KR20070017179A - Cards and Laminates Incorporating Multilayer Optical Films - Google Patents

Abstract

A new structure of a multilayer optical film, laminates thereof and a card comprising the same are disclosed. In a card, the multilayer optical film can be sandwiched between relatively thick polymer layers using an adhesive layer having a thickness of at least 0.5 mils but can collectively occupy a thickness of 3 mils or less. The card can be highly transmissive in visible light if desired but very opaque in the part of infrared light. The card obtained can have reduced angel hair formation, increased interlaminar peel resistance and reduced haze during card stamping.

Multilayer optical films, laminates, cards, adhesives

Description

Cards and Laminates Incorporating Multilayer Optical Films

The present invention relates to a multilayer optical film. The invention also relates to laminates and cards comprising multilayer optical films, and methods associated therewith. At least some embodiments of the films, laminates, and cards selectively reflect or block at least some of the electromagnetic radiation having a high average transmittance of visible light at normal incidence and a wavelength greater than about 700 nm.

Multilayer optical films are known which can provide the desired transmission and / or reflection properties by at least in part an arrangement of optically thin layers (“microlayers”) having different refractive indices. It has long been known to produce such multilayer optical films by depositing a series of inorganic materials as microlayers on a substrate in a vacuum chamber. Typically, the substrate is a relatively thick piece of glass having a limited size due to restrictions on the degree of uniformity possible by vacuum chamber volume and / or deposition process.

A brief summary

The present application discloses an alternative structure for a multilayer optical film, an alternative structure for a laminate comprising the film, and an alternative structure for a card comprising the laminate.

For example, the visible light transmissive card may include a first and second relatively thick polymer layer between which a multilayer optical film is disposed. The thick polymer layers may each have a thickness of at least 5 mils (125 μm), or at least about 10 mils (250 μm), wherein the multilayer optical film has a vertical incident reflection band substantially covering a wavelength range in the range from 800 to 1000 nm. It can have The card also includes a plurality of adhesive layers between the multilayer optical film and the first and second polymer layers, but is configured in such a way that it has a haze of 12% or less, or 10% or less.

As another example, the card may comprise a relatively thick first and second polymer layer with a multilayer optical film disposed therebetween, wherein the multilayer optical film has a vertical incident reflection band covering the desired spectral region. The card also includes a plurality of adhesive layers between the multilayer optical film and the first and second polymer layers. For improved film integrity, the multilayer optical film can include alternating repeating layers of copolyesters such as coPEN and PETG. The multilayer optical film may also include two or more microlayer packets separated by protective boundary layers.

In some aspects, only one adhesive layer lies between the multilayer optical film and each of the thick polymer layers. The adhesive layer preferably has a thickness of at least 0.5 mils, but overall constitutes a thickness of about 2 or 3 mils or less. In some configurations, the cards, laminates, and films are all substantially free of polyvinyl chloride (PVC).

These and other aspects of the invention will be apparent from the detailed description below. In no event, however, should the above summary be regarded as a limitation on the claimed subject matter, which subject matter is defined solely by the appended claims, which may be amended during the process.

Throughout the specification, reference is made to the accompanying drawings, wherein like reference numerals refer to like elements:

1 is a greatly enlarged perspective view of a known multilayer optical film;

2 is a schematic cross sectional view of a known laminate structure comprising a multilayer optical film;

3 is a spectral transmission graph for a known multilayer optical film and a known transparent card into which the multilayer optical film is introduced;

4 is a schematic cross-sectional view of a card or a portion thereof undergoing a peel test;

5 is a graph showing a representative peel strength test for a known card comprising a known laminate structure;

6 is a schematic cross-sectional view of a new laminate structure comprising a novel multilayer optical film;

7 is a spectral transmission graph for the novel multilayer optical film alone and for the card comprising the novel laminate structure.

The present disclosure teaches how another multilayer optical film, laminate and card structure can provide improved transparency, interlaminar peeling properties and manufacturability over existing products. This can be achieved by a suitable combination of adhesive distribution and thickness, adhesive durometer (or “hardness”), interlayer adhesion of the multilayer optical film and tensile strength of the multilayer optical film skin layer.

Multilayer optical films have been realized by coextrusion of alternating polymer layers. See, eg, US Pat. No. 3,610,724 to Rogers; US Patent No. 3,711, 176 to Alfrey, Jr. et al., “Highly Reflective Thermoplastic Optical Materials for Infrared, Visible or Ultraviolet Light”; U.S. Patent 4,446,305 to Rogers et al .; U.S. Patent 4,540,623 to Im et al .; U.S. Patent 5,448,404 to Schrenk et al .; US Patent No. 5,882,774 to Jonza et al. "Optical Films"; US Pat. No. 6,045,894 (Jonza et al.) “Transparent to colored protective films”; US Patent No. 6,531,230 (Weber et al.) "Color transfer film"; PCT Publication WO 99/39224 (Ouderkirk et al.) "Infrared interference filter"; And US Patent Publication 2001-0022982 A1 (Neavin et al.), “Devices for the production of multilayer optical films”. See also PCT Publication WO 03/100521 (Tait et al.), "How to Clean and Quickly Substrate a Multilayer Optical Film". In such polymeric multilayer optical films, polymeric materials are mainly or exclusively used to construct individual layers. Such films are suitable for large scale manufacturing processes and can be made into large sheet and roll goods.

1 shows a known multilayer optical film 20. The film includes individual microlayers 22, 24. The microlayers have different refractive index characteristics so that some of the light is reflected at the interface between adjacent microlayers. The microlayers are sufficiently thin so that light reflected at a plurality of interfaces undergoes constructive or destructive interference to impart desired reflective or transmissive properties to the film. For optical films designed to reflect light at ultraviolet, visible or near-infrared wavelengths, each microlayer generally has an optical thickness of less than about 1 μm (ie, physical thickness multiplied by refractive index). However, thicker layers may be included, such as a skin layer on the outer surface of the film, or a protective boundary layer disposed within the film separating the microlayer packets.

The reflective and transmissive properties of the multilayer optical film 20 are a function of the refractive index of each microlayer. Each microlayer may be characterized at at least localized locations in the film by in-plane refractive indices n _x , n _y , and refractive index n _z associated with the thickness axis of the film. The indices represent the refractive indices of the target material for light polarized along the x-, y- and z-axes that are perpendicular to each other (see FIG. 1). In practice, the refractive index is controlled by the selection of the appropriate material and the process conditions. The film 20 coextrudes typically tens or hundreds of layers of two alternating polymers A, B, and optionally passes the multilayer extrudate through one or more propagation dies to stretch or otherwise align the extrudate. To form a final film. The resulting film is typically composed of tens or hundreds of individual microlayers, the thickness and refractive index of which are tailored to provide one or more reflection bands in the desired region (s) of the spectrum, such as visible or infrared light. In order to obtain high reflectivity with a reasonable number of layers, adjacent microlayers preferably have a difference in refractive index (Δn _x ) for light polarized along the x-axis of at least 0.05. If high reflectivity is required for both vertically polarized light, adjacent microlayers also preferably have a difference in refractive index Δn _y for light polarized along the y-axis of at least 0.05. Otherwise, the refractive index difference Δn _y may be less than 0.05, preferably about 0, to produce a multilayer dummy that reflects vertical incident light in one polarization state and transmits vertical incident light in a vertical polarization state.

If desired, the refractive index difference Δn _z between adjacent microlayers for light polarized along the z-axis may be tailored to obtain the desired reflectivity properties for the p-polarized component of the oblique incident light. For ease of explanation, at any point of interest on the multilayer optical film, the x-axis will be viewed as oriented in the plane of the film such that the magnitude of Δn _x is maximum. Thus, the magnitude of Δn _y may be less than or equal to (less than) the magnitude of Δn _x . In addition, the choice of which material layer to start with when calculating the differences Δn _x , Δn _y , Δn _z is determined by requiring that Δn _x be greater than or equal to zero. In other words, the refractive index difference between the two layers forming the interface is Δn _j = n _1j -n _2j (where j = x, y or z and the indication 1,2 of the layer is n _1x ≥ n _2x , ie Δn _x ≥ Selected to be zero).

In order to maintain high reflectivity of p-polarized light at an oblique angle of incidence, the z-index mismatch Δn _z between the microlayers can be adjusted to be significantly smaller than the maximum in-plane refractive index difference Δn _{x such} that Δn _z ≤ 0.5 ^* Δn _x have. More preferably, Δn _z ≦ 0.25 ^* Δn _x . A zero or nearly zero magnitude z-index mismatch creates an interface between microlayers whose reflectivity for p-polarized light is constant or nearly constant as a function of angle of incidence. Moreover, the z-index mismatch Δn _z can be adjusted to have the opposite polarity compared to the in-plane exponential difference Δn _x , ie Δn _z <0. This condition creates an interface in which the reflectivity for p-polarized light increases with increasing incidence angle, as in the case of s-polarized light.

Otherwise, the multilayer optical film may have a simpler structure in which all polymeric microlayers have isotropic properties, ie n _x = n _y = n _z for each layer. Furthermore, known self-assembled periodic structures such as cholesteric reflective polarizers and certain block copolymers can be considered as multilayer optical films for the purpose of this application. Cholesteric mirrors can be made using a combination of left hand and right hand chiral pitch elements.

Recent trends in card fashion have created the need for visible light transmissive cards ("VLT cards", see definition below) for financial transaction card applications. Such a VLT card may be desirable to be as transparent and clear as possible, but in some cases moderate amounts of haze or coloring may be desirable. Problems arise when these cards have to be used in card reading machines such as ATMs and the like. Such a machine typically includes an edge sensor that uses infrared (IR) to detect the presence of a card. As long as the card does not sufficiently block the IR, the edge sensor is not disturbed and the card reading machine does not recognize the presence of the card. Some card manufacturing devices also use IR edge sensors. The card created on the device must also block the required IR. ISO standard No. 7810 (Rev. 2003) corresponds to optical density (OD)> 1.3 (corresponding to less than 5% transmission) over a range of 850 to 950 nm, and OD> 1.1 (transmission of less than 7.9% over a range of 950 to 1000 nm. It is thought to specify).

Thus, the problem with VLT cards was to be as transparent as possible over the visible wavelengths, but then to substantially block most IR above about 800 to 1000 nm. In the above wavelength range, an average transmittance of less than 5% is preferred, but a transmittance of 8% is also acceptable. In some card detection systems, average IR transmission as high as 10% or 15% is also acceptable. Like other cards, it is generally expected that VLT cards maintain their integrity and appearance and will not delaminate during use.

2 shows a cross-sectional view of a known IR filter laminate 30 used in the construction of a known VLT financial transaction card. Laminate 30 includes outer polyvinyl chloride (PVC) layers 32a and 32b; A central multilayer optical film 34 that is highly transparent in visible light and has an IR reflecting band (individual microlayers and skin layers are not shown for ease of illustration); And compound adhesive layers 36a and 36b. The laminate 30 also includes thin undercoat layers 38a and 38b applied to the major surface of the multilayer optical film 34. The adhesive layers 36a and 36b consisting of polyethylene terephthalate (PET) layers 41a and 41b and sold as KRTY 1/1/1 adhesive by Transilwrap Company (Franklin Park, Illinois) are shown. As on each major surface of the PET layer, layers 40a1, 40a2 and 40b1, 40b2 of hot melt adhesive were applied. The structural specification of the known IR filter laminate 30 is as follows:

PVC layer (32a): nominal thickness 1 mil (25 μm)

Compound Adhesion Layer (36a): Nominal Thickness 3 mil (75 μm). Transyllab KRTY 1/1/1.

Adhesive Layer 40a1: Nominal Thickness 1 mil (25 μm). The composition comprises polyethylene and polyethyl acrylate.

PET layer 41a: nominal thickness of 1 mil (25 μm).

Adhesive layers 40a2, 40b1, 40b2: same as layer 40a1.

Undercoat layer 38a: nominal thickness about 0.1 to 0.2 μm. The layer is derived from a coating composition comprising all of the first and second sulfopolyester components, the surfactant (Triton X-100) and the crosslinking agent (Neocryl CX-100) in the deionized water substrate. The coating composition typically has 5% to 10% solids. The first sulfopolyester component is prepared by standard polyester reaction chemistry using a batch kettle process with the following reaction products: sulfosodium isophthalic acid (2.75 mol%), terephthalic acid (23.5 mol%), isophthalic acid (23.75 mol%) Neopentyl glycol (16.5 mol%), and ethylene glycol (33.5 mol%). The second sulfopolyester component is Eastek 1100 from Eastman Chemical's Rotor Chemical Division of Eastman Chemical. The MOF must be treated with corona discharge before it is coated on the undercoat layer.

Multilayer Optical Film (34): Nominal Thickness 2.55 mil (65 μm). A fully polymeric coextruded biaxially oriented film composed of alternating repeat layers of PET / coPMMA. An outer PET shell layer each having a thickness of 12 to 13 μm, and one central packet of 275 microlayers characterized by a thickness gradient. The coPMMA layer has n _x = n _y = n _z = 1.49; The PET layer has an in-plane index n _x = n _y = 1.65, and an out-of-plane index n _z = 1.49.

Undercoat layer 38b: same as layer 38a.

Compound Adhesion Layer 36b: Same as Layer 36a.

PVC layer 32b: same as layer 32a.

Full laminate (30): nominal thickness 10.5 mil (265 μm).

The IR filter laminate 30 dissipates five separate sheets-PVC layers 32a and 32b, compound adhesive layers 36a and 36b, and an undercoat multilayer optical film 34-from the rolls and feeds them to the heated nip. It is comprised by forming the roll of 30. The laminate 30 is then cut into large sheets, and between two similarly sized sheets of thick PVC card stock (a nominal thickness of about 9 mils (225 μm)), along with printed integrated circuit chips and the like, Sufficient heat and pressure to fuse the adjacent PVC layers together is inserted into a lamination press that applies to the assembled elements. The lamination temperature may range from about 280 to 300 ° F. (137-149 ° C.). The large stiff card sheet obtained is then subjected to a die cutting process in which individual standard size financial transaction cards are punched out of the larger card sheet. See, for example, US Pat. No. 6,581,839 (Lasch et al.) “Trade cards”; US Patent Application Publication US 2002/0145049 A1 (Lasch et al.) “Trade card”; And US 2002/0130186 A1 (Lasch et al.) “Trade Cards”. During the die cutting process, when using a known card sheet comprising a known IR filter laminate 30, an inappropriate amount of heterogeneous polymer filament known as "angel hair" may be produced along the edge of the punched card. Such polymeric filaments can present substantial difficulties for card manufacturers.

Nevertheless, the known cards obtained have high transmittance over the visible area and IR blocking suitable for use in a card reading machine. 3 shows a typical measured spectral transmission 50 of the most transparent portion of such a card (not obstructed by a printed IC chip or the like). 3 also shows the measured spectral transmission 52 of a typical multilayer optical film 30 itself. (The spectral transmission measurement is performed on a Perkin-Elmer lambda-19 spectrophotometer at normal incidence and all light transmitted through the card using an integrated sphere is independent of the scattering direction at the output hemisphere. The measured spectral transmittance is not corrected for surface reflection.) Of course, the reflective band of the multilayer optical film shifts to shorter wavelengths as the angle of incidence increases. The transmission in the visible portion of the spectrum of the finished card is lower than that of the unprocessed multilayer optical film 30. This is believed to be due to the coloring additives of the PVC layer, and the scattering or haze generated by the four relatively thick (1 mil) adhesive layers and the PVC layer. Haze of the finished card is a function of the card sheet stacking conditions of time, temperature and pressure, but is typically in the range of 20 to 41%. However, some experimental attempts, especially at high temperatures, resulted in a haze scale as low as 14%. In this regard, “haze” was measured under standard laboratory conditions on a BYK Gardner Hazehard ^™ plus hazemeter. The haze of the multilayer optical film 30 itself, measured in the same way, is typically about 3%.

Another card property that may be an important consideration is durability or susceptibility to delamination of the card. Standards for existing cards recommend that the "peel strength" between any laminated layers be greater than or equal to 3.5 N / cm (meaning force in Newtons per cm of width of the card laminate) over the entire length of the delamination, but at least Higher values such as 7 N / cm or even 10 N / cm are preferred. If the card comprises a multilayer optical film as a reflective element, such as an IR blocking component, the interlayer integrity of the microlayer, protective boundary layer and skin layer of the multilayer optical film becomes important. In addition, the nature of the adhesive layer in contact with the major surface of the multilayer optical film (either directly or through a thin undercoat layer) may also be important.

4 diagrammatically shows a VLT card or card sheet 54 (or portions thereof) undergoing a peel test to measure the interlaminar peel strength between the adhesive layer 36a and the multilayer optical film 30. The outer layer and the central microlayer packet of film 30 are shown for illustrative purposes (not to scale). Also shown are thick PVC card stock layers 56a, 56b each having a thickness of about 10 mils (each 1-mil PVC layer 32a, 32b fused to a thick PVC card stock sheet and any additional PVC cover layers). Resulting from). Topcoat layers, printing and other card elements are not shown for simplicity. In preparation for the 180 degree peel test, cutting may be performed into a card sheet, or a thin polymer tab 55 may be inserted as indicated at the interface under test prior to the card sheet lamination step. After lamination, peeling was initiated at the cut or tab and the peel strength per linear width was monitored along with the length of the peel. The VLT card sheet 54 was cut into pieces 12.5 cm long. At this time, since each half can be peeled up to 12.5 cm, the maximum peel length of the piece is 25 cm. For cards using the known laminate 30, the results of some typical 180 degree peel tests (see curves 60 and 62) are shown in FIG. As shown, the measured peel strength easily initially exceeds 3.5 N / cm, but the peeled pieces often rupture before reaching the end of the test piece, ie before reaching the complete peel length. See tear 58 shown in FIG. The tear appeared slightly past the 2 cm peel length for curve 62, while the burst of curve 60 occurred at a peel length of about 6 cm. (Note that the device stops collecting data after the rupture even though the strength drops to zero)

Maintain a high average visible light transmission of at least 50%, preferably at least 70% or even 80%, and (2) consistently less than 20%, moreover, while maintaining adequate IR blocking for the card to be suitable for card reading machines It would be advantageous to obtain a haze level of the VLT card which is preferably less than 14%, 12%, or even 10%. It would also be advantageous to improve the strength and integrity (related to interlaminar delamination rupture) of the card introducing the multilayer optical film into its structure. Finally, it would be advantageous to provide a multilayer optical film laminate structure that prevents the formation of heterogeneous polymer filaments during the die cutting process.

The multilayer optical film 34 described above is tough and flexible, but the interlayer adhesion of the PET and coPMMA layers is not high. Therefore, particular attention should be paid to the choice of adhesive for bonding the film to the thick PVC card stock of the card structure. If the adhesive is too hard, brittle, or too thin, the force applied to the opposing card halves is concentrated in a small area in the cleavage area between the two halves. The thick soft adhesive allows the peel force to spread over a wider area at the splitting point of the interlaminar peeling when grabbing half of the cards during the peel test. For this reason, the measured peel strength between the thick PVC card stock and the MOF of the known card discussed above is much higher than the peel strength between the microlayers or between other layers of the multilayer optical film itself. However, a disadvantage of using excessive thickness or soft adhesives can be card punching related problems that can occur, such as gum accumulation of angel hair or die. Because of the practical limitations on adhesive thickness and ductility, the MOF structure itself can be modified to prevent rupture of the MOF while making cards with higher peel strength between the MOF and the adhesive. MOF structures with higher interlayer adhesion than known PET / coPMMA systems can be produced. The inventors have also found that the resistance to rupture of the MOF also depends on the presence of an outer sheath layer with good tensile strength.

The force causing the rupture of the MOF during the peel test depends on at least four variables: the thickness of the adhesive, the ductility / hardness (durometer) of the adhesive, the strength of the adhesive adhesion to the MOF, the interlayer adhesion value of the MOF itself, and some In case the tensile strength of the MOF outer shell layer. These variables can all be controlled to achieve card peel strength that well exceeds the ISO recommended value of 3.5 N / cm while simultaneously preventing spontaneous rupture of the MOF during the peel test. A series of card structures were stacked and tested while varying all of these parameters to determine the peel and tear strength for the adhesive and MOF.

Dissimilar materials of MOF are the root cause of the interlaminar peeling of card laminates. Increasing the adhesive strength between the microlayers of the MOF will result in a corresponding increase in the measured peel strength of the card. Three sets of MOF materials were tested for adhesive strength in the card structure. These were coPEN / PMMA, PET / coPMMA and coPEN / PETG, where coPEN was made of 90/10 ratios of PEN and PET monomers which were then copolymerized. It is difficult to measure only the interlayer adhesion of the MOF because the MOF does not usually split along a single interface across the width and length of the test piece. Instead, several interfaces are involved and the layers tear at the boundary of these regions. Thus, the actual peel strength that can be maintained with card peeling is more appropriate. For coPEN / PETG, a peel strength of 15 to 20 N / cm was found to be extremely low in MOF rupture when MOF adhered to PVC with a 1 mil thick adhesive having a hardness of less than 10 megapascals (MPa) on the laminate samples tested. With low incidence and can be obtained reliably-no MOF rupture was observed in almost 40 test pieces. On the other hand, no adhesive was found that could provide a low incidence of rupture for PET / coPMMA in card laminates with the same peel strength of 15-20 N / cm.

Adhesive thickness values tested ranged from about 12 to 50 μm (1/2 to 2 mil).

The adhesive strength of the adhesive to the MOF can be adjusted by the choice of adhesive and by the choice of undercoat on the MOF. The tested adhesives are listed in the examples below.

Durometers of various adhesives were measured by the nano-indentation method. The method is useful because it is possible to measure the elastic modulus and hardness of the adhesive at the major surface of the adhesive layer before lamination to the card or at its corners after the card is laminated. Details of the nano-indentation method are provided below.

The tensile strength of the MOF sheath layer can be important in structures with low MOF interlayer adhesion. Several MOF skin thickness values and materials were tested in the examples below, where the skin layer consisted of coPEN instead of coPEN / PETG film, or PET instead of PET / coPMMA film.

The influence of the MOF structure and adhesive type on the peel strength of the card laminate was evaluated from a series of film and card structures shown in the examples below. Example Laminates were all made to a thickness of about 0.75 mm, and variations in adhesive and MOF thickness values were compensated for by various PVC sheet thickness values. The peel test performed was a 180 degree peel test on a piece having a width of about 2.54 cm and a length of about 12 cm. Tabs as shown in FIG. 4 were used to initiate peeling.

The adhesives studied were described above in TransylLab KRTY 1-1-1; Quest PVC 4 (3/1) A, sold by Quest Films Inc., Woodstock, Illinois; Transilab 3/1 and 2/1 ZZ; Bemis 5214, available from Bemis Associates Inc., Shirley, Massachusetts; And PETG, a copolyester sold as Eaststar 6763 from Eastman Chemical Company, Kingsport, Tennessee. The 3/1 and 2/1 nomenclature for some adhesives means 3 or 2 mils thick polymer backing material, versus the actual mils of adhesive material. In this regard, a material referred to herein as an "adhesive" can be a compound adhesive layer that actually includes a layer of polymeric material and a layer of adhesive. In the specific examples where the sewers were used, the sewers described above in connection with the layers 38a, 38b made by 3M Company (St. Paul, MN) were used.

Example 1

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) PET / coPMMA KRTY 1-1-1 50 9 12 3M 0.1-0.2

This embodiment is actually a comparative example because it shows a card structure using a commercially available IR filter laminate. Peel tests typically resulted in 15-20 N / cm but almost always resulted in MOF rupture before finishing peeling.

Example 2

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) PET / coPMMA Transil Labs 3/1 ZZ 25 8 12 3M 0.1-0.2

The MOF structure was the same as in Example 1, but the adhesive was thinner and slightly softer. The peel strength was in the range of 12 to 17 N / cm, and the peel strength was smaller than that of the KRTY adhesive of Example 1, but the rupture according to the case of MOF was observed.

Example 3

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) PET / coPMMA Quest PVC 4 (3/1) A 25 19 12 3M 0.1-0.2

Again, the MOF structure is the same as in Example 1. However, the adhesive of this example is twice as hard as that of Examples 1 and 2. As a result, although the average peel strength was only 9 N / cm, the film ruptured at 5 times of 10 peels.

Example 4

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) PET / coPMMA Transil Labs 2/1 ZZ 25 4 2 Coextruded PETG, 12

The MOF used the same polymeric materials as those of Examples 1-3, but arranged in a different configuration as follows: There were two alternating microlayer packets, each of which had 223 microlayers, and the packets were 1.3 The thicknesses were different at the ratio of and each packet was bounded by a 2 micron thick boundary layer of oriented PET (fused in the middle to form a 4 micron gap between the packets). The outer boundary layer of oriented PET can thus be characterized as a skin layer. The effect on the peel test of the MOF skin layer is shown in this example. The PET / coPMMA multilayer optical film was coextruded with the outer layer of PETG instead of the usual thick PET outer layer. The amorphous PETG layer has a lower tensile strength compared to oriented PET. As a result, the peel test resulted in a ruptured MOF after a short peel of about 1 cm. MOFs made with PET / coPMMA and 12 micron oriented PET sheaths (see Example 1) exhibited an average peel length of greater than about 3 cm. This difference is due to the higher tensile strength of the thicker PET sheath layer of Example 1.

Example 5

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) coPEN / PETG Transil Labs 2/1 ZZ 25 4 0 Coextruded PETG, 12

The MOF used in this example has a layer structure as in Example 4, with PET replaced with coPEN and coPMMA replaced with PETG. The protective boundary layer was PETG and the skin layer was also PETG, yielding a MOF structure having no strain cured skin. The outer layer of PETG is considered as the undercoat layer for the film. In contrast to Example 4, however, the MOF without strain cured skin can withstand the peel test in the laminate of PVC with a soft adhesive. The superior interlaminar adhesion of coPEN and PETG compared to PET and coPMMA results in a much higher interlaminar peel strength on the card. Average peel strength was 19 N / cm.

In the above and subsequent MOF films using the coPEN / PETG combination, the PETG layer has n _x = n _y = n _z = 1.564, while the coPEN layer has in-plane exponent n _x = n _y = 1.73 and plane- Has an external index n _z = 1.51.

Example 6

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) coPEN / PETG Coextruded PETG 12 138 0 none

This embodiment uses the same MOF structure as in Example 5. As an example of a card structure with a thin and very hard adhesive, a multilayer infrared reflecting film sample of coPEN / PETG was constructed using a PETG skin layer. PETG and similar amorphous polyesters are strongly bonded to PVC under the heat and pressure typically used in card production. Using this structure, thick card stock of PVC can be directly bonded to the IR blocking optical film without an additional adhesive layer. However, PETG is much harder than TransylLab KRTY or ZZ adhesives. When performing a standard peel test, the MOF bursts soon.

Example 7

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) coPEN / PETG Transil Labs 3/1 ZZ 25 8 12 3M 0.1-0.2

The MOF of this example used the same polymeric material, coPEN and PETG as in Example 5-6, with the following structure: alternating microlayers There were two packets, each of which had 223 microlayers, and the packets of 1.16 The thicknesses differed in proportion, and each packet was bounded by a 2 micron thick boundary layer of PETG (fused in the middle to form a 4 micron spacing between the packets). A 12 micron layer of oriented coPEN was coextruded as the sheath layer. The optical transmission spectrum of the MOF and the optical transmission spectrum of the MOF in card laminates are shown by curve 82 in FIG. 7. Peel strength average for 10 pieces was 22.4 N / cm and there was no rupture of MOF.

Example 8

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) coPEN / PETG Transil Labs 2/1 ZZ 25 4 12 3M 0.1-0.2

This example used the same MOF structure and polymer material as Example 7, but with a measurably softer adhesive. The ZZ adhesive layer in the 2/1 structure should be the same as in the 3/1 structure, but there may be lot-specific variations in adhesive hardness values. The peel strength average for 10 pieces was 25.6 Nt / cm, which is higher than that of Example 7. This is consistent with the lower measured hardness value of the adhesive. Again, no rupture occurred in the peel test.

Example 9

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) coPEN / PETG Bemis 5214 75 33 3M 0.3-0.4

The MOF of this example used the same structures and materials as in Examples 5 and 6. Although not as hard as the adhesive of Example 6, the hardness (33 MPa) of the adhesive combined with the good adhesion of the adhesive and the undercoat layer resulted in an immediate burst of coPEN / PETG MOF in all test pieces. If the adhesion of the adhesive to the MOF is adjusted to a lower value by changing the type of underlay layer, it may be possible to reduce or eliminate the rupture of the MOF used herein.

Example 10

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) coPEN / PETG Quest PVC 4 (3/1) A 25 19 12 3M 0.1-0.2

The MOF of this example used the same structures and materials as in Examples 7 and 8. The card laminate made with the Quest 3/1 adhesive, somewhat softer than the Bemis 5214 adhesive, did not have any coPEN / PETG MOF rupture during the peel test. This is in contrast to Example 3, in which 5 of the 10 PET / coPMMA laminates made with the same adhesive burst during the peel test. The average peel strength was 9 N / cm, which is consistent with the peel strength measured in Example 3 using the same undercoat layer on the MOF.

Example 11

MOF structure Adhesive Name Adhesive thickness on each side (micron) Adhesive Hardness (MPa) MOF jacket thickness each side (micron) MOF Sewer and Thickness (microns) PET / coPMMA Transyl Lab KRTY 1-1 25 Do not measure 12 micron 3M 0.1-0.2

Example 11 consists of all of the materials of Example 1 and includes a MOF that lacks an adhesive layer on one side of the Transil Lab product. A specially constructed adhesive layer, coated on one side of 1 mil PET with KRTY adhesive as in the KRTY 1-1-1 product, was used to laminate the PET / coPMMA product into PVC card laminate. The KRTY coated side of the 1-1 structure was placed facing the MOF, and the uncoated side of PET faced PVC. This did not produce commercially available cards because PVC did not adhere well to PET, but nevertheless laminates with 50% less adhesive than Example 1 were prepared to test haze, transmittance and transparency. The laminate was compressed for 15 minutes at 285 ° F., 100 PSI, similar to all other examples. As shown in the haze and transparency table below, the haze was reduced to less than 9% and the transparency was increased to 97. Since the peel test for the KRTY 1-1-1 laminate of Example 1 resulted in a rupture of the MOF, such as the 1/1 structure described above, which can be produced with PVC as in 1/2 or 3/1 ZZ adhesives Thinner adhesives will result in less strong PET / coPMMA based IR blocking cards. However, the results of Examples 7 and 8 clearly show that by changing to an appropriate set of materials, MOF substrate cards that can not be ruptured in the peel test can be produced, and that cards with good durability and lower haze will be obtained. Thinner adhesives are also expected to produce less angel hair in card punching.

Additional laminate samples were constructed using multilayer optical films similar to those of Examples 5 and 6, replacing PETG with PMMA. The protective boundary layer in the MOF was of coPEN; The outer layer is also coPEN and has a thickness of 12 microns. Adhesive and undercoat were as in Example 1. During the peel test, the sample burst immediately. No meaningful measurements were obtained.

Haze, transmittance and transparency values were obtained on a 0.75 mm thick card laminate made of all adhesives using a Haze-gard Plus instrument from BYK Gardner. Manufacturers express transparency variables as a measure of "see-through quality".

Haze and Transparency Data:

sample Haze Transmittance transparency Angel hair Bemis 5214 6.47 84.3 96.2 Not tested Quest PVC 4 (3/1) A 5.32-7.27 83.6-89.2 96.8-98.1 none Transyl Lab ZZ 8.37-12 81.7-86.2 98 lowness Transyllab KRTY 1-1-1 14-41.5 79-83 71.4-93.5 height Transyl Lab KRTY 1-1 8.2-8.9 83-84 97 Not tested coPEN / PETG MOF w / PVC, no adhesive 6.89 85.4 97 Not tested

A tabulated summary of hardness and modulus is shown below. The common polymer, fluorel, was also tested in the x-section as a check for the accuracy of the measurement method. The nominal value was about 21 MPa.

Adhesive sample up and down up and down X-part X-part Modulus E Average (MPa) Hardness H (MPa) Modulus E Average (MPa) Hardness H (MPa) Transil Labs 2/1 ZZ 45 ± 20 4 ± 2 Transil Labs 3/1 ZZ  67 ± 30 8 ± 3 86 ± 10 10 ± 1 Transyllab KRTY 1-1-1 129 ± 20 9 ± 2 106 ± 2 5 ± 1 Quest PVC 4 (3/1) A 172 ± 40 19 ± 4 198 ± 40 11 ± 2 Bemis 5214 320 ± 10 33 ± 2 PETG outer sheath 1,960 ± 40 138 ± 3 Fluorene standard 34 1.33

In summary, the use of thinner adhesive layers and the choice of various adhesives can provide a card with improved transparency and reduced manufacturing problems. Proper selection of the MOF structure can maintain satisfactory physical properties such as interlaminar peel strength and the ability to pass standard bending tests. To neutralize the effect of making the adhesive thinner, the MOF skin layer can be made with higher tensile strength, or the interlayer adhesion of the MOF layer can be increased. The outer layer of existing IR film laminate products is currently about 30% of the total film thickness (15% on each side). A significant increase of more than twice its thickness is difficult to achieve, and the linear proportionality of the shell thickness / film rupture relationship is still unknown at large numerical skin thicknesses. For this reason, combinations of polymeric materials with higher adhesion than PET / acrylic systems have been studied. Polymer pairs of coPEN / PETG have been identified for use in optical multilayer film structures with improved interlayer adhesion compared to PET / acrylic systems.

The aforementioned peel strength relates to the bond between the adhesive layer of the multilayer optical film and the outer surface or skin layer. If the interlayer adhesion of the multilayer optical film is too low, the force on the skin layer will cause it to be pulled out of the rest of the optical layer, resulting in rupture of the optical film. In order to measure the interlayer adhesion value of the optical film layer itself, the film is placed on both sides of the film with another side, such as, for example, a TransilLab 3 / 1zz or 3/1 KRTY adhesive film It can be laminated on. After lamination and cutting into pieces, the pieces can be scraped with a razor blade to allow the cut to penetrate into the optical film layer. The piece can then be bent along the cut until it is folded to create an interlaminar peeling along some boundary between the layers of the optical film. Next, a 90 degree or 180 degree peel strength test can be performed with the obtained sample.

Care should be taken to produce coPEN / PETG multilayer films to ensure high interlayer adhesion. coPEN and PETG are both co-polyesters and are similar materials in that the extruded molded web has extremely high interlayer adhesion, but orientation conditions must be properly adjusted to ensure that the final film also has similar adhesion between the layers. The orientation process typically involves an elongation ratio of about 3 to 1 or more in each in-plane direction. This results in a 10-fold or more reduction in all layer thicknesses, including interlayer mixing regions of adjacent layers. High index layers are designed to also crystallize upon orientation, which can also affect the cohesive strength of the material in a single layer. Thus, the process of orienting the film can result in a decrease in the adhesive force that withstands the delamination of the oriented multilayer film as compared to the forming web interlayer adhesion.

The inventors have found that the interlaminar adhesion of oriented coPEN / co-polyester multilayer films is enhanced by higher thermal curing (annealing) temperature and longer thermal curing time after stretching. The thermal curing temperature after stretching can be increased until the film melts in the tenter or becomes too vulnerable to handling after exiting the tenter. Typical thermal curing zone control temperatures for PET, PEN or any coPENs in the tenter are about 230 ° C to 245 ° C. Thermal curing without or much lower than this range can result in reduced multilayer film tackiness, depending on the stretching temperature.

In summary, with the time and temperature limits determined experimentally by observing mechanical properties such as film uniformity and heat shrinkage, it has been found that higher thermal cure temperatures and increased thermal cure times improve coPEN / PETG film interlayer adhesion. .

Oriented films typically shrink when later reheated above their glass transition value. Shrinkage values are typically reduced by higher thermal cure temperatures and longer thermal cure times. This can cause problems with card stacking, for example if the card material, such as a thick PVC layer, has a higher shrinkage value than the optical film. The optical film may then be wrinkled if the entire laminate shrinks in the transverse dimension. Such shrinkage problems can typically be solved by variations in card process variables such as heating rate, compression temperature and pressure and cooling rate, pressure and temperature. The choice of PVC grade or other sheet material that more closely matches the shrinkage rate of the optical film can also reduce the tendency of the film to wrinkle during card manufacture.

Adhesive choice

Although there are soft, transparent adhesives that exhibit a wide variety of low hazes, the number of adhesives that can be used under pressures of 100 to 200 psi at high temperatures, such as 285 ° F (141 ° C.), and adheres well to PVC and polyester Rather less. Since the soft adhesive described above exhibits some haze, it should be used with a minimum thickness to construct a card having high transparency and good card punching properties. The adhesive layer can be minimized when a two-sided configuration is used, such as TransilLab 3 / 1zz, 2/1 zz or Quest 3/1 adhesive, as shown in FIG. 6. In that figure, the IR filter laminate 70 has a thin outer PVC layer 72a, 72b (less than 5 mils thick, typically 1-2 mil), adhesive layers 76a, 76b, undercoats 78a, 78b and MOF 74 is included. Minimum thickness requirements lead to the need for MOF with good layer adhesion.

Alternative substance

MOFs can be introduced on cards made of materials other than PVC. The requirements of the adhesive are still as described above. Relatively thick (greater than about 10 microns) soft (less than 30 Mpa) adhesives should still be used in combination with MOFs having relatively high interlayer adhesion, such as the coPEN / PETG examples described above. Common materials useful for such cards are PETG and polypropylene. From the above examples, it can be seen that the same adhesive described herein for adhesion to the MOF will also be adhered to PETG. In the case of polypropylene, appropriate surface treatments such as corona discharge and undercoat layers may be required. The oriented polyester layer may be adhered to a thick cardstock layer made of a suitable undercoat layer, such as, for example, a sulfopolyester or coextruded PETG layer, and introduced into the card to reduce the PVC content. Moreover, the IR filter laminate of FIG. 6 may be composed entirely of PVC-free material, but may then be used with PVC or non-PVC cardstock depending on the card manufacturer's needs or requirements.

Definition of selected terms

"Card" for the purposes of the present application means a substantially flat, thin, stiff article that is small enough for personal use. Examples include, but are not limited to, financial transaction cards (credit cards, debit cards, and smart cards), identity cards, and health cards.

"Infrared" or "IR" for the purposes of the present application means electromagnetic radiation having a wavelength of at least about 700 nm. This of course includes, but is not limited to, near infrared wavelengths of about 700 nm to about 2500 nm.

"Multilayer optical film" (or "MOF") for the purposes of the present application means a film comprising a pile of layers that reflect electromagnetic radiation by constructive interference. Exemplary multilayer optical films can be wholly polymeric in composition for ease of manufacture, handling, and adaptability. Cholesteric reflective polarizers and mirrors are also contemplated as multilayer optical films for the purposes of the present application.

By "reflection band" for the purposes of the present application is meant a region of relatively high reflectivity lying between regions of relatively low reflectivity.

By "visible light" for the purposes of the present application is meant electromagnetic radiation having a wavelength in the range of about 400 nm to about 700 nm.

“Visible light transmissive card” or “VLT card” for the purposes of the present application has at least one region through which at least some visible light is transmitted, said region having at least 50 over a range of 400 to 700 nm. A card having an average transmission (measured with an integrating sphere for collecting all light scattered forward through the card) of%, more preferably at least 70% or even 80%.

The above definition of "transparent card" refers to a card that can have a significant amount of haze (and thus translucent), and colored by the introduction of colored or dyes or pigments, or by suitable placement of reflective bands of the multilayer optical film. Note that it also includes cards.

The "elastic modulus" and "hardness" of the various adhesives reported herein for the purposes of the present application mean the properties measured by the Nanoindentation method described below. Using this method involving the use of microprobes, the modulus and hardness of the card layer can be measured at its free surface before lamination or at the edges of the card laminate.

Background / Method-Prior to testing, the sample is placed on a 3/4 inch diameter aluminum cylinder that serves as a fixture in the nano DCM conversion stage. (Nano Indenter XP from MTS Nano Instruments, Minneapolis, MN or Berlin Germany). Diamond Berkovich probes are used for all experiments. The nominal load rate is fixed at 10 nm / s with a spatial flow fixed point adjusted to a maximum of 0.3 nm / s. A constant strain rate test at 0.05 / s up to a depth of 1500 nm is used to test the film as received in 'up and down' mode. Crossed samples are tested to a depth of 500 nm. When looking through the video screen at 400X magnification, locate the area you want to specify while looking up-down. The test area is selected locally at 400 X video magnification of XP to ensure that the area tested is representative of the desired sample material, i.e. free of voids, inclusions or debris. Furthermore, the microscopic optical axis-to-indenter axis alignment is checked and calibrated before the test indentation is made by a fused quartz standard and tested by an iterative process in which error correction is provided by software in XP.

Nanoindentation Measurement—Place the sample surface through a surface finder function where the probe approaches a surface with spring hardness in the air that changes substantially upon meeting the surface. Once the surface meets, load-displacement data is obtained when the probe marks the surface. The data is then converted into hardness and modulus material properties based on the method described below. Statistical evaluation of the mechanical properties can be performed by repeating the above experiments in different areas of the sample.

Measurement of “elastic modulus” —The elastic modulus measured directly from the load-displacement data is the composite modulus, ie the modulus of the indenter-to-sample mechanical system. The composite modulus for these load-displacement indentation experiments can be determined from the following equation:

Where

"S" solves the differential equations relating the periodic forcing function of the equation below to the coefficients of the sample-indenter mechanical system, i.e., the in-phase and out-of-phase elements of the displacement response to the forcing function, Contact hardness determined through the continuous-hard-method of the MTS nanodevice, which yields a constant k, (ie, hard—and thus contact area), and an out-of-phase attenuation coefficient b:

The default excitation frequency for this test is 75 Hz.

"A" indicates that the indentation replicates the shape of the indenter during indentation, and the indenter shape is modeled through analytical geometry such that the projection area A = h ² + higher order terms (h is the depth of displacement) and higher Contact area (m ² ) assuming the terms of the order are measured substantially.

"β" = 1.034 for Berkovich Indenter

"F" is the composite modulus of elasticity [Gpa].

Next, the elastic modulus (E) of the sample material is obtained from the following equation:

1 / F = (1-u ² ) / K + (1-v ² ) / E

Where

"u" is the Poisson ratio of the diamond indenter = 0.07,

"K" is the elastic modulus of the diamond indenter = 1141 Gpa,

"v" is the Poisson's ratio of the sample (here it is assumed to be ~ 0.4 for the sample).

"Hardness"-Hardness is defined as the threshold contact stress in terms of giga or megapascals resulting in the onset of plastic flow of the specimen. This is represented by the following equation:

H = P / A

Where

"H" is hardness [Gpa];

"P" is the load required for plastic flow;

"A" is the plastic contact area.

Various modifications and variations of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention, and it is to be understood that the invention is not limited to the illustrative aspects described herein.

Claims (14)

First and second polymer layers, each having a thickness of at least 5 mil (125 μm); A multilayer optical film having a vertical incident reflection band substantially in the range of 800 to 1000 nm, disposed between the first and second polymer layers; And A plurality of adhesive layers between the multilayer optical film and the first and second polymer layers And a haze of 12% or less. The card of claim 1, wherein the card has an average transmittance of 8% or less at 800 to 1000 nm. The card of claim 2, wherein the card has an average transmission of 5% or less at 800 to 1000 nm. The card of claim 1 having an average transmission of at least 70% at 400 to 700 nm. The card of claim 1, wherein the plurality of adhesive layers consists primarily of first and second adhesive layers disposed between the multilayer optical film and the first and second polymer layers, respectively. 5. The card of claim 4, wherein said first and second adhesive layers collectively comprise about 3 mils or less of the thickness of the card. The card of claim 1, wherein the plurality of adhesive layers are in direct contact with the major surface of the multilayer optical film or through a thin undercoat layer. The card of claim 1 wherein the card is substantially free of polyvinyl chloride (PVC). First and second polymer layers, each having a thickness of at least 5 mil (125 μm); A multilayer optical film having a vertical incident reflection band comprising a desired spectral region disposed between the first and second polymer layers; And A plurality of adhesive layers between the multilayer optical film and the first and second polymer layers Wherein the multilayer optical film comprises alternating layers of coPEN and copolyester. 9. The card of claim 8, wherein said copolyester comprises PETG. The card of claim 8, wherein the adhesive layer has a thickness of at least about 0.5 mil (13 μm) and has a hardness of less than about 30 MPa. 9. The card of claim 8, wherein the card is substantially free of polyvinyl chloride (PVC). 9. A card according to claim 8, having an average transmission of at least 70% at 400 to 700 nm. The card of claim 8, having a haze of 12% or less.

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