DE1173917B - Method of making a lithographic printing plate - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: B 41 η

German class: 151-2 / 02

Number: 1173 917

File number: L 31620 VI b / 151

Filing date: October 31, 1958

Opening day: July 16, 1964

The invention relates to a method of manufacture a lithographic printing plate in which a water-insoluble, hydrophilic Deposit deposited and applied to this a layer of light-sensitive diazo compounds will.

The base comprises a primer layer applied to the, for example, metallic carrier made of a water-insoluble, hydrophilic, modified urea-aldehyde synthetic resin; these Layer is used to take up a light-reactive diazo compound, with the help of which forming printing and non-printing areas on the plate; further prevents this Layer a contact between the support and the diazo compound. In this way, lithographic Produce plates that allow long-term storage and excellent printing properties exhibit.

In the manufacture, sale and use of diazo presensitized lithographic printing plates, several factors are essential. The uniformity of the panels, their quality, are easy to control during of manufacture, shelf life before use, shelf life in transit through the printing press as well to mention easy control possibility when printing. It is known in the art that the commonly used diazo compounds react with metals and that it is for this reason in the case of lithographic plates with a metal support, between the diazo layer and the metal surface provide a barrier or primer layer to prevent such a reaction. Such barrier or primer layers must adhere to the metal substrate and have a hydrophilic exterior Have area to which the exposed diazo compound adheres permanently during printing, of which, however, the unexposed diazo compound is detachable.

In the case of diazo presensitized printing plates with a metal carrier, the deficiency often occurs that the The primer coat is discontinuous or so thin that there is a reaction between the metal and the Diazo connection occurs. Such defects appear as spots in the prints made from the plate in appearance. Avoiding these disadvantages requires very careful control in the various stages of the plate manufacturing process and subsequent handling. However, there is often a high percentage of rejects.

Method of making a lithographic printing plate

Applicant:

Lithoplate, Incorporated, El Monte, Calif.

(V. St. A.)

Representative:

Dipl.-Phys. G. Liedl, patent attorney,
Munich 22, Steinsdorfstr. 22nd

Named as inventor:

Bucket of Frank Deal, West Covina, Calif.,

Isador M. Richlin, San Gabriel, Calif. (V. St. A.)

Claimed priority:

V. St. v. America November 1, 1957

(693 815)

Another problem encountered in practice is that the water attractiveness the primer layer disappears after a certain period of use in the printing press, so that the The plate begins to "smear". The service life of the plate is shortened by the fact that the hydrophilic primer layer wears out or deteriorates. This can be due to the low thickness of the primer layer or due to a lack of toughness under operating conditions in the printing press. To reduce this effect and to extend the shelf life of the plate when printing, the operator of the printing press must carefully monitor the operating conditions at all times.

Polyacrylic acid and silicon compounds have already been proposed as primer materials, ζ. B. sodium silicate. The material reacts with the metal carrier and forms a water-insoluble, hydrophilic primer or barrier layer. Since a chemical reaction with the metal support is required here the primer must necessarily be quite thin because of the chemical reaction is limited to the interface between the metal support and the primer material. this applies especially when using silicate. In

409 630/262

In many cases, the thickness of the primer layer may only be a few molecules in diameter.

It has now been shown that such a primer layer does not prevent the metal from forming a diazo compound or destroy a diazo resin. Furthermore, there is no possibility of the primer or Forming a barrier layer in the required thickness to prevent the diazo material from decomposing protection. If a silicon primer layer continues, for example due to water loss during dries out during storage, it deteriorates and takes on printing ink in use, so that it unsuitable for use as a lithographic surface due to the lack of an oleophilic counter surface is.

Furthermore, primer layers made of hydrophilic cellulose derivative are known in which the cellulose derivative, z. B. a carboxyalkyloxyalkyl cellulose compound, is rendered water-insoluble by using a urea-aldehyde-amine resin. It So this is a primer layer of two substances, which by adding more finely divided Pigments can still be added. The application of a material consisting of at least two substances Priming layer on the printing plate makes its production cumbersome, increases the Costs and complicates the reproducible setting of the plate characteristics.

The invention is therefore based on the object of remedying the above-mentioned deficiencies and a simplified one Process for the production of lithographic printing plates with improved performance properties to propose. In particular, a support for receiving a light-sensitive Diazo compound are mediated, this compound producing a presensitized lithographic plate is used.

It has been found that lithographic printing plates are produced with particular advantages can, when applied to a carrier or a pad, a hydrophilic, water-insoluble primer layer is applied, which consists essentially solely of modified, water-soluble urea-aldehyde synthetic resins consists. These materials used in the present invention are for lithographic and related Purposes sufficiently hydrophilic and soluble in water so that they can easily be applied to the plate from an aqueous medium can be applied. The curable urea-aldehyde synthetic resins in question can be based on a carrier in particular in the form of a film or a coating are deposited and form after hardening a water-insoluble layer, which is used for lithographic purposes shows a hydrophilic character. The primer or barrier layer of the lithographic plate according to of the invention, as far as can be seen, does not chemically react with metals or with any other Carriers. In any case, a primer layer can always be deposited which is so thick that it is an overlying one Layer of diazo compounds protects. The primer layer can be applied once Immersing the plate in an aqueous solution of the urea-aldehyde synthetic resin with the following Water rinsing will be discontinued. Furthermore, these urea-aldehyde resins adhere well to the Carriers and are used by this during the handling, shipping or use of the Plate not peeled off or otherwise damaged.

Furthermore, the photodecomposition products of the diazo compounds increase significantly after exposure the primer layer material bound.

According to the present invention, a primer layer for a diazo presensitized plate for lithographic printing and related purposes can be made by adding a coating or a Layer of special urea-aldehyde synthetic resins is applied to a support so as to ίο to form a water-insoluble primer layer that shows a hydrophilic character. Afterward an overcoat or film of diazo photosensitive material is applied to the primer layer.

The urea-aldehyde resin used in the present invention may be water-soluble polyfunctional Amino-urea-aldehyde resin or a sulfonated one Urea-aldehyde synthetic resin. A compatible mixture of the two can also be used will. The preferred and commonly used aldehyde is formaldehyde, albeit one Paraformaldehyde has also proven useful.

Since the polyfunctional amino-urea-formaldehyde used according to the invention are water-soluble, they can preferably be applied to a printing plate from an aqueous solution. The production of polyfunctional urea-aldehyde synthetic resins is known per se, so that the production process need not be described in detail here. In general, urea and an aqueous formaldehyde solution are reacted with one another at a temperature of about 70 to 80 ° C. for 15 to 30 minutes under alkaline conditions. Thereafter, a polyfunctional amine is added, after which the _pH value is adjusted to a range of 1 to 4 The reactants are heated to a temperature between 68 ° C. and the boiling point for 15 to 180 minutes, so that no increase in toughness occurs. The temperature is then lowered to a point in the range between room temperature and 55 ° C to cause an increase in viscosity.

The molar ratio of the formaldehyde to the urea appears in the production of a polyfunctional one Amino-urea-formaldehyde not to be critical. Satisfactory results have been obtained achieved with a molar ratio of about 2.0 to about 3.0 moles of formaldehyde per mole of urea. For for best results the ratio of aldehyde to urea is preferably 2.3 to 2.8.

The amount of polyfunctional amine used does not appear to be critical, although one a minimal amount must be present to achieve solubility and other desirable properties. Satisfactory products are obtained when the amine is reacted in any stage of the Reaction. However, it is preferred that the amine be added after the initial reaction of the urea and the aldehyde admit. It is common in the processes for making these synthetic resins to be 2 to 80% polyfunctional Amine based on the weight of urea to be used. Will be used for most areas of application about 6 to 15% preferred. As examples of polyfunctional amines that have been found to be useful have, be the polyamines, e.g. B. ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylene pentamine, the condensation products of

Polyamines, which lead to amine polymers, such as tetraethylene pentamine and epichlorohydrin or tetraethylene pentamine and formaldehyde, lead to the guanidines, the biguanides, the guanylureas and the salts thereof and the hydroxylamines, e.g. B. monoethanolamine, diethanolamine and the like., Mentioned. Any of the above-mentioned amines can be reacted first with part of the total amount of the formaldehyde before it is introduced into the reaction. ao

The sulfonated urea aldehydes are also soluble in water and can accordingly be applied to a plate, preferably from an aqueous medium. The production of a water-soluble, sulfonated urea-formaldehyde is also known, so that a detailed discussion is superfluous. In general, urea, an aqueous solution of formaldehyde and an alkali metal salt of sulfurous acid reacted at reflux temperature and a _pH value which varies between ao 8 and 9.4 at least 30 minutes each other.

The p _n value is then set to a point within the range of 1 to 4. The reaction mixture is again heated to reflux for about 1 hour. Then the mixture to a temperature between 25 and 85 ° C is cooled to give a p _H value is kept by 1 to 4, so that an increase in toughness occurs.

The molar ratios of formaldehyde to urea do not appear to be critical. Useful Synthetic resins were obtained with 1.5 to 3 moles of formaldehyde per mole of urea. However, it is preferred the urea-formaldehyde in proportions of about 2.0 to 2.8 moles of formaldehyde per mole of urea to use. The amount of the alkali metal salt of sulphurous acid used also appears not to be critical. However, it must be a minimum amount of about 5% based on the weight of the Urea, can be used so that the synthetic resin obtained becomes soluble in water. However, there were also up to 60% alkali metal salts, based on the weight of the urea, are used. As an alkali metal salt can e.g. B. sodium bisulfite and sodium metabisulfite are used.

The type of support or carrier is not relevant to the subject matter of the present invention critical, as there is no chemical reaction between the primer material and the carrier, only a physical bond or liability is established with it. In general, as a result of the Intrinsic strength a metallic carrier, especially a plate is preferred. Metals such as aluminum, Zinc, copper, tin, lead, chromium, magnesium, steel or the like. Can be used. aluminum is generally preferred because it gives very satisfactory results. When using Metallic surfaces can be affected by exposure to air or by special treatment be oxidized. In the case of aluminum, for example, the surface can, if desired, chemically or electrolytically anodized, although this is not absolutely necessary.

However, the carrier can also consist of other materials. For example, a sheet of paper or a cardboard box can be used if the back is stiffened accordingly. The sheet of paper can also with a synthetic resin, e.g. B. a thermosetting resin such as phenol formaldehyde, impregnated be. It is preferable to use a heat-resistant synthetic resin as it will damage the paper during the under the action of heat, protects further process steps, such as these for production a lithographic plate according to the method of the present invention can. The term "plate" should therefore be understood in a general way. There are plates under it, Sheets, films, foils or the like, the foil merely being folded over a supporting surface will.

As light-sensitive diazo compounds, those in the relevant art (cf. USA patents 2,679,498, 2,063,631 and 2,667,415) known compounds can be used. One such a compound can, for example, be a condensation product of paraformaldehyde with p-diazodiphenylamine sulfate be. After exposure to, for example, ultraviolet light, the photosensitive ones bump Diazo compounds remove nitrogen from the molecule and form a water-insoluble one hydrophobic and olephilic material that represents the print image. The unexposed areas of the Connection can be made by means of the known developer solutions or by washing with water wash away easily.

To produce a plate according to the present invention, an aqueous solution of the modified Urea-aldehyde resin on a carrier in any suitable manner, e.g. B. by Application by means of a roller, a coating sheet or by dipping or spraying. the Excess synthetic resin can be eliminated, for example, by rinsing. the The concentration of the synthetic resin in the solution is not critical. For example, the urea-aldehyde synthetic resin Make up about 0.3 to about 5 "Vo of the solution. After applying the solution, for example, by dipping and rinsing once, the water is removed to create a primer coat or to deposit a primer film of the synthetic resin and make it insoluble on the substrate close. This is expediently carried out by heating. Any temperature can be used above room temperature are used, the upper temperature limit only is limited by practical considerations. So, of course, temperatures should be avoided that are so high that the metal of the plate is tempered or softened.

During this heating and the removal of the water, further polymerization of the occurs Synthetic resin. This supports the insolubility and the adhesion of the synthetic resin to the Carrier. However, the degree of polymerization and the amount of polymeric increment is in no way at The practice of the invention is critical, with the exception that the resin adhere well and one Should withstand washing with water so that the base plate is not exposed. According to the invention Urea-aldehyde synthetic resins used are dissolved in water (cf. USA patents 2,554,475, 2,559,578) and, as already mentioned above, applied. These resins are at this point partially polymerized or hardened. The heating is then continued up to the specified temperature

temperature range and continued until essentially all of the water is excreted and the resin is further polymerized, so that a layer of the resin is deposited, which the desirable adhesiveness and resistance to water washing Has. It was found, surprisingly, that this layer is hydrophilic and a film made of a diazo compound accepts.

Whether the applied temperature is sufficiently high and / or whether the heating time is sufficiently long, can be easily determined by observing whether the resin layer deposited has those described has the desired characteristics. In practice it has been found that heating to about 140 to about 210 ° C for about 3 to 12 minutes gives good results, although these ranges are also not critical are.

Instead of heating to deposit a layer of synthetic resin as just described, it is it is also possible to accelerate the additional polymeric growth in that the aqueous solution of the synthetic resin is made more acidic. This can be done by taking a salt out of a strong inorganic acid and a weak inorganic base are added to the solution, if this is already above the metal support. Salts that can be used are, for example Ammonium chloride, ammonium nitrate and ammonium sulfate. They are also organic for this purpose Acids, e.g. B. oxalic acid, well suited. Here, too, it is easy to see whether the crowd the added salt or acid to cause the additional polymeric growth is sufficient by determining whether the resin deposited on the carrier is sufficient Has adhesion and adequately withstands water washing. In general, the salt or Acid addition accomplished by immersion in an aqueous solution, which is between Va and 5 percent by weight Contains salt or acid. A time of about 5 minutes at room temperature is sufficient to achieve satisfactory polymeric growth, although these conditions also do not are critical. The water can be removed by evaporation at room temperature or at a slightly elevated temperature, by turning the plate or the like. Removed.

After the synthetic resin layer has settled, an aqueous solution of the diazo compound is applied, for example by roller application, dipping, spraying or the like. A sufficient amount of the compound should be used that the desired area is completely covered by the synthetic resin layer. The strength of the diazo film is not critical. One of the strengths of the residue of about 0.032 g per square meter resin layer is a widely accepted practice. There have also been aqueous solutions up to about I ⁰ Zo diazo compound. The film is deposited by drying off the solvent. Since water is generally used as the solvent, drying is generally carried out at room temperature, although temperatures up to the decomposition temperature of the diazo compound can be used if desired.

The method according to the invention for the production of a lithographic plate can, if desired, be interrupted shortly before the application of the diazo connection, so that a plate that only has the primer material that can be shipped to the consumer. The consumer can then apply the diazo connection at his own discretion.

The following examples serve to further illustrate the invention:

example 1

A 10% aqueous solution of a sulfonated urea-formaldehyde was applied to a support. The carrier was wiped with a rubber squeegee while it was still wet, and then dried at 49 ° C. The assembly was then heated to 150 ° C. for 6 minutes. The plate was then immersed in an aqueous solution containing about 1% of a diazo compound the plate will deposit a continuous layer of this solution. The diazo connection consisted of the essentially from a condensation product of paraformaldehyde with p-diazo-diphenylamine sulfate. This plate was air dried to have a film of the diazo compound over it.

The presensitized plate produced in this way was then placed in a non-staining, plastic lined and packed with paper backed foil. The edges of the slide were heated together sealed to allow plate storage.

Example 2

An aluminum plate was roughened, washed and de-steamed by treatment with a 1% strength aqueous trisodium phosphate solution. The plate was immersed in a 0.8 ⁰ / o aqueous solution of a polyf unktionellen urea-form aldehyde resin. The plate was then heated to 170 ° C. for 6 minutes. A diazo film, as described in Example 1, was applied to the plate.

Example 3

A zinc plate was coated with a 1.5% aqueous solution of a sulfonated urea-formaldehyde synthetic resin treated, which by reacting the formaldehyde with urea in a molar ratio of 2: 1 in the presence of Sodium bisulfite in an amount of 5% based on the urea weight, was formed. The synthetic resin was made according to known methods (U.S. Patent 2,559,578) and was soluble in water. The plate was heated to 49 ° C, until dry and then continued to heat to 160 ° C for 8 minutes. The sulfonated ^ urea-formaldehyde synthetic resin settled as a layer over the plate and adhered strongly to it. the Layer was sufficiently hydrophilic for lithographic purposes. The plate was then turned into a l * / o immersed aqueous solution of a diazo compound and corresponding to that described in Example 1 Finished way.

Example 4

The procedure was as indicated in Example 3, except that the plate was not heated to further polymerize the sulfonated urea-formaldehyde synthetic resin

to effect. The resin-treated plate was immersed in a solution containing 2 percent by weight of ammonium chloride for about 5 minutes. This reduced the _pH value. It was found that the additional polymerisation of the synthetic resin is likely to be accelerated by a catalytic effect. The synthetic resin was deposited as a hydrophilic layer which strongly adhered to the plate. The plate was dried at a temperature not exceeding 49 ° C.

Example 5

A copper plate was coated with a 1.2% aqueous solution of a polyfunctional urea-formaldehyde synthetic resin coated, which had been formed by the reaction of formaldehyde with urea in a molar ratio of 2.3: 1, wherein Triethanolamine was added in an amount of about 10 "Vo, based on the weight of urea. The synthetic resin was prepared according to known methods (U.S. Patent 2554475) and was soluble in water. The plate was heated to 49 ° until dry and then continued Heated to 200 ° C for 5 minutes. The modified urea-formaldehyde synthetic resin sat down as Layer off the plate and adhered strongly to it. The layer was for lithographic purposes sufficiently hydrophilic. The plate was immersed in a 0.7% aqueous solution of a diazo compound. The solution adhering to the plate was thickened into a thin film by pulling the plate rotated in the usual way until dry. The plate produced in this way could immediately be fed to an exposure.

Example 6

The procedure of Example 3 was repeated except that a resin was used as the synthetic resin which according to the procedure given in Example 6 of U.S. Patent 2,559,578 had been made.

Example 7

45

The procedure of Example 5 was repeated except that the synthetic resin used according to the process known from Example 1 of U.S. Patent 2,554,475.

Example 8

A cleaned aluminum plate was soaked in a 2% chromic acid solution for about 4 to 5 minutes 66 ° C to form an oxide layer on the surface. The plate was as in Example 1 specified, further treated.

Claims (11)

Claims: 60 1. A method of making a lithographic printing plate in which on a support a water-insoluble hydrophilic primer layer is deposited and another layer on top of this is applied from light-sensitive diazo compounds, characterized in that that the hydrophilic primer layer is essentially an initially water-soluble polyfunctional Amino-urea-aldehyde synthetic resin and / or a sulfonated urea-aldehyde synthetic resin is used, which is then cured on the plate in a water-insoluble state will. 2. The method according to claim 1, characterized in that as a carrier on which the Primer layer is deposited, aluminum, tin, zinc, magnesium, lead, chromium, copper or iron is used. 3. The method according to claim 1 or 2, characterized in that the deposited hydrophilic Layer a polyfunctional amino-urea-formaldehyde synthetic resin is used in which amino component is ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, a condensation product of tetraethylene pentamine and epichlorohydrin, a condensation product of tetraethylene pentamine and formaldehyde, a guanidine, a biguanide, a guanyl urea or salt thereof, monoethanolamine or diethanolamine. 4. The method according to any one of the preceding claims, characterized in that as deposited hydrophilic layer a polyfunctional amino-urea-formaldehyde synthetic resin which is polymerized to a state where it is substantially not is more dispersible in water, with the resin having a molar ratio of about 2.0 to has about 3.0 moles of formaldehyde per mole of urea and the polyfunctional amine thus in an amount of about 2 to about 80%, based on the weight of urea, is converted. 5. The method according to claim 4, characterized in that a polyfunctional amino-urea-aldehyde synthetic resin, which has a molar ratio of about 2.3 to about 2.8 moles of formaldehyde per mole of urea is used and that polyfunctional amine so in an amount of about 6 to 15%, based on the weight of urea, is implemented. 6. The method according to any one of claims 1 and 2, characterized in that as deposited hydrophilic layer a urea-formaldehyde synthetic resin is used, which is mixed with an alkali metal salt of sulphurous acid is modified. 7. The method according to any one of claims 1 and 2, characterized in that as deposited hydrophilic layer a sulfonated urea-formaldehyde synthetic resin that was originally soluble in water which is polymerized to a state of being substantially non-dispersible in water is, the synthetic resin by reacting about 1.5 to 3 moles of formaldehyde per mole of urea formed with an alkali metal salt of sulphurous acid and the latter in an amount of at least about 5% based on the weight of urea is present. 8. The method according to claim 7, characterized in that that aluminum is used as the carrier and sodium bisulfite as the alkali metal salt of sulphurous acid or sodium metabisulfite is used. 9. The method according to claim 7 or 8, characterized in that the alkali metal salt of .... , "» 4 (19 630/262 Sulphurous acid in an amount of about 5 to 60%, based on the weight of urea, used will. 10. The method according to any one of the preceding claims, characterized in that for Deposition of the hydrophilic layer the aqueous solution, which consists of a partially polymerized polyfunctional amino-urea-aldehyde synthetic resin and / or from a partially polymerized sulfonated urea-aldehyde synthetic resin, for the purpose of further polymerisation and for the deposition of the synthetic resin is made more acidic. 11. The method according to claim 10, characterized in that the aqueous solution by addition a salt of a strong inorganic acid and a weak inorganic base is made more acidic. «9 630/262 7.64 ® Bundesdruckerei Bertin