Multilayer optical films

Abstract

An optical film includes a plurality of optical repeat units (ORUs). The ORUs include opposing first and second endmost ORUs farthest from each other among the ORUs. For first and second middle ORUs in the plurality of ORUs that are spaced apart from each of the first and second endmost ORUs by at least 10 other ORUs in the plurality of ORUs, are spaced apart from each other by no more than about 5 other ORUs in the plurality of ORUs, and have respective average physical thickness H1 and H2, a magnitude of (H1-H2) / ((H1+H2) / 2) is greater than about 1%. For a normally incident light, the plurality of ORUs has an average optical transmittance of at least 60% averaged over a visible wavelength range, and an average optical density of greater than about 3 averaged over a first infrared wavelength range extending continuously from about 800 nm to about 1100 nm.

Description

[0001] MULTILAYER OPTICAL FILMS

[0002] Technical Field

[0003] The disclosure generally relates to optical films, specifically to high optical density broadband reflector films.

[0004] Background

[0005] Multilayer optical films (MOFs) are used in numerous applications, including consumer electronic applications and automotive applications. Polymeric MOFs are formed by coextruding tens to hundreds of molten polymer layers and subsequently orienting or stretching the resulting film. These microlayers have different refractive index characteristics and sufficient thinness so that light is reflected at interfaces between adjacent microlayers. Broadband visible reflectors reflect over all or substantially all of the visible spectrum and may be useful in displays and lighting applications.

[0006] Summary

[0007] Some aspects of the disclosure relate to an optical film including a plurality of optical repeat units (ORUs) co-extruded and co-stretched with one another and numbering at least 15 in total. Each of the ORUs has an average physical thickness of less than about 1000 nm and includes at least two different polymeric layers. The ORUs include opposing first and second endmost ORUs farthest from each other among the ORUs. For first and second middle ORUs in the plurality of ORUs that are spaced apart from each of the first and second endmost ORUs by at least 10 other ORUs in the plurality of ORUs, are spaced apart from each other by no more than about 5 other ORUs in the plurality of ORUs, and have respective average physical thickness Hl and H2, a magnitude of (Hl-H2) / ((Hl+H2) / 2) is greater than about 1%. For a substantially collimated substantially normally incident light, the plurality of ORUs has an average optical transmittance of at least 60% averaged over a visible wavelength range extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first and second polarization states. For a substantially collimated substantially normally incident light, the plurality of ORUs has an average optical density of greater than about 3 averaged over a first infrared wavelength range extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states. Some other aspects of the disclosure relate to an optical film including a plurality of optical repeat units (ORUs) co-extruded and co-stretched with one another and numbering at least 15 in total. Each of the ORUs has an average physical thickness of less than about 1000 nm and includes at least two different polymeric layers. For a substantially collimated incident light, and when an incident angle of the incident light increases from a first incident angle of less than about 10 degrees to a second incident angle of greater than about 35 degrees, an average optical transmittance of the plurality of the ORUs remains greater than about 50% averaged over a visible wavelength range extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first and second polarization states. An average optical density of the plurality of the ORUs remains greater than about 5 averaged over a first infrared wavelength range extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states.

[0008] Some other aspects of the disclosure relate to an optical film including a plurality of optical repeat units (ORUs) co-extruded and co-stretched with one another and numbering at least 15 in total. Each of the ORUs has an average physical thickness of less than about 1000 nm and includes at least two different polymeric layers. For a substantially collimated incident light, an optical density of the optical film as a function of wavelength averaged over mutually orthogonal first and second polarizations includes a high optical density region that is at least 200 nm wide, has an average optical density of greater than about 3 averaged across the high optical density region and averaged over the first and second polarization states, and is disposed in a wavelength region of interest extending continuously between about 600 nm and about 1400 nm. The high optical density region is defined by a left band edge along which the optical density generally increases with increasing wavelength and an opposing right band edge along which the optical density generally decreases with increasing wavelength. A first best linear fit to the left band edge at least across a wavelength range where the optical density increases from about 1 to about 3.5 has a slope that is greater than about 0.06 per nm for a first incident angle of less than about 10 degrees and increases when the incident angle increases to a second incident angle of greater than about 35.

[0009] Some aspects of the disclosure relate to a system including a housing defining an opening for allowing visible light therethrough. The optical film of one or more aspects of the disclosure is disposed on and covers the opening. For a light source emitting a first light having wavelengths in a visible wavelength range extending continuously from about 420 nm to about 680 nm and a second light having wavelengths in the high optical density region, and for all incident angles between the first and second incident angles, the optical film transmits at least 60% of the first light and reflects at least 99% of the second light.

[0010] Brief Description of Drawings

[0011] The various aspects of the disclosure will be discussed in greater detail with reference to the accompanying figures where,

[0012] FIG. 1 schematically shows an multilayer optical film having plurality of optical repeat units (ORUs) according to some embodiments of the disclosure;

[0013] FIGS. 2 A & 2B graphically show the thickness of different optical films as a function of the number of layers of the ORUs,

[0014] FIGS. 3A & 3B graphically show the thickness ratio between two ORUs in the optical film according to some aspects,

[0015] FIGS. 4A & 4B graphically shows the transmission spectra of different optical films as a function of the number of ORUs,

[0016] FIGS. 4C & 4D graphically shows the transmission spectra of different optical films at different wavelengths,

[0017] FIGS. 5 A & 5B graphically show the optical density of different optical films along the left band edge and right band edge as a function of wavelength,

[0018] FIG. 6A schematically shows a system having the optical film according to one or more aspects of the disclosure,

[0019] FIG. 7 graphically shows the optical transmittance of different optical films at mutually orthogonal polarizations and at different incident angles as a function of wavelengths according to some aspects; and

[0020] FIG. 8A graphically represents the index of refraction of two different polymeric layers of an ORU, and

[0021] FIG. 8B graphically represents the difference between indices of refraction of the two different polymeric layers of an ORU.

[0022] The figures are not necessarily 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 given figure is not intended to limit the component in another figure labelled with the same number. Detailed Description of Illustrative embodiments

[0023] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0024] The terms “transmittance” and “transmit” refer to the ratio of total transmission of a layer of a material compared to that received by the material, which may account for the effects of absorption, scattering, reflection, etc. Transmittance (T) may range from 0 to 1 or be expressed as a percentage (T%).

[0025] The term “optical density” refers to the ability of a material to transmit light through it. The higher the optical density, the lower the transmittance. Optical density can be expressed as the minus base 10 logarithm of [transmittance / 100%] and is a unitless quantity.

[0026] The term “optical repeat unit” refers to a stack of at least two individual layers that repeats across the thickness of a multilayer optical film, though all repeating layers need not have the same thickness, unless mentioned otherwise in this disclosure.

[0027] Embodiments of the present disclosure describe multilayer optical films (MOF) that provide very high reflectivity and very low absorption in the near infrared wavelengths, from about 800 nm to about 1100 nm across angles from 0 - 55 degrees, with relatively high visible light transmission levels. The optical film according to one or more embodiments provides sharp band edges to minimize the amount of visible light reflected at all angles.

[0028] In some aspects, the multilayer optical film design according to the disclosure includes a plurality of polymeric optical layers, such as alternating PEN and PMMA layers, across a thickness gradient designed to provide high reflectivity from 780 nm to 1100 nm across angles from 0 to 55 degrees. The film is designed to provide high visible light transmission, high RF transmission, and low absorption over the wavelengths from 400 nm to 1400 nm. The film is also designed to have sharp band edges, and high reflectivity over the targeted reflection region. In some aspects, the film has an outside skin layer on both outside surfaces including a polycarbonate alloy. As illustrated in FIG. 1 , the optical film (200) according to some aspects includes a plurality of optical repeat units (10) (ORUs), also called as multilayer stack. The optical film may include at least 15, or 20, or 50, or 75, or 100, or 150, or 175, or 200, or 250, or 300 ORUs in total. In some aspects, the optical film may include about 650 ORUs. Each ORU may include at least, or only, two different polymeric layers (11, 12) that are co-extruded and co-stretched. For instance, each ORU can be made by co-extrusion of alternating polymer layers (11, 12) having different refractive indices, as described in, for example, U.S Pat. Nos. 5,882,774 (Jonza et al.); 6,045,894 (Jonza et al.); 6,368,699 (Gilbert et al.); 6,531,230 (Weber et al.); 6,667,095 (Wheatley et al.); 6,783,349 (Neavin et al.); 7,271,951 B2 (Weber et al); 7,632,568 (Padiyath et al.); 7,652,736 (Padiyath et al.); and 7,952,805 (McGurran et al.); and PCT Publications WO 95 / 17303 (Ouderkirk et al.) and WO 99 / 39224 (Ouderkirk et al.).

[0029] In some cases, one of the two different polymeric layers (11, 12) includes polyethylene naphthalate (PEN) and the other one of the two different polymeric layers includes polymethyl methacrylate (PMMA). The index of refraction of one of the two different polymeric layers may be greater than about 1.6, or 1.65, or 1.7 for at least one visible wavelength in the visible wavelength range. The index of refraction of the other one of the two different polymeric layers may be less than about 1.6, or 1.55, or 1.5 for the at least one visible wavelength (Refer FIG. 8A). A magnitude of a maximum difference between indices of refraction of the two different polymeric layers (11, 12) in the first infrared wavelength range and averaged over the first and second polarization states may be greater than about 0.05 and about 0.4, or about 0.1 and about 0.3, or about 0.15 and about 0.25 (Refer FIG. 8B).

[0030] The ORUs include opposing first (10a) and second (10b) endmost ORUs farthest from each other among the ORUs. Each ORU has an average physical thickness of less than about 1000 nm, or 900 nm, or 800 nm, or 700 nm, or 600 nm, or 500 nm, or 400 nm, or 300 nm, or 200 nm, or 175 nm, or 150 nm, or 140 nm, or less than 130 nm. FIG. 2A shows different optical films (OF1, OF2, OF3) having about 650 ORUs, including the first (10a) and second (10b) endmost ORUs. As shown in FIG. 2A, the ORU thicknesses of the different optical films (OF1, OF2, OF3) may be less than about 215 nm. The ORUs (10) further include first (10c) and second (lOd) middle ORUs that are spaced apart from each of the first (10a) and second (10b) endmost ORUs by at least 10, or 15, or 20, or 50, or 75, or 100, or 150, or 90, or 100 other ORUs in the plurality of ORUs. In some aspects, the first (10c) and second (lOd) middle ORUs are spaced apart from each other by no more than about 5, or 4, or 3, or 2, or 1, or 0 other ORUs in the plurality of ORUs. In the example illustrated in FIG. 2B, the first (10c) and second (lOd) middle ORUs are spaced apart from each other by about 1 other ORU. The first middle ORU (10c) has an average physical thickness Hl and the second middle ORU (lOd) has an average physical thickness H2. In some optical films, a magnitude of (Hl-H2) / ((Hl+H2) / 2) is greater than about 1%, or 1.5%, or 2%, or 2.5%, or 3%, and in some other optical films, the magnitude of (Hl-H2) / ((Hl+H2) / 2) can be greater than about 4%, or 5%, or 6%, or 8%, or 10%, or 15% as illustrated in FIGS. 3A and 3B.

[0031] Table 1 shows the magnitude of (Hl-H2) / ((Hl+H2) / 2) of different optical films OF1, OF2 and OF3 according to some embodiments of the disclosure.

[0032] TABLE 1

[0033] In some cases, the physical thickness H2 of the second middle ORU (lOd) may be greater than the physical thickness Hl of the first middle ORU (10c).

[0034] The plurality of optical repeat units, in some cases, may be disposed between, and coextruded and co-stretched with, first (13a) and second (13b) skin layers. Each of the two skin layers may have an average thickness of greater than about 500 nm, or 750 nm, or 1000 nm, or 1500 nm, or 2000 nm. These optional skin layers (13a, 13b) may protect the ORUs from damage, aid in the co-extrusion processing, and / or enhance post-processing mechanical properties. The skin layers (13a, 13b) are often thicker than the ORUs (10). The thickness of the skin layers (13a, 13b) is usually at least two times, or at least four times, or at least ten times, the thickness of the individual ORUs. An auxiliary layer (13c) may be disposed between two ORUs in the plurality of ORUs and can be co-extruded and co-stretched with the plurality of ORUs. The auxiliary layer (13c) may be disposed between the opposing first (10a) and second (10b) endmost ORUs and may have an average thickness of greater than about 250nm, or 300nm, or 350nm or 400 nm, or 450 nm, or 500 nm, or 750 nm, or 1000 nm, or 1500 nm, or 2000 nm. In the embodiment illustrated in FIG. 1, the auxiliary layer is disposed between the first and second middle ORUs (10c, lOd).

[0035] In some aspects, the auxiliary layer (13c) may be disposed between a first packet including the first endmost ORU (10a) and first middle ORU (10c) and a second packet including the second endmost ORU (10b) and second middle ORU (lOd) as shown in FIG. 1. The first packet which includes 10a and 10c may have a negative ORU thickness slope while the second packet which includes lOd and 10b may have a positive slope. Alternatively, the first packet may have a positive slope and the second packet may have a negative slope.

[0036] FIG. 4A and FIG. 7 show the average optical transmittance of the multilayer optical film according to some embodiments. The multilayer optical film (200) including at least the plurality of ORUs (10) having alternating first (11) and second (12) polymeric optical layers collectively transmits light at an incident angle (al) of at least one of 0°, 15°, 30°, 45°, 55°, and 60°. For a substantially collimated and substantially normally incident light (20), the plurality of ORUs transmits at least 60% of light averaged over a visible wavelength range (21) extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first (x- axis) and second (y-axis) polarization states. In some cases, the plurality of ORUs may transmit at least 65%, or 70%, or 75%, or 80%, or 90% of the incident light over the visible wavelength range (21) averaged over mutually orthogonal first (x-axis) and second (y-axis) polarization states. When the incident angle (al) of the incident light (20) is increased from substantially normal incidence to a second incident angle of greater than about 35°, or 40°, or 45°, or 50°, or 55°, the average optical transmittance of the plurality of the ORUs remains greater than about 60%, or greater than about 65%, or greater than about 70%. averaged over the visible wavelength range (21), and averaged over the first (x-axis) and second (y-axis) polarization states.

[0037] In some embodiments, for a substantially collimated incident light (20), and when an incident angle (al) of the incident light increases from a first incident angle of less than about 10°to a second incident angle of greater than about 35°, the average optical transmittance of the plurality of the ORUs remains greater than about 50% averaged over a visible wavelength range (21) extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first (x-axis) and second (y-axis) polarization states. In some instances, the first incident angle may be less than 8°, or 6°, or 4°, or 2°, or less than 1°, the second incident angle may be greater than about 40°, or 45°, or 50°, or 55°, and the average optical transmittance of the plurality of the ORUs may remain greater than about 55%, or 60%, or 65%, or 70% averaged over a visible wavelength range (21) extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first (x-axis) and second (y-axis) polarization states.

[0038] The multilayer optical film (200) according to some aspects collectively transmits at least 40% of substantially collimated substantially normally incident light (20) averaged over an infrared wavelength range (23) extending continuously from about 1300 nm to about 1600 nm and averaged over the first and second polarization states. In some cases, the plurality of ORUs may transmit at least 45%, or 50%, or 55%, or 60%, or 65%, or 70%, or 75%, or 80%, or 85% of the incident light over the infrared wavelength range (23) extending continuously from about 1300 nm to about 1600 nm. When the incident angle (al) of the incident light (20) is increased from substantially normal incidence to a second incident angle of greater than about 35°, or 40°, or 45°, or 50°, or 55°, the average optical transmittance of the plurality of the ORUs remains greater than about 40%, or 45%, or 50%, or 55%, or 60%, or 65%, or 70%, or 75%, or 80% averaged over the infrared wavelength range (23) extending continuously from about 1300 nm to about 1600 nm, and averaged over the first and second polarization states.

[0039] The optical film according to the disclosure provides very high reflectivity and very low absorption in the near (first) infrared wavelength range (22) extending from about 800 nm to about 1100 nm across angles from 0 - 55 degrees. For instance, for the substantially collimated substantially normally incident light (20), at least 70%, or 75%, or 80%, or 85%, or 90%, or 95%, or 99%, or 99.5% of the incident light (20) is not transmitted in a first infrared wavelength range (22) extending continuously from about 800 nm to about 1100 nm, and is reflected by the plurality of ORUs. Measured in terms of optical density, as shown in FIG. 4C, the optical film (200) including the plurality of ORUs (10) may have an average optical density of greater than about 3, or 3.5, or 4, or 4.5, or 5, or 5.5 for a substantially collimated substantially normally incident light (20) averaged over the infrared wavelength range (22) extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states. In optical films of another embodiment, the plurality of ORUs (10) may have an average optical density of greater than about 6, or 6.5, or 7, or 7.5, or 8, or 8.5 for a substantially collimated substantially normally incident light (20) averaged over the infrared wavelength range (22) extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states. When the incident angle (al) of the incident light (20) is increased from substantially normal incidence to a second incident angle of greater than about 35°, or 40°, or 45°, or 50°, or 55°, the average optical density of the plurality of the ORUs remains greater than about 3, or 3.5, or 4, or 4.5, or 5, or 5.5, or 6, or 6.5, or 7, or 7.5, or 8, or 8.5 averaged over the infrared wavelength range (22) extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states.

[0040] In some embodiments, for a substantially collimated incident light (20), and when an incident angle (al) of the incident light increases from a first incident angle of less than about 10°to a second incident angle of greater than about 35°, an average optical density of the plurality of the ORUs remains greater than about 5 averaged over a first infrared wavelength range (22) extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states. In some instances, the first incident angle may be less than 8°, or 6°, or 4°, or 2°, or less than 1°, the second incident angle may be greater than about 40°, or 45°, or 50°, or 55°, and, the average optical density of the plurality of the ORUs may remain greater than about 5.5, or 6, or 6.5, or 7, or 7.5, or 8, or 8.5.

[0041] As shown in FIG. 4C, an optical density (30) of the optical film as a function of wavelength averaged over mutually orthogonal first (p) and second (s) polarizations includes a high optical density region (31). The high optical density region (31) is disposed in a wavelength region of interest (24) extending continuously between about 600 nm and about 1400 nm. The wavelength region of interest (24) may vary depending on the intended application. The high optical density region (31) may have a width of at least 200 nm, 220 nm, or 240 nm, or 260 nm, or 280 nm, or 300 nm, or 350 nm. In some optical film embodiments, the average optical density of the high optical density region (31) may be greater than about 3, or 3.5, or 4, or 4.5, or 5. In some other optical film embodiments, the average optical density of the high optical density region (31) may be greater than about 5.5, or 6, or 6.5, or 7, or 7.5, or 8, or 8.5. The average optical density may be averaged across the high optical density region and averaged over the first (p) and second (s) polarization states.

[0042] Table 2 shows the average optical transmittances of different optical film configurations (OF1, OF2, OF3) at a visible wavelength range extending from about 420 nm to about 680 nm, at a first infrared wavelength range extending from about 800 nm to 1100 nm, and at a second infrared wavelength range extending from about 1300 nm to 1600 nm, at incident angles of 0°, 45° and 55° according to some embodiments of the disclosure (Refer FIG. 4A).

[0043] TABLE 2

[0044] Table 3 shows the average optical density of different optical film configurations (OF1, OF2, OF3) at a visible wavelength range extending from about 420 nm to about 680 nm, at a first infrared wavelength range extending from about 800 nm to 1100 nm and at a second infrared wavelength range extending from about 1300 nm to 1600 nm, and at incident angles of 0°, 45° and 55° according to some embodiments of the disclosure (Refer FIG. 4C).

[0045] TABLE 3

[0046] FIGS. 5A-5B graphically show the optical density of different optical films along the left band edge and right band edge as a function of wavelength. The optical film according to one or more embodiments of the present disclosure provides sharp left and right band edges to minimize the amount of visible light reflected at all angles. For instance, FIG. 5A shows a high optical density region defined by a left band edge (32a) for a substantially normally incident light, and a left band edge (32b) for light incident at a second incident angle of greater than about 35°, or 40°, or 45°, or 50°, or 55°. The optical density along the left band edge (32a, 32b) generally increases with increasing wavelength. FIG. 5B shows an optical density region defined by an opposing right band edge (33a) for a substantially normally incident light, and an opposing right band edge (33b) for light incident at a second incident angle of greater than about 35°, or 40°, or 45°, or 50°, or 55°. The optical density along the right band edge (33a, 33b) generally decreases with increasing wavelength.

[0047] Referring to FIG. 5A, a first best linear fit (34a) to the left band edge (32a) at least across a wavelength range where the optical density increases from about 1 to about 3.5, or 4, or 4.5, or 5, or 5.5, or 6 has a positive slope (35a) of greater than about 6% / nm, or greater than about 8% / nm, or greater than about 9% / nm, or greater than about 10% / nm for a substantially normally incident light, or for a first incident angle (al) of less than about 10°, or 8°, or 6°, or 4°, or 2°, or 1°. The first best linear fit (34a), in some embodiments, has an r-squared value of greater than about 0.8, or greater than about 0.9, or greater than about 0.95, or greater than about 0.98.

[0048] For the incident angle of the incident light of greater than about 35°, or 40°, or 45°, or 50°, or 55°, the first best linear fit (34b) has a positive slope (35b) that increases by at least 10%, or by at least 15%, or by at least 20%, or 25%, or 30%, or 35%, or 40%, or 45%, or 50%, or 55%, or 60%, or 65%, or 70%. In some cases, the positive slope (35b) of the linear fit (34b) at a second incident angle may be greater than about 10% / nm, or about 11% / nm, or about 12% / nm, or about 13% / nm, or about 15% / nm, or about 16 % / nm or about 17% / nm. The r-squared value of the first best linear fit (34b) is greater than about 0.8, or greater than about 0.9, or greater than about 0.95, or greater than about 0.98.

[0049] Referring to FIG. 5B, a second best linear fit (36a) to the right band edge (33a) at least across a wavelength range where the optical density increases from about 1 to about 3.5, or 4, or 4.5, or 5, or 5.5, or 6 has a negative slope (37a) having a magnitude that is greater than about 0.06, or 0.07 per nm for the first incident angle. When the incident angle (al) increases to the second incident angle of greater than about 35°, or 40°, or 45°, or 50°, or 55°, the magnitude of the negative slope (37a) of the second best linear fit increases by at least 10%, or by at least 15%, or by at least 20%, or by at least 25%, or by at least 30%. In some cases, the magnitude of the slope of the second best linear fit at a second incident angle may be greater than about 0.07, or 0.08, or 0.09, or 0.10 per nm. The second best linear fit (36a) has an r-squared value of greater than about 0.8, or greater than about 0.9, or greater than about 0.95, or greater than about 0.98.

[0050] FIG. 6A shows a system (300) including the optical film (200) according to one or more embodiments of the disclosure. The system (300) includes a housing (310) defining an opening (320) for allowing visible light therethrough. In some applications, the housing may be a cabin (310) of a vehicle (301), and the opening (320) may be defined in a roof (302) of the vehicle (301). The optical film (200) may be disposed on the opening (320) to cover said opening (320). A light source (330) emits a first light (340) having wavelengths in a visible wavelength range (21) extending continuously from about 420 nm to about 680 nm and a second light (350) having wavelengths in the high optical density region (31, FIG. 4C). For all incident angles between the first and second (bl) incident angles, the optical film (200) may transmit at least 60% of the first light and reflect at least 99% of the second light. In some aspects, for all incident angles between the first and second (bl) incident angles, the optical film (200) may transmit at least 65%, or 70%, or 75%, or 80%, or 90% of the first light. In some aspects, for all incident angles between the first and second (bl) incident angles, the optical film (200) may reflect at least 99.5%, or 99.9%, or 99.99%, or 99.999% of the second light.

[0051] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

Claims1. An optical film comprising a plurality of optical repeat units (ORUs) co-extruded and costretched with one another and numbering at least 15 in total, each of the ORUs having an average physical thickness of less than about 1000 nm and comprising at least two different polymeric layers, the ORUs comprising opposing first and second endmost ORUs farthest from each other among the ORUs, such that for first and second middle ORUs in the plurality of ORUs that are spaced apart from each of the first and second endmost ORUs by at least 10 other ORUs in the plurality of ORUs, are spaced apart from each other by no more than about 5 other ORUs in the plurality of ORUs, and have respective average physical thickness Hl and H2, a magnitude of (Hl-H2) / ((Hl+H2) / 2) is greater than about 1%, and such that for a substantially collimated substantially normally incident light, the plurality of ORUs has an average: optical transmittance of at least 60% averaged over a visible wavelength range extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first and second polarization states; and optical density of greater than about 3 averaged over a first infrared wavelength range extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states.

2. The optical film of claim 1, wherein when the incident angle of the incident light is increased from substantially normal incidence to a second incident angle of greater than about 35 degrees, the average optical transmittance of the plurality of the ORUs remains greater than about 60% averaged over the visible wavelength range, and averaged over the first and second polarization states.

3. The optical film of claim 1, wherein when the incident angle of the incident light is increased from substantially normal incidence to a second incident angle of greater than about 35 degrees, the average optical density of the plurality of the ORUs remains greater than about 3 averaged over the first infrared wavelength range, and averaged over the first and second polarization states.

4. The optical film of claim 1, wherein for the substantially collimated substantially normally incident light, an optical density of the optical film as a function of wavelength averaged over thefirst and second polarizations comprises a high optical density region that is at least 200 nm wide, has an average optical density of greater than about 3 and is disposed in a wavelength region of interest extending continuously between about 600 nm and about 1400 nm.

5. The optical film of claim 4, wherein the high optical density region is defined by a left band edge along which the optical density generally increases with increasing wavelength and an opposing right band edge along which the optical density generally decreases with increasing wavelength, and wherein a first best linear fit to the left band edge at least across a wavelength range where the optical density increases from about 1 to about 3.5 has a slope that is greater than about 0.06 per nm.

6. The optical film of claim 5, wherein when the incident angle of the incident light is increased from substantially normal incidence to a second incident angle of greater than about 35 degrees, the slope of the first best linear fit increases by at least 10%.

7. An optical film comprising a plurality of optical repeat units (ORUs) co-extruded and costretched with one another and numbering at least 15 in total, each of the ORUs having an average physical thickness of less than about 1000 nm and comprising at least two different polymeric layers, such that for a substantially collimated incident light, and when an incident angle of the incident light increases from a first incident angle of less than about 10 degrees to a second incident angle of greater than about 35 degrees: an average optical transmittance of the plurality of the ORUs remains greater than about 50% averaged over a visible wavelength range extending continuously from about 420 nm to about 680 nm, and averaged over mutually orthogonal first and second polarization states; and an average optical density of the plurality of the ORUs remains greater than about 5 averaged over a first infrared wavelength range extending continuously from about 800 nm to about 1100 nm, and averaged over the first and second polarization states.

8. An optical film comprising a plurality of optical repeat units (ORUs) co-extruded and costretched with one another and numbering at least 15 in total, each of the ORUs having an average physical thickness of less than about 1000 nm and comprising at least two different polymeric layers, such that for a substantially collimated incident light, an optical density of the optical film as a function of wavelength averaged over mutually orthogonal first and second polarizations comprises a high optical density region that is at least 200 nm wide, has an average optical density of greater than about 3 averaged across the high optical density region and averaged over the firstand second polarization states, and is disposed in a wavelength region of interest extending continuously between about 600 nm and about 1400 nm, the high optical density region defined by a left band edge along which the optical density generally increases with increasing wavelength and an opposing right band edge along which the optical density generally decreases with increasing wavelength, wherein a first best linear fit to the left band edge at least across a wavelength range where the optical density increases from about 1 to about 3.5 has a slope that is greater than about 0.06 per nm for a first incident angle of less than about 10 degrees and increases when the incident angle increases to a second incident angle of greater than about 35.

9. The optical film of claim 8, wherein a second best linear fit to the right band edge at least across a wavelength range where the optical density increases from about 1 to about 3.5 has a negative slope having a magnitude that is greater than about 0.06 per nm for the first incident angle and increases in magnitude when the incident angle increases to the second incident angle.

10. A system comprising a housing defining an opening for allowing visible light therethrough, and the optical film of claim 8 disposed on and covering the opening, such that for a light source emitting a first light having wavelengths in a visible wavelength range extending continuously from about 420 nm to about 680 nm and a second light having wavelengths in the high optical density region, and for all incident angles between the first and second incident angles, the optical film transmits at least 60% of the first light and reflects at least 99% of the second light.

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