Optical film with asymmetric top-hat transmission

Abstract

A light control film (LCF) includes a light input surface and a light output surface opposite the light input surface, and a plurality of spaced-apart, substantially parallel louvers, each of the louvers having a height H extending between the light input surface and the light output surface, a length L along a length of the LCF, and a width, W, along a width direction of the light control film. Each louver of the plurality of louvers includes a light reflective layer disposed on, and substantially co-extensive along the height and length of the louver with, a light absorbing layer. Each light absorbing layer of each louver faces the light reflective layer of an adjacent louver.

Description

[0001] OPTICAL FILM WITH ASYMMETRIC TOP-HAT TRANSMISSION

[0002] Summary

[0003] In some aspects of the present description, a light control film is provided, the light control film having a structured first major surface opposite a second major surface, the structured first major surface including a plurality of structures extending along a length direction, and arranged along a width direction, of the light control film, each structure comprising a first facet opposite a second facet. The first facet and the second facet extend from a base of the structure along a thickness direction of the light control film. The first facet makes a first angle with the second major surface, and the second facet makes a second angle with the second major surface, such that the first angle is greater than the second angle. At least 80% of the first facets and at most 20% of the second facets are substantially conformally coated with a first cover layer having a substantially uniform first thickness. At least 70% of the first cover layers on the first facets are substantially conformally coated with a second cover layer having a substantially uniform second thickness. For each pair of adjacent first cover layer and second cover layer disposed on a first facet, the first cover layer is disposed between the first facet and the second cover layer. The first cover layer is one of a light reflective layer and a light absorbing layer, and the second cover layer is the other of the light reflective layer and the light absorbing layer.

[0004] In some aspects of the present description, a light control film is provided, the light control film having a light input surface and a light output surface opposite the light input surface 301, and a plurality of spaced-apart, substantially parallel louvers. Each of the louvers has a height, H, extending between the light input surface and the light output surface, a length, L, along a length of the light control film, and a width, W, along a width direction of the light control film. Each louver of the plurality of louvers includes a light reflective layer disposed on, and substantially co-extensive along the height and length of the louver with, a light absorbing layer. Each light absorbing layer of each louver faces the light reflective layer of an adjacent louver.

[0005] In some aspects of the present description, a light control film is provided, the light control film having a plurality of spaced-apart, substantially parallel louvers. Each of the louvers has a primarily specular reflective major first side and a primarily light absorbing opposing major second side. The primarily light absorbing major second side of each louver faces the primarily reflective major first side of an adjacent louver.

[0006] In some aspects of the present description, a method of making a light control film is provided, the method including providing a substantially light transmissive film having a structured first major surface and an opposing second major surface, the structured first major surface including a plurality of structures extending along a length direction, and arranged along a width direction, of the light control film, each structure having a first facet opposite a second facet, conformally coating the first facets and the second facets with a first cover layer having a substantially uniform first thickness; conformally coating the first cover layer on the first facets and the second facets with a second cover layer having a substantially uniform second thickness; and etching the first cover layer and the second cover layer using at least a directional first etching process to remove the first cover layer and the second cover layer from at least about 80% of the second facets but from no more than about 20% of each of the first facets. The first cover layer is one of a light reflective layer and a light absorbing layer, and the second cover layer is the other of the reflective layer and the light absorbing layer. The first facet and the second facet extend from a base of the structure along a thickness direction of the light control film, the first facet makes a first angle with the second major surface, and the second facet makes a second angle with the second major surface, such that the first angle greater than the second angle.

[0007] Brief Description of the Drawings

[0008] FIGS. 1A and IB are side views of a light control film having louvers with a light absorbing side opposite a light reflective side, in accordance with an embodiment of the present description;

[0009] FIGS. A and 2B provide details of structures and louvers of a light control film, in accordance with an embodiment of the present description;

[0010] FIGS. 3A and 3B provide additional details of structures and louvers of a light control film, in accordance with an embodiment of the present description;

[0011] FIGS. 4 A and 4B provide details of structures and louvers of a light control film, in accordance with an embodiment of the present description;

[0012] FIG. 5 illustrates different ray paths of a light control film, in accordance with an embodiment of the present description;

[0013] FIG. 6 is a plot of light transmission versus viewing angle for a light control film, in accordance with an embodiment of the present description;

[0014] FIGS. 7 A and 7B illustrate display systems including a light control film, in accordance with an embodiment of the present description;

[0015] FIG. 8 details a method of making a light control film, in accordance with an embodiment of the present description;

[0016] FIGS. 9 A and 9B provide additional details on a method of making a light control film, in accordance with an embodiment of the present description;

[0017] FIGS. 10A and 10B (Examples) are plots showing the light transmission percentage versus viewing angle for various modeled light control films, in accordance with an embodiment of the present description;

[0018] FIG. 11 (Examples) is a plot showing the light transmission percentage versus viewing angle for a modeled light control film, in accordance with an embodiment of the present description; and FIGS. 12A and 12B (Examples) are plots showing the light transmission percentage versus viewing angle for various modeled light control films, in accordance with an embodiment of the present description.

[0019] Detailed Description

[0020] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0021] There are various applications in displays and optical system for which having an off-axis, broad, top-hat transmission profile is beneficial. Traditionally, this type of transmission profile has been created using conventional louvers, where the louvers are created by backfilling trapezoid-shaped grooves with black resin, leading to bulky asymmetric louvers with comparatively lower efficiency. This low efficiency can be attributed primarily to the width of the louvers, which block a significant portion of the light from being transmitted through the louver film.

[0022] According to some aspects of the present description, an improved light control film provides a significant increase in transmission efficiency (e.g., greater than at least about 70%, or 80%, or 90%). In some embodiments, this transmission efficiency is achieved by providing louvers within the light control film having a highly light reflective first side and an opposing light absorbing second side.

[0023] According to some aspects of the present description, a light control film include a structured first major surface opposite a second major surface, the structured first major surface comprising a plurality of structures extending along a length direction (e.g., a y-direction of the light control film), and arranged along a width direction (e.g., an x-direction of the light control film) In some embodiments, each structure may have a first facet opposite a second facet. In some embodiments, the first facet and the second facet may extend from a base of the structure along a thickness direction (e.g., a z-direction of the light control film).

[0024] A structured surface can be prepared by any suitable method. In one embodiment, a structure, e.g., a microstructured film, can be prepared by a method including the steps of (a) preparing a polymerizable composition; (b) depositing the polymerizable composition onto a master negative microstructured molding surface (e.g., tool) in an amount barely sufficient to fill the cavities of the master; (c) filling the cavities by moving a bead of the polymerizable composition between a (e.g., preformed film) base layer and the master, at least one of which is flexible; and (d) curing the composition. The deposition temperature can range from ambient temperature to about 180°F (82°C). The master can be metallic, such as nickel, chrome- or nickel-plated copper or brass, or can be a thermoplastic material that is stable under the polymerization conditions and has a surface energy that allows clean removal of the polymerized material from the master. When the base layer is a preformed film, one or more of the surfaces of the film can optionally be primed or otherwise be treated to promote adhesion to the organic material of the microstructure.

[0025] The polymerizable resin can comprise a combination of a first and second polymerizable component selected from (meth) acrylate monomers, (meth)acrylate oligomers, and mixtures thereof. As used herein, “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 can comprise a (meth) aery lated urethane oligomer, (meth)acrylated epoxy oligomer, (meth) aery lated polyester oligomer, a (meth)acrylated phenolic oligomer, a (meth)acrylated acrylic oligomer, and mixtures thereof.

[0026] The polymerizable resin can be a radiation curable polymeric resin, such as a UV curable resin. In some cases, polymerizable resin compositions useful for the microstructured film of the present disclosure can include polymerizable resin compositions such as are described in U.S. Patent No. 8,012,567 (Gaides et al.).

[0027] The chemical composition and thickness of the base layer (substrate layer) can depend on the end use of the microstructured film. In typical embodiments, the thickness of the base layer can be at least about 0.025 millimeters (mm) and can be from about 0.05 mm to about 0.25 mm. Useful base layer materials include, for example, styrene-acrylonitrile, cellulose acetate butyrate, cellulose acetate propionate, cellulose triacetate, polyether sulfone, polymethyl methacrylate, polyurethane, polyester, polycarbonate, polyvinyl chloride, polystyrene, polyethylene naphthalate, copolymers or blends based on naphthalene dicarboxylic acids, polyolefin-based material such as cast or orientated films of polyethylene, polypropylene, and polycyclo-olefins, polyimides, and glass. Optionally, the base layer can contain mixtures or combinations of these materials. In some embodiments, the base layer may be multi-layered or may contain a dispersed component suspended or dispersed in a continuous phase.

[0028] Examples of base layer materials include polyethylene terephthalate (PET) and polycarbonate (PC). Examples of useful PET films include photograde polyethylene terephthalate, available from DuPont Films (Wilmington, DE), under the trade designation “Melinex 618”. Examples of optical grade polycarbonate films include LEXAN polycarbonate film 8010, available from GE Polymershapes, Seattle, WA, and Panlite 1151, available from Teijin Kasei, Alpharetta, GA.

[0029] Alternatively, the microstructured film can be prepared by melt extrusion, i.e., casting a fluid resin composition onto a master negative microstructured molding surface (e.g., tool) and allowing the composition to harden. In this embodiment, the protrusions are interconnected in a continuous layer to the base layer. The individual protrusions and connections therebetween generally comprise the same thermoplastic material. The thickness of the land layer (i.e., the thickness excluding that portion resulting from the replicated microstructure) is typically between 0.001 and 0.100 inches and preferably between 0.003 and 0.010 inches. Suitable resin compositions for melt extrusion are transparent materials that are dimensionally stable, durable, weatherable, and readily formable into the desired configuration. Examples of suitable materials include acrylics, which have an index of refraction of about 1.5, such as Plexiglas brand resin manufactured by Rohm and Haas Company (Philadelphia, PA); polycarbonates, which have an index of refraction of about 1.59; reactive materials such as thermoset acrylates and epoxy acrylates; polyethylene based ionomers, such as those marketed under the brand name of SURLYN by Dow Chemical (Midland, MI); (poly)ethylene-co-acrylic acid; polyesters; polyurethanes; and cellulose acetate butyrates. Polycarbonates are particularly suitable because of their toughness and relatively higher refractive index.

[0030] In yet another embodiment, the master negative microstructured molding surface (e.g., tool) can be employed as an embossing tool, such as described in U.S. Pat. No. 4,601,861 (Pricone).

[0031] In some embodiments, the first facet may make a first angle with the second major surface, and the second facet may make a second angle with the second major surface, such that the first angle is greater than the second angle. In some embodiments, each structure of the plurality of structures may be separated from an adjacent structure by a substantially planar landing. In some embodiments, the first facet and the second facet of each structure of the plurality of structures may be connected by a substantially planar top surface. In some such embodiments, the top surface may define a width, W 1, the base of each structure of the plurality of structures may define a width, W2, such that W1 is less than W2. In some other embodiments, the first facet and the second facet of each structure of the plurality of structures may meet at a peak of the structure.

[0032] In some embodiments, at least 80% of the first facets and at most 20% of the second facets may be substantially conformally coated with a first cover layer having a substantially uniform first thickness. In some embodiments, at least 70% of the first cover layers on the first facets may be substantially conformally coated with a second cover layer having a substantially uniform second thickness. For each pair of adjacent first cover layer and second cover layer disposed on a first facet, the first cover layer may be disposed between the first facet and the second cover layer. In some embodiments, the first cover layer may be one of a light reflective layer and a light absorbing layer, and the second cover layer may be the other of the light reflective layer and the light absorbing layer. Stated another way, in some embodiments, the first cover layer may be light reflective and the second cover layer may be light absorbing. In other embodiments, the first cover layer may be light absorbing and the second cover layer may be light reflective.

[0033] In some embodiments, a magnitude of the first angle (e.g., the angle of the first facet on the interior of the structure relative to the second major surface) is less than or equal to about 90 degrees. In some embodiments, a magnitude of the second angle (e.g., the angle of the second facet on the interior of the structure relative to the second major surface) is less than about 75 degrees. In some embodiments, the plurality of structures may have an average height, H, and an average pitch, P, where pitch is defined as a distance between a first facet of a first structure and a corresponding first facet of a second, adjacent structure, such that H / P > about 0.5. In some embodiments, the light control film may further include a planarizing overcoat covering, and substantially planarizing, the structured first major surface (i.e. , at least partially encapsulating the plurality of structures). In some such embodiments, the planarizing overcoat may include an optically clear adhesive. In some embodiments, the refractive index of the planarizing overcoat may be substantially equal to the refractive index of the material of the first major surface.

[0034] In some embodiments, light absorbing layer may absorb light at one more wavelengths in the ultraviolet light range (i.e., 100-400 nm) and / or the visible light range (i.e., 400-700 nm) and / or the infrared light range (i.e., 700 nm - 1 mm). In some embodiments, the light absorbing layer may include a poly electrolyte. In some embodiments, the light absorbing layer may include a plurality of light absorbing particles. In some such embodiments, the light absorbing particles may include one or more of a dye, a pigment, and a carbon black. In some embodiments, the light absorbing layer may have an optical density of greater than about 0.1. For example, the light absorbing cover layer may have an optical density, at one or more wavelengths from 100 nm to 1 mm of greater than about 0.1, or greater than about 0.2, or greater than about 0.4, or greater than about 0.6, or greater than about 0.8, or greater than about 1, or greater than about 1.1, or greater than about 1.2, or greater than about 1.3, or greater than about 1.4, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3, or greater than about

[0035] 3.5, or greater than about 4, or greater than about 4.5, or greater than about 5, or greater than about 5.5, or greater than about 6. In some embodiments, the optical density is less than about 3.0, or less than about

[0036] 2.5, or less than about 2.0. In some embodiments the optical density is between 0.5 and 2.5, or between 1.0 and 2.0 or between 1.2 and 1.8. As used herein, optical density shall be defined as -loglO(T), where T is the optical transmission of the light absorbing cover layer, and T is defined as Io / It, where Iois the intensity of incident light and Itis the intensity of the transmitted light (light passing through the medium). For example, if transmission, T, is 1%, the optical density is calculated as -loglO(O.Ol) which is equal to an optical density of 2.0.

[0037] In some embodiments, the light absorbing layer may include a cladding layer disposed on a core layer, the cladding layer facing away from the light reflective layer. In some such embodiments, the core layer may have a first concentration, Cl, of a light absorbing material and the cladding layer may have a second concentration, C2, of the light absorbing material, such that C2 is less than Cl.

[0038] In some embodiments, the core layer may include 30 wt. % to 100 wt. % of light absorbing material and the cladding layer may include 0.5 wt. % to 50 wt. % of light absorbing material. In some such embodiments, the core layer may include 15 vol. % to 90 vol. % of light absorbing material and the cladding layer may include 0.3 vol. % to 35 vol. % of light absorbing material.

[0039] In some embodiments, the core layer may have an optical density, at one or more wavelengths from 100 nm to 1 mm of greater than about 0.1, or greater than about 0.2, or greater than about 0.4, or greater than about 0.6, or greater than about 0.8, or greater than about 1, or greater than about 1.1, or greater than about 1.2, or greater than about 1.3, or greater than about 1.4, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3, or greater than about 3.5, or greater than about 4, or greater than about 4.5, or greater than about 5, or greater than about 5.5, or greater than about 6.

[0040] In some embodiments, the light absorbing cover layer may be primarily light absorbing but may also be partially reflective. Typical light absorbing cover layers may not include a metal. In some embodiments, the core layer for the light absorbing cover layer may have an extinction coefficient (k) in the visible light range (e.g., at 550 nm) in the range of 0.1 to 0.5. In some embodiments, a cladding layer for the light absorbing cover layer may have a k value in the range of 0.001 to 0.20.

[0041] In some embodiments, the light reflective layer may be a metal layer (e.g., silver, aluminum, nickel, etc.). In some embodiments, the light reflective layer may be an optically clear layer with a refractive index lower than a refractive index of a material of the structures (e.g., lower by at least 0.02, at least 0.04, at least 0.06, at least 0.08, at least 0.10, at least 0.12, or at least 0.14). In some embodiments, the light reflective layer is substantially specularly reflective.

[0042] In some embodiments, the light reflective layer may be primarily light reflective but may also be partially absorptive. When the light reflective layer is a metal, it may have a high extinction coefficient for at least one wavelength in the visible range (e.g., at 550 nm) of, for example, k greater than or equal to about 1, or about 1.5, or about 2, or about 2.5, or about 3, or about 3.5. In some embodiments, when the light reflective layer is optically clear, it may have a small extinction coefficient (e.g., k less than about 0.01, or less than about 0.001, or less than about 0.0001). In some such embodiments, the light reflective layer may have a typical real part of the refractive index (i.e., n) in the visible range (e.g. at 550 nm) of between about 1.40 and 1.60 (under the condition that the RI is lower than that of the material of the structures, or the light transmissive layers between louvers).

[0043] In some embodiments, a transmission profile of the light control film may have a peak transmission greater than about 70%, or greater than about 75%, greater than about 80%, greater than about 85%, or greater than about 90%. In some embodiments, a maximum transmission of a transmission profile of the light control film may vary by less than about 10%, or less than about 7%, or less than about 5%, within a viewing angle range having a width of greater than about 10 degrees (i.e., the transmission profile may have a substantially level “plateau” that extends across a range of viewing angles). In some such embodiments, the viewing angle range (i.e., the “plateau”) may not be centered symmetrically around a 0-degree viewing angle. That is, the light transmission profile may be asymmetric with respect to viewing angle, relative to a viewing angle of 0 degrees.

[0044] According to some aspects of the present description, a display system may include any of the embodiments of a light control film described herein, and a display configured to form an image to a viewer. In some such embodiments, the light control film may be disposed between the viewer and the display. In some such embodiments, the display may include an LCD or an OLED display. In some embodiments, a display system may include a display configured to form an image to a viewer, an extended light source, and any of the embodiments of a light control film described herein. In some such embodiments, the light control film may be disposed between the extended light source and the display. According to some aspects of the present description, a light control film includes a light input surface and a light output surface opposite the light input surface, and a plurality of spaced-apart, substantially parallel louvers. In some embodiments, each of the louvers may have a height, H, extending between the light input surface and the light output surface, a length, L, along a length of the light control film, and a width, W, along a width direction of the light control film. In some embodiments, the ratio H / W may be greater than or equal to about 2. In some embodiments, the ratio L / H may be greater than or equal to about 5. In some embodiments, the plurality of spaced-apart, substantially parallel louvers may have an average height, H, and an average pitch, P, where pitch is defined as a distance between a first major side of a first louver and a corresponding first major side of a second, adjacent louver (or, alternately, from the first facet of a first structure and a corresponding first facet of a second, adjacent structure), such that H / P is greater than about 0.5.

[0045] In some embodiments, each louver of the plurality of louvers may include a light reflective layer disposed on, and substantially co-extensive along the height and length of the louver with, a light absorbing layer. In some embodiments, each light absorbing layer of each louver faces the light reflective layer of an adjacent louver.

[0046] In some embodiments, the light absorbing layer may include a polyelectrolyte. In some embodiments, the light absorbing layer may include a plurality of light absorbing particles. In some such embodiments, the light absorbing particles may include one or more of a dye, a pigment, and a carbon black. In some embodiments, the light absorbing layer may have an optical density of greater than about 0.1.

[0047] In some embodiments, the light reflective layer may be a metal layer. In some embodiments, the light reflective layer may be an optically clear layer with a refractive index lower than a refractive index of a material of the structures.

[0048] In some embodiments, the louvers may be substantially orthogonal to the light input surface. In other embodiments, the louvers may make an angle with the light input surface greater than (or less than) about 90 degrees. That is, the louvers may have a tilt angle relative to a normal to the light input surface. The tilt angle (away from the normal to the light input surface) may have a magnitude of less than about 10 degrees, or less than about 8 degrees, or less than about 6 degrees, or less than about 5 degrees, or less than about 4 degrees, or less than about 3 degrees, or less than about 2 degrees, or less than about 1 degree.

[0049] In some embodiments, the light absorbing layer may include a cladding layer disposed on a core layer, the cladding layer facing away from the light reflective layer. In some such embodiments, the core layer may have a first concentration, Cl, of a light absorbing material and the cladding layer may have a second concentration, C2, of the light absorbing material, such that C2 is less than Cl.

[0050] In some embodiments, the core layer may include 30 wt. % to 100 wt. % of light absorbing material and the cladding layer may include 0.5 wt. % to 50 wt. % of light absorbing material. In some such embodiments, the core layer may include 15 vol. % to 90 vol. % of light absorbing material and the cladding layer may include 0.3 vol. % to 35 vol. % of light absorbing material.

[0051] In some embodiments, the core layer may have an optical density, at one or more wavelengths from 100 nm to 1 mm of greater than about 0.1, or greater than about 0.2, or greater than about 0.4, or greater than about 0.6, or greater than about 0.8, or greater than about 1, or greater than about 1.1, or greater than about 1.2, or greater than about 1.3, or greater than about 1.4, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3, or greater than about 3.5, or greater than about 4, or greater than about 4.5, or greater than about 5, or greater than about 5.5, or greater than about 6.

[0052] In some embodiments, the light reflective layer may be a metal layer (e.g., aluminum). In some embodiments, the light reflective layer may be an optically clear layer with a refractive index lower than a refractive index of a material of the structures (e.g., lower by at least 0.02, at least 0.04, at least 0.06, at least 0.08, at least 0.10, at least 0.12, or at least 0.14). In some embodiments, the light reflective layer is substantially specularly reflective. In some embodiments, the light reflective layer may be substantially specularly reflective.

[0053] In some embodiments, a transmission profile of the light control film may have a peak transmission greater than about 70%, or greater than about 75%, greater than about 80%, greater than about 85%, or greater than about 90%. In some embodiments, a maximum transmission of a transmission profile of the light control film may vary by less than about 10%, or less than about 7%, or less than about 5%, within a viewing angle range having a width of greater than about 10 degrees (i.e., the transmission profile may have a substantially level “plateau” that extends across a range of viewing angles). In some such embodiments, the viewing angle range (i.e., the “plateau”) may not be centered symmetrically around a 0-degree viewing angle. That is, the light transmission profile may be asymmetric with respect to viewing angle, relative to a viewing angle of 0 degrees.

[0054] According to some aspects of the present description, a display system may include any of the embodiments of a light control film described herein, and a display configured to form an image to a viewer. In some such embodiments, the light control film may be disposed between the viewer and the display. In some such embodiments, the display may include an LCD or an OLED display. In some embodiments, a display system may include display configured to form an image to a viewer, an extended light source, and any of the embodiments of a light control film described herein. In some such embodiments, the light control film may be disposed between the extended light source and the display.

[0055] According to some aspects of the present description, a light control film includes a plurality of spaced-apart, substantially parallel louvers, each of the louvers having a primarily specular reflective major first side and a primarily absorbing opposing major second side. In some embodiments, the primarily absorbing major second side of each louver faces the primarily reflective major first side of an adjacent louver. In some embodiments, the primarily light absorbing major second side may include a poly electrolyte. In some embodiments, the primarily light absorbing major second side may include a plurality of light absorbing particles, which may include one or more of a dye, a pigment, and a carbon black. In some embodiments, the primarily light absorbing major second side may have an optical density of greater than about 0.1.

[0056] In some embodiments, the primarily reflective major first side may include a metal. In some embodiments, the primarily reflective major first side may include an optically clear material with a refractive index lower than a refractive index of a material between adjacent louvers (e.g., lower by at least 0.02, at least 0.04, at least 0.06, at least 0.08, at least 0.10, at least 0.12, or at least 0.14).

[0057] In some embodiments, the plurality of spaced-apart, substantially parallel louvers may have an average height, H, and an average pitch, P, where pitch is defined as a distance between a first major side of a first louver and a corresponding first major side of a second, adjacent louver, such that H / P is greater than about 0.5.

[0058] In some such embodiments, the average height, H, may be greater than about 10 microns, or greater than about 20 microns, or greater than about 30 microns, or greater than about 40 microns, or greater than about 50 microns, or greater than about 75 microns, or greater than about 100 microns, or greater than about 125 microns, or greater than about 150 microns, or greater than about 200 microns, or greater than about 250 microns, or up to about 300 microns.

[0059] In some such embodiments, the average pitch, P, may be greater than about 10 microns, or greater than about 20 microns, or greater than about 30 microns, or greater than about 40 microns, or greater than about 50 microns, or greater than about 75 microns, or greater than about 100 microns, or greater than about 125 microns, or greater than about 150 microns, or greater than about 200 microns, or greater than about 250 microns, or greater than about 300 microns, or greater than about 500 microns, or greater than about 750 microns, or up to about 1 millimeter.

[0060] In some embodiments, primarily absorbing major second side may include a cladding layer disposed on a core layer. In some such embodiments, the cladding layer may face away from the primarily specular reflective major first side. In some such embodiments, the core layer may have a first concentration, Cl, of a light absorbing material and the cladding layer may have a second concentration, C2, of the light absorbing material, such that C2 is less than Cl.

[0061] In some embodiments, the core layer may include 30 wt. % to 100 wt. % of light absorbing material and the cladding layer may include 0.5 wt. % to 50 wt. % of light absorbing material. In some such embodiments, the core layer may include 15 vol. % to 90 vol. % of light absorbing material and the cladding layer may include 0.3 vol. % to 35 vol. % of light absorbing material.

[0062] In some embodiments, the core layer may have an optical density, at one or more wavelengths from 100 nm to 1 mm of greater than about 0.1, or greater than about 0.2, or greater than about 0.4, or greater than about 0.6, or greater than about 0.8, or greater than about 1, or greater than about 1.1, or greater than about 1.2, or greater than about 1.3, or greater than about 1.4, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3, or greater than about 3.5, or greater than about 4, or greater than about 4.5, or greater than about 5, or greater than about 5.5, or greater than about 6.

[0063] According to some aspects of the present description, a display system includes any of the embodiments of the light control film described herein, and a display configured to form an image to a viewer. In some such embodiments, the light control film may be disposed between the viewer and the display. In some such embodiments, the display may include an LCD or OLED display.

[0064] In another embodiment, the display system may include a display configured to form an image to a viewer, an extended light source, and any of the light control films described herein. In some such embodiments, the light control film may be disposed between the extended light source and the display.

[0065] In some embodiments, a transmission profile of the light control film may have a peak transmission greater than about 70%, or greater than about 75%, greater than about 80%, greater than about 85%, or greater than about 90%. In some embodiments, a maximum transmission of a transmission profile of the light control film may vary by less than about 10%, or less than about 7%, or less than about 5%, within a viewing angle range having a width of greater than about 10 degrees (i.e., the transmission profile may have a substantially level “plateau” that extends across a range of viewing angles). In some such embodiments, the viewing angle range (i.e., the “plateau”) may not be centered symmetrically around a 0-degree viewing angle. That is, the light transmission profile may be asymmetric with respect to viewing angle, relative to a viewing angle of 0 degrees.

[0066] According to some aspects of the present description, a method of making a light control film, includes providing a substantially light transmissive film having a structured first major surface and an opposing second major surface, the structured first major surface including a plurality of structures extending along a length direction, and arranged along a width direction, of the light control film, each structure having a first facet opposite a second facet, the first facet and the second facet extending from a base of the structure along a thickness direction of the light control film, the first facet making a first angle with the second major surface, the second facet making a second angle with the second major surface, the first angle greater than the second angle; conformally coating the first facets and the second facets with a first cover layer having a substantially uniform first thickness; conformally coating the first cover layers on the first facets and the second facets with a second cover layer having a substantially uniform second thickness; and etching the first cover layer and the second cover layer using at least a directional first etching process to remove the first cover layer and the second cover layer from at least about 80% of the second facets but from no more than about 20% of each of the first facets. In some such embodiments, the first cover layer is one of a light reflective layer and a light absorbing layer, and the second cover layer is the other of the reflective layer and the light absorbing layer.

[0067] In some embodiments, the method of making a light control film may further include covering and substantially planarizing the structured first major surface with a planarizing overcoat. In some such embodiments, the planarizing overcoat covering may include an optically clear adhesive. In such embodiments, the refractive index of the planarizing overcoat may be substantially the same as the refractive index of a material of the first major surface.

[0068] In some embodiments, wherein the light absorbing layer may include a poly electrolyte. In some embodiments, the light absorbing layer may include a plurality of light absorbing particles. In some such embodiments, the light absorbing particles may include one or more of a dye, a pigment, and a carbon black. In some embodiments, the light absorbing cover layer has an optical density of greater than about 0.1.

[0069] In some embodiments, etching the first cover layer and the second cover layer using at least a directional first etching process may include etching with the directional first etching process and a different directional second etching process. For example, a directional first etching process may be used to etch the first cover layer, and a directional second etching process may be used to etch the second cover layer.

[0070] In some embodiments, the plurality of structures may have an average height, H, and an average pitch, P, where pitch is defined as a distance between a first facet of a first structure and a corresponding first facet of a second, adjacent structure, such that H / P is greater than about 0.5.

[0071] In some embodiments, the light absorbing layer may include a cladding layer disposed on a core layer, such that the cladding layer faces away from the light reflective layer. In some such embodiments, the method of making a light control film may include depositing the light absorbing layer in two layers, a core layer and a cladding layer. It should be noted that, in such embodiments, the order of deposition the core layer and the cladding layer may change depending on the order in which the light absorbing layer and light reflective layer are deposited.

[0072] In some such embodiments, the core layer may have a first concentration, Cl, of a light absorbing material and the cladding layer may have a second concentration, C2, of the light absorbing material, such that C2 is less than Cl.

[0073] In some embodiments, the core layer may include 30 wt. % to 100 wt. % of light absorbing material and the cladding layer may include 0.5 wt. % to 50 wt. % of light absorbing material. In some such embodiments, the core layer may include 15 vol. % to 90 vol. % of light absorbing material and the cladding layer may include 0.3 vol. % to 35 vol. % of light absorbing material.

[0074] In some embodiments, the core layer may have an optical density, at one or more wavelengths from 100 nm to 1 mm of greater than about 0.1, or greater than about 0.2, or greater than about 0.4, or greater than about 0.6, or greater than about 0.8, or greater than about 1, or greater than about 1.1, or greater than about 1.2, or greater than about 1.3, or greater than about 1.4, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3, or greater than about 3.5, or greater than about 4, or greater than about 4.5, or greater than about 5, or greater than about 5.5, or greater than about 6.

[0075] Turning now to the figures, FIGS. 1 A and IB are side views of embodiments of a light control film having louvers with a light absorbing side opposite a light reflective side, according to the present description. FIG. 1 A illustrates one embodiment of a light control film and defines it in terms of elements of its internal structure. FIG. IB shows an embodiment of a final light control film without regard to the elements of its internal structure. In the embodiment of FIG. 1 A, the light control film may be assembled using a layer-by-layer deposition (e.g., liquid-phase layer-by-layer assembly, physical vapor deposition, chemical vapor deposition, atomic layer deposition, electroless plating, or the like) of cover layers on top of a plurality of structures, followed by removal of portions of those cover layers. This method is described elsewhere herein. The embodiment of FIG. IB may be created the same way (i.e., the same layer-by-layer method), or could be created by creating a stack of optical layers and skiving the light control film off the stack, or by any other appropriate method.

[0076] Focusing first on FIG. IB, light control film 300 may include a structured first major surface 11 opposite a second major surface 12. In some embodiments, the structured first major surface 11 may include a plurality of structures 10 extending along a length direction (e.g., the y-direction shown in FIG. 1A, which extends into the page), and arranged along a width direction (e.g., the x-direction shown in FIG. 1A), of the light control film 300. In some embodiments, each structure 10 may include a first facet 20 opposite a second facet 30. The first facet 20 and second facet 30 may extend from a base 15 of the structure 10 along a thickness direction (e.g., the z-direction) of the light control film 300. In some embodiments, the first facet 20 may make a first angle (01, see FIG. 2A) with the second major surface 12, and the second facet 30 may make a second angle (02, see FIG. 2A) with the second major surface 12. In some embodiments, the first angle 01 may be greater than the second angle 02.

[0077] In some embodiments, at least 80% of first facet 20, and at most 20% of the second facets 30, may be substantially conformally coated with a first cover layer 41 having a substantially uniform first thickness (Tl, see FIG. 3B). In some embodiments, at least 70% of the first cover layers 41 on the first facets 20 substantially conformally coated with a second cover layer 42 having a substantially uniform second thickness (T2, see FIG. 3B). In some embodiments, for each pair of adjacent first cover layer 41 and second cover layer 42 disposed on a first facet 20, the first cover layer 41 is disposed between the first facet 20 and the second cover layer 42. In some embodiments, first cover layer 41 may be one of a light reflective layer and a light absorbing layer, and the second cover layer 42 may be the other of the light reflective layer and the light absorbing layer. Stated another way, if first cover layer 41 is light absorbing, then second cover layer will be light reflecting, and, conversely, if first cover layer 41 is light reflecting, then second cover layer will be light absorbing. In some embodiments, first cover layer 41 will always be facing a second cover layer 42 of an adjacent structure 10 (i.e., all the light reflecting sides will face the same direction - e.g., all facing to the left of the figure - and all the light absorbing layers will face the opposite direction).

[0078] FIG. IB is provided to present the details of light control film 300 from a different perspective, without reference to internal elements (e.g., structures 10 from FIG. 1 A) which may or may not be part of the embodiment of FIG. IB. In the embodiment of FIG. IB, light control film 300 includes a light input surface 30 land a light output surface 302 opposite the light input surface 301, and a plurality of spaced- apart, substantially parallel louvers 40. In some embodiments, each of louvers 40 extends between light input surface 301 and light output surface 302.

[0079] In some embodiments, each louver 40 of the plurality of louvers 40 may include a light reflective layer 44 disposed on, and substantially co-extensive along the height and length of the louver with, a light absorbing layer 43. In some embodiments, each light absorbing layer 43 of each louver 40 may face the light reflective layer 44 of an adjacent louver 40. It should be noted that, although the embodiment of FIG. IB depicts all light reflective layers 44 on the right side of louvers 40, and all light absorbing layers 43 on the left side of louvers 40, the order of the layers 43 and 44 may be reversed (with all light reflective layers 44 on the left and all light absorbing layers 43 on the right).

[0080] FIGS. A and 2B provide details of structures and louvers for the embodiments of a light control film shown in FIGS. 1A and IB. Labeled elements in FIGS. 2 A and 2B which are common to FIGS. 1A and IB can be assumed to serve the same function unless stated otherwise herein. Common elements may not be described or at least not described in detail.

[0081] FIG. 2A provides a close-up view of a portion of one embodiment of a light control film 300. Light control film 300 may include a plurality of structures 10 which extend up from a first major surface 11. In this embodiment, each structure 10 may have a first facet (a first side surface) 20 and a second facet (a second side surface 30) extending up from a base 15 and meeting at a peak 25. In some embodiments, a louver 40 may be disposed on first facet 20 of each structure 10. In some embodiments, each louver 40 may include a first cover layer 41 and a second cover layer 42. For each louver 40, one of the first cover layer 41 and the second cover layer 42 may be a substantially light reflective layer (e.g., a layer with high specular reflectance) and the other of the first cover layer 41 and the second cover layer 42 may be a substantially light absorbing layer. It should be noted that the determination of which of first cover layer 41 and second cover layer 42 is light reflective and which is light absorbing may be determined by the order in which the light reflective layer and light absorbing layer were deposited during manufacture. In some embodiments, first cover layer 41 may extend just beneath second cover layer 42 (e.g., see area 48 in FIG. 2A). Area 48 may be an artifact of a manufacturing process in which first cover layer 41 and second cover layer 42 are deposited on light control film 300 and then a directional etching process is used to remove first cover layer 41 and second cover layer 42 from portions of the light control film 300 in order to create louvers 40.

[0082] In some embodiments, first facet 20 may make a first angle 01 with second major surface 12 of light control film 300, and second facet 30 may make a second angle 02 with second major surface 12. In some such embodiments, first angle 01 may be greater than second angle 02. For example, in some embodiments, a magnitude of first angle 01 may be substantially orthogonal to second major surface 12 or may be less than or equal to about 90 degrees, or about 85 degrees, with second major surface 12. In some embodiments, a magnitude of second angle 02 may be less than about 75 degrees, or less than about 70 degrees. In some embodiments, the magnitude of first angle 01 determines the “tilt” of louvers 40. The tilt of louvers 40 may, in some embodiments, be used to “fine tune” transmission profile of the light control film 300 (e.g., to shift the maximum transmission and cut off areas to the left or right on a graph of the transmission profile).

[0083] In some embodiments, such as the embodiment shown in FIG. 2B, structures 10 (shown without louvers 40 for clarity) may not meet at a peak but may instead be connected by a substantially planar top surface 27. In some such embodiments, top surface 27 may define a width, Wl, and base 15 of each structure 10 may define a width, W2, such that Wl is less than W2. In some embodiments, each structure 10 may be separated from an adjacent structure 10 by a substantially planar landing 29. In embodiments with landings 29 between structures 10, first facet 20 and second facet 30 may either meet at a peak 25 (as in FIG. 2 A) or may be connected by a substantially planar top surface 27 (as in FIG. 2B).

[0084] FIGS. 3A and 3B provide additional details of structures and louvers for the embodiments of a light control film shown in FIGS. 1A and IB. Labeled elements in FIGS. 3A and 3B which are common to FIGS. 1 A-2B can be assumed to serve the same function unless stated otherwise herein. Common elements may not be described or at least not described in detail. FIG. 3A shows a side view of an embodiment of light control film 300, and FIG. 3B shows a top view of light control film 300.

[0085] Looking at FIGS. 3A and 3B together, light control film 300 includes a plurality of spaced-apart, substantially parallel louvers 40. Each of the louvers has a height, H (extending in the z-direction shown in the figures), a length, L (extending in the y-direction), and a width, W (extending in the x-direction). Each louver 40 of the plurality of louvers may include first cover layer 41 disposed on, and substantially co-extensive along the height and length of the louver, and a second cover layer 42 disposed on the first cover layer 41. The first cover layer 41 may have a uniform first thickness T1 and the second cover layer may have a uniform second thickness T2. In some embodiments, T1 and T2 may be substantially equal. In some embodiments, T1 and T2 may be different by at least about 5%, or about 10%, or about 20%, or about 30%, or about 50%.

[0086] In some embodiments, the plurality of structures 10 may have an average height, H, and an average pitch, P, where pitch is defined as a distance between a first facet of a first structure and a corresponding first facet of a second, adjacent structure, such that the ratio H / P is greater than about 0.5. In some embodiments, the ratio of H / W may be greater than or equal to about 2, or greater than about 10, or greater than about 100, or greater than about 500, or greater than about 1000. In some embodiments, the ratio L / H may be greater than or equal to about 5. In some embodiments, the ratio of H / P defines the angle second facet 30 with second major surface 12 (see, e.g., FIG. 2A).

[0087] FIGS. 4 A and 4B provide details of an alternate louver construction for an embodiment of a light control film, according to the present description. In some embodiments, one of the first cover layer 41 or the second cover layer 42 may be a light absorbing layer. In some applications, light impinging on the light absorbing layer, especially at high angles, may reflect off the light absorbing layer rather than be absorbed, which can lead to unwanted light leakage. To prevent this unwanted reflection, the light absorbing layer can be deposited as two separate layers, an inner core layer and an outer cladding layer, wherein the extinction coefficient, k, of the cladding layer (the surface on which light would first impinge) is lower than the extinction coefficient, k, of the core layer. A high extinction coefficient material is needed to efficiently absorb light in an ultra-thin coating / layer, but can also produce a reflective, metal-like interface with the material of the planarizing overcoat (see, e.g., planarizing overcoat 60, FIG. 1 A). Adding a cladding layer with a lower extinction coefficient over the core layer with a higher extinction coefficient can result in reduced reflection at the interface with the planarizing overcoat material.

[0088] This concept is illustrated in FIGS. 4A and 4B. The embodiments of FIGS. 4A and 4B are similar, but FIG. 4A shows the cladding-core configuration in the second cover layer 42, and FIG. 4B shows the cladding -core configuration in the first cover layer 41. In the case of FIG. 4A, second cover layer 42 is the light absorbing layer and includes an inner core layer 42b and an outer cladding layer 42a. In the case of FIG. 4B, first cover layer 41 is the light absorbing layer and includes an inner core layer 41b and an outer cladding layer 41a. In both cases (both embodiments of FIGS. 4A and 4B), the cladding layer (41a, 42a) is disposed on the side of the core layer (41b, 42b) that is facing “outwards”, away from the opposite cover layer. That is, the cladding layer is always disposed such that light impinging on the louver will first impinge on the cladding layer before reaching the inner core layer. Stated yet another way, the cladding layer of the light absorbing layer always faces away from the light reflective layer.

[0089] In some embodiments, the core layer (41b, 42b) may have a first concentration, Cl, of a light absorbing material and the cladding layer (41a, 42a) may have a second concentration, C2, of the light absorbing material, wherein C2 is less than Cl. In some such embodiments, the core layer (41b, 42b) may include 15 vol. % to 90 vol. % of light absorbing material and the cladding layer (41a, 42a) may include 0.3 vol. % to 35 vol. % of light absorbing material. In some embodiments, core layer (41b, 42b) may have an optical density of greater than about 0.1.

[0090] FIG. 5 illustrates the different ray paths of an embodiment of a light control film, according to the present description. The figure is a side view of one embodiment of a light control film 300. Each louver 40 includes a first cover layer 41, which, in this example, is a highly specular reflective layer, and a second cover layer 42, which, in this example, is a light absorbing layer. The working principle of this embodiment is that light transmission through the film (from light input side 301 toward light output side 302) can achieve an asymmetric top-hat performance, where the transmission profile is defined by the sum of the directly transmitted light 70a and light 70b transmitted after reflection on a light reflecting sidewall (such as light reflective side 41). Light 70c impinging directly on light absorbing layer 42 (second cover layer 42, in this example) is absorbed and not transmitted, and high angle light 70d which is reflected by light reflective layer 41 into light absorbing layer 42 is also absorbed. The location of the center of the resulting top-hat transmission profile can be adjusted by adjusting the overall tilt angles of the louvers.

[0091] An example of such an asymmetric top-hat transmission profile can be seen in FIG. 6. The graph in FIG. 6 plots the transmission profiles for three example louver films created according to the present description, and also includes the transmission profile for a typical privacy film with a “witch hat” profile for a comparison (the solid line, labeled “cmp”, representing a typical privacy louver film with a louver tilt angle of 0 degrees from a normal to the film).

[0092] The three dashed lines represent variations on embodiments of the present description. The legend in the upper right corner of the chart includes an angle which represents the tilt angle of the louvers, where 0 degrees represents a louver that is orthogonal to a major surface of the light control film. Each of these top-hat profiles has a peak transmission greater than about 70%, or greater than about 75%, or greater than about 80%, or greater than about 85%, or greater than about 90%. This peak transmission is an improvement over typical asymmetric top-hat light control films in the art, because there is an increased percentage of light transmission, including light that is directly transmitted through the light control films (without striking a louver) as well as light reflected from the highly specular reflective side of the louvers (which would be otherwise absorbed in a typical light control film in the art in which both sides of the louvers are light absorbing).

[0093] Each of the dashed, top-hat profile lines of FIG. 6A also exhibits a maximum transmission which varies by less than about 10%, or less than about 7.5%, or less than about 5%, across a viewing angle range 60 having a width of greater than about 10 degrees, or greater than about 15 degrees, or greater than about 20 degrees, or greater than about 25 degrees, or greater than about 30 degrees. That is, each of the top-hat profiles includes a “plateau” feature where the maximum transmission percentage remains substantially flat or varies very little across viewing angle range 60. In some embodiments, this plateau may be asymmetric with respect to viewing angle relative to a viewing angle of 0 degrees (i.e., the transmission profile may be shifted to the right, such as shown in the example of FIG. 6, relative to a 0- degree viewing angle, or may be shifted to the left).

[0094] In some embodiments, an average transmission percentage may be less than about 10% for viewing angles having a magnitude greater than about 50 degrees, or greater than about 55 degrees, or greater than about 60 degrees, or greater than about 65 degrees, or greater than about 70 degrees. That is, the maximum transmission percentage may drop significantly outside of the viewing angle range 60. In the plots of FIG. 6, the light reflective layer is assumed to have a percent reflectivity equal to 0.95 (i.e., 95% reflective).

[0095] FIGS. 7 A and 7B illustrate alternate display system embodiments including a light control film according to the present description. In the embodiment of FIG. 7A, display system 400 may include a light control film 300 (such as any embodiments described herein) and a display 70 configured to form an image 71 to the eye of a viewer 80. In this embodiment, light control film 300 is disposed between the eye of the viewer 80 and the display 70. In some embodiments, the display 70 may include an LCD or OLED display. In embodiments where the display 70 is an LCD, display system 400 may further include an extended light source 75. Extended light source 75 may emit light rays 50 which are transmitted by display 70 as image rays 70a-70d (see also FIG. 5) which are transmitted and / or absorbed by light control film 300 as described elsewhere herein. In the embodiment of FIG. 7B, display system 401 includes a display configured 70 to form an image 71 to an eye of a viewer 80, an extended light source 75, and any of the embodiments of a light control film 300 described herein. In the embodiment of FIG. 7B, light control film 300 may be disposed between extended light source 75 and display 70 (i.e., light rays 50 from extended light source 75 pass through light control film 300 before being at least partially transmitted by display 75).

[0096] FIG. 8 details an embodiment of a method of making a light control film, according to the present description. The method detailed in FIG. 8 includes the following: (A) providing a substantially light transmissive film 100 comprising a structured first major surface 11 and an opposing second major surface 12, the structured first major surface 11 comprising a plurality of structures 10 extending along a length direction, and arranged along a width direction, of the light transmissive film 100, each structure having a first facet 20 opposite a second facet 30, the first facet 20 and the second facet 30 extending from a base 15 of the structure 10 along a thickness direction of the light transmissive film 100, the first facet 20 making a first angle with the second major surface 12, the second facet 30 making a second angle with the second major surface 12, such that the first angle greater than the second angle; (B) conformally coating the first facets 20 and the second facets 30 with a first cover layer 41a having a substantially uniform first thickness; (C) conformally coating the first cover layers 41a on the first facets 20 and the second facets 30 with a second cover layer 42a having a substantially uniform second thickness; and (D) etching the first cover layer 41a and the second cover layer 42a using at least a directional first etching process 120 to remove the first cover layer 41a and the second cover layer 42a from at least about 80%, or at least about 85%, or at least about 90%, or at least about 95%, of the second facets 30 but from no more than about 20%, or no more than about 15%, or no more than about 10%, or no more than about 5%, of each of the first facets 20, to create louvers 40 with a first cover layer 41 and a second cover layer 42.

[0097] In some embodiments of the method, the first cover layer 41 is one of a light reflective layer and a light absorbing layer, and the second cover layer 42 is the other of the reflective layer and the light absorbing layer.

[0098] In some embodiments, the method of making a light control film may further include (E) covering and substantially planarizing the structured first major surface 11 (including structures 10 and louvers 40) with a planarizing overcoat 60.

[0099] Finally, FIGS. 9A and 9B illustrate alternate embodiments of processes in method of making a light control film of FIG. 8. FIG. 9A depicts an alternate embodiment of subprocess (C) of FIG. 8. In subprocess (C2) of FIG. 9A, the deposition of layer 42a (which, in this example, would be a light absorbing layer) includes depositing a core layer 42ab followed by depositing a cladding layer 42aa on top of the core layer 42ab. It should be noted that, in other alternate embodiments, the light absorbing layer may be first cover layer 41a, instead of second cover layer 42a, as described elsewhere herein. In such an embodiment, not shown in FIG. 9A, the cladding layer would be deposited on structures 10 first, followed by the deposition of a core layer, and finally the deposition of the light reflecting layer 42a. FIG. 9B illustrates an alternate to subprocess (D) of FIG. 8. In subprocess (D2), the “at least a directional first etching process 120” is replaced with a directional first etching process 120a and a directional second etching process 120b. That is, in some embodiments of the method, a different etching process may be used to remove the second cover layer 42 and the first cover layer 41 (i.e., each removal of a layer may use a etching process that works best for the different materials of the first and second cover layers).

[0100] It should be noted that the methods described in FIGS. 8-9B are not intended to be limiting in any way, and that the light control film of the present description may be made by any appropriate method. For example, an alternate method might be to create a layered stack of materials (e.g., a stack of deposited layers, where each layer in the stack includes a light transmissive sublayer, a light absorbing sublayer, and a specularly reflective sublayer), and then slice individual light control films from an end of the stack using a skiving method.

[0101] Examples / Modeling Results

[0102] Various light control films based on the principles described herein were modeled using commercially available optical modeling software LightTools 2022.03, and plots were generated showing the light transmission percentage versus viewing angle for the modeled films. These plots are included in FIG. 6, FIGS. 10A-10B, FIG. 11, and FIGS. 12A-12B, and the details are provided in the following paragraphs.

[0103] Each of the modeled films in FIGS. 6, 10A-10B, and 11 were based on a light control film as described herein, having louvers with a substantially absorbing first side (left side in these examples) and a substantially specularly reflective second side (right side in these examples). Each of the modeled louvers had a height of 80 microns and a pitch (the distance between the first side of one louver to the first side of a second, adjacent louver) of 30 microns. The highly reflective side is a metal coating. For a metal coating, high reflectivity is not angle-dependent and broad top-hat can be achieved.

[0104] The modeled films described below and illustrated in FIGS. 6, 10A-10B, and 11 show that (1) broad asymmetric top-hat performance can be achieved with the methods described herein, (2) the flatness of the top-hat (the plateau region) can be affected by louver sidewall reflectivity, and (3) the center of the top-hat can be tuned by adjusting louver tilt angle.

[0105] FIG. 10A

[0106] The plot of FIG. 10A shows the transmission profile versus viewing (polar angle) for a film modeled with the following parameters:

[0107] • High peak transmission (around 90%)

[0108] • Top-plateau region 65a is substantially flat

[0109] • Material of the reflective side: Metal, perfect specular reflector R=1

[0110] • Louver height = 80 microns; pitch = 30 microns

[0111] • Refractive index of material between louvers: 1.54

[0112] • Reflectivity of light absorbing side: 0 (no reflection)

[0113] • Reflectivity of light reflecting side: 1.0 (perfect reflection)

[0114] • Louver angles (from normal to light control film): 0, 4, and 8 degrees

[0115] • Comparative plot (cmp) for witch-hat film with perfect absorber on both sides included.

[0116] FIG. 6

[0117] The plot of FIG. 6 shows the transmission profile versus viewing (polar angle) for a film modeled with the following parameters:

[0118] • High peak transmission (around 90%)

[0119] • Top-plateau region 60 is flat, inclined slightly to the right

[0120] • Material of the reflective side: Metal, lossy specular reflector R=0.95

[0121] • Louver height = 80 microns; pitch = 30 microns

[0122] • Refractive index of material between louvers: 1.54

[0123] • Reflectivity of light absorbing side: 0 (no reflection)

[0124] • Reflectivity of light reflecting side: 0.95 Louver angles (from normal to light control film): 0, 4, and 8 degrees

[0125] Comparative plot (cmp) for witch-hat film with perfect absorber on both sides included.

[0126] FIG. 10B

[0127] The plot of FIG. 10B shows the transmission profile versus viewing (polar angle) for a film modeled with the following parameters:

[0128] • High peak transmission (around 90%)

[0129] • Top-plateau region 65b is somewhat flat, inclined to the right.

[0130] • Material of the reflective side: Metal, lossy specular reflector R=0.90

[0131] • Louver height = 80 microns; pitch = 30 microns

[0132] • Refractive index of material between louvers: 1.54

[0133] • Reflectivity of light absorbing side: 0 (no reflection)

[0134] • Reflectivity of light reflecting side: 0.90

[0135] • Louver angles (from normal to light control film): 0, 4, and 8 degrees

[0136] • Comparative plot (cmp) for witch-hat film with perfect absorber on both sides included.

[0137] FIG. 11

[0138] The plot of FIG. 11 shows the transmission profile versus viewing (polar angle) for a film modeled with the following parameters:

[0139] • High peak transmission (around 90%)

[0140] • Top-plateau region 65c is inclined to the right

[0141] • Material of the reflective side: Metal (Aluminum)

[0142] • Louver height = 80 microns; pitch = 30 microns

[0143] • Louvers are of a cladding-core design, as described elsewhere herein with the following parameters: o Cladding: n=1.62; k=0.063; t=325nm o Core: n=1.786; k=0.368; t=325nm

[0144] • Refractive index of material between louvers: 1.54

[0145] • Reflectivity of light absorbing side: 0 (no reflection)

[0146] • Reflectivity of light reflecting side: 0.86

[0147] • Louver angles (from normal to light control film): 0, 4, and 8 degrees

[0148] • Comparative plot (cmp) for witch-hat film with perfect absorber on both sides included.

[0149] Each of the modeled films in FIGS. 12A-12B were based on a light control film as described herein, having louvers with a substantially absorbing first side (left side in these examples) and a substantially specularly reflective second side (right side in these examples). Each of the modeled louvers had a height of 80 microns and a pitch (the distance between the first side of one louver to the first side of a second, adjacent louver) of 30 microns. The highly reflective side is a clear, low-refractive index layer with sufficient thickness to provide strong total internal reflection (TIR). For clear low-refractive index layer, high reflectivity is angle-dependent due to TIR enabling narrow top-hat performance.

[0150] The modeled films described below and illustrated in FIGS. 12A-12B show that (1) narrow asymmetric top-hat performance can be achieved with the methods described herein, (2) the flatness of the top-hat (the plateau region) can be affected by the refractive index difference between low index layer and the clear channel, and (3) the center of the top-hat can be tuned by adjusting louver tilt angle.

[0151] FIG. 12A

[0152] The plot of FIG. 12A shows the transmission profile versus viewing (polar angle) for a film modeled with the following parameters:

[0153] • High peak transmission (around 90%)

[0154] • Top-plateau region 65d is narrow, substantially flat.

[0155] • Material of the reflective side: Low RI clear layer (e.g., acrylic, or any optically clear material with a refractive index of 1.5

[0156] • Louver height = 80 microns; pitch = 30 microns

[0157] • Refractive index of material between louvers: 1.54

[0158] • Refractive index of clear (reflective layer): 1.50

[0159] • Reflectivity of light absorbing side: 0 (no reflection)

[0160] • Reflectivity of light reflecting side: Depends on Fresnel reflection between materials. Not a constant value.

[0161] • Louver angles (from normal to light control film): 0 and 4 degrees

[0162] • Comparative plot (cmp) for witch-hat film with perfect absorber on both sides included.

[0163] FIG. 12B

[0164] The plot of FIG. 12B shows the transmission profile versus viewing (polar angle) for a film modeled with the following parameters:

[0165] • High peak transmission (around 90%)

[0166] • Top-plateau region 65e is narrow, substantially flat.

[0167] • Material of the reflective side: Low RI clear layer (SiOx, or any optical material with a refractive index of 1.48).

[0168] • Louver height = 80 microns; pitch = 30 microns

[0169] • Refractive index of material between louvers: 1.54

[0170] • Refractive index of clear (reflective layer): 1.48

[0171] • Reflectivity of light absorbing side: 0 (no reflection)

[0172] • Reflectivity of light reflecting side: Depends on Fresnel reflection between materials. Not a constant value.

[0173] • Louver angles (from normal to light control film): 0 and 4 degrees

[0174] • Comparative plot (cmp) for witch-hat film with perfect absorber on both sides included.

[0175] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1.

[0176] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially equal” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially equal” will mean about equal where about is as described above. If the use of “substantially parallel” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially parallel” will mean within 30 degrees of parallel. Directions or surfaces described as substantially parallel to one another may, in some embodiments, be within 20 degrees, or within 10 degrees of parallel, or may be parallel or nominally parallel. If the use of “substantially aligned” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially aligned” will mean aligned to within 20% of a width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned to within 10% or to within 5% of a width of the objects being aligned.

[0177] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0178] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed:

1. A light control film comprising a structured first major surface opposite a second major surface, the structured first major surface comprising a plurality of structures extending along a length direction, and arranged along a width direction, of the light control film, each structure comprising a first facet opposite a second facet, the first facet and the second facet extending from a base of the structure along a thickness direction of the light control film; the first facet making a first angle with the second major surface, the second facet making a second angle with the second major surface, the first angle greater than the second angle; at least 80% of the first facets and at most 20% of the second facets substantially conformally coated with a first cover layer having a substantially uniform first thickness; and at least 70% of the first cover layers on the first facets substantially conformally coated with a second cover layer having a substantially uniform second thickness, such that for each pair of adjacent first cover layer and second cover layer disposed on a first facet, the first cover layer is disposed between the first facet and the second cover layer; wherein the first cover layer is one of a light reflective layer and a light absorbing layer, and the second cover layer is the other of the light reflective layer and the light absorbing layer.

2. The light control film of claim 1, further comprising a planarizing overcoat covering, and substantially planarizing, the structured first major surface.

3. The light control film of claim 2, wherein the planarizing overcoat comprises an optically clear adhesive.

4. The light control film of claim 2, wherein a refractive index of the planarizing overcoat is substantially equal to a refractive index of a material comprising the first major surface.

5. The light control film of claim 1, wherein the light absorbing layer comprises a polyelectrolyte.

6. The light control film of claim 1, wherein the light absorbing layer comprises a plurality of light absorbing particles.

7. The light control film of claim 1, wherein the light absorbing layer has an optical density of greater than about 0.1.

8. The light control film of claim 1, wherein the light reflective layer is a metal layer.

9. The light control film of claim 1, wherein the light reflective layer is an optically clear layer with a refractive index lower than a refractive index of a material of the structures.

10. The light control film of claim 1, wherein the light reflective layer is substantially specularly reflective.

11. The light control film of claim 1, wherein each structure of the plurality of structures is separated from an adjacent structure by a substantially planar landing.

12. The light control film of claim 1, wherein the first facet and the second facet of each structure of the plurality of structures are connected by a substantially planar top surface, the top surface defining a width,Wl, the base of each structure of the plurality of structures defining a width, W2, such that W1 is less than W2.

13. The light control film of claim 1, wherein the first facet and the second facet of each structure of the plurality of structures meet at a peak of the structure.

14. The light control film of claim 1, wherein a magnitude of the first angle is less than or equal to about 90 degrees.

15. The light control film of claim 1, wherein a magnitude of the second angle is less than about 75 degrees.

16. The light control film of claim 1, wherein the plurality of structures has an average height, H, and an average pitch, P, where pitch is defined as a distance between a first facet of a first structure and a corresponding first facet of a second, adjacent structure, such that H / P > about 0.5.

17. A display system comprising the light control film of claim 1 and a display configured to form an image to a viewer, the light control film disposed between the viewer and the display.

18. A display system comprising a display configured to form an image to a viewer, an extended light source, and the light control film of claim 1, the light control film disposed between the extended light source and the display.

19. The light control film of claim 1, wherein the light absorbing layer comprises a cladding layer disposed on a core layer, the cladding layer facing away from the light reflective layer.

20. The light control film of claim 19, wherein the core layer has a first concentration, Cl, of a light absorbing material and the cladding layer has a second concentration, C2, of the light absorbing material, wherein C2<C1, and wherein the core layer comprises 15 vol. % to 90 vol. % of light absorbing material and the cladding layer comprises 0.3 vol. % to 35 vol. % of light absorbing material.

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