Printing plate precursor

Abstract

There is provided herein a printing plate precursor (PR) comprising a dimensionally stable support (L1), a photosensitive layer (L2) of a photosensitive composition (PC), and optionally a protective layer (L3), wherein said photosensitive composition (PC) comprises a radical initiator or initiator system (RI), optionally an ethylenically unsaturated compound (EC), and a binder (B); and wherein said photosensitive composition (PC) further comprises a plasticizer (P) being a bio-based plasticizer (bio-P), and a peroxide scavenger (PS).

Description

[0001] PRINTING PLATE PRECURSOR

[0002] The present invention relates to the technical field printing plate precursors, in particular printing plate precursors for flexographic printing. A further aspect relates to a method for manufacturing the printing plate precursor and a method of developing the plate into a printing plate, in particular a flexographic printing plate.

[0003] BACKGROUND

[0004] Printing plate precursors are essential in the creation of printing plates, such as flexographic printing plates. Printing plates transfer ink onto a printing surface during a printing process. Such printing plates are created from printing plate precursors. These precursors include specially formulated materials that undergo a specific process to form the final printing plate. The developing process typically involves imaging the precursor to create a desired pattern on the surface. Subsequently, uncured portions of the precursor are removed, leaving a raised relief structure corresponding to a desired image. This final relief structure on the printing plate allows for efficient ink transfer during the printing process. Traditionally, it is possible that printing plate precursors have incorporated fossil based components, such as white oil, mineral oil or a polybutadiene plasticizers (as these components are petroleum derived products). While these materials offer specific functionalities, their reliance on fossil fuels presents environmental drawbacks, including but not limited to depletion of finite resource, pollution, gas emissions. Hence, there is a need to have less fossil based components included.

[0005] SUMMARY OF THE INVENTION

[0006] It is an object of aspects of the invention to produce a relief precursor while being less reliant on fossil based components.

[0007] Thereto, a first aspect of the invention provides the printing plate precursor according to claim 1 , more in particular, there is provided : a printing plate precursor (PR) comprising a dimensionally stable support (LI), a photosensitive layer (L2) of a photosensitive composition (PC), and optionally a protective layer (L3), wherein said photosensitive composition (PC) comprises a radical initiator or initiator system (RI), optionally an ethylenically unsaturated compound (EC), and a binder (B); and wherein said photosensitive composition (PC) further comprises a plasticizer (P) being a bio-based plasticizer (bio-P), and a peroxide scavenger (PS). It was found that by including the combination of peroxide scavenger and plasticizer as described herein, the need to rely on fossil based components in the plate could be reduced. This is beneficial in view from an environmental standpoint. More specifically, the plasticizer is a plant or animal oil, more preferably a plant or fish oil. As such, the need to rely on fossil based plasticizers is reduced. Additionally, the formation of a printing plate that can be obtained using the printing plate precursor is less sensitive to the choice and variation in quality of the plasticizer. Moreover, by having the combination of peroxide scavenger and plasticizer, a more constant final plate quality can be achieved. Indeed, even with an increased choice and variation in plasticizer quality, a desired performance of the final printing plate could be achieved. More in particular, both high quality plasticizers and low quality plasticizers have been found useful to deliver desired performance, specifically when combined with the peroxide scavenger as disclosed.

[0008] Even if the plasticizers have been processed or transported under unsuitable conditions (which could impact plasticizer quality) are found to promisingly deliver on final plate performance. In this manner, the overall production method is improved as well, since there is a higher rate of getting a high-quality final printing plate. Hence, also the production process of the precursor is more robust since it is less depending on plasticizer processing. The more robust process achieves fewer rejects, saving time and money. Furthermore, a streamlined production process reduces wasted materials and minimizes delays.

[0009] Preferably, the plasticizer (P) is present within the photosensitive composition in an amount of at least 3 %, preferably at least 4 % by weight and / or at most 50 % by weight. In this manner, the final hardness property of the printing plate can be adjusted as set as desired.

[0010] Preferably, the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight, preferably more than 15.0 % by weight, even more preferably more than 20 %. By having enough plasticizer, desired plate production properties can be achieved, in particular in view of thermal and / or solvent development, e.g. faster washout speeds can be achieved and consequently the precursor can be developed into the final plate in a faster time.

[0011] Preferably, the peroxide scavenger (PS) is present within the photosensitive composition in an amount of at least 0.15 % by weight. In this manner, a more constant final plate quality is ensured. More preferably, the peroxide scavenger (PS) is present within the photosensitive composition in an amount higher than 0.20 % by weight, preferably higher than 0.25 %, more preferably higher than 0.4 %. In this manner, a higher rate of achieving a desired final plate quality can be ensured. In case the peroxide scavenger (PS) encompasses multiple scavenger types, it is then understood that the sum of all scavengers is taken and should be at least as disclosed herein, in particular at least 0.15 %, preferably higher than 0.20 % by weight, preferably higher than 0.25 %. According to a preferred embodiment, the peroxide scavenger (PS) and the plasticizer (P) are included in the photosensitive composition in a scavenger / plasticizer ratio (Rs), whereby said scavenger / plasticizer ratio (Rs) is determined as : weight percentage of peroxide scavenger (PS) / weight percentage of plasticizer (P) wherein said scavenger / plasticizer ratio (Rs) is higher than 0.003.

[0012] Notably herein, the peroxide scavenger or plasticizer can each respectively encompass one or more scavengers or one or more plasticizer. In this case, the ratio is determined by the weight percentage of all scavengers / plasticizers.

[0013] By having the ratio higher than 0.003, final plate quality is less dependent on plasticizer quality.

[0014] More preferably, the scavenger / plasticizer ratio (Rs) is higher than higher than 0.004, more preferably higher than 0.005, more preferably higher than 0.007, more preferably higher than 0.008, more preferably higher than 0.010, more preferably higher than 0.013, more preferably higher than 0.015, more preferably higher than 0.017. By respecting such ratio (Rs), the final plate quality can be better ensured as there is less dependency on plasticizer quality.

[0015] According to a preferred embodiment, the scavenger / plasticizer ratio (Rs) is higher than 0.003; and the peroxide scavenger (PS) is present within the photosensitive composition in an amount higher than 0.20 % by weight; and / or wherein the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight. Inventive insights have provided that by including the scavenger and plasticizer in carefully chosen amounts and ratio, a high-quality final printing plate can be achieved, even with a variety of plasticizer. In this manner, the production process can be improved as a final plate quality is less depending on plasticizer quality, consequently the production process is more robust.

[0016] According to a preferred embodiment, wherein the scavenger / plasticizer ratio (Rs) is more than 0,020, preferably more than 0,040. In this manner, the reliability of achieving a high quality plate can be further increased.

[0017] It is preferred that one or more scavengers and one or more plasticizer are included into the composition according to a molar ratio (Rm), wherein said molar ratio is determined as: (parts by weight PS (wt%) / molar mass PS (g mol ’) ) / (parts by weight plasticizer P (w%) / molar mass vegetable oil (g / mol) ) / (functionality PS) , wherein PS is representative for the peroxide scavenger, wherein said molar ratio (Rm) is higher than 0.0003, more preferably higher than 0.0040, more preferably higher than 0.0062, more preferably higher than 0.0100.

[0018] For the molar mass of the plasticizer P, the average molecular weight of a triglyceride with the fatty acid distribution specified in the certificate of analysis of the supplier was used. For peroxide scavengers consisting of a mixture of more than one molecule or oligomers, the respective lower end of Rm and higher end of Rm were calculated using the lowest molar mass and lowest functionality as well as the highest molar mass and highest functionality, respectively.

[0019] According to a preferred embodiment, said molar ratio (Rm) is higher than 0.1 , more in particular said molar ratio (Rm) can be in the range of 0.1 - 1.5, such as between 0.2 - 0.9, even more in particular, the plasticizer can be in the range of 1 - 20 % and the ratio (Rm) can be in the range of 0.1 - 1.5.

[0020] According an embodiment, the composition comprises a bio-plasticizer component (e.g a component of P as described herein) and a peroxide scavenger component (e.g. a individual component PS-1, PS-2. . .) that are included within the composition according to a ratio (Rm) of a scavenger component to a bio-plasticizer component, said ratio (Rm) being higher than 0.0003, more preferably higher than 0.0040, more preferably higher than 0.0062, more preferably higher than 0.0100, even more preferably higher than 0,1, more in particular said ratio (Rm) can be in the range of 0.02 - 1.5, more preferably in the range of 0.1 - 1.5, such as between 0.2 - 0.9, even more in particular in the range of 0.4 - 1.5, wherein said ratio is calculated by the following formula: n=amount [mol] of the respective component (e.g component P or PS-1), f = functionality of the respective component (e.g. functionality of PS-1). According to an embodiment, the plasticizer can be present in a wt%-range of 1 - 20 wt% and the ratio (Rm) can be in the range of 0.03 - 1.5, preferably 0.1 - 1.5 in a wt%-range. In case that the composition includes several types of bioplasticizer component (e.g. P) and / or several types peroxide scavenger component (e.g. PS-1 and PS-4), it is then preferred that at least one a bio-plasticizer component (e.g. P) to peroxide scavenger component (e.g. PS-1) combination is included such that the herein mentioned ratio requirements are met. In doing so, it was found that the bio-plasticizer component and peroxide scavenger component included in the ratio together can achieve beneficial results as described herein, believably because of the interrelationship of the peroxide scavenger component being able to improve or ensure the performance of the bio plasticizer component.

[0021] According a preferred embodiment, the plasticizer (P) is present in an amount below 10.0 wt%, e.g. below 9.5 wt% and wherein the molar scavenger / plasticizer ratio (Rm) is more than 0.020, preferably more than 0.05, such as about 0.1. It was found that such composition achieved desired results.

[0022] Notably, “wt%” and “% by weight” or “weight percentage” are used interchangeably herein, and are based on the total weight of the photosensitive composition.

[0023] According to a preferred embodiment, the plasticizer (P) is present in an amount below 10.0 wt%; and wherein the scavenger / plasticizer ratio (Rs) is more than 0.020, more preferably wherein the ratio is more than 0.1, e.g. the ratio can be 0.25. The ratio is greater than 0.020, which means there's more (S) than (P) relative to their weights. In this manner, a high quality plate can be achieved with plasticizer (P) in an amount below 10.0.

[0024] According to a preferred embodiment, the peroxide scavenger (PS) is chosen from a class of any of the following: a phenol, phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine or any combinations thereof, e.g. when the peroxide scavenger encompasses multiple scavenger components. Preferably, at least one phosphite type scavenger is present in the composition to ensure final quality of the plate in case the plasticizer quality changes.

[0025] The peroxide scavenger (PS) as used herein, can encompass one or more scavengers, more specifically, according to a preferred embodiment, the peroxide scavenger (PS) comprises a first scavenger (PSI) and a second peroxide scavenger (PS2) that differs in structure from the first peroxide scavenger (PSI).

[0026] Preferably, the second peroxide scavenger (PS2) is chosen from a class of any of the following: phenol, a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine, more preferably the second peroxide scavenger (PS2) is chosen from a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine. These types have been found to deliver promising results which can address a variety of the plasticizer types as described herein. Preferably, the first peroxide scavenger (PSI) is chosen from a class of any of the following: a phenol, phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine, preferably the first peroxide scavenger (PSI) is chosen from a phenol, and preferably the second scavenger (PS2) is chosen from a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine, preferably a phosphite, a thioether or amine. According to an embodiment, the photosensitive composition comprises a first peroxide scavenger (PSI) chosen from a phenol ; and a second peroxide scavenger (PS2) is chosen from a class of any of the following: a phenol, a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine. Having at least one phenol type scavenger in combination with another scavenger, preferably a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine or combinations thereof have found to deliver synergistic performance. Phenol scavengers can target different harmful molecules like free radicals or reactive oxygen species (ROS). By combining them, with other types, the scavengers can regenerate each other, creating a cycle where one scavenger helps another reactivate. For instance, a phenol scavenger might react with a peroxide (that is formed undesirably), rendering it harmless, while itself becoming inactive. After reactivation, scavenging performance is reestablished which benefits overall final plate quality assurance. It is understood by the disclosure herein, that several scavenger types can be included, in such embodiment the scavenger / plasticizer ratio (Rs) is determined with the weight percentage of all peroxide scavengers (PSI, PS2, ... ) within the composition and / or all plasticizers within the composition. By including the scavengers and plasticizers in the ratio as described herein, final quality of the plate is better ensured.

[0027] Preferably, the plasticizer (P) comprises at least one triglyceride. Triglycerides are preferred (e.g. compared to mono or diglycerides) since a more final quality of the plate is ensured, due to an improved compatibility within the formulation, in particular in combination with the other components as described herein.

[0028] Preferably, the plasticizer (P) has a central glycerol molecule bonded to three fatty acids. It was found that such a component can deliver on desired plasticizing behavior in the photosensitive composition which can facilitate production of the relief precursor.

[0029] The plasticizer (P) to be used, preferably contain carbon atoms including radioactive carbon- 14. In this manner, a desired origin is ensured, in particular such that a non-fossil based component is used. More preferably, said radioactive carbon- 14 is present in the photosensitive composition (PC) in a concentration (C14%) of more than 0.01 * 1010percent, preferably in the range of 0.01 - 1.25 * 1010percent. The concentration can be determined by combustion at 900°C for 2 to 4 hours and measuring isotopic ratios using accelerator mass spectrometry as described by the European norm EN 16640 Bio-based products using the radiocarbon method (2017).

[0030] Preferably, the plasticizer (P) is extracted from one or more of the following, a seed, a fruit, or any other part of a plant or the plasticizer (P) is extracted from is extracted from an animal, such as a fish like the menhaden fish. Several plasticizers can be used, as will be described further herein, one group that has been found useful for the plasticizer (P) is the group consisting of Cottonseed oil, Corn oil, Soybean oil, Rapeseed or Canola oil, Sunflower oil, Safflower oil, Menhaden oil, Castor oil, Coconut oil, preferably Sunflower oil.

[0031] The plasticizer (P) can be a plant or animal oil, more preferably a plant or fish oil. These components can have a variety in quality which can impact final plate performance. To further improve the quality printing plate, it is preferred the plasticizer (P) is selected based on one or more of the following features: an unsaponifiable fraction, a hydroxyl value, an iodine value, content of oleic acid, average molecular weight, inherent oxidative stability index, content of saturated fatty acids with at least 12 carbon atoms.

[0032] Preferably, the plasticizer (P) is characterized by a hydroxyl value (hv) below 200, preferably below 166, more preferably below 150, even more preferably below 100, most preferably below 50. This value gives a measure of the amount of hydroxyl (OH) groups present in a material. It's expressed in milligrams of potassium hydroxide (KOH) per gram of sample (mg KOH / g). It was found that by carefully choosing the type of plasticizer based on hydroxyl value, a good interaction with the other components in the composition could be achieved which benefits final plate quality.

[0033] Preferably, the plasticizer (P) is characterized by an iodine value (iv) below 200, more preferably below 180, more preferably below 170, more preferably below 160, more preferably below 150, even more preferably below 140, most preferably below 120. A higher iodine value indicates a greater number of double bonds or a higher degree of unsaturation in the plasticizer. The iodine value helps to classify oils according to the degree of unsaturation. The iodine value can be calculated for edible oils directly from fatty acid compositions according to AOCS (American Oil Chemists’ Society) Cd 1-85. By having a lower iodine value, the precursor was found to be better resistant to undesired pre curing before development such that upon development, the intentional curing could achieve a more optimal outcome, this can benefit printing properties with the printing plate. Preferably, the plasticizer (P) is characterized by a content of oleic acid (oa%), wherein said oleic acid content is higher than 5%, more preferably higher than 25%, more preferably higher than 50%. In particular preferred embodiments, the plasticizer can have a oleic acid content in the range of 60 - 90 %, such as 80%.

[0034] A high content of oleic acid gives a stable component to use during extrusion and has little yellowing and peroxide formation which benefits plate production and final performance. The oleic acid content can be determined by gas chromatography. For such oleic acid determination, the sample is converted into fatty acid methyl esters (FAMEs) which are then separated and identified by GC. The peak area corresponding to oleic acid methyl ester is then proportional to its concentration in the sample. In particular, content of oleic acid can be determined according to Ph. Eur. [2.4.22].

[0035] Preferably, the plasticizer (P) is characterized by an average molecular weight (MWp) that is higher than 200 g / mol. A higher molecular weight of the plasticizer results in better compatibility with the formulation and dimensional stability of the printing plate precursor. More preferably, the plasticizer (P) has an average molecular weight higher than 500 g / mol, more preferably higher than 600 g / mol, more preferably higher than 700 g / mol, more preferably higher than 800 g / mol, more preferably higher than 850 g / mol, most preferably higher than 875 g / mol.

[0036] Preferably, the plasticizer (P) is characterized by an inherent oxidative stability index (OXSI) below 32.9, more preferably below 10, more preferably below 8, more preferably below 7, more preferably below 6, more preferably below 5, most preferably below 2. By carefully choosing the inherent oxidative stability index in the defined amounts, undesired peroxides can be quenched more efficiently, e.g. with less scavenger.

[0037] The inherent oxidative stability index of the plasticizer can be determined as described in Richard D O’Brien, Fats and Oils: Formulating and processing for applications, CRC Press, Boca Raton, Third Edition, 2008, p. 276 - 283. The oxidative stability of the plasticizer (P), preferably a plant or animal based oil might depend on factors such as the fatty acid composition, the position of unsaturated fatty acids on the glycerol, the level of isomerized fatty acids, the presence of natural or added antioxidants and the metal content. Several factors contribute to the susceptibility towards oxidation: Cis fatty acids oxidize more readily than trans fatty acids, conjugated double bonds are more reactive than nonconjugated bonds and polyunsaturated fatty acids are more reactive than saturated ones.

[0038] Preferably, the Inherent Oxidative Stability Index (OXSI) of the plasticizer is in the range of 0 to 50, preferably in in the range of 0 to 40, more preferably in the range of 0 to 35, even more preferably in the range of 0 to 20, most preferably in the range of 1 to 15. It was found that by having a plasticizer with such OSI value, that high quality printing plates could be obtained. Preferably, the plasticizer (P) is characterized its Gardner Color (GC). The Gardner Color Scale is a one-dimensional scale used to measure the shade of the color yellow. The Gardner scale and the APHA / Pt-Co / Hazen Color Scale overlap with the Gardner scale measuring higher concentrations of yellow color and the APHA scale measuring very low levels of yellow color. Colors of transparent liquids have been studied visually since the early 19th century. Changes in color can indicate contamination or impurities in the raw materials, process variations, or degradation of products over time. Advantageously, the plasticizer is characterized by a Gardner color lower than 7 according to ISO 4630:2015.

[0039] Preferably, the plasticizer (P) is characterized by a content of saturated fatty acids (FTTY %) with at least 12 carbon atoms, wherein said content is below 95%, more preferably below 90%, more preferably below 80%, more preferably below 70%, more preferably below 60%, even more preferably below 50%, most preferably below 40%. A lower content of saturated fatty acids results in a better compatibility with the formulation and the thermoplastic elastomer. Even more preferably, the content of saturated fatty acids of the plasticizer is in the range of 0 - 50%, more preferably 0 - 40%, even more preferably in the range of 0 - 30%. The content of saturated fatty acids or fatty acid distribution within the plasticizer can be measured by gas chromatography of the fatty acid methyl esters (Method according to Ph. Eur. [2.4.22]). The content of saturated fatty acids with at least 12 carbon atoms is the sum of the content of all fatty acids with at least 12 carbon atoms and without double bond. For example, 14:0 myristic acid: The first number describes the number of carbon atoms and the second number describes the amount of double bonds. According to a particular embodiment, the plasticizer is chosen as an oil having content of saturated fatty acids of the plasticizer is in the range of 0 - 50 %, more preferably 0 - 40 %, even more preferably in the range of 0 - 30%. Exemplary preferred oil species are represented in the table below.

[0040] When the fatty acid distribution is known, the average molecular weight of a triglyceride can be determined by using the molecular weight of the respective fatty acids according to the respective content, adding the molecular weight of glycerol and subtracting the molecular weight of the water formed in an esterification.

[0041] According to an embodiment, the plasticizer (P) is characterized by a content of saturated fatty acids with at least 12 carbon atoms, wherein said content is below 95 wt%, more preferably below 90 wt%, more preferably below 80 wt%, more preferably below 70 wt%, more preferably below 60 wt%, even more preferably below 50 wt%, most preferably below 40 wt%. According to an embodiment, the content of saturated fatty acids of the plasticizer is in the range of 0 - 50 wt%, more preferably 0 - 40 wt%, even more preferably in the range of 0 - 30 wt%. Surprisingly, a lower content of saturated fatty acids results in a better compatibility with the formulation and the thermoplastic elastomer. According to a particular embodiment, the plasticizer is an oil having a content of saturated fatty acids in the range of 0 - 50 wt%, more preferably 0 - 40 wt%, even more preferably in the range of 0 - 30 wt%.

[0042] Preferably, the plasticizer (P) is characterized by an unsaponifiable fraction (imp f), in particular a fraction consisting of one or more of beta-sitosterol, avenasterol, campesterol, stigmasterol, waxes, wherein said fraction is below 10 wt%, more preferably below 5 wt%, even more preferably below 3 wt %, most preferably below 1.5 wt %. By limiting this fraction, the final quality of the printing plate can be improved. The unsaponifiable fraction (imp f) can be determined by according to Ph. Eur. [2.5.7],

[0043] Preferably, the plasticizer is characterized by a UV transmission at 365 nm of a solution of 5 wt% plasticizer in n-hexane of higher than 30%, more preferably higher than 50%, more preferably higher than 60%. The UV transmission at 365 nm is measured in n-hexane with a plasticizer concentration of 5 percent by weight in a macro-cuvette 110-QS, 10 mm (Varian Cary 50, scan Software version: 02.00, beam mode: Dual Beam, baseline correction with a blank sample of pure n-hexane). Advantageously, the plasticizer is characterized by a light transmission in comparison to mediumchain triglycerides (MCT)-oil (= 100% transmission) of higher than 78%. The measurement of the transparent MCT-oil, which is more resistant towards oxidation due to the lack of double bonds, is set as standard with 100% light transmission. The light transmission measured by filling the pure oil was in a macro-cuvette 110-QS, 10 mm, putting the cuvette in a densitometer Gretag Macbeth D 200 II (measuring tube: V (I), measuring aperture: 3 mm diameter) and pressing the probe head on the macro-cuvette. The measurement of the transparent MCT-oil, which is resistant towards oxidation due to the lack of double bonds, is set as standard with 100% transmission. The mean value of 3 measurements is determined.

[0044] Preferably, the peroxide scavenger (PS) is characterized by a polar surface area (PSA) that is higher than 20 A2, preferably higher than 22 A2, even more preferably than 25 A2. It has been found that by choosing the polar surface of the peroxide scavenger as such, the interaction with the plasticizer can be improved which benefits final print plate quality. The polar surface area can be determined by computation with cactus 3.4.8.18. Preferably, the polar surface area of the peroxide scavenger (PS) is in the range of 20 A2- 100 A2, more preferably 20 A2- 80 A2. According to an embodiment, the polar surface area of the peroxide scavenger (PS) is in the range of 22 A2- 100 A2, more preferably 22 A2- 80 A2.

[0045] According to a preferred embodiment, the plasticizer (P) is a plant oil; and wherein the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight, based on the total content of the photosensitive composition; wherein the photosensitive composition (PC) comprises a first scavenger (PSI) and a second peroxide scavenger (PS 2) that differs in structure from the first peroxide scavenger (PSI); wherein the first peroxide scavenger (PSI) is chosen a class chosen from a phenol; and wherein the second peroxide scavenger (PS2) is chosen from a phenol, a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine; and wherein the scavenger / plasticizer ratio (Rs) is more than 0.020. In this manner, the benefits described are even more significant. The combination of the different scavengers as defined allows that a high quality printing plate can be obtained while being less sensitive to the choice and variation in quality of the plasticizer. Hence, even with an increased choice and variation in plasticizer quality, a desired performance of the final printing plate could be achieved.

[0046] Preferably, the peroxide scavenger (PS) is characterized by a partition coefficient (logP), also referred to herein as the logP value, that has a value higher than 5, more preferably higher than 6, even more preferably higher than 10. The partition coefficient, often referred to by its logarithm (logP), can be used to ensure that the peroxide scavenger distributes itself as desired in the photosensitive composition, such that peroxide can be scavenged in an improved manner. Wherein the partition coefficient (logP) can be determined via advanced Chemistry Development (ACD / Labs) Software VI 1.02 (© 1994-2024 ACD / Labs). The software indicates the logP (octanol-water partition coefficient). Preferably, the plasticizer (P) is characterized by a partition coefficient (logP), also referred to herein as the logP value, that has a value between 2 to 50, preferably between 5 to 40, more preferably between 10 to 35. According to an embodiment, the absolute difference in logP value (delta LogPpps) between the plasticizer (P) and the peroxide scavenger is less than 40, preferably less than 30. It is believed that by having similar LogP, the interaction between the plasticizer (P) and the scavenger (PS) can be improved.

[0047] Preferably, the peroxide scavenger (PS) is characterized by molecular weight (MWps) that is higher than 220 g / mol. In this manner, the diffusion of the scavenger within the composition limited such that the scavenger better stays in place to perform it’s scavenging function. More preferably, the peroxide scavenger (PS) is characterized by a molecular weight (MWps) that is higher than 225 g / mol, preferably higher than 300 g / mol, more preferably higher than 400 g / mol, even more preferably higher than 500 g / mol. In this manner, the mobility of the peroxide scavenger is restricted, by limiting diffusion, the scavenger stays put and offers targeted protection.

[0048] Preferably, the plasticizer (P) is a plant oil ; and wherein the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight, based on the total content of the photosensitive composition. Preferably, the peroxide scavenger (PS) is characterized by a polar surface area that is higher than 22 A2, in this manner the interaction with the plasticizer can be improved which benefits the final print plate quality.

[0049] Preferably, photosensitive composition (PC) comprises a first scavenger (PSI) and a second peroxide scavenger (PS2) that differs in structure from the first peroxide scavenger (PSI), more preferably the first peroxide scavenger (PSI) is chosen from a phenol; and wherein the second peroxide scavenger (PS2) is chosen from a phenol, a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine, even more preferably the second peroxide scavenger (PS2) is chosen from second peroxide scavenger (PS2) is chosen from a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine. In this manner, a desired final plate performance can be achieved, even with several kinds of bio based plasticizers.

[0050] Preferably wherein the scavenger / plasticizer ratio (Rs) is more than 0.020. In this manner, a desired final plate performance can be achieved, even with several kinds of bio based plasticizers.

[0051] Preferably, the peroxide scavenger (PS) is present within the photosensitive composition in an amount of more than 2%, preferably in the range of 2 % to 9 % by weight , based on the total content of the photosensitive composition. In this manner, a desired final plate performance can be achieved, even with kinds of bio based plasticizers of which the quality may have been reduced, e.g. during transport or storage. The dimensionally stable support (LI) preferably forms a substrate on which the photosensitive composition (PC) is arranged as a photosensitive layer (L2). More in particular, the dimensionally stable support (LI) is a stable plate substrate on which the photosensitive composition is arranged as a photosensitive layer (L2).

[0052] A further aspect of the invention provides: a production process for producing a printing plate precursor, wherein the production process comprises: provision of a dimensionally stable support (LI); arranging a photosensitive composition (PC) on the dimensionally stable support (LI), preferably to form a photosensitive layer (L2) thereon; wherein the photosensitive composition (PC) is the composition as described herein, more in particular, wherein the photosensitive composition comprises the following components: a radical initiator or initiator system (RI), optionally an ethylenically unsaturated compound (EC), and a binder (B); and wherein said photosensitive composition (PC) further comprises the components: a plasticizer (P) being a bio-based plasticizer (bio-P), and a peroxide scavenger (PS). Any of these components can have the features as described herein.

[0053] By using the photopolymerizable or photosensitive composition (PC) as described herein, the production of the precursor can be improved, specifically, there is no need to test each plasticizer batch before production, which increases productivity and minimizes costs.

[0054] Preferably, the photosensitive composition (PC) is melted and arranged on the support (LI) by extrusion. In this manner, the photosensitive composition can be arranged with precision process control. Namly, extrusion allows for the precise control of production conditions of the melted photosensitive composition (PC). Furthermore, extrusions allows to include improved layer uniformity, enhanced accuracy and control, increased efficiency and scalability, and reduced material waste. More preferably, the photosensitive composition (PC) is calendared via a slot die between a cover film, preferably a cover film with laser-ablatable mask layer and a dimensionally stable support, preferably a carrier film.

[0055] By including the photosensitive composition as described herein, one allows the use of a melt having a complex shear viscosity r|* at 160 °C higher than 50 Pa s, more preferably higher than 100 Pa s, more preferably higher than 200 Pa s, more preferably higher than 300 Pa s. In this manner, the layer can be thicker and more resistant to shearing forces which can create a layer with improved properties.

[0056] A further aspect of the invention provides: a method of developing the printing plate precursor (PR) into a printing plate (PL), wherein said precursor is developed into a printing plate (PL) according to : exposing the relief precursor layer to a source of radiation to cure the photopolymerizable composition (PC) and to form a relief image; and removing uncured portions of the relief precursor layer to form a printing plate, wherein the relief image defines ink-receiving regions and non-ink- receiving regions of the printing plate.

[0057] The printing plate precursor can have any of the features as described herein.

[0058] A further aspect provides: a printing plate, obtained from the printing plate precursor as described herein, having a micro hardness between 20opShA and 80opShA, more preferably between 25opShA and 70opShA. It was found that by setting the hardness of the plate as such, that the plate can provide for achieving desired ink density and maintaining good print quality with sharp details.

[0059] While embodiments are described herein, it is to be understood that the invention is not limited to these specific embodiments. All combinations of the technical features described in this application are considered to be encompassed.

[0060] DETAILED DESCRIPTION

[0061] The Printing Plate Precursor (PR)

[0062] The relief precursor (RP) includes a photosensitive composition (PC) typically as a photopolymer layer (also called photosensitive layer L2) as defined herein, which is applied on a dimensionally stable support (LI), also referred to as a dimensionally stable carrier layer (LI). Such support layer can be a PET sheet. Preferably, the carrier layer LI comprises a metal sheet, a steel, an alloy, a natural or artificial polymer, a polymer blend, a polymer film, or any combination thereof. Examples of suitable dimensionally stable carriers are plates, foils, and also conical and cylindrical tubes, known as sleeves, made of metals such as steel, aluminum, copper or nickel, or of plastics such as polyethylene terephthalate, polybutylene terephthalate, polyamide or polycarbonate, of wovens or nonwovens such as woven glass fiber fabric, or of composite materials composed of glass fibers and plastics. Particularly suitable as dimensionally stable carriers are dimensionally stable carrier foils or metal sheets, examples being polyethylene or polyester foils or steel or aluminum sheets. The carrier foils or metal sheets have a thickness, generally speaking, of 50 to 1500 pm, preferably 75 to 400 pm, for example around 250 pm. If steel is used as carrier material, steel sheets having a thickness of 0.05 to 0.3 mm are preferred. For protection against corrosion, preference is given to using tin-plated steel sheets. These carrier foils or carrier sheets may be coated with a thin, adhesionpromoting layer, for example a layer 0.1 pm to 2 pm thick, on the side of the carrier foil facing the radiation-curable, relief-forming layer. In a preferred embodiment, the carrier layer is a PET carrier layer made from polyethylene terephthalate. Preferably, photosensitive layer L2 has a thickness of in the range of 25 pm to 7000 pm, preferably 0.01 to 4 mm, more preferably 0.02 to 3 mm, and very preferably 0.03 mm to 3 mm. The relief furthermore comprise a mask layer L3, the mask layer comprising at least a compound capable of absorbing electromagnetic radiation and a component capable of being removed by ablation (also known as digital plate precursor). The references LI, L2 and L3 for the layers can but are in no way intended to be limited to a particular sequence. The relief precursor may include further layers if needed, e.g. an oxygen blocking barrier layer, an adhesion layer, a release layer or a disbonding layer, UV / VIS light and / or IR light absorbing layer, a monomer diffusion control layer, a surface control layer, a protection layer, a cover foil, a cover film or combinations thereof. In an embodiment, there may be an adhesion coating layer with an optional top coating layer thereon. Such adhesion coating layers may be, for example, layers of polyurethane adhesion coating materials, as described in DE3045516 for example. Preferably the mask layer is an integral layer of the relief precursor and is in direct contact with the photosensitive layer or with a functional layer disposed between photosensitive layer and mask layer. This functional layer is preferably a barrier layer and blocks oxygen. The mask layer may be imageable by ablation and removable by solvents or by thermal development. The mask layer is heated and removed by irradiation with high energy electromagnetic radiation, whereby an image wise structured mask is formed, which is used to transfer the structure onto the relief precursor. In order to do so the mask layer may be non-transparent in the UV region and absorb radiation in the VIS-IR region of the electromagnetic spectrum. The VIS-IR radiation may then be used to heat and ablate the layer. The optical density of the mask layer in the UV region between 330 and 420 nm is in the range of 1 to 5, preferably in the range of 1.5 to 4 and more preferably in the range of 2 to 4. The layer thickness of the ablatable mask layer may be in the range of 0.1 to 5 pm, preferably 0.3 to 4 pm, more preferably

[0063] 1 to 3 pm. The laser sensitivity of the mask layer (measured as energy needed to ablate 1 cm2) may be in the range of 0.1 to 10 J / cm2, preferably in the range of 0.3 to 5 J / cm2, most preferably in the range of 0.5 to 5 J / cm2.

[0064] The terms “photosensitive” or “photopolymerizable” composition or mixture are used interchangeably herein. Understandably, the photosensitive composition (PC) as described herein may on its own have desired technical benefits, hence according to an aspect, there is provided the photosensitive composition (PC) as described herein. In the context of relief precursors (also described herein as printing plate precursor), the photosensitive composition (PC) is typically present as a photosensitive layer, also described herein as a relief forming layer (L2). Typically, the composition (PC) has at least the following components:

[0065] Radical Initiator (R)

[0066] Useful radical initiators are chemicals that decompose under specific conditions (like light or heat) to generate free radicals. Free radicals are highly reactive molecules with an unpaired electron, making them prime candidates to initiate polymerization reactions usable in the curing of the photosensitive composition, e.g. when developing the relief precursor into the printing plate. The following compounds are found useful as initiators: Azo Compounds: These are thermally or photolytically decomposable initiators. Examples include 2,2'-Azobis(2-methylpropionamidine) (AMPD) and l,l'-Azobis(N,N-dimethylformamide) (ADMF). Benzoyl Peroxides: Thermally decomposing initiators that can be effective at moderate temperatures. Examples include benzoyl peroxide and tert-butyl peroxide. Acylphosphine Oxides: These are photoinitiators that offer good sensitivity to specific wavelengths of light. Examples include 2,4,6- trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Particular preference goes to a benzil dimethyl ketal as an initiator. Combination Initiators: For a wider range of processing options, the composition might include a combination of initiators, such as a blend of a thermally activated and a photoactivated initiator. This allows for potential fine-tuning of the curing process.

[0067] Ethylenically unsaturated compound (EC)

[0068] An Ethylenically Unsaturated Compound (EC) refers to a molecule containing a carbon-carbon double bond (C=C). This double bond facilitates in the photopolymerization process to achieve the raised image areas on the plate. The presence of the C=C double bond makes ECs highly reactive. Common ECs used in plate precursors include: Acrylates: These are monomers with an acrylate functional group (CH2=CH-COO-).

[0069] Examples include methyl methacrylate (MMA) and butyl acrylate (BA). Methacrylates: Similar to acrylates, but with a slightly different functional group (CH2=C(CH3)-COO-). Examples include methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA). Styrene: A common monomer with a vinyl group (CH2=CH-). Preferably, the photopolymer layer (also referred to as photosensitive layer) comprises further at least one component with at least one unsaturated group. Preferably, these components are reactive compounds or monomers which are suitable for the preparation of the mixtures are those which are polymerizable and are compatible with the binders. Useful monomers of this type generally have a boiling point above 100 °C. They usually have a molecular weight of less than 3000 g / mol, preferably less than 2000 g / mol. More preferably, the ethylenically unsaturated monomers are used that ought to be compatible with the binders, and they have at least one polymerizable, ethylenically unsaturated group. As monomers it is possible in particular to use esters or amides of acrylic acid or methacrylic acid with mono- or polyfunctional alcohols, amines, aminoalcohols or hydroxyethers and hydroxyesters, esters of fumaric acid or maleic acid, and allyl compounds. Esters of acrylic acid or methacrylic acid are even more preferred. Preference is given to 1 ,4-butanediol diacrylate, 1 ,6-hexanediol diacrylate, 1 ,6-hexanediol dimethacrylate, 1 ,9-nonanediol diacrylate, or trimethylolpropane tri(meth)acrylate. Mixtures of different monomers can of course be used. The total amount of all the monomers used in the reliefforming layer together is generally 1 to 20 wt%, preferably 5 to 20 wt%, based in each case on the sum of all the constituents of the relief-forming layer. The amount of monomers having two ethylenically unsaturated groups is preferably 5 to 20 wt%, based on the sum of all constituents of the relief-forming layer, more preferably 8 to 18 wt%.

[0070] Binder (B)

[0071] A suitable binder can be included into the photosensitive composition, e.g. depending on the final printing application. According to an embodiment, the binders can be linear, branched or dendritic polymers, which may be homopolymers or copolymers. Copolymers can be random, alternating or block copolymers. As binder, those polymers, which are either soluble, dispersible or emulsifiable in either aqueous solutions, organic solvents or combinations of both are used. Suitable polymeric binders are those conventionally used for the production of letterpress printing plates, such as completely or partially hydrolyzed polyvinyl esters, for example partially hydrolyzed polyvinyl acetates, polyvinyl alcohol derivatives, e.g. partially hydrolyzed vinyl acetate / alkylene oxide graft copolymers, or polyvinyl alcohols subsequently acrylated by a polymer-analogous reaction, as described, for example, in EP-A-0079514, EP-A-0224164 or EP-A-0059988, and mixtures thereof. Also suitable as polymeric binders are polyurethanes or polyamides, which are soluble in water or water / alcohol mixtures, as described, for example, in EP-A-00856472 or DE- A- 1522444. In this case, the printing plate can achieve particular beneficial results when used as letterpress printing plate. For flexographic printing plates, preferably elastomeric binders are used.

[0072] The preferred binder (B) is a thermoplastic elastomer block copolymer, e.g. a diblock copolymer or triblock copolymer. A thermoplastic is a class of polymer that can be softened through heating and then processed. This behavior is advantageous and cause the possibility of producing relief precursor in larger volumes, e.g. by extrusion. Also, processes like injection molding, thermoforming and blow molding can be used when using thermoplastic elastomer block copolymer binders. The choice of thermoplastic binder is advantageous over e.g. SBR rubbers (belonging to the thermoset elastomers) which do not perform well in high volume extrusion production processes. The binder (B) has a first monomer unit being a vinyl aromatic monomer and a second monomer unit, said second monomer unit being an ene-monomer and / or a diene-monomer. An ene-monomer refers to a monomer that contains a carbon-carbon double bond (C=C) in its molecular structure. A diene-monomer refers to a monomer that contains two carbon-carbon double bonds (C=C=C) in its molecular structure. The vinyl aromatics may be, for example, styrene, a-methylstyrene, or vinyltoluene. Styrene is preferable. The dienes are preferably butadiene and / or isoprene. These block copolymers may be linear, branched, or radial block copolymers. Generally speaking, they are triblock copolymers of the A-B-A type, but they may also be diblock polymers of the A-B type, or may be polymers having a plurality of alternating elastomeric and thermoplastic blocks. A-B-A-B-A, for example. In addition star like copolymers and / or branched copolymers may be used or combinations thereof. Mixtures of two or more different block copolymers may also be used. Commercial triblock copolymers frequently include certain fractions of diblock copolymers. The diene units may be 1,2- or 1,4-linked. The double bonds in the backbone of the binders provide a crosslink capability between, among others, the binders in the photosensitive layer causing the curing upon exposure of the relief precursors. Also possible for use, furthermore, are thermoplastic elastomeric block copolymers with styrene and blocks and a random styrene-butadiene middle block. Use may also be made, of course, of mixtures of two or more thermoplastic-elastomeric binders, provided that the properties of the relief-forming layer are not negatively impacted as a result. As well as the stated thermoplastic- elastomeric block copolymers, the photopolymerizable layer may also comprise further elastomeric binders other than the block copolymers. With additional binders of this kind, also called secondary binders, the properties of the photopolymerizable layer can be modified. Examples of a secondary binder are vinyltoluene-a-methylstyrene copolymers. These polymer binders account for in general from 20 to 98%, preferably from 50 to 90% by weight of the total composition. Copolymers, such as styrene -butadiene-styrene (SBS) or styrene-isoprene-styrene (SIS) diblock or triblock copolymers, exhibit benefits over random copolymers, e.g. styrene-butadiene rubber SBR. Random copolymers such as SBR are not to be confused with the styrene-butadiene block copolymer, although being derivable from the same monomers. Random SBR is often used for elastomeric products such as tires, shoe soles, or seals. Due to its irregular molecular structure, SBR does not have a well pronounced microphase separation. As a result, uncured SBR polymers without fillers would not keep their shape during storage. Thus, the addition of filler materials as well as contemporary curing of SBR is required to preserve the shape and to enhance its physical properties. Nevertheless, any filler material added to a printing plate precursor formulation would scatter the UV light and disturb the crosslinking process during intentional curing by UV light. By curing of SBR, which is realized typically by reaction with sulfur, the filler enhanced SBR polymer becomes elastomeric. As the structure is preserved by chemical bonds, cured SBR decomposes under heat rather than melts, and is therefore no thermoplastic. In contrast to (thermoset) SBR random polymers, styrene-butadiene block copolymers are thermoplastic elastomers. They can be melted, mixed and shaped under heat without the need of a solvent. The block copolymer configuration of e.g. SBS or SIS results in a microphase separation of polystyrene and polybutadiene or polyisoprene domains. The elastomeric behavior roots in this network of physical cross-links with an elastic block (polybutadiene) and a restraining block (polystyrene). Printing plate precursors based on styrenebutadiene block copolymers do mostly keep their shape also during longer storage times, typically for one to two years after production. A long storage time is essential for printing plate precursors, as curing of the printing plate precursors takes place not at the production site but rather at repro houses or printing facilities. To conclude, in contrast to block copolymers, SBR as a random copolymer is not a suitable binder for printing plate precursors. Examples of binders are shown below.

[0073] SBR random polymer Block copolymer SBS and SIS

[0074] It is preferred that the binder has a total styrene content in the range of 3 - 50 %, preferably 8 - 38 %, more preferably 10 - 35 %, most preferably 14 - 32 %. These ranges improve the Newtonian behavior of the binder and can set both kinematic and dynamic viscosities of the binder suitable for extrusion production.

[0075] Preferably, the binder is chosen from the binder (B) is chosen from a styrene -butadiene-styrene (SBS) triblock copolymer and / or a styrene-isoprene-styrene (SIS) triblock copolymer. In an embodiment, the binder is chosen from an SBS triblock copolymer having a styrene content in the range of 8 - 48 %, preferably 13 - 43 %, more preferably 18 - 38 %, e.g. around 28 %. In an embodiment, the binder is chosen from a SIS triblock copolymer having a styrene content in the range of 3 - 27 %, preferably 5 - 25 % e.g. around 15 %. In an embodiment, the binder is a diblock copolymer or has triblock copolymer with a diblock fraction in the range of 5 - 30 %, preferably 8 - 28 %, more preferably 10 - 24 %, e.g. around 17 % or 19%. Such fractions has been found to be suitable for extrusion processing.

[0076] Additives

[0077] In addition to the plasticizer component (P), the photosensitive composition (PC) may comprise modified and unmodified natural oils and natural resins, such as high- boiling paraffinic, naphthenic or aromatic mineral oils, synthetic oligomers or resins such as oligostyrene, high-boiling esters, oligomeric styrene-butadiene copolymers, oligomeric alpha-methylstyrene / p-methylstyrene copolymers, liquid oligobutadienes, especially those having a molecular weight of 500 to 5000 g / mol, or liquid oligomeric acrylonitrile -butadiene copolymers or oligomeric ethylene-propyl-ene-diene copolymers. Preference is given to polybutadiene oils (liquid oligobutadienes), especially those having a molecular weight of 500 to 5000 g / mol, high-boiling aliphatic esters such as, in particular, alkyl esters of monocarboxylic and dicarboxylic acids, examples being stearates or adipates and mineral oils.

[0078] Plasticizer (P)

[0079] In view of environmental developments, preferably “bio-based plasticizers” are used as plasticizer within the photosensitive composition. Such biobased plasticizers are at least partially derived from renewable, biological resources such as plants (e.g. agricultural crops or wood), microorganisms (e.g. algae or yeasts), or animals.

[0080] Bio-based plasticizers are environmental friendly, often but not necessary biodegradable. Bio-based materials may be chemically altered, or modified with synthetic compounds, to change for example physical and / or chemical properties. They then still remain bio-based materials. These plasticizers are generally used to maintain softness and flexibility at varying temperature ranges. These plasticizers can at least partly replace other plasticizers, like synthetic plasticizers. Many of the non- bio-based plasticizers, especially the so-called phthalates, are harmful to one's health and may affect the hormone balance. Others are mineral oil or polybutadiene based and not easily biodegradable. It is thus advantageous to at least partly replace them by bio-based plasticizers. We furthermore found that when bio-based plasticizers are being used that for thermal development, a higher relief depth can be achieved for all concentrations investigated. Moreover, the inventors found that using for example rapeseed oil instead of mineral oil this allows for higher washout speeds and results in shorter process times. More preferably, the bio-based plasticizer is one or more of rapeseed oil, sunflower oil, soybean oil, palm oil, palm kernel oil, coconut oil, medium-chain triglycerides (MCT) oil and / or linseed oil. Further examples are acai oil, adeps lanae, ahiflower oil, algea oil, aloe vera, amaranth oil, apricot kernel oil, argan oil, avocado oil, babassu oil, baobab oil, beeswax, black cumin oil, black cumin seed oil, blackcurrant oil, borage oil, brazilnut oil, broccoliseed oil, calendula oil, camelina oil, candelilla wax, carnauba wax, castor oil, cocoa butter, chia oil, Chilean hazelnut oil, cocoa butter, corn oil, cotton seed oil, cupuacu butter, evening primrose oil, fish oil, glycerol, grape seed oil, groundnut oil, hazelnut oil, hemp oil, high-oleic canola oil, high oleic soybean oil, high oleic sunflower oil, illipe butter, jatropha curcas oil, jojoba oil, kukuinut oil, lanolin, laurel oil, macadamia nut oil, marula oil, mango butter, manketti oil, marula oil, meadowfoam seed oil, milk thistle oil, moringa oil, murumuru butter, mustardseed oil, olive oil, olus oil, omega-3-6-9-oil, palmolein, palm stearin, paradise nut oil, passionfruit seed oil, peach kernel oil, peanut oil, pecan nut oil, perilla oil, pistachio nut oil, plum kernel oil, pomegranate oil, poppyseed oil, pumpkin seed oil, rapeseed oil hydrogenated, raw wool grease, rice bran oil, rose hip kernel oil, sacha inchi oil, safflower oil, sal fat, sea buckthorn oil, sesame oil, shea butter, soybean oil hydrogenated, soybean oil partially hydrogenated, squalane, sunflower oil hydrogenated, sunflower wax, sumac wax, tallow, tamanu oil, walnut oil, wheat germ oil, wool fat, wool alcohols.

[0081] Different types of plasticizer might be combined to fine-tune the properties of the layer. E.g. another bio-based plasticizer can be used in as an alternative or in addition to the plasticizers described above. The amount of a plasticizer present can be determined according to the desired properties of the layer.

[0082] Preferably the plasticizer (P) is derived from a plant or animal oil, more preferably a plant or fish oil.

[0083] However, the quality of the plasticizer can depend on various factors such as origin (crop type, animal type) processing conditions, storage conditions and the like. It is therefore preferred that the plasticizer is chosen according one or more of the following Plasticizer Parameters.

[0084] Plasticizer Parameters

[0085] It has now surprisingly be found that the performance both during production and of the printing plate can be improved by including the combination of the scavenger and the plasticizer as described herein.

[0086] The type of plasticizer (P) is preferably characterized by any one or any combination of the following parameters: an unsaponifiable fraction, a hydroxyl value, an iodine value, content of oleic acid, average molecular weight, inherent oxidative stability index, content of saturated fatty acids with at least 12 carbon atoms.

[0087] These parameters of the plasticizer relate to the properties of the plasticizer, specifically it’ s chemical composition and how it performs during development of the precursor and how it impacts final printing plate.

[0088] After extensive testing, the inventors made findings (see preferred values) on the plasticizer parameters to achieve improved results for the printing plate.

[0089]

[0090] According to an embodiment, the plasticizer comprises one or more components chosen from the group consisting of: glycerol tricaproate (logP = 6.330+0.264, CAS: 621-70-5), glycerol tricaprylate (logP = 9.387+0.264, CAS: 538-23-8), glycerol tricaprin (logP = 12.444+0.264, CAS: 621-71-6), glycerol trilaurate (logP = 15.501+0.265, CAS: 538-24-9), glycerol triricinoleate (logP = 18.003+0.382, CAS: 2540-54-7), glycerol trimyristate (logP = 18.558+0.265, CAS: 555-45-3), glycerol trilinolenate (logP = 20.747+0.417, CAS: 14465-68-0), glycerol tripalmitate (logP = 21.615+0.265, CAS: 555-44-2), glycerol trilinoleate (logP = 22.233+0.389, CAS: 537-40-6), glycerol triolein (logP = 23.444+0.279, CAS: 122-32-7), glycerol tristearate (logP = 24.672+0.265, CAS: 555- 43-1), glycerol trierucate (logP = 29.558+0.279, CAS: 2752-99-0), glycerol tribehenate (logP = 30.786+0.266, CAS: 18641-57-1).

[0091] Peroxide scavenger (PS)

[0092] The peroxide scavenger (PS) as used herein can encompass one or more scavenger components. Usable peroxide scavenger (PS) shall now be discussed. Preferably, the one or more scavengers are included into the composition, particularly in the concentration as disclosed herein and / or in accordance with the scavenger to plasticizer ratio (Rs or Rm) as disclosed herein.

[0093] Notably, when applicable, the concentration and ratio of plasticizer (P) and scavenger (PS) are determined by the one or more respective plasticizer or scavenger components encompassed by the plasticizer (P) and scavenger (PS).

[0094] Preferably, the peroxide scavenger (PS) is chosen from one or more of the following scavenger types.

[0095] Non-hindered phenol

[0096] The scavenger (PS) can encompass one or more of the following components:

[0097] Phenol (CAS: 108-95-2) (2R)-2,8-Dimethyl-2-[(4R,8R)-4,8,12-trimethyltridecyl]-2H-l- benzopyran-6-ol (CAS: 119-13-1)

[0098] Hindered phenols with one or two methyl groups in ortho position with regard to the hydroxyl group

[0099] The scavenger (PS) can encompass one or more of the following components:

[0100] (2R)-2,5,7,8-Tetramethyl-2-[(4R,8R)-4,8,12-trimethyltridecyl]-3,4-dihydro-2H-l- benzopyran-6-ol (CAS: 59-02-9)

[0101] (2R)-2,5 ,8-Trimethyl-2- [(4R,8R)-4, 8 , 12-trimethyltridecyl] -3 ,4-dihydro-2H- 1 -benzopyran- 6-ol (CAS: 16698-35-4)

[0102] (2R)-2,7,8-Trimethyl-2- [(4R,8R)-4, 8 , 12-trimethyltridecyl] -3 ,4-dihydro-2H- 1 -benzopyran- 6-ol (CAS: 54-28-4)

[0103] Hindered phenols with only one tert-butyl group in ortho position with regard to the hydroxyl group

[0104] The scavenger (PS) can encompass one or more of the following components:

[0105] 3 -tert-Butyl-4-hydroxy anisole (CAS: 121-00-6) 2,2'-Methylen-bis(6-tert-butyl-4-methylphenol) (CAS: 119-47-1) 2,2’-Ethylidenebis(4,6-di-tert-butylphenol) (CAS: 35958-30-6)

[0106] Phosphines as

[0107] The scavenger (PS) can encompass one or more of the following components:

[0108] Triethylphosphine (CAS: 554-70-1)

[0109] Triisopropylphosphine (CAS: 6476-36-4) Tributylphosphine (CAS: 998-40-3)

[0110] Tricyclohexylphosphine (CAS: 2622-14-2)

[0111] Triphenylphosphine (CAS: 603-35-0)

[0112] Tris(2,4,6-trimethylphenyl)phosphine (CAS: 23897-15-6) Tri(o-tolyl)-phosphine (CAS : 6163-58-2)

[0113] Hindered phenols, tert-butyl substituted in one ortho position with to the hydroxyl

[0114] More preferably, the scavenger (PS) encompasses one or more of the following components: 3-tert-Butyl-4-hydroxyanisol (CAS: 121-00-6)

[0115] Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS: 2082-79-3) l,3,5-Trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzol (CAS: 1709-70-2) 4,4'-Methylen-bis-(2,6-di-tert.-butyl-phenol) (CAS: 118-82-1)

[0116] Triethylene Glycol Bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (CAS: 36443-68-2)

[0117] 4,4’,4"-(l-methylpropanyl-3-ylidene)tris[6-tert-butyl-m-cresol] (CAS: 1843-03-4) 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy-l,l-dimethylethyl)- 2,4,8,10-tetraoxaspiro[5.5]undecane (CAS: 90498-90-1, phenol and ester)

[0118] Ethylene bis[3,3-bis(3-tert-butyl-4-hydroxyphenyl)butyrate] (CAS: 32509-66-3)

[0119] It is generally preferred that at least one hindered phenols, tert-butyl substituted in one ortho position with regard to the hydroxyl group is included as a scavenger, preferably at least one chosen from the group above.

[0120] Hindered phenols, tert-butyl substituted in both ortho positions with regard to the hydroxyl group

[0121] Preferably, the scavenger (PS) encompasses one or more of the following components:

[0122] 2.6-di-t-butyl-p-cresol (BHT)

[0123] 2.6-di-t-butyl-4-ethylphenol

[0124] 1.6-Hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (CAS: 35074-77-2) 3,3’,3",5,5',5"-hexa-tert-butyl-a,a’,a"-(mesitylene-2,4,6-triyl)tri-p-cresol (CAS: 1709-70-2) Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (CAS: 6683-19- 8)

[0125] It is generally preferred that at least one hindered phenols, tert-butyl substituted in both ortho positions with regard to the hydroxyl group is included as a scavenger, preferably at least one chosen from the group above.

[0126] Thioethers

[0127] Preferably, the scavenger (PS) encompasses one or more of the following components:

[0128] Didodecyl 3,3'-thiodipropionate (CAS : 123-28-4)

[0129] Di(tridecyl) 3,3'-thiodipropionate (CAS: 10595-72-9)

[0130] Ditetradecyl 3,3'-Thiodipropionate (CAS: 16545-54-3) Octadecyl 3-[[3-(dodecyloxy)-3-oxopropyl]thio]propionate (CAS: 13103-52-1)

[0131] Octadecyl 3- { [3-(octadecyloxy)-3-oxopropyl] sulfanyl Jpropanoate (CAS: 693-36-7) It is generally preferred that at least one hindered phenols, tert-butyl substituted in both ortho positions with regard to the hydroxyl group is included as a scavenger, preferably at least one chosen from the group above.

[0132] Amines

[0133] Preferably, the scavenger (PS) encompasses one or more of the following components: N-Phenyl-1 -naphthylamine (CAS: 90-30-2) N-Phenyl-2-naphthylamine (CAS: 135-88-6)

[0134] N,N'-Diphenyl-p-phenylendiamin (CAS: 74-31-7)

[0135] N-Cyclohexyl-N' -phenyl- 1 ,4-benzenediamine (CAS: 101-87-1) 4-methoxy-2,2,6,6-tetramethylpiperidine (CAS: 26275-90-1)

[0136] 2.2.6.6-tetramethylpiperidin-4-ol (CAS: 2403-88-5) 4-(Benzyloxy)-2,2,6,6-tetramethylpiperidine (CAS: 26275-91-2)

[0137] 2.2.6.6-tetramethyl-4-piperidyl methacrylate (CAS: 31582-45-3) Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (CAS: 52829-07-9) Bis(2,2,6,6-tetramethylpiperidin-4-yl) hexanedioate (CAS: 24886-40-6) Bis(l,2,2,6,6-pentamethyl-4-piperidyl) Sebacate (CAS: 41556-26-7)

[0138] Preferably, the scavenger (PS) encompasses one or more of the following components: Triisodecyl phosphite (CAS: 25448-25-3)

[0139] Diisodecyl phenyl phosphite (CAS: 25550-98-5)

[0140] Isodecyl diphenyl phosphate (CAS: 29761-21-5)

[0141] Triphenyl phosphite (CAS: 101-02-0)

[0142] Tris(2,4-ditert-butylphenyl) phosphite (CAS: 31570-04-4)

[0143] Tris(nonylphenyl) phosphite (CAS: 26523-78-4)

[0144] Butylidenebis[2-tert-butyl-5-methyl-p-phenylene]-P,P,P',P'-tetratridecylbis(phosphine) (CAS : 13003-12-8)

[0145] Tris(2,4-ditert-butylphenyl) phosphite (CAS: 31570-04-4) Tris[4,4'-thiobis[3-methyl-6-tert-butylphenol]]phosphite (CAS: 36339-47-6) Tris(2,4-ditert-butylphenyl) phosphite (CAS: 31570-04-4) tris[2-(l,l-dimethylpropyl)phenyl] phosphite (CAS: 864-56-2) Tris(2,4-di-tert-amylphenyl) phosphite (CAS: 1065-97-0) tris(2-cyclohexylphenyl) phosphite (CAS: 236-541-6)

[0146] Diisodecyl pentaerythritol diphosphite (CAS: 26544-27-4) 3.9-Bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (CAS: 3806-34- 6)

[0147] 3.9-bis(2,4-di-tert-butylphenoxy)-2,4, 8 , 10-tetraoxa-3 ,9-diphosphaspiro[5.5]undecane (CAS: 26741-53-7)

[0148] Bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate (CAS: 80693-00-1) Generally, it is preferred that at least one or more of the phosphites are included as scavenger (PS), in particular as one type of scavenger from the scavengers within the photosensitive composition. More preferably, is preferred that at least one or more of the phenyl-phosphites type scavengers are included.

[0149] A scavenger having more than one functionality in the same molecule

[0150] Preferably, the scavenger (PS) encompasses one or more components having a plurality of functionality, in particular one or more of the following components:

[0151] Diethyl 3,5-Di-tert-butyl-4-hydroxybenzylphosphonate (CAS: 976-56-7, phenol and phosphite) 4,6-bis(octylthiomethyl)-o-cresol (CAS: 110553-27-0, phenol and thiether) 6,6'-di-tert-butyl-2,2'-methylenedi-p-cresol (CAS: 119-47-1, phenols with different steric hinderance) 4,4'-Thiodi(3-methyl-6-tert-butylphenol) (CAS: 2664-38-2, phenols and disulfide) 2' ,3 -bis [ [3 - [3 ,5 -di-tert-butyl-4-hydroxyphenyl] propionyl] propionohy dr azide (C AS : 32687-78-8, phenols and hydrazine)

[0152] N,N'-hexane-l,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide] (CAS: 23128- 74-7, phenols and amides) l,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-l,3,5-triazine-2,4,6(lH,3H,5H)-trione (CAS: 27676-62-6, phenol and triazine-trione)

[0153] Bis(l,2,2,6,6-pentamethyl-4-piperidyl) Butyl(3,5-di-tert-butyl-4-hydroxybenzyl)malonate (CAS: 63843-89-0, phenol and hindered amine)

[0154] Preferably, the scavenger (PS) includes a combination of at least one phenol type and a phosphite type to achieve synergistic scavenging properties.

[0155] According to an embodiment, the scavenger (PS) comprises 2,6-di-tert-butyl-4-methylphenol as a first scavenger (PSI); and a second scavenger (PS2) chosen from: bis[2,4-bis(2-methylbutan-2- yl)phenyl] 4-(2-methylbutan-2-yl)phenyl phosphite and 2,4-bis(2-methylbutan-2-yl)phenyl bis [4- (2-methylbutan-2-yl)phenyl] phosphite and tris[4-(2-methylbutan-2-yl)phenyl] phosphite , 4- { [4,6- bis(octylsulfanyl)-l,3,5-triazin-2-yl]amino}-2,6-di-tert-butylphenol , Poly([l,3,5-triazine] derivative) , 3,9-bis(2,4-bis(l,l-dimethy)phenoxy) 2,4,8,10-tetraoax-2,9-diphosphaspiro (5,5)undecane , tris(2,4-di-tert-butylphenyl) phosphite , octadecyl 3-(3,5-di-tert-butyl-4- hydroxyphenyl)propanoate , 4-( { 3 ,5-bis [(2,6-di-tert-butyl-4-hydroxyphenyl)methyl] -2,4,6- trimethylphenyl}methyl)-3,5-di-tert-butylphenol , dodecyl 3-{ [3-(dodecyloxy)-3- oxopropyl] sulfanyl jpropanoate ; and wherein the scavenger / plasticizer ratio (Rs) is at least 0.010, preferably at least 0.020.

[0156] Developing the relief precursor (RP) and production of a relief (PL) with relief structures

[0157] The relief precursor (RP) can be imaged by ablation of a mask layer, by exposure through mask or by direct imaging. This way, the precursor can be developed into a relief (e.g. a cliche, or printing plate (PL)) with relief structures. The mask layer can be a separate layer, which is applied to the relief precursor following the removal of a protective layer that may possibly be present, or an integral layer of the precursor, which is in contact with the relief layer or one of the optional layers above the relief layer, and is covered by a protective layer that may possibly be present. The mask layer can also be a commercially available negative which, for example, can be produced by means of photographic methods based on silver halide chemistry. The mask layer can be a composite layer material in which, by means of image-based exposure, transparent layers are produced in an otherwise non-transparent layer, as described, for example in EP 3 139 210 Al, EP 1 735 664 Bl, EP 2987 030, Al EP 2 313 270 Bl. This can be carried out by ablation of a non-transparent layer on a transparent carrier layer, as described, for example, in US 6,916,596, EP 816 920 Bl, or by selective application of a non-transparent layer to a transparent carrier layer, as described in EP 992 846 Bl, or written directly onto the relief-forming layer, such as, for example, by printing with a non-transparent ink by means of ink-jet, as described, for example, in EP 1 195 645 Al. Image wise removal of the mask layer is preferably performed using ablation technology. As a rule, the electromagnetic radiation for ablating the mask will generally be radiation having a wavelength in the range from 300 nm to 20000 nm, preferably in the range from 500 nm to 20000 nm, particularly preferably in the range from 800 nm to 15000 nm, very particularly preferably in the range from 800 nm to 11000 nm. In addition to solid-body lasers, gas lasers or fiber lasers can also be used. Preferably, in laser ablation, use is made of Nd:YAG lasers (1064 nm) or CO2-lasers (9400 nm and 10600 nm). For the selective removal of the mask layer, one or more laser beams are controlled such that the desired printing image is produced. The direct image exposure can be achieved in that the regions to be cross-linked are exposed selectively. This can be achieved, for example, with one or more laser beams which are controlled appropriately, by the use of monitors in which specific image points which emit radiation are activated, by using movable LED strips, by means of LED arrays, in which individual LEDs are switched on and off specifically, by means of the use of electronically controllable masks, in which image points which allow the radiation from a radiation source to pass are switched to transparent, by means of the use of projection systems, in which by means of appropriate orientation of mirrors, image points are exposed to radiation from a radiation source, or combinations thereof. Preferably, the direct exposure is carried out by means of controlled laser beams or projection systems having mirrors. The absorption spectra of the initiators or initiator systems and the emission spectra of the radiation sources must at least partly overlap. The wavelength of the electromagnetic radiation lies in the range from 200 nm to 20000 nm, preferably in the range from 250 nm to 1100 nm, particularly preferably in the UV range, very particularly preferably in the range from 300 nm to 450 nm. Besides broadband irradiation of the electromagnetic radiation, it can be advantageous to use narrow-band or monochromatic wavelength ranges, such as can be produced by using appropriate filters, lasers or light emitting diodes (LEDs). In these cases, wavelengths of 350 nm, 365 nm, 385 nm, 395 nm, 400 nm, 405 nm, 532 nm, 830 nm, 1064 nm (and about 5 nm to 10 nm below and / or above this), on their own or in combination, are preferred. The relief is generated by exposure with electromagnetic radiation through a mask film. On exposure, the exposed regions undergo crosslinking, whereas the unexposed regions of the precursor remain soluble or liquefiable and are removed by appropriate methods. Where an imaged mask is present, irradiation may take place extensively, or, if operating without a mask layer, irradiation may take place in an imaging way over a small area (virtually dot wise) by means of guided laser beams or positionally resolved projection of electromagnetic radiation. The wavelength of the electromagnetic waves irradiated in this case is in the range from 200 to 2000 nm, preferably in the range from 200 to 450 nm, more preferably in the range form 250 nm to 405 nm. The irradiation may take place continuously or in pulsed form or in a plurality of short periods with continuous radiation. In addition to broadband radiation of the electromagnetic waves, it may be advantageous to use narrow-band or monochromatic wavelength ranges, as can be generated using appropriate filters, lasers or lightemitting diodes (LEDs). In these cases, wavelengths in the ranges 350, 365, 385, 395, 400, 405, 532, 830, 1064 nm individually (and about 5-10 nm above and / or below) or as combinations are preferred. The intensity of the radiation here may be varied over a wide range, ensuring that a dose is used which is sufficient to cure the radiation-curable layer sufficiently for the later development procedure. The radiation-induced reaction, possibly after further thermal treatments, must be sufficiently advanced that the exposed regions of the radiation-sensitive layer become at least partially insoluble and therefore cannot be removed in the developing step. The intensity and dose of the radiation are dependent on the reactivity of the formulation and on the duration and efficiency of the developing.

[0158] The intensity of the radiation is in the range from 1 to 15000 mW / cm2, preferably in the range from 5 to 5000 mW / cm2, more preferably in the range from 10 to 1000 mW / cm2. The dose of the radiation is in a range from 0.3 to 6000 J / cm2, preferably in a range from 3 to 100 J / cm2, more preferably in the range from 6 to 20 J / cm2. Exposure to the energy source may also be carried out in an inert atmosphere, such as in noble gases, CO2 and / or nitrogen, or under a liquid which does not damage the relief precursor. Exposure through the mask can be done by using optical devices, for example for beam widening, by a two-dimensional arrangement of multiple point-like or linear sources (for example light guides, emitters), such as fluorescent strip lamps arranged beside one another, by moving a linear source or an elongated arrangement of LEDs (array) relative to the relief precursor, for example by a uniform movement of LEDs or combinations thereof. Preferably, fluorescent strip lamps arranged beside one another or a relative movement between one or more LED strips and the relief precursor is used. The irradiation can be carried out continuously, in a pulsed manner or in multiple short periods with continuous radiation. The removal of the non-cured areas of the precursor is preferably performed by treatment with heat and a developing material configured to adsorb noncured material. More preferably, in step d) the precursor is heated to a temperature in the range of 70 to 200 °C, preferably in the range of 80 to 180 °C, more preferably in the range of 90 to 165 °C. The heating of the exposed relief precursor may be carried out by all of the techniques known to the skilled person, such as, for example, by irradiation with IR light, the action of hot gases (e.g., air), using hot rollers, or any desired combinations thereof. To remove the (viscously) liquid regions it is possible to employ all techniques and processes familiar to the skilled person, such as, for example, blowing, suction, dabbing, blasting (with particles and / or droplets), stripping, wiping, transfer to a developing medium, and any desired combinations thereof. Preferably the liquid material is taken up (absorbed and / or adsorbed) by a developing medium which is contacted continuously with the heated surface of the relief precursor. The procedure is repeated until the desired relief height is reached. Developing media which can be utilized are papers, woven and nonwoven fabrics, and films which are able to take up the liquefied material and may consist of natural fibers and / or polymeric fibers. Preference is given to using non wo vens or non-woven fiber webs of polymers such as celluloses, cotton, polyesters, polyamides, polyurethanes, and any desired combinations thereof, which are stable at the temperatures employed when developing. Alternatively the precursor is treated with a developing liquid to dissolve non-cured material. The techniques applied in this development step may be all of those familiar to the skilled person. The solvents or mixtures thereof, the aqueous solutions, and the aqueous-organic solvent mixtures may comprise auxiliaries which stabilize the formulation and / or increase the solubility of the components of the non-crosslinked regions. Examples of such auxiliaries are emulsifiers, surfactants, salts, acids, bases, stabilizers, corrosion inhibitors, and suitable combinations thereof. For development with these solutions, it is possible to use all of the techniques known to the skilled person, such as, for example, dipping, washing or spraying with the developing medium, brushing in the presence of developing medium, and suitable combinations thereof. Preference is given to developing with neutral aqueous solutions or water, with removal assisted by means of rotating brushes or a plush web. Another way of influencing the development is to control the temperature of the developing medium and to accelerate the development by raising the temperature, for example. In this step, it is also possible for further layers still present on the radiation-sensitive layer to be removed, if these layers can be detached during development and sufficiently dissolved and / or dispersed in the developer medium. Optionally one or more steps of post treatment, post exposure, and / or detackifying are performed. These include, for example, a thermal treatment, a drying, a treatment with electromagnetic rays, with plasma, with gases or with liquids, attachment of identification features, cutting to format, coating, and any desired combinations thereof. A thermal treatment may be utilized, for example, to initiate and / or to complete reactions, to increase the mechanical and / or thermal stability of the relief structure, and to remove volatile constituents. For the thermal treatment, it is possible to use the known techniques, such as heating using heated gases or liquids, IR radiation, and any desired combinations thereof, for example. In these contexts, it is possible to employ ovens, blowers, lamps, and any desired combinations thereof. In addition to disbanding, surface modifications can also be accomplished by the treatment with gases, plasma and / or liquids, especially if in addition there are reactive substances employed as well. Treatment with electromagnetic radiation may be used, for example, for the purpose of detackifying the surfaces of the relief structure, and triggering and / or completing polymerization reactions and / or crosslinking reactions. The wavelength of the irradiated electromagnetic waves in this case is in the range from 200 to 2000 nm.

[0159] According to an embodiment, the developed printing plate (PL) has a micro-Shore A hardness between is preferably 20opShA and 80opShA, more preferably between 25opShA and 70opShA. The hardness of the developed printing plate can be measured as micro-Shore A hardness. In contrast to the conventional Shore A hardness, only the hardness on the surface is measured as the needle for measurement is much smaller. Using triglycerides with different peroxide values and different peroxide scavengers, an influence on the micro-Shore A hardness was observed.

[0160] The skilled person will appreciate on the basis of the above description that the invention can be embodied in different ways and on the basis of different principles. The invention is not limited to the above described embodiments. The above described embodiments and the figures are purely illustrative and serve only to increase understanding of the invention. The invention will not therefore be limited to the embodiments described herein, but is defined in the claims.

[0161] EXAMPLES

[0162] Development procedure to develop the precursor into a printing plate

[0163] In the examples hereafter, printing plate precursors having different photosensitive compositions are tested. In the examples, the printing plate precursors are developed according to the following procedure:

[0164] The laser ablatable mask was imaged using a TfxX 20 laser (Flint Group Germany GmbH, Germany, rotational speed: 10 to 11 rounds / s, power: 35 W (100% intensity)).

[0165] The relief precursor was exposed to UV light from the backside through the carrier foil for 12 to 44 s and from the front side through the mask layer for 15 min (exposure unit: Combi Fill (Flint Group Germany GmbH, Germany; UVA intensity 18 mW / cm2, UVA tube type: Philips TL 80W / 10-R). For solvent development, a flowline Fill system with nylosolv A as solvent and a solid content of 4.8 - 5.1%, a brush height setting of 0 mm and a solvent temperature of 35 °C was used. The washout speed to achieve the desired relief depth was determined according to Section “3.2 Determination of plate processing times” in the nyloflex®UserGuide, page 16, version October 2007. After washout, the plates were dried at 60 °C for 2 h (Combi Fill (Flint Group Germany GmbH, Germany)). For thermal development, non-polymerized material and residual black mask layer were removed using an Xpress thermal developer (Flint Group). Post-curing was performed using UVA and UVC from the front side (machine type: Combi Fill (Flint Group Germany GmbH, Germany); UVA exposure time: 10 min, UVA intensity: 11 mW / cm2, UVA tube type: Philips TL 60W / 10-R, UVC exposure time: 5 min, UVC intensity: 13 mW / cm2, UVC tube type Philips TUV 75W HO G75 T8, UVA and UVC post-exposure were started simultaneously).

[0166] Parameter measurements

[0167] Micro-Shore A Hardness (p-hard) : The micro-Shore A hardness was measured on specimens having a thickness of 1.1 mm. The measurement was performed after exposure, development, drying and post-curing, using a digi test II-M Shore A instrument (Bareiss Priifgeratebau GmbH), which was installed in the B509 test bed (Bareiss Priifgeratebau GmbH) and was controlled by the DTAA control unit (Bareiss Prufgeratebau GmbH). The measuring head (penetration body with 35° angle) was applied to a solid area for the purpose of the measurement, and was pressed by the digi test II analysis instrument with a pressing force of 235 mN and the hardness value was read off after 3 s. Measurement was carried out twice, and the arithmetic mean was formed. The measurements were carried out on the basis of DIN ISO 7619.

[0168] Depth of the 400 pm negative dot (ND) : To evaluate the depth of negative elements, the test motive contains a dot with 400 pm diameter. To achieve good print results, typically a higher depth of negative elements is desirable. The depth measurement was performed with a Dot Check WH 360. Tonal values (TV) : TV on the developed plate were measured using a Peret Flex3 Pro densitometer from X-Rite. The halftone screen value describes the proportion of the area printed to the whole area. Here, 15% on file, 146 Ipi was used.

[0169] Minimum stable halftone screen (HS) : HS at 89 Ipi was determined visually comparing theoretical data on file and obtained elements on the developed plate. If no dots were missing, the halftone screen was evaluated as stable. The value is given in percent. Possible values on file: 0.4%, 0.8%, 1.2%, 1.6%, 2%, 2.4%, 2.8%, 3.2%, 4%, 5%. A lower value indicates a better performance.

[0170] The minimum isolated positive dot (PD) : was determined visually comparing theoretical data on file and obtained elements on the developed plate. Possible values on file: 50 pm, 70 pm, 100 pm, 200 pm, 300 pm, 400 pm. A lower value indicates a better performance.

[0171] Ratio of peroxide scavenger to vegetable oil (Rs) :

[0172] The ratio of peroxide scavenger to vegetable oil is calculated by dividing the total amount of the at least one peroxide scavengers (parts by weight) by the total amount of vegetable oil (parts by weight). Molar ratio of peroxide scavenger to vegetable oil (Rm) :

[0173] The molar ratio of peroxide scavenger is calculated using the formula: Rm = ((parts by weight PS (wt%) / molar mass PS (g mol ’)) / (parts by weight vegetable oil (w%) / molar mass vegetable oil (g / mol)) / (functionality PS). For the molar mass of the vegetable oil, the average molecular weight of a triglyceride with the fatty acid distribution specified in the certificate of analysis of the supplier was used. For peroxide scavengers consisting of a mixture of more than one molecule or oligomers, the respective lower end of Rm and higher end of Rm were calculated using the lowest molar mass and lowest functionality as well as the highest molar mass and highest functionality, respectively. Plate surface images were recorded using a Peret Flex3 Pro densitometer from X-Rite.

[0174] Surface defects (SD) : defects on the surface were evaluated visually under a microscope, qualitatively comparing different elements such as negative text, positive text, solids, positive dots and raster screens. Example for negative text contributing to different grades:

[0175] The complex shear viscosity q* : this parameter was measured by oscillatory rheology using a Kinexus lab+ rheometer (Malvern Instruments Ltd., UK) under isothermal (T = 160 °C) conditions. Data was recorded using the corresponding software rSPACE version 1.76 (Malvern Instruments Ltd., UK). As measurement geometry, parallel plates with a diameter of 2.5 cm of the upper plate were chosen. As sample, a disc of a relief precursor with a diameter of 2.5 cm was used. Prior to measurement, cover foil, carrier foil and mask layers were removed from the relief precursor. Measurements were carried out in oscillation single frequency mode. The frequency was set to 1 Hz and data points were recorded every 15 s. The gap between the parallel plates was set constant to the respective sample thickness. The complex shear viscosity q* was monitored over time t for at least 30 minutes. The value was collected after the measurement stabilized at a constant viscosity, typically after 3 minutes.

[0176] Peroxide Value (Ox): The peroxide value was determined (e.g. in example 7) using the official ferric thiocyanate method of the International Dairy Federation (Anhydrous Fat, Determination of Peroxide Value. IDF Standard 74A; IDF: Brussels, Belgium, 1991) with modifications according to Ueda, S., Hayashi, T., Namiki, M. Agric. Biol. Chem., 1986, 50 (1), 1 - 7. and Undeland, L, Stading, M., Lingnert, H.. J Sci Food Agric, 1998, 78 (3), 441 - 450 as described by Semb, T. N. (2012) in “Analytical methods for determination of the oxidative status in oils” (master's thesis, Department of Biotechnology, Norwegian University of Science and Technology, appendix B page 76 - 78).

[0177] Example 1 - Vegetable Oils

[0178] In example 1, conventional plasticizers (e.g mineral oil or polybutadiene) are compared to different vegetable oils. Production of the relief precursor:

[0179] A photopolymeric mixture containing

[0180] - >59.35 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0181] - 7.5 parts by weight of hexanediol diacrylate,

[0182] - 2.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0183] - 30 parts by weight plasticizer (P) and

[0184] - 0.15 parts by weight of PS-1 (Rs = 0.005) as the scavenger (PS)

[0185] - <1.0 parts by weight of further constituents such as additives and dyes. was melted at elevated temperatures (95 to 180 °C) in an extruder and calendared via a slot die between a cover film with laser-ablatable mask layer having a thickness of 105 pm and a carrier film having a thickness of 175 pm, thus giving the relief precursor (photopolymer + films) with a total thickness of 1.2 mm. The relief precursor was developed according to the procedure described above and the following findings are found:

[0186] nD=not determined.

[0187] In this example, different vegetable oils are compared to a conventional polybutadiene plasticizer in combination with a low concentration of peroxide scavenger PS-1. Albeit the production of the plate precursor using an extrusion setup was well possible, after development, surface defects (SD) are visible for formulation with vegetable oil plasticizers. Example 2 - Vegetable Oils ( with scavenger )

[0188] Example 2 shows conventional plasticizers (e.g. mineral oil or polybutadiene) compared with different vegetable oils and increased concentration of butylated hydroxytoluene (BHT). The production and development of the relief precursor was performed as in example 1 : Photopoly meric mixture:

[0189] - >59.25 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0190] - 7.5 parts by weight of hexanediol diacrylate,

[0191] - 2.0 parts by weight of benzil dimethyl ketal as photoinitiator, - 30 parts by weight plasticizer (P) and

[0192] - 0.25 parts by weight of PS-1 (Rs = 0.008) as the scavenger (PS)

[0193] - <1.0 parts by weight of further constituents such as additives and dyes.

[0194] The relief precursor was developed according to the procedure described above and the following findings are found: d=not determined

[0195] In this example, different vegetable oils as plasticizer are compared to a conventional polybutadiene plasticizer in combination with a higher concentration of peroxide scavenger PS-1. Compared to example 1 above, less surface defects (SD) are visible.

[0196] Preferably, and generally applicable herein, more than 0.15 % by weight of scavenger is included, more preferably more than 0.17 %, even more preferably at least 0,22 wt%, of the scavenger (e.g. 0.25 wt%) is present within the polymeric mixture to reduce and avoid the surface defects.

[0197] As generally used herein, the Rs ratio refers to the ratio (Rs) of (all) peroxide scavengers to the bio-based plasticizer, said (Rs) is preferably higher than 0.003, more preferably higher than 0.004, more preferably higher than 0.005, more preferably higher than 0.007, more preferably higher than 0.008, more preferably higher than 0.010, more preferably higher than 0.013, more preferably higher than 0.015, more preferably higher than 0.017.

[0198] As generally used herein, the Rm ratio refers to the molar ratio of the at least one peroxide scavenger to the bio-based plasticizer and is preferably higher than 0.0003, more preferably higher than 0.0040, more preferably higher than 0.0062, more preferably higher than 0.0100.

[0199] Example 1 - Conventional plasticizer vs vegetable oils ( no scavenger )

[0200] Example 3 is comparing conventional plasticizers such as mineral oil or polybutadiene with two grades of sunflower oil. No peroxide scavenger was added. A photopolymeric mixture was tested containing:

[0201] - >56.0 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0202] - 10 parts by weight of hexanediol diacrylate,

[0203] - 3.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0204] - 30 parts by weight plasticizer (P)

[0205] - no scavenger - <1.0 parts by weight of further constituents such as additives and dyes.

[0206] The components were dissolved in toluene and heated under reflux to obtain a homogeneous solution (concentration in toluene: 45 wt.%). The solution was cast on a carrier sheet and flattened using a doctor blade with a gap of 3 mm distance to the carrier sheet (PET film with 175 pm thickness). The solvent was allowed to evaporate at room temperature for 16 hours followed by heating at 65 °C for 4 hours. To allow digital imaging, a mask layer (ML) coated on a cover sheet (CL) was laminated on top of the relief precursor using an Excelam-Q laminator (GMP Deutschland GmbH, Germany). Lamination was carried out at a temperature of the heated roll of 110 °C, a velocity of 8.8 mm / s, and at a gap of 1.5 mm. To finish the lamination, the cast plate was sandwiched between two aluminum plates and was kept at 65 °C for 3 h.

[0207] The relief precursor was developed according to the procedure described above.

[0208] Sunflower oil is compared to conventional polybutadiene and white oil plasticizers without any additional peroxide scavenger. Albeit the production of the plate precursor using a mild casting setup was well possible, after development, surface defects are visible for formulation with vegetable oil plasticizers in the absence of a peroxide scavenger. A higher peroxide value resulted in more surface defects (compare 3.3 and 3.4).

[0209] Example 3 - Vegetable oils ( with scavenger )

[0210] Example 4 shows that a grade of sunflower oil with high peroxide content was used with different peroxide scavengers. The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture was tested containing:

[0211] - >55.5 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0212] - 10 parts by weight of hexanediol diacrylate, - 3.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0213] - 30 parts by weight sunflower oil (20.8 meq O2 / kg) as plasticizer;

[0214] - 0.5 party by weight of scavenger (PS-1 to PS-4) (Rs = 0.017) as scavenger;

[0215] - <1.0 parts by weight of further constituents such as additives and dyes. In this example, sunflower oil with a high peroxide value (Ox) is used with different peroxide scavengers PS-1 to PS-4 (see further below). All peroxide scavengers resulted in an improvement of the surface defects. Differences in irradiation properties can be observed. Example 4 - Vegetable Oil ( with several types of scavenger ) Example 5 shows that a grade of sunflower oil (P) with high peroxide content was used with combinations of different peroxide scavengers (PS). The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture was tested containing:

[0216] - >55.0 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder, - 10 parts by weight of hexanediol diacrylate,

[0217] - 3.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0218] - 30 parts by weight sunflower oil (20.8 meq O2 / kg)

[0219] - 0.5 parts by weight of peroxide scavenger 1

[0220] - 0.5 parts by weight of peroxide scavenger 2 - <1.0 parts by weight of further constituents such as additives and dyes.

[0221] Notably, a combination of peroxide scavengers is used in this example.

[0222] In this example, sunflower oil with a high peroxide value (Ox) is used with combinations of peroxide scavengers PS-1 to PS-4. All peroxide scavengers resulted in an improvement of the surface defects. Differences in irradiation properties can be observed.

[0223] For peroxide scavenger mixtures (PS+PS2), Rm values were calculated separately for each peroxide scavenger. For calculation of Rs, both peroxide scavengers were added together.

[0224] It can be observed from the table of example 4 that a higher ratio Rs, in particular a scavenger / plasticizer ratio (Rs) of more than 0.020 and even more preferably more than 0.030 indicates enhanced results.

[0225] Remarkably, highly beneficial results are obtained when combining peroxide scavenger, see for example combinations PS-1 and PS-2, combination PS-1 and PS-3, combination PS-1 and PS-4.

[0226] Example 5 - Vegetable oil, and scavenger in different concentrations

[0227] In this example, a grade of sunflower oil with high peroxide content was used with different concentrations of peroxide scavenger, which was counterbalanced by the amount of SBS block copolymer. The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture was tested containing:

[0228] - >51.0 - 55.9 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0229] - 10 parts by weight of hexanediol diacrylate,

[0230] - 3.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0231] - 30 parts by weight sunflower oil

[0232] - 0.2 - 5.0 parts by weight of peroxide scavenger

[0233] - <1.0 parts by weight of further constituents such as additives and dyes. In this example, sunflower oil is used with different concentrations of PS-1 and PS-2. A higher amount of peroxide scavenger resulted in a better improvement with regard to surface defects. Moreover, irradiation properties varied depending on PS-1 and PS-2 and the respective concentration. Improved effects are observed for a higher concentration of scavenger. Generally, the peroxide scavenger is preferably present in an amount of higher than 2% by weight, preferably in the range of 2 % to 9 %. In this manner, stabilization of the biobased plasticizer can be enhanced.

[0234] Example 6 - testing vegetable oils of different quality

[0235] In this example, different grades of rapeseed oil (P) with the same concentration of peroxide scavenger (PS) were used. The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture was tested containing:

[0236] - >57.0 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder

[0237] - 7.5 parts by weight of decanediol diacrylate,

[0238] - 2.0 parts by weight of isobornyl acrylate

[0239] - 2.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0240] - 30 parts by weight rapeseed oil (P) and

[0241] - 0.5 parts by weight of PS-1 (Rs = 0.017, Rm = 0.0664) as scavenger (PS).

[0242] - <1.0 parts by weight of further constituents such as additives and dyes.

[0243] Here, it can be seen that no rapeseed oil (or any other vegetable oil) is the same, indeed the “quality” depends on several factors such as origin (growing conditions), processing methods and storage conditions.

[0244]

[0245] In this example, it is shown that sunflower oil with different peroxide values (Ox), i.e. of different quality can be used. Above a certain peroxide value, and with the set concentration of peroxide scavenger, more surface defects occur. The peroxide value is determined according to the method described above.

[0246] Preferably, and generally applicable herein, the peroxide value of the plasticizer (P) is in the range of 30 to 1 meq Q2 / kg. In particular, it was found that with plasticizers (P) having a peroxide value in the range of 14 to 1 meq Q2 / kg best results were obtained.

[0247] Example 7 - testing different concentrations ( of vegetable oil )

[0248] In this example, different concentrations of cottonseed oil were used. The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture was tested containing:

[0249] - > 59.5 - 86.5 parts by weight of a of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0250] - 7.5 parts by weight of hexanediol diacrylate,

[0251] - 2.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0252] - 3 - 49 parts by weight cottonseed oil as plasticizer (P),

[0253] - 0.2 parts by weight PS-5 as scavenger (PS)

[0254] - < 1.0 parts by weight of further constituents such as additives and dyes.

[0255] In this example, cottonseed oil is used in different concentrations. A higher concentration of cottonseed oil with a fixed concentration of peroxide scavenger resulted in more surface defects. It shows that the scavenger / plasticizer ratio (Rs) has an effect and that less surface defects occur with higher ratios, in particular, it is generally preferred to have a ratio Rs of more than 0,02, in particular in such compositions wherein plasticizer (P) is present in an amount below 10.0 wt%.

[0256] Example 8 - testing different peroxide scavengers

[0257] Example 9 shows the testing of different peroxide scavengers (PS-5 to PS-9) used with a SIS block copolymer as binder. The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture containing:

[0258] - >69.1 parts by weight of a SIS block copolymer with a styrene content of 15% and 19% diblock as binder,

[0259] - 6.0 parts by weight of hexanediol diacrylate, - 3.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0260] - 20.0 parts by weight soybean oil (P) as plasticizer, - 0.9 parts by weight of scavenger (see PS-5 to PS-11) (Rs: 0.05) as scavenger (PS)

[0261] - <1.0 parts by weight of further constituents such as additives and dyes. In this example, different peroxide scavengers are used in combination with soybean oil. Depending on the peroxide scavenger, different degrees of surface defects were observed. PS-5 to PS-9 achieve better SD grades.

[0262] Example 9 - testing different ratios

[0263] This examples shows different ratios (see Rs and Rm) of vegetable oil plasticizer with conventional plasticizers was used. The production and development of the relief precursor was performed as in example 3. A photopolymeric mixture was tested containing:

[0264] - >55.0 parts by weight of a SBS block copolymer with a styrene content of 28.5% and diblock content of 15% as binder,

[0265] - 10 parts by weight of hexanediol diacrylate, - 3.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0266] - 30 parts by weight plasticizer combination (varying amounts of corn oil and convention oils)

[0267] - 1.0 parts by weight of PS-1 as scavenger

[0268] - <1.0 parts by weight of further constituents such as additives and dyes. In this example, different plasticizer mixtures were tested with scavenger PS-1.

[0269] A higher content of corn oil (P) resulted in more surface defects, see for examples contents more than 10.0 percent by weight. By having lower contents of P (e.g. 4 wt%) and respecting the ratio relationship with the scavenger, good grades could be achieved. Preferably, the plasticizer (P) is present in an amount below 10.0 wt% and the ratio Rs is more than 0.020, preferably the ratio Rs is more than 0.1 and / or wherein the ratio Rm is more than 0.5, more preferably more than 0.75.

[0270] Example 10 - testing different bio-based plasticizers (vegetable oil, fish oil)

[0271] In this example, different types vegetable oil plasticizers were used. The production and development of the relief precursor was performed as in example 3. Generally applicable, the plasticizer may be a plant-based oil or a non-plant passed oil, such as a fish oil. Menhaden oil is a type of fish oil derived from menhaden fish, which are abundant in the Atlantic Ocean. A photopolymeric mixture was tested containing:

[0272] - >57.4 parts by weight of a SIS block copolymer with a styrene content of 42.0 - 46.5% and diblock content of below 1 % as binder,

[0273] - 10 parts by weight of hexanediol diacrylate,

[0274] - 1.0 parts by weight of benzil dimethyl ketal as photoinitiator,

[0275] - 30 parts by weight of vegetable oil as plasticizer (P)

[0276] - 0.6 parts by weight of PS-7 as scavenger (PS)

[0277] - <1.0 parts by weight of further constituents such as additives and dyes.

[0278] This example further supports using oils different than vegetable oils.

[0279] In this example, oils were tested with PS-7. A higher oil content resulted in more surface defects. For 11.6, the plate precursor lacks dimensional stability. For 11.8, additional defects due to incompatibility of the plasticizer were observed. For 11.9 inhomogeneities were observed. For 11.10, production of the photopolymer layer was not possible due to phase separation. Thus, according to an embodiment the plasticizer (P) is chosen from any one of: Coconut oil, Castor oil, Menhaden oil, Safflower oil, and while present in the photosensitive composition (PC) in an amount of at most 45 %, preferably at most 40 %, such as in the range of 0,1 - 20 % by weight. More generally applicable herein, the plasticizer (P) is typically present in an amount of at most 45%.

[0280] Scavenger (PS) Materials

[0281] In the examples above, scavengers PS-1 to PS- 11 were tested and are identified as follows:

[0282] LogP: The predicted logP value (temperature: 25 °C) was obtained from the database SciFinder, Advanced Chemistry Development (ACD / Labs) Software VI 1.02 (© 1994-2024 ACD / Labs). It is generally preferred that the LogP value of the scavenger is above 5 and / or below 25, preferably below 20.

[0283] Polar surface area: The predicted polar surface area was obtained from the database SciFinder, Advanced Chemistry Development (ACD / Labs) Software VI 1.02 (© 1994-2024 ACD / Labs). It was found that scavengers (P) having a molecular weight in the range of more than 220, in particular more than 225 where found to be better performing over smaller scavengers.

[0284] Generally, it is preferred that scavengers (P) having a molecular weight in the range of 225 to 2000 g / mol, preferably in the range of 225 to 1500 g / mol, more preferably in the range of 225 to 1250 g / mol, most preferably in the range between 225 and 950 g / mol.

[0285] In this manner, the scavenger is less mobile within the composition such that the scavenger better stays in place delivering on its function.

[0286] Plasticizer (P) Materials

[0287] Functionality: Following chemicals groups were regarded to contribute towards functionality: phenol, phosphite, hindered amine, thioether and secondary amine.

[0288] Cottonseed oil: 14:0 myristic acid (0,6%), 16:0 palmitic acid (22,3%), 16:1 palmitoleic acid (0,5%), 18:0 stearic acid (2,5%), 18:1 oleic acid (16%), 18:2 linoleic acid (57%), 18:3 linolenic acid (0,4%), 20:0 arachidic acid (0,3%), 20:1 eicosenoic acid (0,1%); acid value = 0.11 mg KOH / g, peroxide value Ox according to COA = 4.7 meq 02 / kg, refractive index = 1.4730, relative density = 0.920 g / cm3, average molecular weight = 861,29 g / mol, inherent oxidative stability index = 5.8. Corn oil: 16:0 palmitic acid (11.5%), 18:0 Stearic acid (1.8%), 18:1 oleic acid (31.4%), 18:2 linoleic acid (53%), 18:3 linolenic acid (1%), 20:0 arachidic acid (0.4%), 20:1 eicosenoic acid (0.3%), 22:0 behenic acid (0.2%); acid value = 0.14 mg KOH / g; peroxide value Ox according to COA = 0.1 meq 02 / kg; refractive index = 1.4740; relative density = 0.920 g / cm3; iodine value = 121.8 (g I2 / 100g); water content 0.02%; insaponifiable part < 2.8%; average molecular weight = 879.28 g / mol; inherent oxidative stability index = 6.5. Soybean oil: 14:0 myristic acid (0.1%), 16:0 palmitic acid (10.4%), 16:1 palmitoleic acid (0.1%), 18:0 stearic acid (3.5%), 18:1 oleic acid (27.4%), 18:2 linoleic acid (51.1%), 18:3 linolenic acid (5.9%), 20:0 arachidic acid (0.4%), 20:1 eicosenoic acid (0.3%), 22:0 behenic acid (0.5%); acid value = 0.05 mg KOH / g; peroxide value Ox according to COA delivery = 0.9 meq 02 / kg; refractive index = 1.4743; relative density = 0.921 g / cm3; gardner color = 2.0; water content 0.02%; unsaponifiable fraction < 1.5%; average molecular weight = 872.62 g / mol; inherent oxidative stability index = 7.1.

[0289] Rapeseed oil: 16:0 palmitic acid (4.3%), 16:1 palmitoleic acid (0.2%), 18:0 stearic acid (1.7%), 18:1 oleic acid (62%), 18:2 linoleic acid (19.4%), 18:3 linolenic acid (9.4%), 20:0 arachidic acid (0.6%), 20:1 eicosenoic acid (1.2%), 22:0 behenic acid (0.3%), 22:1 Erucic acid (0.2%), 24:0 lignoceric acid (0.1%), 24:1 nervonic acid (0.2%); acid value = 0.08 mg KOH / g; peroxide value Ox according to COA = 0.1 meq 02 / kg; refractive index = 1.4730, relative density = 0.918 g / cm3; water content 001%; unsaponifiable fraction < 1.5%, average molecular weight = 877.63 g / mol; inherent oxidative stability index = 4.5.

[0290] Sunflower oil: 16:0 palmitic acid (3.5%), 16:1 palmitoleic acid (0.1%), 18:0 stearic acid (3.1%), 18:1 oleic acid (81.8%), 18:2 linoleic acid (9.4%), 18:3 linolenic acid (0.3%), 20:0 arachidic acid (0.3%), 20:1 eicosenoic acid (0.3%), 22:0 behenic acid (0.9%), 24:0 lignoceric acid (0.3%); unsaponifiable fraction < 1.5%; average molecular weight = 885.42 g / mol; inherent oxidative stability index = 1.7.

[0291] Safflower oil: 14:0 myristic acid (0,1%), 16:0 palmitic acid (5,2%), 16:1 palmitoleic acid (0,1%), 18:0 stearic acid (1,9%), 18:1 oleic acid (76,4%), 18:2 linoleic acid (14,4%), 18:3 linolenic acid (0,4%), 20:0 arachidic acid (0,4%), 20:1 eicosenoic acid (0,4%), 22:0 behenic acid (0,3%); acid value = 0.06 mg KOH / g; peroxide value Ox according to COA = 0.4 meq 02 / kg; refractive index = 1.472; relative density = 0.915 g / cm3, color (Gardner) = 0.3; water content = 0.03%; unsaponifiable fraction < 1.5%; average molecular weight = 878.40 g / mol; inherent oxidative stability index = 1.6.

[0292] Menhaden oil: omega-3 fatty acids (30.7%), palmitic acid (18.6%); inherent oxidative stability index = 32.9.

[0293] Castor oil: 16:0 palmitic acid (1,1%), 18:0 stearic acid (1,3%), 18:1 oleic acid (3,5%), 18:2 linoleic acid (4,7%), 18:3 linolenic acid (0,4%), 20:1 eicosenoic acid (0,2%), ricinoleic acid (88,5%); acid value: 0.08 mg KOH / g, peroxide value Ox according to COA = 1.5 meq 02 / kg, refractive index = 1.4792; relative density = 0.962 g / cm3, color (Gardner) = 0.6, color (Ph. Eur.) = brighter than BG3 oder G3, viscosity at 20 °C = 1070 mPa s; iodine value = 85.0 (g I2 / 100g), optical rotation = + 3.6 °; unsaponifiable fraction < 0.37%, saponification value = 180.4 mg KOH / g; hydroxyl value = 166.4 mg KOH / g; uv absorption (at 270 nm) = 1.27; water content = 0.12%. Coconut oil: 6:0 caproic acid (0 - 1.5%, in particular 0.5%), 8:0 caprylic acid (5.0 - 11.0%, in particular 6.9%), C10:0 capric acid (4.0% - 9.0%, in particular 5.4%), C12:0 lauric acid (40.0 - 50.0%, in particular 44.9%), 14:0 myristic acid (15.0 - 20.0%, in particular 18.5%), 16:0 palmitic acid (7.0 - 12.0%, in particular 10.3%), 18:0 stearic acid (1.5 - 5.0%, in particular 3.1%), 18:1 oleic acid (4.0 - 10.0%, in particular 8.2%), 18:2 linoleic acid (1.0 - 3.0%, in particular 2.0%), 18:3 linolenic acid (0 - 0.2%, in particular 2.0%), 20:0 arachidic acid (0 - 0.2%, in particular 0.1%), 20:1 eicosenoic acid (0 - 0.2%, in particular 0.1%); acid value = < 0.5 mg KOH / g, in particular 0.05 mg KOH / g; refractive index (40°C) = 1.449; unsaponifiable fraction < 1.0%; melting point = 23 - 26 °C; water content = <0.1%, in particular 0.02%; peroxide value Ox according to COA = <5 meq 02 / kg, in particular < 0.2 meq 02 / kg; inherent oxidative stability index = 0.2, average molecular weight = 688,88 g / mol.

[0294] MCT (medium-chain triglyceride) oil: 6:0 caproic acid (0 - 2.0%), 8:0 caprylic acid (55.0 - 65.0%), C10:0 capric acid (35.0% - 45.0%), C12:0 lauric acid (0 - 3.0%), C14:0 myristic acid (0 - 1.0%).

[0295] The fatty acid distribution and specifications are depicted as given by the supplier. Other fatty acids are below 0.5%.

[0296] Inherent oxidative stability (IOS): Source: Richard D O’Brien, Fats and Oils: Formulating and processing for applications, CRC Press, Boca Raton, Third Edition, 2008, p. 278.

[0297] The fatty acid distribution: this distribution has been determined as follows: the content of saturated fatty acids with at least 12 carbon atoms is the sum of the content of all fatty acids with at least 12 carbon atoms and without double bond. In the nomenclature used above in the examples (e.g. 14:0 myristic acid), the first number describes the number of carbon atoms and the second number describes the amount of double bonds.

Claims

CLAIMS1. A printing plate precursor (PR) comprising a dimensionally stable support (LI), a photosensitive layer (L2) of a photosensitive composition (PC), and optionally a protective layer (L3), wherein said photosensitive composition (PC) comprises a radical initiator or initiator system (RI), optionally an ethylenically unsaturated compound (EC), and a binder (B); and wherein said photosensitive composition (PC) further comprises a plasticizer (P) being a bio-based plasticizer (bio-P), and a peroxide scavenger (PS).

2. The precursor according to the previous claim, wherein the plasticizer (P) is a plant or animal oil, more preferably a plant or fish oil.

3. The precursor according to any of the previous claims, wherein the plasticizer (P) is present within the photosensitive composition in an amount of at least3 %, preferably at least 4 % by weight and / or at most 50 % by weight, based on the total content of the photosensitive composition.

4. The precursor according to any of the previous claims, wherein the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight, preferably more than 15.0 % by weight, even more preferably more than 20 % by weight, , based on the total content of the photosensitive composition.

5. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is present within the photosensitive composition in an amount of at least 0.15 % by weight, based on the total content of the photosensitive composition.

6. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is present within the photosensitive composition in an amount higher than 0.20 % by weight, preferably higher than 0.25 % by weight, more preferably higher than 0.4 % by weight, based on the total content of the photosensitive composition.

7. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) and the plasticizer (P) are included in the photosensitive composition in a scavenger / plasticizer ratio (Rs), whereby said scavenger / plasticizer ratio (Rs) is determined as : weight percentage of peroxide scavenger (PS) / weight percentage of plasticizer (P) wherein said scavenger / plasticizer ratio (Rs) is higher than 0.003.

8. The precursor according to claim 7, wherein the scavenger / plasticizer ratio (Rs) is higher than higher than 0.004, more preferably higher than 0.005, more preferably higher than 0.007, more preferably higher than 0.008, more preferably higher than 0.010, more preferably higher than 0.013, more preferably higher than 0.015, more preferably higher than 0.017.

9. The precursor according to claim 7, wherein the scavenger / plasticizer ratio (Rs) is higher than 0.003; and wherein the peroxide scavenger (PS) is present within the photosensitive composition in an amount higher than 0.20 % by weight, based on the total content of the photosensitive composition; and / or wherein the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight, based on the total content of the photosensitive composition.

10. The precursor according to claim 7, wherein the scavenger / plasticizer ratio (Rs) is more than 0.020, preferably more than 0.040.

11. The precursor according to any of claims 7 - 10, wherein the plasticizer (P) is present in an amount below 10.0 wt%, based on the total content of the photosensitive composition; and wherein the scavenger / plasticizer ratio (Rs) is more than 0.020, more preferably wherein the ratio is more than 0.1.

12. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is chosen from a class of any of the following:a phenol, phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine or any combinations thereof.

13. The precursor according to any of the previous claims, wherein the photosensitive composition (PC) comprises a first scavenger (PSI) and a second peroxide scavenger (PS2) that differs in structure from the first peroxide scavenger (PSI).

14. The precursor of the previous claim, wherein the second peroxide scavenger (PS2) is chosen from a class of any of the following: a phenol, a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine, preferably the second peroxide scavenger (PS2) is chosen from a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine.

15. The precursor of any of the previous two claims, wherein the wherein the first peroxide scavenger (PSI) is chosen from a class of any of the following: a phenol, phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine, preferably the first peroxide scavenger (PSI) is chosen from a phenol.

16. The precursor of any of claims 7 - 14, wherein the scavenger / plasticizer ratio (Rs) is determined with the weight percentage of all peroxide scavengers (PSI, PS2, . . .) within the composition and / or all plasticizers within the composition.

17. The precursor according to any of the previous claims, wherein the plasticizer (P) comprises at least one triglyceride.

18. The precursor according to any of the previous claims, wherein the plasticizer (P) has a central glycerol molecule bonded to three fatty acids.

19. The precursor according to any of the previous claims, wherein the plasticizer (P) contains carbon atoms including radioactive carbon- 14.

20. The precursor of the previous claim, wherein said radioactive carbon- 14 is present in the photosensitive composition (PC) in a concentration (C14%) of more than 0.01 * 1010percent, preferably in the range of 0.01 - 1.25 * 1010percent; wherein said concentration is determined by combustion at 900°C for 2 to 4 hours and measuring isotopic ratios using accelerator mass spectrometry as described by the European norm EN 16640 Bio-based products using the radiocarbon method (2017).

21. The precursor according to any of the previous claims, wherein the plasticizer (P) is extracted from one or more of the following, a seed, a fruit, or any other part of a plant or is extracted from an animal, such as a fish.

22. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by a hydroxyl value (hv) below 200, preferably below 166, more preferably below 150, even more preferably below 100, most preferably below 50.

23. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by an iodine value (iv) below 200, more preferably below 180, more preferably below 170, more preferably below 160, more preferably below 150, even more preferably below 140, most preferably below 120.

24. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by a content of oleic acid (o%), wherein said oleic acid content is higher than 5%, more preferably higher than 25%, more preferably higher than 50%.

25. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by an average molecular weight (MW) that is higher than 200 g / mol.

26. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by an average molecular weight higher than 500 g / mol, more preferably higher than 600 g / mol, more preferably higher than 700 g / mol, more preferably higher than 800 g / mol, more preferably higher than 850 g / mol, most preferably higher than 875 g / mol.

27. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by an inherent oxidative stability index (OXSI) below 32.9, more preferablybelow 10, more preferably below 8, more preferably below 7, more preferably below 6, more preferably below 5, most preferably below 2.

28. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by a content of saturated fatty acids with at least 12 carbon atoms, wherein said content is below 95wt%, more preferably below 90wt%, more preferably below 80wt%, more preferably below 70wt%, more preferably below 60wt%, even more preferably below 50wt%, most preferably below 40wt%.

29. The precursor according to any of the previous claims, wherein the plasticizer (P) is characterized by an unsaponifiable fraction (imp f), in particular a fraction consisting of one or more of beta-sitosterol, avenasterol, campesterol, stigmasterol, waxes, wherein said fraction is below 10 wt%, more preferably below 5 wt%, even more preferably below 3 wt %, most preferably below 1.5 wt %.

30. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is characterized by a polar surface area that is higher than 20 A2.

31. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is characterized by a partition coefficient (logP) that has a value higher than 5, more preferably higher than 6, even more preferably higher than 10, as determined via advanced Chemistry Development (ACD / Labs) Software VI 1.02 (© 1994-2024 ACD / Labs).

32. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is characterized by a molecular weight (MWps) that is higher than 220 g / mol.

33. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is characterized by a molecular weight (MWps) that is higher than 225 g / mol, preferably higher than 300 g / mol, more preferably higher than 400 g / mol, even more preferably higher than 500 g / mol.

34. The precursor according to any of the previous claims, wherein the dimensionally stable support (LI) is a stable plate substrate on which the photosensitive composition is arranged as the photosensitive layer (L2).

35. The precursor according to any of the previous claims, wherein the plasticizer (P) is a plant oil; and wherein the plasticizer (P) is present within the photosensitive composition in an amount more than 10.0 % by weight, based on the total content of the photosensitive composition.

36. The precursor according to claim 35, wherein the photosensitive composition (PC) comprises a first scavenger (PSI) and a second peroxide scavenger (PS2) that differs in structure from the first peroxide scavenger (PSI).

37. The precursor according any of claims 35 to 36, wherein the peroxide scavenger (PS) is characterized by a polar surface area that is higher than 22 A2.

38. The precursor according any of the claims 35 to 37, wherein the scavenger / plasticizer ratio (Rs) is more than 0.020.

39. The precursor according to claim 36 and any of the claims 35 to 38, wherein the first peroxide scavenger (PSI) is chosen from a phenol; and wherein the second peroxide scavenger (PS2) is chosen from a phenol, a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine.

40. The precursor according to claim 36 and any of the claims 35 to 39, wherein the second peroxide scavenger (PS2) is chosen from second peroxide scavenger (PS2) is chosen from a phosphite, thioether, hindered amine, secondary amine, primary amine, tertiary amine, amine.

41. The precursor according to any of the previous claims, wherein the peroxide scavenger (PS) is present within the photosensitive composition in an amount of more than 2%, preferably in the range of 2 % to 9 % by weight, based on the total content of the photosensitive composition.

42. A production process for producing a printing plate precursor, wherein the production process comprises: provision of a dimensionally stable support (LI); arranging a photosensitive composition (PC) on the dimensionally stable support (LI);wherein the photosensitive composition (PC) is the composition as defined any of the previous claims.

43. The production process according to the previous production process claims, wherein the photosensitive composition (PC) is melted and arranged on the support (LI) by extrusion.

44. The production process of the previous claim, wherein the photosensitive composition (PC) is calendared via a slot die between a cover film, preferably a cover film with laser-ablatable mask layer and a dimensionally stable support, preferably a carrier film45. The production process according to any of the previous production process claims, wherein the photosensitive composition comprises a complex shear viscosity r|* at 160 °C higher than 50 Pa s, more preferably higher than 100 Pa s, more preferably higher than 200 Pa s, more preferably higher than 300 Pa s.

46. A method of developing the printing plate precursor (PR) according to any of the previous precursor claims, wherein said precursor is developed into a printing plate (PL) according to : exposing the relief precursor layer to a source of radiation to cure the photopolymerizable composition (PC) and to form a relief image; and removing uncured portions of the relief precursor layer to form a printing plate, wherein the relief image defines ink-receiving regions and non-ink- receiving regions of the printing plate.

47. A printing plate, obtained from the printing plate precursor according to any of the plate precursor claims, having a micro hardness between 20opShA and 80opShA, more preferably between 25opShA and 70opShA.

Images