Backlight and display system

Abstract

A backlight includes an extended illumination source configured to emit light including an emitted spectrum including an emitted peak at an emitted peak wavelength and a corresponding emitted FWHM. The backlight includes one or more light converting films including blue, green, and red emission spectra including respective blue, green, and red peaks at corresponding respective blue, green, and red peak wavelengths and corresponding non-overlapping blue, green, and red FWHMs. The backlight includes an optical film. For a substantially collimated incident light and for each of mutually orthogonal in-plane first and second polarization states, the optical film has: for wavelengths across the emitted FWHM, an average optical reflectance of greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, and an average optical reflectance of less than about 20% for a second incident angle of no less than about 40 degrees.

Description

[0001] BACKLIGHT AND DISPLAY SYSTEM

[0002] Technical Field

[0003] The present disclosure relates to a display system and a backlight including an optical film.

[0004] Background

[0005] Typically, backlights may provide illumination to display panels configured to display an image on display systems. Nowadays, display panels in high-end display systems include quantum dot films and blue light-emitting diodes (LEDs) in the backlights of the display systems. The quantum dot films may enhance color gamut of the display systems and may provide more vivid colors. However, a quantum dots material used in the quantum dot films may be expensive, and therefore including the quantum dot films in the backlights may be a hurdle to their adoption in a mainstream segment of the display systems.

[0006] Summary

[0007] In a first aspect, the present disclosure provides a backlight for providing an illumination to a display panel configured to display an image. The backlight includes an extended illumination source. The extended illumination source includes one or more light sources. The extended illumination source further includes an extended emission surface. The extended illumination source is configured to emit light through the extended emission surface towards the display panel. The emitted light includes an emitted spectrum. The emitted spectrum includes an emitted peak at an emitted peak wavelength and a corresponding emitted full width at half maximum (FWHM). The backlight further includes one or more light converting films disposed on the extended emission surface of the extended illumination source. The one or more light converting films include blue, green, and red emission spectra including respective blue, green, and red peaks at corresponding respective blue, green, and red peak wavelengths and corresponding non-overlapping blue, green, and red FWHMs. The green FWHM is disposed between the blue and red FWHMs. The one or more light converting fdms are configured to receive the emitted light through the extended emission surface. The one or more light converting fdms are configured to convert at least portions of the received emitted light to blue-, green-, and red-lights having respective blue, green, and red wavelengths disposed in the respective blue, green, and red FWHMs. The backlight further includes an optical film disposed on the one or more light converting films opposite to the extended emission surface. The optical film includes a plurality of polymeric layers numbering at least 10 in total. Each of the polymeric layers has an average thickness of less than about 500 nm. For a substantially collimated incident light and for each of mutually orthogonal inplane first and second polarization states, the optical film has: for wavelengths across the emitted FWHM, an average optical reflectance of greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, and an average optical reflectance of less than about 20% for a second incident angle of no less than about 40 degrees; and for wavelengths across the each of the blue, green, and red FWHMs, an average optical reflectance of less than about 25% for the first incident angle and an average optical reflectance of less than about 10% for the second incident angle.

[0008] In a second aspect, the present disclosure provides a display system. The display system includes one or more light sources configured to emit a violet light. The emitted violet light includes a violet spectmm including a violet peak at a violet peak wavelength and a corresponding violet full width at half maximum (FWHM). The display system includes a blue-light converting material disposed proximate, and enclosing at least 50% of an emission surface of, the one or more light sources and includes a blue emission spectrum including a blue peak at a corresponding blue peak wavelength and a corresponding blue FWHM. The blue-light converting material is configured to receive at least 50% of the emitted violet light and convert at least a portion of the received emitted violet light to a blue light having a blue wavelength disposed in the blue FWHM. The display system further includes a display panel. The display system further includes one or more green- and red-light converting films substantially co-extensive in length and width with the display panel. The one or more green- and red- light converting films include green and red emission spectra including respective green and red peaks at corresponding respective green and red peak wavelengths and corresponding non-overlapping green and red FWHMs. The one or more green- and red-light converting films are configured to receive the blue light from the blue-light converting material and convert at least portions of the received blue light to green and red lights having respective green and red wavelengths disposed in the respective green and red FWHMs. The display system further includes an optical film disposed between, and substantially co-extensive in length and width with, the display panel and the one or more green- and red-light converting films. The optical film includes a plurality of polymeric layers numbering at least 10 in total. Each of the polymeric layers has an average thickness of less than about 500 nm. For a substantially collimated incident light, and for each of mutually orthogonal in-plane first and second polarization states, the optical film has: for wavelengths across the violet FWHM, an average optical reflectance of greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, an average optical reflectance of less than about 20% for a second incident angle of no less than about 40 degrees; and for wavelengths across the each of the blue, green, and red FWHMs, an average optical reflectance of less than about 25% for the first incident angle and an average optical reflectance of less than about 10% for the second incident angle.

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

[0010] Brief Description of the Drawings

[0011] Exemplary embodiments disclosed herein may be more completely understood in consideration of the following detailed description in connection with the following figures. The figures are not necessarily drawn to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

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

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

[0014] FIG. 2B shows a schematic detailed sectional view of a reflective polarizer of the display system, according to an embodiment of the present disclosure;

[0015] FIG. 3 shows a schematic view of a display system, according to another embodiment of the present disclosure; and

[0016] FIG. 4 shows a graph depicting an optical reflectance of the optical film versus wavelength for a substantially collimated incident light incident at different incident angles, according to an embodiment of the present disclosure.

[0017] Detailed Description

[0018] In the following description, reference is made to the accompanying figures that form a part thereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0019] In the following disclosure, the following definitions are adopted.

[0020] As used herein, all numbers should be considered modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably.

[0021] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties).

[0022] The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0023] The term “about”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 5% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0024] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be constmed as limiting of this disclosure. The terms “first” and “second” when used in conjunction with a feature or an element can be interchanged throughout the embodiments of this disclosure. As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0025] As used herein, the term “layer” generally refers to a thickness of material within a film that has a relatively consistent chemical composition. Layers may be of any type of material including polymeric, cellulosic, metallic, or a blend thereof. A given polymeric layer may include a single polymer-type or a blend of polymers and may be accompanied by additives. A given layer may be combined or connected to other layers to form films. A layer may be either partially or fully continuous as compared to adjacent layers or the film. A given layer may be partially or fully coextensive with adjacent layers. A layer may contain sub-layers.

[0026] Typically, backlights may provide illumination to display panels configured to display an image on conventional display systems. Nowadays, display panels in high-end display systems include quantum dot films and blue light-emitting diodes (LEDs) in the backlights of the conventional display systems. The quantum dot films may enhance color gamut of the display systems and may provide more vivid colors. However, a quantum dots material used in the quantum dot films may be expensive, and therefore including the quantum dot films in the backlights may be a hurdle to their adoption in a mainstream segment of the display systems.

[0027] The present disclosure relates to a backlight and a display system including a display panel. The backlight provides an illumination to the display panel configured to display an image. The backlight includes an extended illumination source. The extended illumination source includes one or more light sources. The extended illumination source further includes an extended emission surface. The extended illumination source is configured to emit light through the extended emission surface towards the display panel. The emitted light includes an emitted spectrum. The emitted spectrum includes an emitted peak at an emitted peak wavelength and a corresponding emitted full width at half maximum (FWHM). The backlight further includes one or more light converting films disposed on the extended emission surface of the extended illumination source. The one or more light converting films include blue, green, and red emission spectra including respective blue, green, and red peaks at corresponding respective blue, green, and red peak wavelengths and corresponding non-overlapping blue, green, and red FWHMs. The green FWHM is disposed between the blue and red FWHMs. The one or more light converting films are configured to receive the emitted light through the extended emission surface. The one or more light converting films are configured to convert at least portions of the received emitted light to blue-, green-, and red-lights having respective blue, green, and red wavelengths disposed in the respective blue, green, and red FWHMs. The backlight further includes an optical film disposed on the one or more light converting films opposite to the extended emission surface. The optical film includes a plurality of polymeric layers numbering at least 10 in total. Each of the polymeric layers has an average thickness of less than about 500 nm. For a substantially collimated incident light and for each of mutually orthogonal in-plane first and second polarization states, the optical film has: for wavelengths across the emitted FWHM, an average optical reflectance of greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, an average optical reflectance of less than about 20% for a second incident angle of no less than about 40 degrees; and for wavelengths across the each of the blue, green, and red FWHMs, an average optical reflectance of less than about 25% for the first incident angle and an average optical reflectance of less than about 10% for the second incident angle.

[0028] The light emitted by the extended illumination source may be a violet light. Therefore, the emitted FWHM of the emitted spectrum may lie in a violet wavelength range (e.g., from 399 nm to about 419 nm). The one or more light converting films may have a better efficiency to convert the light in the violet wavelength range to the blue-, green-, and red-lights than converting a light in a blue wavelength range to the blue-, green-, and red-lights. Specifically, the one or more light converting films may include quantum dots material. The quantum dots material may show a much higher absorption rate for the light in the violet wavelength range than the light in the blue wavelength range emitted by blue LEDs of the conventional display systems. Therefore, the amount of the quantum dots material required to convert the light in the violet wavelength range may be substantially less than the amount of the quantum dots material required to convert the light in the blue wavelength range. This may reduce the cost of the one or more light converting films of the backlight. Further, the optical film disposed on the one or more light converting films may reduce the light in the violet wavelength range that reaches eyes of a viewer. Specifically, the optical fdm may reflect a portion of the light in the violet wavelength range which is not absorbed by the quantum dots material to reduce the light in the violet wavelength range that reaches the eyes of the viewer.

[0029] Therefore, the backlight of the present disclosure may reduce the use of the quantum dots material used in the one or more light conversion films in order to reduce the cost of the display systems, while preventing the light in the violet wavelength range to reach the eyes of the viewer.

[0030] Referring now to figures, FIG. 1 is a schematic sectional exploded view of a display system 300, according to an embodiment of the present disclosure.

[0031] The display system 300 defines mutually orthogonal x, y, and z-axes. The x and y-axes are inplane axes of the display system 300, while the z-axis is a transverse axis disposed along a thickness of the display system 300. In other words, the x and y-axes are disposed along a plane of the display system 300, while the z-axis is perpendicular to the plane of the display system 300.

[0032] The display system 300 includes a backlight 200 for providing an illumination 41. The display system 300 includes a display panel 40. Specifically, the backlight 200 provides the illumination 41 to the display panel 40. The display panel 40 is configured to display an image 42. In some embodiments, the display panel 40 is disposed on the backlight 200 and configured to receive the illumination 41 from the backlight 200 and display the image 42. In some embodiments, the display panel 40 includes a liquid crystal display (LCD) panel.

[0033] In some embodiments, the backlight 200 includes an extended illumination source 21. The extended illumination source 21 includes an extended emission surface 22. The display system 300 further includes one or more light sources 20. Specifically, the extended illumination source 21 includes the one or more light sources 20. The extended illumination source 21 is configured to emit light 23 through the extended emission surface 22 toward the display panel 40. In some embodiments, the display panel 40 is configured to receive the light 23 emitted through the extended emission surface 22 and display the image 42. In some cases, the light 23 is a violet light. In such cases, the light 23 may be interchangeably referred to as “the violet light 23”. Therefore, the one or more light sources 20 are configured to emit the violet light 23.

[0034] In some embodiments, the extended illumination source 21 further includes a lightguide 24 for receiving a light 24a from the one or more light sources 20 and propagating the received light 24a therein along a length and a width of the lightguide 24. In some embodiments, the length of the lightguide 24 extends substantially along the x-axis. In some embodiments, the width of the lightguide 24 extends substantially along the y-axis.

[0035] The received light 24a propagates in the lightguide 24 as a propagating light 24b. Further, the propagating light 24b exits the lightguide 24 through an exit surface 25 of the lightguide 24 as an exiting light 24c. In some embodiments, the exit surface 25 is substantially co-extensive in length and width with the extended emission surface 22. In some embodiments, the length of exit surface 25 extends substantially along the x-axis. In some embodiments, the width of the exit surface 25 extends substantially along the y-axis. In some embodiments, the exiting light 24c exits the extended illumination source 21 through the extended emission surface 22 as the emitted light 23. In some embodiments, the exit surface 25 of the lightguide 24 includes the extended emission surface 22.

[0036] In some embodiments, the extended illumination source 21 further includes a back reflector 27. In some embodiments, the back reflector 27 is substantially co-extensive in length and width with the extended emission surface 22. The back reflector 27 may be configured to reflect any light that exits the lightguide 24 toward the back reflector 27 back toward the lightguide 24. The back reflector 27 may include a reflecting surface (e.g., a metallic surface) or may have a multi-layer configuration.

[0037] In some embodiments, the back reflector 27 is spaced apart from the extended emission surface 22. In some embodiments, the extended emission surface 22 and the back reflector 27 defines an optical cavity 28 therebetween. In some embodiments, the lightguide 24 is disposed between the extended emission surface 22 and the back reflector 27.

[0038] In some embodiments, the one or more light sources 20 are disposed proximate one or more edge surfaces 26 of the lightguide 24. In some embodiments, the one or more light sources 20 are disposed in the optical cavity 28.

[0039] The backlight 200 further includes one or more light converting films 15 disposed on the extended emission surface 22 of the extended illumination source 21. The one or more light converting films 15 are configured to receive the emitted light 23 through the extended emission surface 22 and convert at least portions of the received emitted light 23 to blue-, green-, and red-lights 10b, 10g, lOr. The blue-, green-, and red-lights 10b, 10g, lOr have respective blue, green, and red wavelengths.

[0040] In the illustrated embodiment of FIG. 1, the one or more light converting films 15 include a blue-light converting film 15b, a green-light converting film 15g, and a red-light converting film 15r. In some embodiments, the one or more light converting films 15 include one or more of phosphor, fluorescent dye, and quantum dots. In some embodiments, the blue-light converting film 15b includes phosphor. In some embodiments, the one or more green- and red- light converting films 15g, 15r include quantum dots. In some embodiments, the green-light converting film 15g and the red-light converting film 15r are co-extensive in length and width with the display panel 40. In some embodiments, the blue-light converting film 15b is also co-extensive in length and width with the display panel 40.

[0041] In some embodiments, the blue-light converting film 15b is configured to receive the emitted light 23 through the extended emission surface 22 and convert at least a portion of the received emitted light 23 to the blue-light 10b. Further, the green-light converting film 15g is configured to receive the emitted light 23 through the extended emission surface 22 and convert at least a portion of the received emitted light 23 to the green-light 10g. Similarly, the red-light converting film 15r is configured to receive the emitted light 23 through the extended emission surface 22 and convert at least a portion of the received emitted light 23 to the red-light lOr.

[0042] The backlight 200 further includes an optical film 30. The optical film 30 disposed between the display panel 40 and the one or more light converting films 15. In the illustrated embodiment of FIG. 1, the optical film 30 is disposed on the red-light converting film 15r, green-light converting film 15g, and blue-light converting film 15b. In some embodiments, the optical film 30 is bonded to the one or more light converting films 15 via a first bonding layer 70.

[0043] In some embodiments, the backlight 200 further includes an optical diffuser 80 disposed on the optical film 30 opposite the one or more light converting films 15. In some embodiments, the optical film 30 is bonded to the optical diffuser 80 via a second bonding layer 71.

[0044] In some embodiments, the backlight 200 further includes a first prismatic film 90. The first prismatic film 90 is disposed on the optical film 30 opposite the one or more light converting films 15. The first prismatic film 90 includes a plurality of first prisms 91. In some embodiments, the plurality of first prisms 91 extends along substantially a same first longitudinal direction. In some embodiments, the first longitudinal direction extends along the y-axis.

[0045] In some embodiments, the backlight 200 further includes a second prismatic film 92 disposed on the first prismatic film 90 opposite the optical film 30. The second prismatic film 92 includes a plurality of second prisms 93. The plurality of second prisms 93 extends along substantially a same second longitudinal direction different from the first longitudinal direction. In some embodiments, the second longitudinal direction extends along the x-axis.

[0046] In some embodiments, the optical diffuser 80 is disposed between the first prismatic film 90 and the optical film 30. In some embodiments, the optical diffuser 80 is bonded to the first prismatic film 90 via a third bonding layer 72.

[0047] In the illustrated embodiment of FIG. 1, the backlight 200 further includes a reflective polarizer 100 disposed on the optical film 30 opposite the one or more light converting films 15. In some embodiments, the reflective polarizer 100 is bonded to the display panel 40 via a fourth bonding layer 73. In some embodiments, each of the first, second, third, and fourth bonding layers 70, 71, 72, 73 may include an optically clear adhesive (OCA).

[0048] FIG. 2A is a schematic detailed sectional view of the optical film 30, according to an embodiment of the present disclosure.

[0049] The optical film 30 includes a plurality of polymeric layers 43. The plurality of polymeric layers 43 numbers at least 10 in total. In some embodiments, the plurality of polymeric layers 43 numbers at least 20, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, or at least 300 in total. Each of the polymeric layers 43 has an average thickness t of less than about 500 nanometers (nm). The term “average thickness t”, as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the x-y plane) of each of the plurality of polymeric layers 43. In some embodiments, each of the polymeric layers 43 has the average thickness t of less than about 400 nm, less than about 300 nm, or less than about 200 nm.

[0050] In some embodiments, the plurality of polymeric layers 43 includes a plurality of alternating polymeric first and second layers 31, 32. The plurality of alternating polymeric first and second layers 31, 32 is stacked along a thickness direction of the optical film 30. In some embodiments, the thickness direction extends substantially along the z-axis. In some embodiments, the plurality of alternating polymeric first and second layers 31, 32 numbers at least 10 in total. In some embodiments, the plurality of alternating polymeric first and second layers 31, 32 numbers at least 20, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, or at least 300 in total. In some embodiments, each of the first and second polymeric layers 31, 32 has an average thickness of less than about 500 nm. In some embodiments, each of the first and second polymeric layers 31, 32 has the average thickness of less than about 400 nm, less than about 300 nm, or less than about 200 nm.

[0051] In some embodiments, the optical film 30 further includes at least one skin layer 33 disposed on the plurality of polymeric layers 43. In some embodiments, the at least one skin layer 33 has an average thickness st of greater than about 500 nm. The term “average thickness st”, as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the x-y plane) of each of the at least one skin layer 33. In some embodiments, the at least one skin layer 33 has the average thickness st of greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0052] In the illustrated embodiment of FIG. 2 A, the at least one skin layer 33 includes a pair of skin layers 33, and the polymeric layers 43 are disposed between the pair of skin layers 33. The at least one skin layer 33 may protect the polymeric layers 43 and may also provide mechanical stability to the optical film 30. In some cases, the at least one skin layer 33 may act as protective boundary layer (PBL).

[0053] FIG. 2A further illustrates a substantially collimated incident light 34 incident on the optical film 30. In some embodiments, the substantially collimated incident light 34 is incident on the optical film 30 at a first incident angle al. The first incident angle al is less than about 10 degrees. In some embodiments, the first incident angle al is less than about 8 degrees, less than about 6 degrees, less than about 4 degrees, less than about 2 degrees, or less than about 1 degree. In some embodiments, the first incident angle al is about 0 degree.

[0054] In some embodiments, the substantially collimated incident light 34 is incident on the optical film 30 at a second incident angle a2. The second incident angle a2 is of no less than about 40 degrees. In some embodiments, the second incident angle a2 is of no less than about 45 degrees, no less than about 50 degrees, no less than about 55 degrees, or no less than about 60 degrees. In some embodiments, the second incident angle a2 is about 60 degrees.

[0055] FIG. 2B is a schematic detailed sectional view of the reflective polarizer 100, according to an embodiment of the present disclosure.

[0056] In some embodiments, the reflective polarizer 100 includes a plurality of polymeric microlayers 143. The plurality of polymeric microlayers 143 numbers at least 10 in total. In some embodiments, the plurality of polymeric microlayers 143 numbers at least 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 in total. In some embodiments, each of the polymeric microlayers 143 has an average thickness tl of less than about 500 nm. The term “average thickness tl”, as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the x-y plane) of each of the plurality of polymeric microlayers 143. In some embodiments, each of the polymeric microlayers 143 has the average thickness tl 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.

[0057] In some embodiments, the plurality of polymeric microlayers 143 includes a plurality of alternating polymeric first and second microlayers 131, 132. The plurality of alternating polymeric first and second microlayers 131, 132 is stacked along the thickness direction of the reflective polarizer 100. In some embodiments, the plurality of alternating polymeric first and second layers 131, 132 numbers at least 10 in total. In some embodiments, the plurality of alternating polymeric first and second layers 131, 132 numbers at least 20, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, or at least 300 in total. In some embodiments, each of the first and second polymeric layers 131, 132 has an average thickness of less than about 500 nm. In some embodiments, each of the first and second polymeric layers 131, 132 has the average thickness of less than about 400 nm, less than about 300 nm, or less than about 200 nm.

[0058] In some embodiments, the reflective polarizer 100 further includes at least one skin layer 133 disposed on the plurality of polymeric microlayers 143. In some embodiments, the at least one skin layer 133 has an average thickness stl of greater than about 500 nm. The term “average thickness st 1” , as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the x-y plane) of each of the at least one skin layer 133. In some embodiments, the at least one skin layer 133 has the average thickness stl of greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0059] In the illustrated embodiment of FIG. 2B, the at least one skin layer 133 includes a pair of skin layers 133, and the polymeric microlayers 143 are disposed between the pair of skin layers 133. The at least one skin layer 133 may protect the polymeric microlayers 143 and may also provide mechanical stability to the reflective polarizer 100. In some cases, the at least one skin layer 133 may act as protective boundary layer (PBL).

[0060] FIG. 2B further illustrates a substantially normally incident light 35 incident on the reflective polarizer 100, i.e., the light 35 is incident on the reflective polarizer 100 at an angle of 0 degree with respect to a normal to the reflective polarizer 100.

[0061] FIG. 3 is a schematic exploded view of a display system 400, according to another embodiment of the present disclosure.

[0062] The display system 400 is substantially similar to the display system 300 of FIG. 1, with like elements designated by like reference characters. However, the display system 400 includes a backlight 205 and the display panel 40.

[0063] The backlight 205 is also substantially similar to the backlight 200 of FIG. 1, with like elements designated by like reference characters. However, the backlight 205 has a different configuration of the one or more light converting films 15 than that of the backlight 200 shown in FIG, 1. Specifically, in the illustrated embodiment of FIG. 3, the backlight 205 includes the one or more green- and red- light converting films 15g, 15r substantially co-extensive in length and width with the display panel 40. However, the backlight 205 does not include the blue-light converting film 15b (shown in FIG. 1). Further, the backlight 205 includes an extended illumination source 121. The extended illumination source 121 is substantially similar to the extended illumination source 21 shown in FIG. 1. However, a blue-light converting material 16b is disposed proximate the one or more light sources 20. Specifically, the display system 400 includes the blue-light converting material 16b disposed proximate, and enclosing at least 50% of an emission surface 20a of, the one or more light sources 20. In some embodiments, the display system 400 encloses at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of the emission surface 20a of the one or more light sources 20. Specifically, the backlight 205 includes the blue-light converting material 16b disposed proximate, and enclosing at least 50% of the emission surface 20a of, the one or more light sources 20. In some embodiments, the blue-light converting material 16b includes phosphor, and the one or more green- and red-light converting films 15g, 15r include quantum dots.

[0064] Further, as discussed above, the one or more light sources 20 are configured to emit the emitted violet light 23. The blue-light converting material 16b is configured to receive at least 50% of the emitted violet light 23 and convert at least a portion of the received emitted violet light 23 to the bluelight 10b. In some embodiments, the blue-light converting material 16b is configured to receive at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of the emitted violet light 23.

[0065] In the illustrated embodiment of FIG. 3, the lightguide 24 may also receive the blue-light 10b. In such cases, the light 24a may be interchangeably referred to as “the blue-light 24a”. The lightguide 24 propagates the received blue-light 24a therein along the length and the width of the lightguide 24. The received blue light 24a propagates in the lightguide 24 as the propagating light 24b. Further, in the illustrated embodiment of FIG. 3, the optical film 30 is disposed between, and is substantially co-extensive in length and width with, the display panel 40 and the one or more green- and red-light converting films 15g, 15r.

[0066] FIG. 4 is a graph 500 depicting an optical reflectance of the optical film 30 (shown in FIGS. 1, 2A, and 3) versus wavelength for the substantially collimated incident light 34 (shown in FIG. 2A) incident at different incident angles, according to an embodiment of the present disclosure. The graph 500 further depicts an emission spectmm versus wavelength for the light 23 emitted from the one or more light sources 20 (shown in FIGS. 1 and 3). The graph 500 further depicts emission spectra versus wavelength for the blue-, green-, and red-light converting films 15b, 15g, 15r shown in FIG. 1. The emission spectrum for the blue-light converting film 15b is similar to the emission spectrum for the blue-light converting material 16b.

[0067] Wavelength is expressed in nanometers (nm) in abscissa. The optical reflectance is expressed as a reflectance percentage (R%) in the left ordinate, while the emission intensity is expressed in arbitrary units (a.u.) in the right ordinate.

[0068] The graph 500 includes a curve 50 (shown by dash-dot line) depicting blue, green, and red emission spectra 50b, 50g, 50r of the one or more light converting films 15. Specifically, the one or more light converting films 15 include the blue, green, and red emission spectra 50b, 50g, 50r including respective blue, green, and red peaks 51b, 51g, 51r at corresponding respective blue, green, and red peak wavelengths 52b, 52g, 52r and corresponding non-overlapping blue, green, and red full width at half maximum (FWHM) 53b, 53g, 53r. As stated above, the emission spectrum for the blue-light converting film 15b is similar to the emission spectrum for the blue-light converting material 16b. Therefore, the blue-light converting material 16b includes the blue emission spectrum 50b.

[0069] Specifically, the blue emission spectrum 50b includes the blue peak 51b at the blue peak wavelength 52b, the green emission spectrum 50g includes the green peak 51g at the green peak wavelength 52g, and the red emission spectrum 50r includes the red peak 5 Ir at the red peak wavelength 52r. Further, the blue emission spectrum 50b includes the blue FWHM 53b, the green emission spectmm 50g includes the green FWHM 53g, and the red emission spectrum 50r includes the red FWHM 53r. Further, the blue, green, and red FWHMs 53b, 53g, 53r are non-overlapping.

[0070] In some embodiments, the blue peak wavelength 52b is between about 420 nm and about 480 nm. In the illustrated example of FIG. 4, the blue peak wavelength 52b is about 452 nm. In some embodiments, the blue FWHM 53b is disposed in a blue wavelength range extending from about 420 nm to about 480 nm. In the illustrated example of FIG. 4, the blue wavelength range extends from about 445 nm to about 462 nm. In some embodiments, the blue FWHM 53b is at least 5 nm wide. In some embodiments, the blue FWHM 53b is at least 10 nm or at least 15 nmwide. In some embodiments, the blue FWHM 53b is less than about 50 nm wide. In some embodiments, the blue FWHM 53b is less than about 45 nm, less than about 40 nm, less than about 35 nm, less than about 30 nm, less than about 25 nm, or less than about 20 nm wide. In the illustrated example of FIG. 4, the blue FWHM 53b is about 17 nm wide. In some embodiments, the green peak wavelength 52g is between about 490 nm and about 560 nm. In the illustrated example of FIG. 4, the green peak wavelength 52g is about 527 nm. In some embodiments, the green FWHM 53g is disposed in a green wavelength range extending from about 490 nm to about 560 nm. In the illustrated example of FIG. 4, the green wavelength range extends from about 516 nm to about 537 nm. In some embodiments, the green FWHM 53g is at least 5 nm wide. In some embodiments, the green FWHM 53g is at least 10 nm, at least 15 nm, or at least 20 nm wide. In some embodiments, the green FWHM 53g is less than about 50 nm wide. In some embodiments, the green FWHM 53g is less than about 45 nm, less than about 40 nm, less than about 35 nm, less than about 30 nm, or about less than about 25 nm wide. In the illustrated example of FIG. 4, the green FWHM 53g is about 21 nm wide.

[0071] In some embodiments, the red peak wavelength 52r is between about 590 nm and about 670 nm. In the illustrated example of FIG. 4, the red peak wavelength 52r is about 627 nm. In some embodiments, the red FWHM 53r is disposed in a red wavelength range extending from about 590 nm to about 670 nm. In the illustrated example of FIG. 4, the red wavelength range extends from about 607 nm to about 648 nm. In some embodiments, the red FWHM 53r is at least 5 nm wide. In some embodiments, the red FWHM 53r is at least 10 nm, at least 15 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 35 nm, or at least 40 nm wide. In some embodiments, the red FWHM 53r is less than about 80 nm wide. In some embodiments, the red FWHM 53r is less than about 75 nm, less than about 70 nm, less than about 65 nm, less than about 60 nm, less than about 55 nm, less than about 50 nm, or less than about 45 nm wide. In the illustrated example of FIG. 4, the red FWHM 53r is about 41 nm wide.

[0072] As is apparent from the graph 500, the green FWHM 53g is disposed between the blue and red FWHMs 53b, 53r. The blue, green, and red wavelengths of the respective blue-, green-, and red-lights 10b, 10g, lOr (shown in FIG. 1) are disposed in the respective blue, green, and red FWHMs 53b, 53g, 53r. Specifically, the blue wavelength of the blue-light 10b is disposed in the blue FWHM 53b, the green wavelength of the green-light 10g is disposed in the green FWHM 53g, and the red wavelength of the red-light lOr is disposed in the red FWHM 53r.

[0073] Further, referring to FIGS. 1 to 4, the graph 500 includes a curve 51 (shown by dashed line) depicting an emission spectrum 50v of the emitted light 23 from the one or more light sources 20. Specifically, the emitted light 23 includes the emission spectrum 50v including an emitted peak 5 Iv at an emitted peak wavelength 52v, and a corresponding emitted FWHM 53v.

[0074] As discussed above, the light 23 is the violet light 23. In such cases, the emission spectrum 50v may be interchangeably referred to as “the violet spectrum 50v”, the emitted peak 51v may be interchangeably referred to as “the violet peak 51v”, the emitted peak wavelength 52v may be interchangeably referred to as “the violet peak wavelength 52v”, and the corresponding emitted FWHM 53v may be interchangeably referred to as “the corresponding violet FWHM 53v”. Therefore, the emitted violet light 23 includes the violet spectrum 50v including the violet peak 5 Iv at the violet peak wavelength 52v and the corresponding violet FWHM 53v. In some embodiments, the emitted peak wavelength 52v is less than the blue peak wavelength 52b by at least 10 nm. In some embodiments, the emitted peak wavelength 52v is less than the blue peak wavelength 52b by at least 15 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 35 nm, or at least 40 nm. In the illustrated example of FIG. 4, the emitted peak wavelength 52v is less than the blue peak wavelength 52b by about 43 nm. In some embodiments, the emitted peak wavelength 52v is less than about 420 nm. In the illustrated example of FIG. 4, the emitted peak wavelength 52v is about 409 nm.

[0075] In some embodiments, the emitted FWHM 53v is less than about 50 nm wide. In some embodiments, the emitted FWHM 53v is less than about 45 nm, less than about 40 nm, less than about 35 nm, less than about 30 nm, or less than about 25 nm wide. In some embodiments, the emitted FWHM 53v is at least about 5 nm wide. In some embodiments, the emitted FWHM 53v is at least about 10 nm or at least about 15 nm wide. In the illustrated example of FIG. 4, the emitted FWHM 53v extends from about 399 nm to about 419 nm. Therefore, in the illustrated example of FIG. 4, the emitted FWHM 53v is about 20 nm wide. In some embodiments, the emitted FWHM 53v does not overlap the blue FWHM 53b.

[0076] Table 1 provided below summarizes the emitted peak wavelength 52v of the emitted peak 51v of the emission spectrum 50v of the emitted light 23 from the one or more light sources 20, the blue peak wavelength 52b of the blue peak 51b of the blue emission spectrum 50b of the blue-light converting film 15b, the green peak wavelength 52g of the green peak 51g of the green emission spectrum 50g of the green-light converting film 15g, and the red peak wavelength 52r of the red peak 51r of the red emission spectrum 50r of the red-light converting film 15r.

[0077] Table 1

[0078] The graph 500 further includes a curve 30a depicting an optical reflectance of the optical film 30 for the substantially collimated incident light 34 (shown in FIG. 2A) incident at the first incident angle al and for each of mutually orthogonal in-plane first and second polarization states. In some embodiments, the first polarization state extends along the x-axis and the second polarization state extends along the y-axis. In some embodiments, the first polarization state may correspond to a p- polarization state, while the second polarization state may correspond to a s-polarization state.

[0079] Referring to FIGS. 2A and 4, as is apparent from the curve 30a, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, an average optical reflectance of greater than about 20% and less than about 80% for the first incident angle al . In other words, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the violet FWHM 53v, the average optical reflectance of greater than about 20% and less than about 80% for the first incident angle al.

[0080] In some embodiments, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, the average optical reflectance of greater than about 30%, greater than about 40%, or greater than about 50% and less than about 75%, less than about 70%, or less than about 65% for the first incident angle al. In the illustrated example of FIG. 4, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, the average optical reflectance of about 65% for the first incident angle al.

[0081] Thus, the optical film 30 may substantially reflect the substantially collimated incident light 34 incident at the first incident angle al for the first and second polarization states across the emitted FWHM 53v. Therefore, the optical film 30 may substantially reflect the emitted light 23 incident at the first incident angle al.

[0082] Further, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across each of the blue, green, and red FWHMs 53b, 53g, 53r, an average optical reflectance of less than about 25% for the first incident angle al. Specifically, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the blue FWHM 53b, the average optical reflectance of less than about 25% for the first incident angle al; for wavelengths across the green FWHM 53g, the average optical reflectance of less than about 25% for the first incident angle al ; and for wavelengths across the red FWHM 53r, the average optical reflectance of less than about 25% for the first incident angle al.

[0083] In the illustrated example of FIG. 4, for the substantially collimated incident light 34 incident at the first incident angle al, and for the first and second polarization states, the optical film 30 has, for wavelengths across the blue FWHM 53b, the average optical reflectance of about 15.8%; for wavelengths across the green FWHM 53g, the average optical reflectance of about 13.7%; and for wavelengths across the red FWHM 53r, the average optical reflectance of about 11.1%.

[0084] Thus, the optical film 30 may substantially transmit the substantially collimated incident light 34 incident at the first incident angle al for the first and second polarization states across the blue, green, and red FWHMs 53b, 53g, 53r. Therefore, the optical film 30 may substantially transmit the blue-, green-, and red-lights 10b, 10g, lOr incident at the first incident angle al.

[0085] Further, referring to the curve 30a, for the substantially collimated incident light 34 incident at the first incident angle al and for the first and second polarization states, the optical film 30 may be more optically reflective across the emitted FWHM 53v than across the blue, green, and red FWHMs 53b, 53g, 53r. The graph 500 further includes a curve 30b depicting an optical reflectance of the optical film 30 for the substantially collimated incident light 34 (shown in FIG. 2A) incident at 20 degrees, and for each of mutually orthogonal in-plane first and second polarization states.

[0086] As is apparent from the curve 30b, for the substantially collimated incident light 34 incident at 20 degrees, and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, an average optical reflectance of about 44.3%. Further, for the substantially collimated incident light 34 incident at 20 degrees, and for the first and second polarization states, the optical film 30 has, for wavelengths across the blue FWHM 53b, the average optical reflectance of about 14.8%; for wavelengths across the green FWHM 53g, the average optical reflectance of about 11.1%; and for wavelengths across the red FWHM 53r, the average optical reflectance of about 9.7%.

[0087] The graph 500 further includes a curve 30c depicting an optical reflectance of the optical film 30 for the substantially collimated incident light 34 (shown in FIG. 2A) incident at the second incident angle a2 and for each of mutually orthogonal in-plane first and second polarization states. The graph 500 further includes a curve 30d depicting the optical reflectance of the optical film 30 for the substantially collimated incident light 34 (shown in FIG. 2A) incident at the second incident angle a2 and for each of mutually orthogonal in-plane first and second polarization states. In the illustrated example of FIG. 4, the second incident angle a2 is about 40 degrees for the curve 30c and the second incident angle a2 is about 60 degrees for the curve 30d.

[0088] As is apparent from the curves 30c, 30d, for the substantially collimated incident tight 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, an average optical reflectance of less than about 20% for the second incident angle a2. In some embodiments, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, the average optical reflectance of less than about 15%, less than about 10%, or less than about 5% for the second incident angle a2.

[0089] In the illustrated example of FIG. 4, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the emitted FWHM 53v, the average optical reflectance of about 13.2% for the second incident angle a2 of about 40 degrees, and the average optical reflectance of about 2% for the second incident angle a2 of about 60 degrees.

[0090] Further, as is apparent from the curves 30c, 30d, for the substantially collimated incident tight 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across each of the blue, green, and red FWHMs 53b, 53g, 53r, an average optical reflectance of less than about 10% for the second incident angle a2. In some embodiments, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across each of the blue, green, and red FWHMs 53b, 53g, 53r, an average optical reflectance of less than about 8%, less than about 5%, less than about 4%, less than about 3%, or less than about 2% for the second incident angle a2.

[0091] Further, as is apparent from the curve 30c, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the blue, green, and red FWHMs 53b, 53g, 53r, the average optical reflectance of about 8.2%, about 5.8%, about 5.6%, respectively, for the second incident angle a2 of about 40 degrees. Further, as is apparent from the curve 30d, for the substantially collimated incident light 34 and for the first and second polarization states, the optical film 30 has, for wavelengths across the blue, green, and red FWHMs 53b, 53g, 53r, the average optical reflectance of about 1.1%, about 0.5%, about 0.6%, respectively, for the second incident angle a2 of about 60 degrees.

[0092] Referring to the curves 30c, 30d, for the substantially collimated incident light 34 incident at the second incident angle a2 and for the first and second polarization states, the optical film 30 may be more optically reflective, across the emitted FWHM 53v than across the blue, green, and red FWHMs 53b, 53g, 53r.

[0093] Table 2 provided below summarizes average optical transmittances of the optical film 30 for the substantially collimated incident light 34 (shown in FIG. 2A) incident at the different incident angles and across different wavelength ranges (e.g., the emitted FWHM 53v, the blue FWHM 53b, the green FWHM 53g, and the red FWHM 53r).

[0094] Table 2 where, T30(0) refers to the average optical transmittance of the optical fdm 30 for the incident angle of about 0 degree;

[0095] T30(20) refers to the average optical transmittance of the optical film 30 for the incident angle of about 20 degrees;

[0096] T30(40) refers to the average optical transmittance of the optical film 30 for the incident angle of about 40 degrees; and

[0097] T30(60) refers to the average optical transmittance of the optical film 30 for the incident angle of about 60 degrees. Table 3 provided below summarizes average optical reflectances of the optical film 30 for the substantially collimated incident light 34 (shown in FIG. 2A) incident at the different incident angles and across the different wavelength ranges.

[0098] Table 3 where, R30(0) refers to the average optical reflectance of the optical film 30 for the incident angle of about 0 degree;

[0099] R30(20) refers to the average optical reflectance of the optical film 30 for the incident angle of about 20 degrees;

[0100] R30(40) refers to the average optical reflectance of the optical film 30 for the incident angle of about 40 degrees; and

[0101] R30(60) refers to the average optical reflectance of the optical film 30 for the incident angle of about 60 degrees.

[0102] Referring to FIGS. 1, 3, and 4, in some embodiments, the optical diffuser 80 has a diffuse optical transmittance of greater than about 30% for each of the blue, green, and red peak wavelengths 52b, 52g, 52r, and a diffuse optical transmittance of greater than about 10% for the emitted peak wavelength 52v. In some embodiments, the optical diffuser 80 has the diffuse optical transmittance of 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 each of the blue, green, and red peak wavelengths 52b, 52g, 52r, and the diffuse optical transmittance of greater than about 15%, greater than about 20%, greater than about 25%, or greater than about 30% for the emitted peak wavelength 52v.

[0103] Referring to FIGS. 2B and 4, in some embodiments, for the substantially normally incident tight 35 and each of the blue, green, and red peak wavelengths 52b, 52g, 52r, the plurality of polymeric microlayers 143 reflects more than about 60% of the incident light 35 having the first polarization state and transmits more than about 60% of the incident tight 35 having the second polarization state. In some embodiments, for the substantially normally incident light 35 and each of the blue, green, and red peak wavelengths 52b, 52g, 52r, the plurality of polymeric microlayers 143 reflects more than about 70%, more than about 80%, or more than about 90% of the incident light 35 having the first polarization state and transmits more than about 70%, more than about 80%, or more than about 90% of the incident light 35 having the second polarization state.

[0104] Referring to FIGS . 1 to 4, the one or more light converting films 15 may have a better efficiency in converting the light 23 (i.e., having the emission spectrum 50v in the violet wavelength range) to the blue-, green-, and red-lights 10b, 10g, lOr than converting a light in a blue wavelength range to the blue- , green-, and red-lights 10b, 10g, lOr. Further, as discussed above, the one or more light converting films 15 may include quantum dots material. The quantum dots material may show a much higher absorption rate for the light 23 than the light in the blue wavelength range emitted by blue LEDs of conventional display systems. Therefore, the amount of the quantum dots material required to convert the light 23 may be substantially less than the amount of the quantum dots material required to convert the light in the blue wavelength range. This may reduce the cost of the one or more light converting films 15 of the backlight 200, 205. Further, the optical film 30 disposed on the one or more light converting films 15 may reduce the light 23 that reaches eyes of a viewer. Specifically, the optical film 30 may reflect a portion of the light 23 which is not absorbed by the quantum dots material to reduce the light 23 that reaches the eyes of the viewer.

[0105] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0106] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

CLAIMS1. A backlight for providing illumination to a display panel configured to display an image, the backlight comprising: an extended illumination source comprising one or more light sources and an extended emission surface and configured to emit light through the extended emission surface toward the display panel, the emitted light comprising an emitted spectrum comprising an emitted peak at an emitted peak wavelength and a corresponding emitted full width at half maximum (FWHM); one or more light converting films disposed on the extended emission surface of the extended illumination source and comprising blue, green, and red emission spectra comprising respective blue, green, and red peaks at corresponding respective blue, green, and red peak wavelengths and corresponding non-overlapping blue, green, and red FWHMs, the green FWHM disposed between the blue and red FWHMs, the one or more light converting films configured to receive the emitted light through the extended emission surface and convert at least portions of the received emitted light to blue blue-, green green-, and red red- lights having respective blue, green, and red wavelengths disposed in the respective blue, green, and red FWHMs; and an optical film disposed on the one or more light converting films opposite the extended emission surface and comprising a plurality of polymeric layers numbering at least 10 in total, each of the polymeric layers having an average thickness of less than about 500 nm, such that for a substantially collimated incident light, and for each of mutually orthogonal in-plane first and second polarization states, the optical film has: for wavelengths across the emitted FWHM, an average optical reflectance of greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, and an average optical reflectance of less than about 20% for a second incident angle of no less than about 40 degrees; and for wavelengths across each of the blue, green, and red FWHMs, an average optical reflectance of less than 25% for the first incident angle and an average optical reflectance of less than about 10% for the second incident angle.

2. The backlight of claim 1, wherein the emitted peak wavelength is less than the blue peak wavelength by at least 10 nm.

3. The backlight of claim 1, wherein the emitted peak wavelength is less than about 420 nm.

4. The backlight of claim 1, wherein the emitted FWHM does not overlap the blue FWHM.

5. The backlight of claim 1, wherein the one or more light converting films comprise:a blue-light converting film configured to receive the emitted light through the extended emission surface and convert at least a portion of the received emitted light to the blue light having the blue wavelength disposed in the blue FWHM; a green-light converting film configured to receive the emitted light through the extended emission surface and convert at least a portion of the received emitted light to the green light having the green wavelength disposed in the green FWHM; and a red-light converting film configured to receive the emitted light through the extended emission surface and convert at least a portion of the received emitted light to the red light having the red wavelength disposed in the red FWHM.

6. The backlight of claim 1, wherein the plurality of polymeric layers comprises a plurality of alternating polymeric first and second layers stacked along a thickness direction of the optical film and numbering at least 10 in total, each of the first and second polymeric layers having an average thickness of less than about 500 nm.

7. The backlight of claim 1 further comprising a first prismatic film disposed on the optical film opposite the one or more light converting films and comprising a plurality of first prisms extending along substantially a same first longitudinal direction.

8. The backlight of claim 1 further comprising a reflective polarizer disposed on the optical film opposite the one or more light converting films and comprising a plurality of polymeric microlayers numbering at least 10 in total, each of the polymeric microlayers having an average thickness of less than about 500 nm, such that for a substantially normally incident light and each of the blue, green, and red peak wavelengths, the plurality of polymeric microlayers reflects more than about 60% of the incident light having an in-plane first polarization state and transmits more than about 60% of the incident light having an in-plane orthogonal second polarization state.

9. A display system comprising a display panel disposed on the backlight of claim 1 and configured to receive the light emitted through the extended emission surface and display an image, the optical film disposed between the display panel and the one or more light converting films.

10. A display system comprising: one or more light sources configured to emit a violet light, the emitted violet light comprising a violet spectrum comprising a violet peak at a violet peak wavelength and a corresponding violet full width at half maximum (FWHM);a blue-light converting material disposed proximate, and enclosing at least 50% of an emission surface of, the one or more light sources and comprising a blue emission spectrum comprising a blue peak at a corresponding blue peak wavelength and a corresponding blue FWHM, the blue-light converting material configured to receive at least 50% of the emitted violet light and convert at least a portion of the received emitted violet light to a blue light having a blue wavelength disposed in the blue FWHM; a display panel; one or more green- and red-light converting films substantially co-extensive in length and width with the display panel and comprising green and red emission spectra comprising respective green and red peaks at corresponding respective green and red peak wavelengths and corresponding nonoverlapping green, and red FWHMs, the one or more green- and red-light converting films configured to receive the blue light from the blue-light converting material and convert at least portions of the received blue light to green and red lights having respective green and red wavelengths disposed in the respective green and red FWHMs; and an optical film disposed between, and substantially co-extensive in length and width with, the display panel and the one or more green- and red-light converting films and comprising a plurality of polymeric layers numbering at least 10 in total, each of the polymeric layers having an average thickness of less than about 500 nm, such that for a substantially collimated incident light, and for each of mutually orthogonal inplane first and second polarization states, the optical film has: for wavelengths across the violet FWHM, an average optical reflectance of greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, and an average optical reflectance of less than about 20% for a second incident angle of no less than about 40 degrees; and for wavelengths across each of the blue, green, and red FWHMs, an average optical reflectance of less than 25% for the first incident angle and an average optical reflectance of less than about 10% for the second incident angle.

Images