SU626680A3 - Method of making offset printing plates - Google Patents

Description

FIG. I conventionally depict the various stages of the proposed method for the production of offset printing paper; in fig. 2 shows the various stages of making a different form.

In the proposed method, the offset printing plate is made in the following sequence.

First, a layer 2 is applied to the base sheet 1, which serves as an adhesive coating between the hydrophilic layer 3 and the base sheet 1 (Fig. 1a). The hydrophilic layer 3 is shock and durable and is not necessarily permeable to liquid. Preferably, it is made of colloidal silica; in addition, it contains a metal ion reduction promoter.

Then, a layer 3 is applied a layer 4 of a high-contrast photographic emulsion (Fig. 16), which is then subjected to light exposure to produce an image. In exposed to light areas, the silver compound in the emulsion layer 4 is transformed into a hidden restored state in sections 5, remaining unexposed and photosensitive in sections 6 (Fig. 1e).

Next, the printed form is treated with a solution of a developer (Fig. 1d). As a result, the silver compound in the exposed areas 5 is restored to a metallic state and acquires a black color. The soluble silver halide, previously present in areas b, is transferred or diffused along with the solution of the developer into layer 3, in contact with the metal-ion reduction promoter, as a result of which silver is reduced to a metallic state. In fact, silver recovery in layer 3 usually occurs a few seconds later than in the areas 5 of the emulsion layer 4 exposed to light, so that as the image develops, which is negative with respect to the original, it first appears when the areas 5 are blackened and already after this, the entire surface of the plate becomes black due to the reduction of silver to the metallic state in layer 3.

In the last stage (Fig. 1d), an emulsion layer is removed from the plate. Sections 7 of the plate surface containing metallic silver are treated in accordance with the invention to give them oleophilicity (i.e. susceptibility to paint application). For this, sections 7 (or the entire surface of the structure) are treated with a homogeneously stable acidic aqueous salt solution containing a ferrocyanide anion, a complex-like oxidize metallic silver, and an organic cation complexing agent capable of forming a water-insoluble oleophilic complex with oxidized silver.

By a goivogenically stable solution is meant a solution in which the ferrocyanide anion and the organic cationic complexing agent do not actually react with each other.

Background areas 8 remain hydrophilic.

A variant of the offset printing plate is manufactured as follows.

An emulsion layer is deposited on the carrier sheet 9 (Fig. 2a), which is then subjected to light exposure to produce an image (Fig. 26). Then the mold is treated with a solution of the developer, ensuring the saturation of layer 4.

After the layer 4 is saturated with the developer, a composite structure is formed (Phn. 2c), in which the emulsion layer 4 is superimposed on the hydrophilic layer 3 containing the metal-ion promoter. recovery. Under the action of the developer, the soluble silver halide from layer 4 passes or diffuses together with the solution of the developer into layer 3, where it contacts the metal-ion reduction promoter, as a result of which silver is reduced to the metallic state (Fig. 2d).

In the last stage (Fig. 2d), with the plate; -; we remove the emulsion layer. Plate sections contain metallic silver. Q which becomes oleophilic when treated with a homogeneously stable activator solution. Background areas 8 remain hydrophilic.:,

An oxidizing reagent suitable for the proposed method is an alkali metal ferrocyanide, soluble in water, like an example, potassium ferrocyanide K2lFe (CN) gj. When using alkali metal dichromates as oxidizing reagents, an obviously expressed oleophilic region of the silver image is not obtained. Under the clearly pronounced oleophilic areas are understood those areas of the silver image that perceive ink without pretreatment with additives, varnishes, etc. The cationic complexing agent is obtained from a protonized nitrogen-substituted hydrocarbon compound containing the fr.N-imine group, resonantly associated with neighboring groups.

Claims (3)

By resonant coupling is meant such a bond in which a formally imine group, together with neighboring groups of the molecule, exhibits a so-called resonance. This means that the electronic structure of a molecule can be represented by two or more methods with unchanged positions of atoms. In this case, the actual electron state of the molecule is more stable, i.e., higher (in absolute terms) negative potential energy than any separate structure. In order for resonance to occur, a min group in a hydrocarbon compound must be coupled with a group or another imine group, or linked to a nitrogen atom. This can be graphically represented by the following structural designation: D (CN) -Z where Z is a group, OS, or N N can be attached to either a carbon atom or a nitrogen atom and of the mine group. Resonance stabilizes the imine functional group and thus provides a high degree of oleophilicity of image areas with complexed silver. Nitrogen-containing hydrocarbon compounds use cyclic and acyl amide, i.e. compounds that have formally the following chemical groups: - / a where RI and R2 - hydrogen, hydrocarbon, nitrogen-substituted hydrocarbon of any class, alkyl, acryl or aralkyl; and where the cyclic or ring-shaped amidines are supplemented with hydrocarbon groups from Niemi five- or six-membered Col 1:., Zig structures. Examples of acyclic amndine are acetamidine, bekamidine, guanidine, and bi1oanidine. Exemplary cyclic amidines are 2-propyl-2-imidazole, 2-pentyl-2-imidazoline, 2-benzyl-2-imidazoline n naphthazoline. Suitable complexing agents include aromatic nitrogen substitutions. Heterocyclic compounds, such as five- and two-membered cyclic or bicyclic compounds containing one or more nitrogen atoms, including mono- or poly-substituted hydrocarbon or nitrogen-functional hydrocarbons and their derivatives. Examples of aromatic heterocyclic compounds are 2-methylimidazole, I-benzylimidazole, 1-butylimidazole, 2-undelimnimidazole, 2,2-dipyridylamine, 2,4-lutidine, pyrcidine, and N-aminopyridine. Bicyclic compounds include benzimidazole, 2-methylbenzimidazole, I-ethyl-2-methylbenzimidazole. Heterocyclic nitrogen-aromatic compounds must contain at least one nitrogen atom in the initial ring structure, which is sterically uncomplicated, so that it is possible to coordinate with the silver ion, i.e. the possibility of forming a chemical bond with it. Suitable activator solutions can be prepared by simply mixing in water an alkali metal ferrocyamide salt, such as potassium ferricyanide, an organo nitrogen compound and a concentrated acid in sufficient quantity to protonize an organo nitrogen compound, for example, hydrochloric acid. The hydrohalide salt of the organic compound can be used instead of the acid. At least 0.01 mole of the ferrocyanide salt per liter of solution is used to ensure proper oxidation of metallic silver. Cationic derivatives of nitrogen-containing complexing compounds and the ferrocyanide anion {fe (CN) el represent the least soluble ionic pair or salt when mixed in water in the manner described above. When water is evaporated from a solution or other process that affects solubility, salt crystals formed from this least soluble ION pair, which can be separated from the solution, appear. This new ferrocyanide salt, the proton of the incorporated organic nitrogen complex, can subsequently be re-dissolved in water to obtain an activator solution to give the metal-silver surface a pronounced oleophilicity. Salt formed by cationic derivatives of the shale-mentioned organic component and ferrocyanthion anion. should have a solubility in water above 0.01 mol per liter to ensure effective oxidation of metallic silver by ferrocyanide anion. Example I. A sheet, which is a substrate and is a polyethylene terephthalate film 25x40 cm in size and 100 µm thick, is coated on one side with an 8 µm thick organic layer, in a dry state, and the organophilic layer is applied from a solution containing 48 wt.% dry matter, which is a vinyl chloride acetate resin (produced on an industrial scale by Oiion Carbide) and a titanium dioxide pigment at a ratio of 3 h. titanium dioxide to 1 weight. including vinyl chloride resin. The pigment is dispersed in the resin solution in methyl ethyl ketone before coating, grinding in a ball mill for 48 hours. After applying the solution on the substrate, it is dried for 5 minutes at. The substrate is then coated with a hydrophilic layer of the composition, g: Colloidal silica (30% dry matter; produced at industrial level by Nelco Chemical) Water Glycerin15 Fine silver protein (10% dry matter in eofll) .8 (ml) after What is dried 20s at 66 ° C. Next, a high-contrast chlorobromic photographic emulsion is applied to the hydrophilic layer (for example, with a ratio of chloride; bromide 2: 1 and gelatin: silver of 1.2: 1) with a weight of silver coating of 20 mg per dm. To expose, the plate is placed on the vacuum suction of the photographic camera Robertson 320 equipped with lin. image processing system. Exhibit 12 seconds at aperture 32 and obtain an image of a direct, readable, positive line source. The exposed plate is immersed for 30 s at 22 ° C in a bath with a propellant having the following composition, g per 1000 ml of deionized water: Sulfite sodium 80,0 Hydroquinone 35,0 Sodium nitrate 15,0 Na hydroxide 28,5 Potassium bromide 2.5 Benzotrnazole solution water (0.50 / oo) 25 (ml) This developer, the transfer of which is accomplished; {differs by diffusion from the usual photographic developer in that it contains sodium thiosulfate, which acts as a hack of diffusion transfer reagent, a solution n forming a complex with a silver halide, but not with silver om, as in his light-restored, and in the form restored by the manufacturer. Following the neglient silver NZO, immersed in the developer (Grezhene appears on the areas illuminated with light during exposure, and then a positive silver image appears in the hydrophilic layer. The emulsion layer is washed off with flown water with a temperature of approximately 20 s, resulting in the hydrophilic surface is exposed, having a positive silver image (i.e. metallic silver), and at least part of the megalo-silver is on the top of the hydrophilic layer. Next, the plate is immersed for 25 seconds with Room temperature in a homogeneously stable actnvator solution of the following composition, g: Ferrocyande potassium 33.0 Chloride nat {and 17.5 2-Benzyl-2-imidazoline-hydrochloride 10, 0 Denonned water Up to 1 (l) Plastnnu washed with water 5c and dried. areas of positive imaging are susceptible to paint application, and the foaming areas are whitespace areas remain hydrophilic. To further improve the paint: water ratio, the plate can be wiped with a 0.5% solution of sodium oleate in water. The resulting printed form was clamped in a lithographic printing press to receive thousands of prints with high quality. The homogeneously stable solution mentioned above remains stable (i.e., active and homogeneous) indefinitely. After a long exposure, slight film formation is sometimes observed, but this has no effect on the ability of the solution to impart oleophilicity to the surface of metallic silver. Approximately 19 liters of this solution is sufficient to process more than 15,000 plates of the type described in this example. Sodium chloride is added to the activator solution in the above example to improve the oxidation of metallic silver. Other alkali metal halide salts can be used for the same purpose. Other materials can be added if it is necessary to achieve specific goals, but in amounts that do not lead to the reaction of the component with either an organic cationic complexing agent or a ferrocyannd anion. Example 2. The form is made analogously to example I, but the oleophilic activator solutions are prepared separately by mixing 0.06 moles of concentrated hydrochloric acid, 0.03 moles of potassium ferrocyanide and 0.06 moles of an organic compound „bunker in 500 ml of water, after which the volume the solution is made up to 1 l with water. Of the azotorganic compounds, acetamnnn, 2-propyl-2-imidaz1-lin, 2-pentyl-2-imidazolium, guanidine, biguanidine, 1-benzimidazole, 2-methylbenzimidazole, 1-ethyl-2-methyl-benzimidazole, pyridine, 2,4 are used. -lithydine, -aminopyridine and 2 2-dnpirndilamin. By replacing each of these activator solutions used in Example i, the oleophilic portions of the silver image are obtained. Claim 1. The method of preparing an offset printing form, consisting in applying to the substrate an adhesive layer, a hydrophilic layer and a high-contrast photographic emulsion, exposing the image, treating the developer and stabilizing it with a solution, oleophilic printing elements and washing, in that to increase the form stability, oleophilization of the printing elements carried out with a homogeneous stable acidic aqueous salt solution containing a ferrocyanide anion and an organic cationic complexing agent. 2. A method according to claim 1, characterized in that 2-benzyl-2-imidazoline is used as the cationic reagent. 3. A method according to claim 1, characterized in that the solution contains an alkali metal cation and anion of chlorine. Sources of information taken into account in the examination: 1. US Patent No. 3532055, cl. B41 N 1/00, 1970.  W ///// MW / jWAk- If T S T 8 7 T 7 8