High-transmittance light control film with asymmetric light output

Abstract

The present invention relates to a light control film comprising a light input surface, a light output surface opposite the light input surface, and alternating transmissive and absorptive regions disposed between the light input and light output surfaces. The absorptive regions have an aspect ratio of at least 30 and are inclined in the same direction. The alternating transmissive and absorptive regions have a maximum relative transmittance at viewing angles other than 0 degrees.

Description

Technical Field

[0001] The present invention relates to a light control film with asymmetric light output and a method for preparing the same. Background Art

[0002] Louver-based light-collimating films or light control films typically provide a symmetrical light output with peak brightness in the center that gradually falls off over a wide angle. For privacy filter applications, it is often desirable to direct the peak brightness axially toward the viewer's eyes. Summary of the Invention

[0003] For applications other than privacy filters, such as light control films for automotive reflection management, for example, it will be appreciated that it may be advantageous to shift the peak brightness towards other locations in the vehicle rather than directly axially.

[0004] Briefly, in one aspect, the present invention provides a light control film comprising a light input surface, a light output surface facing away from the light input surface, and alternating transmissive and absorptive regions disposed between the light input and light output surfaces. The absorptive regions have an aspect ratio of at least 30 and are inclined in the same direction. The alternating transmissive and absorptive regions have a maximum relative transmittance at viewing angles other than 0 degrees.

[0005] In another aspect, the present invention provides a method for preparing a light control film. The method comprises: (1) providing a microstructured film comprising a bottom surface and a microstructured surface opposite the bottom surface, and a plurality of light transmissive regions alternating with grooves, wherein the microstructured surface is defined by a top surface, a first sidewall, a second sidewall of the light transmissive regions, and a bottom surface of the grooves, wherein the first sidewall forms a wall angle of +1 to +10 degrees or -1 to -10 degrees relative to the bottom surface with respect to a line perpendicular to the light output surface; (2) applying an organic light absorbing material to the microstructured surface; and (3) removing the light absorbing material from the first sidewall or the second sidewall.

[0006] The light control films of the present invention provide high transmittance with tuned peak brightness that redirects light to a desired off-axis angle. The methods of the present invention provide an apparatus for producing light control films with louvers tilted in the same direction, whereas previous methods were limited to producing light control films with louvers orthogonal to the light input surface or with louvers tilted in opposite directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A 2 is a cross-sectional view of a light control film according to a specific embodiment.

[0008] Figure 1B Show Figure 1A The polar cut-off viewing angle of the light control film.

[0009] Figure 2 is a perspective view of a microstructured film.

[0010] Figures 3A to 3D is a cross-sectional view of a microstructured film.

[0011] Figure 4 is a perspective view of a light management film further comprising a cover film bonded to the adhesive layer.

[0012] Figure 5 is a perspective view of a backlit display including an embodied light management film.

[0013] Figure 6 4 is a cross-sectional view of the microstructured film of Preparation Example 1.

[0014] 7A to 7C The figure is a cross-sectional schematic diagram showing a specific embodiment of a method for preparing a light control film. DETAILED DESCRIPTION

[0015] In one embodiment, a light control film ("LCF") is described. Figure 1A (a cross-sectional view of an embodied LCF 100), the LCF includes a light output surface 120 and an opposing light input surface 110. The light output surface 120 is generally parallel to the light input surface 110. The LCF 100 includes alternating transmissive regions 130 and absorptive regions 140 disposed between the light output surface 120 and the light input surface 110. The absorptive regions 140 are tilted in the same direction (i.e., the absorptive regions deviate from a line perpendicular to the light output surface in the same direction).

[0016] In one embodiment, Figure 1A As shown, the transmissive regions 130 are generally integral with the mesa regions "L", meaning that there is no interface between the mesa regions and the base portion 131 of the transmissive regions 130. Alternatively, the LCF may be free of such mesa regions L, or an interface may exist between the mesa regions L and the transmissive regions 130. In this embodiment, the mesa regions are disposed between the alternating transmissive regions 130 and absorptive regions 140 and the light input surface 110.

[0017] Alternatively, in another embodiment, surface 120 can be the light input surface and surface 110 can be the light output surface. In this embodiment, the mesa region is disposed between the alternating transmissive and absorptive regions 130, 140 and the light output surface.

[0018] The transmissive region 130 may have a width “W T " is defined. Except for the mesa region "L", the transmissive region 130 generally has the same nominal height as the absorptive region 140. In a typical embodiment, the height H of the absorptive region AThe height is at least 30, 40, 50, 60, 70, 80, 90, or 100 microns. In some embodiments, the height is no greater than 200, 190, 180, 170, 160, or 150 microns. In some embodiments, the height is no greater than 140, 130, 120, 110, or 100 microns. The LCF typically includes a plurality of transmissive regions having nominally the same height and width. In some embodiments, the transmissive regions have a height "H" of T ”, the maximum width at its widest part “W T " and an aspect ratio H of at least 1.75 T / W T In some embodiments, H T / W T In other embodiments, the aspect ratio of the transmissive regions is at least 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0. In other embodiments, the aspect ratio of the transmissive regions is at least 6, 7, 8, 9, or 10. In other embodiments, the aspect ratio of the transmissive regions is at least 15, 20, 25, 30, 35, 40, 45, or 50.

[0019] The absorbent region 140 has a height “H” defined by the distance between the bottom surface 155 and the top surface 145. A ”, such top and bottom surfaces are generally parallel to the light output surface 120 and the light input surface 110. The absorption region 140 also has a length “L A The absorption region 140 has a maximum width W A , and spaced apart along the surface light output surface 120 at a spacing "P A ”.

[0020] The width "W" of the absorbent region at the base (ie, adjacent to the bottom surface 155) is A ” is typically nominally the same as the width of the absorptive region adjacent to the top surface 145. However, when the width of the absorptive region at the base is different from the width adjacent to the top surface, the width is defined by the maximum width. The maximum widths of multiple absorptive regions can be averaged for a region of interest, such as a region where transmittance (e.g., luminance) is measured. An LCF typically includes multiple absorptive regions having nominally the same height, length, and width. In typical embodiments, the absorptive regions typically have a width of no greater than 10 microns, 9 microns, 8 microns, 7 microns, 6 microns, 5 microns, 4 microns, 3 microns, 2 microns, or 1 micron. In some embodiments, the absorptive regions typically have a width of no greater than 900 nanometers, 800 nanometers, 700 nanometers, 600 nanometers, or 500 nanometers. In some embodiments, the absorptive regions have a width of at least 50 nanometers, 60 nanometers, 70 nanometers, 80 nanometers, 90 nanometers, or 100 nanometers.

[0021] The absorptive region can be defined by its aspect ratio, ie, the height of the absorptive region divided by the maximum length of the absorptive region (L A / W A ). In some embodiments, the aspect ratio of the absorption region is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In advantageous embodiments, the height and width of one or more absorption regions are selected so that one or more absorption regions have an even higher aspect ratio. In some embodiments, the aspect ratio of the absorption region is at least 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100. In other embodiments, the aspect ratio of the absorption region is at least 200, 300, 400, or 500. The aspect ratio can range up to 10,000 or greater. In some embodiments, the aspect ratio is no greater than 9,000, 8,000; 7,000; 6,000, 5,000, 4,000, 3000; 2,000, or 1,000.

[0022] like Figure 1B As shown, LCF 100 includes alternating transmissive regions 130 and absorptive regions 140 tilted in the same direction, and interfaces 150 between the transmissive regions 130 and the absorptive regions 140. Interface 150 forms a wall angle θ with a line 160 perpendicular to light output surface 120.

[0023] Larger wall angles θ reduce transmittance at normal incidence, or in other words, at a viewing angle of 0 degrees. In some embodiments, the wall angle θ is less than 30 degrees, 20 degrees, 10 degrees, 9 degrees, 8 degrees, 7 degrees, 6 degrees, 5 degrees, 4 degrees, 3 degrees, or 2 degrees. In some embodiments, the wall angle is between +1 and +30 degrees, +1 and +20 degrees, +1 and +10 degrees, or +2 and +8 degrees. In some embodiments, the wall angle is between -1 and -30 degrees, -1 and -20 degrees, -1 and -10 degrees, or -2 and -8 degrees.

[0024] When incident light undergoes total internal reflection (TIR) from the interface between the absorptive and transmissive regions, transmittance (e.g., visible light brightness) can be increased. Whether TIR occurs is determined by the angle of incidence of the light on the interface and the difference in refractive index between the materials of the transmissive and absorptive regions.

[0025] As shown in FIG1b, the transmissive regions 130 between the absorptive regions 140 have an interface angle θ defined by the geometry of the alternating transmissive regions 130 and absorptive regions. I .like Figure 1A and Figure 1B As shown, the interface angle θ IIt can be defined by the intersection of two lines. The first line extends from a first point defined by the bottom surface and sidewall surface of the first absorbent region and a second point defined by the top surface and sidewall surface of the nearest second absorbent region. The second line extends from a first point defined by the top surface and sidewall surface of the first absorbent region and a second point defined by the bottom surface and sidewall surface of the second absorbent region.

[0026] The polar plane cutoff viewing angle θP is equal to the sum of the polar plane cutoff half viewing angle θ1 and the polar plane cutoff half viewing angle θ2. In a typical embodiment, the polar plane cutoff half viewing angle θ1 is not equal to the polar plane cutoff half viewing angle θ2.

[0027] Brightness can be measured according to the test methods described in the Examples. A total light control film can be formed in alternating transmissive and absorptive regions (such as shown in FIG. 1 a) or can also include a cover film (such as Figure 4 Brightness is measured on a light control film (as shown in FIG). Relative transmittance (e.g., visible light brightness) is defined as the percentage of brightness at a specified viewing angle or range of viewing angles between a reading with a light control film comprising alternating transmissive and absorptive regions and, optionally, other layers, and a reading without the light control film (i.e., a baseline). Viewing angles can range from -90 degrees to 90 degrees. A viewing angle of 0 degrees is perpendicular to the light input surface 110; while viewing angles of -90 and +90 degrees are parallel to the light input surface 110.

[0028] Unless otherwise indicated, relative transmittance (eg, brightness) refers to the relative transmittance of visible light in the wavelength range of 400 nm to 700 nm as measured by the test method described in more detail in the Examples.

[0029] The alternating transmissive and absorptive regions or the total LCF can exhibit a maximum relative transmittance (e.g., brightness) at a desired viewing angle other than 0 degrees. In some embodiments, the maximum relative transmittance (e.g., brightness) is at least 75%, 80%, 85%, or 90%. The maximum relative transmittance (e.g., brightness) is typically less than 100%. In some embodiments, the maximum relative transmittance (e.g., brightness) is at a viewing angle between -30 and +30 degrees, between -20 and +20 degrees, or between -10 and +10 degrees. In some embodiments, the maximum relative transmittance (e.g., brightness) is at a viewing angle between +1 to +30 degrees, +1 to +20 degrees, +1 to +10 degrees, or +2 to +8 degrees. In some embodiments, the maximum relative transmittance (e.g., brightness) is at a viewing angle between -1 to -30 degrees, -1 to -20 degrees, -1 to -10 degrees, or -2 to -8 degrees.

[0030] LCFs with maximum relative transmittance at viewing angles other than 0 degrees are particularly useful in applications where the viewer is not directly in front of the display (viewing angle is 0 degrees) and where it is desirable to shift the peak brightness off-axis. For example, for an LCF used for automotive reflection management, it may be desirable to shift the peak brightness toward another location in the vehicle.

[0031] Absorbent regions can be formed by coating the surface of the microstructured film. Figure 2 A microstructured film article 200 is shown that can be coated to prepare an LCF. The microstructured film shown includes a microstructured surface 210 comprising a plurality of grooves 201a-201d on a substrate layer 260. Figure 2 As shown, a continuous mesa layer "L" can exist between the bottom of the groove 205 and the top surface 210 of the base layer 260 to the base layer 260. Alternatively, the groove 201 can extend all the way through the microstructured film article 200. In this embodiment (not shown), the bottom surface 205 of the groove can coincide with the top surface of the base layer 260. In a typical embodiment, the base layer 260 is a preformed film that includes a different organic polymer material than the transmissive regions 230, as will be described subsequently.

[0032] The height and width of the protrusion (e.g., transmissive region) 230 are defined by adjacent grooves (e.g., 201a and 201b). The protrusion (e.g., transmissive region) 230 may be defined by a top surface 220, a bottom surface 231, and first and second sidewalls 232 and 233 joining the top surface to the bottom surface.

[0033] In some embodiments, the first sidewall has a wall angle of less than 30 degrees, 20 degrees, 10 degrees, 9 degrees, 8 degrees, 7 degrees, 6 degrees, 5 degrees, 4 degrees, 3 degrees, or 2 degrees. In some embodiments, the first sidewall has a wall angle of +1 to +30 degrees, +1 to +20 degrees, +1 to +10 degrees, or +2 to +8 degrees. In some embodiments, the first sidewall has a wall angle of -1 to -30 degrees, -1 to -20 degrees, -1 to -10 degrees, or -2 to -8 degrees. The first sidewalls may be parallel to each other.

[0034] In some embodiments, top surface 201 can be a relatively flat surface connecting the tops of sidewalls 232, 233. In other embodiments, top surface 201 can be the point where the tops of sidewalls 232, 233 intersect. In some embodiments, bottom surface 205 can be a relatively flat surface connecting the bottoms of sidewalls 232, 233. In other embodiments, bottom surface 205 can be the point where the bottoms of sidewalls 232, 233 intersect.

[0035] The wall angle and length of the second side wall will vary depending on the wall angle and length of the first side wall and the lengths of the top and bottom surfaces.

[0036] Figures 3A to 3D Shows a microstructured membrane that can be used to prepare the LCF according to the present invention.

[0037] In some embodiments, the protrusions (e.g., transmissive regions) 230 have a pitch "P" of at least 10 microns. T The pitch is the distance between the starting point of the first protrusion (e.g., transmissive region) and the starting point of the second protrusion (e.g., transmissive region), as Figure 2 shown. The pitch can be at least 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, or 50 microns. The pitch is generally not greater than 1 mm. The pitch is generally not greater than 900 microns, 800 microns, 700 microns, 600 microns, or 500 microns. In some embodiments, the pitch is generally not greater than 550 microns, 500 microns, 450 microns, 400 microns, 350 microns, 300 microns, 250 microns, or 200 microns. In some embodiments, the pitch is not greater than 175 microns, 150 microns, 100 microns. In typical embodiments, the protrusions are evenly spaced and have a single pitch. Alternatively, the protrusions can be spaced such that the pitch between adjacent protrusions is not the same. In this later embodiment, at least some and generally most (at least 50%, 60%, 70%, 80%, 90% or more of the total protrusions) have the pitch just described.

[0038] The pitch P of the absorption region A is within the same range as just described for the light transmissive region. In some embodiments, P A is between 10 microns and 50 microns.

[0039] The absorption region is formed by providing an absorptive coating on the sidewalls of the protrusions (e.g., transmissive regions) of the microstructured membrane. The thickness of the absorptive coating is equal to the width W of the absorption region A , as previously described. The absorption region can be formed by any method of providing a sufficiently thin and conformal absorptive coating on the sidewalls (e.g., 232, 233).

[0040] In some embodiments, the absorption region includes a core sandwiched between claddings. The core has a first concentration C1 of an absorptive material, and the claddings have a second concentration C2 of the absorptive material, where C2 < C1. The core has a first extinction coefficient k1, and the claddings have a second extinction coefficient k2, where k2 < k1. Examples of claddings and methods of preparing an absorption region having a core and claddings can be found, for example, in co-pending application No. 62 / 713,462.

[0041] In one embodiment, the absorption region is formed by a combination of additive and subtractive methods.

[0042] Light control films can be formed by providing a microstructured film (such as a Figure 2 The method further comprises applying a light absorbing coating to the (e.g., entire) surface of the microstructured film, i.e., the top surface and sidewalls of the protrusions (e.g., transmissive regions) and the bottom surface of the grooves separating the protrusions (e.g., transmissive regions). The method further comprises removing the coating from the first sidewall or the second sidewall. In some embodiments, the method comprises removing at least a portion of the coating from the first sidewall and removing substantially the entire coating from the second sidewall, or vice versa.

[0043] In some embodiments, the method further includes removing the coating from the top surface 320 of the protrusions (eg, transmissive areas) and the bottom surface 305 of the grooves.

[0044] 7A to 7C The microstructured film 700 is shown defining a bottom surface 705, a top surface 720, a first sidewall 732, and a second sidewall 733. The microstructured film 700 may be coated with a light absorbing material 741 (shown in FIG. Figure 7B The absorbing material 741 may then be etched away using RIE. The absorbing material on the bottom surface, top surface, and second sidewalls is etched away faster (e.g., 10%, 20%, 30% or more faster) than the absorbing material on the first sidewall to provide a light control film having absorbing material only on the first sidewall (shown in FIG. Figure 7C middle).

[0045] In some embodiments, the method further includes filling the groove with an organic polymer material 345 such as (e.g., the same) polymerizable resin as the protrusion (e.g., transmissive region), and curing the polymerizable resin. When the groove is not filled with the cured polymerizable resin, the groove is typically filled with air.

[0046] Articles containing microstructures (e.g. Figure 2 The microstructured film article 200 shown in FIG. 2 may be prepared by any suitable method. In one embodiment, the microstructured article (e.g., Figure 2The microstructured film article 200 shown in FIG can be prepared by a method comprising the following steps: (a) preparing a polymerizable composition; (b) depositing the polymerizable composition onto a negative microstructured molding surface of a master mold (e.g., a tool) in an amount just sufficient to fill the cavities of the master mold; (c) filling the cavities by moving droplets of the polymerizable composition between a base layer (e.g., a preformed film) and the master mold, at least one of which is flexible; and (d) curing the composition. The deposition temperature can be in the range of ambient temperature to about 180°F (82°C). The master mold can be a metal (such as nickel, chrome-plated or nickel-plated copper, or brass) material, or can be a thermoplastic material that is stable under polymerization conditions and has a surface energy that allows the polymerized material to be cleanly removed from the master mold. When the base layer is a preformed film, one or more of the surfaces of the film can optionally be primed or otherwise treated to promote adhesion to the organic material of the light-transmitting area.

[0047] The polymerizable resin may comprise a combination of a first polymerizable component and a second polymerizable component selected from the group consisting of (meth)acrylate monomers, (meth)acrylate oligomers, and mixtures thereof. As used herein, a "monomer" or "oligomer" is any substance that can be converted into a polymer. The term "(meth)acrylate" refers to both acrylate and methacrylate compounds. In some cases, the polymerizable composition may comprise a (meth)acrylated urethane oligomer, a (meth)acrylated epoxy oligomer, a (meth)acrylated polyester oligomer, a (meth)acrylated phenolic oligomer, a (meth)acrylated acrylic oligomer, and mixtures thereof.

[0048] The polymerizable resin can be a radiation-curable polymer resin, such as a UV-curable resin. In some cases, the polymerizable resin compositions useful in the LCFs of the present invention can include polymerizable resin compositions such as those described in U.S. Patent No. 8,012,567 (Gaides et al.), provided that such compositions meet the refractive index and absorption characteristics described herein.

[0049] The chemical composition and thickness of the base layer may depend on the end use of the LCF.In typical embodiments, the base layer may have a thickness of at least about 0.025 millimeters (mm), and may be from about 0.05 mm to about 0.25 mm.

[0050] Useful substrate materials include, for example, styrene-acrylonitrile, cellulose acetate butyrate, cellulose acetate propionate, cellulose triacetate, polyethersulfone, polymethyl methacrylate, polyurethane, polyester, polycarbonate, polyvinyl chloride, polystyrene, polyethylene naphthalate, copolymers or blends based on naphthalene dicarboxylic acid, polyolefin-based materials (such as cast or oriented films of polyethylene, polypropylene, and polycycloolefins), polyimides, and glass. Optionally, the substrate may comprise a mixture or combination of these materials. In one embodiment, the substrate may be multilayered or may comprise dispersed components suspended or dispersed in a continuous phase.

[0051] Examples of substrate materials include polyethylene terephthalate (PET) and polycarbonate (PC). Examples of useful PET films include optical grade polyethylene terephthalate available under the trade designation "Melinex 618" from DuPont Films, Wilmington, Del. Examples of optical grade polycarbonate films include LEXAN.RTM. polycarbonate film 8010 available from GE Polymershapes, Seattle, Washington, and Panlite 1151 available from Teijin Kasei, Alpharetta, Ga.

[0052] Some substrate layers may be optically active and may act as polarizing materials. Polarization of light transmitted through the film may be achieved, for example, by including a dichroic polarizer in the film material that selectively absorbs the transmitted light. Light polarization may also be achieved by including an inorganic material (such as an oriented mica wafer) or by discontinuous phases dispersed in a continuous film (such as droplets of light modulating liquid crystals dispersed in a continuous film). Alternatively, films may be prepared from ultra-thin layers of different materials. For example, the polarizing material in the film may be oriented along the polarization direction by employing methods such as stretching the film, applying an electric or magnetic field, and coating techniques.

[0053] Examples of polarizing films include those described in U.S. Patent 5,825,543 (Ouderkirk et al.); U.S. Patent 5,783,120 (Ouderkirk et al.); U.S. Patent 5,882,774 (Jonza et al.); U.S. Patent 5,612,820 (Shrenk et al.); and U.S. Patent 5,486,949 (Shrenk et al.). The use of these polarizing films in conjunction with prismatic brightness enhancement films has been described, for example, in U.S. Patent 6,111,696 (Allen et al.) and U.S. Patent 5,828,488 (Ouderkirk et al.). Commercially available films are multilayer reflective polarizing films, such as 3M® from 3M Company. TM Double Brightness Enhancement Film "DBEF".

[0054] In some embodiments, the base layer is a multilayer film that imparts a color shifting effect, such as described in US 8,503, 122. Suitable color shifting films are described in US Patent No. 6,531,230 to Weber et al.; which is incorporated herein by reference.

[0055] Other suitable color shifting films include multilayer films produced by spin coating, blade coating, dip coating, evaporation, sputtering, chemical vapor deposition (CVD), and the like. Exemplary films include both organic and inorganic materials. Such films are described, for example, in U.S. Patents 7,140,741; 7,486,019; and 7,018,713. Alternatively, articles containing microstructures (e.g., Figure 2 The microstructured film article 200 shown in FIG ) can be prepared by melt extrusion (i.e., pouring a fluid resin composition onto a negative microstructured molding surface of a master mold (e.g., a tool) and allowing the composition to harden). In this embodiment, the protrusions (e.g., light-transmitting areas) are interconnected to the base layer 260 in a continuous layer. The individual protrusions (e.g., light-transmitting areas) and the connections between them typically comprise the same thermoplastic material. The thickness of the mesa layer (i.e., the thickness excluding the portion resulting from the replicated microstructure) is typically between 1 and 100 microns, or between 2 and 25 microns.

[0056] Resin compositions suitable for melt extrusion are transparent materials that are dimensionally stable, durable, weather-resistant, and can be easily formed into desired configurations. Examples of suitable materials include acrylics having a refractive index of about 1.5, such as Plexiglas brand resins manufactured by Rohm and Haas Company; polycarbonates having a refractive index of about 1.59; reactive materials such as thermosetting acrylates and epoxy acrylates; polyethylene-based ionomers such as those sold under the trade name SURLYN by E.I. DuPont de Nemours and Co., Inc.; ethylene acrylic acid copolymers; polyesters; polyurethanes; and cellulose acetate butyrate. Polycarbonates are particularly suitable due to their toughness and relatively high refractive index.

[0057] In another embodiment, a master negative microstructured molding surface (eg, tool) can be used as an embossing tool, such as described in US Patent 4,601,861 (Pricone).

[0058] The absorbing regions are typically formed by coating the surface of the microstructured film. Various coating methods can be used, including, for example, layer-by-layer (LbL) coating, vapor deposition, sputtering, reactive sputtering, and atomic layer deposition (ALD).

[0059] The light-absorbing material that can be used to form the light-absorbing region can be any suitable material that absorbs or blocks light in at least a portion of the visible spectrum. Preferably, the light-absorbing material can be coated or otherwise provided on the sidewalls of the light-transmitting region to form the light-absorbing region in the LCF. Exemplary light-absorbing materials include black or other light-absorbing colorants (such as carbon black, another pigment or dye, or a combination thereof). Other light-absorbing materials can include particles or other scattering elements that can be used to block light from being transmitted through the light-absorbing region.

[0060] When the light absorbing material (e.g., coating) includes particles, the median particle size D50 of the particles is equal to or less than the thickness of the light absorbing material (e.g., coating) or in other words substantially less than the width W of the absorbing region. A .

[0061] The median particle size is generally less than 1 micron. In some embodiments, the median particle size is not more than 900nm, 800nm, 700nm, 600nm or 500nm. In some embodiments, the median particle size is not more than 450nm, 400nm, 350nm, 300nm, 250nm, 200nm or 100nm. In some embodiments, the median particle size is not more than 90nm, 85nm, 80nm, 75nm, 70nm, 65nm, 60nm, 55nm or 50nm. In some embodiments, the median particle size is not more than 30nm, 25nm, 20nm or 15nm. The median particle size is generally at least 1 nanometer, 2 nanometers, 3 nanometers, 4 nanometers or 5 nanometers. For example, the particle size of the nanoparticles in the absorption region can be measured using a transmission electron microscope or a scanning electron microscope.

[0062] "Primary particle size" refers to the median diameter of individual (non-aggregated, non-agglomerated) particles. "Agglomeration" refers to weak associations between primary particles that can be held together by charge or polarity and can be broken down into smaller entities. As used herein with respect to particles, "aggregate" refers to strongly bonded or fused particles, where the resulting surface area can be significantly less than the sum of the calculated surface areas of the individual components. The forces holding the aggregate together are very strong, such as covalent bonds, or forces resulting from sintering or complex physical entanglements. Although agglomerated nanoparticles can be broken down into smaller entities such as discrete primary particles, such as by applying a surface treatment, applying a surface treatment to aggregates only results in surface-treated aggregates. In some embodiments, the majority of the nanoparticles (i.e., at least 50%) are present as discrete, unagglomerated nanoparticles. For example, at least 70%, 80%, or 90% of the nanoparticles (e.g., of a coating solution) are present as discrete, unagglomerated nanoparticles.

[0063] The concentration of the light-absorbing nanoparticles is typically at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50% by weight of the total light-absorbing area. In some embodiments, the concentration of the light-absorbing nanoparticles is at least 55%, 60%, 65%, 70%, or 75% by weight of the total light-absorbing area. The concentration of the light-absorbing nanoparticles can be determined by methods known in the art, such as thermogravimetric analysis.

[0064] In one embodiment, the method includes applying layer-by-layer light absorbing coatings to the surfaces of the microstructured film, ie, the top surfaces and sidewalls of the protrusions and the bottom surfaces of the grooves.

[0065] In some embodiments, the plurality of layers disposed on the surface of the microstructured film include at least two layers deposited by what is commonly referred to as a "layer-by-layer self-assembly process". This process is typically used to electrostatically assemble films or coatings of oppositely charged polymer electrolytes, but other functionalities such as hydrogen bond donors / acceptors, metal ions / ligands, and covalent bond moieties can be the driving force for membrane assembly. "Polyelectrolyte" means a polymer or compound with multiple ionic groups capable of electrostatic interactions. "Strong polymer electrolytes" have a persistent charge over a wide pH range (e.g., polymers containing quaternary ammonium groups or sulfonic acid groups). "Weak polymer electrolytes" have a pH-dependent level of charge (e.g., polymers containing primary, secondary, or tertiary amines, or carboxylic acids). Typically, the deposition process involves exposing a substrate having a surface charge to a series of liquid solutions or baths. This can be achieved by immersing the substrate in a liquid bath (also known as dip coating), spraying, spin coating, roller coating, inkjet printing, and the like. Exposure to a first polyion (e.g., a polymer electrolyte bath) liquid solution having a charge opposite to that of the substrate results in rapid adsorption of charged species near the substrate surface, establishing a concentration gradient and drawing more polymer electrolytes from the bulk solution to the surface. Further adsorption occurs until a sufficient layer has developed to mask the underlying charge and reverse the net charge of the substrate surface. To achieve mass transfer and adsorption, the exposure time is typically on the order of minutes. The substrate is then removed from the first polyion (e.g., bath) liquid solution and exposed to a series of water rinse baths to remove any physically entangled or loosely bound polymer electrolytes. Following these rinse (e.g., bath) liquid solutions, the substrate is then exposed to a second polyion (e.g., polymer electrolyte or inorganic oxide nanoparticle bath) liquid solution having a charge opposite to that of the first polyion (e.g., bath) liquid solution. Because the surface charge of the substrate is opposite to that of the second (e.g., bath) liquid solution, adsorption occurs again. Continued exposure to the second polyion (e.g., bath) liquid solution causes a reversal of the surface charge of the substrate. Subsequent rinses can be performed to complete the cycle. This series of steps is referred to as building a layer pair, also referred to herein as a deposited "bilayer," and can be repeated as needed to further add additional layer pairs to the substrate.

[0066] Some examples of suitable methods include those described in US 8,234,998 to Krogman et al.; US 2011 / 0064936 to Hammond-Cunningham et al.; and US 8,313,798 to Nogueira et al. Layer-by-layer dip coating can be performed using a StratoSequence VI (nanoStrata Inc., Tallahassee, FL) dip coating robot.

[0067] In one embodiment, the plurality of layers deposited by layer-by-layer self-assembly is a polyelectrolyte stack comprising an organic polymer polyion (e.g., cation) containing a light absorbing material (e.g., pigment) and a counterion (e.g., anion). At least a portion of the cationic layer, at least a portion of the anionic layer, or at least a portion of a combination thereof comprises a light absorbing material (e.g., pigment) ionically bonded to the polyelectrolyte.

[0068] The thickness of the bilayer and the number of bilayers are selected to achieve the desired light absorption. In some embodiments, the thickness of the bilayer and the number of bilayers are selected to achieve the desired (e.g., absorption) optical properties using the minimum total thickness of the self-assembled layer and / or the minimum number of layer-by-layer deposition steps. The thickness of each bilayer is typically in the range of about 5 nm to 350 nm. The number of bilayers is typically at least 5, 6, 7, 8, 9, or 10. In some embodiments, the number of bilayers in each stack is no more than 150 or 100. The thickness of the stack is equal to the width W of the absorption region. A , as mentioned above.

[0069] A light-absorbing compound is dispersed within at least a portion of the polymer electrolyte layer. Various polymer electrolytes can be utilized, including inorganic compounds such as silica or silicates, and various phosphonocarboxylic acids and their salts (some of which are described in WO 2015 / 095317; incorporated herein by reference).

[0070] Polyelectrolyte organic polymers may be preferred because such materials can be removed more easily by reactive ion etching than inorganic materials.

[0071] Suitable polycationic organic polymers include, but are not limited to, linear and branched poly(ethyleneimine) (PEI), poly(allylamine hydrochloride), polyvinylamine, chitosan, polyaniline, polyamidoamine, poly(vinylbenzyltrimethylamine), polydiallyldimethylammonium chloride (PDAC), poly(dimethylaminoethyl methacrylate), poly(methacrylamido)propyl-trimethylammonium chloride, and combinations thereof, including copolymers thereof.

[0072] Other examples of suitable polycationic organic polymers include those that are insoluble in water, such as cationic polyurethane dispersions (eg, Sancure 20051 and Sancure 20072 from Lubrizol (Cleveland, Ohio)).

[0073] Suitable polyanionic organic polymers include, but are not limited to, poly(vinyl sulfate), poly(vinyl sulfonate), poly(acrylic acid) (PAA), poly(methacrylic acid), poly(styrene sulfonate), dextran sulfate, heparin, hyaluronic acid, carrageenan, carboxymethylcellulose, alginate, sulfonated tetrafluoroethylene-based fluoropolymers such as Poly(vinyl phosphoric acid), poly(vinyl phosphonic acid), and combinations thereof, including copolymers thereof. Other examples of suitable polyanionic organic polymers include those that are insoluble in water, such as anionic polyurethane dispersions or anionic acrylic polymer emulsions.

[0074] The molecular weight of the polyelectrolyte polymer can vary in the range of about 1,000 g / mol to about 1,000,000 g / mol. In some embodiments, the molecular weight (Mw) of the negatively charged anionic layer (e.g., poly(acrylic acid)) is in the range of 50,000 g / mol to 150,000 g / mol. In some embodiments, the molecular weight (Mw) of the positively charged cationic layer (e.g., polydiallyldimethylammonium chloride) is in the range of 50,000 g / mol to 300,000 g / mol. In some embodiments, the molecular weight (Mw) of the positively charged cationic layer (e.g., poly(ethyleneimine)) is in the range of 10,000 g / mol to 50,000 g / mol.

[0075] At least one of the polyions (eg, polyanions or polycations) comprises a light absorbing material.

[0076] In order to stabilize the colloidal dispersion in water and impart ionic groups, the light-absorbing (e.g., pigment) particles typically also include an ionic surface treatment. In some embodiments, the surface treatment compound is anionic, such as in the case of sulfonates or carboxylates. The light-absorbing (e.g., pigment) particles also serve as polyions with ionic binding groups for the alternating polymer electrolyte layers.

[0077] Suitable pigments are commercially available as colloidally stable aqueous dispersions from manufacturers such as Cabot, Clariant, DuPont, Dainippon, and DeGussa. Particularly suitable pigments include those sold under the trade names Those available from Cabot Corporation, such as 250C (cyan), 260M (magenta), 270Y (yellow), or 352K (black). The light absorbing (e.g., pigment) particles are typically surface treated to impart ionizable functionality. Examples of suitable ionizable functionalities for light absorbing (e.g., pigment) particles include sulfonate functionality, carboxylate functionality, and phosphate or bisphosphonate functionality. In some embodiments, surface treated light absorbing (e.g., pigment) particles having ionizable functionality are commercially available. For example, light absorbing (e.g., pigment) particles are commercially available from Cabot Corporation under the trade names 250C (cyan), 260M (magenta), 270Y (yellow), and 200 (black). The pigment includes sulfonate functionality. For example, it is commercially available from Cabot Corporation under the trade names 352K (black) and 300 (black). The pigment includes carboxylate functionality.

[0078] When the light absorbing (eg, pigment) particles are not pre-treated, the light absorbing (eg, pigment) particles can be surface treated to impart ionizable functionality as is known in the art.

[0079] Multiple light absorbing materials (e.g., pigments) can be used to achieve a specific chromaticity or hue or color in the final product. When multiple light absorbing materials (e.g., pigments) are used, the materials are selected to ensure both their compatibility and performance with each other and with the optical product components.

[0080] In a preferred embodiment, a polymer electrolyte is prepared and applied to the microstructured surface as an aqueous solution or suspension. The term "aqueous" means that the liquid of the coating comprises at least 85 wt % water. It can comprise a higher amount of water, such as, for example, at least 90 wt %, 95 wt % or even at least 99 wt % water or more. The aqueous liquid medium can comprise a mixture of water and one or more water-soluble organic cosolvents, and their amount makes the aqueous liquid medium form a single phase. The example of a water-soluble organic cosolvent comprises methanol, ethanol, isopropanol, 2-methoxyethanol, 3-methoxypropanol, 1-methoxy-2-propanol, tetrahydrofuran and ketone or ester solvents. The amount of the organic cosolvent is usually no more than 15 wt % of the total liquid of the coating composition. The aqueous polymer electrolyte composition for layer-by-layer self-assembly usually comprises at least 0.01 wt %, 0.05 wt % or 0.1 wt %, and is usually not more than 5 wt %, 4 wt %, 3 wt %, 2 wt % or 1 wt % of the polymer electrolyte.

[0081] In some embodiments, the aqueous solution or suspension further comprises a "masking agent," an additive that promotes uniform and reproducible deposition by increasing ionic strength and reducing interparticle electrostatic repulsion. Suitable masking agents include any low molecular weight salt, such as a halide salt, sulfate, nitrate, phosphate, fluorophosphate, etc. Examples of halide salts include chloride salts such as LiCl, NaCl, KCl, CaCl2, MgCl2, NH4Cl, etc., bromide salts such as LiBr, NaBr, KBr, CaBr2, MgBr2, etc., iodide salts such as LiI, NaI, KI, CaI2, MgI2, etc., and fluoride salts such as NaF, KF, etc. Examples of sulfates include Li2SO4, Na2SO4, K2SO4, (NH4)2SO4, MgSO4, CoSO4, CuSO4, ZnSO4, SrSO4, Al2(SO4)3, and Fe2(SO4)3. Organic salts such as (CH3)3CCl, (C2H5)3CCl, etc. are also suitable masking agents.

[0082] Suitable masking agent concentrations may vary with the ionic strength of the salt. In some embodiments, the aqueous solution comprises a masking agent (eg, NaCl) at a concentration in the range of 0.01 M to 0.1 M. The absorption region may comprise trace amounts of the masking agent.

[0083] After the light absorbing coating is applied to (e.g., the entire) surface of the microstructured film and dried, the light absorbing coating is then removed from the first sidewall or the second sidewall. In some embodiments, the coating is substantially or completely removed from one of the sidewalls. In some embodiments, material is removed from both sidewalls, but to different extents. The light absorbing coating may also be removed from the top portion of the transmissive (e.g., protruding) regions, and the light absorbing coating may also be removed from the mesa regions located between the transmissive (e.g., protruding) regions.

[0084] Any suitable method can be used to selectively remove light absorbing material from the surface of the microstructured surface.

[0085] In one embodiment, the light-absorbing material is removed by reactive ion etching. Reactive ion etching (RIE) is a directional etching process that uses ion bombardment to remove material. RIE systems are used to remove organic or inorganic materials by etching surfaces orthogonal to the direction of ion bombardment. The most significant difference between reactive ion etching and isotropic plasma etching is the etching direction. Reactive ion etching is characterized by a ratio of vertical etch rate to lateral etch rate greater than 1. Systems for reactive ion etching are built around a durable vacuum chamber. Before starting the etching process, the chamber is evacuated to a base pressure of less than 1 Torr, 100 mTorr, 20 mTorr, 10 mTorr, or 1 mTorr. Electrodes hold the material to be processed and are electrically isolated from the vacuum chamber. The electrodes can be rotatable electrodes in the shape of a cylinder. A counter electrode is also disposed within the chamber and can be formed from the wall of the vacuum reactor. A gas containing an etchant enters the chamber through a control valve. The chamber gas is continuously evacuated by a vacuum pump to maintain the process pressure. The type of gas used depends on the etching process. Carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), octafluoropropane (C3F8), trifluoromethane (CHF3), boron trichloride (BCl3), hydrogen bromide (HBr), chlorine, argon, and oxygen are commonly used for etching. RF power is applied to the electrodes to generate a plasma. The sample can be transported over the electrodes by the plasma for a controlled period of time to achieve a specified etch depth. Reactive ion etching is known in the art and is further described in US Pat. No. 8,460,568, which is incorporated herein by reference.

[0086] In another embodiment, light-absorbing materials are removed by laser ablation (e.g., pulsed laser ablation). Pulsed laser ablation (PLA) is a directional ablation process that utilizes a photon flux to generate sufficient photon energy density to remove material by oxidation and / or sputtering. PLA systems are used to remove organic or inorganic materials by etching surfaces orthogonal to the direction of the photon energy density, which vaporizes the target during the generation of a plasma plume. PLA depends on the wavelength of the laser and the amount of absorption present in the light-absorbing material at that wavelength. Absorption of the laser pulse generates energy for thermal, chemical, or mechanical evaporation, ablation, and / or plasma formation. The presence of an oxidizing gas in the laser pulse position may alter the amount of chemical oxidation that occurs during the PLA process. Light-absorbing materials require a critical amount of energy density for ablation. The energy density can be varied by optical configuration to change the size and position of the focal spot, and can be varied by the power setting of the laser system. The relative orientation of the laser energy density and the sample allows one skilled in the art to ablate light-absorbing materials coated at oblique angles on a structured surface.

[0087] After removing the light-absorbing coating, the grooves can be filled with an organic polymer material. In some embodiments, the organic polymer material is a polymerizable resin composition, and the method further comprises (e.g., radiation) curing the polymerizable resin. Typically, the same polymerizable resin used to make the microstructured film is used to fill the grooves. Alternatively, different organic polymer materials (e.g., polymerizable resin compositions) are used. When using different organic polymer materials (e.g., polymerizable resin compositions), the composition is typically selected to match the refractive index of the light-transmitting region. The so-called "refractive index matching" means that the refractive index difference between the filling material and the transmissive region is typically less than 0.1 or 0.005. Alternatively, the grooves can be filled with different organic polymer materials (e.g., polymerizable resin compositions) having a refractive index difference greater than 0.1. In another embodiment, the grooves are not filled with an organic polymer material (e.g., polymer resin). In this embodiment, the grooves typically include air with a refractive index of 1.0.

[0088] When the grooves are filled with a cured polymerizable resin, the light management film can optionally include a cover film 470 bonded to the microstructured film with adhesive 410. When the grooves are filled with air, an adhesive film and a cover film are typically included.

[0089] In another embodiment, layer 410 may be a topcoat rather than an adhesive. In this embodiment, cover film 470 may not be present.

[0090] Figure 4 An LCF 400 is shown that also includes an optional cover film 470 that can be the same as or different from the base layer 260. The optional cover film 470 can be bonded to the microstructured surface with an adhesive 410. The adhesive 410 can be any optically clear adhesive, such as a UV-curable acrylate adhesive, a transfer adhesive, and the like.

[0091] The LCF may also include other coatings, typically disposed on exposed surfaces. Various hard coatings, anti-glare coatings, anti-reflective coatings, antistatic coatings, and anti-fouling coatings are known in the art. See, for example, U.S. Patent 7,267,850; U.S. Patent 7,173,778; PCT Publications WO 2006 / 102383, WO 2006 / 025992, WO 2006 / 025956, and U.S. Patent 7,575,847.

[0092] Figure 5A perspective schematic diagram of a backlight display 500 according to one embodiment is shown. The backlight display 500 includes an LCF 530 including a transmissive region 540 and an absorptive region 550, as previously described. As previously described, such an LCF has a polar cutoff viewing angle θP for light exiting an output surface 590 of the LCF 530. The backlight display 500 includes a light source 510 configured to transmit light through the LCF 530, through an image plane 520 (such as an LCD panel), and to an observer 595. The viewing angle at which brightness is maximum may depend on the polar cutoff viewing angle, as previously described.

[0093] Backlit display 500 may also include an optional brightness enhancement film 560 and a reflective polarizing film 570 to further improve the brightness and uniformity of the display. The brightness enhancement film may be a prismatic film such as 3M TM Brightness Enhancement Film "BEF" or Thin Brightness Enhancement Film "TBEF" available from 3M Company. Reflective polarizing film 570 may be a multilayer optical film such as 3M TM Dual Brightness Enhancement Film "DBEF" is available from 3M Company, St. Paul, MN. Brightness enhancement film 560 and reflective polarizing film 570 (if included) can be as follows: Figure 5 Positioning shown.

[0094] In other embodiments, as previously described, a light management film comprising transmissive and absorptive regions can be bonded to an emissive (eg, organic light emitting diode or OLED) display.

[0095] In some embodiments, the LCF described herein (i.e., a first LCF) can be combined with a second LCF. In some embodiments, the second LCF can be an LCF (e.g., a privacy film) such as described in the following patents: US 6,398,370; US 8,013,567; US 8,213,082; and US 9,335,449. In other embodiments, the second LCF is an LCF as described herein (e.g., wherein the light-absorbing region has an aspect ratio of at least 30). The first and second LCFs can be stacked in various orientations.

[0096] Other types of backlit display imaging devices are also contemplated, including non-electronic displays such as sunglasses, document covers, console switches in automotive and aviation applications, aircraft cockpit controls, helicopter cockpit controls, windows, and any number of other devices.

[0097] In other embodiments, the light control films described herein can be used as a coating for glass. For example, the light control films can be laminated onto or within window and door systems. Window and door systems can be selected from glass panels, windows, doors, walls, and skylight systems. Window and door systems can be located on the exterior or interior of a building. These systems can also be automobile windows, train windows, airplane passenger windows, and the like. Advantages of assembling these film stacks into window and door systems include reduced IR transmission (which can result in increased energy savings), ambient light blocking, privacy, and decorative effects.

[0098] This specification should not be considered limited to the specific examples described herein, but should be understood to encompass all aspects of the specification as clearly set forth in the appended claims. Various modifications, equivalent processes, and numerous structures that may be applied to this specification will become apparent to those skilled in the art upon review of this specification. The foregoing description may be better understood by considering the embodiments illustrated by the experimental results and examples that follow.

[0099] Example

[0100] Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

[0101] Unless otherwise indicated, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight. Unless otherwise indicated, all chemicals were obtained or purchased from chemical suppliers such as Sigma-Aldrich Co., St. Louis, Missouri.

[0102] The following is a list of materials used throughout the examples, along with their brief descriptions and sources.

[0103] The components of Resin A used in the casting and curing microreplication process (Preparative Example 1) and the refractive index matching backfill material in the "Method for Backfilling Grooves in a Microstructured Film" are listed below in Table 1. The raw materials used for layer-by-layer coating are listed below in Table 2. The raw materials used for reactive ion etching are listed below in Table 3.

[0104] Table 1: Raw materials used for resin A

[0105]

[0106]

[0107] Table 2: Raw materials used for layer-by-layer coating

[0108]

[0109] Table 3: Raw materials used for reactive ion etching

[0110]

[0111] Preparation Example 1 (PE1): Preparation of "Shark Fin" Microstructured Film

[0112] Use triangular diamonds to cut tools with multiple near-triangular features, such as Figure 6 Resin A was prepared by mixing the materials in Table 4 below.

[0113] Table 4: Composition of Resin A used to prepare microstructured films

[0114] Material parts by weight Photomer 6010 60 SR602 20 SR601 4.0 TMPTA 8.0 PEA (Etermer 2010) 8.0 Darocur 1173 0.35 TPO 0.10 I1035 0.20

[0115] A "cast and cure" microreplication process was performed using Resin A and the tool described above. Line conditions were: resin temperature 150°F, mold temperature 150°F, coater IR 135°F, tool temperature 100°F, and line speed 60 fpm. Curing was performed using a Fusion D lamp with a peak wavelength of 385 nm and operated at 100% power. The resulting microstructured film included a plurality of triangular protrusions (e.g., light-transmitting areas) separated by grooves, as shown in FIG8 . The base layer was a PET film (3M, St. Paul, MN) having a thickness of 2.93 mils (74.4 microns). The side of the PET film that contacted the resin was primed with a thermosetting acrylic polymer (Rhoplex 3208, available from Dow Chemical, Midland, MI). The mesa layer of the cured resin had a thickness of 2 to 3 microns. The triangles of the microstructured film are a negative copy of the uncut portions of the tool between the grooves.

[0116] Method for preparing layer-by-layer self-assembled coatings on microstructured films

[0117] The layer-by-layer self-assembled coatings were prepared using an apparatus purchased from Svaya Nanotechnologies, Inc. (Sunnyvale, CA) and according to US 8,234,998 (Krogman et al.) and the method of Krogman et al. Automated processes for improved uniformity and flexibility in layer-by-layer deposition , Langmuir, 2007, vol. 23, pp. 3137-3141 (Krogman et al. Automated Process for Improved Uniformity and Versatility of Layer-by-Layer Deposition ,Langmuir 2007,23,3137-3141)) is modeled.

[0118] The apparatus includes a pressure vessel loaded with a coating solution. A spray nozzle with a flat spray pattern (available from Spraying Systems, Inc., Wheaton, Illinois) is installed to spray the coating solution and rinse water at a specified time controlled by a solenoid valve. The pressure vessel containing the coating solution (Alloy Products Corp., Waukesha, Wisconsin) is pressurized to 30 psi with nitrogen, while the pressure vessel containing deionized (DI) water is pressurized to 30 psi with air. The flow rate of the coating solution nozzle is 10 gallons per hour, while the flow rate of the DI water rinse nozzle is 40 gallons per hour. The substrate to be coated was adhered at the edges to a glass plate (12" x 12" x 1 / 8" thick) (Brin Northwestern Glass, Minneapolis, MN) with epoxy (Scotch-Weld Epoxy Adhesive, DP100 Clear, 3M Company, St. Paul, MN). Co., Minneapolis, MN) is mounted on a vertical translation workbench and held in place with a vacuum chuck. In a typical coating sequence, a polycation (e.g., PDAC) solution is sprayed onto the substrate while the workbench is moving vertically downward at 76 mm / s. Then, after a dwell time of 12 seconds, a DI water solution is sprayed onto the substrate while the workbench is moving vertically upward at 102 mm / s. The substrate is then dried with an air knife at a speed of 3 mm / s. Then, a polyanion (e.g., pigment nanoparticle) solution is sprayed onto the substrate while the workbench is moving vertically downward at 76 mm / s. Another dwell time of 12 seconds is allowed to pass. The DI water solution is sprayed onto the substrate while the workbench is moving vertically upward at 102 mm / s. Finally, the substrate is dried with an air knife at a speed of 3 mm / s. The above sequence is repeated to deposit a % (polycation / polyanion) solution. n The coated substrate (eg, polymer film) is peeled off from the glass before subsequent processing.

[0119] Preparation Example 2 (PE2): Layer-by-layer self-assembled coating on microstructured film

[0120] A cationic coating solution was prepared by first diluting Sancure 20051 (The Lubrizol Corporation, Wickliffe, Ohio) from 42 wt % to 1 wt % with DI water. Next, Pluronic PL-92 (BASF SE, Ludwigshafen, Germany) surfactant was added to a concentration of 0.1 wt %. The mixture was shaken by hand to dissolve the surfactant. An anionic coating solution was prepared by first diluting CAB-O-JET 200 (Cabot Corporation, Boston, Massachusetts) from 20 wt % to 2.5 wt % with DI water. Next, sodium chloride (Sigma Aldrich Co., St. Louis, Missouri) was added to a concentration of 50 mM, and Pluronic PL-92 (BASF SE, Ludwigshafen, Germany) surfactant was added to a concentration of 0.1 wt %. The mixture was shaken by hand to dissolve the salt and surfactant. A bilayer coating of 10 (abbreviated as (SC20051 / COJ200)10) was deposited onto the microstructured film described in PE1 using the "Method for Preparing Layer-by-Layer Self-Assembled Coatings on Microstructured Films".

[0121] Method for backfilling trenches in microstructured films

[0122] Resin A was heated in an oven to 165°F. After the reactive ion etching or laser ablation steps, the microstructured film samples were taped to an aluminum plate and then placed on a hot plate heated to 150°F. Resin A was pipetted between the microstructured film surface and a piece of primed 3-mil thick PET film placed on top; the construction was then conveyed through a GBC Catena 35 hot roll laminator heated to 135°F at a speed of 5 ft / min. The construction was then conveyed three times through a Heraeus (Hanau, Germany) belt conveyor UV processor (Model DRS(6)) with a 500-watt "H" bulb at a conveyor speed of 50 ft / min. After curing, the PET top film was either left in place or peeled off as specified in the examples.

[0123] Method for measuring the brightness distribution of light from a diffuse light source

[0124] Film sample is placed on Lambertian light source.When light transmission area is cone-shaped, film is positioned so that the widest part of cone-shaped area is closer to light source.Use Eldim L80 conoscope (Eldim SA, HEROUVILLE SAINT CLAIR, France) to detect light output in a hemispherical manner at all polar angles and azimuth angles simultaneously.After detection, read the cross section of transmittance (for example, brightness) reading in the direction orthogonal to the direction of Venetian blinds (expressed as 0 ° orientation angle), unless otherwise specified.Relative transmittance (that is, visible light brightness) is defined as the percentage of axial light brightness under a specific viewing angle between the reading with film and the reading without film.

[0125] The Lambertian light source is from the patent PCT / US18 / 65381 Figure 6 The baseline light intensity distribution is shown as diffuse transmittance composition of the light box. The light box is a six-sided hollow prism measuring approximately 12.5 cm × 12.5 cm × 11.5 cm (L × W × H) and is made of polytetrafluoroethylene (PTFE) diffuser sheet approximately 6 mm thick. One side of the box was selected as the sample surface. The diffuse reflectance of the hollow light box at the sample surface was measured to be approximately 0.83 (e.g., averaged approximately 83% over the wavelength range of 400 nm to 700 nm). During testing, the box was illuminated from within (light shining from the inside toward the sample surface) through an approximately 1 cm circular hole located in the bottom of the box (opposite the sample surface). Illumination was provided using a stable broadband incandescent light source attached to a fiber optic bundle for light guidance (Fostec DCR-II with a 1 cm diameter fiber optic bundle extension, from Schott-Fostec LLC, Marlborough, Mass. and Auburn, NY).

[0126] Example 1: Reactive Ion Etching of Horizontal and Diagonal Surfaces

[0127] Reactive ion etching (RIE) was performed on a sample of material from PE2. This was performed in a homemade parallel plate capacitively coupled plasma reactor. The chamber had a surface area of 18.3 ft 2A central cylindrical powered electrode is placed on the powered electrode. After the microstructured film is placed on the powered electrode, the reaction chamber is pumped down to a base pressure of less than 1.3 Pa (2 mTorr). O2 (oxygen) gas is flowed into the chamber at a rate of 1000 SCCM each. Treatment is performed using a plasma enhanced CVD method by coupling RF power to the reactor at a frequency of 13.56 MHz and an applied power of 9000 watts. A treatment time of 250 s is applied by moving the microstructured film through the reaction zone. After treatment, the RF power and gas supply are stopped and the chamber is returned to atmospheric pressure. Additional information on materials and processes for applying cylindrical RIE and further details on the reactor used can be found in US8460568 B2.

[0128] The etched material was then backfilled with a UV-curable acrylate resin as described in the "Method for Backfilling the Grooves of the Microstructured Film" section above, and measurements were performed as described in the "Method for Measuring the Brightness Distribution of Light from a Diffuse Light Source" section above. The peak transmission angle was obtained from the conoscopic data by finding the angle at which maximum brightness was observed, and this peak transmission angle was determined to be -3 degrees. The maximum relative transmittance was 90.9%.

[0129] Example 2: Laser ablation removal of LbL material from a near-vertical surface

[0130] A sample of a PE2 substrate was illuminated using the laser illumination system described in US Patent No. 6285001B1. The substrate was tilted at a 10-degree angle relative to the focal plane of the laser illumination system. This exposed nearly vertical walls, while diagonal walls of the substrate were in shadow. The substrate was illuminated six times with 248 nm light at 300 mJ / cm² from a Coherent LEAP 200K excimer laser.

[0131] The ablated material was then backfilled with a UV-curable acrylate resin as described above in the "Method for Backfilling the Grooves of the Microstructured Film" section, and measurements were performed as described above in the "Method for Measuring the Brightness Distribution of Light from a Diffuse Light Source" section. The peak transmission angle was obtained from the conoscopic data by finding the angle at which maximum brightness was observed, and this peak transmission angle was determined to be 20 degrees. The maximum relative transmittance was 25.3%.

[0132] The entire disclosure of the patent disclosures cited herein is incorporated herein by reference in their entirety, as if each patent disclosure were incorporated herein individually. Various modifications and alterations of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. It should be understood that the present invention is not intended to be unduly limited to the exemplary embodiments and examples shown herein, and that the above-described examples and embodiments are presented by way of example only, and that the scope of the present invention is intended to be limited only by the claims shown herein below.

Claims

1. A light control film comprising: a light input surface and a light output surface facing away from the light input surface; and alternating transmissive and absorptive regions disposed between the light input surface and the light output surface, wherein the absorptive regions have an aspect ratio of at least 30 and a maximum width of no greater than 5 microns and are inclined in the same direction, and the alternating transmissive and absorptive regions have a maximum relative transmittance at a viewing angle other than 0 degrees, The light control film comprises a microstructured film comprising a plurality of protrusions defined by a bottom surface, a top surface, a first sidewall, and a second sidewall, the protrusions being separated from each other by grooves, wherein the light control film comprises an absorptive material only on the first sidewall, and the absorptive region comprises the absorptive material. 2 . The light control film of claim 1 , wherein the absorptive region has a maximum width no greater than 2 microns.

3. The light control film of claim 1 or 2, wherein the maximum relative transmittance is at a viewing angle between +30 degrees and -30 degrees.

4. The light control film of claim 3, wherein the maximum relative transmittance is at a viewing angle between +10 degrees and -10 degrees.

5. The light control film of claim 1 or 2, wherein the absorptive regions make a wall angle of +1 to +10 degrees or -1 to -10 degrees with respect to a line perpendicular to the light output surface.

6. The light control film of claim 5, wherein the absorptive regions make a wall angle of +2 to +8 degrees or -2 to -8 degrees relative to the light input surface from a line perpendicular to the light output surface.

7. The light control film of claim 1 or 2, wherein the absorptive regions are parallel to each other.

8. The light control film of claim 1 or 2, wherein the absorptive region has an aspect ratio of at least 50.

9. The light control film of claim 8, wherein the absorptive regions have an aspect ratio of at least 100.

10. The light control film of claim 1 or 2, wherein the absorptive regions have an average pitch of 10 microns to 100 microns.

11. The light control film of claim 1 or 2, wherein the absorptive region comprises an organic light absorbing material.

12. The light control film of claim 1 or 2, wherein the absorptive regions comprise carbon black.

13. The light control film of claim 1 or 2, wherein the absorbing region comprises a polymer electrolyte.

14. The light control film of claim 1 or 2, wherein the absorptive region comprises a non-metallic light absorbing material.

15. The light control film of claim 1 or 2, wherein the absorbing region comprises a bilayer in the form of a polymeric electrical stack comprising an organic polymer polyion and a counterion comprising a light absorbing material.

16. The light control film of claim 1 or 2, wherein the absorptive region comprises a layer-by-layer light absorbing coating.

17. The light control film of claim 1 or 2, wherein the alternating transmissive regions are integral with the mesa regions.

18. The light control film of claim 1 or 2, wherein the absorptive region comprises a core sandwiched between cladding layers.

19. A method for preparing a light control film, comprising: Providing a microstructured film comprising a bottom surface and a microstructured surface facing away from the bottom surface, and a plurality of light-transmitting areas alternating with grooves, wherein the microstructured surface is defined by a top surface, a first sidewall, and a second sidewall of the light-transmitting areas, and a bottom surface of the grooves, wherein the first sidewall makes a wall angle of +1 to +10 degrees or -1 to -10 degrees with a line perpendicular to the bottom surface of the grooves; applying an organic light absorbing material to the microstructured surface; as well as A light absorbing material is removed from one of the first sidewall and the second sidewall while retaining the light absorbing material on the other of the first sidewall or the second sidewall, wherein the light absorbing material on the other of the first sidewall or the second sidewall has an aspect ratio of at least 30 and a maximum width of no greater than 5 micrometers and is inclined in the same direction.

20. The method of claim 19, further comprising removing organic light absorbing material from the top surface or the bottom surface.

21. The method of claim 20, wherein removing the organic light absorbing material from the top surface or the bottom surface comprises reactive ion etching.

22. The method of claim 20, wherein removing organic light absorbing material from the top surface or the bottom surface comprises laser ablation.

23. The method according to any one of claims 19 to 22, wherein the organic light-absorbing material comprises a polymer electrolyte.

24. The method of any one of claims 19 to 22, wherein the organic light absorbing material comprises a plurality of light absorbing particles.

25. The method of any one of claims 19 to 22, wherein the organic light absorbing material comprises a layer-by-layer self-assembled coating.

26. The method of any one of claims 19 to 22, wherein removing light absorbing material from the first sidewall or the second sidewall comprises reactive ion etching.

27. The method of any one of claims 19 to 22, wherein removing the organic light absorbing material from the first sidewall or the second sidewall comprises laser ablation.

28. The method of any one of claims 19 to 22, comprising removing organic light absorbing material from the second sidewall without removing light absorbing material from the first sidewall.

29. The method of any one of claims 19 to 22, further comprising filling the trench with an organic polymer material.

30. A light management film comprising a microstructured film comprising a plurality of protrusions separated by grooves, the protrusions and the grooves being defined by a bottom surface, a top surface, a first sidewall, and a second sidewall, wherein the microstructured film has an absorbent material only on the first sidewall, wherein the absorbent material on the first sidewall has an aspect ratio of at least 30 and a maximum width no greater than 5 microns and is sloped in the same direction.

31. The light control film of claim 30, wherein the first sidewall makes a wall angle of +1 to +10 degrees or -1 to -10 degrees with a line perpendicular to the bottom surface.

32. The light control film of claim 30, wherein the first sidewall is at a first wall angle with a line perpendicular to the bottom surface, and the second sidewall is at a second wall angle with the line perpendicular to the bottom surface, and wherein the first wall angle is less than the second wall angle.

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