System and method for applying non-printing marks on a digital flexographic printing plate by

Abstract

Systems and methods for creating non-printed indicia having non-printed protrusions over a base of a flexographic printing plate. The method includes providing a photosensitive polymer printing plate precursor having a front side, a back side, and a laser ablatable mask system (LAMs) layer disposed over the front side; and deploying an oxygen barrier on the LAMs layer, the oxygen barrier having a pattern defining a non-printed mark. The backside of the printing plate precursor is exposed to actinic radiation while the oxygen barrier remains disposed on the LAMs layer. An exemplary system includes a photosensitive polymer printing plate precursor having an LAMs layer, a backside exposure system, and an oxygen barrier, and may also include an ink applicator, such as an inkjet printer, a marking pen, a stamp, or a nozzle.

Description

[0001] Cross-references to related applications This application claims priority to EP application No. 23164991.4, filed on March 29, 2023, entitled “SYSTEM AND METHOD FOR APPLYINGNON-PRINTING INDICIA ON DIGITAL FLEXOGRAPHIC PRINTING PLATES THROUGH ANON-IMAGED MASK”, the entire contents of which are incorporated herein by reference. Background Technology

[0002] A typical workflow for flexographic (flexographic) photopolymer printing plates may include the following steps: 1. Use a raster image processor to process image information at a specific screen resolution to obtain an image file.

[0003] 2. Using a processor, combine image files with other image files to create an imaging job that covers the entire photopolymer plate precursor format.

[0004] 3. By any of the various methods known in the art, an image file is imaged onto a laser ablation mask system (LAMs) layer on top of a photosensitive polymer plate precursor, thereby creating a mask on top of the plate precursor.

[0005] 4. Curing the back side of the printing plate precursor, such as by using UVA light, to build a cured polymer floor.

[0006] 5. Curing photosensitive polymers using a mask on top of the printing plate precursor, such as by utilizing UVA light.

[0007] 6. Process the printing plate precursor to remove uncured polymer from the printing plate precursor, thereby forming the printing plate.

[0008] 7. Optionally, the printing plate is dried to remove the solvent (typically not performed when heat treatment is used).

[0009] 8. Complete the printing plate, such as by applying UVA and UVC light.

[0010] 9. Separate different image files, such as by cutting polymer printing plates into smaller pieces on an xy cutting stage.

[0011] 10. Mount one or more of the printing plate segments onto a printing press, such as a printing press cylinder, each printing plate segment representing one or more image files.

[0012] 11. A printing plate is used in a printing press to print a physical image on a printing receiving substrate.

[0013] 12. Remove the ink from the printing plate, remove the printing plate from the printing press, and store it for future use, such as reprinting.

[0014] It should be noted that the term "plate precursor" may be used herein to refer to any form of printing plate before it reaches its final form and is ready to receive and transfer ink. However, generally, despite one or more additional subsequent processes, the embossed structure of the finished printing plate will at least closely resemble its final form after the uncured polymer removal step. Sometimes, the term "plate" may also be used herein as an abbreviation to refer to the plate precursor, but those skilled in the art will understand the actual state of the printing plate throughout the process.

[0015] Various methods for applying non-printing information onto the substrate of a flexographic printing plate have been described for any of a variety of purposes, including but not limited to: identifying the printing plate, plate segments, or jobs; tracking the printing plate; branding the printing plate; and providing operational parameters for one or more of the aforementioned process steps. Exemplary methods and types of marking are disclosed in the following applications and related equivalents, all of which are incorporated herein by reference and are jointly owned by the applicants of this application: • PCT application serial number PCT / EP2019 / 052536, published as WO2019192764A1, entitled "METHOD FORPERSISTENT MARKING OF FLEXO PLATES WITH WORKFLOW INFORMATION AND PLATESMARKED THEREWITH". • PCT application serial number PCT / EP2019 / 073200, published as WO2020043875A1, entitled "PHOTOSENSITIVE PRINTING FORM FOR A FLEXOGRAPHIC PRINTING METHOD COMPRISINGVISIBLE AND NON-PRINTABLE INFORMATION, AND METHOD FOR PREPARING SUCH APRINTING FORM" • PCT application serial number PCT / EP2019 / 076922, published as WO2020156692A1, entitled "SYSTEM AND PROCESS FOR PERSISTENT MARKING OF FLEXO PLATES AND PLATES MARKED THEREWITH" • PCT application serial number PCT / EP2020 / 078112, published as WO2021069489A1, entitled "SYSTEM AND PROCESS FOR PERSISTENT MARKING OF FLEXO PLATES AND PLATES MARKED THEREWITH," • PCT application serial number PCT / EP2022 / 080376, filed on October 31, 2022, entitled "SYSTEM AND PROCESS FOR PERSISTENT MARKING OF FLEXO PLATES AND PLATES MARKED THEREWITH", an overview of the invention.

[0016] Many of the aforementioned techniques generally involve UV exposure through mask openings or, in addition to routine UV back exposure, UV curing from the back side of the plate carrying image information to create a structure on the plate substrate. These techniques typically involve significant image processing to add image information to the plate substrate.

[0017] Therefore, there is still a need in the field for simpler techniques to provide non-printing information on a printing plate substrate. Summary of the Invention

[0018] One aspect of the present invention relates to a method for creating non-printing marks on a flexographic printing plate, wherein the non-printing marks include a structure having non-printing elevations above a plate substrate. The method includes the steps of: providing a photosensitive polymer printing plate precursor having a front side, a back side opposite the front side, and a laser ablation mask system (LAMs) layer disposed on the front side; disposing an oxygen barrier having a pattern defining the non-printing marks on the LAMs layer; and exposing the back side of the plate precursor to photochemical radiation while the oxygen barrier remains disposed on the LAMs layer.

[0019] Embodiments of this method may include imaging the LAMs layer by laser ablation of openings in the LAMs layer, the openings corresponding to a desired image to be formed by printing a structure on the front side of a printing plate prior to an exposure step. Such embodiments may also include performing a front-side exposure step after or during a back-side exposure step, the front-side exposure step comprising exposing a photosensitive polymer printing plate precursor to photochemical radiation through the openings in the LAMs layer.

[0020] In some embodiments, the oxygen barrier may comprise a planar layer defining a pattern, such as foil or sticker, or the oxygen barrier may comprise a 3D object defining a pattern with raised embossed structures, wherein gaps exist between adjacent embossed structures to allow airflow between them, wherein the 3D object is deployed on a LAMs layer, and the outer surfaces of the raised embossed structures face the LAMs layer. Such a 3D object may comprise a portion of an finished printing plate having structures raised above its base that define the pattern. Embodiments may also include deploying the oxygen barrier by applying a liquid fluid, such as oil, water, ink, or a combination thereof, to the LAMs layer. The liquid fluid may be applied between the LAMs layer and the 3D or planar object defining the pattern. Alternatively, the liquid fluid may define the pattern separately upon application or after evaporating volatile components to leave a dried residue. The liquid fluid may be applied using an inkjet printer or nozzle, via a marker pen or stamp, or by applying a stencil to the LAMs layer, applying the liquid fluid over the stencil, and then removing the stencil.

[0021] The intensity and corresponding duration of the photochemical radiation exposure step can be selected to improve or optimize the formation of non-printing marks relative to operable intensities associated with different (typically shorter) corresponding durations.

[0022] Another aspect of the invention relates to a system for creating non-printing marks having non-printing reliefs above a base of a flexographic printing plate. The system includes: a photopolymer printing plate precursor having a front side, a back side opposite the front side, and a laser ablation mask system (LAMs) layer disposed on the front side; a back-side exposure system configured to expose the back side of the plate precursor to photochemical radiation; and an oxygen barrier having a pattern defining the non-printing marks disposed on the LAMs layer. The oxygen barrier may comprise a planar layer defining the pattern or a three-dimensional object defining the pattern with raised embossed structures, wherein gaps exist between adjacent embossed structures to allow airflow between them, wherein the three-dimensional object is disposed on the LAMs layer, and wherein the outer surface of the raised embossed structures faces the LAMs layer.

[0023] In some embodiments, the system may further include a liquid fluid deployed between the LAMs layer and the outer surface of the raised relief structure of the 3D object. In other embodiments, the oxygen barrier comprises a liquid fluid or a dried residue remaining from a liquid fluid from which volatile components have evaporated. The system may also include an applicator for applying the liquid fluid, such as an inkjet printer, marker, stamp, or nozzle. Some embodiments may include an inkjet printer having a printhead mounted on a carriage of an exposure system. In other embodiments, the system may include an inkjet printer having a printhead mounted on an imaging system. Attached Figure Description

[0024] Figure 1 A flexible photopolymer printing plate precursor undergoing an exemplary back exposure step is schematically depicted.

[0025] Figure 2 An exemplary 3D relief structure suitable for use as an oxygen barrier in embodiments of the present invention is depicted.

[0026] Figure 3 It is a photograph of a finished printing plate that illustrates both the printed structure and the non-printed markings formed according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of an exemplary embodiment of a drum imaging system.

[0028] Figure 5 This is a schematic diagram of an exemplary flat-panel imaging system embodiment. Detailed Implementation

[0029] This document describes methods, apparatus, and systems for applying non-printing marks to the substrate of a digital flexographic printing plate during UV exposure on a UV exposure system by blocking the diffusion of oxygen into the printing plate through laser ablative mask systems (LAMs). This method may be particularly suitable for systems configured to simultaneously expose the printing plate to both the front and back sides (i.e., with a predetermined delay between the front and back exposures) and provide an additional back exposure step, such as the system described in PCT / EP2018 / 057060, disclosed in WO2018 / 172374A1, entitled “PROCESS AND APPARATUS FORADJUSTING THE FLOOR OF A FLEXOGRAPHIC PRINTING PLATE IN A CONTROLLED EXPOSURESYSTEM OR PROCESS,” which is incorporated herein by reference. However, it should be understood that the systems described herein are not limited to use in conjunction with any particular exposure system or method. For example, the principles described herein can also be applied to back-side-only exposure systems that provide a pathway for sufficient oxygen contact from the front side of the printing plate. For example, but not limited to, systems that may be particularly suitable for practicing aspects of the present invention may include the Esko® XPS, XSYS ThermoFlexX Catena-E systems, and certain bank exposure systems (such as, for example, the Cyrel® 3000 ETL-I system) having one set of tubes for front-side exposure and another set for back-side exposure. Aspects of the present invention relate to creating non-printing structures on the substrate of a printing plate by placing an oxygen barrier on top of the LAMs layer of a digital flexographic printing plate. Unlike prior art solutions that may require extensive image processing to add image information to the substrate, the exemplary method described herein utilizes relatively simple tools, such as stamps or stencils, to apply or permit the application of oxygen-barrier inks or other oxygen-barrier liquid fluids to the LAMs layer of the printing plate. Because this process can be applied without penetrating or removing the LAMs, it can be readily performed as an additional step after the plate has been imaged, particularly in non-imaged areas of the plate (e.g., edge areas of the substrate where ink transfer is not intended during the printing step).

[0030] Aspects of this invention can be used to provide plate ID information on printing plates, such as brand logos or watermarks with plate information, such as production dates or customer names. This invention is not limited to any specific content of the non-printable markings thus created, but exemplary content may include alphanumeric characters, non-text graphics, machine-readable codes, one or more lines or combinations thereof, some or all of which may be repeating patterns. Any of the above-described forms of non-printable markings may embody information including job numbers, separation colors, versions, dates, or combinations thereof. The markings may include brand information. In some embodiments, the non-printable markings may include alignment marks for orienting the printing plate relative to elements of the printing plate handling apparatus.

[0031] Although certain markings have been explicitly described, the term "marking" is intended to have the broadest meaning of "indicator" or "distinguishing sign," and is not limited to how the indication or sign can be read; therefore, the "equivalent" of the explicitly described marking is intended to be interpreted broadly. While some machine-readable markings or codes may utilize specialized machine-readable formats to allow for the storage of large amounts of information in a small space, it should be understood that the term "machine-readable," as used herein to refer to markings and codes, is not limited to markings having specialized machine-readable formats. Those skilled in the art will appreciate that human-readable alphanumeric information can also be machine-readable by a reader equipped with suitable optical character recognition (OCR) capabilities, and the hardware and software used to provide such capabilities are well known in the art. Machine vision systems and human operators can also be trained to read non-alphanumeric graphic symbols used to convey information that can be generally understood (e.g., graphic symbols indicating recyclable materials or laundry care recommendations). Therefore, it should be understood that the terms “marking” and “machine-readable” are intended to be interpreted broadly as including, in addition to the other types of marking discussed in detail herein, printed or otherwise visible alphanumeric or graphic information configured to be read and understood by both human operators and machines, as well as combinations of specifically machine-readable marking and marking that is readable by both humans and machines. One advantage of using machine-readable, and at least partially human-readable, marking is that experienced human operators may be able to process and act on at least some of the code faster than the same operator seeking machine assistance.

[0032] In some embodiments, process information may be stored directly or indirectly in a tag, such as in a QR code, although the tag used to provide such information is not limited to any particular type of code. In particular, at least one variable operating parameter may be embodied in the tag or stored in computer memory at a unique, machine-accessible address embodied in the tag. In embodiments, process parameters for one or more stages of the plate processing are directly embodied in code, such that each individual processing unit can derive instructions directly from the code on the plate without a network connection. In other embodiments, the code may include a computer storage address storing such process information and may be used in conjunction with a reader configured to read information embodied in the tag, such as via a hyperlink to a storage address embedded in the information, reading the information from the storage address, and passing the relevant stored information to the processing machine.

[0033] Without adhering to any specific operational theory, it is believed that the mechanism for effectively implementing this method involves preventing oxygen from the surrounding air from entering the photosensitive polymer during back-side curing. This principle is... Figure 1 It is described in the text.

[0034] Figure 1 A flexographic photopolymer plate precursor 100 is depicted, comprising a dimensionally stable back foil 101, a photopolymer layer 102 to be cured by photochemical radiation 120 after complete plate processing to form a plate substrate, another uncured polymer layer 103 (excluding the cured portion of an embossed structure formed above the plate substrate) removed during processing, and a layer of LAMs 104 deployed on the uncured polymer. As is known in the art, the LAMs layer is laser-ablated in an imaging step, and the photopolymer 103 is subsequently front-cured in a subsequent front-side curing step, resulting in cured portions of the photopolymer corresponding to the desired image. These cured portions are retained in the uncured polymer removal step to create the embossed structure. The embossed structure with printable protrusions is configured to receive ink, while the embossed structure with non-printable protrusions can be used to support a printed structure or as a non-printable mark, as described in the Background section herein. It should be noted that although this document discloses and describes in detail specific methods for forming some non-printing marks, this disclosure does not preclude the use of other methods for forming other non-printing marks on the same printing plate.

[0035] Under normal operation, it is believed that during UV exposure from the back side of the printing plate via photochemical radiation 120, free oxygen molecules 110 from the ambient air tend to diffuse into the printing plate through the LAMs layer 104. This process relates to oxygen inhibition of the polymer chain reaction, where oxygen consumes oxygen within the printing plate as it terminates the polymer chains. As the oxygen content within the printing plate is depleted during curing, fresh oxygen from the ambient air migrates into the polymer and can be used for further polymer chain termination. The movement of oxygen within the printing plate occurs at a certain rate, which limits the availability of oxygen in the printing plate environment during the curing process.

[0036] When the oxygen barrier 111 is placed on top of the LAMs layer 104, not all areas of the polymer are supplied with oxygen from the environment during the back-side curing process. This results in oxygen deficiency above the areas adjacent to the oxygen barrier. Therefore, the substrate grows slightly higher in the areas below the oxygen barrier on the LAMs layer compared to areas not below the oxygen barrier. Accordingly, the oxygen barrier defining one or more patterns forming alphanumeric letters, numbers, or codes can thus be used to create 3D, non-printable structures on the printing plate substrate.

[0037] Figure 2 The image depicts the 3D logo 200 printed on a 3D printer (i.e., four letters arranged in a stylized form to form the brand name "Esko"). Figure 3 The image shows a photograph of the first Esko logo 300, with a printed raised structure of approximately 0.54 mm on or near the top of the printing plate, and the second Esko logo 310, formed by a non-printed raised structure of approximately 25 µm. Figure 3 In the example shown, the printing plate is a NEF 114 (i.e., 1.14 mm thick) plate with a base thickness (including the back substrate) of 0.6 mm.

[0038] Various tools or devices can be used to create oxygen barriers in the form of a desired pattern on LAMs layers. In some embodiments, non-printing markings can be applied through the non-imaging portion of the LAMs during a UV back exposure step, such as, for example, by placing a fully processed flexographic printing plate with the printing side facing the LAMs layer. In this embodiment, the relief formed between the printed structure and the substrate, with the printed structure deployed adjacent to the LAMs layer, creates a gap that allows oxygen to flow in during processing. In another embodiment, a 3D structure (e.g., a 3D printed structure) can be placed on the flat side created by a print bed deployed adjacent to the LAMs. Oxygen barriers can also be deployed as planar layers using markers, metal foil, adhesives, or by applying an oxygen-barrier liquid fluid. In some cases, oxygen-barrier fluids, such as oil, water, or ink, can be used to improve 3D objects (such as...) when the contact surfaces of the object are slightly wetted by the fluid. Figure 2The oxygen barrier effect (of the depicted object). In other embodiments, the oxygen barrier fluid may form the oxygen barrier alone. The oxygen barrier fluid may be applied as a dry liquid. The term "liquid" as used herein refers to any non-gaseous fluid and may also refer to a fluid that also contains particulate or non-liquid components, such as a liquid containing volatile components, such that the applied liquid evaporates, leaving only a dry residue. In embodiments, the oxygen barrier fluid may be applied using a stamp, through an opening in a stencil, or by inkjet printing or ink spraying. As is known in the art, a stencil is a type of mask that typically includes a planar sheet having openings therein, and an exemplary process includes applying a stencil to the surface of a layer of LAMs, applying fluid over the stencil such that the fluid becomes deployed on the LAMs layer in the area defined by the stencil, and then removing the stencil. It should be understood that the term "stencil" as used herein is not limited to any particular type of mask structure and may be construed as referring to any type of temporary mask applied during the fluid application step and subsequently removed.

[0039] Exemplary methods and systems may include using a stamp bearing the production date or location name to apply oxygen-barrier ink to LAMs, preferably in a predetermined repeatable area. The stamp may be applied manually by a human user or automatically by a machine. Another exemplary method and system may include using an inkjet head (e.g., mounted on a movable bracket identical to the front exposure head in an exposure system, or mounted within a digital imager for laser ablation of LAMs layers) to print information on the LAMs layers using oxygen-barrier ink.

[0040] Figure 4An exemplary embodiment of a roller (e.g., an imager) is depicted. As is known in the art, such an imager typically includes a drive mechanism 410 (such as a motor and transmission system, including gears, belt drives, etc., not shown) that rotates roller 402 about a rotation axis in a transverse, circumferential direction and advances a carriage 404 on which an imaging device (e.g., a laser for ablation of LAMs layers) is mounted. The carriage moves in a longitudinal (axial) direction parallel to the roller's rotation axis, controlled by a control system 420 and powered by a power supply 430. The printing plate 406 may be in the form of a sleeve or may be a rectangular sheet, wherein the roller is configured to hold the relative edges of the sheet in place using any of the various clamping systems known in the art as the roller rotates. The mechanisms and details of the operation of such an imaging system are well known in the art and will not be further explained herein. According to an aspect of the invention, an additional inkjet printhead 440 is also deployed on the carriage and connected to an oxygen-barrier ink source 442 and a controller 444 for controlling the deposition of oxygen-barrier ink based on the printhead position according to instructions stored in a memory 446 (e.g., an image defining where the ink should and should not be applied), the instructions (e.g., an image) corresponding to the desired non-printing marks described herein. Although shown with... Figure 4 The imaging system in this embodiment is attached to the same carriage, but it should be understood that other embodiments may feature a dedicated carriage for the inkjet head, or even a dedicated roller and inkjet configuration without an imaging component. In embodiments where the non-printing marks are intended to be located only in a specific area, the carriage with the inkjet head may have a travel limited to a portion of the printing plate that is smaller than the full area of ​​the printing plate (e.g., smaller than the entire longitudinal dimension of the printing plate).

[0041] Figure 5A plan view of an exemplary exposure system embodiment 500 is depicted, including a substrate 502 (i.e., typically glass, through which back-side exposure is transferred) for holding the printing plate. A carriage 510 is configured to travel along the Y direction (arrow A) from a first position 512 through the substrate to a second position 514 in a first path, and then return to the first position in the direction of arrow B in the second path. Thus, the travel envelope of the carriage 510 is delineated by a box 516 marked with a first-style dashed line. Typically, pre-exposure photochemical radiation is emitted during travel in the first path, but not during travel in the second path. In some embodiments, the front and back exposure systems are linked to each other and spaced apart by a predetermined distance to allow for a predetermined, repeatable delay after the back exposure and before the front exposure, and / or can be configured to perform only one or more back exposure steps, as further described in U.S. Patent No. 10,732,507 entitled “PROCESS AND APPARATUS FOR CONTROLLED EXPOSURE OF FLEXOGRAPHIC PRINTING PLATES AND ADJUSTING THE FLOORTHEREOF”, jointly owned by the applicants of this application and incorporated herein by reference. This disclosure is not limited to any particular exposure method or system, and details of various exposure systems are well known in the art and will not be further elaborated herein.

[0042] Embodiments of the invention described herein include an inkjet printhead 520 connected to an ink source (not shown) and configured to scan the printing plate raster-wise along the paths of arrows C and D, starting from a storage location 522, within an envelope defined by frame 524 (marked by dashed lines different from those in frame 516), and guided to a location for dispensing oxygen-barrier ink according to instructions stored in a memory (not shown). In a typical method, after the oxygen-barrier ink has been applied, a back-side exposure is provided from below the exposure glass 502, followed by a front-side exposure. A predetermined, repeatable delay may exist between the back-side and front-side exposures, or the back-side exposure step may be independent of the front-side exposure. Although Figure 5 Not shown, but the ink source, controller for the inkjet printhead, and memory for storing instructions can be... Figure 4 The same configuration is illustrated in the diagram. Although in Figure 5 The printhead is shown as a separate bracket, but it should be understood that the printhead can be deployed on the same structure as the exposure head, especially in systems with a rasterized pre-exposure head, so that the pre-exposure head and the inkjet printhead move together, typically with only one of the exposure head or the printhead operating at a time.

[0043] Figure 4 and Figure 5 The exemplary systems depicted are merely illustrative, and the invention is not limited to any particular structure for mounting a fluid applicator to a roller or flat plate system, or to any particular type of fluid applicator.

[0044] The photopolymer curing process is typically a competition between polymer chain growth and oxygen suppression. Therefore, the effects described herein can be controlled or influenced by the amount of UV energy provided over a given time. As is known in the art, UV energy intensity and exposure time are typically inversely proportional to each other, where an increase in one decreases the other. Reducing the back-side UV intensity, resulting in a relatively longer curing time, will result in a stronger formation of the non-printed markings described herein (i.e., the non-printed markings have a larger protrusion over the substrate and are therefore more visible), while applying relatively high back-side curing energy over a relatively short time will reduce the effects of oxygen migration and result in a smaller effect.

[0045] The oxygen permeability of LAMs layers also affects the visibility of the created non-printed structure. Generally, oxygen-impermeable LAMs layers, or printing plate constructions with dedicated additional oxygen barrier layers, will prevent or mitigate this effect, while LAMs layers with relatively good permeability will support this effect.

[0046] Plate thickness also affects the intensity of the effect. Relatively thin plates, such as flexographic plates of 1.7, 1.14, or 0.76 mm thickness, respectively achieve increasingly visible effects as described herein (all other things being equal), while relatively thicker plates exhibit less visible effects. Systems with relatively unfavorable conditions for creating the effects described herein can benefit from providing a relatively large pattern corresponding to the mark to be created on the substrate, thus improving visibility, compared to the pattern size used in systems with more favorable conditions.

[0047] Although the invention has been illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications to the details may be made within the scope and implications of the equivalents of the claims and without departing from the invention.

Claims

1. A method for creating non-printing marks on a flexographic printing plate, the non-printing marks comprising a structure having a non-printing protrusion above a base of the printing plate, the method comprising the following steps: (a) A photosensitive polymer printing plate precursor is provided, having a front side, a back side opposite to the front side, and a laser ablation mask system (LAMs) layer disposed on the front side; (b) Deploy an oxygen barrier on the LAMs layer having a pattern defining the non-printed markings; as well as (c) The back side of the printing plate precursor is exposed to photochemical radiation while the oxygen barrier remains deployed on the LAMs layer.

2. The method according to claim 1, further comprising: (a1) The LAMs layer is imaged by laser ablation of openings in the LAMs layer, the openings corresponding to a desired image to be formed by printing a structure on the front side of the printing plate; Step (a1) is performed before step (c).

3. The method of claim 2, further comprising, after or during, step (c): (d) Performing a front-side exposure step, which includes exposing the photosensitive polymer printing plate precursor to photochemical radiation through the opening in the LAMs layer.

4. The method according to any one of the preceding claims, wherein the oxygen barrier comprises a planar layer defining the pattern.

5. The method of claim 4, wherein the planar layer comprises foil or adhesive.

6. The method according to any one of claims 1-3, wherein the oxygen barrier comprises a 3D object having a raised embossed structure defining the pattern, wherein there are gaps between adjacent embossed structures to allow airflow therebetween, wherein in step (b), the 3D object is deployed on the LAMs layer, wherein the outer surface of the raised embossed structure faces the LAMs layer.

7. The method of claim 6, wherein the 3D object comprises a portion of a finished printing plate having a structure protruding above its base, the structure defining the pattern.

8. The method according to any one of claims 6 or 7, wherein deploying the oxygen barrier comprises applying a liquid fluid between the LAMs layer and the 3D or planar object defining the pattern.

9. The method according to any one of claims 1-5, wherein deploying the oxygen barrier comprises applying a liquid fluid to the LAMs layer.

10. The method according to any one of claims 8 or 9, wherein the liquid fluid comprises oil, water, ink, or a combination thereof.

11. The method according to any one of claims 9 or 10, wherein, The pattern is defined separately when the liquid fluid is applied or when a dry residue is left after the evaporation of volatile components.

12. The method according to any one of claims 8-11, comprising applying the liquid fluid using an inkjet printer or nozzle.

13. The method according to any one of claims 8-11, comprising applying a template to the LAMs layer, applying the liquid fluid to the template, and removing the template.

14. The method according to any one of claims 8-11, comprising applying the liquid fluid using a marker or stamp.

15. The method according to any one of the preceding claims, comprising selecting the intensity and corresponding duration of the photochemical radiation applied in step (b) for improving or optimizing the formation of the non-printed mark with an operable intensity relative to a shorter corresponding duration.

16. A system for creating non-printing marks on a flexographic printing plate, the non-printing marks comprising a structure having a non-printing protrusion above a base of the printing plate, the system comprising: A photosensitive polymer printing plate precursor having a front side, a back side opposite to the front side, and a laser ablation mask system (LAMs) layer deployed on the front side; A back-side exposure system configured to expose the back side of the printing plate precursor to photochemical radiation; as well as Oxygen barrier having a pattern defining the non-printed markings deployed on the LAMs layer.

17. The system of claim 16, wherein the oxygen barrier comprises a planar layer defining the pattern.

18. The system of claim 16, wherein the oxygen barrier comprises a 3D object having a raised embossed structure defining the pattern, wherein there are gaps between adjacent embossed structures to allow airflow therebetween, the 3D object being deployed on the LAMs layer, wherein the outer surface of the raised embossed structure faces the LAMs layer.

19. The system of claim 18, further comprising a liquid fluid deployed between the outer surface of the LAMs layer and the raised relief structure of the 3D object.

20. The system of claim 17, wherein the oxygen barrier comprises a liquid fluid or a dried residue remaining in a liquid fluid from which the volatile components have evaporated.

21. The system of claim 20, wherein the liquid fluid or the dried residue separately defines the pattern.

22. The system according to any one of claims 19-21, wherein the system further comprises an applicator configured to apply the liquid fluid.

23. The system of claim 22, wherein the applicator is selected from the group consisting of: markers, stamps, and nozzles.

24. The system of claim 22, wherein the applicator comprises an inkjet printer, the inkjet printer comprising a printhead mounted on a carriage of an exposure system or a printhead mounted on an imaging system.

Images