DE10347025A1 - Double-sided adhesive tape for fixing printing plate, especially laminated photopolymer printing plate to printing cylinder or sleeve, has film base (partly) modified on one or both sides by plasma treatment, especially plasma coating - Google Patents

Abstract

Double-sided adhesive tape for fixing printing plates, especially laminated photopolymer printing plates to printing cylinders or sleeves, has a film base at least partly modified on one or both sides by plasma treatment, especially plasma coating, to increase its affinity for the adhesive compositions by increasing the surface energy.

Description

The The invention relates to a reversible adhesive pressure sensitive on both sides Adhesive tape with a film carrier, the surface of the film carrier pretreated so that the PSA is extremely well anchored, with the consequence that the printing plate in the flexographic printing process or remove the adhesive tape from the substrate without residue.

Of the Flexographic printing is a process of direct rotary printing with elastic, raised printing forms, different on plate cylinders circumferences be attached. They are doctored off with a roller or a roller Anilox roller dyed and transfer the liquid ones (solvent and water colors) or pasty (UV inks) inks Substrates of any kind.

in the Flexographic printing is the most diverse types of printing plates (Clichés) used as photopolymer printing plates or rubber plates. With the introduction of photopolymer printing plates in the seventies succeeded Dimensionally stable printing plates in a single-stage photomechanical Process to produce. The photopolymer printing plates enabled a significant improvement in print quality to finer grids. From the constant Claim to ever higher printing qualities the development results in the direction of photopolymer plates.

The Pressure plate is made using a double-sided pressure sensitive Adhesive tape on a printing plate cylinder or sleeve system (sleeve system) in Combination with a corresponding receiving system for the sleeve (air cylinder) fixed. The today still very often used format cylinders exist from a steel body with welded-in Cones. In individual cases be at big print lengths also used aluminum cylinder or fiber composites.

Due to the shorter order times and the associated increasingly frequent order changes, sleeve systems are becoming increasingly widespread. A variety of sleeves are offered in the market, with a simple to very complex design. Equally diverse is the nature of the sleeve surface, such as the metallic surface of nickel tubes or sleeves made of glass fiber reinforced plastic or Kevlar ^{® provided} with a top coat such as polyester or polyurethane.

by virtue of of diversity on bonding substrates on the one hand and the variety of print motifs as well as requirements to the print quality needed on the other side the printer a big one Selection between different cliché adhesive tapes.

First, in the flexographic printing plate mounting tape (, 52320, 52325 tesa print ^® 52310, 52315, 52338, 52350 and 52916) were coated with film or fabric (tesa print ^® 52330) is used as carrier material. But there were also required here due to the ever increasing demands on print quality improvements in the sub-construction technology, were new plate mounting tapes with foam carriers (tesa ^® SoftPrint ^® 52060, 52500, 52380, Steel Master, Sleeve Master) developed and successfully implemented quality improving. The advantage of this cliché adhesive tapes is a significant improvement of the halftone print quality due to a lower dot gain in the printed image by printing an optimal halftone dot geometry (halftone dot size and shape).

But halftone printing is only a requirement in flexographic printing, though also a very important one. Also the pressure of full areas or fine lines (line pressure) must be fulfilled by the flexo printing. Combinations of different motifs such as grid and areas in a motif pose another challenge to flexo printing dar. Here are used different hard foam cliché adhesive tapes, each matched to the appropriate print motifs.

Today's cliché adhesive tapes consist at least of the previously described carrier materials coated with acrylate or rubber adhesives with mass orders of 15 to 80 g / m ² . To improve the performance properties such as assembly or disassembly of adhesive tape or cliché partially dimensionally stable films, in particular consisting of polyethylene terephthalate, used in the foam cliché adhesive tapes. These are fixed by means of pressure-sensitive adhesives or physically on the foam carrier. In principle, a distinction can be made between film-stabilized and non-film-stabilized foam cliché adhesive tapes. Since the foam carrier is equipped either on both sides with the coat of paint or on one side with the paint and the other side with the PSA for the stabilizing film, as a requirement, a high adhesive force to the foam surface. As a cover siliconized papers or films are used, the two Separate adhesive layers from each other, protect the surface from contamination and allow application of the cliché adhesive tape on the printing plate cylinder or sleeve.

• • Montage von Klischeeklebeband und Klischee
• • Druckdurchführung
• • Demontage von Klischee und Klischeeklebeband

The printing process can be divided into three main areas:

• • Installation of cliché adhesive tape and cliché
• • Pressure implementation
• • Dismantling of cliché and cliché adhesive tape

This Printing process leaves through a multitude of additional ones expand individual process steps, such as additional Storage times of mounted print format cylinder or interrupted Pressure-throughs.

The individual process steps are different from the cliché adhesive tape influenced with.

The Assembly of the adhesive tape and the cliché becomes very strong through the Make-up tack (tack) of the cliché adhesive tape determined by facilitates a sufficient initial tack. To any required destructive To reposition the adhesive tape or cliché to ensure may initially only a low bond strength.

To the completed assembly and subsequent storage of the cliché on the printing plate cylinder or sleeve and during the printing process must the cliché adhesive tape a secure bond without lifting the cliché edges or the tape-cliché composite.

at the disassembly should be the cliché again easily and without Residues of remove the cliché adhesive tape. Likewise, this should be also disassemble from the printing plate cylinder or sleeve.

The known adhesive tapes fulfill the above requirements are poor. On the one hand are some tapes Although able to reposition due to only weak bonding allow the printing plates, but show insufficient adhesion after prolonged printing, so that the printing plate edges rise during printing. On the other hand, there are adhesive tapes that are characterized by high adhesive forces ensure secure anchoring of the plates on the impression cylinder, but their adhesive layer after printing to the printing cylinder or plate rewind and from there only with the help of solvents to move away from the substrates leaves.

Of the Current state of technology shows some serious disadvantages.

One Disadvantage lies in the significant increase in the bond strength over the Time, that is from assembly to disassembly. A high bond strength However, it is only required after assembly to disassembly. Accordingly, too high a bond strength in the Dismantling to a non-residue-free Remove the adhesive tape. Particularly problematic here are remnants of the adhesive tape the cliché and / or printing plate cylinder.

nowadays one uses physical or chemical pretreatment methods of the carrier material to improve the ground anchorage on the tape. in this connection come as pretreatment methods especially for foam backing the Corona, flame pretreatment and fluorination in question.

All however, these pretreatment methods have specific disadvantages.

The Corona and flame pretreatments often do not achieve the desired results Effect. Fluorination often does not achieve the desired adhesion, In addition, the process still with a high safety Effort is connected.

The Flame pretreatment also means a high thermal for the substrate Load, so that temperature-sensitive substances are not or only can be treated conditionally. In particular, foams are very sensitive in this regard.

All of these methods are used for pretreatment of film and foam carriers, whether as a pure foam cliché adhesive tape or composite adhesive tape of foam and film backing, with all their after-effects share applied. The consequence is that, despite these pretreatment methods, there is no guarantee for disassembly without residual material.

In The printing industry, especially in flexographic printing, as already mentioned in particular also compressible double-sided adhesive tapes for gluing printing plates (Clichés) used on printing cylinders or sleeves, the so-called Foam plate mounting tape.

Cliché adhesive tapes with foam backing can be equipped with or without stabilizing film. Are advantageous Foam plate mounting tapes with stabilizing foil, since this an elongation and thus change of thickness prevents the foam tape during assembly and repositioning. At the same time, the stabilizing foil serves to distribute the force while of the printing process.

There the back to the tape the clichés consists of a PET film that has a high affinity for the adhesive the anchoring of the PSA on the film carrier of the Foil or foam cliché adhesive tape by pretreatment be optimized so that the pressure-sensitive adhesive during disassembly on the tape remains. Only then can a residue-free disassembly be guaranteed become.

In DE 195 25 403 A1 the use of a double-sided adhesive tape is proposed for the fixation of multilayer, plasticized photopolymer printing plates with flexible base on printing cylinders.

The Adhesive tape points as a carrier a polymeric film of polypropylene. Alternative to polypropylene also the use of, for example, PVC as a carrier material possible.

to Coating of the two outer surfaces of the carrier Two different adhesives are used. On the side of the adhesive tape attached to the carrier layer the printing plate is applied, becomes an extremely weak adhesive Natural rubber adhesive coated. The adhesive has an adhesive power from 0.2 to 2 N / cm, preferably 1 N / cm.

The other adhesive coating is made of a highly adhesive layer formed, which is preferably also based on natural rubber. Alternatively, however, it is also possible to use an adhesive which is based on conventional acrylates builds up, be used. This coating is characterized by an adhesive power from 2 to 6 N / cm, preferably 4.5 N / cm.

The specified bond strengths are measured according to AFERA 4001.

The DE 101 29 730 A1 discloses a double-sided adhesive tape for fixing printing plates, in particular multi-layered photopolymer printing plates on printing cylinders or sleeves, wherein the carrier of the adhesive tape is a polyethylene terephthalate (PET) film and self-adhesive coatings are applied to both sides of the film.

The surface The film of polyethylene terephthalate (PET) is one or both sides at least partially using a reagent, in particular an etching process causes, roughened, and / or the surface energy of the surface of the Slide is raised, so that the ground anchorage on the foil is optimized.

The WO 03/057497 A1 describes a pressure-sensitive adhesive tape finished on both sides for fixing printing plates, in particular multi-layered Photopolymer printing plates on printing cylinders or sleeves, the carrier of the pressure-sensitive adhesive tape, a film, foam or a composite both and on the appropriate carrier or composite on both sides self-adhesive coatings are applied, but both at least the side to the printing plate is equipped with a pressure-sensitive adhesive system.

• i.a) 49,5 bis 89,5 Gew.-% (bezogen auf die Monomermischung) Acrylsäureester und/oder Methacrylsäureester beziehungsweise deren freien Säuren mit der folgenden Formel: CH₂=CH(R₁)(COOR₂), wobei R₁ = H oder CH₃ und R₂ ein Alkylrest mit 1 bis 10 C-Atomen oder H ist und das Homopolymer eine statische Glasübergangstemperatur von < –30 °C besitzt;
• i.b) 10 bis 40 Gew.-% (bezogen auf die Monomermischung) Acrylsäureester und/oder Methacrylsäureester mit der folgenden Formel: CH₂=CH(R₃)(COOR₄), wobei R₃ = H oder CH₃ und R₄ ein zyklischer Alkylrest mit mindestens 8 C-Atomen oder ein linearer Alkylrest mit mindestens 12 C-Atomen ist und das Homopolymer eine statische Glasübergangstemperatur von mindestens 30 °C besitzt;
• i.c) 0,5 bis 10 Gew.-% (bezogen auf die Monomermischung) Acrylsäureester und/oder Methacrylsäureester mit der folgenden Formel: CH₂=CH(R₃)(COOR₅), wobei R₃ = H oder CH₃ und R₅ = H oder ein aliphatischer Rest mit einer funktionellen Gruppe X, wobei X = COOH, OH, -NH, NH₂, SH, SO₃H umfasst und das Homopolymer eine statische Glasübergangstemperatur von mindestens 30 °C besitzt.

The pressure-sensitive adhesive tape has a flat carrier material which is coated on both sides with a pressure-sensitive adhesive. At least one side of the carrier material is coated with a polymer-based pressure-sensitive adhesive which can be prepared from a monomer mixture of at least the following components:

• ia) 49.5 to 89.5 wt .-% (based on the monomer mixture) of acrylic acid esters and / or methacrylic acid esters or their free acids having the following formula: CH ₂ = CH (R ₁ ) (COOR ₂ ), wherein R ₁ = H or CH ₃ and R _{2 is} an alkyl radical having 1 to 10 C atoms or H and the homopolymer has a static glass transition temperature of <-30 ° C;
• ib) 10 to 40 wt .-% (based on the monomer mixture) of acrylic acid esters and / or methacrylic acid esters having the following formula: CH ₂ = CH (R ₃ ) (COOR ₄ ), wherein R ₃ = H or CH ₃ and R _{4 is} a cyclic alkyl radical having at least 8 C atoms or a linear alkyl radical having at least 12 C atoms and the homopolymer has a static glass transition temperature of at least 30 ° C;
• ic) 0.5 to 10 wt .-% (based on the monomer mixture) of acrylic acid ester and / or methacrylic acid ester having the following formula: CH ₂ = CH (R ₃ ) (COOR ₅ ), wherein R ₃ = H or CH ₃ and R ₅ = H or an aliphatic radical having a functional group X, wherein X = COOH, OH, -NH, NH ₂ , SH, SO ₃ H and the homopolymer has a static glass transition temperature of at least 30 ° C possesses.

Of the Invention is an object of the invention to provide an adhesive tape, that when using it for example in the printing industry Rewinding the pressure-sensitive adhesive from the cliché adhesive tape to the cliche or pressure cylinder prevented or at least effectively suppressed and at all the disadvantages of the prior art, or at least not has in the scope.

Is solved this object by a double-sided adhesive tape, as stated in the claims further characterized is. The dependent claims relate to advantageous embodiments the invention and a particularly advantageous use of the same.

Accordingly, the invention a double-sided adhesive tape for fixing of printing plates, in particular multilayer photopolymer printing plates on printing cylinders or sleeves, wherein the carrier of the adhesive tape is a film and self-adhesive on both sides of the film Coatings are applied.

The surface the film is on one or both sides at least partially, preferably on both sides and full surface, by Plasma treatment, in particular plasma coating modified in kind, that affinity to the PSA by increasing the surface energy is increased.

The surface the film is on one or both sides of a plasma pretreatment, in particular Plasma polymerization, subjected to surface energy increased by oxygen storage or in particular by applying an adhesion-promoting layer an optimal ground anchorage is achieved.

Surface energy or surface tension refers to the interfacial tension of solids and liquids in relation to the vapor phase or air. The 1 illustrates the importance of surface energy for liquids.

While in the liquid (a) on the molecules same attractions (intermolecular forces) In all directions, these forces are at the liquid / vapor interface (b) not compensated. There is one in the liquid inside directed force, the molecules from the surface in the liquid too trying to drive. The liquid is therefore anxious to their surface to shrink, which is why droplets and try to accept bubbles of spherical shape.

The surface energy is defined as the force in the surface per unit length and has the dimension mN / m (10 ^-3 Newton / meter).

With surface work is the work that you need is to undergo reversible conditions and isothermal course the surface to form or enlarge.

Under certain conditions, the surface energy corresponds to the free or Helmholtz energy of the surface per unit area.

immediate after the formation of the surface receives one values for the surface energy, which deviate from the state of equilibrium. This effect is called as dynamic, the equilibrium value as static surface tension.

• • Meniskus-Bildung und Steighöhe in Kapillaren
• • Blasendruck einer in die Flüssigkeit austretenden Gasblase
• • Ring-Methode
• • Wilhelmy-Methode
• • Gestalt liegender oder hängender Tropfen

The surface energy can be determined among other things by the following methods:

• • Meniscus formation and height of rise in capillaries
• • Bubble pressure of a gas bubble escaping into the liquid
• • Ring method
• • Wilhelmy method
• • Shape lying or hanging drop

For the exam of Surfactants is method (c) according to DIN 53914: 1980-03 standardized.

In an advantageous embodiment The invention is between the film and at least one adhesive a foam is present, in particular between the impression cylinder or the sleeve facing adhesive and the film.

Of Furthermore, it has been found to be advantageous if between the film and at least one adhesive an adhesion promoting layer is applied. Should have one or two foam layers on the film be present, so is the one or both Adhesive layers between foam and adhesive.

The following Parameters describe further advantageous embodiments of the invention, and although the film has a thickness of 5 .mu.m to 500 .mu.m, preferably 5 .mu.m to 100 .mu.m, very particularly preferably 25 microns and / or the foam has a thickness of 200 .mu.m to 4000 .mu.m, preferably 300 .mu.m to 2000 .mu.m, very particularly preferably 500 μm, exhibit.

Of Further, it is preferable if the film is made of PVC, PE or PP.

A outstanding embodiment of the invention, it represents when the film is made of PET and more preferably a thickness of 5 μm to 60 μm, especially preferably 23 microns having.

The used foams consist in a preferred embodiment of the invention of polyurethane, PVC or polyolefin (s). The foams are produced by a polymerization process. Here are in detail, the raw materials such as polyethylene, foaming agents and additives mixed, then extruded, ESH crosslinked and then foamed.

The structural changes can be like in the 2a to 2c represent.

The 2a shows the polymer that 2 B the uncrosslinked PE polymer and 2c the three-dimensionally cross-linked PE polymer.

in the Below, particularly advantageous foams are set forth, without wishing to limit the invention to these.

The foams then have a closed-cell structure and are therefore highly elastic and mechanically extremely resilient. The cell size is between 0.1 and 1.0 mm. The foams have a slightly rough surface structure. The surface energy is between 32 and 34 mN / m. Thus, the foam surface is not suitable for adequate anchoring of the pressure-sensitive adhesive. The foams have a density of 30 to 350 kg / m ³ , preferably 150 to 250 kg / m ³ , in particular 200 kg / m ³ . The foams are at a maximum temperature of 80 to 130 ° C, in particular up to 90 ° C; resilient.

Just in the printing industry it is important if the ones used here tapes a high flexibility have, so to some extent can change their thickness during printing or after removal the strain returns to its original Can take shape. Here high demands are placed on the elasticity of the foam carrier.

Furthermore, the adhesive tape can be provided on one or both sides with a cover made of paper or of a corresponding film, in particular a siliconized on both sides, for the purpose of storage and beque Handling during use.

by virtue of its special properties can be the invention on both sides adhesive-coated Adhesive tape excellent for fixing printing plates, in particular of photopolymer printing plates on printing cylinders or sleeves.

Just In this case, it has proved to be advantageous when for coating the two outer surfaces of the carrier two different adhesives are used.

On the side of the tape attached to the backing layer of the printing plate is then set, then a weak adhesive acrylate adhesive coated. The adhesive in particular has an adhesive force of 0.5 to 5 N / cm, preferably 2.5 N / cm, on.

The other adhesive coating is then formed by a more adhesive layer, which is preferably also based on acrylate. This coating is particularly preferred by an adhesive force of 1 to 6 N / cm 4.5 N / cm, marked. The specified bond strengths are measured according to AFERA 4001.

The desired adhesive forces the respective layer are used by type and amount of Resin variable.

In the 3 the adhesive tape according to the invention is shown in a particularly advantageous embodiment and use, without wishing to unnecessarily limit the invention.

The adhesive tape is used to glue a cliché made of a PET film 2 and a layer of a photopolymer 1 composed.

The layers 3 to 9 form a double-sided adhesive cliché adhesive tape, thanks to its foamed support 8th is compressible.

beginning from the side by which the cliché is glued consists the tape from the following sections:

3

PSA to anchor the cliché

4

The plasma-adhesive-coated upper surface of the polyethylene terephthalate (PET) film 5

5

foil made of polyethylene terephthalate (PET)

6

The plasma-polymerised adhesive-coated lower surface of the polyethylene terephthalate (PET) film 5

7

Pressure-sensitive adhesive for anchoring the foamed carrier 8th on the polyethylene terephthalate (PET) film 5

8th

foamed carrier

9

PSA for anchoring on the printing cylinder

in the Below are the advantages of the adhesive tape of the invention in several Try to exemplify usual tapes shown.

considered was in each case an inventive designed adhesive tape whose carrier a PET film was.

Under Use of an acrylate, natural rubber, synthetic rubber or Polyurethane PSA, in particular acrylate PSA, Comparative measurements on different products were different pretreated PET films performed.

at this invention has been the polyethylene terephthalate (PET) film physically by means of low-pressure plasma treatment, in particular low-pressure plasma polymerization, pretreated or adhesively coated. The treatment took place in the air atmosphere or with gases, especially in acetylene atmosphere.

in this connection became a modified surface the PET film with a high surface energy and adhesive layer for one optimal ground anchorage generated.

example

The polyester film (Hostaphan RN 25 film from Hoechst AG, Frankfurt), transparent, 500 mm wide and 25 μm thick, was subjected to a plasma treatment in an air atmosphere and a plasma coating with acetylene was carried out on the film. The following parameters were set for the experiments.

Subsequently, a transparent acrylate adhesive was applied to the treated surface of the polyester film (Self-polymerization from 48.5% by weight 2-ethylhexyl acrylate, 48.5% by weight butyl acrylate, 1% by weight Acrylic acid, 2% by weight glycidyl) coated from solution (solvent gasoline / acetone, adhesive application after drying 20 g / m ² ). The adhesion between the adhesive and the carrier film was checked by three different anchoring test methods.

Anchoring test 1

One 20 mm wide strip of acrylic test tape (tesa 7475) applied with strong pressure to the substrate, one day at 23 ° C and 50 stored% relative humidity and then at an angle of 180 ° with Deducted 1200 m / min. The adhesion fraction was measured in% to the carrier.

Anchoring test 2

One 50 mm wide strip of 190 μm thick polyester film (from Hoechst Difoil, Wiesbaden) was with strong pressure applied to the substrate, gela siege at 40 ° C for three days and then at an angle of 180 ° with Deducted 1200 m / min. The adhesion fraction was measured in% to the carrier.

Anchoring test 3

One Cliché with the measures 120 cm × 210 cm (from BASF, FAH, 2.54 mm thickness) was adhered to the substrate, three days at 40 ° C stored and then pulled off by hand at an angle of about 130 ° quickly. Measured became the adhesion break in% to the carrier.

The adhesion-promoting layer according to the invention significantly improves the adhesion between the support and the adhesive compared to conventional pretreatment methods.

in this connection The best ground anchoring was clearly for the plasma treated Foil, in particular for the plasma-coated film in comparison to pretreatment methods According to the state of the art.

Claims (8)

Double-sided adhesive tape for fixing printing plates, in particular multi-layered photopolymer printing plates on printing cylinders or sleeves, wherein the carrier of the adhesive tape is a film and on both sides self-adhesive coatings are applied, characterized in that the surface of the film on one or both sides at least partially modified by plasma treatment, in particular plasma coating, in such a way that the affinity for the PSA is increased by an increase in the surface energy. Double-sided adhesive tape according to claim 1, characterized in that between the film and at least an adhesive, a foam is present, in particular between the impression cylinder or sleeve facing adhesive and the film. Double-sided adhesive tape according to claims 1 or 2, characterized in that between the film or the one or more foams and at least one adhesive, an adhesive layer is applied. Double-sided adhesive tape after at least one of the claims 1 to 3, characterized in that the film is a thickness of 5 μm up to 500 μm, preferably 5 μm up to 100 μm, most preferably 25 microns, and / or of the Foam a thickness of 200 microns up to 4000 μm, preferably 300 microns up to 2000 μm, most preferably 500 μm, having. Double-sided adhesive tape after at least one of the preceding claims, characterized in that the foam of polyurethane, PVC or polyolefin (s), in particular polyethylene. Double-sided adhesive tape after at least one of the preceding claims, characterized in that the film consists of PET and preferably a thickness of 5 microns up to 60 μm, more preferably 23 μm having. Double-sided adhesive tape after at least one of the preceding claims, characterized in that the film consists of PVC, PE or PP. Use a double-sided adhesive tape according to at least one of the preceding claims for bonding printing plates, in particular multi-layered Photopolymer printing plates on printing cylinders or sleeves.