Backlight source and display system

Abstract

A backlight includes an extended illumination source configured to emit light having an emission spectrum having an emission peak at an emission peak wavelength and a corresponding emission FWHM. The backlight includes one or more light conversion films having a blue light emission spectrum, a green light emission spectrum, and a red light emission spectrum, the blue light emission spectrum, the green light emission spectrum and the red light emission spectrum have respective blue light peaks, green light peaks and red light peaks at corresponding respective blue light peak wavelengths, green light peak wavelengths and red light peak wavelengths and corresponding non-overlapping blue light FWHM, green light FWHM and red light FWHM. The backlight includes an optical film. For substantially collimated incident light and for each of a first in-plane polarization state and a second in-plane polarization state that are mutually orthogonal, the optical film: for a wavelength across the emission FWHM, has an average optical reflectance of greater than about 20% and less than about 80% for a first angle of incidence of less than about 10 degrees, and having an average optical reflectance of less than about 20% for a second angle of incidence of not less than about 40 degrees.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a display system and a backlight including an optical film. BACKGROUND

[0002] Generally, a backlight can provide illumination to a display panel configured to display images on a display system. Currently, display panels in high-end display systems include quantum dot films and blue light emitting diodes (LEDs) in the backlight of the display system. Quantum dot films can enhance the color gamut of the display system and can provide more vivid colors. However, quantum dot materials used for quantum dot films can be expensive, and thus, including quantum dot films in the backlight can be an obstacle to their adoption in mainstream portions of the display system. SUMMARY

[0003] In a first aspect, the present disclosure provides a backlight for providing 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 toward the display panel. The emitted light has an emission spectrum. The emission spectrum has an emission peak at an emission peak wavelength and a corresponding emission full-width-at-half-maximum (FWHM). The backlight further includes one or more light conversion films disposed on the extended emission surface of the extended illumination source. The one or more light conversion films have a blue emission spectrum, a green emission spectrum, and a red emission spectrum having respective blue, green, and red peaks at respective corresponding blue, green, and red peak wavelengths and respective non-overlapping blue, green, and red FWHMs. The green FWHM is disposed between the blue FWHM and the red FWHM. The one or more light conversion films are configured to receive the emitted light through the extended emission surface. The one or more light conversion films are configured to convert at least a portion of the received emitted light into blue, green, and red light 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 conversion films opposite the extended emission surface. The optical film includes a plurality of polymer layers having a total number of at least 10. Each of the polymer layers has an average thickness of less than about 500 nm. For substantially collimated incident light and for each of an in-plane first polarization state and an in-plane second polarization state orthogonal to one another, the optical film: for wavelengths across the emission FWHM, has an average optical reflectivity for a first incidence angle of less than about 10 degrees that is greater than about 20% and less than about 80%, and has an average optical reflectivity for a second incidence angle of not less than about 40 degrees that is less than about 20%; and for wavelengths across each of the blue, green, and red FWHMs, has an average optical reflectivity for the first incidence angle that is less than about 25%, and has an average optical reflectivity for the second incidence angle that is less than about 10%.

[0004] In a second aspect, the present disclosure provides a display system. The display system includes one or more light sources configured to emit violet light. The emitted violet light has a violet light spectrum with a violet light peak at a violet light peak wavelength and a corresponding violet light full-width-at-half-maximum (FWHM). The display system includes a blue light conversion material disposed proximate to the one or more light sources and encompassing at least 50% of an emission surface of the one or more light sources and having a blue light emission spectrum with a blue light peak at a corresponding blue light peak wavelength and a corresponding blue light FWHM. The blue light conversion 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 blue light having a blue light wavelength disposed in the blue light FWHM. The display system further includes a display panel. The display system further includes one or more green and red light conversion films substantially coextensive in length and width with the display panel. The one or more green and red light conversion films have a green light emission spectrum and a red light emission spectrum with a respective green light peak and red light peak at respective corresponding green light peak wavelength and red light peak wavelength and a corresponding non-overlapping green light FWHM and red light FWHM. The one or more green and red light conversion films are configured to receive the blue light from the blue light conversion material and convert at least a portion of the received blue light to green and red light having respective green light wavelength and red light wavelength disposed in the respective green light FWHM and red light FWHM. The display system further includes an optical film disposed between the display panel and the one or more green and red light conversion films and substantially coextensive in length and width with the display panel and the one or more green and red light conversion films. The optical film includes a plurality of polymer layers having a total number of at least 10. Each of the plurality of polymer layers has an average thickness of less than about 500 nm. For substantially collimated incident light and for each of an in-plane first polarization state and an in-plane second polarization state orthogonal to one another, the optical film has: for wavelengths across the violet light FWHM, an average optical reflectivity for a first incidence angle of less than about 10 degrees of greater than about 20% and less than about 80%, an average optical reflectivity for a second incidence angle of not less than about 40 degrees of less than about 20%; and for wavelengths across each of the blue light FWHM, the green light FWHM, and the red light FWHM, an average optical reflectivity for the first incidence angle of less than about 25% and an average optical reflectivity for the second incidence angle of less than about 10%.

[0005] 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. BRIEF DESCRIPTION OF DRAWINGS

[0006] The exemplary embodiments disclosed herein can be more fully understood in light of the following detailed description taken in conjunction with the accompanying drawings. The drawings are not necessarily drawn to scale. Similar numbers used in the drawings refer to similar parts. However, it should be understood that the use of numbers to refer to parts in a given drawing is not intended to limit parts labeled with the same numbers in another drawing.

[0007] Figure 1 A schematic cross-sectional view of a display system according to an embodiment of the present disclosure is shown; Figure 2A A detailed schematic cross-sectional view of the optical film of a display system according to an embodiment of the present disclosure is shown; Figure 2B A detailed schematic cross-sectional view of the reflective polarizer of a display system according to an embodiment of the present disclosure is shown; Figure 3 A schematic diagram of a display system according to another embodiment of the present disclosure is shown; and Figure 4 A graph depicting the relationship between the optical reflectivity of an optical film and wavelength for substantially collimated incident light incident at different incident angles, according to an embodiment of the present disclosure, is shown. Detailed Implementation

[0008] In the following description, reference is made to the accompanying drawings, which form a part thereof, and various embodiments are illustrated therein. It should be understood that other embodiments may be conceived and made without departing from the scope or spirit of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0009] In the following disclosure, the following definitions are used.

[0010] As used herein, all numbers should be considered as being modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “a or more” are used interchangeably.

[0011] As used herein, as a modifier of a characteristic or attribute, unless otherwise specifically defined, the term “approximately” means that the characteristic or attribute will be easily identifiable by a person of ordinary skill in the art without requiring absolute precision or a perfect match (e.g., within + / - 20% for quantifiable characteristics).

[0012] Unless otherwise specifically defined, the term “substantially” means a high degree of approximation (e.g., within + / -10% for quantifiable properties), but also does not require absolute precision or a perfect match.

[0013] Unless otherwise specifically defined, the term “approximately” means a high degree of approximation (e.g., within + / -5% for quantifiable properties), but also does not require absolute precision or a perfect match.

[0014] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be construed as limiting the scope of this disclosure. Throughout the embodiments of this disclosure, the terms “first” and “second” are used interchangeably when used in conjunction with a feature or element.

[0015] As used in this article, "at least one of A and B" should be understood as meaning "only A, only B, or both A and B".

[0016] As used herein, the term "layer" generally refers to a thickness of material having a relatively uniform chemical composition within a membrane. A layer can be any type of material, including polymers, cellulose, metals, or blends thereof. A given polymer layer may comprise a single polymer type or a blend of polymers and may include additives. A given layer may be combined with or bonded to other layers to form a membrane. A layer may be partially continuous or completely continuous compared to adjacent layers or membranes. A given layer may be partially or completely co-extended with adjacent layers. A layer may contain sublayers.

[0017] Typically, a backlight illuminates a display panel configured to display images on a conventional display system. Currently, display panels in high-end display systems incorporate quantum dot films and blue light-emitting diodes (LEDs) in their backlights. Quantum dot films enhance the color gamut of the display system and provide more vibrant colors. However, the quantum dot materials used in quantum dot films can be expensive, and therefore, including quantum dot films in backlights may be an obstacle to their adoption in the mainstream of display systems.

[0018] This disclosure relates to a backlight and a display system including a display panel. The backlight provides 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 also includes an extended emitting surface. The extended illumination source is configured to emit light toward the display panel through the extended emitting surface. The emitted light has an emission spectrum. The emission spectrum has an emission peak at the emission peak wavelength and a corresponding emission full width at half maximum (FWHM). The backlight also includes one or more light conversion films disposed on the extended emitting surface of the extended illumination source. The one or more light conversion films have a blue light emission spectrum, a green light emission spectrum, and a red light emission spectrum, the blue light emission spectrum, the green light emission spectrum, and the red light emission spectrum having corresponding blue light peaks, green light peaks, and red light peaks at corresponding corresponding blue light peak wavelengths, green light peak wavelengths, and red light peak wavelengths, and corresponding non-overlapping blue light FWHMs, green light FWHMs, and red light FWHMs. The green light FWHM is disposed between the blue light FWHM and the red light FWHM. One or more light conversion films are configured to receive light emitted through an extended emitting surface. The one or more light conversion films are configured to convert at least a portion of the received emitted light into blue, green, and red light having corresponding blue, green, and red wavelengths disposed in corresponding blue, green, and red FWHMs. The backlight also includes an optical film disposed on the one or more light conversion films opposite to the extended emitting surface. The optical film comprises at least 10 polymer layers. Each of these polymer layers has an average thickness of less than about 500 nm. For substantially collimated incident light and for each of the mutually orthogonal in-plane first polarization state and in-plane second polarization state, the optical film has: for the wavelength across the emission FWHM, an average optical reflectance 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 less than about 20% for a second incident angle of not less than about 40 degrees; and for the wavelength across each of the blue, green, and red FWHM, an average optical reflectance less than about 25% for the first incident angle and an average optical reflectance less than about 10% for the second incident angle.

[0019] The light emitted by the extended illumination source can be violet light. Therefore, the emission FWHM of the emission spectrum can be within the violet wavelength range (e.g., from 399 nm to approximately 419 nm). One or more light conversion films can have better efficiency in converting light in the violet wavelength range into blue, green, and red light compared to converting light in the blue wavelength range into blue, green, and red light. Specifically, one or more light conversion films can contain quantum dot materials. Quantum dot materials exhibit a much higher absorption rate for light in the violet wavelength range than light in the blue wavelength range emitted by blue LEDs in conventional display systems. Therefore, the amount of quantum dot material required for converting light in the violet wavelength range can be substantially less than the amount required for converting light in the blue wavelength range. This reduces the cost of one or more light conversion films in the backlight. Furthermore, an optical film disposed on one or more light conversion films can reduce the amount of light in the violet wavelength range reaching the viewer's eyes. Specifically, the optical film can reflect a portion of the light in the violet wavelength range that is not absorbed by the quantum dot material to reduce the amount of light in the violet wavelength range reaching the viewer's eyes.

[0020] Therefore, the backlight of this disclosure can reduce the use of quantum dot materials for one or more light conversion films, thereby reducing the cost of the display system while preventing light in the violet wavelength range from reaching the viewer's eyes.

[0021] Now refer to the attached diagram, Figure 1 This is a schematic exploded cross-sectional view of a display system 300 according to one embodiment of the present disclosure.

[0022] The display system 300 defines mutually orthogonal x-axis, y-axis, and z-axis. The x-axis and y-axis are in-plane axes of the display system 300, while the z-axis is a transverse axis set along the thickness of the display system 300. In other words, the x-axis and y-axis are set along the plane of the display system 300, while the z-axis is perpendicular to the plane of the display system 300.

[0023] Display system 300 includes a backlight 200 for providing illumination 41. Display system 300 includes a display panel 40. Specifically, the backlight 200 provides 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 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.

[0024] In some embodiments, the backlight 200 includes an extended illumination source 21. The extended illumination source 21 includes an extended emitting surface 22. The display system 300 also includes one or more light sources 20. Specifically, the extended illumination source 21 includes one or more light sources 20. The extended illumination source 21 is configured to emit light 23 toward the display panel 40 through the extended emitting surface 22. In some embodiments, the display panel 40 is configured to receive the light 23 emitted through the extended emitting surface 22 and display an image 42. In some cases, the light 23 is violet light. In such cases, the light 23 is interchangeably referred to as "violet light 23". Therefore, one or more light sources 20 are configured to emit violet light 23.

[0025] In some embodiments, the extended illumination source 21 further includes a light guide 24 for receiving light 24a from one or more light sources 20 and propagating the received light 24a along its length and width. In some embodiments, the length of the light guide 24 extends substantially along the x-axis. In some embodiments, the width of the light guide 24 extends substantially along the y-axis.

[0026] The received light 24a propagates in the light guide 24 as propagating light 24b. Furthermore, the propagating light 24b exits the light guide 24 as emitted light 24c through the exit surface 25 of the light guide 24. In some embodiments, the exit surface 25 extends substantially together with the extended emitting surface 22 in both length and width. In some embodiments, the length of the 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 emitted light 24c exits the extended illumination source 21 as emitted light 23 through the extended emitting surface 22. In some embodiments, the exit surface 25 of the light guide 24 includes the extended emitting surface 22.

[0027] In some embodiments, the extended illumination source 21 also includes a back reflector 27. In some embodiments, the back reflector 27 extends substantially together with the extended emitting surface 22 in both length and width. The back reflector 27 may be configured to reflect any light exiting the light guide 24 toward the back reflector 27 back toward the light guide 24. The back reflector 27 may include a reflective surface (e.g., a metallic surface) or may have a multi-layer configuration.

[0028] In some embodiments, the back reflector 27 is spaced apart from the extended emitting surface 22. In some embodiments, the extended emitting surface 22 and the back reflector 27 define an optical cavity 28 between them. In some embodiments, a light guide 24 is disposed between the extended emitting surface 22 and the back reflector 27.

[0029] In some embodiments, one or more light sources 20 are disposed near one or more edge surfaces 26 of the light guide 24. In some embodiments, one or more light sources 20 are disposed within an optical cavity 28.

[0030] The backlight 200 also includes one or more light conversion films 15 disposed on the extended emitting surface 22 of the extended illumination source 21. The one or more light conversion films 15 are configured to receive light 23 emitted through the extended emitting surface 22 and convert at least a portion of the received emitted light 23 into blue light 10b, green light 10g, and red light 10r. The blue light 10b, green light 10g, and red light 10r have corresponding blue, green, and red wavelengths.

[0031] exist Figure 1 In the illustrated embodiments, one or more light conversion films 15 include a blue light conversion film 15b, a green light conversion film 15g, and a red light conversion film 15r. In some embodiments, one or more light conversion films 15 comprise one or more of phosphors, fluorescent dyes, and quantum dots. In some embodiments, the blue light conversion film 15b comprises phosphors. In some embodiments, one or more green light conversion films 15g and red light conversion films 15r comprise quantum dots. In some embodiments, the green light conversion film 15g and red light conversion film 15r are co-extended with the display panel 40 in length and width. In some embodiments, the blue light conversion film 15b is also co-extended with the display panel 40 in length and width.

[0032] In some embodiments, the blue light conversion film 15b is configured to receive light 23 emitted through the extended emission surface 22 and convert at least a portion of the received emitted light 23 into blue light 10b. Furthermore, the green light conversion film 15g is configured to receive light 23 emitted through the extended emission surface 22 and convert at least a portion of the received emitted light 23 into green light 10g. Similarly, the red light conversion film 15r is configured to receive light 23 emitted through the extended emission surface 22 and convert at least a portion of the received emitted light 23 into red light 10r.

[0033] The backlight 200 also includes an optical film 30. The optical film 30 is disposed between the display panel 40 and one or more light conversion films 15. Figure 1 In the illustrated embodiments, the optical film 30 is disposed on the red light conversion film 15r, the green light conversion film 15g, and the blue light conversion film 15b. In some embodiments, the optical film 30 is bonded to one or more light conversion films 15 via a first adhesive layer 70.

[0034] In some embodiments, the backlight 200 further includes an optical diffuser 80 disposed on the optical film 30 opposite to one or more light conversion films 15. In some embodiments, the optical film 30 is bonded to the optical diffuser 80 via a second adhesive layer 71.

[0035] In some embodiments, the backlight 200 further includes a first prism film 90. The first prism film 90 is disposed on the optical film 30 opposite to one or more light conversion films 15. The first prism film 90 includes a plurality of first prisms 91. In some embodiments, the plurality of first prisms 91 extend along substantially the same first longitudinal direction. In some embodiments, the first longitudinal direction extends along the y-axis.

[0036] In some embodiments, the backlight 200 further includes a second prism film 92 disposed on the first prism film 90 opposite to the optical film 30. The second prism film 92 includes a plurality of second prisms 93. The plurality of second prisms 93 extend along a substantially identical second longitudinal direction different from the first longitudinal direction. In some embodiments, the second longitudinal direction extends along the x-axis.

[0037] In some embodiments, the optical diffuser 80 is disposed between the first prism film 90 and the optical film 30. In some embodiments, the optical diffuser 80 is bonded to the first prism film 90 via a third adhesive layer 72.

[0038] exist Figure 1 In the illustrated embodiments, the backlight 200 further includes a reflective polarizer 100 disposed on the optical film 30 opposite to one or more light conversion films 15. In some embodiments, the reflective polarizer 100 is bonded to the display panel 40 via a fourth adhesive layer 73. In some embodiments, each of the first adhesive layer 70, the second adhesive layer 71, the third adhesive layer 72, and the fourth adhesive layer 73 may comprise an optically clear adhesive (OCA).

[0039] Figure 2A This is a detailed schematic cross-sectional view of the optical film 30 according to an embodiment of the present disclosure.

[0040] The optical film 30 includes a plurality of polymer layers 43. The total number of the plurality of polymer layers 43 is at least 10. In some embodiments, the total number of the plurality of polymer layers 43 is 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. Each polymer layer of the polymer layers 43 has an average thickness of less than about 500 nanometers (nm). As used herein, the term "average thickness t" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) of each polymer layer of the plurality of polymer layers 43. In some embodiments, each polymer layer of the polymer layers 43 has an average thickness t of less than about 400 nm, less than about 300 nm, or less than about 200 nm.

[0041] In some embodiments, the plurality of polymer layers 43 includes a plurality of alternating first polymer layers 31 and second polymer layers 32. The plurality of alternating first polymer layers 31 and second polymer layers 32 are stacked along the thickness direction of the optical film 30. In some embodiments, the thickness direction extends substantially along the z-axis. In some embodiments, the total number of the plurality of alternating first polymer layers 31 and second polymer layers 32 is at least 10. In some embodiments, the total number of the plurality of alternating first polymer layers 31 and second polymer layers 32 is 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 some embodiments, each of the first polymer layer 31 and second polymer layer 32 has an average thickness of less than about 500 nm. In some embodiments, each of the first polymer layer 31 and second polymer layer 32 has an average thickness of less than about 400 nm, less than about 300 nm, or less than about 200 nm.

[0042] In some embodiments, the optical film 30 further includes at least one surface layer 33 disposed on a plurality of polymer layers 43. In some embodiments, the at least one surface layer 33 has an average thickness st greater than about 500 nm. As used herein, the term "average thickness st" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) of each of the at least one surface layer 33. In some embodiments, the at least one surface layer 33 has an average thickness st greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0043] exist Figure 2AIn the illustrated embodiment, at least one surface layer 33 comprises a pair of surface layers 33, and a polymer layer 43 is disposed between the pair of surface layers 33. At least one surface layer 33 protects the polymer layer 43 and also provides mechanical stability to the optical film 30. In some cases, at least one surface layer 33 may act as a protective boundary layer (PBL).

[0044] Figure 2A A substantially collimated incident light 34 is further illustrated 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 α1. The first incident angle α1 is less than about 10 degrees. In some embodiments, the first incident angle α1 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 α1 is about 0 degrees.

[0045] In some embodiments, substantially collimated incident light 34 is incident on optical film 30 at a second incident angle α2. The second incident angle α2 is not less than about 40 degrees. In some embodiments, the second incident angle α2 is not less than about 45 degrees, not less than about 50 degrees, not less than about 55 degrees, or not less than about 60 degrees. In some embodiments, the second incident angle α2 is about 60 degrees.

[0046] Figure 2B This is a detailed schematic cross-sectional view of a reflective polarizer 100 according to an embodiment of the present disclosure.

[0047] In some embodiments, the reflective polarizer 100 includes a plurality of polymer microlayers 143. The total number of the plurality of polymer microlayers 143 is at least 10. In some embodiments, the total number of the plurality of polymer microlayers 143 is at least 20, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, at least 300, or at least 400. In some embodiments, each polymer microlayer of the polymer microlayers 143 has an average thickness t1 of less than about 500 nm. As used herein, the term "average thickness t1" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) of each polymer microlayer of the plurality of polymer microlayers 143. In some embodiments, each polymer microlayer of the polymer microlayers 143 has an average thickness t1 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.

[0048] In some embodiments, the plurality of polymer microlayers 143 include a plurality of alternating first polymer microlayers 131 and second polymer microlayers 132. The plurality of alternating first polymer microlayers 131 and second polymer microlayers 132 are stacked along the thickness direction of the reflective polarizer 100. In some embodiments, the total number of the plurality of alternating first polymer layers 131 and second polymer layers 132 is at least 10. In some embodiments, the total number of the plurality of alternating first polymer layers 131 and second polymer layers 132 is 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 some embodiments, each of the first polymer layer 131 and second polymer layer 132 has an average thickness of less than about 500 nm. In some embodiments, each of the first polymer layer 131 and second polymer layer 132 has an average thickness of less than about 400 nm, less than about 300 nm, or less than about 200 nm.

[0049] In some embodiments, the reflective polarizer 100 further includes at least one surface layer 133 disposed on a plurality of polymer microlayers 143. In some embodiments, the at least one surface layer 133 has an average thickness st1 greater than about 500 nm. As used herein, the term "average thickness st1" refers to the average thickness measured at multiple points across a plane (i.e., the xy plane) of each of the at least one surface layer 133. In some embodiments, the at least one surface layer 133 has an average thickness st1 greater than about 750 nm, greater than about 1000 nm, greater than about 1500 nm, or greater than about 2000 nm.

[0050] exist Figure 2B In the illustrated embodiment, at least one surface layer 133 comprises a pair of surface layers 133, and a polymer microlayer 143 is disposed between the pair of surface layers 133. At least one surface layer 133 protects the polymer microlayer 143 and also provides mechanical stability to the reflective polarizer 100. In some cases, at least one surface layer 133 may act as a protective boundary layer (PBL).

[0051] Figure 2B A further example is a substantially perpendicular incident light 35 incident on the reflective polarizer 100, that is, light 35 is incident on the reflective polarizer 100 at an angle of 0 degrees relative to the normal of the reflective polarizer 100.

[0052] Figure 3 This is a schematic exploded view of a display system 400 according to another embodiment of this disclosure.

[0053] Display system 400 is basically similar to Figure 1The display system 300 includes the same components indicated by the same reference numerals. However, the display system 400 includes a backlight 205 and a display panel 40.

[0054] The backlight 205 is basically similar. Figure 1 The backlight 200, wherein the same elements are indicated by the same reference numerals. However, the configuration of one or more light conversion films 15 of the backlight 205 is similar to... Figure 1 The configurations of one or more light conversion films in the backlight 200 shown are different. Specifically, in Figure 3 In the illustrated embodiment, the backlight 205 includes one or more green light conversion films 15g and red light conversion films 15r that extend substantially together with the display panel 40 in length and width. However, the backlight 205 does not include a blue light conversion film 15b. Figure 1 (As shown in the diagram). Furthermore, the backlight 205 includes an extended illumination source 121. The extended illumination source 121 is substantially similar to... Figure 1 The extended illumination source 21 is shown. However, the blue light conversion material 16b is disposed near one or more light sources 20. Specifically, the display system 400 includes the blue light conversion material 16b, which is disposed near one or more light sources 20 and surrounds at least 50% of the emitting surface 20a of the one or more light sources. In some embodiments, the display system 400 surrounds 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 emitting surface 20a of the one or more light sources 20. Specifically, the backlight 205 includes the blue light conversion material 16b, which is disposed near one or more light sources 20 and surrounds at least 50% of the emitting surface 20a of the one or more light sources. In some embodiments, the blue light conversion material 16b comprises phosphor, and one or more green light conversion films 15g and red light conversion films 15r comprise quantum dots.

[0055] Furthermore, as discussed above, one or more light sources 20 are configured to emit emitted violet light 23. Blue light conversion 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 into blue light 10b. In some embodiments, blue light conversion 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.

[0056] exist Figure 3In the illustrated embodiment, the light guide 24 may also receive blue light 10b. In this case, light 24a may be interchangeably referred to as "blue light 24a". The received blue light 24a propagates along the length and width of the light guide 24. The received blue light 24a propagates in the light guide 24 as propagating light 24b.

[0057] In addition, Figure 3 In the illustrated embodiment, the optical film 30 is disposed between the display panel 40 and one or more green light conversion films 15g and red light conversion films 15r, and extends substantially together with the display panel and the one or more green light conversion films and red light conversion films in length and width.

[0058] Figure 4 According to the description of the embodiments of this disclosure, for substantially collimated incident light 34 (incident at different incident angles) Figure 2A The optical film 30 shown in the figure Figure 1 , Figure 2A and Figure 3 The graph 500 shows the relationship between optical reflectivity and wavelength (as shown in the figure). The graph 500 further depicts the relationship between optical reflectivity and wavelength from one or more light sources 20 (as shown in the figure). Figure 1 and Figure 3 The emission spectrum of the emitted light 23 (shown in the figure) is related to its wavelength. Graph 500 further depicts the relationship between the emission spectrum and wavelength. Figure 1 The emission spectra of the blue light conversion film 15b, green light conversion film 15g, and red light conversion film 15r shown are related to wavelength. The emission spectrum of the blue light conversion film 15b is similar to that of the blue light conversion material 16b.

[0059] Wavelength is expressed in nanometers (nm) on the horizontal axis. Optical reflectivity is expressed as a percentage (R%) on the left vertical axis, while emission intensity is expressed in arbitrary units (au) on the right vertical axis.

[0060] Graph 500 includes curve 50 (shown by dashed lines) depicting the blue emission spectrum 50b, green emission spectrum 50g, and red emission spectrum 50r of one or more light conversion films 15. Specifically, one or more light conversion films 15 have a blue emission spectrum 50b, a green emission spectrum 50g, and a red emission spectrum 50r, which have corresponding blue peak 51b, green peak 51g, and red peak 51r at corresponding blue peak wavelength 52b, green peak wavelength 52g, and red peak wavelength 52r, and corresponding non-overlapping full width at half maximum (FWHM) 53b, green FWHM 53g, and red FWHM 53r. As described above, the emission spectrum of the blue light conversion film 15b is similar to the emission spectrum of the blue light conversion material 16b. Therefore, the blue light conversion material 16b has a blue emission spectrum 50b.

[0061] Specifically, the blue light emission spectrum 50b has a blue light peak 51b at the blue light peak wavelength 52b, the green light emission spectrum 50g has a green light peak 51g at the green light peak wavelength 52g, and the red light emission spectrum 50r has a red light peak 51r at the red light peak wavelength 52r. Furthermore, the blue light emission spectrum 50b has a blue light FWHM 53b, the green light emission spectrum 50g has a green light FWHM 53g, and the red light emission spectrum 50r has a red light FWHM 53r. Moreover, the blue light FWHM 53b, green light FWHM 53g, and red light FWHM 53r are non-overlapping.

[0062] In some implementations, the peak wavelength of blue light 52b is between approximately 420 nm and approximately 480 nm. Figure 4 In the illustrated example, the peak blue light wavelength 52b is approximately 452 nm. In some implementations, the blue light FWHM 53b is set within a blue light wavelength range extending from approximately 420 nm to approximately 480 nm. Figure 4 In the illustrated examples, the blue light 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 wide or at least 15 nm wide. 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 wide, less than about 40 nm wide, less than about 35 nm wide, less than about 30 nm wide, less than about 25 nm wide, or less than about 20 nm wide. Figure 4 In the example shown, the blue FWHM 53b is approximately 17 nm wide.

[0063] In some implementations, the peak wavelength of the green light, 52g, is between approximately 490 nm and approximately 560 nm. Figure 4 In the illustrated example, the peak green light wavelength 52g is approximately 527 nm. In some embodiments, the green light FWHM 53g is set within a green light wavelength range extending from approximately 490 nm to approximately 560 nm. Figure 4 In the illustrated examples, the green light 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 wide, at least 15 nm wide, 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 wide, less than about 40 nm wide, less than about 35 nm wide, less than about 30 nm wide, or less than about 25 nm wide. Figure 4In the example shown, the green FWHM 53g is approximately 21 nm wide.

[0064] In some implementations, the peak wavelength of the red light 52r is between approximately 590 nm and approximately 670 nm. Figure 4 In the illustrated example, the peak red light wavelength 52r is approximately 627 nm. In some embodiments, the red FWHM 53r is set within a red light wavelength range extending from approximately 590 nm to approximately 670 nm. Figure 4 In the illustrated examples, the red light wavelength range extends from about 607 nm to about 648 nm. In some embodiments, the red light FWHM 53r is at least 5 nm wide. In some embodiments, the red light FWHM 53r is at least 10 nm wide, at least 15 nm wide, at least 20 nm wide, at least 25 nm wide, at least 30 nm wide, at least 35 nm wide, or at least 40 nm wide. In some embodiments, the red light FWHM 53r is less than about 80 nm wide. In some embodiments, the red light FWHM 53r is less than about 75 nm wide, less than about 70 nm wide, less than about 65 nm wide, less than about 60 nm wide, less than about 55 nm wide, less than about 50 nm wide, or less than about 45 nm wide. Figure 4 In the example shown, the red FWHM 53r is approximately 41 nm wide.

[0065] As is evident from curve 500, the green FWHM 53g is positioned between the blue FWHM 53b and the red FWHM 53r. Correspondingly, the blue 10b, green 10g, and red 10r... Figure 1 The blue, green, and red light wavelengths (shown in the diagram) are set in the corresponding blue FWHM 53b, green FWHM 53g, and red FWHM 53r. Specifically, the blue light wavelength of blue 10b is set in blue FWHM 53b, the green light wavelength of green 10g is set in green FWHM 53g, and the red light wavelength of red 10r is set in red FWHM 53r.

[0066] In addition, refer to Figures 1 to 4 The graph 500 includes a curve 51 (shown by a dashed line) depicting the emission spectrum 50v of the emitted light 23 from one or more light sources 20. Specifically, the emitted light 23 has an emission spectrum 50v with an emission peak 51v at an emission peak wavelength 52v and a corresponding emission FWHM 53v.

[0067] As discussed above, light 23 is violet light 23. In this case, the emission spectrum 50v is interchangeably referred to as the "violet spectrum 50v", the emission peak 51v is interchangeably referred to as the "violet peak 51v", the emission peak wavelength 52v is interchangeably referred to as the "violet peak wavelength 52v", and the corresponding emission FWHM 53v is interchangeably referred to as the "corresponding violet FWHM 53v". Therefore, the emitted violet light 23 has a violet spectrum 50v, which has a violet peak 51v at the violet peak wavelength 52v and a corresponding violet FWHM 53v.

[0068] In some embodiments, the emission peak wavelength 52V is at least 10 nm smaller than the blue light peak wavelength 52B. In some embodiments, the emission peak wavelength 52V is 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 smaller than the blue light peak wavelength 52B. Figure 4 In the illustrated example, the emission peak wavelength 52v is approximately 43 nm smaller than the blue light peak wavelength 52b. In some embodiments, the emission peak wavelength 52v is less than approximately 420 nm. Figure 4 In the example shown, the peak emission wavelength 52V is approximately 409nm.

[0069] In some embodiments, the emitter FWHM 53v is less than about 50 nm wide. In some embodiments, the emitter FWHM 53v is less than about 45 nm wide, less than about 40 nm wide, less than about 35 nm wide, less than about 30 nm wide, or less than about 25 nm wide. In some embodiments, the emitter FWHM 53v is at least about 5 nm wide. In some embodiments, the emitter FWHM 53v is at least about 10 nm wide or at least about 15 nm wide. Figure 4 In the illustrated example, the emission FWHM 53v is extended from approximately 399 nm to approximately 419 nm. Therefore, in Figure 4 In the illustrated example, the emitted FWHM 53v is approximately 20 nm wide. In some implementations, the emitted FWHM 53v does not overlap with the blue FWHM 53b.

[0070] Table 1 below summarizes the emission spectrum 50V, emission peak 51V, emission peak wavelength 52V of the light 23 emitted from one or more light sources 20, the blue light emission spectrum 50b, blue light peak 51b, blue light peak wavelength 52b of the blue light conversion film 15b, the green light emission spectrum 50g, green light peak 51g, green light peak wavelength 52g of the green light conversion film 15g, and the red light emission spectrum 50r, red light peak 51r, red light peak wavelength 52r of the red light conversion film 15r.

[0071]

[0072] Graph 500 also includes curve 30a, which depicts the substantially collimated incident light 34 (incident at a first incident angle a1). Figure 2A (As shown in the diagram) and the optical reflectivity of the optical film 30 for each of the mutually orthogonal in-plane first polarization state and in-plane second polarization state. 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 the p-polarization state, and the second polarization state may correspond to the s-polarization state.

[0073] refer to Figure 2A and Figure 4 As is evident from curve 30a, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance greater than approximately 20% and less than approximately 80% for the wavelength across the emission FWHM 53v at the first incident angle α1. In other words, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance greater than approximately 20% and less than approximately 80% for the wavelength across the violet FWHM 53v at the first incident angle α1.

[0074] In some embodiments, for substantially collimated incident light 34 and for a first polarization state and a second polarization state, the optical film 30 has an average optical reflectivity for a first incident angle α1 that is 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% across the emission FWHM 53v wavelength. Figure 4 In the illustrated example, for substantially collimated incident light 34 and for the first polarization state and the second polarization state, the optical film 30 has an average optical reflectivity of about 65% for the first incident angle a1 across the emission FWHM 53v wavelength.

[0075] Therefore, for both the first and second polarization states of the emission FWHM 53v, the optical film 30 can substantially reflect the substantially collimated incident light 34 incident at the first incident angle a1. Thus, the optical film 30 can substantially reflect the emitted light 23 incident at the first incident angle a1.

[0076] Furthermore, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance of less than about 25% for the first incident angle a1 across the wavelengths of each of the blue FWHM 53b, green FWHM 53g, and red FWHM 53r. Specifically, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance of less than about 25% for the wavelength of blue FWHM 53b; for the wavelength of green FWHM 53g; and for the wavelength of red FWHM 53r, it has an average optical reflectance of less than about 25% for the first incident angle a1.

[0077] exist Figure 4 In the illustrated example, for substantially collimated incident light 34 incident at a first incident angle a1 and for a first polarization state and a second polarization state, the optical film 30 has an average optical reflectance of about 15.8% across the wavelength of blue light FWHM 53b; an average optical reflectance of about 13.7% across the wavelength of green light FWHM 53g; and an average optical reflectance of about 11.1% across the wavelength of red light FWHM 53r.

[0078] Therefore, for the first and second polarization states of blue FWHM 53b, green FWHM 53g, and red FWHM 53r, the optical film 30 can substantially transmit substantially collimated incident light 34 incident at a first incident angle a1. Thus, the optical film 30 can substantially transmit blue light 10b, green light 10g, and red light 10r incident at the first incident angle a1.

[0079] Furthermore, according to reference curve 30a, for substantially collimated incident light 34 incident at a first incident angle a1 and for the first polarization state and the second polarization state, the optical film 30 is more optically reflective across emission FWHM 53v than across blue FWHM 53b, green FWHM 53g and red FWHM 53r.

[0080] Graph 500 also includes curve 30b, which depicts the incident light 34 (which is substantially collimated and incident at 20 degrees) Figure 2A (as shown in the figure) and the optical reflectivity of the optical film 30 for each of the mutually orthogonal in-plane first polarization state and in-plane second polarization state.

[0081] As is evident from curve 30b, for substantially collimated incident light 34 incident at 20 degrees and for both the first and second polarization states, the optical film 30 has an average optical reflectance of approximately 44.3% across the wavelength of emitted FWHM 53v. Furthermore, for substantially collimated incident light 34 incident at 20 degrees and for both the first and second polarization states, the optical film 30 has an average optical reflectance of approximately 14.8% across the wavelength of blue FWHM 53b; approximately 11.1% across the wavelength of green FWHM 53g; and approximately 9.7% across the wavelength of red FWHM 53r.

[0082] Graph 500 also includes curve 30c, which depicts the substantially collimated incident light 34 (incident at a second incident angle a2). Figure 2A (as shown in the diagram) and the optical reflectivity of the optical film 30 for each of the mutually orthogonal in-plane first polarization state and in-plane second polarization state. Graph 500 also includes curve 30d, which depicts the optical reflectivity for substantially collimated incident light 34 incident at a second incident angle a2. Figure 2A (as shown in the diagram) and the optical reflectivity of the optical film 30 for each of the mutually orthogonal in-plane first polarization state and in-plane second polarization state. Figure 4 In the example shown, for curve 30c, the second angle of incidence a2 is about 40 degrees, and for curve 30d, the second angle of incidence a2 is about 60 degrees.

[0083] As is evident from curves 30c and 30d, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance of less than about 20% for the second incident angle a2 across the emission FWHM 53v wavelength. In some embodiments, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance of less than about 15%, less than about 10%, or less than about 5% for the second incident angle a2 across the emission FWHM 53v wavelength.

[0084] exist Figure 4 In the illustrated example, for substantially collimated incident light 34 and for the first polarization state and the second polarization state, the optical film 30 has an average optical reflectance of about 13.2% for a second incident angle a2 of about 40 degrees across the emission FWHM 53v wavelength, and an average optical reflectance of about 2% for a second incident angle a2 of about 60 degrees.

[0085] Furthermore, as is evident from curves 30c and 30d, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has an average optical reflectance of less than about 10% for the second incident angle a2 across the wavelengths of each of the blue FWHM 53b, green FWHM 53g, and red FWHM 53r. In some embodiments, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 has 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 across the wavelengths of each of the blue FWHM 53b, green FWHM 53g, and red FWHM 53r.

[0086] Furthermore, as evident from curve 30c, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 exhibits average optical reflectances of approximately 8.2%, 5.8%, and 5.6% respectively for a second incident angle a2 of approximately 40 degrees across the wavelengths of blue FWHM 53b, green FWHM 53g, and red FWHM 53r. Furthermore, as evident from curve 30d, for substantially collimated incident light 34 and for both the first and second polarization states, the optical film 30 exhibits average optical reflectances of approximately 1.1%, 0.5%, and 0.6% respectively for a second incident angle a2 of approximately 60 degrees across the wavelengths of blue FWHM 53b, green FWHM 53g, and red FWHM 53r.

[0087] Referring to curves 30c and 30d, for substantially collimated incident light 34 incident at a second incident angle a2 and for the first and second polarization states, the optical film 30 is more optically reflective across emission FWHM 53v than across blue FWHM 53b, green FWHM 53g, and red FWHM 53r.

[0088] Table 2 below summarizes the results for substantially collimated incident light incident at different incident angles 34 ( Figure 2A The average optical transmittance of the optical film 30 (as shown in the figure) and across different wavelength ranges (e.g., emitting FWHM 53v, blue FWHM 53b, green FWHM 53g, and red FWHM 53r).

[0089]

[0090] Where T30(0) refers to the average optical transmittance of optical film 30 at an incident angle of approximately 0 degrees; T30 (20) refers to the average optical transmittance of optical film 30 at an incident angle of approximately 20 degrees; T30 (40) refers to the average optical transmittance of optical film 30 at an incident angle of approximately 40 degrees; and T30 (60) refers to the average optical transmittance of optical film 30 at an incident angle of approximately 60 degrees.

[0091] Table 3 below summarizes the results for substantially collimated incident light incident at different incident angles 34 ( Figure 2A (as shown in the figure) and the average optical reflectance of the optical film 30 across different wavelength ranges.

[0092]

[0093] R30(0) refers to the average optical reflectance of optical film 30 at an incident angle of approximately 0 degrees; R30 (20) refers to the average optical reflectance of optical film 30 at an incident angle of approximately 20 degrees; R30 (40) refers to the average optical reflectance of optical film 30 at an incident angle of approximately 40 degrees; and R30 (60) refers to the average optical reflectance of optical film 30 at an incident angle of approximately 60 degrees.

[0094] refer to Figure 1 , Figure 3 and Figure 4 In some embodiments, the optical diffuser 80 has a diffuse optical transmittance greater than about 30% for each of the blue light peak wavelength 52b, the green light peak wavelength 52g, and the red light peak wavelength 52r, and a diffuse optical transmittance greater than about 10% for the emission peak wavelength 52v. In some embodiments, the optical diffuser 80 has a diffuse optical transmittance greater than about 35%, greater than about 40%, greater than about 45%, greater than about 50%, greater than about 55%, or greater than about 60% for each of the blue light peak wavelength 52b, the green light peak wavelength 52g, and the red light peak wavelength 52r, and a diffuse optical transmittance greater than about 15%, greater than about 20%, greater than about 25%, or greater than about 30% for the emission peak wavelength 52v.

[0095] refer to Figure 2B and Figure 4In some embodiments, for each of the substantially perpendicular incident light 35 and the blue light peak wavelength 52b, green light peak wavelength 52g, and red light peak wavelength 52r, the plurality of polymer microlayers 143 reflect more than about 60% of the incident light 35 having a first polarization state and transmit more than about 60% of the incident light 35 having a second polarization state. In some embodiments, for each of the substantially perpendicular incident light 35 and the blue light peak wavelength 52b, green light peak wavelength 52g, and red light peak wavelength 52r, the plurality of polymer microlayers 143 reflect more than about 70%, more than about 80%, or more than about 90% of the incident light 35 having a first polarization state and transmit more than about 70%, more than about 80%, or more than about 90% of the incident light 35 having a second polarization state.

[0096] refer to Figures 1 to 4 One or more light conversion films 15 may have better efficiency in converting light 23 (i.e., having an emission spectrum 50V in the violet wavelength range) into blue light 10b, green light 10g, and red light 10r than in converting light in the blue wavelength range into blue light 10b, green light 10g, and red light 10r. Furthermore, as discussed above, one or more light conversion films 15 may contain quantum dot materials. Quantum dot materials can exhibit a much higher absorption rate for light 23 than light in the blue wavelength range emitted by blue LEDs in conventional display systems. Therefore, the amount of quantum dot material required for converting light 23 can be substantially less than the amount required for converting light in the blue wavelength range. This reduces the cost of one or more light conversion films 15 in the backlights 200, 205. Additionally, an optical film 30 disposed on one or more light conversion films 15 can reduce the amount of light 23 reaching the viewer's eyes. Specifically, the optical film 30 can reflect a portion of the light 23 that is not absorbed by the quantum dot material to reduce the amount of light 23 reaching the viewer's eyes.

[0097] Unless otherwise stated, all figures used in the specification and claims to indicate feature dimensions, quantities, and physical properties should be understood to be modified by the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations and can vary according to the desired properties sought by those skilled in the art using the teachings disclosed herein.

[0098] While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be used in place of the illustrated and described embodiments without departing from the scope of this disclosure. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. A backlight source for providing illumination to a display panel configured to display an image, the backlight source comprising: An extended illumination source includes one or more light sources and an extended emitting surface and is configured to emit light toward the display panel through the extended emitting surface, the emitted light having an emission spectrum having an emission peak at the emission peak wavelength and a corresponding emission full width at half maximum (FWHM). One or more light conversion films are disposed on the extended emitting surface of the extended illumination source and have blue light emission spectra, green light emission spectra, and red light emission spectra. The blue light emission spectrum, the green light emission spectrum, and the red light emission spectrum have corresponding blue light peaks, green light peaks, and red light peaks located at corresponding corresponding blue light peak wavelengths, green light peak wavelengths, and red light peak wavelengths, and corresponding non-overlapping blue light FWHMs, green light FWHMs, and red light FWHMs. The green light FWHM is disposed between the blue light FWHM and the red light FWHM. The one or more light conversion films are configured to receive light emitted through the extended emitting surface and convert at least a portion of the received emitted light into blue light, green light, and red light having corresponding blue light wavelengths, green light wavelengths, and red light wavelengths disposed in the corresponding blue light FWHM, green light FWHM, and red light FWHM. An optical film, disposed opposite to the extended emitting surface on one or more light conversion films, comprises at least 10 polymer layers, each polymer layer having an average thickness of less than about 500 nm, such that for substantially collimated incident light and for each of mutually orthogonal in-plane first polarization state and in-plane second polarization state, the optical film: For the wavelength across the emission FWHM, it has an average optical reflectivity greater than about 20% and less than about 80% for a first incident angle of less than about 10 degrees, and an average optical reflectivity less than about 20% for a second incident angle of not less than about 40 degrees; and For each of the blue FWHM, green FWHM and red FWHM wavelengths, the average optical reflectance is less than 25% for the first incident angle and less than about 10% for the second incident angle.

2. The backlight source according to claim 1, wherein the emission peak wavelength is at least 10 nm smaller than the blue light peak wavelength.

3. The backlight according to claim 1, wherein the emission peak wavelength is less than about 420 nm.

4. The backlight according to claim 1, wherein the emitting FWHM does not overlap with the blue light FWHM.

5. The backlight source according to claim 1, wherein the one or more light conversion films comprise: A blue light conversion film, the blue light conversion film being configured to receive light emitted through the extended emitting surface and convert at least a portion of the received emitted light into blue light having the blue light wavelength disposed in the blue light FWHM; A green light conversion film, the green light conversion film being configured to receive light emitted through the extended emitting surface and convert at least a portion of the received emitted light into green light having the green light wavelength disposed in the green light FWHM; and A red light conversion film is configured to receive light emitted through the extended emitting surface and convert at least a portion of the received emitted light into red light having the red light wavelength disposed in the red light FWHM.

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

7. The backlight according to claim 1, further comprising: A first prism film is disposed on the optical film opposite to the one or more light conversion films and includes a plurality of first prisms extending along substantially the same first longitudinal direction.

8. The backlight according to claim 1, further comprising: A reflective polarizer disposed on the optical film opposite to the one or more light conversion films and comprising a plurality of polymer microlayers totaling at least 10, each of the polymer microlayers having an average thickness of less than about 500 nm, such that for substantially perpendicular incident light and each of the blue light peak wavelength, the green light peak wavelength, and the red light peak wavelength, the plurality of polymer microlayers reflect more than about 60% of the incident light having an in-plane first polarization state and transmit more than about 60% of the incident light having an in-plane orthogonal second polarization state.

9. A display system, the display system comprising: A display panel is disposed on a backlight according to claim 1 and configured to receive light emitted through the extended emitting surface and display an image, wherein the optical film is disposed between the display panel and the one or more light conversion films.

10. A display system, the display system comprising: One or more light sources are configured to emit violet light, the emitted violet light having a violet light spectrum having a violet light peak at the violet light peak wavelength and a corresponding violet light full width at half maximum (FWHM). A blue light conversion material is disposed close to and surrounds at least 50% of the emitting surface of the one or more light sources, and has a blue light emission spectrum having a blue light peak at a corresponding blue light peak wavelength and a corresponding blue light FWHM. The blue light conversion 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 into blue light having a blue light wavelength set in the blue light FWHM. Display panel; One or more green and red light conversion films, the one or more green and red light conversion films extending substantially co-existing with the display panel in length and width and having green light emission spectra and red light emission spectra, the green light emission spectra and the red light emission spectra having corresponding green light peaks and red light peaks located at corresponding corresponding green light peak wavelengths and red light peak wavelengths, and corresponding non-overlapping green light FWHMs and red light FWHMs, the one or more green and red light conversion films being configured to receive blue light from the blue light conversion material and convert at least a portion of the received blue light into green light and red light having corresponding green light wavelengths and red light wavelengths disposed in the corresponding green light FWHMs and red light FWHMs; and An optical film is disposed between the display panel and the one or more green and red light conversion films, and extends substantially together with the display panel and the one or more green and red light conversion films in length and width, and comprises a plurality of polymer layers totaling at least 10, each of the polymer layers having an average thickness of less than about 500 nm. Such that, for substantially collimated incident light and for each of the mutually orthogonal in-plane first polarization state and in-plane second polarization state, the optical film: For wavelengths across the violet FWHM, it has an average optical reflectance 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 not less than about 40 degrees; and For each of the blue FWHM, green FWHM and red FWHM wavelengths, the average optical reflectance is less than 25% for the first incident angle and less than about 10% for the second incident angle.

Images