Relief precursors for printing plates using vegetable oils as plasticizers.

Abstract

The present invention provides a relief precursor comprising: a) a dimensionally stable support; and b) at least one photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiator system, at least one component having at least one unsaturated group, and at least one plasticizer, wherein the at least one plasticizer is a bio-based plasticizer, which has a UV transmittance at 365 nm of more than 15% for a 5% by weight solution of the plasticizer in n-hexane.

Description

FIELD OF THEINVENTION

[0001] The present invention relates to novel relief precursors for flexographic printing elements and to a method of making such precursors. The relief precursors are exposed to electromagnetic radiation in an imaging manner, whereby exposed portions of the photosensitive layer change their solubility or meltability behavior. Such flexographic printing elements are widely used in printing applications. Background of the invention

[0002] Flexographic printing elements are well known in the art and are particularly useful for commercial printing on a variety of products such as flexible plastic containers, cartons, plastic bags, boxes and envelopes. For the purposes of this specification, the uncured plate that will be used to prepare the (cured) flexographic printing element is referred to as the relief precursor. The relief precursor typically comprises, on the side that will be used for printing, a layer prepared from a photocurable polymer composition, which can be selectively cured by exposing the photocurable layer image-wise to light, for example UV light. The unexposed (uncured) parts of the layer can then be removed in a development bath, typically with an organic solvent or aqueous solution. After drying and optional post-exposure, the flexographic printing element is ready for use. It will be appreciated that the removal (development) of the uncured parts of the flexographic printing element must be done in a precise manner. Any unintentional uncured residue remaining on the flexographic printing plate can lead to an unclear image on the flexographic printing plate, and thus an unclear print.

[0003] Another method of making a printing element from the relief precursor is to expose the relief precursor to electromagnetic radiation in an imaging process, whereby the exposed portions of the photosensitive layer change their solubility or meltability behavior. The difference in meltability or solubility allows selective removal of the unexposed material to form a relief printing plate, which is then used to transfer ink from the printing plate to the printing substrate. Removal of the unexposed material can be achieved by treating the precursor with a developer that dissolves the unexposed material, or by thermal treatment that liquefies the unexposed material.

[0004] In EP 0 332 070 a process is described in which the non-exposed material is dissolved in water, aqueous solutions or solvents, and solvent mixtures in combination with mechanical interaction by a brush in a so-called developing unit.

[0005] Another option is to remove the liquefied material by continuously contacting it with an absorbent material. The absorbent developing material may be a nonwoven fabric of polyamide, polyester, cellulose or inorganic fibers onto which the softened material is adhered and then removed. Such methods are described, for example, in US 3,264,103, US 5,175,072 or WO 9,614,603.

[0006] Although the technology has been on the market for some time, there are still some problems to be solved or properties to be improved. A drawback of the above flexographic printing elements is that the printing results are not always consistent, as the filling of the negative lines and dots with ink occurs. Another drawback is that the development times are sometimes long, and the efficiency of the production of flexographic printing elements can still be improved.

[0007] Therefore, there is a need for flexographic printing elements that provide more consistent print results. Additionally, there is a need for shorter development times. Summary of the Invention

[0008] It is an object of the present invention to provide a relief precursor that increases the relief depth for both thermal or solvent development methods. The deeper relief enhances the printing result and prevents or reduces filling of the lines and dots of the negative with ink. A further object of the present invention is to provide a relief precursor that reduces the development time and improves the efficiency of the manufacturing process of the relief plate. Another object of the present invention is to reduce the anisotropy factor of the elastic modulus of the relief plate so that the plate can be used in any orientation. Yet another object of the present invention is to develop a practical method of manufacturing relief structures that can be easily scaled up.

[0009] The present invention therefore relates to a relief precursor as claimed in claim 1. In particular, there is provided a relief precursor comprising a dimensionally stable support and at least one photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiator system, at least one component having at least one unsaturated group, and at least one plasticizer, wherein the at least one plasticizer is a bio-based plasticizer, which has a UV transmittance at 365 nm of more than 15% for a 5% by weight solution of the plasticizer in n-hexane.

[0010] By using bio-based plasticizers, flexographic printing elements can be produced with less anisotropy. Furthermore, a deeper relief on the (thermally developable) relief plate is produced, resulting in a more consistent printing result. It is easier to remove the non-polymerized material more evenly, which improves the end of the printing result. Another advantage is that the relief is produced on the thermally developable relief plate, which requires fewer development cycles. Further advantages are that the print obtained is better, the deeper negative element results in less ink loading, less non-woven or waste material. Furthermore, the development time is shorter, and energy savings are achieved due to the reduced temperature and / or reduced development time. Also, by using bio-based plasticizers, flexographic printing elements can be produced with less stress / damage to the support layer.

[0011] The present invention also provides a method for producing a relief structure comprising the steps of: a) providing a relief precursor comprising a dimensionally stable support and a photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiator system, at least one component having at least one unsaturated group, and at least one plasticizer, wherein the at least one plasticizer is a bio-based plasticizer, which has a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 15%; b) imaging the relief precursor by ablation of a mask layer, by exposure through a mask, or by direct imaging; c) exposing the imaged relief precursor to electromagnetic radiation to harden the imaged areas; d) removing the non-hardened areas; e) optionally performing one or more steps of post-treatment, post-exposure and / or detackification; The present invention also relates to a method comprising the steps of:

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the present invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention.

[0013] Therefore, in the present invention, a relief precursor is provided, comprising a dimensionally stable support and at least one photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiator system, at least one component having at least one unsaturated group, and at least one plasticizer, wherein the at least one plasticizer is a bio-based plasticizer, which has a UV transmittance of more than 15% at 365 nm for a 5% by weight solution of the plasticizer in n-hexane. One of the advantages of this is that a deeper relief is produced on the (thermally developable) relief plate, leading to a more consistent printing result.

[0014] The relief precursor to be used with the claimed method is described below: The relief precursor generally comprises a dimensionally stable support or a support layer made of a first material and an additional layer made of a second material different from said first material. The dimensionally stable support may be a flexible metal, a natural or artificial polymer, paper, or a combination thereof. Preferably, the dimensionally stable support is a flexible metal, or a polymer film or sheet. In the case of a flexible metal, the support layer may comprise a thin film, a sieve-like structure, a mesh-like structure, a woven or non-woven structure, or a combination thereof. Sheets of steel, copper, nickel or aluminum are preferred and may be about 50 to 1000 μm thick. In the case of polymeric films, the films are dimensionally stable but bendable and may be made, for example, from polyalkylenes, polyesters, polyethylene terephthalate, polybutylene terephthalate, polyamides and polycarbonates, polymers reinforced with woven or nonwoven fabrics or layered fibers (for example glass fibers, carbon fibers, polymer fibers), or combinations thereof. Preferably, polyethylene and polyester foils are used, the thickness of which may be in the range of about 100 to 300 μm, preferably in the range of 100 to 200 μm.

[0015] The relief precursor preferably carries at least one further layer. For example, the further layer may be any one of the following: a direct relief printable layer (e.g. by laser), a solvent or water developable layer, a thermally developable layer, a photosensitive layer, a combination of a photosensitive layer and a mask layer. More preferably, the further layer is an adhesive layer under the support, an adhesive layer between the support and the photopolymer layer or between any other layer, a barrier layer, a laser ablatable layer and / or a protective layer. Optionally, one or more further additional layers on top of the further layer may be provided. Such one or more further additional layers may include a cover layer on top of all other layers, which is removed before the imageable layer is imaged. The one or more further additional layers may include a relief layer and an antihalation layer between the support layer and the relief layer or on the side of the support layer opposite the relief layer. The one or more further additional layers may include a relief layer, an imageable layer, and one or more barrier layers between the relief layer and the imageable layer that prevent oxygen diffusion. One or more adhesive layers may be located between the different layers to ensure proper adhesion of the different layers.

[0016] The relief precursor comprises at least a photosensitive polymer layer and may further comprise a mask layer. The mask layer may be ablated or altered in transparency during processing to form a mask with transparent and non-transparent areas. Under the transparent areas of the mask, the photosensitive layer undergoes a solubility and / or flow modification upon irradiation. The modification is used to produce the relief in one or more subsequent steps by removing parts of the photosensitive layer. The modification in solubility and / or flow may be achieved by photoinduced polymerization and / or crosslinking, making the irradiated areas less soluble and less meltable. In other cases, the electromagnetic radiation may cause the breaking of bonds or the cleavage of protective groups, making the irradiated areas more soluble and / or meltable. Preferably, a method using photoinduced crosslinking and / or polymerization is used.

[0017] The relief precursor comprises a photosensitive polymer layer comprising at least one photoinitiator or photoinitiator system. Photoinitiators are compounds that, upon irradiation with electromagnetic radiation, can form reactive species that can initiate polymerization reactions, crosslinking reactions, chain or bond cleavage reactions, which lead to a modification of the solubility and / or meltability of the composition. Photoinitiators are known, which cleave and generate radicals, acids or bases. Such initiators are known to those skilled in the art and are described, for example, in Bruce M. Monroe et al., Chemical Review, 93, 435 (1993), RS Davidson, Journal of Photochemistry and Biology A: Chemistry, 73, 81 (1993), M. Tsunooka et al., 25 Prog. Polym. Sci., 21, 1 (1996), FD Saeva, Topics in Current Chemistry, 1 56, 59 (1990), GG Maslak, Topics in Current Chemistry, 168, 1 (1993), HB Shuster et al., JAGS, 112, 6329 (1990), and IDF Easton et al., JAGS, 102, 3298 (1980), P. Fouassier and JF Rabek, Radiation Curing in Polymer Science and Technology, pp. 77-117 (1993), or K.K. Dietliker, Photoinitiators for free Radical and Cationic Polymerisation, Chemistry & Technology of UV & EB Formulation for Coatings, Inks and Paints, Volume 3, Sita Technology LTD, London 1991; or R.S. Davidson, Exploring the Science, technology and Applications of UV and EB Curing, Sita Technology LTD, London, 1999.Further initiators are described in JP 45-37377, JP 44-86516, U.S. Pat. No. 3,567,453, U.S. Pat. No. 4,343,891, EP 109772, EP 109773, JP 63138345, JP 63142345, JP 63142346, JP 63143537, JP 4642363, JP 59152396, JP 61151197, JP 6341484, JP 2249 and JP 24705, JP 626223, JPB 6314340, JP 1559174831, JP 1304453 and JP 1152109.

[0018] The photopolymer layer of the relief precursor comprises at least one binder. The binder according to the invention is a linear, branched or dendritic polymer, which may be a homopolymer or a copolymer. The copolymer may be a random, alternating or block copolymer. As binders, those polymers are used which are either soluble, dispersible or emulsifiable either in aqueous solutions, in organic solvents or in a combination of both. Suitable polymer binders are those conventionally used for the production of letterpress printing plates, for example fully or partially hydrolyzed polyvinyl esters, for example partially hydrolyzed polyvinyl acetates, polyvinyl alcohol derivatives, for example partially hydrolyzed vinyl acetate / alkylene oxide graft copolymers or polyvinyl alcohols subsequently acrylated by polymer-analogous reactions, for example those described 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 in water / alcohol mixtures, as described, for example, in EP-A-00856472 or DE-A-1522444. For flexographic printing precursors, elastomeric binders are used. The thermoplastic-elastomeric block copolymers comprise at least one block, which essentially consists of an alkenyl aromatics and at least one block essentially consisting of a 1,3-diene. The alkenyl aromatics may be, for example, styrene, α-methylstyrene or vinyltoluene. Styrene is preferred. The 1,3-dienes are preferably butadiene and / or isoprene. These block copolymers may be linear, branched or radical block copolymers. Generally speaking, they are triblock copolymers of the ABA type, but they may also be diblock polymers of the AB type or polymers with several alternating elastomeric and thermoplastic blocks, for example ABABA.Mixtures of two or more different block copolymers can also be used. Commercially available triblock copolymers often contain a certain fraction of diblock copolymers. The diene units can be 1,2- or 1,4-linked. Also usable are further thermoplastic elastomeric block copolymers with styrene and block and random styrene-butadiene midblocks. Also usable are, of course, mixtures of two or more thermoplastic elastomeric binders, provided that the properties of the relief-forming layer are not adversely affected as a result. As well as the mentioned thermoplastic-elastomeric block copolymers, the photopolymerizable layer may also contain further elastomeric binders besides the block copolymers. With this type of additional binder, also called second binder, the properties of the photopolymerizable layer can be modified. An example of a second binder is vinyltoluene-a-methylstyrene copolymer. These polymeric binders generally represent 20-98% by weight, preferably 50-90% by weight, of the total amount of the layer.

[0019] The photopolymer layer further comprises at least one component having at least one unsaturated group. Preferably, these components are reactive compounds or monomers suitable for the preparation of the mixture, which are polymerizable and compatible with the binder. 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, ethylenically unsaturated monomers are used which should be compatible with the binder and which have at least one polymerizable ethylenically unsaturated group. As monomers, it is possible to use, in particular, esters or amides of acrylic or methacrylic acid with mono- or polyfunctional alcohols, amines, amino alcohols, or hydroxyethers and hydroxyesters, esters of fumaric or maleic acid with allyl compounds. Esters of acrylic or methacrylic acid are even more preferred. Preferred are 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 monomers used together in the relief-forming layer is generally 1 to 20% by weight, preferably 5 to 20% by weight, based in each case on the sum of all constituents of the relief-forming layer. The amount of monomers having two ethylenically unsaturated groups is preferably 5 to 20% by weight, more preferably 8 to 18% by weight, based on the sum of all constituents of the relief-forming layer.

[0020] The photopolymer layer may include further components selected from the group consisting of further polymers, fillers, plasticizers, antiblocking agents, monomers, additives (e.g., stabilizers, dyes), crosslinkers, binders, color forming compounds, dyes, pigments, antioxidants, and combinations thereof.

[0021] The relief precursor comprises the above-mentioned photosensitive polymer layer and may further comprise a mask layer, which comprises at least one compound capable of absorbing electromagnetic radiation and a component that can be removed by ablation (also known as a digital plate precursor). 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 arranged between the photosensitive layer and the mask layer. This functional layer is preferably a barrier layer and blocks oxygen. The mask layer may be imageable by ablation and may be removable by a solvent or by thermal development. The mask layer is heated and removed by irradiation with high-energy electromagnetic radiation, thereby forming an image-wise structured mask, which is used to transfer the structure onto the relief precursor. To do so, the mask layer may be opaque in the UV region and absorbs radiation in the VIS-IR region of the electromagnetic spectrum. 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 330-420 nm is in the range of 1-5, preferably in the range of 1.5-4, and more preferably in the range of 2-4.

[0022] The thickness of the ablatable mask layer may be in the range of 0.1 to 5 μm, preferably 0.3 to 4 μm, more preferably 1 to 3 μm. The laser sensitivity (1 cm 2 (measured as the energy required to ablate the 2 within the range of 0.3 to 5 J / cm 2 in the range of 0.5 to 5 J / cm 2 may be within the range.

[0023] The photosensitive polymer layer comprises at least one plasticizer, at least one of which is a bio-based plasticizer. Bio-based plasticizers are derived at least partially from renewable biological sources, such as plants (e.g. agricultural crops or trees), microorganisms (e.g. algae or yeasts) or animals. Bio-based plasticizers are often environmentally friendly, but are not necessarily biodegradable. Bio-based materials may be chemically altered or modified with synthetic compounds, for example to change their physical and / or chemical properties. They then remain bio-based materials. These plasticizers are generally used to maintain softness and flexibility in various temperature ranges. These plasticizers can at least partially replace other plasticizers, such as synthetic plasticizers. Many of the non-bio-based plasticizers, especially the so-called phthalates, are harmful to human health and may affect hormone balance. Others are based on mineral oil or polybutadiene and are not readily biodegradable. It is therefore advantageous to at least partially replace them with bio-based plasticizers. We further found that when bio-based plasticizers are used for thermal development, greater relief depths can be achieved for all concentrations investigated. Moreover, we found that the use of, for example, rapeseed oil instead of mineral oil allows for faster washout rates and results in shorter processing times. Preferably, the bio-based plasticizer is a vegetable oil, a fatty acid, and / or a fatty acid ester of a mono- or polyfunctional alcohol. 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 triglyceride (MCT) oil, and / or linseed oil.Further examples are acai oil, lanolin (adeps lanae), ahiflower oil, algae oil, aloe vera, amaranth oil, apricot kernel oil, argan oil, avocado oil, babassu oil, baobab oil, beeswax, black cumin oil, black cumin seed oil, black currant oil, borage oil, brazil nut oil, broccoli seed oil, calendula oil, camelina oil, candelilla wax, carnauba wax, castor oil, chia oil, chilean hazelnut oil, cocoa butter, corn oil, cottonseed oil, theobroma grandiflorum seed oil, evening primrose oil, fish oil, glycerol, grape seed oil, peanut oil, hazelnut oil, hemp oil, high oleic canola oil, high oleic soybean oil, high oleic sunflower oil, illipe butter, jatropha curcas oil, jojoba oil, kukui nut oil, lanolin, laurel oil, macadamia nut The following oils are also included in the list: corn oil, mango butter, manketty oil, marula oil, meadowfoam seed oil, milk thistle oil, moringa oil, murumuru fat, mustard seed oil, olive oil, orus oil, omega-3-6-9-oil, palm olein, palm stearin, paradise nut oil, passion fruit seed oil, peach kernel oil, peanut oil, pecan nut oil, perilla oil, pistachio nut oil, plum kernel oil, pomegranate oil, poppy seed oil, pumpkin seed oil, hydrolyzed rapeseed oil, raw wool grease, rice bran oil, rosehip kernel oil, sacha inchi oil, safflower oil, sal fat, sea buckthorn oil, sesame oil, shea butter, hydrolyzed soybean oil, partially hydrolyzed soybean oil, squalane, hydrolyzed sunflower oil, sunflower wax, Japan wax, tallow, tamanu oil, walnut oil, wheat kernel oil, wool fat, wool alcohol.

[0024] The composition and properties of vegetable oils and fats are highly dependent on many factors. Fatty acid composition and impurities in the oil affect chemical and physical properties such as UV transmittance, light transmittance, Gardner color and iodine value. The main influencing factors are: type of grain, growing region, breeding, refining and processing (e.g. filtration, bleaching, neutralization, deodorization). Furthermore, the composition and properties of oils can be modified by blending, distillation, fractionation, hydrogenation, transesterification with chemical catalysts, transesterification with specific lipases, enzyme enhancement, biological solutions, domestication of wild grains, breeding of conventional seeds, (intra-seed) genetic engineering, lipids from microorganisms or other non-conventional sources. Depending on these factors, the chemical composition and properties of vegetable oils from different grain types can be more similar to each other than to one type of grain.

[0025] Within the same batch of oil, the properties may depend on the storage. Long storage times, high storage temperatures and / or contact with air and / or oxygen may lead to aging of the oil. Possible effects may be, for example, a decrease in UV transmittance, light transmittance and iodine value, or an increase in Gardner color and hydroxyl value. Virgin and well-processed oils with high UV transmittance and / or high light transmittance and / or low Gardner color and / or low hydroxyl value are preferred compared to aged oils or crude vegetable oils with low UV transmittance and / or low light transmittance and / or high Gardner color and / or high hydroxyl value. Slow aging and storage over time may be accelerated by heating the oil under the influence of air.

[0026] The photopolymer layer comprises at least one plasticizer, at least one of which is a bio-based plasticizer. Other plasticizers may also be present, which may be, as such, a mixture of two or more bio-based plasticizers, or a mixture of at least a bio-based plasticizer and a conventional plasticizer(s). Thus, a mixture of different plasticizers may also be used, as long as at least one plasticizer is a bio-based plasticizer. Examples of other suitable plasticizers include modified and unmodified natural oils and resins, such as high-boiling paraffinic, naphthenic or aromatic mineral oils, synthetic oligomers or resins, such as oligostyrenes, high-boiling esters, oligomeric styrene-butadiene copolymers, oligomeric alpha-methylstyrene / p-methylstyrene copolymers, liquid oligobutadienes, especially those with a molecular weight of 500 to 5000 g / mol, or liquid oligomeric acrylonitrile-butadiene copolymers or oligomeric ethylene-propyl-ene-diene copolymers. Preferred are polybutadiene oils (liquid oligobutadienes), especially those with a molecular weight of 500 to 5000 g / mol, high-boiling aliphatic esters, such as, in particular, alkyl esters of mono- and dicarboxylic acids, examples being stearates or adipates, and mineral oils. Particularly preferred are high-boiling, substantially paraffinic and / or naphthalenic mineral oils. For example, it is possible to use so-called paraffin-based solvents and characteristic oils. With regard to mineral oils, the skilled person distinguishes between technical white oils, which may also have a very low aromatic content, and medical white oils, which are substantially aromatic-free. They are commercially available and equally well suitable. Particularly widespread as plasticizers are white oils or oligomeric plasticizers, such as, in particular, polybutadiene oils, carboxylic esters, phthalates. In this respect, reference may be made via the examples of EP 992849 and EP 2279454. The amount of plasticizer optionally present is determined by the skilled person according to the desired properties of the layer.

[0027] The plasticizer preferably has a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 30%, more preferably greater than 50%, and even more preferably greater than 60%.

[0028] Advantageously, the plasticizer has a light transmittance of more than 78% relative to medium chain triglyceride (MCT) oil (=100% transmittance). The measurement of clear MCT oil, which is more resistant to oxidation due to the lack of double bonds, was set as the standard with 100% light transmittance.

[0029] Plasticizers may be characterized by their Gardner color. The Gardner color scale is a one-dimensional scale used to measure shades of yellow. The Gardner and APHA / Pt-Co / Hazen color scales overlap with the Gardner scale measuring higher concentrations of yellow shades and the APHA scale measuring very low levels of yellow shades. The color of transparent liquids has been studied visually since the early 19th century. Color changes may suggest contaminants or impurities in raw materials, processing variations, or product deterioration over time. Advantageously, the plasticizer has a Gardner color according to ISO 4630:2015 of less than 7.

[0030] A plasticizer may also be characterized by its hydroxyl number. The hydroxyl number is defined as the number of milligrams of potassium hydroxide required to neutralize the acetic acid taken up in the acetylation of one gram of a chemical containing free hydroxyl groups. The hydroxyl number is a measure of the content of free hydroxyl groups in a chemical, usually expressed in units of the mass of potassium hydroxide (KOH) in milligrams equivalent to the hydroxyl content of one gram of the chemical. The analytical method used to determine the hydroxyl number traditionally involves the acetylation of the free hydroxyl groups of a material with acetic anhydride in a pyridine solvent. After completion of the reaction, water is added and the remaining unreacted acetic anhydride is converted to acetic acid, which is measured by titration with potassium hydroxide. The hydroxyl number may then be calculated. Advantageously, the plasticizer has a hydroxyl number according to ASTM D1957-86 of less than 430, preferably less than 250, and even more preferably less than 168.

[0031] Plasticizers can also be characterized by their iodine value. The iodine value in chemistry (or iodine adsorption value or iodine number or iodine index, usually abbreviated as IV) is the mass of iodine in grams consumed by 100 grams of chemical. The iodine number is often used to determine the degree of unsaturation in fats, oils and waxes. In fatty acids, unsaturation occurs mainly as double bonds that are highly reactive towards halogens, in this case iodine. Therefore, the higher the iodine value, the more unsaturated bonds the fat contains. The plasticizers to be used in the relief precursor of the present invention preferably have an iodine value according to ISO3961:2018 of less than 200, more preferably less than 150.

[0032] A plasticizer can be further characterized by its Hansen solubility parameter, δt. Hansen solubility is based on the idea that one molecule will dissolve similarly, which is defined as "similar" to another if it binds to itself in a similar way. A description of the determination of the Hansen solubility parameter can be found in J. Brandrup, EH Immergut, EA Grulke, Polymer Handbook 4th ed., Wiley, New York, 1999, pp. VII / 675-VII / 714. Advantageously, the plasticizer has a Hansen solubility parameter δt in the range of 16.0 to 20.5, more preferably in the range of 16.0 to 17.5.

[0033] The amount of plasticizer optionally present is determined by the skilled artisan according to the desired properties of the layer. The concentration of the plasticizer in the photopolymer layer is preferably in the range of 3-70% by weight, more preferably in the range of 5-65% by weight, even more preferably in the range of 10-65% by weight, and most preferably in the range of 20-60% by weight, based on the total weight of the photopolymer layer.

[0034] For example, a heat treatment may be used to remove volatile components in order to initiate and / or complete the reaction and increase the mechanical and / or thermal stability of the relief structure. For the heat treatment, known techniques can be used, such as, for example, heating with heated gas or liquid, IR radiation, and any desired combination of these. In this context, ovens, blowers, lamps, and any desired combination of these can be used. In addition to debanding, surface modification can also be achieved by treatment with gas, plasma and / or liquid, especially if the reactive substance used is also present. In the present invention, it is preferred that the development step is carried out by heat treatment and removal of the liquefied parts.

[0035] The present invention also provides a method for producing a relief structure comprising the steps of: a) providing a relief precursor comprising a dimensionally stable support and a photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiator system, at least one component having at least one unsaturated group, and at least one plasticizer, wherein the at least one plasticizer is a bio-based plasticizer, which has a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 15%; b) imaging the relief precursor by ablation of a mask layer, by exposure through a mask, or by direct imaging; c) exposing the imaged relief precursor to electromagnetic radiation to harden the imaged areas; d) removing the non-hardened areas; e) optionally performing one or more steps of post-treatment, post-exposure and / or detackification; The present invention is also directed to a method, including

[0036] In step b) of the method for producing a relief structure, the relief precursor is imaged by ablation of a mask layer, by exposure through a mask or by direct imaging. The mask layer can be a separate layer, which is applied to the relief precursor following removal of a possibly present protective layer, or it can be an integral layer of the precursor, which is in contact with the relief layer or with one of the optional layers above the relief layer and is covered by a possibly present protective layer.

[0037] The mask layer can also be a commercially available negative, which can be produced, for example, by means of a photographic method based on silver halide chemistry.The mask layer can also be a composite layer material, in which a transparent layer is produced in an otherwise opaque layer by means of image-based exposure, as described, for example, in EP-A-3139210, EP-A-1735664, EP-A-2987030, EP-A-2313270.This can be carried out by ablation of an opaque layer on a transparent carrier layer, as described, for example, in US Pat. No. 6,916,596, EP-A-816,920, or by selective application of an opaque layer to a transparent carrier layer, as described, for example, in EP-A-992,846, or can be written directly on the relief-forming layer, for example, by printing with an opaque ink by means of inkjet, as described, for example, in EP-A-1195,645.

[0038] The image-wise removal of the mask layer is preferably carried out using an ablation technique. As a rule, the electromagnetic radiation for ablating the mask will generally be radiation having a wavelength in the range of 300 nm to 20000 nm, preferably in the range of 500 nm to 20000 nm, particularly preferably in the range of 800 nm to 15000 nm, very particularly preferably in the range of 800 nm to 11000 nm. In addition to solid-state lasers, gas lasers or fiber lasers can also be used. Preferably, in laser ablation, Nd:YAG lasers (1064 nm) or CO2 lasers (9400 nm and 10600 nm) are used. For selective removal of the mask layer, one or more laser beams are controlled so that the desired print image is generated.

[0039] Direct image exposure can be achieved in that the areas to be crosslinked are selectively exposed. This can be achieved, for example, by using a monitor where a specific image point indicates which emitted radiation is activated, by using a movable LED strip, by means of an LED array where individual LEDs are specifically switched on and off, by means of an electronically controllable mask where an image point indicates which are switched to transparent allowing radiation to pass from the radiation source, by means of a suitable orientation of mirrors, by means of a projection system where the image point is exposed to radiation from the radiation source, or by a combination of these, with one or more laser beams that are appropriately controlled. Preferably, direct exposure is carried out by means of a controlled laser beam or a projection system with mirrors. The absorption spectrum of the initiator or initiator system and the emission spectrum of the radiation source must at least partially overlap.

[0040] The wavelength of the electromagnetic radiation is in the range of 200 nm to 20000 nm, preferably in the range of 250 nm to 1100 nm, particularly preferably in the UV range, very particularly preferably in the range of 300 nm to 450 nm. In addition to broadband radiation of electromagnetic radiation, it may be advantageous to use narrowband or monochromatic wavelength ranges, which can be generated, for example, by using suitable filters, lasers or light-emitting diodes (LEDs). In these cases, the wavelengths 350 nm, 365 nm, 385 nm, 395 nm, 400 nm, 405 nm, 532 nm, 830 nm, 1064 nm (and also about 5 nm to 10 nm shorter and / or longer than this), on their own or in combination, are preferred.

[0041] In step c) of the method for producing a relief structure, the imaged relief precursor is exposed to electromagnetic radiation to harden the imaged areas. The relief is produced by exposure with electromagnetic radiation through a mask film. Upon exposure, the exposed areas undergo crosslinking, while the unexposed areas of the precursor remain soluble or liquefiable and are removed by a suitable method. Where an imaging mask is present, the radiation can be carried out over a large area, or, when operating without a mask layer, the radiation can be carried out in an imaged manner (effectively dotwise) over small areas by means of a guided laser beam or a positionally resolved projection of electromagnetic radiation. The wavelength of the emitted electromagnetic waves in this case is in the range of 200 to 2000 nm, preferably in the range of 200 to 450 nm, more preferably in the range of 250 nm to 405 nm. The radiation can be carried out continuously or in pulsed form or in several short periods with continuous radiation. In addition to broadband radiation of electromagnetic waves, it may be advantageous to use narrow band or monochromatic wavelength ranges, as may be produced with appropriate filters, lasers or light emitting diodes (LEDs). In these cases, wavelengths in the ranges of 350, 365, 385, 395, 400, 405, 532, 830, 1064 nm are preferred, individually (and above and / or below about 5-10 nm) or in combination. The intensity of the radiation may vary widely herein, ensuring that a dose is used that is sufficient to cure the radiation-curable layer sufficiently for the subsequent development procedure. The radiation-induced reaction, possibly after further thermal treatment, must be sufficiently advanced so that the exposed areas of the radiation-sensitive layer become at least partially insoluble and therefore cannot be removed in the development step. The intensity and dose of the radiation depend on the reactivity of the formulation and on the duration and efficiency of the development. The intensity of the radiation may range from 1 to 15000 mW / cm 2 in the range of 5 to 5000 mW / cm 2 in the range of 10 to 1000 mW / cm 2 The radiation dose is in the range of 0.3 to 6000 J / cm 2 within the range of 3 to 100 J / cm 2within the range of 6 to 20 J / cm 2 The exposure to the energy source may also be carried out in an inert atmosphere, for example in rare gases, CO2 and / or nitrogen, or under liquid, which does not damage the relief precursor. The exposure through the mask may be carried out using optical devices, for example for beam expansion, by a two-dimensional arrangement of multiple point-like or linear sources (for example light guides, light emitters), for example fluorescent strip lamps arranged next to each other, by moving a linear source or an extended arrangement of LEDs (arrays) relative to the relief precursor, for example by uniform movement of the LEDs, or by a combination of these. Preferably, fluorescent strip lamps arranged next to each other or a relative movement between one or more LED strips and the relief precursor is used.

[0042] Radiation can be carried out sequentially, in a pulsed manner, or in multiple short bursts using continuous radiation.

[0043] In step d) of the method for producing a relief structure, the non-cured areas are removed. The removal of the non-cured areas of the precursor is preferably carried out by treatment with heat, the developing material being configured to adsorb the non-cured material. More preferably, in step d), the precursor is heated to a temperature in the range of 70-200°C, preferably in the range of 80-180°C, more preferably in the range of 90-165°C. Heating of the exposed relief precursor can be performed by all techniques known to the skilled person, for example by irradiation with IR light, by the action of a hot gas (for example air), by the use of hot rollers, or any desired combination of these. To remove the (tacky) liquid areas, it is possible to use all techniques and methods familiar to the skilled person, for example blowing, suction, dabbing, blasting (with particles and / or droplets), stripping, wiping, transfer to the areas for development, and any desired combination of these. Preferably, the liquid material is taken up (absorbed and / or adsorbed) by the developing medium, which is continuously in contact with the heated surface of the relief precursor. This procedure is repeated until the desired relief height is reached. Development media that can be used are paper, woven and nonwoven fabrics, and films, which are capable of taking up the liquefied material and can be composed of natural and / or polymeric fibers. Preferred are polymeric nonwoven fabrics or nonwoven fibrous webs, such as cellulose, cotton, polyester, polyamide, polyurethane, and any desired combinations thereof that are stable at the temperatures used in development.

[0044] Alternatively, in step d), the precursor is treated with a developing liquid to dissolve the non-cured material. The techniques applied in this development step can be all those familiar to the skilled artisan. The solvent or mixtures thereof, aqueous solutions and aqueous-organic solvent mixtures may contain 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 artisan, such as immersion, washing or spraying with the developing medium, brushing in the presence of the developing medium and suitable combinations thereof. Preference is given to development with neutral aqueous solutions or water, removal assisted by means of a rotating brush or a plush web. Another way of influencing the development is to control the temperature of the developing medium and to accelerate it, for example by increasing the temperature. In this step, it is also possible that further layers are still present on the radiation-sensitive layer to be removed if these layers can be released during development and are sufficiently dissolved and / or dispersed in the development medium.

[0045] In step e) of the method for producing a relief structure, one or more steps of post-treatment, post-exposure and / or detackification are optionally carried out. These include, for example, heat treatment, drying, treatment with electromagnetic radiation, treatment with plasma, treatment with gas or with liquid, attachment of specific features, cutting into formats, coating and any desired combinations thereof. For example, heat treatment may be used to improve the mechanical and / or thermal stability of the relief structure and to remove volatile components, in order to initiate and / or complete the reaction. For heat treatment, known techniques may be used, for example heating with heated gas or liquid, IR radiation and for example any desired combinations thereof. In these contexts, ovens, blowers, lamps and any desired combinations thereof may be used. In addition to debanding, surface modification may also be achieved by treatment with gas, plasma and / or liquid, especially in the case where the applied reactive substance is also present. For example, treatment with electromagnetic radiation may be used for the purpose of detackifying the surface of the relief structure to trigger and / or complete the polymerization and / or crosslinking reactions. In this case, the wavelength of the emitted electromagnetic wave is within the range of 200 to 2000 nm. EXAMPLES

[0046] The following non-limiting examples are provided to illustrate the present invention.

[0047] Determination of UV transmittance: The UV transmittance at 365 nm was measured in n-hexane with a plasticizer concentration of 5 mass in a macrocuvette 110-QS, 10 mm. The UV / Vis spectra were recorded on a Varian Cary50, Scan Software Version: 02.00, Beam Mode: Dual Beam. Baseline correction was performed with a blank sample of pure n-hexane and applied using the instrument's integrated software.

[0048] Determination of light transmittance: Pure oil was filled into a macrocuvette 110-QS, 10 mm, and the light transmittance was measured by placing the cuvette in a density meter Gretag Macbeth D200II (measuring tube: V(λ), measuring aperture: diameter 3 mm) and pressing the probe head on the macrocuvette. The measurement value of a transparent MCT oil, which is resistant towards oxidation due to the lack of double bonds, was set as the standard with 100% transmittance. The average value of three measurements was determined.

[0049] Example 1 As an example of the invention, a material in the form of a plate was produced: Block copolymers of SIS triblock, having a styrene content of 14-15%, a diblock fraction of approximately 26%, and a vinyl group content of 7-8% by weight, as shown in Table 1; 5 parts by weight of hexanediol diacrylate, 2.5 parts by weight of benzyl dimethyl ketal as photoinitiator and plasticizer in the parts by weight shown in Table 1; 1.5 parts by weight of further components, such as inhibitors and dyes The photosensitive polymer mixture containing was melted at elevated temperature (120-180°C) in an extruder and calendared through a slot die between a cover film with a laser-ablatable mask layer having a thickness of 105 μm and a carrier film having a thickness of 125 μm, thus obtaining a relief precursor (photosensitive polymer + film) with a total thickness of 4040 μm.

[0050] Thermal development: The relief precursor was exposed to UVA light from the backside through the carrier foil for 100 seconds (machine type: Combi FIII, UV output 16 mW / cm 2). The laser ablatable mask on the front side was imaged with a Xeikon TfxX20 laser (8.5 U / s rotation, 35 W power (100%)) to form a square 20 cm x 20 cm with a 4.5 cm frame in such a way that the mask layer is still in the center while in the frame part it is removed. The plate was irradiated with UVA light from the front side for 15 minutes (machine type: Combi FIII, UV power 16 mW / cm). 2 ). The non-polymerized material and remaining black mask layer were removed by thermal development using an Xpress thermal developer (Flint Group). Ten passes at a speed of 0.7 in / sec were used with the temperature set at 162.8°C (325°F), IR intensity set at 40%, blower intensity set at 25%, and developer rotation speed set at 100%. The pressure was set at 60 psi during the first four passes, followed by five passes at 80 psi and one final pass at 40 psi. After development, the areas covered by the black mask layer form a "floor" that is lower than the exposed areas, which form the "relief". The floor thickness was measured at nine different points in the center and an average value was determined. The cliché thickness was measured at five different points on the frame and an average value was determined. The relief depth was calculated by subtracting the floor thickness from the cliché thickness and is shown in Table 1.

[0051] Solvent Development: For solvent development, a Flowline FIII system with nylosolv A as the solvent was used, with a solids content of 4.8-5.1%, a brush height setting of 1.5 mm, and a solvent temperature of 35° C. The plates were then dried at 60° C. for 2 hours. The washout rates to achieve a washout depth of 1700 μm were determined according to chapter “3.2 Determination of Plate processing times” in the nyloflex® User Guide, page 16, October 2007 version.

[0052] [Table 1]

[0053] From the results presented in Table 1, it can be concluded that for thermal development, greater relief depths can be achieved when using vegetable oil (rapeseed oil) for all concentrations investigated. Moreover, it becomes clear that the use of rapeseed oil instead of mineral oil allows faster washout rates, resulting in shorter processing times.

[0054] Example 2: A material in the form of a plate was prepared with the following composition: 64.4 parts by weight of an SBS triblock copolymer having a styrene content of 25% and a diblock fraction of approximately 10% as a binder; 10 parts by weight of hexanediol diacrylate, 2.0 parts by weight of benzyl dimethyl ketal as a photoinitiator, 21 parts by weight of a plasticizer, and 2.6 parts by weight of further components, such as inhibitors and dyes A photosensitive polymer mixture comprising:

[0055] The mixture was melted in an extruder at elevated temperature (120-180°C) and calendared through a slot die between a cover film with a laser-ablatable mask layer having a thickness of 105 μm and a carrier film having a thickness of 175 μm, thus obtaining a relief precursor (photosensitive polymer + film) with a total thickness of 1240 μm.

[0056] Thermal development: Plate processing and relief depth evaluation were performed as in Example 1. Backside exposure was reduced to 10 seconds. Thermal development conditions were varied: one pass was used at a speed of 0.7 in / sec, whereby the temperature was set at 290° F., IR intensity was set at 40%, blower intensity was set at 25%, developer spin speed was set at 100%, and pressure was set at 60 psi. Material results are in Table 2.

[0057] Solvent Development: Solvent development was performed as in Example 1 with a target washout depth of 900 μm and a brush height setting of 0 mm. Material results are in Table 2.

[0058] Anisotropy factor: The anisotropy factor was determined by stress-tensile measurements using a zwickiLine universal testing machine and a load cell with a nominal force of 200 N. The test specimens (size 5A, according to ISO 527-2:1996) were placed on an exposure plate with a removable PET foil (machine type: Combi FIII, UV power 16 mW / cm 2 ) stamping. Two measurements were performed, one longitudinal and one transverse to the extrusion direction of the plate. The stress was measured at 125% tension. To obtain the anisotropy factor, the longitudinal stress was divided by the transverse stress. The material results are in Table 2.

[0059] [Table 2]

[0060] From the results presented in Table 2, it can be concluded that for thermal development, a greater relief depth can be achieved when using vegetable oil (rapeseed oil) compared to mineral oil or polybutadiene. Moreover, it is clear that using rapeseed oil instead of mineral oil or polybutadiene allows for a faster washout rate, resulting in shorter processing times and giving a greater washout depth.

[0061] In addition, the anisotropy factor of the plates with mineral oil as a plasticizer is higher than that of the plates with polybutadiene or rapeseed oil. An anisotropy factor of 1.0 is desired, which means that the elastic behavior of the plate is independent of its orientation.

[0062] Example 3: A material in the form of a plate was prepared with the following composition: 45.4 parts by weight of an SBS triblock copolymer having a styrene content of 31% and a diblock fraction of approximately 14% as a binder; 6.5 parts by weight of hexanediol diacrylate, 1.4 parts by weight of benzyl dimethyl ketal as photoinitiator, 26.2 parts by weight of mineral oil as a first plasticizer, 19.5 parts by weight of a second plasticizer, and 1.0 part by weight of further components, such as inhibitors and dyes A photosensitive polymer mixture comprising:

[0063] The mixture was melted in an extruder at elevated temperature (120-180°C) and calendared through a slot die between a cover film with a laser-ablatable mask layer having a thickness of 105 μm and a carrier film having a thickness of 125 μm, thus obtaining a relief precursor (photosensitive polymer + film) with a total thickness of 3280 μm.

[0064] Thermal development: Plate processing and evaluation of relief depth and thermal development were carried out as in Example 1. Material results are in Table 3.

[0065] Solvent Development: Solvent development was performed as in Example 1 with a target washout depth of 1200 μm. Material results are in Table 3.

[0066] 400μm negative dot depth: To evaluate the depth of the negative element, the test model contains a dot with a diameter of 400 μm. To achieve good printing results, a larger depth of the negative element is typically desired. Depth measurements were performed with Dot Check WH360.

[0067] [Table 3]

[0068] From the results presented in Table 3 it can be concluded that for thermal development a greater relief depth can be achieved when using vegetable oil (rapeseed oil) compared to polybutadiene.

[0069] Moreover, it appears that the use of rapeseed oil instead of polybutadiene allows for faster washout rates, resulting in shorter processing times. In addition, the depth of the negative dots increased when rapeseed oil was used.

[0070] Example 4: A material in the form of a plate was prepared with the following composition: 58.0 parts by weight of an SBS triblock copolymer having a styrene content of 30% and no diblock as a binder; 7.5 parts by weight of hexanediol diacrylate, 2.0 parts by weight of benzyl dimethyl ketal as a photoinitiator, 31 parts by weight of a plasticizer (A: polybutadiene B: rapeseed oil), and 1.5 parts by weight of further components, such as inhibitors and dyes A photosensitive polymer mixture comprising:

[0071] The mixture was melted in an extruder at elevated temperature (120-180°C) and calendared through a slot die between a cover film with a laser-ablatable mask layer having a thickness of 105 μm and a carrier film having a thickness of 175 μm, thus obtaining a relief precursor (photosensitive polymer + film) with a total thickness of 1240 μm.

[0072] Thermal development: Plate processing and evaluation of relief depth and thermal development were performed as in Example 2. Material results are in Table 4.

[0073] Solvent Development: Solvent development was performed as in Example 2. Material results are in Table 4.

[0074] [Table 4]

[0075] From the results presented in Table 4, it can be concluded that for thermal development, a greater relief depth can be achieved when using vegetable oil (rapeseed oil) compared to polybutadiene. Moreover, it is evident that using rapeseed oil instead of polybutadiene allows for a faster washout rate, resulting in shorter processing times. In addition, the wash depth and the depth of the negative dots are increased when vegetable oil is used.

[0076] Example 5: A material in the form of a plate was prepared with the following composition: A photopolymer mixture containing the same ratios and components as described in Example 2 was obtained by mixing the components in a solution (solvent: toluene, solvent content: 55 parts by weight) at reflux. The plasticizers were varied as described in Table 5. The mixture was stirred until a homogeneous solution was obtained. After cooling down to room temperature, the solution was cast onto a carrier film with a thickness of 175 μm. A layer was formed by dispersing the solution evenly using the doctor blade method and an air gap of 3160 μm. The layer was dried at 20° C. for 15 hours and then at 65° C. for 4 hours to evaporate the solvent. A cover film with a laser ablatable mask layer with a thickness of 105 μm was laminated on top using a heated roller (110° C.) to obtain a relief precursor (photopolymer+film) with a total thickness of 1200-1300 μm.

[0077] With castor oil, plates could not be produced due to incompatibility with the formulation since an oil film was observed after the photopolymer layer was cooled down to room temperature.

[0078] Thermal development: Plate processing and evaluation of relief depth and thermal development were performed as in Example 2. Material results are in Table 5.

[0079] Solvent Development: Solvent development was performed as in Example 2. Material results are in Table 5.

[0080] Backside Exposure: Backside exposure times to achieve a relief depth of 700 μm for solvent development were determined according to chapter “3.2 Determination of plate processing times” in the nyloflex® User Guide, page 17, version of October 2007, using a Combi FIII, UV output 16 mW / cm 2 It was decided in.

[0081] [Table 5]

[0082] From the results presented in Table 5, it can be concluded that for thermal development, a greater relief depth can be achieved when using vegetable oils (rapeseed oil, aged rapeseed oil, sunflower oil, soybean oil, palm oil, palm kernel oil, coconut oil, MCT oil, linseed oil) compared to polybutadiene. Moreover, it is evident that using vegetable oils instead of polybutadiene allows for faster washout speeds, resulting in shorter processing times and increasing the depth of the negative dots. The UV transmittance of most of the vegetable oils correlates with the backside exposure time, with higher transmittance being preferred. Aged palm oil and rapeseed oil appear to be the exceptions.

[0083] Example 6: Production of materials in plate form: 75.5 parts by weight of SIS triblock copolymer having 19% styrene content and 30% diblock as binder; 5 parts by weight of vinyltoluene-methylstyrene copolymer (CAS: 9017-27-0), 6.7 parts by weight of hexanediol diacrylate, 3.3 parts by weight of hexanediol dimethacrylate, 2.5 parts by weight of lauryl acrylate, 2.5 parts by weight of benzyl dimethyl ketal as photoinitiator, 3 parts by weight of plasticizer (A: mineral oil, B: rapeseed oil), and 1.5 parts by weight of further components, such as inhibitors and dyes The photosensitive polymer mixture containing was melted at elevated temperature (120-180°C) in an extruder and calendered through a slot die between a cover film with a laser ablatable mask layer having a thickness of 105 μm and a carrier film having a thickness of 175 μm, thus obtaining a relief precursor (photosensitive polymer + film) with a total thickness of 1.

[0084] [Table 6]

[0085] From the results presented in Table 6, it can be concluded that for thermal development, slightly greater relief depths can be achieved when using even small amounts (3%) of vegetable oil. Moreover, higher washout depths can be achieved and the anisotropic behavior of the plate is significantly reduced.

[0086] Example 7: The material in plate form was prepared as in Example 5.

[0087] Thermal development: Plate processing and evaluation of relief depth and thermal development were performed as in Example 2. Material results are in Table 7.

[0088] Solvent Development: Solvent development was performed as in Example 2. Material results are in Table 7.

[0089] Backside Exposure: Backside exposure times to achieve a relief depth of 700 μm for solvent development are based on the Nylofex® User Guide, page 17, chapter “3.2 Determination of plate processing times”, version of October 2007, Combi FIII, UV output 16 mW / cm 2 It was decided in.

[0090] [Table 7]

[0091] From the results in Table 7, it can be concluded that the quality of the vegetable oil is important for its use as a plasticizer. If the quality of the oil is not sufficient, it is difficult to produce a good printing plate within the scope of the present invention. More than other values, UV transmittance and light transmittance can be used to evaluate the quality of the vegetable oil and its suitability for the present invention. High UV transmittance and light transmittance are preferred. UV transmittance and light transmittance depend on many factors apart from the general type of grain.

[0092] Properties of plasticizers: The mineral oil used (CAS8042-47-5) had a kinematic viscosity of 70mm at 40°C. 2 / sec.

[0093] The polybutadienes used had a molecular weight of Mw<10000 g / mol and about 34% 1,2-vinyl groups (Examples 2 and 5), a molecular weight of Mw about 5000 g / mol and 1% 1,2-vinyl groups (Example 3), and a molecular weight of Mw<3000 g / mol and 15-25% 1,2-vinyl groups (Example 4).

[0094] Rapeseed oil has a density of 0.916 to 0.923 g / cm at 20°C. 3 It has a refractive index at 20°C of 1.470 to 1.474, an iodine value (g iodine / 100g) of 105 to 126, an acid value (mg KOH / g) of less than 0.5, and a saponification value (mg KOH / g) of 180 to 195.

[0095] Aged rapeseed oil was obtained by heating the same batch of rapeseed oil used for the other experiments to 160° C. for 19 hours.

[0096] Aged linseed oil, aged sunflower oil and aged soybean oil were obtained by heating the same batches of the respective oils used for the other experiments at 160° C. for 19 hours under the influence of air.

[0097] Five hour aged linseed oil was obtained by heating the linseed oil to 160° C. under the influence of air for 5 hours.

[0098] "Linseed oil finis" has a density of 0.95g / cm at 20℃. 2 and was obtained without further specification from MEYER-CHEMIE GmbH & Co. KG.

[0099] Linseed oil Equipur was obtained from VETRIPHARM GmbH without further specification.

[0100] Cold pressed linseed oil was obtained without further specification from Makana Produktion und Vertrieb GmbH.

[0101] Sunflower oil has a density of 0.919-0.925g / cm at 20°C. 3 It has a refractive index at 20°C of 1.473 to 1.476, an iodine value (g iodine / 100g) of 120 to 140, an acid value (mg KOH / g) of less than 0.5, and a saponification value (mg KOH / g) of 184 to 194.

[0102] HO (high oleic acid) sunflower oil has a density of 0.912-0.920g / cm at 20°C. 3 It has a refractive index at 20°C of 1.464 to 1.474, an iodine value (g iodine / 100g) of 78 to 90, an acid value (mg KOH / g) of less than 0.4, and a saponification value (mg KOH / g) of 187 to 197.

[0103] Soybean oil has a density of 0.916-0.922 g / cm at 20°C. 3 It has a refractive index at 20°C of 1.465 to 1.475, an iodine value (g iodine / 100g) of 120 to 141, an acid value (mg KOH / g) of less than 0.5, and a saponification value (mg KOH / g) of 180 to 200.

[0104] Palm oil has a melting point of 33-42°C, a refractive index at 40°C of 1.450-1.460, an iodine value (g iodine / 100g) of 50-57, an acid value (mg KOH / g) of less than 0.4, and a saponification value (mg KOH / g) of 190-210.

[0105] Palm kernel oil has a melting point of 25-30°C, a refractive index at 40°C of 1.448-1.452, an iodine value (g iodine / 100g) of 13-23, an acid value (mg KOH / g) of less than 0.4, and a saponification value (mg KOH / g) of 230-254.

[0106] Coconut oil has a melting point of 20-28°C, a refractive index at 40°C of 1.448-1.451, an iodine value (g iodine / 100g) of 7-12, and an acid value (mg KOH / g) of less than 0.4.

[0107] MCT oil (medium chain triglyceride 60 / 40) has a density of 0.930-0.960g / cm at 20℃. 3 It has a refractive index at 20° C. of 1.440 to 1.452, an iodine value (g iodine / 100 g) of 0 to 1, an acid value (mg KOH / g) of less than 0.2, and a saponification value (mg KOH / g) of 325 to 345.

[0108] Linseed oil has a density of 0.924-0.931g / cm at 20℃. 3 , a refractive index at 20°C of 1.478 to 1.483, an iodine value (g iodine / 100 g) of 170 to 203, an acid value (mg KOH / g) of less than 0.5, a saponification value (mg KOH / g) of 186 to 194, and a Gardner color of less than 6.0.

[0109] Castor oil has a density of 0.955-0.968g / cm at 20℃. 3 , a refractive index at 20° C. of 1.478 to 1.480, an acid number (mg KOH / g) of less than 2, and a Gardner color of less than 4.0.

[0110] In the above, the present invention has been disclosed using examples thereof. However, those skilled in the art will understand that the present invention is not limited to these examples, and that many, many more examples are possible without departing from the scope of the present invention, which is defined by the appended claims and their equivalents.

Claims

1. a) a dimensionally stable support; b) at least one photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiating system, at least one component having at least one unsaturated group, and at least one plasticizer; A relief precursor comprising: A relief precursor, wherein said at least one plasticizer is a bio-based plasticizer, said plasticizer having a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 15%.

2. a) a dimensionally stable support; b) at least one photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiating system, at least one component having at least one unsaturated group, and at least one plasticizer; A relief precursor comprising: the at least one plasticizer is a bio-based plasticizer, and the concentration of the plasticizer in the photopolymer layer is in the range of 10 to 65% by weight; A relief precursor, wherein said plasticizer has a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 30%.

3. 3. Precursor according to claim 1 or 2, wherein the bio-based plasticizer is a vegetable oil, a fatty acid, and / or a fatty acid ester of a mono- or polyfunctional alcohol.

4. 3. The precursor according to claim 1 or 2, comprising a further layer, said further layer being an adhesive layer under the support, an adhesive layer between the support and the photopolymer layer, a barrier layer, a laser ablatable layer and / or a protective layer, or a combination thereof.

5. 3. The precursor according to claim 1 or 2, wherein the plasticizer has a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 50%.

6. 3. Precursor according to claim 1 or 2, wherein the plasticizer has a light transmission relative to medium chain triglyceride (MCT) oil (=100% transmission) of more than 78%.

7. 3. Precursor according to claim 1 or 2, wherein the plasticizer has a Gardner color according to ISO 4630:2015 of less than 7.

8. 3. The precursor according to claim 1 or 2, wherein the plasticizer has a hydroxyl number of less than 430 according to ASTM D1957-86.

9. 3. Precursor according to claim 1 or 2, wherein the plasticizer has an iodine number according to ISO 3961:2018 of less than 150.

10. 3. The precursor according to claim 1 or 2, wherein said plasticizer has a Hansen solubility parameter δt in the range of 16.0 to 20.

5.

11. The precursor according to claim 1 or 2, wherein the concentration of said plasticizer in said photosensitive polymer layer is in the range of 20 to 60% by weight, based on the total weight of the photosensitive polymer layer.

12. 1. A method for producing a relief structure, comprising the steps of: a) providing a relief precursor comprising a dimensionally stable support and a photopolymer layer comprising at least one binder, at least one photoinitiator or photoinitiator system, at least one component having at least one unsaturated group, and at least one plasticizer, said at least one plasticizer being a bio-based plasticizer, said plasticizer having a UV transmittance at 365 nm of greater than 15% for a 5% by weight solution of the plasticizer in n-hexane; b) imaging said relief precursor by ablation of a mask layer, by exposure through a mask, or by direct imaging; c) exposing the imaged relief precursor to electromagnetic radiation to harden the imaged areas; d) removing the uncured areas; e) optionally performing one or more steps of post-treatment, post-exposure and / or detackification; A method comprising:

13. 13. The method of claim 12, wherein the bio-based plasticizer is a vegetable oil, a fatty acid, and / or a fatty acid ester of a mono- or polyfunctional alcohol.

14. 14. The method of claim 12 or 13, wherein the plasticizer has a UV transmittance at 365 nm of a 5% by weight solution of the plasticizer in n-hexane of greater than 30%.

15. 14. The method of claim 12 or 13, wherein the plasticizer has a Gardner color according to ISO 4630:2015 of less than 7.

16. The method of claim 12 or 13, wherein the plasticizer has a hydroxyl number according to ASTM D1957-86 of less than 430.

17. 14. The method of claim 12 or 13, wherein the plasticizer has an iodine value according to ISO 3961:2018 of less than 200.

18. The method according to claim 12 or 13, wherein the plasticizer has a Hansen solubility parameter δt in the range of 16 to 20.

5.

19. The method according to claim 12 or 13, wherein the concentration of the plasticizer in the photopolymer layer is in the range of 3 to 70% by weight, based on the total weight of the photopolymer layer.

20. 14. The method of claim 12 or 13, wherein the removal of the uncured areas of the precursor is performed by treatment with heat and a developer material is configured to adsorb uncured material.

21. The method according to claim 12 or 13, wherein in step d) the precursor is heated to a temperature in the range of 70 to 200°C.

22. 14. The method according to claim 12 or 13, wherein in step d) the precursor is treated with a developer to dissolve non-cured material.