WO2007145812A2 - Diffusely-reflecting polariser and method of making same - Google Patents
Diffusely-reflecting polariser and method of making same Download PDFInfo
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- WO2007145812A2 WO2007145812A2 PCT/US2007/012672 US2007012672W WO2007145812A2 WO 2007145812 A2 WO2007145812 A2 WO 2007145812A2 US 2007012672 W US2007012672 W US 2007012672W WO 2007145812 A2 WO2007145812 A2 WO 2007145812A2
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- fibrils
- fiber
- discontinuous
- fibers
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
- G02B5/0257—Diffusing elements; Afocal elements characterised by the diffusing properties creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
- G02B5/0236—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0268—Diffusing elements; Afocal elements characterized by the fabrication or manufacturing method
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0273—Diffusing elements; Afocal elements characterized by the use
- G02B5/0284—Diffusing elements; Afocal elements characterized by the use used in reflection
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3008—Polarising elements comprising dielectric particles, e.g. birefringent crystals embedded in a matrix
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133528—Polarisers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2913—Rod, strand, filament or fiber
- Y10T428/2933—Coated or with bond, impregnation or core
Definitions
- This invention relates to the field of diffusely reflecting polarizers and polarizing displays and to a fiber useful therein.
- LCD's Liquid crystal displays
- AMLCD's for avionics applications, computer monitors and HDTV LCD's
- Much of this flexibility comes from the light valve nature of these devices, in that the imaging mechanism is decoupled from the light generation mechanism. While this is a tremendous advantage, it is often necessary to trade performance in certain categories such as luminance capability or light source power consumption in order to maximize image quality or affordability. This reduced optical efficiency can also lead to performance restrictions under high illumination due to heating or fading of the light-absorbing mechanisms commonly used in the displays.
- lamp power levels must be undesirably high to achieve the desired luminance.
- the excess heat generated may damage the display.
- this excess heat must be dissipated.
- heat dissipation is accomplished by directing an air stream to impinge upon the components in the display.
- the cockpit environment contains dirt and other impurities which are also carried into the display with the impinging air, if such forced air is even available.
- Presently available LCD displays cannot tolerate the influx of dirt and are soon too dim and dirty to operate effectively.
- Another drawback of increasing the power to a fluorescent lamp is that the longevity of the lamp decreases dramatically as ever higher levels of surface luminance are demanded. The result is that aging is accelerated which may cause abrupt failure in short periods of time when operating limitations are exceeded.
- the previous disclosure does not provide means for maintaining high contrast over normal lighting configurations for transflective displays. This is because the display contrast in the backlit mode is in the opposite sense of that for ambient lighting. As a result, there will be a sizable range of ambient lighting conditions in which the two sources of light will cancel each other and the display will be unreadable.
- a further disadvantage of the previous disclosure is that achieving a diffusely reflective polarizer in this manner is not at all straightforward, and hence the reflective mode is most applicable to specular, projection type systems.
- Cost-effectiveness is achieved by utilizing a unique island-in-the sea fiber design and a unique extrusion process to create a diffusely reflective polarizer.
- the invention provides a fiber comprising a birefringent fibril discontinuous polymeric phase dispersed in a continuous polymeric phase wherein the refractive indices of the discontinuous and continuous phases in the X and Y directions are substantially matched to each other, the refractive indices of the discontinuous and continuous phases in the X and Y directions are substantially mismatched from the refractive index of the fibril discontinuous polymeric phase in the Z direction, and wherein the extrusion melting temperature of the continuous phase is less than the onset melting range of the discontinuous phase.
- the invention also includes a process for making the fiber and an optical element employing the fiber. The invention enables one to improve the optical efficiency of polarized displays, especially direct view liquid crystal displays (LCDs) and to simplify manufacture and reduce the costs thereof.
- LCDs direct view liquid crystal displays
- Fig. IA is an end view of an island-in-the-sea fiber (10) with a continuous phase (20) and internal fibrils (discontinuous phase) 30.
- Fig. IB is a 3D view of an island-in-the-sea fiber 10 with the projection of the fibril 30 is the length direction with a continuous phase polymer (sea) 20 between the fibrils.
- FIG. 2 is a perspective view of the island-in-the-sea fiber 10 with fibril 30 and sea polymer 20.
- the sea polymer and fibrils comprise 3 dimensions of Refractive index.
- the fiber is stretched in the length (Z) direction and therefore there is an ordinary refractive index for the sea polymer and fibrils in the X and Y plane and an extraordinary index in the length (Z) direction as shown by symbol 40 & 41.
- the ordinary and extraordinary indices of the fibril may be different than the sea polymer indices.
- Fig. 3 A is a circular island-in-the-sea fiber 10 with elliptical fibrils 31.
- Fig. 3B is a circular island-in-the-sea fiber 10 with circular fibrils
- Fig. 3 C is an elliptical island-in-the-sea fiber 11 with radial fibrils
- Fig. 3D is an elliptical island-in-the-sea fiber 11 with mixed shapes and size fibrils 30 and 31
- Fig. 3E is a rectilinear shaped island-in-the-sea fiber 12 with elliptical shaped fibrils 31
- Fig. 3F is a rectilinear shaped island-in-the-sea fiber 12 with random rectilinear shaped fibrils 32
- Fig. 3 G is a circular shaped island-in-the-sea fiber 10 with triangular shaped fibrils 33.
- Fig. 4A is a section view of several island-in-the-sea fiber 10 entering the feed port of an extruder barrel 50 prior to melting the sea polymer.
- Fig. 4B is a section view of the melt stream in a pipe exiting the extruder 60 of several fibrils 31 that have been dispersed into the melted sea polymer 20.
- Fig. 5A is a cross machine cross section of the composite sheet (1) showing the fibrils (10) dispersed throughout.
- Fig. 5B is a down machine cross section of the composite sheet (1) showing fibrils 31 dispersed and aligned throughout.
- the present invention provides a process for producing a diffusely reflecting polarizer film made up of a composite of birefringent polymeric fibrils dispersed in an isotropic polymeric phase.
- the birefringent fibrils are created by producing multi -component island-in-the-sea fibers whereby the birefringent fibrils are islands in a sea of a continuous polymeric phase and wherein the refractive indices of the continuous phase in the X and Y directions (see Figure 2) are substantially matched and wherein the extrusion melting temperature of the continuous phase is less than the onset melting range of the discontinuous phase.
- These fibers are then cut to short lengths and either solely extruded or extruded with additional resin pellets comprising either the same polymer as that of the continuous polymeric phase of the island-in-the sea fiber or a polymer with very similar optical and processing properties.
- the extrusion is done at a temperature sufficient to melt the continuous polymeric phase and additional resin pellets but not high enough to initiate melting of the birefringent fibrils.
- the fibrils are mixed and uniformly dispersed in the melted continuous polymeric phase .
- the melted mix is then pumped through a filming extrusion die with narrow enough die lands to produce high pressure and high shear forces on the fibrils thus orienting and aligning the fibrils in the machine direction.
- the extruded film is then cooled and a resulting diffusely reflecting polarizer film is formed.
- fibril is defined as a material phase in a fiber that is discontinuous in the cross sectional plane of the fiber but either continuous in the fiber length direction or otherwise elongated to a dimension in the fiber length direction at least 100 times greater than the largest dimension in the cross section plane.
- Extrusion melting temperature is defined here as a temperature at which the viscosity of the melted polymer is in a range that enables processing at reasonable pressures, and will be defined here as 100 degrees C above the glass transition temperature of the polymer.
- Onset melting temperature is defined here as the temperature near the melting point of the polymer at which thermal energy is first observed to be seen imparted to the birefringent polymer fibril during a standard differential scanning calorimeter measurement.
- Onset melting temperature is defined here as the temperature near the melting point of the polymer at which thermal energy is first observed to be seen imparted to the birefringent polymer fibril during a standard differential scanning calorimeter measurement.
- the cross sectional shape of the fibers can be of any geometry such as circular, rectilinear, elliptical, triangular, tri-lobal, or trapezoidal.
- the fiber cross sectional shape will be circular or elliptical with the most common cross sectional shape being circular.
- the cross sectional shape of the fibrils can be of any geometry such as circular, rectilinear, elliptical, triangular, tri-lobal, or trapezoidal.
- the fibril cross sectional shape will be circular or elliptical with the most common cross sectional shape being circular.
- polymeric surfactants also referred to as compatibilizers may be added to either one or both polymer of the discontinuous and continuous phases of the fibers.
- Typical materials may include blocked or grafted copolymers where segments of the copolymer matches that of either or both the discontinuous and or continuous phases in the polymeric fiber.
- the copolymers may be added in a weight ratio of 0.05 to 10 percent. This range may vary depending on the degree of substitution on the copolymer.
- synthetic fibers Conventionally, two processes are used to manufacture synthetic fibers: a solution spinning process and a melt spinning process.
- the solution spinning process is generally used to form acrylic fibers
- the melt spinning process is generally used to form nylon fibers, polyester fibers, polypropylene fibers, and other similar type fibers.
- a polyester fiber comprises a long-chain synthetic polymer having at least 85 percent by weight of an ester of a substituted aromatic carboxylic acid unit.
- melt spinning process is of particular interest as since a large portion of the synthetic fibers that are used in the textile industry are manufactured by this technique and the process is ubiquitous at production scale. Also, since the present invention also requires unique down stream extrusion processing of the fibers to produce a composite film with oriented fibrils, melt spun fibers are desirable.
- the melt spinning process generally involves passing a molten polymeric material through a device that is known as a spinneret to thereby form a plurality of individual synthetic fibers. Once formed, the synthetic fibers are typically collected into a strand or cut into staple fibers.
- Synthetic fibers are typically used to make knitted, woven, or non- woven fabrics, or alternatively, synthetic fibers can be spun into a yarn to be used thereafter in a weaving or a knitting process to form a synthetic fabric.
- Multi-component fibrils have been well demonstrated in previous disclosures. Such fibers comprise two or more polymers and typically are designed to either split apart due to incompatibility of the polymers or one polymer is dissolved in solvent such that smaller fibrils of the other polymer are left. This method results in much smaller fibers or fibrils than can be traditionally produces via mono-component fiber processes and offers a wider range of final properties of the fiber-based article in which the fibers are used.
- the present invention relates to a multi-component fiber having both a birefringent polymeric fibril component as well as a continuous polymeric phase component with a melt processing temperature lower than the onset melting temperature of the birefringent fibril.
- the birefringent fibrils in the island-in-the-sea fiber of the present invention can comprise any polymer in the general class of polyesters.
- Typical polyesters for such use can be polyethylene(terephlatate), polyethylene(na ⁇ hthalate), or any copolymers of either.
- the most suitable polyester for the birefringent fibril is ⁇ olyethylene(naphthalate).
- the continuous polymeric phase in the island-in-the-sea fiber of the present invention can comprise any polymer in the general classes of polyesters, acrylics, or olefins. Typical polymers for such use can be polyethylene(terephlatate), polymethylmethacrylate), poly(cyclo-olefin), or any copolymers of either.
- the most suitable polymers for the continuous phase is poly(l,4-cyclohexylene dimethylene terephthalate) or poly(ethylene- terephthalate/isophthalate) copolymer.
- the extrusion melting temperature of the continuous polymeric phase of the fibers should be less than the onset melting temperature of the birefringent fibrils. Typically this difference will be greater than 1O 0 C but is preferred to be greater than 40 0 C. Most preferably the extrusion melting temperature of the continuous polymeric phase is greater than 75°C below the onset melting temperature of the birefringent fibrils.
- the island-in-the sea fibers of the present invention are cold drawn after being melt spun as is typical for such a fiber process.
- the cold draw is done with the fibers heated to just above the glass transition temperature (Tg) of the fibrils polymer. Typically the cold draw is done at 2 to 20 0 C above Tg.
- Tg glass transition temperature
- the amount of draw or draw ratio which is the ratio by which the fiber is lengthened relative to its initial length, is important in attaining a high level of birefringence of the fibril. This is important as it creates a large difference in the Z direction (see Figure 2) extraordinary index of the fibril and the eventual Z direction (see Figure 5B) ordinary index of the continuous phase of the composite film.
- the continuous phase of the fiber is melt relaxed during film processing and therefore retains the ordinary index in the Z direction of the final composite film resulting in an isotropic continuous phase.
- the large difference in Z direction index of the fibril and the continuous phase is desired as it results in a high degree of reflection of light that passes through the film that is approaching the film orthogonal to the film surface and is linearly polarized parallel to the length of the fibril.
- the draw ratio should be greater than 2 to 1 and preferably greater than 3 to 1. Most preferably the draw ratio is greater than 3.5 to 1 to maximize the degree of crystallinity and thus birefringence of the fibrils.
- the continuous polymeric phase may also become birefringent in the drawing process but this is not critical. Any birefringence of the continuous phase polymer will be eliminated during the subsequent extrusion process when making the composite polarizing film. Therefore drawing temperature is only critical for the continuous phase polymer to the degree that the polymer will stretch at the draw temperature without cracking and/or sticking to the draw rollers. As mentioned previously, a large number of smaller fibrils in the fibers is preferable as this will ultimately result in many more optical interfaces in the final composite film reflective polarizer.
- the number of fibrils in the fiber is determined by the design of the spin pack. For a given spin pack design the size of the fibrils is then determined by the relative weight ratio of fibril polymer to continuous phase polymer when melt spinning. Typical weight ratios of fibril polymer to continuous phase polymer is less than 2 to 1 and preferably less than 0.8 to 1. Most preferably the weight ratio of fibril polymer to continuous phase polymer is less than 0.3 to one.
- the size, as measured by cross sectional area, of the fibrils is important because more smaller fibrils can be packed into a fiber lending to more optical interfaces.
- Typical cross sectional areas of fibrils is less than 3.0 square microns.
- the cross sectional area is less than 0.6 square microns and most suitably the cross sectional area of the fibrils is less than 0.2 square microns.
- the number of fibrils that are in the fiber is important as discussed previously and is determined by the spin pack design.
- the number of fibrils in a fiber is greater than 50.
- the number of fibrils is greater than 500. Fibers with greater than 1000 fibrils have been demonstrated and are most preferred.
- the X and Y directions are orthogonal and in the plane of the cross section of the fibers and fibrils, see Figure 2.
- the refractive indices in the X and Y directions of the fibrils (ordinary indices) and of the continuous polymeric phase of the fibers should be substantially matched (i.e., differ by less than 0.05) in either the X or Y axes (see Figure T).
- the refractive indices in the X and Y directions of the fibrils (ordinary indices) and of the continuous polymeric phase of the fibers are substantially mismatched (i.e., differ by more than 0.07) from the refractive index of fibrils in the Z axis (see Figure 2).
- the indices of refraction of the continuous and discontinuous phases differ by less than 0.03 in the match direction, and most preferably, less than 0.02.
- the indices of refraction of the fibrils(ordinary indices) and of the continuous polymeric phase of the fibers differ from that of the index of refraction of the fibrils in the Z direction by more than 0.1 , and most preferably by more than 0.2.
- the first step to converting the fibers described previously into a diffusely reflective polarizing film is to cut the fibers into short lengths. This is important as fibers with shorter aspect ratios, defined as length of fibers divided by cross sectional area, can be dispersed in the melted continuous polymeric phase and be oriented through a shear force field much more readily.
- the fibers are cut to a length less than 5 mm.
- the fibers are cut to a length less than 1 mm and most suitably the fibers are cut to a length of less than 0.4 mm.
- the cut fibers are fed into the feed port of a typical single screw or twin screw extruder and processed at the extrusion melting temperature of the continuous polymeric phase of the fibers.
- the cross section of the fibers entering the feed port are illustrated in Figure 4A.
- the fibrils will not melt at this temperature as the continuous polymer is chosen as to have an extrusion melting temperature below the onset melting temperature of the fibrils.
- the extrusion melting temperature will be more than 10 C lower than the onset melting temperature of the fibrils.
- the extrusion temperature will be more than 4OC lower than the onset melting temperature of the fibrils.
- the extrusion temperature will be more than 75C lower than the onset melting temperature of the fibrils.
- the fibrils are already wetted out buy the continuous polymeric phase by the nature of the fiber design. This results in very good dispersion quality of the fibrils in the molten continuous phase polymer as a result of further mixing in the extruder or subsequently to the extruder via any know melt mixing devices.
- Figure 4B illustrates the fibrils being dispersed in the molten mix via a cross section of a pipe exiting the extruder or downstream mixing device.
- the dispersed mixture is subjected to high shear forces via pumping of the mixture through small die gaps in extrusion filming die.
- These high shear forces result in the fibrils being oriented parallel to each other with the length direction of the fibrils parallel to the flow direction through the die. This results in the composite film having the fibrils aligned parallel to each other and parallel to the machine direction of the film.
- the high shear forces are created by attaining melt pressures in the die greater than 1000 psi.
- the die pressures are greater than 2000 psi and most suitably the die pressures are greater than 3000 psi.
- the fibrils being aligned with the machine direction of the film such that the angle between the Z direction axis, see Figure 2, and the machine direction of the film is less than 45 degrees.
- the angle between the Z direction axis and the machine direction of the film is less than 15 degrees and most suitably the angle between the Z direction axis and the machine direction of the film is less than 5 degrees.
- the aligned fibrils are illustrated in Figures 5A and 5B showing the cross machine direction and down machine direction section views of the composite film.
- the continuous phase of the dispersed mixture in the final composite film comprises at least the continuous polymeric phase of the fibers. Additionally the dispersed mixture can comprise any additional resin or polymer that is added to the fibers in the extrusion process. This added polymer must meet all of the requirements of the continuous phase polymer of the fiber and can comprise the same resins that have been described for the fiber continuous phase.
- the indices of refraction of the continuous and discontinuous phases of the composite film are substantially matched (i.e., differ by less than
- the indices of refraction of the continuous and discontinuous phases differ by less than 0.03 in the match direction, and most preferably, less than 0.02.
- the indices of refraction of the continuous and discontinuous phases preferably differ in the mismatch direction by at least 0.07, more preferably, by at least 0.1 , and most preferably, by at least 0.2.
- the mismatch in refractive indices along a particular axis has the effect that incident light polarized along that axis will be substantially scattered, resulting in a significant amount of reflection.
- incident light polarized along an axis in which the refractive indices are matched will be spectrally transmitted or reflected with a much lesser degree of scattering. This effect can be utilized to make a variety of optical devices, including reflective polarizers and mirrors.
- a layer of material which is substantially free of a discontinuous phase may be disposed on one or both major surfaces of the composite film, i.e., the extruded composite the discontinuous phase and the continuous phase.
- the composition of the layer also called a skin layer, may be chosen, for example, to protect the integrity of the discontinuous phase within the extruded blend, to add mechanical or physical properties to the final film or to add optical functionality to the final film. Suitable materials of choice may include the material of the continuous phase or the material of the discontinuous phase.
- a skin layer or layers may also add physical strength to the resulting composite or reduce problems during processing, such as, for example, reducing the tendency for the film to split during the orientation process.
- Skin layer materials which remain amorphous may tend to make films with a higher toughness, while skin layer materials which are semi-crystalline may tend to make films with a higher tensile modulus.
- Other functional components such as antistatic additives, UV absorbers, dyes, antioxidants, and pigments, may be added to the skin layer, provided they do not substantially interfere with the desired optical properties of the resulting product.
- the skin layers may be applied to one or two sides of the extruded blend at some point during the extrusion process, i.e., before the extruded blend and skin layer(s) exit the extrusion die. This may be accomplished using conventional coextrusion technology, which may include using a three-layer coextrusion die. Lamination of skin layer(s) to a previously formed film of an extruded blend is also possible. Total skin layer thicknesses may range from 2% to 50% of the total film thickness. A wide range of polymers are suitable for skin layers.
- Predominantly amorphous polymers include copolyesters based on one or more of terephthalic acid, 2,6-naphthalene dicarboxylic acid, isophthalic acid phthalic acid, or their alkyl ester counterparts, and alkylene diols, such as ethylene glycol.
- Examples of semicrystalline polymers are 2,6-polyethylene naphthalate, polyethylene terephthalate, and nylon materials.
- the films and other optical devices made in accordance with the invention may also include one or more anti-reflective layers. Such layers, which may or may not be polarization sensitive, serve to increase transmission and to reduce reflective glare.
- An anti- reflective layer may be imparted to the resulting film of the of the present invention through appropriate surface treatment, such as coating or sputter etching.
- the optical body may comprise two or more layers in which at least one layer comprises an anti-reflection system in close contact with a layer providing the continuous and discontinuous phases.
- an anti-reflection system acts to reduce the specular reflection of the incident light and to increase the amount of incident light that enters the portion of the body comprising the continuous and discontinuous layers.
- Such a function can be accomplished by a variety of means well known in the art. Examples are quarter wave anti-reflection layers, two or more layer anti- reflective stack, graded index layers, and graded density layers.
- Such antireflection functions can also be used on the transmitted light side of the body to increase transmitted light if desired. More Than Two Phases
- the composite films made in accordance with the present invention may also consist of more than two phases.
- an optical material made in accordance with the present invention can consist of two different discontinuous phases within the continuous phase.
- the second discontinuous phase could be randomly or non-randomly dispersed throughout the fibrils or can be a separate discontinuous phase from the fibrils, and can be aligned along a common axis.
- Composite films made in accordance with the present invention may also consist of more than one continuous phase.
- the optical body may include, in addition to a first continuous phase and a discontinuous phase, a second phase which is co-continuous in at least one dimension with the first continuous phase Multilayer Combinations
- one or more sheets of a continuous/disperse phase film made in accordance with the present invention may be used in combination with, or as a component in, a multilayered film (i.e., to increase reflectivity).
- Suitable multilayered films include those of the type described in WO 95/17303
- the individual sheets may be laminated or otherwise adhered together or may be spaced apart with the polymeric sheet of this invention. If the optical thicknesses of the phases within the sheets are substantially equal (that is, if the two sheets present a substantially equal and large number of scatterers to incident light along a given axis), the composite will reflect, at somewhat greater efficiency, substantially the same band width and spectral range of reflectivity (i.e., "band") as the individual sheets. If the optical thicknesses of phases within the sheets are not substantially equal, the composite will reflect across a broader band width than the individual phases.
- a composite combining mirror sheets with polarizer sheets is useful for increasing total reflectance while still polarizing transmitted light. Additives
- the composite films of the present invention may also comprise other materials or additives as are known to the art.
- Such materials include pigments, dyes, binders, coatings, fillers, compatibilizers, antioxidants (including sterically hindered phenols), surfactants, antimicrobial agents, antistatic agents, flame retardants, foaming agents, lubricants, reinforcers, light stabilizers (including UV stabilizers or blockers), heat stabilizers, impact modifiers, plasticizers, viscosity modifiers, and other such materials.
- the films . and other optical devices made in accordance with the present invention may include one or more outer layers which serve to protect the device from abrasion, impact, or other damage, or which enhance the processability or durability of the device.
- Suitable lubricants for use in the present invention include calcium stearate, zinc stearate, copper stearate, cobalt stearate, molybdenum neodocanoate, and ruthenium (III) acetylacetonate.
- Antioxidants useful in the present invention include 4,4'- thiobis-
- antioxidants that are especially preferred are sterically hindered phenols, including butylated hydroxytoluene (BHT), Vitamin E (di- alphatocopherol), IrganoxTM 1425WL(calcium bis-(O-ethyl(3,5-di-t-butyl- 4hydroxybenzyl))phosphonate), IrganoxTM 1010 (tetrakis(methylene(3,5,di-t- butyl-4- hydroxyhydrocinnamate))rnethane), IrganoxTM 1076 (octadecyl 3,5-di- tert-butyl-4- hydroxyhydrocinnamate), Etha ⁇ oxTM 702 (hindered bis phenolic), Etanox 330 (high molecular weight hindered phenolic), and EthanoxTM 703 (hindered phenolic amine).
- BHT butylated hydroxytoluene
- Vitamin E di- alphatocophe
- Dichroic dyes are a particularly useful additive in some applications to which the optical materials of the present invention may be directed, due to their ability to absorb light of a particular polarization when they are molecularly aligned within the material. When used in a film or other material which predominantly scatters only one polarization of light, the dichroic dye causes the material to absorb one polarization of light more than another.
- Congo Red sodium diphenyl-bis- oc- naphthylamine sulfonate
- CI Color Index
- CI 518
- the properties of these dyes, and methods of making them, are described in E. H. Land, Colloid Chemistry (1946). These dyes have noticeable dichroism in polyvinyl alcohol and a lesser dichroism in cellulose. A slight dichroism is observed with Congo Red in PEN.
- a dichroic dye when used in the optical bodies of the present invention, it may be incorporated into either the continuous or discontinuous phase. However, it is preferred that the dichroic dye is incorporated into the discontinuous phase.
- Dychroic dyes in combination with certain polymer systems exhibit the ability to polarize light to varying degrees.
- Polyvinyl alcohol and certain dichroic dyes may be used to make films with the ability to polarize light.
- Other polymers such as polyethylene terephthalate or polyamides, such as nylon- 6, do not exhibit as strong an s ability to polarize light when combined with a dichroic dye.
- the polyvinyl alcohol and dichroic dye combination is said to have a higher dichroism ratio than, for example, the same dye in other film forming polymer systems. A higher dichroism ratio indicates a higher ability to polarize light.
- Molecular alignment of a dichroic dye within a composite film made in accordance with the present invention is preferably accomplished by stretching the composite film after the dye has been incorporated into it.
- other methods may also be used to achieve molecular alignment.
- the dichroic dye is crystallized, as through sublimation or by crystallization from solution, into a series of elongated notches that are cut, etched, or otherwise formed in the surface of a film., either before or after the composite film has been oriented.
- the treated surface may then be coated with one or more surface layers, may be incorporated into a polymer matrix or used in a multilayer structure, or may be utilized as a component of another optical body.
- the notches may be created in accordance with a predetermined pattern or diagram, and with a predetermined amount of spacing between the notches, so as to achieve desirable optical properties.
- the dichroic dye may be disposed within one or more hollow fibers or other conduits, either before or after the hollow fibers or conduits are disposed within the composite film.
- the hollow fibers or conduits may be constructed out of a material that is the same or different from the surrounding material of the composite film.
- the dichroic dye is disposed along the layer interface of a multilayer construction, as by sublimation onto the surface of a layer before it is incorporated into the multilayer construction.
- the dichroic dye is used to at least partially backfill the voids in a microvoided film made in accordance with the present invention.
- Various functional layers or coatings may be added to the composite films of the present invention to alter or improve their physical or chemical properties, particularly along the surface of the film.
- Such layers or coatings may include, for example, slip agents, low adhesion backside materials, conductive layers, antistatic coatings or films, barrier layers, flame retardants, UV stabilizers, abrasion resistant materials, optical coatings, or substrates designed to improve the mechanical integrity or strength of the film or device.
- the films of the present invention may be given good slip properties by treating them with low friction coatings or slip agents, such as polymer beads coated onto the surface.
- low friction coatings or slip agents such as polymer beads coated onto the surface.
- the morphology of the surfaces of these materials may be modified, as through manipulation of extrusion conditions, to impart a slippery surface to the film; methods by which surface morphology maybe so modified are described in U.S. Ser. No. 08/612,710.
- the composite film of the present invention are to be used as a component in adhesive tapes
- PSAs pressure sensitive adhesives
- Adhesive tapes made in this manner can be used for decorative purposes or in any application where a diffusely reflective or transmissive surface on the tape is desirable.
- the films and optical devices of the present invention may also be provided with one or more conductive layers.
- Such conductive layers may comprise metals such as silver, gold, copper, aluminum, chromium, nickel, tin, and titanium, metal alloys such as silver alloys, stainless steel, and intone, and semiconductor metal oxides such as doped and undoped tin oxides, zinc oxide, and indium tin oxide (ITO).
- the composite film of the present invention may also be provided with antistatic coatings or films.
- coatings or films include, for example, V 2 O 5 and salts of sulfonic acid polymers, carbon or other conductive metal layers.
- the optical films and devices of the present invention may also be provided with one or more barrier films or coatings that alter the transmissive properties of the optical film towards certain liquids or gases.
- the devices and films of the present invention may be provided with films or coatings that inhibit the transmission of water vapor, organic solvents, O 2 , or CO 2 through the film. Barrier coatings will be particularly desirable in high humidity environments, where components of the film or device would be subject to distortion due to moisture permeation.
- the composite films of the present invention may also be treated with flame retardants, particularly when used in environments, such as on airplanes, that are subject to strict fire codes.
- Suitable flame retardants include aluminum trihydrate, antimony trioxide, antimony pentoxide, and flame retarding organophosphate compounds.
- the composite film of the present invention may also be provided with abrasion-resistant or hard coatings, which will frequently be applied as a skin layer.
- abrasion-resistant or hard coatings which will frequently be applied as a skin layer.
- acrylic hardcoats such as Acryloid A-11 and Paraloid K-
- urethane acrylates such as those described in U.S. Pat. No. 4,249,011 and those available from Sartomer Corp., Westchester, Pa.
- urethane hardcoats obtained from the reaction of an aliphatic polyisocyanate (e.g., Desmodur N- 3300, available from Miles, Inc., Pittsburgh, Pa.) with a polyester (e.g., Tone Polyol 0305, available from Union Carbide, Houston, Tex.).
- an aliphatic polyisocyanate e.g., Desmodur N- 3300, available from Miles, Inc., Pittsburgh, Pa.
- a polyester e.g., Tone Polyol 0305, available from Union Carbide, Houston, Tex.
- the composite film of the present invention may further be laminated to rigid or semi-rigid substrates, such as, for example, glass, metal, acrylic, polyester, and other polymer backings to provide structural rigidity, weatherability, or easier handling.
- rigid or semi-rigid substrates such as, for example, glass, metal, acrylic, polyester, and other polymer backings to provide structural rigidity, weatherability, or easier handling.
- the composite film of the present invention may be laminated to a thin acrylic or metal backing so that it can be stamped or otherwise formed and maintained in a desired shape.
- an additional layer comprising PET film or puncture-tear resistant film may be used.
- the composite film and devices of the present invention may also be provided with shatter resistant films and coatings.
- Films and coatings suitable for this purpose are described, for example, in publications EP 592284 and EP 591055, and are available commercially from 3M Company, St Paul, Minn.
- Various optical layers, materials, and devices may also be applied to, or used in conjunction with, the films of the present invention for specific applications.
- These include, but are not limited to, magnetic or magneto-optic coatings or films; liquid crystal panels, such as those used in display panels and privacy windows; photographic emulsions; fabrics; prismatic films, such as linear Fresnel lenses; brightness enhancement films; holographic films or images; embossable films; anti-tamper films or coatings; IR transparent film for low emissivity applications; release films or release coated paper; and polarizers or mirrors.
- the adhesive when an adhesive is applied to the composite film, the adhesive may contain a white pigment such as titanium dioxide to increase the overall reflectivity, or it may be optically transparent to allow the reflectivity of the substrate to add to the reflectivity of the composite film.
- the composite film of the present invention may also comprise a slip agent that is incorporated into the film or added as a separate coating.
- slip agents will be added to only one side of the film, ideally the side facing the rigid substrate in order to minimize haze. Thickness of Composite Film
- the thickness of the composite film is also an important parameter which can be manipulated to affect reflection and transmission properties in the present invention. As the thickness of the composite film increases, diffuse reflection also increases, and transmission, both specular and diffuse, decreases. Thus, while the thickness of the composite film will typically be chosen to achieve a desired degree of mechanical strength in the finished product, it can also be used to directly to control reflection and transmission properties.
- Thickness can also be utilized to make final adjustments in reflection and transmission properties of the composite film.
- the device used to extrude the film can be controlled by a downstream optical device which measures transmission and reflection values in the extruded film, and which varies the thickness of the film (i.e., by adjusting extrusion rates or changing casting wheel speeds) so as to maintain the reflection and transmission values within a predetermined range.
- Example 1
- Polyethylene(na ⁇ hthalate), PEN VFR-40102 from M&G Group
- PEN VFR-40102 from M&G Group
- isophthalic acid modified Co-PET, Crystar® Merge 3991 by DuPont was dried in a desicant dryer at 55 C for 12 hours.
- Island in the sea fibers were produced by feeding the two melt streams into a specially designed spinneret that created 1410 fibrils within each fiber.
- the Co- PET was fed as the continuous phase of the fiber and the PEN was fed as the discontinuous fibrils.
- 72 fibers were produced simultaneously by the spinner. The fibers were air cooled upon exiting the orifices of the spinneret and then heated and stretched 4 times their original length at a temperature of 120°C.
- the final diameter of the fibers was nominally 40 ⁇ m.
- the fibers were wound on bobbins.
- the fibers were then unwound from the bobbins and fed into a cutter and cut to nominally 0.25 mm in length.
- the cut fibers were then dried in a desiccant dryer at 55°C for 12 hours.
- neat Co-PET 3991 pellets were dried in a desiccant dryer at 55°C for 12 hours.
- the dried cut fibers were then dry blended with the dried Co-PET pellets at a 15 to 85 ratio, respectively.
- the blend was fed into a 19mm diameter twin screw extruder where it was melted, mixed and extruded.
- the melted extrudate was then pumped through' an extrusion die with narrow die slots at an inlet pressure of 2500 psi.
- Example 2 This example was made identically to example 1 except the chill roll speed was slowed down to thicken the film to a thickness of 16 ⁇ m. Optical Testing
- the two samples from above were tested optically to determine if they performed as reflective polarizers.
- the test equipment used was a integrating sphere attached to a spectrophotometer (Perkin Elmer Lambda 650S).
- a reflectance is determined at a wavelength of 550 nm.
- a light transmission value is also obtained at a wavelength of 550 nm.
- polarized light was first directed onto the films with the polarization being perpendicular to the machine direction of the film. The percentage of light transmitted is measured as Tmax. The percentage of light reflected is measured as Rmin.
- polarized light was directed onto the films with the polarization being parallel to the machine direction of the film. The percentage of light reflected is measured as Rmax. The percentage of light transmitted is measured as Tmin.
- Table 1 shows the results of the above described optical testing on the example films.
- Tmax should be greater than Tmin and Rmax should be greater than Rmin. The larger these differences are the higher the performance of the film as a reflective polarizer.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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JP2009514306A JP2009540363A (en) | 2006-06-05 | 2007-05-30 | Reflective polarizer, fiber and manufacturing method |
EP07795456A EP2033027A2 (en) | 2006-06-05 | 2007-05-30 | Diffusely-reflecting polariser and method of making same |
Applications Claiming Priority (4)
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US81088806P | 2006-06-05 | 2006-06-05 | |
US60/810,888 | 2006-06-05 | ||
US11/643,071 | 2006-12-21 | ||
US11/643,071 US20070281157A1 (en) | 2006-06-05 | 2006-12-21 | Reflective polarizer, fiber, and process for making |
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WO2007145812A2 true WO2007145812A2 (en) | 2007-12-21 |
WO2007145812A3 WO2007145812A3 (en) | 2008-04-10 |
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PCT/US2007/012672 WO2007145812A2 (en) | 2006-06-05 | 2007-05-30 | Diffusely-reflecting polariser and method of making same |
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US (1) | US20070281157A1 (en) |
EP (1) | EP2033027A2 (en) |
JP (1) | JP2009540363A (en) |
KR (1) | KR20090028609A (en) |
TW (1) | TW200745641A (en) |
WO (1) | WO2007145812A2 (en) |
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CN101595255A (en) * | 2007-01-29 | 2009-12-02 | 株式会社Y.G.K | Luminescent composite yarn |
KR101666570B1 (en) * | 2009-06-15 | 2016-10-17 | 삼성디스플레이 주식회사 | Liquid crystal display apparatus and method of manufacturing the same |
US20110116167A1 (en) * | 2009-11-19 | 2011-05-19 | Skc Haas Display Films Co., Ltd. | Diffusely-reflecting polarizer having substantially amorphous nano-composite major phase |
KR101340107B1 (en) * | 2011-12-29 | 2013-12-10 | 웅진케미칼 주식회사 | Reflective polizer dispered polymer |
WO2013100661A1 (en) * | 2011-12-29 | 2013-07-04 | 웅진케미칼 주식회사 | Reflective polarizer having dispersed polymer |
KR101940327B1 (en) * | 2012-12-06 | 2019-01-18 | 도레이케미칼 주식회사 | Reflective polizer dispered polymer and Manufacturing method thereof |
DE102019120052A1 (en) * | 2019-07-24 | 2021-01-28 | SchäferRolls GmbH & Co. KG | Industrial roll, in particular for paper production, method for introducing a polymer fiber into an empty tube of a technical roll and using a polymer fiber |
Citations (1)
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US20050078371A1 (en) | 1996-02-29 | 2005-04-14 | 3M Innovative Properties Company | Optical film with co-continuous phases |
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US2604817A (en) * | 1948-10-14 | 1952-07-29 | Du Pont | Light polarizing composition |
US3531368A (en) * | 1966-01-07 | 1970-09-29 | Toray Industries | Synthetic filaments and the like |
US5217794A (en) * | 1991-01-22 | 1993-06-08 | The Dow Chemical Company | Lamellar polymeric body |
US5751388A (en) * | 1995-04-07 | 1998-05-12 | Honeywell Inc. | High efficiency polarized display |
US6256146B1 (en) * | 1998-07-31 | 2001-07-03 | 3M Innovative Properties | Post-forming continuous/disperse phase optical bodies |
US6630231B2 (en) * | 1999-02-05 | 2003-10-07 | 3M Innovative Properties Company | Composite articles reinforced with highly oriented microfibers |
US6855422B2 (en) * | 2000-09-21 | 2005-02-15 | Monte C. Magill | Multi-component fibers having enhanced reversible thermal properties and methods of manufacturing thereof |
US20040234724A1 (en) * | 2003-05-22 | 2004-11-25 | Eastman Kodak Company | Immisible polymer filled optical elements |
US7386212B2 (en) * | 2005-02-28 | 2008-06-10 | 3M Innovative Properties Company | Polymer photonic crystal fibers |
US7356229B2 (en) * | 2005-02-28 | 2008-04-08 | 3M Innovative Properties Company | Reflective polarizers containing polymer fibers |
US7356231B2 (en) * | 2005-02-28 | 2008-04-08 | 3M Innovative Properties Company | Composite polymer fibers |
-
2006
- 2006-12-21 US US11/643,071 patent/US20070281157A1/en not_active Abandoned
-
2007
- 2007-05-30 JP JP2009514306A patent/JP2009540363A/en active Pending
- 2007-05-30 WO PCT/US2007/012672 patent/WO2007145812A2/en active Application Filing
- 2007-05-30 KR KR1020097000098A patent/KR20090028609A/en not_active Application Discontinuation
- 2007-05-30 EP EP07795456A patent/EP2033027A2/en not_active Withdrawn
- 2007-06-04 TW TW096119883A patent/TW200745641A/en unknown
Patent Citations (1)
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US20050078371A1 (en) | 1996-02-29 | 2005-04-14 | 3M Innovative Properties Company | Optical film with co-continuous phases |
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US20070281157A1 (en) | 2007-12-06 |
EP2033027A2 (en) | 2009-03-11 |
KR20090028609A (en) | 2009-03-18 |
JP2009540363A (en) | 2009-11-19 |
WO2007145812A3 (en) | 2008-04-10 |
TW200745641A (en) | 2007-12-16 |
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