DK144344B - LAMINATE PLATE FOR MAKING RELIEF PRINT FORMS - Google Patents

Description

in f44 $ 44

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a laminate sheet for the manufacture of relief printing molds of the kind set forth in the preamble of claim 1. The novel and advantageous laminate sheet of the invention exhibits a photo-crosslinkable layer 5 based on a mixture of polymer and monomer, an elastomeric underlying layer, and a stabilizing layer.

Photopolymerizable laminate sheets for the production of ink printing forms for flexo printing are known per se and are e.g. disclosed in German published patent applications Nos. 2 062 563, 2 138 582, 2 215 090 and 2 223 808 and in United States Patent Nos. 2,948,611, 3,024,180, 3,658,531 and 3,674,486.

However, the known materials suffer from some practical disadvantages. Thus, some of the known relief printing molds exhibit unsatisfactory flexibility and elasticity, while others at higher shear stresses and elevated compressive pressures tend to plastic deformation and thereby negatively differ from the properties of vulcanized rubber in conventional rubber cliches. Lack of solvent resistance to color solvents often results in premature destruction of the printing relief layer. A high swelling of the printing form during the washing process results in undesirably long drying times prior to its use. It is known from German Patent Application No. 2,215,090 25 that as a polymer for the relief-forming layer on the basis of a photo-crosslinkable mixture of polymers with monomers, block copolymers of type ABA can be used which between two thermoplastic non-elastomeric polymer blocks exhibits an elastomeric polymer block such as the styrene-isoprene-styrene or styrene-butadiene-styrene-three-block copolymers. A disadvantage of the use of these block copolymers is not only the difficulty in their preparation with still accurately reproducible properties, but also the poor processability of their highly concentrated solutions, e.g. in the manufacture of integral photopolymerizable layers. In addition, there is often a marked tendency for cloud formation in the photopolymerizable layer.

SUMMARY OF THE INVENTION It is an object of the invention to provide a laminate sheet 5 for producing relief printing molds, of the kind specified in the preamble of claim 1, which laminate sheet can be manufactured in a simple manner and economically and with good reproducible properties, the photopolymerizable layers being made according to known casting techniques. 10 with highly concentrated solutions which, in the non-crosslinked state, are well soluble in conventional developer solvents, and if based on illumination and leaching, relief printing forms are well suited for printing and exhibit good resistance to the usual color diluents.

It has been found that the object of the invention is fulfilled by a laminate plate which is characterized by the characterizing part of claim 1.

It is admittedly known from German Publication No. 2020357 a laminate which, however, contains in the relief-forming layer a polyamide and which is not suitable for flexo printing due to the high hardness of the cross-linked state.

It is admittedly also known from German Publication No. 2 301 175 a laminate plate which, however, lacks the stabilizing layer between the relief-forming layer and the elastomeric layer, which stabilization layer is an imperative component of the laminate plate according to the invention. This known laminate plate additionally exhibits a lack of solvent resistance to the dye solvents used in the usual printing inks.

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As two-block copolymers of the type specified, both those with a sharp and also those with a blur can be used, e.g. liquid, transition between the two alone of the diene carbon hydrides or of the styrene monomers, block segments formed by the copolymers. As diene hydrocarbons with 4-5

C atoms are hereby particularly considered butadiene and isoprene and as comonomers of formula C1 = CHR with R = H

R 'or CH 2 and R' = an optionally C 1 -C 4 alkyl-substituted phenyl group should be listed styrene, Λ-methylstyrene, vinyl toluene, tert-butyl styrene and preferably styrene. The content of the two-block copolymer of units of the last-mentioned styrene-type monomers is 5 - 70 and preferably 10 - 40% by weight, and thus the content of polymerized units of the diene hydrocarbons is 30-95 and preferably 60-90% by weight. %. The preparation of the two-block copolymers of the kind disclosed is known per se and may be carried out in particular in the manner described in U.S. Patent No. 3,149,182. In addition, reference should be made to the article by I.Kuntz, J.Polymer Sci. . £ 5 (1961), 569-586 and Y.U. Spirin et al., J. Polymer Sci. ^ 8 (1962) / 1181-1189. The copolymers can be prepared continuously or continuously. In the preparation of the copolymers with sharply separated block segments by incremental copolymerization, it is convenient to begin with the polymerization of the monomer as a whole which is predominantly in terms of quantity. Conveniently, the two-block copolymers are prepared by solvent polymerization, whereby especially hydrocarbons or mixtures thereof and polar solvents such as tetrahydrofuran are well suited as solvents. The nature of the solvent thereby has an influence on the fine structure of the structure of the two-block copolymer as the configuration of the diene polymer segments. The use of hydrocarbons as solvents is preferred. It is particularly advantageous to use the solutions of the direct or concentrated block copolymers prepared by solution polymerization - after addition of the other layer constituents - to prepare the photo-crosslinkable layer by pouring. Also suitable are the partial hydration products of the specified two-block copolymers, whereby one should understand those in which the service segments of the copolymer are fully or preferably partially hydrated. Very suitable are hydration products prepared according to the method described in German published patent application No. 2 013 263.

Suitable two-block copolymers of the kind specified, measured as 0.5% by weight of solutions in toluene, have a viscosity of 60 - 350 ml / g, and in particular 90 - 250 ml / g, corresponding to a range of molecular weight Mv of 75 Of course, it is also possible to use mixtures of two-block copolymers of the kind specified, or for special applications also to mix the two-block copolymers with minor amounts of other compatible polymers, and especially elastomers.

Highly suitable blends of polymers with monomers for the photopolymerizable layer contain 60-95 and especially 70-95 20% by weight of polymers and 5-40 and especially 5-30% by weight of monomers.

As examples of the widely compatible polymeric monomers having at least one photo-crosslinkable or photopolymerizable CC double bond, esters of acrylic acid and / or methacrylic acid with mono- or polyhydric alcohols such as n-butyl acrylate are to be mentioned. n-butyl methacrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2-hydroxypropyl acrylate, hexanediol-1,6-dimethacrylate, 1,1,1-trimethylolpropane triacrylate, pentaerythritite tetraacrylate or diethylene glycol dimethacrylate. In addition, amides of (meth) acrylic acid such as 30 N-methylol-methacrylamide-butyl ether are suitable in smaller amounts. Also suitable are N-vinyl compounds such as N-vinyl pyrrolidone, vinyl esters of aliphatic monocarboxylic acids such as vinyl oleate, vinyl ethers of diols such as butanediol-1,4-divinyl ether, as well as allyl ethers and allyl esters. As mono- more, isocyanate-free reaction products of organic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate or toluylene diisocyanate with hydroxyl group-containing (meth) acrylates, such as glycol monoacrylate, hydroxypropyl methacrylate, or 1,4 favorable, insofar as they are sufficiently compatible with the polymer. The same applies to the reaction products of di- or polyepoxides, such as butanediol-1,4-diglycidyl ether or bisphenol A-diglycidyl ether with (meth) acrylic acid. By a suitable choice of the monomers or mixtures thereof, the properties of the photopolymerizable layer can be modified for the particular purpose. In addition, the layer contains a photoinitiator, generally in an amount between 0.01 and 10, and especially between 0.01 and 5% by weight, such as benzoin 15 or benzoin derivatives, e.g. benzoin methyl or isopropyl ether. In addition, the layer may also contain additional usual additives such as thermal polymerization inhibitors such as p-methoxyphenol, hydroquinone or salts of N-nitrosocyclohexylhydroxylamine, dyes, photochromic agents, antioxidants or plasticizers (to produce better processability of the layer). ).

The thickness of the photopolymerizable layer is suitably between 200 and 3,000 µm, especially between 300 and 2,000 µm.

The constituents of the photopolymerizable layer are selected such that the layer after photot crosslinking at total illumination with actinic light has a hardness of between 30 and 90 and especially between 40 and 70 Shore A and in the photocrosslinked state is as hard or harder than the simultaneously used. 30 substrates. Shore A hardness is measured according to DIN 53 505.

The photo-crosslinkable layers are particularly advantageously prepared from the solutions thereof in suitable solvents such as cyclohexane, toluene, xylene, tetrahydrofuran, by pouring, which is very possible as the tobacco block copolymers used in the laminate of the invention are characterized by low solution viscosities and readily enable good homogenization of the layer constituents in solution. In this way, it is advantageous to avoid the use of higher temperatures as these are used for increasing solubility or in processing from the melt. As a layer carrier for the layer, it is thus possible to use both the stabilizing layer and the substrate, as well as - as will be explained in more detail below - a protective film provided with the coating layer. If necessary, a sustained connection can be achieved between the layers by suitable adhesive adhesives or adhesion intermediate layers.

It is often an advantage of the laminate sheets when additionally applied to the photo-crosslinkable layer with an adhesion-resistant, thin, non-adhesive coating layer, preferably consisting of polymers which form hard, adhesive-free, transparent and tear-resistant films, e.g. in a developing solvent soluble polyamide or copolyamide or of a mixture of such polymer and a small amount (£0.0 wt.%) of a photoblomeric inducible monomer as well as a photoinitiator and optional inhibitor. The thickness of this coating layer is suitably 0.5 - 20 µm.

Due to the coating layer, an adhesive-free, blister-free negative layer is made possible by the relief printing plate manufacture of the laminate sheets, which in many cases is not possible without this due to a surface stickiness of the photo-crosslinkable layer. In developing the illuminated portions 30 of the photo-crosslinkable layer to the relief layer, the coating layer is generally washed away with the non-crosslinked layer portions.

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Furthermore, it is further often advantageous to provide the coating layer with a peelable protective film, such as a polyester film, whereby it can also be applied to the photo-crosslinkable layer together with the coating layer. The protective film 5 is generally peeled off prior to the image illumination of the photo-cross-layer, while generally the coating layer thereby remains on the photo-cross-layer.

The elastomeric substrate has a hardness of 15 - 70 Shore A, and preferably between 25 and 60 Shore A, and it is generally between 0.5 and 6 mm thick, especially between ca. 1 and 4 mm. In the preferred embodiment of the laminate sheets, the hardness of the substrate is equal to or lower than the hardness of the photocrosslinkable layer in the photocrosslinked state.

Suitable elastomeric materials for the substrate are e.g.

15 natural rubber, polybutadiene, butadiene-acrylonitrile copolymers, butadiene-styrene copolymers, silicone rubber, polysulfide rubber, vinylidene chloride-hexafluoropropylene copolymers, isoprene-styrene and butadiene-styrene block copolymers and which can be recovered in a known manner from higher molecular weight polyhydroxyl compounds such as polyesters or polyethers, optionally 1aver Molecular polyols and polyisocyanates, especially diisocyanates. For example, refer to the statements in the book Saunders-Frisch "Polyurethanes", Part II, Chapter IX, Interscience 25 Publishers Inc., New York, 1964. The materials for the substrate should be conveniently processed into layers with low tolerances, e.g. by casting and curing in molds or heating centrifuges or in the case of thermoplastic materials e.g. by calendering. The substrate may also be made of the same material as the photo-crosslinkable layer when processed to the required thickness of the dry layer and then photocrosslinked by total illumination. It is also possible to make the substrate of foamy materials or to use 8

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foams therefor if they exhibit the proper elasticity and if it does not exert a fungal effect (absorbent effect) on the printing inks or the developing solvents. The materials in the substrate are not soluble in the 5 developer solvents used for the photo-crosslinkable layer.

The stabilizing layer is intended to ensure the flawless dimensional stability of the plate and to prevent the casting of the drawing plate during mounting on the printing cylinder, so that a working method with satisfactory tolerances is possible at multi-color printing. The stabilizing layer can hereby, under the layer order (photo-crosslinkable layer) substrate stabilization layer, lie beneath the elastomeric substrate; however, in the preferred embodiment of the laminate sheet according to the invention, the stabilizing layer is provided adhesion-resistant between the photopolymerizable layer and the elastomeric substrate. This embodiment has the additional advantage that during the wet development of the relief, the substrate is not subjected to the influence of the leaching agent, thus avoiding swelling of the substrate and the requirement for a subsequent, longer drying. In the preferred position of the stabilizing layer, it generally has a thickness of 5 to 500, and in particular 10 to 200 µm. Compared to the other layers, the hardness of the stabilizing layer must be considerably greater. Conveniently, it exhibits a modulus of elasticity (measured according to DIN 53 457) of 1 x 10 5. 2.1 x 10 6, preferably 3 between 5 x 10 - 2.1 x 10 Kp / cm. As materials for the stabilization layer, e.g. use resins, metals or cross-linked varnishes which may also be reinforced with woven materials, such as fiberglass or textile fabrics. Preferably, plastic films such as polyester films are used. The layers comprising the substrate, the stabilizing layer, and the phototransverse layer on the one hand and the relief layer on the other are interconnected adhesively. By using suitable and especially chemically structured polymeric materials, for example, easily obtain such an adhesion-resistant compound by lamination under the influence of suitable organic solvents which bring the layers to the starting solution. However, it is often necessary to provide an adhesive-firm connection between the layers in question by single or double-sided application of thin layers of adhesive-mediating agents or adhesives and firm adhesion of the layers, however thinner than 100 µm and preferably thinner than 30 µm. For the adhesion layers, commercial one- and two-component adhesives can be used, the nature of which depends on the type of materials or polymer types used for the layers comprising the substrate, the stabilizing layer and the photocrosslinkable layer. As a frequently suitable adhesive, the commercial reaction adhesives on a polyurethane and polychloroprene base which can be applied to the layers to be bonded to each other by substrate or pour into a suitable layer thickness should be listed. In many cases, in connection with the arrangement of the stabilizing layer between the photo-crosslinkable layer and the substrate, it has been found suitable that the elastomeric substrate on the side facing away from the stabilizing layer exhibits a 0.1 to 20, especially between 0, 2 and 10 µm thick coating layer based on an adhesive-free polymer. Suitable for this purpose are often polymers of the kind that can be used to prepare the coating layer.

Also, the coating layer should preferably be permeable to actinic light.

The laminate sheets according to the invention can be processed in a manner known per se into relief printing forms, especially for flexo printing, by imaging illumination of the photo-transverse layer and subsequent removal, in particular washing out the unlit or non-crosslinked portions of the photo-transverse layer. Suitable for the image illumination that can be made in the form of a flat or circular illumination, is the usual light sources of actinic light, such as commercial UV fluorescence or mercury high-pressure tubes.

The emitted wavelength should preferably be at 300 - 400 µm or be tuned for self-absorption by the photoinitiator layer of the photo-crosslinkable layer.

Examples of suitable developer solvents for leaching the non-crosslinked portions of the photo-crosslinkable layer for relief development of chlorinated hydrocarbons such as trichloroethane acid. tetrachloroethane, tetrachloroethylene, hydrocarbons such as hexane, toluene or other organic solvents such as N-methylpyrrolidone, or mixtures of such solvents with lower alcohols to control the leaching effect.

The laminate sheets according to the invention or the relief printing plates made from these exhibit a combination of a number of advantages. The use of two-block copolymers in the photo-crosslinkable layer, in comparison with the use of three-block copolymers A-B-A according to German published patent application No. 2,215,090, has the advantage of encompassing the simpler and more economical preparation of the two-block copolymers. Also, three-block copolymers are much more difficult to produce with constantly the same and reproducible properties. A further advantage of using the two-block copolymers is their much lower viscosity, even at high concentrations, which also produces a good pourability of solutions with high solids content and thus a more economical preparation of the layers.

The good solubility also produces a positive effect in the development of the relief printing forms. A particular advantage of the photo-crosslinkable layers in the laminate sheet according to the invention in comparison with the layers described in DOS 2 215 090 is that, even with longer storage, they do not exhibit any cloudiness which prevents sharp boundaries between illuminated and unlit segments of made, but remains crystal clear. The two-block copolymers, in admixture with the post-illumination monomers, exhibit a surprisingly large jump improvement in their elastic properties, their flowability and their swelling resistance in the printing ink solvents customary in flexo printing. The photo-crosslinkable layers of partially hydrated two-block copolymers exhibit a particularly poor oxidation sensitivity. Laminate sheets according to the invention are distinguished not only by their simple manufacture, but also by their quick and easy processing into relief molds and the good printing properties thereof. At the same time, due regard for tolerances of the printed fabrics during printing, the printing layer has a constant pressure elongation, which above all is very important in multicolor printing.

15 The parts and percentages given in the following examples refer to the weight, unless otherwise indicated. Volume parts relate to parts by weight such as liters per kg.

EXAMPLE 1 (a) With stirring, a solution of 167.5 parts of a blurry polystyrene-polybutadiene two-block copolymer containing 20% of polymerized styrene units and a viscosity of 142.4 ml / ml was prepared at 65 ° C. g and 0.2 parts of 2,6-di-tert.-butyl-4-methylphenol in 220 parts by volume of tetrahydrofuran. After homogenization, 10 parts of hexanediol-1,6-diacrylate and 20 parts of lauryl acrylate are added. In some tetrahydrofuran with a little methanol, 2 parts of cG-methylol-benzoin methyl ether, 0.2 parts of hydroquinomonomethyl ether and 0.06 parts of a commercial black dye are dissolved and mixed with the polymer solution. The resulting solution is poured onto a 125 µl thick polyethylene terephthalate film (protective film) which is provided with a color knife with an approx. 1 µm thick coating layer of a soluble copolyamide, such that after the drying ring a 670 µm thick photo-crosslinkable layer is formed. After illumination in a commercial flat light with 60 Watt UV fluorine fluorescent lamps, a photo-crosslinked sample of the photo-crosslinkable layer exhibits a hardness of 60 Shore A and a back-bead elasticity according to DIN 53 512 of 55%.

(b) An illuminated sample prepared according to 1 (a) is applied to the free coating side using a commercial, ad-curing two-component polyurethane lacquer having a thickness of 20 µm on a transparent polyethylene terephthalate film having a thickness of 75 which, by its other side, is coated with a similar adhesive varnish to a 2 mm thick elastomeric substrate formed of a polyester glycol, toluylene diisocyanate and activator cured at 130 ° C. The substrate has a hardness of 37 Shore 15 A and a bead elasticity of 45%.

(c) Upon extraction of the 125 µm thick polyester film which first served as a layer carrier for the pouring of the photo-crosslinkable layer, the polyamide film remains due to the better adhesion to the unlabelled, photo-crosslinkable layer and thus enables an adhesive-free, blister-free application of a negative for pictorial or grid-shaped lighting. After approximately 30 seconds of pre-illumination on the entire side of the back surface of the photocrosslinked layer through the substrate (the substrate facing the light source), the photocrosslinkable layer was illuminated image-wise through a negative imprint (with writing and half-inch) for approximately 15 minutes. In a spray washer, the relief was then evaporated with a mixture of trichloroethane and isopropanol (70:34 v / v) for 4 minutes.

After a brief post-drying and 10 minutes of backlighting 30 on the full surface, a relief printing form was found which was distinguished by an excellent reproduction of all the image elements present in the publisher, and exhibiting a flawless printing ratio.

EXAMPLE 2 In the manner set forth in Example 1, a solution of 35 parts of a sharply separated polyisoprene-polystyrene tobacco block copolymer having a viscosity number of 158 ml / g 5 and a content of 25% polymerized styrene units in 65 parts of toluene to which were added 7 parts of butanediol-1,4-dimethacrylate, 0.03 parts of toluhydroquinone, 0.4 parts of cfc-methylol-benzoin methyl ether and 0.05 parts of di-2,6-tert.-butyl-4- methylphenol. From the resulting solution 10, as in Example 1, a photo-crosslinkable layer is prepared and thus, as indicated, a multilayer plate. The photocrosslinkable layer had a hardness of 58 Shore A and a kickback elasticity of 55% in the photocrosslinked state. Relief printing molds made from the laminate sheet as indicated exhibited excellent printing properties.

EXAMPLE 3

Proceed as in Example 2, but 40 parts of a sharply separated polyisoprene-polystyrene two-block copolymer having a viscosity of 82 and a content of 20% of polymerized styrene units are used to prepare the solution for the photo-crosslinkable layer. The hardness of the photo-crosslinkable layer in the photocrosslinked state in the resulting printing plate is 48 Shore A.

Example 4 Proceed as in Example 2, but instead of 7 parts of butanediol-1,4-dimethacrylate, 12 parts of hexanediol-1,6-dimethacrylate are used. The photocrosslinked relief layer has a hardness of 44 Shore A and a kickback elasticity of 53%.

EXAMPLE 5

The material of Example 1 (a) for the photo-crosslinkable layer is cast onto a 50 µm thick polyethylene terephthalate film as stabilizing layer in such a way that a layer having a dry layer thickness of 1.5 µm is obtained. The layer is then totally illuminated by 30 minutes of irradiation with a flat lighting device provided with 60 Watt UV fluorescent lamps, ie. completely photocrosslinked to form a substrate. The free second side of the polyester film (stabilizing layer) is then joined by a commercial chloroprene agent to that of Example. 1 (a) made unlabelled photo-crosslinkable layers, more precisely indicated by the free layer side of the photo-crosslinkable layer. A laminate sheet appears, in conjunction with 14, wherein the photocrosslinked layers (photocrosslinked) and the substrate after the illumination and photocrosslinking of the photocrosslinkable layer have the same mechanical properties.

Claims (3)

144344 A laminate sheet for producing relief printing molds, which plate (1) contains a relief-forming, photo-crosslinkable layer containing a photoinitiator, optionally conventional additives, and a photo-soluble, photo-crosslinkable mixture of at least one soluble copolymer and at least one having the same. copolymer broadly compatible monomer with at least one photopolymerizable CC double bond, whereby the hardness of the relief-forming layer after the photocrosslinking at total illumination with actinic light must be between 30 and 90 Shore A, (2) a non-photocrosslinkable and in the developing solvent for the photocrosslinkable layer of insoluble elastomeric substrate having a hardness of 15-70 Shore A, and 15 (3) a non-photocrosslinkable and in developing solvent easy for the photocrosslinkable layer of insoluble stabilizing layer, whereby the stabilizing layer is 5-500 µm thick, it is strongly interrelated in relation to the neighborhoods photocrosslinkable layers and the elastomeric substrate, characterized in that the photocrosslinkable layer as polymer contains a soluble two-block copolymer of 30-95 wt. S of a diene hydrocarbon having 4-5 C atoms and 5-70 wt.% of a monomer of the formula CH 2 = CHR, ^ I R 'whereby R = H or CH 2; R '= phenyl or C 1 -C 4 alkyl-substituted phenyl, which polymer has a viscosity number of