WO2007025788A1

WO2007025788A1 - Halogen-free self-adhesive protective film

Info

Publication number: WO2007025788A1
Application number: PCT/EP2006/063012
Authority: WO
Inventors: Nicolai Böhm; Michael Janning; Ingo Neubert; German Patino
Original assignee: Tesa Ag
Priority date: 2005-06-24
Filing date: 2006-06-08
Publication date: 2007-03-08
Also published as: DE102005029722A1

Abstract

Self-adhesive protective film for covering, in particular, digital graphics, prints, photographs, reproductions, posters, brochures, pictures, plans, maps and books, consisting of a halogen-free, transparent or translucent backing film coated on one side with a pressure-sensitive adhesive and on the other side with a preferably polysiloxane-based release lacquer.

Description

tesa Aktiengesellschaft Hamburg

description

Halogen-free self-adhesive protective film

The present invention relates to a halogen-free self-adhesive protective film which is suitable for covering, for example, graphics, prints, photos, reproductions, posters, brochures, pictures, plans, maps and books, and the use thereof on said substrates.

Today, a variety of graphics, prints and photos are used in the industrial and private sectors, to name but a few optical reproduction possibilities. In the wake of the widespread adoption of digital processing of image material and digital photography, the proportion of digital printing is increasing significantly in these areas. Digital printing is understood to mean graphics or images that are generated or processed by means of a computer and subsequently printed out by means of printers. Today, for example, digital prints are used in advertising printing, shop window advertising, truck tarpaulins, advertising on building facades, trade fair construction, posters, posters, art prints and digital photography. Conventional printing processes using printing stencils such as screen, gravure, flexographic and offset printing and printing processes without printing stencils such as electrography, laser, inkjet and thermal transfer printing are used as printing processes. In the field of color digital printing, inkjet printing technology is the main method, since this printing process is the most flexible in terms of frequent pattern changes and small print jobs, and ensures excellent color and print quality. In the ink jet printing technique different inks can be used. In the private sector and for office applications mainly water-based inks are used. In the industrial sector and in the advertising industry, however, oil- or solvent-based printing inks are widespread. The reason for the widespread use of oil- and solvent-based Printing inks in these areas is due to the very good anchoring (adhesion) of these printing inks on the various printing media used here. Due to the high level of exposure to solvent fumes in the workplace and from an environmental point of view, however, solvent-free printing inks are also being used to a greater extent in the industrial sector and in the advertising industry. In addition to water-based printing inks, so-called UV printing inks, solvent-free printing inks that crosslink or cure under UV irradiation, are becoming increasingly important in the future. As already mentioned, a wide variety of printing media such as paper, flexible PVC films, textiles, PET films for digital graphics use. The print media often have to be provided with a special coating to ensure high print quality and anchoring of the printing ink.

Depending on the applications (outdoor application, indoor use) and the duration of the application (up to one year), digital prints can be heavily used. In order to withstand these significant environmental influences, the graphic prints must be protected. This is especially true for water- and solvent-based printing inks, which must be protected against mechanical damage, contamination and other environmental influences. The protection of the prints can be done in different ways. One possibility is a full-surface coating with a solvent-based or a UV-curing lacquer. With this method it must be ensured that the varnish is applied very evenly so as not to disturb the visual impression of the print by, for example, viscosity strips. Furthermore, the varnish must not dissolve the printing ink, otherwise there is a blurring or a bleeding of the printing inks. Another possibility of protecting the digital prints results from a full-surface lamination of the same with a protective film, which is coated with a hot melt adhesive. For this purpose, the print and the protective film must be laminated by means of a hot laminator at 60 to 150 ⁰ C. This softens the hot melt adhesive and connects to the graphics. A disadvantage of this method is that when paper is used as the printing medium, a dimensional change of the paper occurs due to drying out during the laminating process, with the consequence of later curling or wrinkling of the protected print. This method is also not suitable for printing media that soften like soft PVC at relatively low temperatures. Another method for protecting digital prints results from a full-surface lamination with a self-adhesive protective film. The use of self-adhesive protective films does not show the previously mentioned disadvantages. Typically, contact-transparent flexible PVC films are used as self-adhesive protective films, which are coated on one side with a pressure-sensitive adhesive. A description of these surface protection films can be found in DE 44 05 568 A1 and DE 42 28 436 A1. All self-adhesive protective films used today are laminated with a siliconized release paper or a siliconized release film which must be removed immediately prior to use. The use of siliconized release paper or release film is based on the one hand in the production process of these protective films and on the other hand ensures an easily removable protection of the PSA prior to use. From the use of these conventional self-adhesive protective films, however, there are some disadvantages. The soft PVC film usually contains 20 to 30% of monomer plasticizer, which evaporate gradually from the film, resulting in a significant odor and health burden, in particular, the commonly used plasticizer DOP is questionable. The plasticizers also tend to migrate into, for example, the adhesive, ink and printing medium. The migration of the plasticizers can adversely affect the prints, so that, for example, color change, bleeding of the color transitions (chromatography) or yellowing can not be excluded. PVC films also contain a significant amount of halogen. Against the background of the discussion about the incineration of plastic waste, however, there is a trend towards the reduction of the halogen content and thus the dioxin formation or to avoid the use of halogen-containing plastics.

Another disadvantage arises from the use of a siliconized release paper or release film which must be removed immediately prior to use, that is, prior to lamination to the print or graphic to be protected. Manual application is therefore quite complicated and often has to be carried out by several employees. Automatic laminators have a rather complex structure due to the necessity of removing the release paper. Furthermore, the siliconized release paper or release film waste, which is obtained in considerable quantities. Particularly annoying and with high financial expenditure for the industrial user connected is that this waste must be disposed of according to legal regulations as special waste in some countries. The object of the present invention is to provide a self-adhesive protective film for covering, for example, in particular digital graphics, prints, photos, reproductions, posters, brochures, pictures, plans, maps and books, which meet today's high environmental standards Avoiding halo-containing plastics and hazardous waste, as well as allowing easy application.

This object is achieved by a self-adhesive protective film, as laid down in the main claim. The subject of the dependent claims are advantageous developments of the subject invention and the use thereof.

Accordingly, the invention relates to a self-adhesive protective film consisting of a halogen-free transparent or translucent carrier film which is coated on one side with a pressure-sensitive adhesive and on the other side with a silicone release-based release coating. The protective film according to the invention is halogen-free in the sense that the halogen content is optionally present only in trace amounts (less than 1000 ppm), as might occur through impurities or as residues of catalysts (for example from the polymerization of polymers), and thus is disregarded. The halogen-free self-adhesive protective film can be wound on itself and requires no additional release film or release paper.

Contact clarity or translucency is the translucent property (in contrast to transparency: transparent bodies allow the light to pass through more than 90% and are still largely clear even with thicker layers). Translucent bodies have light transmittances of less than 90% and are said to be contact-clear if the material alone appears cloudy, but not when in direct contact with a substrate such as a digital graphic.

In order to meet the requirement for freedom from halogens, a carrier film of a PVC replacement material is used in the protective film according to the invention. Monolayer or multilayer films of homo- and copolymers of propylene or ethylene or of polyesters such as, for example, are particularly suitable as carrier film materials Polyethylene terephthalate (PET). The production of the carrier film is carried out with a calender or by extrusion or coextrusion such as in the blow or casting process. The carrier film may be monoaxially or biaxially stretched. Particularly preferred carrier material is a non-stretched extrusion film consisting of a polypropylene copolymer or a biaxially hidden PET film coated on both sides with a polyethylene film.

The thickness of the carrier film is in the range of 30 to 180 .mu.m, preferably 50 to 150 .mu.m. The surface of the carrier film can be structured or smooth.

To avoid disturbing light reflections in the bonded state on a graphic or a print, the surface of the carrier film is preferably matt or slightly matt structured. The matting can be achieved by using a filler with a sufficiently high particle size. For this purpose, the filler is applied for example by means of a coating or by a coextruded outer layer on the carrier film. Preferably, however, the structuring of the film surface is achieved by a roller (for example embossing roller on the calender or matted chili roll or embossing roll in the extrusion process). These processes are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Wiley-VCH 2002 or in "Kunststoff-Folien", Nentwig, Carl Hanser Verlag, 1994, and are well known to those skilled in the art.

In a preferred embodiment, the carrier film contains the customary primary (for example sterically hindered phenols or C radical scavengers) and / or secondary (for example sulfur compounds, phosphites or sterically hindered amines) aging protection agents. An overview can be found, for example, "Plastics Additives Handbook", chapter "Antioxidants", Carl Hansa Verlag, 5th edition.

In a further preferred embodiment, the carrier film of the protective film according to the invention contains UV protectants and advantageously also UV absorbers as further additives. The use of UV protectants is highly recommended, especially in polypropylene or polyethylene backing films, if not absolutely necessary to protect the film from embrittlement and yellowing during use. In use, the graphics and prints adhered to the protective film of the invention are used for up to one year of intensive exposure to light from, for example, luminaires and headlamps in indoor applications or direct sunlight in outdoor applications. applications exposed. In the case of indoor use but above all, of course, in the case of direct irradiation of sunlight in outdoor applications, the protective film undergoes considerable UV exposure to UV light (only long-wave UV-A radiation, 320 to 400 nm, a Rolle) it comes via a radical mechanism to a polymer degradation. The result is embrittlement, brittleness and discoloration of the carrier film. Particularly vulnerable to UV radiation are films made of polyethylene and polypropylene. The polymer degradation and thus the embrittlement of the carrier film can be stopped by the use of UV protection agents. As UV protectants, preference is given to using hindered amines (HALS).

In a preferred embodiment, the self-adhesive protective film according to the invention likewise protects the graphics or prints from the damaging effect of UV radiation. Particularly at risk here are the printing inks, which can fade under the influence of UV radiation. The UV protectants just mentioned in the protective film do not offer effective protection since they only interfere with the polymer degradation process of the film. In order to effectively protect the graphics or the print under the protective film, the use of UV absorbers which absorb or filter out the UV radiation is particularly advantageous. The UV absorbers used are usually benzophenones and benzotriazoles. Ultraviolet absorbers which have good compatibility with the base polymer are particularly preferably used, since the UV absorbers tend to have a high tendency to chalk, which is also known to the person skilled in the art as blooming. Relatively well-tolerated UV absorber based on benzotriazole having long-chain side chains are, for example, Tinuvin ^® 1577 from Ciba, and Cyasorb UV-1164 ^® from Cytec. To avoid Auskreidungen also a combination of different UV absorbers is helpful. The UV absorbers are used in a concentration of 0.2 to 0.6 wt .-% based on the carrier film. The concentration of the UV absorbers in the protective film according to the invention should be selected such that the transmission of light having a wavelength of less than 360 nm (UV light) is less than 40% and preferably less than 30%. UV protectants and UV absorbers are described in "Plastics Additives Handbook", chapter "Light Stabilizers", Carl Hansa Verlag, 5th edition. The self-adhesive protective film according to the invention is coated on one side with a translucent or transparent PSA. The adhesive application is 10 to 40 g / m ^2, preferably 18 to 28 g / m ² (this is the amount after any necessary removal of water or solvent, the numerical values also correspond approximately to the thickness in μm). The coating is preferably applied over the entire surface of the carrier film.

Suitable pressure-sensitive adhesives are all common types. Such pressure-sensitive adhesives may be, for example, homopolymers or copolymers of isobutylene, of 1-butene, of vinyl acetate, of ethylene, of acrylic acid esters, of butadiene or of isoprene. When selecting the pressure-sensitive adhesive, special attention must be paid to aging resistance and compatibility with printing inks and printing media. Especially suitable are formulations based on polymers and copolymers based on acrylic esters or vinyl acetate.

To optimize the properties, the self-adhesive composition used can be mixed with one or more additives, such as tackifiers (resins), plasticizers, fillers, flame retardants, pigments, UV absorbers, light stabilizers, aging inhibitors, photoinitiators, crosslinking agents or crosslinking promoters. When selecting the additives, care must be taken that the transparency of the adhesive is not adversely affected. Tackifiers (resins) are, for example, hydrocarbon resins (for example polymers based on unsaturated C ₅ or C ₉ monomers), terpene-phenolic resins, polyterpene resins from raw materials such as α- or β-pinene, aromatic resins such as cumarone-indene resins or Resins based on styrene or α-methylstyrene, such as rosin and its derivatives, for example disproportionated, dimerized or esterified resins, for example reaction products with glycol, glycerol or pentaerythritol, to name but a few, and also other resins (such as listed in detail) in Ullmann's Encyclopedia of Industrial Chemistry, Volume 12, pages 525 to 555 (4th edition), Weinheim).

Suitable fillers which do not affect the transparency of the adhesive are nano-scale fillers, for example based on titanium dioxide, calcium carbonate, zinc carbonate, silicates or silicic acid. Suitable miscible plasticizers are, for example, aliphatic, cycloaliphatic and aromatic mineral oils, di- or polyesters of phthalic acid, trimellitic acid or adipic acid, liquid rubbers (for example low molecular weight nitrile or Polyisoprenkautschuke), liquid polymers of butene and / or isobutene, acrylic acid esters, polyvinyl ethers, liquid and soft resins based on the raw materials of tackifier resins, wool wax and other waxes or liquid silicones. Crosslinking agents are, for example, isocyanates, phenolic resins or metal chelates, such as aluminum and titanium chelate. Suitable crosslinking promoters are, for example, maleimides, allyl esters, such as triallyl cyanurate, polyfunctional esters of acrylic and methacrylic acid. Anti-aging agents include, for example, hindered phenols, known, for example, under the trade name Irganox ™.

The bond strength of the self-adhesive protective film according to the invention to steel is at least 2.0 N / cm.

In summary, the preferred embodiment of the invention has on one side a pressure-sensitive adhesive based on homopolymers or copolymers of acrylic acid esters, which has been achieved by solvent-containing or particularly preferably by dispersion coating of polyacrylic acid esters. This preferred embodiment of the protective film according to the invention is characterized in particular by its very good aging stability and compatibility with the printing inks and printing media, for example, from flexible PVC films. Even in outdoor applications of up to one year, where the protective film may be exposed to intense sunlight, no change in transparency or occurrence of yellowing of the PSA is observed. Furthermore, there is a very good compatibility with the different printing inks, that is, no chromatography of the various constituents of the printing inks is observed.

It is advantageous to use an adhesion promoter, a so-called primer layer, between the carrier film and the adhesive or a physical pretreatment of the carrier film surface to improve the adhesion of the adhesive to the carrier film. As primers, the known dispersion and solvent systems can be used, for example, based on isoprene- or butadiene-containing rubber, acrylate rubber, polyvinyl, polyvinylidene and / or cyclic rubber. Isocyanates or epoxy resins as additives improve the adhesion and in part also increase the shear strength of the pressure-sensitive adhesive. The adhesion promoter can likewise be applied to the carrier by means of a coextrusion layer. be applied foil. For example, flame treatment, corona or plasma or coextrusion layers are suitable as physical surface treatments.

The back side of the carrier film is coated with a release agent or release agent of preferably polysiloxane. This silicone release coating allows a very easy and uniform unrolling of the protective film according to the invention in the application. This results in the case of the protective film according to the invention over the prior art, the advantage that can be dispensed with the use of a release paper or a release film. When using other known release coatings such as stearyl compounds, however, too high separation forces are observed to PSA, so that a slight unrolling in the application is not possible. The result of this is that so-called trigger or chatter marks form at each start of the unwinding after a stop, which lead to disturbing horizontal stripes at these points on the graph laminated with the protective film. When coated with a polysiloxane-based release coating, such print marks are not observed. Suitable coatings are the customary polysiloxane release coating, for example from Wacker, Rhodia or Dow Corning. Suitable coatings are solvent-based, emulsion-based or 100% systems. These polysiloxane coatings are usually crosslinked by an addition reaction or by a condensation reaction. Advantageously, a very easily separating polysiloxane system is used for the coating, in which the release forces with the test tape tesa ^® 7475 (substrate white PVC film, adhesive acrylate) is less than 30 cN / cm and the unwinding force, the invention wound on itself Protective film, smaller than 0.8 N / cm are. These release and rolling values must not be exceeded even after storage at elevated temperatures. Otherwise, there is a risk that the protective film after a storage period of several months is no longer unrolled free of withdrawal or chatter marks. To improve the anchoring of the release coating, the carrier film is preferably pretreated before the coating by means of corona or likewise coated with a bonding agent.

In the crosslinked by addition or condensation reaction polysiloxane release coatings aging of the release coating system is observed after a few weeks of intensive UV light irradiation, for example, in outdoor use. The aging of the coating manifests itself in a so-called rub-off, which means that the polysiloxane coating, for example, rubs off the surface slightly with the thumb leaves. This effect can adversely affect the appearance of the protected graphics. Furthermore, with the use of certain UV stabilizers in film production, impairment or disturbance of the addition and condensation crosslinking reaction in the polysiloxane release coating is observed, with the result that the release coating is unusable. Surprisingly, the rub-off effect after UV irradiation and the problem of impairment of the siloxane crosslinking in the use of so-called UV silicones do not occur to those skilled in the art. These systems contain epoxy rings that are incorporated in the polysiloxane chains. UV radiation liberates a cation which causes a cationic ring opening followed by a crosslinking reaction via the epoxy rings in the individual polysiloxane chains. This crosslinking method seems to have a stabilizing effect on the aging and UV resistance of the polysiloxane. For example, mention may be made of Syl-Off ^UV® UV silicone systems from Dow Corning.

As already mentioned, no disturbing reflections of light should occur in the prints and graphics laminated with the protective film according to the invention, since they could dazzle the viewer, for example, and adversely affect the visual impression of the prints and graphics. In order to avoid the reflection of light, a structured carrier foil can be used as already described. Surprisingly, matting of the protective film according to the invention is also possible by adding suitable finely divided fillers into the polysiloxane release coating system. The amount added, the grain size and the quality of the filler must be selected such that, on the one hand, the release values and, on the other hand, the transparency or the transmission of the polysiloxane release coating are not impaired. For matting the release coating, the polysiloxane 0.5 to 30 wt .-%, preferably 2 to 10 wt .-% (each based on the amount of release coating) of a filler having a particle size of 1 to 15 microns, preferably 3 to 8 μm added (see also "Plastics Additives Handbook", chapter "Anti-Block Additives", Carl Hansa Verlag, 5th edition). Suitable fillers are, for example, calcium carbonate, Zeo- lite, natural and / or particularly preferred synthetic silica such as Syloid ^® by the company Grace (micronized silica). A description of matted UV lacquers, which, however, without release effect for adhesives, can be found in WO 97/08250 A1 and WO 01/0417 A1. Another possibility of matting the surface is the embossing of structures in the UV-silicone layer in the curing process by means of UV lamps mentioned.

The surface of the self-adhesive protective film according to the invention preferably has a matted surface to avoid light reflection. The measurement of the gloss level reflects this effect. The degree of gloss, measured at 60 °, in the case of the protective film according to the invention is less than 40 and particularly preferably less than 30.

The protective film can be used particularly advantageously as protection for graphics, prints, photos, reproductions, posters, brochures, pictures, plans, maps and books and similar printing units.

Test Methods

Peel strength (bond strength)

The peel strength (bond strength) was tested on the basis of PSTC-1. A 20 mm wide strip of the protective film is glued on a ground steel plate as a test surface by five times double rolling over with a 5 kg roll. The plate is clamped, and the self-adhesive strip is peeled over its free end on a tensile tester at a peel angle of 180 ° at a speed of 0.3 m / min, and determines the force required for this. The measurement results are given in N / cm and averaged over three measurements. All measurements are carried out in an air-conditioned room at 23 ° C and 50% relative humidity.

Separating forces

In this test, the release properties of release coatings are compared to the standard test tapes tesa ^® 7475 and tesa ^® 7476 determined. To determine the separation forces 20 mm wide strips of test tapes tesa ^® 7475 and tesa ^® are glued on the tested release varnish coating 7476th Subsequently, a 24-hour storage takes place under a weight block of 20 kg at 70 ° C (tesa ^® 7475) or at 40 ° C (tesa ^® 7476). After conditioning for 2 h at 23 ° C and 50% relative Humidity is determined by means of a tensile tester at a take-off speed of 0.3 m / min, the force that is required to subtract the test tape at an angle of 180 ° from the tested release coating. This measurement is carried out in accordance with PSTC-4B. In order to test the release forces of release paint coatings against any adhesive coatings, the release forces are preferably determined at higher take-off speeds of 10 and 50 m / min. For this purpose, the adhesive tape is glued in a width of 50 mm on the release coating. The adhesive tape is then peeled off from the release lacquer coating at an angle of 180 ° at 10 or 50 m / min, thereby measuring the required force. Again, between bonding and measurement storage at elevated temperatures is possible. The measurements are carried out.

unwind

To measure the unwind force, 50 mm wide rolls are unrolled at different speeds (10, 20 and 30 m / min). The force needed to unroll the test roll is determined. The unwind force is measured by deflecting the adhesive tape web via a load cell. The measurement is carried out according to PSTC-8.

reflectance values

The determination of the reflection values at reflection angles of 20, 60 and 85 ° takes place in a Refo3 reflexiometer from Dr. Ing. Long according to DIN 67530.

UV resistance

To test the UV resistance of the films and the UV protection function for the graphics, the self-adhesive protective films are bonded to a test print. The test print consists of different shades. Ideally, at the same time test prints are tested with loose ittel containing and water-based colors. For comparison, a narrow opaque strip of, for example, paper over the graphic placed and fixed (to create a color reference). The test print coated with the protective film is now stored for 36 d under UV irradiation (Sanolux HRC 300-280 Radium Lampenwerk GmbH), the samples being examined every 5 days. Subsequently, the color quality and color intensity in relation to the color reference (covered area) as well as the properties (brittleness, discoloration, etc.) of the protective film are evaluated.

In the following, the invention will be explained in more detail with reference to several examples, without thereby wanting to limit the invention unnecessarily. Furthermore, comparative examples show the superiority of the film according to the invention.

Examples

example 1

Includes a transparent PP-blow-film with a glossy (smooth) surface that 0.08 wt .-% of the UV protecting agent Chimasorb ^® 944 (Ciba), is one-sided corona treatment by using the UV silicone release lacquer Syl-Off UV ^® (Dow Corning) coated. In a second step, after renewed corona treatment, the coating of the other side of the film in the Meyer-Barr process with the adhesive dispersion Primal ^® PS83 (aqueous acrylate dispersion, solids content 53 wt .-%, pH 9.1 to 9.8 from Rohm and Haas) in a coating width of 2000 mm. After drying the coating in a drying tunnel at 110 ° C., an adhesive application of 22 g / m ^{2 is obtained} .

This protective film is characterized by a very good contact transparency and a very easy unrollability without chatter marks. Furthermore, this protective film has excellent aging and UV stability, but it should mainly be used only for indoor applications because it does not protect the print or graphics from UV radiation due to the absence of UV absorbers.

Example 2

A transparent PP film is produced using the Cast process, whereby a matted Chill-RoII is used to matt the film. The film containing 0.1 wt .-% Chimasorb ^® 944 (Ciba) and 0.3 wt .-% of the UV absorber Tinuvin ^® 1577 (Ciba). The foil is coated on one side (on the etched side) to corona treatment with the solvent-silicone release coating system Syl-off ^® 7020 (Dow Corning). In a second step, after renewed corona treatment, the coating of the other side of the film in the Meyer-Barr process with a mixture of the 40 wt .-% Acronal ^® DS 3502 (aqueous acrylate dispersion, solids content 55 wt .-%; pH 6.5 to 8.5, T ₉ 4 ⁰ C from BASF) and 60 wt .-% Acronal ^® V 212 (aqueous acrylic dispersion, solids content 69 wt .-%; pH 3.5 to 6.0 , BASF T ₉ -40 ⁰ C) in a coating width of 2000 mm. After drying the coating in a drying tunnel at 110 ° C., an adhesive application of 23 g / m ^{2 is obtained} .

In addition to the very good contact transparency, UV stability, very easy unwindability, this protective film also has good UV absorption, so that the protected graphics are very well protected against fading of the colors in outdoor applications.

Example 3

A transparent PP film is produced using the cast process. The film containing 0.1 wt .-% Chimasorb ^® 944 (Ciba) and 0.3 wt .-% of the UV absorber Cyasorb UV-1164 ^® (Cytec). The foil is coated on one side by corona treatment with the solvent-silicone release coating system Syl-Off UV ^® (Dow Corning) containing 3 wt .-% for matting Sylobloc ^® 44 (Grace Davison). In a second step, after another corona treatment, the coating of the other side of the film in the Meyer-Barr process of the adhesive Airflex ^® EAF 60 (aqueous vinyl acetate / acrylate dispersion, solids content 60 wt .-%, T ₉ -35 ° C of Air Products). After drying the coating in a drying tunnel at 110 ° C., an adhesive application of 20 g / m ^{2 is obtained} .

This protective film shows good contact transparency, UV stability, very easy unwindability and good UV absorption.

Example 4

A 23 μm thick PET film is coated on both sides with 20 g / m ² with a PE layer, wherein the surface of a PE layer is matted by an embossing roller. Subsequently, the matte side is coated after Corona treatment with the silicone release coating system Syl-Off ^® 7400 (Dow Corning). The other side of the film is coated analogously to Example 2 with adhesive.

This protective film shows a very good contact transparency, UV stability, very easy unwindability and good UV absorption.

++ very good; + good; - bad; - very bad counterexamples

Counterexample 1

The standard product Filmolux ^® satin (Neschen AG) consists of a 75 micron satin soft PVC support film (containing about 26% monomeric plasticizer) that on one side with 35 g / m ² acrylate Dispersionsklebmasse is coated with a 65 g / m ² Release paper is covered. The use of a release paper is urgently necessary because otherwise the unwinding of the protective film bales is no longer possible. Other problems arise from the high halogen and plasticizer content that commonly occurs with the use of PVC materials.

Counterexample 2

The product Filmolux ^PP® satin (Neschen AG) consists of a 80 μm silk-matt UV-protected PP carrier film which is coated on one side with 28 g / m ^{2 of} an acrylate dispersion adhesive which is covered with a 80 g / m ² release paper. Again, it is not possible to use the product without release paper, otherwise the unrolling of the bale is no longer possible.

Counterexample 3

An 80 μm PP cast film (without UV protection agent) is coated on the one side with 1.5 g / m ^{2 of} Release Coat KB (Clariant AG) from toluene solution and on the other side with an acrylate dispersion adhesive analogous to Example 1 coated and wound up after drying at 110 ⁰ C without release paper. This protective film can be developed only with relatively high unwinding forces. When unwinding, clear chatter marks are visible, which significantly degrade the optical quality of the protected graphics and prints. In UV storage tests, a clear embrittlement appears after only 5 days and, after 9 days, the appearance of break lines in the protective film. The inks under the protective film bleach very much in the UV test.

Claims

claims

1. Self-adhesive protective film for covering in particular digital graphics, prints, photos, reproductions, posters, brochures, pictures, plans, maps and books consisting of a halogen-free transparent or translucent

Carrier film which is coated on one side with a pressure-sensitive adhesive and on the other side with a release coating on preferably polysiloxane-based.

2. Self-adhesive protective film according to claim 1, characterized in that the self-adhesive protective film is wound on itself and has no additional release film or no additional release paper.

3. Self-adhesive protective film according to claim 1 or 2, characterized in that the halogen-free carrier film consists of polyolefin and preferably of polypropylene or a polypropylene copolymer.

4. Self-adhesive protective film according to at least one of claims 1 to 3, characterized in that the carrier film consists of a laminate, wherein at least one of the outer layers consists of polyolefin, preferably of a biaxially hidded, on both sides with a polyethylene layer befilmten PET Foil.

5. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the surface is structured.

6. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the carrier film contains at least one UV protective agent and preferably also at least one UV absorber.

7. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the transmission of the protective film in the wavelength range less than 360 nm (UV light) is less than 40% and preferably less than 30%.

8. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the carrier film is coated on one side with a transparent or translucent acrylate pressure-sensitive adhesive.

9. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the carrier film is coated on one side with a UV-crosslinked silicone release varnish.

10. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the release coating based on silicone contains at least one additive for matting the surface, preferably at 0.5 to 30 wt .-% based on the silicone release coating, more preferably with a particle size of 1 to 15 microns.

11. Self-adhesive protective film according to at least one of the preceding claims, characterized in that the silicone-based release coating contains as an additive calcium carbonate, zeolites, natural and / or particularly preferred synthetic silica.

12. Use of a protective film according to at least one of the preceding claims as protection for graphics, prints, photographs, reproductions, posters, brochures, pictures, plans, maps and books and similar printing works.