DE2607479A1 - COMPRESSIBLE PRINT PLATE MOUNT - Google Patents

Description

1 B E R LI N 3 3 8 MUNICH

Auguete-Viktoria-Strasse 65 _n nilOOUI / C O OADTMCD Pienzenauerstrasse 2

Pat. Dr. Ing.Ruschke Ur. KUOUni \ t Ot ΓΑΚ IINCK Pat-Anw Dipt-Ing

SÄfÄS5 "- ^lne · PATENTANWÄLTE ^HE ^

Telephone: 030 / «» »» BERLIN - MÖNCHEN

Telegram address:

Quadrature Berlin Telegram address:

. Quadrature Munich

TELEX: 183 786

TELEX: 522767 M 36 7 ο

Minnesota Mining and Manufacturing Company, Saint Paul, Minnesota,

551o1, V ₀ St ₀ A ₀

Compressible plate holder

The invention relates to a new mounting or base material for flexographic letterpress printing plates.

In the case of letterpress printing, a printing element (either a pressure roller or a printing plate) is colored and applied to paper or other sheet material to be printed to form an impression the ink liquid, and that in contrast to the more typical high-pressure process in which a paste-like ink is used .uurch the combination of flexible printing plate and liquid ink results in a printing system that prints can give rise to extremely high speed, such as _o B " with printing speeds of even 300 meters per minute and generally from 90 to 28o meters each

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Minuteo

The quality of that obtained with a high pressure flexographic system Imprint is not only very dependent on the exact setting of the printing plate thickness is adhered to, but also from the fact that extremely small dimensional deviations or »margins are observed in the printing device itself, and in particular between the printing plate and the surface to be colored and the printing plate and the surface for the impression « Variations in a flexographic printing plate (generally with a thickness of about 2.5 to 3.7 mm) over 25 hikrοη cannot be accepted.

Not only must the thickness of the printing plate be adhered to with the utmost precision, but also all elements that the printing roll must also be of great accuracy «The printing plate cylinder to which the printing plate is attached must have a smooth surface and a uniform diameter along its entire length The material used for the printing plate on this column must also have a uniform thickness and be uniform Maintain thickness throughout the printing process.

While pressing, it is important that there be close contact between the printing plate surface and the paper in order to obtain a clear, sharp impression. This becomes common by bringing the printing plate and the impression cylinder

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(or any other surface in contact with the plate) into the correct one Position, so that there is an even constant pressure between these two parts. “If certain areas of the ! Printing plate does not have an even pressure on what is to be printed Applying paper, irregularities or discontinuities in the imprint will be obtained Achieving greater total pressure has resulted in a distortion of the print in the areas where the pressure was originally applied was suitable because neither the pressure plate nor the mounting material is sufficiently compressible to allow such an adjustment, to compensate * If the pressure is too high, the cylinder will hit violently during use, resulting in damage of the entire printing device, the printing speed is limited because of the additional friction in the system and the practical service life of the printing plate drastically shortened «

Although attempts have been made to make compensating compressible supports or pads for flexographic printing plates, no support has been made which overcomes the disadvantages noted above to such an extent that they could not be used within the adjustable range of a conventional high pressure press. Other brackets, such as _o B "are those in which is foamed sponge used as the compressible layer are compressible so that they exhibit the appropriate Druckein-

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Cannot maintain positions in the flexographic high-pressure press for the formation of uniform, clear impressions ₀ Other mountings are too weak to withstand the shear forces exerted on the printrominel surface during de ;. i »iuc .-: -; - io -Lul;„ eten. Other mountings are insufficiently compressible and cannot provide the compensation desired in a printing plate mount.

The invention proposes a new holder for flexographic Printing plates that have sufficient strength and cohesion to hold the printing plate in place for extended periods of use that are strong, yet is flexible and adaptable that can be temporarily squeezed to a significant extent, but very is resistant to permanent damageo

According to the invention, a layer structure is formed from a strong, thin reinforcing layer, a resilient compressible en layer of non-compressible elastomer having dispersed therein and bound large number of very small fragile starrwandiger hollow spheres or _e bubbles broken have been, and indeed uniformly inside the layer to impart compressibility and pressure sensitive adhesive layers exist on the two major exposed surfaces of the structure.

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but are fragile enough to break when subjected to high enough pressure. After the hollow spheres break, the elastomeric compressible layer resembles a closed cell foam of low void volume which has a smooth surface so that the remaining layers adhere to it can ₀

Ίη of the drawing, which a better understanding of the invention serves is the

Figure 1 is a cross-sectional view of a Jjruckplattehalterung Invention and the

FIG. 2 is a cross-sectional view of a printing plate holder mounted in a printing press in a typical position of use.

In FIG. 1, the printing plate holder 1o contains the resilient, compressible layer 11, which is firmly bonded to the tough, strong reinforcing layer 11, as well as pressure-sensitive adhesive layers 14 and 15, which are bonded to each exposed main surface of the two-layer layer structure ₀

In use, the holder 1o is attached to the smooth surface 2o of the printing forme cylinder 21 is adhered through the one pressure-sensitive adhesive layer, while the other pressure-sensitive adhesive layer is glued to the pressure plate 22 and this carries " As shown, a printable sheet 23 receives the previously colored image of raised parts 24 of the printing plate 22,

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if there is between the printing forme cylinder 21 and the u-counter roller 25 is pressed.

The compressibility of the splint 11 is of great importance because almost all of the compression takes place in this layer, and the composition of the layer 11 is the key or essential feature of the invention 4 kg / cm (a typical pressure applied when printing) by about 0.08 to 0.13 Lm and when increasing the load to 17.6 kg / cm by a further 0.1 to 1.5 mm Scnicht a permanent compression of more than 5o microns not in when the j ^ jerk is reduced from 17.6 kg / cm to 1o, 4 kg / cm _o uie compressible layer preferably consists of an elastomer having a Shore a hardness value 2 of at least 2o and preferably less than 4o "If the hardness of the elastomer is substantially less than 2o, the holder obtained is too soft to maintain an accurate pressure setting." Elastomers with a hardness value above 4o result together Compressible layers that are too brittle to be compressible to the extent necessary for the necessary compensation.

The compressible layer 11 should have a total void volume of at least about 3o% have to ensure that the above properties are obtained "If the void volume is less than 3o%, it is difficult to achieve the required compressibility of this layer" An empty volume over 5o% after to the

procedure described here difficult to form »

The elastomer should not be so stiff that extreme process conditions (such as, _e B _o when mixed with high shear) for mixing the same with very small hollow spheres or even to rupture of the hollow spheres during the processing or handling would be required ₆ Preferably, the components, which convert to the elastomer, liquid or the elastomer itself can be made liquid, such as, for example, by heating, in order to facilitate processing. Suitable elastomers for this purpose include polyurethane, poly (acrylonitrile / butadiene) and polychloroprene.

The thickness of the compressible layer can be within the range from 0.25 to 0.75 mm (preferably from 0.38 to 0.63 mm) vary. East all compression takes place in this layer, and if the thickness of this layer is less than 0.25 mm, it is impossible to ensure the required compression in this layer alone «

An essential feature of the invention is that the empty spaces in the compressible layer of the holder are formed by a very large or "infinitely" large number of very small, fragile hollow spheres with rigid walls. The most preferred frangible, rigid-walled hollow spheres for this purpose are spherical, but hollow structures with other shapes, such as .B ₀ tubular or pear-shaped hollow G-shapes are also suitable, "hollow spheres made of glass and phenolic resin, such as solid

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provides excellent results _e

Although the size of the rigid-walled frangible hollow spheres can vary within a wide range, it is generally advantageous to use hollow spheres that are at least 10 microns up to about 300 microns in diameter. Because hollow spheres are readily available within the range of 1o to 15o microns, such hollow spheres are most common in practice of the invention used, the wall thickness of the hollow spheres may vary, but generally should be about 15% the size of the Leuchen, d, h ₀ of the diameter of 'Shine, do not exceed _e Hollow spheres with different diameters have different breaking strengths; therefore it may be desirable to use hollow spheres with an eu ^ er for more convenient processing. Diameter range, Z ₈ B ₀ between about 40 and 100 microns in diameter, should be used.

To prevent the rigid-walled hollow spheres from breaking during processing, the hollow spheres should not collapse under a continuous hydrostatic pressure of at least 14 kg / cm and preferably at least 21 kg / cm. It is assumed that a mass of hollow spheres can withstand such a pressure, if not more than about 1o / o of the original volume of the hollow spheres collapsed under such pressure «

The hollow spheres should be chosen so that a hydrostatic

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Pressure of about 140 kg / cm, practically all of the spheres collapse brings. Any in the collapsible ucnicnt Hollow spheres that remain unbroken are then used as fillers return. The individual collapsed jtionl balls have the effect of that the above-mentioned requirements are met, and it should be noted that a jointed honing ball, expressed in / o of the original volume, not 100 > o can achieve because a certain part of the original volume αer fragile iiohlbugeln is occupied by the wall thickness. Even after all the fragile iioh balls have collapsed therefore the volume occupied by the fragments of the broken hollow spheres assumes such a value that the ex-obtainable highest percentage of the void volume makes up about 9o # of the total hollow sphere volume »

In the structure of the. ^ The invention jerk plate holder is a strong, thin, zähfeste, uniformly thick, contain sized stable backing layer which is bonded adhesively to the compressible layer, ".uie reinforcing layer is preferably either or from a strong non-woven fabric _e web is less elastic strain as or it may be formed of nylon or polyester fibers, or of a biaxially oriented plastic film, such as, _e as a polyethylene terephthalate film, although layers or sheets of any of the other many tenacious flexible materials, such as _o B "woven cloth, metal or plastics, are also suitable _e uie reinforcing layer should be thin, d _o h _e a uicke in the size

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- 1ο -

Order from 25 to 125 Kikron to fit the gap between the mounting material not to increase or decrease the ±> thickness of the The compressible layer is not necessary to make the reinforcement material should have a tensile strength (if it is an IiIm) or a "grip strength" (if it is a fabric) of at least about 1.8 kg per cm of sample width and preferably of at least

about 2.7 kg per cm of sample width to have sufficient strength The "grip strength" to be obtained is determined by first inserting 1o cm of a fabric sample at least 15 cm long in the jaws of an "Instron" measuring device become trapped, -The sample is clamped on its 10 cm sides with a 2.5 cm by 2.5 cm jaw pinched, which is located in the center of one end, and pinched with a 2.5 cm by 5 cm jaw, which is anox'dnet with the 5 cm side in the middle of the other end is, with a distance between two opposite clamping jaws of 7 »5 cm, Lie clamping jaws are then with at a speed of 30 cm per minute from each other: distant, and the force between the jaws to failure of the sample is measured. A reinforcement material, as stated wholly suitable is a nonwoven, bonded nylon web sold under the trade name "Gerex" will »This material has a grip strength of around 3.4 kg / cm.

The one used to form the adhesive layers on any exposed surface pressure sensitive ones used in the printing plate holder Adhesive is any of the many adhesives known for this purpose, which has the four familiar properties, namely adhesive

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ability, cohesiveness, ductility and elasticity, all rolled into one suitable equilibrium possesses a particularly preferred type of such pressure-sensitive adhesives are all adhesives of the acrylate type ",

Although the support material of the invention has been proposed for the application of flexographic relief printing plates to printing cylinders, it can also be used with advantage for attaching any molded elastomeric printing plate or _o shape at the corresponding pressure cylinder or the corresponding pad ,.

The invention is illustrated in the more detailed examples below explained further. In the examples, all parts are based on weight, unless otherwise stated,

example 1

A compressible holder for flexographic printing plates was made using a biaxially oriented polyethylene terephthalate reinforcement layer or film with a thickness of 25 microns, a compressible polyurethane layer with a thickness of 0.68 mm and a void volume of 40 % and two layers of pressure-sensitive acrylate copolymer adhesive each manufactured to a thickness of 50 microns according to the following specifications:

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Components

Polyurethane - part A_

Polypropylene glycol (with a molecular weight of 2ooo) 42, ο

Polypropylenetriol (with a molecular weight of 16000) 7, ο

finely divided silica ("Cab-0-Sil" M5) o, 43

1,4-sutanediol o, 43

Bioctyl phthalate 17.6

Phenylmercury Oileate 0.85 Polyurethane - Part E

Toluene diisocyanate 8, ο3

Polypropylene glycol (44o molecular weight) 3.22

Sucrose acetate isobutyrate 3.55

Ethyl alcohol o.39 Fragile hollow glass spheres

mean particle size of 40 microns and mean specific Weight of o.2 16.5

Las polyurethane elastomer made from Parts A and B a Shore A hardness of 29 if it was free of voids «

Lie glass spheres were intimately mixed with the "A" ingredients in an evacuated kettle to form an "A" slurry «
The "B" ingredients were then ^{mixed with the 11} A "slurry, and the resulting mixture was sealed with a lid
Layer with a wet thickness of about 1 mm applied to the polyester surface of a 25 micron thick polyethylene terephthalate film, which adheres firmly to a 5o micron thick layer of a
pressure-sensitive acrylate copolymer adhesive was connected,

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which was provided with a peelable protective layer * Lie layer became a non-sticky state by heating for about Cured for 4 minutes at about 120 ° C. Complete curing was achieved by letting the layer structure stand for at least 2 'hunt Reached room temperature before further processing

Las obtained cured layer was laminated on its polyurethanes) he b surface to a uniform .bicke of o, abraded 75 mm (without the releasable protective layer) ,, ^ ± e hollow spheres in the obtained composite film were by passing the film through a pair of nip rolls which worked with a pressure of about 90 kg per cm, broke. After breaking, a 50 micron thick layer of pressure-sensitive adhesive was applied to the sanded surface, giving an end product 0.8 mm thick (excluding the protective layer).

If the finished product was subjected to pressure, it was at a

Pressure increased from 0.4 to 4 kg / cm, a compression A further compression of 150 microns was achieved by further increasing the pressure from 4 to 17.6 kg / cm, with a setting of 2o micron obtained

when the pressure was decreased to 0.4 kg / cm ₀

The obtained compressible pressure plate holder was used around a flexographic printing plate with a thickness of about 2.35 microns in a standard flexographic printing press, the press had a back cylinder with an outer

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-H-

catch of 46 cai, the pressure plate had a size of 11.4- χ 16.5
cm, and the aging material extended 2.5 gin across the
Dimensions of the pressure plate
was used to print 43,000 m of polyethylene film with a thickness
of 75 microns used for approximately 9 hours of operation ₀
The quality of the wax * impression was excellent, and in fact essential
improved over those who met at one
However, operation using a mounting material from a
Foamed foam sheet sold under the trade name "Pillow Sticky Back" is obtained.

■ example 2

Components of ropes Polyurethane - Part A

Polypropylene glycol (2,000 molecular weight) 40.69

Polypropylenetriol (with a molecular weight of 160) 7 »o9

1,4-butanediol 1.75

finely divided silica ("Cab-O-Sil" M5) o, 42

Jioctyl phthalate 16.55

Phenylmercury oleate 0.75 Fragile glass hollow spheres

mean particle size of 40 microns and mean specific gravity of 0.216.33

Polyurethane - 'i'eil B

Methylene diisocyanate 14.19

Tripropylene glycol 1.28

Polypropylene glycol (with a molecular weight of 2ooo) o.95

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A compressible printing plate holder with a compressible layer with 40 % void volume, which was formed from the components indicated above, was produced by the process of Example 1. The void-free elastomer had a Shore Α hardness of 29 °

The obtained compressible printing plate holder was used to print two flexographic printing plates with a varnish of 1.8 mm and a size of 12.7 x 35 cm on a printing cylinder with a circumference of 27 cm using a part of the holding material with a size of 26 χ 41 cm to be attached. The plate thickness varied 5o Mkron what had hitherto been possible under any circumstances, because otherwise a part of the cast had not been printed _e The printing press of this example was the successful printing a Gellophanfilms with a thickness of 5o microns at a speed of 15o m per Minute used

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Claims (1)

Claims Compressible mounting material, which is particularly suitable for the collar of a flexographic high-pressure printing plate on a reverse cylinder and contains, in the form of a combination of layers, a compressible layer with pressure-sensitive adhesive layers which are firmly bonded to the separate main surfaces thereof, characterized in that As a compressible layer it contains an oleatom layer with at least 3o / υ evenly distributed voids, the -cilastomer layer has a Shore A-2 hardness value of at least 2o in the vacancy-free state, the voids have a maximum dimension of less than 300 microns, have a shape that is very small rigid-walled fragile hollow spheres, and the broken walls of the hollow spheres contain, as well as a strong, thin, tough, dimensionally stable Y strengthening layer, which is bonded to the elastomer layer, and pressure-sensitive adhesive layers, which are attached to the main exposed surface surface of the layer structure created in this way is bound " 2o mounting material according to claim Ϊ, characterized in that that the elastomer has a Shore Α hardness between 2o and 4o when it is empty. 3o mounting material according to claim 1, characterized in that that the elastomer has been selected from the group consisting of polyurethane, poly (acrylonitrile / butadiene) and polychloroprene, 4o mounting material according to claim 1, characterized in that 6098 35 / 08U that the reinforcement layer is a non-woven webbing or a Sheet is made of a plastic film that is biaxially oriented and has been thermoset, 5ο mounting material according to claim 1, characterized in that that the reinforcement layer has a thickness of 25 to 125 microns «, β ο mounting material according to claim 1, characterized in that that the elastomer consists of polyurethane. 7o mounting material according to claim 1, characterized in that the very small hollow spheres are made of glass or phenolic resin _c 8 ο Process for the production of a cold material used for Attaching a flexographic printing plate to the surface of a printing forme cylinder is particularly suitable, under durable layered bringing together of a compressible layer and a strong, thin, tough, size-stable reinforcing layer and layered application of pressure-sensitive adhesive layers on the exposed main surfaces of the layer image obtained, characterized in that the compressible elastomer layer is one with many evenly distributed and permanently bonded senr Forms small, rigid-walled, fragile hollow spheres with a maximum dimension of less than 300 microns, the hollow spheres being present in proportions that are sufficient to form a void volume in the said layer of at least 3o% , because elastomer has a hardness according to the Shore A-2 hardness scale of at least 2o and you have a sufficient proportion of the hollow 609835 / 08U balls break evenly within the elastomer layer _o 'Dr ₀ Ye / Se 609835/0814