EP0704320B1 - Process for the mechanical roughening of the surface of a printing plate support and cylindrical brush therefor - Google Patents

Abstract

Process for the mechanical roughening of the surface of an Al (alloy) printing plate carrier by wet brushing is novel in that it is wet brushed, with simultaneous application of organic fibres and metal wires placed side by side, with a suspension of 5-80 wt. % abrasive particles in water. Also claimed is a brush roller to carry out the above process having a surface covered with bands of brushes. The brush roller is novel in that the brush bands (8, 9) contain fibres and wires, the fibre material being different to the wire material.

Description

The invention relates to a method for mechanically roughening the surface a printing plate support made of aluminum or an aluminum alloy Wet brushes and a brush roller to carry out the process.

The production of supports for photosensitive printing plates requires a Roughening the support surface, which generally happens in the way that first mechanically and then electrochemically in an electrolyte is roughened. The mechanical roughening can be done by wire brushing, sandblasting, Wet and dry brushing techniques, ball milling and the like Techniques are done.

The printing process is essentially using a printing plate with a flat surface. The pressure plate is roughened and chemical treatment, whether it's a purely chemical treatment in a solution or an electrochemical treatment, prepared so that a printing surface is obtained in the printing areas only accepts the oily ink and rejects water and vice versa takes on water in the non-printing areas and repels the ink. The processed printing plate is moistened to carry out the printing process and applied the ink. Then the printing plate is used for offset printing pressed against a rubber pad that is through the ink transfers the colored print image onto the paper to be printed or at direct printing pressed directly against the paper. It will be high quality We strive for images that are without any noticeable preferred direction should. An undesirable direction can occur if the surface the printing plate has a non-uniform structure. Furthermore, strived to produce consistent, high quality images when the same Printing plate and the same type of printing plate can be used. A not Reproducible image can occur when the surface of the printing plate is not of constant quality or its surface quality in the case of high print runs does not maintain.

A photosensitive printing plate is made by applying a photosensitive Layer on a roughened carrier, which is generally aluminum or made of an aluminum alloy. As mentioned before the surface becomes either mechanical, purely chemical, electrochemical or roughened in combination of two or three of these techniques. An etching, anodizing, usually follows the roughening and a treatment of the surface that makes it hydrophilic if it is should be required. Finally, a light-sensitive layer is roughened on the Surface applied to obtain a presensitized printing plate. This is exposed imagewise using actinic rays, developed and preserved, to get a processed printing plate, which is then in a printing press assembled for printing.

In the field of roughening the surface of substrates for printing plates, a number of methods, as already mentioned above, are known, but some of them have disadvantages. This shows that the edges of the carrier have a different roughness than the center of the carrier during ball milling, so that the plate edges must be separated to ensure a uniform roughness across the width of the carrier. The problem with wire brushing is that the roughness is directed in the direction of rotation of the wire brush. Characteristic mean roughness values R _a of wire-brushed material are 0.25 µm in the running direction of a carrier tape and 0.45 µm transversely to the tape running direction, so that there is an overall 50% difference in the two mutually perpendicular directions.

In the case of sandblasting beams, the spray nozzles are subject to one great wear due to the abrasive sand particles and need to be replaced frequently will. When electrochemical roughening is the electrical energy consumption large and there are problems with the disposal of the acidic Solutions that contain dissolved aluminum ions. Becomes a purely chemical Considered roughening, so is the residence time of the carrier in the chemical Bath relatively long compared to electrochemical roughening.

When wet brushing with a slurry in which small abrasive particles in are dispersed in an aqueous solution, this with a brush or a Set of brushes rubbed against the surface of the substrate. The Bristles of the brushes are usually made of plastic such as nylon or Polypropylene and wet brushing are carried out until the desired surface roughness is reached. The disadvantage here is that the bristles out Plastic is subject to great abrasion and that the edges of the substrate cut off the bristles so that there are significant edges shorter bristles than in the other areas of the brush. Then becomes a Brushed wider carrier tape, so the shorter bristles can the wider Roughen the carrier tape insufficiently in these edge areas so that a significantly lower roughness compared to the other areas becomes.

Are used for wet brushing instead of plastic wire brushes used, there are the disadvantages already mentioned that the surface of the support material is not uniform in roughness but is preferred Identifies alignment. With the wear of the bristles also changes the roughness of the support surface.

The wet brushing of aluminum supports is, for example, in the US patents 3,929,591, column 4, lines 33 through column 5, line 8 and 4,477,317, column 2, Line 55 to column 3, line 5 described.

A brush roller is known from US Pat. No. 4,714,528, column 4, lines 45 to 66, which is used in wet brushing. A support made of aluminum or an aluminum alloy containing 99% by weight of aluminum and small amounts of silicon, iron, copper, zinc, manganese, magnesium, chromium, lead, bismuth, calcium, indium, galium, nickel and the like is included a slurry under high liquid pressure, which slants against the surface of the support. The slurry contains finely ground powder of abrasive substances and, if necessary, may also contain an acid or a base. After this roughening step by means of a slurry, a brush treatment is carried out, the brush roller consisting of nylon fibers, polypropylene fibers, animal hair, steel wire or the like, and the fibers or bristles having a uniform length and being evenly distributed on the base part of the brush roller. The length of the bristles or fibers is 10 to 150 mm and the diameter of the individual fibers or wires ranges from 0.1 mm to 1.5 mm. The brush roller is moved at a speed in the range of 200 to 2000 revolutions per minute. The abrasive slurry is sprayed onto the carrier under high liquid pressure through a spray nozzle before the carrier passes the brush rollers which are pressed against the carrier so that the carrier surface is roughened with constant pressure between the support rollers and the brush rollers. After roughening, the roughened surface of an aluminum carrier has an average roughness R _a of 0.3 to approximately 1.2 μm, in particular 0.35 to 0.8 μm.

EP-A-0 595 179 describes a method for roughening aluminum plates described using two types of nylon bristle brushes will. The two types of brush differ in their different Bristle diameter from each other, the brushes with the smaller bristle diameter in the range of 0.10 to 0.34 mm in the final brush roughening step are used and the brushes with the larger bristle diameter Pre-roughen from 0.57 to 1.20 mm. Both before the pre-roughening and the final roughening step each become a slurry from abrasive particles on the surface of the aluminum plate upset.

The object of the invention is a wet brushing method for roughening carrier materials for printing plates to improve and develop so that very obtain uniform center-line roughness values without pronounced directional orientation and that only a slight wear of the brush roller material in Comparison to known brush rollers occurs. Within the scope of the invention also a brush roller used in the process can be created at constant center roughness a longer service life than conventional brush rollers owns.

This object is achieved according to the method in such a way that at the same time Use of organic fibers and metal wires arranged side by side, with a slurry of 5 to 80% by weight of abrasive particles in Water that is brushed wet.

In an embodiment of the method, the ratio of the organic fibers is too the metal wires in the range of 0.01 to 10. The ratio of is preferably organic fibers to the metal wires in the range of 0.05 to 5, in particular it is 0.1 to 1.0.

In a further development of the method, the particle size in the slurry is 1 to 500 µm, in particular 20 to 50 µm. The wet brushing is carried out in _{such a} way that the mechanically measured mean roughness values R _a differ from one another in the running direction of the printing plate carrier and transversely to the running direction by a maximum of 14%, based on R _a in the running direction. The mean roughness values R _a in the running direction are in the range from 0.32 to 0.47 μm and the mean roughness values R _{a in} the direction of the running direction are in the range from 0.35 to 0.50 μm. It generally applies that the average roughness values R _a can be in each case in the range from 0.2 to 0.6 μm.

The further development of the method results from the patent claims 7 and 8.

A brush roller to perform the procedure, with one of brush strips occupied surface, is characterized in that the brush strips contain adjacent organic fibers and metal wires. In a further embodiment of the brush roller are over the roller surface arranged two groups of brush strips, each Group of brush strips made of a certain material in the form of fibers or wires and the brush strips form a repetitive Pattern from a first number of brush strips of one Group and a second number of brush strips of the other group. It it is also possible that the single brush strip is a mixture of fibers and contains wires and that the fiber material is different from the wire material is.

In a development of the invention, the material of the brush strips is one Group one polymer while the material of the brush strips the other Group is a metal.

Further details of the brush roller according to the invention result from the Features of claims 12 and 14 to 21.

Figur 1

einen Querschnitt durch eine erste Ausführungsform einer erfindungsgemäßen Bürstenwalze, und

Figur 2

einen Längsschnitt durch eine zweite Ausführungsform der erfindungsgemäßen Bürstenwalze.

The invention is explained in more detail below with reference to the drawings. Show it:

Figure 1

a cross section through a first embodiment of a brush roller according to the invention, and

Figure 2

a longitudinal section through a second embodiment of the brush roller according to the invention.

Brush strips 2 and are over a roller surface 7 of a brush roller 1 3 distributed, of which in the cross section of Figure 1 each the front of a first fiber and a first wire are recognizable. The single brush strip 2 or 3 consists of a multitude of in the viewing direction Figure 1 successively lined up fibers or wires and extends over the entire width of the brush roller 1, which is perpendicular to Drawing plane of Figure 1 runs. The fibers of a group 4 of the brush strips 2 are polymer fibers and in FIG. 1 with a greater thickness than the wires another group 5 shown. The polymer of the brush strips 2 is made from the group polyamides, polyacrylonitriles, polyesters, polyethylenes, polyimides, polyolefins, Polypropylenes, polyurethanes, polyvinyl chlorides and cellulose derivatives selected. A preferred fiber material for the brush strips 2 are polyamides such as nylon 6, nylon 6.6; Nylon 6.10 and nylon 6.12. To increase the The polyamides are resistant to abrasion with inert particles such as, for example Silicon carbide filled. The metal of the wires of the brush strips 3 is made from the Group of stainless steel, steel, aluminum, brass, bronze, copper, iron and Alloys of these metals selected. Stainless steel is preferred because of its high abrasion resistance and its inexpensive value for the brush strips 3 used. In the first embodiment shown in Figure 1, each is the individual brush strips 2 and 3 either only from polymer fibers or only from Metal wires formed while in the second embodiment shown in Figure 2 the brush roller 7 this is not the case. As from the drawing can be seen, a lower brush strip 8 consists of groups 12 of metal wires 33 and groups 13 of polymer fibers 22. The individual comprises Group 12, for example, two metal wires 33 and the individual group 13 four Polymer fibers 22. The upper brush strip 9 consists of groups 10 of Metal wires 33 and groups 11 of polymer fibers 22, the individual Group 10 each have two metal wires and the individual group 11 each four Has polymer fibers. Of course, the number of metal wires or the fibers in the individual groups of the specified Numbers deviate upwards and downwards. Groups 10 and 11 of the a category of brush strips 9, of which only a single one in FIG. 2 Brush strips are shown, can be used with groups 12 and 13 of the others Category of brush strips 8, of which only a single one in FIG. 2 Brush strips are shown, cover in their patterns or offset against each other be, as can be seen from Figure 2.

Carrier plates or tapes, which are essentially in the inventive Processes roughened are made of pure aluminum or an aluminum alloy. The alloy is composed of aluminum as the Main component and small proportions of silicon, iron, copper, zinc, Manganese, magnesium, chromium, lead, bismuth, calcium, indium, gallium, nickel, and the like. In any case, the aluminum has a proportion of ≥ 98% by weight on. The thickness of the aluminum support is in the range between 0.01 and 0.5 mm selected, according to the sizes breaking strength, bending strength, mechanical Resistance, elongation and the like, as for a particular application a lithographic printing plate in a printing press have to. Steel plates or bands can also be used, however they are not common because of their relatively high weight and stiffness used.

Before wet brushing with a slurry, apply one or both sides of the aluminum carrier cleaned, degreased and / or by known methods etched. These methods include treatment with a solution that Contains sodium hydroxide with or without degreasing and etching agents. The mixtures can also chemicals such as acetone, methanol, trichlorethylene and the like contain. The solution can also be an aluminum ion source such as sodium aluminate to a concentration that corresponds to the saturation point, included to increase process consistency support. The required concentrations and other treatment conditions depend on what specific surface roughness is set shall be. This step can generally be from 5 seconds to Take 5 minutes. After that, the surface of a wet brush with a slurry subjected.

The slurry consists of water and a finely divided powder one abrasive agent. The fine powdery abrasive is concentrated from 5 to 80% by weight used in the slurry, particularly in the range between 15 to 40% by weight. The slurry can also be an acid or contain an alkali if necessary. Likewise, others Additives such as thickeners, surface treatment agents, and flocculants and the like may be included. Suitable abrasives include diamond dust, Quartz, flint, granite, aluminum oxide, silica, diatomaceous earth, sand, Emery, abrasives made of iron and aluminum silicates, talc, pumice, Corundum, dolomite, magnesium oxide, alumina, zirconia, iron, tungsten carbide and the like or a combination of two or more of the foregoing enumerated means. The abrasives have an average particle size in the range between 5 and 500 µm, preferably between 10 and 100 µm, particularly preferably between 20 and 50 μm.

The abrasive slurry feeder includes a container a capacity in the range between 100 and 10,000 liters, in particular between 1,000 and 5,000 liters. A stirring device is located in the container for the slurry to precipitate solid particles too prevent. The stirring device can be, for example, a propeller stirrer, which extends into the container or a system for circulating the slurry. By constantly moving the slurry, precipitation will occur prevents the solids in the slurry. A pump delivers the slurry to a manifold. The pump delivery rate is like this set for an aluminum carrier belt that the distribution width, the belt speed, the brush speed and the solids in the slurry be taken into account. For example, a pump power of 400 Liters per minute for a distribution width of 1 m, a belt speed of 50 meters per minute, a brush speed of 500 revolutions per minute and a solids content of 20 wt .-% applied. The distributor nozzle distributes the slurry evenly over the aluminum support, especially in the form of a uniform curtain. The nozzle can either a narrow slot or a number of closely spaced apart Have holes. The slurry becomes pre-fed to the manifold filtered to prevent larger agglomerates from forming the slot or the Could clog holes.

For the wet brushing one or more brush rollers 2, as they are based of Figures 1 and 2 have been used. The brush roller or the brush rollers turn in the opposite direction the tape running direction of the carrier material. If the brush roller in the same The direction at which the carrier belt rotates must be the tangential speed of the brush roller differ from the tape running speed. The distributor nozzle carries the slurry onto the aluminum support immediately in front of everyone Brush roller on. The brush rollers can be on one or both Sides of the carrier tape. The carrier tape is preferably horizontal transported when the brush rollers are on one side, namely above the carrier belt and is conveyed vertically when the brush rollers are arranged on both sides of the carrier tape. The number of revolutions the brush rollers are in the range between 100 and 5,000 revolutions per minute, preferably between 200 and 500 revolutions per minute. The diameter of the individual brush roller is 0.1 to 1 m. The contact route of the brush roller circumference with the aluminum belt carrier is one given time is an important factor in determining the roughness of the carrier material. The route is determined by the geometry of the rollers before and after the brush roller, the carrier tape tension, the brush roller diameter and the like parameters are determined. The route can be between 10 and 1,000 mm, preferably between 50 and 500 mm. In general applies that fewer brush rollers are required if the contact distance is large is.

The object of the invention is that the brush roller or Brush rollers neither pure metal wire brushes nor pure polymer fiber brushes are, but instead have groups or brush strips, made from a combination of organic polymer fibers and metal wires consist. The relationship between fibers and wires is in one Range between 0.01 and 10, preferably between 0.05 and 5, and in particular chosen between 0.1 and 1.0. The thickness of the fibers is in the range between 0.05 and 3 mm, in particular between 0.1 and 0.5 mm. The thickness of the The wire is generally less than that of the fibers and moves in the Range between, 0.03 and 2 mm, preferably between 0.07 and 0.3 mm. The Length of the fibers and wires is the same after being on the surface the roller are attached, and their length is 5 to 300 mm, preferably 10 to 100 mm. The tufts of fibers and / or metal wires are on the roller as Brush strips attached. The brush strips contain a suitable mixture from fibers and wires. Optionally, some of the strips can only be fibers and others contain only metal wires, such brush strips in the embodiment according to Figures 1 are shown. Such brush strips will be alternately mounted on the brush roller circumference.

The fibers consist of organic polymers from the group of polyacrylonitriles, Polyamides, polyesters, polyethylenes, polyimides, polyolefins, polypropylenes, Polyurethanes, polyvinyl chlorides and cellulose derivatives can be selected. The preferred fibers consist of aliphatic polyamides, namely different nylon variants. Nylon 6, nylon are particularly preferred 6.6; Nylon 6.10 and nylon 6.12. The polymer fibers can be treated with inert particles such as For example, silicon carbide can be filled to increase their abrasion resistance. The Metal wires consist of metals such as aluminum, brass, bronze, copper, Iron or the alloys of these metals as well as steel, especially stainless steel Steel that does not rust in the aqueous slurry solutions.

When using electrochemically roughened and / or anodized aluminum carrier strips, the electrical current can flow along the aluminum carrier and through the metal wires into the brush roller. Therefore, each brush roller is electrically isolated to prevent current flow through the brush roller. After wet brushing with the slurry, the excess slurry is squeezed and / or rinsed off the roughened surface of the support. Embedded particles of the slurry are removed by etching the roughened aluminum surface. The etching is carried out using an alkaline solution, which is applied to the brushed surface. Preferred alkaline solutions contain sodium hydroxide, potassium hydroxide, sodium metasilicate, sodium carbonate, sodium aluminate and sodium gluconate. The etching treatment can also be carried out using an acidic solution containing acids such as fluoric acid, hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid. The etching is preferably carried out at a temperature ranging from room temperature to 90 ° C. for a period of 5 to 300 seconds with an etching solution which has a concentration of 1 to 50% by weight until about 0.01 up to 10 g / m ^{2 of} aluminum is etched away. An alkali-etched aluminum surface often contains alkali-insoluble substances, namely dirt. The surface is then cleaned of dirt with an acidic solution such as an aqueous solution of nitric acid, sulfuric or phosphoric acid.

Subsequently, the aluminum carrier surface wet-brushed with a slurry is roughened electrochemically. The electrochemical roughening takes place in an electrolyte which contains acids, such as, for example, nitric acid or hydrochloric acid with additives, such as boric acid, hydrogen peroxide, aluminum chloride and aluminum nitrate up to a concentration corresponding to the saturation point, in order to support the process consistency and to strengthen the electrical conductivity of the electrolyte. The electrochemical roughening can take place in two steps, namely a first step with nitric acid, followed by a second step with hydrochloric acid. Usually the nitric or hydrochloric acid is present in the aqueous electrolyte in a proportion of 1 to 20 grams per liter, while maintaining a temperature of 20 to 60 ° C of the electrolyte. Current is applied over the aluminum support and an electrode made of lead or stainless steel over a distance of 0.1 to 20 cm. The applied current density is 0.1 to 200 A / dm ² . The current is direct current or preferably alternating current, or a combination of the two types of current. The roughening time ranges from 1 to 300 seconds, in particular it is less than 30 seconds. The preferred operating parameters of the above sizes are selected within the ranges specified or can be changed within these ranges if necessary. The excess acid on the electrochemically roughened aluminum carrier is squeezed off and / or rinsed off before the next additional treatment.

In order to increase the service life of the printing plate, a wet-brushed and additionally electrochemically roughened aluminum surface is usually anodized by one of the known methods. This is done in electrolytes containing sulfuric, phosphoric or oxalic acid in concentrations up to 200 grams per liter, at a temperature between 20 and 70 ° C. The anodizing is preferably carried out with direct current, current densities of up to about 60 A / dm ^{2 being} applied in order to produce an oxide layer of up to 10 grams per m ² , in particular from 0.3 to 5 grams per m ² . The electrical voltage is 1 to 100 volts and the residence time in the electrolyte is 1 to 300 seconds, in particular 15 seconds. The electrolyte used for the anodizing may also contain further, known and useful components, such as aluminum sulfate with a concentration up to the saturation point, in order to support the process consistency and to increase the electrical conductivity of the electrolyte.

An aluminum carrier with a roughened surface that anodized Has layer, has an excellent hydrophilicity and can directly with coated with a light-sensitive layer. The carrier can optionally are also subjected to a hydrophilic treatment in a known manner, before the photosensitive layer is applied. For example, the Support with a silicate layer using an alkali metal silicate or with a polymer layer using a polyvinylphosphonic acid be equipped.

A photosensitive layer generally comprises a photosensitizer and a resin binder. It can also contain additional components such as dyes, plasticizers, acid stabilizers, surface agents, antistatic compositions, UV absorbers, optical brighteners, inert fillings, Contain lubricants and other coating solutions. A preferred negative working photosensitizer is a photosensitive polymer diazonium salt. A preferred positive working photosensitizer is a photosensitive Naphthoquinone diazide. Other photosensitizers include Azides, photo-cleavable compounds and photo-curable compounds. Some Photosensitizers require an additional coating, in particular to prevent the ingress of oxygen. The resin binder can be made from a Group consisting of vinyl acetal polymers, styrene / maleic anhydride copolymers and phenolic resins can be selected. The proportion is preferably of the resin binder in the photosensitive layer 30 to 95% by weight, especially 50 to 90% by weight. The photosensitive layer can also be coated with a Spacer layer to be coated to the vacuum suction time during exposure lower. The photosensitizer has a proportion of 5 to 70% by weight, preferably from 10 to 50% by weight in the photosensitive layer.

The additives to the photosensitive layer can be mixed with compatible solvents such as ethanol, ethylene glycol monomethyl ether, gamma-butyrolactone, propylene glycol monomethyl ether and with diethyl ketone. The brushed aluminum surface is then coated with such a solution. The photosensitive layer has a preferred dry layer weight between 0.1 and 5 g / m ² , in particular from 0.2 to 2 g / m ² . The photosensitive layer is exposed imagewise according to known techniques. Such exposure can be carried out using a UV light source through a film mask under vacuum frame conditions. Mercury vapor discharge lamps and metal halide lamps are preferred. Other sources of radiation are carbon arc lamps, pulsed xenon lamps and lasers. Light absorption filters can be used to reduce light radiation in the material. After exposure, the photosensitive layer is developed by removing the non-image areas from the photosensitive layer using a suitable developer and then dried. Any developer solution which satisfactorily removes the non-image areas of the photosensitive layer after exposure while keeping the image areas can be used. Suitable developer compositions include solutions containing additives such as sodium metasilicate, trisodium phosphate, monosodium phosphate and alkyl hydroxyls in water for diazide coatings, n-propanol in water for diazonium salt coatings and benzene for azide coatings. The developed image on the printing plate is protected by a preservation treatment.

The examples described below illustrate the invention without restricting the subject matter of the invention, it being noted in relation to the ratio of the number of fibers to the number of metal wires that approximately 10 fibers or 100 metal wires can be arranged on 1 mm ² brush strips.

example 1

Base material made of an aluminum alloy 1100 with a maximum belt width of 1.3 m and a thickness of 0.3 mm is prepared for the production of a printing plate at a belt running speed of 18 m / min. The carrier tape is first cleaned, degreased and lightly etched by treatment in an aqueous alkali solution containing about 20 g per liter of sodium hydroxide, aluminum ions and a degreasing agent, keeping the temperature at about 65 ° C for a 7 second residence time. The carrier tape is then wet-brushed with a slurry, the brush roller having a diameter of 0.6 m, a width of 1.5 m and a speed of rotation of 500 revolutions per minute. 80 brush strips are attached across the roller width, of which 60 brush strips contain nylon 6.6 fibers with a diameter of 0.3 mm and the remaining 20 brush strips contain stainless steel wires with a diameter of 0.1 mm. The brush strips are arranged in repeating groups of 3 strips of nylon with a strip of metal. The contact distance of the brush roller with the aluminum surface is 550 mm. The slurry consists of 20% by weight of abrasive particles in water. The particles consist of 99.6% by weight of silicon oxide, 0.1% by weight of aluminum oxide, 0.02% by weight of iron oxide and 0.2% by weight of other materials. The average particle size is 19 µm. The slurry comprises 3000 liters, which are under constant circulation and are applied to the brush rollers at 200 liters per minute. The roughened carrier tape is then rinsed with water, squeezed off, dried, anodized, hydrophilized and dried again. The anodization is carried out with a solution at 45 ° C. which contains 150 g per liter of concentrated sulfuric acid (95 to 98% by weight) and approximately 6 g per liter of aluminum sulfato octadecahydrate. The direct current density is 26 A / dm ² and the direct current is switched on intermittently for a total of 8 seconds, producing an oxide layer of 2 g / m ² . The anodized surface is made hydrophilic by immersion in an aqueous solution containing 2.2% by weight of polyvinylphosphonic acid at a temperature of 75 ° C.

The ratio of the number of fibers to the number of metal wires is 0.3.

This also applies to Examples 3 to 9.

The bristles of the brush roller 1 are 40 mm long at the beginning of the wet brushing. After 250,000 m of carrier tape have been brushed, the bristles are rubbed down to a length of 7 mm. The surface roughness of the substrate at the start of the wet brushing is similar to that after the passage of 250,000 m of substrate. The average roughness R _a is 0.38 μm in the direction of tape travel and 0.42 μm transverse to the direction of tape travel, so that the difference between the two average roughness values, based on the value in the direction of tape travel, is approximately 10.5%.

Comparative Example A

The wet brushing according to Example 1 is repeated, the brush roller containing only brush strips made of nylon 6.6 fibers. The bristles are rubbed down to a length of 7 mm after the passage of 30,000 m of carrier material. This means that the service life or the service life of the brush roller is only 1/8 of that of Example 1. The surface roughness is similar to that in Example 1, namely with an average roughness R _a of 0.36 µm in the direction of tape travel and 0.41 µm transverse to the direction of tape travel, so that there is a difference between the two average roughness values of approximately 14%, based on the average roughness in the direction of tape travel.

Comparative Example B

Example 1 is repeated with a brush roller 1, but with the 20th Brush strips made of metal wire by an equal number of brush strips made of nylon 6.6 fibers with a diameter of 0.5 mm are replaced. The Bristles of the brush roller are already after 30,000 m belt pass of the carrier material worn down to 7 mm. An increase in lifespan respectively the service life of the brush roller 1 results from this comparative example B not. The surface roughness is similar to that of the example 1.

Comparative Example C

Example 1 is repeated with a brush roller 1, in which 60 brush strips made of fibers with a diameter of 0.3 mm by an equal number of brush strips made of fibers with a diameter of 0.5 mm and 20 brush strips made of metal wire by an equal number of Brush strips made of fibers with a diameter of 0.3 mm can be replaced. As a result, a configuration of the brush roller 1 opposite to that of Comparative Example B is obtained. The bristles are removed after a belt pass of 40,000 m to a length of 7 mm. This represents a slight improvement compared to comparative examples A and B, but the result is nowhere near as good as that according to example 1. The mean roughness value R _a changes considerably in this comparative example C and is 0.68 μm in the direction of strip travel and 0. 80 µm across the strip running direction, which results in a difference of around 17.6% based on the roughness in the strip running direction.

Comparative Example D

Example 1 is repeated with a brush roller 1, in which all Brush strips are made of stainless steel wires. The roughness is similar to of those obtained by dry wire brushing, namely from shallow and directed. Another disadvantage is that higher pulling forces are required as the wires oppose the aluminum surface of the Hollow out the moving carrier tape.

Example 2

Example 1 is repeated with a brush roller 1, in which the number of Fiber brush strips 70 instead of 60 and the number of metal wire brush strips Is 10 instead of 20. The ratio of the number of fibers to that Number of metal wires is 0.7. The surface roughness is similar to that in Example 1. The bristles are after about 150,000 m belt pass removed to a length of 7 mm. It is compared to the comparative example A get five times the life of the brush roller 1.

Example 3

Example 1 is repeated, the average particle size of the slurry being 0.11 µm instead of 0.19 µm. The average roughness value R _a is 0.32 µm in the direction of strip travel and 0.36 µm in the cross direction of the strip.

Example 4

Example 1 is repeated with a slurry in which the slurry concentration is 30% by weight instead of 20% by weight. The average roughness value R _a in the tape running direction is 0.45 µm and 0.51 µm across the tape running direction.

Example 5

Example 4 is repeated, with the belt running speed instead of 45 m / min of 18 m / min and the anodizing current becomes proportional to the tape running speed increased by a factor of 2.5 to the same oxide weight to obtain. The bristles of the brush roller 1 are after a belt pass removed from 400,000 m to 7 mm in length. The surface roughness is slightly lower compared to Example 4, but still uniform. The average roughness values are 0.37 µm in the tape running direction and 0.42 µm across Belt running direction.

Comparative Example E

Example 5 is repeated, but with all brush strips exclusively Contain nylon fibers. The nylon bristles are already after 48,000 m removed to a length of 7 mm. This in turn means a reduction the service life of the brush rollers to 1/8 the value in Example 5. The surface roughness is similar to that after Example 4.

Example 6

Carrier tapes made of an aluminum alloy 3003 with a maximum belt width of 1.2 m and a thickness of 0.4 mm at a belt speed of 18 m / min are prepared for roughening. The tapes are first cleaned and degreased by treatment with an aqueous alkaline solution containing approximately 5% of a weakly alkaline spray degreasing and cleaning agent for metal surfaces with special additives for refining layers of phosphate layers at a temperature of approximately 55 ° C. The strips are then wet-brushed with a slurry using 4 brush rollers, which have a diameter of 0.3 m and a width of 1.5 m. Forty brush strips are arranged on each brush roller, of which 30 brush strips are made of nylon 6.6 fibers with a diameter of 0.3 mm and the remaining 10 brush strips are made of stainless steel wires with a diameter of 0.1 mm. The brush strips are spaced apart in repeating groups of 3 strips of nylon with a strip of metal wire. The contact distance from a brush roller to the aluminum surface is 60 mm. The slurry consists of 22% by weight of abrasive particles in water. The particles are composed of 59.7% by weight of silicon oxide, 22.7% by weight of aluminum oxide and 16.6% by weight of other abrasive materials. The average particle size is 48 µm. The slurry contains 1200 liters that circulate continuously. The roughened carrier tape is rinsed with water, squeezed off, dried, anodized, hydrophilized and dried again. The anodization is carried out at 40 ° C. with a solution which contains 190 g per liter of concentrated sulfuric acid (95 to 98% by weight) and approximately 10 g per liter of aluminum sulfato octadecahydrate. Direct current is applied in order to obtain an oxide layer of 0.5 g / m ² . The anodized surface is hydrophilized at 72 ° C. by immersion in an aqueous solution containing 2% polyvinylphosphonic acid. The bristles on the brush roller are 40 mm long at the start of roughening. After roughly 1 million meters of carrier tape has been roughened, the length of the bristles is still 7 mm. The surface roughness of the material at the beginning is similar to that after the roughening of 1 million meters of carrier tape. The average roughness values R _a are 0.32 µm in the strip running direction and 0.35 µm transverse to the strip running direction.

Comparative Example F

Example 6 is repeated, but all brush strips are made of nylon 6.6 fibers. The bristles are removed to a length of 7 mm after a belt pass of only 200,000 m. This means a reduction in the service life of the brush roller by a factor of 5. The surface roughness is similar to that according to Example 6, namely with mean roughness values R _a of 0.31 µm in the direction of strip travel and 0.35 µm transverse to the direction of strip travel.

Comparative Example G

Example 6 is repeated with the first brush roller only metal wire strips and the other 3 brush rollers are only equipped with nylon fibers are instead of mixed brush strips for all 4 brush rollers. The Roughness of the surface is more aligned than in the case of example 6. The Nylon bristles are up to 7 mm long after only 200,000 m of carrier tape pass worn away.

Comparative Example H

Example 6 is repeated, the first 3 brush rollers having only nylon fibers and the last brush roller being equipped with metal wires only. The surface roughness is more pronounced than in Example 6 and in Comparative Example G, with an average roughness R _a of 0.28 μm in the strip running direction and 0.38 μm transverse to the strip running direction. The nylon bristles are worn down to the same amount as in comparative example G.

Example 7

Example 6 is repeated with the tape being roughened on both sides. Four brush rollers are for roughening one side and 4 other brush rollers are available to roughen the other side. All 8 brush rollers are in a 3: 1 ratio of nylon fibers to metal wires, similar to the example 6, equipped. The mixed bristles are removed to the same extent, as indicated in Example 6.

Example 8

4,116

Ester des Bis-(3-benzoyl-4,5,6-trihydroxyphenyl)-methan und 1,2-Naphthochinon-2-diazid-5-sulfonsäure wie in dem U.S. Patent 4,407,926 beschrieben

3,900

Novolakharz

0,021

öllöslicher gelber Farbstoff (yellow GGN)

10,334

Cyclohexanon

75,856

Ethylenglykolmonomethylether

The aluminum strip of Example 1 is coated with the following positive-working photosensitive layer, which is then dried at 150 ° C. to a dry weight of 2 g / m ² . The tape is cut into presensitized printing plates. The composition of the photosensitive layer is as follows, the numbers relating to percentages by weight:

4,116

Esters of bis (3-benzoyl-4,5,6-trihydroxyphenyl) methane and 1,2-naphthoquinone-2-diazide-5-sulfonic acid as described in US Patent 4,407,926

3,900

Novolak resin

0.021

oil-soluble yellow dye (yellow GGN)

10,334

Cyclohexanone

75.856

Ethylene glycol monomethyl ether

Alnovol PN 429 from Hoechst Aktiengesellschaft is, for example, a novolak resin suitable.

92,3

Wasser

3,96

Natriummetasilikatpentahydrat

3,40

Binatriumphosphatdecahydrat

0,34

Mononatriumphosphatmonohydrat

The presensitized plate obtained is exposed through a screened positive film using a metal halide lamp. The plate is then developed with the developer shown below for 3.5 minutes. The exposed areas are removed by this developer. The plate is then colored and treated with a preservative. The processed plate is used in an offset printing machine and delivers over 100,000 prints of good image quality. For example, the developer has the following composition:

92.3

water

3.96

Sodium metasilicate pentahydrate

3.40

Disodium phosphate decahydrate

0.34

Monosodium phosphate monohydrate

Example 9

4,116

Polykondensationsprodukt von 3-Methoxy-4-diazo-diphenylaminsulfat und 4,4'-bis-methoxymethyldiphenylether niedergeschlagen als Mesitylensulfonat, wie in dem U.S.-Patent 3,839,392 beschrieben

3,900

Polyvinylacetal/Polyvinylalkohol/Polyvinylacetat-Harz mit 76,6 Gew.-% Acetalgruppen, 9,8 Gew.-% Hydroxylgruppen und 13,6 Gew.-% Acetatgruppen, wie im U.S.-Patent 4,808,508 beschrieben

0,288

Phosphorsäure (85 %)

0,021

4-Phenylazodiphenylamin

5,555

Dispersion aus 6,43 Gew.-% Farbpigmenten und 5,47 Gew.-% Polyvinylacetal/Polyvinylalkohol/Polyvinylacetat-Harz mit 76,6 Gew.-% Acetalgruppen, 9,8 Gew.-% Hydroxylgruppen und 13,6 Gew.-% Acetatgruppen im Verhältnis 1:1 von Gamma-butyrolacton zu Propylenglykolmonomethylether

10,334

Gamma-butyrolacton

75,856

Propylenglykolmonomethylether.

The aluminum strip of Example 6 is coated with the following negative working photosensitive layer, which is dried at a temperature of 125 ° C. to a dry weight of 0.7 g / m ² . The figures are in percent by weight.

4,116

Polycondensation product of 3-methoxy-4-diazo-diphenylamine sulfate and 4,4'-bis-methoxymethyldiphenyl ether precipitated as mesitylene sulfonate, as described in U.S. Patent 3,839,392

3,900

Polyvinyl acetal / polyvinyl alcohol / polyvinyl acetate resin with 76.6 wt% acetal groups, 9.8 wt% hydroxyl groups and 13.6 wt% acetate groups as described in U.S. Patent 4,808,508

0.288

Phosphoric acid (85%)

0.021

4-phenylazodiphenylamine

5,555

Dispersion of 6.43% by weight of color pigments and 5.47% by weight of polyvinyl acetal / polyvinyl alcohol / polyvinyl acetate resin with 76.6% by weight of acetal groups, 9.8% by weight of hydroxyl groups and 13.6% by weight % Acetate groups in a 1: 1 ratio of gamma-butyrolactone to propylene glycol monomethyl ether

10,334

Gamma-butyrolactone

75.856

Propylene glycol monomethyl ether.

The propylene glycol monomethyl ether is e.g. to be a product of Dow Chemical, USA.

89,264

Wasser

0,2269

Mononatriumphosphat

2,230

Trinatriumphosphat

8,237

Natriumtetradecylsulfat

The presensitized plate obtained is exposed through a screened negative film and developed with the developer described below, which removes the unexposed areas. The developed plate delivers good image quality even with a print run of more than 60,000. The composition of the developer is:

89.264

water

0.2269

Monosodium phosphate

2,230

Trisodium phosphate

8,237

Sodium tetradecyl sulfate

Claims (22)

1. A process for mechanically roughening the surface of a printing plate support made of aluminium or of an aluminium alloy by wet brushing, characterised in that wet brushing is carried out using a slurry of 5 to 80 % by weight of abrasive particles in water, with the simultaneous use of organic fibres and metal wires disposed side by side.
2. A process according to claim 1, characterised in that the ratio of organic fibres to metal wires is within the range from 0.01 to 10.
3. A process according to claim 2, characterised in that the ratio of organic fibres to metal wires falls within the range from 0.05 to 5, and is 0.1 to 1.0 in particular.
4. A process according to claim 1, characterised in that the particle size of the slurry is 1 to 500 µm, particularly 20 to 50 µm.
5. A process according to claims 1 to 4, characterised in that the average peak-to-valley heights R_a, as measured mechanically, in the direction of travel of the printing plate support and transversely to the direction of travel differ from each other by a maximum of 14% with respect to R_a in the direction of travel.
6. A process according to claim 5, characterised in that the average peak-to-valley heights R_a in the direction of travel fall within the range from 0.32 to 0.47 µm and the average peak-to-valley heights R_a transversely to the direction of travel fall within the range from 0.35 to 0.50 µm.
7. A process according to claim 4, characterised in that the particles in the slurry are composed of 49 to 99.6 % by weight silica, 0.1 to 23.7 % by weight alumina and a balance of 0.2 to 16.6 % by weight of other abrasive materials.
8. A process according to claim 1, characterised in that polymers, particularly polyamide, are used as the organic fibres, and stainless steel is used as the metal wires.
9. A brushing roller for carrying out the process according to claims 1 to 8, having a surface occupied by brush strips, characterised in that the brush strips (2, 3; 8, 9) contain organic fibres and metal wires disposed side by side.
10. A brushing roller according to claim 9, characterised in that two groups (4,5) of brush strips (2,3) are disposed over the roller surface, that each group of brush strips consists of a defined material in the form of fibres or wires, and that the brush strips form a recurring pattern comprising a first number of brush strips (2) of one group (4) and a second number of brush strips (3) of the other group (5).
11. A brushing roller according to claim 9, characterised in that the individual brush strips (8; 9) contain a mixture of fibres (22) and wires (33) and that the fibre material is different from the wire material.
12. A brushing roller according to claim 9, characterised in that the brush strips (8; 9) consist of groups (10,11; 12,13) of metal wires (33) and fibres (22), respectively, and that, with respect to their patterns, the groups (10,11) of one brush strip (8) coincide with the groups (12,13) of the other brush strip (9) or are displaced in relation thereto.
13. A brushing roller according to claim 10, characterised in that that the material of the brush strips (2) of one group (4) is a polymer, whilst the material of the brush strips (3) of the other group (5) is a metal.
14. A brushing roller according to claim 13, characterised in that the polymer is selected from the group comprising polyamides, polyacrylonitriles, polyesters, polyethylenes, polyimides, polyolefines, polypropylenes, polyurethanes, polyvinyl chlorides and cellulose derivatives.
15. A brushing roller according to claim 13, characterised in that the metal is selected from the group comprising stainless steel, aluminium, brass, bronze, copper, steel, iron and alloys of these metals.
16. A brushing roller according to claim 10, characterised in that one group of brush strips (2) consists of polyamide, such as nylon 6, nylon 6,6, nylon 6,10 and nylon 6,12, and the other group of brush strips (3) consists of stainless steel.
17. A brushing roller according to claim 16, characterised in that the fibres of the brush strips (2) which are made of polyamide are filled with inert particles such as silicon carbide.
18. A brushing roller according to claim 13, characterised in that the ratio of polymer fibres to metal wires, which form the different brush strips (2,3) in each case, falls within the range from 0.01 to 10.
19. A brushing roller according to claim 18, characterised in that the ratio of polymer fibres to metal wires is 0.05 to 5.
20. A brushing roller according to claim 18, characterised in that the ratio of polymer fibres to metal wires is 0.1 to 1.0.
21. A brushing roller according to claim 9, characterised in that the fibres have a thickness of 0.05 to 3 mm, particularly of 0.1 to 0.5 mm, and the wires have a thickness of 0.03 to 2 mm, particularly between 0.07 and 0.3 mm.
22. A brushing roller according to claim 9, characterised in that the brush strips (2,3) are of equal length between 5 and 300 mm, particularly between 10 and 100 mm.

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