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Title:
METHOD AND PRINTER FOR PRINTING OF A PRODUCT WITH A LAYER OF PHOTO SENSITIVE MATERIAL THEREON
Document Type and Number:
WIPO Patent Application WO/2010/056116
Kind Code:
A1
Abstract:
The present invention relates to a method for printing a predetermined image, such as a pattern, picture or text, on a product (3), comprising of : arranging a layer (4) with photosensitive material on the product; and illuminating the layer with the photosensitive material with a light source comprising at leas one LED. The invention also relates to a printer (1) for printing a predetermined image, such as a pattern, picture or text, on a product, and a product comprising a carrier on which a layer with a photosensitive material at least can be or is arranged.

Inventors:
LANGBROEK, Ernest Tasso (Numansgors 33 + 34, HA Numansdorp, NL-3281, NL)
Application Number:
NL2009/050382
Publication Date:
May 20, 2010
Filing Date:
June 30, 2009
Export Citation:
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Assignee:
LANGBROEK, Ernest Tasso (Numansgors 33 + 34, HA Numansdorp, NL-3281, NL)
International Classes:
B41J2/435; B41J2/475; G03C1/00; G03F7/004
Foreign References:
JP2005305763A2005-11-04
EP0945763A11999-09-29
JP2003295399A2003-10-15
Attorney, Agent or Firm:
GROOTSCHOLTEN, Johannes Antonius Maria et al. (Sweelinckplein 1, GK The Hague, NL-2517, NL)
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Claims:
CLAIMS

1. Method for printing a predetermined image, such as a pattern, picture or text, on a product, comprising of: arranging a layer with photosensitive material on the product; and illuminating the layer with the photosensitive material with a light source comprising at least one LED.

2. Method as claimed in claim 1, further comprising of: illuminating the layer of photosensitive material with light of a predetermined wavelength using the LED light source.

3. Method as claimed in claim 2, further comprising of selecting a photosensitive material and the wavelength of the LED to correspond to each other, wherein only when illuminated with light from the LED does the photosensitive material react thereto.

4. Method as claimed in claim 2 or 3 , comprising of : selecting the wavelength outside the wavelength range of visible light.

5. Method as claimed in claim 4, comprising of: selecting the wavelength outside the wavelength range of the sun.

6. Method as claimed in at least one of the foregoing claims, further comprising of selecting photochromic pigment as the photosensitive material for irreversible colour change when light with a preselected wavelength is incident thereon. 7. Method as claimed in claim 6, further comprising the use of more than one photochromic pigment in the layer and illuminating thereof with light of more than one wavelength from at least one LED, wherein each selected photochromic pigment is sensitive to light of at least one wavelength and changes colour in reaction thereto.

8. Method as claimed in claim 7, wherein each photochromic pigment takes on an associated colour when illuminated with light of one selected wavelength.

9. Method as claimed in claim 6, 7 or 8, further comprising of selecting at least one photochromic pigment which can take on more than one colour subject to the wavelength of light incident thereon. 10. Method as claimed in at least one of the foregoing claims 1-5, further comprising of: selecting photothermal material as the photosensitive material which, when light of a preselected wavelength is incident thereon, reacts thereto by being heated.

11. Method as claimed in claim 10, further comprising of: arranging thermochromic pigment in the layer in association with the photothermal material so that the thermochromic pigment changes colour at a predetermined temperature of the photothermal material.

12. Method as claimed in claim 10 or 11, further comprising of selecting at least two thermochromic pigments for arranging thereof in the layer on the product.

13. Method as claimed in claim 10, 11 or 12, further comprising of selecting at least two photothermal materials for arranging thereof in the layer on product in order to generate different temperatures when light of at least one predetermined wavelength is incident thereon.

14. Printer for printing a predetermined image, such as a pattern, picture or text, on a product in a method as claimed in at least one of the foregoing claims, which printer comprises: a printer head and a control for controlling the printer head for the purpose of printing the image on the product, wherein the printer head comprises at least one LED.

15. Printer as claimed in claim 14, wherein the printer head comprises at least two types of LED. 16. Product comprising a carrier on which a layer with a photosensitive material at least can be or is arranged for applying in or with a method as claimed in at least one of the foregoing claims 1-13.

17. Product as claimed in claim 16, wherein the layer comprises at least two types of photosensitive material.

Description:
METHOD AND PRINTER FOR PRINTING OF A PRODUCT WITB λ IAYER OF PHOTO

SENSITIVE MATERIAL THEREON

The present invention relates to a method and device, in particular a printer, for printing a predetermined image, such as a pattern, picture or text, on a product. Such an image can be a barcode or a photograph and so on. There is no limitation to any type of image within the scope of the present invention.

For the purpose of arranging an image it is known in the art to make use of inks, pigments and so on. In a conventional printer these are applied to a carrier, such as a sheet of paper. In the case of a laser printer, laser light can be used to define the image, wherein ink or pigment is applied to the carrier and subsequently fixed, for instance using a heat-based fixing process.

It is also known to print products, for instance with a barcode or a best before-date, wherein use can likewise be made of a laser. The colouring agents used herein change colour in a pattern defined by the laser when light of a determined wavelength and an intensity higher than a threshold value is incident thereon. An image (a text or barcode) is thus "burned" into the colouring agent, ink or pigment. No step is then required to fix the thus formed image as in the case of a printer.

The use of lasers does however have a number of serious drawbacks. A laser can thus cause damage to the eyes of staff in the vicinity of such an industrial printer for the printing of products. Strict safety regulations are necessary to protect employees. Partly because of these considerations it is usual in the industrial printing of products, in particular coding thereof with a best before-date and/or a barcode and so on, to continue using inks and organic solvents. Inks and organic solvents, such as MEK, can however also be hazardous to the environment and staff having to work therewith. The present invention has for its object to obviate the above stated drawbacks of the different known techniques, for which purpose a method and a device, in particular a printer, are provided, which all comprise characteristics of independent claims 1 and 9. A layer with photosensitive material is here prearranged on the product, and the layer with the photosensitive material is then illuminated with a light source comprising at least one LED.

The use of a LED makes it possible for considerably lower light intensities to be applied than when a burning laser is applied. The hazardous inks and associated solvents, such as MEK, can moreover be dispensed with.

The present invention has various preferred embodiments as defined in the dependent claims. An embodiment of the invention can thus have the feature of illuminating the layer of photosensitive material with light of a predetermined wavelength using the LED light source. This wavelength can be chosen in accordance with the properties of the photosensitive material, which changes colour when light of this predetermined wavelength is incident thereon. Such a wavelength is preferably predetermined outside the wavelength range of ambient light so-that unintended fading or colour change " in the layer with photosensitive material can be prevented. A LED can thus be chosen, in combination with the photosensitive material in the layer, with a wavelength of 800 nm. This lies outside the wavelength range of ambient light. In addition or as alternative, it is possible to opt for a photosensitive material in which a different colour change occurs at different wavelengths. All the photosensitive material in the layer can then change colour due to the incidence thereon of light with different wavelengths. It can thus be ensured, at least when the colour change is irreversible, that the image does not fade once it has been formed. Use can here be made of LEDs which can be controlled to emit different wavelengths of light, or individual LEDs can be applied which can each emit a single, specific wavelength of light and can be set into operation selectively. For the purpose of forming the image it is in any case desirable that a control is provided which is able to activate individual LEDs in accordance with the image to be formed, or can control the orientation of a single LED or a limited number thereof in order to thus form the desired image.

In addition to the direct use of a photochromic pigment, which changes into a desired or predetermined colour when light of a predetermined wavelength is incident thereon, it is also possible to opt for other materials, all within the scope of the present invention. In a particularly favourable embodiment the photosensitive material can be a photothermal material. When light of a predetermined selected wavelength is incident thereon, photothermal material reacts hereto with a temperature increase. Such a temperature increase can be increased to the extent that an image is as it were burned onto the product. It is however likewise possible to form clusters of such photothermal materials with thermochromic pigment therearound, which can change colour in accordance with the temperature increase generated by the photothermal material at a predetermined temperature of the photothermal material . Diverse combinations of properties are then possible. Photothermal materials are known which can heat to a variable temperature, wherein the temperature reached depends on the intensity or wavelength of the light incident thereon. The wavelength or intensity can thus be varied here in order to reach a desired temperature and so influence the thermochromic material so that it takes on a desired colour. Different types of thermochromic pigment can be associated with a single photothermal material in order to allow selected of these pigments to change colour subject to the temperature reached by the photothermal material. A very fine adjustment of patterns, contours and colours is thus possible which can be realized with an embodiment of the invention.

As noted, the present invention also relates to a printer for printing a predetermined image on a product, wherein the method as set forth above is realized.

In order to improve understanding of the present invention a description of the accompanying drawing will however follow hereinbelow, in which the same or similar parts, components and aspects are designated with the same reference numerals but which are provided in each case only for the purpose of illustrating and not for limiting the invention, and in which: fig.1 shows a perspective view of a printer in use according to the present invention,- fig. 2 shows a schematic view of the configuration of a printer head in a printer such as that of fig. 1; fig. 3 shows an alternative to the configuration of fig. 2; fig. 4 shows a cluster of photothermal material in combination with thermochromic pigment; fig. 5 shows an embodiment of a LED as part of a printer head in a printer such as that of fig. 1; and fig.6 shows an embodiment for realizing the invention with a number of LEDs with focussing means. Fig. 1 shows a printer 1, to which products 3 are supplied over a conveyor belt 2. An example of such a product 3 is a packaging of food products onto which a barcode must be printed. The products 3 for printing are fed in the direction of arrow A to printer 1 after a layer 4 has been arranged over (a part of) the surface thereof. Layer 4 comprises pigment which can be caused to change colour in diverse ways and is arranged in a random manner. Layer 4 can extend over a part of the upper surface of product 3 or, as shown in fig. 1, a limited surface can be provided in a corner of the upper surface of product 3. Layer

4 can be applied with a brush or stamp or, in an automated and industrialized environment, with for instance an automatic applicator. Layer 4 comprises pigment which can be made to change colour with light of a determined wavelength or on the basis of a determined temperature. Pigment which changes colour on the basis of incidence of light with a determined wavelength will be referred to as photochromic pigment, while pigment which changes colour on the basis of temperature will be referred to as thermochromic pigment .

In fig. 1 the product 3 for printing is fed through and into printer 1 with a layer 4 oriented upward and on an outlet side

5 once again drops onto a conveyor belt 6. Colour change of selected parts of layer 4 is effected here in order to print a barcode 7 on product 3. The printed product 3 can then be discharged, again in the direction of arrow A, for instance to a packaging station, where the individual packages are for instance stacked in cardboard boxes. Fig. 2 shows a monochrome arrangement. A row 8 with individual LEDs 9 is here disposed in a line which covers at least the width b of layer 4. Row 8 with LEDs " 9 is monochromic in ' the " sense that each of the LEDs 9 is selected to emit light of a single wavelength when switched on. LEDs 9 are oriented toward layer 4. Layer 4 comprises photosensitive material or pigment, which is sensitive to light with the relevant wavelength of the LEDs when they are switched on.

When product 3 is therefore carried in the direction of arrow A under the series 8 of LEDs 9, which are in per se stationary arrangement, LEDs 9 can be activated selectively. The time for which the LEDs remain in operation determines the width of an element 10 of a barcode 7. LEDs 9 can also be controlled individually instead of together. More complex images, such as texts, photographs and so on, can thus be arranged in and on layer 4. LEDs 9 can also be adapted to emit light with an adjustable wavelength subject to a control voltage applied thereto. When pigment is used, which can be sensitive to different wavelengths in order to change into a different colour, pigments in spaces 11 between elements 10 of barcode 7 can for instance be activated to change into a contrast colour relative to the colour of elements 10. Colour change of the pigments is preferably irreversible, so that no fading of printed code 7 occurs in the case of later incidence of light, for instance of ambient light. Additionally or alternatively, use can also be made for this purpose of wavelengths outside the visible range, and preferably even outside the range of for instance the sun, in order to prevent fading from occurring when packaging 3, and more particularly barcode 7, is illuminated with sunlight.

In the embodiment of fig. 3 different series 8,12 and 13 are each provided with a number of LEDs 9. The LEDs 9 in each of the rows 8,12,13 are formed to emit light with a different wavelength. An alternative can thus be provided to a configuration in which individual LEDs 9 can be controlled for the purpose of emitting light of different wavelengths. Similarly, different kinds or types of pigment can be incorporated in layer 4, each of which change colour, preferably irreversibly, upon the incidence of light with a specific wavelength. In configuration 3, or if LEDs 9 in the configuration of fig. 2 can emit different wavelengths, complex images such as photographs can be formed in layer 4. In addition, it is likewise possible for pigments in layer 4 to be subjected to light with different wavelengths so that they change into a corresponding colour depending on an actually incident wavelength, while individual pigments can also be utilized for this purpose .

Fig, 4 shows a schematic view of thermochromic pigment particles 14 which are clustered round a central photothermal material particle 15. If light of a wavelength corresponding to the photothermal material 15 is incident, the photothermal material particle 15 undergoes an increase in temperature, with which colour change of thermochromic pigment particles 14 can be realized. For a monochrome image it suffices when pigment particles 14 can change into a single colour. Photothermal particle 15 can reach different temperature levels depending on the wavelength of light incident thereon. For this purpose controllable LEDs can be used, which generate a different wavelength subject to a control thereof. Individual LEDs can also be utilized, each of which are suitable for generating a single but mutually differing wavelength. Switching on selected LEDs can then be utilized to effect the generation of a desired wavelength in order to raise photothermal particle 15 to a desired temperature. It is also possible to use different photothermal particles, wherein each particle 15 then only undergoes a temperature increase when a specific associated wavelength is incident thereon. It has thus been found that many- different mutations are possible within the scope of the present invention, although the charm of the embodiment of fig. 4 lies in the use of a reactor in the form of photothermal particles 15. The reactor as it were activates the pigment particles 14 into changing colour in desired manner.

Fig. 5 shows an embodiment of an LED 9 with a glass fibre lens 16 thereon. Glass fibre lens 16 fits on and at least partially over the outer surface of LED 9. The light generated by LED 9 is focussed by glass fibre lens 16, or at least properly bundled to enable a higher resolution to be obtained. Fig. 6 shows an array of a number of LEDs 9, wherein LEDs 9 are suitable and adapted to generate a well-defined light beam 17. A well-defined light beam 17 is understood to mean that the light rays in beam 17 will continue to run parallel over a great distance. It is for this reason that in the embodiment shown in fig. 6 use is made of lenses 18 which are disposed in front of LEDs 9 in order to focus each of the beams 17 at its own focal point 19.

It has thus been found that many additional and alternative embodiments are possible other than those explicitly shown and described here, wherein it must be noted that all these alternative and an additional embodiments must be deemed as lying within the scope of protection of the present invention as defined in the appended claims, unless such additional and alternative embodiments depart from the letter or spirit of the definitions in these claims. LEDs can thus be utilized which can only emit a single wavelength or are associated with a control in order to emit different wavelengths, although as an alternative to this latter it is also possible to opt for an arrangement with different types of LED, which can each be individually controlled and are set into operation to generate different wavelengths at selected moments. Similar considerations apply to the pigments, which can be photochromic or thermochromic, although in the latter case only in combination with a material which is able to convert light with a selected or specific wavelength of the LEDs into a temperature increase, such as photothermal materials.