Patent Application
20240264531
This application claims priority to pending Netherlands patent application serial number NL2034081, filed Feb. 3, 2023, the entirety of which application is incorporated by reference herein.
The field of the invention relates to exposure units for exposing a relief plate precursor, and in particular to exposure units comprising UV light sources such as UV light tubes. The invention relates in particular to the field of exposing flexographic printing plate precursors.
Flexographic printing or letterpress printing are techniques which are commonly used for high volume printing. Flexographic or letterpress printing plate are relief plates with printing elements, typically called reliefs or dots, protruding above non-printing elements in order to generate an image on a recording medium such as paper, cardboard, films, foils, laminates, etc. Also, cylindrically shaped printing plates or sleeves may be used.
Various methods exist for making flexographic or letterpress printing plate precursors. According to conventional methods flexographic or letterpress printing plate precursors are made from multilayer substrates comprising a backing layer and one or more photocurable layers (also called photosensitive layers). Those photocurable layers are cured by exposure to electromagnetic radiation through a mask layer containing the image information or by direct and selective exposure to electromagnetic radiation e.g. by scanning of the plate to transfer the image information in order to obtain a relief plate. After curing the uncured parts are removed either by using liquids that are able to dissolve or disperse the uncured material or by thermal treatment in which the uncured material is liquefied and removed. Removal of the liquefied material may be achieved by adhesion or adsorption to a developer material or by application beams of solids, liquids or gases which may be heated. An alternative is to remove the material in the non-printing area by ablation using high power laser beams.
The relief precursor may be a precursor for an element selected from the group comprising: a flexographic printing plate, a relief printing plate, a letter press plate, an intaglio plate, a (flexible) printed circuit board, an electronic element, a microfluidic element, a micro reactor, a phoretic cell, a photonic crystal and an optical element, such as a Fresnel lens.
An exposure device for exposing a relief plate precursor comprises a source for electromagnetic radiation which delivers light with the required wavelength to the front or back side of a relief precursor. Preferably the wavelengths are in the UV-Vis region of the electromagnetic spectrum. The wavelength of the electromagnetic waves may be in the range from 200 to 800 nm, preferably in the range of 250 to 500 nm, more preferably in the range of 300 to 450 nm, most preferably in the range of 350 to 400 nm. The intensity of the electromagnetic radiation may range from 0.1 mW/cm2 to 1000 mW/cm2, preferably from 1 mW/cm2 to 1000 mW/cm2, more preferably from 10 mW/cm2 to 1000 mW/cm2, for example between 400 and 500 mW/cm2 for front exposure and between 20 and 50 mW/m2 for back exposure. As light sources metal halide lamps, fluorescent lamps, LEDs or flash lamps or combinations of several of these light sources may be used. Preferably, LEDs or fluorescent lamps are installed. The light sources can be connected to the control system which steers the exposure time, the wavelength in case light sources with different emission spectra are installed, the light intensity or combinations thereof. The light source and the plate precursor may be stationary during exposure or may be in relative motion to each other during exposure. Typically, the exposure is performed through a mask which may be an integral part of the plate precursor or a separate mask layer or an electronically switchable mask (e.g. a display like device with switchable transparent and non-transparent regions or pixels). Scanning beams without the use of a mask may be used as well. The exposure compartment may be used under ambient conditions or in specific atmosphere e.g. with reduced oxygen content.
Some exposure units comprise a support structure with a support surface for supporting a relief plate precursor, and a plurality of UV light sources configured to emit UV light to a side of the relief plate precursor. In classical exposure units UV light tubes are used. Different exposure results may be obtained on different parts of a relief plate precursor. This problem is for instance present during back exposure when the floor thickness of the same relief plate precursor is not uniform. This problem may also occur during front exposure with some parts of the precursor being sufficiently exposed and some other parts under-exposed. The printing results using the relief plate precursor thus obtained may accordingly be less optimal.
An object of the present disclosure is to provide an exposure unit which exposes a relief plate precursor in an improved way.
According to a first aspect there is provided an exposure unit for exposing a relief plate precursor. The exposure unit comprises a support structure, a plurality of UV light sources and a light adjustment structure, such as a light adjustment structure. The support structure has a support surface configured for supporting a relief plate precursor. The plurality of UV light sources is arranged next to each other and configured to emit UV light to a side of the relief plate precursor. Said plurality of UV light sources covers a light source area parallel to the support surface. The light adjustment structure is configured to block and/or reflect a portion of the light emitted by the plurality of UV light sources so as to render a light intensity measured in the support surface more uniform as compared to a situation without the light adjustment structure. The light adjustment structure is arranged at least partially between the light source area and the support surface.
Thanks to the blocking and/or reflecting a portion of light emitted by the UV light sources, the light intensity at the support surface becomes more uniform. A more uniform light intensity distribution can be obtained over a larger area on the support surface, especially close to the edges of the light source area. The relief plate precursor can therefore be exposed in a more uniform manner. For instance, for back exposure the floor thickness may become more uniform in at least a part of the exposed relief precursor. In addition or alternatively, for front exposure the printing features may be exposed in a more uniform manner, obtaining a more uniform relief plate precursor. This improves the quality of the relief plate after a subsequent development step. Also, the light adjustment structure being interposed between the light source area and the support surface is able to influence more directly and more effectively the light intensity on the support surface from the UV light sources.
The exposure unit may have one or more of the following features, taking individually or according to any technically possible combinations.
Preferably, the UV light sources are elongated UV light tubes. An elongated UV light tube offers a large illumination area than some other types of UV light sources. Also, elongated UV light tubes are relatively inexpensive and easy to install. Using elongated UV light tubes therefore simplifies the operation and the maintenance of the exposure unit.
The plurality of UV light sources may be arranged to emit light in a main area and in at least one edge area adjacent the main area, said main area and said at least one edge area having together the same surface area as the light source area, and the light adjustment structure may be configured to block more light per surface area in the main area than in the at least one edge area. The plurality of UV light sources according to some embodiments emits light of a higher light intensity in the main area compared to the light intensity in the at least one edge area, because the light sources at the edges do not have neighbours on both sides but only have a neighbour on one side. By having a light adjustment structure blocking more light in the main area than in the edge area, the support surface may receive a more uniform light intensity.
Preferably, the light adjustment structure is configured to block at least 5%, preferably at least 10% more light per surface area in the main area than in the at least one edge area. According to the experiments carried out by the inventors blocking at least 5%, preferably at least 10% more light per surface area in the main area than in the at least one edge area can lead to a substantially uniform light intensity on an area of the support surface corresponding to a plate area of the support surface.
The at least one edge area may be a peripheral area which covers at least 10% of the surface area of the light source area. In this manner, at the support surface, less light intensity from a non-negligible part of the UV light sources is reduced compared to the light intensity from other parts of the UV light source. In this way a relief plate precursor covering a part of the edge area may be able to receive a light intensity which is approximately the same as the main area. The area of the light sources which can be used to homogeneously expose a relief plate precursor is therefore increased.
The UV light tubes may be arranged parallel to each other and extend in a tube direction, and the light adjustment structure may be configured to block more light in the main area than in two cross-tube edge areas extending in a cross-tube direction perpendicular to the tube direction, on either part of the main area. In this application ‘block’ can mean absorb at least a part of light and/or reflect at least a part of light which is emitted from the UV light sources away from the support surface. One of the main causes of light intensity variation within the plurality of UV light source is that the light intensity from a light tube varies in the tube direction. The middle of the light tube often emits a higher light intensity while the edge areas of the light tube emit a lower light intensity. By blocking more light in the main area than in the edge areas of the light tube, the support surface can have a more uniform light intensity in the tube direction.
The light adjustment structure may be configured to block more light in the main area than in two tube-length edge areas extending in the tube direction, on either part of the main area. Another cause of light intensity variation within the plurality of UV light sources is that the support surface receives a higher light intensity from a light tube in the main area compared to from a light tube farther from the main area in the cross-tube direction. By blocking more light in the main area than in two tube-length edge areas, the support surface can have a more uniform light intensity in the cross-tube direction as well. This further increases the part of the light sources that can be used to expose uniformly a relief plate precursor.
Preferably, the light adjustment structure comprises a grid structure extending between the plurality of UV light sources and the support surface. The grid structure typically comprises regular intervals of the parts which block light and the parts which let light through. With the grid structure, the proportion of light blocked compared to light let through can be controlled more easily and accurately.
The light adjustment structure may be a self-supporting mechanical structure.
The light adjustment structure may be made of a metal or plastic material.
The light adjustment structure may comprise a sheet metal in which apertures have been cut out. Producing such a sheet metal is simple, as it only requires apertures to be cut out without complicated manufacturing steps. The light intensity on the support surface can also be controlled more accurately as the size of the apertures can be calculated accurately before the sheet production.
The light adjustment structure may comprise a plurality of bridge structures, each bridge structure thereof being configured to be arranged over one or more UV light sources of said plurality of UV light sources, each bridge structure comprising apertures able to let through at least part of the light emitted by the one or more UV light sources and bridge sections able to block at least part of the light emitted by the one or more light source. The bridge structures for instance have a shape which is adapted to the shape of a light tube, so as to be able to partially surround a light tube. The bridge structure can thus be placed easily over the light sources. The bridge structures may be able to stand on their own without additional fixing element. In addition, the size of the apertures can be determined before producing the bridge structures, so how much light is let through by the bridge structure can be controlled in an accurate way.
The UV light tubes may be arranged parallel to each other and extend in a tube direction, and the apertures may have at least two different dimensions in the tube direction and/or the bridge sections between the apertures may have at least two different dimensions measured in the tube direction. In this way, different amounts of light in the tube direction can be blocked by the bridge structure. Where a greater amount of light needs to be blocked a smaller aperture and/or a wider bridge section (measured in the tube direction) is designed. Where a lower amount of light needs to be blocked a bigger aperture and/or a narrower bridge section (measured in the tube direction) is designed. With the help of the apertures of different dimensions and/or of the bridge sections of different dimensions, the UV light tubes which emit different light intensities in the tube direction can generate more uniform light intensity at the support surface.
The bridge structure may comprise a central portion and at least one peripherical portion as seen in the tube direction, the apertures of the central portion having a dimension in the tube direction smaller than the apertures of the at least one peripherical portion and/or the bridge sections between apertures of the central portion having a dimension in the tube direction bigger than the bridge sections between apertures of the at least one peripherical portion. In this manner, the central portion of the bridge structure blocks a greater amount of light than the peripherical portion. This is particularly suitable for the UV light tubes which emit a higher light intensity in the middle and a lower light intensity in the edge portions. In this way the part of the support surface corresponding to the central portion of the bridge structure and the part of the support surface corresponding to the peripheral portion of the bridge structure can have a closer light intensity.
The central portion may be configured to block at least 5%, preferably at least 10% more light per surface area than the at least one peripheral portion.
The plurality of bridge structures may comprise at least two different bridge structures configured to block a different amount of light. The support surface may receive two different light intensities from two UV light sources. With two different bridge structures these two different light sources can create a more uniform light intensity at the support surface.
The plurality of UV light sources may comprise at least one first edge light source, a plurality of central light sources and at least one second edge light source, said plurality of central light sources being arranged between the at least one first edge light source and the at least one second edge light source. At least one bridge structure placed over the at least one first edge light source and at least one bridge structure placed over the at least one second edge light source may be different from a plurality of bridge structures placed over the plurality of central light sources. The central light sources may generate a higher light intensity at the support surface than the first edge light source and/or the second edge light source. With at least one bridge structure placed over the first edge light source and at least one bridge structure placed over the second edge light source different from the bridge structures placed over the central light sources, the light intensity at the level of the support surface generated by the first and second edge light sources on one hand and the central light sources on the other can be adjusted differently to give a more uniform light intensity at the support surface.
The light adjustment structure may comprise a coating or a sticker or a foil arranged on the UV light sources. For example, a pattern of stripes may be arranged on a UV light tube. For example, the pattern of stripes may be a coating or paint which is printed on the UV tubes. Alternatively, thin metal foils or sheets may be arranged on the UV tubes, e.g., cylindrically shaped metal elements could be clipped or snapped on the tubes according to a determine pattern, wherein the pattern is such that more light is blocked in a main area as compared to at least one edge area.
The light adjustment structure may comprise at least one reflector configured to reflect at least a part of light emitted by the plurality of UV light sources towards the support surface. The reflector redirects a part of light from the UV light sources towards a plate area the support surface which would otherwise travel to locations outside the plate area. This reflection compensates the part of the support surface which would otherwise receive a lower light intensity so as to reach a more uniform light intensity at a plate area of the support surface.
The UV light tubes may be arranged parallel to each other and extend in a tube direction, and the at least one reflector may comprise at least one cross-tube reflector extending in a cross-tube direction perpendicular to the tube direction. More light from the middle of the UV light tubes reaches the support surface compared to light from the edge portions of the UV light tubes. By reflecting light from an edge portion of the light tubes towards a plate area of the support surface, compared with the case without any reflector, more light from the edge portion can reach the support surface, thereby rendering a more uniform light intensity at a plate area of the support surface.
The at least one reflector may comprise at least one tube-length reflector extending in the tube direction and arranged parallel to the UV light tubes. The tube-length reflector can reflect light travelling at least partially in the cross-tube direction towards the support surface.
The exposure unit may comprise a movable shutter or moveable curtain between the plurality of UV light sources and the support surface and the at least one cross-tube reflector may be movable, e.g. rotatable, such that it can be moved away when the moveable shutter or curtain is moved. The moveable shutter is for example configured to block UV light from reaching the support surface when the UV light sources have not reached their optimal work condition, for example during its warming up period when the light intensity increases gradually but has not reached the full output intensity yet. By having a moveable cross-tube reflector any potential interference between the moveable shutter and the cross-tube reflector can be avoided. For example, when the cross-tube reflector is in the way of the moveable shutter when the latter moves, the cross-tube reflector can be moved out of the path of the moveable shutter.
The at least one reflector may comprise at least one peripheral reflector and at least one internal reflector, said at least one peripheral reflector surrounding said at least one internal reflector, wherein an internal reflector reflects less light than a peripheral reflector. According to some embodiments less light from the periphery of the plurality of UV light sources reaches the support surface compared to light from a central portion of the plurality of UV light sources. With an internal reflector reflecting less light than a peripheral reflector, more light from the periphery of the UV light sources can be reflected to reach the support surface. This makes up the previously lower light intensity at an edge portion of the support surface and gives the support surface a more uniform light intensity. This is achieved for example by using an internal reflector smaller than the peripherical reflector.
Preferably, a variation of the light intensity in a plate area of the support surface is at most 10%, preferably at most 5%, said plate area corresponding with the light source area without a peripheral frame area extending at less than 15 cm from the periphery of the light source area.
Preferably, the exposure unit is configured for performing back exposure of the relief plate precursor. A back exposure of the relief place precursor typically requires a lower light intensity than the front exposure of the same relief plate precursor. Blocking a portion of light emitted by the UV light sources and reducing the light intensity on the support surface would not affect the results of back exposure.
Optionally, at least one of the plurality of UV light sources is dimmable.
Optionally, at least one of the plurality of UV light sources has an integrated reflector configured to reflect at least a part of light emitted by the UV light sources towards the support surface. The integrated reflector inside the UV light source(s) can redirect a part of light emitted and/or received by the UV light source(s) towards the support surface as an addition or an alternative to the light adjustment structure described above. This may render the light intensity at the support surface more uniform, for example by increasing the light intensity at a part of the support surface.
Optionally, the exposure unit further comprises an additional UV light source, at least a part of the support surface being located between the additional UV light source and the plurality of UV light sources. The plurality of UV light sources may be configured to carry out a back exposure of the relief plate precursor and the additional UV light source may be configured to carry out a main exposure of the relief plate precursor. The additional UV light source may comprise light-emitting diodes. The additional UV light source may be stationary or may be movable along the support surface. The additional UV light source may cover the entire plate area of the support surface or may a portion thereof. With this layout the exposure unit is able to perform both main exposure and back exposure of the relief plate precursor without having to turn around the relief precursor or having to use different machines for main and back exposure.
Preferably, the support structure comprises a transparent plate, and the plurality of UV light sources is arranged below the support structure. In an alternative embodiment, the support structure is a table and the exposure unit comprises a lid configured to be placed above the table, and the plurality of UV light sources and the light adjustment structure are arranged in the lid, the lid being moveable to a closed position in which the plurality of UV light sources is configured to expose a relief plate precursor placed on the table.
According to a second aspect there is also provided an exposure unit for exposing a relief plate precursor, said exposure unit comprising:
Any feature described in relation to the first aspect can be combined with the exposure unit of the second aspect.
The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of the exposure unit 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:
The plurality of UV light sources 16 are arranged next to each other. The distance between the centre of the UV light sources may be in the range of 20 mm to 200 mm, preferably in the range of 50 mm to 100 mm. According to some embodiments the UV light sources 16 are elongated UV light tubes. The elongated UV light tubes may have a diameter between 15 mm to 50 mm, preferably between 25 mm and 45 mm. The distance dt between the UV light tubes may be between 5 mm and 100 mm, preferably between 5 mm and 50 mm. According some embodiments the distance dt between the neighbouring UV light tubes depends on the distance D between the UV light tubes 16 and the support surface 14. The distance D between the top of the UV light sources 16 and the support surface 14 is for instance between 10 cm and 25 cm.
The elongated UV light tubes define a tube direction in their elongation direction. The elongation direction is typically straight. The elongated UV light tubes also define a cross-tube direction perpendicular to the tube direction. Preferably the UV light tubes are arranged parallel to each other and extend in the tube direction.
The plurality of UV light sources 16 covers a light source area LA (see
The mechanical structure 20 is arranged at least partially between the light source area LA and the support surface 14. Between the light source area LA and the support surface 14 means located in a space between the support surface 14 and the light source area LA, i.e. between the light source area LA and the support surface 14 as seen in a direction perpendicular to the tube direction and the cross-tube direction, as seen in
The plurality of UV light sources 16 is arranged to emit light in a main area M and in at least one edge area E adjacent the main area M. Said main area M and said at least one edge area E have together the same surface area as the light source area LA. The at least one edge area E is for example located in the peripheral area around the main area M. The at least one edge area E may form a connected peripheral area which covers at least 10% of the surface area of the light source area LA. The connected peripheral edge area E comprises two cross-tube edge areas CE extending in the cross-tube direction perpendicular to the tube direction, on either part of the main area M. The edge area E also comprises two tube-length edge areas TE extending in the tube direction, on either part of the main area M. The two tube-length edge areas TE may have a total dimension in the cross-tube direction of less than 10%, preferable less than 7%, even more preferably less than 5% of the dimension of the light area LA in the cross-tube direction. The two tube-length edge areas TE have a total dimension which corresponds to at least twice the diameter of a UV light tube. The two cross-tube edge areas CE may have a total dimension in the tube direction of less than 15%, preferable less than 10%, even more preferably less than 8% of the dimension of the UV light tubes 16 in the tube direction.
Preferably, the mechanical structure 20 is configured to block more light per surface area in the main area M than in the peripheral edge area E. For example, the mechanical structure 20 is configured to block at least 5%, preferably at least 10% more light per surface area in the main area M than in the peripheral edge area E. More generally, the mechanical structure 20 may be configured to block more light in the main area M than in a cross-tube edge area CE and/or may be configured to block more light in the main area M than in a tube-length edge area TE. If no mechanical structure 20 is used, the intensity in the edge areas would be lower as compared to the main area; by using the mechanical structure 20 which blocks more light in the main area, this effect is compensated for, and the intensity is rendered more uniform.
According to some of the embodiments with a flatbed, the plurality of UV light sources 16 comprises at least one first edge light source 24, a plurality of central light sources 26, and at least one second edge light source 28. The plurality of central light sources 26 is arranged between the at least one first edge light source 26 and the at least one second edge light source 28. The central light sources 26 for instance correspond to the main area M. The at least one first edge light source 24 and/or the at least one second edge light source 28 for instance corresponds to the tube-length edge area TE.
Referring to
The grid structure is for example made of aluminium. The distance between the grid structure and the UV light sources 16 is below 5 cm, more preferably below 3 cm, more preferably below 2 cm. This distance depends on the distance between the top of the UV light sources 16 and the support surface 14.
As shown in
The bridge structure 32 preferably blocks a portion of light emitted by the plurality of UV light sources 16 by reflecting it back towards the light sources 16. Optionally the bridge structure 32 may also absorb or partially absorb the light emitted on its surface.
The bridge structure 32, and in particular the cross-tube side 36, comprises apertures 40 able to let through at least a part of light emitted by one or more UV light sources 16. The bridge structure 32, and in particular the cross-tube side 36, also comprises bridge sections 42 between the apertures 40.
The bridge sections 42 block at least a part of light emitted from the one or more UV light sources 16. According to some embodiments the bridge sections 42 are able at least partially to reflect light. At least a part of the apertures 40 is present on the cross-tube side 36 of the bridge structure 32, extending in the cross-tube direction. The apertures 40 may extend across the entire cross-tube side 36 in the cross-tube direction. Preferably, as shown in
The bridge section 42 may be in contact with at least one UV light source 16. Alternatively the distance between the bridge section 42 and at least one UV light source 16 is less than 5 cm, preferably less than 3 cm, more preferably less than 2 cm.
Preferably, as seen in
Preferably, and as illustrated in
The central portion 46 of the first bridge structure 32a may be configured to block between 25% and 35% of light from the UV light sources 16, and the peripherical portion 48 of the first bridge structure 32a may be configured to block between 15% and 25% of light from the UV light sources 16. The transition from the central portion 46 of the first bridge structure 32a to the peripherical portion 48 is preferably gradual, which may be achieved by gradually varying the size of the apertures 40 and/or bridge sections 42, as seen in
The central portion 46 of the second bridge structure 32b may be configured to block between 5% and 15% of light from the UV light sources 16, and the peripherical portion 48 of the second bridge structure 32b may be configured to block between 0 and 5% of light from the UV light sources 16. The transition from the central portion 46 of the second bridge structure 32b to the peripherical portion 48 is preferably gradual, which may be achieved by gradually varying the size of the apertures 40 and/or bridge sections 42, as seen in
The cross-sectional shape of the bridge structure 32 may be in the form of a V, a U such as a polygonal U or a circular U, or combinations thereof.
According to some embodiments the mechanical structure 20 is configured to render a light intensity measured in the support surface 14 more uniform as compared to a situation without the mechanical structure 20.
Thanks to the mechanical structure 20, preferably, the variation of the light intensity, in a plate area PA of the support surface 14, is at most 10%, preferably at most 5%. Typically, the plate area PA corresponds with the light source area LA without a peripheral frame area extending at less than 15 cm from the periphery of the light source area LA.
Although
In the illustrated embodiments the mechanical structure 20 is a separate self-supported structure arranged over the plurality of light sources 16. However, in other embodiments the mechanical structure may be integrated with the light sources. For example, the mechanical structure may comprise or consist of a coating, e.g. a paint, arranged on the transparent or translucent tubes of the UV light tubes and configured to block a portion of the light emitted by the corresponding light source. The coating may be arranged according to a grid-like pattern, e.g. a pattern similar to the pattern of the bridge structures described above, wherein stripes of coating are arranged at a distance of each other on the tubes. In another embodiment, a patterned sticker or foil may be arranged on a UV light source. The sticker or foil may be provided with a pattern of apertures in a similar manner as the pattern that was described above for the bridge structures. The foil may be configured to be clipped onto and fixed to the UV light tube(s).
In the illustrated embodiment of
Preferably the UV light sources 16 are configured to emit UV light to a backside of a relief plate precursor to carry out back exposure. Alternatively or in addition the UV light sources 16 are configured to emit UV light to a front side of a relief plate precursor to carry out front exposure. The illustrated embodiment of
Now referring to
According to some embodiments, such as the one in
In addition or alternatively, as shown in
According to some embodiments the mechanical structure 20 comprises a reflector which is arranged at least partially between the plurality of UV light sources 16 and the support surface 14. Some examples of the location are shown by the internal cross-tube reflector 56a and internal tube-length reflector 56b in
As shown in
In addition or alternatively, the at least one reflector 50 comprises at least one internal reflector 56, see
Preferably an internal reflector 56 (the internal cross-tube reflector 56a and/or the internal tube-length reflector 56b respectively) reflects less light than a peripheral reflector 54 (the peripheral cross-tube reflector 54a and/or at least one peripherical tube-length reflector 54b respectively). This is for example achieved by having an internal reflector 56 having a lower height (measured in a height direction perpendicular to the tube direction and to the cross-tube direction) than the peripherical reflector 54. Preferably the distance between the internal reflector 56 and the support surface 14 is less than five centimetres, preferably less than three centimetres, more preferably less than one centimetre.
Alternatively, the exposure unit 10 of
According to another embodiment (not illustrated) the exposure unit comprises a housing and a lid. The plurality of UV light sources 16 and the mechanical structure 20 are arranged in the lid of the exposure unit.
According to another embodiment (not illustrated), there may be provided a stationary additional UV light source for the main exposure in combination with a plurality of stationary UV light sources 16 as illustrated in
According to any of the embodiments described above, the exposure unit 10 may comprise a moveable shutter 70 (only shown in
In any embodiment described above, at least one of the plurality of UV light sources 16 may be dimmable. For example, each light source may be individually dimmable or groups of light sources may be dimmable.
In any embodiment described above, the UV light sources 16 may be elongated fluorescent tubes configured to emit UV light. According to one embodiment the UV light sources 16 are elongated tubes with LEDs configured to emit UV light. According to one embodiment the UV light sources 16 comprise arc lamps, such as high pressure mercury lamps.
In any embodiment described above, at least one of the plurality of UV light sources 16 may have an integrated reflector (not shown in the Figures) configured to reflect at least a part of light emitted by and/or received by the UV light sources 16 towards the support structure 12. The integrated reflector is for example a coating on the lower inner half of the (for example transparent) wall of the UV light sources 16, for example on the lower half of the elongated UV light tubes facing away the support surface 14.
In any embodiments described above, the plurality of UV light sources 16 is for example configured to generate a light intensity of 15-50 mW/cm2 on the support surface 14, when the UV light sources 16 are used for back exposure. For front exposure the values could be much higher. For example, the plurality of UV light sources 16 may be configured to generate a light intensity of 20-45 mW/cm2 on the support surface 14 measured using Ophir Starlite with sensor PD300RM-UV.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2034081 | Feb 2023 | NL | national |
