BRPI0802427A2 - Process for the treatment of aluminum plate surfaces for use in printing digitized images, Process for the production of pre-sensitized aluminum plates and plate - Google Patents

Abstract

PROCESS FOR TREATMENT OF ALUMINUM SHEET SURFACES FOR USE IN SCANNING IMAGE PRINTING, PROCESS FOR PRODUCING PRESENSITIVE ALUMINUM SHEET AND PLATE. The present invention relates to a process for treating aluminum plate work surfaces for use in printing scanned images comprising the steps of: a) degreasing and deoxidizing an aluminum plate with alkaline solution; b) granulation by immersion of the aluminum plate in a bath containing solution of one or more acids, in the presence of an alternating electric current transferred by graphite electrodes; c) simultaneous cleaning of the plate surfaces by the action of a solution containing an acid or alkali; d) anodizing by immersion of the aluminum plate in a bath containing an acid solution, in the presence of a direct current transferred by electrodes; and e) chemically treating both aluminum plate working surfaces with a radiation sensitive composition suitable to provide a photosensitive coating on both said aluminum plate working surfaces. The present invention further relates to a process for producing a pre-sensitized aluminum plate for use in printing digital images containing a radiation sensitive composition applied to both sides and the lithographic image printing plate. digital.

Description

Patent Descriptive Report for "PROCESSING TREATMENT OF ALUMINUM PLATE SURFACES FOR PRINTING OF DIGITAL IMAGES, PROCESSING PRE-SENSITIVE ECHAPA ALUMINUM PLATE PRODUCTION".

FIELD OF INVENTION

The invention relates to novel pre-sensitized sale kita ?? aluminum plates coated on both working faces with compositions usable for digital imaging, as well as a process for the production of lithographic printing plates and treatment process. aluminum plate surfaces for use in printing scanned images.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide printing plates for use in forming digital images coated on both sides of the work with radiation sensitive compositions especially suitable for use in printing plates.

It is another object of the present invention to provide a process for producing off-set digital lithographic printing plates coated with radiation sensitive compositions.

It is yet another object of the present invention to provide a method for treating aluminum plate surfaces for use in printing scanned images.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a scanned image printing plate containing radiation sensitive composition comprising:

1) an electrochemically granulated aluminum plate, anodized and suitably treated with a product which makes it adherent and hydrophilic on both sides;

2) a photosensitive coating of one or more layers applied to the two work surfaces (on the sides or opposite sides of the sheet work) of the aluminum plate. The sheet coated on both sides or work surfaces is placed in a receiving device. radiation and form images. These imaging devices can work at any wavelength. There are currently two commonly employed wavelengths. A commercially available laser emitting diode system at 830 nm manufactured by several companies (eg CREO, Vancouver, Canada) and another emitting diode system in the region of 405 to 410 nm (eg Plate Rite Micra manufactured by Screen, USA).

Each wavelength has its own advantages and disadvantages. Both, however, are capable of producing acceptable images in one mode of production.

The digitized information is then used to modulate the laser's potential power. The energy is directed to the surface of the plate where energy transfer mechanisms, reactions and so on occur.

Depending on the type of composition, the area affected by the energy becomes the image while the rest of the coating is removed in the development process or, if the reaction causes photosolubilization, the energy-affected coating is removed in the development process and the unaffected area. becomes the image.

Depending on the wavelength used for image formation and the specific composition, the energy supplied by the laser may be sufficient to properly initiate the reaction and complete it. In cases where this is not sufficient, additional energy is required, which is typically applied as a preheating step. This is accomplished by passing the plate through a greenhouse after the image has been formed and before it is developed.

After exposure to radiation, aluminum plates coated on both sides or work surfaces can be developed in developing solutions suitable for the type of coating, being processed in automatic machines or manually in cuvettes, taking into account the temperature and the time required for each type. coating

Photosensitive coatings formed from radiation sensitive compositions are known to those skilled in the art. As an example, we cite those which are described in U.S. Pat. Nos. 292924, U.S. 6,933,093, U.S. 7,241,557, U.S. 6,953,652, U.S. 7,205,084 and U.S. 6,780,576.

In general, aluminum alloys used in the manufacture of pre-sensitized aluminum sheets are special and aluminum represents about 70% of the cost of the product.

One of the advantages of the present invention is the use of metal with the use of two faces, allowing the user, when finishing a job with the printing plate, to use the other side and to print another job.

Another advantage is increased productivity in a pre-sensitized sheet factory, where simultaneous production allows us to double the usable product area with the same resources.

Another advantage is the reduction in the total cost of fabrication by taking into account that with the same processing time as single-sided sheets (surface treatment, coating, cutting and packaging), twice the usable area of the sheets is obtained. double side.

Another advantage is the reduction of resource consumption such as water, energy and wood products for packaging (paper, cardboard, and crates). Another advantage is the reduction of freight and storage area, since the user now uses half.

The invention further relates to the process for producing a pre-sensitized aluminum plate for use in scanning digital images containing a radiation sensitive composition applied to both faces, comprising:

- chemical and electrochemical treatment of sheet surfaces using aqueous chemical solutions;

- plate drying;

- application of photosensitive coatings in liquid form on two surfaces with subsequent drying.

The surface treatment process of aluminum can be done continuously (in coils) or discontinuous (in cut sheets). The material treatment sequence is as follows:

- a degreasing and deoxidizing step of the alkaline aluminum solution;

- electrochemical treatment of granitation performed simultaneously on both faces in the presence of alternating current in a bath containing

one or more acids for the purpose of increasing surface roughness of aluminum plate;

- cleaning the surfaces simultaneously by the action of an acid or alkali-containing solution to remove impurities from the electrochemical treatment of granitation;

- an electrodic anodizing treatment done simultaneously on both sides, with the presence of a direct current in a bath containing an acid solution to oxidize the surfaces, increasing its resistance with the formed aluminum oxide; and

- a simultaneous chemical treatment on both sides to make the surface hydrophilic and adherent by the action of a solution applied by dipping or sprays or other suitable mechanism to provide a photosensitive coating on aluminum plate surfaces containing products capable of react with aluminum oxide.

Among the most commonly used products capable of reacting with aluminum oxide are polyvinyl phosphonic acid, sodium silicate, a mixture of monosodium phosphate with sodium fluoride. In general, steaking is done using a temperature ranging from 65 to 95 ° C for 20 to 30 s. The concentrations employed for this product are low, ranging from 0.1 to 5%.

In the degreasing / deoxidation step, preferably by the action of sprays, alkaline solutions containing sodium hydroxide at a concentration of 2 to 5%, depending on the amount of material used to protect the metal to be removed, at a temperature ranging from 45 to 65 ° C for 20 to 40 s.

The electrochemical treatment of granitation is done by immersing the aluminum in a bath containing a solution of one or more acids, in the presence of an alternating electric current transferred by graphite electrodes.

Diluted acid solutions at temperatures of 26 to 45 ° C are used as electrolyte, being the most used hydrochloric acid. The electrolyte may also contain a hydrochloric acid salt (AlCl3) and an associated weak acid (acetic acetic acid). In general the concentration of hydrochloric acid is 8 to 15 g / l. Depending on the dilution of the acid and the electrical charge applied to the process, the desired average roughness is obtained. In general, the medium roughness Ra is 40 to 50u.m.

The next step to the surface cleaning step is the hot acid or alkali portion. In acid treatment phosphoric or sulfuric acid is used at a concentration of 100 to 160g / l at a temperature between 50 and 90 ° C. When sodium hydroxide solution is employed, both concentration and temperature must be attenuated to avoid destruction of the peaks formed in the previous step, avoiding loss of adhesion of the coating to the aluminum substrate. In this case, the concentration of the solution is 0.1 to 0.2 g / l at a temperature of 45 to 50 ° C.

The anodizing treatment is done by dipping aluminum into a tank containing an acid solution in the presence of a direct current transferred by lead or graphite electrodes.

The acids commonly employed in the oxidation process are sulfuric acid and / or phosphoric acid. Depending on the type of oxide desired and its thickness, the acid, its concentration, the temperature of the solution and the electric charge to be applied are selected. Normally the concentration ranges from 150 to 200g / l, the temperature from 27 to 38eC and the electric charge from 20 to 50 A / dm2.

At the end of each step, it is necessary to wash the aluminum surface, eliminating all water before entering the next step to avoid contamination between baths.

After the treatment sequence, the aluminum surface is dried and then the coating solution is applied on both sides according to the type of product. The photosensitive coating is applied in dilute solutions which are dried with the aid of hot air dryers. These solutions may be aqueous or solvent mixture. Depending on the type of coating, more than one layer per side may be required.

Properly treated aluminum, as set forth above, in continuous (coil) or discontinuous (sheet) form, is coated with a photosensitive coating solution. These solutions may be aqueous or organic solvents. Examples of such solvents include, but are not limited to: 1-methoxy-2-ethanol, 1-methoxy-2-propanol, acetone, methyl ethyl ketone, diisobutyl ketone, methyl isobutyl ketone, n-propanol, isopropanol, tetrahydrofuran, butyrolactone and methyl lactate.

Coating components may be added at various solids levels based on the technique used to apply the coating to the substrate being coated. Quantities of each of the coating components are generally described as a percentage of total solids.

The coating components are dissolved in the desired solvent system. The coating solution is applied to the chosen substrate. The coating is applied to have a dry coating weight in the range from approximately 1.0 g / m2 to approximately 3.0 g / m2, more preferably from approximately 1.3 g / m2 to approximately 2.2 g / m2. and most preferably from approximately 1.5 g / m2 to approximately 2.0 g / m2.

The coating is dried under conditions that will effectively remove all solvent, but not so aggressively to avoid causing any degradation of any component of the solution.

If a second layer is required to make up the photosensitive composition, it should be applied with a solvent that does not dissolve the first layer. Depending on the type of composition, this second layer may range from 5 mg / m2 to 2 g / m2.

There are several systems for applying these solutions to aluminum surfaces. The most commonly used are: reverse roll application system, dip system and slotdie system.

The application of photosensitive coating on both sides of aluminum can be done simultaneously or not. The same is true if the photosensitive composition is composed of two layers.

Example

An aluminum plate was treated on both sides as follows:

- first was degreased by action of aqueous solution spray jets containing 20 g / l sodium hydroxide at 50 ° C for 15 s.

It was then washed with running water for 5 s;

The plate was then electrochemically granitized by immersion in a tank containing an aqueous solution comprising 10 g / l hydrochloric acid and 4 g / l aluminum chloride at 30 ° C using alternating current. A current density of 150 A / dm2 per face was applied to obtain an average roughness (Ra) around 0.45 æm;

- After washing with running water for 5 s, the plate was treated with a 90 g / l aqueous solution of phosphoric acid at 85 ° C by spray jets for 5 sec and washed again with running water for 5 s;

- the plate was subjected to anodic oxidation in a tank containing an aqueous solution containing 150 g / l sulfuric acid at a temperature of 35 ° C and a current density of 30 A / dm2 to form an oxide film of 2.1 g / m2 After this step the plate was washed with running water for 5 s;

The plate was then treated by dipping with an aqueous solution containing 20g / l sodium silicate at 95 ° C for 30s, washed with running water and dried.

On the aluminum plate treated as above, solutions were first applied on one side to make up a positive photosensitive composition for use in forming digital images, and then the plate was dried. Subsequently, coating was applied on the other side of the plate. Each of the coatings were made according to the example cited in U.S. Patent 7,029,824 of IBF - Brazilian Film Industry, in order to obtain a homogeneous dry film on both sides.

After refilling the guillotine plate in order to square the material, it was placed on a Screen 8100 image forming device with a cylinder rotation speed of 700 rpm and varying laser power, which obtained varied energies of 80 mJ / cm 2 to 200 mJ / cm 2 at intervals of 20 mJ / cm 2.

After exposure on one side, the plate was replaced with the imaging device mentioned above to expose the other side with the same conditions as above.

The plate was then processed in an IBF automatic double-sided plate processor containing Million HP developer produced by IBF at a temperature of 25Â ° C with an immersion time set to 26 sec. The plates were protected with IBF finishing solution.

It was observed that both sides of the developed plate showed positive image with good contrast and good resolution. Based on a UGRA scale, on both sides the microline results were 8/10 and halftone dot resolution 2 - 98. Under standard printing conditions using a Heidelberg GTO printing machine it was observed that the plate printed approximately 50,000 good copies with each side.

Claims (30)

1. Process for the treatment of aluminum sheet work surfaces for use in printing digitized images, characterized in that it comprises the steps of: a) degreasing and deoxidizing an aluminum plate with alkaline solution; aluminum plate in a bath containing solution of one or more acids in the presence of an alternating electric current transferred by graphite electrodes c) simultaneous cleaning of the plate surfaces by the action of a solution containing an acid or alkali d) anodizing by immersion aluminum plate in a bath containing solution of an acid, in the presence of a direct current transferred by electrodes; ee) chemical treatment of both aluminum foil work surfaces with an appropriate radiation sensitive composition to provide a photosensitive coating on both said aluminum plate work surfaces. Process according to Claim 1, characterized in that it is made in continuous or discontinuous form. Process according to Claim 2, characterized in that the surface treatment of the aluminum plate is carried out in coils. Process according to Claim 2, characterized in that the surface treatment of the aluminum plate is made of cut sheet metal. Process according to any one of claims 1 to 4, characterized in that step (a) is carried out by the action of spray jets. Process according to any one of claims 1 to 5, characterized in that said alkaline solution of step (a) contains sodium hydroxide at a concentration of 2 to 5%. Process according to any one of claims 1 to 6, characterized in that step (a) is carried out at 45 to 65 ° C for 20 to 40 s. Process according to any one of claims 1 to 7, characterized in that the electrodes of step (b) are graphite electrodes. Process according to any one of claims 1 to 8, characterized in that dilute acid solutions at a temperature of 26 to 45 ° C are employed as electrolyte in step (b). Process according to Claim 9, characterized in that the dilute acid is hydrochloric acid. Process according to Claim 9 or 10, characterized in that the electrolyte may also contain a hydrochloric acid salt associated with a weak acid. Process according to Claim 11, characterized in that the hydrochloric acid salt is aluminum chloride and the weak acid is acetic acid. Process according to any one of claims 9 to 11, characterized in that the concentration of hydrochloric acid is from -8 to 15 g / l. Process according to any one of claims 1 to 13, characterized in that said acid treatment is carried out with phosphoric or sulfuric acid at a concentration of 100 to 160 g / l at a temperature between 50 and 90 ° C. Process according to any one of claims 1 to 13, characterized in that said alkali treatment is carried out with sodium hydroxide at a concentration of 0.1 to 0.2 g / l at a temperature of 45 to 50 ° C. Process according to any one of claims 1 to 15, characterized in that the electrodes of step (d) are lead or graphite. Process according to any one of claims 1 to 16, characterized in that the acid used in step (d) is sulfuric acid and / or phosphoric acid. Process according to Claim 17, characterized in that the acid concentration ranges from 150 to 200g / l, the temperature from 27 to 38 ° C. Process according to Claim 17 or 18, characterized in that the electric charge is 20 to 50 A / dm2. Process according to any one of claims 1 to 19, characterized in that step (e) is performed at a temperature of 65 to 959 ° C for 20 to 30 s. Process according to any one of claims 1 to 20, characterized in that said solution comprises products which react with aluminum oxide. Process according to claim 21, characterized in that the concentration of said product is 0.1 to 5%. Process according to claim 22, characterized in that said products are selected from polyvinylphosphonic acid, sodium silicate or a mixture of monosodium phosphate and sodium fluoride. Process according to any one of claims 1 to 23, characterized in that after each step, the aluminum surface is washed off and dried. 25. A process for producing a pre-sensitized aluminum plate for use in printing digital images containing a radiation sensitive composition applied to both sides, characterized by the fact that it comprises: a) surface treatment process of aluminum sheets as defined in any one of claims 1 to 24, (b) drying the sheet; c) application of photosensitive coatings in liquid form on both surfaces with subsequent drying. Process according to Claim 25, characterized in that the photosensitive coating is applied in dilute solutions and is dried with the aid of hot air dryers. Process according to either of Claims 25 and 26, characterized in that said solutions may be aqueous or solvent mixture. Process according to claim 27, characterized in that the solvents include: 1-methoxy-2-ethanol, 1-methoxy-2-propanol, acetone, methyl ethyl ketone, diisobutyl ketone, methyl isobutyl ketone, n-propanol isopropanol, tetrahydrofuran, butyrolactone and methyl lactate. Plate, characterized in that it is produced by the process as defined in any one of claims 1 to 28. 30. A plate for the printing of digitized images, containing a radiation sensitive composition, characterized by the fact that it comprises: an electrochemically granulated aluminum plate, anodized and properly treated with a product that makes it adherent and hydrophilic on both sides, a photosensitive coating one or more layers applied to both working surfaces of the aluminum plate