Optical films, backlights and display systems

Abstract

The optical film includes a plurality of first layers disposed on a plurality of polymeric second layers, at least 30% of the first layers each including at least 30% by weight of an inorganic material. For substantially perpendicular incident light, the blue wavelength range extends from about 420 nm to about 480 nm, the green wavelength range extends from about 490 nm to about 560 nm, and the red wavelength range extends from about 590 nm to about 670 nm, and the optical film and the plurality of second layers have respective average light reflectances Rof(b) and R2(b) in the blue wavelength range, Rof(g) and R2(g) in the green wavelength range, and Rof(r) and R2(r) in the red wavelength range, where 0≦Rof(b)-R2(b)≦25%, Rof(g)-R2(g)>30%, each of Rof(r) and R2(r) is greater than about 60%, and |Rof(r)-R2(r)| is less than about 20%.

Description

Summary of the Invention

[0001] In some embodiments, the present disclosure provides a method for manufacturing a multi-layered ... <N1<50、N2-N1> 10. Each of the first and second layers may have an average thickness of less than about 500 nm. At least 30% of the first layers each include at least 30% by weight of inorganic material, and for substantially normal incidence light, the blue wavelength range extends from about 420 nm to about 480 nm, the green wavelength range extends from about 490 nm to about 560 nm, and the red wavelength range extends from about 590 nm to about 670 nm, and the optical film and the plurality of polymeric second layers have respective average light reflectances Rof(b) and R2(b) in the blue wavelength range, Rof(g) and R2(g) in the green wavelength range, and Rof(r) and R2(r) in the red wavelength range. In some embodiments, 0≦Rof(b)−R2(b)≦25%, Rof(g)−R2(g)>30%, each of Rof(r) and R2(r) is greater than about 60%, and the magnitude of the difference between Rof(r) and R2(r) is less than about 20%.

[0002] In some embodiments, the present disclosure provides an optical stack comprising one or more light conversion films having a blue emission spectrum with at least one blue peak at a corresponding blue wavelength, a green emission spectrum with at least one green peak at a corresponding green wavelength, and a red emission spectrum with at least one red peak at a corresponding red wavelength. The optical stack comprises an optical film disposed on the one or more light conversion films and substantially coextensive in length and width with the one or more light conversion films. The optical film comprises a plurality of inorganic first layers, a total of at least 3, and a plurality of polymeric second layers, a total of at least 20, each of the inorganic first layers and the polymeric second layers having an average thickness of less than about 500 nm, and for substantially unpolarized substantially perpendicularly incident light, the optical film has an optical transmittance of greater than about 60% at blue wavelengths and an optical reflectance of greater than about 70% at each of the green and red wavelengths.

[0003] In some aspects, provided herein is an optical film comprising a plurality of layers totaling less than about 600, the plurality of layers comprising a plurality of first layers totaling 3-50 disposed on a plurality of polymeric second layers totaling at least 20, at least 30% of the first layers each comprising at least 30% by weight of an inorganic material, each of the first layers and the polymeric second layer having an average thickness less than about 500 nm, and for substantially unpolarized substantially normally incident light, the light reflectance versus wavelength of the polymeric second layer has a first reflection band comprising a first full width at half maximum FWHM1 that is at least 100 nm wide and that includes at least one wavelength in a red wavelength range extending from about 590 nm to about 670 nm, but does not include any wavelengths in a green wavelength range extending from about 490 nm to about 560 nm. The plurality of first layers extend FWHM1 such that the optical film has a second reflection band having a second full width at half maximum FWHM2, at least 20 nm greater than FWHM1 and including at least one wavelength in the green wavelength range. The optical film and the plurality of second layers have respective average optical reflectances Rof(r) and R2(r) in the red wavelength range, and the magnitude of the difference between Rof(r) and R2(r) can be less than about 3%.

[0004] In some aspects, the present disclosure provides an optical film including a plurality of first layers, a total of 3-50, disposed on a plurality of alternating second and third polymer layers, a total of at least 20. At least 30% of the first layers can each include at least 30% by weight of an inorganic material, and each of the second polymer layers can include at least 80% by weight of polyethylene terephthalate. Each of the first, second, and third layers has an average thickness of less than about 500 nm, and for substantially unpolarized substantially normally incident light, the optical reflectance of the optical film, the plurality of first layers, and the plurality of alternating second and third polymer layers has respective first, second, and third reflection bands including respective first, second, and third full widths at half maximum extending between a respective smaller wavelength and a respective larger wavelength. Each of the first, second, and third full widths at half maximum can be at least 50 nm wide. The magnitude of the difference between the smaller wavelength of the first full width at half maximum and the third full width at half maximum can be less than about 20 nm. The wavelength of the smaller third full width half maximum can be at least 20 nm smaller than the wavelength of the smaller second full width half maximum. The wavelength of the larger first full width half maximum can be at least 5 nm greater than the wavelength of the larger second full width half maximum.

[0005] In some aspects, the present disclosure provides a backlight for providing illumination to a display panel configured to display an image. The backlight includes a plurality of light-emitting elements arranged in a two-dimensional manner and spaced apart from one another and configured to emit light having emission wavelengths, and one or more light conversion films disposed on the light-emitting elements and having first, second and third emission spectra including respective first, second and third peaks at corresponding respective first, second and third peak wavelengths and corresponding non-overlapping first, second and third full widths at half maximum (FWHM), where the second FWHM is disposed between the first FWHM and the third FWHM. The one or more light conversion films are configured to receive emitted light from the light-emitting elements and convert at least a portion of the received emitted light into second light and third light having respective second and third wavelengths disposed within the respective second and third FWHMs. The backlight includes an optical film disposed between the light emitting elements and the one or more light conversion films, the optical film including a plurality of inorganic first layers, a total of less than 50, and a plurality of polymeric second layers, a total of at least 20. Each of the inorganic first layers and the polymeric second layers can have an average thickness less than about 500 nm, and for substantially unpolarized substantially normally incident light, the optical film has an optical transmittance of greater than about 60% at the emission wavelength and an optical reflectance of greater than about 70% at each of the second and third wavelengths.

[0006] These and other aspects will become apparent from the following detailed description, but in no way should this brief summary be construed as limiting the claimed subject matter. [Brief description of the drawings]

[0007] [Figure 1A] 1 is a schematic cross-sectional view of a multilayer optical film according to some embodiments. [Figure 1B] 1 is a schematic cross-sectional view of a multilayer optical film according to some embodiments. [Diagram 2]1 is a plot of reflectance versus wavelength for multiple layers and for optical films according to some embodiments. [Diagram 3] 3 is a plot of reflectance of the optical film and emission intensity of one or more light conversion films of FIG. 2 versus wavelength, according to some embodiments. [Figure 4] FIG. 2 is a schematic exploded cross-sectional view of a display system including a backlight including an optical stack including an optical film 200 disposed on one or more light conversion films according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0009] A backlight using a two-dimensional (2D) arrangement of mini / micro light-emitting diodes (LEDs) for liquid crystal displays (LCDs) can be used as a competitive approach to organic light-emitting diode (OLED) displays. Such 2D backlights can enable significantly higher dynamic contrast ratios compared to conventional LCD displays by dimming LEDs in low-luminance areas according to a technique called 2D zoning. In addition, down-conversion using light conversion film(s) (e.g., containing phosphors and / or quantum dots) can be used to increase the color gamut of LCD displays. System efficiency and uniformity in such backlights can be improved by using an optical film that substantially transmits blue light and substantially reflects green and red light on-axis to recycle the green and red light emitted by the light conversion film(s).

[0010] Multilayer optical films can include alternating high and low index optical layers to achieve optical reflectance in a desired wavelength range. Polyethylene naphthalate (PEN) is commonly used as the high index optical layers in multilayer optical films because it has a high refractive index contrast with respect to polymethyl methacrylate (PMMA), which is commonly used as the low index optical layer in such films. However, PEN can suffer from photodegradation and dimming, especially under blue light illumination, which limits its lifetime in applications such as down-converting 2D backlights. To improve the lifetime of optical films in down-converting 2D backlights, polyethylene terephthalate (PET) can be used as the high index optical layers. However, PET has a smaller refractive index contrast with respect to the low index optical layers, which can result in reduced reflectance (e.g., about 2-3% reduction) for green and red wavelengths, which can result in reduced device efficiency and brightness. An alternative to PET-based multilayer optical films is a reflector that includes multiple inorganic layers to provide the desired reflection, but such reflectors are limited in layer thickness and number and / or large area due to mechanical constraints. However, it has been found that by providing a reflector that includes at least some inorganic layers disposed on a (e.g., PET-based) polymeric multilayer reflector, improved reflectance can be provided for green and red wavelengths compared to PET-based multilayer optical films without the limitations of inorganic reflectors. For example, a PET-based film can mainly reflect red and near-infrared wavelengths, and a reflector that includes at least some inorganic layers can mainly reflect green wavelengths, so that the entire optical film can reflect over the entire green and red wavelength ranges. According to some embodiments, it has been found that the optical films described herein can provide high device efficiency and on-axis brightness even when the transmittance of the optical film in the blue wavelength range is reduced (e.g., the reflectance in the blue wavelength range can be more than 10 percent) compared to, for example, a PEN-based multilayer optical film.Additionally, because the films include inorganic layers, the films, according to some embodiments, can provide, for example, a water and oxygen barrier to protect the phosphor and quantum dot coatings from quenching over time.

[0011] 1A is a schematic cross-sectional view of a multilayer optical film 200 according to some embodiments. FIG. 1B is a schematic cross-sectional view of a multilayer optical film 200 according to some other embodiments. In some embodiments, the optical film 200 includes a plurality of first layers 11, 12, a total of N1, disposed on a plurality of second polymer layers 21, 22, a total of N2, 20, and substantially coextensive in length and width with the plurality of second polymer layers. <N1<50、N2-N1> The first layers 11, 12 may, for example, total at least 3, 4, 6, 8, 10, 12, 15, or 20. The polymer second layers 21, 22 may, for example, total at least 20, 30, 50, 75, 100, 150, or 200. The polymer second layers 21, 22 may, for example, total less than about 600, 550, 500, or 450. Each of the first and second layers may have an average thickness of less than about 500, 400, 300, 250, or 200 nm. Each of the first and second layers may, for example, have an average thickness of more than about 3, 5, 10, 20, 40, or 50 nm. For example, in some embodiments, at least some of the first layers are inorganic layers, each inorganic layer has a thickness of more than about 3 or 5 nm, and each polymer layer has a thickness of more than about 40 or 50 nm. In some embodiments, at least 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90%, or 100% of the first layers each contain at least 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90%, or 95% by weight of inorganic material. For example, at least 30% of the first layers each can contain at least 30% by weight of inorganic material, or at least 40% of the first layers each can contain at least 60% by weight of inorganic material, or each of the first layers can contain at least 80% by weight of inorganic material. In some embodiments, about half of the first layers are inorganic layers, and about half or the first layers are polymer layers. In other embodiments, each of the first layers is an inorganic layer. A polymeric layer generally refers to a layer composed primarily of (eg, greater than about 60, 70, 80, 90, or 95 weight percent) organic polymers.An inorganic layer generally refers to a layer that is composed primarily of (eg, greater than about 60, 70, 80, 90, or 95 weight percent) inorganic materials.

[0012] The first layers 11, 12 of the plurality 10 can be disposed on the same side of the second layers 21, 22 of the plurality 20, as shown generally in Figure 1A. Alternatively, a first portion 10' of the first layer 11, 12 of the plurality 10 can be disposed on a first side of the second layers 21, 22 of the plurality 20, and a different second portion 10'' of the first layer 11, 12 of the plurality 10 can be disposed on a second side of the second layers 21, 22 of the plurality 20, opposite the first side, as shown generally in Figure 1B. By using different portions 10', 10'' of the first layers 11, 12 of the plurality 10 on opposite sides of the second layers 21, 22 of the plurality 20, the coefficient of friction of the optical film against adjacent films can be varied, which can be beneficial when the optical film is used in a display system in contact with other films.

[0013] The second layers 21, 22 of the plurality 20 may be formed by coextrusion and costretching as generally described, for example, in U.S. Patents 5,882,774 (Jonza et al.), 6,783,349 (Neavin et al.), 6,949,212 (Merrill et al.), 6,967,778 (Wheatley et al.), and 9,162,406 (Neavin et al.). The first layers 11, 12 of the plurality 10 may then be formed on one or both sides of the first layers 11, 12 of the plurality 10 by, for example, vapor deposition. Suitable deposition methods are described, for example, in U.S. Patent Nos. 5,440,446 (Shaw et al.), 5,877,895 (Shaw et al.), 6,010,751 (Shaw et al.), 6,413,645 (Graffet et al.), 7,018,713 (Padiyath et al.), 9,997,657 (Weigel et al.), and 10,636,920 (Spagnola et al.). Alternatively, the plurality 10 of first layers 11, 12 can be formed on a separate substrate, which is then laminated to the plurality 10 of first layers 11, 12. The optical film 200 may optionally include other layers, such as skin or protective boundary layers 131, 132, which may be coextruded with the first layers 21, 22 of the plurality 20, and / or a protective layer 140, which may be disposed on the outer surface of the first layers 11, 12 of the plurality 10.

[0014] In some embodiments, the optical film 200 includes a plurality of layers (11, 12, 21, 22) totaling less than about 600, 550, 500, or 450. The plurality of layers can, for example, total at least 10, 20, 50, or 100. The plurality of layers can include a plurality of 10 first layers 11, 12 totaling between 3 and 50, 45, 40, 35, 30, 25, or 20 (inclusive) disposed on a plurality of 20 polymeric second layers 21, 22 totaling at least 20, 30, 50, 75, 100, 150, or 200. For example, in some embodiments, the plurality of 10 first layers 11, 12 totals 3-50 and the plurality of 20 polymeric second layers 21, 22 totals at least 20; or the plurality of 10 first layers 11, 12 totals 3-45 and the plurality of 20 polymeric second layers 21, 22 totals at least 50; or the plurality of 10 first layers 11, 12 totals 3-40 and the plurality of 20 polymeric second layers 21, 22 totals at least 75. In some embodiments, at least 30% (or within ranges described elsewhere herein) of the first layers 11, 12 each comprise at least 30% by weight (or within ranges described elsewhere herein) of inorganic material. Each of the first layers and polymeric second layers has an average thickness of less than about 500 nm (or the average thickness can be within ranges described elsewhere herein).

[0015] In some embodiments, the plurality 20 of polymer layers 21, 22 includes a plurality of alternating polymer layers 21 (also referred to as second layers) and 22 (also referred to as third layers). The polymer layer 21 may be, for example, a polyethylene terephthalate (PET) layer, and the polymer layer 22 may be a copolyester, a polymethyl methacrylate (PMMA) layer, or a blend of PMMA with other polymers, such as polyvinylidene fluoride (PVDF). In some embodiments, each of the layers 11, 12, 21, 22 includes less than about 20, 15, 10, 5, 4, 3, 2, or 1 weight percent naphthalate groups. The polymer layer 21 may be birefringent, and the polymer layer 22 may be substantially optically isotropic. The birefringent layer can have a maximum birefringence (e.g., absolute value of the refractive index difference in the x- and z-directions) of, for example, greater than about 0.05, 0.08, 0.1, 0.12, or 0.15 at a first wavelength (e.g., 532 nm, 550 nm, or 633 nm) in a wavelength range of about 400 nm to about 700 nm. The substantially isotropic layer can have a maximum birefringence of, for example, less than about 0.025, 0.02, 0.015, 0.01, or 0.005 at the first wavelength. The birefringent layer can have a refractive index along at least one direction that is, for example, at least about 0.05, 0.08, 0.1, 0.12, or 0.15 greater than the refractive index of the substantially isotropic layer, at least for the first wavelength. The maximum difference in refractive index between different layers along the same direction or between different directions within the same layer may be, for example, up to about 0.5, 0.4, or 0.3 at the first wavelength. In some embodiments, the first layers 11, 12 of the plurality 10 include alternating polymer layers (e.g., 11) and inorganic layers (e.g., 12). The polymer layers may be acrylate (e.g., PMMA) layers, and the inorganic layers may be inorganic oxide (e.g., SiO, TiO, or NbO) layers or metal (e.g., Ag) layers. The first layers 11, 12 may be substantially optically isotropic.Other useful materials are described, for example, in U.S. Pat. Nos. 5,882,774 (Jonza et al.), 6,783,349 (Neavin et al.), 6,949,212 (Merrill et al.), 6,967,778 (Wheatley et al.), 9,162,406 (Neavin et al.), 5,440,446 (Shaw et al.), 5,877,895 (Shaw et al.), 6,010,751 (Shaw et al.), 6,413,645 (Graffet et al.), 7,018,713 (Padiyath et al.), 9,997,657 (Weigel et al.), and 10,636,920 (Spagnola et al.).

[0016] In some embodiments, the optical film 200 includes a plurality of 10 first layers 11, 12, a total of 3-50 (or within ranges as described elsewhere herein), disposed on a plurality of alternating polymeric second layers (21) and polymeric third layers (22), a total of at least 20 (or within ranges as described elsewhere herein), with at least 30% (or within ranges as described elsewhere herein) of the first layers each comprising at least 30% by weight (or within ranges as described elsewhere herein) of inorganic material. In some embodiments, each of the polymeric second layers 21 comprises at least 80% by weight polyethylene terephthalate (PET). Each of the first, second, and third layers may have an average thickness of less than about 500 nm (or within ranges as described elsewhere herein).

[0017] 2 is a plot of reflectance versus wavelength for the plurality of 10 layers 11, 12, the plurality of 20 layers 21, 22, and for optical film 200, according to some embodiments. The light reflectance 36 versus wavelength of the plurality of 10 first layers 11, 12 includes a reflection band 36', the light reflectance 34 versus wavelength of the plurality of 20 polymer second layers 21, 22 includes a reflection band 34', and the light reflectance 35 versus wavelength of optical film 200 includes a reflection band 35'. The average reflectance (expressed as a fraction, e.g., 0.994 is equal to 99.4%) of substantially unpolarized substantially normally incident light 30 for the plurality of 10 layers 11, 12, the plurality of 20 layers 21, 22, and for the optical film 200 of FIG. 2 for various wavelength ranges is shown in the table below.

[0018] [Table 1]

[0019] In some embodiments, the optical film 200 has a blue wavelength range 31 extending from about 420 nm to about 480 nm, a green wavelength range 32 extending from about 490 nm to about 560 nm, and a red wavelength range 33 extending from about 590 nm to about 670 nm, for substantially normal incident light 30, and the optical film 200 and the plurality 20 of polymer second layers 21, 22 have respective average light reflectances Rof(b) and R2(b) in the blue wavelength range, Rof(g) and R2(g) in the green wavelength range, and Rof(r) and R2(r) in the red wavelength range. In some embodiments, 0≦Rof(b)-R2(b)≦25, 20, or 15%. In some such embodiments, or in other embodiments, 2, 3, 5, 7, or 9%≦Rof(b)-R2(b). In some such embodiments, or in other embodiments, Rof(g)-R2(g)>30, 35, 40, 45, 50, 55, or 60%. In some such embodiments, or in other embodiments, Rof(r) and R2(r) are each greater than about 60, 65, 70, 75, 80, 85, 90, or 95%, and the magnitude of the difference between Rof(r) and R2(r) is less than about 20, 15, 10, 5, 4, 3, 2, or 1%.For example, in some embodiments, Rof(r) and R2(r) are each greater than about 60% and the magnitude of the difference between Rof(r) and R2(r) (i.e., |Rof(r)-R2(r)|) is less than about 20%, or Rof(r) and R2(r) are each greater than about 65% and the magnitude of the difference between Rof(r) and R2(r) is less than about 15%, or Rof(r) and R2(r) are each greater than about 70% and the magnitude of the difference between Rof(r) and R2(r) is less than about 10%, or Rof(r) and R2(r) are each greater than about 75% and the magnitude of the difference between Rof(r) and R2(r) is less than about 20%. or each of Rof(r) and R2(r) is greater than about 80% and the magnitude of the difference between Rof(r) and R2(r) is less than about 4%; or each of Rof(r) and R2(r) is greater than about 85% and the magnitude of the difference between Rof(r) and R2(r) is less than about 3%; or each of Rof(r) and R2(r) is greater than about 90% and the magnitude of the difference between Rof(r) and R2(r) is less than about 2%; or each of Rof(r) and R2(r) is greater than about 95% and the magnitude of the difference between Rof(r) and R2(r) is less than about 1%. In some embodiments, 0≦Rof(b)-R2(b)≦20%, Rof(g)-R2(g)>50%, and each of Rof(r) and R2(r) is greater than about 80%, and the magnitude of the difference between Rof(r) and R2(r) is less than about 5%, or 0≦Rof(b)-R2(b)≦15%, Rof(g)-R2(g)>60%, and each of Rof(r) and R2(r) is greater than about 90%, and the magnitude of the difference between Rof(r) and R2(r) is less than about 3%. In some embodiments, Rof(b) is in the range of about 10-30% or about 15-25%.

[0020] In some embodiments, the optical film 200 has an optical reflectivity 34 versus wavelength of the polymer second layer 21, 22 for substantially unpolarized (e.g., less than 30, 20, 10, or 5% degree of polarization) light 30 that is substantially normally incident (e.g., incident within 30, 20, 10, or 5 degrees of normal) light 30 that includes a first reflective band 34′ having a first full width at half maximum FWHM1 34a that is at least 100 nm wide and includes at least one wavelength 34b in a red wavelength range 33 extending from about 590 nm to about 670 nm, but does not include wavelengths in a green wavelength range 32 extending from about 490 nm to about 560 nm, and the optical film 200 has a second reflective band 35′ having a second full width at half maximum FWHM2 34b that is at least 20 nm greater than FWHM1 and includes at least one wavelength 35b in the green wavelength range. The plurality of first layers 11, 12 extend FWHM1 to have a second reflection band 35' including FWHM1 34a. In some embodiments, FWHM1 34a is at least 100, 125, 150, 175, 200, 225, 250, 275, or 300 nm. In some such embodiments, or in other embodiments, FWHM2 35a is at least 20, 30, 40, 50, 60, 70, 80, 90, or 100 nm greater than FWHM1 34a. FWHM2 35a can be, for example, up to about 250, 200, or 150 nm greater than FWHM1 34a. In some embodiments, the optical film 200 and the plurality of second layers 21, 22 have respective average light reflectances Rof(r) and R2(r) in the red wavelength range, and the magnitude of the difference between Rof(r) and R2(r) is less than about 3, 2.5, 1, 1.5, or 1%. Rof(r) and R2(r) can be in any of the ranges described elsewhere herein. For example, in some embodiments, Rof(r) and R2(r) are each greater than about 85%.

[0021] In some embodiments, the optical film 200 is such that, for substantially unpolarized substantially normally incident light 30, the optical reflectivities of the optical film (35), the plurality of first layers (36), and the plurality of alternating polymeric second and third layers (34) have respective first, second and third reflective bands 35', 36' and 34' including respective first full width at half maximum (35a), second full width at half maximum (34a), and third full width at half maximum (36a) extending between respective smaller wavelengths (35L, 34L, 36L) and respective larger wavelengths (35R, 34R, 36R), each of the first full width at half maximum, second full width at half maximum, and third full width at half maximum being at least 50, 75, 100, 125, 150, 175, or 200 nm wide. In some embodiments, the magnitude of the difference between the smaller wavelengths (35L, 36L) of the first and third full widths at half maximum is less than about 20, 15, 10, or 5 nm. In some such embodiments, or in other embodiments, the smaller wavelength 36L of the third full width at half maximum 36a is at least 20, 30, 40, or 50 nm less than the smaller wavelength 34L of the second full width at half maximum 34a. In some such embodiments, or in other embodiments, the larger wavelength 35R of the first full width at half maximum 35a is at least 5, 10, 15, 20, 25, 30, 35, or 40 nm greater than the larger wavelength 34R of the second full width at half maximum 34a. The smaller wavelength 36L of the third full width at half maximum 36a can be, for example, at most about 200, 150, or 100 nm less than the smaller wavelength 34L of the second full width at half maximum 34a. The larger wavelength 35R of the first full width at half maximum 35a can be, for example, up to about 150, 100, or 75 nm greater than the larger wavelength 34R of the second full width at half maximum 34a.

[0022] FIG. 3 is a plot of the reflectance of the optical film 200 and the emission intensity of one or more light conversion films versus wavelength according to some embodiments. FIG. 4 is a schematic exploded cross-sectional view of a display system 500 including a backlight 400 including an optical stack 300 including the optical film 200 disposed on one or more light conversion films 40 according to some embodiments. In the illustrated embodiment, the one or more light conversion films 40 include light conversion films 40a, 40b, and 40c. The light conversion films 40a, 40b, and 40c may include, for example, quantum dots or phosphorus. Suitable light conversion films are known in the art and include Quantum Dot Enhancement Film (QDEF) available from 3M Company (St. Paul, MN). The backlight 400 is for providing illumination (e.g., light 52, 53, 54) to a display panel 90 configured to display an image 91. The optical film 200 may substantially transmit blue light (e.g., light 51, 54', which may have wavelength 43b) and may substantially reflect green and red light (e.g., light 52', 53', which may have wavelengths 43g and 43b, respectively) emitted by one or more optical conversion films 40 (e.g., light 52'', 53'') toward the optical film 200.

[0023] In some embodiments, the optical stack 300 includes one or more light conversion films 40, 40a having a blue emission spectrum 41b including at least one blue peak 42b at a corresponding blue wavelength 43b, a green emission spectrum 41g including at least one green peak 42g at a corresponding green wavelength 43g, and a red emission spectrum 41r including at least one red peak 42r at a corresponding red wavelength 43r. The optical stack can include an optical film 200 disposed on the one or more light conversion films 40 and substantially coextensive in length and width with the one or more light conversion films 40. In some embodiments, the optical film 200 includes a plurality of inorganic first layers (e.g., layer 11, or layer 12, or layer 11 and layer 12) totaling at least 3 (or within ranges described elsewhere herein) and a plurality of polymeric second layers 21, 22 totaling at least 20 (or within ranges described elsewhere herein). In some embodiments, the inorganic first layer and the polymeric second layer each have an average thickness of less than about 500 nm (or within ranges described elsewhere herein), and for substantially unpolarized substantially normally incident light 30, the optical film 200 has a light transmittance Tb of greater than about 60% at blue wavelengths and a light reflectance Rg, Rr of greater than about 70% at each of the green and red wavelengths. In some such embodiments, or in other embodiments, the light transmittance Tb is greater than about 60, 65, 70, 75, 80, or 85% at the blue wavelengths 43b. In some such embodiments, or in other embodiments, the light reflectance Rg, Rr is greater than about 70, 75, 80, 85, 90, or 95% at each of the green wavelengths 43g and red wavelengths 43r.For example, in some embodiments, the light transmittance Tb of the optical film 200 is greater than about 70% at the blue wavelengths 43b, and the light reflectances Rg, Rb of the optical film are greater than about 80% at each of the green wavelengths 43g and the red wavelengths 43r; or the light transmittance Tb of the optical film 200 is greater than about 75% at the blue wavelengths 43b, and the light reflectances Rg, Rb of the optical film are greater than about 85% at each of the green wavelengths 43g and the red wavelengths 43r; or the light transmittance Tb of the optical film 200 is greater than about 80% at the blue wavelengths 43b, and the light reflectances Rg, Rb of the optical film are greater than about 95% at each of the green wavelengths 43g and the red wavelengths 43r.

[0024] In some embodiments, the backlight 400 is for providing illumination to a display panel 90 configured to display an image 91 . In some embodiments, the backlight 400 includes a plurality of light-emitting elements 50 arranged two-dimensionally (e.g., in the xy plane), spaced apart from one another, and configured to emit light 51 having an emission wavelength (e.g., a blue wavelength such as 45b, or an ultraviolet wavelength); and one or more light conversion films 40 disposed on the light-emitting elements and having first (41b), second (41g), and third (41r) emission spectra including respective first (42b), second (42g), and third (42r) peaks at corresponding respective first (43b), second (43g), and third (43r) peak wavelengths and corresponding non-overlapping first (44b), second (44g), and third (44r) full widths at half maximum (FWHM), with the second FWHM disposed between the first FWHM and the third FWHM. The one or more light conversion films are configured to receive emitted light 51 from the light emitting element and convert at least a portion of the received emitted light to second (52) and third (53) light having second (45g) and third (45r) wavelengths located within the respective second and third FWHMs. In some embodiments, the one or more light conversion films are further configured to convert at least a portion of the received emitted light to first light 54 having a first wavelength 45b, the wavelength located within the first FWHM. In some embodiments, the first, second and third FWHMs are at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 nm apart. The first, second and third FWHMs may each be located within a range of, for example, about 400 nm to about 700 nm. The backlight 400 includes an optical film 200 disposed between the light emitting element 50 and one or more light conversion films 40 and including a plurality of inorganic first layers (11 and / or 12) totaling less than 50, 45, 40, 35, 30, 25, 20, 15, or 10 (or within ranges described elsewhere herein) and a plurality of polymeric second layers (21, 22) totaling at least 20 (or within ranges described elsewhere herein).The inorganic layers may total at least 3, 4, 6, 8, 10, 12, 15, or 20. Each of the inorganic first layer and the polymeric second layer may have an average thickness of less than about 500 nm (or within ranges described elsewhere herein), and for substantially unpolarized substantially normally incident light 30, the optical film 200 has an optical transmittance of greater than about 60% at the emission wavelength and an optical reflectance of greater than about 70, 75, 80, 85, 90, or 95% at each of the second and third wavelengths. The optical film 200 may have an optical transmittance of greater than about 65, 70, 75, 80, or 85% at the emission wavelength.

[0025] In some embodiments, the backlight 400 further includes a first prism film 60 disposed on the one or more light conversion films 40 opposite the optical film 200 and including a plurality of first prisms 61 extending along a first longitudinal direction (y-direction). In some embodiments, the backlight 400 further includes a second prism film 62 disposed on the first prism film 60 opposite the optical film 200 and including a plurality of second prisms 63 extending along a second longitudinal direction (x-direction) different from the first longitudinal direction. The first and second longitudinal directions can be, for example, substantially orthogonal. Suitable prism films are known in the art and are described, for example, in U.S. Pat. Nos. 5,932,626 (Fong et al.), 6,280,063 (Fong et al.), 7,622,164 (Jones et al.), and 9,423,553 (Saito).

[0026] In some embodiments, the backlight 400 further includes a light diffuser 70 disposed between the optical film 200 and the light emitting elements 50 and configured to receive and scatter the emitted light 51. Suitable diffusers are known in the art and include, for example, bulk diffusers (e.g., having beads dispersed in a matrix) and surface diffusers (e.g., having a highly defined surface configured to scatter light).

[0027] In some embodiments, the backlight further includes a reflective polarizer 80, with one or more light conversion films 40 disposed between the reflective polarizer 80 and the optical film 200. The reflective polarizer 80 can be a multilayer optical film and can generally correspond to layers 21, 22. In some embodiments, the reflective polarizer includes a plurality of polymeric third layers (e.g., corresponding to layers 21, 22) totaling at least 10, 20, 50, 75, 100, 150, 200, 250, 300, or 400, each of the polymeric third layers having an average thickness of less than about 500, 400, 350, 250, or 200 nm, and for a substantially normally incident light 30, the plurality of polymeric third layers reflects more than about 60% of the incident light having an in-plane first polarization state (e.g., polarized along the x-axis) and transmits more than about 60% of the incident light having an in-plane orthogonal second polarization state (e.g., polarized along the y-axis). In some embodiments, the plurality of polymeric third layers reflects greater than about 70%, or greater than 80%, or greater than 90% of incident light having an in-plane first polarization state. In some such embodiments, or in other embodiments, the plurality of polymeric third layers transmits greater than about 70%, or greater than 80%, or greater than 90% of incident light having an in-plane second polarization state. Suitable reflective polarizers are described, for example, in U.S. Pat. Nos. 5,882,774 (Jonza et al.), 6,783,349 (Neavin et al.), 6,949,212 (Merrill et al.), 6,967,778 (Wheatley et al.), and 9,162,406 (Neavin et al.), including, for example, those available from 3M Company under the trade names DBEF and APF.

[0028] In some embodiments, the display system 500 includes a display panel 90 disposed over the backlight 400 and configured to receive at least the second light 52 and the third light 53 and form an image 91. The display panel 90 typically also receives the first light 54. The display panel 90 may be, for example, a liquid crystal display (LCD) panel. The display system 500 may be configured to utilize 2D zoning to provide a high dynamic contrast ratio.

[0029] The following table provides the average reflectance (Ravg) for normally incident unpolarized light in the wavelength range of 525 nm to 825 nm for various optically modeled films. The high index optical (HIO) and low index optical (LIO) layer materials are shown for the plurality of 10 layers 11, 12 and the plurality of 20 layers 21, 22. The plurality of 20 layers 21, 22 includes 424 layers, and the number of layers in the plurality of 10 layers 11, 12 is shown in the table. Known refractive indices of the various layer materials were used in the optical modeling. The acrylate of film numbers 3-6 was modeled as having a refractive index of about 1.529 at 550 nm. Film numbers 3, 4, and 7-10 included all layers of the plurality of 10 layers 11, 12 disposed on one side of the plurality of 20 layers 21, 22. Film number 11 included 10 layers of the plurality of 10 layers 11, 12 on each side of the plurality of 20 layers 21, 22. The PVDF30 used in film number 12 was a blend of 30 weight percent PVDF in PMMA. PVDF can be used to lower the refractive index of the PMMA layer. However, in some cases it may be preferred that the optical film does not contain a fluorinated polymer such as PVDF.

[0030] [Table 2]

[0031] Terms such as "about" will be understood by those of skill in the art in the context in which they are used and described herein. Unless otherwise clear to one of skill in the art in the context in which they are used and described herein, the use of "about" as applied to quantities expressing feature sizes, amounts, and physical properties will be understood to mean within 10 percent of a particular value. An amount given as about a particular value may be exactly that particular value. For example, unless otherwise clear to one of skill in the art in the context in which they are used and described herein, an amount having a value of about 1 means that the amount has a value between 0.9 and 1.1, and may even be 1.

[0032] Terms such as "substantially" will be understood by those of ordinary skill in the art in the context in which they are used and described in this description. If the use of "substantially" with respect to a property or characteristic is not clear to one of ordinary skill in the art in the context in which it is used and described in this description, and if it is clear to one of ordinary skill in the art what is meant by the opposite of that property or characteristic, then the term "substantially" will be understood to mean that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited.

[0033] Layers or elements may be described as being substantially coextensive in length and width with one another if more than 50% of the length and width of each layer or element is coextensive with more than about 50% of the length and width of each other layer or element. In some embodiments, for layers or elements to be described as being substantially coextensive in length and width with one another, at least about 60%, or at least about 70%, or at least about 80%, or at least about 90% of each layer or element is coextensive in length and width with at least about 60%, or at least about 70%, or at least about 80%, or at least about 90% of the length and width of each other layer or element.

[0034] All references, patents, or patent applications referenced above are hereby incorporated by reference in their entirety. In the event of any inconsistency or contradiction between any of the incorporated references and this application, the information in the foregoing description shall prevail.

[0035] Descriptions of elements in the drawings should be understood to apply equally to corresponding elements in other drawings unless otherwise indicated. Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent implementations without departing from the scope of the present disclosure. The present application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and the equivalents thereof.

Claims

1. 1. A multilayer optical film comprising a total of N1 first layers disposed on a total of N2 polymer second layers and substantially coextensive in length and width with the plurality of polymer second layers, wherein 2<N1<50, N2-N1>10, wherein each of the first and second layers has an average thickness less than about 500 nm, and at least 30% of the first layers each comprise at least 30% by weight of an inorganic material, for substantially normally incident light, a blue wavelength range extends from about 420 nm to about 480 nm, a green wavelength range extends from about 490 nm to about 560 nm, and a red wavelength range extends from about 590 nm to about 670 nm, and the optical film and the plurality of polymer second layers have respective average light reflectivities Rof(b) and R2(b) in the blue wavelength range, Rof(g) and R2(g) in the green wavelength range, and Rof(r) and R2(r) in the red wavelength range, 0≦Rof(b)−R2(b)≦25%, Rof(g)-R2(g)>30%, A multilayer optical film, wherein each of Rof(r) and R2(r) is greater than about 60%, and the magnitude of the difference between Rof(r) and R2(r) is less than about 20%.

2. The multilayer optical film of claim 1 , wherein at least 40% of the first layers each comprise at least 60% by weight inorganic material.

3. 0≦Rof(b)−R2(b)≦20%, Rof(g)-R2(g)>50%, 3. The multilayer optical film of claim 1, wherein each of Rof(r) and R2(r) is greater than about 80% and the magnitude of the difference between Rof(r) and R2(r) is less than about 5%.

4. An optical laminate, one or more light conversion films comprising a blue emission spectrum including at least one blue peak at a corresponding blue wavelength, a green emission spectrum including at least one green peak at a corresponding green wavelength, and a red emission spectrum including at least one red peak at a corresponding red wavelength; an optical film disposed on the one or more light conversion films and having a length and width substantially coextensive with the one or more light conversion films, the optical film comprising a plurality of inorganic first layers totaling at least 3 and a plurality of polymeric second layers totaling at least 20, each of the inorganic first layers and the polymeric second layers having an average thickness less than about 500 nm, and for substantially unpolarized substantially normally incident light, the optical film has an optical transmittance of greater than about 60% at the blue wavelengths and an optical reflectance of greater than about 70% at each of the green wavelengths and the red wavelengths.

5. 5. The optical stack of claim 4, wherein the light transmittance of the optical film is greater than about 70% at the blue wavelengths and the light reflectance of the optical film is greater than about 80% at each of the green and red wavelengths.

6. 1. An optical film comprising a plurality of layers totaling less than about 600, the plurality of layers comprising a plurality of first layers totaling 3 disposed on a plurality of polymeric second layers totaling at least 20, at least 30% of the first layers each comprising at least 30% by weight of an inorganic material, each of the first layers and the polymeric second layers having an average thickness less than about 500 nm, and for substantially unpolarized substantially normally incident light: the optical film includes a first reflection band having a first full width at half maximum FWHM1, the first reflection band being at least 100 nm wide and including at least one wavelength in a red wavelength range extending from about 590 nm to about 670 nm, but not including a wavelength in a green wavelength range extending from about 490 nm to about 560 nm; the first layers extend the FWHM1 such that the optical film has a second reflection band having a second full width at half maximum FWHM2, the ...

7. 7. The optical film of claim 6, wherein Rof(r) and R2(r) are each greater than 85%.

8. 1. An optical film comprising a plurality of first layers, a total of 3 to 50, disposed on a plurality of alternating second and third polymer layers, a total of at least 20, wherein at least 30% of said first layers each comprise at least 30% by weight of an inorganic material, each of said second polymer layers comprises at least 80% by weight of polyethylene terephthalate, each of said first layers, said second layers, and said third layers have an average thickness of less than about 500 nm, and for substantially unpolarized substantially normally incident light: the optical reflectance of the optical film, the plurality of first layers, and the plurality of alternating polymer second and third layers comprises respective first, second and third reflection bands including respective first, second and third full widths at half maximum extending between a respective smaller wavelength and a respective larger wavelength, each of the first, second and third full widths at half maximum having a width of at least 50 nm; a magnitude of a difference between the smaller wavelength of the first full width at half maximum and the third full width at half maximum is less than about 20 nm; the smaller wavelength of the third full width at half maximum is at least 20 nm less than the smaller wavelength of the second full width at half maximum; The greater wavelength of the first full width at half maximum is at least 5 nm greater than the greater wavelength of the second full width at half maximum.

9. 1. A backlight for providing illumination to a display panel configured to display images, comprising: a plurality of light emitting elements arranged in a two-dimensional array and spaced apart from one another and configured to emit light having an emission wavelength; one or more light conversion films disposed on the light emitting element and including first, second and third emission spectra including respective first, second and third peaks at corresponding respective first, second and third peak wavelengths and corresponding non-overlapping first, second and third full widths at half maximum (FWHM), the second FWHM being disposed between the first FWHM and the third FWHM, the one or more light conversion films configured to receive the light emitted from the light emitting element and convert at least a portion of the received emitted light into second light and third light having respective second and third wavelengths disposed within the respective second and third FWHMs; an optical film disposed between the light-emitting element and the one or more light conversion films, the optical film comprising a plurality of inorganic first layers, less than 50 in total, and a plurality of polymeric second layers, at least 20 in total, wherein each of the inorganic first layers and the polymeric second layers has an average thickness less than about 500 nm, and for substantially unpolarized, substantially normally incident light, the optical film has a light transmittance of greater than about 60% at the emission wavelength and a light reflectance of greater than about 70% at each of the second wavelength and the third wavelength.

10. 10. The backlight of claim 9, wherein the one or more light conversion films are further configured to convert at least a portion of the received emitted light to a first light having a first wavelength disposed within the first FWHM.

11. The backlight of claim 9 , wherein the first FWHM, the second FWHM, and the third FWHM are at least 10 nm apart.

12. 10. The backlight of claim 9, further comprising a first prism film disposed on the one or more light conversion films opposite the optical film and comprising a plurality of first prisms extending along a first longitudinal direction.

13. 13. The backlight of claim 12, further comprising a second prism film disposed on the first prism film opposite the optical film and comprising a plurality of second prisms extending along a second longitudinal direction different from the first longitudinal direction.

14. 10. The backlight of claim 9, further comprising a reflective polarizer, the one or more light conversion films being disposed between the reflective polarizer and the optical film, the reflective polarizer comprising a plurality of polymer third layers totaling at least 10, each of the polymer third layers having an average thickness of less than about 500 nm, and for substantially normally incident light, the plurality of polymer third layers reflects greater than about 60% of the incident light having an in-plane first polarization state and transmits greater than about 60% of the incident light having an in-plane orthogonal second polarization state.

15. A display system comprising a display panel disposed on the backlight according to any one of claims 9 to 14 and configured to receive at least the second light and the third light to form an image.

Images