NL8201871A - METHOD FOR MODIFYING THE SURFACES OF FLEXOGRAPHIC PRINTING PLATES - Google Patents

Description

- 1 - * ƒ

v Reg.No. 117142 / AvdA / JvdB

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Method for modifying the surfaces of flexo; graphic printing plates.

The invention relates to a method for the surface treatment of photosensitive flexographic printing plates. More particularly, the invention relates to the surface treatment of flexographic printing plates in which the photosensitive layer contains a polymer of a conjugated diolefin hydrocarbon. Even more particularly, the invention relates to a bromine surface treatment of a photosensitive elastomeric layer containing a polymer of a conjugated diolefin hydrocarbon.

Photosensitive flexographic printing plates are becoming increasingly important in the printing world. Particularly useful materials for making such flexographic printing plates include: materials containing addition polymerizable ethylenically unsaturated compounds, photoinitiators and as polymeric binders or block copolymers such as styrene-butadiene-styrene and styrene-isoprene-styrene. polymers, or butadiene / acrylonitrile polymers with optional carboxyl groups. The former materials which are in commercial use are particularly useful with alcohol or alcohol acetate based inks.

The latter materials, which are new to the printing world, are particularly applicable with hydrocarbon ... based inks.

The flexographic printing plates described above, as well as those made from other natural or synthetic polymers of conjugated diolefin hydrocarbons, generally require treatment after image exposure and development to reduce the tackiness of the embossed printing surface. Both chlorine and bromine treatments are known to reduce the tackiness of the layer. The bromine treatment has proven effective with flexographic printing plates and in particular those flexographic printing plates containing a butadiene / acrylonitrile polymer with optional carboxyl groups. The bromine treatment solutions generally require handling acid, acidic vapors and / or free elemental bromine in the liquid or gaseous state sometime in their preparation. For the ! personnel safety it is desirable to eliminate handling of such aggressive and hazardous reagents.

An object of the present invention is to provide a method of treating flexographic printing plates that eliminates the use of a separate acid and of free bromine. Another object is to provide such a method that is practicable over a pH range: from about neutral to acid. Another goal is such. providing a method in which dry solid components of; the treatment solution stable and easily available! | and can be combined to provide a stable mixture that can be stored in the dry state prior to mixing with water and subsequent use as a bromine treating agent.

According to the invention, a method I is provided for modifying the surfaces of flexot! Graphic relief printing plates in which the reliefs are produced by imagewise exposure with actinic radiation and liquid development of the unexposed parts of a layer of a photosensitive elastomeric material, comprising a polymer of a conjugated diolefin hydrocarbon and a non-gaseous ethylenically unsaturated compound that! contains at least one terminal ethylene group containing the! - characteristic that, after drying, the treated surface, in a sequence of choice, is (1) afterglowed with a source of actinic! 35 radiation, and (2) contacted with an aqueous 8201871%. w - 3 - * treatment liquid of an alkali monopersulfate and a bromide salt for about 15 seconds to 40 minutes.

The photosensitive elastomeric materials used in the process of the invention include a polymer of a conjugated diolefin hydrocarbon, a non-gaseous, ethylenically unsaturated compound, an organic, radiation-sensitive, free-radical generating photoinitiator or system, as well as others discussed below additives. The materials can be used in the form of a layer or the layer can be adhered to flexible supports, or a temporary support can be used. Another configuration may consist of a cover sheet and a polymeric layer on both sides of the photosensitive layer. Useful flexible supports include: plastic foils and metal sheets, open or closed cell foams, compressible rubber layers or a combination of foams and rubber layers with plastic foils. When the combination carrier is used, the plastic film generally abuts the photosensitive layer. A polyamide-coated film, for example, polyester, such as polyethylene terephthalate, provides a suitable temporary support. Examples of such carriers include, but are not limited to, polymeric film carriers such as polyethylene terephthalate, flame-treated polyethylene terephthalate, electron discharge-treated polyethylene terephthalate, polyimide, eg film as described in U.S. Pat. No. 3,179,634, etc. ., and thin metal carriers, such as aluminum, tinned steel (dull or shiny). The polymeric carriers generally have a thickness of 0.025 to 0.18 mm. The metal supports generally have a thickness of 0.25 to 0.29 mm for aluminum and from 0.20 to 0.25 mm for aluminum. tind steel. Examples of foamed carriers include, - open or closed cell foams, for example, polyvinyl chloride, polyurethane, ethylene-propylene diene rubber, neoprene, etc. Examples of compressible rubbers include styrene / isoprene block copolymers, butadiene / acrylonitrile - copolymers, natural rubber, etc.

8201871 - 4 - V *} ->; The photosensitive materials described herein are developable in the unexposed state in aqueous, semi-aqueous basic or solvent solutions depending on the particular polymeric binder or binders present in the photosensitive material. The photosensitive layers have a thickness of about 0.013 to 6.35 mm or more.

An essential component of the photosensitive elastomeric material is an elastomeric polymer binder. Suitable binders include natural or synthetic polymers of conjugated diolefin hydrocarbons. Examples of the binders include: 1,2-polybutadiene, 1,4-polybutadiene, butadiene / acrylonitrile, butadiene / styrene, J block copolymers of the ABA, e.g. styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, Etc. and copolymers of the binders. The block copolymers can be of the linear, radial or sequential type.

The preferred binders are the styrene-isoprene-styrene or styrene-butadiene-styrene block copolymers and butadiene / acrylonitrile / copolymers optionally with a carboxyl content.

Useful linear block copolymers of the invention have at least one unit of the general formula ABA, wherein each A is an independently selected non-elastomeric polymer block having a number average molecular weight (Mn) of 2000-100,000 and a glass transition temperature above 25 ° C. and B is an elastomeric polymer block having an average molecular weight between about 25,000 and 1,000,000 and | a glass transition temperature is below about 10 ° C. The non-elastomeric blocks A with an elastomeric block B interposed together comprise the unit A-B-A which represents the copolymers uniquely suitable for use in combination with the photopolymerizable components in the materials of the invention. This unit may include the entire "" general formula of the copolymer; it can be hung on another polymer chain; or it can be repeated. It is of course possible the exact nature of the! within the scope of the invention, e.g. 8201871 - · · · - * * · ---- ¢. '- * -5 -% example by using two different non-elastomeric terminal blocks A or by block or graft polymeric. create substitutions in blocks A and B. Preferably, the elastomeric center blocks B are polymers of aliphatic conjugated diolefins while the non-elastomeric blocks A are those formed by polymerizing alkenyl aromatic hydrocarbons, preferably vinyl-substituted aromatic hydrocarbons, and more preferably vinyl monocyclic aromatic hydrocarbons. The block copolymers are described in U.S. Pat. No. 3,265,765 and the corresponding British Pat. No. 1,000,090. Particularly preferred types of the present copolymers include block copolymers of polystyrene terminal groups bonded through a polyisoprene or polybutadiene center, e.g. image polystyrene-polyisoprene-polystyrene or polystyrene-polybutadiene-polystyrene, the polydiene block constituting 70 to 90% by weight of the block copolymer. Other typical block copolymers useful in the present invention are polystyrene-polybutadiene-polystyrene and polystyrene polyisoprene-polystyrene block copolymers which have been hydrogenated according to U.S. Patents 3,431,323 and J 3,333,024. The hydrogenated block copolymers have the added advantage of improved thermal and oxidative properties i firmness. Any residual unsaturation in hydrogenation! However, the block copolymers are desirable since only very small concentrations of monomer are then required in the photosensitive materials to avoid solubility in solvent after exposure. to reduce actinic radiation. Any other ! typical block copolymers useful in the present invention are those in which the terminal blocks are polyalkyl styrenes, for example poly- (α-methyl-styrene) -1- --polyisoprene-poly- (α-methyl-styrene), and those composed of a plurality of polymer blocks, for example, polyisoprene-polystyrene-polybutadiene-polystyrene-polyisoprene.

| 35 The number average molecular weights for | the block copolymers can be determined by membrane osmometry, - 6 - using a gel-cellophane 600 W membrane, manufactured by Arro Laboratories, Inc., Joliet, IL and toluene as a solvent at 29 ° C. The Mn for the non-elastomeric polymer blocks and the elastomeric polymer blocks are preferably determined as follows: A. The molecular weight of the first block (polystyrene) can be measured by gel permeation chromatography (GPC) of a terminated sample removed immediately after polymerization. The chromatogram is calibrated using commercially available polystyrene molecular weight standards.

B. The Mn of the second block (polyisoprene or polybutadiene) can be determined in the following manner: (1) measurement by suitably calibrated GPC of the Mn of a sample of polystyrene-polyisoprene (or polybutadiene) diblock polymer, terminated and removed immediately after its polymerization, and (2) subtracting this value from the Mn of the first block as determined above under A.

] 20 C. The Mn of the third block (polystyrene)! can be determined in the same general manner: (1) measurement by suitably calibrated GPC of the Mn of the sample of polystyrene-polyisoprene (or polybutadiene) polystyrene triblock polymer, and subtract this value from the Mn | of the diblock polymer obtained under B. above. The block copolymers are manufactured by Shell Chemical Company and marketed under the brand name "Kraton”

Useful butadiene / acrylonitrile copolymers are high molecular weight butadiene / acrylonitrile copolymers (a) having a number average molecular weight (Mn) in the range of from about 20,000 to about 75,000, preferably in the trajectory • from approximately 25,000 to approximately 50,000. The Mn for the polymers described herein can be determined by gel permeation chromatography using a butadiene standard. The | Acrylonitrile content of the polymers ranges from about 8201871 # *. «---------- t '* - 7 - * 10 to about 50 wt%, preferably from about 15 to about 40 wt% . Optionally, the copolymer has a carboxyl content from 0 to about 15% by weight. When the copolymer contains carboxyl groups, the carboxyl content is preferably in the range of about 1 to about 15% by weight, most preferably in the range from about 2 to about 10% by weight. The copolymer is present in an amount of about 55 to 90% by weight, based on the total weight of the material, and preferably about 60 to about 75% by weight. At least about 55% by weight of the copolymer is required to provide adequate flexibility and physical integrity to the photosensitive elements, especially for flexographic plates.

Carboxyl groups can be used in the high molecular weight 15 copolymers are incorporated by adding to the polymerization process a carboxyl-containing monomer, for example acrylic acid or methacrylic acid, or a monomer that can are converted into a carboxyl-containing group, for example, maleic anhydride or methyl methacrylate. Such polymers 20 are commercially available from various sides, for example, from B.F. Goodrich Chemical Company under the trade name Hycarv.

t j Another essential element of the photo! sensitive materials of the invention is a non-gaseous, ethylenically unsaturated compound containing at least one | terminal ethylene group contains (b). This compound must be able to form a high polymer by passing through free! radicals-initiated chain-propagating addition polymerization and are compatible with the high molecular weight polymers (a) described above. Ethenically unsaturated compounds compatible with the block copolymers of the A-B-A type J - 'as described above are described in British. Patent 1,366,769. Many of these monomers are listed here; under named by name. A class of suitable ethylenically unsaturated compounds includes unsaturated esters of alcohols, especially such esters of α-methylene carbon acids and substituted α-methylene carboxylic acids, more particularly such esters of alkylene polyols and polyalkylene polyols and most especially alkylene polyol di- and triacrylates and polyalkylene polyol di- and tri acrylates prepared from alkylene polyols having 2 to 15 carbon atoms or polyalkylene ether polyols or glycols having 1 to 10 ether bonds.

The following specific compounds further illustrate this class: ethylene glycol diacrylate, diethylene 10 glycol diacrylate, glycerol diacrylate, glycerol triacrylate, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, 1,3-propanediol dimethacrylate, 1,2,4 butanotriol trimethacrylate, 1,4-cyclohexanediol diacrylate, 1,4-benzenediol di-methacrylate, 1,2-benzenedimethanol diacrylate, pentaerythri-15 toll triacrylate, pentaerythritol tetramethacrylate, 1,3-pro pan diol diacrylate, 1,3-pentanediol dimethacrylate, ρ-α, α-dimethylbenzylphenyl acrylate, t-butyl acrylate, N, N-diethyl aminoethyl acrylate, diethylaminoethyl methacrylate, 1,4-butane diol diacrylate, hexamethylene glycol diacrylate, deca-20 methylene glycol diacrylate, 2,2-dimethylolpropane diacrylate, 1 tripropylene glycol diacrylate, 2,2-di (p-hydroxyphenyl) propane diacrylate, 2,2-di (p-hydroxyphenyl ) propane dimethacrylate, J polyoxyethyl-2,2-di (p-hydroxyphenyl) propane triacrylate | (molecular weight 462), 1,4-butanediol dimethacrylate, hexamethylene glycol dimethacrylate, 2,2,4-trimethyl-1,3-pentanedi-1-dimethacrylate, 1-phenylethylene-1,2-dimethacrylate, tri- methylolpropane trimethacrylate, triethylene glycol diacrylate, ethylene glycol acrylate phthalate, polyoxyethyl trimethylol propane triacrylate, diacrylate and dimethacrylate esters of 30 epoxy polyethers derived from aromatic polyhydroxy compounds such as bisphenols, novolacs and the like those described in U.S. Patent 3,661,576, the bis-acrylates and methacrylates of polyethylene glycols having a molecular weight of 200-500, etc. Another class of suitable ethylenically unsaturated compounds includes the compounds described in 8201871 - 9 - U.S. Pat. No. 2,927,022, for example, those having multiple addition polyraerisable ethylenic bonds, especially when present in the form of terminal bonds and especially those in which at least one and preferably most such bonds are conjugated with a doubly-bonded carbon, including carbon which is doubly-bonded to carbon and to heteroatoms, such as nitrogen, oxygen and sulfur. Preference is given to such materials in which the ethylenically unsaturated groups, in particular the vinyls, are used. 10 deen groups, conjugated with ester or amide structures.

; Specific examples of such compounds include unsaturated amides, in particular those of α-methylene-earbon acids, in particular α, diam-diamines interrupted by α, ω-diamines, such as methylene bis-acrylamide. , methylene-15 bis-methacrylamide, ethylene-bis-methacrylamide, 1,6-hexamethylene-bis-acrylamide, diethylene triamine trismethacrylamide, bis (methacrylamidopropoxy) ethane, β-methacrylamidoethyl-methacrylate, N- (β-hydroxyethyl) β- (methacrylamido) ethyl acrylate and N, N-bis (e-methacryloxyethyl) acrylamide; vinyl esters such as divinyl succinate, divinyl adipate, divinyl phthalate, di-vinyl terephthalate, divinyl benzene-1,3-disulfonate and divinyl-butane-1,4-disulfonate, diallyl fumarate, etc.

Other ethylenically unsaturated compounds which can be used include styrene and derivatives thereof: 1,4-diisopropenylbenzene, 1,3,5-triisopropenylbenzene; itaconic anhydride adducts with hydroxyethyl acrylate (1: 1), itaconic anhydride adducts with liquid butadiene / acrylonitrile polymers containing terminal amino groups, and itaconic anhydride adducts with the diacrylate and dimethacrylic acid. 30 late esters of dipoxy polyethers, described in the American se patent 3,661,576; polybutadiene and butadiene / acrylo-! nitrile copolymers which contain terminal and side vinyl

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_; contain groups; and unsaturated aldehydes, such as sorbaldehyde j (2,4-hexadienal).

! Ethenically unsaturated compounds which are water-soluble or contain carboxyl or other alkali-reactive groups. 8201871-10 groups are particularly suitable when it comes to aqueous base-developable systems. Furthermore, the polymerizable ethylenically unsaturated polymers of U.S. Pat. Nos. 3,043,805 and 2,929,710 and similar materials may be used alone or in admixture with other materials. Acrylic and methacrylic acid esters of ethylene oxide and polyhydroxy compound adducts such as those described in U.S. Patent 3,380,831 are also useful. The photo-crosslinkable polymers described in U.S. Patents 3,418,295 and 3,448,089 may also be used.

The ratio of the weight of the block copolymer used to the weight of the addition polymerizable ethylenically unsaturated compound used is from 99: 1 to about 1: 1.

The amount of unsaturated compound present in a photosensitive material containing a butadiene / acrylonitrile copolymer should be in the range of about 2 to about 40% by weight based on the total weight of the material. The specific amount for! optimal results will vary depending on the specific polymers used. Preferably, the amount is unaltered. saturated compound from about 5 to about 25%.

The ethylenically unsaturated compound preferably has a boiling point at normal pressure of at least about 100 G. The most preferred ethylenically unsaturated compounds are triethylene glycol diacrylate, triethylene glycol dimethacrylate, hexamethylene glycol dimethacrylate and hexamethylene glycol. diacrylate.

The photosensitive materials of the invention practically do not scatter active radiation when in the form of thin layers, as described above. To a close-up! To ensure a transparent blend, that is, a blend that does not scatter radiation, the polymeric binder medium components should be compatible with, and preferably to be releasable in the ethylenically unsaturated compound in the proportions used.

By "compatible" is meant the ability of two or more components to remain dispersed in each other without causing any significant scattering of actinic radiation. Compatibility is often limited by the relative amounts of the components j, and incompatibility is evidenced by the formation of a haze in I the photocomponent material. A light haze can be added with such materials before or during the exposure at i | The production of pressure reliefs, but if a fine detail is desired, this haze should be completely avoided.

The amount of the ethylenically unsaturated compound or any other component used is therefore limited to those concentrations which do not cause unwanted light scattering or haziness.

Another essential component of the photosensitive materials according to the invention is an organic, radiation-sensitive, free-radical generating system (c).

J Practically any organic, radiation sensitive, free radicals generating system that polymerizes the unsaturated! initiates bonding and does not excessively terminate the polymerization can be used in the photosensitive materials of the invention. The term "organic" is used in the present application to denote compounds containing carbon and one or more of oxygen, hydrogen, nitrogen, sulfur and halogen, but no metal. Because process transparencies | transmitting heat originating from conventional sources of actinic radiation and since the photosensitive materials are usually prepared under conditions resulting in elevated temperatures, preferred free radical generating compounds are thermally inactive below 85 ° C and even more preferably below 185 ° C. They have to ! are dispersible in the material to the extent necessary; is to initiate the desired polymerization or | 35 crosslinking under the influence of the amount of radiation absorbed during relatively short exposures. This one.......

β. 820-1871-12 initiators are useful in amounts from about 0.001 to about 10% by weight, and preferably from about 0.1 to about 5%, based on the total weight of the solvent-free photosensitive material.

The free radical generating system absorbs radiation within the range of about 200 to about 800 nm and has at least one component having an active radiation absorption band with molar extension coefficient of at least about 50 within the range of about 250 to about 800 nm and preferably about 250 to about 500 nm. With the term "active radiation absorption band".

it is intended a band of radiation that is active in producing the free radicals necessary to initiate polymerization or cross-linking of the unsaturated material.

The free radical generating system may comprise one or more compounds that directly supply free radicals when activated by radiation. It may also include multiple compounds, one of which yields free radicals after being forced to do so by a sensitizer activated by the radiation.

A large number of such free radical generating compounds can be used in the practice of the invention are used and these include aromatic ketones such as! 25 Benzophenone, Michler's Ketone, | / 4,4 * bis (dimethylamino) benzophenone /, 4,4T-bis (diethylamino) benzophenone, 4-acryloxy-4'-dimethylaminobenzophenone! 4-acryloxy-4'-diethylamino-benzophenone, 4-methoxy-4-dimethylaminobenzophenone, | 2-phenyl-2,2-dimethoxyacetophenone (2,2-dimethoxy-1,2-diphenyl-ethanone), 2-ethylanthraquinone, phenanthraquinone, 2-t-butylan | thraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2,3-dichloromaphthoquinone, benzil dimethyl acetal, and other aromatic ketones; benzoin. benzoin ethers such as benzoin methyl ether, benzoxy ethyl ether, benzox isobutyl ether and 820 1 871 v-13 benzoin phenyl ether, methyl benzoin, ethyl benzoin and other benzoins, and 2,4,5-triarylimidazolyl dimers such as 2- (o-chlorophenyl) -4,5-diphenylimidazolyl-dimer, 2- (o-chlorophenyl-4,5-di (m-methoxyphenyl) -imidazolyl-dimer, 5 2- (o-fluorophenyl) -4,5 diphenylimidazolyl dimer, 2- (o-methoxyphenyl) -4,5-diphenylimidazolyl dimer, 2- (p-methoxyphenyl) -4,5-diphenylimidazolyl dimer, 2,4-di (p-methoxyphenyl) -5-phenylimidazolyl dimer, 2- (2,4-dimethoxyphenyl) -4,5-diphenylimidazolyl dimer, 10 2- (p-methyl mercaptophenyl) -4,5-diphenyl imidazolyl dimer, etc., as described in United States patents 3,479,185 and 3,784,557 and United Kingdom patents 997,396 and 1,047,569.

[j The imidazolyl dimers can be used] with a free radical producing electron donor, such as! ! 2-mercaptobenzoxazole, Leuco Kristal Violet or tri (4-diethyl-amino-2-methylphenyl) methane. Sensitizers such as i • Michler's ketone can be added. Various energy transfer dyes, such as Bengal Rose and Eosin Y, can also be used. Further examples of suitable initiators are described in U.S. Patent 2,760,863.

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The photosensitive materials may also contain a small amount of thermal addition polymerization inhibitor, for example 0.001 to 2.0%, based on the weight of the total solvent-free photosensitive material. Suitable inhibitors include hydroquinone and alkyl and aryl substituted hydroquinones, 2,6-di-tert-butyl-4-i! methylphenol, p-methoxyphenol, tert-butylpyrocatechol, pyrogallol, β-naphthol, 2,6-di-tert-butyl-p-cresol, phenothiazine, pyridine, nitrobenzene, dinitrobenzene and the nitroso dimer inhibitor | Systems described in U.S. Patent No. 4,168,982. Other useful inhibitors include p-toluchinone, chloranil and thiazine dyes, for example Thionine i Blue G (Cl 52025), Methylene Blue B (Cl 52015) and Toluidine

Blue (Cl 52040). Such materials can be photopolymerized or ViFS - 8201871-14 - or photo-crosslinked without removal of the inhibitor. The preferred inhibitors are 2,6-di-tert-butyl-4-methylphenol and p-methoxyphenol.

The oxygen and ozone resistance of the pressure reliefs can be improved by incorporating in the photosensitive material an appropriate amount of compatible well known antioxidants and / or antiozonants. Anti-! oxidants useful in the present invention include: alkylated phenols, for example 2,6-di-tert-butyl-4-methylphenyl; alkylated bis-phenols, for example 2,2-methylene-bis- (4-methyl-6-tert-butylphenol); 1,3,5-trimethyl-2,4,6-tris- (3,5-di-tert-butyl-4-hydroxybenzyl) benzene; 2- (4-hydroxy-3,5-di-tert-butylanilino) -4,6-bis- (n-octylthio) -1,3,5-triazine; polymerized trimethyl dihydro-15 quinone and dilauryl thiopropionate.

Anti-ozonants that can be used in the present invention include: microcrystalline wax and paraffin wax; dibutyl thiourea; 1.11S-tetramethyl-thio-urea; Antiozonant AFD, a product of Nafton Co .; norbornenes, for example di-5-norbornene-2-methyl adipate, di-5-norbornene-2-methyl terephthalate; Ozone Protector 80, a product of Reichhold Chemical Co .; N-phenyl-2-naphthylamine; unsaturated vegetable oils, for example rapeseed oil, linseed oil, safflower oil; polymers and resins, for example ethylene / vinyl acetate copolymer resin, chlorinated polyethylene, chlorosulfonated polyethylene, chlorinated ethylene / methacrylic acid copolymer, polyurethanes, polypentadienes, polybutadienes, furfural-derived resins, ethylene glycol / propylene / diene ester of rosin and o-methyl-30 styrene / vinyl toluene copolymer. The ozone resistance of the pressure relief produced can also be improved by annealing it at elevated temperatures prior to use, * If desired, the photosensitive materials may also contain immiscible, polymeric or non-polymeric, organic or inorganic fillers or reinforcing agents, which are substantially transparent at the wavelengths used for exposing the layer of the photosensitive material and which do not scatter actinic radiation, for example polystyrene, the organophilic silicon dioxide, bentonites, silica, powdered glass, colloidal carbon, as well as diver-5 se types of dyes and pigments. Such materials are used den used in amounts varying with the desired properties shelves of the elastomeric materials. The fillers are useful in improving the strength of the elastomeric layer, reducing tack, and further as coloring agents.

| The photosensitive layer preferably contains a compatible plasticizer to lower the glass transition temperature of the binder and facilitate selective development. The plasticizer may be any of the conventional | Plasticizers that are compatible with the polymeric binders.

Among the common plasticizers are dialkyl phthalates, alkyl phosphates, polyethylene glycol, polyethylene glycol esters and polyethylene glycol ethers. Other useful plasticizers include! oleic acid, lauric acid, etc. Polyesters are preferred) * 20 plasticizers, for example, polyethylene bacate, etc. The plasticizer is generally present in an amount of 1 to 15% by weight, based on the weight of the total solid i fabric of the photosensitive material.

The photosensitive materials of the invention can be prepared in any suitable manner by mixing the ingredients, ie (a) the polymeric | binder, (b) the compatible ethylenically unsaturated <; compound and (c) the free radical generating system.

i; For example, flowable materials can be made by mixing these ingredients and other desired additives in any order and optionally using a solvent such as chlorinated hydrocarbons, eg methylene chloride, chloroform, methyl chloroform, chlorobenzene, trichlorethylene, tetrachlorethylene and chlorotoluene; | Ketones, for example methyl ethyl ketone, diethyl ketone and methyl isobutyl ketone; aromatic hydrocarbons, for example, 8201871 - 16 - benzene, toluene and xylene; and tetrahydrofuran. The above solvents can be used as diluents acetone; low molecular weight alcohols, for example, methanol, ethanol and propanol; and esters, for example, methyl, ethyl and butyl 15 acetate. The solvent can be removed later by heating the mixture or the extruded layer.

| Conventional grinding, mixing and dissolving techniques can be used in the preparation of these materials, the specific technique varying with the | 10 differences in properties of the respective components.

| The homogeneous, virtually no radiation scattering materials are sheeted in any desired manner.

; For example, solvent casting, hot pressing, calendering! or extrude suitable methods for making layers of the desired thickness.

The photosensitive elements of the invention can be made by solvent casting or by extrusion, calendering or pressing at an elevated temperature. rature of the photosensitive material in the form of a layer I 20 or a self-supporting sheet on a suitable cast wheel, belt or plate. The layer or sheet can be laminated to the surface! face of the flexible support described above and can be bonded by means of an adhesive mixture as described below. wrote.

When using a solution, the coating can be made on an adhesive-bearing carrier.

j The thickness of the photosensitive layer is a direct function of the thickness desired in the relief; image and it will depend on the subject to be reproduced and on the final use of the relief, for example! thick soft reliefs are useful for flexographic printing and thin hard reliefs for p-lanographic printing. In the -"! Generally, the thickness of the polymerizable layer will be less than about 0.635 cm, and will range, for example, from about 0.00127 to about 0.635 cm. Layers that fall within this thickness range will be used for most printing plates.

: Preferably, between the photosensitive layer of butadiene / acrylonitrile printing plate and the flexible support, a layer of an adhesive mixture comprising at least two polymers is taken from a group of the following four polymers: (1) Polyester resin, a condensation polymer of ethylene glycol, terephthalic acid, isophthalic acid and azelaic acid in a molar ratio of about 6: 2: 1: 3 with an Mn of 19,000 and an Mw of 37,000; (2) Polyether polyurethane resin, a crystalline thermoplastic resin with a Brookfield viscosity of 100 to 1200 cP, using 15 weight percent solids in methyl ethyl ketone and a Brookfield axis No. 3 at 12 rpm. min.

* 15 and an adhesive activation temperature in the range of 54 to 63 ° C. The polyether polyurethane has an elongation at yield of 15 Z, an elongation at break of 615 Z, a modulus at 2400 Z elongation of 42.18 kg / cm and a recrystallization temperature of about 49 ° C; 20 (3) Polyamide resin, a light brown shining resin, with a ball and ring softening temperature of 132 to 145 ° C, a melt viscosity of 40 to 60 P at 210 ° C, a flash point above 299 ° C, a percentage | water absorption after one day 0.7, after seven days 1.6, a yield strength of 32.34 kg / cm, a tensile strength of 31.64 I 2 j kg / cm and an elongation at break of 560 Z (The yield strength,

tensile strength and elongation at break are determined at 24 ° C

j according to ASTM Procedure D-1708); and ! (4) Polyamide resin, a light brown through-; Shining resin with a ball and ring softening temperature j of 150 to 160 ° C; a viscosity of 28 to 38 P at 21.0 ° C, - a percentage water absorption after a day of 1.5 and after seven days of 2.8 and with the yield strength shown below, | tensile strength and elongation:! 35 r 8201871 - 18 -

-18 ° C 24 ° C 60 ° C

Pick-up strength 68.89 28.12 4.92 (kg / αα)

Tensile strength 154.66 25.33 3.52 (kg / cin) Elongation 350 250 40 (%) j (The yield strength, tensile strength and elongation are determined at the temperatures indicated according to ASTM Procedure D-1708).

The number average molecular weights (Mn) of the resins can be determined by gel permeation chromatography (GPC) using a known standard, eg, butadiene, as known to those skilled in the art. The weight average molecular weights (wfw) of the resins can be determined using a light scattering technique using known standard samples, for example, polystyrene, polymethaeric acid, polymethyl methacrylate, etc. as known to those skilled in the art. this area.

i | The specific polymers may be present in the adhesive mixture in the following ranges, e.g. the total weight of resin in the adhesive material. | material: (1) 0 to 78 wt%, (2) 0 to 78 wt%, (3) 0 to ί | 94 wt% and (4) 0 to 97 wt%. Preferred adhesive! Agent mixtures containing four, three and two resin components are shown below, the percentages being by weight based on the total resin content,

The percentage ranges for the quaternary adhesive mixtures are: 30 O) 25 to 31%, preferably 25%, (2) 25 to 31%, preferably 25%, 25 (19) 25 to 19%, preferably 25%, I (4) 25 to 19%, preferably 25%.

> 'i; The percentage trajectories for two tertiary! Adhesive mixtures, A and B, are: i A. (1) 1 to 78%, preferably 1 to 65%, (2) 1 to 78%, preferably 1 to 65%, ________ ...... .... 8201871 - 19 - (3) 1 to 94%, preferably 1 to 90%, B. (1) 1 to 63%, preferably 1 to 45%, (3) 1 to 93%, preferably 1 to 85%, j (4) 1 to 97%, preferably 1 to 90%.

I 5 The percentage ranges for five binary | adhesive mixtures, C to G, are: IC: (1) 7 to 77%, preferably 15 to 50%, love 30% and j (3) 93 to 23%, preferably 85 to 50%, most preferably 70% .

| (This adhesive mixture is particularly preferred.) D. (1) 3 to 60%, most preferably 5 to 30%, and (4) 97 'to 40%, most preferably 95 to 70%,' E. (1) 23 to 77%, preferably 35 to 45%, and I (2) 77 to 23%, most preferably 65 to 55%.

! 15 F. (2) 10 to 16%, preferably 25 to 30%, and (4) 90 to 40%, preferably 75 to 70%, and G. (2) 7 to 72%, preferably 15 to 50 %, and i (3) 93 to 28%, preferably 85 to 50%.

The adhesive mixtures according to the invention. 20 provide an adhesive value for the photosensitive layer to the support of at least 53.57 kg / m and generally much stronger adhesion, for example in the range of 142.86 kg / m or more. These adhesive values are sufficient when the elements according to the invention are used as printing plates, in particular flexographic printing plates.

The adhesive mixtures preferably contain additives such as anti-blocking agents, coloring agents, for example dyes, etc. Useful anti-blocking agents include: preferably polyolefin particles or beads, but also other hard particles or beads, such as silicon dioxide, etc. Dioctyl sodium sulfosuccinate, a surface active means can be used. A preferred polyolefin material is described in the foregoing; images described. The bead size of the anti-blocking agents may be greater than the thickness of the adhesive layer, so that [| 35 beads partially protrude from the layer of the adhesive mixture. Such a configuration appears to have little or no effect on the degree of adhesion. Many types of colorants or dyes are also useful in the adhesive layer. A preferred dye is Du Pont Vollers Blue BL (Cl Acid Blue 59). Other useful dyes include: 5 Methylene Violet (Cl Basic Violet 5), "Luxol" Fast Blue MBSN (Cl Solvent Blue 38), "Pontacyl" Wool Blue BL (Cl Acid Blue 59 or Cl 50315), "Pontacyl" Wool Blue GL (Cl Acid Blue 102 or Cl 50320), Victoria Pure Blue B0 (CX Basic Blue 7 or Cl 42595), Cl 109 Red Dye, Rhodamine 3 GO 10 (Cl Basic Red 4), Rhodamine 6 GDN (Cl Baisch Red 1 or Cl 4516O), Fuehsine Dye (Cl 42510), Calcocide Green S (CX 44090) and Anthraquinone Blue 2 GA (Cl Acid Blue 58).

An adhesive solution is prepared by generally adding the ingredients to the solvent in the following order with continuous stirring: polymers, polyolefin antiblock, colorants. Useful solvents include mixtures, for example, methylene chloride / ethyl acetate, methylene chloride / n-butyl acetate, methylene chloride / cyclohexanone, methylene chloride / methanol / Cellosolve®, etc., and preferably a mixture of methylene chloride / Cellosolve®, 90/10 parts . Additional solvent can be added to compensate for any weight loss. The choice of the solvents is governed by the need to provide the fastest practical drying rates without flaking the coating and without leaving small amounts of solvent. The solvents should also have a solubilizing effect on the dyes that may be present.

The adhesive solution is then applied to the flexible support by known means, for example, applied using an iron knife or in a commercially available continuous web coating drier to provide a dry coating weight in 2. range of about 80 to 500 mg / dm, preferably about 260 to 300 mg / dm A most preferred coating weight of the adhesive layer is about 260 mg / dm. In general, the adhesive layer has a dry thickness of 0.020 up to 0.025 mm In a continuous coating the web speed can vary, for example from 4.57 to 45.72 meters per minute, the drying temperature ranges from 60 to 130 ° C, preferably 80 to 90 ° C.

A preferred flexible support is flame-treated polyethylene terephthalate, 0.025 to 0.18 mm thick, preferably 0.13 mm thick. Flame treatment of polymeric films is known. The following U.S. patents describe useful procedures and equipment for flame treatment of polymeric films: 3,145,242, 3,360,029, and 3,391,912. The fuel equivalence ratio of the combustible gas mixture, φ, 10 is 1.4, which equals 5 (propane flow rate) /.

/ (oxygen flow rate) + (0.21 air flow rate) _ /. All flow rates are in standard liters per minute.

The web speed is 53.34 meters per minute.

The dried adhesive coated support 15 can be immediately adhered to the photosensitive layer or can be saved for later adhesion. The adhesive-coated support can be laminated to the photosensitive layer in a press, for example at 140 to 160 ° C at a pressure of 2 1406 to 2109 kg / cm for up to about 3 minutes, followed by cooling in the press to less than 60 ° C. Preferably, the photosensitive element is prepared by calendering.

The photosensitive layer, which is preferably formed by extrusion through an aperture, bears on the side remote from the side adjacent to the adhesive layer a 0.13 mm thick polyethylene terephthalate film which then acts as a protective cover sheet. Other films can be used, such as polystyrene, polyethylene, polypropylene or other removable material. Preferably, between the photosensitive layer and the film cover sheet, there is a thin hard, flexible, solvent-soluble layer, such as a flexible polymeric film or layer, for example, a polyamide or a copolymer of ethylene and vinyl acetate. The flexible polymeric film remains * __ ... ! on the back of the photosensitive layer after removing the film cover sheet as described above. The flexible polymer film 35 protects an image-bearing negative or transparent superimposed thereon before use or improves contact with or attachment to the photosensitive surface. Before image-wise exposure using the sources described below, the element is exposed through the support to polymerize a predetermined thickness of the photosensitive layer 5 adjacent to the adhered support. This polarized portion of the photosensitive layer is referred to as a floor. The spot thickness varies with the exposure time, the exposure source, etc. The exposure generally takes place for 1 to 30 minutes.

f! Pressure reliefs can be made according to the invention by exposing selected parts of a photosensitive layer j of an element described above to active radiation, for instance via a process transparent, ie an image-bearing transparent or stencil with j 15 virtually transparent to actinic radiation and with nearly uniform optical density and regions which are opaque to actinic radiation and of substantially uniform optical density until substantial addition polymerization or photo-crosslinking occurs. During the addition polymerization or cross-linking, the polymeric binder and ethylenically unsaturated compound material is converted to the insoluble state in the radiation exposed; portions of the layer in which no significant polymerization or cross-linking takes place in the unexposed portions or areas of the layer. The unexposed parts of the | removed by a liquid developer for the polymeric binders. The process transparency may be constructed from any suitable material, including cellulose acetate film and oriented polyester film.

Actinic radiation from any source and of any type can be used in the photopolymerization process.

i The radiation may originate from point sources, or may be in the * J form of parallel rays or divergent beams. By | utilizing a wide radiation source located relatively close to the image-bearing transparency, the | radiation passing through the clear areas of the transparency enters as divergent beams and thus irradiates a continuous $ 4.

8201871 * - 23 - diverging area in the photosensitive layer under the clear areas of the transparency. This results in a polymer relief having its greatest width at the bottom of the photosensitive layer, ie a truncated cone, the top surface of the relief corresponding to the dimensions of the bright area.

Since the free radical generating systems that are activatable by actinic radiation generally exhibit their maximum sensitivity in the ultraviolet region, the radiation source should provide an effective amount of this tI radiation, preferably with a wavelength range between about 250 and 500 nm. Suitable sources of such radiation, in addition to sunlight, include carbon arcs, mercury vapor arcs, fluorescent lamps with ultraviolet radiation emitting phosphors, argon incandescent lamps, electron flash units and photographic lamps. Electron accelerators and electron beam sources through an appropriate mask can also be used. Of these, the mercury vapor lamps, in particular the! solar lamp or the "black light" type and the fluorescent solar lamps are most suitable.

The irradiation exposure time can vary from j fractions of a second to minutes, depending on the intensity • and the spectral energy distribution of the radiation, t its distance from the material and the nature and quantity of the available material. . Usually, a mercury vapor arc, a solar lamp or fluorescent tubes with a high yield of ultraviolet radiation are used at a distance »| from about 3.8 t & t about 152 cm from the photosensitive material. The exposure temperatures are not particularly critical, but it is preferable to operate at about ambient temperatures or slightly higher, that is, about

* O

- 20 to about 35 C.

After exposure, the image can be developed by washing with a suitable developer. The developing liquid serves to dissolve or swell well to act on the polymeric binder material and __ 8201871 - 24 - r β ___ ethylenically unsaturated compound and little effect on the insolubilized image or on the support or adhesive layer in the period necessary to process the unpolymerized or non-crosslinked portions to delete. Suitable developers include: organic solvents, for example, 2-butanone, benzene, toluene, xylene, trichloroethane, trichlorethylene, methylchloroform, tetrachlorethylene, and solvent mixtures, for example, tetrachlorethylene / n-butanol, etc. When the high molecular weight butadiene polymer component includes carboxyl groups, suitable developers: aqueous base to which a water-soluble organic solvent may be added. Suitable specific developer mixtures include sodium hydroxide / isopropyl alcohol / water, sodium carbonate / water, sodium carbonate / 2-butoxyethanol / water, sodium borate / 2-butoxyethanol / water, sodium ilate / 2-butoxyethanol / glycero] / water, sodium carbonate / 2- (2 -butoxyethoxy) ethanol / water and sodium hydroxide (0.5 wt%) in 16.6 volume% 2- (2-butoxy-ethoxy) -ethanol in water, which is preferred. The specific developer combination selected will depend on the carboxyl content of the photosensitive material and on the properties and amounts of the binders used. Other aqueous developer combinations that can be used are described in U.S. Pat. No. 3,796,602. These combinations of aqueous base and water-soluble organic solvent may be preferred in some cases because of their low price, their flammability and their reduced toxicity.

The development can be carried out at about 25 ° C, but the best results are sometimes obtained when the solvent is hot, for example 30 to 60 ° C. The development time can vary from 1 to 120 minutes, ! . preferably 1 to 25 minutes.

In the developing step in which the relief is formed, the developer can be applied in any suitable manner, for example, by casting, immersion, etc. spraying or applying with a roller. Brushing helps unpoly- 8201871 · £ & -.- £. "____________ i» - 25 - ·> to remove merised or unbonded parts of the material. When the printing plate undergoes aqueous development, a water rinse is then applied, for example, for about 5 to 300 seconds, to the developed plate to remove traces of developer from the plate surface j. The term "aqueous development" includes the water rinse.

After solvent development, the printing plate is dried at a temperature in the range of ka-10. temperature to about 325 ° C, preferably 60 ° C for 1 hour. After aqueous development, the printing plate can be dried, but it has been found that the rinsed aqueous developed plate can be contacted with the aqueous bromine-containing solution while still wet. Hot air drying can be performed using a forced hot air dryer or other suitable drying device.

The plate is then contacted with an aqueous treatment solution prepared as described below. The plate can either be flooded with the aqueous treatment solution or immersed in the treatment solution, the latter being preferred. The treatment solution is kept in contact with the printing plate for 15 seconds to 40 minutes, more preferably from 1 minute to 10 minutes. The treatment solution is preferably used at ambient temperature but can be warmed to about 35 ° C. The treatment solution is prepared by dissolving an alkali monopersulfate, for example, potassium mono-persulfate triple salt (2KHS0, - .KHSO ^. ^ SO ^) and a bromide salt, for example, potassium bromide, in aqueous solution. Since the two components are solids and do not react with each other in the absence of moisture, they can be mixed dry and stored in anhydrous containers for a long time before use. The ratios of the dry ingredients in the mixture are from 98 to 10 alkali metal monosulfate and from 2 to 90 bromide salt. The potassium; salts are particularly preferred because they are significantly less

IfA: * A'Ar * · - ’8201871 - 26 -> are moisture sensitive. However, other alkali salts, for example of sodium, lithium, etc., are useful if they are kept separate from each other until dissolving. No acid needs to be added to the treatment solution, which is advantageous. The treatment solution is useful at higher pH ranges than hitherto known bromine or chlorine [treatment solutions, including pH values in the neutral region and above, for example, 7 to 8.5 or more. The total pH range is from 0.7 to 8.5 or more.

| The printing plate can be post-illuminated with a source of actinic radiation after development, either before or after the treatment described above. The post-treatment generally takes place for 5 to 15 minutes, preferably with the actinic exposure used for the image-wise exposure. i 15 radiation source. After both treatments, the printing plate is ready i

for use. The best ways to practice the invention are illustrated in Example VII, in which the treatment solutions are neutral (pH about 6.8) and low pH

| (about 2.0). At the higher pH, the treatment times are preferably 2 to 10 minutes. At the lower pH, the preferred treatment time range is 1 to 2 minutes. The printing reliefs made from the photosensitive flexographic elements of the invention can be used for all types of printing, but are most widely used in those types of printing where clear height difference between printing areas and non-printing areas is required and in particular flexographic printing where a resilient printing area is required, for example for printing on deformable printing surfaces. These types of printing include those in which the ink is carried by the raised portion of the emboss, such as in dry offset printing, conventional letterpress printing, the latter requiring greater height differences between printing areas and non-printing areas, and which The ink is carried by the lower parts of the relief, such as with intaglio printing, for example, line and inverted halftone. The plates are particularly useful for ^ 8201871

V

- 27 - multi-color printing.

The relief images and the printed images that are obtained exhibit an exact match with the original transparency, both in the small details and in the overall dimensions, even when the element is image | is exposed on a cylindrical support. The reliefs have a high impact resistance, are strong and abrasion resistant, have a wide ink compatibility and those reliefs of a plate based on acrylonitrile / butadiene binders have improved solvent resistance, especially against the alcohol solvents of alcohol based inks, at treatment in accordance with the present invention.

The following examples illustrate the invention, the parts and percentages being by weight.

15 Ink / Solvent Compatibility Test.

The following procedure is used to determine the compatibility and utility of printing inks and solvent with flexographic printing plates with a layer of photosensitive elastomeric material as described herein.

An exposed and developed printing plate is determined after | its thickness, Shore®A hardness (ANSI / ASTM D2240-75) and its weight immersed for 24 hours in a specific solution. release agent or some ink. After removal from the solvent or the ink and patting dry, the thickness, Shore A hardness and weight are determined again. If the yer ·· changes in thickness (AT), expressed in millimeters, Shore A hardness (AH) and weight (A% W) meet the following standards, the printing plate is considered compatible or excellent (U) with respect to the solvent and / or the ink: 30 AT: 0.076 mm AH: -5 Shore®A units '' A% W: <3.5%.

_ _ * J When the following standards are met or exceeded, the printing plate is considered incompatible or insufficient 35 (0) with respect to the solvent and / or the ink: 8201871 - 28 - ΔΤ: _> Oj305 mm _ ΔΗ: £ - 20 Shore v / A units; A% W: ^ 7.0%

In the intermediate area between the above two standards 5, the treated printing plates are of variable or intermediate (T) utility with respect to the solvent and / * or the ink. The global ratings are shown in the examples below.

Adhesion Test 10 The exposed and developed printing plate according to the invention can be tested for tack as follows: (1) The surface is wiped clean with isopropanol, (2) Tissue, such as Scott No. 510 toilet tissue 15 is weighed using 500 g pressed against the plate surface (2.54 x 5.08 cm) for 30 seconds, (3) The tissue is removed observing the results: (A) No tackiness: free of tack 20 (B) Slight tackiness: sticks but can be peeled off the surface (C) Sticky: can be peeled off but some fibers remain on the plate j '(D) Very sticky: sticks and the tissue tears when peeled.

Experts can identify non-sticky printing plate surfaces (grade (A)) on the feeling that i! ie by touching them with their fingertips. Both methods have been applied. All samples below are free from tackiness.

- - Image I

An adhesive solution is prepared from the following ingredients: 35 8201871 'fflê-' ............... ^ - - 29 - I Ingredient Quantity - (din) i Polyamide resin (3) Lot No.0F5237 * 63.1! 2 'Polyester resin (1), 27.0 .3, Polyolefine 9.8 5 Du Pont Fuller Blue BL dye, 0.1 C.I. Acid Blue 59 i

CÊD

1. The polyamide resin, Maeromelt ^ 6238, a product of Henkel Adhesives Company, a division of Henkel Corp., 10 4620 West 77th Street, Minneapolis, MN is a translucent light brown resin, has a ball-and-ring softening point of 132-145 ° C; a melt viscosity of 40 to 60 poise at 210 ° C; a flash point greater than 299 ° C; % water absorption after 1 day 0.7, after 7 days 1.6; yield strength i o 2 1 15 32.34 kg / cm; tensile strength 31.64 kg / cm and elongation at break I 560%. (The yield strength, tensile strength and elongation at break are determined at 24 ° C according to ASTM Procedure 13-1708).

2. The polyester resin is the reaction product of ethylene glycol, terephthalic acid, isophthalic acid and azelaic acid (mole ratio 6: 2: 1: 3) with an Mn of 19,000 and an Mw of 37,000.

(iD

3. The polyolefin, Vestofine SF-616, a product of Dura Commodities Corp., Ill Calvert Street, Harrison,! 25 New York, is snow white in color, has a molecular weight of about 1600, a density at 20 ° C of about 0.96, a penetration hardness at 25 ° C of 0.5 to 1.0, a melting point of about 118-128 ° C, particle size: about 85% 10 µm or smaller, about 15% 10-20 µm.

! 30

The above ingredients are added in order to a mixture of 90 parts of methylene chloride and 10 parts of 1% Cellosolve solvent to provide a solution of about 16% solid. The polyolefin beads do not dissolve 35 on. The mixture is stirred continuously during and after the addition of the ingredients to effect dissolution.

8201871 - 30 -

Any weight loss during mixing is compensated by the addition of methylene chloride.

The adhesive solution is applied to the flame-treated surface of a polyethylene terephthalate film support of about 0.13 mm thickness using a continuous web coater dryer to provide a dry coating weight of about 260 mg / dm. is about 13.72 meters per minute and the drying * temperature is 86 ° C.

10 The adhesive-coated polyethylene terephthalate support is placed with the adhesive upwards! - in a steel platen, dammed to a thickness of 2.03 ram, place the thickness of the finished printing plate. The adhesive coated • f | carrier and the platen are placed on a press and an extruded sheet, about 2.29 mm thick, of a photopolymerizable material on a 0.13 mm thick polyethylene terephthalate. The cover sheet on which a layer of polyamide resin with a dry thickness of 0.004 mm is applied, is applied thereon with the cover side up and is covered with a steel plate.

The cover sheet with the polyamide layer thereon is obtained by coating the polyethylene terephthalate film with the following solution, using a; | coating device with an extrusion opening: I Ingredient Quantity (%) | Methylene Chloride 81.0 Methanol 2.0 N-methylpyrrolidone 10.0

Polyamide resin · 7.0 1 The polyamide resin, Macromelt® 6900, a product of! 30 Henkel Adhesives Company, a division of Henkel Corporation, 4620 West 77th Street, Minneapolis, MN is nearly colorless, has a bullet / ring softening ···. {! point of 130-150 ° C; a melt index at 175 ° C of 5-10 4 g / 10 minutes; a flash point of 299 ° C; a water absorption of 0.2% after 1 day and of 0.5% after 7 days; a . j yield strength of 8.28 MPa; a tensile strength of 24.15 µ MPa and an elongation at break of 540%. The yield strength, tensile strength and elongation at break are determined at 24oC according to ASTM procedure D-1708.

40 The extruded sheet of the photopolymerizable material is prepared from the following ingredients which are mixed and the mixture is extruded through an orifice at 170 ° C.

M 8201871 - 31 - i Component Quantity (parts) i Acrylonitrile (27) / butadiene I (70) / acrylic acid (3), high molecular weight, (mean 81.59; Mooney viscosity 45.0, Hycar ^ 1472 x 26 BF Goodrich Chemical Co.

Hexamethylene diacrylate 10.0 4

Polyethylenebacate 5.0 i 10 Dibutyltin-SjS'-bis-isoctyl- 2.0 mercaptoacetate | 2-phenyl-2,2-dimethoxyaceto-1,25-phenon-2,6-di-t-butyl-4-methyl-phenol 0.10 1,4,4-trimethyl-2,3-diazabicyclo- 0.05 ( 3,2,2) -non-2-en-2,3-dioxide

Du Pont Full Blue BL dye, 0.01 (dry) C.I. Acid Blue 59 (10% dispersion • in ethylene glycol).

4. 20 Paraplex® G-30, a low molecular weight polyester resin manufactured by Rohm and Haas, Philadelphia, PA.

! .

The temperature is increased and pressure is gradually applied which transfers the photopolymerizable sheet! spreads the entire dammed area of the platen.

; After the sheet is evenly distributed, the temperature I is raised to 160 ° C and a pressure in the range of 1406 to | 2109 kg / cm is applied and maintained for 3 minutes. The assembly is cooled in the press to less than 60 ° C by flowing water through the press dies. The formed laminated element is removed from the press and i is placed carrier side up in the exposure unit indicated below. The element receives a global exposure in air at atmospheric pressure for 4 minutes through the support to polymerize a predetermined thickness of the photopolymerizable layer adjacent to the attached support. This polymerized part of the element i j is referred to as a floor.

Wi '82 0 1 8 7 1 - 32 -

After removing the cover sheet, the polyamide resin layer side up element is placed in a Cyrel®3040 Illumination Unit (brand name of E.l. du Pont de Nemours and Company) equipped with Sylvania BL-VHO fluorescent lamps. An image-bearing transparent (negative) is placed on the surface of the element and the element is exposed under vacuum for> 15 minutes. The exposure time is a function of the photopolymer field thickness, the thickness of the polymerized floor and the type of the image-bearing used; 10 transparent.

After the exposure, the transparent is removed and the exposed element is placed in a rotary drum brush type Cyrel ^ 3040 Processor. The unpolymerized regions of the element are removed in the processor by washing for 15 minutes with 0.5 wt% sodium hydroxide in 16.6 vol% 2- (2-butoxyethoxy) ethanol in water, followed by rinsing with water for 2 minutes. A relief image of 0.89 mm is obtained. The developed element (pressure plate) is placed in a forced hot air dryer or other suitable dryer and dried at 60 ° C for 1 hour. The dry plate is post-exposed in air for 10 minutes using the same exposure source as used for the image-wise exposure described above. The board has a Shore A2 hardness in the range of 56 to 60.

The dry printing plate is dipped in either the monopersulfate bromide treatment solution or the chlorine solution at room temperature as shown in Time A below. The changes in sheet thickness, hardness and | 30 weight percent of the exposed, developed and dried printing plate are determined for a variety of solutions. - medium mixtures and / or other usual printing ink components.

The values shown in Table A are determined using the ink / solvent compatibility test described above. An evaluation is made on each sample.

4 8201871 - 33 - j! j

Table A

Sample Solvent or Bromine Treatment (a). _mix (%) _ AT (mm) AH A% W Assessment

j 1 1 (100) 0.013 -0.3 -1.2 U

2 1. (100) 0.010 -0.3 0.8 U '

3 1 (95), 2 (5) 0.010 -1.0 1.4 U

4 1 (90), 2 (10) 0.028 -3.5 2.6 U

5 1 (80), 2 (20) 0.89 -20.0 14.3 0 y 6 1 (60), 2 (40) 0.93 -27.8 52.9 0

I 7 1 (90), 3 (10) 0.013 -1.0 1.5 U

I 8 1 (65), 3 (35) 0.036 -2.0 2.6 U

! 9 1 (50), 3 (50) 0.051 -6.8 3.5 U

10 1 (95), 4 (5) 0.036 -3.0 2.4 U

11 1 (90), 4 (10) 0.12 -8.8 6.5 T.

I 12 1 (80), 4 (20) 1.10 -20.5 23.4 0

1 13 1 (95), 5 (5) 0.013 -1.0 1.1 U

14 (90), 5 (10) 0.0076 -0.8 1.1 U

! 15 1 (80), 5 (20) 0.02 -1.5 1.7 U

.16 6 (20% in Η £ 0) 0.0051 -0.5 0.6 U

I 17 6 (100) 1.90 -20.5 29.6 0

18 7 (50) / H 2 O (50) 0.0076 -0.3 0.3 U

i j i i * r. 'i .. ____ • v - 8201871! £ · * * ·' - · ......

itf-., - 34 -; Table A (continued)

Sample Solvent or Chlorine treatment (b) I _mix (%) AT (mm) ΔΗ A% W Assessment

| 1 1 (100) 0.14 -9.3 5.0 T

: 5 2 1 (100) 0.18 -10.3 4.7 T

3 1 (95), 2 (5) 0.48 -15.0 7.8 0 .4 1 (90), 2 (10) 0.75 -20.3 11.8 0 5 1 (80), 2 (20) 1.60 -24.5 24.5 0 6 1 (60), 2 (40) 0.41 -26.5 57.7 0

10 7 1 (90), 3 (10) 0.28 -13.0 5.4 T

8 1 (65), 3 (35) 0.27 -12.0 6.6 T

9 1 (50), 3 (50) 0.60 -16.0 7.8 O

i.

10 1 (95), 4 (5) 0.54 -18.8 10.0 O.

'11 1 (90), 4 (10) 1.40 -20.0 20.5 0 ΐ 15 12 1 (80), 4 (20) 2.30 -27.0 42.8 0

! 13 1 (95), 5 (5) 0.25 -13.0 5.6 T

! 14 1 (90), 5 (10) 0.25 -14.0 6.1 T

15 1 (80), 5 (20) 0.39 -12.8 7.1 0 'i 16 6 (20% in H 2 O) 0.018 -1.0 0.8 20 20 17 6 (100) 2.0 - 24.0 36.6 0 i

18 7 (50) / H 2 O (50) 0.0025 0 0.3 U

(a) 94.8% HoO / 4.7% Potassium Monopersulfate Compound 25 KHSO2 KHSO2 I2 SO2) / 0.5% potassium bromide; treatment time 2 minutes; ; (b) 90 parts by volume of water / 9 parts by volume of Clorox® / 1 parts by volume of conc.

I HCl; treatment time 2 minutes.

1. 2-propanol 5. ethanolamine (g) 30 2. ethyl acetate 6. ethyl cellosolve ^ 3. mixed hexanes 7. ethylene glycol.

4.2-nitropropane -r | ^! 35 8201871 - 35 - I From the results shown in Table A | it appears that the bromine treatment results in improved printing plates compared to the printing plates treated with the chlorine solution. The intermediate and insufficient qualifications 5 resulting after bromine treatment are observed with solvents or solvent mixtures outside the normal solvent concentration ranges known to those skilled in the art as useful.

Example II

10 This example compares the ink / solvent | agent compatibility of bromine and chlorine-treated photosensitive flexographic printing plates described in Example 1, except that the unexposed image areas are removed in the processor by washing with 0.5 15 wt% sodium hydroxide in 16.6 for 15 minutes vol.% 2- (2-butoxyethoxy) ethanol in water, followed by rinsing with water for 2 minutes. In Table B below, a variety of solvent mixtures and / or other conventional ink components, i are identified by the numbers indicated in Example I; 20 compared with respect to ΔΤ, ΔΗ, A% W and an assessment is indicated for each of the samples.

| } * *; 8201871

- 36 -Table B

! Sample Solvent or Bromine Treatment (a) _mix (%) _ AT (mm) ΔΗ_A% W_Assessment

1 1 (100) 0.010 -1.2 1.6 U

5 2 1 (100) 0.023 -2.0 1.2 U

3 1 (100) 0.0025 0 1.2 U

4 "1 (90), 2 (10) 0.20 -14.8 8.0 T

5 1 (80), 2 (20) 1.20 -24.8 23.7 0 6 1 (80), 2 (20) 1.60 -25.5 23.7 0 10 7 1 (80), 2 (20) 0.56 -17.3 12.6 0 8 1 (60), 2 (40) 2.0 -23.0 53.7 0

9 1 (50) / H 2 O (50) 0.018 -1.8 1.2 U

10 I (25) / H20 (75) 0.013 -2.0 0.9 ü 11 1 (15) / H20 (85) 0.013 -1.0 0.7 ü

15 12 7 (50) / H 2 O (50) 0.0051 -1.5 0.3 U

13 7 (50) / H 2 O (50) 0.0025 -1.8 0.3 U

i * '8201871

J

- 37 - i Table B (continued)! Sample Solvent or Chlorine treatment (b) _ mixture (%) _ AT (mm) ΔΗ A% W Assessment

1 1 (100) 0.013 -9.3 4.6 T

5 2 1 (100) 0.19 -11.0 5.5 T

3 1 (100) 0.18 -11.5 5.5 T (c) 4 1 (90), 2 (10) 0.90 -21.8 12.7 0 4A 1 (90), 2 (10) 0.60 -21.5 12.1 0 (e) 5 1 (80), 2 (20) 1.50 -25.5 23.6 0 10 6 1 (80), 2 (20) 1.50 - 26.0 24.4 0 '7 1 (80), 2 (20) 1.40 -25.5 23.6 0 (d) 8 1 (60), 2 (40) 2.10 -25.8 55 , 8 0

9 1 (50) H 2 O (50) 0.064 -5.2 2.7 U

9A 1 (50) / H20 (50) 0.056 -4.5 2.5 U (f) 15 10 1 (25) / H20 (75) 0.038 -3.0 1.6 µm 10A 1 (25) / H20 (75) 0.03 -3.2 1.4 U (g) I 11 1 (15) / H 2 O (85) 0.02 -1.8 1.0 µm! 1 IA 1 (15) / H20 (85) 0.023 -1.2 0.8 U (h)

I 12 7 (50) / H 2 O (50) 0.0076 -0.5 0.4 U

! 20 13 7 (50) / H 2 O (50X 0.076 -1.3 0.4 U

i (a) Same treatment as Example I.

(b) Same treatment as Example I.

25 (c) and (d) in Table B referring to samples 3 and 7, respectively, mean that the sample in question has not been treated. (e), (f), (g) and (h) in Table) B referring to samples 4A, 9A, 10A and 11A, respectively, are not Clorox®-treated comparative samples. f »+ ' * 8201871 - 38 - I The results shown in Table B show that chlorine treatment has virtually no effect with regard to ink solvents. Improved results are achieved with the bromine treatment. Samples 5 to 5 show an unsatisfactory rating due to the fact that the solvent mixture is outside the known useful concentration range.

Example III

This example illustrates the interchangeability in the post-exposure step and the aqueous treatment step.

Three types of photosensitive flexographic printing plates are manufactured. A plate, referred to as plate A, is prepared as described in Example II. A second plate, referred to as plate B, is prepared as described in Example 1. A third plate, plate C, is a flexographic printing plate, for example about 2.85 mm thick, which contains a styrene-isoprene-styrene block copolymer and is known as Cyrel®II flexographic printing plate. Cyrel is ^! 20 a trademark of E. I. du Pont de Nemours and Company, Wilmington, I DE ..

I Plates A, B and C are placed with the carrier side up in a Cyrel®340 Exposure; unit (brand of E.I. du Pont de Nemours and Company) equipped with Sylvania BL-VHO fluorescent lamps and exposed in air at atmospheric pressure for 240 seconds.

The plates are then exposed imagewise (plate C then has the cover sheet removed) as described in example I.

for 10 minutes, followed by either a wash for 30 minutes with a mixture of 75% by volume perchlorethylene and 25% by volume n-butanol (plates B and C) or a wash for 15 minutes minutes with 0.5 wt.% sodium hydroxide in. 16 vol.% 2- (2-butoxyethoxy) ethanol in water (plate A). Each of the developed plates is probed as described in Example I, either preceded or followed by a 2 minute aqueous treatment as described in ____ 8201871 - 39 - I Example I. All treated plates are treated for 24 hours | soaked in the indicated solvent (see Example I for the designation of the solvent), and the A% W of the dry I plates are determined. The results are shown in Table G, wherein "before" indicates aqueous treatment for the post-exposure.

Table C

Solvent Plate A Plate B Plate C

mixture (%) A% W A% W. 4% W A% W 4% W A% W

10 _ before after_ before_ after before after! 1 (100) 1.20 1.08 1.20 0.96 0.67 0.66; 1 (80), 2 (20) 12.56 12.43 14.29 11.46 6.45 6.47 1 (60), 2 (40) 53.69 55.16 52.94 50.21 17, 21 17.48 7 (50) / H 2 O (50) 0.35 0.32 0.27 0.28 0.05 0.05 15

From the results shown in Table C | it appears that there is no significant difference between the results! results obtained with both orders.

Example IV

i 20 This example illustrates the effect of the

Vary the duration of the aqueous treatment with the solution of the invention and a chlorine solution.

Photopolymerizable elements are prepared as described in Example III (Plates A, B and C) with the following variations: The back side exposure takes place for 150 seconds; i! The image-wise exposure has been retained globally (without image-bearing transparent) with the cover sheet for 10 minutes;

The aqueous development is 15 minutes;

The forced hot air drying takes place for 30 minutes, the duration of the aqueous treatment according to! The invention is 0 (comparison) and 2 and 8 minutes (indicated by I) and 8201871-40 - the chlorine treatment time (indicated by 2) is 0.5 and 2 minutes.

The changes in plate thickness, hardness and weight percentage are determined according to the ink-solvent compatibility test for all elements over the indicated time, expressed in minutes, to give the results shown in Table D. The solvent / mixture numbers are the same as used in Example 1. The values for the changes in the plate thickness' 10 (ΔΤ) are expressed in mm. 1 8201871 - 41 -

; Table D

Plate A

J Solvent / mixture (%) (1) 100 (1) 80.2 (20) 1 (60), 2 (40) 7 (50) / H20 (50) ΤΤ 0.089 1.34.

0.5, 0.12 1.42 1.98 0.0076; 2.0, 0.0025 0.56 2.03 0 '2.0, 0.13 1.47 2.06 I 8.0 0.0051 0.21 2.27 0.0025 ΔΗ i 0, -7.25 -23.0 0.5, -8.3 -25.0 -29.8 -1.3 I 2.0, 0 -17.3 -23.0 -1.3 i 2.0, -9, 3 -26.0 -25.8 -0.5: 8.0 -1.0 -17.3 -29.5 -1.0

i A% W

! 0-3.8 2i; 3 0.5, 4.9 24.4 56.0 0.36 1 2.0, 1.18 12.56 53.69 0.35 y 2.0, 4.6 24 .4 55.8 0.37 I 8.0 1.12 12.07 46.95 0.30 I Assessment 0, T 0

1. 0.5, T 0 0 U

2.0, U 0-T 0 U

2.0, T 0 0 U

8.0 U 0-T 0 U

! i i ^ - i 8201871 - 42 - ί Table D (continued)

I Plate B

i Solvent / Mixture (%); (1) 100 (1) 80, 2 (20) 1 (60), 2 (40) 7 (50) / ^ 0 (50) ΔΤ 0 „0.22 - 0.5, 0.18 1.57 0 .42 0.013 2.0 * 0.013 0.89 0.93 0.0076 2.0, 0.14 1.50 0.41 0.0025 8.0 0.010 0.15 0.78 0.0076 ΔΗ 0 -9.0 0, 5.9.3 -24.5 -15.8 -0.0076; 2.0 * 0.3 -20.0 -27.8 0.3 i 2.0, -9.3 -26.8 -26.5 0! 8.0 -0.5 - 9.8 -24.8 0.3 y

A% W

• i 0 4.6 0.5, 4.6 24.7 56.36 10.29 2.0 * 1.20 14.29 52.94 0.27 2.0, 5.0 24.60 57.73 0 29 8.0 1.1 9.39 51.86 0.25 I '

Evaluation 0 „T

0.5, TOO U

1 2.0: U 0 0 U

! 2.0, T 0 0 U

1 8.0 U T O U

i 'I ^ -X; '! 8201871 - 43 - I Table D (continued)

! Plate C

| Solvent / Mixture I (1) 100 (1) 80.2 (20), 1 (60), 2 (40) 7 (50) / H20 (50) ΔΤ ': 0 2 0.5, 0.028 0.19 0 .50 0.0076! 2, o: 0.018 0.19 0.49 0.0051! 2.0, 0.025 0.19 0.49 0.025 8.0 0.018 0.18 0.49 0.0076 'ΔΗ 0 2 ~ ~ 0.5, -1.0 -7.8 -25.8 -0, 3 2.0 * -1.0 -7.8 -25.5 -0.3 i 2.07 -0.8 -7.5 -25.3 -0.5 8.0 * -0.5 - 7.8 -25.8 -0.3

A% W

"O 2! 0.5, 0.90 6.6 17.4 0.07! 2.0 * 0.67 6.4 17.2 0.05! 2.07 0.91 6.8 17.5 0.08; 8.0 0.63 6.4 17.5 0.04! ! Assessment 0 2

I 0.5, U T 0 U

! 2.0 * UT 0 U

2.0, U T 'O U

8.0 * UT O U

i i t i

a

Sift „8201871 t J '"' · * '' ..... ...... ............ ......

- 44 - | From the results shown in Table D | it appears that there is no significant change in plate rating! division is when the treatment time increases from 0.5 to | 2.0 minutes for chlorine treatment (2) and from 2 to 8 minutes in the treatment according to the invention (1).

Example V

This example illustrates stability; of a mixture of potassium monopersulfate triple salt and. potassium bromide, used to prepare an aqueous treatment solution.

! 20.0 g of 2KHS05.KHSO2, K2SO2 and 2.0 g of potassium bromide (dry powders) are mixed together and stored in an air and moisture tight plastic bottle for 9 months. There is no obvious change in the appearance 15 of the powder observed upon storage. At the end of the period, 11.0 g of the mixture is dissolved in 100 ml of water! and the solution (pH 1.7) is used to treat the printing plates A and IC described in Examples II and III, respectively. The rating of the printing plates is U. This example is repeated, with the exception that the preparation of the treatment solution the potassium salts are added to the water without any combined storage.

| These printing plates are rated U.

•; From the results of this example, it can be seen that there is no change in plate rating when the mixture of dry powders is used to prepare the treatment solution of the invention for a long time; compared to individually mixing the salt components immediately prior to use.

Example VI

This example illustrates the improvement obtained using the aqueous treatment solution of the invention over a chlorine treatment.

35 Photosensitive flexographic printing plates; are prepared as described in Example 1. In Table E below, a variety of solvent mixtures and / or other conventional ink components, indicated by the numbers used in Example I, are compared with | with respect to ΔΤ, ΔΗ, and an assessment is given for each 5 of the samples.

(i

i Table E

I '• Sample Solvent or Treatment (a) Evaluate! mixture (%) ΔΤ (ππη) ΔΗ 4% W division 10 1 1 (100) 0.010 -0.3 0.82! 2 1 (95), 2 (5) 0.010 rl, 0 1.35 3 1 (90), 2 (10) 0.028 -3.5 2.59 4 1 (90), 3 (10) 0.013 -1.0 1.46 5 1 (65), 3 (35) 0.036 -2.0 2.63 15 6 1 (50), 3 (50) 0.051 -6.8 3.47; 7 1 (95), 4 (5) 0.036 -3.0 2.40 | 8 1 (90), 4 (10) 0.12 -8.8 6.53 9 1 (80), 4 (20) 1.1 -20.5 28.35 10 3 (95), 5 (5) 0.013 -1.0 1.06 '20 11 1 (90), 5 (10) 0.0076 -0.8 1.14: 12 1 (80), 5 (20) 0.020 -1.5 1.72 13 6 (20) / H „0 (80) 0.0051 -0.5 0.50! *; 14 6 (100) 1.9 -28.5 29.55! 25.

i i! i i 8201871 ƒ ·· - 46 - Λ -

Table Ε (continued)

Sample Solvent or Chlorine Treatment (b) Evaluate. . mixture (%) AT (mm) AH_A% W division 1 1 (100) 0.018 -10.3 4.72 5 2 1 (95), 2 (5) 0.48 -15.0 7.84 3 1 (90 ), 2 (10) 0.75 -20.3 11.83 4 1 (90), 3 (10) 0.628 -13.0 5.41 5 1 (65), 3 (35) 0.27 -12, 0 6.63 6 1 (50), 3 (50) 0.60 -16.0 7.78; 10 7 1 (95), 4 (5) 0.54 -18.8 9.97 8 1 (90), 4 (10) 1.4 -20.0 20.52 9 1 (80), 4 (20 ) 2.3 -27.0 42.83 10 1 (95), 5 (5) 0.25 -13.0 5.57 11 1 (90), 5 (10) 0.2576 -14.0 6, 06 15 12 1 (80), 5 (20) 0.39 -12.8 7.04 13 6 (20) / H20 (80) 0.018 -1.0 0.77 y 14 6 (100) 2.0 - 24.0 36.01 20 (a) Ratio of 2KHS05.KHSO ^ .E ^ SO ^ / KBr is 100/10 in grams / liter of solution (b) chlorine treatment equal to that described in example IJ i '-

! Example VII

{I ............. . II, I

I This example illustrates the use of | preferred aqueous treatment solutions of the invention, one having a pH of about 6.8 and another. j with a pH of about 2.0, in various solvents or mixtures of solvents, i Photosensitive flexographic printing plates - - are described in example II (plate A), example I 'i (plate B) and example III (plate C ). The procedure shown in Example III is used to illuminate and develop these printing plates. The post-exposure takes place before; based on the aqueous treatment as described in example r 8201871 * £ - 47 -

I and the aqueous treatment lasts 2 minutes. The preferred! treatment solutions are used to remove plates A, B

| and C and the plates are then tested in the stippled solvents or solvent mixtures identified by the numbers used in Example I. The changes in thickness, hardness and weight percentages determined and the assessment of each of the treated plates are shown in Table F below.

Treatment solution A (pH 1.8 + 0.2). j 10 This solution is prepared as follows: 100 g of 2KHS0 ^ .KHS0 ^ .K2S0 ^ are added to 1 liter of water with good stirring. Then, 5 g of KBr is added, followed by good stirring. Treatment solution A is particularly useful at a treatment time of 1 to 2 minutes, Treatment solution B (pH 6.6 + 0.2).

i This solution is prepared as follows:

10 g of 2KHSO2 .KHSO2 .K2SO2 is added to 1 liter of water with good stirring. Then 10 g of KBr are added, followed by good stirring. Treatment solution B is particularly useful at a treatment time of 2 to 10 minutes.

i 25 i i i i! i * 820 1 871 f. ? v - 48 -

Table F

Treatment Solvent / Evaluation mixture (%) ΔΤ (ππη) ΔΗ A% W division of solution 5 plate ^

B 1 (100) 0.023 -2.0 1.8 U

A 1 (100) 0.0025 0 1.2 U

B 1 (80), 2 (20) 1.2 -24.8 23.7 0

10 A 1 (80), 2 (20) 0.56 -17.3 12.6 0-T

, B 1 (80), 2 (40) 2.3 -29.8 54.3 0 A 1 (80), 2 (40) 2.0 -22.8 56.8 0

| B 7 (50) / tLO (50) 0.0051 -1.5 0.33 U

A. 7 (50) / 0 (50) 0.0025 -1.3 0.35 U

| 15 Plate B

i B 1 (100) 0.018 -1.5 1.7 U

I A 1 (100) 0.013 0.3 1.2 U

B 1 (80), 2 (20) 1.4 -25.5 23.1 0 .20 A 1 (80), 2 (20) 0.89 -28.0 22.9 0 B 1 (80), 2 (40) 0.39 -20.5 57.9 0! A 1 (80), 2 (40) 0.93 -27.9 52.9 0 I B 7 (50) / H20 {50) 0.0051 -1.0 0.3 µ

A7 (50) H (50) 0.0076 -0.3 0.3 U

i *!

I 25 Plate C

B 1 (100) 0.028 0 0.84 µ

A 1 (100) 0.018 -1.0 0.67 U

i B 1 (80), 2 (20) 0.18 -7.5 6.6 T

A 1 (80), 2 (20) 0.19 -7.8 6.4 T

I 30 B 1 (80), 2 (40) 0.50 -25.5 17.3 0 j A 1 (80), 2 (40) 0.49 -25.5 17.2 0

B 7 (50) / H 2 O (50) 0.0076 -0.5 0.08 U

I A 7 (50) / H ^ 0 (50) 0.0051 -0.3 0.05 U

j j 35 From the results shown in table P! it appears that the plate rating does not change significantly when the pH of the treatment solution used on three types of plates is varied from about 2.0 to about 6.8.

40. - '' I *, 5 t ί 8201871 - 49 - <

Vi I ——

- I Example. VIII

• -.

A photosensitive printing plate is manufactured as described in Example II, except that after I the aqueous alkaline development and the rinse with water! The printing plate is immersed in the treatment solution as indicated in example I. The printing plate is then dried; and is verified as described in example Ir Usage- ·· ;.

Using 2-propanol as a solvent, the printing plate is rated U.

"Ί ί

.V- I

• T i - J - i; ·· '- | "'I * *, ·· - ·.

"| ! •. · "T

R. I

4 i! •> * 'f ;, *% .:' '

Im *. *

. V.v. I

* | ί- | • V i. · * .... 820 1 8 71

Claims (12)

1. Method for modifying the surfaces of. flexographic relief printing plates, wherein the 5 reliefs are obtained by imagewise exposure and: liquid development of the unexposed areas of a layer of a photosensitive elastomeric material, comprising | a polymer of a conjugated diolefin hydrocarbon J and a non-gaseous ethylenically unsaturated compound containing at least one terminal ethylene group, characterized in that the developed surface after drying is randomly monitored (1) with a source of actinic radiation and | 15 (2) contacted with an aqueous λ. treatment solution of an alkali monopersulfate and a bromide salt for about 15 seconds to 40 minutes. 2. A method according to claim 1, characterized in that the printing plate is immersed in the aqueous treatment solution. 3. Process according to claim 1 or 2, characterized in that the conjugated diolefin hydrocarbon polymer is selected from butadiene / acrylonitrile, butadiene / acrylonitrile / acrylic acid, butadiene / styrene, styrene-butadiene-styrene block copolymer and styrene -isoprene-styrene block copolymer. Method according to claim 1 or 2, characterized in that the flexographic relief printing plate is obtained by imagewise exposure and liquid development of a photosensitive elastomer element, comprising '(A) a flexible support and * (B) a layer of a photosensitive elastomeric material, comprising, based on the total weight of the material, I (a) 55 to 90% by weight of a high molecular S; 8201871 V; "J. * - 51 - butadiene / acrylonitrile copolymer having a number average molecular weight of 20,000 to 75,000, an acrylonitrile content of 10 to 50% by weight, and a carboxyl content of 0 to 1. wt.%, 5 (b) 2 to 40 wt.% of a non-gaseous, ethylenically unsaturated compound containing at least one terminal ethylenic group, which compound is capable of forming a high polymer by free-radical initiator The chain-propagating addition polymerization is compatible with polymer (a); (c) 0.001 to 10% by weight of an organic, radiation sensitive, free radical generating system, activatable by actinic radiation, polymerization of the unsaturated compound initiates, and 15 (d) 0 to 15% by weight of a compatible plasticizer, with a layer of adhesive optionally present between layers (A) and (B). 5. Method according to claim 1 or 2, characterized in that the flexographic embossing printing plate is obtained by image-wise exposure and liquid development of a photosensitive elastomer element, comprising j (A) a sheet-shaped support. (B) a layer of a photosensitive elastomeric material applied to said support, the material comprising the following components: j (1) at least 30% by weight of at least one J of solvent-soluble thermoplastic elastomer block copolymer. j more that at least two thermoplastic non-elastomeric! 30 polymer blocks with a glass transition temperature above 25 ° C 1 and a number average molecular weight of 200 to 100,000 - and, between the aforementioned thermoplastic, non-elastomeric polymer blocks, an elastomeric polymer block with a glass transition temperature below 10 ° C and a number average molecular weight of about 25,000 to 1,000,000; j (2) at least 1 wt% of an addition ib-8201871? r t / - 52 - • N. . ~! polymerizable ethylenically unsaturated compound which contains at least one terminal ethylene group, and! ! (3) a polymerization effective amount of polymerization initiator that can be activated by actinic radiation; a flexible cover sheet; and a flexible polymer film located between the cover sheet and the surface of said; low. 6. Process according to claim 4 or 5, characterized in that the treatment solution is approximately neutral and consists essentially of 5 to 20 parts by weight of alkali monopersulfate, 5 to 20 parts by weight of alkali bromide and 1000 parts by weight. water. 7. Method according to claim 4 or 5! Characterized in that the treatment solution is acidic and consists essentially of 50 to 100 parts by weight of alkali monopersulfate, 15 parts by weight of alkali bromide and 1000 parts by weight of water. 8. Process according to claim I, characterized in that the treatment solution is prepared by combining a dry mixture of an alkali monopersulfate salt, a bromide salt and water. Method according to claim 8, with the | characterized in that the monopersulfate salt and the bromide salt are 2KHSO 4,. KHSO 4,. and potassium bromide. 1 25 A method according to claim 8, with the; characterized in that the ratio of the dry ingredients in the mixture is from 98 to 10 alkali monopersulfate and from 2 to 90%! Salt. 11. A method according to claim 9, characterized in that the treatment solution is at a pH of about 0.7 to 8.5. 12. Methods and products essentially as described in the description and / or the examples. 35 I - 'β v η 8201871