METHOD FOR PROVIDING A RECESS PATTERN IN A FOIL

Abstract: The invention relates to a method for providing in a foil a number of recesses which are arranged relative to each other in a recess pattern extending along a first side of the foil, each recess extending from a first side in the direction of an opposite, second side of the foil, the method comprising at least the following steps: (a) applying a medium pattern onto the unprocessed foil, the medium comprising a medium solvable in solvent, the medium pattern corresponding to the recess pattern to be provided; (b) applying the masking layer onto the foil; (c) bringing the foil, with the masking layer applied thereto, into contact with a solvent, whereby the parts of the masking layer applied substantially on the medium pattern are removed from the foil upon dissolution of the medium pattern; and (d) at least partly exposing the foil with the pattern of openings to a foil etching environment, whereby the recess pattern is created, characterized in that in step (a) the application of a medium pattern is executed with the aid of a printing technique.

Description: Title: Method for providing a recess pattern in a foil. The invention relates to a method for providing a number of recesses in a foil which are arranged relative to each other in a recess pattern extending along a first side of the foil, each recess extending from a first side in the direction of a second side of the foil opposite the first side, the method comprising at least the following steps: (a) a medium pattern is applied to the unprocessed foil, the medium pattern comprising a medium soluble in a solvent, and the medium pattern corresponding to the recess pattern to be provided, (b) a masking layer is applied onto the foil, (c) the foil with the masking layer applied thereto is brought into contact with a solvent, whereby parts of the masking layer which have been substantially applied to the medium pattern are removed from the foil upon dissolution of the medium pattern so that a masking layer with a pattern of openings is obtained, and (d) the foil with the pattern of openings is at least partly exposed to a foil etching environment, whereby the recess pattern is created. Such a method is known per se. With such a method, in step (a) a photoresistive layer is applied onto the foil. This photoresistive layer is exposed to light, while parts of the layer are unexposed due to the presence of a mask screen provided with openings. With the aid of this screen, the exposure pattern is formed. The exposure pattern here corresponds with the pattern of openings. During exposure of the photoresistive layer, the mask screen is placed between a light source and the photoresistive layer. The exposed parts of the photoresistive layer cure. Subsequently, the unexposed parts of the photoresistive layer are washed away. The pattern of cured photoresistive material remaining on the film is the medium pattern corresponding to the recess pattern. After step (b), the application of the masking layer, has been executed, in step (c) parts of the masking layer present on the medium pattern are removed from the foil with the aid of a lift-off technique known per se. Here, the foil provided with a masking layer is brought into contact with a medium in which the cured, photoresistive layer dissolves. This has as a result that the masking layer is provided with a pattern of openings. In step (d), subsequently, with techniques known per se, the recess pattern is provided in the foil. A drawback of such a method is that for providing a new recess pattern, a new mask screen has to be provided with a new exposure pattern. Manufacturing a new screen with a new exposure pattern is costly. This limits the flexibility in recess patterns to be provided. The object of the invention is to provide a method for providing a recess pattern in a foil, which method is simple, faster and inexpensive compared with the current method. The above-mentioned object is achieved with the method according to the invention, which is characterized in that in step (a) the application of a medium pattern is executed with the aid of a printing technique. An advantage of the method according to the invention is that the medium pattern is applied to the foil in a simple, fast and low cost manner. Each new medium pattern to be applied can be applied to the foil in a direct manner with a known printing technique. Thus, the method for providing a recess pattern in a foil has become simpler, faster and inexpensive. The invention will now be further elucidated with reference to the drawing. In the drawing: Fig. 1 shows a finished foil provided with recesses; Fig. 2 shows step (a) of a possible method according to the invention; Fig. 3 shows a foil with a medium pattern provided with a masking layer; Fig. 4 schematically shows step (c) of a possible method according to the invention; Fig. 5 shows a cross section of the foil provided with a masking layer in which the pattern of openings has been provided. Fig. 1 shows a finished foil 1, provided with a recess pattern according to the method of the invention. The recess pattern comprises through-going recesses 2 extending from a first side 3 in a direction of the second side 4 of the foil 1, opposite the first side. The method according to the invention is directed to the provision of such a recess pattern in the foil. The foil can comprise a plastic, such as, for instance, polyimide (trade name kapton) or polyethylene terephthalate. A special embodiment of the method according to the invention will now be discussed on the basis of the following figures. Fig. 2 shows step (a) in which, with the aid of a printer 5, the foil 6 is provided with a medium pattern 7. In this case, the medium pattern 7 comprises an ink pattern or a toner pattern. The medium pattern corresponds to the recess pattern. The printer 5 is driven by a computer 8. In this case, the printer is an inkjet or laser printer. In step (b), with the aid of a technique known per se, the masking layer 9 is applied to the foil 1 which is provided with a medium pattern 7. The product of this step is shown in Fig. 3. Subsequently, the product of step (b) shown in Fig. 3 is brought into contact, in step (c), with a medium dissolving solvent 10, as shown in Fig. 4. In the embodiment of the method shown in Fig. 4, the foil 1 with medium pattern 7 and masking layer 9, is immersed in the medium dissolving solvent 10. Schematically, at position A, B and C, three different phases of the provision of the pattern of openings in the masking layer 9 are indicated. The positions of the recesses 2 to be provided in the foil 1 are indicated by means of a dotted line. At position A, the medium pattern 7, in this case an ink pattern, is visible. The medium dissolving solvent 10, in this case an ink dissolving medium, for instance acetone, penetrates into the masking layer 9, which is indicated with arrows. At position B, the ink dissolves and a part 11 of the masking layer 9 which was situated above the ink pattern 7 comes loose from the masking layer 9. This technique is also called the lift-off technique. At position C, the pattern of openings 12 is formed. Fig. 4 is schematic. The thickness of the masking layer is dependent on the material used and lies between 10 nanometers and 100 micrometers. The diameter of a cylinder shaped recess to be provided in the foil is in many cases between 1 and 100 micrometers. Consequently, the diameter of a part 11 which is removed from the masking layer is also between 1 and 100 micrometers. The product of step (c) is shown in Fig. 5, in which the foil 1 is provided with a mask 9 with a pattern of openings 12. Step (d), the provision of the recess pattern, is not shown. This step comprises, for instance, a wet-chemical etching process known per se. A plasma-etching technique, known per se, such as a plasma etching process in which use is made of oxygen, is also possible. Optionally, with the aid of another etching technique known per se, for instance a plasma etching technique in which use is made of oxygen or CF , the masking layer is removed from the foil 1 provided with the recess pattern. Such embodiments of the method can be used for the provision of a recess pattern comprising at least one recess extending from the first side over only a part of the thickness of the foil in the direction of the second side. Such embodiments of the method can also be used for the provision of a recess pattern comprising at least one recess extending from the first side over the entire thickness of the foil in the direction of the second side. Between the first side and the second side, the recesses can taper from the first side to the second side. With the aid of techniques known per se, the foil etching environment can have a regulating effect on the design of the recess. The design can be co-determined by a predetermined choice of the foil etching environment. The method can be used in a simple manner for the provision of a recess pattern comprising a plurality of recesses. The method is not limited to the example shown. The medium can also be toner. In that case, the medium dissolving solvent is a toner dissolving solvent. In an alternative embodiment of the method, the masking layer is evaporated onto the foil. The masking layer can comprise a metal. However, the masking layer can also comprise a plastic. In that case, the masking layer is preferably applied by means of spincoating or screen printing. The masking layer protects the foil from the foil etching environment and moreover has the property that the solvent can penetrate into the layer. Removing the masking layer can be supported by heating and/or generating an ultrasonic vibration in, for instance, a liquid in which the foil is immersed. Such variants are all understood to fall within the scope of the invention.

Claims: Claims 1. A method for providing in a foil a number of recesses which are arranged relative to one another in a recess pattern extending along a first side of the foil, each recess extending from a first side in the direction of a second side of the foil opposite the first side, the method comprising at least the following steps: (a) a medium pattern is applied to the unprocessed foil, the medium pattern comprising a medium soluble in a solvent and the medium pattern corresponding to the recess pattern to be provided, (b) a masking layer is applied onto the foil, (c) the foil, with the masking layer applied thereto, is brought into contact with a solvent, whereby parts of the masking layer which are applied substantially to the medium pattern are removed from the foil upon dissolution of the medium pattern, so that a masking layer with a pattern of openings is obtained, and (d) the foil with the pattern of openings is at least partly exposed to a foil etching environment, whereby the recess pattern is created, characterized in that in step (a) the application of a medium pattern is executed with the aid of a printing technique. 2. A method according to claim 1, characterized in that the solvent is a medium dissolving solvent. 3. A method according to claim 1 or 2, characterized in that the printing technique comprises the use of a printer. 4. A method according to any one of claims 1 - 3, characterized in that the medium pattern is at least partly applied to the foil with the aid of an inkjet printer. 5. A method according to claim 3 or 4, characterized in that the medium pattern is at least partly applied to the foil with the aid of a laser printer. 6. A method according to any one of the preceding claims, characterized in that the medium comprises ink. 7. A method according to any one of the preceding claims, characterized in that the medium comprises toner. 8. A method according to any one of the preceding claims, characterized in that the solvent comprises an ink dissolving medium. 9. A method according to any one of the preceding claims, characterized in that the solvent comprises a toner dissolving medium. 10. A method according to any one of the preceding claims, characterized in that the solvent comprises acetone. 11. A method according to any one of the preceding claims, characterized in that the solvent can penetrate into the masking layer. 12. A method according to any one of the preceding claims, characterized in that step (b) takes place by means of spincoating or screen printing. 13. A method according to any one of the preceding claims, characterized in that the masking layer comprises a polymer. 14. A method according to any one of claims 1 - 11, characterized in that step (b) takes place by means of evaporation. 15. A method according to any one of the preceding claims, characterized in that the masking layer comprises a metal. 16. A method according to any one of the preceding claims, characterized in that the masking layer comprises an inorganic material. 17. A method according to any one of the preceding claims, characterized in that the foil comprises a plastic. 18. A method according to claim 17, characterized in that the foil comprises polyimide (trade name kapton). 19. A method according to claim 17, characterized in that the foil comprises polyethylene terephthalate. 20. A method according to any one of the preceding claims, characterized in that the foil etching environment comprises a wet-chemical etching process. 21. A method according to any one of claims 1 - 19, characterized in that the foil etching environment comprises a plasma. 22. A method according to claim 21, characterized in that the plasma is formed at least from oxygen. 23. A method according to any one of the preceding claims, characterized in that the masking layer, after the provision of the recess pattern in the foil, is removed from the foil. 24. A method according to claim 23, wherein the masking layer, after the provision of the recess pattern in the foil, is removed from the foil with the aid of a wet-chemical etching process. • 25. A method according to claim 23, characterized in that the masking layer, after the provision of the recess pattern in the foil, is removed from the foil with the aid of a plasma etching process. 26. A method according to claim 25, characterized in that the plasma is formed at least from oxygen. 27. A method according to any one of the preceding claims, characterized in that the recess pattern comprises at least one recess extending from the first side through only a part of the thickness of the foil in the direction of the second side. 28. A method according to any one of the preceding claims, characterized in that the recess pattern comprises at least one recess extending from the first side over the entire thickness of the foil in the direction of the second side. 29. A method according to any one of the preceding claims, characterized in that the recess pattern comprises a plurality of recesses. 30. A method according to any one of the preceding claims, characterized in that the at least one recess tapers between the first and the second side in the direction from the first to the second side. 31. A method according to any one of the preceding claims, characterized in that a design of the at least one recess is co-determined by a predetermined choice of the foil etching environment.

Inventors: HADZIIOANNOU GEORGES, HEIER JAKOB, HADZIIOANNOU, GEORGES, HEIER, JAKOB
Applicants: HADZIIOANNOU GEORGES, HEIER JAKOB, ZETFOLIE B V, HADZIIOANNOU, GEORGES, HEIER, JAKOB, ZETFOLIE B.V.
Application year: 2001
Main classification: B41M3
IPC codes: B01F1, B41J2, B41M3, B41M5, H01L21