Integral multilayer optical film

Abstract

An integral multilayer optical film includes a plurality of interference layers, a structured layer disposed on the interference layers and including a plurality of particles dispersed in a binder, and a barrier layer disposed between the structured layer and the interference layers and co-extruded with the interference layers and the structured layer. The structured layer has a first major surface facing away from the interference layers and a second major surface facing the interference layers. The barrier layer causes the particles to impart a greater surface roughness to the first major surface than to the second major surface, such that when the optical film is illuminated with a light source, the optical film has a first average effective transmittance T1 when the first major surface faces the light source and a second average effective transmittance T2 when the first major surface faces away from the light source, where T1 - T2 ≥ 5%.

Description

Background Technology

[0001] Optical films may include reflective polarizers and beaded layers coated on the reflective polarizers. Summary of the Invention

[0002] This disclosure generally relates to optical films comprising a structured layer co-extruded with at least one other layer.

[0003] In some aspects of this disclosure, an integral multilayer optical film is provided, comprising a plurality of polymer interference layers, a structured layer disposed on the interference layers, and a barrier layer disposed between the structured layer and the interference layers and co-extruded with at least the interference layers and the structured layer. The plurality of polymer interference layers may total at least 30, and for at least one wavelength in a wavelength range extending from about 400 nm to about 1500 nm, reflect and transmit light primarily by optical interference. The structured layer is disposed on the interference layers and includes a plurality of particles dispersed in a binder and opposing first and second main surfaces. The first main surface faces away from the interference layers, and the second main surface faces the interference layers. The barrier layer causes the particles to impart a larger surface roughness to the first main surface than to the second main surface, such that when the optical film is illuminated by a light source, the optical film has a first average effective transmittance T1 when the first main surface faces the light source, and a second average effective transmittance T2 when the first main surface faces away from the light source, wherein T1-T2≥5%.

[0004] In some aspects of this disclosure, a monolithic multilayer optical film is provided, comprising a plurality of stacked polymer layers and a structured layer disposed on the polymer layers. The plurality of stacked polymer layers may total at least 30. Each polymer layer has an average thickness of less than about 500 nm. The structured layer comprises a plurality of particles dispersed in a binder and has a first main surface facing away from the polymer layers and comprising a plurality of structures formed by the particles. The structured layer is co-extruded and co-stretched with the polymer layers such that, for each of the plurality of particles, the particle is disposed in a corresponding void elongated along a first direction.

[0005] In some aspects of this disclosure, a monolithic multilayer optical film is provided, comprising a strain-curing polymer layer having an average thickness greater than about 1 micrometer, and a structured layer disposed on and co-extruded with the strain-curing polymer layer. The structured layer comprises a plurality of particles dispersed in a thermoplastic binder and has a first main surface facing away from the strain-curing polymer layer and comprising a plurality of structures formed by the particles. When the optical film is irradiated with a light source, the optical film has a first average effective transmittance T1 when the first main surface faces the light source and a second average effective transmittance T2 when the first main surface faces away from the light source, wherein T1-T2 ≥ 5%.

[0006] These and other aspects will become apparent from the detailed description that follows. However, in no way should this brief overview be construed as limiting the subject matter for which protection can be claimed. Attached Figure Description

[0007] Figures 1 to 2 This is a schematic cross-sectional view illustrating an integral multilayer optical film.

[0008] Figure 3 It is an illustrative schematic cross-sectional view of multiple layers.

[0009] Figure 4 This is a schematic top view illustrating an integrated multilayer optical film.

[0010] Figure 5 This is a schematic cross-sectional view of an illustrative integrated multilayer optical film, which schematically shows the voids.

[0011] Figure 6 This is a schematic cross-sectional view illustrating an integral multilayer optical film.

[0012] Figure 7 This is a schematic top-down plan view of an example layer.

[0013] Figure 8A It is an image of the cross-section of the optical film.

[0014] Figure 8B yes Figure 8A A top-view image of the optical film.

[0015] Figure 9A This is an image of a cross-section of another type of optical film.

[0016] Figure 9B yes Figure 9A A top-view image of the optical film.

[0017] Figure 10A This is an image of a cross-section of an exemplary integrated multilayer optical film.

[0018] Figure 10B yes Figure 10A A top-view image of the optical film.

[0019] Figure 11A This is an image of a cross-section of another exemplary integrated multilayer optical film.

[0020] Figure 11B yes Figure 11A A top-view image of the optical film. Detailed Implementation

[0021] Reference is made in the following description to the accompanying drawings, which form part of the invention and illustrate various embodiments by way of example. The drawings are not necessarily drawn to scale. It should be understood that other embodiments may be conceived and practiced without departing from the scope or spirit of this specification. Therefore, the following detailed description should not be considered limiting.

[0022] In many consumer electronics displays, it is desirable to have uniform light projection toward the viewer. This can be achieved using a volumetric diffuser film with high haze that allows visible light scattering. This scattering of visible light allows for better uniformity but can also reduce effective brightness. To prevent a decrease in brightness, or even to improve on-axis brightness, while maintaining high haze, a beaded surface can be coated onto a substrate. The resulting film is commonly referred to as a beaded gain diffuser. Beaded gain diffusers are known in the art and are described, for example, in U.S. Patent Application Publication 2008 / 0002256 (Sasagawa et al.).

[0023] Beaded gain diffusers are typically coated in a second step after the preparation of the base film. Beads are contained within a beaded layer, which is typically also a structured layer with a structured master surface. Preferably, the beads in the beaded gain diffuser at least roughly approximate hemispheres on the surface of the beaded layer. Previous attempts to co-extrude and optionally co-stretch layers containing micron-sized beads at high loadings in a binder have resulted in low bead uniformity and / or bead aggregation, resulting in relatively few beads approximating hemispheres on the surface of the beaded layer. The uniformity of the approximately hemispherical protrusions of the beads can be characterized by the difference in the effective transmittance of the film for light incident on the structured surface of the beaded layer and light incident on the opposite surface. A portion of the light incident on the surface opposite to the structured surface is reflected back through the film at the bead surface, resulting in a reduction in effective transmittance. Therefore, the difference in effective transmittance characterizes the uniformity of the approximately hemispherical protrusions of the beads. According to some embodiments, the optical film described herein can provide a much higher effective transmittance difference than that produced by previous attempts to co-extrude / co-stretch layers containing micron-sized particles, such as beads or other particles.

[0024] Effective transmittance refers to the light transmittance of incident light that is approximately perpendicular to the polarization. Unless otherwise specified, incident light can be understood as unpolarized light. Average effective transmittance is the effective transmittance measured or averaged over substantially the entire area of ​​the optical film, or over a sufficiently large area (e.g., at least about 0.5 mm, or at least about 1 mm, or at least about 5 mm in diameter) to average out the effects of local inhomogeneities (e.g., particle aggregation). Average effective transmittance can be determined as light transmittance according to ASTM D1003-13. As shown in the ASTM D1003-13 test standard, light transmittance is based on the 1987 International Commission on Illumination (Commission Internationale de l'... The transmittance is the weighted transmittance of the CIE spectral luminous efficiency function V(). Haze can also be determined according to the ASTM D1003-13 test standard. This test standard describes the measurement of haze using a haze meter purchased from BYK-Gardner. The haze meter can also be used to measure transparency (e.g., using the test method described in the BYK-Gardner HAZE-GARD haze meter manual). In some embodiments, the optical film has a haze greater than about 85% or greater than about 90%. In some such embodiments, or in other embodiments, the optical film has a transparency less than about 35% or less than about 30%. Unless otherwise stated, haze and transparency are measured with the structured surface facing the light source.

[0025] According to some embodiments of this disclosure, it has been found that when a barrier layer or strain-hardening layer is disposed between a structured layer (e.g., a beaded layer) and a lower layer, a high-load particle (e.g., beads or other particles that may be microspheres) can be co-extruded and co-stretched with the lower layer. The barrier layer or strain-hardening layer prevents particles from becoming trapped in the lower layer and / or can push particles out of the plane of the structured layer in a direction away from the lower layer to create a structured surface. Furthermore, it has been found that, according to some embodiments, for example, co-extruded a protective layer on the beaded layer can prevent particle release during high-temperature processes. In some embodiments, the protective layer is co-extruded with the structured layer and other layers and then removed. In some embodiments, the protective layer is co-extruded, co-stretched, and then removed. In some embodiments, the protective layer is co-extruded, co-stretched, and kept in contact with the structured layer to facilitate downstream processes prior to web processing, roll forming, and / or removal. In some embodiments, the protective layer imparts additional robustness and / or cleanliness to downstream processes.

[0026] Figure 1This is a schematic cross-sectional view of an exemplary integral multilayer optical film 100 according to some embodiments. In the illustrated embodiment, the optical film 100 includes layers 110, 120, and 130. Layer 110 may be a plurality of polymer interference layers, a plurality of stacked polymer layers, and / or may include at least one layer with a birefringence greater than about 0.1. Layer 130 is a structured layer having a first primary surface 136 and a second primary surface 138. Layer 120 may be a barrier layer and / or a strain-hardening layer included such that particles 132 impart a greater surface roughness Ra to the first primary surface 136 than to the second primary surface 138. Layers 110, 120, and 130 may be integrally formed (manufactured together, rather than separately and subsequently bonded).

[0027] In some embodiments, layer 110 is a plurality of polymer interference layers, totaling at least 30, and reflects and transmits light primarily by optical interference for at least one wavelength in a wavelength range extending from about 400 nm to about 1500 nm. Layer 130 is a structured layer disposed on interference layer 110 and comprising a plurality of particles 132 dispersed in binder 134 and having opposing first principal surfaces 136 and second principal surfaces 138, wherein the first principal surface 136 faces away from interference layer 110 and the second principal surface 138 faces interference layer 110. Layer 120 may be a barrier layer disposed between structured layer 130 and interference layer 110, and is at least co-extruded with interference layer 110 and structured layer 130. The barrier layer 120 allows the particles 132 to impart a larger surface roughness Ra to the first main surface 136 than to the second main surface 138, such that when the optical film 100 is illuminated by the light source 151 or 152, the optical film 100 has a first average effective transmittance T1 when the first main surface 136 faces the light source 151, and a second average effective transmittance T2 when the first main surface 136 faces away from the light source 152. In some embodiments, T1-T2 ≥ 5%, or T1-T2 ≥ 6%, or T1-T2 ≥ 8%, T1-T2 ≥ 10%, or T1-T2 ≥ 12%, or T1-T2 ≥ 14%. When the integrated optical film is used in a liquid crystal display, a higher T1-T2 generally results in higher gain. Suitable materials for the barrier layer 120 include strain-curing polymers, such as, for example, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) or copolymers thereof. Suitable copolymers that can be used for barrier layer 120 are described, for example, in U.S. Patent 8,012,571 (Liu et al.) and U.S. Patent Application Publication 2019 / 0391311 (Nevitt et al.), and include, for example, PETg (diol-modified PET), PENg (diol-modified PEN) and PHEN (a naphthalene-based copolyester containing 10 mol% to 15 mol% hexanediol instead of ethylene glycol).

[0028] When the reflectivity and transmittance of the interferometer layer can be reasonably described by optical interference, or when the reflectivity and transmittance of the interferometer layer can be reasonably and accurately modeled as a result of optical interference, the interferometer layer can be described as reflecting or transmitting light primarily through optical interference. The interferometer layer may have an average thickness, for example, less than about 500 nm or less than about 300 nm.

[0029] In some embodiments, binder 134 is a thermoplastic binder. In some embodiments, binder 134 comprises polymethyl methacrylate copolymer and polylactic acid. Polylactic acid may be included to lower the glass transition temperature of the binder. It has been found that, according to some embodiments, binders with lower glass transition temperatures result in improved layer elongation, for example, at lower temperatures and / or higher tensile rates. In some embodiments, the thermoplastic binder has lower crystallinity than the barrier layer. In some embodiments, the thermoplastic material has a lower melting point than the barrier layer. In some embodiments, the binder comprises copolyester PET (e.g., EASTAR copolyester GN071, available from Eastman Chemical Company). Copolyester PET has a lower Tg, crystallinity, and melting point than, for example, coPEN90 / 10 (a PEN in which 10% of the carboxylate ester units are replaced by terephthalate ester units), which is a material that can be used for barrier layers and high-refractive-index optical layers. CoPEN90 / 10 may also be referred to as low-melting-point PEN or LMPEN. In some embodiments, the binder comprises a plasticizer (e.g., 1% to 10% by weight). Suitable plasticizers include those from Segetis, Inc., Golden Valley, MN, USA, traded under the name SEGETIS (e.g., levulinic acid-ketal plasticizer), and those from Hallstar, Chicago, IL, USA, traded under the name HALLGREEN. The binder may also comprise a bead-binder compatibilizer (e.g., 1% to 10% by weight). Suitable compatibilizers include styrene-maleic anhydride. It has been found that the inclusion of a plasticizer and / or a compatibilizer can provide a better bead arrangement during orientation, resulting in increased T1-T2.

[0030] In some embodiments, particle 132 is or comprises a polymer. For example, particle 132 may be formed from a crosslinkable polymer. In some embodiments, the polymer comprises polymethyl methacrylate or polystyrene.

[0031] In some embodiments, particles 132 have an average diameter ranging from about 3 micrometers or about 5 micrometers to about 20 micrometers or about 15 micrometers or about 10 micrometers. For example, in some embodiments, the average diameter ranges from about 5 micrometers to about 20 micrometers. The average diameter may be taken as the median diameter (the median diameter in the volumetric particle size distribution), which may be determined, for example, by laser diffraction. In some embodiments, the particles are substantially monodisperse. In some embodiments, particles 132 are substantially spherical (e.g., particles 132 may be microspheres, such as polymer microspheres). A particle may be considered substantially spherical if the profile of the particle lies within an intermediate space between two concentric, truly spherical profiles, the diameters of which differ by less than 50% of the diameter of the larger of these profiles. In some embodiments, at least a majority of each particle in particles 132 lies within an intermediate space between two concentric, truly spherical profiles, the diameters of which differ by up to about 30%, or up to about 20%, or up to about 10% of the diameter of the larger of these profiles.

[0032] In some embodiments, particles 132 have a refractive index greater than about 1.45. Alternatively or additionally, in some embodiments, binder 134 has a refractive index greater than about 1.45. In some embodiments, the refractive indices of the particles and binder are each in the range of about 1.45 to about 1.8. Unless otherwise specified, the refractive index is understood to be measured at a wavelength of 633 nm. In some embodiments, the absolute value of the difference between the refractive indices of particles 132 and binder 134 is less than about 0.2, or less than about 0.15, or less than about 0.1.

[0033] In some embodiments, the first primary surface 136 of the structured layer 130 has a surface roughness Ra (the average value of the displacement of the surface from the average plane) in the range of 0.5 micrometers to 20 micrometers or 1 micrometer to 10 micrometers. The surface roughness Ra can be determined by surface profilometry methods known in the art. The surface roughness Ra can be determined according to, for example, the ISO 4287:1997 standard.

[0034] In some embodiments, layer 120 has a glass transition temperature Tg1, and binder 134 has a glass transition temperature Tg2, wherein Tg1 > Tg2. In some such embodiments or in others, layer 120 has an average thickness h greater than about 1 micrometer. In some such embodiments or in others, layer 120 is or comprises a strain-hardening polymer. In some embodiments, Tg1-Tg2 is greater than about 5°C, or greater than about 10°C, or greater than about 20°C, or greater than about 30°C. In some embodiments, the optical film is stretched and / or thermally stabilized at temperatures, for example, above Tg1 and / or above Tg2 + 30°C. In some cases, increasing the stretching and / or thermal stabilization temperature (e.g., increasing it to at least Tg2 + 30°C, but below the melting point of layer 120) can reduce the agglomeration of beads in the structured layer.

[0035] Figure 2 This is a schematic cross-sectional view of an exemplary integrated multilayer optical film 200 according to some embodiments, which may correspond to optical film 100, except that optical film 200 includes layer 140 and a substrate or layer 150. Figure 2 The illustrated embodiment includes both layers 140 and 150. In other embodiments, one or both of these layers may be omitted.

[0036] In some embodiments, the integrated multilayer optical film 200 includes a protective polymer layer 140 disposed on the structured layer 130 opposite to the polymer layer 110. In some embodiments, the protective layer 140 is co-extruded and co-stretched with the structured layer 130 and the polymer layer 110. In some embodiments, the protective layer 140 is co-extruded and optionally co-stretched with the structured layer 130 and the polymer layer 110, and then removed. The protective layer 140 may be removed after co-extrusion but before stretching, or it may be removed after stretching. The protective layer 140 may be included within the film to protect and / or stabilize the layer 130 during film manufacturing and subsequent processing of the film before final application.

[0037] In some embodiments, the optical film 200 further includes a polymer substrate 150, wherein layer 110 is disposed between the polymer substrate 150 and the structured layer 130. The substrate 150 may have an average thickness H greater than, for example, about 10 micrometers. The substrate 150 may be a structured layer to improve the overall strength of the film (e.g., tensile strength). In some embodiments, the integral multilayer optical film 200 further includes a bead layer or granular layer opposite to layer 110 on the substrate layer 150 for slip control. The bead layer or granular layer for slip control may be co-extruded and co-stretched with the structured layer 130 and the polymer layer 110. Slip control layers are described, for example, in U.S. Patent Application Publication 2015 / 0226883 (Derks et al.).

[0038] Figure 3 This is a schematic cross-sectional view of an exemplary plurality of layers 115 (e.g., stacked polymer layers and / or polymer interference layers) corresponding to layer 110 according to some embodiments. In some embodiments, layer 115 includes alternating first polymer layers 111 and second polymer layers 112, which provide desired reflection of light 30 incident substantially perpendicularly (e.g., within 20 degrees, or within 10 degrees, or within 5 degrees, or perpendicularly incident) in the wavelength range λ1 to λ2. As is known in the art, multilayer optical films comprising alternating polymer layers can be used to provide desired reflection and transmission in a desired wavelength range by appropriately selecting the layer thickness. Multilayer optical films and methods of manufacturing multilayer optical films are described, for example, in U.S. Patents 5,882,774 (Jonza et al.); 6,179,948 (Merrill et al.); 6,783,349 (Neavin et al.); 6,967,778 (Wheatley et al.); and 9,162,406 (Neavin et al.). In some embodiments, each of the first and second layers has an average thickness of less than about 500 nm or less than about 300 nm. Additional layers, such as surface layers or protective interface layers, may be included in the multilayer optical film, as is known in the art. Each additional layer may have a thickness greater than about 1 micrometer or greater than about 3 micrometers. A portion 31 of light 30 is transmitted, and a portion 32 of light is reflected. In some embodiments, the integral multilayer optical film 100 or 200, or the plurality of layers 115, is a reflective polarizer. The transmitting portion 31 may be primarily used for a first polarization state (e.g., polarized along the x-axis), while the reflecting portion 32 may be primarily used for an orthogonal second polarization state (e.g., polarized along the y-axis). The wavelength λ1 may be about 400 nm, and the wavelength λ2 may be about 1500 nm. In some embodiments, layer 115 is a plurality of polymer interference layers, totaling at least 30, and for at least one wavelength λ in a wavelength range extending from about 400 nm to about 1500 nm, light is reflected and transmitted primarily by optical interference.

[0039] Figure 4 This is a schematic top view of an exemplary monolithic multilayer optical film 300 according to some embodiments, which may correspond to, for example, optical films 100 or 200. In some embodiments, the monolithic multilayer optical film 100, 200, or 300 comprises a plurality of stacked polymer layers 110 totaling at least 30, wherein each polymer layer has an average thickness t of less than about 500 nm (see, for example...). Figure 3The structured layer 130 is disposed on the polymer layer 110. The structured layer 130 comprises a plurality of particles 132 dispersed in the binder 134 and has a first main surface 136 facing away from the polymer layer 110 and comprising a plurality of structures 137 formed of the particles. In some embodiments, the structured layer 130 is co-extruded and co-stretched with the polymer layer 110 such that for each of the sub-particles (e.g., 132a, 132b) (e.g., 132a), the particle is disposed in a corresponding void 213 extending along a first direction 215. The sub-particles in the plurality of particles are at least two particles, but fewer than all particles. The sub-particles may comprise, for example, less than about 10%, or less than about 5%, or less than about 3% of the particles in the plurality of particles. Figure 5 It is a schematic cross-sectional view through particle 132 according to some embodiments, which schematically shows void 213.

[0040] In some implementations, the optical defect density generated by the voids 213 in the planar view of the structured layer 130 is less than about 0.3 / mm. 2 or less than approximately 0.2 / mm 2 or less than approximately 0.15 / mm 2 or less than approximately 0.12 / mm 2 or less than approximately 0.1 / mm 2 When the gap 213 is large enough to substantially scatter light, an optical defect is formed at the particle set in the gap 213. Figure 4 Two optical defects are schematically shown. Optical defects caused by voids can be observed and counted in a top-view optical microscopic image of the structured layer. The structured layer can be planarized, for example, by coating with a UV-curable resin and curing the coating. Other suitable coatings may optionally be used. Planarizing the structured layer in this way can make voids visible or more easily visible in the microscopic image. The coating can be matched to the refractive index of the structured surface to improve the visibility of voids. It has been found that thermal stabilization or heat setting of the film after co-extrusion and co-stretching can reduce the density of optical defects caused by voids 213.

[0041] In some embodiments, as further described elsewhere, the integral multilayer optical film 300 also includes a layer 120 disposed between the structured layer 130 and the stacked polymer layer 110, wherein the layer 120 is co-extruded with the stacked polymer layer 110 and the structured layer 130. Layer 120 may be referred to as a barrier layer, a strain-hardening layer, or a first layer. In some embodiments, the first layer 120 has an average thickness h greater than about 1 micrometer (see, for example...). Figures 1 to 2In some such embodiments, or in others, the first layer 120 comprises or is formed of a strain-hardening polymer. In some such embodiments, or in others, the first layer 120 has a glass transition temperature Tg1, the binder 134 has a glass transition temperature Tg2, and Tg1 > Tg2. Tg1-Tg2 can be within any range described elsewhere. In some such embodiments, or in others, the barrier / strain-hardening polymer layer is provided as a surface layer or protective interface layer of a multilayer optical film. Including a suitable layer 120 (e.g., a barrier layer and / or a strain-hardening layer) and / or including layer 140 during film processing can result in a reduction in the density of optical defects generated by voids 213.

[0042] Figure 6 This is a schematic cross-sectional view of an exemplary monolithic multilayer optical film 400 according to some embodiments, which may correspond to, for example, monolithic multilayer optical films 100, 200, or 300, except that the optical film 400 includes one or more polymer layers 155. In some embodiments, the one or more polymer layers 155 include at least one layer with a birefringence greater than about 0.1 (e.g., 155a, or 155b, or 155a and 155b). For example, layer 110, described elsewhere, may be one or more layers 155, or may be replaced by one or more layers. In other embodiments, the one or more polymer layers 155 are omitted. In some embodiments, the birefringence is in-plane birefringence (e.g., nx-ny, where nx and ny are the birefringences in the x and y directions, respectively). In some embodiments, the birefringence is out-of-plane birefringence (e.g., nz-1 / 2(nx+ny), where nz is the birefringence in the z direction or the thickness direction).

[0043] In some embodiments, the integral multilayer optical film 400 includes one or more polymer layers 155, each polymer layer including at least one layer (e.g., 155a, or 155b, or 155a and 155b) having a birefringence greater than about 0.1, and a structured layer 130 disposed on and co-extruded with the one or more polymer layers 155. The structured layer 130 may contain a plurality of particles 132 dispersed in a thermoplastic binder 134, and includes a first main surface 136 opposing the one or more polymer layers 155 and including a plurality of structures 137 formed by the particles 132. In some embodiments, when using a light source (e.g., Figure 1When the light source 151 or 152 (shown) irradiates the optical film 400, the optical film 400 has a first average effective transmittance T1 when the first main surface 136 faces the light source 151, and a second average effective transmittance T2 when the first main surface 136 faces away from the light source 152, wherein T1-T2 ≥ 5% or T1-T2 can be within any range described elsewhere. In some embodiments, one or more polymer layers 155 comprise a plurality of stacked polymer layers totaling at least 30, wherein each polymer layer has an average thickness of less than about 500 nm, as further described elsewhere.

[0044] In some embodiments, the optical film 400 further includes a barrier layer and / or strain-hardening layer 120 disposed between the structured layer 130 and one or more polymer layers 155, wherein the barrier layer and / or strain-hardening layer 120 is co-extruded with one or more polymer layers 155 and the structured layer 130. The barrier layer and / or strain-hardening layer 120 may cause the particles 132 to impart a larger surface roughness Ra to the first primary surface 136 of the structured layer 130 than to the opposite second primary surface 138 of the structured layer 130, as further described elsewhere.

[0045] In some embodiments, the integrated multilayer optical film 400 includes a strain-curing polymer layer 120 having an average thickness greater than about 1 micrometer; and a structured layer 130 disposed on and co-extruded with the strain-curing polymer layer 120. The structured layer comprises a plurality of particles 132 dispersed in a thermoplastic binder 134 and has a first main surface opposing the strain-curing polymer layer 120 and comprising a plurality of structures 137 formed by the particles 132. In some embodiments, the integrated multilayer optical film 400 further includes one or more polymer layers 155 disposed on the strain-curing polymer layer 120 opposite to the structured layer 130, wherein the one or more polymer layers 155 are co-extruded with the strain-curing polymer layer 120 and the structured layer 130. In some embodiments, the one or more polymer layers 155 comprise at least one layer with a birefringence greater than about 0.1.

[0046] In some implementations, the uniformity of the layer can be characterized by the deviation of a characteristic determined in a square region of the layer from the average value of the layer's characteristics. Figure 7 This is a schematic top view of floor 230, showing a side with length L and area L. 2The square region 181. Layer 230 may correspond to, for example, layer 130. In some embodiments, in a top plan view of the structured layer, particles 132 are distributed such that for each square region 181 of the structured layer having sides of length L of about 50 micrometers, the number of particles per unit area in the region is within about 25%, or about 20%, or about 15% of the average number of particles per unit area of ​​the structured layer. In such embodiments, particles 132 may be described as substantially uniformly distributed on the structured layer.

[0047] Example

[0048] Transmittance, haze and transparency test methods

[0049] The transmittance (T, %), haze (H, %), and transparency (C, %) of multilayer films were tested using a HAZE-GARD instrument (BYK-Garner USA, Wallingford, CT, USA). Transmittance and haze were measured according to ASTM D1003-13. Transparency was measured according to the test methods described in the instrument manual.

[0050] Material

[0051] The materials used throughout the embodiments are as described below and obtained as shown:

[0052] For example, the intrinsic viscosity of polyethylene terephthalate (PET) measured at 23°C in 60 / 40 wt% phenol / o-dichlorobenzene is 0.62 dL / g; 3M Company, St. Paul, MN, USA.

[0053] Polyethylene 2,6-naphthalenedicarboxylate-co-terephthalate, wherein 90 mol% of the dicarboxylic acid portion is 2,6-naphthalenedicarboxylic acid (LMPEN); 3M Company, St. Paul, MN, USA.

[0054] 0.60 dL / g intrinsic viscosity polyethylene terephthalate, wherein 0.18 mol% of the glycol portion is replaced by trimethylolpropane (reference PET [described in U.S. Patent Application Publication 2011 / 0051040 (Johnson et al.)]); 3M Company, St. Paul, MN, USA.

[0055] Polyethylene terephthalate-co-isophthalate, wherein 80 mol% of the dicarboxylic acid portion is terephthalic acid (COPETI).

[0056] Polyethylene terephthalate-sodium co-isophthalate sulfonate (polyester K [described in U.S. Patent Application Publication 2007 / 0298271 (Liu et al.)]); 3M Company, St. Paul, MN, USA.

[0057] EASTAR copolyester GN071 is a natural amorphous diol-modified polyester (EASTAR GN071); Eastman Chemical, Kingsport, TN, USA.

[0058] EASTMAN 14285 amorphous diol modified polyester 0.59 dL / g intrinsic viscosity (COPET14285); Eastman Chemical, Kingsport, TN, USA.

[0059] MOR-ESTER AF-429-P copolyester (AF-429-P); Dow Chemical Co., Midland, MI

[0060] OPTIX CA-24 is a poly[(methyl methacrylate)-ran-(ethyl acrylate)] (OPTIX CA-24); Plaskolite, Columbus, OH, USA.

[0061] INGEO 4032D polylactic acid (INGEO 4032D); NatureWorks LLC, Minnetonka, MN, USA.

[0062] CHEMISNOW MX-500 cross-linked polymethyl methacrylate microspheres (MX-500); Soken Engineering and Chemical Co., Ltd., Tokyo, Japan.

[0063] CHEMISNOW MX-2000 cross-linked polymethyl methacrylate microspheres (MX-2000); Soken Engineering and Chemical Co., Ltd., Tokyo, Japan.

[0064] CHEMISNOW MZ-5HN crosslinked polymethyl methacrylate microspheres (MZ-5HN); Soken Engineering and Chemical Co., Ltd., Tokyo, Japan.

[0065] CHEMISNOW MZ-10HN crosslinked polymethyl methacrylate microspheres (MZ-10HN); Soken Engineering and Chemical Co., Ltd., Tokyo, Japan.

[0066] PP9074MED Poly[(propylene)-ran-(ethylene)] (PP9074MED); ExxonMobil Chemical Co., Spring, TX, USA.

[0067] PELESTAT 230 is an antistatic agent for polyether-polyolefin block copolymers. It is manufactured by Sanyo Chemical Industries, Ltd., Tokyo, Japan.

[0068] TECHPOLYMER SBX-6 cross-linked polystyrene microspheres (SBX-6); Sekisui American Corporation, Sekacus, NJ.

[0069] PRO-FAX SR549M polypropylene copolymer (PRO-FAX SR549M); LyondellBasell Industries, Houston, TX.

[0070] KRATON G1645 is a poly[(styrene)-block-(ethylene / butene)-block-(styrene)] (KRATONG1645); Kraton Corp., Houston, TX, USA.

[0071] KURARITY LA4285 is poly[(methyl methacrylate)-block-(n-butyl acrylate)-block-(methyl methacrylate)] (LA4285); Kuraray Co., Ltd., Tokyo, Japan.

[0072] ESCORENE 1024E4 polypropylene homopolymer; ExxonMobil Corp., Irving, TX, USA.

[0073] 3860X polypropylene homopolymer (3860X); Total Petrochemicals & Refining USA, Inc., Houston, TX.

[0074] DYLARK 332-80 poly[(styrene)-ran-(maleic anhydride)] (15% by weight of maleic anhydride with a number average molecular weight of 171,000; Nova Chemicals, Calgary, CA, Canada).

[0075] SEGETIS 9300D levulinic acid-ketal plasticizer CAS 1259300-69-0 (1,3-dioxolane-2-propionic acid, 2,4-dimethyl-,2,2'-(1,4-butadiyl) ester) (SEGETIS 9300D); SEGETIS Inc. of Golden Valley, Minnesota, USA, was acquired by GFBiochemicals (GFBiochemicals, Milan, IT) of Milan, Italy.

[0076] Comparative Example 1 (C1)

[0077] 0.62 PET, EASTAR GN071 and polyester K were fed into the first twin-screw extruder at 621 lb / hr, 71.2 lb / hr and 18.3 lb / hr respectively, conveyed, melted (575℉) and mixed.

[0078] 0.62 PET and EASTAR GN071 were fed into the second twin-screw extruder at 42 lb / hr and 4.8 lb / hr respectively, conveyed, melted (568℉), and mixed.

[0079] OPTIX CA-24 was fed into the third twin-screw extruder at 26 lb / hr, conveyed, melted (535℉), and mixed.

[0080] INGEO 4032D, OPTIX CA-24, and MX-500, with an average diameter of 5 μm, were fed into and conveyed to the fourth twin-screw extruder at rates of 3.92 lb / hr, 2.21 lb / hr, and 6.38 lb / hr, respectively. INGEO 4032D and OPTIX CA-24 were melted (535℉) and mixed with solid microspheres.

[0081] PP9074MED and PELESTAT 230 were fed into the fifth twin-screw extruder at 103 lb / hr and 3 lb / hr respectively, conveyed, melted (516℉), and mixed.

[0082] Five melting unit assemblies are then extruded through a feed block and a die. The first melting unit assembly feeds a first outer layer adjacent to a group of more than 30 alternating inner layers fed by the second and third melting unit assemblies. These alternating inner layers have an average layer thickness of less than 500 nm during stretching (excluding the two outermost layers of this group). The two outermost layers of this group are fed by the second melting unit assembly. The fourth melting unit assembly feeds an inner layer adjacent to the alternating layer group, opposite to the first outer layer. The fifth melting unit assembly feeds the second outer layer. The layers are cast using electrostatic nails against a cooling wheel, with the second outer layer adjacent to the wheel, having a total casting web thickness of 884 μm and a thickness of 20 μm, respectively, similar to the inner layer thickness of the fourth melting unit assembly.

[0083] The cast web is fed into a tenter frame, heated to 230℉, and stretched transversely to approximately a draw ratio of four and a quarter. The oriented film is then thermally stabilized by heating to 320℉ while maintaining tension, cooled, and then wound into a roll. The second outer layer is mechanically peeled off the film, exposing the microsphere-filled inner layer from the fourth melting device assembly. The transmittance, haze, and transparency of the film are measured in a HAZE-GARD instrument with the microsphere-filled layer facing the light source. Transmittance is also measured with the microsphere-filled layer facing the detector. The measured results are provided in Table 3. As shown in Examples 2-3, the difference between the average effective transmittance with the microsphere-filled layer facing the light source and the average effective transmittance with the microsphere-filled layer facing the detector can be increased by increasing the draw ratio so that the barrier layer / strain-hardening layer causes the microspheres to protrude further from the surface. Figure 8A This is an image of the cross-section of the optical film in Comparative Example 1. Figure 8B This is a top view image of the optical film of Comparative Example 1.

[0084] Comparative Example 2 (C2)

[0085] The cast web was extruded in the same manner as in Comparative Example 1, with the differences described in Tables 1 and 2. The second outer layer was mechanically removed from the cast web, exposing the microsphere-filled inner layer. The cast web (now with the microsphere-filled outer layer) was fed into a tenter frame, where it was heated to 200℉ and stretched laterally to approximately four and a quarter draw ratios. The oriented film was then thermally stabilized by heating to 450℉ while holding it under tension, cooled, and then wound into rolls. The film was measured in the same manner as in Comparative Example 1. The measured results are provided in Table 3. As shown in Example 4, the difference (ΔT) between the average effective transmittance of the microsphere-filled layer facing the light source and the average effective transmittance of the microsphere-filled layer facing the detector can be increased by increasing the initial thickness of the microsphere-filled layer.

[0086] Comparative Examples 3-4 (C3-C4)

[0087] The cast webs were extruded, stretched, thermally stabilized, and measured in the same manner as Comparative Example 1, with the differences described in Tables 1 and 2. The measured results are provided in Table 3. Comparative Example C3 was stretched at a high stretching temperature and a high thermal stabilization temperature, where the second outer layer was removed, which helped achieve a relatively low ΔT. Comparative Example 4 showed microsphere agglomeration, which was reduced in Example 18 by increasing the stretching temperature. Figure 9A This is a cross-sectional image of the optical film of Comparative Example 4, in which the aggregation of microspheres can be observed. Figure 9B This is a top view image of the optical film of Comparative Example 4.

[0088] Examples 1-18 (E1-E18)

[0089] The cast webs were extruded, stretched, thermally stabilized, and measured in the same manner as Comparative Example 1, with the differences shown in Tables 1 and 2. The outermost layer of the group formed by the second and third melt flows facing the microsphere-filled layer is a barrier layer / strain-hardening layer. The results are provided in Table 3. Figure 10A This is an image of the cross-section of the optical film of Example 7. Figure 10B This is a top view image of the optical film of Example 7.

[0090] Example 19 (E19)

[0091] The cast web was extruded in the same manner as Comparative Example 1, with the differences described in Tables 1 and 2. The second outer layer was mechanically removed from the cast web, exposing the microsphere-filled inner layer. When the cast web was bent to a small radius of less than half an inch and the microsphere-filled layer was located on the convex surface of the bent cast web, the outer microsphere-filled layer now remained intact on the adjacent LMPEN layer (the outermost layer of the alternating layer group). The cast web was stretched, thermally stabilized, and measured as described in Tables 2 and 3. Masking tape (3M Universal Masking Tape #2030, 1 inch wide, 3M Company, St. Paul, Minnesota, USA) was applied to the microsphere-filled outer layer of the finished film, and 90-degree peeling was initiated in both the MD and TD directions. The microsphere-filled outer layer remained intact on the LMPEN layer (the outermost layer of the alternating layer group).

[0092] Example 20 (E20)

[0093] The cast web was extruded in the same manner as in Comparative Example 1, with the differences described in Tables 1 and 2. The second outer layer was mechanically removed from the cast web, exposing the microsphere-filled inner layer. When the cast web was bent to a small radius of less than half an inch and the microsphere-filled layer was located on the convex surface of the bent cast web, the outer microsphere-filled layer delaminated from the adjacent LMPEN layer (the outermost layer of the alternating layer group). The cast web was stretched, thermally stabilized, and measured as described in Tables 2 and 3.

[0094] Masking tape is applied to the microsphere-filled outer layer of the finished film, and 90-degree peeling is initiated in both the MD and TD directions. The microsphere-filled outer layer is removed with tape, exposing the LMPEN layer (the outermost layer of the alternating layer group).

[0095] Figure 11A This is an image of the cross-section of the optical film of Example 20. Figure 11B This is a top view image of the optical film of Example 20.

[0096] Example 21 (E21)

[0097] The cast web was extruded in the same manner as in Comparative Example 1, with the differences described in Tables 1 and 2. The second outer layer was mechanically removed from the cast web, exposing the microsphere-filled inner layer. When the cast web was bent to a small radius of less than half an inch and the microsphere-filled layer was located on the convex surface of the bent film, the outer microsphere-filled layer now remained intact on the adjacent LMPEN layer (the outermost layer of the alternating layer group). The cast web was stretched, thermally stabilized, and measured as described in Tables 2 and 3. Masking tape was applied to the microsphere-filled outer layer of the finished film, and 90-degree peeling was initiated in both the MD and TD directions. The microsphere-filled outer layer remained intact on the LMPEN layer (the outermost layer of the alternating layer group).

[0098] Example 22 (E22)

[0099] The control PET (dried to a dew point of -40℉) is fed into the first extruder (single screw type) at 30 lb / hr, conveyed, melted (551℉) and mixed.

[0100] The control PET was fed into the second extruder (twin-screw type) at 15 lb / hr, conveyed, melted (551℉) and mixed.

[0101] INGEO 4032D, OPTIX CA-24, and MZ-10HN, with a volume average particle size of 10 μm, were fed into a third extruder (twin-screw type) at rates of 2.81 lb / hr, 0.94 lb / hr, and 3.75 lb / hr, respectively. INGEO 4032D and OPTIX CA-24 were melted (479℉) and mixed with solid microspheres.

[0102] PRO-FAX SR549M and KRATON G1645 were fed into the fourth extruder (twin-screw type) at 22 lb / hr and 3 lb / hr respectively, conveyed, melted (526℉) and mixed.

[0103] Then, four melting device assemblies are extruded through the feeding block and die head. The first melting device assembly feeds the first outer layer, the second melting device assembly feeds the first inner layer adjacent to the first outer layer, the third melting device assembly feeds the second inner layer adjacent to the first inner layer, and the fourth melting device assembly feeds the second outer layer adjacent to the second inner layer. The layers are cast by pressing them against a cooling wheel with electrostatic nails. The second outer layer is adjacent to the wheel and has a total thickness of 207 μm and a second inner layer thickness of 27 μm, respectively.

[0104] The second outer layer was mechanically removed from the cast web, exposing the microsphere-filled inner layer. The cast web was sliced ​​and stretched transversely at 239℉ in a batch stretcher at a constant stretching rate of 5% / s to achieve a stretch ratio of 3.5. The transmittance, haze, and transparency of the film were measured in a HAZE-GARD instrument with the microsphere-filled layer facing the detector. Transmittance was also measured with the microsphere-filled layer facing the source. The measured results are provided in Table 3.

[0105] Example 23 (E23)

[0106] The casting webs were extruded, stretched, thermally stabilized, and measured in the same manner as in Example 22, with the differences described in Tables 1 to 3. Compared to Example 22, the inclusion of SEGETIS 9300D plasticizer resulted in an increased difference between the average effective transmittance of the microsphere-filled layer facing the light source and the average effective transmittance of the microsphere-filled layer facing away from the light source.

[0107] Example 24 (E24)

[0108] LMPEN is fed into the first twin-screw extruder at 20 lb / hr, conveyed, melted (551℉), and mixed.

[0109] LMPEN is fed into the second twin-screw extruder at 15 lb / hr, conveyed, melted (549℉), and mixed.

[0110] EASTAR GN071 (dried to a dew point of -40℉) and SBX-6, with an average diameter of 6 μm, were fed into and conveyed to a third twin-screw extruder at 3.63 lb / hr and 3.52 lb / hr, respectively. The EASTAR GN071 was melted (516℉) and mixed with solid microspheres.

[0111] PRO-FAX SR549M and KRATON G1645 were fed into the fourth twin-screw extruder at 7.2 lb / hr and 1.8 lb / hr, respectively, conveyed, melted (492℉), and mixed.

[0112] Then, four melting device assemblies are extruded through the feeding block and die head. The first melting device assembly feeds the first outer layer, the second melting device assembly feeds the first inner layer adjacent to the first outer layer, the third melting device assembly feeds the second inner layer adjacent to the first inner layer, and the fourth melting device assembly feeds the second outer layer adjacent to the second inner layer. The layers are cast by pressing them against a cooling wheel with electrostatic nails. The second outer layer is adjacent to the wheel and has a total thickness of 130 μm and a second inner layer thickness of 21 μm, respectively.

[0113] The second outer layer was mechanically removed from the cast web, exposing the microsphere-filled inner layer. The cast web was sliced ​​and stretched transversely at 275℉ in a batch stretching machine to achieve a stretch ratio of 5 at a constant stretching rate of 10% / s. The transmittance, haze, and transparency of the film were measured in a HAZE-GARD instrument with the microsphere-filled layer facing the detector. Transmittance was also measured with the microsphere-filled layer facing the source. The measured results are provided in Table 3.

[0114] Example 25 (E25)

[0115] Prior to extrusion, DYLARK 332-80 was dried to a dew point of -40℉. The cast webs were extruded, stretched, thermally stabilized, and measured in the same manner as in Example 24, with the differences described in Tables 1 through 3. Compared to Example 24, the inclusion of DYLARK 332-80 maleic anhydride compatibilizer resulted in an increase in the difference between the average effective transmittance of the microsphere-filled surface facing the light source and the average effective transmittance of the microsphere-filled surface facing the detector.

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122] Table 2

[0123]

[0124] Table 3

[0125]

[0126] Terms such as “about” will be understood in the context in which they are used and described by those skilled in the art. If it is unclear to those skilled in the art in the context of their use and description of “about” to express quantities of characteristic size, quantity, and physical properties, then “about” will be understood to mean within 10% of a specified value. A quantity given a specified value as “about” can be precisely the specified value. For example, if it is unclear to those skilled in the art in the context of their use and description of this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and that the value can be 1.

[0127] All cited references, patents, and patent applications are incorporated herein by reference in their entirety in a consistent manner. In the event of any inconsistency or contradiction between the incorporated references and this application, the information in the foregoing description shall prevail.

[0128] Unless otherwise stated, the description of elements in the accompanying drawings should be understood to apply equally to corresponding elements in the other drawings. While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be used instead of the illustrated and described embodiments without departing from the scope of this disclosure. This application is intended to cover any modifications, variations, or combinations of the specific embodiments discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. A one-piece multilayer optical film, comprising: Multiple polymer interference layers, totaling at least 30, and for at least one wavelength in a wavelength range extending from 400 nm to 1500 nm, primarily reflect and transmit light through optical interference; A structured layer is disposed on the interference layer and includes a plurality of particles dispersed in an adhesive and opposing first and second main surfaces, the first main surface facing away from the interference layer and the second main surface facing the interference layer; as well as A barrier layer is disposed between the structured layer and the interference layer and is co-extruded with at least the interference layer and the structured layer. The barrier layer causes the particles to impart a larger surface roughness to the first main surface than to the second main surface, such that when the optical film is illuminated by a light source, the optical film has a first average effective transmittance T1 when the first main surface faces the light source and a second average effective transmittance T2 when the first main surface faces away from the light source, where T1-T2 ≥ 5%. The structured layer is co-stretched with the interference layer and the barrier layer, such that for each of the plurality of sub-particles of the particle, the particle is disposed in a corresponding void elongated along a first direction, and In the planar view of the structured layer, the optical defect density caused by the voids is less than 0.3 / mm. 2 .

2. The integrated multilayer optical film according to claim 1, wherein the adhesive comprises polymethyl methacrylate copolymer and polylactic acid.

3. The integrated multilayer optical film according to claim 1, wherein the particles comprise a polymer.

4. The integrated multilayer optical film according to claim 3, wherein the polymer comprises polymethyl methacrylate or polystyrene.

5. The integrated multilayer optical film according to claim 1, wherein the particles have an average diameter in the range of 5 micrometers to 20 micrometers.

6. The integrated multilayer optical film according to claim 1, wherein the particles are spherical.

7. The integrated multilayer optical film according to claim 1, wherein the particles have a refractive index greater than 1.

45.

8. The integrated multilayer optical film according to claim 1, wherein the blocking layer has an average thickness of more than 1 micrometer.

9. The integrated multilayer optical film according to any one of claims 1 to 8, wherein the integrated multilayer optical film is a reflective polarizer.

10. A one-piece multilayer optical film, comprising: Multiple stacked polymer layers, totaling at least 30, each polymer layer having an average thickness of less than 500 nm; as well as A structured layer, disposed on the polymer layer and comprising: Multiple particles, said multiple particles being dispersed in the binder; as well as A first primary surface, facing away from the polymer layer and comprising a plurality of structures formed of the particles, the structured layer being co-extruded and co-stretched with the polymer layer such that, for each of the plurality of sub-particles of the particles, the particles are disposed in corresponding voids elongated along a first direction, and In the planar view of the structured layer, the optical defect density caused by the voids is less than 0.3 / mm. 2 .

11. The integrated multilayer optical film according to claim 10, wherein in a planar view of the structured layer, the optical defect density caused by the voids is less than 0.15 / mm. 2 .

12. The integrated multilayer optical film according to claim 10, wherein the integrated multilayer optical film further comprises a protective polymer layer disposed on the structured layer opposite to the plurality of stacked polymer layers, the protective polymer layer being co-extruded and co-stretched with the structured layer and the plurality of stacked polymer layers.

13. The integral multilayer optical film according to any one of claims 10 to 12, the integral multilayer optical film further comprising a first layer disposed between the structured layer and the stacked polymer layers with an average thickness greater than 1 micrometer, the first layer being co-extruded with the stacked polymer layers and the structured layer, the first layer having a glass transition temperature Tg1 and comprising a strain-hardening polymer, the binder having a glass transition temperature Tg2, Tg1>Tg2.

14. A one-piece multilayer optical film, comprising: A strain-hardening polymer layer having an average thickness greater than 1 micrometer; as well as A structured layer, disposed on and co-extruded with the strain-hardening polymer layer, the structured layer comprising: Multiple particles, said multiple particles being dispersed in a thermoplastic binder; as well as A first primary surface, the primary surface being opposite to the strain-hardening polymer layer and comprising a plurality of structures formed by the particles. When the optical film is illuminated by a light source, the optical film has a first average effective transmittance T1 when the first main surface faces the light source, and a second average effective transmittance T2 when the first main surface faces away from the light source, where T1-T2≥5%. The structured layer is co-stretched with the strain-hardening polymer layer such that, for each of the plurality of sub-particles of the particle, the particle is disposed in a corresponding void elongated along a first direction, and In the planar view of the structured layer, the optical defect density caused by the voids is less than 0.3 / mm. 2 .

15. The integrated multilayer optical film according to claim 14, further comprising one or more polymer layers disposed on the strain-curing polymer layer opposite to the structured layer, the one or more polymer layers being co-extruded with the strain-curing polymer layer and the structured layer, the one or more polymer layers comprising at least one layer having a birefringence greater than 0.1.

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