Field of invention

[001] This invention relates to a printing method and apparatus for implementing the method and, in particular, a method of performing ultra-violet print techniques.

Background to the invention

[002] In known ultra-violet (UV) printing processes, UV light is used within a printing device to dry specially formulated UV-curable inks. This means that the UV ink is dry when the sheet, upon which printing occurs, exits the press, not wet as in traditional offset printing. However, broad range UV light, usually from high pressure mercury vapour lamps, tends to be highly inefficient in terms of power consumption, as well as being dangerous to workers exposed to its high intensity radiation.

[003] Mercury vapour lamps are known that emit UV radiation at wavelengths that will be effective for ink curing. UV radiation with wavelengths of 365:366 nanometers (nm) provides the proper amount of penetration into the wet ink film to effect drying. (See http://printwiki.org/Ultraviolet_Curing_lnk.)

[004] Stereolithography is a known method for making solid objects by successively

"printing" thin layers of ultraviolet radiation-curable material one on top of the other. In patent number US4575330 to Hull, a concentrated beam of ultraviolet light is focused onto the surface of a vat filled with a liquid photopolymer. The light beam, moving under computer control, draws each layer of the object onto the surface of the liquid. Wherever the beam strikes the surface, the photopolymer polymerizes/crosslinks and changes to a solid. Advanced CAD/CAM/CAE software mathematically slices the computer model of the object into a large number of thin layers. The process then builds the object layer by layer starting with the bottom layer, on an elevator that is lowered slightly (by about the thickness of a layer) after solidification of each successive layer. [005] An emerging technology, referred to as LED UV printing, utilises advances in

UV reactive inks and irradiation from narrow band (360 nm to 400 nm) LEDs to produce polymerisation. Polymerisation in this context is a molecular process that converts the ink from liquid to solid. As this process utilises no solvent, it is suitable for printing on a wide range of substrates including, papers, cardboard, polypropylene and polystyrene.

Objects of the invention

[006] It is an object of this invention to address the shortcomings of the prior art and, in doing so, to provide a safe way of utilising laser UV printing.

[007] A further object of the invention is to provide a method of renewing previously written on or printed surfaces for re-use.

[008] The renewing process described herein is designed to "reinvent" or regenerate unwanted or discarded consumer products for recycling or re-use.

[009] The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia or elsewhere at the date of this application.

[0010] Further, and unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense - that is to say, in the sense of "including, but not being limited to" - as opposed to an exclusive or exhaustive sense - that is to say meaning "including this and nothing else".

Summary of invention

[0011] According to a first aspect of the invention there is provided surface treatment apparatus for altering the appearance of a surface of a medium, said apparatus comprising • an ink source charged with a solvent-free, UV-curable ink;

• an ink-discharging print head operatively located to direct ink at a surface to be treated, the print head being in fluid communication with the ink source; and

• a diode oriented for emitting UV radiation at the surface, the diode having been programmed so that the emitted radiation is in a range selected for causing curing of the ink.

[0012] In a preferred form of the invention, the apparatus comprises a marking detector configured to detect and locate undesired markings on the surface.

[0013] In a further preferred form of the invention the marking detector comprises a scanner oriented for scanning the surface to be treated.

[0014] Still further according to the invention, the apparatus comprises a data processor programmed for causing the print head to apply ink in a coating that covers substantially no more than the undesired marking, in a sufficiently marking-obliterating dose.

[0015] Optionally, the data processor is programmed to cause the print head to apply indicia, in addition to the coating, to the surface substantially simultaneously.

[0016] Still further, in an embodiment, the print head is a piezo-electric print head.

[0017] In a further preferred embodiment, the print head is free-floating.

Accordingly, the head is removably attached within the apparatus to be in data communication with the processor.

[0018] In an embodiment, the print head is moveable for traversal of the surface in a controlled manner and discharging the ink.

[0019] Preferably the UV radiation is limited to a wavelength range from 360nm to

400nm. Further preferably, the range is from 364nm to 388nm. [0020] In a yet further preferred form of the invention the apparatus comprises a housing defining an internal print zone. Within the print zone, the surface of the medium to be treated is exposed to the UV radiation.

[0021] In preferred embodiments, the print zone has an intake and an outlet for a print medium on which printing is required to pass through.

[0022] In a preferred embodiment, the zone is at least partly bounded by a shroud comprising a UV reflective interior surface.

[0023] Further, the apparatus preferably comprises respective UV-blocking shrouds covering the intake and the outlet. In preferred embodiments, said shrouds have a UV reflective coating.

[0024] Preferably, the UV reflective coating is a dielectric substance. The dielectric is preferably an oxide of a metal.

[0025] In a still further preferred form of the invention, a logic control board is mounted to the housing, the control board having the data processor mounted thereon.

[0026] Preferably, the print head is located to be remote from the logic control board while being in digital communication therewith.

[0027] According to a second aspect of the invention, there is provided a method of reconditioning an already printed surface of a medium for re-printing, the method comprising steps of

Providing printing apparatus having a treatment zone configured for exposure to a surface requiring reconditioning;

Exposing the surface to the zone,

Causing a detector to detect and locate an existing undesired marking on the surface; Causing treatment means to apply a coating of UV-curable ink to at least the undesired marking in a quantity sufficient to obliterate said marking to a desired degree when cured, and.

Irradiating the coated surface with UV radiation having a wavelength selected for curing the ink coating, for sufficient time to cause curing.

[0028] Preferably the UV radiation is limited to a wavelength range from 360nm to

400nm. Further preferably, the range is from 364nm to 388nm.

[0029] In a preferred form of the invention, the method comprises operating a digital scanner to obtain an image of the surface prior to the coating being applied. Preferably, the scanner is operated to scan the surface image to a digital image format.

[0030] In a further preferred form of the invention, the method includes the step of transferring the medium into the zone.

[0031] In a further preferred form of the invention, the method includes rendering the surface to be of substantially uniform colouring such that the previously-existing marking is substantially invisible to the naked eye.

[0032] In a preferred embodiment, the method includes covering a portal to the zone with a shroud having UV blocking properties.

[0033] Preferably, the shroud is made of a material having a UV reflective coating.

Further preferably, the UV transmissibility of the coated shroud is 2% or less. Preferably, the coating is a dielectric reflective coating. Preferably the dielectric coating comprises a metal oxide.

[0034] In a further preferred embodiment, the method includes positioning the shroud to exert holding pressure on a portion of the surface being reconditioned, for stabilising the medium against unwanted movement.

[0035] In a preferred form of the invention, the method includes irradiating the surface with UV radiation from a monochrome laser. [0036] Further preferably, the method includes applying the coating by means of a piezo electric print head. The head is positionable for applying the coating to substantially no more than the undesired existing marking. The coating is applied in a sufficiently marking-obliterating dose.

[0037] In a further embodiment, the method includes the step of applying indicia to the surface, in addition to the coating, while the surface is exposed to the zone. Application of the indicia occurs substantially simultaneously with the coating.

Brief description of drawings

[0038] In order that the invention may be readily understood, and put into practical effect, reference will now be made to the accompanying figures. Thus:

Figure 1 shows in an exploded schematic front view of a preferred embodiment of the

UV printing apparatus of this invention.

Figure 2 is a schematic side view of apparatus according to a further embodiment of the invention.

Figure 3 is a partially exploded side view of a further embodiment of apparatus according to the invention.

Figure 4 is a partially exploded side view of an embodiment of hand-held marking apparatus according to the invention.

Figure 5 is a partially exploded side view of an embodiment of alternative hand-held apparatus according to the invention.

Detailed description of an embodiment of the invention

[0039] Referring to figure 1, in a preferred embodiment of this invention, a printer is generally denoted by the number 10 and shown in an exploded schematic front view. It has an outer housing 12 made of metallised polypropylene. It will be appreciated that various suitable alternative housing materials exist and that these should be considered to be included in the scope of this invention. [0040] The housing defines an internal space 14, through which extends a support rail 16, below which is defined a treatment zone 18, bounded below by a spring-loaded paper tray 20 having a print medium conveying surface 22, over which the medium 24, on which printing is to take place, is caused to travel by rollers (not shown) in a direction from feed intake ramp 26 to output tray ramp 28. A first suspended, generally vertically-hanging shroud 30 covers intake end 32 and a second shroud 34 of like construction covers output end 36. A scanner head 38 is positioned to enable an image of the medium 24, and in particular its upper-facing surface 44 to be captured, as will be discussed below.

[0041] Both shrouds 30 and 34 are made of a flexible, elastomeric sheet material, coated on their internal zone-facing surface 40, 42 with a dielectric UV-reflective substance (one that has a refractive index from the substrate), so as to inhibit the escape of UV radiation from the zone. The curable inks used in this example have a polymerisation wavelength in the band 360nm to 400nm. Under UV radiation exposure in this band, the ink solidifies. No solvent is needed.

[0042] In this embodiment, the shroud sheets are of silicone rubber, which provides a substrate on to which a dielectric UV-reflective substance is deposited as a thin layer. Suitable dielectric materials include magnesium fluoride, calcium fluoride and various other metal oxides.

[0043] The shrouds extend down to the upper surface 22 of tray 20 and are pushed to bend, as shown at zone end 32, in the direction of travel of medium 24, while maintaining substantial contact with the print-receiving surface 44 of the medium, thereby maintaining a barrier inhibiting escape of UV radiation from zone 18.

[0044] Meanwhile, with the medium in printable position and exposing its printable surface 44 to print heads 46, flanked by UV light emitting diodes (LEDs) 48, 50, the print heads traverse zone 18, powered by a carriage drive motor, 52, which drives a print head carriage assembly 54 along support rail 16, under the control of a processor on a logic control board 56. [0045] UV curable ink, solvent-free and activated by radiation in the wavelength range 360nm to 400nm, is available from a bank of cartridges 60, holding various colours: White 62, black 64, cyan 66, magenta 68 and yellow 70. A supplier of ink of this nature is Sinoinks, having the web address www.smoinks.bet and being contactable also at http://sinoinks.ecrater.com.au/contact.php. The ink is fed via a manifold 72 to pump 74, which transfers the ink to the carriage head assembly 54, via delivery tube 76, from where it is introduced to piezo-electric print heads 46, for controlled deposition on the waiting surface of the printable medium as it is moved through the treatment zone from end 32 to end 36 and out on to output delivery ramp 28.

[0046] Thus in operating the printer 10, recyclable pre-printed pages, destined for renewal, are placed on feeder ramp 26. The user inputs commands via touch screen 78, or via a remotely located input device such as a personal computer or tablet or smartphone. For example, the user may input a command that selects a reprint of the entire surface, such as that of a sheet of paper already having been printed on. The instruction causes the print carriage to traverse the entire surface and cause the print heads to deposit a coating of white ink, or ink of a different selectable colour, throughout.

[0047] Alternatively, the user may select a command for carrying out the renewal by reprinting of only a portion of the incoming sheet. In this case, the command causes software, with which a processor on the control board 56 is programmed, to operate the apparatus so that incoming upper-facing surface 44 is scanned using scanner head 38, in order to form an image of the sheet. From running software for analysing the pixellation of the image, a portion or portions of the sheet to be renewed are identified. In an embodiment, the user may determine that only a particular existing colour is to be renewed, with either the same colour (restoration) or a different colour, including white. Once the selected colouring has been applied to the selected portion, the sheet is expelled by being passed under shroud 34 and on to delivery output ramp 28, for manual retrieval or for adding to a stack of earlier printed sheets or other media in a receiving tray (not shown). The portion selected for reprinting or recoating may be greater than the initially identified portion by a desired margin. [0048] The contact between the lower edge of shrouds 30, 34 and the print medium surface 44 exerts a slight pressure on the surface as it passes beneath the shroud. In cases where progress of the medium through the treatment zone is paused for printing, the pressure of the shroud is exerted on the outer peripheral end edges of the surface to the extent of 1mm to 2mm approximately. This assists in stabilising the surface against unwanted movement while the ink is being applied and allowed to cure. The software that operates the system is designed to prevent activation of the LED unless the shrouds are correctly in place, their position being determined by means of proximity sensors (not shown) installed within the housing.

[0049] It will be appreciated that the printing process described may combine a reconditioning or renewal coating with a new print job: For example, previous printing may be obliterated by means of a white coating over which new characters are added in black, or other font colour. The print programming may alternatively apply the white and font colour simultaneously, with the white ink being applied only to portions to which the font colour will not be applied, enabling the print job to be completed in a single pass.

[0050] In other words, the process in this embodiment comprises

• performing a scan to determine the existing appearance of the medium surface to be renewed,

• comparing the proposed new appearance with the existing,

• identifying which pixels of the surface are to be recoloured and the colour to be applied to each,

• causing the print head to apply the allocated colours to the respective pixels,

• allowing the ink to cure under the UV radiation, and

• expelling the medium once curing has sufficiently progressed.

[0051] The absence of solvents in the process makes it suitable for printing on a wide range of substrates. Non-limiting examples of suitable substrates are paper, cardboard, and plastics such as polypropylene and polystyrene.

[0052] The provision of the dielectric UV-reflective coating on the shrouds allows for increased process efficiency by increasing the intensity through availability of the UV light. This results in improved fixation throughout the printing step. Reducing losses from the treatment zone 18 also helps reduce operator exposure and therefore safety. The shroud also functions as a barrier to contaminants entering the treatment zone and to the escape of volatile organic compounds from the zone.

[0053] For additional functionality of the apparatus, the printer housing is configurable to accommodate drop-on-demand printing, the print head assembly being equipped with a distance sensor for detecting the height of the print heads above thicker, dropped-in items requiring printing treatment, for example Manila folders, small parcels and the like.

[0054] In Figure 2 there is shown an alternative embodiment of the invention in a schematic side view. Here the apparatus 100 comprises a housing 112 defining an internal space 114, and being configured for having installed therein an input tray 102 for receiving sheets of pre-printed paper and an output tray 104 for delivery of re-decorated or renewed or recycled paper that has been processed so that the image produced is static flood coat for the sheet size.

[0055] The apparatus comprises a UV laser printing assembly of known design. In this embodiment, it is configured for applying toner of a selected colour to a pre-printed surface, in this case that of a paper sheet 116. The colour in this embodiment is white. The apparatus and process is set up to apply a coating of the selected colour to the entire sheet, after which the sheet is removed to storage, or is sent to a different printing device, for fresh reprinting on the treated and renewed surface.

[0056] The laser printing assembly comprises a laser source 106 emitting in the narrow, selected UV range, a prism mirror 108, lenses 110, an image drum 120 and a connected UV-reactive toner container 122.

[0057] Direction arrows 124 illustrate the route the print media take from input tray

102 to output tray 104, first passing through a treatment station 126, defined at the pinch between the image drum 120, rotating clockwise, and a set of rollers 128 rotating anticlockwise, where the toner is applied. After application of the toner, the sheet passes around the rollers to the waiting output tray. The access portals to the input and output trays are shrouded with flexible sheets (not shown) having internally reflecting UV- reflective coatings comprising metal oxides.

[0058] It will be appreciated that the apparatus described with reference to Figure 2 serves the sole purpose of applying a block-out image to a page, so that the page may be used again in a different printer. This device allows printer users to renew a page many times.

[0059] In an alternative embodiment for restoring a printed page back to blank, as illustrated schematically in Figure 3, the numeral 140 generally designates apparatus wherein the laser printing assembly of Figure 2 is replaced by a static assembly having UV- LEDs 48 and inkjet printing heads 46, the latter being in fluid communication with an ink receiver 142, so as to be chargeable therefrom via feeder line 144. The ink used is a UV- curable ink, previously described in relation to Figure 1. Like parts, appearing in earlier illustrations already described above, are like numbered.

[0060] In operation, a sheet of paper 116 is transferred from input tray 102 to treatment zone 18 and is propelled around rollers 128, passing beneath the static printing head assembly 46 and UV LEDs 48 and on to receiving output tray 104 in the direction of directional arrow 124. The invention allows for strings of print heads to be used, thereby facilitating fast printing because of the multiple heads. The apparatus is able to be designed to meet any application regardless of size, print speed or quality required.

[0061] As in the case of the embodiment of Figure 2, apparatus 140 serves the sole purpose of applying a block-out image to a page, so that the page may be used again in a different printer. This device allows printer users to renew a page many times.

[0062] An example of a handheld marking device according to the invention is illustrated in Figure 4. Figure 4(a) is a schematic front view (partly exploded) and Figure 4(b) is a view from the right hand side of the apparatus in Figure 4(a).

[0063] The apparatus generally denoted by means of the numeral 150 is for handheld use in small label image applications. By way of example, these applications include price marking, date coding, batch coding and variable data. Generally, the maximum print area required is no more than about 60mm x 60mm.

[0064] The device prints a formatted label from a graphic file, directly applied to a receiving surface of a packaging container. It is particularly suited to carton labelling. Optionally, it can be configured for 2 colours (black and white) printing, for basic labelling requirements, or for colour printing using 3 colours, for example black and white, as well as one colour selected from cyan, magenta and yellow. In technical literature, this combination is denoted by the letters B/W/(C/M/Y). A 3-port ink receiver 152 is provided for receiving ink cartridges 154.

[0065] Universal serial bus (USB) ports 158, 158' are provided for facilitating data transfer, such as print files and software from a computer device. They are also able to be used for power and battery recharge. In alternative embodiments, the apparatus may be wirelessly enabled for data transfer, such as by means of Bluetooth, WiFi and other developing standards of wireless communication. A touch screen 160, in data communication with the logic board 156, provides a user interface for the inputting of commands via a virtual keyboard and for the outputting of information to the user, such as command prompts. Alternatively, the input means may include voice command capability.

[0066] The apparatus is powered by an on-board rechargeable battery 162, preferably of the lithium-ion type, or alternatively nickel-cadmium or equivalent.

[0067] In this device, the print area shrouds 30, 30' serve several functions:

• Ensuring consistent and correct positioning of the print head/s in relation to the printable surface;

• Providing a barrier against contaminants entering the print area.

• Being made from UV-blocking high-density plastics materials lined with a dielectric UV- reflective metal oxide coating, it reflects the UV radiation in the polymerisation frequency range (360nm to 400nm) back on to the print area, allowing for greater efficiency of UV light utilisation, and better fixation throughout the print process, • Affording operators protection from UV exposure.

[0068] To operate the device, the user places the device so that the shrouds are on the waiting medium surface, and exerts downward pressure, so that the shrouds are pushed upwardly in relation to the print heads, causing the latter to be lowered relatively within the cavity defining treatment zone 18, to a position about 3mm - 5mm from the medium surface. With the surface area surrounded by the shrouds and wall portions of the housing, the printable area of the surface is protected from wind disturbance and airborne contaminants. The user is shielded from direct UV radiation and volatile organic compound gases. Slide guides 164 and 164' are shown in Figure 4(b), extending from the base 166 of the housing 112 for protection of the shrouds.

[0069] It will be appreciated that although a 3-port ink receiver is disclosed in this particular embodiment, receivers with other port numbers may also be employed, by way of non-limiting example a 4- or 5-port receiver. For example, the 5-port receiver is able to be configured for B/W/C/M/Y operation.

[0070] The handheld unit will be supplied with a UV shielding mat to minimise UV leakage or reflective transfer. In addition, the unit will be supplied with protective eyewear for the user.

[0071] Figure 5 illustrates a further embodiment of a handheld marking apparatus denoted generally by means of the numeral 180. It has a housing 112 of a rigid plastics material and an ink cartridge receiver 182 configured and equipped with 5 inline cartridge- receiving ports. This embodiment employs UV ink-printing technology comprising a pump 74 fed from the receiver 182 and emitting ink via the print-head 46 mounted to a carriage 48 to which are mounted suitable LEDs. The carriage assembly is movable along supporting rail 16 in response to instructions from the software programming implemented through the logic controller 156.

[0072] The apparatus of this embodiment is designed for the handheld application of image labels, such as in the logistics field where it is useable in carton labelling. This apparatus has a maximum printable area of 110mm x 160mm. It is capable of printing formatted labels as a graphic file directly to a receiving surface of a packaging container. The unit is configurable for basic 2-colour B&W labelling or for 5-colour B/W/C/M/Y for full colour printing as shown in Figure 5(b).

[0073] The handheld unit enables the reuse of cartons for shipping, including those having existing transport bar codes. The user simply uses the apparatus to flood coat the print area to cover precious printing or other markings, instead of applying a fresh carrier or label.

[0074] These embodiments merely illustrate particular examples of the method and apparatus of the invention providing for the reprinting of previously printed surfaces. With the insight gained from this disclosure, the person skilled in the art is well placed to discern further embodiments by means of which to put the claimed invention into practice.