APPARATUS AND METHOD FOR EXPOSURE OF RELIEF PRECURSORS

Abstract

An apparatus for exposure of a relief precursor includes a substrate layer and at least one photosensitive layer. The apparatus includes a first light source configured to illuminate a first side of the relief precursor, a movable second light source configured to illuminate a second side of the relief precursor opposite the first side, a movable shield located between the first light source and the second light source and configured to capture at least a portion of the light of the second light source transmitted through the relief precursor, and a moving means configured to move the movable shield simultaneously with the second light source.

Claims

1. An apparatus for exposure of a relief precursor which comprises a substrate layer and at least one photosensitive layer, said apparatus comprising: a first light source comprising a light emitting diode (LED) array configured to illuminate a first side of the relief precursor, a second light source configured to illuminate a second side of the relief precursor opposite the first side, wherein the first light source comprises a support having a light absorbing surface facing the second light source, such that light reflected or transmitted in the direction of the first light source is absorbed at least partially by the light absorbing surface of the support.

2. The apparatus of claim 1, wherein the light absorbing surface is a black surface.

3. The apparatus of claim 1, wherein the support is a printed circuit board (PCB).

4. The apparatus of claim 1, further comprising a moving means configured to move the second light source relative to the relief precursor.

5. The apparatus of claim 4, further comprising a movable shield located between the first light source and the second light source and configured to capture at least a portion of the light of the second light source transmitted through the relief precursor.

6. The apparatus of claim 1, wherein the first light source substantially extends in a plane intended for being parallel to the relief precursor; and wherein the second light source is movable in a plane parallel to the plane of the first light source.

7. The apparatus of claim 5, wherein the first light source is configured to illuminate a first illumination area of a plane and the second light source is configured to illuminate a second illumination area of said plane, wherein said plane is located between the shield and the second light source and corresponds with a plane in which the first side of the relief precursor is intended to be located, wherein the second illumination area is at least two times, more preferably at least three times, and most preferably at least five times smaller than the first illumination area.

8. The apparatus of claim 5, wherein the shield is non-transparent to electromagnetic radiation emitted from the second light source, wherein preferably a surface of the shield which is facing the second light source is configured to absorb more than 80% of electromagnetic radiation that is received on said surface, preferably more than 95%.

9. The apparatus of claim 5, wherein a perpendicular projection of the shield on a plane located between the shield and the second light source and corresponding with a plane in which the first side of the relief precursor is intended to be located, is 1 to 10% larger, preferably 5 to 10% larger than an illumination area of the second light source on said plane, wherein the illumination area is defined by the area where the intensity is higher than 10% of a maximum value of the light intensity in said area.

10. The apparatus of claim 1, further comprising a carrying structure configured for supporting the relief precursor, said carrying structure being located between the second light source and the shield, wherein preferably the carrying structure is transparent to electromagnetic radiation emitted from the first light source, wherein preferably a distance (d) between the carrying structure and the movable shield is less than 50 mm, preferably less than 20 mm, more preferably less than 10 mm.

11. The apparatus of claim 1, further comprising a control means for controlling the first light source in function of a location of the second light source.

12. The apparatus of claim 5, further comprising a control means for controlling the first light source in function of a location of the second light source, wherein the control means is configured for simultaneously powering the first and the second light source, wherein the first light source is controlled such that a group of light emitting elements of the LED array facing the shield are switched off whilst the other light emitting elements of the LED array are switched on, and wherein said group is changing as the shield is moved.

13. A method for exposing a relief precursor, preferably using an apparatus according to any preceding claim, said method comprising: a. placing a relief precursor between a first light source comprising a LED array and a second light source; b. exposing the relief precursor with the first light source; c. exposing the relief precursor with the second light source; d. absorbing at least a portion of the light emitted by the second light source and transmitted through the relief precursor, in a direction of the first light source, in a light absorbing surface of a support of the first light source, said support facing the second light source; and e. removing the relief precursor and performing optional further steps.

14. The method of claim 13, further comprising moving the second light source whilst exposing the relief precursor with the second light source.

15. The method of claim 13, further comprising absorbing at least a portion of the light emitted by the second light source and transmitted through the relief precursor by moving a shield in a space between the first light source and the relief precursor during the exposing by the second light source.

16. The method of claim 13, wherein steps b and c are performed simultaneously, and in step b) the intensity distribution of the light output by the first light source is correlated to the movement of the second light source in step c).

17. The method of claim 13, wherein steps b and c are performed simultaneously, and the timing is adjusted such that whilst the first light source exposes at a high power level, the second light source is moved multiple times back and forth so that each portion of the relief precursor has received the same dose at the end of the exposure by the first light source.

18. An apparatus for exposure of a relief precursor which comprises a substrate layer and at least one photosensitive layer, said apparatus comprising: a first light source comprising a LED array configured to illuminate a first side of the relief precursor, wherein the first light source substantially extends in a plane intended for being parallel to the relief precursor, and a second light source configured to illuminate a second side of the relief precursor opposite the first side, wherein the first light source comprises a printed circuit board having a black light absorbing surface facing the second light source, such that light reflected or transmitted in the direction of the first light source is absorbed at least partially by the black light absorbing surface of the printed circuit board.

19. The apparatus of claim 18, wherein the second light source is movable in a plane parallel to the plane of the first light source.

20. The apparatus of claim 19, further comprising a control means for controlling the first light source in function of a location of the second light source.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0055] The accompanying drawings are used to illustrate presently preferred non limiting exemplary embodiments of the apparatus and method of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0056] FIGS. 1-3 are schematic sectional views of exemplary embodiments of an apparatus for exposure of a relief precursor; and

[0057] FIG. 4 is a perspective view of another exemplary embodiment of an apparatus for exposure of a relief precursor.

DETAILED DESCRIPTION OF EMBODIMENTS

[0058] FIG. 1 schematically illustrates an apparatus for exposure of a relief precursor P which comprises a substrate layer and at least one photosensitive layer. The apparatus comprises a first light source 1, a movable second light source 2, a carrying structure 4, and a movable shield 3. The first light source 1 is configured to illuminate a first side of the relief precursor P, here a lower side also called back side. The movable second light source 2 is configured to illuminate a second side of the relief precursor P, opposite the first side. The second side is typically a top side of the relief precursor P. The movable shield 3 is located between the first light source and the second light source 2, and more in particular between the first light source 1 and the carrying structure 4.

[0059] The shield 3 is configured to capture at least a portion of the light of the second light source 2 transmitted through the relief precursor P, see arrow L. The shield 3 is non-transparent to electromagnetic radiation emitted from the second light source. The shield has a surface 32, here un upper surface, which is facing the second light source 2 and which is configured to absorb more than 80% of light that is received on said surface, preferably more than 95%. This upper surface 32 may be a black surface. In the illustrate embodiment, the shield 3 is a plate with a flat upper surface 32, but the skilled person understands that the shield may have any suitable shape, and may be e.g. a rod with a black outer surface. The shield 3 may be mechanically coupled to the second light source 2 or may be independently movable. Optionally, the apparatus may further comprising a cooling means (not shown) configured to cool the movable shield 3.

[0060] The first light source 1 substantially extends in a plane parallel to the relief precursor P. The first light source 1 is stationary. The second light source 2 is movable back and forward as indicated with arrow A1, in a plane parallel to the plane of the first light source 1. Also the shield 3 is movable back and forward as indicated with arrow A2, in a plane parallel to the plane of the first light source 1.

[0061] Preferably, the first light source 1 is configured to illuminate a first illumination area of a plane (having a width w1 in FIG. 1) and the second light source is configured to illuminate a second illumination area of said plane (having a width w2 in FIG. 1), wherein said plane is located between the shield and the second light source and corresponds with a plane in which the first side of the relief precursor is intended to be located. The term illumination area of a plane is defined by the area where the intensity is higher than 10% of a maximum value of the light intensity in said plane. When a carrying structure 4 is present, the plane corresponds with a support surface of the carrying structure 4. Preferably, the second illumination area (having a width w2 in FIG. 1) is at least two times, more preferably at least three times, and most preferably at least five times smaller than the first illumination area (having a width w1 in FIG. 1). In typical embodiments, the first light source 1 is used to illuminate substantially the entire first side (i.e. the entire backside) of the relief precursor, whilst the second light source 2 illuminates a smaller area of the second side (i.e. the upper side) of the relief precursor, typically with a higher light intensity.

[0062] A perpendicular projection of the shield 3 on the plane as defined above is 1 to 10% larger, preferably 5 to 10% larger than the second illumination area of the second light source 2 on said plane (having a width w2 in FIG. 1). For example, the width w3 of the shield 3 may be at least 5 mm more than the width w2 of the second illumination area. Preferably, the width w2, w2 and w3 are between 100 mm and 600 mm, e.g. between 200 mm and 400 mm. Preferably, the width w1 is between 1500 mm and 3000 mm, e.g. between 1800 mm and 2500 mm.

[0063] The carrying structure 4, e.g. a glass plate, is configured for supporting the relief precursor, and is located between the second light source 2 and the shield 3. The carrying structure 4 may be transparent to electromagnetic radiation emitted from the first light source 1. Preferably, a distance d between the carrying structure 4 and the movable shield is less than 50 mm, preferably less than 20 mm, more preferably less than 10 mm. Preferably, the carrying structure is a plate with a thickness tc between 0.5 and 20 mm (preferably between 1 and 15 mm). Preferably, the distance d2 between the second light source 2 and the carrying structure 4 is between 10 mm and 100 mm, e.g. between 20 mm and 50 mm. Preferably, the distance dl between the first light source 1 and a support surface of the carrying structure 4 is between 10 mm and 150 mm, e.g. between 20 mm and 100 mm. Preferably, the thickness tp of the relief precursor P is between 0.5 mm and 10 mm (preferably between 1 and 7 mm).

[0064] The first light source 1 may be selected from the group comprising: a plurality of LEDs, a set of fluorescent lamps, a flash lamp, a set of light tubes, an LCD screen, a light projection system (with movable mirrors), a sun light collection system, and combinations thereof. The second light source 2 may be selected from the group comprising an LED array, a set of fluorescent lamps, a flash lamp, a set of light tubes arranged in a linear fashion, a (scanning) laser, an LCD screen, a light projection system (with movable mirrors), and combinations thereof.

[0065] In the embodiment of FIG. 2, the first light source 1 comprises a set of UV light tubes. The driving of the first and second light source 1, 2 is done by a control means 5. The control means 5 may be configured for powering the first light source 1 during a first time period and for powering and moving the second light source 2 during a subsequent time period after said first period of time, when the first light source is off. It is also possible to perform the powering of the first and second light source 1, 2 according to two or more cycles, wherein these cycles may be periodic or non periodic. For example after a first exposure with the first light source 1 and a first exposure with the second light source 2, a second or subsequent exposure with the first light source 1 and a second or subsequent exposure with the second light source 2 may be performed. The second or subsequent exposure with the first light source 1 may be performed after or during the backward movement of the second light source 2.

[0066] FIG. 2 illustrates a moving means M1 configured to move the movable shield 3, and a moving means M2 configured to move the second light source 2. The control means 5 may control the moving means M1, M2 such that the second light source 2 and the shield 3 move synchronously, and the shield 3 performs an optimal shielding function. A shutter 6 which may be open or closed may be used to shield the UV light tubes 1 during preconditioning.

[0067] In the embodiment of FIG. 3, the first light source 1 comprises a LED array and the control means 5 is configured for simultaneously powering the first and the second light source 1, 2, wherein the first light source is controlled such that a group of light emitting elements 1a of the LED array facing the shield are switched off whilst the other light emitting elements 1b of the LED array are switched on, wherein said group 1a is changing as the shield 3 is moved. The first light source 1 comprises a support 10, typically a PCB, having a light absorbing surface 12, e.g. a black surface, facing the second light source 2.

[0068] FIG. 3 illustrates a moving means M configured to move the movable shield 3 simultaneously with the second light source 2. The control means 5 may control the moving means M such that the second light source 2 and the shield 3 move together, and may control the driving of the first light source such that the light distribution of the first light source 1 is adjusted in function of the position of the shield 3.

[0069] The exposing the relief precursor with the first light source 1 may be finished before the exposing of the relief precursor with the second light source 2, or vice versa. For example, for thin relief precursors the back-exposure by the first light source 1 may be finished before the main exposure by the second light source, and for thick plates the main exposure by the second light source 2 may be finished before the back-exposure by the first light source 1. Further, the exposure by the first and second light sources 1, 2 may be done in multiple cycles. For example, the main exposure may comprise one or more first fast cycles where the second light source 2 is moved back and forth and is controlled to emit light with a first intensity and one or more second slow cycles where the second light source 2 is moved back and forth and is controlled to emit light with a second different intensity, preferably a second lower intensity. The first fast cycles with a high intensity may be used to remove oxygen from the system, whilst the second slower cycles may slow down the polymerization. Simultaneously, the back-exposure by the first light source may be done. More generally, the timing and intensity of the exposing and moving steps by the first and second light source may be controlled in any possible manner, and may be adjusted e.g. in function of the type of relief precursor. For example, it is possible to adjust the timing such that whilst the first light source exposes at a high power level, the second light source is moved multiple times back and forth, so that each portion of the relief precursor has received the same dose at the end of the exposure by the first light source.

[0070] FIG. 4 illustrate in detail an exemplary embodiment which uses the same main components as the embodiment of FIGS. 1-3, and those components will not be described again. The apparatus comprises a housing 100 with a lower housing portion 130 comprising the first light source and an upper housing portion 110 optionally comprising an additional light source. The relief precursor P may be manually or automatically brought onto a carrying structure 4, such that the relief precursor is located between the first light source in the lower housing portion 130 and the upper housing portion 110. The apparatus comprises a second light source 2 comprising a moveable LED bar. The movable LED bar structure 2 can be moved from right to left and back.

[0071] In non-illustrated embodiments, a post-treatment unit may be provided to perform a post-treatment on the relief precursor, e.g. washing, drying, post-exposure, heating, cooling, removing of material, etc. Further, in non-illustrated embodiments, a pre-treatment unit may be provided to perform a pre-treatment on the relief precursor, said pre-treatment being selected from the group comprising: cutting, ablation, exposure to electromagnetic radiation, and combinations thereof.

[0072] A relief precursor generally comprises a support layer and at least one photosensitive layer. The support layer may be a flexible metal, a natural or artificial polymer, paper or combinations thereof. Preferably the support layer is a flexible metal or polymer film or sheet. In case of a flexible metal, the support layer could comprise a thin film, a sieve like structure, a mesh like structure, a woven or non-woven structure or a combination thereof. Steel, copper, nickel or aluminium sheets are preferred and may be about 50 to 1000 m thick. In case of a polymer film, the film is dimensionally stable but bendable and may be made for example from polyalkylenes, polyesters, polyethylene terephthalate, polybutylene terephthalate, polyamides und polycarbonates, polymers reinforced with woven, nonwoven or layered fibres (e.g. glass fibres, Carbon fibres, polymer fibres) or combinations thereof. Preferably polyethylene and polyester foils are used and their thickness may be in the range of about 100 to 300 m, preferably in the range of 100 to 200 m.

[0073] In addition to the photosensitive layer and the support layer, the relief precursor may comprise one or more further additional layers. For example, the further additional layer may be any one of the following: a direct engravable layer (e.g. by laser), a solvent or water developable layer, a thermally developable layer, a mask layer, a cover layer, a barrier layer, etc. Between the different layers described above one or more adhesion layers may be located which ensure proper adhesion of the different layers.

[0074] Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.