CH618123A5 - Thermoplastic film with radiation-modifying particles - Google Patents

Description

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PATENT CLAIMS

1. Thermoplastic plastic film which contains undissolved particles which convert radiated, invisible, electromagnetic radiation into visible light, characterized in that the film contains the radiation-changing particles in such a small amount that, when irradiated, the luminous effect produced by a single particle is separated from that Luminous effect of other particles of the same type can be seen with the naked eye on non-luminous or differently luminous surfaces.

2. Thermoplastic plastic film according to claim 1, characterized in that it contains soluble or insoluble, not separately perceptible finely divided, fluorescent substances.

3. Thermoplastic plastic film according to claim 1, characterized in that it contains mixtures of different radiation-changing particles with one another.

4. Thermoplastic plastic film according to claim 1, characterized in that the radiation-changing particles are grains, rods, threads or fibers, the grain diameter or the thickness in the size range from 0.3 to 600 li and the length of the rods, threads or fibers in Range is 0.03 to 20 mm.

5. Thermoplastic plastic film according to claim 2, characterized in that it contains one or more substances fluorescent when irradiated with ultraviolet light in amounts of 0.001 to 1% by weight, based on the total film weight, in the plastic film in such a fine and uniform distribution exist that the fluorescence is largely evenly perceived by the naked eye over the entire surface of the film.

6. Plastic film according to claim 1, characterized in that it contains largely soluble optical brighteners in quantities of 0.001 to 1% by weight, based on the total film weight, in the film mass.

7. Plastic film according to claim 1, characterized in that it is colored with non-radiation-converting pigments in a hue that largely corresponds to the hue of the radiation-changing particles when viewed in visible light.

8. Plastic film according to claim 1, characterized in that it contains, as radiation-changing particles with small amounts of heavy metals, activated salts of metals of group II of the periodic system.

9. Plastic film according to claim 1, characterized in that it contains activated zinc sulfide as radiation-changing particles with small amounts of heavy metals.

10. Plastic film according to claim 1, characterized in that it contains the radiation-changing particles in amounts of 0.03 to 10% by weight, based on the total weight of the film.

11. Use of plastic films according to claim 1 as an information carrier.

12. Use according to claim 11, characterized in that the information carrier is constructed as a composite with other foils and / or paper.

13. Use according to claim 11 as identification, check or credit cards.

Articles of daily use that represent a certain value, such as documents, means of payment, etc., should be such that, on the one hand, their counterfeiting or falsification is as difficult as possible, on the other hand, it is easy and quick to recognize.

Recently, thermoplastic films for the production of such consumer goods, such as. B. ID cards, check cards, credit cards. Here are mainly composites of such films with each other and with other mostly printed, described or coated information carriers, such as. As paper, photographs, magnetic layer carriers, common, these composites can also contain metal foils, all over or in strips.

It is known to use hard-to-copy print samples and certain special printing inks to increase counterfeit protection. It is also known to mark the print carrier with watermarks or with colored fibers. Especially in the case of plastic films, the latter methods cannot be used because, for. B. when incorporating fibers in the usual form of paper processing difficulties due to flow disturbances, etc., in addition, a partially differently colored substrate is often undesirable because it affects, for example, the clear visibility of the print particularly in unfavorable lighting conditions and is often not aesthetically satisfactory. In addition, a marking that is visible without any aids is easily recognized by a possible counterfeiter, which reduces the protective effect and reduces the possibility of catching the user of a forged document or means of payment in the act.

It has now been found that these disadvantages are avoided by a thermoplastic plastic film which contains undissolved particles which convert incident, invisible, electromagnetic radiation into visible light, with the characteristic that the film contains these particles in such a small amount, if appropriate in the presence of Soluble or insoluble, not separately perceptible finely divided, fluorescent substances contains that when irradiated, the luminous effect created by individual particles can be perceived with the naked eye on a non-luminous or otherwise luminous surface separately from the luminous effect of other particles of the same type.

The particles are generally present in the film in amounts of expediently 0.03 to 10% by weight, preferably 0.3 to 2% by weight, based on the total weight of the film. In principle, it is also possible to contain amounts below 0.03% by weight and above 10% by weight; with quantities below 0.03% by weight, however, there is an unfavorable optical impression and with quantities above 10% by weight, difficulties arise on the one hand in the thermoplastic processing of the composition into a film and, on the other hand, the individual particles can no longer be perceived completely separately from one another.

The range of thicknesses of the thermoplastic films is variable within wide limits. It is generally in the range from about 2 to 2000 fi, preferably 15 to 1000 / i, in particular 25 to 750 fi. The lower film thicknesses of about 2 to 20 / u, preferably 3 to 15 u, are preferably by coating from solutions or dispersions on a suitable carrier material, such as. B. a thermoplastic film or paper, according to known methods, for example by roller or anilox application, Gies-ser, Fliesser, with or without dosing, for example by squeegee or air brush, and then drying the solvent or dispersant.

From about 20 to about 2000 fi, the known production processes for thermoplastic plastic films, such as extrusion, calendering or pressing, are preferably used to produce the films which contain the radiation-converting particles, a composite production with other films or paper being advantageous in some cases can be carried out together or immediately after the production of the films according to the invention. Also a combination of the coating and incorporation process5

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driving is possible, for example in the case of a coated film, to produce different lighting effects in the layer and in the carrier film. The coating method is preferably used when the radiation-changing particles cannot withstand the higher temperature and shear stresses that occur in the thermoplastic processing methods.

Preferred particles which convert invisible electromagnetic radiation into visible light (hereinafter referred to as “radiation-changing particles”) are those which fluoresce in visible light when excited with ultraviolet light; e.g. B. inorganic phosphors, such as sulfides, selenides, silicates and tungstates of alkaline earth metals, zinc and cadmium, as well as calcium halophosphates, the activation of heavy metal traces, such as copper, silver, antimony, bismuth, tin, lead, titanium or manganese as individual components or in Contain mixture with each other, as well as the so-called «Lenard phosphates». Activated zinc sulfide is particularly suitable.

Organic luminous pigments are also suitable, provided they do not dissolve largely homogeneously under the film or coating production conditions, for example 2,5-bis- [5'-tertiary-butylbenzoxazolyl- (2 ')] thiophene and di-benzoxazolylnaphthalene when used in aqueous dispersion in the coating process. Regarding further illuminating pigments suitable according to the invention, reference is made to Ullmann Encyclopedia of Technical Chemistry, 3rd edition (1960), Vol. 11, pp. 651-679; Kirk-Othmer "Encyclopedia of Chemical Technology, Second Edition (1967), vol. 12 pp. 619-625 and Römpp" Chemie Lexikon ", 7th edition (1973), vol. 3, p. 1959.

The known substances or bodies can also be present as radiation-changing particles, provided they do not largely dissolve homogeneously under the film or coating production conditions and contain the inorganic or organic radiation-changing substance, for example plastic particles (grains, rods, fibers) which are coated with optical Brighteners are provided.

The radiation-changing particles are not bound to any particular shape, and their size can vary within wide limits. There is a limit to the size of the particles downwards in that the particle size of the individual particle is too small when the particles are too small, or appears too weak to the human eye without aids. Conveniently, they are in the form of grains - the geometric shape is not critical - rods or threads or fibers; the grain diameter or the rod or thread or fiber thickness is generally in the range from about 0.3 to 600 ju, preferably from 0.5 to 100 fi, in particular from 1 to 30 m, and the length of the rod or Threads or fibers preferably in the range from 0.03 to 20 mm, preferably from 0.5 to 5 mm.

In order to avoid processing difficulties, the particle size (diameter) should generally not exceed 4 / s of the thickness of the film in which the particles are contained. Mixtures of different radiation-changing particles can also be contained in a film according to the invention.

The insolubility of the radiation-changing particles in the film mass can either be a basic property of the radiation-changing substance, such as. B. with zinc sulfide. It can also be achieved by using radiation-soluble substances which are soluble or dispersible in the film composition in substances, e.g. B. Insoluble polymers in the film mass, dissolves or disperses or binds to these by absorption or chemical reaction, so that they do not or only slightly dissolve when the largely insoluble in the film mass, such as polymer particles, distributed during processing of the film mass will.

The radiation-changing particles are the ready-to-process plastic mixture according to known methods, z. B. mixed in a fluid mixer. In special cases, the mixture can then be used gently for homogenization. be ground, but care must be taken to ensure that the particles are not crushed too much. The same also applies to subsequent processing steps, provided that high shear stresses occur.

Suitable thermoplastic materials for the production of the films are all customary thermoplastic polymers which are largely inert to the radiation-converting particles, such as, for. B. polystyrene, copolymers and graft polymers of styrene with acrylonitrile, butadiene and acrylic esters, polyvinylidene halides, such as polyvinylidene chloride and polyvinylidene fluoride, polyamides, polyolefins such as polyethylene or polypropylene, polyacrylic and vinyl esters, thermoplastic polyurethanes, cellulose esters and Polyvinyl chloride and co- and 20 graft polymers of vinyl chloride. The following monomers are suitable, for example, for copolymerization with vinyl chloride: olefins, such as ethylene, propylene or butylene, vinyl esters of straight-chain or branched carboxylic acids having 2 to 20, preferably 2 to 4, carbon atoms, such as vinyllace-25 tat, propionate, butyrate, -2 -ethylhexoate, vinyl isotridecanoic acid reester; Vinyl halides, such as vinyl fluoride, vinylidene fluoride, vinylidene chloride, vinyl ether, vinyl pyridine, unsaturated acids, such as maleic, fumaric, acrylic, methacrylic acid and their mono- or diesters with mono- or dialcohols having 1 to 10 30 carbon atoms; Acrylonitrile, styrene, N-substituted maleinimides. The copolymerization can also be carried out using monomer mixtures.

For graft polymerization with vinyl chloride, for example, elastomeric polymers can be used which have been obtained by polymerizing one or more of the following monomers: dienes, such as butadiene, cyclopentadiene; Olefins such as ethylene, propylene; Styrene, unsaturated acids, such as acrylic or methacrylic acid, and their esters with mono- or dialcohols with 1 to 10 carbon atoms, 40 acrylonitrile, vinyl compounds, such as vinyl esters and straight-chain or branched carboxylic acids with 2 to 20, preferably 2 to 4 carbon atoms, vinyl halides, such as vinyl chloride, vinylidene chloride.

In the case of copolymers or graft polymers, the proportion of the base monomer such as, for example, styrene or vinyl chloride is advantageously at least 70% by weight, preferably at least 80% by weight.

These thermoplastics can be used alone or as a mixture with one another. Furthermore, the usual processing aids such as stabilizers, inhibitors, lubricants, plasticizers, solvents, dispersants, etc. can be added, taking care that the effect of the radiation-changing particles is retained and not by chemical change or excessive general 55 sorption for the effective, invisible, electromagnetic radiation is prevented.

If the use requires or permits, the films according to the invention can advantageously contain colored non-radiation-changing pigments, a color preferably being chosen which comes very close to the intrinsic color of the radiation-changing pigments in visible light, as a result of which the presence of these radiation-changing pigments largely without aids becomes unrecognizable.

In addition to the radiation-changing particles not dissolved in the film mass, the films according to the invention can contain one or more substances which fluoresce when irradiated with ultraviolet light, preferably in amounts of 0.001 to 1%, preferably 0.005 to 0.2%, based on the amount of film

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total weight, included, these substances must be soluble or dispersible in the plastic mass in such a fine and uniform distribution that their fluorescence is largely evenly perceived by the naked eye over the entire surface. Optical brighteners are particularly suitable for this purpose, for example compounds with aromatic or heterocyclic ring systems which are substituted with optionally nucleus-substituted benzoxazolyl radicals, or derivatives of coumarin or stilbene with optionally substituted benzotriazole or riazine radicals which are largely soluble in the film. The particles which are preferably fluorescent in the plastic film according to the invention with light of a different wavelength then appear as a "starry sky" on a differently and preferably weakly shining background.

Composites containing films with radiation-changing particles are produced in the usual way by thermoplastic pressing, welding or gluing, embossing being able to be applied simultaneously or subsequently.

The thermoplastic plastic films according to the invention can be used wherever inconspicuously marked films are required, for example as information carriers for receiving a printed and / or embossed image, a writable layer or a magnetic tone layer, in the latter two cases a one-sided covering of the markings may be necessary must be taken if you do not prefer to provide the layer itself with radiation-changing particles. The foils according to the invention are preferably used as a component of composites with other foils and / or paper, it being possible for these foils or the paper itself to serve as information carriers in the manner described above. Photographs or other photomechanical reproductions can also be used together with the films according to the invention.

The films according to the invention are particularly suitable for the production of identification, check or credit cards and in similar fields of application, but their use is not restricted to these fields.

Advantages of the films according to the invention include a. the less complex production, the inconspicuous labeling, which can be checked using simple, non-destructive methods. For higher demands on the marking, red dot counters, which are additionally tuned to specific wavelengths of the light emitted by the radiation-converting particles, can be used.

The invention is explained in more detail below with the aid of examples, without restricting it to these examples.

example 1

A mixture of 96 parts by weight of polyvinyl chloride, 3 parts by weight of montanic acid ester wax, 1 part by weight of dibutyltin dithioglycolate stabilizer, 6 parts by weight of titanium dioxide and 0.5 part by weight of phosphor based on zinc sulfide, average particle size 18 μm, is homogenized in a fluid mixer for 2 minutes, plasticized on a rolling mill at 150 ° C. and applied a four-roll calender at temperatures of 160 to 180 ° C with brief heating to 220 ° C into a 0.3 mm thick film. This film is pressed between heated plates at 170 ° C. After cooling with illumination with normal daylight or artificial light, it shows a uniform pure white color. Under an ultraviolet radiation source, the film appears dark and littered with bright greenish dots. A film made of the same mixture without the addition of a phosphor appears uniformly dark in ultraviolet light.

Example 2

A mix of

56.5 parts by weight of polyvinyl chloride

40 parts by weight of a copolymer of acrylonitrile, butadiene and styrene (ABS), 1.5 parts by weight of dibutyltin dithioglycolate stabilizer, 0.5 parts by weight of montanic acid wax, 0.5 parts by weight of stearic acid

1 part by weight of glycerol monooleate

10 parts by weight of titanium dioxide

2 parts by weight of phosphor based on zinc sulfide with an average particle size of 18 m is, as described in Example 1, processed to a film of 0.15 mm thickness, temperatures of approximately 200 ° C. being used on the calender. After cooling, the film shows a uniformly pure white color when illuminated with normal daylight or artificial light. Under an ultraviolet radiation source, the film appears dark with a multitude of greenish, bright spots. A film made of the same mixture without the addition of a phosphor appears uniformly dark in ultraviolet light.

Example 3

A mix of

92.4 parts by weight of polyvinyl chloride 6 parts by weight of a copolymer of vinyl

acetate and ethylene 1 part by weight of dibutyltin dithiocarboxylic acid ester 0.3 part by weight of montanic acid wax 0.3 part by weight of stearic acid

10 parts by weight of titanium dioxide 0.05 part by weight of di-benzoxazolylnaphthalene 4 parts by weight of phosphor based on zinc sulfide, average particle size 18 fi, as described in Example 2, processed into a film of 0.5 mm thickness. After cooling with illumination in normal daylight, the film shows a uniform white color. Under an ultraviolet radiation source, the film glows moderately light bluish violet and is littered with a multitude of bright yellow-green glowing dots that stand out clearly from the differently colored background.

Example 4

A mix of

100 parts by weight of a copolymer of acrylonitrile, butadiene and styrene (ABS) 0.3 parts by weight of montanic acid ester wax 0.3 parts by weight of stearic acid 12 parts by weight of titanium dioxide 0.005 parts by weight of 2,5-bis- [5'-tertiary butylbenzoxazolyl-

(2 ')] - Thiophene 8 parts by weight of phosphorus based on zinc sulfide with an average particle size 18 fi is heated in a heating-cooling mixer to 140 ° C, cooled and on a single-screw extruder with 90 mm screw diameter and slot die at housing temperatures of 170 to 180 ° C extruded into a film which after treatment in a smoothing mill at 85 ° C has a thickness of 0.7 mm. The film shows the same behavior in daylight and ultraviolet light as described in Example 3.

Example 5

A film as described in Example 2, but without a phosphor, is coated with an aqueous dispersion containing 40% by weight ei5

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nes methyl methacrylate polymer with other vinyl compounds and 0.15% by weight dispersed di-benzoxazolyl-naphthalene with an average particle size of 2 u, coated with 5 g / m2 dry weight (approx. 4 // layer thickness) and at approx. 70 ° C dried in an air stream. The coated film shows a practically identical white color on both sides in normal daylight or artificial light. Under an ultraviolet radiation source, the film appears uniformly dark on the uncoated side, on the coated side it is littered with a large number of fine, bluish-bright spots 5.