A coextruded biaxially oriented composite film comprising a polyester substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer, wherein said strippable sacrificial layer comprises an ethylene-methacrylic acid (EMAA) copolymer.
This application is a National Stage filing of International Application No. PCT/GB2012/000240, filed 13 Mar. 2012, and claims priority of GB Application No. 1104565.5, filed 17 Mar. 2011, the entireties of which applications are incorporated herein by reference.
The present invention is concerned with a polyester film (particularly a polyethylene terephthalate (PET) film) having a strippable sacrificial protective layer, and with a process for the production thereof.
The advantageous mechanical properties, dimensional stability and optical properties of biaxially oriented polyester films are well-known. These properties have led to the use of polyester films in electronic and opto-electronic devices including electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally). For these and other applications, it is sometimes necessary to provide a very smooth and flat surface for the further processing of the polyester film, for instance to ensure the integrity of subsequently applied coatings, such as a conductive coating or a barrier coating, in order to avoid breaks or pin-pricks therein. In the manufacture of flexible electronic or opto-electronic display devices, for instance, a conductive layer such as indium tin oxide (ITO) may be disposed on a film substrate via a sputtering technique, and non-uniformity in the substrate surface can cause non-uniformity and/or discontinuities in the conductive layer, resulting in for example non-uniform conductivity or pixel yield problems, depending on the type of electronic device.
It is known to reduce defects in layers subsequently applied to a substrate by the provision of an intermediate planarising layer, as taught in WO-03/087247-A for instance. An alternative approach is to provide strippable sacrificial protective layers which are easily peelable from a substrate surface, in order to protect that surface from damage, contamination and/or debris during storage or transport. The sacrificial layers are then stripped from the substrate to leave a clean surface immediately prior to the further processing or installation of the substrate. For instance, WO-2009/105427-A discloses a composite optical compensation film comprising a polyolefin substrate and strippable layers comprising from a variety of polymeric materials including other polyolefins, polyesters, and ionomers. EP-0345884-A discloses a coextruded strippable polyolefin or polyamide film on the surface of a polycarbonate sheet to avoid loss of a volatile UV stabiliser in the polycarbonate, to protect the production equipment from exuded amounts of the stabiliser, and to protect the polycarbonate surface during handling and shipping. EP-0663867-A teaches the provision of strippable sacrificial layers to a multilayer polymeric body by coating and lamination techniques. Other disclosures of strippable skin layers include U.S. Pat. No. 4,540,623 and U.S. Pat. No. 7,396,632. The prior art, however, is primarily focussed on the need to protect a substrate surface from extrinsic debris or physical damage during storage or transport.
It would be desirable to provide a polyester film wherein one or both surfaces thereof exhibit minimal or no surface defects (low intrinsic process defects), and high surface cleanliness (i.e. low extrinsic debris).
According to the present invention, there is provided a coextruded biaxially oriented composite film comprising a polyester substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer, wherein said strippable sacrificial layer comprises an ethylene-methacrylic acid (EMAA) copolymer, and wherein the polyester is derived from: (i) one or more diol(s); (ii) one or more aromatic dicarboxylic acid(s); and (iii) optionally, one or more aliphatic dicarboxylic acid(s) of formula CnH2n(COOH)2 wherein n is 2 to 8, wherein said aromatic dicarboxylic acid(s) is/are present in the polyester in an amount of from about 80 to about 100 mole % based on the total amount of dicarboxylic acid components in the polyester.
FIG. 1A is a large-area metrology (LAM) image showing a pinch-point defect in a polyester substrate.
FIG. 1B is a LAM image showing a smooth circular defect in a polyester substrate.
FIG. 2 is a LAM image showing depressions in a polyester substrate, characterised by a central crater and associated raised areas around the crater.
FIG. 3 is a LAM image showing gel-like features or streaks in a polyester substrate, characterised by globular surface features or elongated regions of raised ridges and associated shallow valleys either side of the ridges.
The cleanliness and smoothness of the substrate surface after removal of the strippable sacrificial layer can be described in terms of "extrinsic" and "intrinsic" roughness. As used herein, the term "extrinsic" roughness refers to roughness resulting from air-borne debris and/or handling damage which the substrate may suffer during storage and/or transport. As used herein, the term "intrinsic" roughness refers to roughness which is present in the substrate itself or is a result of the process history of the film. The intrinsic roughness of the substrate includes any roughness induced by the presence of the strippable sacrificial layer or its removal.
(i) The film is manufactured by coextrusion and hence its production process is more economic and efficient than a two-step process in which the sacrificial layer is applied to a finished substrate. Thus, the strippable sacrificial layer is not only peelable from the polyester substrate but it is also co-extrudable with the polyester substrate.
(ii) The strippable sacrificial layer is reliably extrudable and processible under the conditions conventionally used to manufacture biaxially oriented polyester films, and is extrudable with a uniform thickness and without MD lines. The composite film thereby exhibits good windability and allows the formation of a uniform roll of film, which can be a problem with some conventional strippable sacrificial layers.
(iii) The strippable sacrificial layer is easily peelable from the polyester substrate, but the interfacial adhesive strength is not so low that it spontaneously peels apart from the substrate during manufacture, during storage or during transport of the composite film, which can be a problem with some conventional strippable sacrificial layers. Furthermore, while modulation of interfacial adhesion between the substrate and strippable layers has conventionally been possible by using an intermediate tie-layer therebetween, it is an advantage of this invention that there is no need for intermediate tie-layer, which provides economy and process efficiency in the manufacturing process.
(iv) The strippable sacrificial layer is easily peelable from the polyester substrate, especially in a roll-to-roll process, without leaving remnants or residue of itself on the surface of the polyester substrate or otherwise disrupting the surface of the polyester substrate when peeled, which can be a problem with some conventional strippable sacrificial layers. Thus, the strippable sacrificial layer of the present invention exhibits an easy and clean peel.
(v) The strippable sacrificial layer performs the required function of protecting the polyester substrate from damage or extrinsic debris during storage or transport until it is ready to be used or further processed. However, the strippable sacrificial layer must retain, or at least not significantly degrade, the intrinsic surface smoothness of the underlying polyester substrate, as well as other properties (such as haze) of the substrate. A problem with many strippable sacrificial layers is that they impart significant additional texture or roughness or other defect to the surface of the underlying substrate which would not have been present in the absence of the strippable layer. For example, while the present inventors do not intend to be bound by theory, it is believed that the presence of gels or other particulates in the polymer matrix of strippable sacrificial layers can induce depressions in the underlying substrate layer which remain after removal of the sacrificial layer. The preferred strippable sacrificial layers of the present invention reduce such problems.
(vi) Moreover, the preferred strippable layers of the present invention can advantageously reduce the intrinsic surface defects of the film. Thus, the presence of the strippable layer during processing can improve the surface smoothness of the polyester substrate, when compared to the same polyester substrate manufactured under the same conditions in the absence of the strippable layer. Such surface defects are discussed in more detail below and include, for instance, scratches, pinch-point defects, smooth circular defects, gels, streaks, flow-lines, MD-lines, die-lines and handling marks (for instance as a result of surface imperfections in the rollers on the film line) which can arise during manufacture of the film. Pinch-point defects are a primary source of disruption to a subsequently applied layer, and their reduction is a particular objective of this invention. They have a much greater disruptive effect to subsequently applied layers than, for example, the smooth circular defects.
It is very surprising that the biaxially oriented polyester base layer and EMAA strippable layer of the present invention exhibit this combination of properties.
The biaxially oriented composite film is a self-supporting film or sheet by which is meant a film or sheet capable of independent existence in the absence of a supporting base. According to the present invention, both the polyester substrate and the strippable layer are also self-supporting.
The term "polyester" as used herein includes a polyester homopolymer in its simplest form or modified, chemically and/or physically. The term "polyester" further includes copolyesters. A copolyester may be a random, alternating or block copolyester. In a preferred embodiment, the dicarboxylic acid(s) which make up said polyester are aromatic dicarboxylic acid(s). In a preferred embodiment, the polyester comprises only one diol and only one dicarboxylic acid, which is preferably an aromatic dicarboxylic acid.
The aromatic dicarboxylic acid is preferably selected from terephthalic acid, isophathalic acid, phthalic acid, 1,4-, 2,5-, 2,6- or 2,7-naphthalenedicarboxylic acid, and is preferably terephthalic acid or 2,6-naphthalenedicarboxylic acid, preferably 2,6-naphthalenedicarboxylic acid. The diol is preferably selected from aliphatic and cycloaliphatic glycols, e.g. ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol and 1,4-cyclohexanedimethanol, preferably from aliphatic glycols. Preferably the polyester contains only one glycol, preferably ethylene glycol. The aliphatic dicarboxylic acid may be succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azeleic acid or sebacic acid. Preferred homopolyesters are polyesters of 2,6-naphthalenedicarboxylic acid or terephthalic acid with ethylene glycol. It will be appreciated by those skilled in the art that polyesters suitable for use in the present invention are water-insoluble.
The polyester resin is the major component of the substrate, and makes up at least 50%, preferably at least 65%, preferably at least 80%, preferably at least 90%, and preferably at least 95% by weight of the total weight of the substrate.
The intrinsic viscosity (IV) of the polyester from which the substrate is manufactured is typically at least about 0.58, more typically at least about 0.60, and typically no more than about 0.70. In a preferred embodiment, a PET polyester has an IV in the range of from about 0.6 to about 0.65, and a PEN polyester has an IV in the range of from about 0.58 to about 0.68. In an alternative embodiment, the substrate can be manufactured from a polyester with a higher intrinsic viscosity, for instance, having an IV of at least about 0.70, and in a further embodiment at least about 0.80, and typically no more than 0.90.
The polyester is obtainable from said dicarboxylic acid(s) or their lower alkyl (up to 6 carbon atoms) diesters with one or more diols. Formation of the polyester is conveniently effected in a known manner by condensation or ester interchange, generally at temperatures up to about 295° C. In one embodiment, solid state polymerisation may be used to increase the intrinsic viscosity to the desired value, using conventional techniques well-known in the art, for instance using a fluidised bed such as a nitrogen fluidised bed or a vacuum fluidised bed using a rotary vacuum drier.
wherein R is hydrogen, C1-C18 alkyl, C2-C6 alkyl substituted by halogen or by C1-C12 alkoxy, or is benzyl and R1 is hydrogen or methyl. R is preferably C1-C12 alkyl or benzyl, more preferably C3-C6 alkyl, and particularly hexyl. R1 is preferably hydrogen. An especially preferred UV-absorber is 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxy-phenol, which is commercially available as Tinuvin™ 1577 FF from Ciba-Additives.
The amount of UV-absorber is preferably in the range from 0.1% to 10%, more preferably 0.2% to 7%, more preferably 0.6% to 4%, particularly 0.8% to 2%, and especially 0.9% to 1.2% by weight, relative to the total weight of the substrate.
The substrate may also comprise an anti-oxidant, which may be present in addition to, or instead of, said UV-stabiliser. A range of antioxidants may be used, such as antioxidants which work by trapping radicals or by decomposing peroxide. Suitable radical-trapping antioxidants include hindered phenols, secondary aromatic amines and hindered amines, such as Tinuvin™ 770 (Ciba-Geigy). Suitable peroxide-decomposing antioxidants include trivalent phosphorous compounds, such as phosphonites, phosphites (e.g. triphenyl phosphate and trialkylphosphites) and thiosynergists (e.g. esters of thiodipropionic acid, such as dilauryl thiodipropionate). Hindered phenol antioxidants are preferred. A preferred hindered phenol is tetrakis-(methylene 3-(4′-hydroxy-3′,5′-di-t-butylphenyl propionate) methane, which is commercially available as Irganox™ 1010 (Ciba-Geigy). Other suitable commercially available hindered phenols include Irganox™ 1035, 1076, 1098 and 1330 (Ciba-Geigy), Santanox™ R (Monsanto), Cyanox™ antioxidants (American Cyanamid) and Goodrite™ antioxidants (BF Goodrich). The concentration of antioxidant present in the substrate is preferably in the range from 50 ppm to 5000 ppm of the polyester, more preferably in the range from 300 ppm to 1500 ppm, particularly in the range from 400 ppm to 1200 ppm, and especially in the range from 450 ppm to 600 ppm. A mixture of more than one antioxidant may be used, in which case the total concentration thereof is preferably within the aforementioned ranges. Incorporation of the antioxidant into the substrate may be effected by conventional techniques, and preferably by mixing with the monomeric reactants from which the polyester is derived, particularly at the end of the direct esterification or ester exchange reaction, prior to polycondensation.
The polyester substrate may further comprise any other additive conventionally employed in the manufacture of polyester films. Thus, agents such as cross-linking agents, dyes, fillers, pigments, voiding agents, lubricants, radical scavengers, thermal stabilisers, flame retardants and inhibitors, anti-blocking agents, surface active agents, slip aids, gloss improvers, prodegradents, viscosity modifiers and dispersion stabilisers may be incorporated as appropriate. Such components may be introduced into the polymer in a conventional manner. For example, by mixing with the monomeric reactants from which the film-forming polymer is derived, or the components may be mixed with the polymer by tumble or dry blending or by compounding in an extruder, followed by cooling and, usually, comminution into granules or chips. Masterbatching technology may also be employed.
The substrate may, in particular, comprise a particulate filler which can improve handling and windability during manufacture, and can be used to modulate optical properties. The particulate filler may, for example, be a particulate inorganic filler (e.g. metal or metalloid oxides, such as alumina, titania, talc and silica (especially precipitated or diatomaceous silica and silica gels), calcined china clay and alkaline metal salts, such as the carbonates and sulphates of calcium and barium). Any inorganic filler present should be finely-divided, and the volume distributed median particle diameter (equivalent spherical diameter corresponding to 50% of the volume of all the particles, read on the cumulative distribution curve relating volume % to the diameter of the particles—often referred to as the "D(v,0.5)" value) thereof is preferably in the range from 0.01 to 5 μm, more preferably 0.05 to 1.5 μm, and particularly 0.15 to 1.2 μm. Preferably at least 90%, more preferably at least 95% by volume of the inorganic filler particles are within the range of the volume distributed median particle diameter ±0.8 μm, and particularly ±0.5 μm. Particle size of the filler particles may be measured by electron microscope, coulter counter, sedimentation analysis and static or dynamic light scattering. Techniques based on laser light diffraction are preferred.
Typically, the polyester substrate is optically clear, since the majority of end-uses of the substrate demand good aesthetic appearance. Preferably the substrate has a % of scattered visible light (haze) of no more than 15%, preferably no more than 10%, preferably no more than 6%, more preferably no more than 3.5%, more preferably no more than 1.5%, and particularly no more than 1.0%, and/or a total luminous transmission (TLT) for light in the visible region (400 nm to 700 nm) of at least 80%, preferably at least 85%, more preferably at least about 90%. In this embodiment, any filler in the substrate is typically present in only small amounts, generally not exceeding 0.5% and preferably less than 0.2% by weight of a layer, and the filler is preferably silica. In this embodiment, the windability of the film (i.e. the absence of blocking or sticking when the film is wound up into a roll) is improved, without an unacceptable reduction in haze or other optical properties.
In an alternative embodiment, the substrate is opaque. An opaque film preferably exhibits a Transmission Optical Density (TOD) of at least 0.4, preferably at least 0.5, preferably at least 0.6, preferably at least 0.7, preferably at least 1.0 and preferably at least 1.5, and in one embodiment preferably at least 2.0, preferably at least 3.0, and preferably at least 4.0. An opaque film may be pigmented as required, and in one embodiment, the substrate is white, grey or black. Suitable whitening agents include a particulate inorganic filler such as those referred to hereinabove, an incompatible resin filler, or a mixture of two or more such fillers. Suitable opacifying agents include carbon black, or a metallic filler such as aluminium powder, as is known in the art.
The intrinsic viscosity of the polyester substrate is typically lower than that of the polyester from which it is manufactured, and the IV drop during the preparation of a biaxially oriented polyester film from a polyester raw material can be as much as 0.15, particularly for polyesters having a relatively high initial IV. Typically, however, the IV drop is less than about 0.06. In one embodiment, the IV of the polyester substrate is at least about 0.52, preferably at least about 0.60 and typically no more than about 0.70. Typically, a PET substrate has an IV in the range of from about 0.57 to about 0.65, and preferably at least about 0.60. A PEN substrate has an IV in the range of from about 0.52 to about 0.68, and preferably at least about 0.60. In an alternative embodiment, the polyester substrate has a higher intrinsic viscosity, for instance, having an IV of at least about 0.70, preferably at least about 0.75, and typically no more than about 0.80.
The polyester substrate preferably exhibits a low shrinkage, preferably no more than 3% at 150° C. over 30 minutes, preferably no more than 2%, preferably no more than 1.5%, and preferably no more than 1.0%, particularly in the machine (longitudinal dimension) of the film, and preferably in both dimensions of the substrate (i.e. the longitudinal and transverse dimensions). The substrate should not undergo unacceptable dimensional distortion, such as curl, when subjected to subsequent processing conditions, for instance processing involving elevated temperature (such as sputtering to deposit a subsequent layer), which may be used for instance in the manufacture of electronic display devices.
The strippable layer comprises (and suitably consists, or consists essentially, of) an ethylene-methacrylic acid (EMAA) copolymer. In a preferred embodiment, the methacrylic acid is present in the copolymer in the range of from about 2 to about 15 wt % of the copolymer, more preferably in the range of from about 2 to about 10 wt %, and preferably in the range of from about 7 to about 10 wt %. In an alternative embodiment, the methacrylic acid is present in the copolymer in the range of from about 2 to less than about 7 wt %. The copolymers are preferably branched and preferably random. Suitable EMAA copolymers include Nucrel® resins (DuPont), particularly Nucrel® grades 0411HS and 0908HS. Optionally, the copolymer has been partially or completely reacted with metallic salts, enabling the formation of ionic cross-links between the acid groups within a chain, or between neighbouring chains. Such copolymers are known as ionomers, defined herein as a polymer made up primarily of non-polar repeat units with a minor proportion (typically no more than about 15 wt %) of metal salt-containing units of methacrylic acid. Preferred ionomers are the copolymers of ethylene and methacrylic acid partially or completely neutralised with alkali metals or zinc. Suitable commercially available compounds include Surlyn® resins (DuPont), particularly grades 1605 and 1652. The metal cation is typically selected from alkali metals such as lithium and sodium. Zinc or magnesium may also be used. Typically, the metal cation is present at no more than about 15 mol %. Preferably, the EMAA copolymer is not an ionomer and does not contain metal ions.
In a preferred embodiment, the melting temperature of the EMAA copolymer is at least about 90° C., and preferably no more than about 250° C., preferably no more than about 200° C., preferably no more than about 150° C., more preferably no more than about 120° C. In a further preferred embodiment, the VICAT softening point of the EMAA copolymer is at least about 60° C., and typically in the range from about 60° C. to about 110° C., more typically in the range from about 70° C. to about 100° C.
Formation of the composite film is effected by conventional co-extrusion techniques well-known in the art. In general terms the process comprises the steps of extruding layers of molten polymer at a temperature within the range of from about 280 to about 300° C., quenching the extrudate and orienting the quenched extrudate. Orientation may be effected by any process known in the art for producing an oriented film, for example a tubular or flat film process. Biaxial orientation is effected by drawing in two mutually perpendicular directions in the plane of the film to achieve a satisfactory combination of mechanical and physical properties. In a tubular process, simultaneous biaxial orientation may be effected by extruding a thermoplastics polymer tube which is subsequently quenched, reheated and then expanded by internal gas pressure to induce transverse orientation, and withdrawn at a rate which will induce longitudinal orientation. In the preferred flat film process, the film-forming polymer is extruded through a slot die and rapidly quenched upon a chilled casting drum to ensure that the substrate polyester is quenched to the amorphous state. Orientation is then effected by stretching the quenched extrudate in at least one direction at a temperature above the glass transition temperature of the substrate polyester. Sequential orientation may be effected by stretching a flat, quenched extrudate firstly in one direction, usually the longitudinal direction, i.e. the forward direction through the film stretching machine, and then in the transverse direction. Forward stretching of the extrudate is conveniently effected over a set of rotating rolls or between two pairs of nip rolls, transverse stretching then being effected in a stenter apparatus. Stretching is generally effected so that the dimension of the oriented film is from 2 to 5, more preferably 2.5 to 4.5 times its original dimension in the or each direction of stretching. Typically, stretching is effected at temperatures higher than the Tg of the polyester, preferably about 15° C. higher than the Tg. Greater draw ratios (for example, up to about 8 times) may be used if orientation in only one direction is required. It is not necessary to stretch equally in the machine and transverse directions although this is preferred if balanced properties are desired.
A stretched film may be, and preferably is, dimensionally stabilised by heat-setting under dimensional support at a temperature above the glass transition temperature of the substrate polyester but below the melting temperature thereof, to induce the desired crystallisation of the polyester. During the heat-setting, a small amount of dimensional relaxation may be performed in the transverse direction (TD) by a procedure known as "toe-in". Toe-in can involve dimensional shrinkage of the order 2 to 4% but an analogous dimensional relaxation in the process or machine direction (MD) is difficult to achieve since low line tensions are required and film control and winding becomes problematic. The actual heat-set temperature and time will vary depending on the composition of the film and its desired final thermal shrinkage but should not be selected so as to substantially degrade the toughness properties of the film such as tear resistance. Within these constraints, a heat set temperature of about 180 to 245° C. is generally desirable. After heat-setting the film is typically quenched rapidly in order induce the desired crystallinity of the substrate polyester.
In one embodiment, the film may be further stabilized through use of an on-line relaxation stage. Alternatively the relaxation treatment can be performed off-line. In this additional step, the film is heated at a temperature lower than that of the heat-setting stage, and with a much reduced MD and TD tension. The tension experienced by the film is a low tension and typically less than 5 kg/m, preferably less than 3.5 kg/m, more preferably in the range of from 1 to about 2.5 kg/m, and typically in the range of 1.5 to 2 kg/m of film width. For a relaxation process which controls the film speed, the reduction in film speed (and therefore the strain relaxation) is typically in the range 0 to 2.5%, preferably 0.5 to 2.0%. There is no increase in the transverse dimension of the film during the heat-stabilisation step. The temperature to be used for the heat stabilisation step can vary depending on the desired combination of properties from the final film, with a higher temperature giving better, i.e. lower, residual shrinkage properties. A temperature of 135 to 250° C. is generally desirable, preferably 150 to 230° C., more preferably 170 to 200° C. The duration of heating will depend on the temperature used but is typically in the range of 10 to 40 seconds, with a duration of 20 to 30 seconds being preferred. This heat stabilisation process can be carried out by a variety of methods, including flat and vertical configurations and either "off-line" as a separate process step or "in-line" as a continuation of the film manufacturing process. Film thus processed will exhibit a smaller thermal shrinkage than that produced in the absence of such post heat-setting relaxation.
Co-extrusion is effected either by simultaneous coextrusion of the respective film-forming layers through independent orifices of a multi-orifice die, and thereafter uniting the still molten layers or, preferably, by single-channel coextrusion in which molten streams of the respective polymers are first united within a channel leading to a die manifold, and thereafter extruded together from the die orifice under conditions of streamline flow without intermixing thereby to produce a multi-layer film, which is oriented and heat-set as hereinbefore described. It will therefore be appreciated by those skilled in the art that the strippable sacrificial layer is disposed directly on one or both surface(s) of said polyester substrate, i.e. without any intermediate layer.
The thickness of the composite film is preferably in the range of from about 5 to about 750 μm, and more preferably no more than about 500 μm, and typically between about 12 μm and 250 μm. The thickness of the substrate layer is preferably in the range of from about 5 to about 500 μm, and typically between about 12 μm and 300 μm. The thickness of the strippable layer is preferably in the range of from about 2 to about 200 μm, and typically no more than about 100 μm, and typically between about 5 μm and 50 μm, and in preferred embodiment between about 5 and 25 μm. It is preferred that the substrate layer makes up greater than 50%, preferably at least 60%, preferably at least 70%, and preferably at least 80% of the total thickness of the composite film, but typically no more than about 95% of the total thickness. In one embodiment, the substrate layer makes up from about 75 to about 95% of the total thickness of the composite film. The strippable layer typically ends up as waste film and becomes uneconomical if it is too thick, but the strippable layer must have a sufficient thickness and mechanical strength to allow an easy and clean peel.
The adhesive strength of the strippable sacrificial layer to the polyester substrate is such that the peel force is preferably in the range of from about 5 to about 250 gF (grams-Force), preferably at least about 10 gF, preferably at least about 20 gF, preferably at least about 35 gF, typically at least about 50 gF, and typically no more than about 200 gF, measured as described herein.
In the present invention, the intrinsic surface roughness of the polyester substrate after removal of the strippable layer is primarily analysed by two methods.
The first method analyses the intrinsic "micro-roughness", i.e. the background surface roughness between major surface defects, measured as described herein and preferably characterised by the conventional parameters of Ra and/or Rq. Preferably, the polyester substrate exhibits an Ra value, of less than 10 nm, preferably less than 7 nm, preferably less than 5 nm, preferably less than 2 nm, and preferably less than 1 nm.
(a) Pinch-point defects are characterised by a crater either side of a central peak (see FIG. 1A). It is believed that such defects are caused by inclusions which reside relatively near the surface of the substrate, which generate greater localised stress/strain regions during the stretching steps of film manufacture.
(2) Depressions are characterised by a central crater, sometimes associated with raised areas around the crater (see FIG. 2). The inventors believe such defects are caused primarily by imperfections (such as gels or gel-like features) in the strippable sacrificial layer.
(3) Gel-like features or streaks are characterised by globular surface features or elongated regions of raised ridges sometimes associated with shallow valleys either side of the ridge (see FIG. 3). The inventors believe such defects result from extrusion events, such as die-lip edge flow disturbances and extruded degraded polymer.
(i) The number (NDT) of all defects with a vertical amplitude, orthogonal to the film plane (i.e. peaks and troughs), of greater than about 0.25 μm and less than about 30 μm above and/or below the mean surface (as defined herein) is no more than 1000, preferably no more than 750, preferably no more than 500, preferably no more than about 400, preferably no more than about 300, preferably no more than 200, preferably no more than 100, preferably no more than 75, preferably no more than 50, and preferably no more than 25, per 31×33 cm area of film surface.
(ii) The number (NPP) of pinch-point peaks (1a) with a peak height of greater than about 0.25 μm and less than about 30 μm is no more than 100, preferably no more than 80, preferably no more than 70, preferably no more than 60, preferably no more than 50, preferably no more than 40, preferably no more than 30, and preferably no more than 20, per 31×33 cm area of film surface.
(iii) The number (NGS) of gel-like features or streaks (3) with a peak height of greater than about 0.25 μm and less than about 30 μm is no more than 10, preferably no more than 5, preferably no more than 2, and preferably zero, per 31×33 cm area of film surface.
is preferably at least 2, preferably at least 4, preferably at least 6, preferably at least 7, preferably at least 10.
is at least 2, preferably at least 4, preferably at least 6, preferably at least 7, preferably at least 10.
If desired, the techniques described herein to measure the intrinsic macro-roughness can also be used to measure the lateral dimensions of the defects attributable to extrinsic roughness. Such extrinsic defects are defined herein as irregularly shaped features having positive topography (i.e. features which are above the mean surface level of the film) with substantially no negative topography (i.e. features which are below the mean surface level of the film). If desired, the film can be characterised in terms of the number (NE) of extrinsic defects (as defined above) with a minimum lateral dimension of greater than 7.14 μm, per 31×33 cm area of film surface, and measured by single frame interferometry (SFI) in the LAM technique as described hereinbelow.
The composite film of the present invention may be advantageously used in any application which requires a high-quality defect-free polyester substrate surface exhibiting high cleanliness and high smoothness. Thus, the composite film may be advantageously used in to provide a clean polyester substrate suitable for use in the manufacture of electronic or opto-electronic devices, such as electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic (PV) cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally), particularly flexible such devices. Other applications include the provision of optical films, medical devices and decorative films.
A subsequently applied layer may be a barrier layer, i.e. a layer which provides high resistance to gas and solvent permeation, which is typically applied in a sputtering process at elevated temperatures. A barrier layer may be organic or inorganic, should exhibit good affinity for the layer deposited thereupon, and be capable of forming a smooth surface. Materials which are suitable for use to form a barrier layer are disclosed, for instance, in U.S. Pat. No. 6,198,217.
A subsequently applied layer may be a conductive layer, which is often applied in a sputtering process at elevated temperatures.
According to a further aspect of the invention, there is provided the use of a layer comprising an ethylene-methacrylic acid (EMAA) copolymer as a strippable sacrificial layer in a coextruded biaxially oriented composite film further comprising a polyester substrate layer, as described herein, wherein said EMAA layer is disposed on one or both surfaces of said polyester substrate layer.
(ii) reducing the intrinsic surface defects of said polyester substrate, relative to the same polyester substrate manufactured under the same conditions in the absence of said strippable sacrificial layer.
(ii) removing said strippable sacrificial layer from said substrate prior to use or further processing of said substrate.
(iii) applying said functional layer to said substrate.
According to a further aspect of the invention, there is provided an electronic or opto-electronic device, optical film, medical device or decorative film derived from the coextruded biaxially oriented composite film defined herein from which said strippable sacrificial layer has been removed.
According to a further aspect of the invention, there is provided an electronic or opto-electronic device comprising a polyester substrate layer, wherein said polyester substrate layer is derived from a coextruded biaxially oriented composite film comprising a polyester substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer comprising an ethylene-methacrylic acid (EMAA) copolymer as defined herein, wherein said strippable sacrificial layer has been removed from said composite film prior to or during incorporation into or manufacture of said electronic or opto-electronic device.
(ii) removing said strippable sacrificial layer from said substrate prior to the use of said substrate in said electronic or opto-electronic device or medical device, or in or as said optical or decorative film.
The electronic or opto-electronic device may further comprise a barrier or conductive layer disposed on said polyester substrate. Of particular interest are electronic or opto-electronic devices selected from electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic (PV) cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally), particularly flexible such devices.
(i) Clarity is evaluated by measuring total luminance transmission (TLT) and haze (% of scattered transmitted visible light) through the total thickness of the film using an M57D spherical hazemeter (Diffusion Systems) according to the standard test method ASTM D1003.
(ii) Transmission Optical Density (TOD) is measured using a Macbeth Densitometer TR 927 (obtained from Dent and Woods Ltd, Basingstoke, UK) in transmission mode.
ηred=reduced viscosity (in dL/g), which is equivalent to (ηre1−1)/c (also expressed as ηsp/c where ηsp is the specific viscosity).
(iv) Thermal shrinkage is assessed for film samples of dimensions 200 mm×10 mm which were cut in specific directions relative to the machine and transverse directions of the film and marked for visual measurement. The longer dimension of the sample (i.e. the 200 mm dimension) corresponds to the film direction for which shrinkage is being tested, i.e. for the assessment of shrinkage in the machine direction, the 200 mm dimension of the test sample is oriented along the machine direction of the film. After heating the specimen to the predetermined temperature of 150° C. (by placing in a heated oven at that temperature) and holding for an interval of 30 minutes, it was cooled to room temperature and its dimensions re-measured manually. The thermal shrinkage was calculated and expressed as a percentage of the original length.
(v) Melt Flow Index (MFI) is measured herein according to ASTM D1238 or ISO-1133, depending on the polymer used. The EMAA copolymers used in the present invention are analysed in accordance with ASTM D1238 at a temperature of 190° C. and a mass of 2.16 kg. Suitable MFI ranges for the EMAA copolymers used in the present invention are in the range from about 0.5 to about 50 g/10 min, preferably from about 1 to about 25 g/10 min, typically from about 2 to about 20 g/10 min, and more typically from about 2 to about 15 g/10 min.
(vi) Layer thickness is measured by Mercer 122D gauge.
(vii) MD lines are localised high spots or circumferential bands on reels caused by poor film thickness profile and/or reel buckling. Die lines are straight lines in the machine direction that remain in the same location on the melt during filming. Flow lines are lines in the machine or transverse direction that do not remain in the same location on the melt during filming; they are thought to be caused by the transient or migratory presence of polymeric spherical gels (cross-linked) which cause a disturbance in the polymer curtain. The presence of each of these defects in the film was assessed qualitatively by visual inspection by the naked eye (i.e. without a microscope).
(viii) Scratches are low amplitude (typically up to about 1000 nm deep and up to about 1000 nm wide) elongated depressions in the film. They are thought to result from imperfections in the die and rollers used in film manufacture, or from film handling. Scratches are classified herein as intrinsic surface defects, and their presence in the film was assessed qualitatively by optical microscopy (at 2.5× magnification). Of course, extrinsic surface roughness resulting from handling damage during storage or transport can also include the scratching of the film surface, but such defects are not measured herein.
Grade 1: strippable layer removable in its entirety, with no sign of residue from the strippable layer remaining on the substrate.
Grade 2: strippable layer removable in its entirety, with spots of residue visible on the substrate.
Grade 3: strippable layer fractures when peeled.
Averaging Parameter—Roughness Average (Ra): the arithmetic average of the absolute values of the measured height deviations within the evaluation area and measured from the mean surface.
Averaging Parameter—Root Mean Square Roughness (Rq): the root mean square average of the measured height deviations within the evaluation area and measured from the mean surface.
Peak-to-Valley value (PV95): this parameter may be obtained from the frequency distribution of positive and negative surface heights as a function of surface height referenced to the mean surface plane. The value PV95 is the peak-to-valley height difference which envelops 95% of the peak-to-valley surface height data in the distribution curve by omitting the highest and lowest 2.5% of datapoints. The PV95 parameter provides a statistically significant measure of the overall peak-to-valley spread of surface heights.
(xii) The macro-roughness of the substrate surface was analysed by large-area metrology (LAM) using a Wyko SSP9910 Single Frame Interferometer, also equipped with both PSI and VSI capability, in order to arrive at values for the parameters of Maximum Profile Peak Height (Rp) and Maximum Profile Crater Depth (Rv), defined as the height (or depth) of the highest peak (or crater/trough) in the evaluation area, as measured from the mean surface. The measurement area of the film was 31×33 cm.
The first step of the technique is to conduct measurements in the SFI (Single Frame Interferometry) mode to produce a low magnification (×2.5) map in order to determine the location of major surface defects in the film area studied. In the SFI mode, the modulation threshold was set at 1%, and the cut-off threshold (another user-determined parameter selected to define the minimum vertical amplitude constituting a major surface defect) was set at 0.25 μm above the mean surface. The skilled man will appreciate that for some laterally smaller defects the pixel size is large in comparison with the peak area in SFI mode, and so at this low magnification the measured peak height measured (which is averaged over the pixel) may be weighted downwards as a result of the larger pixel area. Thus, intrinsic defects in SFI mode are defined as those having a peak height of at least 0.25 μm and spanning greater than 2 adjoining pixels (1 pixel=3.57 μm); and extrinsic defects were considered as those spanning at least 3 adjoining but not necessarily co-linear pixels (7.14 μm in at least one lateral dimension). Intrinsic and extrinsic defects were differentiated herein according to the reflectance profile (extrinsic defects exhibit a reflectance profile which is different from the polyester matrix and typically exhibit a lower reflectance). Intrinsic and extrinsic defects may also be differentiated according to the lateral profile of the defect. The first step in the technique produces (x,y)-coordinates of all the user-defined defects in the film surface.
(xiii) Further surface analysis was conducted using XPS and static SIMS spectroscopy, using a Kratos "Axis Ultra" instrument and an lon-T of "ToFSIMS IV" instrument, respectively. The objective of the analyses was to determine the presence of any residue from the strippable sacrificial layer on the polyester substrate layer after stripping of the strippable layer.
X-ray photoelectron spectroscopy (XPS) is a quantitative spectroscopic technique which measures the elemental composition, empirical formula, chemical and electronic states of elements that exist within a material. XPS spectra are obtained by using X-rays to irradiate a material while measuring the kinetic energy and number of the emitted electrons from the top 1 to 10 nanometers of the material. The detection limit is around 1 atom in 1000 (excluding H, i.e. 0.1 atomic percent or 1000 ppm).
Secondary ion mass spectrometry (SIMS) is a technique involving sputtering material surfaces with a primary ion beam and collecting and analyzing emitted secondary ions. A mass spectrometer is used to measure the secondary ions to determine the elemental and/or molecular composition of the material surface. Static SIMS is the process used in atomic monolayer analysis of material surfaces, and has a typical sampling depth of about 1 nm. SSIMS is not generally suitable as a quantitative technique for individual analyses, but can usefully be used to compare a series of similar sample surfaces via analysis of peak area ratios as a measure of the relative amounts of identified species present in those surfaces.
Freshly peeled surfaces were generated by cutting and tearing the coated polyester substrate. Both sides of the peel were analysed. Small pieces (ca. 1 cm×1 cm) were cut from the main sample for analysis (ca. 10 cm×15 cm) using clean stainless steel scissors. Samples for analysis were mounted on to suitable sample holders using small pieces of silicone-free double-sided tape. The samples for analysis were handled using clean stainless steel tweezers at all times.
For the XPS analysis, data were recorded from a ca. 300 μm×700 μm elliptical area using monochromated Alka X-rays. A survey scan was recorded at 160 eV pass energy to identify all elements present on the surface; these were also used to quantify the surface composition. High-resolution spectra were also recorded at 20 eV pass energy in order to identify the chemical environment for specific elements. The results are presented as relative atomic percentage compositions. The expanded uncertainty (Y) in atomic percentage units, associated with a measured atomic percentage composition (X) was calculated for polymer and organic materials analysed using survey scan conditions from the expression Y=mX+c where m=0.027 and c=0.14. The reported expanded uncertainty is based on a standard uncertainty multiplied by a coverage factor of k=2, providing a level of confidence of approximately 95%.
For the SSIMS analysis, positive and negative ion spectra were recorded from fresh areas of each sample with high mass resolution (m/Δm ca. 6000) up to m/z 2000 in all cases.
(xiv) Melting temperature is determined by differential scanning calorimetry (DSC) according to ASTM D3418.
(xv) The VICAT softening point is determined by ASTM D1525.
The invention is further illustrated by the following examples. The examples are not intended to limit the invention as described above. Modification of detail may be made without departing from the scope of the invention.
Attempts were made to manufacture a series of coextruded films having an AB layer structure. A polymer composition comprising unfilled PET was co-extruded with a series of polymers (see Table 1), cast onto a cooled rotating drum, optionally pre-heated to a temperature of 80 to 81° C. and stretched in the direction of extrusion to approximately 3.4 times its original dimensions. Where possible, the film was heated to a temperature of about 95° C., passed into a stenter oven at a temperature of 110° C. where the film was stretched in the sideways direction to approximately 3.6 times its original dimensions, and then the biaxially-stretched film was heat-set by successive heating in three zones of defined temperature (225, 225 and 190° C.) by conventional means at a film-web speed of 10.8 m/min; approximate residence time in each of the three zones was 40 seconds. Table 1 characterises the manufacturing processes and the resulting films.
Where it was possible to manufacture a biaxially oriented composite film which exhibited adequate mechanical strength and little or no inter-layer delamination during manufacture, the film was analysed using the hand-peel test described herein. In this test, Examples 1 to 4 and 9 satisfied grade 1; Example 5 satisfied grade 2, while the remaining Examples either were categorised as grade 3 or 4 or were unable to be manufactured as a biaxially oriented composite film. The peel force of Examples 1 to 5 and 9 was then measured according to the method described herein, and the results are set out in Table 2 below.
The haze, TLT and Ra of the polyester substrate immediately after peeling were examined for Examples 1 to 5 and 9, and the results are reported in Table 2 below, along with a control film consisting of the mono-layer PET film corresponding to the substrate of the Examples. The haze values of Examples 1 to 5 were excellent, whereas the haze for Example 9 was significantly worse. Similarly, the Ra values for surface micro-roughness of Examples 1 to 5 were all much lower than that of Example 9, indicating that the polypropylene strippable layer had disadvantageously imparted some additional texture or roughness or other defect during manufacture or storage of the composite film, or during the act of stripping.
The presence of scratches on the film surface was assessed by optical microscopy, as described herein. The surface of the control film exhibited a significant number of scratches, whereas the freshly peeled surfaces of Examples 1 to 5 and 9 exhibited none.
The experiments demonstrate that the EMAA strippable layers uniquely and unexpectedly show the required combination of properties.
The films of Examples 1 and 2 were also analysed by the XPS and SSIMS techniques described hereinabove in order to determine the presence of any chemical residue on the substrate immediately after peeling away the strippable layer. In both analyses, no evidence for any chemical residue of the strippable layer was found on the PET substrate for either Example 1 or Example 2.
In the XPS analyses, the chemical composition (measured as relative atomic percentage composition) and high-resolution spectra of the surface of the freshly peeled PET substrate corresponded to those typically observed for PET film. Thus, the measured level for the relative atomic percentage of carbon of the freshly peeled surface fell within the typical range for PET surfaces of 72.0-76.4 atomic %. The C1s and O1s high resolution spectra from the surface of the freshly peeled PET substrate were also typical of clean PET, showing C—C, C—O, O—C═O in the expected proportions.
In the SSIMS analyses, the spectra recorded from the surface of the freshly peeled PET substrate were consistent with the presence of a pristine PET layer.
The EMAA-coated examples from the first set of experiments were investigated further, in particular by measuring the intrinsic surface roughness by the LAM technique described hereinabove. Example 25 (Nucrel®0908HS) and Example 26 (Nucrel®0411HS) are coextruded films manufactured according to Examples 1 and 2. Example 24 is a control example which consists of a coextruded bi-layer PET film in which both layers have the same composition as the substrate layer in Example 1, and otherwise processed in the same way as Example 1. The total thickness, and each layer thickness, of Example 24 were the same as those in coextruded films of Example 25 and 26, in order to provide similarity in processing conditions. Thus, the film of Example 24 is made up of a thin PET layer A and a thick PET layer B. The surfaces of the polyester substrate in Examples 25 and 26 were analysed directly after stripping the sacrificial EMAA layer by hand. The surface of the thin PET layer A of the polyester substrate of control Example 24 was analysed directly after manufacture. The results are presented in Table 3 below. The values for NDT, NPP and NGS are derived from PSI scans. The values for Δ-NDT, Δ-NPP and Δ-NGS are calculated for Examples 25 and 26 using Example 24 as the control film. All three examples were manufactured on a standard film-forming line and no special steps were taken to provide to a clean environment or to reduce the amount of air-borne dust and debris.
The data in Table 3 demonstrate that not only does the strippable layer protect the polyester substrate from extrinsic debris (and the damage that results from such extrinsic debris), it also unexpectedly improves (i.e. decreases) the intrinsic surface roughness of the substrate.
The EMAA-coated examples were investigated further using the LAM technique. Example 27 is a further control example and consists of a monolayer of unfilled PET of the same composition as the PET layers in the coextruded bi-layer film of (control) Example 24. Example 28 is a coextruded film corresponding to Example 26, comprising a substrate layer of the same unfilled PET of Example 27, and a strippable sacrificial layer of Nucrel®0411HS. The PET layer in each of Examples 27 and 28 is the same thickness and is derived from the same (primary) extruder. The surface of the PET substrate in Example 28 was analysed as before and directly after stripping the sacrificial layer by hand, and then compared with the control surface of the PET monolayer film of Example 27 which was analysed directly after manufacture. The results are presented in Table 4 below. The absolute defect numbers in Table 4 are lower than in Table 3 because additional steps were taken during film manufacture to provide a clean environment. Nevertheless, the data confirm the unexpected result observed from the comparison of Examples 24 and 26.
1. A coextruded biaxially oriented composite film comprising a polyethylene terephthalate substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer, wherein said strippable sacrificial layer consists of an ethylene-methacrylic acid (EMAA) copolymer, and wherein said one or both surfaces exhibit(s) an Ra of less than 10 nm upon removal of the strippable sacrificial layer(s), wherein the strippable sacrificial layer has a thickness in the range of from about 2 to about 200 μm and the ethylene-methacrylic acid (EMAA) copolymer has a melt flow index of 0.5 to 50 g/10 min, measured according to ASTM D1238.
2. The film according to claim 1 wherein the methacrylic acid is present in the EMAA copolymer in the range of from about 2 to about 15 wt % of the copolymer.
3. The film according to claim 1 wherein the EMAA copolymer is an ionomer comprising a minor proportion of metal salt-containing units of methacrylic acid.
4. The film according to claim 3 wherein the metal is selected from alkali metals, magnesium and zinc.
5. The film according to claim 1 wherein the EMAA copolymer is an ionomer selected from copolymers of ethylene and methacrylic acid partially or completely neutralised with metal cation(s).
6. The film according to claim 5 wherein the metal is selected from alkali metals, magnesium and zinc.
7. The film according to claim 1 wherein the thickness of the substrate layer is in the range of from about 5 to about 500 μm and/or the thickness of the strippable layer is in the range of from about 2 to about 100 μm.
8. The film according to claim 1 wherein the adhesive strength of the strippable sacrificial layer to the polyethylene terephthalate substrate layer is such that the peel force is in the range of from about 20 to about 250 gF.
9. The film according to claim 1 wherein the polyethylene terephthalate substrate layer has a haze of no more than 15% and/or a total luminous transmission (TLT) for light in the visible region (400 nm to 700 nm) of at least 80%.
10. The film according to claim 1 wherein the polyethylene terephthalate substrate layer exhibits a shrinkage of no more than 3% at 150° C. over 30 minutes.
12. The method according to claim 11 wherein the wherein the ethylene-methacrylic acid (EMAA) copolymer consists of units of ethylene and units of one or both of methacrylic acid and metal salt-containing units of methacrylic acid.
13. The method according to claim 11 wherein the EMAA copolymer is not an ionomer and does not contain metal ions.
15. The method according to claim 14 wherein said functional layer is a conductive layer or barrier layer.
16. The method according to claim 14 wherein the ethylene-methacrylic acid (EMAA) copolymer consists of units of ethylene and units of one or both of methacrylic acid and metal salt-containing units of methacrylic acid.
17. The method according to claim 14 wherein the EMAA copolymer is not an ionomer and does not contain metal ions.
18. An electronic or opto-electronic device, optical film, medical device or decorative film derived from a coextruded biaxially oriented composite film as defined in claim 1 from which said strippable sacrificial layer(s) has/have been removed, wherein said one or both surfaces exhibit(s) an Ra of less than 10 nm upon removal of the strippable sacrificial layer(s).
19. The electronic or opto-electronic device according to claim 18 comprising a polyethylene terephthalate substrate layer derived from the coextruded composite film comprising said polyethylene terephthalate substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer, wherein said strippable sacrificial layer is removed from said composite film prior to or during incorporation into or manufacture of said electronic or opto-electronic device.
20. The electronic or opto-electronic device according to claim 18, further comprising a barrier or conductive layer, wherein said barrier or conductive layer is disposed on said polyethylene terephthalate substrate layer in said electronic or opto-electronic device.
21. The electronic or opto-electronic device according to claim 18, selected from electroluminescent (EL) display devices, electrophoretic display devices, photovoltaic cells and semiconductor devices.
22. The electronic or opto-electronic device, optical film, medical device or decorative film according to claim 18 wherein the ethylene-methacrylic acid (EMAA) copolymer consists of units of ethylene and units of one or both of methacrylic acid and metal salt-containing units of methacrylic acid.
23. The electronic or opto-electronic device, optical film, medical device or decorative film according to claim 18 wherein the EMAA copolymer is not an ionomer and does not contain metal ions.
[NGS of said control polyester substrate]/[(NGS) of surface of said polyester substrate layer upon removal of said strippable sacrificial layer].
[NDT of said control polyester substrate]/[(NDT) of surface of said polyester substrate layer upon removal of said strippable sacrificial layer].
[NPP of said control polyester substrate]/[(NPP) of surface of said polyester substrate layer upon removal of said strippable sacrificial layer].
27. A method of using a layer consisting of an ethylene-methacrylic acid (EMAA) copolymer as a strippable sacrificial layer in a coextruded biaxially oriented composite film further comprising a polyethylene terephthalate substrate layer, as defined in claim 1, wherein said EMAA layer is disposed on one or both surfaces of said polyethylene terephthalate substrate layer, said method comprising stripping the layer consisting of the ethylene-methacrylic acid (EMAA) copolymer from the polyethylene terephthalate substrate layer.
28. The method according to claim 27 wherein the ethylene-methacrylic acid (EMAA) copolymer consists of units of ethylene and units of one or both of methacrylic acid and metal salt-containing units of methacrylic acid.
29. The method according to claim 27 wherein the EMAA copolymer is not an ionomer and does not contain metal ions.
30. The film according to claim 1 wherein the ethylene-methacrylic acid (EMAA) copolymer consists of units of ethylene and units of one or both of methacrylic acid and metal salt-containing units of methacrylic acid.
31. The film according to claim 1 wherein the EMAA copolymer is not an ionomer and does not contain metal ions.
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of the Eagle XL Series.
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text:
Sergio Ramos's Net Worth: How much money does he have?
By Mensah Courage September 9, 2022
Sagio Ramos Garcia is a Spanish professional footballer who was born on March 30th, 1986 in Camas, Spain.
He currently plays as a defender in Paris Saint-Germain F. C.
He has a height of 6 ft(1.83m)
Ramos is known to currently hold the record as the most capped player in the history of the Spanish national team. He also holds the record for most international victories for Spain with 131 matches won.
Sagio Ramos is married to Pilar Rubio. Their children are;Alejandro Ramos Rubio, Macro Ramos Rubio, Sagio Ramos Rubio, and more.
Sergio Ramos's Net Worth
He is a player who has a net worth of $80 million dollars and an annual salary of $25 million.
Ramos makes 13.7 million a year while playing as a defender for Paris Saint-Germain.
He made 11.6 million GBP(2022).

redpajama_set_name: RedPajamaCommonCrawl


text:
Michael Herron Talks About Absentee Voting in a Pandemic
The elections expert comments in advance of the Sept. 8 New Hampshire state primary.
With an expected increase in absentee voting during the COVID-19 pandemic, any disruption in U.S. Postal Service deliveries could have severe consequences for the 2020 election, says Michael Herron, the Remsen 1943 Professor of Government and chair of the Program in Quantitative Social Science.
Herron has worked extensively on U.S. elections and voting procedures, conducting research on balloting for more than a decade in Florida, North Carolina, Ohio, New Hampshire, Maine, and other states. One of his findings is that, even under normal circumstances, a large number of absentee ballots arrive on the day of the election or one day before.
Michael Herron
In Maine before the pandemic, for example, Herron and his co-author, Professor Daniel Smith of the University of Florida, found that about 10 percent of absentee ballots arrived within 24 hours of election day—and in some cases more than 10 percent. In Florida in 2018, about 200,000 ballots arrived on or one day before election day. Both Florida and Maine reject absentee ballots that arrive late.
According to the National Conference of State Legislatures, 32 of the 50 states—including New Hampshire—reject ballots that arrive after election day.
"A lot of ballots are barely on time, so a small delay would have large consequences," Herron says. "The fear is, if there are disruptions in postal service, a large number of ballots could be rejected."
In Florida in 2018, if mail delivery had been delayed by one day, the number of rejected ballots would have been greater than the margin of victory in the races for governor and U.S. senator, both of which went to recounts, Herron says.
Even when an election is not close, the ramifications of rejected ballots are profound, he says. "One ballot wrongfully rejected is an affront to the right to vote."
There have been mounting calls for absentee ballots to be counted if they are postmarked by election day, Herron says. Currently, 18 states and the District of Columbia count mail-in ballots that are postmarked by election day, including Alaska, California, Nevada, and New Jersey.
Advice for Absentee Voting
Other common reasons absentee ballots are rejected, Herron says, arise from procedural mistakes, such as the voter not signing the ballot, not using the correct envelope, or including ballots of multiple household members in a single envelope.
"My advice to anyone voting absentee this year is, be very careful to sign your ballot, read the return instructions carefully, and mail it early—don't risk being late."
And while voting early is a good strategy in a time when there is the danger of mail delays coupled with a high volume of absentee ballots due to the pandemic, it is not ideal, Herron says.
"The call to vote early has a downside. Voters don't get to consider late developments—we want citizens to have as much information as possible when they vote," he says.
All these factors underline the importance of patience on the part of voters, elected officials, and candidates, so that the upcoming November election can proceed in an orderly and efficient way, Herron says. "I think that people really need to give up on the idea of elections being called during an election night broadcast. The last thing we want is to impose unreasonable deadlines on certifying the presidential election when we will have so many vote-by-mail ballots."
While much of the attention on election night will be on one race, there is much more at stake, he says.
"It is not just the presidential election. There are races up and down the ballot in every state that could be very close, and we don't want to risk a significant number of ballots being invalidated."
The Local Ballot
The New Hampshire state primary is Tuesday, Sept. 8. There are eight Democrats and no Republicans running for the four house seats in Grafton County District 12 representing Hanover and Lyme, including two Dartmouth-affiliated candidates: Riley Gordon '22, a Dartmouth government major, and Russell Muirhead, the Robert Clements Professor of Democracy and Politics. Dartmouth student Victoria Xiao '22, who dropped out of the race in July, is also listed on the ballot but she has said if elected, she will not serve. Incumbent Rep. Garrett Muscatel '20 graduated in June and moved out of state, stepping down in the last months of his two-year term.
There are two Democrats and one Republican running for the New Hampshire senate district 5 seat, including one Dartmouth faculty member. Beatriz Pastor, a professor of Spanish and comparative literature, is running as a Democrat. Incumbent Sen. Martha Hennessey '76 announced in May that she would not seek a third term.
Voting Procedures
In-person voting will take place from 7 a.m. to 7 p.m. on Tuesday, Sept. 8, at Leverone Field House, 26 South Park Street, Hanover.
The Hanover town clerk's office reminds residents that, due to COVID-19 election provisions, all voters can request an absentee ballot. Absentee ballots must be received by the Hanover town clerk no later than 5 p.m. on election day. To be counted, ballots must be delivered by mail, delivered to the town hall drop box, or handed to designated election workers outside the polling place by the 5 p.m. deadline.
Those voting by mail must place their marked ballot in the affidavit envelope provided by the Hanover town clerk. This affidavit envelope must be signed on the designated line in order to be counted. The ballot in the sealed and signed affidavit envelope must then be placed in the outer envelope provided, which is already addressed to the Hanover town clerk. This envelope includes the individual's voting address and name as listed in the town clerk's office.
William Platt can be reached at william.c.platt@dartmouth.edu.


"Between Here and There" An Installation by the Artist Ernst Kraft. | Marbella Marbella – Adelante!
Exhibition room: Sala Manual Barbadillo, Av.comandante benítez 7, Malaga. Opening hours: Tuesday – Sunday from 17 – 20 h. (or by appointment: Call at opening hours 952 22 57 74) Opening 1st of August 2013.at 20.00 h.
Dutch artist Ernst Kraft, who has made large-scale in and outdoor installations in Europe and South America, some of them still visible by satellite photos of Google Earth, will present to the public a new construction, titled "Between here and there" (or "Entre el aquí y el allá", in its original Spanish title) in the Malaga contemporary art gallery Sala Manuel Barbadillo.
Jacob and the ladder, the tower of Babel, the Aymara "Gate of the sun" in Bolivia, or the voyage of Columbus, they are examples of this dream-desire to reach the other level, the other side.
In former installations, like the Stone maze in Passau, Germany and the Transparent maze, the crux was finding the road, the path… In his new work Kraft reflects about the transcendence of spaces by dividing them. One gateway is enough to divide the world in two; it takes just one stairway to create a space above and below.
The artist choose for his construction plexiglass, stating that a gate, even when showing what is behind, still divides and unites even equal looking spaces, just like a transparent and moving stairway creates different levels.
The installation will be open to the public throughout the month of August.
VITALUX – Because the Exceptional is Seldom Enough!
Disclaimer: The views, opinions and positions expressed within this guest article are those of the author Ernst Kraft alone and do not represent those of the Marbella Marbella website. The accuracy, completeness and validity of any statements made within this article are not guaranteed. We accept no liability for any errors, omissions or representations. The copyright of this content belongs to Ernst Kraft and any liability with regards to infringement of intellectual property rights remains with the author.


EXCUSE FROM SERVICE: Jurors will only be excused if serving will cause an undue or extreme physical or financial hardship. Reasons for excusal: (1) Mental or physical hardship (doctor's statement required on form available in Clerk's Office or downloadable below; (2) Financial hardship (does the juror work for an employer who is not required to compensate juror and declines to do so voluntarily) (affidavit required); (3) The juror is a caregiver for personal care of a person without a substitute caregiver available (affidavit required).
An affidavit is a document that the requesting Juror must be sworn to, thereby confirming the facts stated within the affidavit.
Any juror who requests disqualification pursuant to the above (Nos. 1-3) shall report to the Circuit Court Clerk's Office at least seven (7) days before their report date to complete the appropriate affidavit and/or to deliver an appropriate doctor's statement.
Failure to provide satisfactory documentation may result in the denial of a request to be excused.
Pursuant to TCA 22-1-103, Effective January 1, 2009, all competent adults summoned must serve unless excused.
For sole professional practitioners: A former absolute exemption has been eliminated.


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VCs portal
PoS Universe
Tetra Staking Wallet
Orbs network status
V1 Rewards Dashboard
About Orbs
Why Proof-Of-Stake Systems Can Benefit From External Oversight
By Tal Kol in The Orbs Project
The final season of Game of Thrones is currently airing. The long-anticipated conclusion to the epic battle over The Iron Throne – rule over the Seven Kingdoms of Westeros.
Consider the "final episode" (don't worry, this is all made up, no spoilers here): The last battle is upon us; The northern armies led by the Starks approach the battlefield; the armies of Daenerys are there too; and so are the Lannister armies, led by Cersei. John Snow, ever the responsible adult, proposes an alternative: "Instead of bloodshed, why don't we just have a democratic election?" Everybody nods in agreement. The soldiers cheer. Credits.
Cersei volunteers to run the elections. House Lannister places voting booths in all reaches of Westeros and every citizen in the Seven Kingdoms writes their desired ruler's name on a ballot. The ballots are then all shipped to King's Landing where Cersei counts the votes and announces the winner.
The process goes through and Cersei is excited to announce that she won. Would you trust these elections?
As it turns out, not all democracies are equal. If you're interested to see the leaderboard, check out how every country ranks at the 2018 Democracy Index:
Most of the countries in the list, notably those with the low ranking in red, openly pride themselves as being democratic and celebrate periodic elections where the populous get a chance to choose their leaders. But evidently, some democratic processes are prone to manipulation allowing existing leaders to maintain their positions of power regardless of where the populous tries to shift it.
Pseudo-democracies are not the only ones with problems. There are issues with the top 15% in the list. Take a look at the US for example, number 25 in the list and the historical epitome of modern democracy (no cynicism intended). "Gerrymandering" is one example of a US problem where the political party in power can draw lines between voting districts that are favorable to itself.
Democracies are complicated to implement, the nuances are plenty. And through their analysis and criticism, we have the chance to improve on them. To design processes that better guarantee their purity and withstand corruption.
Proof-of-Stake systems behave in a very similar way. Voting, or the degree of influence, is based on ownership of stake instead of citizenship, but otherwise, the process is prone to similar nuances and must be designed to withstand manipulation. We must also continuously criticize PoS implementations so we have the chance to improve them.
And surely – there is plenty of criticism of PoS in the crypto world. The spectrum ranges from belief that the problems of PoS are solvable, debating the pros and cons of various implementations, to outright skepticism whether PoS can work at all.
Take for example the views of Joseph Lubin, co-founder of Ethereum and founder of ConsenSys, from the recent Deconomy: "How about EOS? As has been debated endlessly, a platform controlled by 21 crypto bros is just not all that decentralized. They can collude and censor if they wish. Governments and other well-resourced actors can bribe them or force them to act against their will and against the well being and the security of the people using the platform".
Let's try to analyze Lubin's argument why EOS, the dominant PoS implementation to date, is flawed. The 21 elected nodes of EOS "can collude and censor if they wish." But what would happen if these nodes indeed collude against the interests of the entire network? If the effects aren't minor, like a decline in token price, stakeholders will spring to action and just replace the colluding nodes. Elections on EOS rely on stake of the entirety of the network, and the majority of stake is assumed to be honest. So where's the risk?
The risk is only if the colluding nodes could prevent their own replacement. The core of the matter, in my opinion, is that they are the ones running the elections. They are the ones counting the votes.
This isn't all that different from Cersei counting the Westeros votes by herself.
The majority of PoS implementations are closed systems. The voting process is part of the protocol and the protocol is executed by nodes running the network, that are chosen according to the protocol. There is an essence of circular trust here.
What about Proof-of-Work algorithms? Is PoW prone to the same circular trust weakness?
Not really. Albeit its shortcomings in terms of efficiency and cost, PoW has several wonderful properties making it an excellent choice for decentralized trust. The primary of which is strong objectivity.
Objectivity (I'm using Vitalik's definition here) means that a new node coming onto the network with no knowledge except (i) the protocol definition and (ii) the set of all blocks and other "important" messages that have been published can independently come to the exact same conclusion as the rest of the network on the current state.
What does this mean? Let's say I'm an observer of the network and I want to be convinced that the state presented by the nodes in the network is indeed the "correct" one. Am I able to verify everything all by myself?
I can easily verify the amount of work in PoW by myself (that's the point, hashes are easy to verify but hard to produce). And since PoW algorithms work according to the longest chain rule, I can objectively know which competing portrayals of the state (competing forks) is the right one.
You can say, in a sense, that the work itself is external to the system, and since the system is not closed anymore and does not vouch for itself using itself only, it becomes very trustworthy.
The objectivity property is unique to PoW (and similar methods like VDFs) but missing from most PoS implementations, leading to the circular trust weakness of a closed system.
Why is the lack of objectivity painful in PoS networks? The core offering of these networks is trust. As clients of the network, we should be able to verify the correctness of the relevant state and transactions. Verifying the correctness of data requires knowledge of the elected validators, since they are the ones allowed to sign blocks. In order to verify the elected validators, one can attempt to verify the election calculations. However, the calculations and the votes reside on the chain itself, signed by the same validators that we're trying to verify in the first place. This cyclic dependency prevents the client from objectively verifying the correctness of their data. There are workarounds like trusting one of the validators, but these solutions are suboptimal. When our core offering is trust, we should hold ourselves to a higher standard.
If we could add objectivity to PoS, this will provide us with the missing external oversight – and give us a PoS implementation that is much more trustworthy. This will also give a pretty good answer to Lubin's fears that the elected nodes in the system can collude and censor (particularly regarding the voting process that elects them).
So, is it possible to use PoW for this purpose without affecting the efficiency of PoS? There is a straightforward way to do this and it's actually pretty simple. All you have to do is store the votes externally – preferably on a different decentralized network that is based on PoW.
Going back to our Westeros example, this would mean that the voting booths where the ballots are stored, will no longer be under Lannister control. The voting booths will be controlled by somebody else (external to the Game of Thrones universe) that will guarantee the sanctity of the elections. Once the elections have been made, whichever king is elected is free to rule inside Westeros without external involvement.
The last part is important. If we are to maintain the efficiency of PoS, the rest of the network operation – mainly executing smart contracts on the PoS network, storing the state under consensus, doing everything a blockchain does – must not rely on PoW anymore. The only thing PoW will provide is an external guarantee of objectivity that will let any observer confirm that the PoS network is not colluding and has indeed been purely elected.
This is how this approach is different from layer 2 solutions. Second layers delegate all security and trust to the base layer. The base layer can overturn smart contract results, for example, or override state modifications made by the second layer. Our approach will still make the PoS system retain its own security and trust and thus hold value of its own.
So how would that work in practice?
The natural choice for a PoW network to store election votes is Ethereum. It is popular and obviously secure enough (in terms of hash power) as a standard of trust to be sufficiently disconnected incentives-wise from our own PoS network, and its smart contracts offer the flexibility for a proper integration.
If storing election votes on Ethereum is a simple solution, why don't we see more PoS blockchains taking this approach?
One reason may be ego. Many PoS systems position themselves as potential "Ethereum-killers" – the scalable place to run apps until Ethereum reaches its own scalability milestones. Elections are also a crucial part of your solution, and using somebody else for a crucial part may "leak" some of your own perceived value to this somebody. We don't share these views at Orbs. We see enormous value in existing ecosystems that have already been built. Not everything has to be replaced. We attempt to use existing infrastructures where they show advantage in order to make our own solution better.
Another reason this approach is difficult for many PoS blockchains is the utility of the token used for staking. Most PoS systems rely on the token for settlement related to the main purpose of these platforms – running apps. In other words, app developers use the token to pay nodes for running their apps.
Performing staking on Ethereum will also mean the utility of payment for app execution will have to be done on Ethereum as well. Since most PoS systems rely on a per-transaction gas model and aim for very high transaction throughputs, this would make Ethereum fees (in Ether) extremely high and inefficient – and thus miss the whole point of the efficiency of PoS.
This is another place where the Orbs architecture comes to our advantage. We've made a product decision long ago (see the original Position Paper) to have apps pay monthly subscription fees to Orbs nodes for executing their apps, instead of a per-transaction gas model. This product decision brings multiple benefits crucial for a pragmatic app execution platform such as predictable fees and the ability for apps to subsidize their users' fees to encourage adoption (the same way Facebook subsidizes your Messenger costs and doesn't charge you for their infrastructure fees per sending each chat message). This is part of our strategy to bring the AWS product experience to app developers in blockchain.
Apps on Orbs run on virtual chains that have dedicated and isolated resources. Subscriptions for resource dedication in virtual chains are paid monthly (or even longer if you want to guarantee future data availability). Making the payment once a month on Ethereum means Ether fees are negligible. There will be no impact on the efficiency of PoS.
The Orbs network is a PoS-based blockchain. It relies on the ORBS token which is used for paying infrastructure fees for running apps and also for staking and electing validators. The voting process is performed on Ethereum and thus ORBS is an ERC20 token.
Orbs is not a layer 2 for Ethereum though. Orbs does not delegate security and trust to Ethereum, and holds its own value in its permissionless validator pool based on the PoS ecosystem of the ORBS token and its incentives model. Ethereum provides an external objective guarantee that any observer can verify that elected nodes on Orbs are indeed the ones the stakeholders voted for. For this important governance function, Ethereum is a crucial component in the Orbs design.
Apps running on Orbs are not executed on Ethereum, allowing them to fully enjoy the efficiency and decentralization in PoS, extremely low operation fees, extremely high scale and many other Orbs-specific benefits such as governance isolation, smart contracts in any language and more.
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Q: Approximating sample mean by expected value Suppose that $X\sim \mathrm{Bin}(n,p)$. Then $E[X]=np$.
I know that, by the Law of Large Numbers, if a have a sample $X_1$ $,...,X_n $, then $\displaystyle\lim_{x\to\infty} P(|\overline{X} - p| < \epsilon) = 1, \forall \epsilon > 0$.
So in a sense, we can say that for large enough $n$, $X\approx np$ (right?)
My question is: suppose that I have a function of $X$, say $f(X, \theta)$, in which $\theta$ is not stochastic. Suppose that it is too complicated for me to compute $E[f(X, \theta)]$. Can I approximate this function by computing $f(np, \theta)$? That is, can I say that  $\displaystyle\lim_{x\to\infty}$ $P(|E[f(X, \theta] - f(np, \theta)| < \epsilon) = 1, \forall \epsilon > 0$?
My intuition tells me that yes, but I'm not sure this is correct.

A: If you mean $X \approx np$ where $X \sim \text{Bin}(n,p)$ then that is not true. I think you meant $\overline{X}$, so that $\overline{X} \to np$ as $n \to \infty$ (by the SLLN). So if you had a continuous function $f(\overline{X}, \theta)$, then for large $n$, this would converge to $f(np, \theta)$ by the continuous mapping theorem (this theorem also works for convergence in probability).

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