Display system, backlight source and integrated optical film

Abstract

A one-piece optical film is provided that includes a plurality of alternating first layers and polymeric second layers in a total number of at least 10, and has an average total thickness of less than about 50 microns. For substantially normal incident light, each of first and second polarizations orthogonal to each other, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the unitary optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% within the first wavelength range, an average optical reflectance R2avg over the second wavelength range of greater than about 60% and less than about 98%, and an optical reflectance (R1avg + R2avg) / 2 at a first mid-wavelength longer than about 500 nm and shorter than about 540 nm.

Description

Technical Field

[0001] This disclosure relates to a display system including a backlight, and more particularly to a backlight including an integrated optical film. Background Technology

[0002] Typically, display systems include a blue light lens configured to isolate down-converted white light from the blue light emitting backplane of the backlight unit and facilitate more efficient polarization and angle recycling. The blue light lens may be designed as a self-supporting film to maximize recycling efficiency and durability within the backlight unit of the display system. In some cases, one or more layers (e.g., quantum dot layers) may be optically coupled to the blue light lens. Summary of the Invention

[0003] In a first aspect, this disclosure provides a monolithic optical film. The monolithic optical film comprises at least 10 alternating first layers and polymer second layers. The monolithic optical film has an average total thickness of less than about 50 micrometers. Each of the first layer and the polymer second layer has an average thickness of less than about 300 nanometers (nm). For substantially normally incident light, each of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the monolithic optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% in the first wavelength range, an average optical reflectance R2avg of greater than about 60% and less than about 98% in the second wavelength range, and an optical reflectance (R1avg + R2avg) / 2 at a first mid-wavelength longer than about 500 nm and shorter than about 540 nm.

[0004] In a second aspect, this disclosure provides a backlight source for illuminating a display panel configured to display an image. The backlight source includes an integral optical film of the first aspect, disposed on an extended emitting surface of an extended illumination source. The extended illumination source includes one or more light sources and is configured to emit light toward the display panel through the extended emitting surface. The emitted light includes an emission peak wavelength shorter than a first intermediate wavelength of the integral optical film. The backlight source further includes one or more light conversion films disposed on the integral optical film, opposite the extended emitting surface of the extended illumination source. The one or more light conversion films are configured to receive emitted light passing through the integral optical film and convert at least a portion of the received emitted light into green and red light having wavelengths within the second wavelength range disposed on the integral optical film.

[0005] In a third aspect, this disclosure provides a display system including a display panel disposed on a backlight source of the second aspect. The display panel is configured to receive light emitted through an extended emitting surface and to display an image. One or more light conversion films are disposed between the display panel and the integrated optical film.

[0006] In a fourth aspect, this disclosure provides a monolithic optical film. The monolithic optical film comprises at least 10 alternating first layers and polymer second layers. The monolithic optical film has an average total thickness of less than about 50 micrometers. Each of the first layer and the polymer second layer has an average thickness of less than about 200 nm. For substantially normally incident light, at least one of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the monolithic optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% in the first wavelength range, an average optical reflectance R2avg of greater than about 60% and less than about 98% in the second wavelength range, and an optical reflectance as a function of wavelength including a band edge. At least across a transition wavelength range where the optical reflectance decreases from about 70% to about 20%, the best linear fit of the optical reflectance to the band edge with respect to wavelength has a slope greater than about 0.9% / nm.

[0007] In a fifth aspect, this disclosure provides an integral optical film. The integral optical film comprises at least 10 alternating first layers and polymer second layers. The integral optical film has an average total thickness of less than about 50 micrometers. Each of the first layer and the polymer second layer has an average thickness of less than about 200 nm. For substantially normally incident light, at least one of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the integral optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% in the first wavelength range, an average optical reflectance R2avg of greater than about 60% and less than about 98% in the second wavelength range, and an optical reflectance as a function of wavelength including a first band edge and a second band edge, the first band edge separating the first wavelength range and the second wavelength range. At least across the transition wavelength range where the optical reflectance varies from about 70% to about 20%, the optimal first and second linear fits for the corresponding first and second band edges, relating the optical reflectance to the wavelength of each of the first and second band edges, have corresponding first positive and second negative slopes. The ratio of the magnitude of the second negative slope to the first positive slope is greater than about 1.1.

[0008] Details of one or more examples of this disclosure are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of this disclosure will become apparent from the description, the drawings, and the claims. Attached Figure Description

[0009] The exemplary embodiments disclosed herein can be more fully understood in light of the following detailed description taken in conjunction with the accompanying drawings. The drawings are not necessarily drawn to scale. Similar numbers used in the drawings refer to similar parts. However, it should be understood that the use of numbers to refer to parts in a given drawing is not intended to limit parts labeled with the same numbers in another drawing.

[0010] Figure 1 A cross-sectional view of an integral optical film according to an embodiment of the present disclosure is shown;

[0011] Figure 2 A graph depicting the optical reflectivity of an integral optical film against wavelength for substantially normally incident light, according to an embodiment of the present disclosure, is shown.

[0012] Figure 3 A graph depicting a portion of the first strip edge of the integral optical film, according to an embodiment of the present disclosure, is shown as an enlarged view.

[0013] Figure 4 A graph depicting a portion of the second strip edge of the integral optical film, according to an embodiment of the present disclosure, is shown as an enlarged view.

[0014] Figure 5 A schematic cross-sectional view of a display system according to an embodiment of the present disclosure is shown; and

[0015] Figure 6 A graph depicting the layer thickness of the first layer and the polymer second layer of the integral optical film versus the number of layers is shown according to an embodiment of the present disclosure. Detailed Implementation

[0016] In the following description, reference is made to the accompanying drawings, which form a part thereof, and various embodiments are illustrated therein. It should be understood that other embodiments may be conceived and made without departing from the scope or spirit of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0017] In the following disclosure, the following definitions are used.

[0018] As used herein, all numbers should be considered as being modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “a or more” are used interchangeably.

[0019] As used herein, as a modifier of a characteristic or attribute, unless otherwise specifically defined, the term “approximately” means that the characteristic or attribute will be easily identifiable by a person skilled in the art without requiring absolute precision or a perfect match (e.g., within + / - 20% for quantifiable characteristics).

[0020] Unless otherwise specifically defined, the term “substantially” means a high degree of approximation (e.g., within + / -10% for quantifiable properties), but also does not require absolute precision or a perfect match.

[0021] Unless otherwise specifically defined, the term “approximately” means a high degree of approximation (e.g., within + / -5% for quantifiable properties), but also does not require absolute precision or a perfect match.

[0022] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be construed as limiting the scope of this disclosure. Throughout the embodiments of this disclosure, the terms “first” and “second” are used interchangeably when used in conjunction with a feature or element.

[0023] As used in this article, "at least one of A and B" should be understood as meaning "only A, only B, or both A and B".

[0024] As used herein, the term "layer" generally refers to a thickness of material having a relatively uniform chemical composition within a membrane. A layer can be any type of material, including polymers, cellulose, metals, or blends thereof. A given polymer layer may comprise a single polymer type or a blend of polymers and may include additives. A given layer may be combined with or bonded to other layers to form a membrane. A layer may be partially continuous or completely continuous compared to adjacent layers or membranes. A given layer may be partially or completely co-extended with adjacent layers. A layer may contain sublayers.

[0025] Typically, display systems include a blue light lens configured to isolate down-converted white light from the blue light emitting backplane of the backlight unit and facilitate more efficient polarization and angle recycling. The blue light lens can be designed as a self-supporting film to maximize recycling efficiency and durability within the backlight unit of the display system. In some cases, one or more layers (e.g., quantum dot layers) may be optically coupled to the blue light lens. As the use of downconversion in display systems expands to new architectures, thinner and more conformal versions of the blue light lens may be required.

[0026] This disclosure provides a monolithic optical film. The monolithic optical film includes at least 10 alternating first layers and polymer second layers. The monolithic optical film has an average total thickness of less than about 50 micrometers. Each of the first layer and the polymer second layer has an average thickness of less than about 300 nm. For substantially normally incident light, each of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the monolithic optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% in the first wavelength range, an average optical reflectance R2avg of greater than about 60% and less than about 98% in the second wavelength range, and an optical reflectance of (R1avg + R2avg) / 2 at a first mid-wavelength longer than about 500 nm and shorter than about 540 nm.

[0027] The integrated optical film disclosed herein exhibits a significantly lower average optical reflectivity in a first wavelength range (i.e., the blue wavelength range) than in a second wavelength range for substantially normally incident light and for each of mutually orthogonal first and second polarizations. Therefore, the integrated optical film can function as a blue light lens and can provide brightness enhancement by improving recycling efficiency. Furthermore, the integrated optical film has an average total thickness of less than about 50 micrometers. Therefore, the integrated optical film can be substantially thinner than a typical blue light lens. Consequently, the integrated optical film can provide greater conformal capability and flexibility.

[0028] Now refer to the attached diagram, Figure 1 This is a schematic cross-sectional view of an integral optical film 200 according to an embodiment of the present disclosure.

[0029] The integrated optical film 200 defines three mutually orthogonal axes: x, y, and z. The x-axis and y-axis are in-plane axes of the integrated optical film 200, while the z-axis is a transverse axis set along the thickness of the integrated optical film 200. In other words, the x-axis and y-axis are set along the plane of the integrated optical film 200, while the z-axis is perpendicular to the plane of the integrated optical film 200.

[0030] The integrated optical film 200 includes a plurality of alternating first layers 11 and polymer second layers 12. These alternating first layers 11 and polymer second layers 12 may be collectively referred to as "the plurality of alternating first layers and polymer second layers 10". The total number of the plurality of alternating first layers 11 and polymer second layers 12 is at least 10. In some embodiments, the total number of the plurality of alternating first layers 11 and polymer second layers 12 is at least 15 or at least 20.

[0031] The plurality of alternating first layers 11 and polymer second layers 12 have an average total thickness t1 of less than about 50 micrometers. As used herein, the term "average total thickness t1" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) spanning the first layers 11 and polymer second layers 12. In some embodiments, the plurality of alternating first layers 11 and polymer second layers 12 have an average total thickness t1 of less than about 40 micrometers, less than about 45 micrometers, less than about 30 micrometers, less than about 35 micrometers, less than about 20 micrometers, less than about 25 micrometers, less than about 20 micrometers, less than about 15 micrometers, less than about 14 micrometers, less than about 13 micrometers, less than about 12 micrometers, less than about 11 micrometers, less than about 10 micrometers, less than about 9 micrometers, less than about 8 micrometers, less than about 7 micrometers, less than about 6 micrometers, less than about 5 micrometers, less than about 4 micrometers, less than about 3 micrometers, or less than about 2 micrometers. Thus, the integral optical film 200 can be substantially thin, flexible, and conformal.

[0032] Each of the first layer 11 and the polymer second layer 12 has an average thickness t2 of less than about 300 nanometers (nm). As used herein, the term "average thickness t2" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) spanning each of the first layer 11 and the polymer second layer 12. In some embodiments, each of the first layer 11 and the polymer second layer 12 has an average thickness of less than about 250 nm, less than about 200 nm, less than about 175 nm, or less than about 150 nm.

[0033] In some embodiments, the first layer 11 is polymeric. In some embodiments, the polymeric first layer 11 comprises one or more of polyethylene naphthalate (PEN) and polyethylene terephthalate (PET).

[0034] Furthermore, in some embodiments, the polymer first layer 11 has a refractive index greater than about 1.6 for at least one visible wavelength in the visible light wavelength range extending from about 420 nm to about 680 nm. In some embodiments, the polymer first layer 11 has a refractive index greater than about 1.65 or greater than about 1.7 for at least one visible wavelength in the visible light wavelength range. In one embodiment, the polymer first layer 11 comprises PEN and has a refractive index of about 1.74 for at least one visible wavelength within the visible wavelength range.

[0035] In some embodiments, the first layer 11 is inorganic. In some embodiments, the inorganic first layer 11 comprises one or more of titanium dioxide (TiO2), zirconium oxide (ZrO), titanium oxide (TiO), Nb2O5, Ta2O5, HfO2, SiAlOxNy, Si3N4, Nb-doped TiO2, and ZrO2.

[0036] Furthermore, in some embodiments, the first layer 11 has a refractive index greater than about 1.7 for at least one visible wavelength in the visible light wavelength range. In some embodiments, the first layer 11 has a refractive index greater than about 1.8, greater than about 1.9, greater than about 2, greater than about 2.1, or greater than about 2.2 for at least one visible wavelength in the visible light wavelength range. In one embodiment, the first layer 11 comprises TiO2 and has a refractive index of about 2.295 for at least one visible wavelength in the visible light wavelength range.

[0037] In some embodiments, the polymer second layer 12 comprises one or more of polymethyl methacrylate (PMMA), a copolymer of PMMA (CoPMMA), an aliphatic-aromatic polyester, and a copolymer of aliphatic-aromatic polyester.

[0038] Furthermore, in some embodiments, the polymer second layer 12 has a refractive index of less than about 1.52 for at least one visible wavelength in the visible light wavelength range. In some embodiments, the polymer second layer 12 has a refractive index of less than about 1.51, less than about 1.5, less than about 1.49, less than about 1.48, or less than about 1.47 for at least one visible wavelength in the visible light wavelength range. In one embodiment, the polymer second layer 12 has a refractive index of about 1.49 for at least one visible wavelength in the visible light wavelength range.

[0039] In some embodiments, the integrated optical film 200 further includes at least one surface layer 13 disposed on a plurality of alternating first layers and polymer second layers 10 and having an average thickness st greater than about 500 nm. As used herein, the term "average thickness st" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) of each of the at least one surface layer 13. In some embodiments, the at least one surface layer 13 has an average thickness st greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0040] exist Figure 1 In the illustrated embodiment, at least one surface layer 13 comprises a pair of surface layers 13, and the plurality of alternating first layers and polymer second layers 10 are disposed between the pair of surface layers 13. At least one surface layer 13 protects the plurality of alternating first layers and polymer second layers 10 and also provides mechanical stability to the integral optical film 200. In some cases, at least one surface layer 13 may act as a protective boundary layer (PBL).

[0041] In some embodiments, the first layer 11 and polymer second layer 12 of the plurality of alternating first layers and polymer second layers 10 include a first terminal layer 14a and a corresponding second terminal layer 14b. Further, in some embodiments, the remaining layers 11, 12 of the first layer 11 and polymer second layer 12 are disposed between the first terminal layer 14a and the second terminal layer 14b. Additionally, in some embodiments, any other layer of the integral optical film 200 disposed between the first terminal layer 14a and the second terminal layer 14b has an average thickness of less than about 300 nm. In some embodiments, any other layer of the integral optical film 200 disposed between the first terminal layer 14a and the second terminal layer 14b has an average thickness of less than about 250 nm, less than about 200 nm, less than about 175 nm, or less than about 150 nm.

[0042] In some embodiments, the first end layer 14a and the second end layer 14b are separated by a distance s1 of less than about 50 micrometers. In some embodiments, the first end layer 14a and the second end layer 14b are separated by a distance s1 of less than about 40 micrometers, less than about 45 micrometers, less than about 30 micrometers, less than about 35 micrometers, less than about 20 micrometers, less than about 25 micrometers, less than about 20 micrometers, less than about 15 micrometers, less than about 14 micrometers, less than about 13 micrometers, less than about 12 micrometers, less than about 11 micrometers, less than about 10 micrometers, less than about 9 micrometers, less than about 8 micrometers, less than about 7 micrometers, less than about 6 micrometers, less than about 5 micrometers, less than about 4 micrometers, less than about 3 micrometers, or less than about 2 micrometers.

[0043] The integrated optical film 200 has a main side 15a and a main side 15b opposite to the main side 15a. In some embodiments, a first end layer 14a is close to the main side 15a, and a second end layer 14b is close to the other main side 15b.

[0044] Figure 1 Further illustrated is a substantially normal incident light 20 having a first polarization p and a second polarization s that are mutually orthogonal. The first polarization p and the second polarization s can be interchangeably referred to as "first polarization state p and second polarization state s". In some embodiments, the first polarization p may be a p-polarization state. In some embodiments, the second polarization s may be an s-polarization state. In some embodiments, the first polarization p may extend substantially along the x-axis. In some embodiments, the second polarization s may extend substantially along the y-axis.

[0045] Figure 2 It describes an embodiment according to this disclosure, for substantially normally incident light 20 ( Figure 1 As shown), integrated optical film 200 ( Figure 1 The optical reflectance versus wavelength curve (shown in Figure 500) is shown.

[0046] Specifically, graph 500 depicts the optical reflectivities 32p, 32s, 33p, and 33s of exemplary optical films OF1 and OF2 relative to wavelength for substantially normally incident light 20. Optical films OF1 and OF2 are related to... Figure 1 An example of an integrated optical film 200 is shown and described. Wavelength is expressed in nanometers (nm) on the horizontal axis, and optical reflectance is expressed as a percentage (%) on the vertical axis.

[0047] The graph 500 includes curve 501, which depicts the optical reflectivity 32p of the optical film OF1 against wavelength for substantially normal incident light 20 having a first polarization state p; and curve 502, which depicts the optical reflectivity 32s of the optical film OF1 against wavelength for substantially normal incident light 20 having a second polarization state s.

[0048] exist Figure 2 In the example shown, curves 501 and 502 substantially overlap each other. Therefore, for optical film OF1, the optical reflectivity 32p of substantially normal incident light 20 with a first polarization state p and the optical reflectivity 32s of substantially normal incident light 20 with a second polarization state s can be substantially similar to each other with respect to wavelength.

[0049] Furthermore, the graph 500 includes curve 503, which depicts the optical reflectivity 33p of the optical film OF2 with a substantially normal incident light 20 in a first polarization state p against the wavelength; and curve 504, which depicts the optical reflectivity 33s of the optical film OF2 in a second polarization state s.

[0050] Graph 500 further depicts the first wavelength range 30 and the second wavelength range 31. The first wavelength range 30 extends from about 420 nm to about 480 nm, and the second wavelength range 31 extends from about 560 nm to about 800 nm.

[0051] See Figure 1 and Figure 2For substantially normally incident light 20 and at least one of a first polarization p and a second polarization s that are mutually orthogonal, the integrated optical film 200 has an average optical reflectance R1avg of less than about 45% and greater than about 5% within a first wavelength range 30. In some embodiments, for substantially normally incident light 20 and at least one of a first polarization p and a second polarization s that are mutually orthogonal, the integrated optical film 200 has an average optical reflectance R1avg of less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 20%, or less than about 15% and greater than about 10%, greater than about 15%, greater than about 20%, or greater than about 25% within a first wavelength range 30.

[0052] As is evident from curves 501, 502, 503, and 504, for each of the substantially normally incident light 20 and the mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an average optical reflectance R1avg of less than about 45% and greater than about 5% within a first wavelength range 30. In some embodiments, for each of the substantially normally incident light 20 and the mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an average optical reflectance R1avg of less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 20%, or less than about 15% and greater than about 10%, greater than about 15%, greater than about 20%, or greater than about 25% within a first wavelength range 30.

[0053] Specifically, as is evident from curves 501 and 502, for substantially normally incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF1 has an average optical reflectivity of approximately 30% within a first wavelength range 30. Similarly, as is evident from curves 503 and 504, for substantially normally incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF2 has an average optical reflectivity of approximately 15% within a first wavelength range 30.

[0054] Furthermore, for substantially normally incident light 20 and at least one of mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an average optical reflectance R2avg greater than about 60% and less than about 98% within a second wavelength range 31. In some embodiments, for substantially normally incident light 20 and at least one of mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an average optical reflectance R2avg greater than about 65%, greater than about 70%, greater than about 75%, or greater than about 80% and less than about 97%, less than about 96%, less than about 95%, less than about 94%, less than about 93%, less than about 92%, less than about 91%, less than about 90%, less than about 88%, or less than about 86% within a second wavelength range 31.

[0055] As is evident from curves 501, 502, 503, and 504, for each of the substantially normally incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an average optical reflectance R2avg greater than about 60% and less than about 98% within a second wavelength range 31. In some embodiments, for each of the substantially normally incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an average optical reflectance R2avg greater than about 65%, greater than about 70%, greater than about 75%, or greater than about 80% and less than about 97%, less than about 96%, less than about 95%, less than about 94%, less than about 93%, less than about 92%, less than about 91%, less than about 90%, less than about 88%, or less than about 86% within a second wavelength range 31.

[0056] Specifically, as evident from curves 501 and 502, for substantially normal incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF1 has an average optical reflectance of approximately 92% within the second wavelength range 31. Similarly, as evident from curves 503 and 504, for substantially normal incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF2 has an average optical reflectance of approximately 84% within the second wavelength range 31.

[0057] Furthermore, for each of the substantially normally incident light 20 and the mutually orthogonal first polarization p and second polarization s, the integrated optical film 200 has an optical reflectivity (R1avg+R2avg) / 2 at a first intermediate wavelength 30a, 30b that is longer than about 500 nm and shorter than about 540 nm. In some embodiments, the first intermediate wavelengths 30a, 30b are longer than about 505 nm, longer than about 510 nm, longer than about 515 nm, longer than about 520 nm, or longer than about 525 nm and shorter than about 535 nm, shorter than about 530 nm, or shorter than about 525 nm.

[0058] exist Figure 2 In the example shown, for substantially normal incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF1 has an optical reflectivity of approximately 61% at a first intermediate wavelength 30b of approximately 527 nm. Similarly, for substantially normal incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF2 has an optical reflectivity of approximately 50% at a first intermediate wavelength 30a of approximately 521 nm.

[0059] In some embodiments, the integrated optical film 200 further has an optical reflectance (R1avg+R2avg) / 2 at a second intermediate wavelength 31a1, 31a2, 31b that is longer than about 870 nm and shorter than about 920 nm. In some embodiments, the second intermediate wavelengths 31a1, 31a2, 31b are longer than about 875 nm, longer than about 880 nm, longer than about 885 nm, or longer than about 890 nm and shorter than about 915 nm, shorter than about 900 nm, or shorter than about 895 nm.

[0060] exist Figure 2 In the example shown, for substantially normally incident light 20 and each of the mutually orthogonal first polarization p and second polarization s, optical film OF1 has an optical reflectance of approximately 61% at a second intermediate wavelength 31b of approximately 895 nm. Furthermore, for substantially normally incident light 20 and the first polarization p, optical film OF2 has an optical reflectance of approximately 50% at a second intermediate wavelength 31a1 of approximately 900 nm. Additionally, for substantially normally incident light 20 and the second polarization s, optical film OF2 has an optical reflectance of approximately 50% at a second intermediate wavelength 31a2 of approximately 892 nm.

[0061] Table 1 below summarizes the average optical reflectance R1avg in the first wavelength range 30, the average optical reflectance R2avg in the second wavelength range 31, the optical reflectance (R1avg+R2avg) / 2 at the first intermediate wavelengths 30a and 30b, and the optical reflectance (R1avg+R2avg) / 2 at the second intermediate wavelengths 31a1, 31a2, and 31b for each of the optical films OF1 and OF2.

[0062]

[0063] Where W1 refers to the first wavelength; and

[0064] W2 refers to the second wavelength.

[0065] Table 2 below summarizes the average optical absorption Abs, average optical reflectance Ravg(p), and average optical reflectance Ravg(s) for each of the optical films OF1 and OF2 for each of the first wavelength range 30 and the second wavelength range 31.

[0066]

[0067] Where Ravg(p) refers to the average optical reflectivity of essentially normally incident light 20 with first polarization p; and

[0068] Ravg(s) refers to the average optical reflectivity of essentially normally incident light 20 with a second polarization s.

[0069] As is evident from Tables 1 and 2, for substantially normal incident light 20 having at least one of a first polarization p and a second polarization s, the optical reflectivity of optical films OF1 and OF2 in the first wavelength range (i.e., 420 nm–480 nm) is substantially lower than that in the second wavelength range (i.e., 560 nm–800 nm). Therefore, the integrated optical film 200 can function as a blue light lens and can provide brightness enhancement by improving recycling efficiency. Furthermore, optical films OF1 and OF2 can have substantially low optical absorption for each of the first polarization p and the second polarization s, and for each of the first wavelength range 30 and the second wavelength range 31.

[0070] In some embodiments, for substantially normally incident light 20 and at least one of mutually orthogonal first polarization p and second polarization s, the optical reflectivity 33p, 33s of the integral optical film 200 (e.g., optical film OF2) as a function of wavelength includes band edges 34p, 34s ​​that separate the first wavelength range 30 and the second wavelength range 31.

[0071] As shown in graph 500, in some embodiments, for each of the substantially normally incident light 20 and the mutually orthogonal first polarization p and second polarization s, the optical reflectivity 33p, 33s of the integral optical film 200 as a function of wavelength includes band edges 34p, 34s ​​that separate the first wavelength range 30 and the second wavelength range 31.

[0072] Specifically, in Figure 2 In the example shown, for substantially normally incident light 20 and a first polarization p, the optical reflectivity 33p of the integrated optical film 200 (e.g., optical film OF2) as a function of wavelength includes a band edge 34p separating the first wavelength range 30 and the second wavelength range 31. Further, for substantially normally incident light 20 and a second polarization s, the optical reflectivity 33s of the integrated optical film 200 (e.g., optical film OF2) as a function of wavelength includes a band edge 34s separating the first wavelength range 30 and the second wavelength range 31. The band edges 34p and 34s can be interchangeably referred to as "first band edges 34p and 34s".

[0073] As shown in graph 500, in some embodiments, the optical reflectivity 32p, 33s of the integral optical film 200 as a function of wavelength includes band edges 37p, 38s for substantially normally incident light 20 and at least one of mutually orthogonal first polarization p and second polarization s.

[0074] Specifically, in Figure 2 In the example shown, for substantially normally incident light 20 and a first polarization p, the optical reflectivity 32p of the integrated optical film 200 (e.g., optical film OF1) as a function of wavelength includes a band edge 37p. Further, for substantially normally incident light 20 and a second polarization s, the optical reflectivity 33s of the integrated optical film 200 (e.g., optical film OF2) as a function of wavelength includes a band edge 38s. The band edges 37p and 38s can be interchangeably referred to as "second band edges 37p and 38s".

[0075] Figure 3 The optical reflectance 33p, 33s of an integral optical film 200 (e.g., optical film OF2) as a function of wavelength is described according to an embodiment of this disclosure. Figure 2 The graph 600 is an enlarged view of a portion of the image with edges 34p and 34s. In the graph 600, the wavelength is expressed in nanometers (nm) on the horizontal axis, and the optical reflectance is expressed as a percentage (%) on the vertical axis.

[0076] Further, as shown in graph 600, in some embodiments, the optimal linear fit 35p, 35s of the optical reflectivity 33p, 33s to the wavelength-dependent band edge 34p, 34s ​​comprises a slope 36p, 36s greater than about 0.7% / nm, spanning at least the transition wavelength range from about 20% to about 70% of the optical reflectivity 33p. Specifically, in some embodiments, the optimal linear fit 35p of the optical reflectivity 33p to the wavelength-dependent band edge 34p comprises a slope 36p greater than about 0.7% / nm, spanning at least the transition wavelength range from about 20% to about 70% of the optical reflectivity 33p. Similarly, in some embodiments, the optimal linear fit 35s of the optical reflectivity 33s to the wavelength-dependent band edge 34s comprises a slope 36s greater than about 0.7% / nm, spanning at least the transition wavelength range from about 20% to about 70% of the optical reflectivity 33s. The best linear fits 35p and 35s can be interchangeably referred to as "best first linear fits 35p and 35s". The slopes 36p and 36s can be interchangeably referred to as "first positive slopes 36p and 36s".

[0077] In some implementations, the best linear fit 35p, 35s has a slope 36p, 36s greater than about 0.75% / nm, greater than about 0.8% / nm, greater than about 0.85% / nm, greater than about 0.90% / nm, or greater than about 0.95% / nm.

[0078] exist Figure 3 In the example shown, the best linear fit 35p has a slope of approximately 0.977% / nm for 36p. Furthermore, the best linear fit 35s has a slope of approximately 0.941% / nm for 36s.

[0079] In some implementations, the best first linear fits 35p and 35s have an r-squared value R² greater than about 0.8. Specifically, the best first linear fit 35p has an r-squared value R² greater than about 0.8 and the best first linear fit 35s has an r-squared value R² greater than about 0.8.

[0080] In some implementations, the best first linear fit 35p, 35s has an r-squared value R² greater than about 0.85, greater than about 0.9, or greater than about 0.95.

[0081] In the example, the best first linear fit 35p is based on Equation 1 provided below.

[0082] y = 0.9772x - 452.8 [Equation 1]

[0083] In Equation 1, y represents optical reflectivity, and x represents wavelength. In this example, the slope 36p = 0.9772 and R² = 0.8603.

[0084] In the example, the best linear fit 35s is based on Equation 2 provided below.

[0085] y = 0.9411x - 435.79 [Equation 2]

[0086] In Equation 2, y represents the light reflectance, and x represents the wavelength. In this example, the slope 36s = 0.9411 and R² = 0.847.

[0087] Figure 4 This describes an integrated optical film 200 according to an embodiment of the present disclosure. Figure 1 The optical reflectance as a function of wavelength (as shown) 32p, 33s (as shown) Figure 2 The curve 700 is an enlarged view of a portion of the edge 37p and 38s (as shown).

[0088] Specifically, graph 700 depicts a portion of the integrated optical film 200 (e.g., optical film OF1) with an optical reflectance of 32p as a function of wavelength at the band edge 37p and a portion of the integrated optical film 200 (e.g., optical film OF2) with an optical reflectance of 33s as a function of wavelength at the band edge 38s.

[0089] In graph 700, wavelength is expressed in nanometers (nm) on the horizontal axis, and optical reflectance is expressed as a percentage (%) on the vertical axis.

[0090] Further, as shown in graph 700, in some embodiments, the optimal linear fit 39p and 110s of the optical reflectivity 32p and 33s to the wavelength-dependent band edge 37p and 38s, at least across the transition wavelength range from about 70% to about 20%, includes slopes 111p and 112s with a magnitude greater than about 0.9% / nm. Specifically, in some embodiments, the optimal linear fit 39p of the optical reflectivity 32p to the wavelength-dependent band edge 37p, at least across the transition wavelength range from about 70% to about 20%, includes a slope 111p with a magnitude greater than about 0.9% / nm. Similarly, in some embodiments, the optimal linear fit 110p of the optical reflectivity 33s to the wavelength-dependent band edge 38s, at least across the transition wavelength range from about 70% to about 20%, includes a slope 112s with a magnitude greater than about 0.9% / nm. The best linear fits 39p and 110s can be interchangeably referred to as the "best second linear fits 39p and 110s". The slopes 111p and 112s can be interchangeably referred to as the "second negative slopes 111p and 112s".

[0091] In some implementations, the best linear fits 39p and 110s have slopes greater than about 0.95% / nm, greater than about 1% / nm, greater than about 1.05% / nm, greater than about 1.1% / nm, greater than about 1.15% / nm, greater than about 1.2% / nm, greater than about 1.25% / nm, greater than about 1.3% / nm, or greater than about 1.35% / nm, respectively.

[0092] exist Figure 4 In the examples shown, the best linear fit 39p has a slope of approximately 1.334% / nm for 111p, and the best linear fit 110s has a slope of approximately 1.285% / nm for 112s.

[0093] In some embodiments, the best second linear fit 39p, 110s has an r-squared value R² greater than about 0.8. Specifically, in some embodiments, the best second linear fit 39p has an r-squared value R² greater than about 0.8 and the best second linear fit 110s has an r-squared value R² greater than about 0.8. In some embodiments, the second linear fit 39p, 110s has an r-squared value R² greater than about 0.85, greater than about 0.9, or greater than about 0.95.

[0094] In the example, the best linear fit 39p is based on Equation 3 provided below.

[0095] y = -1.3338x + 1253.6 [Equation 3]

[0096] In Equation 3, y represents the light reflectance, and x represents the wavelength. In this example, the slope 111p = -1.3338 and R² = 0.9912.

[0097] In the example, the best linear fit 110s is based on Equation 4 provided below.

[0098] y = -1.2847x + 1193 [Equation 4]

[0099] In Equation 4, y represents the light reflectance, and x represents the wavelength. In this example, the slope 112s = -1.2847 and R² = 0.8992.

[0100] refer to Figure 3 and Figure 4In some embodiments, at least across a transition wavelength range where the optical reflectance 33p, 33s, 32p, 33s varies from about 70% to about 20%, the optical reflectance 33p, 33s, 32p, 33s with the wavelength of each of the first band edges 34p, 34s ​​and the second band edges 37p, 38s has a corresponding first positive slope 36p, 36s and a second negative slope 111p, 112s for the best first linear fit 35p, 35s and the second linear fit 39p, 110s for the corresponding first band edge 34p, 34s ​​and the second band edge 37p, 38s.

[0101] Specifically, in some embodiments, the optimal first linear fit 35p, 35s of the optical reflectivity 33p, 33s to the first band edges 34p, 34s, which varies from about 70% to about 20% across at least the transition wavelength range, has a first positive slope 36p, 36s related to the wavelength of each of the first band edges 34p, 34s. Similarly, in some embodiments, the optimal second linear fit 39p, 110s of the second band edges 37p, 38s, which varies from about 70% to about 20% across at least the transition wavelength range, has a second negative slope 111p, 112s related to the wavelength of each of the second band edges 37p, 38s.

[0102] As described above, the first positive slope 36p is approximately 0.977% / nm, and the first positive slope 36s is approximately 0.941% / nm. Furthermore, as described above, the second negative slope 111p is approximately -1.334% / nm, and the second negative slope 112s is approximately -1.285% / nm.

[0103] In some embodiments, the ratio of the second negative slope to the first positive slope is greater than about 1.1. In some embodiments, the ratio of the second negative slope to the first positive slope is greater than about 1.15, greater than about 1.2, greater than about 1.25, greater than about 1.3, greater than about 1.35, or greater than about 1.4. Figure 3 and Figure 4 In the example shown, the ratio of the magnitude of the second negative slope to the first positive slope is in the range of about 1.315 to about 1.418.

[0104] Figure 5This is a schematic cross-sectional view of a display system 400 according to an embodiment of the present disclosure. In some embodiments, the display system 400 includes a backlight 300 and a display panel 40 configured to display an image 42. The display panel 40 is disposed on the backlight 300. In some embodiments, the display panel 40 includes a liquid crystal display panel. In some embodiments, the backlight 300 provides illumination 41 to the display panel 40.

[0105] In some embodiments, the backlight 300 includes an integrated optical film 200 disposed on the extended emitting surface 52 of the extended illumination source 50. The extended illumination source 50 includes one or more light sources 51 and is configured to emit light 53 toward the display panel 40 through the extended emitting surface 52. The display panel 40 is configured to receive the light 53 emitted through the extended emitting surface 52.

[0106] In some embodiments, the emitted light 53 includes a first intermediate wavelength 30a, 30b shorter than that of the integrated optical film 200. Figure 2 The emission peak wavelength (as shown). In some embodiments, the emission peak wavelength is shorter than about 480 nm.

[0107] In some embodiments, the backlight 300 further includes one or more light conversion films 60 disposed on the integrated optical film 200, opposite the extended emitting surface 52 of the extended illumination source 50. The one or more light conversion films 60 are disposed between the display panel 40 and the integrated optical film 200. In some embodiments, the one or more light conversion films 60 comprise one or more of phosphors, fluorescent dyes, and quantum dots.

[0108] The one or more light conversion films 60 are configured to receive emitted light 53 passing through the integrated optical film 200, and to convert at least a portion of the received emitted light 53 into light having a second wavelength range 31 disposed in the integrated optical film 200. Figure 2 The wavelengths of green light 53g and red light 53r are shown in the figure.

[0109] In some embodiments, one or more light conversion films 60 include a green light conversion film 60g and a red light conversion film 60r. In some embodiments, the green light conversion film 60g is configured to receive emitted light 53 through the extended emitting surface 52 and convert at least a portion of the received emitted light 53 into green light 53g within a second wavelength range 31 of the integrated optical film 200. Furthermore, in some embodiments, the red light conversion film 60r is configured to receive emitted light 53 through the extended emitting surface 52 and convert at least a portion of the received emitted light 53 into red light 53r within the second wavelength range 31 of the integrated optical film 200.

[0110] In some embodiments, the backlight 300 further includes an optical diffuser 80 disposed on one or more light conversion films 60, opposite the integral optical film 200, and having a diffuse optical transmittance greater than about 30% for at least one visible light wavelength in the visible light wavelength range. In some embodiments, the optical diffuser 80 has a diffuse optical transmittance greater than about 35%, greater than about 40%, greater than about 45%, greater than about 50%, greater than about 55%, or greater than about 60% for at least one visible light wavelength in the visible light wavelength range.

[0111] In some embodiments, the backlight 300 includes a first prism film 90 disposed on one or more light conversion films 60, opposite the integral optical film 200. The first prism film 90 includes a plurality of first prisms 91 extending along substantially the same first longitudinal direction. In some embodiments, the plurality of first prisms 91 extend along the y-axis.

[0112] Furthermore, in some embodiments, the backlight 300 includes a second prism film 92 disposed on the first prism film 90, opposite to one or more light conversion films 60. The second prism film 92 includes a plurality of second prisms 93 extending along a substantially identical second longitudinal direction different from the first longitudinal direction. In some embodiments, the plurality of second prisms 93 extend along the x-axis.

[0113] In some embodiments, the backlight 300 further includes a reflective polarizer 100 disposed on one or more light conversion films 60, opposite the integrated optical film 200. In some embodiments, the integrated optical film 200 and the reflective polarizer 100 may have substantially similar constructions.

[0114] In some embodiments, the reflective polarizer 100 includes a plurality of polymer microlayers 11, 12, totaling at least 10. Figure 1 (As shown). In some embodiments, the total number of the plurality of polymer microlayers 11, 12 is at least 20, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, at least 300, or at least 400.

[0115] In some embodiments, each polymer microlayer of polymer microlayers 11, 12 has an average thickness of less than about 500 nm. In some embodiments, each polymer microlayer of polymer microlayers 11, 12 has an average thickness of 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.

[0116] Furthermore, in some embodiments, for substantially normally incident visible light (e.g., substantially normally incident light 20 within the visible light wavelength range), the plurality of polymer microlayers 11, 12 reflect more than about 60% of the incident light 20 having an in-plane first polarization state p. In some embodiments, for substantially normally incident visible light, the plurality of polymer microlayers 11, 12 reflect more than about 70%, more than about 80%, or more than about 90% of the incident light 20 having an in-plane first polarization state p. Furthermore, in some embodiments, for substantially normally incident visible light, the plurality of polymer microlayers 11, 12 transmit more than about 60% of the incident light 20 having an in-plane orthogonal second polarization state s. In some embodiments, for substantially normally incident visible light, the plurality of polymer microlayers 11, 12 transmit more than about 70%, more than about 80%, or more than about 90% of the incident light 20 having an in-plane orthogonal second polarization state s.

[0117] In some embodiments, the reflective polarizer 100 further includes at least one surface layer 13 ( Figure 1 As shown), the at least one surface layer has an average thickness greater than about 500 nm. In some embodiments, the at least one surface layer 13 has an average thickness greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0118] Figure 6 It depicts a first layer 11 and a polymer second layer 12 of an integral optical film 200 (e.g., optical film OF1 and optical film OF2) according to an embodiment of the present disclosure. Figure 1 The graph 800 shows the layer thickness versus the number of layers. The layer number is represented on the horizontal axis, and the layer thickness is represented in nanometers (nm) on the vertical axis. Graph 800 shows layer thicknesses from 50 nm to 150 nm and layer numbers from 0 to 90.

[0119] In graph 800, curves 802 and 804 depict the layer thickness versus number of layers of the corresponding first layer 11 and polymer second layer 12 of optical film OF1, and curves 806 and 808 depict the layer thickness versus number of layers of the corresponding first layer 11 and polymer second layer 12 of optical film OF2.

[0120] Specifically, curve 802 depicts the layer thickness versus number of layers of the plurality of first layers 11 of optical film OF1, and curve 804 depicts the layer thickness versus number of layers of the plurality of polymer second layers 12 of optical film OF1. Similarly, curve 806 depicts the layer thickness versus number of layers of the plurality of first layers 11 of optical film OF2, and curve 808 depicts the layer thickness versus number of layers of the plurality of polymer second layers 12 of optical film OF2.

[0121] As is evident from curves 802 and 806, the average thickness of the first layer 11 along the integral optical film 200 ( Figure 1 The thickness direction of the integral optical film 200 extends from one of its main sides 15a (as shown). Figure 1 (as shown) to another main side 15b ( Figure 1 (As shown) it changes monotonically. In other words, the average thickness of the first layer 11 changes monotonically along the z-axis. In some implementations, the monotonous change includes a linear change.

[0122] Furthermore, as evident from curves 804 and 808, the average thickness of the second polymer layer 12 varies monotonically along the thickness direction of the integral optical film 200 from one main side 15a to the other main side 15b. In other words, the average thickness of the second polymer layer 12 varies monotonically along the z-axis. In some embodiments, the monotonous variation includes a linear variation.

[0123] exist Figure 6 In the example shown, compared to optical film OF2, optical film OF1 has a larger average total thickness t1 and a greater number of first layers 11 and polymer second layers 12.

[0124] Table 3 below summarizes the average total thickness t1 of optical films OF1 and OF2.

[0125]

[0126] refer to Figures 1 to 6 For substantially normally incident light 20 and each of the mutually orthogonal first polarization s and second polarization p, the integrated optical film 200 has a significantly lower average optical reflectivity 32p, 32s, 33p, 33s in the first wavelength range 30 than in the second wavelength range 31. Therefore, the integrated optical film 200 can act as a blue light lens and provide brightness enhancement by improving recycling efficiency. Furthermore, the integrated optical film 200 has an average total thickness t1 of less than about 50 micrometers. Therefore, the integrated optical film 200 can be substantially thinner than a typical blue light lens. Furthermore, the integrated optical film 200 can provide greater conformal capability and flexibility.

[0127] Unless otherwise stated, all figures used in the specification and claims to indicate feature dimensions, quantities, and physical properties should be understood to be modified by the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations and can vary according to the desired properties sought by those skilled in the art using the teachings disclosed herein.

[0128] While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be used in place of the illustrated and described embodiments without departing from the scope of this disclosure. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. An integral optical film comprising a plurality of alternating first layers and polymer second layers totaling at least 10, and having an average total thickness of less than about 50 micrometers, each of the first layers and the polymer second layers having an average thickness of less than about 300 nm, such that for substantially normally incident light, each of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the integral optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% in the first wavelength range, an average optical reflectance R2avg of greater than about 60% and less than about 98% in the second wavelength range, and an optical reflectance (R1avg + R2avg) / 2 at a first mid-wavelength longer than about 500 nm and shorter than about 540 nm.

2. The integrated optical film of claim 1, wherein for the substantially normally incident light and each of the mutually orthogonal first and second polarizations, the optical reflectivity of the integrated optical film as a function of wavelength includes a band edge separating the first wavelength range and the second wavelength range, wherein at least across a transition wavelength range in which the optical reflectivity increases from about 20% to about 70%, the best linear fit of the optical reflectivity to the band edge in relation to wavelength has a slope greater than about 0.7% / nm.

3. The integrated optical film according to claim 1, wherein the first layer is inorganic.

4. A backlight source for providing illumination to a display panel configured to display an image, the backlight source comprising: The integrated optical film according to claim 1, wherein the integrated optical film is disposed on an extended emitting surface of an extended illumination source including one or more light sources, and is configured to emit light toward the display panel through the extended emitting surface, the emitted light including an emission peak wavelength shorter than the first intermediate wavelength of the integrated optical film; and One or more light conversion films are disposed on the integrated optical film, opposite to the extended emitting surface of the extended illumination source, and configured to receive the emitted light passing through the integrated optical film, and to convert at least a portion of the received emitted light into green and red light having wavelengths within the second wavelength range disposed on the integrated optical film.

5. The backlight according to claim 4, wherein the emission peak wavelength is shorter than about 480 nm.

6. The integrated optical film of claim 1, wherein for the substantially normally incident light and at least one of the mutually orthogonal first polarization and second polarization, the optical reflectivity of the integrated optical film as a function of wavelength includes a band edge, wherein at least across a transition wavelength range in which the optical reflectivity decreases from about 70% to about 20%, the best linear fit of the optical reflectivity to the band edge as a function of wavelength has a slope greater than about 0.9% / nm.

7. The integrated optical film according to claim 1, wherein the integrated optical film further has an optical reflectivity of (R1avg+R2avg) / 2 at a second mid-wavelength longer than about 870 nm and shorter than about 920 nm.

8. The integral optical film of claim 1, wherein the first layer and the second polymer layer of the plurality of alternating first layers and polymer second layers include a first end layer and a corresponding second end layer in the first layer and the second polymer layer, wherein the remaining layers in the first layer and the second polymer layer are disposed between the first end layer and the second end layer, and wherein the first end layer and the second end layer are separated by a distance of less than about 50 micrometers.

9. A monolithic optical film comprising at least 10 alternating first layers and polymer second layers, having an average total thickness of less than about 50 micrometers, each of the first layers and the polymer second layers having an average thickness of less than about 200 nm, such that for substantially normally incident light, at least one of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the monolithic optical film has an average optical reflectance R1avg of less than about 45% and greater than about 5% in the first wavelength range, an average optical reflectance R2avg of greater than about 60% and less than about 98% in the second wavelength range, and an optical reflectance as a function of wavelength including a band edge, wherein at least across a transition wavelength range in which the optical reflectance decreases from about 70% to about 20%, the best linear fit of the optical reflectance to the band edge in relation to wavelength has a slope greater than about 0.9% / nm.

10. A monolithic optical film comprising at least 10 alternating first layers and polymer second layers having an average total thickness of less than about 50 micrometers, each of the first layers and the polymer second layers having an average thickness of less than about 200 nm, such that for substantially normally incident light, at least one of mutually orthogonal first and second polarizations, a first wavelength range extending from about 420 nm to about 480 nm, and a second wavelength range extending from about 560 nm to about 800 nm, the monolithic optical film has an average optical reflectance Ravg of less than about 45% and greater than about 5% in the first wavelength range, and in the second wavelength range... The average optical reflectance R2avg is greater than about 60% and less than about 98%, and the optical reflectance as a function of wavelength includes a first band edge and a second band edge, the first band edge separating the first wavelength range and the second wavelength range, wherein at least across a transition wavelength range in which the optical reflectance changes from about 70% to about 20%, the optical reflectance has a corresponding first positive slope and a second negative slope for the best first linear fit and the best second linear fit of the respective first band edge and the second band edge in relation to the wavelength of each of the first band edge and the second band edge, wherein the ratio of the magnitude of the second negative slope to the first positive slope is greater than about 1.1.

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