Apparatus and method for exposing a relief precursor

Abstract

An apparatus for exposing a relief precursor (P) comprising a substrate layer and at least one photosensitive layer is disclosed, the apparatus comprising: a first light source (1) configured to illuminate a first side of the relief precursor; a second light source (2) movable configured to illuminate a second side of the relief precursor opposite the first side; a movable shield (3) located between the first light source and the second light source (2) and configured to capture at least a portion of the light of the second light source that passes through the relief precursor (P); and a moving device configured to move the movable shield simultaneously with the second light source.

Description

Technical Field

[0001] The present invention relates to the exposure of relief precursors, particularly to printing plate precursors, and even more particularly to apparatus and methods for exposing printing plate precursors on the front and back sides. Background Technology

[0002] An embossed structure can be formed by transferring image information onto an imageable layer and removing a portion of the imageable layer. The resulting emboss can then be used to transfer information onto a substrate during a printing step. An example of an embossed precursor is a printing plate precursor. Flexible printing plate precursors capable of digital imaging are known and typically include at least a dimensionally stable support layer, a photosensitive layer, and a digital imaging layer. The digital imaging layer can be, for example, a laser-ablable layer. In the case of a conventional printing plate precursor, a mask attached to the photosensitive layer is used instead of the digital imaging layer.

[0003] To produce a printing plate from a printing plate embossing precursor, existing methods first involve writing a mask into a digitizable imaging layer based on image data to be printed. After writing the mask, the plate is exposed to radiation through the mask, causing the photosensitive layer to undergo polymerization, cross-linking, or reactions that alter the solubility or flowability of the photosensitive layer in areas not covered by the mask. After exposure, residues from the mask and the unexposed portions of the photosensitive layer are removed. This can be done in a cleaning apparatus using one or more liquids or by thermal development, where the unexposed material of the photosensitive layer is liquefied and removed by increasing the temperature.

[0004] Exposure apparatuses for printing plate precursors are known. An exposure apparatus may include a first light source for back exposure and a second light source for front exposure. Back exposure can be performed using a set of UV (ultraviolet) lamps. Back exposure produces a solid layer (substrate) on which an embossed structure is formed. Front exposure can also be performed using a set of UV lamps, or it can be performed using a movable UV light source (e.g., a movable laser or LED strip). Depending on the need, some exposure apparatuses perform only front exposure or only back exposure. In some cases, the exposure apparatus is capable of exposure from both sides, and embodiments of the invention relate to such cases.

[0005] US2016 / 0368260A1 discloses an autonomous apparatus for photopolymerization of a flexographic printing plate, the plate including a main surface and a base opposite the main surface. The apparatus includes an exposure chamber in which at least a first photopolymerization device is mounted on the base of the plate. The apparatus also includes a moving device configured to drag the plate along a feed direction. The first photopolymerization device includes a row of LEDs arranged in a direction substantially orthogonal to the feed direction.

[0006] US2018 / 0210345A1 discloses a method for exposing a photosensitive printing plate to a predetermined radiation density from the main side (top) and from the back side (bottom). The method includes performing a main exposure after a certain time delay following the back exposure. Summary of the Invention

[0007] The purpose of this invention is to provide an apparatus and method for exposing an embossed precursor comprising a substrate layer and at least one photosensitive layer, which uses a first light source to illuminate a first side of the embossed precursor and a second light source to illuminate a second side of the embossed precursor, while avoiding ghosting and limiting the heating of the first light source by the second light source.

[0008] According to a first aspect of the invention, the device includes a first light source, a movable second light source, a movable shield, and a moving device. The first light source is configured to illuminate a first side of the relief preform. The movable second light source is configured to illuminate a second side of the relief preform opposite to the first side. The movable shield is located between the first and second light sources and is configured to capture at least a portion of the light transmitted through the relief preform from the second light source. The moving device is configured to move the movable shield and the second light source simultaneously.

[0009] Therefore, according to embodiments of the invention, a shielding member is used, which travels along with the second light source to limit the amount of light from the second light source toward the first light source, and thus limit the amount of reflection from components of the first light source (e.g., a support on which an optical element is mounted) or from components near the first light source (e.g., a light-shielding member arranged above the first light source). This prevents or reduces the presence of ghosting caused by reflected light. Furthermore, it reduces heating of components of the first light source and components near the first light source. In particular, when the light-shielding member is present above the first light source, the heat generated by the first light source can be reduced, and its burn-out can be prevented.

[0010] Preferably, the first light source extends generally in a plane intended to be parallel to the orientation of the relief front; and the second light source is movable in a plane parallel to the plane of the first light source. The first light source may include a plurality of first light-emitting elements (e.g., lamps or LEDs), and the plane is therefore the plane in which the plurality of first light-emitting elements are located. Similarly, the second light source may include a plurality of second light-emitting elements, and the plane is therefore the plane in which the plurality of second light-emitting elements are located.

[0011] Preferably, the first light source is fixed. However, in other embodiments, such as when an LED array is used as the first light source, the first light source may also be movable.

[0012] Preferably, a first light source is configured to illuminate a first illumination area of ​​a plane, and a second light source is configured to illuminate a second illumination area of ​​the plane, wherein the plane is located between the shield and the second light source and corresponds to a plane on which the first side of the relief precursor is intended to be located, and wherein the illumination area of ​​the plane is defined by an area with an intensity greater than 10% of the maximum light intensity in the plane. When a supporting structure is present, this plane corresponds to the support surface of the supporting structure. Preferably, the second illumination area is at least two times smaller than the first illumination area, more preferably at least three times smaller, and most preferably at least five times smaller. In a typical embodiment, the first light source is used to illuminate approximately the entire first side of the relief precursor, while the second light source typically illuminates a smaller area of ​​the second side of the relief precursor with a higher light intensity.

[0013] As described above, the shield is configured to capture at least a portion of the electromagnetic radiation emitted by the second light source through the relief precursor. The term "capture" should be interpreted as including absorbing a portion of the radiation and / or guiding a portion of the radiation away from or near the first light source.

[0014] Preferably, the shielding is opaque to electromagnetic radiation emitted from the second light source.

[0015] Preferably, the surface of the shield facing the second light source is configured to absorb more than 80% of the electromagnetic radiation received on the surface, preferably more than 95%. This can be easily achieved by having a black surface.

[0016] Preferably, the shielding element is a plate-shaped component, but other shapes are also possible. For example, the shielding element can be a rod with a black outer surface or a sheet mounted in a frame.

[0017] According to one possible embodiment, the movable shield is mechanically coupled to the second light source, allowing them to move easily simultaneously. According to another embodiment, the shield and the second light source can move independently, and the moving device includes a moving mechanism for moving the second light source and a moving mechanism for moving the shield. In the latter case, the control device can control the two moving mechanisms to achieve synchronized movement of the second light source and the shield.

[0018] According to a preferred embodiment, the vertical projection of the shielding member onto a plane intended to correspond to the first side of the relief precursor during operation is 1% to 10% larger than the illumination area of ​​the second light source on the plane, preferably 5% to 10%, wherein the illumination area is defined by a region with an intensity higher than 10% of the maximum light intensity in the plane.

[0019] Preferably, the device further includes a support structure configured to support the relief front. The support structure may be located between the second light source and the shielding element. Preferably, the support structure is transparent to electromagnetic radiation emitted from the first light source. The support structure may be, for example, a transparent glass plate, a screen of transparent material, or transparent plastic.

[0020] Preferably, the distance between the load-bearing structure and the movable shield is less than 50 mm, more preferably less than 20 mm, and even more preferably less than 10 mm. This increases the shielding capability of the shield while keeping the size of the shield limited.

[0021] Preferably, the supporting structure is a plate, and the thickness of the supporting plate is between 2 mm and 20 mm. Preferably, the distance between the second light source and the supporting structure is between 10 mm and 100 mm.

[0022] Preferably, the second light source includes a support (e.g., a printed circuit board (PCB)) on which multiple light-emitting elements (e.g., an LED array) are mounted. Preferably, the support has a width of less than 500 mm (e.g., between 100 mm and 400 mm).

[0023] Optionally, multiple second light sources and multiple shielding elements may be provided. For example, two second light sources and two associated shielding elements may be provided, each second light source being designed to move along the relief precursor and partially illuminate the relief precursor (e.g., half of the relief precursor).

[0024] Optionally, the device further includes a cooling device configured to cool the movable shield. For example, the movable shield can be cooled using a gas or fluid. In an exemplary embodiment, the movable shield may be provided with a cooling channel through which a cooling medium is delivered. Alternatively, a cold airflow may be generated around the shield.

[0025] According to an exemplary embodiment, the first light source is selected from the group consisting of multiple LEDs, fluorescent lamp groups, flash lamps, lamp tube groups, LCD screens, light projection systems (with movable reflectors), sunlight collection systems, and combinations thereof. Preferably, the first light source is in the form of an LED array comprising multiple LEDs.

[0026] Preferably, the device further includes a control device for controlling the first light source based on the position of the movable shield.

[0027] According to an exemplary embodiment, where the first light source comprises a set of lamps or an LED array, the control device can be configured to power the first light source during a first time period and to power and move the second light source during a subsequent time period. In other words, the first and second light sources operate one after the other. Thus, back-side exposure will not be obstructed by the light emitted by the shielding or the second light source. UV tubes have the advantages that virtually the entire first side (i.e., the entire back side of the embossed precursor) can be exposed simultaneously, commonly referred to as full-sheet exposure. The intensity output of the UV tube is fairly uniform along its axis, and through the dense stacking of the tubes, the uniformity is sufficient for producing printing plates.

[0028] According to another exemplary embodiment, the first light source includes an LED array, and a control device can be configured to simultaneously power the first and second light sources. The first light source is controlled such that a portion of the light-emitting elements of the LED array facing the shield are turned off, while the other light-emitting elements of the LED array are turned on, wherein said portion varies with movement of the shield. In this way, the amount of light emitted by the first light source toward the shield can be kept very low, thereby avoiding or reducing undesirable reflections on the side of the shield facing the first light source. This will also limit any heating of the shield due to light from the first light source. LEDs are advantageous for the first light source because they have a narrow emission spectrum and low energy consumption.

[0029] Preferably, the first light source includes a support member having a light-absorbing surface (e.g., a black surface) facing the second light source. For example, when the first light source is an LED array, the LEDs can be mounted on a PCB, and the PCB can have a black outer surface. In this way, any light reflected or transmitted in the direction of the first light source can be at least partially absorbed by the light-absorbing surface of the support member.

[0030] According to an exemplary embodiment, the first light source is an LED array comprising multiple subsets of one or more LEDs, each subset being individually controllable. Preferably, the first light source is configured to simultaneously illuminate a predetermined surface area. The surface area can be adjusted for different relief precursor sizes. The control unit can be configured to individually control the multiple subsets, ensuring that the illumination intensity variation in the predetermined surface area is within a predetermined range. By using an LED array with individually controllable subsets of LEDs, the illumination intensity of the subsets can be adjusted to achieve approximately uniform illumination of the surface area to be illuminated. This allows for the achievement of an underlayer with a substantially constant thickness. Furthermore, when an LED fails, the subsets can be controlled by the control unit configured to individually control the subsets to compensate for the failed LED, ensuring that uniformity is not significantly affected, and eliminating the need to replace the failed LED. Further details regarding these exemplary embodiments can be found in the applicant's patent application NL2023537, which is incorporated herein by reference.

[0031] Preferably, the first light source is configured to be movable in a direction perpendicular to a plane perpendicular to the relief precursor (typically perpendicular to the transparent support plate used to support the relief precursor). Note that the LED array can be movable and / or the support structure can be movable. Using such an adjustment device, the uniformity of illumination in the desired plane can be further improved. For example, the distance between the support structure and the LED array can be adjusted according to the thickness of the relief precursor.

[0032] Preferably, the first light source is configured to deliver an intensity lower than that of the second light source. For example, the first light source may be configured to deliver an intensity equal to or less than 100 mW / cm². 2 The intensity of the second light source can be configured to deliver more than 100 mW / cm². 2 Preferably above 350mW / cm 2 The intensity.

[0033] In an exemplary embodiment, the second light source is selected from the group consisting of LED arrays, fluorescent lamp groups, flash lamps, linearly arranged lamp tube groups, (scanning) lasers, LCD screens, light projection systems (with movable mirrors), and combinations thereof. Preferably, the second light source is an LED array comprising multiple subsets of one or more LEDs, each subset being individually controllable. Each LED of the second light source can be controlled to illuminate an area with a substantially uniform intensity. Preferably, the intensity delivered by the second light source is higher than 100 mW / cm². 2 More preferably above 350mW / cm 2 .

[0034] Preferably, the first light source and / or the second light source emit radiation with wavelengths in the range of 200 nm to 2000 nm, more preferably from 250 nm to 500 nm, even more preferably from 300 nm to 450 nm, and most preferably from 270 nm to 410 nm (e.g., mainly at 365 nm).

[0035] According to another embodiment, the device includes a light-shielding element located between the first light source and the movable shield. The light-shielding element may be required when using fluorescent lamps, and it needs to be pre-adjusted before exposure begins to generate stable light output. The light-shielding element is made of a material that is opaque to the electromagnetic radiation emitted by the first light source. The light-shielding element can be a rigid flat sheet, a combination of several flat sheets, a foldable structure, a curtain, or a flexible material that can be wound onto a reel.

[0036] According to an exemplary embodiment, the moving device for the second light source and / or the movable shield is one or more linear motors, one or more chains, cables or belts, one or more lead screws, creep drivers, one or more gears, timing pulleys, belts or combinations thereof.

[0037] Optionally, one or more sensors may be provided, such as light sensors, magnetic sensors, proximity sensors, temperature sensors, overheat sensors, flow sensors, intensity sensors, pressure sensors, thickness sensors, etc. Then, the movement of the second light source and / or the shield, as well as the driving of the first light source and / or the second light source, can be further controlled based on the sensor data measured by the one or more sensors.

[0038] Optionally, the device may include an additional light source, an additional cooling device, a heating or cooling device, a conveying device, a feeding device, an unloading device, a positioning device, an identification device, and combinations thereof. Optionally, the device may also include a controller to control various components of the device and / or a housing having one or more openings (for loading and unloading the relief precursor). Optionally, the device may include one or more additional processing units selected from the group consisting of loading and unloading units, imaging units, liquid developing units, thermal developing units, drying units, post-processing units, pre-processing units, storage units, and combinations thereof.

[0039] According to another aspect of the invention, a method for exposing an embossed precursor is provided, preferably using the apparatus according to any of the above embodiments. The method includes:

[0040] a. Place the relief sculpture between the first light source and the second light source;

[0041] b. Expose the relief preform using the first light source;

[0042] c. Move the second light source while simultaneously exposing the relief foreground with the second light source;

[0043] d. In the space between the first light source and the relief precursor, absorb at least a portion of the light emitted by the second light source and transmitted through the relief precursor; and

[0044] e. Remove the embossing precursor and perform optional additional steps.

[0045] Preferably, absorption is performed by moving a shield in the space between the first light source and the relief precursor during exposure by the second light source. This shield may have any of the features described above regarding the device.

[0046] Steps b) and c) can be performed sequentially, simultaneously, or in reverse order. When performed simultaneously, step b) can be completed while step c) is still in progress, and vice versa. For example, for a thin plate, step b) can be completed before step c), and for a thick plate, step c) can be completed before step b). For example, as described above, when the first light source comprises a set of lamps, the first and second light sources can be powered continuously. In another example, when the first light source comprises multiple LEDs, the first and second light sources can be powered simultaneously.

[0047] Further, step b) may include multiple exposure cycles and / or step c) may include multiple exposure and movement cycles, wherein the exposure cycles of steps b) and c) may be performed simultaneously or sequentially in any order, wherein optionally, the exposure cycle of step b) may be performed between two exposure cycles of step c) and / or the exposure cycle of step c) may be performed between two exposure cycles of step b). For example, step c) may include performing one or more first cycles and one or more second cycles, in which the second light source moves back and forth and is controlled to emit light with a first intensity, and in the second cycle, the second light source moves back and forth and is controlled to emit light with a second different intensity (preferably a second lower intensity). More generally, the timing and intensity of the exposure and movement in steps b) and c) can be controlled in any possible manner and can be adjusted, for example, according to the type of relief precursor. For example, when steps b) and c) are performed simultaneously, the timing can be adjusted such that when the first light source exposes at a high power level, the second light source moves back and forth multiple times, such that the various parts of the relief precursor receive the same dose at the end of the exposure by the first light source. Steps b) and c) can also be performed according to two or more cycles, where these cycles can be periodic or non-periodic. For example, after a first exposure with a first light source and a first exposure with a second light source, a second or subsequent exposure with the first light source and a second or subsequent exposure with the second light source can be performed. The second or subsequent exposure with the first light source can be performed after or during the backward movement of the second light source.

[0048] Step c) can be performed by moving the second light source once or cyclically moving the second light source several times on the relief front. Further, in step c), the second light source can move forward or backward or both forward and backward on the relief front, and the second light source can be controlled to emit light during forward movement, backward movement, or both movements.

[0049] In step c), the moving speed of the second light source can be the same or different for forward and backward movement. Further, in step d), the forward movement speed can be faster than the backward movement speed, and vice versa. Optionally, in step c), the movement of the second light source can be performed periodically or with increasing or decreasing forward and / or backward movement speeds.

[0050] According to a further improved embodiment, in steps b) and / or c), the intensity distribution of the light output of the first light source and / or the second light source can be changed during movement. For example, in step c), the intensity of the light output can be different for forward and backward movement and / or in different cycles. Moreover, in steps b) and / or c), the intensity of the light output can be changed over time. Further, when the first light source includes an LED array, in step b), the intensity of the light output of a subset of the LED array can be changed.

[0051] In an exemplary embodiment, steps b) and c) are performed simultaneously, and in step b), the intensity distribution of the light output from the first light source is related to the movement of the second light source in step c). For example, when the first light source comprises an LED array, the first and second light sources can be powered simultaneously, wherein the first light source is controlled such that a portion of the light-emitting elements of the LED array facing the shield are turned off, while the other light-emitting elements of the LED array are turned on, wherein said portion changes as the shield moves. Therefore, the intensity distribution of the first light source will change as the shield moves. In this way, the amount of light emitted by the first light source toward the shield can be kept very low, thereby avoiding or reducing undesirable reflections on the side of the shield facing the first light source. This will also limit any heating of the shield due to light from the first light source.

[0052] Preferably, the embossed precursor is a precursor for an element selected from the group consisting of flexographic printing plates, embossed printing plates, type, gravure, (flexible) printed circuit boards, electronic components, microfluidic components, microreactors, phoretic cells, photonic crystals and optical components, and Fresnel lenses.

[0053] Optional additional steps may be selected from the group of uncured material removal, cleaning, drying, heating, post-exposure, grinding, cutting, and combinations thereof. Attached Figure Description

[0054] The accompanying drawings are provided to illustrate currently 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 from the following detailed description, and the invention will be better understood, when read in conjunction with the accompanying drawings, in which:

[0055] Figures 1 to 3 A schematic cross-sectional view of an exemplary embodiment of an apparatus for exposing a relief precursor; and

[0056] Figure 4 This is a perspective view of another exemplary embodiment of a device for exposing an embossed precursor. Detailed Implementation

[0057] Figure 1 An apparatus for exposing an embossed precursor P is schematically illustrated, the precursor P comprising a substrate layer and at least one photosensitive layer. The apparatus includes a first light source 1, a movable second light source 2, a support structure 4, and a movable shield 3. The first light source 1 is configured to illuminate a first side of the embossed precursor P, here the lower side, also referred to as the back side. The movable second light source 2 is configured to illuminate a second side of the embossed precursor P opposite the first side. The second side is typically the top side of the embossed precursor P. The movable shield 3 is located between the first light source and the second light source 2, and more particularly between the first light source 1 and the support structure 4.

[0058] The shield 3 is configured to capture at least a portion of the light transmitted through the relief precursor P from the second light source 2, see arrow L. The shield 3 is opaque to electromagnetic radiation emitted from the second light source. The shield has a surface 32, here the upper surface, facing the second light source 2 and configured to absorb more than 80%, preferably more than 95%, of the light received on said surface. The upper surface 32 may be a black surface. In the illustrated embodiment, the shield 3 is a plate with a flat upper surface 32, but those skilled in the art will understand that the shield can have any suitable shape and can be, for example, 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 device may also include a cooling device (not shown) configured to cool the movable shield 3.

[0059] The first light source 1 extends approximately in a plane parallel to the relief front P. The first light source 1 is fixed. The second light source 2 can move back and forth in a plane parallel to the plane of the first light source 1, as indicated by arrow A1. Furthermore, the shielding member 3 can move back and forth in a plane parallel to the plane of the first light source 1, as indicated by arrow A2.

[0060] Preferably, the first light source 1 is configured as the first irradiation area of ​​the irradiation plane (in Figure 1The second light source is configured to illuminate a second illumination area (in the plane) having a width w1', and the second light source is configured to illuminate the second illumination area (in the plane) of the plane. Figure 1 The plane has a width w2'), wherein the plane is located between the shield and the second light source and corresponds to the plane on which the first side of the relief precursor is intended to be located. The irradiation area of ​​the plane is defined by an area with an intensity higher than 10% of the maximum light intensity in the plane. When a support structure 4 is present, this plane corresponds to the support surface of the support structure 4. Preferably, the second irradiation area (in Figure 1 The width w2' of the middle is greater than that of the first irradiation area (in Figure 1 The width w1' is at least twice as small, more preferably at least three times smaller, and most preferably at least five times smaller. In a typical embodiment, the first light source 1 is used to illuminate almost the entire first side (i.e., the entire back side) of the relief precursor, while the second light source 2 typically illuminates a smaller area of ​​the second side (i.e., the upper side) of the relief precursor with a higher light intensity.

[0061] The vertical projection of the shield 3 onto the plane defined above is greater than the second illumination area of ​​the second light source 2 on the plane (in Figure 1 The width w3 of the shielding element 3 is 1% to 10% larger than the width w2' of the second irradiation area, preferably 5% to 10%. For example, the width w3 of the shielding element 3 can be at least 5 mm larger than the width w2' of the second irradiation area. Preferably, the widths w2, w2', and w3 are between 100 mm and 600 mm, for example, between 200 mm and 400 mm. Preferably, the width w1' is between 1500 mm and 3000 mm, for example, between 1800 mm and 2500 mm.

[0062] A support structure 4 (e.g., a glass plate) is configured to support the relief precursor and is located between the second light source 2 and the shield 3. The support structure 4 can be transparent to electromagnetic radiation emitted from the first light source 1. Preferably, the distance d between the support structure 4 and the movable shield is less than 50 mm, more preferably less than 20 mm, and more preferably less than 10 mm. Preferably, the support structure is a plate with a thickness tc between 0.5 mm and 20 mm (preferably between 1 mm and 15 mm). Preferably, the distance d2 between the second light source 2 and the support structure 4 is between 10 mm and 100 mm, for example, between 20 mm and 50 mm. Preferably, the distance d1 between the first light source 1 and the supporting surface of the support structure 4 is between 10 mm and 150 mm, for example, 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 mm and 7 mm).

[0063] The first light source 1 can be selected from the group consisting of: multiple LEDs, fluorescent lamp groups, flash lamps, lamp tube groups, LCD screens, light projection systems (with movable reflectors), sunlight collection systems, and combinations thereof. The second light source 2 can be selected from the group consisting of: LED arrays, fluorescent lamp groups, flash lamps, lamp tube groups arranged in a linear manner, (scanning) lasers, LCD screens, light projection systems (with movable reflectors), and combinations thereof.

[0064] exist Figure 2 In this embodiment, the first light source 1 includes a UV lamp assembly. The driving of the first light source 1 and the second light source 2 is performed by a control device 5. The control device 5 can be configured to power the first light source 1 during a first time period, and to power the second light source 2 and move the second light source 2 during a subsequent time period after the first time period when the first light source is turned off. The power supply of the first light source 1 and the second light source 2 can also be performed according to two or more cycles, wherein these cycles can 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 can be performed. The second or subsequent exposure with the first light source 1 can be performed after or during the backward movement of the second light source 2.

[0065] Figure 2 An example is shown: a moving device M1 configured to move the movable shield 3, and a moving device M2 configured to move the second light source 2. A control device 5 controls the moving devices M1 and M2 so that the second light source 2 and the shield 3 move synchronously and the shield 3 performs optimal shielding. A shutter 6, which can be opened or closed, can be used to shield the UV lamp 1 during pre-conditioning.

[0066] exist Figure 3 In one embodiment, the first light source 1 includes an LED array, and the control device 5 is configured to simultaneously power the first light source 1 and the second light source 2. The first light source is controlled such that a portion 1a of the light-emitting elements 1a of the LED array facing the shield is turned off, while the other light-emitting elements 1b of the LED array are turned on. The portion 1a changes as the shield 3 moves. The first light source 1 includes a support 10 (typically a PCB) having a light-absorbing surface 12 (e.g., a black surface) facing the second light source 2.

[0067] Figure 3 An example of a moving device M is shown, which is configured to move the movable shield 3 and the second light source 2 simultaneously. A control device 5 can control the moving device M so that the second light source 2 and the shield 3 move together, and can control the driving of the first light source so that the light distribution of the first light source 1 is adjusted according to the position of the shield 3.

[0068] Exposure of the embossed precursor with the first light source 1 can be performed before exposure with the second light source 2, and vice versa. For example, for a thin embossed precursor, the back exposure with the first light source 1 can be performed before the main exposure with the second light source, and for a thick precursor, the main exposure with the second light source 2 can be performed before the back exposure with the first light source 1. Further, the exposure with the first light source 1 and the second light source 2 can be performed in multiple cycles. For example, the main exposure may include one or more first fast cycles and one or more second slow cycles, in which the second light source 2 moves back and forth and is controlled to emit light with a first intensity, and in the second slow cycles, the second light source 2 moves back and forth and is controlled to emit light with a second different intensity (preferably a second lower intensity). The high-intensity first fast cycle can be used to remove oxygen from the system, while the second slow cycle can slow down polymerization. Simultaneously, the back exposure with the first light source can be performed. More generally, the timing and intensity of the exposure and movement steps with the first and second light sources can be controlled in any possible manner and can be adjusted, for example, according to the type of embossed precursor. For example, the timing can be adjusted so that when the first light source is exposed at a high power level, the second light source moves back and forth multiple times, so that each part of the relief precursor receives the same dose when the exposure by the first light source ends.

[0069] Figure 4 Detailed examples of use and Figures 1 to 3 The exemplary embodiments of the same main components as those in the previous embodiments are described again. The device includes a housing 100 having a lower housing portion 130 including a first light source and an upper housing portion 110 optionally including an additional light source. An embossing precursor P can be manually or automatically brought onto the support structure 4 such that the embossing precursor is positioned between the first light source in the lower housing portion 130 and the upper housing portion 110. The device includes a second light source 2 comprising a movable LED strip. The movable LED strip structure 2 can move from right to left and rearward.

[0070] In embodiments not illustrated, a post-processing unit may be provided to perform post-processing on the relief precursor (e.g., cleaning, drying, post-exposure, heating, cooling, material removal, etc.). Further, in embodiments not illustrated, a pre-processing unit may be provided to perform pre-processing on the relief precursor, said pre-processing being selected from the group consisting of: cutting, ablation, exposure to electromagnetic radiation, and combinations thereof.

[0071] The embossed precursor typically comprises a support layer and at least one photosensitive layer. The support layer can be a flexible metal, a natural or synthetic polymer, paper, or a combination thereof. Preferably, the support layer is a flexible metal or polymer film or sheet. In the case of a flexible metal, the support layer can comprise a thin film, a sieve structure, a mesh structure, a woven or nonwoven structure, or a combination thereof. Steel, copper, nickel, or aluminum plates are preferred and can be from about 50 μm to 1000 μm thick. In the case of a polymer film, the film is dimensionally stable but flexible and can be made, for example, of polyalkylene, polyester, polyethylene terephthalate, polybutylene terephthalate, polyamide and polycarbonate, polymers reinforced with woven, nonwoven, or layered fibers (e.g., glass fiber, carbon fiber, polymer fiber), or combinations thereof. Preferably, polyethylene and polyester foil are used, and their thickness can be in the range of about 100 μm to 300 μm, preferably in the range of 100 μm to 200 μm.

[0072] In addition to the photosensitive layer and the support layer, the embossing precursor may also include one or more additional layers. For example, these additional layers may be any of the following: a layer that can be directly engraved (e.g., by laser), a solvent- or water-developable layer, a thermally developable layer, a mask layer, a cover layer, a barrier layer, etc. One or more adhesive layers may be positioned between these different layers to ensure proper adhesion between them.

[0073] Although the principles of the invention have been explained above with reference to specific embodiments, it should be understood that this description is by way of example only and not as a limitation on the scope of protection defined by the appended claims.

Claims

1. An apparatus for exposing a relief precursor (P), the relief precursor (P) comprising a substrate layer and at least one photosensitive layer, the apparatus comprising: - a first light source (1) configured to illuminate a first side of the relief precursor; - a second light source (2) movable configured to illuminate a second side of the relief precursor opposite the first side; - a movable shield (3) located between the first light source and the second light source (2) and configured to capture at least a portion of the light of the second light source that transmits through the relief precursor (P); and - a moving device configured to move the movable shield simultaneously with the second light source. The first light source extends substantially in a plane intended to be 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.

2. The apparatus of claim 1, wherein, The first light source is fixed.

3. The apparatus of any of the preceding claims, 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 the plane, wherein the plane is located between the shield and the second light source and corresponds to a plane in which the first side of the relief precursor is intended to be located, wherein the second illumination area is at least twice smaller than the first illumination area.

4. The apparatus of claim 1 or 2, wherein, The shield is opaque to electromagnetic radiation emitted from the second light source.

5. The apparatus of claim 1 or 2, wherein, A surface of the shield facing the second light source is configured to absorb more than 80% of the electromagnetic radiation received on the surface.

6. The apparatus of claim 1 or 2, wherein, The movable shield is mechanically coupled to the second light source or is independently movable.

7. The apparatus of claim 1 or 2, wherein, A vertical projection of the shield on a plane located between the shield and the second light source and corresponding to a plane in which the first side of the relief precursor is intended to be located is 1% to 10% larger than an illumination area of the second light source on the plane, wherein the illumination area is defined by the areas in which the light intensity is more than 10% of the maximum of the light intensity in the area.

8. The apparatus of claim 1 or 2, wherein, 9. The apparatus according to claim 1 or 2, further comprising a carrying structure (4) configured for supporting the relief precursor, the carrying structure being located between the second light source and the shield. The carrying structure is transparent to electromagnetic radiation emitted from the first light source.

10. The apparatus of claim 9, wherein, A distance (d) between the carrying structure and the movable shield is less than 50 mm.

11. The apparatus of claim 9 or 10, wherein, 12. The apparatus according to claim 1 or 2, further comprising a cooling device configured to cool the movable shield. The first light source is selected from the group comprising a plurality of LEDs, a fluorescent lamp, a flash lamp, a set of light tubes, an LCD screen, a light projection system, a solar light collection system, and combinations thereof.

13. The apparatus of claim 1 or 2, wherein, 14. The apparatus according to claim 1 or 2, further comprising a control device for controlling the first light source as a function of the position of the movable shield. ​ 15. The apparatus of claim 14, wherein, The first light source comprises a set of light tubes, and wherein the control device is configured for powering the first light source during a first time period and for powering the second light source and moving the second light source during a subsequent time period.

16. The apparatus of claim 14, wherein, The first light source comprises an array of LEDs, wherein the control device is configured to associate an intensity profile of light output by the array of LEDs with the movement of the second light source relative to the relief precursor.

17. The apparatus of claim 16, wherein, The control device is configured for powering the first light source and the second light source simultaneously, wherein the first light source is controlled such that a portion of light emitting elements of the array of LEDs facing the shield is switched off, while other light emitting elements of the array of LEDs are switched on, wherein the portion varies as the shield moves.

18. The apparatus of claim 1 or 2, further comprising a controller for controlling the moving device, the first light source and the second light source, the controller being configured to perform at least one of the following steps: adjusting the exposure time of the first light source and the second light source such that when the first light source exposes at a first power level, the second light source moves back and forth a number of times such that individual portions of the relief precursor receive the same dose at the end of exposure by the first light source; adjusting the exposure time of the first light source and the second light source such that after a first exposure with the first light source and a first exposure with the second light source, a second or subsequent exposure is performed with the first light source and a second or subsequent exposure is performed with the second light source.

19. The apparatus of claim 1 or 2, wherein, The first light source comprises a support having a light absorbing surface facing the second light source.

20. The apparatus of claim 19, wherein, The first light source comprises an array of LEDs, the support comprising a printed circuit board having a black outer surface.

21. The apparatus of claim 1 or 2, wherein, The first light source is configured to deliver a lower intensity than the intensity of the second light source.

22. The apparatus of claim 1 or 2, wherein, The second light source is selected from the group comprising an array of LEDs, a set of fluorescent tubes, a flash light, a set of light tubes arranged in a linear fashion, a laser, an LCD screen, a light projection system, and combinations thereof.

23. The apparatus of claim 1 or 2, comprising a light shield (6) located between the first light source and the movable shield.

24. A method for exposing a relief precursor, the method comprising: a. placing a relief precursor between a first light source and a second light source; b. exposing the relief precursor with the first light source; c. moving the second light source while 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 space between the first light source and the relief precursor while exposing the relief precursor with the first light source; and e. removing the relief precursor, and performing optional additional steps. The absorbing is performed by moving a shield in the space between the first light source and the relief precursor during exposure by the second light source.

25. The method of claim 24, wherein, ​ 26. The method of claim 24 or 25, wherein, Said steps b) and c) are executed sequentially in any order or simultaneously, wherein said step b) can be completed before, after or simultaneously with step c).

27. The method of claim 24 or 25, wherein, Said step b) comprises a plurality of exposure cycles and / or wherein Said step c) comprises a plurality of exposure and movement cycles, wherein said exposure cycles of steps b) and c) can be executed simultaneously or sequentially in any order.

28. The method of claim 24 or 25, wherein, Said step c) is executed by moving said second light source once over said relief precursor or moving said second light source several times in cycles.

29. The method of claim 24 or 25, wherein, In said step c) said second light source is moved forward or backward or both over said relief precursor and wherein said second light source is emitting light during said forward movement, said backward movement or during both movements.

30. The method of claim 29, wherein, In said step c) the intensity of the light output of said second light source is varied during said movement.

31. The method of claim 29, wherein, Said steps b) and c) are executed simultaneously and in said step b) the intensity profile of the light output of said first light source is related to said movement of said second light source in said step c).

32. The method of claim 24 or 25, wherein, Said relief precursor is a precursor for an element selected from the group comprising flexographic printing plates, relief printing plates, letterpress plates, intaglio, printed circuit boards, electronic components, microfluidic components, microreactors, electrophoresis cells, photonic crystals and optical elements, Fresnel lenses.

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