METHOD AND APPARATUS FOR APPLYING A LAYER HAVING A RELIEF ON A FLAT FACE OF A SUBSTRATE

Abstract

A method for applying a layer having a relief on a substrate includes, steps of securing the substrate, applying a layer of a curable liquid on the substrate, bringing a mould having a relief being the negative of the relief to be provided on the substrate, into contact with a part of the upper surface of the liquid layer, curing the liquid layer while the mould is in contact with the liquid and separating the mould from the substrate. Initially the mould is brought into contact with the liquid in a bent position while the substrate is kept flat and subsequently the mould is brought into contact over an increasing surface area keeping the mould in a bent position until the complete liquid layer is in contact with the mould.

Claims

1. A method for applying a layer having a relief on a flat surface of a substrate, the method comprising the following steps: securing the substrate with the surface onto which the relief is to be provided on top; applying a layer of a curable liquid on the upper surface of the substrate; bringing a mould having a relief being the negative of the relief to be provided on the substrate, into contact with at least a part of the upper surface of the liquid layer; curing the liquid layer while the mould is in contact with the curable liquid; and separating the mould from the substrate; wherein: initially the mould is brought into contact with the upper surface of the liquid layer in a bent position while the substrate is kept flat wherein the profile of the mould is a catenary; and subsequently the mould is brought into contact over an increasing surface area keeping the mould in a bent position until the complete liquid layer is in contact with the mould and at least the part of the mould in contact with the liquid layer is flat, keeping the substrate flat, wherein the profile of the mould not being in contact with the surface is kept as the same catenary over the whole process of bringing the mould into contact with the surface.

2. The method claimed in claim 1, wherein the mould is initially brought into contact with the liquid layer on the substrate over a line.

3. The method as claimed in claim 1, wherein the mould is initially brought into contact with the liquid layer on the substrate in a point.

4. The method as claimed in claim 1, wherein the initial contact location coincides with a side of the upper surface of the substrate and that subsequently the mould is brought into contact with the further upper surface area of the liquid layer in a single direction.

5. The method as claimed in claim 1, wherein the initial contact location is located on a distance from the sides of the upper surface of the substrate and that subsequently the mould is brought into contact with the further surface area of the liquid layer in two opposite directions.

6. The method as claimed in claim 1, wherein the liquid layer applied is substantially transparent for curing radiation when liquid and transparent for visible light when cured.

7. An apparatus for applying a layer having a relief on a flat surface of a substrate, the apparatus comprising: a frame; fixation means connected to the frame and adapted to fixate the substrate with the surface of the substrate onto which the relief is to be applied on top; a mould carrying a counter relief; and a radiation source adapted to emit radiation curing the liquid applied in a layer on the substrate; wherein the mould is flexible and that the flexible mould has a profile of a catenary before being brought in contact with the upper surface of the liquid layer and that the apparatus comprises a manipulator connected to the frame, the manipulator being adapted to initially bring the bent mould into contact with the upper surface of the liquid layer and to subsequently bring the mould into contact over an adjacent upper surface area of the liquid layer until the complete liquid layer is in contact with the mould wherein the mould is kept bent until the complete liquid layer is in contact with the mould and at least the part of the mould in contact with the liquid layer is flat, wherein the manipulator is adapted to guide the mould such that the profile of the mould not being in contact with the surface is kept as the same catenary over the whole process of bringing the mould into contact with the surface.

8. The apparatus as claimed in claim 7, wherein the mould is substantially transparent for radiation emitted by the radiation source.

9. The apparatus as claimed in claim 7, wherein the manipulator comprises two clamps, each being adapted to grip one of two opposite sides of the mould and each being connected with a yoke moveable in a vertical direction and comprising driving means for driving the vertical movement of the yoke.

10. The apparatus as claimed in claim 9, wherein the clamps are connected to the yoke rotatable over an axis extending between the centres of the clamps.

11. The apparatus as claimed in claim 9, wherein at least one of the clamps is mounted on the yoke rotatable around an axis extending parallel to the contact line and that the apparatus comprises rotation coupling means adapted to couple the rotation movement of the at least one clamp relative to the yoke to the vertical movement of the yoke.

12. The apparatus as claimed in claim 9, wherein at least one of the clamps is mounted on the yoke translatable in horizontal direction and that the apparatus comprises coupling means adapted to couple the horizontal movement of the at least one clamp relative to the yoke.

13. The apparatus as claimed in claim 10, wherein the clamps are arranged symmetrically relative to the centre of the fixation means.

14. The apparatus as claimed in claim 13, wherein the rotation coupling means comprise: an arm of which one end is rotatably connected to the frame and the other end is solidly connected to the clamp; and the yoke comprising a part slidably connected to the arm.

15. The apparatus as claimed in claim 7, wherein the fixation means for fixation of the substrate, comprise a block provided with switchable vacuum fixation means.

16. The apparatus as claimed in claim 15, wherein the block is moveable in substantial horizontal direction on a rail.

17. The apparatus as claimed in claim 7, wherein the radiation source is formed by a LED mounted on the yoke.

18. The apparatus as claimed in claim 7, wherein the apparatus comprises an applicator for application of the layer of liquid on the substrate.

19. The apparatus as claimed in claim 7, wherein the clamps each comprise a pair of jaws mutually moveable between an active and an inactive position and a spring adapted to urge the jaws towards one another in the active position, both jaws being adapted to pinch opposite strips of the mould.

20. The apparatus as claimed in claim 19, wherein at least one of the jaws on its pinching surface comprises a friction layer, such as a layer of sanding paper.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Subsequently the present invention will be elucidated with the help of the following drawings, wherein depict:

[0032] FIGS. 1A-1C: cross sectional diagrams depicting three phases in the process of applying the mould to the liquid layer according to a first embodiment;

[0033] FIGS. 2A-2C: diagrams depicting three phases in the process of applying the mould to the liquid layer according to a second, alternative embodiment;

[0034] FIG. 3: a diagrammatic perspective view of an apparatus adapted to perform a method according to the second embodiment;

[0035] FIGS. 4A-4E: diagrams showing different constructional possibilities of the second embodiment;

[0036] FIG. 5: a cross section view of a clamp to be used in the apparatus according to the invention; and

[0037] FIG. 6: a view similar to FIG. 3, depicting an alternative embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0038] The present invention relates to the application of a relief layer on a substrate such as a plastic card, like a credit card. The method according to the invention comprises—assuming the presence of a card with a layer of curable liquid—the application of a mound on the liquid, wherein the mould has a relief which is the negative of the relief to be applied to the layer. The invention provides the gradual bringing into contact of the mould with the layer avoiding the inclusion of air between the mould and the liquid. After the mould has been brought into contact with the liquid, the liquid is cured by radiation. The gradual contact between the mould and the liquid requires a flexible or bendable mould. This mould is initially brought into contact with the liquid on the substrate in a single line, and FIG. 1 depicts a first embodiment in cross section.

[0039] FIGS. 1A-C depict a card 1, acting as a substrate onto which a thin layer 2 of curable liquid has been provided. In FIG. 1A an edge 4 of a mould 3 is brought into contact with the liquid layer 2. This figure shows that the part of the mould 3 in contact with the liquid extends substantially parallel to the surface of the liquid as a preparation for the next step. In FIG. 1B roughly half of the surface of the liquid layer 2 is covered by the mould 3. Again the part 3a of the mould 3 in contact with the liquid layer 2 extends parallel to the surface of said layer. Due to the flexibility of the mould, the angle of the part 3b of the mould not in contact with the liquid 2 with the horizontal increases gradually from zero, as caused by the flexibility of the mould 3. In the final situation, depicted in FIG. 1C, the complete mould 3 extends parallel to the surface of the liquid layer 2. It is however also possible that only the part of the mould extending parallel to the substrate is flat and that the part of the mould not in contact with the substrate is curved, but the tangent to the curve at the border of the substrate is parallel to the substrate.

[0040] It can be seen in a comparison from FIG. 1A and 1B that the end of the mould being lowered does not only follow a vertical downward movement but that at the same time the end moves horizontally outwards. Thus, the profile of the mould can keep the same catenary and thus the conditions at the line of contact are the same during the whole process of lowering the mould.

[0041] In the embodiment discussed above, it is assumed that the substrate is substantially rectangular, and that the initial contact line between the edge 4 of the mould coincides with an edge of the liquid layer on the substrate. It is however also possible that the substrate 1 has another, non-rectangular shape and or that the initial contact line is formed by a single point on a corner of the substrate 1.

[0042] Another possibility is represented in FIG. 2. Herein the middle of the flexible mould 3 is initially brought into contact with a line 4 traversing the surface area of the liquid layer 2. This situation is represented in FIG. 2A. This embodiment is preferably although not necessarily symmetrical. The process of bringing the mould 3 into contact with the liquid layer 2 is substantially equivalent to that described with the help of the FIG. 1, although performed at both sides of the initial contact line. Again the parts 3b, 3b′ respectively not being in contact with the liquid layer extend under an increasing angle with the horizontal. Comparing FIGS. 2A and 2C one can see the curve that the extreme of the left part of the mould 3b describes. In FIG. 2A this extreme point of the part of the mould 3b is at point S. When lowering the mould onto the surface, this extreme point travels to point T as shown in FIG. 2B. By this guidance, the profile of the mould not being in contact with the surface keeps the form of a catenary like the catenary of the mould in FIG. 2A. Following through until the final position as shown in FIG. 2C, the extreme point is in position U. Here, the mould is parallel to the surface of the liquid layer 2. In FIG. 2C the whole curve from points S to U via T can be seen and this curve of the extreme point of the mould allows for the mould not being in contact with the surface to keep the profile of a catenary with the same parameters than the catenary of the free hanging mould. When the edges of the mould 3 are lowered, the surface area of the part 3a of the mould 3 being into contact with the liquid layer 2 increases, as is represented in FIG. 3b. This process is continued until the full surface area of the liquid layer 2 is covered by the mould 3, as is represented in FIG. 2C.

[0043] The above two figures only relate to the actual process. An apparatus is required to allow the process to be performed. FIG. 3 depicts an embodiment of such an apparatus. This apparatus comprises a base plate 10 onto which a column 11 is solidly connected. The base plate 10 and the column 11 together form a frame. On the column 11 a yoke 12 is slidably connected, to drive the yoke in the vertical direction drive means not depicted in the drawing, comprising and electric motor, and possibly a rack and pinion system may be provided. The yoke 12 comprises two clamps 13A, 13B connected symmetrically to the yoke 12. The clamps 13 are adapted to clamp the two opposite edges of the flexible mould 3. Under the position between the clamps a support 14 is provided for supporting and fixating the substrate to be provided of a relief layer. This support may be firmly connected to the base plate 10, but in the embodiment depicted, it is slidably connected to a rail 15, allowing the support to be transferred between the position under the mould 3 and a second position 16 in which the substrate may be provided with the liquid layer or in which the substrate may be provided complete with a liquid layer. Further, the substrate 2, complete with the cured layer 3 can be removed from said second position 16, to allow further processing. Finally a LED 17 functioning as a radiation source is provided on the yoke 12. The Led 17 may however also be located in another position adapted to let the radiation emitted by the LED to reach the liquid layer to be cured.

[0044] The connection between the clamps 13 and the yoke 12 can be embodied in different ways. The connection may be fixed, so that the clamps 13 are fixed to the yoke 12. This embodiment is only applicable if the mould 3 is substantially longer than the length of the substrate 2, to allow the flexibility of the mould 3 to cater for the variations in shape of the mould 3, such as the rate of sagging.

[0045] It is however preferred that the clamps 13 are connected slidably with a horizontal component to the yoke 12 to allow variation of the distance between the clamps 13. This variation caters for the decreasing rate of sagging of the mould 2 when the yoke 12 is lowered and the contact surface area between the mould 3 and the liquid layer 2 increases. The horizontal movement of the clamps 13 is preferably coupled to the vertical movement of the yoke 12 .

[0046] It is also preferred to connect the clamps 13 rotatably to the yoke 12, possibly in combination with the slidable connection between the clamps 13 and the yoke 12. This feature allows to cater for the decreasing angle at the clamps 13 between the mould 3 and the horizontal when the mould 12 covers an increasing area of the fluid layer 2. It is possible to have the clamps 13 freely rotatable, but it is preferred that the rotation of the clamps 13 is preferably coupled to the vertical movement of the yoke 12.

[0047] FIGS. 4A-4E show several different embodiments of the connection between the clamps and the yoke. It is noted that only a half of a yoke 12 is depicted in drawing. In the embodiment depicted in FIG. 4A a carriage 18 has been slidably mounted to the yoke 12 and the clamp 13 is rotatably connected to the carriage 18 by a shaft 19, thus allowing for both translation and rotation of the clamp 13. In the shaft 19 a through going slot 20 has been provided and a curved leaf spring 21 fixed to the column extends through the slot 20. The vertical movement of the yoke 12 relative to the column 11 results in a relative movement of the shaft 19 relative to the leaf spring 21 and the curved shape of the leaf spring 21 results in both rotation and translation of the shaft 19 and the clamp 13 connected to the shaft 19. Your attention is drawn to the fact that only one half of the apparatus is depicted in this figure and that the complete apparatus comprises a second mirrored half. Further it is possible that the complete apparatus comprises a single leaf spring 21 with double length extending to both sides of the column 11.

[0048] The embodiment depicted in FIG. 4B comprises a rack rail 23 extending over the base plate 10 and a gear 24 of which the teeth engage the rack rail 23. A first end of an arm 26 is rigidly connected with the gear 24, so that the rotation of the arm 26 causes rotation of the gear 24 and, as caused by the rack rail 23, translation of the gear 24 and of the first end of the arm 26. A slot 25 is located in the arm and a pin 25A is connected to the yoke 12 and extends through the slot 25. The clamp 13 is fixed to the second end of the arm 26. Vertical movement of the yoke 12 results in both a rotation and translation of the arm 26 relative to the base. This results in an involute movement of the clamp 13.

[0049] A simpler embodiment is depicted in FIG. 4C; one end of an arm 27 is rotatably connected to the base plate 10 or the column 11. A slot 28 is provided in the arm 27 and a pin 29 connected to the yoke 12 extends into the slot 28, allowing relative translation and rotation of the arm 27 relative to the yoke 12. The clamp 13 is fixed to the second end of the arm 27. Vertical movement of the yoke 12 results in both rotation of the arm 27, wherein the second end of the arm and hence the clamp 13 describes a rotation and a translation.

[0050] An embodiment allowing more freedom in design is depicted in FIG. 4D. This embodiment comprises a plate 30 extending in vertical direction perpendicular to the rail 15 and wherein two slots 31, 32 have been provided. The slots 31, 32 have a curved shape and they both extend with a horizontal and a vertical component. A carriage 33 is attached to the clamp 13 and two pins 34, 35 extend from the carriage 33 through the slots 31. The shape of the slots 31, 32 determine the path of the carriage 33 and of the clamp 13. One of the pins 34 extends also into a horizontal slot 36 provided in the yoke 12. Vertical movement of the yoke 12 results in vertical movement of the pin 34. As the pin 34 also extends through the slot 31 which has a horizontal component, the pin 34 also moves in horizontal direction, also moving the other pin 35, of which the movement is determined by the other slot 32. Now that the path of the movement of the both pins 34, 35 is determined, the path of the carriage 33 and the clamp 13 connected thereto is determined, both in translation and rotation.

[0051] Finally FIG. 4E shows an embodiment wherein the both the translation and the rotation of the clamp can be freely determined. Contrary to the embodiments discussed hitherto, each comprising one column 11 this embodiment comprises two columns 40, 41, one for each of the clamps 13 and only one of the columns 40 is depicted. The column 40 is mounted on a carriage 42, which is movable over a rail 44 mounted on the base plate. A controllable motor 46 is provided to drive the carriage over the rail 44. A yoke 48 is mounted movable in vertical direction over the column 40 and a controllable motor 50 is provided to drive the yoke 48 over the column 40. The clamp 13 is mounted rotatable relative to the yoke 48, and a controllable motor 52 is provided to drive the clamp 13. It will be clear that a similar, preferably mirrored structure is present to control the other clamp 13. By controlling the motors 46, 50 and 52, the position in two directions and the angle of the clamp is controllable.

[0052] An embodiment of the clamps is shown in FIG. 5. As stated before the mould 3 has to be flexible, and at the same time to have a certain thickness to contain a counter relief, making the clamping of such a mould 3 cumbersome. The embodiment of the clamp 13 depicted in FIG. 5 comprises a fixed part 60 and a moveable part 61 connected to the fixed part 60 by a shaft 62, allowing the moveable part 61 to move relative to the fixed part 60. On the moveable part 61 a pressing member 63 has been mounted, into which a cavity 64 has been provided. The cavity comprises a continuation 65 having a smaller diameter and extending through the moveable part 61. A screw 66 extends through the cavity 64 and its continuation 65 and it is screwed into the fixed part of the clamp 13. A helical spring 67 is pressed between the bottom of the cavity and the head of the screw 66, pressing the pressing member 63 and hence the moveable part 61 of the clamp to the fixed part thereof, thus providing a controllable pressing force for pressing the mould 3 between the two parts 60, 61 of the clamp. To increase the friction between the clamp 13 and the mould 2, a piece of sanding paper 68 is glued to the fixed part 60 of the clamp 13. However other friction materials may be used as well.

[0053] FIG. 6 depicts an apparatus similar to that depicted in FIG. 3, but wherein the connection between the clamps 13 to the yoke 12 has been modified to allow rotation or tilt of the clamps 13 around an axis extending in the longitudinal direction of the mould 3. As the mould 3 extends between the clamps, the axis extends between the centres of the clamps 13. To control the tilt, two electric motors 70 are connected to the ends of the yoke 12 and a shaft 71 extends from each of the motors 70 to the clamps 13. The clamps 13 are fixed to the shafts 71. The motors 70 are controlled such that the motors rotate simultaneously. Tilting of the clamps 13 makes the mould 3 tilt such that, when the assembly of the yoke 12, the motors 70, the clamps 13 and the mould 3 lowers, the mould 3 initially touches the substrate 1, or rather the liquid layer 2 on the substrate 1 in a point, rather than over a line, as is the case in the situation depicted in FIG. 3. When the assembly is lowered further, the initial tilt of the mould 3 is to be reversed, preferably simultaneously with the lowering of the mould 3, to allow the mould to extend over the full surface area of the liquid layer 2 of the substrate 1.

[0054] Especially, though not exclusively, it appears to be attractive to apply the kinematic variations mentioned before in this embodiment, for instance by providing a lift for the block carrying the substrate.

[0055] The above description elucidates some embodiments of the invention, but the invention is not restricted to these embodiments, of which different features may be combined; rather the scope of the invention is determined by the claims.

[0056] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.