Multilayer optical film, roll of multilayer optical film, backlight, and display system

Abstract

A multilayer optical film includes a plurality of alternating polymeric first layers and polymeric second layers totaling at least 20. The polymeric first layers include between about 10 wt.% and 50 wt.% polyethylene terephthalate and between about 50 wt.% and 90 wt.% polyethylene naphthalate. For substantially normally incident light and for the visible wavelength range, the multilayer optical film has a respective average optical transmission of between about 10% and 30% when the incident light is polarized along a first direction, and a respective average optical transmission of greater than about 60% when the incident light is polarized along a second direction that is orthogonal in-plane. For p-polarized incident light and for at least one wavelength in the infrared wavelength range, the multilayer optical film has optical transmissions T1 and T2 for respective angles of incidence less than about 10 degrees and greater than about 40 degrees, where T2 - T1 is less than about 40%.

Description

Technical Field

[0001] This disclosure relates to a multilayer optical film. This disclosure also relates to a roll of multilayer optical film, a backlight including the multilayer optical film, and a display system including the backlight. Background Technology

[0002] A display system includes a backlight for providing light to the display panel. The backlight typically includes a multilayer optical film that can have a polarizing effect; that is, the multilayer optical film acts as a polarizer. A polarizer is an optical element that allows incident light of one polarization to substantially pass through it while substantially blocking light of another polarization. Summary of the Invention

[0003] In a first aspect, this disclosure provides a multilayer optical film comprising at least 20 alternating polymer first layers and polymer second layers. Each polymer layer has an average thickness of less than about 500 nanometers (nm). The polymer first layer comprises between about 10 wt% and about 50 wt% polyethylene terephthalate (PET) and between about 50 wt% and about 90 wt% polyethylene naphthalate (PEN). For substantially perpendicular incident light and for the visible light wavelength range extending from about 420 nm to about 680 nm, when the incident light is polarized in a first in-plane direction within the multilayer optical film, the multiple alternating polymer first layers and polymer second layers have an average optical transmittance between about 10% and about 30%. Furthermore, for substantially perpendicular incident light and for the visible light wavelength range, when the incident light is polarized in a second in-plane orthogonal direction within the multilayer optical film, the multiple alternating polymer first layers and polymer second layers have an average optical transmittance greater than about 60%. Furthermore, for p-polarized incident light propagating in an incident plane including the first direction and for at least one wavelength in an infrared wavelength range extending from about 700 nm to about 960 nm, the plurality of alternating polymer first layers and polymer second layers have optical transmittances T1 and T2 for corresponding incident angles of less than about 10 degrees and greater than about 40 degrees, wherein (T2-T1) is less than about 40%.

[0004] In a second aspect, this disclosure provides a roll of the multilayer optical film of the first aspect, the roll having a width of at least 140 centimeters (cm) and a length of at least 40 meters (m). Along this length of the multilayer optical film, the multilayer optical film has an average effective transmittance ET1 in the central region and an average effective transmittance ET2 in the side regions, wherein (ET1 / ET2) ≤ 0.97.

[0005] In a third aspect, this disclosure provides a backlight source including an extended illumination source configured to emit light through and across its extended emitting surface for illuminating a display panel. The extended illumination source includes at least one light source. The backlight source also includes the multilayer optical film of the first aspect, disposed on the extended emitting surface and substantially co-extending with the extended emitting surface in length and width.

[0006] In a fourth aspect, this disclosure provides a display system including a display panel disposed on the backlight source of the third aspect. The display panel is configured to receive emitted light and form an image.

[0007] In a fifth aspect, this disclosure provides a backlight source including an extended illumination source configured to emit light through and across its extended emitting surface for illuminating a display panel. The extended illumination source includes at least one light source. The backlight source also includes a reflective polarizer disposed on and substantially co-extended with the extended illumination source in length and width. The reflective polarizer includes a plurality of alternating first and second polymer layers, totaling at least 20. Each of these first and second polymer layers has an average thickness of less than about 500 nm. For substantially perpendicular incident light and for a visible light wavelength range extending from about 420 nm to about 680 nm, when the incident light is polarized in the reflective polarizer along a first in-plane direction, the plurality of alternating first and second polymer layers have an average optical transmittance between about 10% and about 30%. Furthermore, for the substantially perpendicular incident light and for the visible light wavelength range, when the incident light is polarized in the reflective polarizer along a second direction orthogonal in the plane, the plurality of alternating polymer first and polymer second layers have an average optical transmittance greater than about 60%. In addition, the reflective polarizer has an average effective transmittance between about 1.65 and about 1.4.

[0008] In a sixth aspect, this disclosure provides a display system including a display panel disposed on the backlight source of the fifth aspect. The display panel is configured to receive emitted light and form an image. Attached Figure Description

[0009] A more complete understanding of the exemplary embodiments disclosed herein will be gained from the following detailed description in conjunction with the figures below. The figures are not necessarily drawn to scale. Similar numbers used in the figures refer to similar parts. However, it should be understood that the use of numbers to refer to parts in a given figure is not intended to limit parts labeled with the same numbers in another figure.

[0010] Figure 1A detailed schematic cross-sectional view of a multilayer optical film according to one embodiment of the present disclosure is shown;

[0011] Figure 2A An embodiment depicting the present disclosure is shown. Figure 1 The graph shows the corresponding optical transmittance of multilayer optical films and conventional optical films for substantially perpendicular incident light.

[0012] Figure 2B A table is shown that lists some exemplary values ​​of the corresponding average optical transmittance and corresponding optical transmittance for multilayer optical films and conventional optical films, corresponding to Figure 2A A curve graph;

[0013] Figure 2C An embodiment depicting the present disclosure is shown. Figure 1 The graphs show the optical transmittance of multilayer optical films and conventional optical films for incident angles greater than approximately 40 degrees.

[0014] Figure 2D A table is shown that lists some exemplary values ​​of the corresponding average optical transmittance and corresponding optical transmittance for multilayer optical films and conventional optical films, corresponding to Figure 2C A curve graph;

[0015] Figure 3A An embodiment according to this disclosure is shown. Figure 1 A perspective view of a roll of multilayer optical films;

[0016] Figure 3B A graph depicting the corresponding changes in average effective transmittance across the respective widths of two multilayer optical films and a conventional optical film according to one embodiment of the present disclosure is shown.

[0017] Figure 3C A table is shown listing some exemplary values ​​for the corresponding average effective transmittance of two multilayer optical films and a conventional optical film, corresponding to... Figure 3B A curve graph;

[0018] Figure 4A A detailed schematic cross-sectional view of a display system according to one embodiment of the present disclosure is shown;

[0019] Figure 4B An embodiment according to this disclosure is shown. Figure 4A A detailed schematic cross-sectional view of the extended lighting source of the display system; and

[0020] Figure 4C Another embodiment according to this disclosure is shown. Figure 4A A detailed schematic cross-sectional view of the extended lighting source of the display system. Detailed Implementation

[0021] In the following description, reference is made to the accompanying drawings, which form a part thereof, and various embodiments are illustrated therein. It should be understood that other embodiments are contemplated and made without departing from the scope or spirit of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0022] In the following disclosure, the following definitions are used.

[0023] As used herein, the terms “a,” “an,” “the,” “at least one,” and “a or more” are used interchangeably.

[0024] As used herein, as a modifier of a characteristic or attribute, unless otherwise specifically defined, the term “approximately” means that the characteristic or attribute will be easily identifiable by a person skilled in the art without requiring absolute precision or a perfect match (e.g., within + / - 20% for quantifiable characteristics).

[0025] Unless otherwise specifically defined, the term “substantially” means a high degree of approximation (e.g., within + / -10% for quantifiable properties), but also does not require absolute precision or a perfect match.

[0026] As used in this article, all figures should be considered as being modified by the term “approximately”. Unless otherwise specifically defined, the term “approximately” means a high degree of approximation (e.g., within + / - 5% for quantifiable properties), but also does not require absolute precision or a perfect match.

[0027] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be construed as limiting the scope of this disclosure. Throughout the embodiments of this disclosure, the terms “first” and “second” are used interchangeably when used in conjunction with a feature or element.

[0028] As used herein, when a first material is referred to as “similar” to a second material, at least 90% by weight of the first material and the second material are identical, and any variation between the first material and the second material accounts for less than about 10% by weight of each of the first material and the second material.

[0029] As used in this article, "at least one of A and B" should be understood as meaning "only A, only B, or both A and B".

[0030] As used herein, the term "membrane" generally refers to a material having a very high length or width-to-thickness ratio. A membrane has two main surfaces defined by its length and width. Membranes typically exhibit good flexibility and can be used in a wide variety of applications, including displays. Membranes may also have a certain thickness or material composition, making them semi-rigid or rigid. The membranes described in this disclosure can be composed of various polymeric materials. Membranes can be single-layered, multilayered, or blends of different polymers.

[0031] As used herein, the term "layer" generally refers to the thickness of a material within a membrane that has a relatively uniform chemical composition. A layer can be any type of material, including polymers, cellulose, metals, or blends thereof. A given polymer layer may comprise a single polymer type or a blend of polymers and may include additives. A given layer may be combined with or bonded to other layers to form a membrane. A layer may be partially continuous or completely continuous compared to adjacent layers or membranes. A given layer may be partially or completely co-extended with adjacent layers. A layer may contain sublayers.

[0032] As used herein, unless otherwise explicitly defined, the term "between about..." generally refers to a range of inclusion or closure. For example, if parameter X is between about A and B, then A ≤ X ≤ B.

[0033] As used herein, unless otherwise specifically defined, the term "refractive index" generally refers to the refractive index of a material or layer. Similarly, unless otherwise specifically defined, the term "refractive index" generally refers to the refractive index of multiple materials or layers.

[0034] Multilayer optical films (e.g., reflective polarizers) can be used in applications where it may be necessary to allow light of one polarization to essentially pass through the polarizer while essentially blocking light of another polarization.

[0035] Conventional multilayer optical films can substantially transmit substantially perpendicular incident light polarized along a first direction within a desired wavelength range, and substantially block substantially perpendicular incident light polarized along an orthogonal second direction.

[0036] However, in some applications, it may be necessary to transmit a portion of substantially perpendicular incident light polarized along a second direction within the desired wavelength range.

[0037] In addition, in some applications, multilayer optical films may be exposed to solvents such as isopropanol (IPA), acetone, toluene, methyl ethyl ketone (MEK), etc., which may damage the multilayer optical films. Therefore, in some applications, multilayer optical films with chemical resistance may be desired.

[0038] In one aspect, this disclosure provides a multilayer optical film comprising at least 20 alternating polymer first layers and polymer second layers. Each polymer layer has an average thickness of less than about 500 nanometers (nm). The polymer first layer comprises between about 10 wt% and about 50 wt% polyethylene terephthalate (PET) and between about 50 wt% and about 90 wt% polyethylene naphthalate (PEN). For substantially perpendicular incident light and for the visible light wavelength range extending from about 420 nm to about 680 nm, when the incident light is polarized in a first in-plane direction within the multilayer optical film, the alternating polymer first layers and polymer second layers have an average optical transmittance between about 10% and about 30%. Furthermore, for substantially perpendicular incident light and for the visible light wavelength range, when the incident light is polarized in a second in-plane orthogonal direction within the multilayer optical film, the alternating polymer first layers and polymer second layers have an average optical transmittance greater than about 60%. Furthermore, for p-polarized incident light propagating in an incident plane including the first direction and for at least one wavelength in an infrared wavelength range extending from about 700 nm to about 960 nm, the plurality of alternating polymer first layers and polymer second layers have optical transmittances T1 and T2 for corresponding incident angles of less than about 10 degrees and greater than about 40 degrees, wherein (T2-T1) is less than about 40%.

[0039] Since the first polymer layer comprises between about 10% and about 50% by weight of PET and between about 50% and about 90% by weight of PEN, the multilayer optical film can have an average optical transmittance between about 10% and about 30% for substantially perpendicular incident light in the visible light wavelength range when the incident light is polarized along the first direction. In other words, the multilayer optical film can be a weak polarizer. Such polarizers may be desirable in several optical applications, including windshields, virtual reality / augmented reality, and head-up display (HUD) applications.

[0040] Furthermore, since (T2-T1) is less than about 40%, for at least one wavelength in the infrared wavelength range, the multilayer optical film transmits at least a portion of the p-polarized incident light, regardless of the incident angle of the p-polarized incident light.

[0041] Furthermore, applying one or more of IPA, acetone, toluene, and MEK to the multilayer optical film may not damage the multilayer optical film of this disclosure. Therefore, the multilayer optical film can be used in applications requiring chemical resistance to one or more of the aforementioned solvents.

[0042] Now refer to the attached diagram, Figure 1A detailed schematic cross-sectional view of a multilayer optical film 200 according to one embodiment of the present disclosure is shown. The multilayer optical film 200 defines mutually orthogonal x-axis, y-axis, and z-axis. The x-axis and y-axis correspond to in-plane axes of the multilayer optical film 200, while the z-axis is a transverse axis disposed along the thickness of the multilayer optical film 200. In other words, the x-axis and y-axis are disposed along the plane of the multilayer optical film 200 (i.e., the xy plane), and the z-axis is disposed perpendicular to the plane of the multilayer optical film 200. The multilayer optical film 200 also defines mutually orthogonal first direction, second direction, and thickness direction. The first direction, second direction, and thickness direction may be substantially along the x-axis, y-axis, and z-axis of the multilayer optical film 200, respectively.

[0043] In some embodiments, the multilayer optical film 200 includes opposite outermost surfaces 201, 202. In some embodiments, at least one of the opposite outermost surfaces 201, 202 may be exposed to the external environment. In some embodiments, each of the opposite outermost surfaces 201, 202 may be exposed to the external environment. In some embodiments, the external environment may include air.

[0044] The multilayer optical film 200 includes a plurality of alternating polymer first layers 10 and polymer second layers 11, totaling at least 20. In some embodiments, the total number of the plurality of polymer first layers 10 and polymer second layers 11 is at least 30, at least 40, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, or at least 300.

[0045] Each polymer layer in polymer first layer 10 and polymer second layer 11 has an average thickness tp of less than about 500 nanometers (nm). The average thickness tp is defined along the z-axis of each polymer layer in polymer first layer 10 and polymer second layer 11. As used herein, the term "average thickness tp" refers to the average thickness of each polymer layer in polymer first layer 10 and polymer second layer 11 measured at multiple points in a plane (i.e., the xy plane) across each polymer layer in polymer first layer 10 and polymer second layer 11. In some embodiments, each polymer layer in polymer first layer 10 and polymer second layer 11 has an average thickness tp of less than about 400 nm, less than about 300 nm, less than about 250 nm, less than about 200 nm, less than about 150 nm, less than about 100 nm, or less than about 50 nm.

[0046] The polymer first layer 10 comprises between about 10 wt% and about 50 wt% polyethylene terephthalate (PET). In some embodiments, the polymer first layer 10 comprises between about 20 wt% and about 40 wt% PET. In some embodiments, the polymer first layer 10 comprises about 30 wt% PET. In some embodiments, the polymer first layer 10 comprises a copolymer of PET (coPET) between about 10 wt% and about 50 wt%. In some embodiments, the polymer first layer 10 comprises between about 20 wt% and about 40 wt% coPET. In some embodiments, the polymer first layer 10 comprises about 30 wt% coPET.

[0047] The polymer first layer 10 further includes between about 50% and about 90% by weight polyethylene naphthalate (PEN). In some embodiments, the polymer first layer 10 includes between about 60% and about 80% by weight of PEN. In some embodiments, the polymer first layer 10 includes about 70% by weight of PEN. In some embodiments, the polymer first layer 10 includes between about 50% and about 90% by weight LmPEN (a stoichiometric blend of about 90% PEN and about 10% PET). In some embodiments, the polymer first layer 10 includes between about 60% and about 80% by weight LmPEN. In some embodiments, the polymer first layer 10 includes about 70% by weight LmPEN.

[0048] In some embodiments, the polymer second layer 11 comprises polycarbonate (PC) and coPET. In some embodiments, the polymer second layer 11 may comprise between about 35% to about 50% PC and between about 50% to about 65% coPET.

[0049] In some embodiments, the multilayer optical film 200 further includes at least one surface layer 12 having an average thickness ts greater than about 500 nm. The average thickness ts is defined along the z-axis of the at least one surface layer 12. As used herein, the term "average thickness ts" refers to the average thickness of the at least one surface layer 12 measured at multiple points across a plane (i.e., the xy-plane) of the at least one surface layer 12. In some embodiments, the at least one surface layer 12 has an average thickness ts greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm. The at least one surface layer 12 may serve as a protective layer for the multilayer optical film 200. Figure 1 In the illustrated embodiment, the multilayer optical film 200 includes a pair of opposite surface layers 12, which include opposite outermost surfaces 201, 202. The pair of surface layers 12 of the multilayer optical film 200 can serve as protective boundary layers (PBLs).

[0050] In some embodiments, the multilayer optical film 200 further includes at least one intermediate layer 13 disposed between two alternating polymer first layers and polymer second layers in the alternating polymer first layer 10 and polymer second layer 11. Figure 1 In the illustrated embodiment, the multilayer optical film 200 includes an intermediate layer 13 disposed between a polymer first layer 10a and a polymer second layer 11a. In some embodiments, at least one intermediate layer 13 has an average thickness ti greater than about 500 nm. The average thickness ti is defined along the z-axis of at least one intermediate layer 13. As used herein, the term "average thickness ti" refers to the average thickness of at least one intermediate layer 13 measured at multiple points across a plane (i.e., the xy-plane) of at least one intermediate layer 13. In some embodiments, at least one intermediate layer 13 has an average thickness ti greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0051] In some embodiments, at least one surface layer 12 and at least one intermediate layer 13 may comprise one or more polymeric materials, such as polyethylene hexyl naphthalate (PHEN), PEN, copolymers containing PHEN, PEN and / or other polyesters (e.g., PET or polyesters containing benzoic acid), ethylene glycol-modified polyethylene terephthalate (PETg), PC, poly(methyl methacrylate) (PMMA), or blends of these classes of materials.

[0052] In some embodiments, the polymer first layer 10 and polymer second layer 11, at least one surface layer 12 and at least one intermediate layer 13 may be substantially co-extended with each other, or have comparable in-plane dimensions (i.e., length and width). In other words, the polymer first layer 10 and polymer second layer 11, at least one surface layer 12 and at least one intermediate layer 13 may be substantially co-extended with each other in the xy plane.

[0053] Based on the desired application properties, the multilayer optical film 200 may have an average thickness t. The average thickness t is defined along the z-axis of the multilayer optical film 200. As used herein, the term "average thickness t" refers to the average thickness of the multilayer optical film 200 measured at multiple points across a plane (i.e., the xy-plane) of the multilayer optical film 200. In some embodiments, the multilayer optical film 200 has an average thickness t of less than about 40 micrometers. In some embodiments, the multilayer optical film 200 has an average thickness t of less than about 35 micrometers, less than about 32 micrometers, less than about 30 micrometers, less than about 28 micrometers, or less than about 27 micrometers. In some embodiments, the multilayer optical film 200 has an average thickness t of about 26 micrometers. Therefore, the multilayer optical film 200 may have an average thickness comparable to that of conventional multilayer optical films.

[0054] In some embodiments, the multilayer optical film 200 may include additional layers such as an adhesive layer (not shown) to bond any two of the plurality of polymer first layers 10 and polymer second layers 11, at least one surface layer 12, and at least one intermediate layer 13 of the multilayer optical film 200. In some embodiments, the adhesive layer may be substantially optically transparent. As used herein, the term "optically transparent" may mean having an average optical transmittance greater than about 90% for light in the wavelength range of about 400 nm to about 1000 nm. In some embodiments, the adhesive layer may include an optically transparent adhesive (OCA). In some other embodiments, the adhesive layer may include an epoxy resin, a laminate, or any other suitable layer.

[0055] In some embodiments, the minimum average peel strength between two portions of the multilayer optical film 200 is greater than about 100 grams per inch (g / inch). As used herein, the term "average peel strength" refers to the average load applied per unit width to the adhesive layer to separate the two portions of the multilayer optical film 200. In some embodiments, each of the two portions includes at least one polymer layer 10, 11 of a plurality of alternating polymer first layers 10 and polymer second layers 11. In some embodiments, at least one of the two portions may include at least one intermediate layer 13. In some embodiments, the minimum average peel strength between two portions of the multilayer optical film 200 is greater than about 150 g / inch, greater than about 200 g / inch, greater than about 250 g / inch, greater than about 300 g / inch, greater than about 350 g / inch, greater than about 400 g / inch, greater than about 450 g / inch, or greater than about 500 g / inch.

[0056] In some embodiments, the first polymer layer 10 and the second polymer layer 11 have corresponding refractive indices nx1 and nx2 along a first direction (i.e., the x-axis) of the multilayer optical film 200. In some embodiments, the first polymer layer 10 and the second polymer layer 11 have corresponding refractive indices ny1 and ny2 along a second direction (i.e., the y-axis) of the multilayer optical film 200. In some embodiments, the first polymer layer 10 and the second polymer layer 11 have corresponding refractive indices nz1 and nz2 along a thickness direction (i.e., the z-axis) of the multilayer optical film 200 orthogonal to the first and second directions.

[0057] In some implementations, for the visible light wavelength range 21 extending from about 420 nm to about 680 nm Figure 2AFor at least one wavelength in the visible light wavelength range 21 (shown), the difference between nx1 and nx2 is greater than or equal to about 0 and less than or equal to about 0.4, i.e., 0 ≤ (nx1 – nx2) ≤ 0.4. In some embodiments, for at least one wavelength in the visible light wavelength range 21, 0 ≤ (nx1 – nx2) ≤ 0.35, 0 ≤ (nx1 – nx2) ≤ 0.3, 0 ≤ (nx1 – nx2) ≤ 0.25, 0 ≤ (nx1 – nx2) ≤ 0.2, or 0 ≤ (nx1 – nx2) ≤ 0.15. In some embodiments, for at least one wavelength of about 633 nm, nx1 is between about 1.75 and about 1.85. In some embodiments, for at least one wavelength of about 633 nm, nx2 is between about 1.55 and about 1.57.

[0058] In some embodiments, for at least one wavelength in the visible light wavelength range 21, the magnitude of the difference between ny1 and ny2 is less than about 0.04, i.e., |ny1–ny2|<0.04. In some embodiments, |ny1–ny2|<0.035, |ny1–ny2|<0.03, or |ny1–ny2|<0.025. In some embodiments, for at least one wavelength in the visible light wavelength range 21, ny1 and ny2 may be substantially equal, and the magnitude of the difference between ny1 and ny2 may be 0, i.e., |ny1–ny2| may be 0. In some embodiments, for at least one wavelength of about 633 nm, ny1 is between about 1.57 and about 1.56, and ny2 is between about 1.55 and about 1.57.

[0059] In some embodiments, for at least one wavelength in the visible light wavelength range 21, the magnitude of the difference between nz1 and nz2 is less than about 0.04, i.e., |nz1–nz2|<0.04. In some embodiments, |nz1–nz2|<0.035, |nz1–nz2|<0.03, or |nz1–nz2|<0.025. In some embodiments, for at least one wavelength in the visible light wavelength range 21, nz1 and nz2 may be substantially equal, and the magnitude of the difference between nz1 and nz2 may be 0, i.e., |nz1–nz2| may be 0. In some embodiments, for at least one wavelength of about 633 nm, nz1 is between about 1.53 and about 1.57, and nz2 is between about 1.54 and about 1.57.

[0060] In some embodiments, for at least one wavelength in the visible light wavelength range 21, at least one of nx1, ny1, and nz1 may be greater than nx2, ny2, and nz2, respectively. Therefore, for at least one wavelength in the visible light wavelength range 21 and at least along one of the first direction, the second direction, and the thickness direction, the first polymer layer 10 may be a high refractive index optical (HIO) layer, and the second polymer layer 11 may be a low refractive index optical (LIO) layer. In some embodiments, for at least one wavelength in the visible light wavelength range 21, each of nx1, ny1, and nz1 may be greater than nx2, ny2, and nz2, respectively.

[0061] Generally speaking, birefringence is a measure of the optical anisotropy in the layers of a multilayer optical film 200. Furthermore, birefringence is measured as the difference between the two refractive indices of the layers along two mutually perpendicular directions (e.g., a first direction and a second direction).

[0062] It can be observed that for at least one wavelength of about 633 nm, and for the first polymer layer 10, the birefringence |nx1-ny1| is between about 0.1 and about 0.29, the birefringence |nx1-nz1| is between about 0.1 and about 0.32, and the birefringence |ny1-nz1| is between about 0 and about 0.04.

[0063] Additionally, it can be observed that for at least one wavelength of about 633 nm, and for the polymer second layer 11, the birefringence |nx2-ny2| is between about 0 and about 0.02, the birefringence |nx2-nz2| is between about 0 and about 0.03, and the birefringence |ny2-nz2| is between about 0 and about 0.03.

[0064] Therefore, the polymer first layer 10 and polymer second layer 11 of the multilayer optical film 200 can have a low birefringence. A low birefringence results in higher transmittance of incident light through the polymer first layer 10 and polymer second layer 11 of the multilayer optical film 200. Furthermore, the low birefringence of the polymer first layer 10 can be attributed to the inclusion of 10% to 50% by weight of PET in the polymer first layer 10.

[0065] In some embodiments, the desired optical properties of the multilayer optical film 200 can be achieved by varying various parameters, such as the material, total number, and average thickness of the plurality of alternating polymer first layers 10 and polymer second layers 11, at least one surface layer 12, and at least one intermediate layer 13. Additionally, the desired optical properties of the multilayer optical film 200 can be achieved by varying at least one of the refractive indices nx1, ny1, nz1, nx2, ny2, and nz2 of the plurality of polymer first layers 10 and polymer second layers 11.

[0066] In some embodiments, the multilayer optical film 200 may be a reflective polarizer. In such embodiments, the multilayer optical film 200 may be interchangeably referred to as "reflective polarizer 200". Thus, the reflective polarizer 200 comprises a plurality of alternating polymer first layers 10 and polymer second layers 11, totaling at least 20.

[0067] Figure 1 Incident light 20, propagating in an incident plane P including a first direction (i.e., the x-axis) and incident on the outermost surface 201 of the multilayer optical film 200 onto a plurality of alternating polymer first layers 10 and polymer second layers 11, is also shown. In such embodiments, the incident plane P is substantially along the xz plane of the multilayer optical film 200. The incident light 20 is substantially perpendicular to the plurality of alternating polymer first layers 10 and polymer second layers 11, i.e., the incident light 20 forms an angle of less than about 10 degrees with the normal N of the multilayer optical film 200 along the z-axis or thickness direction of the multilayer optical film 200. Therefore, the incident light 20 can be interchangeably referred to as "substantially perpendicular incident light 20".

[0068] In some embodiments, the incident light 20 propagating in the incident plane P may be polarized in a first in-plane direction within the multilayer optical film 200. In other words, in such embodiments, the incident light 20 propagating in the incident plane P may be polarized along the x-axis within the multilayer optical film 200. In some embodiments, the incident light 20 propagating in the incident plane P may be polarized in a second orthogonal in-plane direction within the multilayer optical film 200. In other words, in such embodiments, the incident light 20 propagating in the incident plane P may be polarized along the y-axis within the multilayer optical film 200.

[0069] Figure 1 Incident light 22, propagating in the incident plane P including the first direction (i.e., the x-axis) and incident on the outermost surface 201 of the multilayer optical film 200 onto a plurality of alternating polymer first layers 10 and polymer second layers 11 of the multilayer optical film 200, is also shown. The incident light 22 is incident on the plurality of alternating polymer first layers 10 and polymer second layers 11 at an incident angle θ relative to the normal N. In some embodiments, the incident angle θ is less than about 10 degrees. In some embodiments, the incident angle θ is less than about 8 degrees, less than about 6 degrees, less than about 4 degrees, less than about 2 degrees, or less than about 1 degree. In some embodiments, the incident angle θ is about 0 degrees. In such embodiments, the incident light 22 may be equivalent to substantially perpendicular incident light 20. In some embodiments, the incident angle θ is greater than about 40 degrees. In some embodiments, the incident angle θ is greater than about 45 degrees, greater than about 50 degrees, or greater than about 55 degrees. In some embodiments, the incident angle θ is about 60 degrees.

[0070] In some embodiments, the incident light 22 propagating in the incident plane P including the first direction may be p-polarized incident light. In such embodiments, the incident light 22 may be interchangeably referred to as "p-polarized incident light 22 propagating in the incident plane P including the first direction".

[0071] In some embodiments, the incident plane P' (not shown) includes an orthogonal second direction (i.e., the y-axis). In such embodiments, the incident plane P is substantially along the yz plane of the multilayer optical film 200. In some embodiments, the incident light 22 propagating in the incident plane P' including the second direction may be p-polarized incident light. In such embodiments, the incident light 22 is interchangeably referred to as "p-polarized incident light 22 propagating in the incident plane P' including the second direction".

[0072] Figure 2A A multilayer optical film 200 according to one embodiment of the present disclosure is shown. Figure 1 (as shown) and conventional optical films for substantially perpendicular incident light 20 ( Figure 1 The corresponding optical transmittance curves (shown) are plotted in Figure 210. Specifically, Figure 210 shows the corresponding optical transmittance of the multilayer optical film 200 and the conventional optical film for substantially perpendicular incident light 20 polarized along a first direction and along an orthogonal second direction. Figure 2A The optical transmittance of the multilayer optical film 200 and the conventional optical film for p-polarized incident light 22 propagating in an incident plane P including a first direction, and for p-polarized incident light 22 propagating in an incident plane P' including a second direction and incident at an incident angle θ of less than about 10 degrees, is also depicted. Wavelength is expressed in nanometers (nm) on the horizontal axis. Optical transmittance is expressed as a percentage of transmittance on the left vertical axis.

[0073] In some embodiments, conventional optical films may have a structure substantially similar to that of multilayer optical films 200. However, the multiple first layers of a conventional optical film may include approximately 100% by weight of LmPEN.

[0074] Now for reference Figure 1 and Figure 2A Graph 210 includes curves 211 corresponding to the optical transmittance of a plurality of alternating polymer first layers 10 and polymer second layers 11 for substantially perpendicular incident light 20 propagating in the incident plane P and polarized along a first direction in the multilayer optical film 200. Therefore, curve 211 corresponds to the optical transmittance of a plurality of alternating polymer first layers 10 and polymer second layers 11 for p-polarized incident light 22 propagating in the incident plane P including the first direction and for an incident angle θ of less than about 10 degrees.

[0075] Graph 210 also includes curve 212 corresponding to the optical transmittance of the conventional optical film for substantially perpendicular incident light 20 propagating in the incident plane P and polarized along a first direction in the conventional optical film. Thus, curve 212 corresponds to the optical transmittance of the conventional optical film for p-polarized incident light 22 propagating in the incident plane P including the first direction and for an incident angle θ of less than about 10 degrees.

[0076] Graph 210 also includes curve 213 corresponding to the optical transmittance of the plurality of alternating polymer first layers 10 and polymer second layers 11 for substantially perpendicular incident light 20 propagating in the incident plane P' and polarized in the second direction in the multilayer optical film 200. Therefore, curve 213 corresponds to the optical transmittance of the plurality of alternating polymer first layers 10 and polymer second layers 11 for p-polarized incident light 22 propagating in the incident plane P' including the second direction and for an incident angle θ of less than about 10 degrees.

[0077] Graph 210 also includes curve 214 corresponding to the optical transmittance of the conventional optical film for substantially perpendicular incident light 20 propagating in the incident plane P' and polarized in the conventional optical film along a second orthogonal direction. Therefore, curve 214 corresponds to the optical transmittance of the conventional optical film for p-polarized incident light 22 propagating in the incident plane P' including the second direction and for an incident angle θ less than about 10 degrees.

[0078] Figure 2B The diagram shows a list of multilayer optical films 200 ( Figure 1 (as shown) and conventional optical films for substantially perpendicular incident light 20 ( Figure 1 Table 250 shows some exemplary values ​​of the corresponding average optical transmittance for the visible light wavelength range 21. Table 250 also lists the values ​​of the multilayer optical film 200 and conventional optical films for substantially perpendicular incident light 20 and for the infrared wavelength range 23 extending from about 700 nm to about 960 nm. Figure 2A Some exemplary values ​​of the corresponding optical transmittance for at least one wavelength W1 in (shown). Table 250 corresponds to... Figure 2A The curve is 210.

[0079] Table 250 includes multiple column headers in row 251. The column headers in row 251 include substantially perpendicular incident light 20 polarized along a first direction and substantially perpendicular incident light 20 polarized along a second direction. Table 250 also includes multiple column subheadings in row 252. The column subheadings in row 252 include multilayer optical films 200 and conventional optical films for each of substantially perpendicular incident light 20 polarized along the first direction and substantially perpendicular incident light 20 polarized along the second direction. Column 253 includes at least one wavelength W1 (approximately 760 nm) in the visible light wavelength range 21 (approximately 420 nm to approximately 680 nm) and the infrared wavelength range 23 (approximately 700 nm to approximately 960 nm).

[0080] Table 250 includes a unit 230 indicating the value of the average optical transmittance 30 of the multilayer optical film 200 for the visible light wavelength range 21 and for substantially perpendicular incident light 20 polarized along a first direction. Table 250 also includes a unit 231 indicating the value of the average optical transmittance 31 of the multilayer optical film 200 for the visible light wavelength range 21 and for substantially perpendicular incident light 20 polarized along a second direction. Table 250 also includes a unit 255 indicating the optical transmittance T1 of the multilayer optical film 200 for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 in the infrared wavelength range 23, and for an incident angle θ of less than about 10 degrees.

[0081] refer to Figure 1 and Figures 2A to 2B As is evident from curve 211, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along a first direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 30 between about 10% and about 30%. In some embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along a first direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 30 between about 12% and about 25%, between about 14% and about 20%, between about 15% and about 20%, or between about 16% and about 20%.

[0082] In some embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along a first direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 30 of about 18.64%. In some other embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along a first direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 30 of about 20.57%.

[0083] In addition, for p-polarized incident light 22 propagating in the incident plane P including the first direction and for at least one wavelength W1 in the infrared wavelength range 23, a plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T1 for an incident angle θ of less than about 10 degrees.

[0084] In some embodiments, for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of 0 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T1 of about 33.93%. In some other embodiments, for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of 0 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T1 of about 38.86%.

[0085] As is evident from curve 212, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the first direction, the conventional optical film has an average optical transmittance of less than about 5%. In some embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the first direction, the conventional optical film has an average optical transmittance of about 2.24%.

[0086] Furthermore, for p-polarized incident light 22 propagating in the incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 0 degrees, the conventional optical film has an optical transmittance T1' of about 2.24%.

[0087] Therefore, as is evident from curves 211 and 212, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the first direction, the average optical transmittance 30 of the multilayer optical film 200 is greater than the average optical transmittance of a conventional optical film.

[0088] In addition, the optical transmittance T1 of the multilayer optical film 200 is basically greater than the optical transmittance T1' of the conventional optical film.

[0089] As is evident from curve 213, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the second direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 31 greater than about 60%. In some embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the second direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 31 greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85%.

[0090] In some embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along a second direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 31 of approximately 89%. In some other embodiments, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along a second direction in the multilayer optical film 200, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance 31 of approximately 88.78%.

[0091] Furthermore, for p-polarized incident light 22 propagating in the incident plane P' including the second direction and for at least one wavelength W1 in the infrared wavelength range 23, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T1s for an incident angle θ of less than about 10 degrees.

[0092] In some embodiments, for p-polarized incident light 22 propagating in an incident plane P' including the second direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of 0 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T1s of about 91.98%. In some other embodiments, for p-polarized incident light 22 propagating in an incident plane P' including the second direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of 0 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T1s of about 89.89%.

[0093] Furthermore, as is evident from curves 211 and 213, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, the average optical transmittance 30 of the plurality of alternating polymer first layers 10 and polymer second layers 11 when the incident light 20 is polarized along a first direction is less than the average optical transmittance 31 of the plurality of alternating polymer first layers 10 and polymer second layers 11 when the incident light 20 is polarized along a second direction. Therefore, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, the multilayer optical film 200 can act as a reflective polarizer.

[0094] Reference curve 214 shows that, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the second direction, the conventional optical film has an average optical transmittance of approximately 88.49%.

[0095] Furthermore, for p-polarized incident light 22 propagating in the incident plane P' including the second direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 0 degrees, the conventional optical film has an optical transmittance T1s' of about 89.79%.

[0096] As is evident from curves 213 and 214, for substantially perpendicular incident light 20 and for the visible light wavelength range 21, when the incident light 20 is polarized along the second direction, the average optical transmittance of the multilayer optical film 200 is comparable to that of a conventional optical film.

[0097] In addition, the optical transmittance T1s of the multilayer optical film 200 is comparable to that of the conventional optical film T1s'.

[0098] As is evident from curves 211 to 214, when the incident light 20 is polarized along the first direction, the average optical transmittance 30 of the multilayer optical film 200 is greater than that of a conventional optical film for substantially perpendicular incident light 20 and for the visible light wavelength range 21. Therefore, the multilayer optical film 200 can be a weaker reflective polarizer compared to conventional optical films. A weaker reflective polarizer may be desirable in several optical applications such as windshields, virtual reality / augmented reality, and head-up display (HUD) applications.

[0099] Figure 2C A multilayer optical film 200 according to one embodiment of the present disclosure is shown. Figure 1 (as shown) and conventional optical films for p-polarized incident light 22 propagating in the incident plane P including the first direction (as shown) Figure 1 (As shown in the figure) and a graph 220 showing the corresponding optical transmittance of p-polarized incident light 22 propagating in the incident plane P' including the second direction and incident at an incident angle θ greater than about 40 degrees. Wavelength is expressed in nanometers (nm) on the horizontal axis. Optical transmittance is expressed as a percentage of transmittance on the left vertical axis.

[0100] Now for reference Figure 1 and Figure 2C The graph 220 includes curves 221 corresponding to multiple alternating polymer first layers 10 and polymer second layers 11 for p-polarized incident light 22 propagating in an incident plane P including a first direction and for an incident angle θ greater than about 40 degrees.

[0101] The graph 220 also includes a curve 222 corresponding to the optical transmittance of a conventional optical film for p-polarized incident light 22 propagating in an incident plane P including the first direction and for an incident angle θ greater than about 40 degrees.

[0102] The graph 220 also includes a graph 223 corresponding to multiple alternating polymer first layers 10 and polymer second layers 11 for p-polarized incident light 22 propagating in an incident plane P' including the second direction and for an incident angle θ greater than about 40 degrees.

[0103] The graph 220 also includes a curve 224 corresponding to the optical transmittance of a conventional optical film for p-polarized incident light 22 propagating in an incident plane P' including the second direction and for an incident angle θ greater than about 40 degrees.

[0104] Figure 2D The diagram shows a list of multilayer optical films 200 ( Figure 1 (as shown) and conventional optical films for p-polarized incident light 22 propagating in the incident plane P including the first direction (as shown) Figure 1Table 260 shows some exemplary values ​​for the average optical transmittance of p-polarized incident light 22 propagating in the incident plane P' including the second direction and incident at an incident angle θ greater than about 40 degrees, and for the corresponding visible light wavelength range 21. Table 260 also lists some exemplary values ​​for the optical transmittance of the multilayer optical film 200 and conventional optical films for p-polarized incident light 22 propagating in the incident plane P including the first direction and incident at an incident angle θ greater than about 40 degrees, and for at least one wavelength W1 in the infrared wavelength range 23. Table 260 corresponds to... Figure 2C The curve is 220.

[0105] Table 260 includes multiple column headers in row 261. The column headers in row 261 include p-polarized incident light 22 propagating in an incident plane P including a first direction and p-polarized incident light 22 propagating in an incident plane P' including a second direction. Table 260 also includes multiple column subheadings in row 262. The column subheadings in row 262 include multilayer optical films 200 and conventional optical films for each of the p-polarized incident light 22 propagating in an incident plane P including a first direction and p-polarized incident light 22 propagating in an incident plane P' including a second direction. Column 263 includes at least one wavelength W1 (about 760 nm) in the visible light wavelength range 21 (about 420 nm to about 680 nm) and the infrared wavelength range 23 (about 700 nm to about 960 nm).

[0106] Table 260 includes a unit 265 indicating the optical transmittance T2 of the multilayer optical film 200 for p-polarized incident light 22 propagating in an incident plane P including a first direction, for an incident angle θ greater than about 40 degrees, and for at least one wavelength W1 in the infrared wavelength range 23.

[0107] refer to Figure 1 and Figures 2C to 2D As is evident from curve 221, in some embodiments, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance of about 6.19% for p-polarized incident light 22 propagating in an incident plane P including the first direction, for the visible light wavelength range 21, and for an incident angle θ of about 60 degrees. In some other embodiments, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance of about 8.12% for p-polarized incident light 22 propagating in an incident plane P including the first direction, for the visible light wavelength range 21, and for an incident angle θ of about 60 degrees.

[0108] In addition, for p-polarized incident light 22 propagating in the incident plane P including the first direction and for at least one wavelength W1 in the infrared wavelength range 23, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T2 for an incident angle θ greater than about 40 degrees.

[0109] In some embodiments, for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 60 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T2 of about 58.8%. In some other embodiments, for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 60 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T2 of about 56.15%.

[0110] For example, from curve 221 and curve 211 ( Figure 2A As shown, it is evident that for p-polarized incident light 22 propagating in an incident plane P including the first direction and for at least one wavelength W1 in the infrared wavelength range 23, the plurality of alternating polymer first layers 10 and polymer second layers 11 have optical transmittances T1 and T2 for corresponding incident angles θ less than about 10 degrees and greater than about 40 degrees.

[0111] Additionally, the difference between T2 and T1 is less than approximately 40%, i.e., (T2–T1) < 40%. In some implementations, (T2–T1) < 35%, (T2–T1) < 30%, or (T2–T1) < 25%.

[0112] In some embodiments, for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23, T1 is about 33.93% and T2 is about 58.8%. Therefore, in such embodiments, (T2–T1) is about 24.87%.

[0113] In some other implementations, for p-polarized incident light 22 propagating in an incident plane P including the first direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23, T1 is about 38.86% and T2 is about 56.15%. Therefore, in such implementations, (T2–T1) is about 17.29%.

[0114] As is evident from curve 222, for p-polarized incident light 22 propagating in the incident plane P including the first direction and for the visible light wavelength range 21, the conventional optical film has an average optical transmittance of about 0.35% for an incident angle θ of about 60 degrees.

[0115] Furthermore, for p-polarized incident light 22 propagating in the incident plane P including the first direction and for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23, the conventional optical film has an optical transmittance T2' of about 52.43% for an incident angle θ of about 60 degrees.

[0116] For example, from curve 212 ( Figure 2A As shown in Figure 222 and curve 222, it is evident that for conventional optical films, for p-polarized incident light 22 propagating in the incident plane P including the first direction, for at least one wavelength W1 of approximately 760 nm in the infrared wavelength range 23, T1' is approximately 2.24% and T2' is approximately 52.43%. Therefore, (T2'-T1') is approximately 50.19%.

[0117] Therefore, the difference between T2 and T1 of the multilayer optical film 200 is smaller than the difference between T2' and T1' of the conventional optical film.

[0118] As is evident from curve 223, in some embodiments, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance of approximately 97.64% for p-polarized incident light 22 propagating in an incident plane P' including the second direction, for the visible light wavelength range 21, and for an incident angle θ of approximately 60 degrees. In some other embodiments, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an average optical transmittance of approximately 97.04% for p-polarized incident light 22 propagating in an incident plane P' including the second direction, for the visible light wavelength range 21, and for an incident angle θ of approximately 60 degrees.

[0119] Furthermore, for p-polarized incident light 22 propagating in the incident plane P' including the second direction and for at least one wavelength W1 in the infrared wavelength range 23, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T2s for an incident angle θ greater than about 40 degrees.

[0120] In some embodiments, for p-polarized incident light 22 propagating in an incident plane P' including the second direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 60 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T2s of about 99.11%. In some other embodiments, for p-polarized incident light 22 propagating in an incident plane P' including the second direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 60 degrees, the plurality of alternating polymer first layers 10 and polymer second layers 11 have an optical transmittance T2s of about 98.61%.

[0121] As is evident from curve 224, for p-polarized incident light 22 propagating in the incident plane P' including the second direction, for the visible light wavelength range 21, and for an incident angle θ of about 60 degrees, the conventional optical film has an average optical transmittance of about 95.95%.

[0122] Furthermore, for p-polarized incident light 22 propagating in the incident plane P' including the second direction, for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 and for an incident angle θ of about 60 degrees, the conventional optical film has an optical transmittance T2s' of about 99.4%.

[0123] Figure 3A A perspective view of a roll 310 of a multilayer optical film 200 according to one embodiment of the present disclosure is shown. The multilayer optical film 200 may be wound into a roll 310 during the commercial manufacturing of the multilayer optical film 200. The multilayer optical film 200 may be wound into a roll 310 by a roll-to-roll process during the manufacturing of the multilayer optical film 200. The multilayer optical film 200 includes a central region 311 defined near a central axis 312 of the multilayer optical film 200 and side regions 313 defined near corresponding edges 314 of the multilayer optical film 200.

[0124] In some embodiments, the multilayer optical film 200 has a width B of at least 140 centimeters (cm). The width B may be defined between the edges 314 of the multilayer optical film 200. In some embodiments, the multilayer optical film 200 has a width B of at least 145 cm, at least 150 cm, at least 170 cm, at least 190 cm, at least 200 cm, at least 210 cm, at least 220 cm, or at least 225 cm.

[0125] In some embodiments, the multilayer optical film 200 has a length L of at least 40 meters (m). The length L may be defined along the central axis 312 of the multilayer optical film 200. For illustrative purposes, in Figure 3AThe length L is shown in the middle. In some embodiments, the multilayer optical film 200 has a length L of at least 50m, at least 75m, at least 95m, at least 100m, at least 125m, at least 150m, at least 175m, at least 200m, at least 300m, at least 400m, or at least 500m.

[0126] Figure 3B A multilayer optical film 200 according to one embodiment of the present disclosure is shown. Figure 3A Volume 310 (as shown) Figure 3A (As shown) along the length L of the multilayer optical film 200 and across its width B Figure 3A The graph 320 shows the average effective transmittance of the multilayer optical film (as shown) and the corresponding changes in the average effective transmittance along the roll of the conventional optical film, its length, and its width. Width is expressed in inches on the horizontal axis. Average effective transmittance is expressed on the vertical axis. The width B of the multilayer optical film 200 and the width of the conventional optical film are approximately 17 inches.

[0127] As used herein, the term "average effective transmittance" refers to the average light transmittance of substantially perpendicularly incident light. Substantially perpendicularly incident light can be unpolarized or polarized. Average effective transmittance is the effective transmittance measured or averaged over substantially the entire area of ​​a multilayer optical film 200 or a conventional 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 indicated in the ASTM D1003-13 test standard, light transmittance is a transmittance weighted according to the spectral luminous efficiency function V(λ) of the 1987 International Commission on Illumination (CIE).

[0128] Graph 320 includes a curve 321 depicting the variation of the average effective transmittance of the multilayer optical film 200 along its length L and across its width B according to a first embodiment of the present disclosure.

[0129] Graph 320 includes a curve 322 depicting the variation of the average effective transmittance of the multilayer optical film 200 along its length L and across its width B according to a second embodiment of the present disclosure.

[0130] The graph 320 also includes a curve 323 depicting the variation of the average effective transmittance of the conventional optical film along its length and across its width.

[0131] Figure 3C Table 350 shows some exemplary values ​​of the average effective transmittance of multilayer optical films 200 and conventional optical films along their respective lengths and across their respective widths, according to the first and second embodiments.

[0132] Table 350 includes multiple column headers in row 351. The column headers in row 351 include the multilayer optical film 200 according to the first embodiment, the multilayer optical film 200 according to the second embodiment, and a conventional optical film. Column 352 includes the corresponding widths of the multilayer optical film 200 according to the first embodiment, the multilayer optical film 200 according to the second embodiment, and the conventional optical film, the corresponding minimum average effective transmittance ET1, the corresponding maximum average effective transmittance ET2, and the ratio between ET1 and ET2. Table 350 also includes multiple cells corresponding to different values ​​of the average effective transmittance across the corresponding widths of the multilayer optical film 200 according to the first embodiment, the multilayer optical film 200 according to the second embodiment, and the conventional optical film.

[0133] refer to Figures 3A to 3C As is evident from curves 321 and 322, the multilayer optical film 200 according to the first and second embodiments has a corresponding minimum average effective transmittance ET1 in the corresponding intermediate region 311 (approximately 9 inches). Furthermore, the multilayer optical film 200 according to the first and second embodiments has a corresponding maximum average effective transmittance ET2 in the corresponding side regions 313 (approximately 1 inch and approximately 17 inches, respectively).

[0134] Therefore, along the length L of the multilayer optical film 200, the multilayer optical film 200 has an average effective transmittance ET1 in the middle region 311 and an average effective transmittance ET2 in the side region 313.

[0135] In some embodiments, the ratio between ET1 and ET2 is less than or equal to about 0.97, i.e., (ET1 / ET2) ≤ 0.97. In some embodiments, (ET1 / ET2) ≤ 0.96, (ET1 / ET2) ≤ 0.95, or (ET1 / ET2) ≤ 0.94. Therefore, the average effective transmittance ET2 in the side region 313 of the multilayer optical film 200 is greater than the average effective transmittance ET1 in the middle region 311 of the multilayer optical film 200.

[0136] In some embodiments, ET1 is approximately 1.513 and ET2 is approximately 1.593. Therefore, (ET1 / ET2) is approximately 0.95. In some embodiments, ET1 is approximately 1.468 and ET2 is approximately 1.569. Therefore, (ET1 / ET2) is approximately 0.936.

[0137] Additionally, the multilayer optical film 200 has an average effective transmittance of less than about 1.68. In some embodiments, the multilayer optical film 200 has an average effective transmittance of less than about 1.66, less than about 1.64, less than about 1.62, less than about 1.6, less than about 1.58, less than about 1.56, less than about 1.54, less than about 1.52, less than about 1.5, or less than about 1.48. In some embodiments, the multilayer optical film 200 has an average effective transmittance between about 1.65 and about 1.4. In some embodiments, the multilayer optical film 200 has an average effective transmittance between about 1.63 and about 1.42, or between about 1.61 and about 1.44.

[0138] Referring to curve 323, in some embodiments, the conventional optical film has an average effective transmittance ET1 of approximately 1.693 and an average effective transmittance ET2 of approximately 1.717. Therefore, (ET1 / ET2) is approximately 0.986. Thus, for the conventional optical film, the average effective transmittances ET1 and ET2 are substantially similar. As is evident from curve 323, the conventional optical film exhibits a substantially flat profile.

[0139] In some embodiments, the multilayer optical film 200 has suitable chemical resistance to one or more solvents such as isopropanol (IPA), acetone, toluene, and methyl ethyl ketone (MEK). In some embodiments, applying one or more of IPA, acetone, toluene, and MEK to the multilayer optical film 200 will not damage it. In some embodiments, damage to the multilayer optical film 200 can be assessed by measuring the optical haze of the multilayer optical film 200 before and after applying one or more solvents. Generally, applying one or more solvents to the multilayer optical film 200 increases the optical haze of the multilayer optical film 200.

[0140] As used herein, the term "optical haze" refers to the scattering of light as it passes through a material. Optical haze refers to the specific light transmission and wide-angle light scattering characteristics of a planar portion of a material. Optical haze can be determined according to ASTM D-1003-07 ("Standard Test Method for Haze and Light Transmittance for Transparent Plastics"). Optical haze values ​​are reported as a percentage. Materials with high haze values ​​are generally more turbid and less transparent. Materials with low haze values ​​are generally less turbid and more transparent.

[0141] In some embodiments, applying one or more of IPA, acetone, toluene, and MEK to the multilayer optical film 200 increases the optical haze of the multilayer optical film 200 by no more than about 10%. In some embodiments, applying one or more of IPA, acetone, toluene, and MEK to the multilayer optical film 200 increases the optical haze of the multilayer optical film 200 by no more than about 8%, no more than about 6%, no more than about 5%, no more than about 4%, no more than about 2%, or no more than about 1%. Therefore, the increase in optical haze of the multilayer optical film 200 after the application of one or more solvents is substantially small, indicating that the multilayer optical film 200 has high chemical resistance to one or more solvents.

[0142] Figure 4A A detailed schematic cross-sectional view of a display system 400 according to one embodiment of the present disclosure is shown. The display system 400 includes a display panel 50 disposed on a backlight 300. The backlight 300 includes an extended illumination source 40 configured to emit light 41 through and across its extended emitting surface 42 for illuminating the display panel 50. The extended illumination source 40 includes at least one light source 43, 44. Figure 4A In the illustrated embodiment, the extended lighting source 40 includes two light sources 43, 44. Therefore, at least one light source 43, 44 comprises two light sources 43, 44. The light sources 43 may be arranged in series, and the light source 44 may be positioned at the edge of the extended lighting source 40. Figure 4A In the illustrated embodiment, the extended lighting source 40 includes a plurality of light sources 43 arranged in series. Additionally, the extended lighting source 40 includes at least two light sources 44 disposed on opposite edges of the extended lighting source 40.

[0143] The backlight 300 also includes a multilayer optical film 200. The multilayer optical film 200 is disposed on the extended emitting surface 42 and is substantially co-extended with the extended emitting surface in length and width.

[0144] Light 41 may be interchangeably referred to as "emitted light 41". The display panel 50 is configured to receive the emitted light 41 and form an image 51.

[0145] In some embodiments, the backlight 300 includes a first prism film 90 disposed between the multilayer optical film 200 and the extended illumination source 40. In some embodiments, the first prism film 90 may be a brightness enhancement film. In some embodiments, the first prism film 90 includes a plurality of first prisms 91 extending along a first longitudinal direction. In some embodiments, the first longitudinal direction may be along the y-axis.

[0146] In some embodiments, the backlight 300 further includes a second prism film 92 disposed between the multilayer optical film 200 and the first prism film 90. In some embodiments, the second prism film 92 includes a plurality of second prisms 93 extending along a second longitudinal direction different from the first longitudinal direction. In some embodiments, the second longitudinal direction may be along the x-axis.

[0147] In some embodiments, the backlight 300 further includes at least one optical diffuser film 100, 101 disposed between the multilayer optical film 200 and the extended illumination source 40 and configured to receive and scatter the emitted light 41. Figure 4A In the illustrated embodiment, at least one optical diffuser film 100, 101 comprises two optical diffuser films 100, 101. The optical diffuser film 100 is disposed between the extended illumination source 40 and the first prism film 90. The optical diffuser film 101 is disposed between the second prism film 92 and the multilayer optical film 200.

[0148] Figure 4B A detailed schematic cross-sectional view of an extended illumination source 40' according to one embodiment of the present disclosure is shown. In some embodiments, an extended illumination source 40' may be used in the backlight 300 instead of an extended illumination source 40 (…). Figure 4A (As shown). In some embodiments, the extended illumination source 40' includes a light guide 60 for propagating light 61, 62 therein primarily by total internal reflection along the length and width of the light guide 60. In some embodiments, the length of the light guide 60 is along the x-axis and the width of the light guide 60 is along the y-axis. In some embodiments, the light guide 60 is a solid light guide. In some embodiments, the light guide 60 is a substantially hollow light guide.

[0149] In some implementations, the light guide 60 includes an extended emitting surface 42.

[0150] In some embodiments, the extended lighting source 40' also includes at least one light source 44 disposed near the side surfaces 53, 53a of the light guide 60. Figure 4B In the illustrated embodiment, at least one light source 44 includes two light sources. One of the two light sources 44 is positioned near the side surface 53, and the other of the two light sources 44 is positioned near the side surface 53a.

[0151] In some embodiments, the extended illumination source 40' includes a back reflector 70 configured to reflect light 62 exiting the light guide 60 toward the back reflector 70. In some embodiments, the back reflector 70 may reflect light 62 back toward the light guide 60. The light reflected from the back reflector 70 may be referred to as "reflected light 63". In some embodiments, the reflected light 63 exits the extended illumination source 40' through the extended emitting surface 42.

[0152] In some embodiments, the back reflector 70 may be highly reflective. For example, the back reflector 70 may have an axial average reflectivity of at least 90%, 95%, 98%, 99%, or greater. Such reflectivity values ​​may include both specular and diffuse reflection. In some embodiments, the back reflector 70 may be primarily a specular reflector, a diffuse reflector, or a combination of specular and diffuse reflectors, whether spatially uniformly distributed or patterned. In some embodiments, the back reflector 70 may be a semi-specular reflector. In some cases, the back reflector 70 may comprise a rigid metal substrate with a high-reflectivity coating or a high-reflectivity film laminated to a supporting substrate. In some embodiments, the back reflector 70 may comprise one or more elements, such as silver, aluminum, a white coating, a non-conductive coating, etc.

[0153] Figure 4C A detailed schematic cross-sectional view of an extended lighting source 40” according to another embodiment of this disclosure is shown. In some embodiments, an extended lighting source 40” may be used in the backlight 300 instead of an extended lighting source 40 ( Figure 4A (As shown). In some embodiments, the extended illumination source 40” includes an optically diffuser layer 80 for scattering light. In some embodiments, the optically diffuser layer 80 may comprise any suitable diffuser film or plate configured to diffuse or scatter light. For example, the optically diffuser layer 80 may diffuse light by using a textured surface of a substrate or by other means such as incorporating light-diffusing particles within the matrix of the film. In some embodiments, the optically diffuser layer 80 may be substantially similar to or similar to the optically diffuser film 100.

[0154] In some embodiments, the optical diffuser layer 80 includes an extended emitting surface 42. In some embodiments, the extended illumination source 40" includes a back reflector 71 facing the optical diffuser layer 80. The back reflector 71 may be substantially similar to Figure 4B The back reflector 70 is shown. In some embodiments, an optical cavity 72 is defined between the back reflector 71 and the optical diffuser layer 80. In some embodiments, at least one light source 43 is disposed in the optical cavity 72. In some embodiments, the optical cavity 72 may form a recovery cavity.

[0155] Unless otherwise stated, all figures used in the specification and claims to indicate feature dimensions, quantities, and physical properties should be understood to be modified by the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations and can vary according to the desired properties sought by those skilled in the art using the teachings disclosed herein.

[0156] 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 in place of the illustrated and described embodiments without departing from the scope of this disclosure. This application is intended to cover any modifications or variations 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 plurality of alternating polymer first layers and polymer second layers, totaling at least 20, each polymer layer having an average thickness of less than 500 nanometers, wherein the polymer first layer comprises between 10 wt% and 50 wt% polyethylene terephthalate and between 50 wt% and 90 wt% polyethylene naphthalate, such that for substantially perpendicular incident light and for the visible light wavelength range extending from 420 nm to 680 nm, the plurality of alternating polymer first layers and polymer second layers: When the incident light is polarized along a first in-plane direction in the multilayer optical film, it has an average optical transmittance between 10% and 30%; and When the incident light is polarized in the multilayer optical film along a second direction orthogonal in the plane, it has an average optical transmittance of more than 60%. Wherein, for p-polarized incident light propagating in an incident plane including the first direction and for at least one wavelength in an infrared wavelength range extending from 700 nm to 960 nm, the plurality of alternating polymer first layers and polymer second layers have optical transmittances T1 and T2 for corresponding incident angles of less than 10 degrees and greater than 40 degrees, and wherein T2-T1 is less than 40%, and The first polymer layer and the second polymer layer have corresponding refractive indices nx1 and nx2 along the first direction, corresponding refractive indices ny1 and ny2 along the second direction, and corresponding refractive indices nz1 and nz2 along the thickness direction of the multilayer optical film orthogonal to the first and second directions, such that for at least one wavelength in the visible light wavelength range: 0 ≤ nx1 - nx2 ≤ 0.4; The magnitude of the difference between ny1 and ny2 is less than 0.04; and The difference between nz1 and nz2 is less than 0.

04.

2. The multilayer optical film of claim 1, wherein the minimum average peel strength between two portions of the multilayer optical film is greater than 100 g / inch, and wherein each of the two portions comprises at least one polymer layer located in one of the plurality of alternating polymer first layers and polymer second layers.

3. A roll of a multilayer optical film according to claim 1, having a width of at least 140 cm and a length of at least 40 m, wherein along the length of the multilayer optical film, the multilayer optical film has an average effective transmittance ET1 in the middle region and an average effective transmittance ET2 in the side regions, ET1 / ET2 ≤ 0.

97.

4. A backlight, comprising: An extended illumination source is configured to emit light through and across its extended emitting surface for illuminating a display panel, the extended illumination source comprising at least one light source; and According to claim 1, the multilayer optical film is disposed on the extended emitting surface and substantially coexists with the extended emitting surface in length and width.

5. The backlight source according to claim 4, wherein the extended illumination source comprises: An optical guide for propagating light therein primarily by total internal reflection along its length and width, the optical guide including the extended emitting surface; The at least one light source is disposed near the side surface of the light guide; and A back reflector configured to reflect light exiting the light guide toward the back reflector, the reflected light exiting the extended illumination source through the extended emitting surface.

6. The backlight source according to claim 4, wherein the extended illumination source comprises: An optically diffused layer, the optically diffused layer being used to scatter light and including the extended emitting surface; A back reflector facing the optical diffuser layer, defining an optical cavity between the back reflector and the optical diffuser layer; and The at least one light source is disposed in the optical cavity.

7. A display system, comprising: A display panel is disposed on a backlight according to claim 6, the display panel being configured to receive emitted light and form an image.

8. A backlight, comprising: An extended illumination source is configured to emit light through and across its extended emitting surface for illuminating a display panel, the extended illumination source comprising at least one light source; and A reflective polarizer, disposed on the extended illumination source and substantially co-extending with the extended illumination source in length and width, comprises at least 20 alternating polymer first and polymer second layers, each polymer layer having an average thickness of less than 500 nm, such that for substantially perpendicular incident light and for the visible light wavelength range extending from 420 nm to 680 nm, the alternating polymer first and polymer second layers: When the incident light is polarized in a first in-plane direction within the reflective polarizer, it has an average optical transmittance between 10% and 30%; and When the incident light is polarized in the reflective polarizer along a second orthogonal direction within the plane, it has an average optical transmittance greater than 60%. The reflected polarizer described herein has an average effective transmittance between 1.65 and 1.

4. Wherein, for p-polarized incident light propagating in an incident plane including the first direction and for at least one wavelength in an infrared wavelength range extending from 700 nm to 960 nm, the plurality of alternating polymer first layers and polymer second layers have optical transmittances T1 and T2 for corresponding incident angles of less than 10 degrees and greater than 40 degrees, and wherein T2-T1 is less than 40%, and The first polymer layer and the second polymer layer have corresponding refractive indices nx1 and nx2 along the first direction, corresponding refractive indices ny1 and ny2 along the second direction, and corresponding refractive indices nz1 and nz2 along the thickness direction of the reflective polarizer orthogonal to the first and second directions, such that for at least one wavelength in the visible light wavelength range: 0 ≤ nx1 - nx2 ≤ 0.4; The magnitude of the difference between ny1 and ny2 is less than 0.04; and The difference between nz1 and nz2 is less than 0.

04.

9. The backlight according to claim 8, wherein the polymer first layer comprises between 10% and 50% by weight of PET and between 50% and 90% by weight of PEN.

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