KR100706143B1 - Multi-layer polymeric film and the use thereof - Google Patents

Abstract

In the use of a multi-layer film comprising at least two different types of layers for the storage or retrieval of information correlated with the multi-layer structure of the film, each type of layer exhibits different optical properties and the multi-layer film Use comprising a plurality of layers in each of at least two different types of layers; A method of storing information, a method of retrieving stored information, and a method of preventing forgery or fraud using the multilayer film.

Polyester films, opacifiers, multilayer films.

Description

Multilayer polymer film and use thereof {MULTI-LAYER POLYMERIC FILM AND THE USE THEREOF}             

The present invention relates to the use in the storage and retrieval of information in a multilayer film characterized by including different types of layers which can be distinguished by their different optical properties. Multilayer films are used as anti-counterfeiting devices.

Counterfeiting is a growing problem worldwide, causing global economic losses in excess of $ 250 billion annually. Many products are forged, including credit cards, documents, clothing, video, auto parts and aircraft parts.

A commonly used device for storing information is a barcode. It is known that barcodes can be displayed as mathematical codes when optically scanned using appropriate equipment and software. Hand-held scanners are typically used. The mathematical code can then be correlated with the code stored in the database to retrieve or query the desired information. The database may be a local database located at the scanning point or may be remotely accessed by known means of telecommunications. One disadvantage of barcodes is that they can be easily copied because the structure of the barcode can be easily identified. For this reason, conventional optical scanning barcodes are not very suitable for use as anti-counterfeiting devices.

Many other existing anti-counterfeiting techniques, for example holograms, rely on how people can see them. It would be desirable to provide a technique associated with code that is invisible to the naked eye or difficult to imitate to identify. Recent developments in the field of high security relate to subsurface laser marking in labels. This method provides a high level of security, but the manufacturing method and data retrieval are relatively complex and difficult.

Polyester films are already used as substrates in the field of cards and labels. The security properties present as absolute properties of the film enhance the usefulness of the polyester film in this field. Polyester films with embedded cords that are not visible to the naked eye would be particularly useful in the art.

The manufacturing method of a multilayer film is known. U.S. Patent No. 3647612 provides increased numbers by mechanically manipulating the streams by providing at least two streams of thermoplastic and arranging, splitting and recombining the at least two streams into a single stream having a plurality of generally parallel layers. A method for producing a multilayer film is disclosed that includes forming a stream into a thin sheet or film after providing a layer of. The layer consists of a dendritic material that is transparent to visible light and the multilayer film structure has an iridescent appearance. EP 0426636 also discloses a multi-layer coextruded light reflecting film comprising a plurality of generally swollen layers of transparent thermoplastic dendritic material.

EP 0592284 discloses a tear resistant multilayer film comprising an alternating layer of rigid and ductile polymeric material that can be useful as a laminate for preventing scattering of glossy members.

U. S. Patent No. 5759467 discloses a multilayer polyester film comprising a plurality of alternating layers of terephthalic acid polyester and naphthalene dicarboxylic acid polyester. Films are taught to have increased tensile strength and in particular to be used in magnetic media substrates.

European Patent No. 0492894 discloses a method and apparatus for producing a multilayer film by interfacial generation in a fluid. The method splits the first composite stream into two or more branch streams, repositions the branch stream, symmetrically expands along one axis, symmetrically shrinks along the other axis, and branches the first stream into the first composite stream. Recombining into a second composite stream comprising a larger number of separate layers of polymeric material, wherein the expansion and contraction steps are performed on individual branch streams or on a second composite stream.

International Application Publication No. WO98 / 06587 discloses polyester films having a white outer layer on both sides thereof for use as photo sheets or other imaging applications and having a core layer with a light density greater than 2.0 and opaque, preferably black. It is. For a similar use, WO 98/07068 discloses a polyester film having a light density greater than 2.0 and an opaque, preferably black, first layer and white second layer.

It is an object of the present invention to provide a high security, high anti-counterfeiting and convenient and inexpensive technique for combating fraud.

Summary of the Invention

According to the present invention, there is provided the use of a multi-layered film comprising at least two different types of layers for the storage or retrieval of information correlated with the multi-layered structure of the film, wherein each layer is of different optical type. Exhibiting properties and said multilayer film comprises a plurality of layers of each of at least two different types of layers.

The present invention will be described with reference to the following drawings.

1 is a schematic of a layer propagation arrangement apparatus that may be used to make a multilayer film.

2 is a micrograph of a cross section of a cast multilayer film.

3 is a micrograph of an oriented multilayer film cross section.

4 is a micrograph of FIG. 2 in which the float of the luminance profile (or RGB value) obtained by digitizing the micrograph according to the procedure described herein is doubled.

In one preferred embodiment, the differences in the optical properties of each type of layer are related to the different reflectivity of each type of layer for light incident on top thereof. That is, one type of layer reflects light more incident on its top than the other type of layer. The difference in relative reflectivity may be related to any wavelength or wavelength range of electromagnetic radiation. Of particular interest are wavelengths in the visible and ultraviolet regions of the electromagnetic spectrum or portions thereof. Thus, in one preferred embodiment, each type of layer exhibits a difference in reflectivity relative to visible light (or a selected wavelength or region of its wavelengths) or relative to ultraviolet light (or a selected wavelength or region of its wavelengths) The difference in reflectivity is shown. In another embodiment, each type of layer exhibits a difference in relative reflectivity to planar polarization.

In another embodiment, the difference in the optical properties of each type of layer is related to the different fluorescence of each type of layer. That is, one type of layer is relatively fluorescent than other types of layers.

The difference in optical properties is preferably the difference in the relative reflectivity of light in the visible range of the electromagnetic spectrum. It is particularly preferred that each type of layer exhibits a difference in its relative reflectivity for substantially all wavelengths of visible light incident upon it.

There is no upper limit to the number of layers in the film, and it is also possible to produce films with more than 1000 layers.

However, films with a small number of layers also equally fulfill the object of the present invention. In one embodiment, the number of layers is 4 to 100, preferably 6 to 80, more preferably 8 to 50, particularly preferably 10 to 30.

In one preferred embodiment, the multilayer film comprises only two different types, namely a plurality of type A layers and a plurality of type B layers, wherein the type A layers are optically different and distinct from the optical properties of the type B layers. Properties. The number of layers of each type in the film exceeds 2 to 1000.

In one particularly preferred embodiment, the multilayer film comprises only two different types, A type and B type layers which are distinguished from each other on the basis of the relative reflectivity of the light incident on top thereof. In this embodiment, the layer of type A is preferably at least 50%, more preferably at least 65%, even more preferably at least 80%, even more preferably at least 90%, of the light incident on top of it, Even more preferably at least 95%, even more preferably at least 99%, the layer of type B preferably has less than 50%, more preferably less than 65%, even more light incident thereon. Preferably less than 80%, even more preferably less than 90%, even more preferably less than 95%, even more preferably less than 99%. In this embodiment, the layer of type B has at least 50%, preferably at least 65%, more preferably at least 80%, even more preferably at least 90%, even more preferably at least 50% of the light incident on it. 95% or more, even more preferably 99% or more are absorbed.

Thus, a multilayer film comprises a series of layers that can be distinguished based on their optical properties when the film is viewed in cross section along its edge. As noted above, barcodes can be represented as mathematical codes when optically scanned using appropriate equipment and software. In a related manner, the multilayer film structure can also be represented as a mathematical code when optically scanned using appropriate equipment and software. Thus, the multilayer film can be read and queried by optically scanning using an electronic scanner in a manner similar to conventional barcodes. Thus, the multilayer film can be queried to retrieve the code held therein and can be correlated with the information held in the database for verification of the certainty of the code or for the retrieval of the information.

Standard barcodes are typically alternating with white and black bands of varying widths. Similarly, the "barcode" retained in the cross section of the multilayer film includes layers that are optically distinguishable from adjacent layers of the film. Of course, the thickness of each layer in the film varies as the widths of alternating white and black bands of conventional barcodes vary. The layers that are optically distinguishable from adjacent layers may consist of a single separate layer or may consist of a number of individual layers, each having the same optical properties.

The total thickness of the multilayer film used in the present invention is preferably about 5 μm to about 5 mm, more preferably about 5 μm to about 1 mm, even more preferably about 5 μm to about 500 μm, even more preferably About 12 μm to about 350 μm, even more preferably about 30 μm to about 200 μm. Thus, the dimensions of the "barcode" retained in the film cross section are much smaller than the dimensions of conventional optically scanned barcodes. Thus, the "barcode" structure of the multilayer film and the information retained therein will be impossible or very difficult to replicate because there are few places in the world where multilayer polyester films are made.

Smaller dimensions also mean that it will be more difficult to access the "barcode" in the cross section of the multilayer film and the information retained therein without special provision. In embodiments of the invention that depend on the difference in optical properties in the visible light region of each layer, the discrete layers of the multilayer film are usually not visible to the naked eye.                 

Therefore, the multilayer film used in the present invention may include a code or fingerprint and is suitable for use in a field where high security is required. Accordingly, the present invention is directed to any other field where banknotes, passports, identity cards, access cards, banks and credit cards, luxury goods labels, packaging and security information need to be encrypted or where the origin of goods or services is important and valuable. Can be used extensively. Multilayer films used in the present invention will have the advantage that the manufacturing and data retrieval methods are less expensive and more efficient than, for example, subsurface laser marking in security labels.

In addition, polyester films are already being used as substrates in the field of security cards and labels as described above. Therefore, the multilayer film used in the present invention can function both as the substrate and also as the security device itself, thereby reducing the cost. In addition to the improved efficiency and economics of manufacturing, the present invention also provides the advantage that the level of security is increased. As mentioned above, there are few places in the world where multi-layer films can be produced. In addition, in a security system which is an "additional" system in which a security device is applied to or included in an item such as an identity card or credit card, the single manufacturing method of the integrated substrate / security device according to the present invention is a security device, or a code therein. Reduce the risk of being stolen or inadvertently disclosed.

The layers of the multilayer film can be any film forming material, such as one or more dicarboxylic acids or lower alkyl (up to six carbon atoms) diesters, such as terephthalic acid, isophthalic acid, phthalic acid, 2,5-, 2 , 6- or 2,7-naphthalenedicarboxylic acid, succinic acid, sebacic acid, adipic acid, azelaic acid, 4,4'-diphenyldicarboxylic acid, hexahydro-terephthalic acid or 1,2-bis-p -Carboxyphenoxyethanes (optionally monocarboxylic acids such as pivalic acid) can be used in combination with one or more glycols, in particular aliphatic or cycloaliphatic glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl It may be formed from synthetic linear polyesters obtainable by condensation with glycols and 1,4-cyclohexanedimethanol. Aliphatic glycols are preferred. Polyethylene terephthalate or polyethylene naphthalate is the preferred polyester. Polyethylene terephthalate is particularly preferred.

In a preferred embodiment of the invention, each type of layer of the multilayer film comprises the same material, preferably the same polyester. Preferably the materials making up the various layers can be processed at the same temperature and have a similar melt viscosity to avoid degradation of low melting point materials. Thus, the residence time and the processing temperature can be adjusted according to the properties of each layer material. It is also preferred that the layers comprise crystalline and / or semicrystalline polyester material.

Each type of layers in the multilayer film can be uniaxially oriented, but preferably biaxially oriented by stretching in two mutually perpendicular directions of the film plane so that a satisfactory combination of mechanical and physical properties can be achieved. The orientation can be carried out by any method known in the art for producing oriented films, for example tubular or flat film methods.

In the tubular method, the simultaneous biaxial orientation can be performed by extruding the thermoplastic polyester tube and then quenching, reheating, and then expanding by internal gas pressure to induce transverse orientation and remove at a rate that can induce longitudinal orientation. Can be.

In a preferred flat film process, the layered polyester is extruded through a slot die and then rapidly quenched on a cold casting drum to allow the polyester to cool to atmosphere. The orientation is performed by stretching the quenched extrudate at a temperature above the glass transition temperature of the polyester in at least one direction. Continuous orientation may be performed by first stretching the flat quenched extrudate in one direction, usually in the longitudinal direction, ie in the advancing direction of the film stretching machine and then in the transverse direction. Progressive stretching of the extrudate is conveniently performed on a set of rotary rolls or between two pairs of nip rolls, and transverse stretching is performed in a stenter device. Stretching is carried out to the extent determined by the properties of the polyester, for example polyethylene terephthalate usually has the dimensions of the orientation film in the stretching direction or in each stretching direction from 2 to 5 times the original dimension, more preferably from 2.5 times to It is stretched to 4.5 times. Larger draw ratios (eg, up to about 8 times) can be used when orientation in only one direction is desired. Although desirable when a balancing property is desired, it does not need to be stretched equally in the machine and transverse directions.

The stretched film can be dimensionally stabilized by inducing crystallization of the polyester, preferably by thermal curing under dimensional restraint at a temperature above the glass transition temperature of the polyester, but below its melting point. In applications where film shrinkage is not important, the film may or may not be thermally cured at relatively low temperatures. Meanwhile, as the temperature at which the film is thermally cured increases, the tear resistance of the film may change. Therefore, the actual heat cure temperature and time may vary depending on the composition of the film and its intended application but should not be selected so that the tear resistance of the film is substantially eliminated. Under these limitations, thermal curing temperatures of about 135 ° C. to 205 ° C. are generally preferred.

The formation of the multilayer film can be carried out by any technique known in the art. However, the composite film coextrudes each film forming layer simultaneously through separate orifices of a multi-orifice die and then combines the molten layers, or preferably melt streams of each film forming layer material first in the channel. After combining and leading to the die manifold, it is conveniently formed by coextrusion by single channel coextrusion, which does not mix and extrudes together from the die orifice under the conditions of the streamline flow.

One technique as described above is disclosed in US Pat. No. 3,565,985 (Schrenk et al.). In making multilayer films, melt coextrusion by a feedblock method may be used in which a multi-manifold die or each layer meets under laminar flow conditions to provide an integrated multilayer film. More particularly, separate flows of each layer material in the flow state are each divided into a predetermined number of smaller sub-streams. These small streams combine into a predetermined pattern of layers to form an arrangement of these layers in the flow state. Each layer is in intimate contact with an adjacent layer in the array. This arrangement generally consists of a long stack of layers, which are then compressed to their length. In the multi-matfold die approach, the width of the film remains intact upon compression of the stack, while in the feedblock approach the width is increased. In each case, a relatively thin and wide film is produced. Layer multipliers can also be used in which the film produced is divided into a number of separate subfilms and then combined to increase the number of layers in the final film.

In one embodiment, the preparation of the multilayer film can be carried out using a layer propagator on a composite stream comprising separate layers of coextruded polymeric material, as described below and in FIG. The axis is the flow direction of the first composite stream, the x-axis extends in the transverse direction of the first composite stream along the cross section of the layer interface, and the y-axis extends in the thickness direction of the layer of the first composite stream perpendicular to the layer interface. :

(1) expansion of the first composite stream comprising coextruded, separate layers in the x-direction, wherein the interfaces between the layers are located in the x-z plane;

(2) dividing the first composite stream into multiple branch streams along the x-axis;

(3) re-orientation in which branched streams flow along the z-axis so that they accumulate along the y-axis;

(4) recombination of branched streams forming a second composite stream;

(5) Contraction along the y axis of the second composite stream.

The layer propagation device is located after the various polymers have been combined in the co-extrusion block. After the melt exits the bed propagator, it is passed through a die and made into the desired crystalline film. This method can be carried out using any number of extruders to provide the required first composite stream. The first composite stream may be subjected to bed multiplication using one or more bed multipliers arranged in sequence or in parallel.                 

Other manufacturing techniques such as lamination, coating or extrusion coating can be used to assemble the multilayer film. For example, in lamination, a plurality of preformed layers of essentially different optical properties are joined together under temperature and / or pressure (eg using a heated lamination roller or heated presser) to adhere adjacent layers to each other. . Films may also be produced by continuous casting of one or more layer (s) to one or more preformed layer (s). When it is desirable to pretreat selected layers of the multilayer film or when the material cannot be easily coextruded, extrusion coating may be preferred over the melt coextrusion method as described above. In extrusion coating, the first layer is extruded into a cast web, uniaxially oriented film or biaxially oriented film and the following layers are successively coated onto the first provided layer. An example of this method is US Patent 3741253.

In the production of multilayer films, any combination of the above method techniques can be employed. For example, using two or more extruders and stacking two or more coextruded films may produce films of more complex structure that can store more complex codes.

Each layer of the multilayer film need not be a continuous layer. Therefore, a given layer can be continuous or discontinuous throughout the film. The most important requirement is that a given layer must be optically distinguished from adjacent layer (s) so that the cross section of the film can represent a mathematical code.

In a preferred embodiment, the multilayer film comprises a plurality of white layers and a plurality of dark layers.                 

As used herein, the term “white layer” is relatively more reflective to light, preferably to light in substantially all wavelength regions of the visible region of the electromagnetic spectrum, as compared to other types of layers present in the multilayer film. It means a layer of type. As used herein, the term "dark layer" is relatively less for light, and more preferably for light in substantially all wavelength regions of the visible region of the electromagnetic spectrum as compared to other types of layers present in the multilayer film. By reflective layer is meant. In a preferred embodiment, the term "dark layer" as used herein refers to light as compared to other layers present in the multilayer film, preferably to light in substantially all wavelength regions of the visible region of the electromagnetic spectrum. By relatively more absorbent or more permeable type of layer is meant.

In a preferred embodiment, the term "white layer" as used herein refers to a layer that reflects substantially all wavelengths in the visible region of the electromagnetic spectrum of light incident on top thereof, and the term "dense" as used herein. "Color layer" means a layer that absorbs substantially all wavelengths in the visible range of the electromagnetic spectrum of light incident on top thereof.

The following description relates to preferred embodiments of the present invention, each related to the absorption and reflection of visible light by the dark and white layers of the multilayer film of the present invention. However, the specific films described in detail below are merely to illustrate the principles of the present invention and the present invention is not limited to such types of films.

The dark layer is opaque and has a transmission light density (TOD) measured as described herein, greater than 2.0, preferably 2.5 to 10, more preferably 3.0 to 7.0, especially 3.5 to 6.0, more particularly 4.5 to 5.5 It means to indicate the range of. The TOD range is particularly applicable to dark colored layers of 20 μm thickness. The dark layer is easily opaque by incorporating an effective amount of an opaque agent such as carbon black or a metal filler such as aluminum powder. Carbon black is a particularly preferred opacifying agent, in particular carbon black known as Furnace type carbon black.

The dark layer is preferably from 0.05% to 10%, more preferably from 1% to 7%, in particular from 2% to 6%, more particularly from 3 to 5%, based on the weight of the first layer polyester It includes. The opacifying agent, preferably carbon black, suitably has an average particle diameter of 0.005 to 10 μm, more preferably 0.01 to 1.5 μm, especially 0.015 to 0.1 μm, more particularly 0.02 to 0.05 μm.

The opacifying agent preferably has a BET surface area measured according to conventional techniques known in the art in the range of 20 to 300, more preferably 50 to 200, particularly preferably 110 to 160 m ² gm ⁻¹ .

The dark layer is suitably gray, or preferably black, more preferably its outer surface has a CIE in the range of 10 to 60, more preferably 15 to 50, in particular 20 to 40, more particularly 25 to 35 Represents the laboratory color coordinate L ^* value.

In one embodiment of the invention, the dark layer further comprises at least one brightener as described below. The dark layer preferably comprises the same brightener (s) as present in the white layer, ie the dark layer and the white layer preferably contain at least one common brightener, preferably barium sulphate. Include. The dark layer preferably ranges from 5% to 95%, more preferably from 10% to 70%, in particular from 20% to 50%, more particularly from 25% to 35% by weight of the same brightener present in the white layer. Brighteners, preferably barium sulphate.

The thickness of the dark layer is preferably in the range from 0.1 to 50 μm, more preferably from 0.2 to 20 μm, in particular from 0.5 to 15 μm, more particularly from 1 to 12 μm.

The white layer preferably exhibits a transmission light density (TOD) in the range of 0.4 to 1.75, more preferably 0.6 to 1.3, in particular 0.7 to 1.1, more particularly 0.8 to 1.0. The TOD range is particularly applicable to 60 μm thick white layers. The white layer can be conveniently whitened by incorporating an effective amount of brightener therein. Suitable brighteners include particulate inorganic fillers, immiscible resin fillers, mixtures of two or more of these fillers.

Particulate inorganic fillers suitable for preparing the white layer include conventional inorganic pigments and fillers, in particular metal or metalloid oxides such as alumina, silica and titania and alkaline earth metal salts such as carbonates and sulfates of calcium and barium. . Suitable inorganic fillers are homogeneous and may consist essentially of a single filler material or compound, such as titanium dioxide or barium sulphate alone. Alternatively, at least some of the fillers may be heterogeneous and the main filler material may be combined with additional modifying components. For example, the main filler particles may be treated with surface modifiers such as pigments, soaps, surfactant coupling agents or other modifiers to promote or alter the extent of filler blending into the white layer polymer.

Suitable particulate inorganic fillers may be of nonporous or pore type. By voids is meant to include a cellular structure comprising at least some distinct, closed cells. Barium sulphate is one example of a filler that causes the formation of voids. Titanium dioxide may be of the pore or non-pore type depending on the specific type of titanium dioxide used. In a preferred embodiment of the invention, the white layer comprises titanium dioxide or barium sulphate, in particular mixtures thereof.

The amount of inorganic filler incorporated into the white layer should preferably not be greater than 5% or greater than 60% based on the weight of the white layer polyester. Particularly satisfactory whiteness levels are those in which the concentration of the filler is preferably 10% to 55%, more preferably 15% to 50%, especially 20% to 45%, more particularly 25%, based on the weight of the white layer polyester Achievement is in the range of -35%. In a particularly preferred embodiment of the invention, the white layer is titanium dioxide present in a weight ratio of 3 to 0.3: 1, more preferably 2 to 0.5: 1, especially 1.5 to 0.7: 1, more particularly 1.1 to 0.9: 1. And barium sulphate particles.

Titanium dioxide filler particles may be anatase or rutile crystalline. The titanium dioxide particles preferably comprise a significant amount of anatase, more preferably at least 60% by weight, in particular at least 80% by weight, more particularly approximately 100% by weight of anatase. The particles can be prepared using standard methods, such as the chloride method, or preferably the sulfate method.

In one embodiment of the invention, the titanium dioxide particles are preferably coated with an inorganic oxide such as aluminum, silicon, zinc, magnesium or mixtures thereof. Preferably the coating further comprises an organic compound, such as a fatty acid and preferably an alkanol, preferably having from 8 to 30, preferably from 12 to 24 carbon atoms. Polydiorganosiloxane or polyorganohydrogensiloxanes such as polydimethylsiloxane or polymethylhydrosiloxane are suitable organic compounds.

The coating is suitably applied to the titanium dioxide particles present in the aqueous suspension. Inorganic oxides are precipitated from water-soluble compounds such as sodium aluminate, aluminum sulfate, aluminum hydroxide, aluminum nitrate, silicic acid or sodium silicate in an aqueous suspension.

The individual or primary titanium dioxide particles suitably have an average crystal size in the range of 0.05 to 0.4 μm, preferably 0.1 to 0.3 μm, more preferably 0.2 to 0.25 μm, as measured by electron microscopy. In a preferred embodiment of the invention, the primary titanium dioxide particles aggregate to form agglomerates or aggregates comprising a plurality of titanium dioxide particles. The agglomeration method of the main titanium dioxide particles can be carried out during the actual synthesis of the titanium dioxide and / or during the polyester and / or polyester film production process.

The inorganic filler, suitably agglomerated titanium dioxide and / or barium sulphate, preferably has a volume distribution of 0.1 to 1.5 μm, more preferably 0.2 to 1.2 μm, especially 0.4 to 1.0 μm, more particularly 0.6 to 0.9 μm. Median particle diameters (referred to as equivalent spherical diameter-often "D (v, 0.5)" values corresponding to 50% of all particle volumes read in cumulative distribution curves relating volume% to particle size).

It is preferred that none of the filler particles incorporated in the white layer have an actual particle size of greater than 20 μm. Particles exceeding this size may be removed by sieving methods known in the art. However, not all particles larger than the selected size can always be removed by the sieving process. Therefore, in practice, the size of 99.9% of the number of particles should not exceed 20 μm. Most preferably, the size of 99.9% of the particles should not exceed 10 μm. Preferably at least 90%, more preferably at least 95% of the filler particles are in the range of volume distribution median particle diameter + 0.5 μm, in particular + 0.3 μm.

Particle sizes of filler particles described herein can be measured by electron microscopy, coulter counters, sedimentation assays, and static or dynamic light scattering. Techniques based on laser light diffraction are preferred. The median particle size can be measured by plotting a cumulative distribution curve representing the percentage of particle volume below the selected particle size and measuring the 50th percentile. The volume distribution median particle diameter of the filler particles is appropriately measured using the Malvern Instruments Masterizer MS 15 Particle Sizer after the filler is dispersed in ethylene glycol in a high shear force (eg Chemcoll) mixer.

By "immiscible resin" is meant a resin that does not melt at the highest temperature during extrusion and processing of the white layer or is substantially immiscible with the polyester. The resins include homopolymers and copolymers of polyamide and olefin polymers, in particular mono-alpha-olefins containing up to 6 carbon atoms in their molecules, for incorporation into polyester films. Particularly preferred materials for incorporation into the polyethylene terephthalate white layer are olefin polymers such as low or high density homopolymers, in particular polyethylene, polypropylene or poly-4-methylpentene-1, olefinic copolymers, in particular ethylene-propylene copolymers, Or mixtures of two or more thereof. Random, block or graft copolymers can be used.

Dispersibility in the white layer of the olefin polymer may be insufficient to impart desired properties. Therefore, preferably, the dispersant is incorporated with the olefin polymer softener. Dispersants conveniently comprise carboxylated polyolefins, in particular carboxylated polyethylene. Suitable carboxylated polyolefins include those having a Brookfield viscosity (140 ° C.) in the range of 150-100000 cps (preferably 150-50000 cps) and an acid value of 5-200 mg KOH / g (preferably 5-50 mg KOH / g). And the acid value is mg of KOH needed to neutralize 1 g of polymer.

The amount of dispersant may be selected so that the required degree of dispersibility can be provided, but is conveniently in the range of 0.05% to 50%, preferably 0.5% to 20%, based on the weight of the olefin polymer.

The amount of immiscible resin filler present in the white layer is preferably 2% to 30%, more preferably 3% to 20%, especially 4% to 15%, more particularly 5 based on the weight of the white layer polyester It is the range of% to 10%.

In one embodiment of the invention, the white layer comprises an optical brightener. Optical brighteners may be included at any stage of polymer or polymer film preparation. Preferably the optical brightener is added to the glycol, or thereafter, to the polyester prior to the formation of the polyester film, for example by injection during extrusion. The optical brightener is preferably added in an amount in the range of 50 to 1500 ppm, more preferably 100 to 1000 ppm, in particular 200 to 600 ppm, more particularly 260 to 350 ppm, based on the weight of the white layer polyester. Suitable optical brighteners are commercially available under the trade names "Uvitex" MES, "Uvitex" OB, "Leucopur" EGM and "Eastobrite" OB-1.

The components of the dark layer and / or white layer composition may be mixed together by conventional methods. For example, the components may be mixed with the monomer reactants from which the polyester is derived, or the components may be mixed with the polyester by tumble or dry mixing, or by blending in an extruder, and then cooled, usually granules or Crush into chips. Alternatively masterbatching techniques can be used.

The surface of the white layer has the following CIE laboratory color coordinate values, L ^* , a ^*, and b ^* values, measured as described herein. The L ^* value is suitably above 85, preferably in the range from 90 to 100, more preferably from 93 to 99, in particular from 95 to 98. The a ^* value is preferably in the range of -2 to 3, more preferably -1 to 2, in particular 0 to 1.5, more particularly 0.3 to 0.9. The b ^* value is preferably in the range of -10 to 0, more preferably -10 to -3, especially -9 to -5, more particularly -8 to -7.

Color coordinate values can be changed by incorporating suitable dyes, such as blue and / or magenta dye (s), into the film forming polyester of the white layer. For example, a blue dye may be used at a concentration in the range of preferably 10 to 1000 ppm, more preferably 30 to 500 ppm, in particular 50 to 200 ppm, more particularly 100 to 150 ppm, relative to the weight of the white layer polyester. Alternatively, or additionally, magenta dyes may be used at concentrations ranging from 2 to 200 ppm, more preferably from 4 to 100 ppm, in particular from 7 to 50 ppm, more particularly from 10 to 15 ppm, by weight of the white layer polyester.

The surface of the white layer exhibits a whiteness index, measured as described herein, preferably in the range from 80 to 120, more preferably from 85 to 110, in particular from 90 to 105, more particularly from 95 to 100 units.

The thickness of the white layer is preferably in the range from 0.1 to 50 μm, more preferably from 0.2 to 20 μm, in particular from 0.5 to 15 μm, more particularly from 1 to 12 μm.

The polyester film layer may include any additives commonly used in the manufacture of polymer films, if desired. Therefore, dyes, pigments, voids, lubricants, antioxidants, antiblocking agents, surfactants, slip aids, gloss improvers, prodegradants, flame retardants, UV stabilizers, viscosity modifiers and dispersion stabilizers can be incorporated as appropriate. have.

In embodiments of the invention that involve absorption and reflection of ultraviolet wavelengths to distinguish each layer, each type of layer comprises different levels of one or more UV absorber (s). The UV absorber (s) may be any of those known to those skilled in the art that are miscible with other materials used to make the multilayer films of the present invention. UV absorbers can absorb substantially all wavelengths in the ultraviolet region of the electromagnetic spectrum, or substantially all wavelengths within the wavelength of a selected band of the ultraviolet region. In a preferred embodiment of the invention in which there are only two types, A type and B type layers, the layer of type A is substantially free of UV absorbers, while the type B layer is a suitable UV source and detector It includes a UV absorber in an amount effective to distinguish it from a layer of type A when analyzing using.

In principle, any organic or inorganic UV absorber, in particular those suitable for use with polyester, can be used in the present invention. Suitable examples include the organic UV absorbers disclosed in Encyclopedia of Chemical Technology, Kirk-Othmer, 3rd edition, John Wiley & Sons, Vol. 23, pages 615-627. Specific examples of UV absorbers include benzophenone, benzotriazole (US Pat. No. 4684679, US Pat. No. 4812498, and US Pat. No. 4681905), Benzoxazine (US Pat. No. 4446262, US Pat. No. 5251064, and US Pat. 5264539) and triazines (US Pat. No. 3244708, US Pat. No. 3843371, US Pat. No. 4619956, US Pat. No. 5288778 and WO 94/05645). Said patent is incorporated herein by reference. Preferably the UV absorbers are nonvolatile and do not cause excessive yellowing of the product.

In one embodiment of the invention, the UV absorbers may be chemically incorporated into the chains of the layered polyester. Preferred UV stabilized polyesters incorporate benzophenones into the polyester as described, for example, in European Patent Application No. 0006686, European Patent Application No. 0031202, European Patent Application No. 0031203 and European Patent Application No. 0076582. Which is hereby incorporated by reference.

In a preferred embodiment of the invention, the UV absorber comprises at least one triazine, more preferably hydroxyphenyltriazine, in particular a hydroxyphenyltriazine compound of formula (1).

In the above formula, R is hydrogen, C ₁ -C ₁₈ alkyl, C ₂ -C ₆ alkyl or benzyl substituted by halogen or C ₁ -C ₁₂ alkoxy and R ¹ is hydrogen or methyl. R is preferably C ₁ -C ₁₂ alkyl or benzyl, more preferably C ₃ -C ₆ alkyl, in particular hexyl. R ¹ is preferably hydrogen. Particularly preferred UV absorbers are 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyl) oxy-phenol, which is Ciba-Additives Commercially available from Tinuvin ^™ 1577FF. Further examples of preferred UV absorbers are benzylidene malonate esters (commercially available as Sanduvor ^™ PR-25 from Sandoz) and benzoxazinone (Cyasorb ^™ 3683 from Cytec). Is).

Suitable inorganic UV absorbers include metal oxide particles such as zinc oxide or titanium dioxide. Particular preference is given to titanium dioxide particles such as those described above.

The amount of UV absorber incorporated into the layer is generally 0.1 to 10%, more preferably 0.5% to 9%, more preferably 1.2% to 8%, especially 2% to 6%, based on the weight of the polymer of the layer, More specifically, it is 3.2%-5.5% of range. In one embodiment of the invention, both organic UV absorbers, preferably triazines and inorganic UV absorbers, preferably titanium dioxide are present. The weight ratio of inorganic to organic UV absorbers is preferably in the range from 0.5 to 10: 1, more preferably from 1 to 5: 1 and in particular from 1.5 to 2.5: 1.

In other embodiments of the present invention, each type of layer may comprise pigments of different colors. In this embodiment, each type of layer in the multilayer film is distinguished because each type of layer reflects light of different wavelengths in the visible region of the electromagnetic spectrum. Alternatively, each type of layer can include different UV absorbers that absorb UV light at different wavelengths in the ultraviolet region of the electromagnetic spectrum. It is possible to combine (i) a layer of a type that reflects selected wavelengths of visible light, or substantially all wavelengths, and (ii) a layer of a type that reflects selected wavelengths of ultraviolet light, or substantially all wavelengths, in a multilayer film. In this case, of course, it would be necessary to optically scan the film for wavelengths in both the visible and ultraviolet regions of the electromagnetic spectrum. In this way, highly complex structures can be created to create complex security code and to store larger amounts of information.

The multilayer film may also include an ink soluble coating. Ink-soluble coatings improve the adhesion of the ink to the film, thereby broadening the range of inks that can be easily applied to the surface. The ink water soluble coating can be any coating known to those skilled in the art. For example, the ink water soluble coating may comprise an acrylic component and a crosslinking component (eg melamine formaldehyde) such as a coating as disclosed in European Patent Application No. 0429179, which patent application is incorporated by reference. Is cited.

As noted above, the film structure of a multilayer film can be converted to a code, such as a mathematical code, so that the film can be encrypted with electronically readable information for retrieval immediately and when needed. The retrieval of the information can be performed by optically scanning the cross section of the film using an electronic scanner. One method of reading the film structure is to obtain a micrograph of the film cross section, for example using a microscope. Next, using techniques known in the art, the micrograph is divided into pixels and analyzed to convert the micrograph into digital code, ie mathematical code. Mathematical codes are correlated with codes stored in local or remote databases and the necessary information is retrieved. However, it is desirable to scan and digitize the multilayer film in one operation.

According to another aspect of the present invention there is provided a multilayer film comprising a plurality of white layers and a plurality of dark layers as described herein.

According to another aspect of the invention:

(i) providing a multilayer film comprising at least two different types of layers, wherein each type of layer exhibits different optical properties and the multilayer film comprises a plurality of layers of each of at least two different types of layers;

(ii) optically scanning the cross section of the film along its edge to convert the multilayer structure of the film into a code;

(iii) designate the code as one or more items of information;

(iv) A method of storing information is provided that includes optionally providing a database comprising one or more items of information and codes assigned thereto.

According to a further aspect of the invention:

(i) providing a multilayer film comprising at least two different types of layers, wherein each type of layer exhibits different optical properties and the multilayer film comprises a plurality of layers of each of at least two different types of layers;                 

(ii) optically scanning the cross section of the film along its edge and converting the multilayer structure into a code to query the multilayer film;

(iii) correlate the code with one or more items of information;

(iv) A stored information retrieval method is provided that includes optionally providing a database containing one or more items of information and codes assigned thereto.

According to another aspect of the invention:

(i) providing a multilayer film comprising at least two different types of layers, wherein each type of layer exhibits different optical properties and the multilayer film comprises a plurality of layers of each of at least two different types of layers;

(ii) optically scanning the cross section of the film along its edge to convert the multilayer structure of the film into a first code;

(iii) optionally designating the first code with one or more items of information;

(iv) storing the first code, and optionally the information specified therein, in the database;

(v) optically scanning the cross section of the film along its edge and converting the multilayer structure into a second code to query the multilayer film;

(vi) A method of preventing forgery or fraud, comprising correlating a second code thus obtained with a first code stored in a database.

In this method, the code may be a mathematical or other typical code.

Referring to FIG. 1, a two layer composite melt stream 1 passes through a coextrusion block 2 and then through a four lane bed multiplier 3. The polymeric material is then passed through a die 4 to provide an eight layer composite stream 5.

2, 3 and 4, the micrograph clearly shows alternating white and dark layers of the multilayer film. In FIG. 4, the x axis is micron and the y axis is luminance.

In the present specification, the following test methods were used to determine the specific properties of the film:

(i) The transmission light density (TOD) of the film was measured using Macbeth Densinometer TR 927 (purchased from Dent and Woods Limited, Basingstoke, UK) in transmission mode.

(ii) The L ^* , a ^*, and b ^* color coordinate values (CIE (1976)) and whiteness index of the white layer outer surface are based on the principles described in ASTM D313, based on the principles described in Colorgard System 2000, Model / 45 (Pacific Scientific). (Manufactured by Pacific Scientific).

The invention is further illustrated with reference to the following examples. All parts and percentages are by weight unless otherwise indicated.

Film manufacturing

 12 layers of a three-layer white / grey / white composition formed by a conventional coextrusion method having a thickness of 100 μm through a layer propagation device (BABBABBABBAB, where B = white layer and A = gray layer) A film was prepared.

The 12 layer film was produced using a conventional polyolefin film production line. The film was made using two extruders. A white polymer comprising 20% titanium dioxide was extruded in the main extruder, which comprised approximately 62% of the total film weight. The gray polymer comprising 20% titanium dioxide and 0.5% carbon black was extruded in a coextruder to constitute about 38% of the total weight of the film. All of these polymer blends were prepared by mixing unfilled PET with a masterbatch.

Once the polymer was extruded independently, the melt stream was passed along a connecting block that placed the melt in the order of BAB, where B is the white layer and A was the gray layer. The melt streams were contacted in the desired order of BAB using a “cam-type” injection block. The resulting composite three layer melt stream was passed through two melt separators to obtain the final structure of BABBABBABBAB. This 12 layer melt stream was then extruded onto a cooled cast roll using a conventional die. The film was sequentially stretched 3.0 times in the machine direction at 80 ° C. and 3.3 times in the transverse direction at 110 ° C.

The cross sections of the white and gray layers of both the cast film and the oriented film were observed under a microscope and micrographs were obtained (see FIGS. 2 and 3). The image was "digitized" using the method described below.

Film analysis

The image of a PC consists of a number of small dots of color or pixels. A closer look at a small part of the image appeared as a collection of pixels. Each pixel was defined using RGB (red green blue) values representing the amounts of red, green, and blue used to form the pixel's color. These values range from 0 to 255. In the case of the grayscale (“black and white”) phase, the pixels are shades of gray and consequently equivalent amounts of red, green and blue were used to represent the color of each pixel. Any one of the RGB values for the pixels on the grayscale was taken to efficiently test the luminance of that point represented by the values in the range 0 (black) and 255 (white).

The following method was used to distinguish the layers of the film:

1. Take an enlarged edge-on image of the film and save it to the PC in Tagged Image File Format (TIFF). TIFF is a standard bitmap format that includes formatting information in addition to pixel color information. The image was converted to Raw Data Format (Raw) (using Paintshop Pro) to access pixel cell information. Raw format stores an image as a series of 8-bit binary digits representing each of the RGB values of a pixel. Eight bits (one byte) represent decimal numbers from 0 to 255, and thus represent RGB values of pixels. The three-channel (color) phase will use 3 bytes per pixel while the grayscale phase will use only 1 byte per pixel. For example, the first five pixels of a grayscale raw data file, i.e. 5 bytes (8 bits = 1 byte), would be as follows.

Yes. 10010001 00001000 01000010 00010001 11100001 ...

2. One pixel wide sample area was selected from the image.

3. Using a Visual Basic application, you converted a binary raw data file to a text file, storing the decimal represented by each byte in the raw file.                 

4. Excel 97 reads the data stored in the text file into a spreadsheet that can be used to plot the chart. You could use a mathematical filter to convert the text file into a bar code.

The examples demonstrated that the multilayer film can be encrypted with electronically readable information. To make a more unique security code, the structure of the film can of course be transformed into a much more complex structure than the structure of the simple 12 layer film of the examples.

Claims (20)

A multi-layer film comprising a plurality of layers, wherein the plurality of layers each include a plurality of at least two layers, each of which is reflective, absorptive, transmissive, or fluorescence different from each other, the different properties being a multi-layer film in the inner cross section of the multilayer film. Forming a pattern over a thickness of wherein the information is in the form of a barcode, the pattern defining the barcode. The bar code of claim 1, wherein the two layers exhibit a difference in their relative reflectivity to light incident on top thereof. The barcode of claim 1, wherein the two layers exhibit a difference in their relative reflectivity to visible light incident on top thereof. The barcode of claim 1, wherein the two layers exhibit a difference in their relative reflectivity to substantially all wavelengths of visible light incident thereon. The barcode of claim 1, wherein at least one layer comprises a polyester. The barcode according to claim 5, wherein the dicarboxylic acid component of the polyester is terephthalic acid. The barcode according to claim 5, wherein the diol acid component of the polyester is ethylene glycol. The barcode of claim 1, wherein said film comprises two types of layers. The barcode of claim 8, comprising a plurality of white layers and a plurality of dark layers. 10. The barcode according to claim 9, wherein the dark layer comprises an opaque agent in the range of 0.05% to 10% by weight based on the weight of the polyester of the dark layer. The barcode of claim 10, wherein the opacity agent comprises carbon black. 10. The barcode of claim 9 wherein the outer surface of the dark layer exhibits a CIE laboratory color coordinate L ^* value in the range of 10 to 60. 10. The barcode of claim 9 wherein the white layer comprises a brightener in the range of 5% to 60% by weight based on the weight of the polyester of the white layer. 10. The barcode of claim 9 wherein the surface of the white layer exhibits a CIE laboratory color coordinate value L ^* greater than 85. 10. The barcode of claim 9 wherein the surface of the white layer exhibits a whiteness index in the range of 80 to 120 units. A multi-layer film comprising a plurality of layers, wherein the plurality of layers each include a plurality of at least two layers, each of which is reflective, absorptive, transmissive, or fluorescence different from each other, the different properties being a multi-layer film in the inner cross section of the multilayer film. Forming a pattern over a thickness of wherein the information is in the form of a barcode, the pattern defining a barcode. The device of claim 16, wherein the multilayer film comprises a plurality of white layers and a plurality of dark layers. delete delete delete

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