Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
  • G02B5/3083—Birefringent or phase retarding elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
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  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/16—Dicarboxylic acids and dihydroxy compounds
  • C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
  • C08G63/181—Acids containing aromatic rings
  • C08G63/185—Acids containing aromatic rings containing two or more aromatic rings
  • C08G63/187—Acids containing aromatic rings containing two or more aromatic rings containing condensed aromatic rings
  • C08G63/189—Acids containing aromatic rings containing two or more aromatic rings containing condensed aromatic rings containing a naphthalene ring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/78—Preparation processes
  • C08G63/82—Preparation processes characterised by the catalyst used
  • C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/56—Organo-metallic compounds, i.e. organic compounds containing a metal-to-carbon bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
  • C08L67/03—Polyesters derived from dicarboxylic acids and dihydroxy compounds the dicarboxylic acids and dihydroxy compounds having the carboxyl- and the hydroxy groups directly linked to aromatic rings
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/06—Unsaturated polyesters
  • C08L67/07—Unsaturated polyesters having terminal carbon-to-carbon unsaturated bonds
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/08—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of polarising materials
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
  • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
  • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2250/00—Layers arrangement
  • B32B2250/24—All layers being polymeric
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
  • B32B2264/10—Inorganic particles
  • B32B2264/105—Metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/30—Properties of the layers or laminate having particular thermal properties
  • B32B2307/308—Heat stability
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
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• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
  • B32B2307/418—Refractive
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
  • B32B2307/42—Polarizing, birefringent, filtering
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/51—Elastic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
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  • B32B2307/00—Properties of the layers or laminate
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  • B32B2307/708—Isotropic
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2457/00—Electrical equipment
  • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays
  • B32B2457/202—LCD, i.e. liquid crystal displays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2551/00—Optical elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2551/00—Optical elements
  • B32B2551/08—Mirrors
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
  • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C08J2333/10—Homopolymers or copolymers of methacrylic acid esters
  • C08J2333/12—Homopolymers or copolymers of methyl methacrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
  • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising

Definitions

• Multilayer polymeric optical films are widely used for various purposes, including as mirrors and polarizers. These films often have extremely high reflectivity, while being lightweight and resistant to breakage. Exemplary applications for these films include compact electronic displays, including liquid crystal displays (LCDs) placed in mobile telephones, personal data assistants, computers, televisions and other devices.
• LCDs liquid crystal displays
• One type of polymer that is useful in creating polarizer or mirror films is a polyester.
• a polyester-based polarizer includes a stack of polyester layers of differing composition.
• a polyester is prepared by reactions of one or more different dicarboxylate monomers (e.g., compounds with two or more carboxylic acid or ester functional groups) with one or more different glycol monomers (e.g., compounds with two or more hydroxy functional groups).
• One example of a polyester useful in multilayer optical films is polyethylene naphthalate (PEN) which can be made, for example, by reactions of naphthalene dicarboxylic acid (or ester) with ethylene glycol.
• PEN polyethylene naphthalate
• the present disclosure relates to birefringent polyester films that exhibit low optical absorption, high birefringence and low haze. These birefringent polyester films may also exhibit a high melt elasticity that can be similar to other polymer film layers for co-extrusion into multilayer films.
• the birefringent polyester film may include naphthalate units, ethylene units, a titanate compound, a planar branching unit, and 1 to 80 ppm metal content.
• the birefringent polyester film has an out-of-plane birefringence of at least 0.1 at 633 nm and a Tan Delta value in a range from 3 to 8.
• a birefringent polyester film includes naphthalate units, ethylene units, a titanate compound, 0.1 to 2 mol% planar branching unit, based on total mol% of naphthalate and branching units, and 1 to 80 ppm metal content.
• the birefringent polyester film has an out-of-plane birefringence of at least 0.1 at 633 nm.
• a multilayer film in another aspect, includes a first birefringent polyester layer having an out-of-plane birefringence of at least 0.10 at 633 nm, and a second polymer layer having a lower birefringence than the first birefringent polyester layer and disposed on the first birefringent polyester layer.
• the polyester layer includes naphthalate units, ethylene units, a titanate compound, 0.1 to 2 mol% planar branching unit, based on total mol% of naphthalate and branching units, and 1 to 80 ppm metal content.
• a multilayer optical film in another aspect, includes a plurality of first birefringent polyester layers each having an out-of-plane birefringence of at least 0.10 at 633 nm and a metal content of less than 100 ppm, and having a first Tan Delta value at 280 degrees Celsius and a shear rate of 10 sec "1 , and a plurality of second isotropic acrylate layers alternating between first birefringent polyester layers and each second isotropic acrylate layer having a second Tan Delta value at 280 degrees Celsius and a shear rate of 10 sec "1 .
• the first Tan Delta value is within 30% or less of the second Tan Delta value.
• Index of refraction refers to a refractive index of a material in the plane of the material with respect to light at 633 nm and normal or near normal (for example, 8 degrees or less off-set) incidence, unless otherwise indicated.
• Birefringent refers to the indices of refraction in orthogonal x, y, and z directions are not all the same.
• the axes are selected so that x and y axes are in the plane of the layer and the z axis is normal to the plane of the layer and typically corresponds to the thickness or height of the layer. Birefringence values are reported with respect to light at 633 nm and normal incidence, unless otherwise indicated.
• High refractive index and “low refractive index” are relative terms; when two layers are compared in both in-plane directions of interest, the layer that has a greater average in-plane refractive index is the high refractive index layer, and the layer that has a lower average in-plane refractive index is the low refractive index layer.
• Polymer refers to, unless otherwise indicated, polymers and copolymers (i.e., polymers formed from two or more monomers or comonomers, including terpolymers, for example), as well as copolymers or polymers that can be formed in a miscible blend by, for example, coextrusion or reaction, including transesterification, for example. Block, random, graft, and alternating polymers are included, unless indicated otherwise.
• Polymer refers to a polymer that contains an ester functional group in the main polymer chain. Copolyesters are included in the term "polyester”.
• Tan Delta value is the ratio of viscous modulus (G") to elastic modulus (G') and refers to the viscoelasticity of the polymer, where a lower Tan Delta value indicates a more elastic material. Tan Delta values reported or referred to herein are determined with an Ares Plate-on-Plate rheometer (commercially available from TA Instruments, New Castle, DE, USA) at a shear rate of 10 sec "1 at 280 degrees Celsius.
• the present disclosure relates to birefringent polyester films that exhibit low optical absorption, high birefringence and low haze. These birefringent polyester films may also exhibit a high melt elasticity that can be similar to other polymer film layers for co-extrusion into multilayer films.
• birefringent polyester films may have a low metal content such as less than 100 ppm metal or less than 80 ppm metal or less than 30 ppm metal.
• the birefringent polyester film may include naphthalate units, ethylene units, a titanate compound, and a planar branching unit.
• the birefringent polyester film has an out- of-plane birefringence of at least 0.1 and a Tan Delta value in a range from 3 to 8.
• PEN Polyethylene naphthalate
• PEN Polyethylene naphthalate
• PEN is known to have orders of magnitude higher absorption than other polymers (such as acrylates or olefins) utilized in multilayer film constructions.
• PEN is also known to have a different melt elasticity than other polymers (such as acrylates or olefins) utilized in multilayer film constructions.
• These rheological differences tend to result in layer control and uniformity issues, especially in the transverse or cross- web direction of a multilayer film construction.
• This disclosure describes PEN polymer and articles of film made therefrom which still provide the high levels of birefringence desired for multi-layer film applications, but also provides this performance with the previously unrealized performance combination of high % transmission (low absorption), low haze, and high melt elasticity. While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the examples provided below.
• a birefringent polyester film includes naphthalate units, ethylene units, a titanate compound, 0.1 to 2 mol% planar branching unit, based on total mol% of naphthalate and branching units, and 1 to 80 ppm metal content.
• the birefringent polyester film has an out- of-plane birefringence of at least 0.1 or at least 0.15 or at least 0.2 at 633 nm.
• the birefringent polyester film exhibits a low metal content.
• the birefringent polyester film may exhibit a total metal content of less than 100 ppm, or less than 80 ppm or less than 30 ppm or less than 10 ppm or less than 5 ppm.
• the birefringent polyester film may exhibit a total metal content in a range from 1 to 100 ppm or in a range from 1 to 80 ppm or in a range from 1 to 30 ppm or in a range from 1 to 10 ppm or in a range from 1 to 5 ppm.
• the birefringent polyester film may exhibit a total metal content of 4 ppm, or 3 ppm, or 2 ppm or 1 ppm.
• Birefringent polyester film and particularly polyethylene naphthalate benefit from a low metal content. It is believed that one or both of optical absorption and haze is reduced by reducing the amount of metal in the polyester film.
• the metal content includes a titanate compound or titanium.
• the metal content is primarily, sustainably, or only a titanate compound or titanium.
• the titanate compound may be utilized as a polymerization catalyst for the production of polyester. Any useful titanate compound can be utilized.
• the titanate compound may be a titanium alkoxide.
• titanium compound or titanium alkoxide examples include, tetra-n-propyl titanate, tetra-i -propyl titanate, tetra-n-butyl titanate, tetra- n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and tetrabenzyl titanate.
• One useful titanate compound is tetra-n-butyl titanate (TBT).
• polyester polymeric materials may be described herein with reference to the overall composition, that is, 100 mol% units derived from 50 mol% carboxylate or acid units and 50 mol% glycol or diol units. Polyester polymeric materials may also be described herein with reference to the mol% of carboxylate or acid subunits and mol% glycol or diol subunits (that is, 100 mol% of carboxylate or acid subunits are reacted with 100 mol% of glycol or diol subunits in the preparation of the copolyester).
• the polyester is generally made by reactions of naphthalene dicarboxylic acid (or ester) with ethylene glycol and at least one additional comonomer that contributes a planar branching unit. In some embodiments, the polyester is generally made by reactions of naphthalene dicarboxylic acid (or ester) with ethylene glycol and at least one additional comonomer that contributes branched or cyclic C4-C10 alkyl units. In further,
• the polyester is generally made by reactions of naphthalene dicarboxylic acid (or ester) with ethylene glycol and at least a comonomer that contributes a planar branching unit and a comonomer that contributes branched or cyclic C4-C10 alkyl units.
• Suitable naphthalene carboxylate monomer molecules for use in forming the naphthalate subunits of the polyester include naphthalene carboxylate monomers that have two or more carboxylic acid or ester functional groups.
• the naphthalene carboxylate monomer may include naphthalene dicarboxylic acid such as 2,6-naphthalene dicarboxylic acid monomer and isomers thereof.
• the naphthalene carboxylate monomer may include naphthalene dicarboxylic ester such as 2,6-naphthalene dicarboxylic ester monomer and isomers thereof.
• the 2,6-naphthalene dicarboxylic acid (or ester) monomer and/or isomers thereof is employed at a concentration such that 95 to 100 mol % of the carboxylate subunits comprise naphthalate subunits.
• at least 96, 97, 98, 99, 99.25, 99.5 or 99.75 mol % of the carboxylate subunits comprise naphthalate subunits.
• the birefringent polyester layer or film may include a planar branching unit. The planar branching unit increases the molecular weight of the polyester material while maintaining the orientation or birefringence of the birefringent polyester layer or film.
• the planar branching unit may be present in the birefringent polyester layer or film in an amount ranging from 0.1 to 2 mol% based on total mol% of naphthalate and branching units forming the polyester material. In many embodiments the planar branching unit may be present in the birefringent polyester layer or film in an amount ranging from 0.1 to 1 mol% based on total mol% of naphthalate and branching functional units forming the polyester material. In some embodiments, the planar branching unit may be present in the birefringent polyester layer or film in an amount ranging from 0.2 to 0.8 mol% based on total mol% of naphthalate and branching units forming the polyester material. The planar branching unit may be derived from trimesic acid or trimellitic acid, for example.
• Suitable glycol monomer molecules for use in forming ethylene subunits of the polyester include ethylene glycol.
• the ethylene glycol is employed at a concentration such that 95 to 100 mol % of the diol subunits comprise ethylene subunits.
• at least 97.5, 98, 98.5, 99, or 99.5 mol % of the diol subunits comprise ethylene subunits.
• the birefringent polyester layer or film may include a branched or cyclic C4-C10 alkyl unit that is derived from a branched or cyclic C4-C10 alkyl glycol such as neopentyl glycol, cyclohexanedimethanol, and mixtures thereof.
• the branched or cyclic C4-C10 alkyl unit may be present in the birefringent polyester layer or film in an amount less than 2 mol% or less, or less than 1.5 mol%, or less than 1 mol%, based on total mol% of ethylene and branched or cyclic C4-C10 alkyl units used to from the polyester material.
• the birefringent polyester layer or film may exhibit a reduced Tan Delta value.
• a conventional PEN layer or film may exhibit a Tan Delta value in a range from 18 to 25, as measured at 280 degrees Celsius and at 10 sec "1 shear rate, for examples.
• Utilizing the planar branching unit described herein may reduce the Tan Delta value in a range from 3 to 8, as measured at 280 degrees Celsius and at 10 sec "1 shear rate, for example.
• a multilayer film may include a first birefringent polyester layer having an out-of- plane birefringence of at least 0.10 or at least 0.15 or at least 0.2 at 633 nm, and a second polymer layer having a lower birefringence than the first birefringent polyester layer and disposed on the first birefringent polyester layer.
• the polyester layer is described above.
• the second polymer layer can be isotropic or have a birefringence of less than 0.05 or less than 0.01.
• isotropic refers to indices of refraction (measured at 633 nm) in orthogonal x, y, and z directions are all the within 0.02 of each other, or within 0.01 of each other, or substantially equal.
• the second polymer layer includes acrylate units. In some embodiments the second polymer layer includes olefin units.
• the first birefringent polyester layer and the second polymer layer may each have a Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 within 3 or within 2 or within 1 of each other, or within 30% or within 25% or within 20% or within 10% of each other.
• An exemplary second polymer is a polyacrylate such as polymethlymethacrylate
• PMMA for co-extrusion
• V044 Plexiglas from Arkema, Paris, FR
• Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 of about 7.9.
• Another exemplary second polymer is co-PMMA for co-extrusion (commercially available under the trade designation Atoglas 51 OA from Arkema, Paris, FR), having a Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 of about 5.0.
• An exemplary second polymer is polyolefin such as polypropylene (PP) for co-extrusion (commercially available under the trade designation SR549 PP from Lyondell-Bassell, Houston, TX), having a Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 of about 2.9.
• the first birefringent polyester layer may have a Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 in a range from 2 to 9, or in a range from 3 to 8, or in a range from 4 to 7.
• the multilayer film can have a low haze value.
• the multilayer film may have a haze value of 2% or less or 1.5% or less or 1% or less or 0.5% or less.
• the multilayer film can have a high visible light transmission.
• the multilayer film may have a high visible light transmission of 85% or greater, or 90% or greater
• a multilayer optical film includes a plurality of first birefringent polyester layers each having an out-of-plane birefringence of at least 0.10, or at least 0.15, or at least 0.2 at 633 nm and a metal content of less than 100 ppm, or less than 80 ppm, or less than 30 ppm, or less than 10 ppm, or less than 5 ppm, and having a first Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 , and a plurality of second isotropic layers (that may include acrylate) alternating between first birefringent polyester layers and each second isotropic layer having a second Tan Delta value at 280 degrees Celsius at a shear rate of 10 sec "1 .
• the first Tan Delta value is within 30% or less, or within 25% or less, or within 20%) or less of the second Tan Delta value.
• the second polymer layer can be isotropic or have a birefringence of less than
• the second polymer layer includes acrylate units.
• the first birefringent polyester layer and the second isotropic polymer layer may each have a Tan Delta value, at 280 degrees Celsius at a shear rate of 10 sec "1 , within 3, or within 2, or within 1, of each other, or within 30%, or within 25%, or within 20%, or within 10% of each other.
• PMMA has a Tan Delta value, at 280 degrees Celsius at a shear rate of 10 sec "
• the first birefringent polyester layer may have a Tan Delta value, at 280 degrees Celsius at a shear rate of 10 sec "1 , in a range from 2 to 9 or in a range from 3 to 8 or in a range from 4 to 7.
• the reflective and transmissive properties of multilayer optical film are a function of the refractive indices of the respective layers and the thicknesses and thickness distribution of the layers.
• Each layer can be characterized at least in localized positions in the film by in-plane refractive indices n x , n y , and a refractive index n z associated with a thickness axis of the film. These indices represent the refractive index of the subject material for light along mutually orthogonal x-, y-, and z-axes, respectively.
• the refractive indices are controlled by judicious materials selection and processing conditions.
• a multilayer film is made by co-extrusion of a large number, e.g. tens or hundreds of layers of two alternating polymers A, B, optionally followed by passing the multilayer extrudate through one or more layer multiplication device(s), and a casting die, thus casting a web and then stretching or otherwise orienting the extrudate to form a final film.
• the resulting film is typically composed of many hundreds of individual layers or microlayers whose thicknesses and refractive indices are tailored to provide one or more reflection bands in desired region(s) of the spectrum, such as in the visible or near infrared.
• the multilayer optical film may include at least 100 layers, or at least 300 layers, or at least 400 layers, or at least 500 layers.
• the multilayer optical film may include a number of layers in a range from 400 to 800, or from 500 to 700, or from 550 to 650.
• the multilayer optical film may include at least 700 layers, or at least 800 layers, or at least 900 layers, or at least 1000 layers.
• the multilayer optical film may include a number of layers in a range from 800 to 1500, or from 900 to 1200, or from 1000 to 1150.
• the layers may alternate between the first birefringent polyester layers and the second isotropic layers.
• the multilayer optical film can have a low haze value.
• the multilayer optical film may have a haze value of 2%, or less or 1.5%, or less or 1%, or less or 0.5% or less.
• the multilayer optical film can form a mirror film.
• the mirror film may reflect at least 99.0%, or at least 99.1%, or at least 99.2%, or at least 99.3%, or at least 99.4%, or at least 99.5%, or at least 99.6% of incident light.
• This reflection property may be described as "hemispheric reflectivity," Rhemi( ), meaning the total reflectivity of a component (whether a surface, film, or collection of films) when light (of a certain wavelength or wavelength range of interest) is incident on it from all possible directions.
• the component is illuminated with light incident from all directions (and all polarization states, unless otherwise specified) within a hemisphere centered about a normal direction, and all light reflected into that same hemisphere is collected.
• the ratio of the total flux of the reflected light to the total flux of the incident light for the wavelength range of interest yields the hemispheric reflectivity or Rhemi( ).
• the first birefringent polyester layers may have an out-of-plane birefringence of at least 0.20 at 633 nm
• the second isotropic (for example, acrylate) layers may have an out-of-plane refractive index (measured at 633 nm) within 0.05, or within 0.04, or within 0.03, or within 0.02, or within 0.01, of an out-of-plane refractive index of the first birefringent polyester layers.
• Trimesic trimesic acid— Alfa Aesar (Ward Hill, MA)
• a room temperature 10 gallon stainless steel, oil jacketed batch reactor was charged with amounts of monomers and catalysts indicated in Table 1 below. The contents were pressurized to 239.2 kPa utilizing nitrogen and heated to 257 °C. During transesterification, the resultant methanol and water by-product was removed via separation column. After the methanol and water were removed, the batch pressure was reduced to atmospheric pressure. In some cases, the stabilizer TEPA was added to the batch at this point. The batch was then heated to 280 °C and the pressure was reduced (via vacuum) to below 500 Pa.
• Table 2 lists the resultant composition of the polymers in these examples.
• Monomers are represented on a molar basis in which the ester and acid functional monomers are grouped to add to 100% and the glycol functional monomers are grou] add to 100 %. Catalysts and stabilizers are listed on a PPM basis.
• Resin kinetics are compared by the amount of time (in minutes) it takes for the resin to achieve the desired viscosity build associated with a 0.48 IV target.
• Viscoelasticity of the resins is compared utilizing the calculated Tan Delta value of these resins, also generated from the 280 degree Celsius nitrogen purged plate-on-plate Ares rheometer at a shear rate of 10 sec "1 .
• Quench morphology is measured via Differential Scanning Calorimetry (DSC) test method. The materials were tested using DSC (Q2000 commercially available from TA Instruments, New Castle, Del.). A sample of about 5-10 mg was used for each resin. In particular, the resins are heated (melted) to 300 degree Celsius and then cooled at a controlled rate (at either 5 degree C/min or 10 degree C/min). Quench morphology can be characterized by measuring the energy deviation associated with the resultant
• Table 4 below provides Tan Delta values for exemplary polymer resins (acrylates or olefins), that can be co-extruded with the polyester resins described herein.
• An exemplary acrylate is a PMMA commercially available under the trade designation V044 Plexiglas PMMA commercially from Arkema (Paris, FR).
• Another exemplary acrylate is a co-PMMA commercially available under the trade designation Atoglas 51 OA co-PMMA commercially from Arkema (Paris, FR).
• An exemplary olefin is PP is SR549 PP available from Lyondell-Bassell (Houston, TX). Table 4
• the polyester resins described herein may have a Tan Delta value in range from about 3 to about 8 to provide a similar melt or viscoelasticity as the a coextruded resin to provide uniform physical and optical properties across the machine and transverse direction of a coextruded film.
• the example polyesters were then extruded through a twin-screw extruder, necktube, feedblock and die, with a progressive temperature profile peaking at 282 °C.
• the extruded material was cast and quenched into 20 mil films.
• the cast web films were evaluated for transmission performance and % haze.
• RI Refractive Index
• in-plane birefringence In order to measure the birefringent nature of a uniaxially stretched film, in-plane birefringence is used. In-plane birefringence concerns the difference of the indices (nx and ny) in the orthogonal in-plane directions. More specifically for a uniaxially stretched film, in-plane birefringence refers to the difference between the stretching direction and the non-stretching direction. For example, assuming a film is uniaxially stretched in MD direction, the in-plane birefringence is expressed as the following:
• nx is the refractive index in the stretching direction (in this case, MD)
• ny is the non-stretching direction (in this case, TD).
• the in-plane birefringence is relatively small and sometimes close to zero if balanced. Instead, out-of-plane birefringence is more indicative of the birefringent nature of the stretched film.
• Out-of-Plane Birefringence An ou t: In order to measure the birefringent nature of a biaxially oriented film, out-of-plane birefringence is used. Out-of-plane birefringence concerns the difference between average of in-plane indices (MD and TD) and the index normal to the film (TM). Out-of-plane birefringence can be expressed as following:
• nx is the refractive index (RI) in the machine direction (MD) and ny is the refractive index (RI) in the transverse direction (TD) and nz is the refractive index (RI) in the thickness direction (TM).
• Haze measurements were conducted using a BYK Haze-gard Haze Meter from BYK-Gardner GmbH, Geretsried, Germany.
• the condensation reaction by-product ethylene glycol
• ethylene glycol was continually removed via separation column until a polymer resin achieved the desired viscosity build associated with a polyethylene naphthalate having an intrinsic viscosity of about 0.50 dL/g, as measured in 60/40 wt% phenol/o-dichlorobenzene at 30 °C, was produced.
• the condensation reaction was unable to proceed to a viscosity build associated with a -0.50 dL/g endpoint, topping out at a reduced viscosity, resulting in a polymer with reduced physical properties.
• Table 7 lists the resultant composition of the polymers in these examples.
• Monomers are represented on a molar basis in which the ester and acid functional monomers are grouped to add to 100% and the glycol functional monomers are grouped to add to 100 %. Catalysts and stabilizers are listed on a PPM (parts per million) basis.
• Resin kinetics are also compared in Table 7 by the amount of time (in minutes) it takes for the resin to achieve the desired viscosity build associated with a 0.48 IV target. As Example A-6 did not reach endpoint, a result of n.a. (not applicable) is indicated. Complex viscosity as measured by an Ares plate-on-plate viscometer at 100 sec "1 at 280°C is included for reference.

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