Optical structures and display systems

Abstract

The optical construction includes a reflective polarizer and an optical diffusing film disposed on the reflective polarizer. The reflective polarizer includes an outer layer including a plurality of first particles partially protruding from a first major surface to form a structured major surface. The first optical diffusing layer is conformally disposed on the structured major surface. The optical diffusing film includes a second optical diffusing layer including a plurality of nanoparticles dispersed therein and a structured layer including a structured major surface. For substantially normally incident light, and for the visible wavelength range of about 450 nm to about 650 nm and the infrared wavelength range of about 930 nm to about 970 nm, the second optical diffusing layer has an average specular transmittance Vs in the visible wavelength range and an average specular transmittance Is in the infrared wavelength range, where Is / Vs is ≧2.5.

Description

Background Art

[0001] A liquid crystal display (LCD) can include a reflective polarizer between the LCD panel and the optical waveguide.

Summary of the Invention

[0002] The present disclosure generally relates to an optical structure including a reflective polarizer and an optical diffuser film, and a display system including the optical structure.

[0003] In some aspects of the present specification, the optical structure includes a reflective polarizer and an optical diffuser film disposed on the reflective polarizer. The reflective polarizer includes a plurality of polymer layers and a first outer layer. The plurality of polymer layers can total at least 50 and can be coextruded with the first outer layer. The first outer layer has an average particle size of about 7 to about 9 microns and includes a plurality of first particles that partially protrude from the first major surface to form a first structured major surface. The reflective polarizer further includes a first optical diffuser layer disposed to conform to the first structured major surface, and the opposing first and second major surfaces of the first optical diffuser layer substantially conform to the first structured major surface. The first optical diffuser layer includes a plurality of nanoparticles dispersed therein, and the nanoparticles define a plurality of gaps therebetween. The optical diffuser film includes an optical substrate layer, a second optical diffuser layer disposed on the optical substrate layer, facing the reflective polarizer, and including a plurality of nanoparticles dispersed therein, and a structured optical layer disposed on the optical substrate layer, facing away from the reflective polarizer, and including a plurality of spaced-apart elongated structures extending along the same first direction and including a structured major surface facing away from the optical substrate layer. The plurality of spaced-apart elongated structures can be disposed at a substantially uniform density across the structured major surface of the structured optical layer. For substantially normal incident light, and for 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 second optical diffuser layer has an average positive transmittance Vs in the visible wavelength range and an average positive transmittance Is in the infrared wavelength range, and Is / Vs≧2.5.

[0004] In some aspects of this specification, an optical structure includes a reflective polarizer and an optical diffusion film disposed on the reflective polarizer. The reflective polarizer includes a plurality of polymer layers and a first outer layer. The plurality of polymer layers may total at least 50 and can be co-extruded with the first outer layer. The first outer layer includes a plurality of first particles, which may have an average particle size of about 7 to about 9 microns, and partially protrudes from the first main surface to form a first structured main surface. The reflective polarizer further includes a first optical diffusion layer disposed to conform to the first structured main surface, such that the opposing first and second main surfaces of the first optical diffusion layer substantially conform to the first structured main surface. The first optical diffusion layer includes a plurality of nanoparticles dispersed internally, the nanoparticles defining a plurality of gaps between them. In some embodiments, the reflective polarizer also includes a second outer layer opposite the first outer layer, the second outer layer can be co-extruded with a plurality of polymer layers and the first outer layer, and the second outer layer includes a plurality of second particles that partially protrude from the second main surface to form a second structured main surface.

[0005] In some aspects of this specification, a display system for sensing a user's finger is provided applied to a display system. The display system includes a display panel configured to produce an image for a user to see; an optical waveguide for providing illumination to the display panel; an optical structure disposed between the display panel and the optical waveguide, comprising a plurality of polymer layers and including a reflective polarizer having a first structured principal surface disposed between the display panel and the plurality of polymer layers; a sensor for sensing a user's finger disposed in close proximity to the optical waveguide on the opposite side of the reflective polarizer; and an infrared light source configured to emit infrared light toward the user's finger, wherein the sensor is configured to receive at least a portion of the infrared light reflected by the finger. In some embodiments, the display system further includes a structured mirror disposed between the optical waveguide and the sensor and including an optical mirror; and an array of separate, spaced optical protrusions formed on the optical mirror and facing the optical waveguide. In some embodiments, with respect to substantially perpendicularly incident light, the optical mirror has an average light reflectance of more than about 30% in the visible wavelength range for at least a first polarization state, and a positive transmittance of more than about 20% at at least one wavelength in the infrared wavelength range for each of the first polarization state and the second orthogonal polarization state.

[0006] These and other aspects will become apparent from the detailed description below. However, in no case should this brief summary be construed as limiting the subject matter of the claims. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of an exemplary reflecting polarizer. [Figure 2A] This is a schematic cross-sectional view of an exemplary reflecting polarizer. [Figure 2B] This is a schematic cross-sectional view of an exemplary reflecting polarizer. [Figure 2C] This is a schematic cross-sectional view of an optical film. [Figure 3A]This is a schematic cross-sectional view of an exemplary reflective polarizer having an outer layer containing particles that partially protrude from the main surface. [Figure 3B] These are images of a partial cross-section of an exemplary reflective polarizer, with each image showing particles partially protruding from the outer layer of the reflective polarizer. [Figure 3C] These are images of a partial cross-section of an exemplary reflective polarizer, with each image showing particles partially protruding from the outer layer of the reflective polarizer. [Figure 4A] This is a schematic cross-sectional view of an exemplary optical diffusion layer. [Figure 4B] This is an example of a scanning electron microscope (SEM) image of an optical diffusion layer. [Figure 5A] This is a schematic cross-sectional view of an exemplary optical diffusion film. [Figure 5B] This is a schematic plan view of an exemplary structured main surface. [Figure 6A] This is a schematic diagram of the shape and structure of an example of an elongated structure. [Figure 6B] This is a schematic diagram of the shape and structure of an example of an elongated structure. [Figure 6C] This is a schematic diagram of the shape and structure of an example of an elongated structure. [Figure 7A] This is a schematic diagram of the surface features of an exemplary optical layer. [Figure 7B] This is a schematic diagram of the surface features of an exemplary optical layer. [Figure 7C] This is an image of the optical layer. [Figure 8A] This is a plot of the power spectral density of an exemplary structured surface of an optical layer having an elongated structure. [Figure 8B] This is a plot of the power spectral density of an exemplary structured surface of an optical layer having an elongated structure. [Figure 8C] This is a plot of the power spectral density of an exemplary structured surface of an optical layer having an elongated structure. [Figure 9A] This is a plot of autocorrelation of an exemplary structured surface of an optical layer having an elongated structure. [Figure 9B] This is a plot of autocorrelation of an exemplary structured surface of an optical layer having an elongated structure. [Figure 10A] It is a schematic cross-sectional view of a layer or film showing substantially vertically incident light, as well as scattered and directly transmitted light. [Figure 10B] It is a schematic cross-sectional view of a layer or film showing substantially vertically incident light, as well as scattered and directly transmitted light. [Figure 11] It is a schematic cross-sectional view of an exemplary optical structure. [Figure 12A] It is a schematic cross-sectional view of an exemplary structured mirror. [Figure 12B] It is a schematic cross-sectional view of an exemplary structured mirror. [Figure 13A] It is a schematic plot of transmittance versus wavelength. [Figure 13B] It is a schematic plot of transmittance versus wavelength. [Figure 14] It is a schematic plot of transmittance versus wavelength. [Figure 15] It is a plot of layer thickness versus layer number in an exemplary polymer layer packet. [Figure 16A] It is a plot of transmittance versus wavelength for an exemplary reflective polarizer. [Figure 16B] It is a part of the plot in FIG. 16A. [Figure 16C] It is a part of the plot in FIG. 16A. [Figure 17] It is a plot of transmittance of substantially vertically incident light versus wavelength for an exemplary reflective polarizer. [Figure 18] It is a plot of transmittance of substantially vertically incident light versus wavelength for an exemplary optical diffusion film. [Figure 19] It is a schematic exploded cross-sectional view of an exemplary display system. [Figure 20] It is a schematic exploded cross-sectional view of an exemplary display system. [Figure 21] It is a schematic exploded cross-sectional view of an exemplary display system. [Figure 22A] It is a plot of transmittance versus wavelength for an exemplary reflective polarizer for s-polarized and p-polarized light. [Figure 22B] It is a view of the layer thickness profile of the reflective polarizer in FIG. 22A. [Figure 23] This is a plot of transmittance versus wavelength for exemplary reflecting polarizers for s-polarization and p-polarization. [Figure 24] This is a plot of transmittance versus wavelength for exemplary reflecting polarizers for s-polarization and p-polarization. [Figure 25] This is a plot of transmittance versus wavelength for exemplary reflecting polarizers for s-polarization and p-polarization. [Modes for carrying out the invention]

[0008] The following description refers to the accompanying drawings, which form part of this specification and illustrate various embodiments. The drawings are not necessarily to scale. It should be understood that other embodiments may be conceived and implemented without departing from the scope or spirit of this specification. Therefore, the embodiments for carrying out the invention described below should not be construed as restrictive.

[0009] According to some embodiments, the optical structure includes a reflective polarizer and at least one optical diffusion layer. For example, the optical structure may include a reflective polarizer having a structured outer surface and a first optical diffusion layer disposed on and conforming to the structured outer surface, and may further include an optical diffusion film having a second optical diffusion layer. The optical diffusion layer (e.g., at least one of the first and second optical diffusion layers) may include particles dispersed to form aggregates of particles having gaps (voids) between them. In some embodiments, the optical diffusion layer provides substantially higher positive transmittance in the infrared range than in the visible range. Alternatively or additionally, according to some embodiments, the optical diffusion layer can provide substantially higher diffuse transmittance in the visible range than in the infrared range. In some embodiments, the particles are nanoparticles, and the aggregates have an average particle size of less than about 1 micron. In other embodiments, the aggregates may 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).

[0010] According to the embodiment, multiple spaced elongated structures can be arranged on the optical layer (e.g., on the optical diffusion film side opposite the reflective polarizer) to reduce the coefficient of friction and impart a surface roughness that eliminates or reduces damage to adjacent films, thereby preventing optical defects between adjacent films (e.g., wet-out, moiré patterns, Newton's rings, and similar effects). The elongated structures may be called anti-wet-out (AWO) structures. In some cases, these elongated structures may be printed on the optical film or fabricated and arranged by another process (e.g., microreplication).

[0011] According to several embodiments, optical structures are useful in display applications or other applications where it is desirable to minimize scattering of light in the infrared range (e.g., substantially optically direct transmission) and provide scattering of visible light (e.g., substantially optically diffuse transmission). For example, in a liquid crystal display (LCD) including a fingerprint detection system having an infrared light source and an infrared sensor behind the backlight, it is typically desirable that infrared light from the infrared light source is transmitted to the outer surface of the display, then reflected by the finger if a finger is present, and transmitted to the infrared sensor through the display and backlight with minimal scattering. The LCD backlight also includes, for example, one or more optical diffusers to conceal defects. Conventional optical diffusers typically scatter both visible and infrared light in the wavelength range (e.g., the wavelength range of about 930 nm to about 970 nm), making them unsuitable or undesirable for use in backlights when fingerprint detection using infrared light is desired. According to several embodiments, optical structures provide desired optical diffusion of visible light without substantially scattering infrared light.

[0012] According to some embodiments, the display system includes an optical structure. In some embodiments, the display system further includes a structured mirror having a discontinuous coating on the surface of the optical mirror. The discontinuous coating can provide a surface roughness that reduces the coefficient of friction and eliminates or reduces damage to adjacent films. In some embodiments, the discontinuous coating may be substantially transparent to near-infrared wavelengths, enabling infrared sensor functionality behind the LCD panel. In some embodiments, the discontinuous coating may include individual raised features, such as rounded ridges. In some embodiments, the individual features may be added to the optical mirror using a technique such as flexographic printing (or a similar printing process). In some embodiments, other techniques or processes may be used to add the individual features to the optical mirror.

[0013] Figure 1 is a schematic cross-sectional view of a reflective polarizer 100, including a reflective polarizer 10 and an optical diffusion layer 30, according to several embodiments. The reflective polarizer 10 has a first outer layer 20 which may include a first structured main surface 21 and a plurality of spaced first structures 22 arranged across the first structured main surface 21. The first structures 22 may be included to reduce or prevent wet-out with adjacent films (wet-out in this context generally refers to the unintended integration of two contacting surfaces that results in undesirable optical effects) and / or to reduce friction with adjacent films, for example, to reduce damage to the reflective polarizer 100 or adjacent films. The first structures 22 may be formed using particles as further described elsewhere herein. The reflective polarizer 10 includes a plurality of polymer layers 14 (individual layers are not shown in the schematic diagram of Figure 1; see, for example, Figures 2A-2C). The first structured main surface 21 faces away from the plurality of polymer layers 14. The optical diffusion layer 30 is positioned to conform to the first structured main surface 21 of the outer layer 20, so that the opposing first and second main surfaces 31 and 32 of the optical diffusion layer 30 substantially conform to the first structured main surface 21. For example, the first and second main surfaces 31 and 32 can conform to the first structured main surface 21, or can nominally conform to the first structured main surface 21, or can conform to the first structured main surface 21 within a small variation of the height of the first structure 22 (e.g., less than about 30%, less than about 20%, or less than 10%). In some embodiments, the first and second main surfaces 31 and 32 define an average spacing S between them of about 200 to about 5000 nm. In some embodiments, the average spacing S is about 200 nm to about 2000 nm, or about 200 nm to about 1500 nm, or about 300 nm to about 1200 nm. The reflection and transmission characteristics of the reflective polarizer 100 can be described in terms of substantially perpendicular incident light 40 (for example, light incident nominally perpendicularly, or, when the optical structure extends in the xy plane and has thickness in the z direction, light incident within 30 degrees, 20 degrees, or 10 degrees from the normal (z direction) to the xy plane).Light 40 can be incident on either side of the reflecting polarizer 100 (for example, along the -z direction so that the light first enters the optical diffusion layer 30 as schematically shown in Figure 1, or along the +z direction so that the light first enters the reflecting polarizer 10 as schematically shown in Figure 3A). Similarly, incident light shown in the other figures can also be incident on either side of the illustrated optical elements.

[0014] In some embodiments, the reflective polarizer 10 is a multilayer optical film reflective polarizer. As is known in the art, a multilayer optical film comprising alternating polymer layers can be used, and by suitably selecting the layer thickness, a desired reflectance and transmittance can be obtained in a desired wavelength range. Multilayer optical films and methods for producing multilayer optical films are described, for example, in U.S. Patent No. 5,882,774 (Jonza et al.), No. 6,179,948 (Merrill et al.), No. 6,783,349 (Neavin et al.), No. 6,967,778 (Wheatley et al.), and No. 9,162,406 (Neavin et al.).

[0015] Figures 2A-2B are schematic cross-sectional views of a reflective polarizer according to several embodiments. In the embodiments of Figures 2A-2B, the reflective polarizer 10 includes a plurality of polymer layers 11, 12 (for example, layers 11 and 12 alternating with each other). The number of layers can be substantially greater than that shown in the schematic diagrams of Figures 2A-2B. In some embodiments, the number of polymer layers 11, 12 is at least 20 in total (for example, 20-1000, or 30-500, or 40-400). Each of the polymer layers 11, 12 may have an average thickness t of less than about 500 nm, or less than about 350 nm, or less than about 300 nm. The polymer layers 11, 12 may be called interference layers or microlayers. The reflective polarizer 10 further includes a first outer layer 20 which can be co-extruded and / or co-stretched together with a plurality of polymer layers 11, 12 (for example, the first outer layer 20 may be the outermost layer co-extruded with the polymer layers 11, 12). The first outer layer 20 may have an average thickness t1 of more than about 0.5 microns, or more than about 1 micron, or more than about 2 microns, or more than about 3 microns, or more than about 5 microns. The first outer layer 20 includes a first structured main surface 21 which faces away from the first and second polymer layers and includes a plurality of spaced first structures 22 arranged across the first structured main surface 21.

[0016] In some embodiments, the reflective polarizer 10 further includes a second outer layer 50 having an average thickness t2 greater than approximately 0.5 microns, which may be co-extruded and / or co-stretched with the polymer layers 11, 12 on the opposite side of the first outer layer 20 (for example, the second outer layer 50 may be the outermost layer co-extruded with the polymer layers 11, 12). In some embodiments, the second outer layer 50 includes a second structured main surface 51, which faces the side opposite to the polymer layers 11, 12 and includes a plurality of spaced second structures 52 arranged across the second structured main surface 51. The second structures 52 may be included, for example, to reduce wet-out with adjacent films and / or to reduce friction with adjacent films, thereby reducing damage to the reflective polarizer 10 or adjacent films. In other embodiments, the second structures 52 may be omitted. In some embodiments, the reflective polarizer 10 includes protective boundary layers on each side of the polymer layers 11, 12 packets to protect the polymer layers 11, 12 during processing, as is known in the art. In some embodiments, as schematically shown in Figure 2B, the reflective polarizer 10 includes two packets of polymer layers 11, 12, and the plurality of polymer layers 11, 12 include a plurality of first polymer layers (a set of upper layers 11, 12 in Figure 2B, sometimes referred to as the first packets) separated along the thickness direction (z direction) of the reflective polarizer by one or more intermediate layers 43a, 43b. The one or more intermediate layers 43a, 43b may be, for example, two protective boundary layers, or a single layer formed from two protective boundary layers. In some embodiments, each of the first and second polymer layers 11, 12 has an average thickness of less than about 350 nm or less than about 300 nm, and each of the one or more intermediate layers 43a, 43b has an average thickness tc of more than about 500 nm, or more than 1 micron, or more than 3 microns, or more than about 5 microns. In some embodiments, the minimum distance between the first outer layer 20 and one or more intermediate layers 43a, 43b is S1, and the minimum distance between the second outer layer 50 and one or more intermediate layers 43a, 43b is S2, where S1 > S2. In some embodiments, S1 > 1.1 × S2, or S1 > 1.2 × S2.When the reflective polarizer 10 is used in a display, the first outer layer 20 can face the display panel and the second outer layer 50 can face the backlight (see, for example, Figures 19-21). The first packet (a plurality of first polymer layers having a total thickness S1) may be used primarily for reflection in the infrared range, while the second packet (a plurality of first polymer layers having a total thickness S1) may be used primarily for reflection in the visible range. According to some embodiments, by facing the second packet to the backlight and the first packet to the display panel, the light-reflecting layer faces the backlight, so that visible light from the backlight is reflected more quickly and color shift of the display output is reduced.

[0017] A substantially perpendicularly incident light 40 and light 170 incident at a certain angle of incidence θ are schematically shown in Figure 2A. The first and second polarization states 171 (polarized in the xz plane) and 172 (polarized along the y axis) are schematically shown. In some embodiments, the first polarization state 171 is a passing polarization state, and the second polarization state 172 is a cutoff polarization state. Alternatively, the cutoff polarization state and the passing polarization state may be called the first polarization state and the second polarization state, respectively. A portion of the incident light 40 and 170 is transmitted as light 240 and 270, respectively. Light 240 and 270 are typically polarized primarily in the first polarization state when the first polarization state is a passing state for the reflecting polarizer. In some embodiments, the reflecting polarizer 10 is a collimated reflecting polarizer. Collimated reflective polarizers are known in the art and are described, for example, in U.S. Patent No. 9,441,809 (Nevitt et al.) and No. 9,551,818 (Weber et al.). In some embodiments, in a first polarization state 171 and in the visible wavelength range (e.g., 450 nm to 650 nm), the reflective polarizer 10 has a higher average light transmittance (e.g., light 240) for light incident at a smaller angle of incidence (e.g., light 40) and a lower average light transmittance (e.g., light 270) 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 at the plane of incidence), and the larger angle of incidence is less than about 50 degrees or less than about 40 degrees. In some embodiments, the reflective polarizer has a higher average light transmittance for light incident at smaller angles of incidence and a lower average light transmittance for light incident at larger angles of incidence, for each of the passing polarization states of p-polarization and s-polarization. In some embodiments, the difference between the higher average light transmittance and the lower average light transmittance is at least about 10%, or at least about 20%, or at least about 30%.

[0018] The mirror film or optical mirror may appear as schematically shown in Figures 2A-2B. In some embodiments, the outer layers 20, 50 are unstructured. Figure 2C is a cross-sectional view of a multilayer optical film 10', which may be, for example, a reflective polarizer or an optical mirror. In some embodiments, the optical film 10' is an optical mirror comprising a plurality of alternating first and second polymer layers 11 and 12, each of the first and second polymer layers having a thickness of less than about 500 nm, or less than about 350 nm, or less than about 300 nm. In some embodiments, the optical film 10' includes a single packet (for example, shown in Figure 2A) between the first outer layer 20 and the second outer layer 50, and each layer between the outer layers 20 and 50 has an average thickness of, for example, less than 350 nm or less than 300 nm. In some embodiments, the plurality of polymer layers 11, 12 include a plurality of first polymer layers separated from a plurality of second polymer layers along the thickness direction of the reflecting polarizer by one or more intermediate layers (see, for example, Figure 2B), each of the plurality of first and second polymer layers having an average thickness of less than about 350 nm, and each of the one or more intermediate layers having an average thickness of more than about 500 nm.

[0019] Other suitable reflective polarizers and optical mirrors are described in U.S. Provisional Simultaneous Pending Applications No. 63 / 021743 and No. 62 / 704400, both filed on 8 May 2020, and are incorporated herein by reference to the extent not inconsistent with this specification.

[0020] Figure 3A is a schematic cross-sectional view of a reflective polarizer 200 according to several embodiments. The reflective polarizer 200 may correspond in general to the reflective polarizer 100, except that the reflective polarizer 200 includes a second outer layer 50 on the opposite side of the first outer layer 20, and the first outer layer 20 includes particles 23. In some embodiments, the first outer layer 20 includes a plurality of first particles 23 that partially protrude from its first main surface 21' to form a first structured main surface 21. A plurality of polymer layers 14 can be co-extruded with the first outer layer 20. In some embodiments, the second outer layer 50 is co-extruded with the plurality of polymer layers 14 and the first outer layer 20. In some embodiments, the second outer layer 50 includes a plurality of second particles 53 that partially protrude from its second main surface 51' to form a second structured main surface 51. In some embodiments, the first particles 23 have an average particle size of about 7 to about 9 microns. It has been found that undesirable optical effects (e.g., interference fringes) can occur when a reflective or partially reflective film (e.g., another reflective polarizer) is placed on a reflective polarizer having a structured surface. It has been found that these undesirable optical effects are substantially reduced or eliminated when the average particle size of the first particles is selected in the range of about 7 to about 9 microns. In some embodiments, the second particles may also have an average particle size of about 7 to 9 microns. In other embodiments, the average particle sizes of the second particles 53 and the first particles 23 are in different ranges, as the second structured surface 51 is typically positioned to face a diffuser rather than a more reflective film (see, for example, Figure 11). In some embodiments, the second particles 53 have an average particle size smaller than that of the first particles 23. In some embodiments, the second particles 53 have an average particle size of less than about 6 microns, or the average particle size may be, for example, in the range of about 1 micron or about 2 to about 6 microns. In some embodiments, the second particle 53 has an average particle size that is approximately the same as (e.g., within 10% or 5%) as the average particle size of the first particle 23. In some embodiments, the second particle 53 has an average particle size that is larger than the average particle size of the first particle 23. In some embodiments, the second particle 53 has an average particle size of more than about 3 microns, more than about 5 microns, more than about 10 microns, or more than about 15 microns.In some embodiments, the second particles have an average particle size in the range of, for example, about 3 microns to about 20 microns.

[0021] In some embodiments, the second outer layer 50 includes a plurality of particles 53 that partially sink inward to form a second structured principal surface 51. In some embodiments, the first outer layer 20 includes a plurality of particles 23 that partially sink inward to form a first structured principal surface 21. Related reflective polarizers having structured outer principal surfaces are described in U.S. Provisional Simultaneous Pending Application No. 63 / 021765, filed 8 May 2020, entitled “REFLECTIVE POLARIZER WITH IMPROVED OPTICAL CHARACTERISTICS,” which is incorporated herein by reference to the extent not inconsistent with this specification.

[0022] An optical film can be formed by coating the outermost principal surface of a cast web with particles, drying the coating, and stretching the cast web (e.g., stretching the film uniaxially or biaxially). This allows the particles to partially protrude from the principal surface of the outer layer, as they partially sink into the outer layer of the film. The coating can be optionally applied during the sequential stretching process to alter the modulus / thickness of the outermost layer, which may affect the particles that partially sink into the outermost layer. Figure 3B is a scanning electron microscope (SEM) image of a portion of a cross-section of a multilayer optical film reflective polarizer, showing particles 53 that partially protrude from the principal surface of the outer layer 50 of the reflective polarizer to form a structured principal surface. Figure 3C is an SEM image of a portion of a cross-section of a multilayer optical film reflective polarizer, showing particles 23 that partially protrude from the principal surface of the outer layer 20 of the reflective polarizer to form a structured principal surface. The reflective polarizer includes an optical diffusion layer 30 that substantially conforms to the structured principal surface. When a continuous portion of an outer layer (e.g., a continuous polymer phase) is co-extruded with multiple polymer layers, the outer layer of a film can be described as co-extruded with multiple polymer layers of the film, because the layer exhibits the properties of a co-extruded layer (e.g., bonding to adjacent layers without adhesive), even if particles or other components (e.g., polymers from particle coatings) are subsequently added to the outer layer (after co-extrusion). For example, an outer layer co-extruded with polymer layers 11, 12 may be described as containing particles partially embedded in the outer layer, or it may be described as co-extruded with polymer layers 11, 12 even if the particles partially embedded in the layer after the outer layer was initially formed by co-extrusion with polymer layers 11, 12. The particles may be surface-coated particles, where the surface coating on the particles is formed from a polymer from a mixture used to coat the particles onto the outer layer. In some embodiments, the mixture containing the particles contains polyester (e.g., the mixture may be an aqueous mixture containing a water-soluble polyester), and in some embodiments, the co-extruded outer layer contains polyester.In some such embodiments, this provides a tight refractive index match between the coated polyester and the co-extruded layer, allowing the coated polyester to be stretched under similar conditions to the co-extruded web. Furthermore, the coated polyester may be compatible with the coated optical diffusion layer.

[0023] Alternatively, instead of describing the co-extruded outer layer as containing particles added after co-extrusion, the reflective polarizer can be described as containing particles that partially protrude from the main surface of the co-extruded layer.

[0024] In other embodiments, particles are included in one of the first and second outer layers but not in the other, forming the main surfaces of each. For example, the structured surface can be formed by embossing, casting and hardening, or other techniques that do not utilize particles for the structure.

[0025] Figure 4A is a schematic cross-sectional view of an optical diffusion layer 30 according to several embodiments. The optical diffusion layer 30 schematicly shown in Figure 4A may be, for example, a part of the optical diffusion layer 30 schematicly shown in Figure 1, and / or, for example, a part of the optical diffusion layer 120 in Figure 5A. Figure 4B is a scanning electron microscope (SEM) image of an exemplary optical diffusion layer 30. The optical diffusion layer 30 includes a plurality of nanoparticles 33 dispersed between a first main surface 31 and a second main surface 32 of the optical diffusion layer 30. The nanoparticles may have an average particle size of about 10 nm to about 150 nm or about 20 nm to about 150 nm and define a plurality of gaps 34 between them. In some embodiments, the nanoparticles 33 in the optical diffusion layer 30 aggregate to form a plurality of nanoparticle aggregates 35 having an average particle size of about 100 nm to about 10 microns or about 100 nm to about 1000 nm. In other embodiments, the aggregates may be larger (e.g., up to about 10 microns, or about 1 to about 10 microns, or about 5 to about 10 microns). In some embodiments, the polymer material 36 binds nanoparticles 33 together to form a plurality of nanoparticle aggregates 35 in which gaps 34 can be defined between them. In some embodiments, in the plane of the cross-section of the optical diffusion layer 30 (e.g., the xz plane) in the thickness direction (e.g., the z direction) of the optical diffusion layer 30, the gaps 34 occupy about 5% to about 50% of the area of ​​the plane of the cross-section. In some embodiments, the gaps 34 occupy about 5% to about 45% or about 40% of the area of ​​the plane of the cross-section. In some embodiments, the gaps 34 occupy about 10% or about 15% to about 50%, or about 45%, or about 40% of the area of ​​the plane of the cross-section.

[0026] In some embodiments, the optical diffusion layer 30 is formed by coating a mixture of particles, monomer, and solvent, and then curing and drying the mixture. The monomers cure to become a polymer binder (polymer material 36), which binds aggregates of particles together, and the solvent evaporates to form gaps between the aggregates. The solvent can evaporate at least partially during curing and / or the evaporation of the solvent can be completed using a subsequent drying step. In some embodiments, curing and drying include a pre-curing step, followed by a drying step, followed by a post-curing step. In some embodiments, the monomer is ultraviolet (UV) curable, and a photoinitiator is included in the mixture. The aggregate size can be adjusted by varying the UV power used to cure the monomer, with higher power generally resulting in smaller aggregate sizes. It has been found that relatively small amounts of photoinitiator with relatively high UV power result in small aggregate sizes and a non-brittle layer, while relatively large amounts of photoinitiator may result in a brittle layer. The porosity can be adjusted by varying the amount of solvent used in the mixture, with higher solvent loading generally resulting in higher porosity. In some embodiments, the mixture contains about 20 to about 60% by weight of solids.

[0027] In some embodiments, the polymer material 36 is or comprises a radiation-curable (e.g., UV-curable) polymer. In some embodiments, the polymer material 36 is or comprises an acrylate. In some embodiments, the polymer material 36 is or comprises pentaerythritol triacrylate.

[0028] The average particle size of the nanoparticles 33 or other particles described herein may be average or median size. For example, the average particle size may be Dv50 size (median size in volume distribution, or equivalently, particle size provided by particles having a size of Dv50 size or less for 50 percent of the total volume of particles). In some embodiments, the nanoparticles 33 have an average particle size 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. In some embodiments, the nanoparticles 33 are silica or contain silica.

[0029] The percentage of the cross-sectional area occupied by the gaps 34 can be determined using image analysis techniques. For example, an optical diffusion layer can be cut with a microtome, then a scanning electron microscope (SEM) image of the cross-section can be taken, and then the image can be analyzed using image analysis software to determine the percentage of the area occupied by the gaps. The average particle size of the aggregates can also be determined from the image analysis. The particle size of the aggregates in the cross-section may be the equivalent circle diameter of the aggregate (i.e., the diameter of a circle that has the same area as the aggregate in the cross-section).

[0030] The particles 23 or structures 22 may have an average particle size (e.g., diameter) at least about 2, 3, 5, 10, 20, or 50 times the average particle size of the particle aggregate 35.

[0031] The relevant optical diffusion layer is described in U.S. Provisional Simultaneous Pending Application No. 63 / 021751, filed on 8 May 2020, entitled "OPTICAL FILMS AND STACKS INCLUDING OPTICALLY DIFFUSIVE LAYER," and is incorporated herein by reference to the extent not inconsistent with this specification.

[0032] Figure 5A is a schematic cross-sectional view of an optical diffusion film 300 according to several embodiments. Figure 5B is a schematic plan view of the main surface 131 of an optical diffusion film 300 according to several embodiments. The optical diffusion film 300 includes an optical substrate layer 110 having a first main surface 111 and a second main surface 112, and an optical layer 130 disposed on the second main surface 112 of the optical substrate layer 110. In some embodiments, an adhesive layer 133 may be disposed between the optical layer 130 and the optical substrate layer 110. Alternatively, the optical layer 130 may be formed directly on the optical substrate layer 110, and the adhesive layer 133 may be omitted. In some embodiments, the optical layer 130 includes a structured main surface 131 and an unstructured main surface 132. In some embodiments, the structured main surface 131 faces away from the optical substrate layer 110 and includes a plurality of spaced elongated structures 140.

[0033] In some embodiments, the elongated structure 140 may extend along the same first direction (e.g., the x-direction as shown in Figure 5A) and be arranged at a substantially uniform density across the structured main surface 131 (e.g., as shown in Figures 5B and 7C). In some embodiments, the optical diffusion film 300 further includes an optical diffusion layer 120 disposed on the first main surface 111 of the optical substrate layer 110. In some embodiments, an adhesive layer 133' is disposed between the optical diffusion layer 120 and the optical substrate layer 110. Alternatively, the optical diffusion layer 120 may be formed directly on the optical substrate layer 110, and the adhesive layer 133' may be omitted.

[0034] In some embodiments, the optical diffusion layer 120 includes a plurality of nanoparticles 121 dispersed therein. In some embodiments, the nanoparticles 121 have an average particle size of about 10 nm to about 300 nm. In some embodiments, the nanoparticles 121 include silica (for example, the nanoparticles 121 may be silica nanoparticles) and can provide diffusion (scattering effect) of light at least several wavelengths. The optical diffusion layer 120 may be described as an optical diffusion layer 30. For example, in some embodiments, the optical diffusion layer 120 includes a polymer material (for example, corresponding to polymer material 36) that binds the nanoparticles of the optical diffusion layer 120 together to form a plurality of nanoparticle aggregates (for example, corresponding to aggregates 35) that define a plurality of gaps (for example, corresponding to gaps 34) between them. In some embodiments, in the plane of the cross-section of the optical diffusion layer 120 in the thickness direction of the second optical diffusion layer, the nanoparticles 121 of the optical diffusion layer 120 have an average particle size of about 20 nm to about 150 nm, the average particle size of the nanoparticle aggregates is in the range of about 100 nm to about 10 microns, and the gaps occupy about 5% to about 50% or about 15% to about 45% of the area of ​​the plane of the cross-section, or any other range described elsewhere.

[0035] The elongated structures 140 may be arranged in an irregular, random pattern, or in an optionally regular arrangement or pattern. In some embodiments, the elongated structures 140 extend along a first direction, such as the x-axis shown in Figures 5A-5B (i.e., have their longest dimensions), and are arranged along a second orthogonal direction, such as the y-axis shown in Figures 5A-5B. The assignment of coordinate / reference systems (i.e., x, y, and z directions) shown in Figures 5A-5B are merely illustrative examples, and other reference systems and configurations may be used in accordance with the present disclosure.

[0036] Figures 6A to 6C provide detailed graphs of the shape and configuration of the elongated structure according to several embodiments and should be considered together for the following description. Figure 6A is a top view of one embodiment of the elongated structure 140 including a peak 41 (the highest point of the curve). Figure 6B is a plot showing the profile in the xz plane (for example, as shown by the reference frame in Figures 5A to 5B), and is a side view of the "canoe" shape (along the longitudinal dimension). Figure 6C is a plot showing the profile in the yz plane, and is a front view of the "canoe" shape (along the width dimension). Looking at Figure 6B, in some embodiments the elongated structure 140 has a length La and a full width at half maximum (FWHM, i.e., the width seen at half the height of the elongated structure 140) Wa. In some embodiments the elongated structure 140 may have a substantially flat upper region 42 of length d, thereby resulting in a height variation of less than about 5%, or less than about 2.5%, or less than about 1% over length d. In some embodiments, the d / La ratio is about 0.15 or greater, or about 0.10 or greater, or about 0.05 or greater. Referring to Figure 6C, in some embodiments, the elongated structure 140 may have a total length Lb (length in the yz plane) and an FWHM Wb, thereby the Wb / Wa ratio being about 0.6 or less, or about 0.5 or less, or about 0.4 or less. In some embodiments, the elongated structure 140 has an average length (e.g., La) along a first direction and an average width (e.g., Lb) along a second orthogonal direction, where the average length is at least about 2 times or at least about 2.5 times the average width. In some embodiments, the elongated structure 140 has an average peak height H of about 2 microns to about 7 microns or about 3 microns to about 6.5 microns. Figures 6A to 6C show one possible embodiment of the shape, size, and configuration of the elongated structure 140, but are not intended to limit it. The values ​​plotted in Figures 6B and 6C are in microns (μm), and the curves shown in the figures do not necessarily represent the aspect ratio of the actual elongated structure 140 (i.e., the figures provide actual measurement data for one embodiment, but the lines in the figures do not necessarily represent a realistic depiction of the elongated structure 140; for example, the x-axis has been compressed to allow the graph to be presented on a single page and maintain readability).

[0037] Figures 7A to 7C show surface features of (e.g., a single) optical layers prepared using a high-resolution process (a process used to generate microstructures) according to some embodiments of this specification. Figure 7A shows a portion of an optical layer 130 featuring a plurality of substantially parallel linear structures 90 produced by the high-resolution process. In some embodiments, producing a film using a high-resolution process involves producing a template or master tool, which may take the form of a roll material having periodic surface features (e.g., molded depressions, cuts, or concave areas, or molded protrusions or convex structures). A soft material can then be passed between the roll material and a second roller or surface, and the periodic surface features on the roll material produce corresponding features on the passing material that are essentially the opposite of the features on the roll material surface. For example, a canoe-shaped depression on the roll material produces a corresponding canoe-shaped structure or protrusion on the surface of the material. As the material passes through the system, it is cured (for example, by ultraviolet light or heat) to create a structured film.

[0038] Before periodic surface features can be machined onto the surface of the roll material, the outer surface of the roll material often has to be prepared using a process that removes the initial rough outer surface of the roll material by pressing a hardened tool onto the surface of the roll material and cutting the surface in a series of passes. The outer surface of the roll material becomes much smoother after this process, but the tool used in this process may form very small grooves or ruts on the surface of the roll material. Even after periodic surface features have been machined or otherwise created on the surface of the roll material, small grooves remain on the surface of the roll material. These very small grooves in the roll material generate corresponding inverse ridges within the fabricated film, such as substantially parallel linear structures 90 shown in the optical layer 130 in Figure 7A. These linear structures 90 are relatively small, as shown in Figure 7B, and in some embodiments, the average difference d4 in height between the peaks 92 and valleys 93 may be about 10 nm to about 100 nm, or about 80 nm, or about 60 nm. When this average height difference d4 is compared with the height of a typical elongated structure 140, as shown in Figure 6B, which is about 5 microns in some embodiments, it can be seen that the relative height of the linear structure 90 is significantly lower than the average height of the elongated structure 140.

[0039] Figure 7C is an image showing a plan view of the optical layer 130 fabricated using a high-resolution process. Faint lines on the image of the optical layer 130 are produced by the difference in illumination generated by alternating peaks 92 and valleys 93 (see Figure 7B) of substantially parallel linear structures 90. Thus, the surface of the optical layer 130 includes a plurality of elongated structures 140, with substantially parallel linear structures 90 formed in the regions 91 between the elongated structures 140. The linear structures 90 extend along the same direction as the elongated structures 140 (e.g., the x-direction shown in Figure 7C), and both the linear structures 90 and the elongated structures 140 are aligned along a second orthogonal direction (e.g., the y-direction shown in Figure 7C).

[0040] There exist mathematical and scientific methods that provide a way to characterize the structure and performance of a film by enabling the measurement and characterization of the uniformity or regularity of elongated structures on an optical layer. Figures 8A to 8C are plots showing the power spectral density of a structured surface of an optical layer (e.g., a single) having elongated structures. Figures 9A to 9B are plots showing the autocorrelation of a structured surface of an optical layer (e.g., a single) having elongated features. Figure 8A shows an image of the power spectral density (PSD) 60 obtained for a structured surface 131 of an optical layer 130 according to several embodiments, and Figures 8B and 8C are plots showing the intensities measured by the PSD on the x and y axes, respectively. Figure 8B shows a first peak 61 along a first direction (e.g., the x axis) with a first peak intensity I1, and Figure 8C shows a second peak 62 along a second direction (e.g., the y axis) with a second peak intensity I2. In some embodiments, the ratio I1 / I2 is about 1 or greater (or about 10 or greater, or about 100 or greater) and about 10,000 or less. In some embodiments, the power spectral density 60 of the structured main surface 131 of the structured optical layer 130 has a first peak 61 along a first direction having a first peak intensity I1 and a second peak 62 along an orthogonal second direction having a second peak intensity I2, and 1 ≤ I1 / I2 ≤ 10,000 or 10 ≤ I1 / I2 ≤ 5000.

[0041] Figures 9A and 9B provide the results of autocorrelation performed on the structured surface of an optical layer. Figure 9A shows the autocorrelation 70 along a first direction (e.g., the x-axis) showing a first peak 71, a second peak 72, and a third peak 73 located at a first (minimum) distance d1, a second (next smallest) distance d2, and a third (third smallest) distance d3, respectively. The first peak 71 has a first peak intensity J1, the second peak 72 has a second peak intensity J2, and the third peak 73 has a third peak intensity J3. In some embodiments, each of the second peak intensity J2 and the third peak intensity J3 is greater than the first peak intensity J1. Figure 9B shows the autocorrelation 80 along a second direction (e.g., the y-axis), showing either no significant peaks or a peak 81 at a distance ta that is greater than or equal to the first distance d1. In some embodiments, the autocorrelation 70 of the structured principal surface 131 of the structured optical layer 130 along a first direction has a first peak 71 at the smallest positive first distance d1 with a first peak intensity J1, and a second peak 72 at the next smallest positive second distance d2 with a second peak intensity J2, where J2 > J1, or J2 > 1.1 × J1. The autocorrelations 70 and 80 are indicated as "Med" in Figures 9A and 9B. The autocorrelation function (ACF) for the structured surface having a structure extending at 0 degrees with respect to the x-axis and having a large (indicated as "high") height and a small (indicated as "low") height is also shown in Figures 9A and 9B.

[0042] Figures 10A and 10B are schematic cross-sectional views of layer or film 150 and layer or film 150', respectively, where light 40a and 40b are incident substantially perpendicularly on the layer or film. Layer or film 150 may correspond to, for example, an optical diffusion layer or optical diffusion film or a reflective polarizer or optical structure as described herein. Layer or film 150' may correspond to, for example, a substrate layer or an optical layer as described herein. Light 40a has a wavelength in the range of λ1 to λ2, and light 40b has a wavelength 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 450 nm, λ2 is about 650 nm, λ3 is about 930 nm, and λ4 is about 970 nm. For light 40a in the wavelength range λ1 to λ2, the layer or film 150 has an average positive transmittance Vs, an average diffuse transmittance Vd, and an average total transmittance Vt (Vt = Vs + Vd). For light 40b in the wavelength range λ3 to λ4, the layer or film 150 has an average positive transmittance Is, an average diffuse transmittance Id, and an average total transmittance It (It = Is + Id). A high diffuse transmittance (e.g., a high Vd) corresponds to a high optical haze.

[0043] In some embodiments, for substantially perpendicular incident light (40, 40a, 40b), and for the visible wavelength range of about 450 nm to about 650 nm and the infrared wavelength range of about 930 nm to about 970 nm, the optical diffusion layer (e.g., 30, 120, or 150) has an average positive transmittance Vs in the visible wavelength range and an average positive transmittance Is in the infrared wavelength range, where Is / Vs ≥ 2.5. In some embodiments, Is / Vs ≥ 3. In some embodiments, the optical diffusion layer has an average total transmittance It in the infrared wavelength range, where Is / It ≥ 0.6 or Is / It ≥ 0.7. In some embodiments, the optical diffusion layer has an average total transmittance Vt in the visible wavelength range, where It / Vt > 1, or It / Vt > 2, or It / Vt > 3.

[0044] In some embodiments, with respect to substantially perpendicular incident light (40, 40a, 40b), in each of the mutually orthogonal first and second polarization states (171, 172), the optical substrate layer (e.g., 110 or 150') has an average positive transmittance (Vs, Is) greater than about 70% in each of the visible and infrared wavelength ranges. In some embodiments, the optical substrate layer (e.g., 110 or 150') is or includes a polyester film (e.g., polyethylene terephthalate [PET] film).

[0045] In some embodiments, the optical structure includes a reflective polarizer (e.g., reflective polarizer 100 or 200) disposed on an optical diffusion film (e.g., optical diffusion film 300). Figure 11 is a schematic cross-sectional view of an optical structure 400 according to some embodiments. In some embodiments, the optical structure 400 includes a reflective polarizer 200 and an optical diffusion film 300 disposed on the reflective polarizer 200. In some embodiments, the reflective polarizer 200 includes a plurality of polymer layers 14 (e.g., corresponding to layers 11, 12; individual layers are not shown in the schematic diagram of Figure 11) co-extruded with a first outer layer 20. The number of polymer layers may be at least 50 in total. The first outer layer 20 includes a plurality of first particles 23 that partially protrude from a first main surface to form a first structured main surface 21. The first particles 23 may have an average particle size of about 7 to about 9 microns. The reflective polarizer 200 further includes a first optical diffusion layer 30 positioned to conform to a first structured main surface 21, wherein the opposing first and second main surfaces of the first optical diffusion layer 30 substantially conform to the first structured main surface 21. The first optical diffusion layer 30 may contain a plurality of nanoparticles 33 dispersed internally, the nanoparticles defining a plurality of gaps 34 between them (see, for example, Figures 4A-4B). The optical diffusion film 300 includes an optical substrate layer 110, a second optical diffusion layer 120 disposed on the optical substrate layer 110 and facing the reflective polarizer 200, and containing a plurality of nanoparticles 121 dispersed inside, and a structured optical layer 130 disposed on the optical substrate layer 110 and facing away from the reflective polarizer 200, and including a structured main surface 131 facing away from the optical substrate layer 110, and containing a plurality of spaced elongated structures 140 extending along the same first direction (e.g., x-direction) and arranged at a substantially uniform density across the structured main surface 131 of the structured optical layer 130. In some embodiments, with respect to substantially perpendicular incident light, and to the visible wavelength range of about 450 nm to about 650 nm and the infrared wavelength range of about 930 nm to about 970 nm, the second optical diffusion layer 120 has an average positive transmittance Vs in the visible wavelength range and an average positive transmittance Is in the infrared wavelength range, where Is / Vs ≥ 2.5 or any range among those described elsewhere in this specification.

[0046] In some embodiments, the optical diffusion film 300 and the reflective polarizer 200 define a gap 551 between them. In the illustrated embodiment, the gap 551 is provided by particles 53. In some embodiments, the reflective polarizer 100 may be used in place of the reflective polarizer 200 in an optical structure 400. In such embodiments, the gap 551 may not be present, or a rim tape or other separation method may be used to provide the gap. The optical diffusion film 300 and the reflective polarizer 200 may be further separated using a rim tape or other separation method.

[0047] As further described elsewhere in this specification, a display system including the optical structure 400 may also include a structured mirror. The structured mirror may include optical ridges on the optical mirror. The optical ridges can be formed, for example, by printing or high-resolution (e.g., casting and curing).

[0048] Figures 12A and 12B provide alternative embodiments of the structured mirror 700 having spaced optical ridges as described herein. Figure 12A shows the structured mirror 700 comprising an optical mirror 710 and a discontinuous layer 721 comprising an array of individual spaced optical ridges 720. In the embodiment of Figure 12A, the optical ridges 720 are spaced in an array that may be regular (e.g., rectangular, square, or hexagonal) or irregular (e.g., random or pseudo-random) and are positioned directly on the surface of the optical mirror 710. In some embodiments, the optical ridges 720 are rounded ridges that cover a certain percentage of the surface area of ​​the optical mirror 710 and contribute to wet-out resistance (and reduction of other undesirable optical effects such as Newton's rings) while maintaining substantially transmittance to at least some wavelengths of near-infrared light. In some embodiments, the surface area coverage of the optical mirror 710 may be about 10% to about 40%.

[0049] Suitable materials for optical raised surfaces 720 and 720' include, for example, OP1028 Premium Gloss HS Overprint Varnish, OP2018 Imprintable Matte UV Varnish, and 9308 UV Flexo Ink (all manufactured by Nazdar Ink Technologies (Shawnee, KS)).

[0050] Figure 12B shows an alternative embodiment of the structured mirror 700', which includes an optical mirror 710 and a continuous layer 721' featuring an optical ridge 720' separated by a substantially planar land portion 722. The embodiment in Figure 12B differs from the embodiment in Figure 12A mainly in that the continuous layer 721' and the optical ridge 720' are formed as a single component placed on the optical mirror 710, rather than having the optical ridge 720 directly placed on the optical mirror 710 (as in Figure 12A). Similar to the embodiment in Figure 12A, in some embodiments, the embodiment in Figure 12B may have an area coverage of the optical ridge 720' on the optical mirror 710 (including the land portion 722 of the continuous layer 721') of about 10% to about 40%.

[0051] In some embodiments, with respect to substantially perpendicularly incident light, the optical mirror 710 has an average light reflectance of more than about 30% (or within the range described elsewhere herein) in the visible wavelength range for at least a first polarization state, and a positive transmittance of more than about 20% (or within the range described elsewhere herein) at at least one wavelength in the infrared wavelength range for each of the first polarization state and the orthogonal second polarization state. In some embodiments, the optical protrusions 720, 720' have an average light transmittance of more than about 50%, or more than about 60%, or more than about 70% for each of the visible and infrared wavelength ranges in each of the first and second polarization states.

[0052] The relevant optical elevations are described in U.S. Provisional Simultaneous Pending Application No. 63 / 021773, filed on 8 May 2020, entitled "Optical Film with Discontinuous Coating," and are incorporated herein by reference to the extent not inconsistent with this Specified.

[0053] The optical mirror 710 may include a plurality of alternating first and second polymer layers 11 and 12 (see, for example, Figures 2A-2C), each of the first and second polymer layers having a thickness of less than about 500 nm, or less than about 350 nm, or less than about 300 nm. The optical mirror may include a single packet or multiple packets separated by a thicker intermediate layer, as further described elsewhere in this specification. In some embodiments, the optical mirror 710 includes alternating first and second dielectric layers, at least one of the first and second layers being an inorganic layer. For example, the optical mirror 710 may be a dielectric reflector. In some embodiments, the optical mirror 710 is a metal layer, or includes a metal layer.

[0054] Figures 13A and 13B are schematic plots of transmittance versus wavelength for a reflective polarizer, or an optical structure containing a reflective polarizer, or another optical element, with respect to substantially normally incident light 40 in a first polarization state (transmittance 133 in Figure 13A) and an orthogonal second polarization state (transmittance 134 in Figure 13B), respectively, according to several embodiments. In some embodiments, with respect to substantially normally incident light 40 and a given wavelength range (e.g., λ1 to λ2 and / or 450 nm to 650 nm), the reflective polarizer 100 or 200 has an average light transmittance Tp of at least about 40% in the first polarization state 171 and an average light reflectance R of at least about 70% in the orthogonal second polarization state 172. In some embodiments, the average light transmittance Tp is at least about 50%, or at least about 55%, or at least about 60%. In some embodiments, the average light reflectance R is at least about 80%, or at least about 85%, or at least about 90%. The transmittance 135 versus wavelength for light 170 incident at a certain angle of incidence θ is also schematically shown in Figure 13A. In some embodiments, in a first polarization state and a given wavelength range (e.g., the visible range from about 450 nm to about 650 nm, the infrared range from about 930 nm to about 970 nm, or the range from about 400 nm to about 800 nm), the reflecting polarizer or optical structure has a high average light transmittance (e.g., transmittance 133) for light incident at a small angle of incidence and a low average light transmittance (e.g., transmittance 135) for light incident at a large angle of incidence. The small angle of incidence can be in the range of 0 degrees to about 20 degrees, or for example, about 0 degrees. The large angle of incidence can be in the range of about 30 degrees to about 50 degrees, or for example, about 45 degrees. In some embodiments, for a given wavelength range, the reflective polarizer or optical structure has a high average light transmittance for substantially perpendicularly incident light and a low average light transmittance for light incident at an incident angle of about 45 degrees in a first (pass-through) polarization state with respect to any incident plane. In some embodiments, the difference between the high average light transmittance and the low average light transmittance is at least 10%, or at least 20%, or at least 30%.

[0055] In some embodiments, the transmittance for substantially normally incident light in the second polarization state is high for shorter wavelengths within a given wavelength range and low for longer second wavelengths within the given wavelength range. Such a sloped cutoff state transmittance can reduce, for example, color shift with respect to the viewing angle.

[0056] The average transmittance (each reflectance) is the average of the transmittances (each reflectance) over a given wavelength range. For a reflective polarizer or optical structure where absorption is negligibly small, the reflectance R is approximately 100% minus the transmittance. Transmittance 133 is the transmittance of the reflective polarizer or optical structure in the through state, and transmittance 134 is the transmittance of the reflective polarizer or optical structure in the blocked state. Alternatively, transmittance 134 can represent, for example, the total transmittance or positive transmittance of an optical mirror for any polarization state or unpolarized state. Unless otherwise indicated, transmittance and reflectance can be understood as total transmittance and total reflectance, respectively. The average transmittance Tp in the first (through) polarization state and the average transmittance Tbl in the second (blocked) polarization state (or any polarization state of the optical mirror) for substantially normally incident light 40 in the wavelength range λ1 to λ2 are shown in Figures 13A and 13B. The value of R shown is approximately the average optical reflectance for effectively perpendicularly incident light 40 within the wavelength range of λ1 to λ2.

[0057] In some embodiments, for example, λ1 may be about 400 nm or about 450 nm, and λ2 may be about 650 nm, about 700 nm, or about 800 nm. In some embodiments, for example, λ3 may be about 930 nm or about 950 nm, and λ4 may be about 1100 nm or about 970 nm.

[0058] In some embodiments, transmittance 134 represents the transmittance of the optical mirror (e.g., optical mirror 710). In some embodiments, for substantially normally incident light 40, the optical mirror has an average light reflectance R greater than 30% in the visible wavelength range of about 450 nm to about 650 nm in at least one of the first polarization states (e.g., one or both of polarization states 171 and 172). In some embodiments, the average light reflectance R is greater than 50%, or greater than 60%, or greater than 70%, or greater than 80% in the visible wavelength range in each of the first and second polarization states. In some embodiments, transmittance 134 represents the positive transmittance of the optical mirror. In some embodiments, for substantially normally incident light 40, the optical mirror has a positive transmittance greater than 20% for at least one wavelength in the infrared wavelength range of about 930 nm to about 970 nm (e.g., λ3 or λ4 or wavelengths in between) in each of the first polarization state and the orthogonal second polarization state. In some embodiments, the positive transmittance is greater than about 40%, or greater than about 50%, or greater than about 60%, or greater than about 70%, or greater than about 80% for at least one wavelength in the infrared wavelength range in each of the first and second polarization states.

[0059] Figure 14 is a schematic plot of optical transmittance 630 versus wavelength of a reflective polarizer (e.g., reflective polarizer 100 or 200) in a first (cutoff) polarization state for substantially normally incident light 40. The optical transmittance 630 has a band edge 631. In some embodiments, the best linear approximation for the band edge 631 that correlates the optical transmittance to wavelength over at least a wavelength range where the optical transmittance along the band edge increases from about 10% to at least about 70% (e.g., from about 10% to about 70%, or from about 10% to about 80%) has a slope of greater than about 2.5% / nm, greater than about 3% / nm, greater than about 3.5% / nm, greater than about 4% / nm, greater than about 4.5% / nm, or greater than about 5% / nm. In some embodiments, with respect to a first wavelength range R1 extending from a short wavelength L1 to a long wavelength L2, 30 nm ≤ L2 - L1 ≤ 50 nm, and L1 is longer than the wavelength L3 corresponding to about 50% light transmittance along the band edge 631, and within about 20 nm of L3, the light transmittance 630 has an average T1 greater than about 75%, or greater than about 80%, or greater than about 85%. In some embodiments, the reflective polarizer is used in a display system having an infrared light source configured to emit light having a first wavelength W1 toward the user's finger for fingerprint detection. In some embodiments, the first wavelength W1 is within the first wavelength range R1. W1 can be, for example, about 850 nm or about 940 nm. In some embodiments, the wavelength L3 is in the range of about 800 nm to about 1100 nm, or about 810 nm to about 840 nm, or about 900 nm to about 930 nm. For example, in some embodiments, the wavelength L3 is in the range of approximately 810 nm to approximately 840 nm and the wavelength W1 is approximately 850 nm, or the wavelength L3 is in the range of approximately 900 nm to approximately 930 nm and the wavelength W1 is approximately 940 nm.

[0060] In some embodiments, high transmittance in the first wavelength range R1 is achieved at least in part by a sharp band edge. For example, the band edge 631 may have a gradient within the range described elsewhere. Optical films with sharp band edges are known in the art and are described, for example, in U.S. Patent No. 6,967,778 (Wheatley et al.). In some embodiments, high transmittance in the first wavelength range R1 is achieved at least in part by the shape of the layer thickness profile (see, for example, Figure 15). The thicknesses of the outer layers 20 and 50 may also affect the transmission spectrum of the reflective polarizer in the first wavelength range R1 due to light reflected from the surface of the outer layers which may be subject to optical interference with light reflected from other layers. In some embodiments, each of the outer layers 20 and 50 has an average thickness in the range of, for example, about 1 micron to about 5 microns.

[0061] Figure 15 is a plot of layer thickness versus layer number in an exemplary packet of polymer layers, according to several embodiments in which the layer profile results in a sharp bandwidth edge. In some embodiments, the layer profile includes a first portion 641 having a layer thickness profile that increases substantially with a first gradient, and a second portion 642 adjacent to the first portion and having a layer thickness profile that decreases substantially with a second gradient having a magnitude substantially larger than the first gradient. The relevant optical film is described in U.S. Provisional Simultaneous Pending Application No. 63 / 021743, entitled “OPTICAL FILM,” filed on 8 May 2020.

[0062] Figure 16A is a plot of the optical transmittance 730 of a reflected polarizer for substantially normally incident light 40 having a block polarization state, according to several embodiments. Figure 16B is a portion of the plot of Figure 16A near the band edge 731. In some embodiments, the best linear approximation 132 for the band edge 731 (see, e.g., Figure 16B), which correlates the optical transmittance with wavelength over at least a wavelength range where the optical transmittance along the band edge increases from about 10% to at least about 70%, has a gradient 733 greater than about 2.5% / nm, or within any range described elsewhere for the band edge gradient (e.g., greater than about 4% / nm). Figure 16C is a portion of the plot of Figure 16A near the band edge 731, where the wavelength range R1 is close to the band edge 731. In some embodiments, for a wavelength range R1 extending from a short wavelength L1 to a long wavelength L2, 30 nm ≤ L2 - L1 ≤ 50 nm, and L1 is greater than the wavelength L3 corresponding to about 50% light transmittance along the band edge 731, and within about 20 nm from L3, the light transmittance 730 has an average of more than about 75%, or within any range described elsewhere in this specification. In the plots of Figures 16A to 16C, the reflecting polarizer did not include the optical diffusing layer 30.

[0063] Figure 17 is a plot of transmittance versus wavelength for substantially perpendicular incident light 40 for exemplary reflective polarizers (e.g., corresponding to reflective polarizer 100 or 200), where the incident light 40 was unpolarized and the reflective polarizer included an optical diffuse layer. In some embodiments, for substantially perpendicular incident light 40, the reflective polarizer has average diffuse light transmittances Tb, Tg, and Tr in the respective wavelength ranges of about 450–485 nm (wavelength range 180), about 500–565 nm (wavelength range 181), and about 625–680 nm (wavelength range 182), where 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 greater than about 1%, or greater than about 2%, respectively. In some embodiments, Tr-Tg is greater than about 3%, or greater than about 5%. In some embodiments, for substantially perpendicularly incident light 40, the total transmittance of the reflected polarizer has first and second plateau regions 183 and 184 spaced between approximately 800 and 1100 nm, with each plateau region being at least 20 nm wide. The first and second plateau regions 183 and 184 have average total transmittances P1 and P2, respectively. In some embodiments, P2 is greater than P1 by approximately 20%, 25%, 30%, or 35%. In some embodiments, the first plateau region 183 is located between 800 nm and the second plateau region 184. In some embodiments, the first plateau region 183 includes 860 nm, and the second plateau region 184 includes 950 nm.

[0064] For the reflective polarizer in Figure 17, with substantially perpendicular incidence and unpolarized 40a, and in the visible wavelength range of approximately 450 nm to approximately 650 nm, the reflective polarizer has an average total transmittance of approximately 25.27% Vt, an average diffuse transmittance of approximately 10.75% Vd, and an average positive transmittance of approximately 14.52% Vs. For the reflective polarizer in Figure 17, with substantially perpendicular incidence and unpolarized 40b, and in the infrared wavelength range of approximately 930 nm to approximately 970 nm, the reflective polarizer has an average total transmittance of approximately 86.66% It, an average diffuse transmittance of approximately 13.89% Id, and an average positive transmittance of approximately 75.77% Is.

[0065] Figure 18 is a plot of transmittance against wavelength for substantially perpendicularly incident light 40 for exemplary optical diffusion films (corresponding to, for example, optical diffusion film 300) according to several embodiments. In some embodiments, for substantially perpendicularly incident light 40 which may be unpolarized, the optical diffusion film has average diffuse light transmittances Tb, Tg, and Tr in the respective wavelength ranges of about 450 to about 485 nm (wavelength range 180), about 500 to about 565 nm (wavelength range 181), and about 625 to about 680 nm (wavelength range 182), where 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 about 2%. In some embodiments, Tb-Tr is greater than about 5% or about 10%. In some embodiments, the optical diffusion film has a diffuse light transmittance that decreases generally over the wavelength range of about 450 nm to about 970 nm (e.g., decreases monotonically or does not increase) and a normal light transmittance that increases generally over the wavelength range of about 450 nm to about 970 nm (e.g., increases monotonically or does not decrease). In some such embodiments, the total light transmittance generally increases over the wavelength range of about 450 nm to about 970 nm.

[0066] For the optical diffusion film in Figure 18, with substantially perpendicular incidence and unpolarized light 70a and a visible wavelength range of approximately 450 nm to approximately 650 nm, the optical diffusion film has an average total transmittance of approximately 76.06% Vt, an average diffuse transmittance of approximately 57.43% Vd, and an average positive transmittance of approximately 18.63% Vs. For the optical diffusion film in Figure 18, with substantially perpendicular incidence and unpolarized light 40b and an infrared wavelength range of approximately 930 nm to approximately 970 nm, the optical diffusion film has an average total transmittance of approximately 86.94% It, an average diffuse transmittance of approximately 25.69% Id, and an average positive transmittance of approximately 61.25% Is.

[0067] Figure 19 is a schematic exploded cross-sectional view of a display system 1000 for sensing a user's finger 261, applied to the display system 1000 according to several embodiments. The display system 1000 includes a display panel 370 configured to produce an image 371 for the user 260 to see, an optical waveguide 190 for providing illumination 188 to the display panel 370, an optical structure 400 positioned between the display panel 370 and the optical waveguide 190, a sensor 125 positioned in close proximity to the optical waveguide 190 on the opposite side of a reflective polarizer 200 for sensing the user's finger 261, and an infrared light source 220 configured to emit infrared light 221 toward the user's finger 261 (directly or indirectly). The sensor 125 is configured to receive at least a portion of the infrared light 222 reflected by the finger 261. A first structured main surface 21 is positioned between the display panel 370 and a plurality of polymer layers 14.

[0068] In the illustrated embodiment, the display system 1000 further includes a structured mirror 700'' positioned between the optical waveguide 190 and the sensor 125. The structured mirror 700'' may correspond to the structured mirror 700 or 700' described elsewhere. The structured mirror 700'' includes an optical mirror 710'' and an array of individual, spaced-out optical protrusions 720'' formed on the optical mirror 710'' and facing the optical waveguide 190.

[0069] In some embodiments, the optical waveguide 190 includes a light guide plate 191 and at least one light source 192 configured to emit light 193 into the light guide plate 191. In some embodiments, the light guide plate 191 extends in two orthogonal directions defining the plane of the light guide plate 191 (e.g., the xy-plane), and the light (e.g., illumination 188) exiting the light guide plate 191 generally propagates in a direction that makes an angle with respect to the plane of the light guide plate 191 in the range of about 70 degrees or about 80 to about 89 degrees. That angle can be, for example, about 85 degrees.

[0070] The infrared light source 220 may have a peak emission wavelength of, for example, about 850 nm or about 940 nm. The optical components (e.g., optical structure 400, light guide plate 191, and structured mirror 700") positioned between the finger 261 and the sensor 125 are preferably at least partially transparent to the peak emission wavelength.

[0071] The infrared light source 220 can be placed at any suitable location within the display system. For example, the infrared light source 220 can be placed adjacent to any various layers of the display system. Figures 19 to 21 schematically show various possible locations for the infrared light source. The locations of the sensing light source shown in Figures 19 to 21 are illustrative and not limiting in any sense.

[0072] Figure 20 is a schematic exploded cross-sectional view of a display system 1000' for sensing the finger 261 of a user 260, applied to the display system 1000' according to several embodiments. The display system 1000' generally corresponds to the display system 1000, except for the arrangement of the infrared light source 220'. The display system 1000' includes a cover glass 372 positioned above the display panel 370 and configured to transmit an image 371 for the user 260 to view. The infrared light source 220' is positioned below the cover glass 372.

[0073] Figure 21 is a schematic exploded cross-sectional view of a display system 1000'' for sensing the finger 261 of a user 260, applied to the display system 1000'' according to several embodiments. The display system 1000'' generally corresponds to the display system 1000 or 1000', except for the arrangement of the infrared light source 220''. The infrared light source 220'' is arranged such that a structured mirror 700'' is between the infrared light source 220'' and the optical waveguide 190.

[0074] As will be further described elsewhere in this specification, in some embodiments, the reflective polarizer 200 is a collimated reflective polarizer having a high average light transmittance for visible-pass-state light (e.g., p-polarized-pass-state light) incident at a small angle of incidence and a low average light transmittance for light incident at a large angle of incidence. Such a polarizer can provide a collimating effect by reflecting light with a large angle of incidence back toward the reflector 700'' to reuse the light. Liquid crystal displays (LCDs) often include a brightness-enhancing prism film (typically a cross-prism film) to improve the on-axial brightness of the display. In some cases, such a film can be omitted when a collimated reflective polarizer is included. In some embodiments of the display systems 1000, 1000', 1000'', no brightness-enhancing prism film is placed between the display panel 370 and the structured mirror 700''.

[0075] The relevant display system is described in U.S. Provisional Simultaneous Pending Application No. 63 / 021760, filed on 8 May 2020, entitled “DISPLAY SYSTEM WITH FINGER SENSING,” and is incorporated herein by reference to the extent not inconsistent with this specification.

[0076] Exemplary reflective polarizer Multilayer optical films (MOFs) comprising specific alternating layers of polymer materials with different refractive indices were prepared and coated with different acrylic beads during the manufacturing of the MOF films described herein. The diameter and distribution of the beads were optimized to eliminate interference fringes that appear due to multiple reflections between the MOF surface and reflective polarizing films used in display devices such as smartphones.

[0077] All parts, percentages, ratios, etc., are based on weight unless otherwise specified.

[0078] [Table 1]

[0079] Preparation of bead coating solution: First, the precursor solution WB50 was prepared as follows: 111.9 g (5.5 mol%) of 5-sodiosulfisophthalic acid, 592.1 g (47.0 mol%) of terephthalic acid, 598.4 g (47.5 mol%) of isophthalic acid, 705.8 g of ethylene glycol, 599 g of neopentyl glycol, 0.7 g of antimony oxide, and 2.5 g of sodium acetate were placed in a 1-gallon polyester kettle. The mixture was heated to 230°C for 2 hours under nitrogen at 345 kPa (50 psi) with stirring, during which the generation of water was observed. The temperature was increased to 250°C, then the pressure was reduced, a vacuum was applied (0.2 torr), and the temperature was increased to 270°C. The viscosity of the material increased over 45 minutes, after which a high molecular weight, clear, viscous sulfopolyester was discharged. This sulfopolyester was found to have a Tg of 70.3°C by DSC. The theoretical sulfonate equivalent was 3847 g of polymer per mole of sulfonate. 500 g of the polymer was dissolved at 80°C in a mixture of 2000 g of water and 450 g of isopropanol. The temperature was then raised to 95°C to remove the isopropanol (and some of the water). The final dispersion consisted of an aqueous dispersion with a solid content of 20% by weight.

[0080] The coating solution was prepared by mixing the ingredients detailed in the table below and stirring until homogeneous.

[0081] [Table 2]

[0082] reflective polarizer 1 A multilayer optical (MOF) film was manufactured using two consecutive (laminated) packets of microlayers, with 325 individual microlayers in each packet surrounded by a packet bonding layer. The microlayers within each packet were arranged as alternating layers of material A and material B. Material A was birefringent polyester PEN, and material B was a PC:PCTG and PETg blend in an 85:15 ratio. The microlayer packets were designed to have a reflectivity band spanning the visible and near-IR wavelength regions. The film was then continuously stretched transversely at a 6:1 stretch ratio on a standard tenter and constrained longitudinally (without stretching or slackening). The oven temperature used for stretching was 270°F. The process conditions for manufacturing this film were selected so that the measured spectrum matched the spectrum calculated using wavelength-dependent refractive index values, as shown in the table below. Material n x , n y , and n z The refractive indices of each element are along the x-direction (horizontal direction), the y-direction (vertical direction), and the z-direction (thickness direction). iso This is the isotropic refractive index of PC:PCTG and PETg blends.

[0083] [Table 3]

[0084] Representative spectra of the reflected polarizer 1 were measured for incident planes with an angle φ of 90 degrees, 0 degrees (perpendicular incidence), and 60 degrees with respect to the transverse direction in the s-polarized and p-polarized states, and are shown in Figure 22A. The layer thickness was measured using an atomic force microscope (Dimension ICON manufactured by Bruker Instruments (Billerica, MA)) and is shown in Figure 22B.

[0085] reflective polarizer 2 Solution A was continuously coated onto the surface of packet 1 of unstretched cast webs using a gravure roll with a reverse kiss configuration. The coated webs were then passed through a coating oven maintained at a temperature above 65°C for at least 5 seconds. The beads were observed under a microscope on unstretched cast webs that were not grouped together, and the beads appeared to be delivered to the surface of the webs at the same concentration as in the coating solution. This bead-coated cast film was stretched and drawn to obtain a bead-coated MOF as described for reflecting polarizer 1.

[0086] Using a Keyence microscope, the number of beads per unit area was counted to be approximately 175 beads / mm². 2 This was found. A representative spectrum of the reflecting polarizer 2 was measured and is shown in Figure 23.

[0087] reflective polarizer 3 Solution A was continuously coated onto the surface of packet 1 of the unstretched cast web using a gravure roll with a reverse kiss configuration. The coated web was then passed through a coating oven maintained at a temperature above 65°C for at least 5 seconds. Next, the other side of the cast web coated with solution A (the surface of packet 2) was continuously coated with solution B and dried in the same manner as with solution A. Beads were observed under a microscope on the unstretched cast webs that were not grouped together, and the beads appeared to be delivered to the surface of the web at the same concentration as in the coating solution. This bead-coated cast film was stretched and drawn to obtain a double-sided bead-coated MOF as described for reflecting polarizer 1. The number of beads per unit area was counted using a Keyence microscope and was approximately 175 beads / mm². 2 It was found that this was the case.

[0088] reflective polarizer 4 A reflective polarizer 4 was prepared that was very similar to reflective polarizer 3, except that coating solution B was replaced with coating solution C. The number of beads per unit area was counted using a Keyence microscope and was found to be approximately 182 beads / mm2. The cross-section of reflective polarizer 4 was similar to the cross-section schematically shown in Figure 3A, but without the optical diffusion layer 30. A representative spectrum of reflective polarizer 4 was measured and is shown in Figure 24.

[0089] reflective polarizer 5 The surface of a thick packet of MOF film, as described in Reflective Polarizer 4, was coated with a conformal diffuser using a slurry of silica nanoparticles in acrylic monomer dissolved in the solvent, as described below.

[0090] First, a coating precursor solution was prepared by adding 5.95 g of A-174 and 0.5 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (5% by weight; 4H-2,2,6,6-TMP1-0) to a mixture of 400 g of NALCO2329 and 450 g of 1-methoxy-2-propanol in a glass jar, stirring for 10 minutes at room temperature. The jar was sealed and placed in an oven at 80°C for 16 hours. Next, water was removed from the resulting solution using a rotary evaporator at 60°C until the solids content of the solution was close to 45% by weight. 200 g of 1-methoxy-2-propanol was added to the resulting solution, and then the remaining water was removed using a rotary evaporator at 60°C. This latter step was repeated twice to further remove water from the solution. Finally, by adding 1-methoxy-2-propanol, the total silica nanoparticle concentration was adjusted to 42.5% by weight, yielding a silica solution containing surface-modified silica nanoparticles with an average particle size of 75 nm.

[0091] Next, a coating solution was prepared. The coating solution consisted of 20.96 wt% of the above transparent precursor solution, 5.94 wt% of SR444, 71.55 wt% of isopropyl alcohol, 1.48 wt% of IRGACURE184, and 0.07 wt% of IRGACURE819. The coating solution was pumped (using a pressure pot) into a slot-type coating die at a rate that produced a wet layer thickness of 7 microns on the reflective polarizer 4.

[0092] Next, the coated substrate was passed through a UV-LED curing chamber containing a quartz window that allowed UV radiation to pass through, thereby polymerizing the coating. The UV-LED curing chamber contained a rectangular array of 160 UV-LEDs and four downwebs with 40 crosswebs (covering an area of ​​approximately 42.5 cm × 4.5 cm). The LEDs (available from Nichia Inc. (Tokyo, Japan)) operated at a nominal wavelength of 385 nm and, when operated at 10 amps, provided a UV-A dose of 0.035 joules / cm². The UV-LEDs were operated at 3 amps to fabricate the films described in this embodiment. The water-cooled UV-LED array was powered by a Lambda power supply (available from TDK-Lambda (Neptune, NJ)). The UV-LEDs were positioned above the quartz window of the curing chamber, at a distance of approximately 2.5 cm from the substrate. A nitrogen stream was supplied to the UV-LED curing chamber at a flow rate of 141.6 liters / mm. The total oxygen level in the UV-LED chamber was controlled by introducing air into a nitrogen supply source. The oxygen concentration in the UV-LED curing chamber was monitored using a Series 3000 oxygen meter (available from Alpha Omega Instruments (Cumberland, RI)).

[0093] After polymerization with UV-LED, the solvent in the cured coating was removed and the coating was dried at 66°C for 30 seconds. Next, the dried coating was post-cured using a Fusion System Model 1600 configured with a D-valve (available from Fusion UV Systems (Gaithersburg, MD)). A nitrogen stream was supplied to the UV Fusion chamber, resulting in an oxygen concentration of approximately 50 ppm. This yielded a diffuser coating film with a conformal coating of beads.

[0094] A schematic cross-section of the reflecting polarizer 5 is shown in Figure 3A. A representative spectrum of the reflecting polarizer 5 was measured and is shown in Figure 25.

[0095] exemplary optical diffusion film

[0096] [Table 4]

[0097] Sample Preparation 1 A coating precursor solution was prepared. 5.95 grams of 3-methacrylateoxypropyl-trimethoxysilane (A-174, Momentive (Waterford, NY)) and 0.5 grams of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (5% by weight; 4H-2,2,6,6-TMP1-0, Sigma Aldrich (Milwaukee, WI)) were added to a mixture of 400 grams of 75 nm diameter SiO2 sol (NALCO2329, Nalco Company (Naperville, IL)) and 450 grams of 1-methoxy-2-propanol (Sigma Aldrich (Milwaukee, WI)) in a glass jar, while stirring for 10 minutes at room temperature. The jar was sealed and placed in an oven at 80°C for 16 hours. Next, water was removed from the resulting solution using a rotary evaporator at 60°C until the solids content of the solution was close to 45% by weight. 200 grams of 1-methoxy-2-propanol were added to the resulting solution, and the remaining water was removed using a rotary evaporator at 60°C. This latter step was repeated twice to further remove water from the solution. Finally, by adding 1-methoxy-2-propanol, the total concentration of SiO2 nanoparticles was adjusted to 42.5% by weight, producing an SiO2 sol containing surface-modified SiO2 nanoparticles with an average particle size of 75 nm.

[0098] A coating solution "A" was prepared. Coating solution "A" consisted of 27.98 wt% of the above transparent precursor solution, 7.9 wt% of pentaerythritol triacrylate monomer (SR444, Sartomer), 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 into a slot-type coating die using a Viking CMD (Viking Pump, (Cedar Falls, IA)) pump at a rate that produced a wet layer thickness of 15 microns on the undercoated polyester substrate.

[0099] Next, the coated substrate was passed through a UV-LED curing chamber containing a quartz window that allowed UV radiation to pass through, thereby polymerizing the coating. The UV-LED curing chamber contained a rectangular array of UV-LEDs. The LEDs (available from Nichia Inc. (Tokyo, Japan)) operated at a nominal wavelength of 385 nm and, when operated at 10 amps, yielded a UV-A dose of 0.035 joules / cm². The UV-LEDs were operated at the currents shown in the table below. The water-cooled UV-LED array was powered by a Genesys 150-22 power supply (available from TDK-Lambda (Neptune, NJ)). The UV-LEDs were positioned above the quartz window of the curing chamber, approximately 2.5 cm from the substrate. To maintain oxygen levels below 50 ppm, a nitrogen stream was supplied to the UV-LED curing chamber at a flow rate of 22 cubic feet / min. The oxygen level inside the UV-LED curing chamber was monitored using a Series 3000 oxygen meter (available from Alpha Omega Instruments (Cumberland, RI)).

[0100] After polymerization with UV-LED, the solvent in the cured coating was removed by transporting the coated substrate to a drying oven at 150°F (66°C) for 30 minutes. Next, the dried coating was post-cured using a Fusion System Model 1600P configured with an H-valve (available from Fusion UV Systems (Gaithersburg, MD)). A nitrogen stream was supplied to the UV Fusion chamber, resulting in an oxygen concentration of approximately 50 ppm. This yielded a porous coated polyester film. Diffusers 1-6 were prepared using Sample Preparation 1.

[0101] Sample preparation 2 Coating solution "B" was prepared. Coating solution "B" consisted of 42.22 wt% of the transparent 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 IRGACURE184, and 0.01 wt% of IRGACURE819. Coating solution B was pumped into a slot-type coating die using a Viking CMD (Viking Pump (Cedar Falls, IA)) pump at a rate that produced a wet layer thickness of 20 microns on the undercoated polyester substrate, using the same process described above in Sample Preparation 1. Diffusers 7-14 were prepared using Sample Preparation 2.

[0102] Sample preparation 3 The coating solution "B" from Sample Preparation 2 was pumped into a slot-type coating die using a Viking CMD (Viking Pump (Cedar Falls, IA)) pump at a rate that produced a wet layer thickness of 7.75 microns on the undercoated polyester substrate. The coating was processed as described in Sample Preparation 1. Diffusers 15-25 were prepared using Sample Preparation 3.

[0103] Sample preparation 4 The coating solution "B" from Sample Preparation 2 was pumped into a slot-type coating die using a Viking CMD (Viking Pump, Cedar Falls, IA) pump at a rate that produced a wet layer thickness of 7 microns on the undercoated collimated multilayer optical film substrate. The coating was processed as described in Sample Preparation 1. Diffusers 26-31 were prepared using Sample Preparation 4.

[0104] Sample preparation 5 Coating solution "C" consisted of 20.96 wt% of the transparent precursor solution described in Sample Preparation 1, 5.94 wt% of pentaerythritol triacrylate monomer (SR444, Sartomer), 71.55 wt% of isopropyl alcohol, 1.48 wt% of IRGACURE 184, and 0.07 wt% of IRGACURE 819. Coating solution "C" was pumped into a slot-type coating die using a Viking CMD (Viking Pump (Cedar Falls, IA)) pump at a rate that produced a wet layer thickness of 6 microns on the undercoated collimated multilayer optical film substrate. The coating was processed as described in Sample Preparation 1. Diffusers 32-36 were prepared using Sample Preparation 5.

[0105] Test methods and results The total near-infrared transmittance and diffuse near-infrared transmittance were measured for each diffuser using a spectrometer (ULTRASCAN PRO, Humterlab (Reston, VA)). The near-infrared scattering ratio was calculated from these measurements by dividing the diffuse near-infrared transmittance by the total near-infrared transmittance. The results are shown in the table below.

[0106] [Table 5]

[0107] For each diffuser, visible transmittance (%T), haze (%H), and transparency (%C) were measured using a haze meter (Haze-gard Plus, BYK-Gardner (Columbia, MD)). The results are shown in the table below.

[0108] [Table 6]

[0109] Cross-sectional images of various diffuser samples were obtained by cutting the diffuser film using a microtome. First, the SEM cross-sectional images were converted to 8-bit using National Institute of Health ImageJ software. The target region was selected using ImageJ software. The threshold was adjusted using the software until the area of ​​the image below the threshold was approximately equal to the area below the foreground of the image. 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 porosity. The results are provided in the table below.

[0110] [Table 7]

[0111] The optical diffusion film was fabricated by forming a structured optical layer on a substrate of diffuser 2 (any of the above diffusers could be used) on the opposite side of the optical diffusion layer. The structured optical layer was generally schematically shown in Figures 5A and 5B and appeared as the structured optical layer 130 shown in Figure 7C.

[0112] The geometric shape of the structured surface was characterized by the following parameters: 1. X1: Tip radius of the feature area of ​​the structured surface (e.g., corresponding to the elongated structure 140) 2. X2: Feature density (number of features per square millimeter) 3. The height of the characteristic feature was 5 microns.

[0113] Rolls for high-resolution structures were fabricated according to the parameters in the table below.

[0114] [Table 8]

[0115] For each roll, a structured optical layer was formed on the diffuser substrate opposite the optical diffusion layer by a continuous process of high-resolution processing from the roll using a 100% solid UV-curable resin with a curing refractive index of approximately 1.5067, as shown in the table below.

[0116] [Table 9]

[0117] Terms such as "about" will be understood by those skilled in the art in the context in which they are used and described herein. Where the use of "about" applied to the size, quantity, and quantities representing the physical properties of a feature is not obvious to those skilled in the art in the context in which they are used and described herein, "about" will be understood to mean within 10 percent of a particular value. A quantity given as about a particular value may be exactly a particular value. For example, where it is not obvious to those skilled in the art in the context in which it is used and described herein, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and that value may be 1.

[0118] All references, patents, or patent applications cited above are incorporated herein by reference in their entirety. In the event of any inconsistency or contradiction between the incorporated references and this application, the information in the foregoing description shall prevail.

[0119] Descriptions of elements in the figures should be understood to apply equally to corresponding elements in other figures unless otherwise indicated. While specific embodiments are illustrated and described herein, it will be understood by those skilled in the art that these specific embodiments may be replaced by various alternative and / or equivalent embodiments without departing from the scope of this disclosure. This application is intended to encompass any adaptation, modification, or combination of any specific embodiment discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents. The following are exemplary embodiments. [Item 1] A reflective polarizer A plurality of polymer layers, totaling at least 50, co-extruded with a first outer layer, wherein the first outer layer comprises a plurality of first particles having an average particle size of about 7 to about 9 microns and partially protruding from a first main surface to form a first structured main surface, A first optical diffusion layer disposed to conform to the first structured main surface, wherein the opposing first and second main surfaces of the first optical diffusion layer substantially conform to the first structured main surface, and the first optical diffusion layer includes a plurality of nanoparticles dispersed therein, the nanoparticles defining a plurality of gaps therebetween, A reflective polarizer, An optical diffusion film disposed on the reflective polarizer, Optical substrate layer, A second optical diffusion layer disposed on the optical substrate layer, facing the reflective polarizer, and containing a plurality of nanoparticles dispersed internally, wherein, with respect to substantially perpendicular incident light, and the visible wavelength range of approximately 450 nm to approximately 650 nm and the infrared wavelength range of approximately 930 nm to approximately 970 nm, the second optical diffusion layer has an average positive transmittance Vs in the visible wavelength range and an average positive transmittance Is in the infrared wavelength range, and Is / Vs ≥ 2.5, and A structured optical layer disposed on the optical substrate layer, having a structured principal surface facing away from the reflective polarizer and away from the optical substrate layer, comprising a plurality of spaced elongated structures extending along the same first direction and arranged at a substantially uniform density across the structured principal surface of the structured optical layer, An optical diffusion film including, An optical structure equipped with [the necessary components]. [Item 2] The optical structure according to item 1, wherein the optical substrate layer has an average positive transmittance of more than 70% in each of the visible and infrared wavelength ranges for substantially perpendicular incident light and each of the first and second polarization states which are orthogonal to each other. [Item 3] The optical structure according to item 1 or 2, wherein the reflective polarizer further includes a second outer layer on the opposite side of the first outer layer, the second outer layer being co-extruded with the plurality of polymer layers and the first outer layer, and the second outer layer forming a second structured main surface comprising a plurality of second particles partially protruding from the second main surface. [Item 4] In the plane of the cross-section of the first optical diffusion layer in the thickness direction of the first optical diffusion layer, The nanoparticles in the first optical diffusion layer have an average particle size of about 20 nm to about 150 nm. The gap occupies approximately 5% to approximately 50% of the area of ​​the plane of the cross-section. An optical structure described in any one of items 1 to 3. [Item 5] The optical structure according to any one of items 1 to 4, wherein the second optical diffusion layer further comprises a polymer material that binds the nanoparticles of the second optical diffusion layer to each other, forming a plurality of nanoparticle aggregates that define a plurality of gaps between them. [Item 6] An optical structure according to any one of items 1 to 5, wherein each elongated structure includes a peak, is parallel to the first direction, and in the plane of the cross-section of the elongated structure including the peak, the elongated structure has a height variation of less than 5% over a substantially flat upper region having a length La and a length d, such that d / La ≥ 0.05. [Item 7] The optical structure according to any one of items 1 to 6, wherein the elongated structure has an average length along the first direction and an average width along the second direction perpendicular to it, and the average length is at least about twice the average width. [Item 8] An optical structure according to any one of items 1 to 7, wherein, with respect to substantially normally incident light and a predetermined wavelength range, the reflecting polarizer has an average light transmittance of at least about 40% for a first polarization state and an average light reflectance of at least about 70% for a second orthogonal polarization state. [Item 9] The optical structure according to item 8, wherein, in the first polarization state and the predetermined wavelength range, the reflective polarizer has a higher average light transmittance for light incident at a smaller angle of incidence and a lower average light transmittance for light incident at a larger angle of incidence. [Item 10] The optical structure according to any one of items 1 to 9, wherein the reflective polarizer is located on the opposite side of the first outer layer and further comprises the plurality of polymer layers and a second outer layer co-extruded with the first outer layer, the plurality of polymer layers comprising a plurality of first polymer layers disposed between the first outer layer and the second outer layer and separated from the plurality of second polymer layers along the thickness direction of the reflective polarizer by one or more intermediate layers, each of the plurality of first and second polymer layers totaling at least 100, each of the first and second polymer layers having an average thickness of less than about 350 nm, and each of the one or more intermediate layers having an average thickness of more than about 500 nm. [Item 11] The optical structure according to item 10, wherein the minimum distance between the first outer layer and the one or more intermediate layers is S1, the minimum distance between the second outer layer and the one or more intermediate layers is S2, and S1 > S2. [Item 12] The optical structure according to any one of items 1 to 9, wherein the reflective polarizer is located on the opposite side of the first outer layer and further comprises the plurality of polymer layers and a second outer layer co-extruded with the first outer layer, and the reflective polarizer comprises a single packet of the polymer layers disposed between the first outer layer and the second outer layer, and each layer between the first outer layer and the second outer layer has an average thickness of less than about 350 nm. [Item 13] For substantially perpendicularly incident light, the light transmittance of the reflected polarizer with respect to wavelength in the first polarization state includes the band edge, The best linear approximation to the band edge that correlates the light transmittance with the wavelength over at least a wavelength range in which the light transmittance along the band edge increases from about 10% to about 70% has a gradient greater than about 2.5% / nm. An optical structure according to any one of items 1 to 12, wherein, for a first wavelength range extending from a short wavelength L1 to a long wavelength L2, 30 nm ≤ L2 - L1 ≤ 50 nm, and when L1 is longer than the wavelength L3 corresponding to about 50% light transmittance along the edge of the band and within about 20 nm from L3, the light transmittance has an average of more than about 75%. [Item 14] A display system for sensing a user's finger, applied to a display system, A display panel configured to generate an image for the user to view, An optical waveguide for providing illumination to the aforementioned display panel, An optical structure according to any one of items 1 to 13, disposed between the display panel and the optical waveguide, wherein the first structured main surface is disposed between the display panel and the plurality of polymer layers, A sensor for sensing the user's finger is positioned in close proximity to the optical waveguide on the opposite side of the reflective polarizer. An infrared light source configured to emit infrared light toward the user's finger, wherein the sensor is configured to receive at least a portion of the infrared light reflected by the finger, A display system equipped with these features. [Item 15] The display system according to item 14, further comprising a structured mirror disposed between the optical waveguide and the sensor, the structured mirror comprising an optical mirror and an array of separate, spaced optical protrusions formed on the optical mirror and facing the optical waveguide, wherein, with respect to substantially normally incident light, the optical mirror has an average optical reflectance of more than 30% in the visible wavelength range in at least a first polarization state, and a positive transmittance of more than 20% for at least one wavelength in the infrared wavelength range for each of the first polarization state and the orthogonal second polarization state.

Claims

1. A reflective polarizer A plurality of polymer layers, totaling at least 50, co-extruded with a first outer layer, wherein the first outer layer comprises a plurality of first particles having an average particle size of 7 to 9 microns and partially protruding from a first main surface to form a first structured main surface, A first optical diffusion layer disposed to conform to the first structured main surface, wherein the opposing first and second main surfaces of the first optical diffusion layer substantially conform to the first structured main surface, and the first optical diffusion layer includes a plurality of nanoparticles dispersed therein, the nanoparticles defining a plurality of voids between them, A reflective polarizer, An optical diffusion film disposed on the reflective polarizer, Optical substrate layer, A second optical diffusion layer disposed on the optical substrate layer, facing the reflective polarizer, and containing a plurality of nanoparticles dispersed therein, wherein the second optical diffusion layer contains a polymer material, the polymer material of the second optical diffusion layer binds the plurality of nanoparticles contained in the second optical diffusion layer to each other to form a plurality of nanoparticle aggregates, the plurality of nanoparticle aggregates contained in the second optical diffusion layer define voids between them, the average particle size of the plurality of nanoparticle aggregates contained in the second optical diffusion layer is 100 nm to 10 microns, and with respect to substantially perpendicular incident light, and the visible wavelength range of 450 nm to 650 nm and the infrared wavelength range of 930 nm to 970 nm, the second optical diffusion layer has an average positive transmittance Vs in the visible wavelength range and an average positive transmittance Is in the infrared wavelength range, and Is / Vs ≥ 2.5, A structured optical layer disposed on the optical substrate layer, having a structured main surface facing away from the reflective polarizer and away from the optical substrate layer, comprising a plurality of spaced elongated structures extending along the same first direction and arranged at a substantially uniform density across the structured main surface of the structured optical layer, An optical diffusion film including, An optical structure equipped with [the necessary components].

2. The optical structure according to claim 1, wherein the optical substrate layer has an average positive transmittance of more than 70% in each of the visible and infrared wavelength ranges for substantially normally incident light and each of the first and second polarization states which are orthogonal to each other.

3. The optical structure according to claim 1, wherein the reflective polarizer further includes a second outer layer on the opposite side of the first outer layer, the second outer layer is co-extruded with the plurality of polymer layers and the first outer layer, and the second outer layer includes a plurality of second particles that partially protrude from the second main surface to form a second structured main surface.

4. In the plane of the cross-section of the first optical diffusion layer in the thickness direction of the first optical diffusion layer, The nanoparticles in the first optical diffusion layer have an average particle size of 20 nm to 150 nm. The aforementioned void occupies 5% to 50% of the area of ​​the plane of the cross-section. The optical structure according to claim 1.

5. The optical structure according to claim 1, wherein the first optical diffusion layer comprises a polymer material, the polymer material of the first optical diffusion layer binds the plurality of nanoparticles contained in the first optical diffusion layer to each other to form a plurality of nanoparticle aggregates, the plurality of nanoparticle aggregates contained in the first optical diffusion layer define voids between them, and the average particle size of the plurality of nanoparticle aggregates contained in the first optical diffusion layer is 100 nm to 10 microns.

6. The optical structure according to claim 1, wherein each elongated structure includes a peak, is parallel to the first direction, and in the plane of the cross-section of the elongated structure including the peak, the elongated structure has a substantially flat upper region such that the height variation of the elongated structure is less than 5% over that region, and when the total length of the elongated structure is La and the length of the substantially flat upper region is d, d / La ≥ 0.

05.

7. The optical structure according to claim 1, wherein the elongated structure has an average length along the first direction and an average width along the second direction perpendicular to it, and the average length is at least twice the average width.

8. The optical structure according to claim 1, wherein, with respect to substantially normally incident light and a predetermined wavelength range, the reflecting polarizer has an average light transmittance of at least 40% for a first polarization state and an average light reflectance of at least 70% for a second orthogonal polarization state.

9. The optical structure according to claim 8, wherein, in the first polarization state and the predetermined wavelength range, the reflective polarizer has a higher average light transmittance for light incident at a smaller angle of incidence and a lower average light transmittance for light incident at a larger angle of incidence.

10. The optical structure according to claim 1, wherein the reflective polarizer is located on the opposite side of the first outer layer and further comprises the plurality of polymer layers and a second outer layer co-extruded with the first outer layer, the plurality of polymer layers comprising a plurality of first polymer layers disposed between the first outer layer and the second outer layer and separated from the plurality of second polymer layers along the thickness direction of the reflective polarizer by one or more intermediate layers, each of the plurality of first and second polymer layers totals at least 100, each of the first and second polymer layers has an average thickness of less than 350 nm, and each of the one or more intermediate layers has an average thickness of more than 500 nm.

11. The optical structure according to claim 10, wherein the minimum distance between the first outer layer and the one or more intermediate layers is S1, the minimum distance between the second outer layer and the one or more intermediate layers is S2, and S1 > S2.

12. The optical structure according to claim 1, wherein the reflective polarizer is located on the opposite side of the first outer layer and further comprises the plurality of polymer layers and a second outer layer co-extruded with the first outer layer, and the reflective polarizer comprises a single packet of the polymer layers disposed between the first outer layer and the second outer layer, and each layer between the first outer layer and the second outer layer has an average thickness of less than 350 nm.

13. For substantially perpendicularly incident light, the light transmittance of the reflected polarizer with respect to wavelength in the first polarization state includes the band edge, The best linear approximation to the band edge that correlates the light transmittance with the wavelength over at least the wavelength range in which the light transmittance along the band edge increases from 10% to 70% has a gradient greater than 2.5% / nm. The optical structure according to claim 1, wherein, for a first wavelength range extending from a short wavelength L1 to a long wavelength L2, 30 nm ≤ L2 - L1 ≤ 50 nm, and when L1 is longer than the wavelength L3 corresponding to 50% light transmittance along the edge of the band and within 20 nm from L3, the light transmittance has an average of more than 75%.

14. A display system for sensing a user's finger, applied to a display system, A display panel configured to generate an image for the user to view, An optical waveguide for providing illumination to the display panel, An optical structure according to any one of claims 1 to 13, disposed between the display panel and the optical waveguide, wherein the first structured main surface is disposed between the display panel and the plurality of polymer layers, A sensor for sensing the user's finger is positioned in close proximity to the optical waveguide on the opposite side of the reflective polarizer. An infrared light source configured to emit infrared light toward the user's finger, wherein the sensor is configured to receive at least a portion of the infrared light reflected by the finger, A display system equipped with these features.

15. The display system according to claim 14, further comprising a structured mirror disposed between the optical waveguide and the sensor, the structured mirror comprising an optical mirror and an array of separate, spaced optical protrusions formed on the optical mirror and facing the optical waveguide, wherein, with respect to substantially normally incident light, the optical mirror has an average light reflectance of more than 30% in the visible wavelength range in at least a first polarization state, and a positive transmittance of more than 20% for at least one wavelength in the infrared wavelength range for each of the first polarization state and the orthogonal second polarization state.

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