

At the laminating station L there is provided a supply roll 46 of substrate material 51, for example white polyester having a thickness of 80cm. The substrate material 51 is drawn from the supply roll 46 by drive roller pair 47 coupled to an independently controllable drive motor 48. An optional substrate cutter 49 cuts the substrate into sheets which are then fed by a sheet feed belt 50, which is optionally also driven by the same drive motor 48. The substrate cutter 49 is particularly useful when the substrate material is valuable and any wastage thereof is to be avoided. The substrate material 51 is brought into contact with the printed transparent material web 12, and the two pass together through a heated pair of laminating rollers 54, 56, with the tonercarrying inside face of the transparent material being in contact with the substrate 51.The laminating rollers 54, 56 are, for example, heated by internal radiant heating elements to a surface temperature of 1200C, sufficient to securely laminate the transparent material to the substrate and to complete fixing of the toner image. The heated rollers 54, 56 are biased together sufficiently to cause lamination of the plastic material LAMINATE web 12 to the substrate web 51 without causing damage thereto. One of the heated rollers, namely roller 56 is driven by a controllable motor 53 which serves to convey the substrate web 51 through the laminating station.

After lamination, the product passes to the cutting station 20 and is collected in the product receiving tray 52.

The independent control of motor 48 enables the adjustment of the position of the substrate relative to the transparent material web prior to lamination, thereby to ensure correct register where this is critical (for example where the substrate already carries its own image which is to have a critical positional relationship to the toner image carried on the transparent material web).

Various features of the apparatus need to be controlled in timed relationship to each other. These are in particular drum exposure, substrate pick-up and web cutting. A microprocessor may be employed to control such functions in a manner well known in the art.

LAMINATE By way of example, the following operation sequence may be described: A) STANDBY Motors 23b, 53 and 48 are stopped. Cutters 20 and 49 are open. The substrate web is cut at the position of cutter 49.

B) PRINT (NO LAMINATION) Motors 23b and 53 are running. Motor 48 is stopped.

Cutter 20 cuts sheets of transparent material. Cutter 49 is open. The substrate web is cut at the position of cutter 49.

C) PRINT AND LAMINATE Motors 23b, 53 and 48 are running. Cutter 20 cuts sheets of transparent material. Cutter 49 is open. The substrate is fed into the laminator and is cut into sheets after lamination.

D) STOP -TRANSFER TO STANDBY Motors 23b, 53 and 48 are stopped. Cutter 20 is open.

Cutter 49 cuts the substrate web as soon as the two webs have stopped.

Claims

LAMINATE

CLAIMS 1. A method of forming a printed article comprising the steps of: (i) applying a mirrored toner image onto a web of transparent material; and thereafter (ii) laminating the transparent material with a relatively opaque substrate, with said substrate in contact with the image-carrying face of the transparent material, thereby to form a printed article in which the image is visible through the transparent material.
2. A method according to claim 1, wherein step (i) includes: - forming a charged image on a rotatable endless surface; - applying toner to said charged image to form a toner image; and - transferring the toner image to the web of transparent material.
3. A method according to claim 1 or 2, wherein the toner image is applied to one face only of the transparent material.

LAMINATE
4. A method according to any preceding claim, wherein said toner image is at least partly fixed on said transparent material before step (ii).
5. A method according to claim 4, wherein step (ii) includes hot lamination, thereby to complete the fixing of the toner image.
6. A method according to any preceding claim, wherein the web of transparent material is cut after step (ii).
7. A method according to any preceding claim, wherein the transparent material has a thickness of at least lym, preferably from 5ym to 100cm.
8. A method according to any preceding claim, wherein the transparent material is selected from plastics material films.
9. A method according to any preceding claim, wherein the substrate has a thickness of more than 100cm, preferably from 200m to lmm.
10. A method according to any preceding claim, wherein the substrate is in the form of a web.

LAMINATE
11. A method according to any preceding claim, wherein substrate is selected from plastics materials, paper, card, textiles, wood, vitreous materials, ceramics, and metals.
12. A method according to any preceding claim, wherein the surface of the substrate has a high gloss.
13. A method according to any preceding claim, wherein said toner image is a multi-coloured toner image.
14. An apparatus for forming a printed article, comprising: (a) electrostatographic printing means for applying a mirrored toner image onto a web of transparent material; (b) laminating means for laminating the transparent material with a relatively opaque substrate, with said substrate in contact with the image-carrying face of the transparent material, thereby to form a printed article in which the image is visible through the transparent material.

LAMINATE
15. An apparatus according to claim 14, wherein said electrostatographic printing means comprises: - a plurality of toner image-producing electrostatographic stations each having rotatable endless surface means onto which a toner image can be formed; - means for conveying the transparent material web past said stations; and - transfer means for transferring the toner image on each rotatable surface means onto the web.
16. An apparatus according to claim 15, further comprising means for at least partly fixing said toner image onto said transparent material.
17. An apparatus according to any one of claims 14 to 16, wherein said laminating means comprises a heated roller pair through which said web and said substrate pass.
18. An apparatus according to any one of claims 14 to 17, further comprising web cutting means.
19. An apparatus according to claim 18, wherein said cutting means is located downstream of the laminating means.