Optical film with embedded and surface elements

Abstract

An optical film includes an optical layer including a plurality of particles embedded therein and arranged into a plurality of irregularly arranged and substantially tightly packed domains. Each domain includes a plurality of the particles regularly arranged in the domain. The optical layer has opposing first and second major surfaces, where for at least one of the first and second major surfaces, the major surface includes a plurality of features such that in a plan view and for at least a majority of the features and at least a majority of the particles, the particles and the features are aligned in one-to-one correspondence.

Description

[0001] PA102429W002

[0002] OPTICAL FILM WITH EMBEDDED AND SURFACE ELEMENTS

[0003] TECHNICAL FIELD

[0004] The present description relates generally to optical films, and more specifically to optical films including embedded and surface elements.

[0005] BACKGROUND

[0006] Sparkle in a display is an undesired optical effect that may be described as a grainy pattern that appears to flicker with small changes in position of a viewer relative to the display.

[0007] SUMMARY

[0008] In some aspects, the present description provides an optical film including an optical layer including a plurality of particles embedded therein and arranged into a plurality of irregularly arranged and substantially tightly packed domains. Each domain includes a plurality of the particles regularly arranged in the domain. The optical layer has opposing first and second major surfaces, where for at least one of the first and second major surfaces, the major surface includes a plurality of features such that in a plan view and for at least a majority of the features and at least a majority of the particles, the particles and the features are aligned in one-to-one correspondence.

[0009] In some aspects, the present description provides an optical film including an optical layer including a plurality of first diffractive elements embedded therein and arranged into a plurality of irregularly arranged and substantially tightly packed domains. Each domain includes a plurality of the first diffractive elements regularly arranged in the domain. The optical layer comprising opposing first and second major surfaces, where for at least one of the first and second major surfaces, the major surface comprises a plurality of second diffractive elements such that in a plan view and for at least majorities of the first and second diffractive elements, the first and second diffractive elements are aligned in one-to- one correspondence.

[0010] In some aspects, the present description provides a film including a release surface; and a plurality of spaced-apart features fixedly disposed on the release surface and arranged into a plurality of irregularly arranged domains. Each domain includes a plurality of the features regularly arranged in the domain. An average spacing between adjacent domains is no more than about 0.5 times an average largest lateral dimension of the adjacent domains. An average of a minimum gap between adjacent features of each domain is at least 0.02 times an average center-to-center spacing between adjacent features of the domain.

[0011] These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1A is a schematic cross-sectional view of an optical layer including particles and surface features, according to some embodiments.

[0013] FIG. IB is a schematic plan view of an optical layer, according to some embodiments.

[0014] FIG. 1C is a schematic cross-sectional view of an optical film that includes the optical layer of FIGS. 1A-1B, according to some embodiments.

[0015] FIG. 2A is a schematic cross-sectional view of an optical layer, according to some embodiments.

[0016] FIG. 2B is a schematic cross-sectional view of a film, according to some embodiments.

[0017] FIG. 2C is a schematic cross-sectional view of another optical layer, according to some embodiments.

[0018] FIG. 2D is a schematic cross-sectional view of another film, according to some embodiments.

[0019] FIG. 3 is a schematic plot of displacement versus radius of a feature that may be a protruding structure or a recessed structure, according to some embodiments.

[0020] FIGS. 4A-4C schematically illustrate a method of making an optical film, according to some embodiments.

[0021] FIGS. 5A-5B are schematic plan views of portions of films illustrating embedded or surface structures, according to some embodiments.

[0022] FIG. 6 is a schematic plan view of a portion of a film illustrating domains of structures, according to some embodiments.

[0023] FIG. 7 is a schematic cross-sectional view of an optical film, light substantially normally incident on the film, and light transmitted by the optical film, according to some embodiments.

[0024] FIG. 8 is a schematic geometry for the measurement of scattering profile and a schematic conoscopic plot of a scattering distribution function, according to some embodiments.

[0025] FIG. 9 is a schematic plot representing an azimuthally averaged intensity distribution as a function of scattering angle or a scattering distribution function as a function of scattering angle, according to some embodiments.

[0026] FIG. 10 is a schematic plot of a peak intensity versus azimuthal angle at a specific scattering angle, according to some embodiments.

[0027] FIG. 11 is schematic cross-sectional view of a display that includes an optical film, according to some embodiments.

[0028] FIG. 12 is a schematic top view of a display panel having a pixelated display surface, according to some embodiments.

[0029] FIG. 13 is an optical microscope image of a tool for making an optical film, according to some embodiments.

[0030] FIG. 14 is a plot of sparkle of displays including an optical film that includes a backfill layer disposed on a beaded layer as a function of the refractive index (RI) of the backfill layer, according to some embodiments. FIG. 15 is a plot of a distinctiveness of image (DOI), which is related to modulation transfer function (MTF), for displays including an optical film that includes a backfill layer disposed on a beaded layer as a function of the refractive index (RI) of the backfill layer, according to some embodiments.

[0031] FIG. 16 is a box plot of sparkle for various displays, according to some embodiments.

[0032] FIG. 17 is a box plot of DOI for the displays of FIG. 16.

[0033] FIG. 18 is a plot of sparkle decrease versus MTF decrease for the displays of FIGS. 16-17.

[0034] FIG. 19 is a plot of normalized azimuthally averaged intensity distributions of light transmitted by optical films, according to some embodiments.

[0035] FIG. 20 is a plot of normalized azimuthally averaged intensity distributions of light transmitted by an optical film and a corresponding release film, according to some embodiments.

[0036] DETAILED DESCRIPTION

[0037] 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.

[0038] Optical films described herein may be useful in applications where a substantially azimuthally symmetric scattering distribution is desired and where it is desired to eliminate any substrate (e.g., a substrate disposed on radiation cured layer(s) of the optical film) from the optical film, according to some embodiments. It may be desired to eliminate the substrate because of undesired optical properties (e.g., birefringence) of the substrate and / or to make the optical film thinner. In some embodiments, the optical film includes embedded diffractive elements (e.g., beads) and surface diffractive elements (e.g., surface structures) where the embedded diffractive elements provide most of the diffractive scattering of the optical film with the surface diffractive elements supplementing the scattering. Suitable applications of the optical films include sparkle reduction and OLED color correction. Sparkle and methods of sparkle reduction are described in U.S. Pat. No. 10,353,214 (Sitter et al.), for example. OLED color correction is generally described in U.S. Pat No. 10,566,391 (Freier et al.), for example. Other films described herein may be useful in applications where a substantially azimuthally symmetric scattering distribution with relatively weak scattering desired, according to some embodiments. The strength of the scattering in such films may be increased by backfilling the surface features of the film with a high index coating which may be an inorganic coating, for example.

[0039] FIG. 1A is a schematic cross-sectional view of an optical layer 100, according to some embodiments. FIG. IB is a schematic (e.g., bottom) plan view of the optical layer 100, according to some embodiments. An optical film may include optical layer 100 and one or more additional layers, or optical layer 100 may be an (e.g., free-standing) optical film, according to some embodiments. FIG. 1C is a schematic cross-sectional view of an optical film 200 that includes the optical layer 100 of FIGS. 1A-1B, according to some embodiments.

[0040] In some embodiments, an optical film 100, 200 (or 400c described elsewhere herein) includes an optical layer 100 including a plurality of particles 514 embedded in the optical layer 100. In some embodiments, the particles 514 are beads such as substantially spherical beads, for example. In some embodiments, the particles include irregularly shaped or irregular faceted particles, for example. The optical layer has opposing first and second major surfaces 121 and 122. In some embodiments, as described further elsewhere herein (see, e.g., FIG. 5A where structures 512 can correspond to particles 514), the particles are arranged into a plurality of irregularly arranged and substantially tightly packed domains 510, where each domain 510 includes a plurality of the particles regularly arranged in the domain 510. In some embodiments, for at least one of the first and second major surfaces 121, 122, the major surface includes a plurality of features 235 such that in a (e.g., bottom) plan view and for at least a majority (i.e., greater than 50%) of the features and at least a majority of the particles, the particles and the features are aligned in one-to-one correspondence (see, e.g., FIG. IB). In some embodiments, the features 245 and particles 514 are aligned such that in the plan view, each feature of the at least the majority of features is substantially centered on a particle of the at least the majority of particles. In some embodiments, the at least the majority of the features 235 includes at least 60, 70, 80, 90, or 95 percent of the features 235. In some such embodiments, or in other embodiments, the at least the majority of the particles 514 includes at least 60, 70, 80, 90, or 95 percent of the particles 514. In some embodiments, the particles 514 are substantially coplanar.

[0041] In some embodiments, the particles 514 have an average diameter of at least about 20, 30, 40, 50, 75, 100, 125, 150, 300, 500, or 800 nm or at least about 1, 2, 3, or 4 micrometers. In some such embodiments, or in other embodiments, the average diameter of the particles 514 is no more than about 15, 12, 10, 8, 6, 4, 2, or 1 micrometer or no more than 800, 600, 500, 400, 300, 250, 200, or 150 nm. Smaller particles (e.g., diameter no more than about 1 micrometer) may be desired for some applications (e.g., color correction in OLED displays) while larger particles (e.g., diameter of at least 4 micrometers) may be desired for other applications (e.g., sparkle reduction). For example, in some embodiments, the particles 514 have an average diameter in a range from about 20 nm to about 1 micrometer. As another example, in some embodiments, the particles 514 have an average diameter in a range from about 4 micrometers to about 15 micrometers. In some embodiments, the particles 514 have an average diameter in a range from about 2 micrometers to about 15 micrometers, or about 3 micrometers to about 15 micrometers, or about 4 micrometers to about 15 micrometers, or about 5 micrometers to about 15 micrometers, or about 5 micrometers to about 12 micrometers, or about 5 micrometers to about 11 micrometers, or about 6 micrometers to about 10 micrometers, or about 7 micrometers to about 9 micrometers.

[0042] The particles 514 may be disposed in polymeric material. For example, as described elsewhere herein, the particles 514 may be dispersed in a mixture of monomer and solvent and then coated onto a substrate. Then the monomers can be cured (e.g., via applying actinic radiation). Another polymeric layer (backfdl) can be coated onto the resulting layer so that the particles 514 are embedded in the layer including the two coated layers (e.g., layers 140 and 110 schematically illustrated in FIGS. 4B-4C). In some embodiments, the plurality of particles 514 is disposed in polymeric material where for each particle of the plurality of particles 514, at least 75, 80, 85, 90, 95, 96, 97, 98, or 99 percent of a total surface area of the particle contacts the polymeric material. The polymeric material can include first and second portions (which may correspond to respective layers 140 and 110, for example) which may have the same or different compositions. In some embodiments, the optical layer 100 comprises a radiation- cured polymer (e.g., corresponding to a polymer of layer 140 or the combined polymer of layers 140 and 110) with the particles 514 disposed in the radiation-cured polymer. The radiation-cured polymer can be cured with actinic radiation such as electron-beam radiation or ultraviolet (UV) radiation. Any suitable radiation-cured polymer may be used. Illustrative examples include acrylates and methacrylates. In some embodiments, the polymeric layer (backfdl), which can correspond to layer 110, has a storage modulus at 20 deg. C of no more than 2500, 2000, 1500, 1000, 900, 800, 700, or 600 MPa. In some such embodiments, or in other embodiments, the storage modulus at 20 deg. C is at least 1, 5, 10, 20, 50, or 100 MPa.

[0043] In some embodiments, the layer 100 is formed on a substrate, radiation cured from the top side (the side facing surface 121), the substrate is subsequently removed, and removal of the substrate results in the structures 235 being formed on major surface 122. Without intending to be limited by theory, it is believed that the particles 514 partially focus the radiation and this promotes formation of the structures 235 opposite the radiation source when the substrate is removed. Optionally, a second substrate can be applied to surface 121 prior to curing the layer. Removing the second substrate can lead to similar structures on the major surface 121. Curing from both sides, for example, can promote surface structure formation on both major surfaces 121 and 122. In some embodiments, (e.g., a polymeric) material is transferred from the substrate(s) to the optical layer when the substrate(s) is removed. This can lead to the features 235 being protruding features. In some embodiments, (e.g., a polymeric) material is transferred from the optical layer to the substrate(s) when the substrate(s) is removed. This can lead to the features 235 being recessed features. Whether material is transferred to or from the optical layer 100 to the substrate(s) can depend on the relative adhesive and cohesive strengths of the material of the optical layer 100 adjacent to the substrate and of the material of the substrate adjacent to the optical layer. When the adhesive strength between the layer 100 and the substrate is higher than the cohesive strength of the binder of the layer 100, binder can be transferred to the substrate from the layer 100 leading to the features 235 being recessed features. When the adhesive strength between the layer 100 and the substrate is lower than the cohesive strength of the binder of the layer 100, material can be transferred from the substrate to the layer 100 leading to the features 235 being protruding features. The adhesive and cohesive strengths generally depend on material choice (e.g., a material with high tensile strength, for example, can have a high cohesive strength), curing conditions (e.g., degree of cure can affect cohesive strength of the binder and adhesion to the release surface), and release surface (e.g., lower surface energy can lower adhesive strength relative to cohesive strength). For example, in some embodiments, the binder includes diacrylates and higher functionality acrylates (e.g., triacrylates), and the cohesive strength of the cured binder can be adjusted by changing the ratio of the diacrylates to the higher functionality acrylates so that this ratio may be adjusted to result in recessed or protruding features (see, e.g., Examples 9 and 10). In some embodiments, at least one of the substrates comprises a metal layer that at least partially transfers to the optical layer 100 upon removal of the substrate. In some embodiments, at least a portion of the at least one of the first and second major surfaces 121 and 122 comprises metal.

[0044] In some embodiments, after the substrate(s) is removed, the resulting optical layer 100 is not directly fixedly attached to any other layer (e.g., release liners may be applied to one or both major surfaces 121, 122 of optical layer 100). In some embodiments, an adhesive layer is applied to one or both major surfaces 121, 122 of optical layer 100. In some embodiments, for each of the first and second major surfaces 121 and 122, the major surface is not directly fixedly attached to any other layer or is directly fixedly attached to a room-temperature adhesive layer substantially coextensive with the major surface.

[0045] As used herein, a “room-temperature adhesive” is an adhesive adapted to form a bond to a nonadhesive layer at room temperature (about 23 deg. C). A room -temperature adhesive can be a pressure sensitive adhesive and / or an optically clear adhesive, for example. A light (e.g., ultraviolet light) cured adhesive is a room-temperature adhesive when elevated temperature is not needed for the adhesive to cure and form a bond to an adjacent layer. A hot-melt adhesive that needs an elevated temperature to achieve bonding is not a room-temperature adhesive. A thermoplastic polymer layer bonded to adjacent thermoplastic polymer layers as a result of the layers being coextruded at an elevated temperature is not a room-temperature adhesive. Useful room-temperature adhesives include, for example, optically clear adhesives available from 3M Company (St. Paul, MN) or Norland Products (Jamesburg, NJ). An optically clear adhesive is generally an adhesive with a high visible light transmittance (e.g., greater than 75, 80, 85, or 90 percent) and a low optical haze (e.g., less than 10, 5, 4, 3, or 2 percent).

[0046] In some embodiments, the particles 514 are diffractive elements and the features 235 are diffractive elements. In some embodiments, an optical film 100, 200 (or 400c described elsewhere herein) includes an optical layer 100 including a plurality of first diffractive elements 514 embedded in the optical layer 100 and arranged into a plurality of irregularly arranged and substantially tightly packed domains, where each domain includes a plurality of the first diffractive elements regularly arranged in the domain. In some embodiments, the plurality of first diffractive elements 514 is disposed in polymeric material where for each first diffractive element of the plurality of first diffractive elements 514, at least 75, 80, 85, 90, 95, 96, 97, 98, or 99 percent of a total surface area of the first diffractive element contacts the polymeric material. The optical layer 100 has opposing first and second major surfaces 121 and 122. For at least one of the first and second major surfaces 121 and 122, the major surface comprises a plurality of second diffractive elements 235 (or 246, 256 described elsewhere herein) such that in a plan view and for at least majorities of the first and second diffractive elements, the first and second diffractive elements are aligned in one-to-one correspondence (see, e.g., FIG. IB). In some embodiments, the at least majorities of the first and second diffractive elements include at least 60, 70, 80, 90, or 95 percent of the respective first and second diffractive elements. In some embodiments, the plurality of first diffractive elements includes a plurality of particles. In some embodiments, the plurality of first diffractive elements includes a plurality of substantially spherical beads. In some embodiments, the plurality of second diffractive elements includes a plurality of protruding structures or a plurality of recessed structures.

[0047] In some embodiments, the first and second release liners 131 and 132 have respective higher and lower peel forces Fl and F2 from the optical film 200. The peel forces can be measured in a 90-degree peel test, for example. In some embodiments, the first release liner 131 is selected to have a higher peel force than that of the second release liner 132 (Fl > F2 via suitable selection of release coatings or release layers utilized) since it is typically desired that the first release liner 131 remain attached while the layer 230 is removed from the optical film (see, e.g., FIGS. 4B-4C). The release coatings can comprise silicone, polydimethylsiloxane (PDMS), fluoropolymer, or other known release chemistries. Useful silicone-based and non-silicone-based release liners are available from 3M Company (St. Paul, MN), for example. Instead of a release-coated film, a film with a suitably low surface energy (e.g., biaxially oriented polypropylene) may be used as a release liner.

[0048] FIG. 2A is a schematic cross-sectional view of an optical layer 100, according to some embodiments. FIG. 2B is a schematic cross-sectional view of a film 230, according to some embodiments. FIG. 2C is a schematic cross-sectional view of an optical layer 100, according to some embodiments. FIG. 2D is a schematic cross-sectional view of a film 230, according to some embodiments. The film 230 can be a substrate on which the optical layer 100 is formed where the substrate is subsequently removed from the optical layer resulting in the features 246, 256, 266, 276 being formed. The features 246, 256 can correspond to features 235. In some embodiments, the features

[0049] 246 are recessed features. The recessed features can include a central portion 248 and an annular portion

[0050] 247 surrounding the central portion 248. In some embodiments, the features 256 are protruding features. The protruding features can include a central portion 258 and an annular portion 257 surrounding the central portion 258. The features of the film 235 can be inverted relative to the features of the optical layer 100. For example, when the features 235 comprise recesses structures 246 (see, e.g., FIG. 2A), the film 230 formed with the optical layer 100 can comprise protruding structures 266 (see, e.g., FIG. 2B) which may include a central portion 268 and an annular portion 267 surrounding the central portion. Similarly, when the features 235 comprise protruding structures 256 (see, e.g., FIG. 2C), the film 230 formed with the optical layer 100 can comprise recessed structures 276 (see, e.g., FIG. 2D) which may include a central portion 278 and an annular portion 277 surrounding the central portion. The film 230 can have a release surface 270 with the features 266, 276 disposed thereon. The film 230 can be an optical film where the features 266, 276 are diffractive elements. FIG. 3 is a schematic plot of displacement versus radius of a feature (e.g., corresponding to any of 235, 246, 256, 266, 276) that may be a protruding structure or a recessed structure depending on the direction of the displacement, according to some embodiments. In some embodiments, the displacement versus radius is substantially independent of azimuthal coordinate Phi so that the feature has an approximate cylindrical symmetry. The feature can include a central portion 348 and an annular portion 347 surrounding the central portion 348.

[0051] In some embodiments, the features 235 comprise protruding structures 256. In some embodiments, for each protruding structure of at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent of the protruding structures 256, the protruding structure includes an annular portion 257 surrounding a central portion 258, where the annular portion 257 protrudes relative to the central portion 258. In some embodiments, the protruding structures 256 comprise release material (e.g., transferred from release surface 270). In some embodiments, the features 235 comprise recessed structures 246. In some embodiments, for each recessed structure of at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent of the recessed structures 246, the recessed structure includes an annular portion 247 surrounding a central portion 248, where the annular portion 247 is recessed relative to the central portion 248.

[0052] The optical fdm 100 can include structures 235 arranged into domains 510 as described further elsewhere herein (see, e.g., FIG. 5A). Similarly, the fdm 230 can include features 266, 276 arranged into domains 510 (see, e.g., FIG. 5B). In some embodiments, a fdm 230 includes a release surface 270; a plurality of spaced-apart features 266, 276 fixedly disposed on the release surface and arranged into a plurality of irregularly arranged domains 510, where each domain includes a plurality of the features regularly arranged in the domain (see, e.g., FIG. 5B where structures 512 can correspond to features 266 or 276). In some embodiments, as described further elsewhere herein, an average spacing S2 (see, e.g., FIGS. 5B and 6) between adjacent domains is no more than about 0.5, 0.4, 0.3, 0.2, or 0.1 times an average largest lateral dimension of the adjacent domains (e.g., dl schematically illustrated in FIG. 6). In some embodiments, an average of a minimum gap between adjacent features of each domain is at least 0.02, 0.03, 0.05, 0.075, 0.1, 0.125, 0.15, 0.175, or 0.2 times an average center-to-center spacing (e.g., corresponding to the pitch p schematically illustrated in FIG. 4A) between adjacent features of the domain. In some embodiments, the features comprise protruding structures 266. In some embodiments, for each protruding structure of at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent of the protruding structures 266, the protruding structure comprises an annular portion 267 surrounding a central portion 268, where the annular portion 267 protrudes relative to the central portion 268. In some embodiments, the features comprise recessed structures 276. In some embodiments, for each recessed structure of at least 10, 20, 30, 40, 50, 60, 70, 80, or 90 percent of the recessed structures 276, the recessed structure comprises an annular portion 277 surrounding a central portion 278, where the annular portion 277 is recessed relative to the central portion 278.

[0053] In some embodiments, the fdm 230 is formed of a polymer such as a polyester (e.g., polyethylene terephthalate) and a release coating is added to a major surface of the polymer layer. Suitable release coatings are described further elsewhere herein and include silicone-containing, hydrocarbon-containing, and fluorinated coatings. In other embodiments, the film 230 is formed from a polymer having a sufficiently low surface energy that a major surface of the polymer layer is inherently a release surface. Suitable low surface energy polymers include biaxially oriented polypropylene (BOPP), for example. In some embodiments, the release surface 270 has a first composition, and the features 266, 276 have a second composition different from the first composition. For example, material can be transferred from the optical layer 100 to the surface 270 and this material can have a different composition than that the surface 270. As another example, material can be transferred from the surface 270 to the optical layer 100 and material remaining under the material that was transferred can have a different composition than that of the surface 270. In some embodiments, the release surface 270 has a surface energy lower than a surface energy of the features 266, 276. In some embodiments, the release surface 270 has a surface energy of no more than about 55, 50, 45, 40, 35, 34, 33, 32, 31, or 30 dyne / cm. In some such embodiments, or in other embodiments the release surface 270 has a surface energy of at least about 14, 15, 16, 17, 18, or 20 dyne / cm. For example, in some embodiments, the release surface 270 has a surface energy in a range of about 14 to 55 dyne / cm, or about 14 to 40 dyne / cm, or about 15 to 35 dyne / cm, or about 15 to 33 dyne / cm, or about 15 to 32 dyne / cm, or about 16 to 30 dyne / cm. Here, surface energy can be the surface free energy determined by a surface analyzer that derives the surface free energy from contact angle measurements. Suitable surface analyzers include the KRUSS Mobile Surface Analyzer MSA One-Click SFE (available from KRUSS Scientific Instruments, Inc., Matthews, NC), for example.

[0054] FIGS. 4A-4C schematically illustrate a method of making an optical film or optical stack, according to some embodiments.

[0055] FIG. 4A is a schematic illustration of a film 400a including a layer 241 disposed on a substrate 230, according to some embodiments. The layer 241 has a major structured surface 212 that includes structures 312. FIG. 4B shows an optical stack 400b including a layer 110 formed (e.g., coated and then cured) on the structured surface 212 of the layer 241. An adhesive layer 141 and liner 131 can then added to the layer 110. The substrate 230 is then removed from the layer 241 resulting in features 235 being formed on major surface 122. An adhesive layer (e.g., corresponding to adhesive layer 142 schematically illustrated in FIG. 1C) can be added to surface 122 and then the release liner 132 added to the adhesive layer. In this way, a substrateless (no substrate other than release liners which can be subsequently removed) optical film can be made in a process that utilizes a single release step (releasing the substrate 230 from the layer 241).

[0056] The film 400a includes beads or particles 514 dispersed in a binder 140 (e.g., a polymeric binder). A layer 241 including the particles 514 in the binder 140 is disposed on a substrate 230 which can be a polymeric substrate (e.g., polyethylene terephthalate (PET), or an amorphous polyester such as polyethylene terephthalate glycol (PETG), or cyclo olefin polymer (COP), or BOPP), for example. The particles 514 have an average diameter d, an average pitch p, and an average spacing g between adjacent particles. The particles 514 define structures 312 in a structured major surface 212 having have an average peak-to-valley height h. Here, the valley can be defined as the lowest point between three adjacent particles when the particles are arranged in an approximately triangular lattice, for example. The average peak-to-valley height h should be understood to be the mean of the peak-to-valley height over domains 510 (see, e.g., FIG. 5A) of the structures. In some embodiments, the binder 140 substantially covers an entire surface of each particle in at least a majority of the particles 514. In other embodiments, the binder 140 may not wet the surface of the particles 514 and may leave a significant portion of the surface (e.g., top surface) of the particles 514 exposed.

[0057] The beads or particles 514 can be coated onto substrate 230 in a mixture including monomers and solvent. The solvent can be evaporated and the monomers cured to form the binder 140. As the solvent is removed, the particles 514 can self-assemble into ordered domains. The self-assembly may be driven by capillary action. Useful methods for processing particles, monomers and solvent are described in U.S. Pat. Appl. Pub. No. 2015 / 0011668 (Kolb, et al.), for example.

[0058] The average peak-to-valley height h can be controlled by selecting the ratio (e.g., by volume or by weight) of monomer to particles. In some embodiments, a ratio of particles to binder by weight is in a range of about 0.3 to about 3, or about 0.4 to about 2.8, or about 0.5 to about 2.5, for example. In some embodiments, the average peak-to-valley height h is no more than about half the average largest lateral dimension (e.g., SI illustrated in FIG. 5 A which may be about equal to the pitch p in FIG. 4A) of the structures 512. In some embodiments, the average peak-to-valley height h is no more than about 0.4 times the average largest lateral dimension of the structures 512. In some embodiments, the average peak-to- valley height h is in a range of about 0.2 to about 0.4 times the average largest lateral dimension of the structures 512. In some embodiments, the average peak-to-valley height h is at least about half the average largest lateral dimension. In some embodiments, the average peak-to-valley height h is in a range of about 0.4 to about 0.6, or about 0.5 to about 0.6 times the average largest lateral dimension of the structures 512. In some embodiments, the average peak-to-valley height h is about half the average largest lateral dimension. The desired average peak-to-valley height h can depend on the refractive index contrast across the structured interface between layers 110 and 241. A higher refractive index contrast can be used with a lower height h or a lower refractive index contrast can be used with a higher height h, for example. The particles 514 and the binder 140 can be index matched or can have different refractive indices. The difference in refractive indices of layer 100 and binder 140 can be substantially greater (e.g., at least by 0. 1) than the difference in refractive indices of the particles 514 and the binder 140. Refractive indices are determined at a wavelength of 532 nm, unless specified differently.

[0059] FIGS. 5A-5B are a schematic plan views of an illustrative portion of a film 500, according to some embodiments. The film 500 can schematically represent any film (e.g., 100, 200, 400c, 235) of the present description. The film 500 includes a plurality of structures 512 that can correspond to particles 514 (e.g., in FIG. 5A, the structures 512 can be defined by particles 514) or to features 235, 246, 256, 266, 276 (e.g., in FIG. 5B, the structures 512 may correspond to any such features) that can form a plurality of substantially coplanar structured domains 510. Substantially coplanar domains can be coplanar or approximately coplanar but with some minor variation about, or displacements from, a plane such as those that would be expected from ordinary manufacturing variations, for example. Each structured domain includes a substantially regular array of structures 512 arranged along orthogonal first and second directions (e.g., x- and y-directions). The first and second directions are typically in-plane directions orthogonal to a thickness direction (e.g., z-direction) of the film 500. A substantially regular array or substantially regular arrangement can be a regular array or arrangement or an array or arrangement that is approximately regular but with some minor displacements of structures from nominal positions such as those that would be expected from ordinary manufacturing variations, for example. Similarly, a substantially periodic arrangement can be a periodic arrangement or an arrangement that is approximately periodic but with some minor displacements of structures from nominal positions such as those that would be expected from ordinary manufacturing variations, for example.

[0060] In some embodiments, the arrays of adjacent domains have different orientations. The substantially regular array of structures 512 can be characterized as including structures 512 substantially repeating along first and second basis vectors 521 and 522 (which are along differing first and second directions). The basis vectors 521, 522 are not colinear so that the basis vectors can define a two- dimensional array. The basis vectors for different domains 510 can be different. Domains 510a-510d are schematically illustrated in FIGS. 5A-5B and the basis vectors 521, 522 are shown for domains 510b and 510d. The basis vector 521 of domain 510b is not parallel to eitherthe basis vector 521 or the basis vector 522 of domain 5 lOd. In some embodiments, for each domain, the plurality of substantially regularly arranged structures are substantially periodically arranged along each of different (not parallel) in-plane first and second directions 521 and 522, where the first and second directions 521 and 522 change irregularly from domain to domain. In some embodiments, for each domain, the in-plane first and second directions define an angle in a range of about 30 to 90 degrees therebetween. In some embodiments, the angle between the first and second directions 521 and 522 remain substantially constant from domain to domain as the first and second directions 521 and 522 change irregularly from domain to domain. For example, the angle for each of the domains can be about equal to a same angle which may be about 60 degrees, for example. In-plane directions refer to directions in the plane (xy-plane) of the film 500. For example, the film 500 can extend primarily along orthogonal width and length directions which define the plane of the film 500.

[0061] The structures and domains of the film 500 schematically illustrated in FIGS. 5A-5B can schematically represent structures and domains of the particles 514 or can schematically represent structures and domains of the features 235, for example. In some embodiments, the surface feature size may be substantially smaller than the particle size. For example, the size S 1 of the structures 512 depicted in FIG. 5A may correspond to particle size, while the size SI of the structures 512 depicted in FIG. 5B may correspond to surface feature size. In other embodiments, the size SI corresponding to surface feature size may be comparable to the size SI corresponding to particle size. In some embodiments, the particles 514 are disposed substantially in a monolayer of the particles. The particles 514 can be considered substantially in a monolayer even when a small number of the particles are missing from a full monolayer or a small number of the particles are stacked on other particles. In some embodiments, for each domain 510 in greater than 50, 60, 70, 80, 90, or 95 percent of the domains, the particles 514 in the domain are disposed substantially in a monolayer of the particles. In some embodiments, the particles 514 form less than a full monolayer. This may be referred to as a submonolayer. In some embodiments, the structures 512 and / or particles 514 (or surface features) define lake regions 516 between structured domains 510 that are free or substantially free of structures 512 and / or particles 514. For example, in some embodiments, the plurality of particles 514 defines lake regions 516 between structured domains 510 where each lake region 516 is free of the particles 514. In some embodiments, the particles 514 include a two-dimensional array of particles 514 and further include additional particles (e.g., corresponding to structure 518 schematically illustrated in FIG. 5A) disposed on the two-dimensional array of particles 514. A layer of particles including particles in addition to particles of a full monolayer may be referred to as a supra-monolayer. In some embodiments, the particles 514 of each domain 510 are arranged to form a regular two-dimensional first array of the particles 514. In some embodiments, for each domain in a sub-plurality (at least two but less than all) of the domains 510 (e.g., domains 510c and 5 lOd), the plurality of particles 514 further include at least one particle disposed on the particles arranged in the regular two-dimensional first array. In some embodiments, for each domain 510, the plurality of particles 514 further includes at least one particle 518 disposed on the particles arranged in the regular two-dimensional first array (e.g., each domain can appear as domain 510c or 5 lOd).

[0062] In some embodiments, including the optical film (e.g., optical film 100) in a display reduces the sparkle of the display but may also reduce the modulation transfer function (MTF) of the display. The preferred particle concentration (e.g., from sub-monolayer to supra-monolayer) can depend on a desired balance between maximizing the reduction in sparkle and minimizing the reduction in MTF. The preferred particle concentration may also depend on the refractive index contrast between layers 241 and 100. Typically, this index contrast is at least about 0.1.

[0063] FIG. 6 is a schematic plan an illustrative portion of a film 500, according to some embodiments. The structured domains 510 have orthogonal lateral dimensions dl and d2 and have an average spacing S2 therebetween. The structures of the structured domains 510 are not explicitly shown in the schematic illustration of FIG. 6. The structures can correspond to those schematically illustrated in FIG. 5A or FIG. 5B. In some embodiments, each structured domain in at least a majority of the structured domains has orthogonal first and second lateral dimensions dl and d2 where at least one of dl and d2 is greater than about 4, or greater than about 5, or greater than about 6 times an average largest lateral dimension S 1 (see, e.g., FIGS. 5A-5B) of the structures 512. In some embodiments, each structured domain in at least a majority of the structured domains has orthogonal first and second lateral dimensions dl and d2 where each of dl and d2 is greater than about 4, or greater than about 5, or greater than about 6 times an average largest lateral dimension SI of the structures. In some embodiments, the at least a majority of the structured domains includes at least about 60%, or at least about 70%, or at least about 80% of the structured domains.

[0064] The structures 512 of the fdm have an average largest lateral dimension S 1. The average is the unweighted mean of largest lateral dimension (e.g., diameter) of each structure 512. The largest lateral dimension of a structure corresponding to a particle may be approximately equal to the diameter of the particle or to an average pitch of the particles in a domain. The average diameter of the particle may be denoted by d (see, e.g., FIG. 4A). The plurality of domains 510 have an average spacing S2 therebetween. In some embodiments, S2 / S1 > 0.5. In some embodiments, S2 / S1 is at least about 0.6, 0.7, 0.8, 0.9 or 1. In some embodiments, S2 / S1 is no more than about 100, 50, 25, 15, 10, 8, 6, 4, 3, 2, 1.5, or 1.2. S2 / S 1 may be larger for the domains of features 235 (or other surface features) than for the domains of particles 514, for example, since S2 is typically the same or about the same in these cases, but S 1 may be smaller for the features than for the particles.

[0065] The layer 241 of the fdm 400a (see, e.g., FIG. 4A) has a structured first major surface 212 including a plurality of irregularly arranged and substantially tightly packed domains (e.g., 510a-5 lOd), where each of the domains includes a plurality of substantially regularly arranged structures (e.g., structures 512 defined by particles 514 or features 235). The domains can be described as substantially tightly packed when adjacent domains are spaced apart by gaps (e.g., defining the average spacing S2) substantially smaller (e.g., by at least a factor of 2, 3, 5, 10, or 20) than an average largest lateral dimension of the adjacent domains.

[0066] In some embodiments, the particles 514 have an average diameter d in a range of about 20 nm to about 15 micrometers or in another range described elsewhere herein. In some embodiments, the particles 514 are substantially spherical or ellipsoidal particles. In some embodiments, the particles 514 are substantially spherical. The structures 512 (of the tool or the resulting optical film) can have an average in-plane diameter in any of these ranges (e.g., in some embodiments, each of the structures 512 has an average in-plane diameter in a range from about 4 micrometers to about 15 micrometers, or from about 5 micrometers to about 12 micrometers). The average in-plane diameter is the mean of the diameter (largest dimension) over directions in the plane (xy-plane) of the optical film. A particle can be considered substantially spherical if its outline fits within the intervening space between two, concentric, truly spherical outlines differing in diameter from one another by up to about 30% of the diameter of the larger of these outlines. In some embodiments, each particle in at least a majority of the particles fits within the intervening space between two, concentric, truly spherical outlines differing in diameter from one another by up to about 20% or 10% of the diameter of the larger of these outlines. In the case of a non-spherical particle, the diameter of the particle can be understood to be the diameter of a sphere having the same volume as the particle. The average diameter d can be the mean or median particle diameter. For example, the average diameter can be the Dv50 size (median size in a volume distribution or, equivalently, particle size where 50 percent of the total volume of the particles is provided by particles having a size no more than the Dv50 size). In some embodiments, the plurality of particles has a substantially monodispersed particle size distribution (e.g., in some embodiments, at least 80% of the particles can have a diameter within 20% of the average diameter or at least 90% of the particles can have a diameter within 10% of the average diameter).

[0067] FIG. 7 is a schematic cross-sectional view of an illustrative film 600 (e.g., corresponding to films 100, 200, 400a, or 235), substantially normally incident (e.g., nominally normally incident or within 20 degrees, or 15 degrees, or 10 degrees, or 5 degrees to a normal to a major surface of the film or to the x-y plane when the film extends generally along orthogonal x- and y-directions) light 333 which can have a wavelength X in a wavelength range of I to X2, and transmitted light 334, according to some embodiments. The light 333 can be in a visible wavelength range (i.e., the wavelength(s) of the light 333 can be in a visible wavelength range). Visible wavelength ranges can be understood to be any range between about 380 nm and about 720 nm. For example, the wavelength range of I to X2 can be a visible wavelength range from about 380 nm to about 720 nm, or from about 400 nm to about 700 nm, or can be a narrower range (e.g., having a width of less than about 40 nm or less than about 20 nm) about a specified wavelength (e.g., 532 nm). In some embodiments, the visible wavelength range is a green wavelength range (e.g., about 500 nm to about 580 nm or about 520 nm to about 560 nm). For example, XI can be about 500 nm and X2 can be about 560 nm. In some embodiments, the substantially normally incident light 333 has a wavelength X of about 532 nm. For example, the light 333 can be substantially monochromatic (e.g., having an intensity versus wavelength having a peak intensity at a peak wavelength and a FWHM of less than 2% of the peak wavelength) light having a wavelength (e.g., the peak wavelength) of about 532 nm. In some embodiments, light 333 is a substantially Gaussian light beam. A substantially Gaussian light beam is a light beam having an intensity distribution (e.g., intensity versus position or angle) that can reasonably accurately be described as having a Gaussian shape. For example, laser light beams are often substantially Gaussian light beams. The light beam can have a beam waist diameter which is conventionally defined as diameter where the beam intensity is e-2(about 0. 135) times a peak intensity of the beam. The beam waist diameter can be expressed as twice a beam waist radius which can be expressed as an angle measured from an axis of the beam where the beam intensity is e-2times the peak intensity of the beam. For example, the beam waist diameter can be twice the angle “BW / 2” depicted in FIG. 19. The beam waist diameter can be determined using the same test instrument (e.g., imaging sphere) used to determine the scattering distribution function by removing the optical film from the test instrument. In some embodiments, light 333 is a substantially normally incident substantially Gaussian light beam having a beam waist diameter of 0.9 to 1.3 degrees, or 0.95 to 1.2 degrees, or 0.98 to 1.15 degrees, or 1 to 1.12 degrees, or about 1.06 degrees, and a wavelength of about 532 nm. For example, light 333 can be from a 532 nm laser. Optical film 600 can be any film described herein. At least a portion of the incident light 333 is transmitted as a transmitted light 334.

[0068] A scattering distribution function describes the relative intensity of scattered incident light and is generally a function of a scattering angle 0 and an azimuthal angle <p defining the direction of the scatered light. Scatering angles should be understood to be non-negative unless indicated differently. The scatering distribution function can be defined as the bidirectional scatering distribution function (BSDF) for substantially normally incident light 333 and for transmited light 334 (also referred to as the bidirectional transmitance distribution function or BTDF). An example of measuring the scatering distribution function is schematically depicted in FIG. 8. The azimuthally averaged intensity distribution function can be determined by averaging the scatering distribution function over all azimuthal angles (p. The substantially normally incident light 333 can be a substantially Gaussian light beam having a beam waist diameter in a range described elsewhere herein. It is typically desired to specify a range of the beam waist diameter since the scatering distribution function generally depends on this diameter.

[0069] FIG. 8 is a schematic geometry for the measurement of scatering profde and a schematic conoscopic plot of an illustrative scatering distribution function 450, according to some embodiments. The scatering distribution function along a scatering direction defined by azimuthal angle (p is the scatering distribution function along a radial direction (a direction of changing 0 for fixed <p) in a conoscopic plot. A scatering direction 444 is schematically illustrated. The conoscopic plot is shown in a detector plane 452 (x'y’-plane referring to the illustrated x'y’z’ coordinate system). The scatering angle 0 may be referred to as a polar angle (angle between the direction of scatered light 334 and z’ direction which can be a direction normal to the optical film 600) and the azimuthal angle cp is an angle between the direction 444 (direction defined by projection of the direction of scatered light 334 onto the detector plane 452) and the x' direction. The z' direction in FIG. 8 can correspond to the negative z-direction in FIG. 7 and other figures. In some embodiments, the scatering distribution function is substantially azimuthally symmetric (substantially independent of the azimuthal angle <p) . For example, the scatering distribution function 450 is substantially azimuthally symmetric in the embodiment schematically illustrated in FIG. 8. The degree of azimuthal non-uniformity can be characterized by the azimuthal nonuniformity parameter ANU defined by taking the standard deviation divided by the mean of the scatering distribution function over the full range of azimuthal angles for a given scatering angle and then averaging this quantity over scatering angles in a range of 10 to 70 degrees and multiplying by 100. A scatering distribution function having an ANU less than about 20 can be considered substantially azimuthally symmetric. In some embodiments, the ANU is less than about 15, or less than about 10, or less than about 8. In comparison, the ANU for an optical film having a single crystalline ordered domain is about 225.

[0070] FIG. 9 is a schematic plot representing an azimuthally averaged intensity distribution as a function of scatering angle or a scatering distribution function as a function of scatering angle which can be for a given azimuthal angle or can be an average over azimuthal angles or can be integrated over azimuthal angles, according to some embodiments. The illustrated scatering distribution function can schematically represent the scatering distribution function for a film 100, 200, 400c, or 230, for example. Typically, the scatering distribution function falls off faster with increasing scatering angle for a film 230 having surface elements but not embedded elements than for a fdm 100, 200, 400c including both surface and embedded elements (see, e.g., FIG. 20). The distribution 550 schematically illustrated in FIG. 9 may correspond to the scattering distribution function 450 along the scattering direction 444, for example. The scattering distribution function can be substantially azimuthally symmetric so that the normalized (divided by first peak Ip 1) scattering distribution function for a given azimuthal angle can be substantially the same as the normalized azimuthally averaged intensity distribution. The size of the structures of the optical film can affect the intensity distribution. The size of the particles 514, for example, can be in any of the ranges described elsewhere herein. For example, the particles 514 may have an average diameter in a range of about 4 micrometers to about 15 micrometers to result in an intensity distribution suitable for sparkle reduction.

[0071] In some embodiments, for a substantially normally incident substantially Gaussian light beam 333 having a beam waist diameter BW (see, e.g., FIG. 19) of 0.9 to 1.3 degrees (or in a range described elsewhere herein) and a wavelength of about 532 nm (or in a range described elsewhere herein), an azimuthally averaged intensity distribution of light transmitted by the optical film as a function of scattering angle measured from a normal to the optical film comprises first and second scattering bands (e.g., bands with scattering angles in the schematically illustrated local full-width at half maxima) having respective first 170 and second 171 scattering peaks 170 and 171 (peaks should be understood to be local maxima) and a valley 181 (valleys should be understood to be local minima) disposed therebetween, where the first and second scattering peaks 170 and 171 have corresponding first and second peak intensities Ipl and Ip2 and the valley 181 has a corresponding valley intensity Ivl. The first scattering peak 170 can be located at a first scattering angle al less than about 2 degrees, the valley can be located at a second scattering angle Va greater than the first scattering angle and less than about 6, 5.5, 5, 4.5, 4, or 3.5 degrees (e.g., when the optical film is configured to reduce sparkle). The azimuthally averaged intensity distribution can further include at least third through fifth scattering peaks 172, 173 and 174 at corresponding scattering angles a3, a4 and a5 with corresponding peak intensities Ip3, Ip4 and Ip5. The first through fifth peaks 170-174 can alternate with first through fourth valleys 181, 182, 183 and 184 at respective first through fourth valley scattering angles Va, Vb, Vc, and Vd. In some embodiments, the azimuthally averaged intensity distribution transmitted by the optical film as a function of scattering angle measured from a normal to the optical film comprises first through fourth scattering bands having respective first through fourth scattering peaks having respective peak intensities Ipl, Ip2, Ip3, and Ip4 located at increasing respective first through fourth scattering angles al, a2, a3, and a4, where the first scattering angle al less than about 2 degrees from a normal to the optical film, and where each of (a3- a2) / (a2-al) and (a4-a3) / (a2-al) is in a range of about 0.7 to about 1.1, or about 0.8 to about 1.05, or about 0.85 to about 1. Scattering angles should be understood to be polar angles unless indicated differently. In some embodiments, an integral over scattering angle of the azimuthally averaged intensity distribution from a scattering angle of no more than the first scattering angle al (e.g., from the first scattering angle al or from zero degrees) to the second scattering angle Va (or first valley scattering angle Va) is II, and an integral over scattering angle of the azimuthally averaged intensity distribution from the second scattering angle Va (or first valley scattering angle Va) to a (e.g., third) scattering angle in a range of about 10 to 12 degrees (e.g., 9.5, 10, 11, 12 or 12.5 degrees) is 12. The third scattering angle can correspond to Vc, for example. In some embodiments, Ip2 / Ivl < 15, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2.5, 2.25, or 2. In some embodiments, 12 / 11 > 0.3, 0.35, 0.4, 0.5, 0.6, 0.7, or 0.8. In some embodiments, Ip 1 / Ip2 < 100, 75, 50, 40, 30, 20, 18, 16, 15, 14, 12, 10, 9, 8.5, 8, or 7.5. In some embodiments, Ip 1 / Ip2 > 0.5, 0.7, 0.9, 1, 1.2, 1.5, 1.75, or 2. In some embodiments, Ipl / Ivl < 150, 140, 120, 100, 90, or 85, for example. In some embodiments, Ipl / Ivl > 5, 7, 10, 15, 20, 40, 50, 60, or 70. In some embodiments, the azimuthally averaged intensity distribution further comprises a third scattering band having a third scattering peak 172 having a third peak intensity Ip3, where the second scattering band is disposed between the first and third scattering bands, and where Ip2 / Ip3 < 8, 7, 6, 5.5, 5, 4.5, 4, 3.5, 3, 2.8, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2, 1.9, 1.8, 1.7. or 1.6, for example. In some embodiments, Ip2 / Ip3 > 0.5, 0.7, 0.9, 1, 1.1, or 1.2, for example. In some embodiments, 1 < Ip3 / Ip4 < 10, 8, 6, 5, 4, or 3.5.

[0072] In some embodiments, the scattering intensity at a scattering angle of about 20 degrees is less than a scattering intensity at a scattering angle of about 4 degrees or at the scattering angle Va or a2 by at least a factor of about 4, 5, 6, 8, 10, 12, 15, 20, or 25. It has been found, according to some embodiments, that a substantial fall off in scattering intensity between about 4 degrees, Va or a2 and about 20 degrees can result in only a modest reduction in effective resolution or DOI, for example. In some embodiments, the azimuthally averaged intensity distribution drops by a factor of at least 4, 5, 6, 8, 10, 12, 15, 20, or 25 between the second scattering angle (or first valley polar angle) Va and a scattering angle of about 20 degrees. In some embodiments, the scattering distribution function of the optical film along the first scattering direction 444 drops by a factor of at least 4, 5, 6, 8, 10, 12, 15, 20, or 25 between the first valley scattering angle Va and a scattering angle of about 20 degrees.

[0073] Typically, al < Va < a2 < Vb < a3. In some embodiments, additional peaks and valleys are present such that a3 < Vc < a4 and, in some embodiments, a4 < Vd < a5. In some embodiments, al is less than about 2, 1.5, 1, or 0.5 degrees. In some embodiments, al is substantially 0 degrees (e.g., less than about 1, 0.5, or 0.25 degrees). In some embodiments, the second scattering peak 171 is located at a scattering angle a2 in a range of about 3 degrees to about 8, 7.5, 7, 6.5, 6, 5.5, or 5 degrees. The scattering angle a2 can be at least about 3.25, 3.5, 3.75, or 4 degrees. In some embodiments, for each pair of adjacent scattering angles in the first through fourth scattering angles, the scattering angles in the pair are separated by at least about 1 degree and no more than about 8, 7, 6, or 5 degrees. The scattering angles of each pair can be separated by at least about 2, 2.5, 3, or 3.5 degrees, for example. The various scattering angles can generally be determined by the size of the particles 514 and the packing density and irregularity of the arrangement of the particles 514 in the tool used to make the structures of the optical film. In some embodiments, al is substantially 0 degrees, and ai for i=2 through 4 is Thetal times i-1 where Thetal is in a range of about 3.5 degrees to about 5 degrees, or about 3.8 degrees to about 4.8 degrees, or about 4 degrees to about 4.6 degrees.

[0074] In some embodiments, the scattering peaks extend from a baseline curve 190 of the azimuthally averaged intensity distribution that smoothly connects valleys of the azimuthally averaged intensity distribution. In some embodiments, an integral over the baseline curve from the first scattering angle al to a scattering angle of about 60 degrees is lb, an integral over the azimuthally averaged intensity distribution from the first scattering angle al to the scattering angle of about 60 degrees is Is, and Ib / Is > 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, and 0.37. Ib / Is can be up to about 1, 0.8, 0.6, or 0.5, for example.

[0075] In some embodiments, the first scattering band has a full width at half maximum FWHM1. Half of the FWHM1 of the first scattering band is shown in FIG. 8, for example, since the distribution can be substantially symmetrically extended to negative scattering angles (corresponding to a positive scattering angle and an azimuthal angle changed by 180 degrees). In some embodiments, the second through fourth scattering bands have respective second through fourth local full width at half maxima FWHM2 through FWHM4, where each of the FWHM2 through FWHM4 is in a range of about 1 to 4 degrees, or about 1.5 to 3 degrees. In some embodiments, 1 degree < FWHM2 < 3 degrees and FWHM3 > 1.1 x FWHM2. In some embodiments, FWHM2 < FWHM3 < FWHM4.

[0076] In some embodiments, for a substantially normally incident substantially Gaussian light beam 333 having a beam waist diameter of about 0.9 to 1.3 degrees (or in a range described elsewhere herein) and a wavelength of about 532 nm (or in a range described elsewhere herein), a scattering distribution function of the optical film along at least a first scattering direction (e.g., x-direction or scattering direction 444) in a first plane (e.g., xz-plane or the plane defined by the scattering direction 444 and the z' -direction in FIG. 8) substantially perpendicular (e.g., within 20, 15, 10, or 5 degrees of perpendicular to the plane of the optical film) to the optical film comprises first through third scattering bands having respective first through third scattering peaks having respective first through third peak intensities Ip 1, Ip2, and Ip3 located at increasing respective first through third scattering angles al through a3, where the first scattering angle al is less than about 2 degrees from a normal to the optical film. The scattering distribution function can be substantially azimuthally symmetric so that the normalized (divided by first peak Ip 1) scattering distribution function along the first scattering direction can be substantially the same as the normalized azimuthally averaged intensity distribution. The peak and valley intensities of the scattering distribution function along the first scattering direction can have ratios in any of the respective ranges described for the azimuthally averaged intensity distribution of the optical film. For example, in some embodiments, the scattering distribution function along the first scattering direction is such that Ipl / Ip2 < 100, 75, 50, 40, 30, 20, 18, 16, 14, 12, 10, 9, 8.5, 8, or 7.5. In some such embodiments, or in other embodiments, the scattering distribution function along the first scattering direction is such that Ip2 / Ip3 < 8, 7, 6, 5.5, 5, 4.5. 4, 3.5, 3, 2.8, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2, 1.9, 1.8, 1.7, or 1.6. In some such embodiments, or in other embodiments, the scattering distribution function of the optical film along at least the first scattering direction in the first plane comprises a valley disposed between the first and second scattering peaks, where the valley has a valley intensity Ivl, and where Ipl / Ivl < 180, 170, 160, 150, 140, 120, 100, 90, or 85.

[0077] In some embodiments, the domains 510 (see, e.g., FIGS. 5A-5B) are arranged sufficiently irregularly so that Ipl / Ivl < 150 (or in a range described elsewhere herein) and / or so that Ip2 / Ivl < 10 (or in a range described elsewhere herein) and / or so that the scattering distribution function of the optical film is substantially azimuthally symmetric, for example. For regularly arranged domains the scattering distribution function can be azimuthally asymmetric and / or Ivl can be small so that Ipl / Ivl is much larger than 150 and / or Ip2 / Ivl is much larger than 10.

[0078] The peaks and valleys of the scattering distribution function along the first scattering direction can be at scattering angles in any of the ranges described for the azimuthally averaged intensity distribution of light transmitted by the optical film. For example, the second scattering angle a2 of the scattering distribution function can be located at a scattering angle in a range of about 3 degrees to about 8 degrees or in another range described elsewhere herein.

[0079] In some embodiments, the scattering peaks extend from a baseline curve 190 of the scattering distribution function that smoothly connects valleys of the scattering distribution function in the first plane, where an integral over the baseline curve from the first scattering angle al to a scattering angle of about 60 degrees is lb, and an integral over the scattering distribution function in the first plane from the first scattering angle al to the scattering angle of about 60 degrees is Is. In some embodiments, Ib / Is > 0.3 (or Ib / Is can be in a range described elsewhere herein).

[0080] In some embodiments, optical characteristics of the particles and media surrounding the particles (e.g., refractive indices of the particles and the media surrounding the particles) are chosen so that the scattering distribution function has the properties (e.g., ratio of peak intensity to valley intensity, FWHM, etc.) described elsewhere herein.

[0081] In some embodiments, when the optical film is configured to reduce sparkle, the relatively strong scattering (e.g., compared to color correcting optically diffusive films) needed for an optical film to substantially reduce sparkle results in the optical film having a relatively high optical haze. In some embodiments, the optical film has an optical haze of greater than about 80, 81, 82, 83, or 84 percent. The optical haze can be up to about 95 or 90 percent, for example. The optical haze can be determined according to the ASTM DI 003- 13 test standard, for example.

[0082] FIG. 10 is a schematic plot of the first peak intensity Ip2 versus azimuthal angle, according to some embodiments. In some embodiments, the first peak intensity Ip2 is substantially constant over an azimuthal range of at least 180 degrees (e.g., from <p I to <p2) so that a ratio of a standard deviation o to an average Ip2avgof the first peak intensity over the azimuthal range is less than about 0.5, 0.4, 0.3, 0.2, 0.15, 0.1, or 0.08. The azimuthal range can be 360 degrees or can be less than 360 degrees. In some embodiments, the azimuthal range is at least 250 degrees. In some embodiments, for substantially normally incident light 333 in a visible wavelength range, a scattering distribution function of the optical fdm 100, 200, 400c is substantially azimuthally symmetric. In some embodiments, for substantially normally incident light 333 in a visible wavelength range, a scattering distribution function of the film 230 is substantially azimuthally symmetric.

[0083] The film 235 can provide similar intensity profiles as the optical film 100, 200, 400c, but typically with substantially faster drop off of normalized intensity with scattering (polar) angle (see, e.g., FIG. 20). In some embodiments, for a substantially normally incident substantially Gaussian light beam 333 having a beam waist diameter of 0.9 to 1.3 degrees and a wavelength of about 532 nm, an azimuthally averaged intensity distribution of light transmitted by the film as a function of scattering angle measured from a normal to the film comprises first and second scattering bands having respective first and second scattering peaks 170, 171 and a valley 181 disposed therebetween. The first and second scattering peaks 170 and 171 can have corresponding first and second peak intensities Ipl and Ip2. The first scattering peak 170 can be located at a first scattering angle less than about 2 degrees. The valley 181 can be located at a second scattering angle greater than the first scattering angle and less than about 6 degrees. Ip2 / Ip 1 can be greater than about 0.0001 or greater than about 0.001. Ip2 / Ip 1 can be less than about 0.1 or less than about 0.01. For example, in some embodiments, Ip2 / Ip 1 is greater than about 0.0001 and less than about 0.1 or greater than about 0.001 and less than about 0.01.

[0084] FIG. 11 is a schematic cross-sectional view of an illustrative display 760 that includes an optical film 600, which can be any of the optical films described herein, disposed on a display panel 680, which can be a liquid crystal display panel (LCD) or an organic light emitting diode (OLED) panel, for example. The pixels can be arranged at pitches Pl and P2 in respective first and second in-plane directions (x- and y-directions). FIG. 12 is a schematic top view of the display panel 680, according to some embodiments. In some embodiments, the optical film reduces sparkle of the display 760 (e.g., by at least 15% or in a range described elsewhere herein) without substantially reducing an effective resolution of the display (e.g., without reducing effective resolution as characterized by MTF and / or DOI by more than about 45% or in a range described elsewhere herein). The optical film typically reduces the sparkle without generating significant rainbow mura.

[0085] In some embodiments, a display 760 includes a pixelated display surface 681 and an optical film 600 disposed thereon. In some embodiments, the display 760 can include a circular polarizer (e.g., one of 631 and 631'). For example, the display can 760 can be an OLED display which includes a circular polarizer to reduce ambient reflection as is conventional for OLED displays. In some embodiments, the display 760 includes a circular polarizer 631, where the optical film 600 is disposed between the circular polarizer 631 and the display surface 681. In some embodiments, the display 760 includes a circular polarizer 631' disposed between the optical film 600 and the display surface 681. In some embodiments, the display 760 includes an anti-glare layer 633 (e.g., anti-glare cover glass), where the optical film 600 is disposed between the anti-glare layer 633 and the display surface 681. The display 760 may further include other elements commonly included in displays. In some embodiments, the display 760 includes a display panel 680 having a pixelated display surface 681 having a pixel spatial frequency (e.g., 1 / P1 or 1 / P2; if Pl and P2 are different, the pixel spatial frequency can be taken to be the smallest spatial frequency defined by Pl and P2); and any of the optical films of the present description disposed adjacent to, and spaced apart from, the pixelated display surface 681. In some embodiments, the optical film reduces sparkle of the display by at least 15% without decreasing a modulation transfer function (MTF) at the pixel spatial frequency by more than about 45, 40, 35, 30, or 25, 23, 21, 20, 19, 18, or 17 percent. In some such embodiments, or in other embodiments, the optical film reduces sparkle of the display by at least 15, 18, 20, 22, 24, 26, 28, 30, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, or 43 percent. For example, the sparkle of the display can be reduced from about 7% without the optical film to about 4.5% when the optical film is included (a reduction of about 35.7%). The sparkle can be determined as a ratio of standard deviation to a mean of an intensity distribution of a light output 761 of the display panel low pass filtered to remove display pixel modulation from the intensity distribution. The sparkle can be expressed as a percent by multiplying the ratio by 100%. The MTF may be decreased by the optical film by at least 5%, for example. The sparkle can be determined according to IEC 62977-3-9 (2023). Annex B2 of that test standard describes suitable low pass filtering to remove the display pixel modulation from the intensity distribution. A suitable instrument for measuring sparkle is the SMS- 1000 Sparkle Measurement System available from Display-Messtechnik & Systeme, Rottenburg am Neckar, Germany. The SMS- 1000 can also determine a distinctiveness of image (DOI) which is defined as a modulation transfer factor (MTF) for a spatial frequency of the pixel pattern of the display as a percent of a reference MTF at the same spatial frequency determined from the display without the sparkle reduction optical film and without the antiglare cover glass of the display. The percentage reduction in MTF at the pixel spatial frequency can be determined as the percentage reduction in DOI determined by the SMS-1000.

[0086] EXAMPLES

[0087] All parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight, unless noted otherwise. Abbreviations include um = micrometer; scfin = standard cubic feet per minute; and ppm = parts per million. Other standard abbreviations may also be used.

[0088] Sparkle and DOI Measurements

[0089] The sparkle performance of optical films was evaluated using a custom-built test system. The optical film under test was placed in between a photolithographically patterned chromium mask (with 75.6 um x 23.5 um pixels that are separated by 72.5 um in one direction and 20.2 um in orthogonal direction mimicking a typical LCD pixel layout) and -1100 um thick matte cover glass (EAGLEETCH XS AG 70 Gloss glass, available from Europtec). The whole stack was then illuminated by a Lambertian white light source (Part # 83873 Metaphase Technologies, Bristol, PA). For sparkle measurements, the pixels on the mask were then imaged using a complementary metal oxide semiconductor (CMOS) camera (Blackfly, Teledyne FLIR LLC, Wilsonville, OR) equipped with a 50mm lens with f / 8 aperture (C203218, Tamron Co. Ltd. Japan). The sparkle values were then calculated as the variance of local intensity after removing the low frequency modulations from the pixels. Detail description of calculations of sparkle is described in U.S. Pat. No. 10,353,214 (Sitter et al.), or in the product literature of a sparkle measurement system SMS- 1000 (Display-Messtechnik & Systeme, Rottenburg am Neckar, Germany), for example. The same images captured by the camera were used to calculate the Distinctness of Image (DOI) by measuring the intensity modulation (peak-to-valley amplitude) with the mask only and then with the test film and cover glass on top of the mask. DOI is calculated as: DOI = (Modulation with test film and cover glass / modulation with mask only) * 100 %.

[0090] Materials Used in the Examples

[0091] Prepatory Examples PE1-PE3

[0092] Particle formulations A, B and C were prepared according to the following table. Solutions were supplied through a hopper, which had a pneumatic mixer with the blade near the hopper outlet, constantly running to prevent particle settling, to a gear pump. The solution was filtered through a filtration system A recirculation loop was used to recycle the coating solution when not coating. The filtered coating solution was fed to a slot die where it was coated onto a 2mil (50 um) PET substrate. The solvent was then removed in a conventional flotation oven with three ten-foot (3m) zones. Typical temperature set points for Zones 1, 2, and 3 were 220 (104.4), 140 (60), 160 (71.1) degrees Fahrenheit (Celsius), respectively. A final cure step was then used to complete the cure of the coating using an inerted UV curing unit with an H-bulb. The coated product was then wound onto a core at one pound per lineal inch (175.1 Newtons per lineal meter) tension. Substantially monolayer particle coatings with 8um (SSX-108) and 5um (MX-500) diameter particles were made with at or near hemisphere particle exposure based on particle / monomer ratio. Process conditions are provided in the following table.

[0093] An optical microscope image of the monolayer particle coating of Prepatory Example PEI is shown in FIG. 13.

[0094] Particle coatings were then overcoated / backfill coated with an optically clear high refractive index formulation. High index formulations with indices ranging from 1.68 to 1.53 were made by addition of varying amounts SR399LV monomer (refractive index of 1.527) to a base UV curable high index 1.6815 formulation. The formulation of the base UV curable high index 1.6815 formulation is provided the table below. Formulations having refractive indices of 1.64, 1.61, 1.59 and 1.57 included 10, 20, 30 and 40 wt.% of SR399LV with the remainder of the formulation being the base UV curable high index 1.6815 formulation.

[0095] Overcoating / backfill formulations were coated with a #12 Mayer rod. The coatings then travelled a 10 ft (3 m) span in the room environment, and passed through two 5 ft (1.5 m) long zones of small gap drying with plate temperatures set at 190 °F (88 °C). Related gap drying is described in U.S. Pat. Nos. 5,581,905 (Huelsman et al.); 5,694,701 (Huelsman et al.); and 6,134,808 (Y apel et al.), for example. The substrate was moving at a speed of 305 (cm / min). Finally, the dried coating entered a UV chamber equipped with a Fusion System Model I300P where an H-bulb was used. The UV chamber was purged by nitrogen at a flow rate of 11 scfin (310 liters / min) which resulted in an oxygen concentration of approximately 50 ppm.

[0096] Sparkle measurements of high index overcoated beaded coatings were made versus blank (no anti-sparkle solution) and a comparative anti-sparkle film (Comparative Example CE1) made as described in U.S. Pat. No. 10,353,214 (Sitter et al.) with a 2-dimensonal sinusoidal structured interface (see, e.g., FIGS. 6A-6B of that reference) with an 8 um pitch for comparison. Sparkle and DOI measurements were made as described under “Sparkle and DOI Measurements” where the backfilled optical film was disposed between the antiglare cover glass and the chromium with the backfill layer facing the chromium mask. Sparkle and DOI results are shown in FIGS. 14-15, respectively, as a function of the refractive index of the backfill layer. Sparkle and DOI results for Prepatory Examples PEI - PE3 were roughly comparable to those of CE1 but Prepatory Examples PE1-PE3 did not produce the undesired rainbow mura produced by CE1.

[0097] The transmission scattering distribution function for various samples were determined using an imaging sphere (Radiant Vision Systems IS-SA) modified to accept a substantially normally incident light having a wavelength of 532 nm (Thorlabs CPS532). Transmission versus scattering angle was tabulated by taking an azimuthal average over a uniform section of the output conoscopic image. The substantially normally incident light was a substantially monochromatic substantially Gaussian light beam having a beam waist diameter of about 1.06 degrees as determined using the imaging sphere. Prepatory Example PEI with a 1.61 index backfill resulted in an Ip 1 / Ip2 of about 5.

[0098] Prepatory Examples PE4-PE8

[0099] Particle formulation D was prepared according to the following table.

[0100] Solutions were supplied through a hopper, which had a pneumatic mixer with the blade near the hopper outlet, constantly running to prevent particle settling, to a gear pump. The solution was fdtered through a fdtration system. A recirculation loop was used to recycle the coating solution when not coating. The fdtered coating solution was fed to a slot die where it is coated onto a 15um COP substrate with a 2mil (50um) carrier PET fdm. The solvent was then removed in a gap dryer with four, five-foot (1.5 m) zones set to 130 (54.4), 160 (71.1), 175 (79.4), and 175 (79.4) degrees Fahrenheit (Celsius), respectively, followed by a conventional flotation oven with two fifteen-foot (4.6 m) zones. The gap dryer was similar to those described in U.S. Pat. Nos. 5,581,905 (Huelsman et al.); 5,694,701 (Huelsman et al.); and 6,134,808 (Y apel et al.), for example. Temperature set points for Zones 1 and 2 were 220 (104.4) and 160 (71.1) degrees Fahrenheit (Celsius), respectively. A final cure step was then used to complete the cure of the coating using an inerted UV curing unit with H-bulbs. The coated product was then wound onto a core at one pound per lineal inch (175.1 Newtons per lineal meter) tension. Substantially monolayer particle coatings with 8um (SSX-108) diameter particles were made with at or near hemisphere particle exposure based on particle / monomer ratio. The coating line speed was 60 ft / min (1828.8 cm / min). The pump rates that were used are given in the following table.

[0101] Overcoat / Backfill formulation E was prepared according to the following table. Overcoating / backfill formulations were supplied through a hopper, to a gear pump. The solution was filtered through a filtration system. A recirculation loop was used to recycle the coating solution when not coating. The filtered coating solution was fed to a slot die where it is coated onto the particle coated film on COP, as outlined above. The solvent was then removed in a gap dryer with four, five-foot zones set to 80 (26.7), 80 (26.7), 100 (37.8), and 100 (37.8) degrees Fahrenheit (Celsius), respectively, followed by a conventional oven with two fifteen-foot (4.6 meters) zones. The gap dryer was similar to those described in U.S. Pat. Nos. 5,581,905 (Huelsman et al.); 5,694,701 (Huelsman et al.); and 6,134,808 (Yapel et al.), for example. Temperature set points for Zones 1 and 2 were 120 (48.9) and 140 (60) degrees Fahrenheit (Celsius), respectively. A final cure step was then used to complete the cure of the coating using an inerted UV curing unit with H-bulbs. The coated product was then wound onto a core at one pound per lineal inch tension. The coating line speed was 30 ft / min (914.4 cm / min) and the pump rate was 4.4 g / min per inch width (1.72 g / min per cm width) for each of these Examples.

[0102] Comparative Example CE2 was made as described for Example 13 of Int. Pat. Appl. Pub. No. WO 2021 / 240268 (Menke et al.). For comparison, a sample with no anti-sparkle film (“No AS”) but with a PET spacer layer of about the same thickness as the optical film examples was also tested.

[0103] Sparkle and DOI measurements were made as described under “Sparkle and DOI Measurements” where the backfilled optical film was disposed between the antiglare cover glass and the chromium mask with the backfill facing the chromium mask. Results for sparkle and DOI are shown in FIGS. 16-17, respectively. A corresponding scatter plot of sparkle decrease versus MTF decrease relative to the display without an anti-sparkle film (“No AS”) is shown in FIG. 18.

[0104] The scattering intensity distribution was determined using the imaging sphere as described elsewhere in the Examples. The intensity distribution was azimuthally averaged and normalized (so that Ipl = 1). The resulting normalized scattering distributions are shown in FIG. 19. Results are provided in the following table which includes results for the light source without an optical film. The first scattering angle al was about 0 degrees. The ratio 12 / 11 was determined where II is an integral over scattering angle of the azimuthally averaged intensity distribution from about zero degrees to the first valley scattering angle Va, and an 12 is integral over scattering angle of the azimuthally averaged intensity distribution from the first valley scattering angle Va to a scattering angle of 11 degrees. Results are provided in the following table.

[0105] Examples 1-8

[0106] Examples 1-8 are prepared by making samples as in Prepatory Examples P1-P8, respectively.

[0107] Then a liner with an adhesive layer is attached to the resulting backfill layer and then the substrate (e.g., corresponding to film 235) is removed from the optical layer (e.g., corresponding to optical layer 100). The Prepatory Examples P1-P8 can be modified by including a release coating on the substrate or by choosing a substrate (e.g. BOPP) with a surface energy sufficiently low to facilitate release from the optical layer 100. The resulting optical film has a similar scattering intensity distribution, sparkle reduction, and DOI as the respective Prepatory Examples PE1-PE8 when the resulting surface features (e.g., corresponding to features 235) contribute substantially less to the scattering intensity distribution than the particles embedded in the optical layer (see, e.g., FIG. 20 were Ip2 / Ip 1 is about two orders of magnitude lower for the structures on the removed release film than for the beaded optical film).

[0108] Example 9

[0109] A particle formulation was prepared according to the following table: The binder of the particle formulation when cured had a refractive index of 1.495 at 532 nm. Solutions were supplied through a hopper, which had a pneumatic mixer with the blade near the hopper outlet, constantly running to prevent particle settling, to a gear pump. The solution was filtered through a filtration system. A recirculation loop was used to recycle the coating solution when not coating. The filtered coating solution was fed to a slot die where it is coated onto a PET substrate having a nonsilicone non-fluorinated release surface with a surface free energy of 16.5 dyne / cm as determined using a KRUSS Mobile Surface Analyzer MSA One-Click SFE (available from KRUSS Scientific Instruments, Inc., Matthews, NC). The solvent was then removed in a gap dryer with two, five-foot (1.5 m) zones set to 120(48.9) and 150(65.6)degrees Fahrenheit (Celsius), respectively, followed by a conventional flotation oven with three ten foot (3.05m) zones. The gap dryer was similar to those described in U.S. Pat. Nos. 5,581,905 (Huelsman et al.); 5,694,701 (Huelsman et al.); and 6,134,808 (Y apel et al.), for example. Temperature set points for Zones 1, 2, and 2 were 200(93.3), 140(60), and 100(37.8) degrees Fahrenheit (Celsius), respectively. A final cure step was then used to complete the cure of the coating using an inerted UV curing unit with H-bulbs. The coated product was then wound onto a core at one pound per lineal inch (175.1 Newtons per lineal meter) tension. Substantially monolayer particle coatings with 8um (SSX-108) diameter particles were made with at or near hemisphere particle exposure based on particle / monomer ratio. The coating line speed was 30 ft / min (914.4 cm / min) and the pump setting was 5.625 g / min per in width (2.215 g / min / cm).

[0110] Overcoat / Backfill formulation F was prepared according to the following table.

[0111] Overcoating / backfill formulations were supplied through a syringe pump. The solution was filtered through a filtration system. The filtered coating solution was fed to a slot die where it is coated onto the particle coated film, as outlined above. The solvent was then removed by a conventional oven with three ten-foot (3.05 meters) zones. Temperature set points for Zones 1, 2, and 3 were 120 (48.9), 120 (48.9) and 120 (48.9) degrees Fahrenheit (Celsius), respectively. A final cure step was then used to complete the cure of the coating using an inerted UV curing unit with H-bulbs. The coated product was then wound onto a core at one pound per lineal inch tension. The coating line speed was 30 ft / min (914.4 cm / min) and the pump rate was 3.72 cc / min / in (1.46 cc / min / cm) for this example. CEF18 optically clear adhesive was then hand laminated to a section of the cured backfill, and then to a glass layer, and then the release substrate was removed. Material was transferred to the release substrate resulting in protruding structures formed on the release substrate and corresponding recessed structures formed on the optical layer having the particles embedded therein. The recessed structures were aligned with the particles. The scatering intensity distribution was determined for the resulting optical film (e.g., corresponding to optical film 100, 200, 400c) and for the removed release substrate (e.g., corresponding to film 235) using the imaging sphere as described elsewhere in the Examples. The intensity distribution was azimuthally averaged and normalized (so that Ipl = 1). The resulting normalized scatering distributions are shown in FIG. 20.

[0112] Example 10

[0113] An optical layer was formed on a non-silicone non-fluorinated release substrate as generally described for Example 9 except that the following particle formulation was used:

[0114] CEF 18 optically clear adhesive was hand laminated to a section of the optical layer, and then to a glass layer, and then the release substrate was then removed. Material was transferred from the release substrate resulting in recessed structures formed on the release substrate and corresponding protruding structures formed on the optical layer including the particles. The protruding structures were aligned with the particles.

[0115] 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.

[0116] 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” with reference to a property or characteristic 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 and when it would be clear to one of ordinary skill in the art what is meant by an opposite of that property or characteristic, the term “substantially” will be understood to mean that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited.

[0117] 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.

[0118] 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, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

1. What is claimed is:

1. An optical film comprising: an optical layer comprising a plurality of particles embedded therein and arranged into a plurality of irregularly arranged and substantially tightly packed domains, each domain comprising a plurality of the particles regularly arranged in the domain, the optical layer comprising opposing first and second major surfaces, wherein for at least one of the first and second major surfaces, the major surface comprises a plurality of features such that in a plan view and for at least a majority of the features and at least a majority of the particles, the particles and the features are aligned in one-to-one correspondence.

2. The optical film of claim 1, wherein the features comprise protruding structures.

3. The optical film of claim 2, wherein for each protruding structure in at least 10% of the protruding structures, the protruding structure comprises an annular portion surrounding a central portion, the annular portion protruding relative to the central portion.

4. The optical film of claim 2, wherein the protruding structures comprise release material.

5. The optical film of claim 1, wherein the features comprise recessed structures.

6. The optical film of claim 5, wherein for each recessed structure in at least 10% of the recessed structures, the recessed structure comprises an annular portion surrounding a central portion, the annular portion recessed relative to the central portion.

7. The optical film of claim 1, wherein the particles have an average diameter in a range from about 20 nm to about 15 micrometers.

8. The optical film of claim 1, wherein for each of the first and second major surfaces, the major surface is not directly fixedly attached to any other layer or is directly fixedly attached to a room-temperature adhesive layer substantially coextensive with the major surface.

9. The optical film of claim 1, wherein for substantially normally incident light in a visible wavelength range, a scattering distribution function of the optical film is substantially azimuthally symmetric.

10. A display comprising a pixelated display surface and the optical film of any one of claims 1 to 9 disposed thereon, wherein the optical film reduces sparkle of the display by at least 15 percent withoutdecreasing a modulation transfer function (MTF) of the display at a pixel spatial frequency of the pixelated display surface by more than about 45 percent.

11. An optical film comprising: an optical layer comprising a plurality of first diffractive elements embedded therein and arranged into a plurality of irregularly arranged and substantially tightly packed domains, each domain comprising a plurality of the first diffractive elements regularly arranged in the domain, the optical layer comprising opposing first and second major surfaces, wherein for at least one of the first and second major surfaces, the major surface comprises a plurality of second diffractive elements such that in a plan view and for at least majorities of the first and second diffractive elements, the first and second diffractive elements are aligned in one-to-one correspondence.

12. The optical film of claim 11, wherein the plurality of first diffractive elements comprises a plurality of particles.

13. The optical film of claim 11 or 12, wherein the plurality of second diffractive elements comprises a plurality of protruding structures or a plurality of recessed structures.

14. A film comprising: a release surface; and a plurality of spaced-apart features fixedly disposed on the release surface and arranged into a plurality of irregularly arranged domains, each domain comprising a plurality of the features regularly arranged in the domain, an average spacing between adjacent domains being no more than about 0.5 times an average largest lateral dimension of the adjacent domains, an average of a minimum gap between adjacent features of each domain being at least 0.02 times an average center-to-center spacing between adjacent features of the domain.

15. The film of claim 14, wherein the release surface has a first composition, and the features have a second composition different from the first composition.

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