Optical film and optical system

Abstract

An optical system includes a display and an optical film. For a substantially collimated incident light, a red wavelength range extending from about 590 nm to about 670 nm, a visible wavelength range extending from about 420 nm to about 680 nm, an infrared wavelength range extending from about 850 nm to about 1600 nm, and for at least one of mutually orthogonal in-plane first and second polarization states: for an angle of incidence of less than about 10 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 60% in the visible wavelength range and an average optical transmittance of less than about 70% in the infrared wavelength range; and for an angle of incidence of at least about 70 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 50% in the red wavelength range.

Description

[0001] OPTICAL FILM AND OPTICAL SYSTEM

[0002] Technical Field

[0003] The present disclosure relates generally to an optical film, and in particular, to an optical system including the optical film.

[0004] Background

[0005] In some applications, optical systems include outdoor displays. The outdoor displays may therefore be exposed to sunlight. Such optical systems including the outdoor displays may be used in automotive display systems, public information display systems, and the like.

[0006] Summary

[0007] In a first aspect, the present disclosure provides an optical system. The optical system includes a display configured to be used outdoors and exposed to sunlight while forming an image for viewing by a viewer. The optical system further includes an optical film disposed on, and between the viewer and, the display. The optical film includes a plurality of polymeric microlayers numbering at least 10 in total. Each of the polymeric microlayers has an average thickness of less than about 500 nm. For a substantially collimated incident light, a red wavelength range extending from about 590 nm to about 670 nm, a visible wavelength range extending from about 420 nm to about 680 nm, an infrared wavelength range extending from about 850 nm to about 1600 nm, and for at least one of mutually orthogonal in-plane first and second polarization states: for an angle of incidence of less than about 10 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 60% in the visible wavelength range and an average optical transmittance of less than about 70% in the infrared wavelength range; and for an angle of incidence of at least about 70 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 50% in the red wavelength range.

[0008] In a second aspect, the present disclosure provides an optical film configured to be used outdoors and exposed to sunlight. The optical film includes a plurality of polymeric microlayers numbering at least 50 in total. Each of the polymeric microlayers has an average thickness of less than about 500 nm. For a substantially collimated substantially normally incident light, and for each of mutually orthogonal in-plane first and second polarization states, the plurality of polymeric microlayers has an average optical transmittance of greater than about 60% in a visible wavelength range extending from about 420 nm to about 680 nm, and an average optical transmittance of less than 70% in an infrared wavelength range extending from about 850 nm to about 1600 nm. For a substantially collimated light incident on the optical film from an illuminant D65, the optical film reflects the incident substantially collimated light with the reflected light, in a CIE Lab color space, having colorimetric parameters A* and B* such that as an incident angle of the substantially collimated light incident varies continuously from about zero degree to about 89 degrees, A* remains in a first range extending from about -5 to about 4 and B* remains in a second range extending from about -7 to about 4.

[0009] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

[0010] Brief Description of the Drawings

[0011] Exemplary embodiments disclosed herein may be more completely understood in consideration of the following detailed description in connection with the following figures. 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 given figure is not intended to limit the component in another figure labeled with the same number.

[0012] FIG. 1 shows a schematic sectional view of an optical system, according to an embodiment of the present disclosure;

[0013] FIG. 2 shows a schematic detailed sectional view of an optical film, according to an embodiment of the present disclosure;

[0014] FIG. 3 shows a schematic detailed sectional view of an optical film, according to another embodiment of the present disclosure;

[0015] FIG. 4 shows a schematic detailed sectional view of an optical film, according to another embodiment of the present disclosure;

[0016] FIG. 5 shows a schematic sectional view of a plurality of polymeric microlayers of the optical film, according to an embodiment of the present disclosure;

[0017] FIG. 6 shows a graph depicting an optical transmittance of the plurality of polymeric microlayers of the optical film versus wavelength for a substantially collimated incident light and for a first polarization state, according to an embodiment of the present disclosure;

[0018] FIG. 7 shows a graph depicting an optical transmittance of the plurality of polymeric microlayers of the optical films versus wavelength for the substantially collimated incident light and for a second polarization state, according to an embodiment of the present disclosure;

[0019] FIG. 8 shows a schematic sectional view of the optical film and an illuminant D65, according to an embodiment of the present disclosure;

[0020] FIG. 9 shows a graph depicting delta C* for the optical system including the optical film versus incident angles, according to an embodiment of the present disclosure;

[0021] FIGS. 10A to IOC show a graph depicting a variation between A* and B* for different incident angles for the optical system including the optical film, according to an embodiment of the present disclosure;

[0022] FIG. 10D shows a magnified view of a portion of the graph shown in FIGS. 10A-10C;

[0023] FIG. 10E shows a magnified view of another portion of the graph shown in FIGS. 10A-10C; and FIG. 10F shows a magnified view of the portion of the graph shown in FIG. 10E.

[0024] Detailed Description

[0025] In the following description, reference is made to the accompanying figures that form a part thereof 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 disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0026] In the following disclosure, the following definitions are adopted.

[0027] As used herein, all numbers should be considered modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably.

[0028] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties).

[0029] The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0030] The term “about”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 5% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0031] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be constmed as limiting of this disclosure. The terms “first” and “second” when used in conjunction with a feature or an element can be interchanged throughout the embodiments of this disclosure.

[0032] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0033] As used herein, the term “layer” generally refers to a thickness of material within a film that has a relatively consistent chemical composition. Layers may be of any type of material including polymeric, cellulosic, metallic, or a blend thereof. A given polymeric layer may include a single polymer-type or a blend of polymers and may be accompanied by additives. A given layer may be combined or connected to other layers to form films. A layer may be either partially or fully continuous as compared to adjacent layers or the film. A given layer may be partially or fully coextensive with adjacent layers. A layer may contain sub-layers.

[0034] In some applications, optical systems include outdoor displays. The outdoor displays may therefore be exposed to sunlight. Such optical systems including the outdoor displays may be used in automotive display systems, public information display systems, and the like. Sunlight incident on outdoor displays of the optical systems may cause thermal management issues by heating the outdoor displays. In some cases, optical films that reflect a portion of sunlight in an infrared wavelength range extending from about 850 nm to about 1600 nm may be used in such optical systems. However, such optical films may also reflect a portion of light in a red wavelength range extending from about 590 nm to about 670 nm, especially at oblique angles (e.g., greater than about 70 degrees). This may negatively affect the color performance of the display and may cause color artifacts.

[0035] Therefore, a suitable solution may be desired which may provide a better thermal management without compromising the color performance of the optical systems in outdoor applications.

[0036] The present disclosure relates to an optical system including a display configured to be used outdoors and exposed to sunlight while forming an image for viewing by a viewer. The present disclosure further relates to an optical film configured to be used outdoors and exposed to sunlight. The optical system includes the optical film.

[0037] The optical film is disposed on, and between the viewer and, the display and includes a plurality of polymeric microlayers numbering at least 10 in total. Each of the polymeric microlayers has an average thickness of less than about 500 nm. For a substantially collimated incident light, a red wavelength range extending from about 590 nm to about 670 nm, a visible wavelength range extending from about 420 nm to about 680 nm, an infrared wavelength range extending from about 850 nm to about 1600 nm, and for at least one of mutually orthogonal in-plane first and second polarization states: for an angle of incidence of less than about 10 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 60% in the visible wavelength range and an average optical transmittance of less than about 70% in the infrared wavelength range; and for an angle of incidence of at least about 70 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 50% in the red wavelength range.

[0038] Therefore, for the first polarization state, and for the angle of incidence of at least about 70 degrees, the optical film of the present disclosure may substantially transmit the substantially collimated incident light in the red wavelength range, while providing thermal management for the optical system by reducing the transmission of the substantially collimated incident light having the at least one of the first and second polarization states in the infrared wavelength range incident at the angle of incidence of less than about 10 degrees. This may reduce or prevent visible color artifacts.

[0039] Referring now to figures, FIG. 1 is a schematic sectional view of an optical system 300, according to an embodiment of the present disclosure.

[0040] The optical system 300 defines mutually orthogonal x, y, and z-axes. The x and y-axes are inplane axes of the optical system 300, while the z-axis is a transverse axis disposed along a thickness of the optical system 300. In other words, the x and y-axes are disposed along a plane of the optical system 300, while the z-axis is perpendicular to the plane of the optical system 300. The optical system 300 includes a display 10 configured to display an image 11. The display 10 is configured to be used outdoors and exposed to sunlight 20 while forming the image 11 for viewing by a viewer 30.

[0041] In some embodiments, the display 10 includes one or more of a liquid crystal display (LCD), an organic light emitting diode (OLED) display, and a micro-LED display. In some embodiments, the micro-LED display includes a plurality of individually and independent operable micro-LEDs 12.

[0042] The optical system 300 further includes an optical film 40 configured to be used outdoors and exposed to the sunlight 20. The optical film 40 is disposed on, and between the viewer 30, and the display 10.

[0043] In some embodiments, the optical system 300 further includes a first substrate layer 60 disposed on the optical film 40 opposite the display 10. In some embodiments, the first substrate layer 60 includes one or more of a glass and a plastic. In some embodiments, the first substrate layer 60 is bonded to the optical film 40 via an adhesive layer 70. In some embodiments, the adhesive layer 70 may include an optically clear adhesive (OCA).

[0044] In some embodiments, the optical system 300 further includes a second substrate layer 61 disposed between the optical film 40 and the display 10. In some embodiments, the second substrate layer 61 includes one or more of a glass and a plastic. In some embodiments, the second substrate layer 61 is bonded to the optical film 40 and the display 10 via first and second adhesive layers 71, 72. Specifically, the second substrate layer 61 is bonded to the optical film 40 via the first adhesive layer 71 and the second substrate layer 61 is bonded to the display 10 via the second adhesive layer 72. In some embodiments, the optical film 40 may include an optical film 40a (shown in FIG. 2), an optical film 40b (shown in FIG. 3), or an optical film 40c (shown in FIG. 4). In some embodiments, each of the first and second adhesive layers 71, 72 may include an OCA.

[0045] FIG. 2 illustrates a schematic detailed sectional view of the optical film 40a, according to an embodiment of the present disclosure. The optical film 40a may be used in the optical system 300 of FIG. 1 as the optical film 40.

[0046] The optical film 40a includes a plurality of polymeric microlayers 43 numbering at least 10 in total. In some embodiments, the optical film 40a includes the plurality of polymeric microlayers 43 numbering at least 20, at least 50, at least 100, at least 150, at least 200, at least 250, or 300 in total.

[0047] In some embodiments, the plurality of polymeric microlayers 43 includes a plurality of alternating polymeric first and second microlayers 41, 42 numbering at least 10 in total and stacked along a thickness direction of the optical film 40a. In some embodiments, the plurality of polymeric microlayers 43 includes the plurality of alternating polymeric first and second microlayers 41, 42 numbering at least 20, at least 50, at least 100, at least 150, at least 200, at least 250, or at least 300 in total and stacked along the thickness direction of the optical film 40a. In some embodiments, the plurality of polymeric microlayers 43 includes the plurality of alternating polymeric first and second microlayers 41 , 42 numbering about 225 in total and stacked along the thickness direction of the optical film 40a. In some embodiments, the thickness direction of the optical film 40a extends substantially along the z-axis.

[0048] Each of the polymeric microlayers 43 has an average thickness t of less than about 500 nm. The term “average thickness f as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the x-y plane) of each of the polymeric microlayers 43. In some embodiments, each of the polymeric microlayers 43 has the average thickness t of less than about 400 nm, less than about 300 nm, or less than about 200 nm. Therefore, each of the polymeric first and second micro layers 41, 42 may have the average thickness t of less than about 500 nm.

[0049] In some embodiments, the polymeric first microlayers 41 include a polyethylene terephthalate (PET), and the polymeric second microlayers 42 include a copolymer of polymethyl methacrylate (CoPMMA). In some embodiments, the polymeric second microlayers 42 include copolymers of aliphatic-aromatic polyesters having a refractive index Ri less than 1.52, i.e., Ri <1.52 for a visible wavelength range 51 (shown in FIG. 6) extending from about 420 nm to about 680 nm. In some embodiments, Ri <1.5. In some embodiments, the polymeric second microlayers 42 include any suitable material having the refractive index Ri <1.52 for the visible wavelength range 51 and an optical transparency Ot of greater than or equal to about 80%, i.e., Ot > 80% and / or an optical haze Oh of less than about 1%, i.e., Oh < 1%.

[0050] In some embodiments, the optical film 40a further includes at least one skin layer 46. Each of the at least one skin layer 46 has an average thickness ts of greater than about 500 nm. The term “average thickness ts”, as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the x-y plane) of each of the at least one skin layer 46. In some embodiments, each of the at least one skin layer 46 has the average thickness ts of greater than about 750 nm, greater than about 1000 nm, greater than about 1250 nm, greater than about 1500 nm, greater than about 1750 nm, or greater than about 2000 nm. In some embodiments, the at least one skin layer 46 includes a PET.

[0051] In the illustrated embodiment of FIG. 2, the at least one skin layer 46 includes a pair of skin layers 46, and the polymeric microlayers 43 are disposed between the pair of skin layers 46. The at least one skin layer 46 may protect polymeric microlayers 43, and may also provide mechanical stability to the optical film 40a. In some cases, the at least one skin layer 46 may act as protective boundary layer (PBL).

[0052] FIG. 3 illustrates a schematic detailed sectional view of the optical film 40b, according to another embodiment of the present disclosure. The optical film 40b may be used in the optical system 300 of FIG. 1 as the optical film 40. The optical film 40b of FIG. 3 is substantially similar to the optical film 40a of FIG. 2, with common components being referred to as by the same numerals.

[0053] In the illustrated embodiment of FIG. 3, the plurality of polymeric microlayers 43 includes a plurality of first optical repeat units 44a and a plurality of second optical repeat units 44b.

[0054] In some embodiments, the plurality of first optical repeat units 44a numbers at least 10 in total. In some embodiments, the plurality of first optical repeat units 44a numbers at least 15, at least 20, at least 50, at least 100, or at least 150 in total. In some embodiments, the plurality of second optical repeat units 44b numbers at least 10 in total. In some embodiments, the plurality of second optical repeat units 44b numbers at least 15, at least 20, at least 50, at least 100, at least 200, at least 250, or at least 300, in total.

[0055] In some embodiments, each of the first optical repeat units 44a has at least microlayers Al (shown as 41a in FIG. 3) and microlayers B 1 (shown as 41b in FIG. 3) having different compositions. The microlayer Al may be referred to herein as “the microlayer Al 41a”, and the microlayer Bl may be referred to herein as “the microlayer Bl 41b”. In other words, a composition of the at least microlayers Al 41a of each of the first optical repeat units 44a is different from a composition of the at least microlayers Bl 41b of each of the first optical repeat units 44a.

[0056] In some embodiments, one of the microlayers Al and Bl 41a, 41b includes a PET, and the other one of the microlayers Al and Bl 41a, 41b includes a CoPMMA. In some embodiments, the other one of the microlayers Al and Bl 41a, 41b includes copolymers of aliphatic-aromatic polyesters having the refractive index Ri <1.52 for the visible wavelength range 51 (shown in FIG. 6). In some embodiments, Ri <1.5. In some embodiments, the other one of the microlayers Al and Bl 41a, 41b includes any suitable material having the refractive index Ri <1.52 for the visible wavelength range 51 and the optical transparency Ot > 80% and / or the optical haze Oh < 1%.

[0057] In some embodiments, each of the first optical repeat units 44a includes one of the microlayer Al 41a and one of the microlayer Bl 41b arranged as A1B1.

[0058] In some embodiments, each of the second optical repeat units 44b has at least microlayers A2 (shown as 42a in FIG. 3), microlayers B2 (shown as 42b in FIG. 3), and microlayers C2 (shown as 42c in FIG. 3) having different compositions. The microlayer A2 may be referred to herein as “the microlayer A2 42a, the microlayer B2 may be referred to herein as “the microlayer B2 42b”, and the microlayer C2 may be referred to herein as “the microlayer C2 42c”. In some embodiments, at least one of the microlayers Al 4 la and the microlayers B 1 4 lb has a different composition than at least one of the microlayers A2 42a, the microlayers B2 42b, and the microlayers C2 42c.

[0059] In some embodiments, a first one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a PET, a second one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a CoPMMA, and a third one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a glycol-modified polyethylene terephthalate (PETg).

[0060] In some embodiments, the second one of the microlayers A2, B2, and C2 42a, 42b, 42c includes copolymers of aliphatic-aromatic polyesters having the refractive index Ri <1.52 for the visible wavelength range 51 (shown in FIG. 6). In some embodiments, Ri <1.5. In some embodiments, the second one of the microlayers A2, B2, and C2 42a, 42b, 42c includes any suitable material having the refractive index Ri <1.52 for the visible wavelength range 51 and the optical transparency Ot > 80% and / or the optical haze Oh < 1%.

[0061] In some embodiments, the third one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a material having a refractive index Ric less than about 1.6, i.e., Ric <1.6 for the visible wavelength range 51 and the optical transparency Ot > 80% and / or the optical haze Oh < 1%. In some embodiments, Ric <1.58 or Ric <1.57.

[0062] Each of the microlayers 41a, 41b, 42a, 42b, 42c in the first and second optical repeat units 44a, 44b has the average thickness t of less than about 500 nm. In some embodiments, each of the micro layers 4 la, 4 lb, 42a, 42b, 42c in the first and second optical repeat units 44a, 44b has the average thickness t of less than about 450 nm, less than about 400 nm, less than about 350 nm, less than about 300 nm, less than about 250 nm, or less than about 200 nm.

[0063] In some embodiments, the plurality of first optical repeat units 44a is disposed on and separated by at least one spacer layer 45 from the plurality of second optical repeat units 44b. In the illustrated embodiment of FIG. 3, the plurality of first optical repeat units 44a is disposed on and separated by one spacer layer 45 from the plurality of second optical repeat units 44b.

[0064] Further, in some embodiments, each of the at least one spacer layer 45 has an average thickness tsl of greater than about 500 nm. In some embodiments, each of the at least one spacer layer 45 has the average thickness tsl of greater than about 400 nm, greater than about 300, or greater than about 200 nm.

[0065] In some embodiments, each of the second optical repeat units 44b includes one of the microlayer A2 42a, two of the microlayer B2 42b, and one of the microlayer C2 42c arranged as A2B2C2B2.

[0066] FIG. 4 illustrates a schematic detailed sectional view of the optical film 40c, according to another embodiment of the present disclosure. The optical film 40c may be used in the optical system 300 of FIG. 1 as the optical film 40. The optical film 40c of FIG. 4 is substantially similar to the optical film 40b of FIG. 3 with common components being referred to as by the same numerals. However, the optical film 40c of FIG. 4 does not include the first optical repeat units 44a and the at least one spacer layer 45 shown in FIG. 3.

[0067] Therefore, in the illustrated embodiment of FIG. 4, the plurality of polymeric microlayers 43 includes the plurality of optical repeat units 44b (previously referred to as “the second optical repeat units 44b”). The plurality of optical repeat units 44b numbers at least 10 in total. In some embodiments, the plurality of optical repeat units 44b numbers at least 15, at least 20, at least 50, at least 100, at least 200, at least 250, or at least 300 in total. Each of the optical repeat units 44b has at least the microlayers A2, B2, and C2 42a, 42b, 42c having different compositions. In some embodiments, each of the optical repeat units 44b includes one of the microlayer A2 42a, two of the microlayer B2 42b, and one of the micro layer C2 42c arranged as A2B2C2B2.

[0068] As discussed above, in some embodiments, a first one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a PET, a second one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a CoPMMA, and a third one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a PETg.

[0069] In some embodiments, the second one of the microlayers A2, B2, and C2 42a, 42b, 42c includes copolymers of aliphatic-aromatic polyesters having the refractive index Ri <1.52 for the visible wavelength range 51 (shown in FIG. 6). In some embodiments, Ri <1.5. In some embodiments, the second one of the microlayers A2, B2, and C2 42a, 42b, 42c includes any suitable material having the refractive index Ri <1.52 for the visible wavelength range 51 and the optical transparency Ot > 80% and / or the optical haze Oh < 1%.

[0070] In some embodiments, the third one of the microlayers A2, B2, and C2 42a, 42b, 42c includes a material having the refractive index Ric less than about 1.6, i.e., Ric <1.6 for the visible wavelength range 51 and the optical transparency Ot > 80% and / or the optical haze Oh < 1%. In some embodiments, Ric <1.58 or Ric <1.57.

[0071] FIG. 5 illustrates a schematic sectional view of the plurality of polymeric microlayers 43 of the optical film 40 (shown in FIG. 1), according to an embodiment of the present disclosure. The plurality of polymeric microlayers 43 are shown schematically as a single block in FIG. 5.

[0072] As illustrated in FIG. 5, the plurality of polymeric microlayers 43 is configured to receive a substantially collimated incident light 31. In some embodiments, the plurality of polymeric microlayers 43 receives the substantially collimated incident light 31 at an angle of incidence al.

[0073] In some embodiments, the angle of incidence al is less than about 10 degrees. In some embodiments, the angle of incidence al 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 al is about 0 degree.

[0074] In some other embodiments, the angle of incidence al is at least about 70 degrees. In some embodiments, the angle of incidence al is at least about 75 degrees or at least about 80 degrees. In some embodiments, the angle of incidence al is about 80 degrees.

[0075] FIG. 6 illustrates a graph 600 depicting an optical transmittance of the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c (shown in FIGS. 2, 3, and 4, respectively) versus wavelength for the substantially collimated incident light 31 (shown in FIG. 5) and for a first polarization state, according to an embodiment of the present disclosure. Further, the graph 600 depicts an optical transmittance of a comparative optical film versus wavelength for the substantially collimated incident light 31 (shown in FIG. 5) and for the first polarization state. In some embodiments, the first polarization state is a p-polarization state. In some embodiments, the first polarization state is along the x-axis.

[0076] Wavelength is expressed in nanometers (nm) in abscissa. The optical transmittance is expressed as a transmission percentage (%) in the ordinate.

[0077] The graph 600 includes a curve 602 depicting the optical transmittance of the optical film 40a for the angle of incidence al of less than about 10 degrees and for the first polarization state, a curve 604 depicting the optical transmittance of the optical film 40b for the angle of incidence al of less than about 10 degrees and for the first polarization state, and a curve 606 depicting the optical transmittance of the optical film 40c for the angle of incidence al of less than about 10 degrees and for the first polarization state. The graph 600 further includes a curve 608 depicting the optical transmittance of the comparative optical film for the angle of incidence al of less than about 10 degrees and for the first polarization state. Specifically, the curves 602, 604, 606, 608 depict the optical transmittance s of the optical films 40a, 40b, 40c, and comparative optical film, respectively, for the angle of incidence al of about 0 degree and for the first polarization state.

[0078] The graph 600 further includes a curve 612 depicting the optical transmittance of the optical film 40a for the angle of incidence al of at least about 70 degrees and for the first polarization state, a curve 614 depicting the optical transmittance of the optical film 40b for the angle of incidence al at least about 70 degrees and for the first polarization state, and a curve 616 depicting the optical transmittance of the optical film 40c for the angle of incidence al of at least about 70 degrees and for the first polarization state. The graph 600 further includes a curve 618 depicting the optical transmittance of the comparative optical film for the angle of incidence al of at least about 70 degrees and for the first polarization state. Specifically, the curves 612, 614, 616, 618 depict the optical transmittances of the optical films 40a, 40b, 40c, and comparative optical film, respectively, for the angle of incidence al of about 80 degrees and for the first polarization state.

[0079] FIG. 7 illustrates a graph 700 depicting an optical transmittance of the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c (shown in FIGS. 2, 3, and 4, respectively) versus wavelength for the substantially collimated incident light 31 (shown in FIG. 5) and for a second polarization state, according to an embodiment of the present disclosure. Further, the graph 700 depicts an optical transmittance of the comparative optical film versus wavelength for the substantially collimated incident light 31 (shown in FIG. 5) and for the second polarization state. In some embodiments, the second polarization state is an s-polarization state. In some embodiments, the second polarization state is along the y-axis.

[0080] Wavelength is expressed in nanometers (nm) in abscissa. The optical transmittance is expressed as a transmission percentage (%) in the ordinate.

[0081] The graph 700 includes a curve 702 depicting the optical transmittance of the optical film 40a for the angle of incidence al of less than about 10 degrees and for the second polarization state, a curve 704 depicting the optical transmittance of the optical film 40b for the angle of incidence al of less than about 10 degrees and for the second polarization state, and a curve 706 depicting the optical transmittance of the optical film 40c for the angle of incidence al of less than about 10 degrees and for the second polarization state. The graph 700 further includes a curve 708 depicting the optical transmittance of the comparative optical film for the angle of incidence al of less than about 10 degrees and for the second polarization state. Specifically, the curves 702, 704, 706, 708 depict the optical transmittances of the optical films 40a, 40b, 40c, and comparative optical film, respectively, for the angle of incidence al of about 0 degree and for the second polarization state.

[0082] The graph 700 further includes a curve 712 depicting the optical transmittance of the optical film 40a for the angle of incidence al of at least about 70 degrees and for the second polarization state, a curve 714 depicting the optical transmittance of the optical film 40b for the angle of incidence al at least about 70 degrees and for the second polarization state, and a curve 716 depicting the optical transmittance of the optical film 40c for the angle of incidence al of at least about 70 degrees and for the second polarization state. The graph 700 further includes a curve 718 depicting the optical transmittance of the comparative optical film for the angle of incidence al of at least about 70 degrees and for the second polarization state. Specifically, the curves 712, 714, 716, 718 depict the optical transmittances of the optical films 40a, 40b, 40c, and comparative optical film, respectively, for the angle of incidence al of about 80 degrees and for the second polarization state.

[0083] Referring to FIGS. 5, 6, and 7, for the substantially collimated incident light 31, a red wavelength range 50 extending from about 590 nm to about 670 nm, the visible wavelength range 51 extending from about 420 nm to about 680 nm, an infrared wavelength range 52 extending from about 850 nm to about 1600 nm, and for at least one of the mutually orthogonal in-plane first and second polarization states, for the angle of incidence al of less than about 10 degrees (depicted by the curves 602, 604, 606, 702, 704, 706), the plurality of polymeric microlayers 43 has an average optical transmittance of greater than about 60% in the visible wavelength range 51.

[0084] In some embodiments, for the substantially collimated incident light 31, the red wavelength range 50, the visible wavelength range 51, the infrared wavelength range 52, and for the at least one of the first and second polarization states, for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has the average optical transmittance of greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85% in the visible wavelength range 51.

[0085] In some embodiments, for the substantially collimated substantially normally incident light 31, and for each of the mutually orthogonal in-plane first and second polarization states, the plurality of polymeric microlayers 43 has the average optical transmittance of greater than about 60% in the visible wavelength range 51.

[0086] As is apparent from the curves 602, 604, 606, for the substantially collimated incident light 31, for the first polarization state, and for the angle of incidence al of about 0 degree, the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c has respective average optical transmittances of about 87.9%, 87.9%, 88.1% in the visible wavelength range 51.

[0087] Further, as is apparent from the curves 702, 704, 706, for the substantially collimated incident light 31, for the second polarization state, and for the angle of incidence al of about 0 degree, the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c has respective average optical transmittances of about 87.6%, 86.7%, 86.8% in the visible wavelength range 51.

[0088] Therefore, for the substantially collimated incident light 31, for each of the mutually orthogonal in-plane first and second polarization states, and for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 of each of the optical films 40a, 40b, 40c has the average optical transmittance of greater than about 60% in the visible wavelength range 51.

[0089] In some embodiments, for each of the mutually orthogonal in-plane first and second polarization states, and for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has the average optical transmittance of greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85% in the visible wavelength range 51. Further for the substantially collimated incident light 31, and for the at least one of mutually orthogonal in-plane first and second polarization states, for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than 70% in the infrared wavelength range 52.

[0090] In some embodiments, for the substantially collimated incident light 31, and for the at least one of mutually orthogonal in-plane first and second polarization states, for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has the average optical transmittance of less than about 65%, less than about 60%, less than about 55%, less than about 50%, less than about 45%, less than about 40%, or less than about 35% in the infrared wavelength range 52.

[0091] In some embodiments, for the substantially collimated substantially normally incident light 31, and for each of the mutually orthogonal in-plane first and second polarization states, the plurality of polymeric microlayers 43 has the average optical transmittance of less than about 70% in the infrared wavelength range 52.

[0092] As is apparent from the curves 602, 604, 606, for the substantially collimated incident light 31, for the first polarization state, and for the angle of incidence al of about 0 degree, the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c has respective average optical transmittances of about 59.2%, 31.4%, 44.1% in the infrared wavelength range 52.

[0093] Further, as is apparent from the curves 702, 704, 706, for the substantially collimated incident light 31, for the second polarization state, and for the angle of incidence al of about 0 degree, the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c has respective average optical transmittances of about 57%, 23.9%, 34.9% in the infrared wavelength range 52.

[0094] Therefore, for the substantially collimated incident light 31, for each of the mutually orthogonal in-plane first and second polarization states, and for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 of each of the optical films 40a, 40b, 40c has the average optical transmittance of less than about 70% in the infrared wavelength range 52.

[0095] Further, for the substantially collimated incident light 31, the red wavelength range 50, the visible wavelength range 51, the infrared wavelength range 52, and for the at least one of mutually orthogonal in-plane first and second polarization states, for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of greater than about 50% in the red wavelength range 50.

[0096] In some embodiments, for the substantially collimated incident light 31, the red wavelength range 50, the visible wavelength range 51, the infrared wavelength range 52, and for the at least one of mutually orthogonal in-plane first and second polarization states, for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 has the average optical transmittance of greater than about 55%, greater than about 60%, or greater than about 65% in the red wavelength range 50.

[0097] As is apparent from the curves 612, 614, 616, for the substantially collimated incident light 31, for the first polarization state, and for the angle of incidence al of about 80 degrees, the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c has respective average optical transmittances of about 65.4%, 51.7%, 53.2% in the red wavelength range 50.

[0098] Therefore, for the substantially collimated incident light 31, for the first polarization state, and for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 of each of the optical films 40a, 40b, 40c has the average optical transmittance of greater than about 50% in the red wavelength range 50. Thus, for the first polarization state and for the angle of incidence al of at least about 70 degrees, the optical films 40a, 40b, 40c may substantially transmit the substantially collimated incident light 31 in the red wavelength range 50.

[0099] On the contrary, as is apparent from the curve 618, for the substantially collimated incident light 31, for the first polarization state, and for the angle of incidence al of about 80 degrees, the comparative optical film has the average optical transmittance of about 46% in the red wavelength range 50. Thus, for the first polarization state and for the angle of incidence al of at least about 70 degrees, the comparative optical film may substantially block the substantially collimated incident light 31 in the red wavelength range 50.

[0100] This may impact colors as viewed by the viewer 30 (shown in FIG. 1) at the angle of incidence al of at least about 70 degrees. Since, for the first polarization state and for the angle of incidence al of at least about 70 degrees, the optical films 40a, 40b, 40c may substantially transmit the substantially collimated incident light 31 in the red wavelength range 50, the optical films 40a, 40b, 40c may have a better color performance at larger angles (i.e., at least about 70 degrees). This may also reduce or prevent visible color artifacts.

[0101] In some embodiments, for the at least one of the mutually orthogonal in-plane first and second polarization states, and for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than about 20% in the infrared wavelength range 52.

[0102] In some embodiments, for the at least one of the mutually orthogonal in-plane first and second polarization states, and for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than about 15%, or less than about 10% in the infrared wavelength range 52.

[0103] As is apparent from the curves 714, 716, for the substantially collimated incident light 31, for the second polarization state, and for the angle of incidence al of about 80 degrees, the plurality of polymeric micro layers 43 of the optical films 40b, 40c has respective average optical transmittances of about 7.6%, 8.4% in the infrared wavelength range 52. Thus, for the substantially collimated incident light 31, for the second polarization state, and for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 of each of the optical films 40b, 40c has the average optical transmittance of less than about 20% in the infrared wavelength range 52.

[0104] On the contrary, as is apparent from the curve 718, for the substantially collimated incident light 31, for the second polarization state, and for the angle of incidence al of about 80 degrees, the comparative optical film has the average optical transmittances of greater than about 20% (i.e., 22.8%) in the infrared wavelength range 52.

[0105] Therefore, for the second polarization state and for the angle of incidence al of at least about 70 degrees, the optical films 40b, 40c may block more of the substantially collimated incident light 31 in the infrared wavelength range 52 than the comparative optical film. Therefore, the optical films 40b, 40c may provide improved solar reflectivity for the second polarization state and for the angle of incidence al of at least about 70 degrees, and, in turn, a better thermal management than the comparative optical film.

[0106] In some embodiments, for the substantially collimated incident light 31, an ultraviolet (UV) wavelength range 58 extending from about 350 nm to about 400 nm, and for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than about 30% for the first polarization state. In some embodiments, for the substantially collimated incident light 31, the UV wavelength range 58, and for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has the average optical transmittance of less than about 25% for the first polarization state.

[0107] As is apparent from the curves 602, 604, for the substantially collimated incident light 31, the UV wavelength range 58, for the first polarization state, and for the angle of incidence al of about 0 degree, the plurality of polymeric microlayers 43 of the optical films 40a, 40b has respective average optical transmittances of about 23.2%, 27.5%.

[0108] In some embodiments, for the substantially collimated incident light 31, the UV wavelength range 58, and for the angle of incidence al of less than about 10 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than about 20% for the second polarization state. In some embodiments, for the substantially collimated incident light 31, the UV wavelength range 58, andforthe angle of incidence al of less thanabout 10 degrees, the plurality ofpolymeric microlayers 43 has the average optical transmittance of less than about 15% for the second polarization state.

[0109] As is apparent from the curves 702, 704, for the substantially collimated incident light 31, the UV wavelength range 58, for the second polarization state, and for the angle of incidence al of about 0 degree, the plurality of polymeric microlayers 43 of the optical films 40a, 40b has respective average optical transmittances of about 11.8%, 16.4%.

[0110] In some embodiments, for the substantially collimated incident light 31, the UV wavelength range 58, and for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than about 30% for the second polarization state. In some embodiments, for the substantially collimated incident light 31, the UV wavelength range 58, and for the angle of incidence al of at least about 70 degrees, the plurality of polymeric microlayers 43 has an average optical transmittance of less than about 25% for the second polarization state.

[0111] As is apparent from the curves 712, 714, 716, for the substantially collimated incident light 31, the UV wavelength range 58, for the second polarization state, and for the angle of incidence al of about 80 degrees, the plurality of polymeric microlayers 43 of the optical films 40a, 40b, 40c has respective average optical transmittances of about 22.1%, 23.1%, 22%.

[0112] Therefore, the optical films 40a, 40b, 40c may substantially block the substantially collimated incident light 31 in the UV wavelength range 58 for the first polarization state. Further, the optical films 40a, 40b, 40c may substantially block the substantially collimated incident light 31 in the UV wavelength range 58, for the angle of incidence al of about 80 degrees, and for the second polarization state. This may prevent and / or reduce the substantially collimated incident light 31 in the UV wavelength range 58 to reach the viewer 30 shown in FIG. 1.

[0113] Table 1 below demonstrates the average optical transmittance of the plurality of polymeric microlayers 43 of the optical film 40a (shown in FIG. 2), for the different wavelength ranges, for the different values of the angle of incidence al, and the different polarization states.

[0114] Table 1

[0115] Table 2 below demonstrates the average optical transmittance of the plurality of polymeric microlayers 43 of the optical film 40b (shown in FIG. 3), for the different wavelength ranges, for the different values of the angle of incidence al, and the different polarization states.

[0116] Table 2

[0117] Table 3 below demonstrates the average optical transmittance of the plurality of polymeric microlayers 43 of the optical film 40c (shown in FIG. 4), for the different wavelength ranges, for the different values of the angle of incidence al, and the different polarization states. Table 3

[0118] Table 4 below demonstrates the average optical transmittance of the plurality of polymeric microlayers 43 of the comparative optical film, for the different wavelength ranges, for the different values of the angle of incidence al, and the different polarization states. Table 4 where, TPO refers to the average optical transmittance for the angle of incidence al of about 0 degree and for the first polarization state; TSO refers to the average optical transmittance for the angle of incidence al of about 0 degree and for the second polarization state;

[0119] TP80 refers to the average optical transmittance for the angle of incidence al of about 80 degrees and for the first polarization state; and

[0120] TS80 refers to the average optical transmittance for the angle of incidence al of about 80 degrees and for the second polarization state.

[0121] FIG. 8 illustrates a schematic sectional view of the optical film 40 and an illuminant D65 33, according to an embodiment of the present disclosure. As illustrated in FIG. 8, a substantially collimated light 32 is incident on the optical film 40 from the illuminant D65 33 at an incident angle a2. The substantially collimated light 32 is reflected from the optical film 40 as a reflected light 34.

[0122] FIG. 9 illustrates a graph 900 depicting delta C* for the optical system 300 including the optical film 40 (shown in FIG. 8) versus the incident angle a2 (shown in FIG. 8), according to an embodiment of the present disclosure. Angle is expressed in degrees (deg) in abscissa. Delta C* is expressed in the ordinate.

[0123] The graph 900 includes a curve 902 depicting the delta C* for the optical system 300 including the optical film 40a for the incident angle a2, a curve 904 depicting the delta C* for the optical system 300 including the optical film 40b for the incident angle a2, and a curve 906 depicting the delta C* for the optical system 300 including the optical film 40c for the incident angle a2. The graph 900 further includes a curve 908 depicting the delta C* for the optical system 300 including the comparative optical film for the incident angle of a2. The graph 900 further includes a curve 910 depicting the delta C* for the optical system 300 without any optical film for the incident angle of a2.

[0124] Referring to FIGS. 8 and 9, in some embodiments, for the substantially collimated light 32 incident on the optical film 40 from the illuminant D65 33, and for a first incident angle of less than about 10 degrees (i.e., the incident angle a2 < 10 degrees) and a second incident angle of about 89 degrees (i.e., the incident angle a2 = 89 degrees), the optical film 40 (e.g., the optical films 40a, 40b, 40c) reflects the incident substantially collimated light 32 with the reflected light 34, in a CIE Lab color space, having chroma parameters Cl* and C2* for the respective first and second incident angles.

[0125] As is apparent from the curves 902, 904, 906 for the respective optical fdms 40a, 40b, 40c, a difference between C2* and Cl* is greater than or equal to -6.8, i.e., C2*-C1* > -6.8. In some embodiments, C2*-C1* > -5.2. In some embodiments, C2*-C1* > -4.6. In some embodiments, C2*- Cl* > -4.2. In some embodiments, C2*-C1* > -6.5, C2*-C1* > -6.0, C2*-C1* > -5.5, C2*-C1* > -5.0, C2*-C1* > -4.5, C2*-C1* > -4.0, or C2*-C1* > -3.5. On the other hand, as is apparent from the curve 908, a difference between C2* and Cl* is less than -6.8 for the comparative optical film.

[0126] In some embodiments, the first incident angle 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.

[0127] In some embodiments, for the substantially collimated light 32 incident on the optical film 40 from the illuminant D65 33, and for the first incident angle of less than about 10 degrees (i.e., the incident angle a2 < 10 degrees) and each third incident angle in an incident angle range 53 extending from about 86 degrees to about 89 degrees (i.e., 89 degrees > the incident angle a2 > 86 degrees), the optical film 40 (e.g., the optical films 40a, 40b, 40c) reflects the incident substantially collimated light 32 with the reflected light 34, in the CIE Lab color space, having chroma parameters Cl* and C3* for the respective first and third incident angles.

[0128] As is apparent from the curves 902, 906, for the respective optical films 40a, 40c, a difference between C3* and Cl* is greater than or equal to -4.6, i.e., C3*-C1* > -4.6. In some embodiments, C3*- Cl* > -4.2. In some embodiments, C3*-C1* > -4.2. In some embodiments, C3*-C1* > -4.4, C3*-C1* > -4.5, C3*-C1* > -4.2, C3*-C1* > -4.0, C3*-C1* > -3.7, or C3*-Cl* > -3.5. On the other hand, as is apparent from the curve 908, a difference between C3* and Cl* is less than -4.6 for the comparative optical film.

[0129] FIGS. 10A-10C illustrate a graph 1000 depicting a variation between A* and B* for different incident angles (i.e., different values of the incident angle a2 shown in FIG. 8) for the optical system 300 including the optical film 40, according to an embodiment of the present disclosure. FIG. 10D is a magnified view of a portion of the graph 1000. FIG. 10E is a magnified view of another portion of the graph 1000. FIG. 10F is a magnified view of the portion of the graph 1000 shown in FIG. 10E. A* is expressed in abscissa. B* is expressed in the ordinate.

[0130] The graph 1000 includes a curve 1002 depicting the A* and B* for the optical system 300 including the optical film 40a, a curve 1004 depicting the A* and B* for the optical system 300 including the optical film 40b, and a curve 1006 depicting the A* and B* for the optical system 300 including the optical film 40c. The graph 1000 further includes a curve 1008 depicting the A* and B* for the optical system 300 including the comparative optical film. The graph 1000 further includes a curve 1010 depicting the A* and B* for the optical system 300 without any optical film.

[0131] Referring to FIGS. 8 and 10A, as is apparent from the curves 1002, 1004, 1006 for the respective optical films 40a, 40b, 40c, for the substantially collimated light 32 incident on the optical film 40 from the illuminant D65 33, the optical film 40 reflects the incident substantially collimated light 32 with the reflected light 34, in the CIE Lab color space, having colorimetric parameters A* and B* such that as the incident angle a2 of the substantially collimated light 32 incident varies continuously from about zero degree to about 89 degrees, A* remains in a first range 54a extending from about -5 to about 4 and B* remains in a second range 54b extending from about -7 to about 4. An overlap between the first range 54a and the second range 54b is shown as a shaded region in FIG. 10A.

[0132] On the contrary, as is apparent from the curve 1008, A* for the comparative optical fdm does not remain in the first range 54a. In other words, a portion of the curve 1008 lies outside the shaded region shown in FIG. 10 A.

[0133] Referring to FIGS. 8 and 10B, as is apparent from the curves 1002, 1006 for the respective optical films 40a, 40c, in some embodiments, as the incident angle a2 of the incident substantially collimated light 32 varies continuously from about zero degree to about 89 degrees, A* remains in a first range 55a extending from about -2 to about 4 and B* remains in a second range 55b extending from about -7 to about 1. An overlap between the first range 55a and the second range 55b is shown as a shaded region in FIG. 10B.

[0134] On the contrary, as is apparent from the curve 1008, A* for the comparative optical fdm does not remain in the first range 55a. In other words, a portion of the curve 1008 lies outside the shaded region shown in FIG. 10B.

[0135] Referring to FIGS. 8 and 10C, as is apparent from the curve 1006 for the optical films 40c, in some embodiments, as the incident angle a2 of the incident substantially collimated light 32 varies continuously from about zero degree to about 89 degrees, A* remains in a first range 56a extending from about -2 to about 4 and B* remains in a second range 56b extending from about -5 to about 1. An overlap between the first range 56a and the second range 56b is shown as a shaded region in FIG. 10C.

[0136] On the contrary, as is apparent from the curve 1008, A* and B* for the comparative optical film do not remain in the respective first and second ranges 56a, 56b. In other words, a portion of the curve 1008 lies outside the shaded region shown in FIG. 10C.

[0137] Referring to FIGS. 8 and 10D-10F, as is apparent from the curves 1002, 1004, 1006 for the respective optical films 40a, 40b, 40c, in some embodiments, for an incident angle of the substantially collimated light 32 incident at about 89 degrees (i.e., the incident angle a2 = 89 degrees), A* lies in a first range 57a extending from about -0.5 to about 0.3 and B* lies in a second range 57b extending from about -1 to about 1. In some embodiments, the first range 57a extends from about 0.25, about 0.2, about 0.15, or about O.l. On the contrary, as is apparent from the curve 1008, A* for the comparative optical film is about 0.42.

[0138] Referring to FIGS. 9 and 10A-10F, the color performance of the optical film 40 (shown in FIG. 1) may be better than that of the comparative optical film. Further, the optical film 40 may reduce or prevent visible color artifacts.

[0139] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0140] 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 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 system comprising: a display configured to be used outdoors and exposed to sunlight while forming an image for viewing by a viewer; and an optical film disposed on, and between the viewer and, the display and comprising a plurality of polymeric microlayers numbering at least 10 in total, each of the polymeric microlayers having an average thickness of less than about 500 nm, such that for a substantially collimated incident light, a red wavelength range extending from about 590 nm to about 670 nm, a visible wavelength range extending from about 420 nm to about 680 nm, an infrared wavelength range extending from about 850 nm to about 1600 nm, and for at least one of mutually orthogonal in-plane first and second polarization states: for an angle of incidence of less than about 10 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 60% in the visible wavelength range and an average optical transmittance of less than about 70% in the infrared wavelength range; and for an angle of incidence of at least about 70 degrees, the plurality of polymeric microlayers has an average optical transmittance of greater than about 50% in the red wavelength range.

2. The optical system of claim 1, wherein for a substantially collimated light incident on the optical film from an illuminant D65, and for a first incident angle of less than about 10 degrees and a second incident angle of about 89 degrees, the optical film reflects the incident substantially collimated light with the reflected light, in a CIE Lab color space, having chroma parameters Cl* and C2* for the respective first and second incident angles, and wherein C2*-C1* > -6.8.

3. The optical system of claim 1, wherein for a substantially collimated light incident on the optical film from an illuminant D65, and for a first incident angle of less than about 10 degrees and each third incident angle in an incident angle range extending from about 86 degrees to about 89 degrees, the optical film reflects the incident substantially collimated light with the reflected light, in a CIE Lab color space, having chroma parameters Cl* and C3* for the respective first and second incident angles, and wherein C3*-C1* > -4.6.

4. The optical system of claim 1, wherein the plurality of polymeric microlayers comprises a plurality of first optical repeat units numbering at least 10 in total disposed on, and separated by at least one spacer layer from, a plurality of second optical repeat units numbering at least 10 in total, each ofthe first optical repeat units having at least microlayers Al and Bl having different compositions, each of the second optical repeat units having at least microlayers A2, B2, and C2 having different compositions, at least one of the microlayers Al and Bl having a different composition than at least one of the microlayers A2, B2, and C2, each of the microlayers in the first and second optical repeat units having an average thickness of less than about 500 nm, each of the at least one spacer layer having an average thickness of greater than about 500 nm.

5. The optical system of claim 4, wherein a first one of the microlayers A2, B2, and C2 comprises a polyethylene terephthalate (PET), a second one of the microlayers A2, B2, and C2 comprises a copolymer of polymethyl methacrylate (CoPMMA), copolymers of aliphatic-aromatic polyesters having a refractive index Ri for the visible wavelength range, or a material having the refractive index Ri for the visible wavelength range and an optical transparency Ot, and a third one of the microlayers A2, B2, and C2 comprises a glycol-modified polyethylene terephthalate (PETg) or a material having a refractive index Ric for the visible wavelength range and the optical transparency Ot, Ri <1.52, Ric <1.6, and Ot > 80%.

6. The optical system of claim 5, wherein each of the optical repeat units comprises one of the microlayer A2, two of the microlayer B2, and one of the micro layer C2 arranged as A2B2C2B2.

7. An optical film configured to be used outdoors and exposed to sunlight, the optical film comprising a plurality of polymeric microlayers numbering at least 50 in total, each of the polymeric microlayers having an average thickness of less than about 500 nm, such that: for a substantially collimated substantially normally incident light, and for each of mutually orthogonal in-plane first and second polarization states, the plurality of polymeric microlayers has an average optical transmittance of greater than about 60% in a visible wavelength range extending from about 420 nm to about 680 nm, and an average optical transmittance of less than about 70% in an infrared wavelength range extending from about 850 nm to about 1600 nm; and for a substantially collimated light incident on the optical film from an illuminant D65, the optical film reflects the incident substantially collimated light with the reflected light, in a CIE Lab color space, having colorimetric parameters A* and B * such that as an incident angle of the substantially collimated light incident varies continuously from about zero degree to about 89 degrees, A* remains in a first range extending from about -5 to about 4 and B* remains in a second range extending from about -7 to about 4.

8. The optical film of claim 7, wherein as the incident angle of the substantially collimated light incident varies continuously from about zero degree to about 89 degrees, A* remains in a first rangeextending from about -2 to about 4 and B* remains in a second range extending from about -7 to about 1.

9. The optical film of claim 7, wherein as the incident angle of the substantially collimated light incident varies continuously from about zero degree to about 89 degrees, A* remains in a first range extending from about -2 to about 4 and B* remains in a second range extending from about -5 to about 1.

10. The optical film of claim 7, wherein for an incident angle of the substantially collimated light incident at about 89 degrees, A* lies in a first range extending from about -0.5 to about 0.3 and B* lies in a second range extending from about -1 to about 1.

Images