Optical films and stacks including optical diffuser layers

Abstract

The optical film and stack include at least one optical diffuser layer. The optical diffuser layer may include a plurality of nanoparticles and a polymer material that bonds the nanoparticles to each other to form a plurality of nanoparticle aggregates defining a plurality of voids therebetween. For substantially normally incident light and a visible wavelength range of about 450 nm to about 650 nm and an infrared wavelength range of about 930 nm to about 970 nm: in the visible wavelength range, the optical film or optical diffuser layer has an average specular transmittance Vs; and in the infrared wavelength range, the optical film or optical diffuser layer has an average total transmittance It and an average specular transmittance Is, Is / It≥0.6, Is / Vs≥2.5.

Description

Background Art

[0001] Optical diffusers can be used to diffuse light in a variety of applications. For example, optical diffusers can be used in display applications to reduce hot spots and increase uniformity. Summary of the invention

[0002] The present disclosure generally relates to optical films and optical stacks that include at least one optically diffuse layer.

[0003] In some aspects of the present disclosure, an optical film including a plurality of optical diffusion layers is provided. The optical diffusion layer has opposite first and second major surfaces, and includes a plurality of nanoparticles dispersed between and across the first and second major surfaces. The optical diffusion layer includes a polymer material that bonds the nanoparticles to each other to form a plurality of nanoparticle aggregates defining a plurality of voids therebetween. The nanoparticles may be or include silicon dioxide. In the plane of a cross section of the optical diffusion layer in the thickness direction of the optical diffusion layer: the average particle size of the nanoparticles may be between about 20 nm and about 150 nm; the average particle size of the nanoparticle aggregates may be between about 100 nm and about 1000 nm; and the voids may occupy between about 15% and about 45% of the area of ​​the plane of the cross section. For substantially normally incident light and a visible wavelength range of about 450 nm to about 650 nm and an infrared wavelength range of about 930 nm to about 970 nm: in the visible wavelength range, the optical film has an average specular transmittance Vs; and in the infrared wavelength range, the optical film has an average total transmittance It and an average specular transmittance Is. Is / It≥0.6 and Is / Vs≥2.5. Bending the optical film at a first bending position on an inner diameter of up to 10 mm results in no damage or only minimal damage to the optical diffuser layer at the first bending position.

[0004] In some aspects of the present disclosure, an optical stack is provided, the optical stack including a reflective polarizer disposed between a first optical diffuser layer and a second optical diffuser layer. Each of the first optical diffuser layer and the second optical diffuser layer includes a plurality of non-uniformly dispersed particles, the plurality of non-uniformly dispersed particles defining a plurality of voids therein. For substantially normally incident light and a visible wavelength range of about 450 nm to about 650 nm and an infrared wavelength range of about 930 nm to about 970 nm: the reflective polarizer transmits at least 40% of the incident light of a first polarization state for each wavelength in the visible wavelength range, reflects at least 70% of the incident light of an orthogonal second polarization state for each wavelength in the visible wavelength range, and transmits at least 40% of the incident light of each of the first polarization state and the second polarization state for each wavelength in the infrared wavelength range; and in the visible wavelength range, each of the first optical diffuser layer and the second optical diffuser layer has an average total transmittance Vt and an average specular transmittance Vs, and in the infrared wavelength range, each of the first optical diffuser layer and the second optical diffuser layer has an average total transmittance It and an average specular transmittance Is. Is / It≥0.6 and Is / Vs≥2.5.

[0005] These and other aspects will become apparent from the following detailed description.This brief summary, however, should not be construed in any way as limiting the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A is a schematic cross-sectional view of an exemplary optical film including an optical diffuser layer.

[0007] Figure 1B to Figure 1C is a scanning electron microscope (SEM) image of an exemplary optical diffuser layer.

[0008] Figures 2 to 3 is a schematic cross-sectional view of an exemplary optical stack including an optically diffuse layer.

[0009] FIG. 4A to FIG. 4B is a schematic cross-sectional view of a film or layer schematically illustrating substantially normally incident light as well as diffuse and specularly transmitted light.

[0010] Figure 5 is a schematic cross-sectional view of an optical film or stack bent around a cylinder.

[0011] Figure 6 to Figure 7 is a schematic graph of an exemplary particle size distribution.

[0012] Figure 8 is a schematic cross-sectional view of an exemplary optical film including an optically diffuse layer disposed on a structured surface.

[0013] Fig. 9Ais a schematic cross-sectional view of an exemplary plurality of alternating layers.

[0014] FIG. 9B to FIG. 9C is a schematic cross-sectional view of an exemplary multilayer film.

[0015] Fig. 10A , Fig. 10B and Fig.11 is a schematic graph of transmittance versus wavelength.

[0016] Figure 12 to Figure 13 is a graph of transmission versus wavelength for an exemplary optical film.

[0017] Fig.14A is a graph of transmission versus wavelength for an exemplary optical film.

[0018] FIG. 14B to FIG. 14C yes Fig.14A part of a graph.

[0019] Fig.15A is a schematic plan view of an exemplary bottom major surface.

[0020] Fig. 15B is a schematic cross-sectional view of an optical film or stack having a structured major surface.

[0021] Fig.16 is a schematic exploded cross-sectional view of an exemplary display system. DETAILED DESCRIPTION

[0022] In the following description, reference is made to the accompanying drawings, which form a part of the present invention and in which various embodiments are shown by way of example. The drawings are not necessarily drawn to scale. It should be understood that other embodiments may be conceived and carried out without departing from the scope or essence of the present description. Therefore, the following specific embodiments should not be considered to have a limiting meaning.

[0023] According to some embodiments, the optical film or optical stack includes at least one optical diffuser layer including dispersed particles so as to form aggregates of particles having interstices (air spaces) between the aggregates. In some embodiments, the optical diffuser layer provides a substantially higher degree of specular transmittance in the infrared range than in the visible range. Alternatively, or in addition, according to some embodiments, the optical diffuser layer can provide a substantially higher diffuse transmittance in the visible range than in the infrared range.

[0024] In some embodiments, the particles are nanoparticles, and the average particle size of the aggregates is less than about 1 micron. In other embodiments, the aggregates can be larger (e.g., up to about 10 microns, or about 1 micron to about 10 microns, or about 5 microns to about 10 microns). It has been found that optical films or stacks including one or more optical diffuser layers can be flexible and non-fragmentary even when the aggregates are small (e.g., the average particle size is less than about 1 micron) and / or even when the voids occupy a significant portion of the cross-section of the optical diffuser layer in the thickness direction (z-axis) of the optical diffuser layer (e.g., about 15% or more).

[0025] According to some embodiments, the optical film or stack can be used in display applications or other applications where it is desirable to provide scattering of visible light (e.g., substantially optical diffuse transmission) with minimal scattering of light in the infrared range (e.g., substantially optical specular transmission). For example, in a liquid crystal display (LCD) including a fingerprint detection system having an infrared light source and an infrared sensor behind a backlight, it is generally desirable that infrared light from the infrared light source is transmitted to the outer surface of the display, and then, if a finger is present, is reflected from the finger and transmitted through the display and reaches the infrared sensor through the backlight with minimal scattering. For example, LCD backlights generally also include an optical diffuser for defect hiding. Conventional optical diffusers generally scatter both light in the wavelength range of visible light and infrared light sources (e.g., in the wavelength range of about 930nm to about 970nm), making them unsuitable or undesirable for use in backlights when fingerprint detection is desired. According to some embodiments, the optical film or stack provides the desired optical diffusion of visible light without substantially scattering infrared light. The optical film or stack can be used in one or more of various positions within the backlight. For example, the backlight may include a reflective polarizer for light recycling. In some embodiments, an optical film or stack comprising a reflective polarizer and an optical diffuser layer disposed on at least one side of the reflective polarizer can be used as a reflective polarizer in a backlight. Alternatively, or in addition, an optical film or stack comprising at least one optical diffuser layer can be disposed, for example, between a reflective polarizer and a light guide plate of a backlight. Alternatively, or in addition, an optical film comprising an optical mirror and an optical diffuser layer facing an LCD panel can be used as a back reflector of a backlight. Alternatively, or in addition, an optical film comprising an absorbing polarizer and an optical diffuser layer facing a backlight can be used, for example, as an absorbing polarizer of an LCD panel.

[0026] Figure 1A is a schematic cross-sectional view of an optical film 100 including an optical diffusion layer 10 according to some embodiments. Figure 1B to Figure 1C is a scanning electron microscope (SEM) image of an exemplary optical diffuser layer. Figures 2 to 32 are schematic cross-sectional views of exemplary optical stacks 200 and 200', each including a first optical diffuse layer 10 and a second optical diffuse layer 10' or 10", according to some embodiments. The optical properties of the optical film 100 and / or the optical stack 200 or 200' and / or the optical diffuse layer 10, 10', or 10" can be described in terms of average specular transmission, diffuse transmission, and / or total transmission of light 70 at substantially normal incidence (e.g., nominal normal incidence or within 30 degrees, or within 20 degrees, or within 10 degrees of a normal to the xy plane (z direction) when the optical film extends in the xy plane and has a thickness in the z direction) over one or more wavelength ranges. The optical diffuse layers 10' and 10" can generally be as described for the optical diffuse layer 10, and can have similar or different transmission characteristics. The light 70 can be incident on the optical diffuse layer 10 (light propagating in the -z direction), for example, as Figure 1A As schematically shown, alternatively, light 70 may be incident on substrate 110 (light propagating in the +z direction), for example as Figure 8 Schematically shown, alternatively light 70 may be incident on the optical diffuser layer 10'. Similarly, the incident light depicted in the other figures may be incident from either side of the depicted optical element.

[0027] exist Figure 1A In the illustrated embodiment, the optical film 100 includes a substrate 110 disposed on the optical diffuser layer 10. The substrate 110 can be or include, for example, one or more of a polymer layer, a reflective polarizer, an absorbing polarizer, or an optical mirror. Figure 2 In the illustrated embodiment, the optical stack 200 includes a layer or film 60 combined with a first optically diffuse layer 10 and a second optically diffuse layer 10'. Figure 3 In the illustrated embodiment, the optical diffuser layer 10 is disposed on a layer or film 60, and an air gap 190 separates the optical diffuser layer 10" from the layer or film 60. The optical diffuser layer 10" can be disposed on a substrate 110. The layer or film 60 can be or include, for example, one or more of a polymer layer, a reflective polarizer, an absorptive polarizer, or an optical mirror. In some embodiments of the optical stack 200', the layer or film 60 is a reflective polarizer and the substrate 110 is a polymer layer.

[0028] In some embodiments, the optical stack 200, 200' includes a reflective polarizer 60 disposed between a first optical diffuse layer (10) and a second optical diffuse layer (10', 10"), wherein each of the first optical diffuse layer and the second optical diffuse layer includes a plurality of non-uniformly dispersed particles 20 defining a plurality of voids 50 therein. In some embodiments, as Figure 2As schematically shown in FIG. 1 , each of the first optical diffuser layer 10 and the second optical diffuser layer 10′ is bonded to the reflective polarizer 60 via adhesive layers 180 and 181, respectively. In some embodiments, each of the first optical diffuser layer 10 and the second optical diffuser layer 10′ is directly coated on the reflective polarizer 60 without adhesive layers 180 and 181. In some embodiments, as Figure 3 As schematically shown in FIG. 1 , one of the first and second optical diffuser layers (e.g., 10 ) is directly coated on the reflective polarizer 60, and an air gap 190 is defined between the reflective polarizer 60 and the other of the first and second optical diffuser layers (e.g., 10 ”).

[0029] In some embodiments, substrate 110 comprises one or more of polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyolefin, polyethylene, polyethylene naphthalate, cellulose acetate, polystyrene, and polyimide. In some embodiments, substrate 110 comprises alternating first and second layers. For example, the first layer can be or include one of these materials, and the second layer can be or include a different one of these materials. In some embodiments, the alternating layers can be, for example, a reflective polarizer or an optical mirror. In some embodiments, substrate 110 comprises an absorbing polarizer.

[0030] In some embodiments, the average thickness T1 of the optical diffuser layer 10, 10' and / or 10" is between about 0.1 microns and about 20 microns, or between about 1 micron and about 20 microns, or between about 1.5 microns and about 10 microns, or between about 2 microns and about 8 microns.

[0031] In some embodiments, the average thickness T2 of substrate 110 is between about 20 microns and 500 microns, or between about 20 microns and 300 microns, or between about 20 microns and 200 microns, or between about 20 microns and 100 microns.

[0032] The optical diffuser layer 10 has opposite first and second major surfaces 11, 12, and includes a plurality of particles 20 dispersed between and across the first and second major surfaces 11, 12. The optical diffuser layer 10 includes a polymer material 30 that bonds the particles to each other to form a plurality of particle aggregates 40 defining a plurality of voids 50 therebetween. The optical diffuser layer 10' and / or 10" may be similarly described. In some embodiments, the plurality of particles 20 are a plurality of nanoparticles, and the plurality of particle aggregates 40 are a plurality of nanoparticle aggregates. In some embodiments, the particles 20 are or include silicon dioxide. For example, the particles 20 may be silicon dioxide nanoparticles.

[0033] In some embodiments, in the plane of the cross section of the optical diffuser layer in the thickness direction (z direction) of the optical diffuser layer (e.g., the xz-plane of the xyz coordinate system of FIG. 1 ): the average particle size of the nanoparticles 20 is between about 10 nm and 150 nm or between about 20 nm and about 150 nm; the average particle size of the nanoparticle aggregates 40 is between about 100 nm and about 1000 nm; and the voids 50 occupy about 5% to about 50% of the area of ​​the plane of the cross section. In other embodiments, the aggregates 40 may be larger than 1000 nm. In some embodiments, in the plane of the cross section of the optical diffuser layer in the thickness direction of the optical diffuser layer, the voids occupy about 5%, or about 10%, or about 15% to about 50%, or about 45%, or about 40% of the area of ​​the plane of the cross section. For example, in some embodiments, in the plane of the cross section of the optical diffuser layer in the thickness direction of the optical diffuser layer, the voids occupy about 15% to about 45% of the area of ​​the plane of the cross section.

[0034] In some embodiments, for at least one of the first optical diffuser layer (10) and the second optical diffuser layer (10' or 10"), the particles in the plurality of non-uniformly dispersed particles 20 form a plurality of particle aggregates 40 defining a plurality of voids 50 therebetween, such that a plane of a cross section of the optical diffuser layer in the thickness direction (z direction) of the optical diffuser layer (e.g., reference Figures 2 to 3In some embodiments, for at least one of the first optical diffuser layer (10) and the second optical diffuser layer (10' or 10"), the particles of the plurality of non-uniformly dispersed particles form a plurality of particle aggregates 40 defining a plurality of voids 50 therebetween, such that in the plane of the cross section of the optical diffuser layer in the thickness direction (z-axis) of the optical diffuser layer: the average particle size of the particle aggregates is between about 5 microns and about 10 microns; and the voids 50 occupy about 5% to about 50% of the area of ​​the plane of the cross section. In some embodiments, the voids 50 occupy about 15% to about 45% (or any range described elsewhere) of the area of ​​the cross section.

[0035] The percentage of the cross-sectional area occupied by the voids 50 can be determined using image analysis techniques. For example, the optical diffusion layer can be cut by a microtome, and then a scanning electron microscope (SEM) image of the cross section can be taken, and then image analysis software (e.g., as described in the embodiments) is used to analyze it to determine the percentage of area occupied by the voids. The average particle size of the aggregates can also be determined by analysis of the image. The particle size of the aggregates in the cross section can be the equivalent circular diameter of the aggregates (i.e., the diameter of a circle having the same area as the aggregates in the cross section).

[0036] FIG. 4A to FIG. 4B1 is a schematic cross-sectional view of a film or layer 150, 150', which shows that light 70a and 70b are substantially normally incident on the film or layer 150, 150'. The film or layer may correspond to any of the optical films or optical diffuser layers described herein. The wavelength of light 70a is in the range of λ1 to λ2, and the wavelength of light 70b is in the range of λ3 to λ4. In some embodiments, the range of λ1 to λ2 is the visible range, and the range of λ3 to λ4 is the infrared range. For example, in some embodiments, λ1 is about 450nm, λ2 is about 650nm, λ3 is about 930nm, and λ4 is about 970nm. For light 70a within the wavelength range λ1 to λ2, the film or layer 150, 150' has an average specular transmittance Vs, an average diffuse transmittance Vd, and an average total transmittance Vt (Vt=Vs+Vd). For light 70b within the wavelength range λ3 to λ4, the film or layer 150, 150' has an average specular transmittance Is, an average diffuse transmittance Id, and an average total transmittance It (It = Is + Id). For the film or layer 150, 150', the quantities Vs, Vd, Vt, Is, Id may be the same or different. For example, in some embodiments, the film or layer 150 corresponds to one of the optical diffuse layers in the optical stack 200 or 200', and the film or layer 150' corresponds to the other of the optical diffuse layers. For example, the ratio Is / Vs may be higher for one of the optical diffuse layers than for the other of the optical diffuse layers, and / or the ratio It / Vt may be higher for one of the optical diffuse layers than for the other of the optical diffuse layers.

[0037] In some embodiments, for substantially normally incident light 70, 70a, 70b and a visible wavelength range of about 450 nm to about 650 nm and an infrared wavelength range of about 930 nm to about 970 nm: in the visible wavelength range, the optical film 100 (optical diffuser layer 10, 10', 10") has an average specular transmittance Vs; and in the infrared wavelength range, the optical film 100 (optical diffuser layer 10, 10', 10") has an average total transmittance It and an average specular transmittance Is. In some embodiments, Is / It ≥ 0.6 and Is / Vs ≥ 2.5. In some embodiments, Is / Vs ≥ 3. In some embodiments, It / Vt> 1, or It / Vt> 2, or It / Vt> 3. In some embodiments, Is / It ≥ 0.7.

[0038] In some embodiments, for substantially normal incident light 70, 70a, 7b and visible wavelength ranges of about 450 nm to about 650 nm and infrared wavelength ranges of about 930 nm to about 970 nm: within the visible wavelength range, each of the first optical diffusive layer (10) and the second optical diffusive layer (10' or 10") has an average total transmittance Vt and an average specular transmittance Vs; and within the infrared wavelength range, each of the first optical diffusive layer and the second optical diffusive layer has an average total transmittance It and an average specular transmittance Is. In some embodiments, Is / It ≥ 0.6 and Is / Vs ≥ 2.5. In some embodiments, for at least one of the first optical diffusive layer and the second optical diffusive layer, Is / Vs ≥ 3. In some embodiments, for one of the first optical diffusive layer and the second optical diffusive layer, Is / Vs < 4; and for the other of the first optical diffusive layer and the second optical diffusive layer, Is / Vs ≥ 4.5. In some embodiments, for one of the first optical diffusive layer and the second optical diffusive layer, 1 < It / Vt < 2.5; and for the other of the first optical diffusive layer and the second optical diffusive layer, 2.5 < It / Vt < 4. In some embodiments, for one of the first optical diffusive layer and the second optical diffusive layer, 1 < It / Vt < 2.5; and for the other of the first optical diffusive layer and the second optical diffusive layer, 2.5 < It / Vt < 4.

[0039] If the polarization state of the incident light is not specified, the incident light can be assumed to be unpolarized unless the context clearly indicates otherwise.

[0040] High diffusive transmittance (e.g., high Vd) corresponds to high optical haze. In some embodiments, the optical film or stack or optical diffusive layer has an optical haze of at least about 20%, or at least about 30%, or at least about 40%, or at least about 50%. Optical haze is the ratio of diffusive transmittance to total transmittance and can be determined, for example, according to the ASTM D1003-13 test standard.

[0041] In some embodiments, the optical diffuser layer 10, 10', 10' is formed by coating a mixture of particles, monomers and solvents, and then curing and drying the mixture. The monomer is cured into a polymer binder (polymer material 30) that binds the aggregates of the particles together, and the solvent evaporates, thereby forming gaps between the aggregates. The solvent can be at least partially evaporated during curing and / or a subsequent drying step can be used to complete the evaporation of the solvent. In some embodiments, curing and drying include a pre-curing step, followed by a drying step, and then a post-curing step. In some embodiments, the monomer is ultraviolet (UV) curable and includes a photoinitiator in the mixture. The size of the aggregate can be adjusted by changing the UV power used to cure the monomer with a higher power, usually resulting in a smaller aggregate size. It has been found that a relatively low amount of photoinitiator with a relatively high UV power produces a smaller aggregate size and a non-fragmented layer, while a higher amount of photoinitiator can produce a more brittle layer. The void ratio can be adjusted by changing the amount of solvent used in the mixture, wherein a higher solvent load usually results in a higher void ratio. In some embodiments, the mixture includes from about 20 to about 60 weight percent solids.

[0042] In some embodiments, polymer material 30 is or includes a radiation-cured (eg, UV-cured) polymer. In some embodiments, polymer material 30 is or includes an acrylate. In some embodiments, polymer material 30 is or includes pentaerythritol triacrylate.

[0043] Figure 5 is a schematic cross-sectional view of an optical film or stack 100a bent around a cylinder 136 having a diameter D. In some embodiments, the optical film or optical stack can be as Figure 5 100a, with no or minimal damage to the optical diffuser layer of the optical film or to the optical diffuser layer of the optical stack. In some embodiments, bending the optical film 100a at a first bend location 101 on an inner diameter D of at most 10 mm results in no or minimal damage to the optical diffuser layer 10 at the first bend location 101. Minimal damage refers to damage that is not easily visible when the diffuser layer 10 is viewed with the naked eye of a person with 20 / 20 vision.

[0044] In some embodiments, the particles or nanoparticles 20 are substantially spherical. In some embodiments, in the plane of a cross section of the optical diffuser layer 10, 10', 10" in the thickness direction of the optical diffuser layer, the particles or nanoparticles 20 are substantially circular. A particle's cross section can be considered substantially circular (respectively substantially spherical) if its contour fits within the intermediate space between two concentric true circular (respectively spherical) contours, the diameters of which differ by up to about 30% of the diameter of the larger of these contours. In some embodiments, each of at least a majority of the particles is within the intermediate space between two concentric true circular contours, the diameters of which differ by up to about 20% or 10% of the diameter of the larger of these contours. In some embodiments, each of at least a majority of the particles in the cross section is within the intermediate space between two concentric true circular contours, the diameters of which differ by up to about 20% or 10% of the diameter of the larger of these contours.

[0045] The particles may have a unimodal, bimodal or multimodal particle size distribution. Figure 6 to Figure 7 is a schematic particle size distribution graph according to some embodiments. Figure 6 In the embodiment of the present invention, the particle size distribution 115 has a peak 117 at the particle size d. The particles have an average particle size Davg. Depending on the shape of the particle size distribution, the average particle size can be less than, greater than, or approximately equal to the particle size d. In some embodiments, the plurality of nanoparticles 20 have a nanoparticle size distribution 115 that includes a peak 117 at a nanoparticle size d of about 20 nm to about 150 nm or about 20 nm to about 100 nm.

[0046] exist Figure 7 , the particle size distribution 215 has a first peak 217 at a particle size d1 and a second peak 219 at a particle size d2. In some embodiments, the plurality of nanoparticles 20 has a nanoparticle size distribution 215 including a first peak 217 at a first nanoparticle size d1 of about 5 nm to about 40 nm and a second peak 219 at a second nanoparticle size d2 of about 50 nm to about 100 nm. The average particle size Davg of the particles may be between d1 and d2.

[0047] The average particle size Davg of distribution 115 or 215 can be an average or median particle size. For example, the average particle size Davg can be a Dv50 particle size (the median particle size in a volume distribution or equivalently, the particle size where 50% of the total volume of the particles is provided by particles having a particle size not exceeding the Dv50 particle size). In some embodiments, the average particle size of the nanoparticles 20 is in the range of about 20 nm to about 150 nm, or about 30 nm to about 120 nm, or about 30 nm to about 100 nm, or about 50 nm to about 90 nm, or about 60 nm to about 90 nm.

[0048] In some embodiments, the optically diffuse layer 10 , 10 ′, and / or 10 ″ is disposed on a structured layer. The structured layer may include structures having an average largest lateral dimension that is substantially larger than the particles 20 or substantially larger than the particle aggregates 40 .

[0049] Figure 8 1 is a schematic cross-sectional view of an optical film 100' according to some embodiments. The optical film 100' includes a structured layer 120 disposed between a substrate 110 and an optical diffuser layer 10a (e.g., corresponding to optical diffuser layer 10, 10', or 10") . The structured layer has a structured first major surface 121 facing the optical diffuser layer 10a and an opposite second major surface 122 facing the substrate 110. The first major surface 11a and the second major surface 12a of the optical diffuser layer 10a are substantially conformal to the structured first major surface 121 of the structured layer 120. In some embodiments, the structured layer 120 includes dispersed A plurality of particles 123 in a binder 124, wherein the particles 123 form a structured first major surface 121 of a structured layer 120. In other embodiments, for example, the structured layer 120 is formed by other means, such as embossing or micro-replication. In some embodiments, for example, the average particle size of the particles 123 can be at least about 2 times, 3 times, 5 times, or 10 times the average particle size of the particle aggregates 40. For example, the optical film 100' can have the specular transmission characteristics, diffuse transmission characteristics, and total transmission characteristics described for the optical film 100.

[0050] In some embodiments, substrate 110 or layer or film 60 is or includes a multilayer optical film. As is known in the art, multilayer optical films including alternating polymer layers can be used to provide desired reflection and transmission over a desired wavelength range by appropriately selecting layer thicknesses. Multilayer optical films and methods of making multilayer optical films are described, for example, in U.S. Pat. Nos. 5,882,774 (Jonza et al.); 6,179,948 (Merrill et al.); 6,783,349 (Neavin et al.); 6,967,778 (Wheatley et al.); 9,162,406 (Neavin et al.).

[0051] Fig. 9A9 is a schematic cross-sectional view of a substrate, layer or film 110a of a plurality of alternating first polymer layers 111 and second polymer layers 112. The number of layers may be substantially greater than the number shown in the schematic diagram of FIG9. In some embodiments, the plurality of alternating first polymer layers 111 and second polymer layers 112 total at least 20 (e.g., 20 to 1000 layers, or 30 to 500 layers, or 40 to 400 layers). In some embodiments, the average thickness of each of the first polymer layer 111 and the second polymer layer 112 is less than about 350 nm.

[0052] The substrate, layer or film 110a may include layers in addition to the first polymer layer 111 and the second polymer layer 112. For example, the substrate layer or film 110a may include a protective boundary layer on each side of the package of polymer layers 111, 112 to protect the polymer layers 111 and 112 during processing, as is known in the art.

[0053] In some embodiments, such as Fig. 9B Schematically shown, substrate, layer or film 110b includes a single package 49 of polymer layers 111, 112 between opposing first and second outer layers 46, 47. In some embodiments, first and second outer layers 46, 47 each have an average thickness ta, tb greater than about 500 nm.

[0054] In some embodiments, such as Fig. 9C Schematically shown, substrate, layer or film 110c includes two packages of polymer layers 111, 112, so that multiple polymer layers include multiple first polymer layers 41 spaced apart from multiple second polymer layers 42 along the thickness direction of substrate, layer or film 110c by one or more intermediate layers 43a, 43b. In some embodiments, each of multiple first polymer layers 41 and second polymer layers 42 totals at least 200, and is disposed between opposite first outer layer 46 and second outer layer 47 and coextruded and costretched with the first outer layer and second outer layer. For example, one or more intermediate layers 43a, 43b can be two protective boundary layers, or a single layer formed by two protective boundary layers. In some embodiments, each of the first polymer layer and the second polymer layer has an average thickness of less than about 350nm or less than about 300nm, and each of one or more intermediate layers 43a, 43b has an average thickness tc greater than about 500nm.

[0055] In some embodiments, one or both of the outer layers 46, 47 include a plurality of particles to provide a structured major surface facing away from the polymer layers 111, 112, as generally described in co-pending U.S. provisional application 63 / 021,765, filed on May 8, 2020, entitled “REFLECTIVE POLARIZER WITH IMPROVED OPTICAL CHARACTERISTICS” and incorporated herein by reference to the extent not inconsistent with this specification.

[0056] The average thicknesses ta, tb, tc may each be greater than about 500 nm, or greater than about 1 micron, or greater than about 3 microns, or greater than about 5 microns.

[0057] For example, substrate, layer or film 110a, 110b or 110c may be a reflective polarizer or optical mirror.Substantially normally incident light 70 and light 170 incident at an angle of incidence θ are schematically illustrated in FIG. 9 .

[0058] The substrate, layer or film 110a, 110b or 110c may have different transmission and reflection characteristics of light 70 and 170. A first polarization state 171 (polarized in the xz plane) and a second polarization state 172 (polarized along the y axis) are schematically shown. In some embodiments, the substrate, layer or film 110a, 110b or 110c is a reflective polarizer, and the first polarization state 171 is a pass polarization state, and the second polarization state 172 is a blocking polarization state. Portions of the incident light 70 and 170 are transmitted as light 270 and 370, respectively. When it is a pass state for a reflective polarizer, light 270 and 370 are typically polarized primarily in the first polarization state. In some embodiments, the reflective polarizer is a collimating reflective polarizer. Collimating reflective polarizers are known in the art and are described, for example, in U.S. Pat. Nos. 9,441,809 (Nevitt et al.) and 9,551,818 (Weber et al.). In some embodiments, for the first polarization state 171 and the visible wavelength range (e.g., 450nm to 650nm), the reflective polarizer has a greater average optical transmittance (e.g., light 270) for light incident at a smaller angle of incidence (e.g., light 70) and a smaller average optical transmittance (e.g., light 370) for light incident at a larger angle of incidence (e.g., θ) (e.g., light 170). In some embodiments, the first polarization state is a p-polarization state (polarized in the plane of incidence), and the larger angle of incidence is less than about 50 degrees, or less than about 40 degrees.

[0059] Other suitable reflective polarizers are described in co-pending U.S. Provisional Application No. 63 / 021,743, entitled “OPTICAL FILM,” and co-pending U.S. Provisional Application No. 62 / 704,400, entitled “OPTICAL FILM,” both filed on May 8, 2020 and incorporated herein by reference to the extent not inconsistent with this specification.

[0060] In some embodiments, substrate 110 (or 60 or 110a, 110b or 110c) is or includes a reflective polarizer such that for substantially normally incident light 70 and a predetermined wavelength range (e.g., λ1 to λ2, or λ3 to λ4), the reflective polarizer has an average optical transmittance of at least 40% for a first polarization state (e.g., polarization state 171 or polarization along the x-axis), and an average optical reflectance of at least 70% for an orthogonal second polarization state (e.g., polarization state 172 or polarization along the y-axis). In some embodiments, for substantially normally incident light 70 and a predetermined wavelength range (e.g., λ1 to λ2, or λ3 to λ4), the reflective polarizer has an average optical transmittance of at least 50% or at least 60% for the first polarization state, and an average optical reflectance of at least 70% or at least 80% for the second polarization state. In some embodiments, substrate 110 (or 60 or 110a, 110b, or 110c) is or includes a reflective polarizer such that for substantially normally incident light 70 and a visible wavelength range of about 450 nm to about 650 nm and an infrared wavelength range of about 930 nm to about 970 nm: the reflective polarizer transmits at least 40% of incident light in a first polarization state for each wavelength in the visible wavelength range, reflects at least 70% of incident light in an orthogonal second polarization state for each wavelength in the visible wavelength range, and transmits at least 40% of incident light in each of the first polarization state and the second polarization state for each wavelength in the infrared wavelength range. In some embodiments, for substantially normally incident light 70: the reflective polarizer transmits at least 50% or at least 60% of incident light in a first polarization state for each wavelength in the visible wavelength range, reflects at least 70% or at least 80% of incident light in a second polarization state for each wavelength in the visible wavelength range, and transmits at least 50% or at least 60% of incident light in each of the first polarization state and the second polarization state for each wavelength in the infrared wavelength range.

[0061] FIG. 10A to FIG. 10B are respectively according to some embodiments for the first polarization state ( Fig. 10A The transmittance in 133) and for the orthogonal second polarization state ( Fig. 10B134 in ) is a schematic graph of the transmittance of the reflective polarizer versus wavelength for substantially normally incident light 70. The transmittance 135 of the reflective polarizer versus wavelength for light 170 incident at an angle of incidence θ is also schematically shown. In some embodiments, for a first polarization state and a predetermined wavelength range, the reflective polarizer has a greater average optical transmittance (e.g., transmittance 133) for light incident at a smaller angle of incidence, and a smaller average optical transmittance (e.g., transmittance 135) for light incident at a larger angle of incidence. For example, the smaller angle of incidence can be in the range of zero degrees to about 20 degrees, or can be about zero degrees. For example, the larger angle of incidence can be in the range of about 30 degrees to about 50 degrees, or can be about 45 degrees. In some embodiments, for a predetermined wavelength range, for any plane of incidence first (pass) polarization state, the reflective polarizer has a greater average optical transmittance for substantially normally incident light, and a smaller average optical transmittance for light incident at an angle of incidence of about 45 degrees. In some embodiments, the difference between the greater average optical transmittance and the lesser average optical transmittance is at least 10%, or at least 20%, or at least 30%.

[0062] In some embodiments, the transmission of substantially normally incident light of the second polarization state is higher for smaller wavelengths within the predetermined wavelength range and lower for larger second wavelengths within the predetermined wavelength range.Such a sloped blocking state transmittance can provide a color shift that decreases with viewing angle.

[0063] The average transmittance (reflectance, absorptance, respectively) is the average of the transmittance (reflectance, absorptance, respectively) over a predetermined wavelength range. For a reflective polarizer with negligible absorptance, the reflectance R is approximately 100% minus the transmittance. For substantially normally incident light 70 over the wavelength range λ1 to λ2, the average transmittance Tp of the first (pass) polarization state and the average transmittance Tbl of the second (block) polarization state are approximately FIG. 10A to FIG. 10B For substantially normally incident light 70 within the wavelength range of λ1 to λ2, the indicated value of R is approximately the average optical reflectance.

[0064] Transmittance 133 is the pass state transmittance of the reflective polarizer, and transmittance 134 is the block state transmittance of the reflective polarizer. Alternatively, transmittance 134 can schematically represent the transmittance of the optical mirror in each of two orthogonal polarization states. In some embodiments, substrate 110 (or 60 or 110a, 110b or 110c) is or includes an optical mirror such that for substantially normally incident light 70 and a predetermined wavelength range, the optical mirror has an average optical reflectivity (average value of R within the predetermined wavelength range) of at least 60% or at least 70% or at least 80% for each of a mutually orthogonal first polarization state (e.g., polarized along the x-axis) and a second polarization state (e.g., polarized along the y-axis).

[0065] Fig.11 is a schematic graph of transmittance versus wavelength for an absorptive polarizer for substantially normally incident light 70 for a first polarization state (transmittance 233) and for an orthogonal second polarization state (transmittance 234) according to some embodiments. For an absorptive polarizer with negligible reflectance, the absorptivity A is approximately 100% minus the transmittance. For substantially normally incident light 70 in the wavelength range of λ1 to λ2, the average transmittance Tp of the first (pass) polarization state and the average transmittance Tbl of the second (block) polarization state are approximately 100%. Fig.11 For substantially normally incident light 70 within the wavelength range of λ1 to λ2, the indicated value of A is approximately the average optical absorbance.

[0066] In some embodiments, substrate 110 (or 60 or 110a, 110b or 110c) is or includes an absorbing polarizer such that for substantially normally incident light 70 and a predetermined wavelength range, the absorbing polarizer has an average optical transmittance of at least 40% for a first polarization state (e.g., 171) and an average optical absorptance of at least 60% for an orthogonal second polarization state (e.g., 172). In some embodiments, for substantially normally incident light 70 and a predetermined wavelength range, the absorbing polarizer has an average optical transmittance of at least 50% or at least 60% for the first polarization state and an average optical absorptance of at least 70% or at least 80% for the second polarization state. Absorption and transmittance can be adjusted by appropriate selection of dye concentration.

[0067] For example, the predetermined wavelength range for determining the average reflectance, transmittance, and / or absorbance may be, for example, about 450 nm to about 650 nm or about 930 nm to about 970 nm.

[0068] Fig.1270 is a graph of transmission and wavelength of substantially normal incident light 70 of an optical film according to some embodiments. In the illustrated embodiment, the optical film (e.g., corresponding to 100 or 100') includes an optical diffusion layer disposed on a reflective polarizer, and the light 70 is unpolarized. In some embodiments, for substantially normal incident light 70, the optical film has average diffuse optical transmittances Tb, Tg, and Tr in the corresponding wavelength ranges of about 450nm to about 485nm (wavelength range 80), about 500nm to about 565nm (wavelength range 81), and about 625nm to about 680nm (wavelength range 82), wherein Tb>Tg>Tr. In some embodiments, Tb, Tg, and Tr are less than about 30%, or less than about 25%, or less than about 20%. In some embodiments, Tb-Tg and Tg-Tr are each greater than about 1% or greater than about 2%. In some embodiments, Tr-Tg is greater than about 3% or greater than about 5%. In some embodiments, for substantially normal incident light 70, the total transmittance of the optical film is between about 800nm ​​and 1100nm with a first platform region 83 and a second platform region 84 spaced apart, wherein the width of each platform region is at least 20nm. The first platform region 83 and the second platform region 84 have corresponding average total transmittances P1 and P2. In some embodiments, P2 is greater than about 20%, or greater than 25%, or greater than 30%, or greater than 35% greater than P1. In some embodiments, the first platform region 83 is set between 800nm ​​and the second platform region 84. In some embodiments, the first platform region 83 includes 860nm and the second platform region 84 includes 950nm.

[0069] for Fig.12 The optical film has an average total transmittance Vt of about 25.27%, an average diffuse transmittance Vd of about 10.75%, and an average specular transmittance Vs of about 14.52% for substantially normally incident non-polarized light 70a and a visible wavelength range of about 450 nm to about 650 nm. Fig.12 The optical film, for substantially normally incident non-polarized light 70b and an infrared wavelength range of about 930 nm to about 970 nm, has an average total transmittance It of about 86.66%, an average diffuse transmittance Id of about 13.89%, and an average specular transmittance Is of about 75.77%.

[0070] Fig.13It is a graph of the transmission and wavelength of substantially normal incident light 70 of an optical film according to some embodiments. In the illustrated embodiment, the optical film includes an optical diffusion layer without a reflective polarizer or mirror film. In some embodiments, for substantially normal incident light 70, which may be non-polarized, the optical film has average diffuse optical transmittances Tb, Tg, and Tr in the corresponding wavelength ranges of about 450nm to about 485nm (wavelength range 80), about 500nm to about 565nm (wavelength range 81), and about 625nm to about 680nm (wavelength range 82), wherein Tb>Tg>Tr. In some embodiments, Tb is less than about 80% or less than about 70%. In some embodiments, Tb is greater than about 40% or greater than about 50%. In some embodiments, Tr is greater than about 35% or greater than about 40%. In some embodiments, Tr is less than about 65% or less than about 60%. In some embodiments, Tb-Tg and Tg-Tr are each greater than about 1% or greater than about 2%. In some embodiments, Tr-Tg is greater than about 5% or greater than about 10%. In some embodiments, the optical film has a diffuse optical transmittance that generally decreases (e.g., monotonically decreases or does not increase) in a wavelength range of about 450nm to about 970nm and a specular optical transmittance that generally increases (e.g., monotonically increases or does not decrease) in a wavelength range of about 450nm to about 970nm. In some such embodiments, the total optical transmittance generally increases in a wavelength range of about 450nm to about 970nm.

[0071] for Fig.13 The optical film has an average total transmittance Vt of about 76.06%, an average diffuse transmittance Vd of about 57.43%, and an average specular transmittance Vs of about 18.63% for substantially normally incident non-polarized light 40a and a visible wavelength range of about 450 nm to about 650 nm. Fig.13 The optical film, for substantially normally incident non-polarized light 40b and an infrared wavelength range of about 930 nm to about 970 nm, has an average total transmittance It of about 86.94%, an average diffuse transmittance Id of about 25.69%, and an average specular transmittance Is of about 61.25%.

[0072] Fig.14A is a graph of optical transmittance 130 versus wavelength for substantially normally incident light 70 of an optical film according to some embodiments. In the illustrated embodiment, the optical film is a reflective polarizer, and the substantially normally incident light 70 is in a blocking state of the reflective polarizer. FIG. 14B to FIG. 14C yes Fig.14A13. In some embodiments, the optical transmittance 130 of the reflective polarizer versus the wavelength of the second (blocking) polarization state includes the band edge 131, wherein the best linear fit 132 of the optical transmittance 130 versus the wavelength of the band edge 131 has a slope 137 greater than about 2.5% / nm at least in the wavelength range where the optical transmittance along the band edge increases from about 10% to at least about 70%. In some embodiments, for a first wavelength range R1 extending from a smaller wavelength L1 to a larger wavelength L2, where 30 nm ≤ L2 - L1 ≤ 50 nm and L1 is greater than a wavelength 139 and within about 20 nm of the wavelength 139, which corresponds to an optical transmittance of about 50% along the band edge, the average value of the optical transmittance is greater than about 75%, or greater than about 80%, or greater than about 85%. For example, the wavelength range R1 can include at least one of about 850 nm or about 940 nm. In some embodiments, the slope 137 is greater than about 3% / nm, or greater than about 3.5% / nm, or greater than about 4% / nm. Optical films with sharp band edges are known in the art and are described, for example, in U.S. Pat. No. 6,967,778 (Wheatley et al.). In some embodiments, the reflective polarizer is a collimating reflective polarizer with a layer profile with an apodized toe, as generally described, for example, in U.S. Pat. No. 9,551,818 (Weber et al.). In some embodiments, the layer profile includes a first portion with a substantially increasing layer thickness profile having a first slope and a second portion (e.g., an apodized toe portion) adjacent to the first portion and having a substantially decreasing layer thickness profile with a second slope, the magnitude of the second slope being substantially higher than the first slope. Related reflective polarizers are described in a co-pending application entitled "OPTICAL FILM" filed on the same day as the present application (Agent Docket No. 83108US002). An optically diffusive layer or layers may be disposed on the reflective polarizer, as further described elsewhere herein.

[0073] Fig.15A77 is a schematic bottom plan view of a major surface 777 of a layer 776. Layer 776 may correspond to an outer layer of an optical film or stack described elsewhere herein, or may be an additional layer applied to a major surface of an optical film or stack. In some embodiments, major surface 777 may correspond to, for example, a major surface of substrate 110 opposite to optical film 100 or optical stack 200', or a major surface of optical diffuser layer 10' opposite to layer or film 60 in optical stack 200, or a major surface of layer or film 60 opposite to optical diffuser layer 10 in optical stack 200', or a major surface of an optical layer disposed on any of these major surfaces. Major surface 777 includes a plurality of bumps or structures 779. In some embodiments, structured layer 776 includes a plurality of particles (e.g., corresponding to particles 123, but on the opposite side of substrate 110) dispersed in a binder (e.g., corresponding to binder 124), wherein the particles form a structured major surface 777 of structured layer 776. In some embodiments, the optical film includes an optically diffuse layer and a substrate disposed on the optically diffuse layer, wherein the substrate has a structured major surface 777 opposite the optically diffuse layer.

[0074] In some embodiments, the optical film or stack of the present specification includes an array of discrete spaced optical bumps 779 formed on the main surface 777 of the optical film or stack. For each of the first polarization state and the second polarization state, the optical bump may have an average optical transmittance greater than about 50% for each of the visible wavelength range (e.g., λ1 to λ2) and the infrared wavelength range (e.g., λ3 to λ4). The bumps may impart surface roughness, which reduces the coefficient of friction and eliminates or reduces damage to adjacent films. In some embodiments, optical bumps may be added to the substrate using techniques such as flexographic printing (or similar printing processes) or via micro-replication (e.g., casting and curing). The relevant optical bumps are described in U.S. Provisional Co-Pending Application 63 / 021773, filed on May 8, 2020, entitled "Optical Film with Discontinuous Coating (OPTICAL FILM WITH DISCONTINUOUSCOATING)" and incorporated herein by reference to the extent not inconsistent with this specification.

[0075] In some embodiments, for example, an optical film or stack of the present specification includes an optical layer 776 disposed on a major surface of the optical film or stack, wherein the optical layer includes a structured major surface 777 to prevent wetting with an adjacent film (in this context, wetting generally refers to the unintentional integration of two contacting surfaces, resulting in undesirable optical effects). Fig. 15Bis a schematic cross-sectional view of an optical film or stack 700 that includes an optical diffuser layer 210, a substrate 310 disposed on the optical diffuser layer 210, and an optical layer 776 disposed on the substrate 310 opposite the optical diffuser layer 210. The optical layer 776 is disposed on the major surface 313 of the substrate 310. The optical layer 776 includes a structured major surface 777 facing away from the substrate 310. The structured major surface 777 includes a plurality of spaced-apart elongated structures 779 extending along the same first direction (x-direction). The elongated structures can have a first average length along the first direction that is at least twice as long as a second average length along an orthogonal second direction (y-direction), wherein the first direction and the second direction are each orthogonal to the thickness direction (z-direction). The elongated structures 779 can be arranged in a substantially uniform density across the structured major surface (e.g., as Fig.15A ). The optical diffuser layer 210 may correspond to any of the optical diffuser layers described elsewhere herein. The substrate 310 may correspond to any of the substrates described elsewhere herein.

[0076] In some embodiments, the optical film 700 includes an optical diffuser layer 210 and a substrate 610 disposed on the optical diffuser layer 210. In the illustrated embodiment, the substrate 610 includes a substrate 310 and an optical layer 776. In some embodiments, the substrate 310 and the optical layer 776 are formed of the same material, so that there may be no discernible interface between the substrate 310 and the optical layer 776. In some embodiments, the substrate 610 is a unitary layer. The substrate 610 includes a structured major surface 777 facing away from the optical diffuser layer 210. The structured major surface 777 includes a plurality of spaced apart elongated structures extending along the same first direction.

[0077] In some embodiments, the optical layer 776 or substrate 610 can be formed by a process in which elongated structures are molded into a material that passes over a tool (e.g., a roller with cutouts or notches that act as a mold for the material). Related structured optical layers are described in U.S. Provisional Co-Pending Application No. 63 / 021,756, filed May 8, 2020, entitled "OPTICALLY DIFFUSIVE FILM WITH ELONGATED STRUCTURES" and which is hereby incorporated by reference to the extent not inconsistent with this specification.

[0078] Fig.16is a schematic exploded cross-sectional view of a display system 1000 for sensing a finger 61 of a user 160 applied to the display system 1000. The display system 1000 includes a display panel 770 configured to generate an image 71 for viewing by the user 160; a light guide 90 for providing illumination 88 to the display panel 770; an optical film or stack 400; a sensor 125 for sensing the finger 61 of the user 160, the sensor being disposed adjacent the light guide 90 opposite the optical film or stack 400; an optical film or stack 500 disposed between the light guide 90 and the sensor 125; and an infrared light source 220 configured to emit infrared light 221 (directly or indirectly) toward the finger 61 of the user 160, wherein the sensor 125 is configured to receive at least a portion 222 of the infrared light 221 reflected by the finger 61. The infrared light source 220 may be disposed at any suitable location in the display system. For example, infrared light source 220 can be disposed adjacent to any of the layers of the display system. In some embodiments, infrared light source 220 is disposed below a cover glass of display system 1000. In some embodiments, infrared light source 220 is disposed below optical film or stack 500 (e.g., infrared light source 220 can be disposed such that optical film or stack 500 is between light guide 90 and infrared light source 220).

[0079] The optical film or stack 400 is or includes a reflective polarizer and can correspond to any of the optical films or stacks including reflective polarizers described herein. In some embodiments, the optical film or stack 400 includes an optical diffuser layer 410 and a reflective polarizer 460. The optical diffuser layer 410 is disposed between the display panel 770 and the reflective polarizer 460. In some such embodiments, the optical film or stack 400 includes a second optical diffuser layer 10' or 10" (see Figures 2 to 3 ), such that the reflective polarizer is disposed between the optical diffuser layer 10 and the second optical diffuser layer 10' or 10". For example, the optical film or stack 400 may correspond to the optical film 100 or the optical stack 200 or the optical stack 200', wherein the optical film or stack is such as that formed by Figure 1A , Figure 2 , Figure 3 and Fig.16 In some embodiments, the reflective polarizer is a collimating reflective polarizer as further described elsewhere herein.

[0080] The optical film or stack 500 includes an optical mirror 560 and can correspond to any of the optical films or stacks including optical mirrors described herein. The optical film or stack 500 includes an optical layer 510 disposed on the optical mirror 560. In some embodiments, the optical layer 510 corresponds to an optical diffuser layer described elsewhere. For example, the optical film or stack 500 can correspond to the optical film 100, wherein the optical diffuser layer 10 faces the light guide 90 and the substrate 110 includes an optical mirror. In some embodiments, the optical layer 510 corresponds to an optical layer including optical bumps as described elsewhere herein.

[0081] As further described elsewhere herein, in some embodiments, the reflective polarizer of the optical film or stack 400 is a collimating reflective polarizer that has a greater average optical transmittance for visible pass state light (e.g., p-polarized pass state light) incident at a smaller angle of incidence, and a smaller average optical transmittance for light incident at a larger angle of incidence. Such a polarizer can provide a collimating effect by reflecting light having a larger angle of incidence back to the optical film or stack 500 to recycle the light. In some embodiments, when included in the optical film or stack 400, the optical diffuser layer 10' or 10" scatters at least a portion of the light reflected from the reflective polarizer so that when the light is incident on the reflective polarizer again after reflecting from the optical film or stack 500, at least a portion of the light has a lower angle of incidence. Liquid crystal displays (LCDs) typically include brightness enhancement prismatic films (typically crossed prismatic films) to increase the on-axis brightness of the display. In some cases, such films can be omitted when a collimating reflective polarizer is included. In some embodiments of the display system 1000, there is no brightness enhancement prismatic film disposed between the display panel 770 and the optical film or stack 500.

[0082] In some embodiments, light guide 90 includes a light guide plate 91 and at least one light source 92 configured to project light 93 into light guide plate 91. In some embodiments, light guide plate 91 extends in two orthogonal directions defining a plane (e.g., an xy plane) of light guide plate 91, and light (e.g., illumination 88) exiting light guide plate 91 generally propagates in a direction that makes an angle in the range of about 70 degrees or about 80 degrees to about 89 degrees with the plane of light guide plate 91. For example, the angle can be about 85 degrees.

[0083] For example, infrared light source 220 may have a peak emission wavelength of about 850 nm or about 940 nm. Optical components disposed between finger 61 and sensor 125 (e.g., optical film or stack 400, light guide plate 91, and optical film or stack 500) are preferably at least partially transmissive to the peak emission wavelength.

[0084] A related display system including an optical diffuser layer is described in U.S. provisional co-pending application 62 / 704,399, filed on May 8, 2020, entitled “OPTICAL CONSTRUCTION AND DISPLAY SYSTEM INCLUDING SAME,” and which is hereby incorporated by reference to the extent not inconsistent with this specification. Other related display systems are described in U.S. provisional co-pending application 63 / 021,760, filed on May 8, 2020, entitled “DISPLAY SYSTEM WITH FINGER SENSING,” which is hereby incorporated by reference to the extent not inconsistent with this specification, and U.S. provisional co-pending application 63 / 021,739, filed on May 8, 2020, entitled “OPTICAL CONSTRUCTION AND DISPLAY SYSTEM,” which is hereby incorporated by reference to the extent not inconsistent with this specification.

[0085] Example

[0086] Unless otherwise indicated, all parts, percentages, ratios, etc. in the examples, as well as the remainder of the specification, are by weight.

[0087] Material

[0088]

[0089]

[0090] Sample preparation 1

[0091] The coating precursor solution was prepared. 5.95 g of 3-methacryloxypropyl-trimethoxysilane (A-174, Momentive, Waterford, NY) and 0.5 g of 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (5 wt %; 4H-2,2,6,6-TMP 1-0, Sigma-Aldrich, Milwaukee, WI) were added to a mixture of 400 g of 75 nm diameter SiO2 sol (NALCO 2329, Nalco, Naperville, IL) and 450 g of 1-methoxy-2-propanol (Sigma-Aldrich, Milwaukee, WI) in a wide-mouthed glass bottle and stirred at room temperature for 10 minutes. The wide-mouthed bottle was sealed and placed in an oven at 80° C. for 16 hours. Water was then removed from the resulting solution using a rotary evaporator at 60° C. until the solid content of the solution was close to 45 wt %. 200 g of 1-methoxy-2-propanol was charged to the resulting solution, and then the remaining water was removed using a rotary evaporator at 60° C. The following steps were repeated again to further remove water from the solution. Finally, the total concentration of SiO2 nanoparticles was adjusted to 42.5% by weight by adding 1-methoxy-2-propanol to obtain a SiO2 sol containing surface-modified SiO2 nanoparticles with an average particle size of 75 nm.

[0092] Coating solution "A" was prepared. Coating solution "A" consisted of 27.98 wt% of the above clear precursor solution, 7.9 wt% of pentaerythritol triacrylate monomer (SR444, Sartomer, Exton, PA), 63.3 wt% of isopropyl alcohol, 0.8 wt% of IRGACURE 184 (BASF, Vandalia, IL), and 0.02 wt% of IRGACURE 819 (BASF, Vandalia, IL). Coating solution "A" was pumped to a slot-type coating die using a Viking CMD (Viking Pump, Cedar Falls, IA) pump at a rate that produced a 15 micron wet layer thickness on a primed polyester substrate.

[0093] Subsequently, the coating is polymerized by passing the coated substrate through a UV-LED curing chamber, which includes a quartz window that allows UV radiation to pass through. The UV-LED curing chamber includes a rectangular array of UV-LEDs. The LED (available from Nichia Inc., Tokyo Japan) operates at a nominal wavelength of 385nm, and when running at 10 amperes, a UV-A dose of 0.035 joules / square centimeter is obtained. The UV-LED operates at the current indicated in the table below. The water-cooled UV-LED array is powered by a Genesys 150-22 power supply (available from TDK-Lambda, Neptune NJ, Neptune NJ). The UV-LED is positioned above the quartz window of the curing chamber at a distance of approximately 2.5cm from the substrate. The UV-LED curing chamber is supplied with a nitrogen flow at a flow rate of 22 cubic feet / minute to keep the oxygen content below 50 parts ppm. A 3000 Series Oxygen Analyzer (available from Alpha Omega Instruments, Cumberland RI) was used to monitor oxygen levels in the UV-LED curing chamber.

[0094] After polymerization by UV-LED, the solvent in the cured coating is removed by transferring the coated substrate to a drying oven at 150°F (66°C) for 30 seconds. Next, the dried coating is post-cured using a Fusion System Model 1600 (available from Fusion UV Systems, Gaithersburg, MD.) equipped with an H bulb. The UV Fusion chamber is supplied with a nitrogen flow that results in an oxygen concentration of approximately 50 ppm in the chamber. This produces a porous coated polyester film. Examples 1-6 are prepared using Sample Preparation 1.

[0095] Sample preparation 2

[0096] Coating solution "B" was prepared. Coating solution "B" consisted of 42.22 wt% of the clear precursor solution described in Sample Preparation 1, 11.96 wt% of pentaerythritol triacrylate monomer (SR444, Sartomer), 45.50 wt% of isopropyl alcohol, 0.3 wt% of IRGACURE 184, and 0.01 wt% of IRGACURE 819. Using the same process previously described in Sample Preparation 1, coating solution "B" was pumped to a slot-type coating die using a Viking CMD (Viking Pump Company, Cedar Falls, Iowa) pump at a rate that produced a 20 micron wet layer thickness on a primed polyester substrate. Examples 7-14 were prepared using Sample Preparation 2.

[0097] Sample preparation 3

[0098] Coating Solution "B" from Sample Preparation 2 was pumped to a slot-type coating die using a Viking CMD (Viking Pump Co., Cedar Falls, Iowa) pump at a rate to produce a 7.75 micron wet layer thickness on a primed polyester substrate. The coating was processed as described in Sample Preparation 1. Examples 15-25 were prepared using Sample Preparation 3.

[0099] Sample preparation 4

[0100] Coating Solution "B" from Sample Preparation 2 was pumped to a slot-type coating die using a Viking CMD (Viking Pump Company, Cedar Falls, Iowa) pump at a rate to produce a 7 micron wet layer thickness on the primed collimated multilayer optical film substrate. The coating was processed as described in Sample Preparation 1. Examples 26-31 were prepared using Sample Preparation 4.

[0101] Sample preparation 5

[0102] Coating solution "C" was composed of 20.96 wt% of the clear precursor solution described in Sample Preparation 1, 5.94 wt% pentaerythritol triacrylate monomer (SR444, Sartomer), 71.55 wt% isopropyl alcohol, 1.48 wt% IRGACURE 184, and 0.07 wt% IRGACURE 819. Coating solution "C" was pumped to a slot-type coating die using a Viking CMD (Viking Pump Company, Cedar Falls, Iowa) pump at a rate to produce a 6 micron wet layer thickness on the primed collimated multilayer optical film substrate. The coatings were processed as described in Sample Preparation 1. Examples 32-36 were prepared using Sample Preparation 5.

[0103] Test methods and results

[0104] The total near infrared transmission and diffuse near infrared transmission of each example were measured using a spectrometer (ULTRASCAN PRO, Hunterlab, Reston, VA). The near infrared scattering ratio was calculated from these measurements by dividing the diffuse near infrared transmission by the total near infrared transmission. The results are provided in the following table.

[0105]

[0106]

[0107] Visible transmission (%T), haze (%H), and clarity (%C) of each example were measured using a haze meter (Haze-gard Plus, BYK-Gardner, Columbia, MD). The results are provided in the following table.

[0108]

[0109]

[0110] The cross-sectional images of various diffuser samples were obtained by cutting the diffuser film using a microtome. The SEM cross-sectional images were first converted to 8 bits using the ImageJ software of the National Institute of Health. The area of ​​interest was selected using ImageJ software. The threshold was adjusted using software until the image area below the threshold was roughly the same as the area below the image front plane. The software automatically calculated the area below the threshold. The ratio of the area below the threshold to the total image area was used as the void ratio. The results are provided in the following table.

[0111] Example Total area Area below threshold %area Minimum threshold Maximum Threshold 21 301644 106656 35.4 0 103 23 419739 148224 35.3 0 105 24 296172 90740 30.6 0 104 25 311606 83479 26.8 0 109

[0112] Terms such as "about" will be understood by one of ordinary skill in the art in the context of use and description in this specification. If it is not clear to one of ordinary skill in the art in the context of use and description in this specification that "about" should be used to express the amount of feature size, quantity, and physical properties, then "about" will be understood to mean within 10% of the specified value. A quantity given as about a specified value may be exactly the specified value. For example, if it is not clear to one of ordinary skill in the art in the context of use and description in this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and the value may be 1.

[0113] All references, patents, and patent applications cited above are hereby incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or conflicts between an incorporated reference portion and the present application, the information in the foregoing description shall prevail.

[0114] Unless otherwise indicated, the description of the elements in the drawings should be understood to be equally applicable to the corresponding elements in the other drawings. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that the specific embodiments shown and described may be replaced with a variety of alternative and / or equivalent implementations without departing from the scope of the present disclosure. The present application is intended to cover any modification or variation or combination of the specific embodiments discussed herein. Therefore, the present disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. An optical film, comprising an optical diffusion layer, wherein the optical diffusion layer comprises: first and second opposing major surfaces; a plurality of nanoparticles, the plurality of nanoparticles being dispersed between and spanning the first major surface and the second major surface, the nanoparticles comprising silicon dioxide; and a polymer material that bonds the nanoparticles to each other to form a plurality of nanoparticle aggregates defining a plurality of voids therebetween, such that in a plane of a cross section of the optical diffusion layer in a thickness direction of the optical diffusion layer: The average particle size of the nanoparticles is between 20 nm and 150 nm; The average particle size of the nanoparticle aggregates is between 100 nm and 1000 nm; and The voids occupy 5% to 50% of the area of ​​the plane of the cross section, Where for incident light within 30 degrees of the normal direction and a visible wavelength range of 450nm to 650nm and an infrared wavelength range of 930nm to 970nm: In the visible wavelength range, the optical film has an average specular transmittance Vs; and In the infrared wavelength range, the optical film has an average total transmittance It and an average specular transmittance Is, Is / It≥0.6, Is / Vs≥2.5; and Wherein bending the optical film at a first bending location over an inner diameter of at most 10 mm results in no damage or only minimal damage to the optical diffuser layer at the first bending location. 2 . The optical film of claim 1 , wherein the plurality of nanoparticles have a nanoparticle size distribution including a first peak at a first nanoparticle size of 5 nm to 40 nm and a second peak at a second nanoparticle size of 50 nm to 100 nm. 3 . The optical film according to claim 1 , wherein in the plane of the cross section of the optical diffusion layer in the thickness direction of the optical diffusion layer, the voids occupy 5% to 45% of the area of ​​the plane of the cross section.

4. The optical film according to claim 1, further comprising a substrate disposed on the optical diffusion layer and comprising one or more of polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyolefin, polyethylene, polyethylene naphthalate, cellulose acetate, polystyrene, and polyimide. 5 . The optical film of claim 4 , wherein the substrate comprises a plurality of alternating first and second polymer layers, at least 20 in total, wherein the average thickness of each of the first and second polymer layers is less than 350 nm.

6. The optical film of claim 5, wherein for the first polarization state and the visible wavelength range, the reflective polarizer has a greater average optical transmittance for light incident at a smaller angle of incidence and a less average optical transmittance for light incident at a larger angle of incidence.

7. An optical film according to claim 4, wherein the substrate includes an absorbing polarizer so that for incident light within 30 degrees of the normal direction and a predetermined wavelength range, the absorbing polarizer has an average optical transmittance of at least 40% for a first polarization state and an average optical absorptivity of at least 60% for an orthogonal second polarization state.

8. An optical film according to claim 4, wherein the substrate includes an optical mirror so that for incident light within 30 degrees of the normal direction and a predetermined wavelength range, the optical mirror has an average optical reflectivity of at least 60% for each of a first polarization state and a second polarization state that are orthogonal to each other.

9. The optical film according to any one of claims 4 to 8, further comprising a structured layer disposed between the substrate and the optical diffuser layer, the structured layer comprising a structured first major surface facing the optical diffuser layer and an opposite second major surface facing the substrate, the first major surface and the second major surface of the optical diffuser layer conforming to the structured first major surface of the structured layer.

10. The optical film of claim 9, wherein the structured layer comprises a plurality of particles dispersed in a binder, wherein the particles form a structured first major surface of the structured layer.

11. The optical film of claim 1 further comprising a substrate disposed on the optically diffuse layer, the substrate comprising a structured major surface facing away from the optically diffuse layer, the structured major surface comprising a plurality of spaced apart elongated structures elongated along a same first direction.

12. An optical stack comprising a reflective polarizer disposed between a first optical diffuse layer and a second optical diffuse layer, each of the first optical diffuse layer and the second optical diffuse layer comprising a plurality of non-uniformly dispersed particles defining a plurality of voids therein such that for incident light within 30 degrees of a normal direction and a visible wavelength range of 450 nm to 650 nm and an infrared wavelength range of 930 nm to 970 nm: the reflective polarizer transmits at least 40% of the incident light in a first polarization state for each wavelength in the visible wavelength range, reflects at least 70% of the incident light in an orthogonal second polarization state for each wavelength in the visible wavelength range, and transmits at least 40% of the incident light in each of the first polarization state and the second polarization state for each wavelength in the infrared wavelength range; and In the visible wavelength range, each of the first optical diffuser layer and the second optical diffuser layer has an average total transmittance Vt and an average specular transmittance Vs, and in the infrared wavelength range, each of the first optical diffuser layer and the second optical diffuser layer has an average total transmittance It and an average specular transmittance Is, Is / It≥0.6 and Is / Vs≥2.

5.

13. The optical stack according to claim 12, wherein one of the first optical diffusive layer and the second optical diffusive layer is directly coated on the reflective polarizer, and an air gap is defined between the reflective polarizer and the other of the first optical diffusive layer and the second optical diffusive layer.

14. The optical stack according to claim 12, wherein for one of the first optical diffusive layer and the second optical diffusive layer, 1 < It / Vt < 2.5; and wherein for the other of the first optical diffusive layer and the second optical diffusive layer, 2.5 < It / Vt < 4.

15. The optical stack according to any one of claims 12 to 14, wherein for at least one of the first optical diffusive layer and the second optical diffusive layer, the particles among the plurality of non-uniformly dispersed particles form a plurality of particle aggregates that define a plurality of voids therebetween, such that in a plane of a cross-section of the optical diffusive layer in the thickness direction of the optical diffusive layer: the average particle size of the particle aggregates is between 5 micrometers and 10 micrometers; and the voids account for 5% to 50% of the area of the plane of the cross-section.

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