Multilayer optical film including two optical stacks and having a near infrared reflective band

Abstract

A multilayer optical film includes a first optical stack and a second optical stack. The first optical stack includes a plurality of alternating first and second layers, and the second optical stack includes a plurality of optical repeat units. Each of the optical repeat units includes at least four layers arranged in sequence. The total number of layers of the optical film can be about 1200 layers or less. For substantially normally incident light: each of the first and second optical stacks has a first order reflection band disposed at a wavelength between about 700 nm and about 2500 nm, wherein the first order reflection band of the second optical stack extends to a greater wavelength than the first order reflection band of the first optical stack, and the optical film can have an average optical reflectivity greater than about 50% over a wavelength range extending at least from about 900 nm to 1300 nm.

Description

Technical Field

[0001] This manual covers the entirety of multilayer optical films. Background Technology

[0002] Multilayer optical films may include multiple polymer layers arranged as optical repeating units. Multilayer optical films may be reflective polarizers or mirrors. Summary of the Invention

[0003] In some aspects, this specification provides a multilayer optical film comprising a first polymer optical stack disposed on a second polymer optical stack. The first optical stack comprises at least 10 alternating first and second layers. The second optical stack comprises at least 5 optical repeating units. Each optical repeating unit of the second optical stack comprises at least four sequentially arranged first to fourth individual layers. Each of the first and second layers of the first optical stack and each of the first to fourth individual layers of each optical repeating unit of the second optical stack may have an average thickness of less than about 500 nm. The total number of layers in the optical film may not exceed about 1200. For each polarization state of substantially perpendicular incident light and for each polarization state of at least one polarization state including a first polarization state along a first in-plane direction of the optical film: each of the first optical stack and the second optical stack has a first-order reflection band, wherein the first-order reflection band of each of the first optical stack and the second optical stack is disposed at a wavelength between about 700 nm and about 2500 nm, wherein the first-order reflection band of the second optical stack extends to a larger wavelength than the first optical stack; the optical film has an average optical transmittance of more than about 80% in the visible wavelength range of about 450 nm to about 650 nm; and the optical film has an average optical reflectance of more than about 50% in the near-infrared wavelength range of at least from about 900 nm to about 1300 nm. For incident light incident on the optical film at an angle of incidence greater than approximately 45 degrees: for p-polarized light and incident on a plane including a first in-plane direction, the optical film has an average optical transmittance greater than 75% in the visible wavelength range; and for s-polarized light and incident on a plane including a second in-plane direction orthogonal to the first in-plane direction of the optical film, the optical transmittance of the optical film in the visible wavelength range comprises a plurality of alternating peaks and valleys, including a first peak and a second peak separated by a first valley. The difference in optical transmittance between each of the first peak and the second peak and the first valley is greater than approximately 10%, and the first peak and the second peak are separated by at least approximately 5 nm in wavelength.

[0004] In some aspects, this specification provides a multilayer optical film comprising a first polymer optical stack disposed on a second polymer optical stack. The first optical stack comprises at least 10 alternating first and second layers. The second optical stack comprises at least 5 optical repeating units. Each optical repeating unit of the second optical stack comprises at least four sequentially arranged first to fourth individual layers. Each of the first and second layers of the first optical stack and each of the first to fourth individual layers of each optical repeating unit of the second optical stack may have an average thickness of less than about 500 nm. The total number of layers in the optical film may not exceed about 1200. For each polarization state of substantially perpendicular incident light and for each of at least one polarization state including a first polarization state along a first in-plane direction of the optical film: each of the first optical stack and the second optical stack has a first-order reflection band, wherein the first-order reflection band of each of the first optical stack and the second optical stack is disposed at a wavelength between about 700 nm and about 2500 nm, wherein the first-order reflection band of the second optical stack extends to a greater wavelength than the first optical stack; the optical film has an average optical transmittance greater than about 80% in the visible wavelength range of about 450 nm to about 650 nm; the optical film has an average optical reflectance greater than about 40% in a first near-infrared wavelength range extending from about 1200 nm to about 1700 nm; and the average optical reflectance of the optical film in the second near-infrared wavelength range extending from about 900 nm to about 1200 nm is at least 10% greater than the average optical reflectance in the first near-infrared wavelength range. For incident light incident on the optical film at an incident angle greater than about 45 degrees and for the p-polarized state and the incident plane including the first in-plane direction, the optical film has an average optical transmittance of greater than 75% in the visible wavelength range.

[0005] In some aspects, this specification provides a multilayer optical film comprising a first polymer optical stack disposed on a second polymer optical stack. The first optical stack comprises at least 10 alternating first and second layers. The second optical stack comprises at least 5 optical repeating units. Each optical repeating unit of the second optical stack comprises at least four sequentially arranged first to fourth individual layers. Each of the first and second layers of the first optical stack and each of the first to fourth individual layers of each optical repeating unit of the second optical stack may have an average thickness of less than about 500 nm. The total number of layers in the optical film may not exceed about 1200. For substantially perpendicular incident light and for each of the two mutually orthogonal polarization states: each of the first and second optical stacks has a first-order reflection band, wherein the first-order reflection band of each of the first and second optical stacks is located at a wavelength between about 700 nm and about 2500 nm, wherein the first-order reflection band of the second optical stack extends to a greater wavelength than the first optical stack; the optical film has an average optical transmittance greater than about 80% in the visible wavelength range of about 450 nm to about 650 nm; and the optical film has an average optical reflectance greater than about 50% in the near-infrared wavelength range extending at least from about 900 nm to about 1300 nm. For incident light incident on the optical film at an incident angle greater than about 45 degrees: for the p-polarized state, the optical film has an average optical transmittance greater than about 80% in the visible wavelength range; and for the s-polarized state, the optical film has a first average optical transmittance, a second average optical transmittance, and a third average optical transmittance in the corresponding first, second, and third wavelength ranges. The first wavelength range is from about 450 nm to about 510 nm, the second wavelength range is from about 510 nm to about 580 nm, and the third wavelength range is from about 580 nm to about 650 nm. Each of the first, second, and third optical transmittances is in the range of about 30% to about 70%, wherein the maximum difference between the first, second, and third optical transmittances is less than about 10%.

[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 may be claimed. Attached Figure Description

[0007] Figure 1 This is a schematic cross-sectional view of a multilayer optical film according to some implementation schemes.

[0008] Figures 2 to 3 This is a graph showing the relationship between the thickness and number of layers of an optical film according to some implementation schemes.

[0009] Figures 4 to 5 This is a graph showing the relationship between the transmittance of an optical film and wavelength for vertically incident light and for light with an incident angle of 70 degrees, based on some implementation schemes. Detailed Implementation

[0010] Reference is made in the following description to the accompanying drawings, which form part of this disclosure and in which various embodiments are illustrated 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.

[0011] As is known in the art, multilayer optical films comprising multiple optical repeating units (e.g., alternating first and second polymer layers) can be used to provide desired reflection and transmission within a desired wavelength range by appropriately selecting layer thicknesses and refractive index differences. Multilayer optical films and methods of manufacturing multilayer optical films are described, for example, in U.S. Patents 5,882,774 (Jonza et al.); 6,783,349 (Neavin et al.); 6,949,212 (Merrill et al.); 6,967,778 (Wheatley et al.); 9,162,406 (Neavin et al.); and 11,493,677 (Haag et al.). The optical repeating unit of a multilayer optical film is typically the smallest distinct unit of an optical layer that repeats along the thickness direction of the optical film. Optical repeating units typically comprise at least two distinct layers (e.g., a first layer with a higher refractive index and a second layer with a lower refractive index) and may optionally include additional layers described, for example, in U.S. Patents 5,103,337 (Schrenk et al.); 5,360,659 (Arends et al.); 5,540,978 (Schrenk); and 6,207,260 (Wheatley et al.), and international application publication WO 2022 / 195373 (Huseby et al.).

[0012] Optical films that are substantially reflective of the near-infrared wavelength range and substantially transmissive of visible light can be used as window films in buildings or automobiles to reflect near-infrared sunlight, thereby reducing solar heating of buildings or automobiles. Multilayer optical films comprising alternating first and second polymer layers have been used for such window films. These optical films can be characterized by an f-ratio (the ratio of the optical thickness of the higher refractive index layer to the total optical thickness of the optical repeating unit), where an f-ratio of 0.5 is typically used to maximize the intensity of the first-order reflection band. The optical repeating unit typically provides first-order reflection of perpendicularly incident light primarily at a wavelength twice the optical thickness of the optical repeating unit, and nth-order reflection primarily at a wavelength twice the optical thickness divided by n. An f-ratio of 0.5 suppresses second-order harmonics but not third-order harmonics. To prevent the main reflection band in the near-infrared range from generating third-order harmonics that overlap with a portion of the visible wavelength range, the main reflection band is typically limited to wavelengths below approximately 1200 nm. However, significant solar heating exists at wavelengths greater than 1200 nm. Multilayer optical films comprising four optical repeating units can be used to provide a primary reflection band over a wider range of near-infrared wavelengths without higher-order harmonics appearing in the visible range, because various layer thicknesses in the optical repeating units can be selected to suppress second to fourth-order harmonics, as generally described in U.S. Patent 6,207,260 (Wheatley et al.) and International Patent Application Publication WO 2022 / 195373 (Huseby et al.). For example, layer thicknesses can be selected such that the f-ratio (optical thickness of the layers in the optical repeating unit divided by the total optical thickness of the optical repeating unit) of the first to fourth individual layers is approximately 1 / 3, 1 / 6, 1 / 3, and 1 / 6, respectively, to suppress second to fourth-order harmonics. However, using four optical repeating units compared to two optical repeating units results in a greater number of layers required to achieve the desired reflection, and this can lead to a total film thickness that is typically higher than the required total film thickness. Furthermore, conventional four-layer optical repeating units can result in p-polarized reflectivity for obliquely incident visible light, which can undesirably reduce overall visible light transmittance.

[0013] According to some embodiments, it has been found that combining a first optical stack and a second optical stack (where the first optical stack comprises alternating first and second layers, and the second optical stack comprises four layers of optical repeating units) can provide the desired reflectivity in the near-infrared wavelength range extending above 1200 nm, for example, without undesirable harmonics in the visible wavelength range for substantially perpendicularly incident light (e.g., within approximately 25, 20, 15, or 10 degrees of perpendicular incident), and with a limited total number of layers (e.g., no more than approximately 1200 layers). In some embodiments, in order to maintain the total number of layers within the desired range while providing the desired solar near-infrared blocking, the reflectivity provided by the second optical stack is lower than that provided by the first optical stack. In some embodiments, the optical film has s-polarized reflectivity at an oblique incident angle and exhibits significant oscillations in the visible wavelength range. However, according to some embodiments, the average reflectivity, for example, in the 50 nm wavelength range or in the red, green, and blue wavelength ranges, can be substantially uniform or substantially smoothly varying. According to some embodiments, the oscillation is influenced by limiting the total number of layers (e.g., limiting it to no more than about 1200 layers). For example, according to some embodiments, for a smaller total number of layers, the spacing between adjacent peaks of the oscillating transmittance may be larger. Furthermore, in some embodiments, a layer of four optical repeating units can be selected to suppress second harmonics even at oblique incident angles: this is done by selecting layer materials such that three of the four layers are birefringent, as this allows the refractive indices of the four layers to be substantially matched along the thickness direction, as further described elsewhere herein. Thus, according to some embodiments, multilayer optical films can have high transmittance (e.g., greater than about 75%) in the visible range for obliquely incident light (e.g., incident angles greater than about 45 degrees).

[0014] Figure 1 This is a schematic cross-sectional view of a multilayer optical film 100 according to some embodiments. The multilayer optical film 100 includes a first polymer optical stack 101 disposed on a second polymer optical stack 102. Incident light 230, 231, and 232 in an incident plane (a plane defined by the light direction and the surface normal) are schematically illustrated. Light 230 is incident substantially perpendicularly. Polarization states 131 and 132 are schematically illustrated. Light 232 has an s-polarization state 132 (an electric field orthogonal to the incident plane), and light 231 has a p-polarization state 131 (an electric field parallel to the incident plane).

[0015] The first optical stack 101 includes a plurality of alternating first layers 11 and second layers 12, with a total number of at least 10. In some embodiments, for example, the total number of alternating first layers 11 and second layers 12 is at least 20, 30, 40, 60, 80, or 100. In some embodiments, for example, the total number of alternating first layers 11 and second layers 12 is at most 600, 500, 400, 300, 250, or 200. In some embodiments, for example, the total number of alternating first layers 11 and second layers 12 is between 80 and 250.

[0016] The second optical stack 102 includes a plurality of optical repeating units 10, with a total number of at least five. In some embodiments, the total number of optical repeating units 10 is, for example, at least 10, 20, 40, 60, or 70. In some embodiments, the total number of optical repeating units 10 is, for example, at most 300, 250, 200, 150, 125, or 100. In some embodiments, for example, the total number of optical repeating units 10 is 50 to 150. Each optical repeating unit 10 in the second optical stack 102 includes at least four sequentially arranged first to fourth individual layers (A, C1, B, C2). In some embodiments, each optical repeating unit 10 is a four-layer optical repeating unit. In some embodiments, the first to fourth individual layers have corresponding first to fourth compositions. In some embodiments, the first composition is different from the third composition, and the second and fourth compositions are identical compositions that are different from each of the first and third compositions. In some embodiments, the second layer C1 and the fourth layer C3 are along at least one in-plane direction and have a refractive index between that of the first layer A and the third layer B for at least one wavelength in the range of about 400 nm to about 2500 nm.

[0017] In some embodiments, each first individual layer of each optical repeating unit 10 of the second optical stack 102 and each first layer 11 of the first optical stack 101 have the same first composition, and each third individual layer of each optical repeating unit 10 of the second optical stack 102 and each second layer 12 of the first optical stack 101 have the same second composition, which differs from the first composition. In some embodiments, each second individual layer and fourth individual layer of each optical repeating unit 10 of the second optical stack 102 have the same third composition, which differs from each of the first and second compositions.

[0018] Suitable materials for the various layers of the multilayer optical film 100 include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate, polymethyl methacrylate (PMMA), copolyesters, and blends or copolymers thereof. Other suitable materials are described in the multilayer optical film references provided elsewhere herein.

[0019] For example, PEN can be used as a high refractive index layer (e.g., first layer 11 and / or first individual layer A), PMMA can be used as a low refractive index layer (e.g., second layer 12 and / or third individual layer B), and a thermoplastic polyester elastomer optionally blended with the copolymer can be used as an intermediate refractive index layer (e.g., second individual layer C1 and third individual layer C2). For example, available thermoplastic polyester elastomers can be prepared by replacing at least a portion of ethylene glycol with, for example, polytetramethylene ether glycol and optionally butanediol during the preparation of PET. Suitable thermoplastic polyester elastomers include those available under the trade name HYTREL from DuPont de Nemours, Inc., Wilmington, DE. For example, the thermoplastic polyester elastomer can be a PBT polyether block copolymer. Suitable copolymers that can be blended with thermoplastic polyester elastomers include copolymers made from dimethyl terephthalate (DMT), cyclohexanediol (CHDM), and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). Suitable copolymers include copolymers available under the trade name TRITAN from Eastman Chemical Company, Kingsport, TN. In some embodiments, each first layer 11 of the first optical stack 101 and each first individual layer A of each optical repeating unit 10 of the second optical stack 102 comprises PEN, and each second layer 12 of the first optical stack 101 and each third individual layer B of each optical repeating unit 10 of the second optical stack 102 comprises PMMA, and each second individual layer C1 and fourth individual layer C2 of each optical repeating unit 10 of the second optical stack 102 comprises a PBT polyether copolymer. The PEN and PBT-polyether copolymers (optionally blended with another copolymer) may be birefringent. In some embodiments, each second individual layer C1 and fourth individual layer C2 of each optical repeating unit 10 of the second optical stack 102 further comprises a copolyester blended with a PBT polyether copolymer, wherein the copolyester comprises a reaction product of a composition comprising DMT, CHDM and CBDO.

[0020] For example, PET can be used as a high refractive index layer (e.g., first layer 11 and / or first single layer A), coPMMA can be used as a low refractive index layer (e.g., second layer 12 and / or third single layer B), and diol-modified PET (PETG) can be used as an intermediate refractive index layer (e.g., second single layer C1 and third single layer C2). Diol-modified PET can be described as PET in which at least some of the diol units are replaced by different units (such as those derived from cyclohexanediethanol). Suitable PETGs include PCTg and EASTAR GN071 (both available from Eastman Chemical Company, Knoxville, TN). For example, PCTg can be birefringent or isotropic, depending on the heat-setting conditions (e.g., heat-setting below the glass transition temperature of the layer can result in the layer remaining birefringent). In some embodiments, each first layer 11 of the first optical stack 101 and each first individual layer A of each optical repeating unit 10 of the second optical stack 102 comprises PET, and each second layer 12 of the first optical stack 101 and each third individual layer B of each optical repeating unit 10 of the second optical stack 102 comprises coPMMA, and each second individual layer C1 and fourth individual layer C2 of each optical repeating unit 10 of the second optical stack 102 comprises glycol-modified PET. The PET and glycol-modified PET may be birefringent. In some embodiments, the glycol-modified PET comprises PCTg.

[0021] In some embodiments, for each optical repeating unit 10 of the second optical stack 102, each of the first, second, and fourth individual layers is substantially birefringent, and the third individual layer is substantially optically isotropic. In some embodiments, each first layer 11 of the first optical stack 101 is substantially birefringent, and each second layer 12 of the first optical stack 101 is substantially optically isotropic. A layer can be described as substantially birefringent when its birefringence (maximum refractive index minus minimum refractive index) is greater than 0.05 for at least one wavelength in the wavelength range of about 450 nm to about 900 nm. For example, a substantially birefringent layer may have a birefringence greater than about 0.06, 0.07, 0.08, 0.09, or 0.1 for at least one wavelength. For example, the birefringence may be at most about 0.24, 0.22, 0.2, or 0.18. A layer can be described as substantially optically isotropic when its birefringence is less than 0.03 for at least one wavelength in the wavelength range of about 450 nm to about 900 nm. For example, a substantially optically isotropic layer may have a birefringence of less than about 0.025, 0.02, 0.015, 0.01, or 0.005 for at least one wavelength.

[0022] In some embodiments, each of the first layer 11 and the second layer 12 of the first optical stack 101 and each of the first to fourth individual layers of each optical repeating unit 10 of the second optical stack 102 has an average thickness of less than about 500 nm, 450 nm, 400 nm, 350 nm, 300 nm, or 250 nm. In some embodiments, each of the first layer 11 and the second layer 12 of the first optical stack 101 and each of the first to fourth individual layers of each optical repeating unit 10 of the second optical stack 102 has an average thickness greater than about 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. In some embodiments, each optical repeating unit 10 has an average total thickness of less than about 1 micrometer or less than about 900 nm, 850 nm, 800 nm, 750 nm, or 700 nm. For example, the average total thickness of each optical repeating unit 10 can be greater than approximately 100 nm, 150 nm, 200 nm, or 250 nm. The average thickness of a layer is the average thickness over the area of ​​that layer. The average total thickness of an optical repeating unit is the average of the sum of the thicknesses of the individual layers. The layers of the first layer 11, the second layer 12, and the optical repeating unit 10 can be referred to as optical layers, microlayers, or interference layers.

[0023] In some embodiments, a plurality of alternating first layers 11 and second layers 12 and a plurality of optical repeating units 10 are disposed on at least one layer 124, 125, 126 with an average thickness greater than about 500 nm, 750 nm, 1000 nm, 1500 nm, or 2000 nm. Such layers may be referred to as macroscopic layers. For example, each of at least one layer 124, 125, 126 may have a thickness less than about 20 micrometers, 10 micrometers, or 5 micrometers. In some embodiments, a first optical stack 101 and a second optical stack 102 are disposed between macroscopic layers 124 and 126 with an average thickness in any of these ranges (e.g., greater than about 1000 nm and less than about 20 micrometers). In some embodiments, as those skilled in the art will understand, the multilayer optical film 100 includes additional macroscopic layers (e.g., protective boundary layers). For example, at least one macroscopic layer 125 may be disposed between the first optical stack 101 and the second optical stack 102.

[0024] In some embodiments, the total number of layers of the multilayer optical film 100 does not exceed about 1200, 1000, 800, 750, 700, 650, 600, 550, or 500 layers. The total number of layers includes alternating first layers 11 and second layers 12; layers of optical repeating units 10; and any macroscopic layers 124, 125, or 126 of the multilayer optical film 100. In some embodiments, for example, the total number of layers of the multilayer optical film 100 is at least 100, 200, 300, 350, 400, or 450 layers.

[0025] In some embodiments, the multilayer optical film 100 has a total thickness of less than about 105 micrometers, 100 micrometers, 95 micrometers, 90 micrometers, or 85 micrometers. In some embodiments, the total thickness is at least about 50 micrometers, 60 micrometers, or 70 micrometers.

[0026] In some embodiments, the first optical stack 101 and the second optical stack 102 are integrally formed with each other. As used herein, "integrally formed" of the first element with respect to the second element means that the first element and the second element are manufactured together, rather than manufactured separately and then bonded. Integral formation includes manufacturing the first element, followed by manufacturing the second element on the first element. In some embodiments, the multilayer optical film 100 is integrally formed. An optical film comprising multiple layers is integrally formed if the layers are manufactured together (e.g., co-extruded and combined into a melt flow, and then cast onto a cooling roll to form a cast film having each of these layers, and then stretched such that each of these layers is co-stretched with each other) rather than manufactured separately and then bonded thereafter. In some embodiments, the first optical stack 101 and the second optical stack 102 are co-extruded and co-stretched with each other. In some embodiments, all layers of the multilayer optical film 100 are co-extruded and co-stretched with each other.

[0027] For many applications, it is desirable for the multilayer optical film 100 to reflect near-infrared wavelengths of each of two orthogonal polarization states. Therefore, in some embodiments, the multilayer optical film 100 is an infrared reflector. In other embodiments, the multilayer optical film 100 is an infrared reflective polarizer.

[0028] Figures 2 to 3This is a graph showing the relationship between the layer thickness and the number of layers of the optical layers (e.g., layers 11, 12, A, C1, B, C2) of the optical film 100 according to some embodiments, wherein the layers are numbered sequentially from one side of the optical film (e.g., closest to layer 124) to the opposite side (e.g., closest to layer 126). In some embodiments, each optical layer of each optical stack varies substantially continuously with the number of layers, except that the layers of the second optical stack 102 may optionally have discontinuous transitions, which correspond to the omission of layer thicknesses corresponding to one or more wavelengths near 1400 nm, where solar energy in the solar spectrum is significantly reduced due to water absorption. For example, in Figure 2 The middle layer number 287 and near and Figure 3 A discontinuity exists near layer number 343. Alternatively or otherwise, discontinuity jumps may exist when it is desired to create a transmission notch in the spectrum to allow the sensor to operate through the optical film. According to some embodiments, including discontinuity jumps in the layer thickness distribution can allow a given solar energy barrier to be achieved with fewer layers compared to not including jumps.

[0029] Figures 4 to 5 This is a graph showing the transmittance versus wavelength of an optical film for perpendicularly incident light (tp0) and for light at an incident angle θ of 70 degrees (tp70 and ts70 for p-polarized and s-polarized states), according to some implementation schemes. More generally, transmittance can be specified for incident angles θ greater than approximately 45, 50, 55, 60, 62, 64, or 65 degrees. For example, the incident angle θ can be up to approximately 86, 84, 82, 80, 78, 76, 75, or 74 degrees. Figures 4 to 5 The optical transmittance is obtained using standard optical modeling techniques. Figures 2 to 3 The layer thickness distribution shown is calculated. Figures 4 to 5 The optical film is modeled as an optical mirror having substantially the same transmittance for perpendicularly incident light for each of the two orthogonal polarization states. For the corresponding first to fourth individual layers of the four optical repeating units 10, the first optical stack 101 is modeled with an f ratio of approximately 0.5, and the second optical stack 102 is modeled with f ratios of approximately 1 / 3, 1 / 6, 1 / 3, and 1 / 6, respectively. Figure 4 The optical film comprises alternating layers of PEN and PMMA in a first optical stack 101 and layers of PEN, Hytrel / Tritan blend, PMMA, and HYTREL / TRITAN blend in a second optical stack 102. Figure 4 In the first optical stack 101, there are a total of 108 optical layers, and the second optical stack 102 includes a total of 425 optical layers (106 optical repeating units and an additional first separate layer at the end of the stack). Figure 5The optical film comprises alternating layers of PET and coPMMA in a first optical stack 101 and layers of PET, PCTg, coPMMA, and PCTg in a second optical stack 102. Figure 5 In the model, the first optical stack 101 comprises a total of 162 optical layers, and the second optical stack 102 comprises a total of 325 optical layers. The refractive indices at 630 nm for the various materials used in the model are given in the table below.

[0030]

[0031] For p-polarized incident light incident on the optical film at an incident angle of 70 degrees, Figure 4 The optical film exhibits an average optical transmittance of 87.0% in the visible wavelength range of 450 nm to 650 nm. For comparison, an isotropic coPEN with a refractive index of 1.62 in each direction at 630 nm was used instead. Figure 4 The HYTREL / TRITAN blend results in an average transmittance of 56.5% for p-polarized light in the visible range at an incident angle of 70 degrees. For p-polarized incident light incident on the optical film at an incident angle of 70 degrees, Figure 5 The optical film exhibits an average optical transmittance of 89.3% in the visible wavelength range of 450 nm to 650 nm. For comparison, it is replaced with isotropic PETG with a refractive index of 1.56 in each direction at 630 nm. Figure 5 The PCTg results in an average transmittance of 72.8% for p-polarized light in the visible range at an incident angle of 70 degrees.

[0032] In some embodiments, for substantially perpendicular incident light 230 and for each of at least one polarization state (e.g., 131 or 131 and 132) of a first polarization state 131 along a first in-plane direction (x-direction) of the optical film 100: each of the first optical stack 101 and the second optical stack 102 has first-order reflection bands 201, 202, respectively; the optical film 100 has an average optical transmittance greater than about 80% in the visible wavelength range of about 450 nm to about 650 nm; and the optical film has an average optical reflectance greater than about 50%, 60%, 65%, 70%, 75%, 80%, or 85% in the near-infrared wavelength range of at least from about 900 nm to about 1300 nm (e.g., about 880 nm, 900 nm, or 920 nm to about 1700 nm, 1650 nm, or 1600 nm). Figures 4 to 5(Ri is schematically shown in the diagram). In some embodiments, at least one polarization state further includes a second polarization state 132, wherein the second polarization state 132 is along a second in-plane direction (y-direction) of the optical film 100 orthogonal to the first in-plane direction. For example, the average optical transmittance in the visible wavelength range of about 450 nm to about 650 nm may be greater than about 82%, 84%, 86%, or 88%. The in-plane direction of the optical film 100 is the direction in the plane of the film (e.g., the xy plane), which may be a sectional plane at the incident position if the film is curved. Unless otherwise indicated, the optical reflectance and transmittance of the optical film are measured on the film in air.

[0033] In some embodiments, the near-infrared wavelength range extending at least from about 900 nm to about 1300 nm is the range from about 900 nm to about 1700 nm. In some embodiments, optical absorption in the visible and near-infrared wavelength ranges is negligible, such that the reflectance is approximately 100% minus the transmittance. In some embodiments, the first-order reflection band of each of the first optical stack 101 and the second optical stack 102 is positioned at wavelengths between about 700 nm and about 2500 nm, wherein the first-order reflection band 202 of the second optical stack 102 extends to a larger wavelength than the first-order reflection band 201 of the first optical stack 101. For example, the first-order reflection band 201 may extend from about 900 nm to about 1200 nm, and the first-order reflection band 202 may extend from about 1200 nm to about 1700 nm. For example, there may be some overlap between the first-order reflection bands 201 and 202 near 1200 nm. In some embodiments, the first-order reflection band 201 of the first optical stack 101 is disposed between about 800 nm and about 1300 nm, 1250 nm, or 1200 nm. The first-order reflection band 201 may have a width of at least about 150 nm or 200 nm. In some embodiments, the first-order reflection band 202 of the second optical stack 102 is disposed between about 1100 nm, 1150 nm, or 1200 nm and about 2100 nm, 2000 nm, or 1900 nm. For example, the first-order reflection band 202 may be disposed between about 1100 nm and about 2100 nm or between about 1150 nm and about 1900 nm. The first-order reflection band 202 may have a width of at least about 400 nm, 450 nm, or 500 nm.

[0034] In some embodiments, for incident light 231, 232 incident on the optical film at an incident angle θ greater than about 45 degrees: for p-polarized state 131 and an incident plane (xz plane) including a first in-plane direction (x direction), the optical film has an average optical transmittance greater than 75%, 76%, 78%, 80%, 82%, 84%, and 86% in the visible wavelength range (about 450 nm to about 650 nm); and in some embodiments, for s-polarized state 132 and an incident plane (yz plane) including a second in-plane direction orthogonal to the first in-plane direction, the optical transmittance of the optical film in the visible wavelength range as a function of wavelength includes a plurality of alternating peaks and valleys, including a first peak 220 and a second peak 222 separated by a first valley 221. In some embodiments, the difference in optical transmittance between each of the first peak and the second peak and the first valley is greater than about 10%, 11%, 12%, 13%, 14%, or 15%. Since optical transmittance is expressed as a percentage, the difference in optical transmittance is also expressed as a percentage (e.g., the difference between 60% peak transmittance and 46% valley transmittance is 14%). In some embodiments, the first peak 220 and the second peak 222 are spaced apart in wavelength by at least about 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, or 20 nm. For example, the interval between the first peak 220 and the second peak 222 may be at most about 100 nm, 80 nm, 60 nm, or 40 nm. In some embodiments, the average interval between adjacent peaks and valleys in the visible wavelength range is at least about 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, or 20 nm. For example, the average interval may be at most about 100 nm, 80 nm, 60 nm, or 40 nm.

[0035] In some embodiments, for substantially perpendicular incident light 230 and for each of at least one polarization state including a first polarization state 131 along a first in-plane direction: the optical film 100 has an average optical transmittance greater than about 80% (or within the range described elsewhere herein) in the visible wavelength range of about 450 nm to about 650 nm; the optical film has an average optical reflectance greater than about 40%, 45%, 50%, 55%, 60%, or 65% in a first near-infrared wavelength range extending from about 1200 nm to about 1700 nm; and the average optical reflectance of the optical film in a second near-infrared wavelength range extending from about 900 nm to about 1200 nm is at least 10% greater than the average optical reflectance in the first near-infrared wavelength range. The average optical reflectance in the second near-infrared wavelength range may be at least 12%, 14%, 16%, or 18% greater than the average optical reflectance in the first near-infrared wavelength range. In some embodiments, for substantially perpendicular incident light 230 and for each of two mutually orthogonal polarization states 131, 132, the optical film 100 has an average optical reflectivity greater than about 55%, 60%, 65% or 70% in a near-infrared wavelength range extending from about 900 nm to about 1700 nm.

[0036] In some embodiments, for substantially perpendicular incident light 230 and for each of the two mutually orthogonal polarization states 131, 132, the optical film 100 has an average optical reflectance greater than about 40%, 45%, 50%, 55%, 60%, or 65% in a first near-infrared wavelength range extending from about 1200 nm to about 1700 nm. In some embodiments, for substantially perpendicular incident light 230 and for each of the two mutually orthogonal polarization states 131, 132, the average optical reflectance of the optical film 100 in a second near-infrared wavelength range extending from about 900 nm to about 1200 nm is at least 10%, 12%, 14%, 16%, or 18% greater than the average optical reflectance in the first near-infrared wavelength range.

[0037] For example, for a first polarization state or for each of two mutually orthogonal polarization states, the average optical reflectance in the second near-infrared wavelength range may be in the range of X% to 100%, 99.5% or 99%, and the average optical reflectance in the second near-infrared wavelength range may be in the range of 40%, 45%, 50%, 55%, 60% or 65% to X%-10%, for example, where X% may be 75%, 80%, 85% or 90%.

[0038] In some embodiments, for incident light 231, 232 incident on the optical film 100 at an incident angle greater than about 45 degrees: for p-polarized state 131, the optical film 100 has an average optical transmittance greater than about 80% (or within the range described elsewhere herein) in the visible wavelength range; and for s-polarized state 132, the optical film 100 has a first average optical transmittance, a second average optical transmittance, and a third average optical transmittance in the corresponding first wavelength range 331, second wavelength range 332, and third wavelength range 333 (see, for example...). Figure 5 The first wavelength range is from about 450 nm to about 510 nm; the second wavelength range is from about 510 nm to about 580 nm; and the third wavelength range is from about 580 nm to about 650 nm. In some embodiments, each of the first, second, and third optical transmittances is in the range of about 30% to about 70%, wherein the maximum difference between the first, second, and third optical transmittances is less than about 10%, 8%, 6%, 5%, 4%, 3%, or 2%. The maximum difference is the maximum of the absolute values ​​of the differences between the first and second optical transmittances, the absolute values ​​of the differences between the first and third optical transmittances, and the absolute values ​​of the differences between the second and third optical transmittances. In some embodiments, for example, each of the first, second, and third optical transmittances is in the range of about 35% or 40% to about 65%. Figure 5 For an incident angle of 70 degrees, the optical film has a first optical transmittance, a second optical transmittance, and a third optical transmittance of 47.8%, 46.1%, and 47.4%, respectively.

[0039] Terms such as “about” will be understood in the context in which they are used and described in this specification by those skilled in the art. If the use of “about” to express quantities of characteristic size, quantity, and physical properties is unclear to those skilled in the art in the context in which it is used and described in this specification, then “about” will be understood to mean within 10% of the 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 in which it is used and described in this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and that the value can be 1.

[0040] The term “substantially” will be understood by those skilled in the art in the context of its use and description in this specification. If, in the context of its use and description in this specification, the use of “substantially” regarding a property or characteristic is not readily apparent to those skilled in the art, and when the opposite meaning of such property or characteristic is clear to those skilled in the art, the term “substantially” will be understood to mean that the property or characteristic is more pronounced than its opposite meaning.

[0041] 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.

[0042] Unless otherwise indicated, 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 multilayer optical film comprising a first polymer optical stack disposed on a second polymer optical stack, the first optical stack comprising at least 10 alternating first and second layers, the second optical stack comprising at least 5 optical repeating units, each optical repeating unit of the second optical stack comprising at least four sequentially arranged first to fourth individual layers, each of the first and second layers of the first optical stack and each of the first to fourth individual layers of each optical repeating unit of the second optical stack having an average thickness of less than about 500 nm, the total number of layers of the optical film not exceeding about 1200 layers. Wherein, for substantially perpendicular incident light and for each of at least one polarization state, the at least one polarization state includes a first polarization state along a first in-plane direction of the optical film: Each of the first optical stack and the second optical stack has a first-order reflection band, the first-order reflection band of each of the first optical stack and the second optical stack being disposed at a wavelength between about 700 nm and about 2500 nm, wherein the first-order reflection band of the second optical stack extends to a larger wavelength compared to the first-order reflection band of the first optical stack. The optical film has an average optical transmittance of greater than about 80% in the visible wavelength range of about 450 nm to about 650 nm; and The optical film has an average optical reflectance of greater than about 50% in a near-infrared wavelength range extending from about 900 nm to about 1300 nm. For incident light incident on the optical film at an angle of incidence greater than approximately 45 degrees: For the p-polarized state and the incident plane including the first in-plane direction, the optical film has an average optical transmittance greater than 75% in the visible wavelength range; and For an s-polarized state and an incident plane including the optical film with a second in-plane direction orthogonal to the first in-plane direction, the optical transmittance of the optical film in the visible wavelength range comprises a plurality of alternating peaks and valleys, the plurality of alternating peaks and valleys including a first peak and a second peak separated by a first valley, the difference in optical transmittance between each of the first peak and the second peak and the first valley being greater than about 10%, and the first peak and the second peak being separated by at least about 5 nm in wavelength.

2. The multilayer optical film according to claim 1, wherein the at least one polarization state further includes a second polarization state, the second polarization state being along the in-plane direction of the second polarization state.

3. The multilayer optical film according to claim 1, wherein the first-order reflection band of the first optical stack is disposed between about 800 nm and about 1300 nm and has a width of at least about 150 nm, and the first-order reflection band of the second optical stack is disposed between about 1100 nm and about 2100 nm and has a width of at least about 400 nm.

4. The multilayer optical film of claim 1, wherein for the substantially perpendicular incident light and for each of the two mutually orthogonal polarization states, the optical film has an average optical reflectivity greater than about 55% in a near-infrared wavelength range extending from about 900 nm to about 1700 nm.

5. The multilayer optical film according to claim 1, wherein for the substantially perpendicular incident light and for each of the two mutually orthogonal polarization states, the optical film has an average optical reflectivity greater than about 40% in a first near-infrared wavelength range extending from about 1200 nm to about 1700 nm.

6. The multilayer optical film of claim 5, wherein for the substantially perpendicular incident light and for each of the two mutually orthogonal polarization states, the average optical reflectance of the optical film in a second near-infrared wavelength range extending from about 900 nm to about 1200 nm is at least 10% greater than the average optical reflectance in the first near-infrared wavelength range.

7. The multilayer optical film according to claim 1, wherein the near-infrared wavelength range, at least extending from about 900 nm to about 1300 nm, is a range from about 900 nm to about 1700 nm.

8. The multilayer optical film of claim 1, wherein for each optical repeating unit of the second optical stack, each of the first individual layer, the second individual layer and the fourth individual layer is substantially birefringent, and the third individual layer is substantially optically isotropic.

9. The multilayer optical film according to claim 1, wherein each first individual layer of each optical repeating unit of the second optical stack and each first layer of the first optical stack have the same first composition, and each third individual layer of each optical repeating unit of the second optical stack and each second layer of the first optical stack have the same second composition, the second composition being different from the first composition.

10. The multilayer optical film of claim 9, wherein each second individual layer and fourth individual layer of each optical repeating unit of the second optical stack has the same third composition, the third composition being different from each of the first composition and the second composition.

11. A multilayer optical film comprising a first polymer optical stack disposed on a second polymer optical stack, the first optical stack comprising at least 10 alternating first and second layers, the second optical stack comprising at least 5 optical repeating units, each optical repeating unit of the second optical stack comprising at least four sequentially arranged first to fourth individual layers, each of the first and second layers of the first optical stack and each of the first to fourth individual layers of each optical repeating unit of the second optical stack having an average thickness of less than about 500 nm, the total number of layers of the optical film not exceeding about 1200 layers. Wherein, for substantially perpendicular incident light and for each of at least one polarization state, the at least one polarization state includes a first polarization state along a first in-plane direction of the optical film: Each of the first optical stack and the second optical stack has a first-order reflection band, the first-order reflection band of each of the first optical stack and the second optical stack being disposed at a wavelength between about 700 nm and about 2500 nm, wherein the first-order reflection band of the second optical stack extends to a larger wavelength compared to the first-order reflection band of the first optical stack. The optical film has an average optical transmittance of more than about 80% in the visible wavelength range of about 450 nm to about 650 nm. The optical film has an average optical reflectance of greater than about 40% in a first near-infrared wavelength range extending from about 1200 nm to about 1700 nm; and The optical film has an average optical reflectance in a second near-infrared wavelength range extending from about 900 nm to about 1200 nm that is at least 10% greater than its average optical reflectance in the first near-infrared wavelength range. For incident light incident on the optical film at an angle of incidence greater than approximately 45 degrees: For the p-polarized state and the incident plane including the first in-plane direction, the optical film has an average optical transmittance of greater than 75% in the visible wavelength range.

12. The multilayer optical film of claim 11, wherein for each optical repeating unit of the second optical stack, each of the first individual layer, the second individual layer, and the fourth individual layer is substantially birefringent, and the third individual layer is substantially optically isotropic, wherein each first layer of the first optical stack is substantially birefringent, and each second layer of the first optical stack is substantially optically isotropic.

13. A multilayer optical film comprising a first polymer optical stack disposed on a second polymer optical stack, the first optical stack comprising at least 10 alternating first and second layers, the second optical stack comprising at least 5 optical repeating units, each optical repeating unit of the second optical stack comprising at least four sequentially arranged first to fourth individual layers, each of the first and second layers of the first optical stack and each of the first to fourth individual layers of each optical repeating unit of the second optical stack having an average thickness of less than about 500 nm, the total number of layers of the optical film not exceeding about 1200 layers. For essentially perpendicular incident light and for each of the two mutually orthogonal polarization states: Each of the first optical stack and the second optical stack has a first-order reflection band, the first-order reflection band of each of the first optical stack and the second optical stack being disposed at a wavelength between about 700 nm and about 2500 nm, wherein the first-order reflection band of the second optical stack extends to a larger wavelength compared to the first-order reflection band of the first optical stack. The optical film has an average optical transmittance of greater than about 80% in the visible wavelength range of about 450 nm to about 650 nm; and The optical film has an average optical reflectance of greater than about 50% in a near-infrared wavelength range extending from about 900 nm to about 1300 nm. For incident light incident on the optical film at an angle of incidence greater than approximately 45 degrees: For the p-polarized state, the optical film has an average optical transmittance greater than approximately 80% in the visible wavelength range; and For the s-polarization state, the optical film has a first average optical transmittance, a second average optical transmittance, and a third average optical transmittance in corresponding first, second, and third wavelength ranges, wherein the first wavelength range is from about 450 nm to about 510 nm, the second wavelength range is from about 510 nm to about 580 nm, and the third wavelength range is from about 580 nm to about 650 nm, each of the first, second, and third optical transmittances being in the range of about 30% to about 70%, wherein the maximum difference between the first, second, and third optical transmittances is less than about 10%.

14. The multilayer optical film of claim 13, wherein the near-infrared wavelength range, at least extending from about 900 nm to about 1300 nm, is a range from about 900 nm to about 1700 nm.

15. The multilayer optical film according to any one of claims 1 to 14, wherein the first optical stack and the second optical stack are co-extruded and co-stretched with each other.

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