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

Abstract

The multilayer optical film includes a plurality of alternating first and second polymer layers totaling at least 20. The first polymer layer includes about 10%-50% by weight polyethylene terephthalate and about 50%-90% by weight polyethylene naphthalate. The multilayer optical film has, for a visible wavelength range, an average optical transmittance of about 10%-30% when the incident light is polarized along a first direction and an average optical transmittance of greater than about 60% when the incident light is polarized along an in-plane, orthogonal, second direction, for substantially perpendicular incident light. The multilayer optical film has optical transmittances T1 and T2 for at least one wavelength in the infrared wavelength range for p-polarized incident light, for angles of incidence less than about 10 degrees and greater than about 40 degrees, respectively, where T2-T1 is less than about 40%.

Description

[Technical field]

[0001] The present disclosure relates to multilayer optical films. The present disclosure further relates to rolls of the multilayer optical films, backlights including the multilayer optical films, and display systems including the backlights. [Background technology]

[0002] A display system includes a backlight that provides light to a display panel. The backlight typically includes a multilayer optical film that can have a polarizing effect, i.e., the multilayer optical film can act as a polarizer. A polarizer is an optical element that allows incident light of one polarization state to be substantially transmitted through the polarizer while substantially blocking light of another polarization state. Summary of the Invention

[0003] In a first aspect, the present disclosure provides a multilayer optical film comprising a plurality of alternating first and second polymer layers totaling at least 20. Each of the first and second polymer layers has an average thickness of less than about 500 nanometers (nm). The first polymer layer comprises about 10% to about 50% by weight of polyethylene terephthalate (PET) and about 50% to about 90% by weight of polyethylene naphthalate (PEN). The plurality of alternating first and second polymer layers have an average optical transmittance of about 10% to about 30% for a visible wavelength range of about 420 nm to about 680 nm for substantially perpendicular incident light, when the incident light is polarized along a first direction in the plane of the multilayer optical film. Furthermore, the plurality of alternating first and second polymer layers have an average optical transmittance of more than about 60% for a visible wavelength range, when the incident light is polarized along an orthogonal second direction in the plane of the multilayer optical film, for substantially perpendicular incident light. Further, the plurality of alternating first and second polymer layers have optical transmittances T1 and T2 for at least one wavelength in the infrared wavelength range of about 700 nm to about 960 nm, for p-polarized incident light propagating in a plane of incidence that includes the first direction, for angles of incidence less than about 10 degrees and greater than about 40 degrees, respectively, where (T2-T1) is less than about 40%.

[0004] The present disclosure provides, in a second aspect, a roll of the multilayer optical film of the first aspect having a width of at least 140 centimeters (cm) and a length of at least 40 meters (m), the multilayer optical film having an average effective transmission ET1 in the middle region and an average effective transmission ET2 in the side regions along the length of the multilayer optical film, where (ET1 / ET2)≦0.97.

[0005] The present disclosure provides in a third aspect a backlight including an extended illumination source configured to emit light through and across an extended emission surface of the illumination source to illuminate a display panel. The extended illumination source includes at least one light source. The backlight further includes a multilayer optical film of the first aspect disposed on the extended emission surface and substantially coextensive in length and width with the extended emission surface.

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

[0007] The present disclosure provides, in a fifth aspect, a backlight including an extended illumination source configured to emit light through and across an extended emission surface of the illumination source to illuminate a display panel. The extended illumination source includes at least one light source. The backlight further includes a reflective polarizer disposed on the extended illumination source and substantially coextensive in length and width with the extended illumination source. The reflective polarizer includes a plurality of alternating first and second polymer layers totaling at least 20. Each of the first and second polymer layers has an average thickness of less than about 500 nm. The plurality of alternating first and second polymer layers have an average light transmittance of about 10% to about 30% for a visible wavelength range ranging from about 420 nm to about 680 nm for substantially perpendicular incident light, when the incident light is polarized along a first direction in the plane of the reflective polarizer. Additionally, the plurality of alternating first and second polymer layers have an average light transmission of greater than about 60% over the visible wavelength range for substantially normally incident light when the incident light is polarized along an orthogonal second direction in the plane of the reflective polarizer, and the reflective polarizer has an average effective transmission of from about 1.65 to about 1.4.

[0008] The present disclosure provides in a sixth aspect a display system including a display panel disposed on the backlight of the fifth aspect, the display panel being configured to receive emitted light and form an image. [Brief description of the drawings]

[0009] Exemplary embodiments disclosed herein will be more fully understood by consideration of the following Detailed Description in conjunction with the following figures, in which the figures are not necessarily drawn to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a particular figure is not intended to limit the component in another figure bearing the same number. [Figure 1] FIG. 2 is a detailed cross-sectional schematic diagram of a multilayer optical film according to one embodiment of the present disclosure. [Figure 2A] 2 is a plot illustrating the optical transmission for substantially normally incident light for the multilayer optical film of FIG. 1 and a conventional optical film, respectively, according to one embodiment of the present disclosure. [Figure 2B] 2B is a table listing the average light transmission of each of the multilayer optical films and conventional optical films, and some exemplary values ​​of the respective light transmission, corresponding to the plot of FIG. 2A. [Figure 2C] 2 is a plot showing the light transmission for an incidence angle greater than about 40 degrees for the multilayer optical film of FIG. 1 and a conventional optical film, respectively, according to one embodiment of the present disclosure. [Figure 2D] 2D is a table listing the average light transmission of each of the multilayer optical films and conventional optical films, and some exemplary values ​​of the respective light transmission, corresponding to the plot of FIG. 2C. [Figure 3A] 2 is a perspective view of a roll of multilayer optical film including the optical film of FIG. 1 according to one embodiment of the present disclosure. [Figure 3B] 1 is a plot showing the respective variation across a range of average effective transmission for two multilayer optical films according to one embodiment of the present disclosure and a conventional optical film. [Figure 3C] 3C is a table listing several exemplary values ​​of the average effective transmission for each of two multilayer optical films and a conventional optical film, corresponding to the plot of FIG. 3B. [Figure 4A] FIG. 2 is a detailed cross-sectional schematic diagram of a display system according to one embodiment of the present disclosure. [Figure 4B] FIG. 4B is a detailed cross-sectional schematic diagram of an extended illumination source of the display system of FIG. 4A according to one embodiment of the present disclosure. [Figure 4C] FIG. 4B is a detailed cross-sectional schematic diagram of an extended illumination source of the display system of FIG. 4A according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0011] In the disclosure that follows, the following definitions apply:

[0012] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably.

[0013] The term "generally," when used herein as a modifier to a characteristic or attribute, unless specifically defined otherwise, means that the characteristic or attribute is one that would be readily recognized by one of ordinary skill in the art, but does not require absolute precision or perfect agreement (e.g., within ±20% for quantifiable characteristics).

[0014] The term "substantially" means, unless specifically defined otherwise, a close degree of approximation (e.g., within ±10% for quantifiable characteristics), but again does not require absolute precision or perfect agreement.

[0015] All numbers described herein are to be considered as modified by the term "about," which, unless otherwise specifically defined, means a high degree of approximation (e.g., within ±5% for quantifiable properties), but again does not require absolute precision or exact agreement.

[0016] As used herein, the terms "first" and "second" are used as identifiers. Thus, such terms should not be interpreted as limiting the present disclosure. When used in conjunction with features or elements, the terms "first" and "second" can be interchanged throughout the embodiments of the present disclosure.

[0017] As used herein, when a first material is said to be "similar" to a second material, at least 90% by weight of the first and second materials are identical, and if there is a variation between the first and second materials, the variation is less than about 10% by weight of each of the first and second materials.

[0018] As used herein, "at least one of A and B" should be understood to mean "A only, B only, or both A and B."

[0019] As used herein, the term "film" generally refers to a material with a very high ratio of length or width to thickness. A film has two major surfaces defined by a length and a width. A film typically has good flexibility and can be used in a wide variety of applications, including displays. A film can also be of a thickness or material composition such that it is semi-rigid or rigid. The films described in this disclosure can be constructed from a variety of polymeric materials. A film can be a single layer, a multilayer, or a blend of different polymers.

[0020] As used herein, the term "layer" generally refers to a thickness of material having a relatively consistent chemical composition within a film. A layer may be any type of material, including polymeric, cellulosic, metallic, or blends thereof. A given polymer layer may include a single polymer type or a blend of polymers, and may include additives. A given layer may be bonded or connected to other layers to form a film. A layer may be partially or completely continuous compared to an adjacent layer or film. A given layer may be partially or completely coextensive with an adjacent layer. A layer may include sub-layers.

[0021] As used herein, the term "between about" generally refers to an inclusive or closed range unless specifically defined otherwise. For example, if a parameter X is between about A and B, then A≦X≦B.

[0022] As used herein, the term "index" generally refers to the refractive index of a material or layer unless specifically defined otherwise. Similarly, the term "refractive index" generally refers to the refractive index of multiple materials or layers unless specifically defined otherwise.

[0023] Multilayer optical films, such as reflective polarizers, may be used in applications where there may be a requirement to allow light of one polarization state to be substantially transmitted through the polarizer, while substantially blocking light of another polarization state.

[0024] A conventional multilayer optical film can substantially transmit substantially normally incident light polarized along a first direction and substantially block substantially normally incident light polarized along an orthogonal second direction in a desired wavelength range.

[0025] However, in some applications it may be necessary to transmit a portion of substantially normally incident light polarized along a second direction in a desired wavelength range.

[0026] Additionally, in some applications, the multilayer optical films may be exposed to solvents such as isopropyl alcohol (IPA), acetone, toluene, methyl ethyl ketone (MEK), etc., which may damage the multilayer optical films. Thus, in some applications, multilayer optical films that are chemically resistant may be desirable.

[0027] In one aspect, the present disclosure provides a multilayer optical film comprising a plurality of alternating first and second polymer layers totaling at least 20. Each of the first and second polymer layers has an average thickness less than about 500 nanometers (nm). The first polymer layer comprises about 10% to about 50% by weight polyethylene terephthalate (PET) and about 50% to about 90% by weight polyethylene naphthalate (PEN). The plurality of alternating first and second polymer layers have an average optical transmittance of about 10% to about 30% for a visible wavelength range ranging from about 420 nm to about 680 nm for substantially perpendicular incident light, when the incident light is polarized along a first direction in the plane of the multilayer optical film. Furthermore, the plurality of alternating first and second polymer layers have an average optical transmittance of greater than about 60% for a visible wavelength range, when the incident light is polarized along an orthogonal second direction in the plane of the multilayer optical film, for substantially perpendicular incident light. Further, the plurality of alternating first and second polymer layers have optical transmittances T1 and T2 for at least one wavelength in the infrared wavelength range of about 700 nm to about 960 nm, for p-polarized incident light propagating in a plane of incidence that includes the first direction, for angles of incidence less than about 10 degrees and greater than about 40 degrees, respectively, where (T2-T1) is less than about 40%.

[0028] Since the first polymer layer comprises about 10% to about 50% by weight PET and about 50% to about 90% by weight PEN, the multilayer optical film may have an average light transmission of about 10% to about 30% for substantially normally incident light in the visible wavelength range when the incident light is polarized along a first direction. In other words, the multilayer optical film may be a weak polarizer. Such a polarizer may be desirable in some optical applications, including windshield, virtual reality / augmented reality, and head-up display (HUD) applications.

[0029] Furthermore, because (T2-T1) is less than about 40%, the multilayer optical film transmits at least a portion of the p-polarized incident light, regardless of the angle of incidence of the p-polarized incident light, for at least one wavelength in the infrared wavelength range.

[0030] Furthermore, application of one or more of IPA, acetone, toluene, and MEK to the multilayer optical film may not damage the multilayer optical film of the present disclosure, and thus the multilayer optical film may be used in applications requiring chemical resistance to one or more of the aforementioned solvents.

[0031] Turning now to the figures, FIG. 1 shows a detailed cross-sectional schematic diagram of a multilayer optical film 200 according to one embodiment of the present disclosure. The multilayer optical film 200 defines mutually orthogonal x-axis, y-axis, and z-axis. The x-axis and y-axis correspond to the in-plane axes of the multilayer optical film 200, and 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 further 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.

[0032] In some embodiments, the multilayer optical film 200 includes opposing outermost surfaces 201, 202. In some embodiments, at least one of the opposing outermost surfaces 201, 202 may be exposed to an external environment. In some embodiments, each of the opposing outermost surfaces 201, 202 may be exposed to an external environment. In some embodiments, the external environment may include air.

[0033] The multilayer optical film 200 includes a plurality of alternating first and second polymer layers 10, 11 totaling at least 20. In some embodiments, the plurality of first and second polymer layers 10, 11 totals 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.

[0034] Each of the first and second polymer layers 10, 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 of the first and second polymer layers 10, 11. As used herein, the term "average thickness tp" refers to the average thickness of each of the first and second polymer layers 10, 11 measured at a plurality of points across a plane (i.e., the xy plane) of each of the first and second polymer layers 10, 11. In some embodiments, each of the first and second polymer layers 10, 11 has an average thickness tp of less than about 400 nm, or less than about 300 nm, or less than about 250 nm, or less than about 200 nm, or less than about 150 nm, or less than about 100 nm, or less than about 50 nm.

[0035] The first polymer layer 10 comprises about 10% to about 50% by weight polyethylene terephthalate (PET). In some embodiments, the first polymer layer 10 comprises about 20% to about 40% by weight PET. In some embodiments, the first polymer layer 10 comprises about 30% by weight PET. In some embodiments, the first polymer layer 10 comprises about 10% to about 50% by weight copolymer of PET (coPET). In some embodiments, the first polymer layer 10 comprises about 20% to about 40% by weight coPET. In some embodiments, the first polymer layer 10 comprises about 30% by weight coPET.

[0036] The first polymer layer 10 further comprises about 50% to about 90% by weight of polyethylene naphthalate (PEN). In some embodiments, the first polymer layer 10 comprises about 60% to about 80% by weight of PEN. In some embodiments, the first polymer layer 10 comprises about 70% by weight of PEN. In some embodiments, the first polymer layer 10 comprises about 50% to about 90% by weight of LmPEN (a stoichiometric mixture of about 90% PEN and about 10% PET). In some embodiments, the first polymer layer 10 comprises about 60% to about 80% by weight of LmPEN. In some embodiments, the first polymer layer 10 comprises about 70% by weight of LmPEN.

[0037] In some embodiments, the second polymer layer 11 includes polycarbonate (PC) and coPET. In some embodiments, the second polymer layer 11 can include about 35% to about 50% by weight PC and about 50% to about 65% by weight coPET.

[0038] In some embodiments, the multilayer optical film 200 further comprises at least one skin layer 12 having an average thickness ts of greater than about 500 nm. The average thickness ts is defined along the z-axis of the at least one skin layer 12. As used herein, the term "average thickness ts" refers to the average thickness of the at least one skin layer 12 measured at a plurality of points across the plane of the at least one skin layer 12 (i.e., the xy plane). In some embodiments, the at least one skin layer 12 has an average thickness of greater than about 750 nm, or greater than about 1000 nm, or greater than about 1500 nm, or greater than about 2000 nm. The at least one skin layer 12 may function as a protective layer for the multilayer optical film 200. In the illustrated embodiment of FIG. 1, the multilayer optical film 200 comprises a pair of double-sided skin layers 12 including double outermost surfaces 201, 202. The pair of skin layers 12 of the multilayer optical film 200 may function as a protective boundary layer (PBL).

[0039] In some embodiments, the multilayer optical film 200 further comprises at least one intermediate layer 13 disposed between two of the alternating first and second polymer layers 10, 11. In the illustrated embodiment of FIG. 1, the multilayer optical film 200 comprises one intermediate layer 13 disposed between the first polymer layer 10a and the second polymer layer 11a. In some embodiments, the 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 the at least one intermediate layer 13. As used herein, the term "average thickness ti" refers to the average thickness of the at least one intermediate layer 13 measured at a plurality of points across the plane of the at least one intermediate layer 13 (i.e., the xy plane). In some embodiments, the 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.

[0040] In some embodiments, at least one skin layer 12 and at least one intermediate layer 13 may comprise one or more polymeric materials, such as polyhexylethylene naphthalate (PHEN); PEN; copolymers containing PHEN, PEN, and / or other polyesters (e.g., PET or polyesters containing dibenzoic acid); glycol modified polyethylene terephthalate (PETg); PC; poly(methyl methacrylate) (PMMA); or mixtures of these material classes.

[0041] In some embodiments, the first and second polymer layers 10, 11, the at least one skin layer 12, and the at least one intermediate layer 13 may be substantially coextensive with one another or may have similar in-plane dimensions (i.e., length and width). In other words, the first and second polymer layers 10, 11, the at least one skin layer 12, and the at least one intermediate layer 13 may be substantially coextensive with one another in the xy plane.

[0042] The multilayer optical film 200 may have an average thickness t based on desired application attributes. 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 the plane of the multilayer optical film 200 (i.e., the xy plane). In some embodiments, the multilayer optical film 200 has an average thickness t of less than about 40 microns. In some embodiments, the multilayer optical film 200 has an average thickness t of less than about 35 microns, or less than about 32 microns, or less than about 30 microns, less than about 28 microns, or less than about 27 microns. In some embodiments, the multilayer optical film 200 has an average thickness t of about 26 microns. Thus, the multilayer optical film 200 may have an average thickness comparable to that of conventional multilayer optical films.

[0043] In some embodiments, the multilayer optical film 200 may include additional layers, such as a bonding layer (not shown) for bonding any two of the first and second polymer layers 10, 11, the at least one skin layer 12, and the at least one intermediate layer 13 of the multilayer optical film 200. In some embodiments, the bonding layer may be substantially optically transparent. As used herein, the term "optically transparent" may mean having an average light transmittance of greater than about 90% for light in a wavelength range of about 400 nm to about 1000 nm. In some embodiments, the bonding layer may include an optically clear adhesive (OCA). In some other embodiments, the bonding layer may include an epoxy, a laminate, or any other suitable layer.

[0044] In some embodiments, the minimum average peel strength between the 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 per unit width applied to the bonding 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 the multiple alternating first and second polymer layers 10, 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 the 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.

[0045] In some embodiments, the first and second polymer layers 10, 11 have refractive indices nx1 and nx2, respectively, along a first direction (i.e., the x-axis) of the multilayer optical film 200. In some embodiments, the first and second polymer layers 10, 11 have refractive indices ny1 and ny2, respectively, along a second direction (i.e., the y-axis) of the multilayer optical film 200. In some embodiments, the first and second polymer layers 10, 11 have refractive indices nz1 and nz2, respectively, along a thickness direction (i.e., the z-axis) of the multilayer optical film 200 that is orthogonal to the first and second directions.

[0046] In some embodiments, for at least one wavelength in the visible wavelength range 21 (shown in FIG. 2A) of about 420 nm to about 680 nm, the difference between nx1 and nx2 is about 0 or more and about 0.4 or less, i.e., 0≦(nx1-nx2)≦0.4. In some embodiments, for at least one wavelength in the visible 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 about 1.75 to about 1.85. In some embodiments, for at least one wavelength of about 633 nm, nx2 is about 1.55 to about 1.57.

[0047] For at least one wavelength in the visible wavelength range 21, the magnitude of the difference between ny1 and ny2 may be 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 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| is 0. In some embodiments, for at least one wavelength of about 633 nm, ny1 is about 1.57 to about 1.56 and ny2 is about 1.55 to about 1.57.

[0048] For at least one wavelength in the visible wavelength range 21, the magnitude of the difference between nz1 and nz2 may be 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 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| is 0. In some embodiments, for at least one wavelength of about 633 nm, nz1 is about 1.53 to about 1.57 and nz2 is about 1.54 to about 1.57.

[0049] In some embodiments, at least one of nx1, ny1, nz1 may be greater than nx2, ny2, nz2, respectively, for at least one wavelength in the visible wavelength range 21. Thus, the first polymer layer 10 may be a high index optical (HIO) layer and the second polymer layer 11 may be a low index optical (LIO) layer along at least one of the first direction, the second direction, and the thickness direction for at least one wavelength in the visible wavelength range 21. In some embodiments, each of nx1, ny1, nz1 may be greater than nx2, ny2, nz2, respectively, for at least one wavelength in the visible wavelength range 21.

[0050] Generally, birefringence refers to a measure of the optical anisotropy in a layer of the multilayer optical film 200. Furthermore, birefringence is measured as the difference between two refractive indices of that layer along two mutually perpendicular directions (e.g., a first direction and a second direction).

[0051] For at least one wavelength of about 633 nm, the first polymer layer 10 can be observed to have a birefringence |nx1-ny1| of about 0.1 to about 0.29, a birefringence |nx1-nz1| of about 0.1 to about 0.32, and a birefringence |ny1-nz1| of about 0 to about 0.04.

[0052] Furthermore, for at least one wavelength of about 633 nm, in the second polymer layer 11, it can be observed that the birefringence |nx2-ny2| is about 0 to about 0.02, the birefringence |nx2-nz2| is about 0 to about 0.03, and the birefringence |ny2-nz2| is about 0 to about 0.03.

[0053] Thus, the first and second polymer layers 10, 11 of the multilayer optical film 200 may have a relatively low birefringence. The relatively low birefringence may result in a relatively high transmittance of incident light through the first and second polymer layers 10, 11 of the multilayer optical film 200. Furthermore, the relatively low birefringence of the first polymer layer 10 may result from the first polymer layer 10 including 10% to 50% by weight of PET.

[0054] In some embodiments, desired optical properties of the multilayer optical film 200 may be achieved by varying various parameters, such as at least one of the material, total number, and average thickness of the plurality of alternating first and second polymer layers 10, 11, at least one skin layer 12, and at least one intermediate layer 13. Additionally, desired optical properties of the multilayer optical film 200 may be achieved by varying at least one of the refractive indices nx1, ny1, nz1, nx2, ny2, and nz2 of the plurality of first and second polymer layers 10, 11.

[0055] In some embodiments, the multilayer optical film 200 can be a reflective polarizer. In such embodiments, the multilayer optical film 200 can be synonymously referred to as a "reflective polarizer 200." The reflective polarizer 200 thus includes a plurality of alternating first and second polymer layers 10, 11 totaling at least 20.

[0056] 1 further illustrates the incident light 20 propagating in a plane of incidence P that includes a first direction (i.e., the x-axis) and incident on the plurality of alternating first and second polymer layers 10, 11 of the multilayer optical film 200 at the outermost surface 201 of the multilayer optical film 200. In such an embodiment, the plane of incidence P is substantially along the xz plane of the multilayer optical film 200. The incident light 20 is incident on the plurality of alternating first and second polymer layers 10, 11 substantially perpendicularly, i.e., the incident light 20 makes an angle of less than about 10 degrees with the normal N to the multilayer optical film 200 along the z-axis, i.e., the thickness direction of the multilayer optical film 200. Thus, the incident light 20 may be synonymously referred to as "substantially perpendicular incident light 20."

[0057] In some embodiments, incident light 20 propagating in plane of incidence P may be polarized along a first direction in the plane of the multilayer optical film 200. In other words, in such embodiments, incident light 20 propagating in plane of incidence P may be polarized along the x-axis of the multilayer optical film 200. In some embodiments, incident light 20 propagating in plane of incidence P may be polarized along an orthogonal second direction in the plane of the multilayer optical film 200. In other words, in such embodiments, incident light 20 propagating in plane of incidence P may be polarized along the y-axis of the multilayer optical film 200.

[0058] FIG. 1 further illustrates incident light 22 propagating in a plane of incidence P that includes a first direction (i.e., the x-axis) and incident on the plurality of alternating first and second polymer layers 10, 11 of the multilayer optical film 200 at an outermost surface 201 of the multilayer optical film 200. The incident light 22 is incident on the plurality of alternating first and second polymer layers 10, 11 at an angle of incidence θ relative to a normal N. In some embodiments, the angle of incidence θ is less than about 10 degrees. In some embodiments, the angle of incidence 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 angle of incidence θ is about 0 degrees. In such embodiments, the incident light 22 may be equivalent to a substantially normal incident light 20. In some embodiments, the angle of incidence θ is greater than about 40 degrees. In some embodiments, the angle of incidence θ is greater than about 45 degrees, greater than about 50 degrees, or greater than about 55 degrees. In some embodiments, the angle of incidence θ is about 60 degrees.

[0059] In some embodiments, incident light 22 propagating in a plane of incidence P that includes a first direction may be p-polarized incident light. In such embodiments, incident light 22 may be synonymously referred to as "p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction."

[0060] In some embodiments, the plane of incidence P' (not shown) includes an orthogonal second direction (i.e., the y-axis). In such embodiments, the plane of incidence P is substantially along the yz-plane of the multilayer optical film 200. In some embodiments, the incident light 22 propagating in the plane of incidence P' including the second direction can be p-polarized incident light. In such embodiments, the incident light 22 can be synonymously referred to as "p-polarized incident light 22 propagating in the plane of incidence P' including the second direction."

[0061] FIG. 2A is a plot 210 illustrating the respective optical transmission of the multilayer optical film 200 (shown in FIG. 1 ) and a conventional optical film for substantially normally incident light 20 (shown in FIG. 1 ) according to one embodiment of the present disclosure. Specifically, the plot 210 illustrates the respective optical transmission of the multilayer optical film 200 and a conventional optical film for substantially normally incident light 20 polarized along a first direction and polarized along an orthogonal second direction. FIG. 2A further illustrates the respective optical transmission of the multilayer optical film 200 and a conventional optical film for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction, and for p-polarized incident light 22 propagating in a plane of incidence P′ that includes a second direction and incident at an incidence angle θ of less than about 10 degrees. Wavelength is represented in nanometers (nm) on the abscissa. Optical transmission is represented as a transmittance percentage on the left ordinate axis.

[0062] In some embodiments, the conventional optical film can have a structure substantially similar to multilayer optical film 200, except that the first layers of the conventional optical film can include about 100% by weight LmPEN.

[0063] 1 and 2A, plot 210 includes a curve 211 that corresponds to the optical transmission through the plurality of alternating first and second polymer layers 10, 11 for substantially normally incident light 20 propagating in a plane of incidence P and polarized along a first direction in the multilayer optical film 200. Thus, curve 211 corresponds to the optical transmission through the plurality of alternating first and second polymer layers 10, 11 for p-polarized incident light 22 propagating in a plane of incidence P that includes the first direction at an incidence angle θ of less than about 10 degrees.

[0064] Plot 210 further includes a curve 212 that corresponds to the optical transmission through the conventional optical film for substantially normally incident light 20 propagating in a plane of incidence P and polarized along a first direction in the conventional optical film. Thus, curve 212 corresponds to the optical transmission through the conventional optical film for p-polarized incident light 22 propagating in a plane of incidence P that includes the first direction, at an incidence angle θ of less than about 10 degrees.

[0065] Plot 210 further includes a curve 213 corresponding to the optical transmission through the plurality of alternating first and second polymer layers 10, 11 for substantially normally incident light 20 propagating in a plane of incidence P' and polarized along a second direction in the multilayer optical film 200. Thus, curve 213 corresponds to the optical transmission through the plurality of alternating first and second polymer layers 10, 11 for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction at an incidence angle θ of less than about 10 degrees.

[0066] Plot 210 further includes a curve 214 that corresponds to the optical transmission of the conventional optical film for substantially normally incident light 20 propagating in a plane of incidence P' and polarized along a second orthogonal direction of the conventional optical film. Thus, curve 214 corresponds to the optical transmission of the conventional optical film for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction, at an incidence angle θ of less than about 10 degrees.

[0067] Figure 2B shows a table 250 listing several exemplary values ​​of average optical transmittance for each of multilayer optical film 200 (shown in Figure 1) and conventional optical films for a visible wavelength range 21 for substantially normally incident light 20 (shown in Figure 1). Table 250 further lists several exemplary values ​​of optical transmittance for each of multilayer optical film 200 and conventional optical films for at least one wavelength W1 within an infrared wavelength range 23 (shown in Figure 2A) ranging from about 700 nm to about 960 nm for substantially normally incident light 20. Table 250 corresponds to plot 210 of Figure 2A.

[0068] Table 250 includes a number of column headings in row 251. The column headings in row 251 include substantially vertically incident light 20 polarized along a first direction and substantially vertically incident light 20 polarized along a second direction. Table 250 further includes a number of column subheadings in row 252. The column subheadings in row 252 include multilayer optical film 200 and conventional optical film for each of substantially vertically incident light 20 polarized along a first direction and substantially vertically incident light 20 polarized along a second direction. Column 253 includes at least one wavelength W1 (about 760 nm) in a visible wavelength range 21 (about 420 nm to about 680 nm) and an infrared wavelength range 23 (about 700 nm to about 960 nm).

[0069] Table 250 includes a cell 230 that lists values ​​of average optical transmission 30 of multilayer optical film 200 for substantially normally incident light 20 polarized along a first direction for the visible wavelength range 21. Table 250 further includes a cell 231 that lists values ​​of average optical transmission 31 of multilayer optical film 200 for substantially normally incident light 20 polarized along a second direction for the visible wavelength range 21. Table 250 further includes a cell 255 that lists optical transmission T1 of multilayer optical film 200 at least one wavelength W1 in the infrared wavelength range 23 at an angle of incidence θ of less than about 10 degrees for p-polarized incident light 22 propagating in a plane of incidence P that includes the first direction.

[0070] 1 and 2A-2B, as is evident from curve 211, the plurality of alternating first and second polymer layers 10, 11 have an average light transmittance 30 for a visible wavelength range 21 of about 10% to about 30% for substantially perpendicular incident light 20, when the incident light 20 is polarized along a first direction in the multilayer optical film 200. In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an average light transmittance 30 for a visible wavelength range 21 of about 12% to about 25%, about 14% to about 20%, about 15% to about 20%, or about 16% to about 20% for substantially perpendicular incident light 20, when the incident light 20 is polarized along a first direction in the multilayer optical film 200.

[0071] In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an average light transmission 30 of about 18.64% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along a first direction in the multilayer optical film 200. In some other embodiments, the plurality of alternating first and second polymer layers 10, 11 have an average light transmission 30 of about 20.57% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along a first direction in the multilayer optical film 200.

[0072] Furthermore, the multiple alternating first and second polymer layers 10, 11 have an optical transmittance T1 for at least one wavelength W1 in the infrared wavelength range 23 at an incidence angle θ of less than about 10 degrees for p-polarized incident light 22 propagating in a plane of incidence P that includes the first direction.

[0073] In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmittance T1 of about 33.93% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of 0 degrees for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction. In some other embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmittance T1 of about 38.86% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of 0 degrees for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction.

[0074] As evident from curve 212, the conventional optical film has an average light transmission of less than about 5% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along a first direction. In some embodiments, the conventional optical film has an average light transmission of about 2.24% over the visible wavelength range 21, for substantially normally incident light 20, when the incident light 20 is polarized along a first direction.

[0075] Furthermore, the conventional optical film has an optical transmittance T1' of about 2.24% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of about 0 degrees for p-polarized incident light 22 propagating in an incident plane P that includes a first direction.

[0076] Thus, as is evident from curves 211, 212, for substantially perpendicular incident light 20, the average light transmittance 30 of the multilayer optical film 200 is greater than the average light transmittance of a conventional optical film for the visible wavelength range 21 when the incident light 20 is polarized along a first direction.

[0077] Furthermore, the light transmission T1 of multilayer optical film 200 is substantially greater than the light transmission T1' of conventional optical films.

[0078] As evident from curve 213, the plurality of alternating first and second polymer layers 10, 11 have an average optical transmission 31 of greater than about 60% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along the second direction in the multilayer optical film 200. In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an average optical transmission 31 of greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along the second direction in the multilayer optical film 200.

[0079] In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an average optical transmission 31 of about 89% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along the second direction in the multilayer optical film 200. In some other embodiments, the plurality of alternating first and second polymer layers 10, 11 have an average optical transmission 31 of about 88.78% over the visible wavelength range 21 for substantially normally incident light 20, when the incident light 20 is polarized along the second direction in the multilayer optical film 200.

[0080] Furthermore, the multiple alternating first and second polymer layers 10, 11 have an optical transmittance T1s for at least one wavelength W1 in the infrared wavelength range 23 at an incidence angle θ of less than about 10 degrees for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction.

[0081] In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmission T1s of about 91.98% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of 0 degrees for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction. In some other embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmission T1s of about 89.89% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of 0 degrees for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction.

[0082] Furthermore, as is evident from curves 211, 213, for substantially normally incident light 20, over the visible wavelength range 21, the average optical transmission 30 of the multiple alternating first and second polymer layers 10, 11 when the incident light 20 is polarized along a first direction is less than the average optical transmission 31 of the multiple alternating first and second polymer layers 10, 11 when the incident light 20 is polarized along a second direction. Thus, the multilayer optical film 200 can function as a reflective polarizer over the visible wavelength range 21 for substantially normally incident light 20.

[0083] Referring to curve 214, the conventional optical film has an average light transmission of about 88.49% over the visible wavelength range 21 for substantially perpendicular incident light 20 when the incident light 20 is polarized along a second direction.

[0084] Furthermore, the conventional optical film has an optical transmittance T1s' of about 89.79% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incident angle θ of about 0 degrees for p-polarized incident light 22 propagating in an incident plane P' that includes the second direction.

[0085] As is evident from curves 213, 214, for substantially perpendicular incident light 20, when the incident light 20 is polarized along the second direction, the average light transmittance of the multilayer optical film 200 is comparable to the average light transmittance of a conventional optical film over the visible wavelength range 21.

[0086] Moreover, the light transmittance T1s of multilayer optical film 200 is comparable to the light transmittance T1s' of conventional optical films.

[0087] As is evident from curves 211-214, for substantially normal incident light 20, the average light transmittance 30 of multilayer optical film 200 is greater than the average light transmittance of conventional optical films for the visible wavelength range 21 when the incident light 20 is polarized along a first direction. Thus, multilayer optical film 200 can be a weaker reflective polarizer than conventional optical films. A weaker reflective polarizer may be desirable in some optical applications, such as windshields, virtual reality / augmented reality, and head-up display (HUD) applications.

[0088] 2C illustrates a plot 220 showing the optical transmission of multilayer optical film 200 (shown in FIG. 1 ) and a conventional optical film, respectively, for p-polarized incident light 22 propagating in a plane of incidence P comprising a first direction (shown in FIG. 1 ) and for p-polarized incident light 22 propagating in a plane of incidence P′ comprising a second direction and incident at an incidence angle θ greater than about 40 degrees, in accordance with one embodiment of the present disclosure. Wavelength is represented in nanometers (nm) on the abscissa. Optical transmission is represented as a transmittance percentage on the left ordinate axis.

[0089] 1 and 2C, plot 220 includes a curve 221 corresponding to the optical transmittance of a plurality of alternating first and second polymer layers 10, 11 at an incidence angle θ greater than about 40 degrees for p-polarized incident light 22 propagating in an incidence plane P that includes a first direction.

[0090] Plot 220 further includes a curve 222 corresponding to the optical transmission of the conventional optical film for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction at incidence angles θ greater than about 40 degrees.

[0091] The plot 220 further includes a curve 223 corresponding to the optical transmittance of the multiple alternating first and second polymer layers 10, 11 at an incidence angle θ greater than about 40 degrees for p-polarized incident light 22 propagating in an incidence plane P' that includes a second direction.

[0092] Plot 220 further includes a curve 224 corresponding to the optical transmission of the conventional optical film for p-polarized incident light 22 propagating in a plane of incidence P' that includes a second direction, at incidence angles θ greater than about 40 degrees.

[0093] 2D shows a table 260 listing some exemplary values ​​of average optical transmission of the multilayer optical film 200 (shown in FIG. 1 ) and the conventional optical film, respectively, for the visible wavelength range 21, for p-polarized incident light 22 (shown in FIG. 1 ) propagating in a plane of incidence P including a first direction and p-polarized incident light 22 propagating in a plane of incidence P′ including a second direction, incident at an incident angle θ of greater than about 40 degrees. Table 260 further lists some exemplary values ​​of optical transmission of the multilayer optical film 200 and the conventional optical film, respectively, for at least one wavelength W1 in the infrared wavelength range 23, for p-polarized incident light 22 propagating in a plane of incidence P including a first direction and p-polarized incident light 22 propagating in a plane of incidence P′ including a second direction, incident at an incident angle θ of greater than about 40 degrees. Table 260 corresponds to plot 220 of FIG. 2C.

[0094] Table 260 includes a number of column headings in row 261. The column headings in row 261 include p-polarized incident light 22 propagating in a plane of incidence P including a first direction and p-polarized incident light 22 propagating in a plane of incidence P' including a second direction. Table 260 further includes a number of column subheadings in row 262. The column subheadings in row 262 include multilayer optical film 200 and conventional optical film for each of p-polarized incident light 22 propagating in a plane of incidence P including a first direction and p-polarized incident light 22 propagating in a plane of incidence P' including a second direction. Column 263 includes at least one wavelength W1 (about 760 nm) in a visible wavelength range 21 (about 420 nm to about 680 nm) and an infrared wavelength range 23 (about 700 nm to about 960 nm).

[0095] Table 260 includes cells 265 that show the optical transmittance T2 of the multilayer optical film 200 for at least one wavelength W1 within the infrared wavelength range 23 at an incident angle θ greater than about 40 degrees for p-polarized incident light 22 propagating in an incident plane P that includes a first direction.

[0096] 1 and 2C-2D, as evident from curve 221, in some embodiments, the multiple alternating first and second polymer layers 10, 11 have an average optical transmittance of about 6.19% over the visible wavelength range 21 for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction at an incidence angle θ of about 60 degrees. In some other embodiments, the multiple alternating first and second polymer layers 10, 11 have an average optical transmittance of about 8.12% over the visible wavelength range 21 for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction at an incidence angle θ of about 60 degrees.

[0097] Furthermore, the multiple alternating first and second polymer layers 10, 11 have an optical transmittance T2 for at least one wavelength W1 in the infrared wavelength range 23 at an incidence angle θ greater than about 40 degrees for p-polarized incident light 22 propagating in an incidence plane P that includes the first direction.

[0098] In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmittance T2 of about 58.8% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of about 60 degrees for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction. In some other embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmittance T2 of about 56.15% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of about 60 degrees for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction.

[0099] As is evident from curves 221 and 211 (shown in FIG. 2A ), the multiple alternating first and second polymer layers 10, 11 have optical transmittances T1 and T2 for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction, for at least one wavelength W1 in the infrared wavelength range 23, for angles of incidence θ less than about 10 degrees and angles of incidence θ greater than about 40 degrees, respectively.

[0100] Further, the difference between T2 and T1 is less than about 40%, i.e., (T2-T1)<40%. In some embodiments, (T2-T1)<35%, (T2-T1)<30%, or (T2-T1)<25%.

[0101] In some embodiments, for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction, T1 is about 33.93% and T2 is about 58.8% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23. Thus, in such embodiments, (T2-T1) is about 24.87%.

[0102] In some other embodiments, for p-polarized incident light 22 propagating in a plane of incidence P that includes the first direction, T1 is about 38.86% and T2 is about 56.15% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23. Thus, in such embodiments, (T2-T1) is about 17.29%.

[0103] As can be seen from curve 222, the conventional optical film has an average light transmittance of about 0.35% over the visible wavelength range 21 at an incidence angle θ of about 60 degrees for p-polarized incident light 22 propagating in an incident plane P that includes a first direction.

[0104] Furthermore, the conventional optical film has an optical transmittance T2' of approximately 52.43% for at least one wavelength W1 of approximately 760 nm in the infrared wavelength range 23 at an incident angle θ of approximately 60 degrees for p-polarized incident light 22 propagating in an incident plane P that includes a first direction.

[0105] As evident from curves 212 (shown in FIG. 2A) and 222, for p-polarized incident light 22 propagating in a plane of incidence P that includes a first direction, in the conventional optical film, T1' is about 2.24% and T2' is about 52.43% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23. Thus, (T2'-T1') is about 50.19%.

[0106] Thus, the difference between T2 and T1 for multilayer optical film 200 is less than the difference between T2' and T1' for conventional optical films.

[0107] As evident from curve 223, in some embodiments, the multiple alternating first and second polymer layers 10, 11 have an average optical transmission of about 97.64% over the visible wavelength range 21 for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction at an incidence angle θ of about 60 degrees. In some other embodiments, the multiple alternating first and second polymer layers 10, 11 have an average optical transmission of about 97.04% over the visible wavelength range 21 for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction at an incidence angle θ of about 60 degrees.

[0108] Furthermore, the multiple alternating first and second polymer layers 10, 11 have an optical transmittance T2s for at least one wavelength W1 in the infrared wavelength range 23 at an incident angle θ greater than about 40 degrees for p-polarized incident light 22 propagating in an incident plane P' that includes the second direction.

[0109] In some embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmission T2s of about 99.11% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of about 60 degrees for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction. In some other embodiments, the plurality of alternating first and second polymer layers 10, 11 have an optical transmission T2s of about 98.61% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incidence angle θ of about 60 degrees for p-polarized incident light 22 propagating in a plane of incidence P' that includes the second direction.

[0110] As can be seen from curve 224, the conventional optical film has an average light transmittance of approximately 95.95% over the visible wavelength range 21 at an incidence angle θ of approximately 60 degrees for p-polarized incident light 22 propagating in an incidence plane P' that includes the second direction.

[0111] Furthermore, the conventional optical film has an optical transmittance T2s' of about 99.4% for at least one wavelength W1 of about 760 nm in the infrared wavelength range 23 at an incident angle θ of about 60 degrees for p-polarized incident light 22 propagating in an incident plane P' that includes the second direction.

[0112] 3A shows a perspective view of a roll 310 of multilayer optical film 200 according to one embodiment of the disclosure. The multilayer optical film 200 may be wound into the roll 310 during commercial production of the multilayer optical film 200. The multilayer optical film 200 may be wound into the roll 310 by a roll-to-roll process during manufacturing of the multilayer optical film 200. The multilayer optical film 200 includes an intermediate region 311 defined proximate a central axis 312 of the multilayer optical film 200 and side regions 313 defined proximate respective edges 314 of the multilayer optical film 200.

[0113] In some embodiments, multilayer optical film 200 has a width B of at least 140 centimeters (cm). Width B can be defined between edges 314 of multilayer optical film 200. In some embodiments, 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.

[0114] In some embodiments, multilayer optical film 200 has a length L of at least 40 meters (m). Length L may be defined along a central axis 312 of multilayer optical film 200. Length L is partially shown in FIG. 3A for illustrative purposes. In some embodiments, multilayer optical film 200 has a length L of at least 50 m, at least 75 m, at least 95 m, at least 100 m, at least 125 m, at least 150 m, at least 175 m, at least 200 m, at least 300 m, at least 400 m, or at least 500 m.

[0115] 3B is a plot 320 illustrating the variation of average effective transmittance across a width B (shown in FIG. 3A) along the length L of multilayer optical film 200 (shown in FIG. 3A) for a roll 310 (shown in FIG. 3A) of multilayer optical film 200 according to one embodiment of the disclosure, and across the width B (shown in FIG. 3A) along the length L of the conventional optical film for a roll of conventional optical film. Width is represented in inches on the abscissa. Average effective transmittance is represented on the ordinate. Width B of multilayer optical film 200 and the width of the conventional optical film are approximately 17 inches.

[0116] As used herein, the term "average effective transmittance" refers to the average luminous transmittance of substantially normal incidence light. The substantially normal incidence light may be unpolarized or polarized. The average effective transmittance is the effective transmittance measured or averaged over substantially the entire area of ​​the multilayer optical film 200 or a conventional optical film, or over an area large enough to average out the effects of local non-uniformity (e.g., particle clustering) (e.g., at least about 0.5 mm in diameter, or at least about 1 mm in diameter, or at least about 5 mm in diameter). The average effective transmittance may be measured as the luminous transmittance measured according to ASTM D1003-13. As set forth in the ASTM D1003-13 test standard, the luminous transmittance is the transmittance weighted according to the 1987 Commission Internationale de l'Eclairage (CIE) spectral luminous efficiency function V(λ).

[0117] Plot 320 includes a curve 321 that illustrates the variation of the average effective transmission of a multilayer optical film 200 along the length L and across the width B of the multilayer optical film 200 according to a first embodiment of the present disclosure.

[0118] Plot 320 includes a curve 322 that illustrates the variation of the average effective transmission of a multilayer optical film 200 along the length L and across the width B of the multilayer optical film 200 according to a second embodiment of the present disclosure.

[0119] Plot 320 further includes a curve 323 that illustrates the variation of the average effective transmission of the conventional optical film across the width along the length of the conventional optical film.

[0120] FIG. 3C shows a table 350 that lists several exemplary values ​​of the average effective transmission along their respective lengths and across their respective widths for the multilayer optical films 200 according to the first and second embodiments, as well as a conventional optical film.

[0121] Table 350 includes a number of column headings in row 351. The column headings in row 351 include multilayer optical film 200 according to a first embodiment, multilayer optical film 200 according to a second embodiment, and a conventional optical film. Column 352 includes the widths of multilayer optical film 200 according to the first embodiment, multilayer optical film 200 according to the second embodiment, and the conventional optical film, their respective minimum average effective transmittances ET1, their respective maximum average effective transmittances ET2, and the ratio between ET1 and ET2. Table 350 further includes a number of cells corresponding to various values ​​of the average effective transmittances of multilayer optical film 200 according to the first embodiment, multilayer optical film 200 according to the second embodiment, and the conventional optical film across the respective widths of multilayer optical film 200 according to the first embodiment, multilayer optical film 200 according to the second embodiment, and the conventional optical film.

[0122] 3A-3C, as is apparent from curves 321 and 322, the multilayer optical films 200 according to the first and second embodiments have respective minimum average effective transmittances ET1 in the respective middle regions 311 (at about 9 inches). Furthermore, the multilayer optical films 200 according to the first and second embodiments have respective maximum average effective transmittances ET2 in the respective side regions 313 (at about 1 inch and about 17 inches).

[0123] Thus, multilayer optical film 200 has an average effective transmission ET 1 in middle region 311 and an average effective transmission ET 2 in side regions 313 along the length L of multilayer optical film 200 .

[0124] In some embodiments, the ratio between ET1 and ET2 is about 0.97 or less, i.e., (ET1 / ET2)≦0.97. In some embodiments, (ET1 / ET2)≦0.96, (ET1 / ET2)≦0.95, or (ET1 / ET2)≦0.94. Thus, the average effective transmittance ET2 of the side regions 313 of the multilayer optical film 200 is greater than the average effective transmittance ET1 of the central region 311 of the multilayer optical film 200.

[0125] In some embodiments, ET1 is about 1.513 and ET2 is about 1.593. Therefore, (ET1 / ET2) is about 0.95. In some embodiments, ET1 is about 1.468 and ET2 is about 1.569. Therefore, (ET1 / ET2) is about 0.936.

[0126] Additionally, the multilayer optical film 200 has an average effective transmission of less than about 1.68. In some embodiments, the multilayer optical film 200 has an average effective transmission 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 transmission of from about 1.65 to about 1.4. In some embodiments, the multilayer optical film 200 has an average effective transmission of from about 1.63 to about 1.42, or from about 1.61 to about 1.44.

[0127] Referring to curve 323, in some embodiments, the conventional optical film has an average effective transmittance ET1 of about 1.693 and an average effective transmittance ET2 of about 1.717. Thus, (ET1 / ET2) is about 0.986. Thus, in 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.

[0128] In some embodiments, the multilayer optical film 200 has suitable chemical resistance to one or more solvents, such as isopropyl alcohol (IPA), acetone, toluene, and methyl ethyl ketone (MEK). In some embodiments, application of one or more of IPA, acetone, toluene, and MEK to the multilayer optical film 200 does not damage the multilayer optical film 200. In some embodiments, damage to the multilayer optical film 200 may be assessed by measuring the optical haze of the multilayer optical film 200 before and after application of one or more solvents to the multilayer optical film 200. In general, application of one or more solvents to the multilayer optical film 200 may increase the optical haze of the multilayer optical film 200.

[0129] As used herein, the term "optical haze" refers to the scattering of light as it passes through a material. It refers to the specific light transmission and wide-angle light scattering properties of a planar portion of a material. Optical haze may be measured according to ASTM D-1003-07 ("Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics"). Optical haze values ​​are expressed as a percentage. Materials with high haze values ​​are generally relatively hazy and less transparent materials. Materials with low haze values ​​are generally relatively transparent materials that are less hazy.

[0130] In some embodiments, application of one or more of IPA, acetone, toluene, and MEK to multilayer optical film 200 increases the optical haze of multilayer optical film 200 by no more than about 10%. In some embodiments, application of one or more of IPA, acetone, toluene, and MEK to multilayer optical film 200 increases the optical haze of 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%. Thus, the increase in optical haze of multilayer optical film 200 after application of one or more solvents is substantially less, indicating that multilayer optical film 200 has high chemical resistance to one or more solvents.

[0131] FIG. 4A shows a detailed cross-sectional schematic diagram of a display system 400 according to an embodiment of the present disclosure. 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 an extended emitting surface 42 to illuminate the display panel 50. The extended illumination source 40 includes at least one light source 43, 44. In the illustrated embodiment of FIG. 4A, the extended illumination source 40 includes two light sources 43, 44. Thus, the at least one light source 43, 44 includes two light sources 43, 44. The light source 43 may be arranged in a row, and the light source 44 may be arranged at an edge of the extended illumination source 40. In the illustrated embodiment of FIG. 4A, the extended illumination source 40 includes a plurality of light sources 43 arranged in a row configuration. Furthermore, the extended illumination source 40 includes at least two light sources 44 arranged at opposite edges of the extended illumination source 40.

[0132] Backlight 300 further includes multilayer optical film 200. Multilayer optical film 200 is disposed over extended emitting surface 42 and is substantially coextensive in length and width with extended emitting surface 42.

[0133] Light 41 may be synonymously referred to as “emitted light 41.” Display panel 50 is configured to receive emitted light 41 and form an image 51.

[0134] In some embodiments, the backlight 300 further 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 can be a brightness enhancing 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 can be along the y-direction.

[0135] 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 that is different from the first longitudinal direction. In some embodiments, the second direction may be along the y-direction.

[0136] In some embodiments, the backlight 300 further includes at least one light diffusing 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. In the illustrated embodiment of FIG. 4A, the at least one light diffusing film 100, 101 includes two light diffusing films 100, 101. The light diffusing film 100 is disposed between the extended illumination source 40 and the first prism film 90. The light diffusing film 101 is disposed between the second prism film 92 and the multilayer optical film 200.

[0137] FIG. 4B shows a detailed cross-sectional schematic diagram of an extended illumination source 40' according to an embodiment of the present disclosure. In some embodiments, the extended illumination source 40' may be used in place of the extended illumination source 40 (shown in FIG. 4A) in the backlight 300. In some embodiments, the extended illumination source 40' includes a light guide 60 for propagating light 61, 62 internally along the length and width of the light guide 60 primarily by total internal reflection. 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 may be a solid light guide. In some embodiments, the light guide 60 may be a substantially hollow light guide.

[0138] In some embodiments, the light guide 60 includes an extended emitting surface 42 .

[0139] In some embodiments, the extended illumination source 40' further includes at least one light source 44 disposed proximate a side 53, 53a of the light guide 60. In the illustrated embodiment of Figure 4B, the at least one light source 44 includes two light sources, one of which is disposed proximate the side 53 and the other of which is disposed proximate the side 53a.

[0140] In some embodiments, the extended illumination source 40' includes a back reflector 70 that is configured to reflect light 62 exiting the light guide 60 toward the back reflector 70. In some embodiments, the back reflector 70 may reflect the 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.

[0141] In some embodiments, the back reflector 70 may be highly reflective. For example, the back reflector 70 may have an on-axis average reflectance of at least 90%, 95%, 98%, 99%, or more. Such reflectance values ​​may include both specular and diffuse reflection. In some embodiments, the back reflector 70 may be a predominantly specular reflector, a diffuse reflector, or a combination of specular / diffuse reflectors, whether spatially uniform or patterned. In some embodiments, the back reflector 70 may be a semi-specular reflector. In some cases, the back reflector 70 may include a rigid metal substrate with a highly reflective coating, or a highly reflective film laminated to a supporting substrate. In some embodiments, the back reflector 70 may include one or more elements such as silver, aluminum, a white coating, a non-conductive coating, and the like.

[0142] FIG. 4C shows a detailed cross-sectional schematic diagram of an extended illumination source 40″ according to another embodiment of the present disclosure. In some embodiments, the extended illumination source 40″ may be used in the backlight 300 in place of the extended illumination source 40 (shown in FIG. 4A ). In some embodiments, the extended illumination source 40″ includes an optical diffusion layer 80 for scattering light. In some embodiments, the optical diffusion layer 80 may include any suitable diffusion film or plate configured to diffuse or scatter light. For example, the optical diffusion layer 80 may diffuse light by using a textured surface of the substrate or by other means such as incorporating optical diffusion particles into the matrix of the film. In some embodiments, the optical diffusion layer 80 may be the optical diffusion film 100 or substantially similar to the optical diffusion film 100.

[0143] In some embodiments, the light diffusing layer 80 includes an extended emitting surface 42. In some embodiments, the extended illumination source 40'' includes a back reflector 71 facing the light diffusing layer 80. The back reflector 71 may be substantially similar to the back reflector 70 shown in FIG. 4B. In some embodiments, the back reflector 71 and the optically diffusing layer 80 define an optical cavity 72 therebetween. In some embodiments, the at least one light source 43 is disposed within the optical cavity 72. In some embodiments, the optical cavity 72 may form a recirculating cavity.

[0144] Unless otherwise specified, all numbers expressing feature sizes, quantities and physical properties used in the specification and claims are to be understood as being modified by the term "about." Accordingly, unless specifically indicated to the contrary, the numerical parameters set forth in the above specification and appended claims are approximations that may vary depending upon the desired properties one of ordinary skill in the art would seek to obtain using the teachings disclosed herein.

[0145] Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent implementations without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Accordingly, it is intended that the present disclosure be limited only by the claims and their equivalents.

Claims

1. 1. A multilayer optical film comprising a plurality of alternating first and second polymer layers totaling at least 20, each of the first and second polymer layers having an average thickness of less than about 500 nanometers (nm), the first polymer layer comprising from about 10% to about 50% by weight polyethylene terephthalate (PET) and from about 50% to about 90% by weight polyethylene naphthalate (PEN), and the plurality of alternating first and second polymer layers exhibiting, for substantially normally incident light, a visible wavelength range of from about 420 nm to about 680 nm of: an average light transmission of about 10% to about 30% when the incident light is polarized along a first direction in the plane of the multilayer optical film; having an average light transmission of greater than about 60% when the incident light is polarized along an orthogonal second direction in the plane of the multilayer optical film; the plurality of alternating first and second polymer layers have optical transmittances T1 and T2 for p-polarized incident light propagating in a plane of incidence that includes the first direction, for at least one wavelength in an infrared wavelength range of about 700 nm to about 960 nm, for angles of incidence less than about 10 degrees and greater than about 40 degrees, respectively, where T2-T1 is less than about 40%. Multilayer optical films.

2. the first and second polymer layers have respective refractive indices nx1 and nx2 along the first direction, respective refractive indices ny1 and ny2 along the second direction, and respective refractive indices nz1 and nz2 along a thickness direction of the multilayer optical film perpendicular to the first direction and the second direction, for at least one wavelength in the visible wavelength range: 0≦nx1−nx2≦0.4, the magnitude of the difference between ny1 and ny2 is less than about 0.04; the magnitude of the difference between nz1 and nz2 is less than about 0.04; The multilayer optical film of claim 1 .

3. 2. The roll of multilayer optical film of claim 1 having a width of at least 140 centimeters (cm) and a length of at least 40 meters (m), and along the length of the multilayer optical film, the multilayer optical film has an average effective transmission ET1 in the middle region and an average effective transmission ET2 in the side regions, where ET1 / ET2≦0.

97.

4. A backlight, an extended illumination source configured to emit light through and across an extended emission surface of the extended illumination source to illuminate a display panel, the extended illumination source comprising at least one light source; and the multilayer optical film of claim 1 disposed on said extended emitting surface and substantially coextensive in length and width with said extended emitting surface. Backlight.

5. the extended illumination source comprising: a light guide for propagating light internally along a length and width of the light guide primarily by total internal reflection, the light guide comprising the extended emitting surface; the at least one light source disposed proximate a side of the light guide; a back reflector configured to reflect the light exiting the light guide toward the back reflector, the reflected light exiting the extended illumination source through the extended emitting surface; The backlight of claim 4 comprising:

6. the extended illumination source comprising: a light diffusing layer having said extended emitting surface for scattering light; a back reflector facing the light diffusing layer, the back reflector and the light diffusing layer defining an optical cavity therebetween; and the at least one light source disposed within the optical cavity. The backlight of claim 4.

7. 7. A display panel disposed over the backlight of claim 6, the display panel configured to receive the emitted light and form an image. Display system.

8. 2. The multilayer optical film of claim 1, wherein a minimum average peel strength between two portions of the multilayer optical film is greater than about 100 grams per inch (g / inch), and each of the two portions includes at least one polymer layer of the plurality of alternating first and second polymer layers.

9. A backlight, an extended illumination source configured to emit light through and across an extended emission surface of the extended illumination source to illuminate a display panel, the extended illumination source comprising at least one light source; a reflective polarizer disposed over the extended illumination source and substantially coextensive in length and width with the extended illumination source, the reflective polarizer comprising a plurality of alternating first and second polymer layers totaling at least 20, each of the first and second polymer layers having an average thickness of less than about 500 nm, the plurality of alternating first and second polymer layers providing, for substantially normally incident light, a visible wavelength range of about 420 nm to about 680 nm: an average light transmission of about 10% to about 30% when the incident light is polarized along a first direction in the plane of the reflective polarizer; a reflective polarizer having an average light transmission of greater than about 60% when the incident light is polarized along an orthogonal second direction in the plane of the reflective polarizer; the reflective polarizer has an average effective transmission of about 1.65 to about 1.4; Backlight.

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

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