Patent Application
20250208514
The field of the invention relates to imaging a mask layer in the field of printing technology. Various embodiments in this document relate to methods for imaging a mask layer, control modules, and computer programs for use in imaging a mask layer, and to methods and systems for imaging and exposing a relief precursor.
In known methods for imaging a mask layer a fine high-resolution pattern may be included in the image file in a half-tone area and/or in a solid area in order to generate a texture on a surface of a printing dot. Such pattern is typically superimposed on the original image file and may consist of a regular pattern or an irregular pattern, e.g. a checkerboard pattern or a pattern where an imaging pixel is surrounded by eight non-imaging pixels, etc. Such pattern results in a relief structure, i.e. a texture on the printing dots and is intended to improve the ink transfer and thus the printing quality.
Such known methods are however not entirely satisfactory. One problem may be the ink density. A developed spot corresponding to the solid and/or the halftone area may not be able to hold enough ink, such that the ink density of the printed material may appear insufficient, i.e. not dark enough. Another problem may be what is called ‘a trailing edge void’. The trailing edge void appears when the edge of a developed solid spot is badly inked. A third problem that may arise is when a sampling pattern is applied on the solid area and/or the halftone area. The sampling pattern can interfere with the existing pattern of halftone dots in the halftone area.
Some embodiments of the present disclosure relate to a mask layer imaging method which may improve the ink density of the printed material. Some embodiments of the present disclosure relate to a mask layer imaging method which may reduce or eliminate the issue of trailing edge voids. Some embodiments may reduce the interference caused by a sampling pattern.
According to a first aspect of the disclosure, a method for imaging a mask layer, comprises the steps of the provision of a mask layer, receiving an image file and detecting at least one solid area and at least one halftone area in the image file, imaging an area of the mask layer corresponding to said at least one solid area using a first imaging setting, and imaging an area of the mask layer corresponding to said at least one halftone area using a second imaging setting. Prior to or during the imaging a sampling pattern is superimposed on pixels of the at least one solid area, so that either all or only a portion of the pixels of the at least one solid area is imaged. The second imaging setting is different from the first imaging setting.
By using a suitable sampling pattern in the solid area an appropriate surface structure can be obtained on the corresponding solid printing relief(s) of a printing plate, and ink on a solid printing relief will be more evenly distributed. As such the trailing edge voids can be much reduced. Indeed, by using a sampling pattern, channels are created in the upper surface of a solid relief such that a resulting printing relief is not in contact with the substrate over a too large area while printing. This reduces the trailing edge void.
In addition, by using different imaging settings when imaging the mask layer corresponding to the solid area and the halftone area, any potential interference under one imaging setting may be prevented from causing interference under another imaging setting. In some embodiments no sampling pattern is applied in the halftone areas, and thus no interference is present in those areas. However, even if a sampling pattern is used in a halftone area and were to cause some interference to the halftone area, interference can be much reduced as the imaging settings of the halftone area can be chosen independently of the imaging settings of the solid area.
Preferably, the resolution of the sampling pattern is chosen in a range from 1000 dpi to 2540 dpi. Preferably, when an ink roll is used to bring the ink on the plate, the resolution is chosen such that it is higher than a resolution of a surface structure of the ink roll.
The first aspect of the disclosure may comprise any one of, or any technically possible combinations of the following features:
Compared to an ink cell which comprises an ink well containing ink surrounded by a wall preventing ink from escaping from the ink well, the surface structure of hills surrounded by valleys allows ink to distribute evenly across many hills.
By using larger imaged spots for the solid area where a sampling pattern is used, the imaged spots may be located closer to each other or overlap, resulting in more “hill” surface area, and the printing result from the solid area can have a darker colour. By using smaller imaged spots in a halftone area, also when no sampling pattern is used, a hill structure can be obtained and a good ink transfer can be obtained.
Alternating imaging pixels with non-imaging pixels across the whole block leads to a regular sampling i.e. a regular selection of the imaging pixels over the whole block.
By not applying any sampling pattern in the halftone area, any potential interference between the sampling pattern and the second imaging setting can be totally avoided.
By applying a sampling pattern also to the halftone area, a selection can be made as to which of the imaging pixels actually are to be imaged according to the second imaging setting. For example, depending on the tonal values used in the image to be printed, it may be beneficial to use also a sampling pattern in one or more halftone areas. It is further possible to make a distinction between different halftone areas and to apply different sampling patterns (including the option of not including a sampling pattern) in different halftone areas, e.g. depending on a value representative for a tonal value or tonal value range. Also, the second imaging setting may be different for different halftone areas. Optionally, the second imaging setting may be chosen in function of a value representative for a tonal value or for a tonal value range.
Here, whether a sampling pattern is added to the halftone area depends on the tonal value in the halftone area. For low tonal values all imaging pixels in the halftone area are to be imaged on the mask layer. All information related to the low tonal values will therefore be represented in the mask layer. For high tonal values a selection as to which imaging pixels are to be imaged on the mask layer is carried out via the sampling pattern. In this way a good balance between the depth of the colour and the application of the sampling pattern may be achieved.
By using at least two different imaging settings for the halftone areas, the image setting may be adapted, e.g. based on the tonal value of the halftone area and/or on other properties of the halftone area. By providing at least two imaging settings for the halftone area, various results inside the halftone areas can be obtained.
The 1-bit-per-pixel possibility simplifies the image file and the imaging process, while the multiple-bits-per-pixel embodiment increases the number of imaging options contained in a single image file.
In this way, the information about the solid area(s)/halftone area(s) can be derived from the original image file, e.g. a pdf file, which contains typically information about grey values, also called contones, an indication of areas with characters or line work and an indication of areas with contones, etc., which may facilitate the detection and make it more accurate. For example, line work will typically correspond with a solid area whilst contones result in halftone areas, optionally with a solid area within the contones.
By doing the detection on the raster image file, e.g. a tiff file, the method becomes independent of any prior image processing steps, such as a raster image processing step or other image processing step done beforehand, which allows the method to be used in any imager regardless of prior image processing steps. In such an embodiment, the method may detect groups of clustered pixels to determine the solid and halftone areas.
These features integrate an indication of the imaging setting to be used into a single modified image file. During the imaging of the mask layer, it is then only necessary to extract information from this modified image file without having to refer to other files and/or without the need for having multiple raster image files.
A further aspect of the disclosure concerns a method for imaging and exposing a relief precursor, comprising the steps of the provision of a relief precursor comprising a substrate layer, a photosensitive layer, and a mask layer; imaging the mask layer by a method according to any one of the embodiments disclosed above; exposing the relief precursor through the imaged mask layer with electromagnetic radiation, preferably UV radiation, so that a portion of the photosensitive layer is cured, and developing the exposed relief precursor by removing a portion of the photosensitive layer that was not exposed.
According to one embodiment of the method for imaging and exposing the relief precursor, a solid area of said at least one solid area is such that, after the exposing and developing, a single printing relief with a first surface structure of hills surrounded by valleys is generated in said solid area, and a halftone area of said at least one halftone area is such that, after developing, multiple dots with a second surface structure of hills surrounded by valleys is generated in said halftone area.
In this way an appropriate texture is given to both the one or more solid printing reliefs corresponding with the one or more solid areas and to the halftone dots corresponding with the at least one halftone area, resulting in a good ink transfer.
Another aspect of the present disclosure also relates to an imaging system, the imaging system being configured to perform the method as described above.
Another aspect of the present disclosure relates to a control module configured to receive an image file and to detect at least one solid area and at least one halftone area in an image file. The control module is configured to control an imager so that an area of the mask layer corresponding to said at least one solid area is imaged using a first imaging setting. Prior to or during the imaging the control module is configured to superimpose a sampling pattern on pixels of the at least one solid area, so that only a portion of the pixels of the at least one solid area is imaged, and so that an area of the mask layer corresponding to said at least one halftone area is imaged using a second imaging setting.
The control module of the disclosure may comprise any one of, or any technically possible combinations of the following features:
According to another aspect, there is provided a method for imaging a mask layer, comprising the steps: provision of a mask layer, receiving an image file and detecting at least one solid area and at least one halftone area in the image file; imaging an area of the mask layer corresponding to said at least one solid area, using a first imaging setting; imaging an area of the mask layer corresponding to said at least one halftone area, using a second imaging setting which is different from the first imaging setting, wherein prior to or during the imaging a sampling pattern is superimposed on pixels of a halftone area of the at least one halftone area, so that only a portion of the pixels of said halftone area is imaged.
In this manner the at least one solid area may be imaged in a robust and simple manner without using a sampling pattern, whilst a suitable sampling pattern may be used in one or more halftone areas. Preferably, the sampling pattern is then chosen such that Moiré effects are avoided or limited.
In such embodiments, the first and second imaging settings may be such that an imaged spot corresponding to an imaging pixel of the at least one solid area is smaller than an imaged spot corresponding to an imaging pixel of the halftone area.
In such embodiments, for a halftone area of said at least one halftone area having a tonal value below a predetermined value, e.g. in the high-lights, no sampling pattern may be added in said halftone area, and for a halftone area having a tonal value above the predetermined value, a sampling pattern may be added in the halftone area. All halftone areas with a tonal value above the predetermined value may use the same or different sampling patterns.
Preferably, the sampling pattern and said first and second imaging settings are chosen such that, after exposing a relief precursor through the imaged mask layer and developing of the exposed relief precursor, a first surface structure of hills surrounded by valleys is generated on a relief corresponding with said at least one solid area and a second surface structure of hills surrounded by valleys on printing dots corresponding with said at least one halftone area. Such structure will limit any suction effects when the printing plate with ink is pressed against a substrate.
According to a corresponding aspect there is provided a control module configured to receive an image file and to detect at least one solid area and at least one halftone area in the image file. The control module is configured to control an imager so that an area of a mask layer corresponding to said at least one solid area is imaged using a first imaging setting and an area of the mask layer (12) corresponding to a halftone area at least one halftone area is imaged using a second imaging setting which is different from the first imaging setting, wherein prior to or during the imaging a sampling pattern is superimposed on pixels of a halftone area of the at least one halftone area, so that only a portion of the pixels of said halftone area is imaged.
According to another aspect, there is provided a method for imaging a mask layer, comprising the steps: provision of a mask layer, receiving an image file and detecting at least a first and a second halftone area having a different first and second tonal value ranges in the image file; for said first halftone zone, determining a first imaging setting based on a value representative for the first tonal value range; for said second halftone zone, determining a second imaging setting based on a value representative for the second tonal value range; and imaging an area of the mask layer corresponding to said first and second halftone areas, using said determined first and second imaging settings.
In that manner, the surface structure of the relief elements may be adapted in function of the tonal value range. E.g. for larger tonal values the size of the imaged spots may have a larger diameter than for lower tonal values.
Preferably, the first and second tonal value range are ranges above 10%, more preferably above 20%. For example, the first range may be from P1 to P2 and the second range may be all values above P2, wherein P1 is a value between 10% and 30% and P2 a value between 40% and 60%.
Optionally, prior to or during the imaging a sampling pattern may be superimposed on pixels of the first and/or second halftone area, so that only a portion of the pixels of the first and/or second halftone area is imaged. Optionally, whether or not to use a sampling pattern, and/or which sampling pattern to use may also be determined in function of the tonal value of the respective area.
Optionally the method further comprises detecting a solid area in the image file, wherein prior to or during the imaging a sampling pattern is superimposed on pixels of the solid area, so that only a portion of the pixels of the solid area is imaged.
Preferably, the first and second imaging settings are chosen such that, after exposing a relief precursor through the imaged mask layer and developing of the exposed relief precursor, a first surface structure of hills surrounded by valleys is generated on printing dots in said first halftone area and a second surface structure of hills surrounded by valleys on printing dots in said second halftone area.
Preferably, the sampling pattern is any one for sampling patterns disclosed above in connection with other aspects.
Preferably, the first and second imaging settings define any one or more of the parameters disclosed above in connection with other aspects.
Optionally, the step of detecting is done during a raster image processing step.
Alternatively, the image file is a raster image file and the step of detecting in the image file is performed after a raster image processing step. For example, a pattern and size of clusters of imaging pixels may be determined, and based thereon different halftone and solid areas of the image file may be determined.
In an exemplary embodiment a first raster image file is generated containing only the first halftone area and a second raster image file containing only the second halftone area. In such an embodiment, the first and second raster images file may be for example a first one-bit-per-pixel file for the first halftone area and a second one-bit-per-pixel file for the second halftone area. If more than two imaging settings are used, more than two raster image files may be generated. Alternatively, a multi-bit per pixel file may be generated, as has been explained above.
According to a corresponding aspect there is provided a control module configured to receive an image file and to detect at least a first and a second halftone area having a different first and second tonal value ranges in the image file; and to determine, for said first halftone zone, a first imaging setting based on a value representative for the first tonal value range, and for said second halftone zone, a second imaging setting based on a value representative for the second tonal value range; and to control the imaging an area of a mask layer corresponding to said first and second halftone areas, using said determined first and second imaging settings.
A further aspect of the present disclosure concerns a method for imaging a mask layer comprising the steps of generating an image file with at least two bits per pixel, and imaging said mask layer with said image file so that each pixel is imaged in accordance with the associated at least two bits in the image file. Said at least two bits indicate one of the following:
By generating such a modified imaging file, the imager can be instructed in a convenient manner, whilst allowing to vary the imaging settings. In this way the imaging settings can be changed during the imaging in a convenient manner.
This further aspect of the disclosure may comprise any one of, or any technically possible combinations of the following features:
A further aspect of the present disclosure concerns a control module for controlling an imager for imaging a mask layer. The control module is configured to generate an image file with at least two bits per pixel, and to control the imaging of the mask layer with said image file so that each pixel is imaged in accordance with the associated at least two bits in the image file. The at least two bits indicate one of the following:
In preferred embodiments according to any one of the aspects disclosed above, the first imaging setting is such that, where the first image settings are used, an imaged spot corresponding to a imaging pixel does not overlap with an adjacent imaged spot corresponding to an adjacent imaging pixel; and/or the second imaging setting is such that, where the second image settings are used, an imaged spot corresponding to a imaging pixel does not overlap with an adjacent imaged spot corresponding to an adjacent imaging pixel. In that manner it is avoided that isolated “wells” are created which may cause a sucking of the ink towards the printing plate.
A further aspect of the present disclosure relates to a method for treating a relief precursor, comprising the steps of: the provision of a relief precursor comprising a substrate layer, a photosensitive layer, and a mask layer; imaging the mask layer by a method as disclosed above in relation to the any one of the aspects of the present disclosure; exposing the relief precursor with electromagnetic radiation, preferably UV radiation, so that a portion of the photosensitive layer is cured, and developing the exposed relief precursor by removing a portion of the photosensitive layer that was not exposed.
Preferably the imaging is such that, after the exposing and developing, printing reliefs with a surface structure of hills surrounded by valleys are generated.
A further aspect of the present disclosure also relates to an imaging system, the imaging system being configured to perform any one of the embodiments of the method as disclosed above.
The present disclosure also concerns a control module configured to carry out any one of the embodiments of the method of the present disclosure.
Another aspect of the present disclosure also relates to a system for imaging and optionally further processing a relief precursor, comprising
The control module is configured to control the imager according to any one of the embodiments disclosed above.
Preferably, the system further comprises any one or more of the following: at least one transport system configured to transport the relief precursor, a storage system, an exposure means configured to expose the relief precursor through the imaged mask layer, a developing means configured to remove at least a part of non-exposed material from the relief precursor, a drying system, a post-exposure device, a cutting device, a mounting station, a heater. The transport system may comprise one system that connects all the different treatment means or may comprise one or more transport means that connect the different treatment means. The storage system is configured to store the relief precursor and/or the resulting relief plate at any stage of the process, e.g. upstream of the imager, at the end of a mounting station or anywhere in-between.
In exemplary embodiments the imaging of the at least one halftone area and the imaging of the at least one solid area may be done sequentially (in any order) or preferably simultaneously. Preferably, multiple beams are used for the imaging and individual beams thereof can be controlled independently so that imaging can be done simultaneously with different imaging settings. In another embodiment, the multiple beams may comprise a first group of beams and a second group of beams, wherein the first group can be controlled independently of the second group so that imaging can be done simultaneously with the first and second group with different imaging settings
Some embodiments of the present disclosure relate to a computer program comprising computer-executable instructions to control an embodiment of the method as described above in relation to any one of the aspects of the disclosure, when the program is run on a computer.
Some embodiments of the present disclose relate to a digital data storage medium encoding a machine-executable program of instructions to perform any one of the steps of the method as described above in relation to any one of the aspects of the disclosure.
Some embodiments of the present disclose relate to a computer program product comprising computer-executable instructions for controlling or performing the method as described above in relation to any one of the above aspects of the disclosure, when the program is run on a computer.
Any feature of the first aspect of the present disclosure may be combined with any feature of a further aspect of the present disclosure.
The above and further aspects of the disclosure will be explained in more detail below on the basis of a number of embodiments, which will be described with reference to the appended drawings. In the drawings:
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 printing plate precursors. According to conventional methods flexographic 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 imaged by exposure to electromagnetic radiation through a mask layer containing the image information or by direct and selective exposure to light e.g. by scanning of the plate to transfer the image information in order to obtain a relief plate.
In flexographic printing, ink is transferred from a flexographic plate to a print medium. More in particular, the ink is transferred on the relief parts of the plate, i.e. in the halftone dots or solid reliefs, and not on the non-relief parts. During printing, the ink on the relief parts is transferred to the print medium. Greyscale images are typically created using half-toning using a screening pattern, preferably an AM screening pattern. By greyscale is meant, for a plate printing in a particular colour, the amount of that colour being reproduced. For example, a printing plate may comprise different half-tone dot regions to print with different densities in those regions. In order to increase the amount of ink transferred and to increase the so-called ink density on the substrate, an additional very fine structure is applied to the surface of the printing dots, i.e. the relief areas. This fine surface structure is typically obtained by adding a fine high resolution sampling pattern to the image file, so that it is then transferred to the corresponding mask used for exposure.
Images reproduced by flexographic plates typically include both solid image areas and a variety of grey tone areas, also called halftone areas. A solid area corresponds with a single relief in the printing plate which is completely covered by ink so as to produce the highest density on a print material. A grey tone or halftone area corresponds with an area with multiple printing dots at a distance of each other, i.e. an area where the appearance of the printed image is of a density intermediate between pure white (total absence of ink) and pure colour (completely covered by ink). Grey areas are produced by the process of half-toning, wherein a plurality of relief elements per unit area is used to produce the illusion of different density printing. These relief elements are commonly referred to in the printing industry as ‘halftone dots’. Image presentation is achieved by changing a percentage of area coverage (dot intensity) from region to region. Dot intensity may be altered by altering the dot size (AM screening) and/or the dot density, i.e. the dot frequency (FM screening).
In a flexographic plate, the halftone dots are relief areas having their surface at the top surface of the plate. The plate in the area surrounding the dot has been etched to a depth which reaches to a floor. The height of a halftone dot is the distance of the surface of the dot (and of the plate surface) to the floor. The halftone relief is the relief extending from the floor to the top surface.
For imaging the mask layer 12, first an image file 18 is received. The image file 18 for example represents two-dimensional image data, as shown in the top part of
Once the image file 18 is received, the method detects at least one image file solid area 20 and at least one image file halftone area 22 in the image file 18. The image file solid area 20 contains a cluster of at least one solid area imaging pixel 24. The image file halftone area 22 comprises a plurality of imaging pixel clusters (here three imaging pixel clusters are shown) each containing at least one halftone area imaging pixel 26. Prior to or during the imaging a sampling pattern 44 is superimposed on pixels of the at least one solid area 20, so that only a portion of the pixels 24 of the at least one solid area 20 is imaged, see the resulting modified image file portion 18′ in
As will explained below, after the mask layer 12 is imaged, it comprises at least one solid zone 32 and at least one halftone zone 34. Each solid zone 32 corresponds to a corresponding solid relief 36 (visible on
A solid area imaging pixel 24 is configured to image a solid zone imaged spot 40 in the solid zone 32. A halftone area imaging pixel 26 is configured to image a halftone zone imaged spot 41 in the halftone zone 34.
It is noted that the imaged spots 40, 41 which are shown schematically in the cross section of
The original image file 18 may either be a raster image file such as a TIF file or a more high-level image file such as a PDF or PS file. After detection of the at least one solid area 20 and the at least one halftone area 22, the original image file 18 may be converted in a first raster image file containing only the solid areas 20 with the superimposed sampling pattern, and a second raster image file containing only the halftone areas 24. It is noted that the sampling pattern may also be applied during imaging, “on the fly”, in which case it is not included in the first raster image file. The first raster image file is then be used for imaging with the first imaging setting and the second raster image file is then be used for imaging with the second imaging setting. According to another embodiment the original image file 18 is converted in a multi-level image file which for each pixel, indicates an imaging setting to be used.
According to one embodiment the step of detecting at least one image file solid area 20 and/or at least one image file halftone area 22 is done during a raster image processing step.
According to another embodiment the image file 18 is a raster image file. The step of detecting at least one image file solid area 20 and at least one image file halftone area 22 is performed after a raster image processing step.
The solid zone 32 of the mask layer 12 is imaged using a first imaging setting. The halftone zone 34 of the mask layer 12 is imaged using a second imaging setting. The second imaging setting is different from the first imaging setting.
The first and second imaging setting may specify a value representative for the size of the resulting first and second imaged spot 40, 41. The first and second imaging settings may define any one or more of the following parameters:
Referring back to
The solid zone 32 of the mask layer of
The halftone zone 34 of the mask layer of
According to one embodiment the solid zone imaged spot 40 is larger than the halftone zone imaged spot 41, as shown in
According to a preferred embodiment, no sampling pattern is added in the at least one halftone area 22. This is to say that no sampling pattern is superimposed on the halftone area imaging pixels 26. As a result, all information on the halftone area imaging pixels 26 is imaged without omission and/or additional modifications.
As a variant, a sampling pattern (not shown) is added in the at least one halftone area 22. This is to say that a sampling pattern is superimposed on the halftone area imaging pixels 26. As a result, not all halftone area imaging pixels 26 of a halftone area 22 of the original image file 18 are imaged. The sampling pattern 44 added in the solid area 36 can be the same as or different from the sampling pattern added in a halftone area 22.
As another variant, whether a sampling pattern is added in the at least one halftone area 20 may be made dependent on the tonal value of a halftone area. According to one embodiment, for tonal values below a predetermined value, no sampling pattern is added in the at least one halftone area 22. For tonal values above the predetermined value, a sampling pattern is added in the at least one halftone area 22.
In addition or as an alternative, whether a sampling pattern is added in an area of the image file may be dependent on the size of an isolated cluster of pixels in the image file. For example, for an isolated cluster of pixels with a number of pixels below a predetermined value, no sampling pattern is added. For an isolated cluster of pixels with a number of pixels above the predetermined value, a sampling pattern is added.
According to a preferred embodiment, the sampling pattern 44 and the first and second imaging settings are chosen such that, after exposing a relief precursor through the imaged mask layer 12 and developing an exposed relief plate, a first surface structure of hills surrounded by valleys is generated on the at least one solid relief 36 and a second surface structure of hills surrounded by valleys on the halftone dots 38. Hills here mean the structures protruding further from the floor of the photosensitive layer 16. Valleys here mean the grooves which protrude less far from the floor of the photosensitive layer 16 compared with the hills. Hills surrounded by valleys here means the structures protruding further from the floor alternate with the grooves.
According to one embodiment, the depth of the valleys of the surface structure on the solid relief 36 is 0.5 μm and 10 μm. According to one embodiment, the depth of the valleys of the surface structure on the halftone dots is between 0.5 μm and 20 μm, preferably between 1 and 10 μm, more preferably between 3 and 10 μm. The total relief depth (i.e. the maximum relief depth in large areas where no imaging pixels are present) is preferably between 100 μm and 4 mm, more preferably between 100 μm and 2 mm, and most preferably between 100 μm and 1 mm. The intermediate relief depth (i.e. the relief depth in an area between halftone dots 38) is preferably between 40 and 60% of the total intermediate depth, e.g. between 30 μm and 2 mm, more preferably between 40 μm and 1 mm.
According to one embodiment, after the relief precursor 10 is exposed and developed, a single printing relief 36 with a first surface structure of hills surrounded by valleys is generated in a solid area 20, and multiple halftone dots 38 with a second surface structure of hills surrounded by valleys is generated in a halftone area 22.
According to one embodiment, prior to the imaging a modified image file is generated. The modified image file has at least two bits per pixel. Said at least two bits indicate for each pixel whether the pixel is one of the following:
According to this embodiment the imaging of the mask layer 12 is carried out based on the modified image file.
The bits in the image file 18 for example indicate a size, e.g. the diameter of the imaging beam. As an alternative, the bits in the image file 18 indicate an intensity level of the beam. This embodiment especially corresponds to the case when the imaging is carried out by laser beams.
Amongst
According to one embodiment the sampling pattern 44 is a repetition of a block in which one or more imaging pixels are combined with one or more non-imaging pixels.
Generally, the finer patterns, i.e. the patterns with relatively small pixel clusters or the single pixel files are preferred for high quality colour work, such as for printing on labels and some packaging materials. For other materials, such as corrugated cardboard, the multiple pixel patterns are generally preferred. Further, the image setting of an area may be chosen in function of the choice of the sampling pattern. For example, for multiple pixel patterns, the size of the beam may have a larger diameter than for single pixel patterns, or the size may be chosen in function of the multiple pixel pattern used.
After the mask layer 12 is imaged in the imager 110, the relief precursor 10 is exposed to electromagnetic radiation in the exposure means 120 so that a portion of the photosensitive layer 16 is cured. The electromagnetic radiation may have a wavelength in the range of 200 to 2000 nm, preferably it is ultraviolet (UV) radiation with a wavelength in the range of 200 to 450 nm.
After a portion of the photosensitive layer 16 is cured, the exposed relief precursor 10 is developed by the developing means 130 by removing a portion of the photosensitive layer 16 that was not exposed to the electromagnetic radiation and that is therefore not cured. A skilled person is familiar with various ways of exposing the relief precursor 10 to electromagnetic radiation, and of developing an exposed relief precursor 10.
In a second step 220 an image file 18 is analysed to detect at least one solid are and/or at least one halftone area. Either different raster image files may be generated as explained above or a modified image file with at least two bits per pixel may be generated after the analysis in the manner described above.
The first and second imaging settings are different. Under the optional choice in this embodiment, the third imaging setting is different from the first and second imaging settings.
Next the mask layer 12 is imaged in step 230, 240; 330 either using with the modified two-bit-per-pixel image file which has been generated, or using multiple raster image files and further instructions regarding the first and second imaging settings. Each imaging pixel is imaged with the corresponding imaging setting to create corresponding imaged spots in the mask layer 12. It is noted that steps 230 and 240 may be done in any order or even simultaneously. Preferably, multiple beams are used for the imaging and individual beams thereof or multiple sets of beams thereof can be controlled independently so that imaging can be done simultaneously with different imaging settings.
According to an exemplary embodiment, the image settings used in steps 230, 240; 330 are such that an imaged spot corresponding to an imaging pixel to be imaged with a first imaging setting is larger than an imaged spot corresponding to an imaging pixel to be imaged with a second imaging setting. This is for example achieved by using a beam with a higher intensity value under the first imaging setting compared with the intensity value of the beam under the second imaging setting. Alternatively, this is achieved by using a beam with a larger diameter under the first imaging setting compared with the diameter of the beam under the second imaging setting.
According to an exemplary embodiment shown in
After the mask layer 12 is imaged, in step 250, 340 the relief precursor 10 is exposed to electromagnetic radiation so that a portion of the photosensitive layer 16 is cured. The electromagnetic radiation may have a wavelength in the range of 200 to 2000 nm, preferably it is ultraviolet (UV) radiation with a wavelength in the range of 200 to 450 nm.
After a portion of the photosensitive layer 16 is cured, the exposed relief precursor 10 is developed in step 260, 350 by removing a portion of the photosensitive layer 16 that was not exposed to the electromagnetic radiation and that is therefore not cured.
According to one embodiment the first and second imaging settings are chosen such that, after the relief precursor 10 is exposed and developed, a first surface structure of hills surrounded by valleys is generated in at least a first area and a second surface structure of hills surrounded by valleys in at least a second area, for example as illustrated in
According to one embodiment the halftone zone 34 of the mask layer 12 comprises a first halftone zone (not represented in the Figures) and a second halftone zone (not represented in the Figures). The first halftone area is imaged using the first imaging setting as explained above. The second halftone area is imaged a using third imaging setting different from the first imaging setting. Preferably the third imaging setting is different from the second imaging setting as well.
According to one embodiment the third imaging setting at least differs from the first imaging setting in that the intensity of the beam (optical power per unit area in W/cm2) used to generate the features in the second halftone zone is different from the intensity of the beam used to generate the features in the first halftone zone and/or in that the diameter of the beam used to generate the features in the second halftone zone is different from the diameter of the beam used to generate the features in the first halftone zone. This will result in the imaged spots in the first halftone zone being smaller i.e. having a lower diameter than those in the second halftone zone.
As illustrated in
According to one embodiment prior to or during the imaging of the first halftone zone of the mask layer 12, a first halftone sampling pattern may be superimposed on the pixels configured for imaging the first halftone zone. According to an embodiment prior to or during the imaging of the second halftone zone of the mask layer 12, a sampling pattern may be superimposed on the pixels configured for imaging the second halftone zone. The sampling pattern superimposed on the pixels for imaging the first halftone zone may be identical to or different from the sampling pattern superimposed on the pixels for imaging the second halftone zone. According to another embodiment the imaging of neither the first halftone zone nor the second halftone zone involves superimposing a sampling pattern.
According to some embodiments the photosensitive layer 16 in the present disclosure is essentially identical to the substrate layer described in WO 2020/188041 A1 in the name of the applicant, which in included herein by reference.
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 |
|---|---|---|---|
| 2031133 | Mar 2022 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/055101 | 3/1/2023 | WO |
