Optical film, backlight source and display system

Abstract

A backlight includes an illumination system and an optical film. The illumination system is configured to emit light from its emission surface. The emitted light includes at least red light including a red emission spectrum including a first red emission peak at a first red peak wavelength, the total red width at maximum 70% at the first red peak wavelength being FWr1. The optical film disposed on the red light emitting element includes at least one spacer layer disposed between a plurality of first layers and a plurality of second layers. For substantially vertical incident light, and for a first polarization state, an optical transmittance of the optical film with respect to wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600 nm, the total red-infrared width at maximum 70% at the first red-infrared peak wavelength being FWri1. The red-infrared peak wavelength is at least 10 nm greater than the red peak wavelength, and FWri1 / FWr1 > = 7.

Description

Technical Field

[0001] The present disclosure relates generally to an optical film, and particularly to a display system and a backlight including the optical film. Background Art

[0002] Typically, a backlight source may provide illumination to a display panel configured to display an image on a display device such as a handheld device. Today, the display panel of a handheld device may require functions such as an under-display fingerprint sensing function. However, the use of a prismatic film in a display device may distort the fingerprint image and may negatively affect the under-display fingerprint sensing function. Summary of the invention

[0003] In a first aspect, the present disclosure provides a backlight source for providing illumination to a display panel configured to display an image. The backlight source includes an illumination system configured to emit light from its emitting surface. The emitted light includes at least red light, the red light includes a red emission spectrum, the red emission spectrum includes a first red emission peak at a first red peak wavelength, and the red full width at 70% of the maximum value at the first red peak wavelength is FWr1. The backlight source also includes an optical film disposed on a red light-emitting element. The optical film includes at least one spacer layer disposed between a plurality of first layers and a plurality of second layers. The total number of the first layer and the second layer is at least 10. Each of the first layer and the second layer has an average thickness of less than about 500nm. Each of the at least one spacer layer has an average thickness of at least about 5 microns. For substantially vertical incident light, and for at least a first polarization state, the optical transmittance of the optical film relative to wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600 nm, and the red-infrared full width at 70% of the maximum value at the first red-infrared peak wavelength is FWri1. The red-infrared peak wavelength is at least 10 nm greater than the red peak wavelength, and FWri1 / FWr1≥7.

[0004] In a second aspect, the present disclosure provides a backlight source for providing illumination to a display panel configured to display an image. The backlight source includes an illumination system configured to emit light from its emitting surface. The emitted light includes at least red light, the red light includes a red emission spectrum, the red emission spectrum includes a first red emission peak at a first red peak wavelength, and the red full width at 70% of the maximum value at the first red peak wavelength is FWr1. The backlight source also includes an optical film disposed on a red light-emitting element. The optical film includes at least one spacer layer disposed between a plurality of first layers and a plurality of second layers. The total number of the first layer and the second layer is at least 10. Each of the first layer and the second layer has an average thickness of less than about 500nm. Each of the at least one spacer layer has an average thickness of at least about 5 microns. For incident light incident on the optical film at an incident angle greater than about 15 degrees, and for at least a first polarization state, the optical transmittance of the optical film relative to wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600 nm, and the red-infrared full width at 50% of the maximum value at the first red-infrared peak wavelength is FW'2. The red-infrared full width FW'2 at 50% of the maximum value at the first red-infrared peak wavelength completely covers the red full width FWr1 at 70% of the maximum value at the first red peak wavelength. In addition, FW'2 / FWr1≥2.

[0005] In a third aspect, the present disclosure provides an optical film, the optical film comprising at least one spacer layer disposed between a plurality of first layers and a plurality of second layers. The total number of the first layer and the second layer is at least 50. Each of the first layer and the second layer has an average thickness of less than about 500nm. Each of the at least one spacer layer has an average thickness of at least about 5 microns. A scatter plot of the layer thickness of at least 30 first layers and second layers arranged and numbered in sequence relative to the layer number of the plurality of first layers and the plurality of second layers comprises a first group of scattered points and a remaining group of scattered points spaced along the thickness direction. The scattered points in the first group and the remaining group are located on a substantially straight first line and a second line, respectively. When the optical film is disposed on a substantially Lambertian light source emitting light, the light has a corresponding blue emission spectrum, a green emission spectrum, and a red emission spectrum, the corresponding blue emission spectrum, the green emission spectrum, and the red emission spectrum include corresponding blue peaks, green peaks, and red peaks, the corresponding blue full width, green full width, and red full width at 70% of the maximum values ​​at the corresponding blue peaks, green peaks, and red peaks are FWb1, FWg1, and FWr1, respectively, wherein FWb1 is at least 2 times greater than FWr1, and FWg1 is at least 5 times greater than FWr1, the optical film transmits the emitted light so that the transmitted light has a color shift relative to the emitted light, the color shift varies as a function of the transmission angle in a plane substantially perpendicular to the optical film, has a main color shift peak at a transmission angle of less than about 10 degrees, and a color shift platform region that is at least 5 degrees wide and located at a transmission angle of greater than about 2 degrees. The main color shift peak has a full width at 80% of the maximum value greater than about 1 degree, and the color shift across the color shift platform region varies with a standard deviation of less than about 0.5.

[0006] 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 become apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The exemplary embodiments disclosed herein may be more fully understood with reference to the following detailed description in conjunction with the accompanying drawings. The accompanying drawings are not necessarily drawn to scale. Like numbers used in the accompanying drawings refer to like components. However, it should be understood that the use of numbers to refer to components in a given figure is not intended to limit the components labeled with the same number in another figure.

[0008] Figure 1 shows a schematic cross-sectional exploded view of a display system according to one embodiment of the present disclosure;

[0009] Figure 2 A schematic cross-sectional view showing an optical film of a display system according to an embodiment of the present disclosure;

[0010] Figure 3shows a graph depicting optical transmittance of an optical film and each of a plurality of first layers and a plurality of second layers of the optical film with respect to wavelength for substantially normally incident light and for a first polarization state according to one embodiment of the present disclosure;

[0011] Figure 4 Shows Figure 3 an enlarged view of a portion of a graph of;

[0012] Figure 5 shows a graph depicting changes in layer profiles of a plurality of first layers and a plurality of second layers of an optical film according to an embodiment of the present disclosure;

[0013] Figure 6 An embodiment according to the present disclosure is shown Figure 5 an enlarged view of a portion of a graph depicting layer thicknesses of a set of first and second layers relative to layer numbers;

[0014] Figure 7 shows a graph depicting optical transmittance of an optical film for incident light incident at an angle of incidence and for at least a first polarization state according to another embodiment of the present disclosure;

[0015] Figure 8 Shows Figure 7 an enlarged view of a portion of a graph of;

[0016] Fig. 9 shows a schematic diagram of a substantially Lambertian light source and an optical film according to one embodiment of the present disclosure;

[0017] Fig.10 shows a graph depicting the color shift of transmitted light relative to emitted light as a function of transmission angle in a plane substantially perpendicular to the optical film according to one embodiment of the present disclosure;

[0018] Fig.11 shows a schematic diagram of a reflective polarizer according to one embodiment of the present disclosure; and

[0019] Fig.12 A schematic cross-sectional exploded view of a display system according to another embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0020] In the following description, reference is made to the accompanying drawings which form a part thereof, and in which various embodiments are shown by way of example. It should be understood that other embodiments may be conceived and made without departing from the scope or essence of the present disclosure. Therefore, the following specific embodiments should not be considered to have a limiting meaning.

[0021] In the following disclosure, the following definitions apply.

[0022] As used herein, all numbers should be considered to be modified by the term "about". As used herein, "a", "an", "said", "at least one" and "one or more" are used interchangeably.

[0023] As used herein, as a modifier of a characteristic or property, unless otherwise specifically defined, the term "substantially" means that the characteristic or property will be readily discernible by a person of ordinary skill without requiring absolute precision or a perfect match (e.g., within + / - 20% for quantifiable characteristics).

[0024] Unless specifically defined otherwise, the term "substantially" means a high degree of approximation (eg, within + / - 10% for a quantifiable characteristic), but again does not require an absolutely precise or perfect match.

[0025] Unless specifically defined otherwise, the term "about" means a close approximation (eg, within + / - 5% for a quantifiable property), but again does not require absolute precision or a perfect match.

[0026] As used herein, the terms "first" and "second" are used as identifiers. Therefore, such terms should not be understood as limitations on the present disclosure. Throughout the embodiments of the present disclosure, the terms "first" and "second" are interchangeable when used in conjunction with a feature or element.

[0027] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0028] As used herein, the term "layer" generally refers to a thickness of material having a relatively consistent chemical composition within a film. A layer can be any type of material, including polymers, cellulose, metals, or blends thereof. A given polymer layer can contain a single polymer type or a blend of polymers, and can be accompanied by additives. A given layer can be combined or connected with other layers to form a film. A layer can be partially continuous or completely continuous compared to adjacent layers or films. A given layer can be partially coextensive or completely coextensive with adjacent layers. A layer can contain sublayers.

[0029] As used herein, the term "band edge" refers to a portion of a light transmission spectrum where light transmission increases substantially steadily, or where light transmission decreases substantially steadily.

[0030] Typically, a backlight source may provide illumination to a display panel configured to display an image on a display device, such as a handheld device. Today, the display panel of a handheld device may require functions such as an under-display fingerprint sensing function. In order to implement the under-display fingerprint sensing function, a backlight source having infrared transmission properties and a collimation function may be required. However, the use of a prismatic film in the backlight source of a display device may distort the fingerprint image and may have a negative impact on the under-display fingerprint sensing function. Therefore, in some cases, an infrared transmission collimating film may be used to implement the under-display fingerprint sensing function while enhancing the brightness of the display panel.

[0031] Nowadays, high color gamut light emitting diode (LED) light sources are widely used in liquid crystal display (LCD) display devices. Compared with traditional LED light sources, high color gamut LED light sources usually have several sharp emission peaks. However, when used with high color gamut LED light sources, infrared transmission collimating films may cause serious color artifacts. Specifically, the sharp emission peaks of the high color gamut LED light source may be aligned with the spectral ringing in the transmission spectrum of the infrared transmission collimating film, and color banding artifacts may result. Therefore, the infrared transmission collimating film may be incompatible with the high color gamut LED light source.

[0032] Therefore, a suitable solution may be needed that can realize under-display fingerprint sensing function while being compatible with high color gamut LED light sources. Specifically, a solution may be needed that can provide infrared transmission and collimation functions while reducing or preventing severe color artifacts when used with high color gamut LED light sources.

[0033] The present disclosure relates to an optical film compatible with a lighting system to form a backlight source for providing illumination to a display panel configured to display an image. The present disclosure also relates to a display system, the display system comprising a display panel disposed on the backlight source. The display system may be a handheld device with an under-display fingerprint sensing function.

[0034] The backlight source includes an illumination system configured to emit light from its emitting surface. The emitted light includes at least red light, the red light includes a red emission spectrum, the red emission spectrum includes a first red emission peak at a first red peak wavelength, and the red full width at 70% of the maximum value at the first red peak wavelength is FWr1. The backlight source also includes an optical film, which is disposed on a red light-emitting element. The optical film includes at least one spacer layer disposed between a plurality of first layers and a plurality of second layers. The total number of the first layer and the second layer is at least 10. Each of the first layer and the second layer has an average thickness of less than about 500nm. Each of the at least one spacer layer has an average thickness of at least about 5 microns. For substantially vertical incident light, and for at least a first polarization state, the optical transmittance of the optical film relative to wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600nm, and the red-infrared full width at 70% of the maximum value at the first red-infrared peak wavelength is FWri1. The red-infrared peak wavelength is at least 10 nm greater than the red peak wavelength, and FWri1 / FWr1≥7.

[0035] Therefore, the first red-infrared transmittance peak of the red light and the first red emission peak may not overlap each other. Any substantial overlap between the first red-infrared transmittance peak of the red light and the first red emission peak may otherwise result in spectral ringing and may cause severe color artifacts. Therefore, a backlight including the optical film of the present disclosure can provide the infrared transmission and collimation functions while reducing or preventing the severe color artifacts.

[0036] Now referring to the accompanying drawings, Figure 1 is a schematic cross-sectional exploded view of a display system 300 according to one embodiment of the present disclosure.

[0037] 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 lateral axis disposed along the thickness of the display system 300. In other words, the x-axis and y-axis are disposed along the plane of the display system 300, while the z-axis is perpendicular to the plane of the display system 300.

[0038] The display system 300 includes a display panel 20 configured to display an image 21. The display panel 20 may include various elements, such as an electroluminescent panel, an incandescent or phosphorescent light source, a cathode ray tube (CRT), a light emitting diode (LED), a lens, a collimator, a reflector, and / or a polarizer. In some embodiments, the display panel 20 may include a liquid crystal display (LCD) panel. The image 21 may be substantially monochromatic, polychromatic, narrowband, or broadband, but preferably overlaps at least a portion of the visible spectrum.

[0039] The display system 300 also includes a backlight 200 for providing illumination 10 to a display panel 20 configured to display an image 21. The display panel 20 is disposed on the backlight 200 and is configured to receive the illumination 10 from the backlight 200 and display an image 21.

[0040] The backlight source 200 includes an illumination system 70. The illumination system 70 includes a red light emitting element 30r. In some embodiments, the illumination system 70 further includes a blue light emitting element 30b and a green light emitting element 30g. Figure 1 In the illustrated embodiment, the lighting system 70 has a backlight configuration. In some embodiments, the lighting system 70 may include a high color gamut LED light source. For example, the blue light emitting element 30b, the green light emitting element 30g, and the red light emitting element 30r may include a high color gamut LED light source. The lighting system 70 is configured to emit light 11 from its emitting surface 71. Figure 1 In the illustrated embodiment, the emitted light 11 of the illumination system 70 includes blue light 11b, green light 11g and red light 11r. Specifically, blue light 11b is emitted by the blue light emitting element 30b, green light 11g is emitted by the green light emitting element 30g, and red light 11r is emitted by the red light emitting element 30r.

[0041] The backlight source 200 further includes an optical film 40, which is disposed on the red light emitting element 30r. Figure 1 In the illustrated embodiment, the optical film 40 is disposed on the blue light emitting element 30b, the green light emitting element 30g, and the red light emitting element 30r.

[0042] In some embodiments, the backlight 200 further includes an optical diffuser 100 disposed between the optical film 40 and the illumination system 70 for at least one of diffusing the light 11 incident thereon and redirecting the light 11 incident thereon.

[0043] In some embodiments, the backlight 200 further includes a first prismatic film 110 disposed on the optical film 40 opposite to the illumination system 70 and including a plurality of first prisms 111 extending along a substantially same first longitudinal direction. In some embodiments, the backlight 200 further includes a second prismatic film 120 disposed on the first prismatic film 110 opposite to the optical film 40 and including a plurality of second prisms 121 extending along a substantially same second longitudinal direction different from the first longitudinal direction. However, in some other embodiments, the backlight 200 does not include any prismatic film for redirecting and recycling the light 11.

[0044] The plurality of first prisms 111 of the first prism film 110 may be substantially similar to the plurality of second prisms 121 of the second prism film 120. Figure 1In the illustrated embodiment, the plurality of first prisms 111 and the plurality of second prisms 121 include triangular prisms. However, in some other embodiments, the plurality of first prisms 111 and the plurality of second prisms 121 may include prisms of different shapes. Figure 1 In the illustrated embodiment, the first longitudinal direction is substantially along the y-axis, and the second longitudinal direction is substantially along the x-axis. In some embodiments, the first longitudinal direction and the second longitudinal direction are substantially orthogonal to each other.

[0045] In some embodiments, the backlight 200 further includes a reflective polarizer 130 disposed on the optical film 40 opposite to the illumination system 70. Figure 1 In the illustrated embodiment, the reflective polarizer 130 is disposed between the display panel 20 of the display system 300 and the second prism film 120 of the backlight 200 .

[0046] As discussed above, the display panel 20 is configured to receive illumination 10 from the backlight 200. Figure 1 In the illustrated embodiment, the display panel 20 receives illumination 10 from a reflective polarizer 130 of a backlight 200 .

[0047] Figure 2 A schematic cross-sectional view of an optical film 40 according to one embodiment of the present disclosure is illustrated.

[0048] The optical film 40 has one side 45a and an opposite side 45b. The optical film 40 includes at least one spacer layer 43, 44 disposed between the plurality of first layers 41 and the plurality of second layers 42. Figure 2 In the illustrated embodiment, the optical film 40 includes two spacer layers 43, 44 disposed between the plurality of first layers 41 and the plurality of second layers 42. However, in some other embodiments, the optical film 40 may include any number of spacer layers 43, 44 disposed between the plurality of first layers 41 and the plurality of second layers 42.

[0049] The total number of first layer 41 and second layer 42 is at least 10. In some embodiments, the total number of first layer 41 and second layer 42 is at least 25, at least 50, at least 100, at least 200, at least 300, at least 400, at least 500, or at least 600. In some embodiments, at least one spacer layer 43, 44 and first layer 41 and second layer 42 are coextruded and costretched.

[0050] In some embodiments, each of the first layer 41 and the second layer 42 has an average thickness TH1 of less than about 500 nanometers (nm). As used herein, the term "average thickness" refers to the average value of the thickness measured at multiple points across the plane (i.e., the xy plane) of each of the first layer 41 and the second layer 42. In some embodiments, each of the first layer 41 and the second layer 42 has an average thickness TH1 of less than about 400nm, less than about 300nm, or less than about 200nm.

[0051] In some embodiments, each of the at least one spacer layer 43, 44 has an average thickness TH2 of at least about 5 microns. As used herein, the term "average thickness" refers to the average value of the thickness measured at multiple points across the plane (i.e., xy plane) of each of the at least one spacer layer 43, 44. In some embodiments, each of the at least one spacer layer 43, 44 has an average thickness TH2 of at least about 10 microns, at least about 15 microns, at least about 20 microns, at least about 25 microns, at least about 30 microns, at least about 35 microns, at least about 40 microns, at least about 45 microns, or at least about 50 microns.

[0052] exist Figure 2 In the illustrated embodiment, the optical film 40 further includes an intermediate layer 46 disposed between the spacer layers 43, 44. However, in some other embodiments, the optical film 40 may not include any intermediate layer disposed between the spacer layers 43, 44.

[0053] In some embodiments, the optical film 40 further comprises at least one surface layer 47 having an average thickness TH3 greater than about 500 nm. In some embodiments, at least one surface layer 47 has an average thickness TH3 greater than about 750 nm, greater than 1000 nm, greater than about 1500 nm, or greater than about 2000 nm. Figure 2 In the illustrated embodiment, optical film 40 includes two skin layers 47. At least one skin layer 47 can protect first layer 41 and second layer 42, and can also provide mechanical stability to optical film 40. In some cases, at least one skin layer 47 can act as a protective boundary layer (PBL).

[0054] In some embodiments, the optical film 40 is configured to receive substantially normal incident light 12. In some embodiments, the optical film 40 receives incident light 13 at an incident angle α1 greater than about 15 degrees. Figure 2 In the illustrated embodiment, the optical film 40 receives incident light 13 at an incident angle al of about 30 degrees. In some embodiments, the incident angle al is greater than about 20 degrees, greater than about 25 degrees, or greater than about 30 degrees.

[0055] Figure 3and Figure 4 An example of a depiction optical film 40 (eg Figure 2 400 of optical transmittance relative to wavelength. Figure 4 An enlarged view of the graph 400 is illustrated for wavelengths from 580 nm to 740 nm. Specifically, the graph 400 depicts the wavelengths for substantially vertical incident light 12 (e.g., Figure 2 ) and the optical transmittance of the optical film 40 relative to the wavelength for at least a first polarization state. In some embodiments, at least the first polarization state is along the x-axis. In some other embodiments, at least the first polarization state is along the y-axis.

[0056] The graph 400 also depicts a plurality of first layers 41 and a plurality of second layers 42 (eg, Figure 2 The wavelength is expressed in nanometers (nm) on the horizontal axis. The optical transmittance is expressed as a transmittance percentage on the left vertical axis, while the emission intensity is expressed in arbitrary units (au) on the right vertical axis. The emission intensity in arbitrary units corresponds to the emission intensity of the illumination system 70 (e.g., Figure 1 The emitted light 11 (such as Figure 1 Emission spectra 31b, 31g, 31r shown).

[0057] The graph 400 includes a curve 50 depicting the optical transmittance of the optical film 40, a curve 56a depicting the optical transmittance of the plurality of first layers 41, and a curve 56b depicting the optical transmittance of the plurality of second layers 42. Figure 4 In the illustrated embodiment, some components of graph 400 (such as curves 56a, 56b) are not shown for illustrative purposes.

[0058] refer to Figures 1 to 4 As discussed above, the illumination system 70 is configured to emit light 11 from its emission surface 71. The emitted light 11 includes at least red light 11r, the red light including a red emission spectrum 31r, the red emission spectrum including a first red emission peak 32r at a first red peak wavelength 33r, the red full width at 70% of the maximum value at the first red peak wavelength is FWr1 34r (as shown in FIG. Figure 4 The red full width FWr1 at 70% of the maximum value is Figure 4 Indicated by 34r.

[0059] exist Figure 3 and Figure 4 In the illustrated embodiment, the first red peak wavelength 33r of the first red emission peak 32r is about 631 nm, and the red full width FWr1 32r at 70% of the maximum value is about 3 nm.

[0060] In some embodiments, the light 11 emitted from the emitting surface 71 of the illumination system 70 also includes blue light 11b having a blue emission spectrum 31b including a first blue emission peak 32b at a first blue peak wavelength 33b, and a blue full width at 70% of the maximum value at the first blue peak wavelength is FWb1 34b. Figure 3 In the illustrated embodiment, the first blue peak wavelength 33b of the first blue emission peak 32b is about 455 nm, and the blue full width FWb1 34b at 70% of the maximum value is about 12 nm. Figure 3 Indicated by 34b.

[0061] In some embodiments, the light 11 emitted from the emitting surface 71 of the illumination system 70 also includes green light 11g having a green emission spectrum 31g including a first green emission peak 32g at a first green peak wavelength 33g, and a green full width at 70% of the maximum value at the first green peak wavelength is FWg1 34g. Figure 3 In the illustrated embodiment, the first green peak wavelength 33g of the first green emission peak 32g is about 538nm, and the green full width FWg1 34g at 70% of the maximum value is about 38nm. Figure 3 Indicated by 34g.

[0062] In some embodiments, each of the blue full width FWb1 34b at 70% of the maximum value and the green full width FWg1 34g at 70% of the maximum value is at least 2 times the red full width FWr1 34r at 70%. In some embodiments, each of the blue full width FWb1 34b at 70% of the maximum value and the green full width FWg1 34g at 70% of the maximum value is at least 2.5 times, at least 3 times, at least 3.5 times, or at least 4 times the red full width FWr1 34r at 70%.

[0063] In some embodiments, the green full width FWg1 34g at 70% of the maximum value is at least 5 times the red full width FWr1 34r at 70% of the maximum value. In some embodiments, the green full width FWg1 34g at 70% of the maximum value is at least 6 times, at least 7 times, at least 8 times, at least 9 times, or at least 10 times the red full width FWr1 34r at 70% of the maximum value.

[0064] As depicted by curve 50, for substantially vertical incident light 12, and for at least a first polarization state, the optical transmittance of the optical film 40 with respect to wavelength has a first red-infrared transmittance peak 51ri at a first red-infrared peak wavelength 52ri greater than about 600nm, and the red-infrared full width at 70% of the maximum value at the first red-infrared peak wavelength is FWri153ri. The red-infrared full width at 70% of the maximum value FWri1 is Figure 4 In some embodiments, the first red-infrared peak wavelength 52ri is greater than about 610nm, greater than about 620nm, greater than about 630nm, greater than about 640nm, greater than about 650nm, or greater than about 660nm. Figure 3 and Figure 4 In the illustrated embodiment, the first red-infrared peak wavelength 52ri is about 666 nm, and the red-infrared full width FWri1 53ri at 70% of the maximum value is about 32 nm.

[0065] The first red-infrared peak wavelength 52ri is at least 10 nm greater than the first red peak wavelength 33r. In some embodiments, the first red-infrared peak wavelength 52ri is at least 15 nm, at least 20 nm, at least 25 nm, at least 30 nm, or at least 35 nm greater than the first red peak wavelength 33r. Figure 3 and Figure 4 In the illustrated embodiment, the first red-infrared peak wavelength 52ri is approximately 35 nm greater than the first red peak wavelength 33r. Therefore, the first red-infrared transmittance peak 51ri and the first red emission peak 32r of the red light 11r may not substantially overlap each other. Any substantial overlap may otherwise result in spectral ringing and may cause severe color artifacts. Therefore, the backlight 200 including the optical film 40 can provide infrared transmission and collimation functions while reducing or preventing severe color artifacts.

[0066] In addition, the relationship between FWri1 and FWr1 is given by the following formula: FWri1 / FWr1≥7. In other words, the red-infrared full width FWri1 53ri at 70% of the maximum value is a certain multiple of the red full width FWr1 34r at 70% of the maximum value, and the multiple is greater than or equal to 7. In some embodiments, the red-infrared full width FWri1 53ri at 70% of the maximum value is a certain multiple of the red full width FWr1 34r at 70% of the maximum value, and the multiple is greater than about 8, greater than about 9, or greater than about 10. In other words, FWri1 / FWr1 is greater than about 8, greater than about 9, or greater than about 10. Figure 3 and Figure 4In the illustrated embodiment, the ratio of the red-infrared full width FWri1 53ri at 70% of the maximum value to the red full width FWr1 34r at 70% of the maximum value is 10.7:1, ie, FWri1 / FWr1 34r=10.7.

[0067] The graph 400 also includes a first wavelength range 54 that is at least 10 nm wide and is disposed within a range of 420 nm to 680 nm. In some embodiments, the first wavelength range 54 is at least 20 nm, at least 30 nm, at least 40 nm, or at least 50 nm. Figure 3 In the illustrated embodiment, the first wavelength range 54 is 50 nm wide and is disposed within 500 nm to 550 nm.

[0068] For substantially normally incident light 12, for at least a first polarization state, and for a first wavelength range 54, the optical film 40, the plurality of first layers 41, and the plurality of second layers 42 have average optical transmittances T, T1, and T2, respectively. Figure 3 In the illustrated embodiment, and as is apparent from curves 50, 56a, 56b, for substantially vertically incident light 12, for at least the first polarization state, and for the first wavelength range 54, the average optical transmittance T of the optical film 40 has a value of approximately 48.2%, the average optical transmittance T1 of the plurality of first layers 41 has a value of approximately 49.2%, and the average optical transmittance T2 of the plurality of second layers 42 has a value of approximately 90%.

[0069] In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for the first wavelength range 54, the relationship between the average optical transmittances of the optical film 40 and the plurality of first layers 41 is given by: 0.7≤T1 / T≤1.3. In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for the first wavelength range 54, the relationship between the average optical transmittances of the optical film 40 and the plurality of first layers 41 is given by: 0.8≤T1 / T≤1.2, or 0.9≤T1 / T≤1.1. Figure 3 In the illustrated embodiment, and as is apparent from curves 50, 56a, for substantially normally incident light 12, for at least the first polarization state, and for the first wavelength range 54, the average optical transmittance T of the optical film 40 is substantially equal to the average optical transmittance T1 of the plurality of first layers 41. In other words, T1 is equal to T, or T1 / T=1.

[0070] Thus, for substantially normally incident light 12, for at least the first polarization state, and for the first wavelength range 54, the average optical transmittances of the optical film 40 and the plurality of first layers 41 are substantially equal to one another.

[0071] In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for the first wavelength range 54, the relationship between the average optical transmittances of the plurality of first layers 41 and the plurality of second layers 42 is given by: T1 / T2≤0.9. In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for the first wavelength range 54, the relationship between the average optical transmittances of the plurality of first layers 41 and the plurality of second layers 42 is given by: T1 / T2≤0.8, T1 / T2≤0.7, or T1 / T2≤0.6. Figure 3 In the illustrated embodiment, and as is apparent from curves 56a, 56b, for substantially normally incident light 12, for at least the first polarization state, and for the first wavelength range 54, the ratio of the average optical transmittance of the plurality of first layers 41 to the average optical transmittance of the plurality of second layers 42 is about 1:2. In other words, T1 / T2=0.5.

[0072] Thus, for substantially normally incident light 12 , for at least the first polarization state, and for the first wavelength range 54 , the average optical transmittance of the plurality of second layers 42 is greater than the average optical transmittance of the plurality of first layers 41 .

[0073] The graph 400 also includes a second wavelength range 55 that is at least 10 nm wide and is disposed within a range of 680 nm to 1200 nm. In some embodiments, the second wavelength range 55 is at least 20 nm, at least 30 nm, at least 40 nm, or at least 50 nm. Figure 3 In the illustrated embodiment, the second wavelength range 55 is 50 nm wide and is disposed within 730 nm to 780 nm.

[0074] For substantially normally incident light 12, for at least the first polarization state, and for the second wavelength range 55, the optical film 40, the plurality of first layers 41, and the plurality of second layers 42 have average optical transmittances T', T1', and T2', respectively. Figure 3 In the illustrated embodiment, and as is apparent from curves 50, 56a, 56b, for substantially vertically incident light 12, for at least a first polarization state, and for a second wavelength range 55, the average optical transmittance T' of the optical film 40 has a value of approximately 38.1%, the average optical transmittance T1' of the plurality of first layers 41 has a value of approximately 90.2%, and the average optical transmittance T2' of the plurality of second layers 42 has a value of approximately 37.2%.

[0075] In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for a second wavelength range 55, the relationship between the average optical transmittances of the optical film 40 and the plurality of second layers 42 is given by: 0.7≤T2' / T'≤1.3. In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for a second wavelength range 55, the relationship between the average optical transmittances of the optical film 40 and the plurality of second layers 42 is given by: 0.8≤T2' / T'≤1.2, or 0.9≤T2' / T'≤1.1. Figure 3 In the illustrated embodiment, and as is apparent from curves 50, 56b, for substantially normally incident light 12, for at least the first polarization state, and for the second wavelength range 55, the average optical transmittance T' of the optical film 40 is substantially equal to the average optical transmittance T2' of the plurality of second layers 42. In other words, T2' is equal to T', or T2' / T'=1.

[0076] Thus, for substantially normally incident light 12, for at least the first polarization state, and for the second wavelength range 55, the average optical transmittances of the optical film 40 and the plurality of second layers 42 are substantially equal to one another.

[0077] In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for the second wavelength range 55, the relationship between the average optical transmittances of the plurality of first layers 41 and the plurality of second layers 42 is given by: T1' / T2'≥1.2. In some embodiments, for substantially normal incident light 12, for at least the first polarization state, and for the second wavelength range 55, the relationship between the average optical transmittances of the plurality of first layers 41 and the plurality of second layers 42 is given by: T1' / T2'≥1.4, T1' / T2'≥1.6, T1' / T2'≥1.8, T1' / T2'≥2, T1' / T2'≥2.1, T1' / T2'≥2.2, or T1' / T2'≥2.3. Figure 3 In the illustrated embodiment, and as is apparent from curves 56a, 56b, for substantially normally incident light 12, for at least the first polarization state, and for the second wavelength range 55, the ratio of the average optical transmittance of the plurality of first layers 41 to the average optical transmittance of the plurality of second layers 42 is about 2.4:1. In other words, T1' / T2'=2.4.

[0078] Thus, for substantially normally incident light 12 , for at least the first polarization state, and for the second wavelength range 55 , the average optical transmittance of the plurality of first layers 41 is greater than the average optical transmittance of the plurality of second layers 42 .

[0079] In some embodiments, for substantially normally incident light 12, and for at least a first polarization state, the optical transmittance of the optical film 40 at a first red-infrared peak wavelength 52ri is Tp. Figure 4 In the illustrated embodiment, and as is apparent from curve 50, for substantially normal incident light 12, and for at least the first polarization state, the optical transmittance of the optical film 40 at the first red-infrared peak wavelength 52ri is about 59.7%. In other words, Tp=59.7%. In addition, in some embodiments, T <Tp。

[0080] Thus, for substantially normally incident light 12, and for at least a first polarization state, the optical transmittance of optical film 40 at first red-infrared peak wavelength 52ri is greater than the average optical transmittance of optical film 40.

[0081] In some embodiments, for substantially normal incident light 12, and for at least a first polarization state, the optical transmittance wavelength with respect to the wavelength of each of the plurality of first layers 41 and the plurality of second layers 42 includes a band edge 57a, 57b that extends across a transmission range from at least about 35% to at most about 85%. Specifically, the optical transmittance with respect to the wavelength of the plurality of first layers 41 includes a band edge 57a, and the optical transmittance with respect to the wavelength of the plurality of second layers 42 includes a band edge 57b. In some embodiments, for substantially normal incident light 12, and for at least a first polarization state, the optical transmittance with respect to the wavelength of each of the plurality of first layers 41 and the plurality of second layers 42 includes a band edge 57a, 57b that extends across a transmission range from at least about 45% to at most about 75%, from at least about 40% to at most about 80%, from at least about 35% to at most about 85%. In some embodiments, the band edges 57a, 57b intersect each other.

[0082] like Figure 3 As shown, in some embodiments, the band edges 57a, 57b intersect each other at a wavelength 57c no more than 20 nm from the first red-infrared peak wavelength 52ri. In some embodiments, the band edges 57a, 57b intersect each other at a wavelength 57c no more than about 15 nm, 20 nm, or about 5 nm from the first red-infrared peak wavelength 52ri. Figure 3 In the illustrated embodiment, the wavelength 57c at which the band edges 57a, 57b intersect each other is approximately 653 nm, which is within 10 nm of the first red-infrared peak wavelength 52ri (ie, 666 nm).

[0083] Additionally, in some embodiments, the band edges 57a, 57b intersect each other at a wavelength 57c that is at least 10 nm greater than the first red peak wavelength 33r. In some embodiments, the band edges 57a, 57b intersect each other at a wavelength 57c that is at least 15 nm, at least 20 nm, at least 25 nm, at least 30 nm, or at least 35 nm greater than the first red peak wavelength 33r. In some embodiments, the band edges 57a, 57b intersect each other at a wavelength 57c that is no more than 40 nm from the first red peak wavelength 33r. In some embodiments, the band edges 57a, 57b intersect each other at a wavelength 57c that is no more than about 35 nm, about 30 nm, about 25 nm, or about 20 nm from the first red peak wavelength 33r. Figure 3 In the illustrated embodiment, the wavelength 57c at which the band edges 57a, 57b intersect each other is approximately 653 nm, which is 22 nm greater than the first red peak wavelength 33r (i.e., 631 nm). Therefore, the wavelength 57c is at least 10 nm greater than the first red peak wavelength 33r and is within 40 nm of the first red peak wavelength 33r.

[0084] Figure 5 An example of a depiction optical film 40 (eg Figure 2 Graph 500 of changes in layer profiles of a plurality of first layers 41 and a plurality of second layers 42 of an optical film 40 (as shown). Specifically, graph 500 depicts layer thicknesses of a plurality of first layers 41 and a plurality of second layers 42 of an optical film 40 relative to layer numbers. The layer numbers are represented in the abscissa, and the average layer thickness is represented in nanometers (nm) in the ordinate. Figure 6 A diagram depicting a set 60 of first and second layers 41 and 42 according to one embodiment of the present disclosure (eg, Figure 5 A graph 500 of layer thickness versus layer number for a device having a layer thickness as shown in FIG. 5 is shown.

[0085] refer to Figures 1 to 6 The graph 500 includes a scatter plot 61 of layer thicknesses of at least 30 sequentially arranged and numbered first layers 41 and second layers 42 relative to layer numbers among the plurality of first layers 41 and the plurality of second layers 42 .

[0086] In addition, the set 60 of first layers 41 and second layers 42 includes a total of at least 30 first layers 41 and second layers 42. In some embodiments, the set 60 of first layers 41 and second layers 42 includes a total of at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, or at least 100 first layers 41 and second layers 42. The set 60 of first layers 41 and second layers 42 includes substantially equal numbers of first layers 41 and second layers 42. Figure 5 In the illustrated embodiment, the first layer 41 and the second layer 42 (eg Figure 2 As shown) are numbered sequentially from 275 to 375.

[0087] refer to Figure 5 and Figure 6 In some embodiments, when a set 60 of first and second layers 41 and 42 having a total of at least 30 layers, including substantially equal numbers of first and second layers 41 and 42 and including first and second layers 41a and 42a closest to each other in the optical film 40, the first and second layers 41 and 42 in the set 60 are located from one side 45a (e.g., Figure 2 ) to the opposite side 45b of the optical film 40 (as shown Figure 2 When the first layer 41 and the second layer 42 in the set 60 are numbered sequentially (as shown in FIG. 1 ), the scatter plot 61 of the layer thickness relative to the layer number of the first layer 41 and the second layer 42 in the set 60 includes a first group of scatter points 62a and a remaining group of scatter points 62b that are spaced at least 5 nm along the thickness direction (i.e., along the ordinate). In some embodiments, the first group of scatter points 62a and the remaining group of scatter points 62b may be spaced at least 7 nm, at least 9 nm, at least 11 nm, at least 12 nm, or at least 13 nm along the thickness direction.

[0088] In addition, from Figure 6 It is apparent that the scattered points in the first group 62a and the remaining group 62b are located on the substantially straight first line 63a and the second line 63b, respectively. In some embodiments, the substantially straight first line 63a and the second line 63b are substantially parallel.

[0089] Figure 7 and Figure 8 An example of a depiction optical film 40 (eg Figure 2 600 of optical transmittance relative to wavelength. Figure 8 An enlarged view of the graph 600 for wavelengths from 600 nm to 660 nm is illustrated. Specifically, the graph 600 depicts the incident light 13 (eg Figure 2 ) and the optical transmittance of the optical film 40 with respect to wavelength for at least a first polarization state.

[0090] The wavelength is expressed in nanometers (nm) on the horizontal axis. The optical transmittance is expressed as a transmittance percentage on the left vertical axis, and the emission intensity is expressed in arbitrary units (au) on the right vertical axis. The emission intensity in arbitrary units corresponds to the emission intensity generated by the illumination system 70 (e.g. Figure 1 The emitted light 11 (such as Figure 1 Emission spectra 31b, 31g, 31r shown).

[0091] refer to Figure 7 and Figure 8, the graph 600 includes a curve 50', which depicts the incident angle α1 (eg Figure 2 ) incident light 13 incident on the optical film 40 and the optical transmittance of the optical film 40 with respect to wavelength for at least a first polarization state. Specifically, curve 50' depicts the optical transmittance of the optical film 40 with respect to wavelength for incident light 13 incident on the optical film 40 at an incident angle α1 of about 30 degrees and the optical transmittance of the optical film 40 with respect to wavelength for at least a first polarization state.

[0092] refer to Figure 1 to Figure 2 as well as Figures 7 and 8 As depicted by curve 50', for incident light 13 incident on the optical film 40 at an incident angle α1 greater than about 15 degrees, and for at least a first polarization state, the optical transmittance of the optical film 40 with respect to wavelength has a first red-infrared transmittance peak 51'ri at a first red-infrared peak wavelength 52'ri greater than about 600nm, and the red-infrared full width at 50% of the maximum value at the first red-infrared peak wavelength is FW'2 53'ri. The red-infrared full width at 50% of the maximum value FW'2 is Figure 8 In the 53'ri. Figure 7 and Figure 8 In the illustrated embodiment, and as is apparent from the curve 50', the first red-infrared peak wavelength 52'ri is about 635.5 nm, and the red-infrared full width at 50% of maximum value FW'2 53'ri is about 36 nm.

[0093] The red-infrared full width FW'2 53'ri at 50% of the maximum value of the first red-infrared peak wavelength 52'ri completely covers the red full width FWr1 34r at 70% of the maximum value of the first red peak wavelength 33r. In addition, the relationship between the red-infrared full width FW'2 53'ri at 50% of the maximum value and the red full width FWr1 34r at 70% of the maximum value is given by the following formula: FW'2 / FWr1≥2. In some embodiments, the relationship between the red-infrared full width FW'2 53'ri at 50% of the maximum value and the red full width FWr1 34r at 70% of the maximum value is given by the following formula: FW'2 / FWr1≥3, FW'2 / FWr1≥4, FW'2 / FWr1≥5, FW'2 / FWr1≥6, FW'2 / FWr1≥7, FW'2 / FWr1≥8, FW'2 / FWr1≥9, FW'2 / FWr1≥10, FW'2 / FWr1≥11, FW'2 / FWr1≥15, or FW'2 / FWr1≥20. Figure 7 and Figure 8 In the illustrated embodiment, the ratio of the red-infrared full width FW'253'ri at 50% of the maximum value to the red full width FWr1 34r at 70% of the maximum value is about 12:1.

[0094] In some embodiments, the optical transmittance of the optical film 40 at the first red-infrared transmittance peak 51'ri is less than about 80%. In some embodiments, the optical transmittance of the optical film 40 at the first red-infrared transmittance peak 51'ri is less than about 75%, less than about 70%, less than about 65%, less than about 60%, less than about 55%, or less than about 50%. Figure 7 and Figure 8 In the illustrated embodiment, the optical transmittance of the optical film 40 at the first red-infrared transmittance peak 51 'ri is about 51%.

[0095] Fig. 9 A schematic diagram of a substantially Lambertian light source 80 and an optical film 40 is illustrated according to one embodiment of the present disclosure.

[0096] refer to Figures 1 to 4 as well as Fig. 9 , the optical film 40 is disposed on the basic Lambertian light source 80. The basic Lambertian light source 80 emits light 11 toward the optical film 40. Specifically, the basic Lambertian light source 80 emits light 11 having a corresponding blue emission spectrum 31b, a green emission spectrum 31g, and a red emission spectrum 31r, the corresponding blue emission spectrum, green emission spectrum, and red emission spectrum including a corresponding blue peak 32b, a green peak 32g, and a red peak 32r, and the corresponding blue full width, green full width, and red full width at 70% of the maximum value at the corresponding blue peak, green peak, and red peak are FWb1 34b, FWg1 34g, and FWr1 34r, respectively.

[0097] When the substantially Lambertian light source 80 emits light 11, the optical film 40 transmits the emitted light 11 as transmitted light 14. The optical film 40 transmits the transmitted light 14 with a color shift 90v, 90h relative to the emitted light (e.g. Fig.10 The color shift varies as a function of the transmission angle θ in a plane substantially perpendicular to the optical film 40. In some embodiments, the plane is the xz plane. In some other embodiments, the plane is the yz plane.

[0098] Fig. 9 Also illustrated is an optical detector 94 that is configured to detect at least a portion of the transmitted light 14 emitted from the optical film 40 . Fig.10A graph 700 is illustrated depicting the color shift 90v, 90h of the transmitted light 14 relative to the emitted light as a function of the transmission angle θ in a plane substantially perpendicular to the optical film 40. Specifically, the color shift 90v of the transmitted light 14 relative to the emitted light is depicted as a function of the transmission angle θ in the xz plane, and the color shift 90h of the transmitted light 14 relative to the emitted light is depicted as a function of the transmission angle θ in the yz plane. The viewing angle is represented in degrees in the abscissa. The color shift (dE) is represented in the ordinate. The color shift is calculated based on a Lambertian light source (e.g., Lambertian light source 80) with a D65 spectral standard. The color space used is CIE LAB. For each viewing angle, the LAB color coordinates are evaluated. In order to calculate the final color shift for each viewing angle, the average color point of all viewing angles is used as a reference. The color shift formula is as follows.

[0099]

[0100] Where L, A, B are the LAB color coordinates for each viewing angle; and

[0101] is the average color point for all viewing angles.

[0102] refer to Fig. 9 and Fig.10 , color shifts 90v, 90h have main color shift peaks 91v, 91h at a transmission angle less than about 10 degrees. Specifically, color shift 90v has a main color shift peak 91v at a transmission angle less than about 10 degrees, and color shift 90h has a main color shift peak 91h at a transmission angle less than about 10 degrees. Fig.10 In the illustrated embodiment, the color shift 90v, 90h has a main color shift peak 91v, 91h at a transmission angle of about 0 degrees. In some embodiments, the color shift 90v, 90h has a main color shift peak 91v, 91h at a transmission angle of less than about 7 degrees, less than about 6 degrees, less than about 5 degrees, less than about 4 degrees, less than about 3 degrees, less than about 2 degrees, or less than about 1 degree.

[0103] The color shifts 90v, 90h also have a color shift plateau region 92 that is at least 5 degrees wide and located at a transmission angle greater than about 2 degrees. Fig.10 In the illustrated embodiment, the color shifting plateau region 92 is about 16 degrees wide. In some embodiments, the color shifting plateau region 92 is at least 7 degrees, at least 9 degrees, at least 10 degrees, at least 12 degrees, at least 15 degrees, at least 17 degrees, at least 19 degrees, or at least 20 degrees wide. In some embodiments, the color shifting plateau region 92 is located at a transmission angle greater than about 3 degrees, greater than about 4 degrees, or greater than about 5 degrees.

[0104] In addition, the main color shift peaks 91v, 91h have full widths 93v, 93h at 80% of the maximum value greater than about 1 degree. Specifically, the main color shift peak 91v has a full width 93v at 80% of the maximum value greater than about 1 degree, and the main color shift peak 91h has a full width 93h at 80% of the maximum value greater than about 1 degree. Fig.10 In the illustrated embodiment, each of the main color shift peaks 91v, 91h has a full width 93v, 93h at 80% of the maximum value of about 5 degrees. In some embodiments, the main color shift peaks 91v, 91h have a full width 93v, 93h at 80% of the maximum value of greater than about 1.5 degrees, greater than about 2 degrees, greater than about 2.5 degrees, greater than about 3 degrees, greater than about 3.5 degrees, greater than about 4 degrees, greater than about 4.5 degrees, or greater than about 5 degrees.

[0105] The color shifts 90v, 90h across the color shift plateau region 92 vary with a standard deviation of less than about 0.5. Fig.10 In the illustrated embodiment, the color shift 90v varies with a standard deviation of about 0.20016 across the color shift plateau region 92. Additionally, the color shift 90h varies with a standard deviation of about 0.21127 across the color shift plateau region 92. In some embodiments, the color shifts 90v, 90h across the color shift plateau region 92 vary with a standard deviation of less than about 0.45, less than about 0.4, less than about 0.35, less than about 0.3, less than about 0.25, or less than about 0.2.

[0106] Fig.11 A schematic diagram of a reflective polarizer 130 according to an embodiment of the present disclosure is illustrated. The reflective polarizer 130 includes a plurality of polymer layers 131, 132 having a total number of at least 10. In some embodiments, the reflective polarizer 130 includes a plurality of polymer layers 131, 132 having a total number of 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, the plurality of polymer layers 131, 132 are arranged in an alternating manner. Each of the polymer layers 131, 132 has an average thickness TP1 of less than about 500 nm. In some embodiments, each of the polymer layers 131, 132 has an average thickness TP1 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.

[0107] In some embodiments, reflective polarizer 130 further comprises at least one surface layer 133 having an average thickness TP2 greater than about 500 nm. In some embodiments, at least one surface layer 133 has an average thickness TP2 greater than about 750 nm, greater than 1000 nm, greater than about 1500 nm, or greater than about 2000 nm. Fig.11 In the illustrated embodiment, reflective polarizer 130 includes two skin layers 133. At least one skin layer 133 can protect polymer layers 131, 132 and can also provide mechanical stability to reflective polarizer 130. In some cases, at least one skin layer 133 can act as a protective boundary layer (PBL).

[0108] In some embodiments, for substantially normal incident light 135 and at least one wavelength in the visible range extending from about 420 nm to about 680 nm, the plurality of polymer layers 131, 132 reflect greater than about 60% of the incident light 135 having an in-plane first polarization state, and transmit greater than about 60% of the incident light 135 having an orthogonal in-plane second polarization state. In some embodiments, the in-plane first polarization state is along the x-axis and the in-plane second polarization state is along the y-axis.

[0109] In some embodiments, for substantially vertically incident light 135 and at least one wavelength in the visible light range extending from about 420 nm to about 680 nm, the multiple polymer layers 131, 132 reflect greater than about 70%, greater than about 80%, or greater than about 90% of the incident light 135 having an in-plane first polarization state, and transmit greater than about 70%, greater than about 80%, or greater than about 90% of the incident light 135 having an in-plane second polarization state.

[0110] Fig.12 2 shows a schematic cross-sectional exploded view of a display system 350 according to another embodiment of the present disclosure. The display system 350 is substantially similar to the display system 300. However, in Fig.12 In the illustrated embodiment, the lighting system 70 has an edge-lit configuration. Specifically, the lighting system 70 of the display system 350 includes at least one light-emitting element 352 disposed at an edge of the lighting system 70. The at least one light-emitting element 352 includes a red light-emitting element 30r (e.g., Figure 1 In some embodiments, at least one light emitting element 352 further includes a blue light emitting element 30b (eg, Figure 1 As shown) and green light emitting element 30g (as Figure 1 shown).

[0111] Additionally, in some embodiments, the illumination system 70 further includes a light guide 354 for propagating light emitted by the at least one light emitting element 352 along the length and width of the light guide 354. Light emitted by the at least one light emitting element 352 can enter the light guide 354 from one side of the light guide 354. In some embodiments, the light guide 354 is a solid light guide. In some embodiments, the light guide 354 is a substantially hollow light guide. In some embodiments, the light guide 354 can be a stepped wedge light guide.

[0112] In some embodiments, the lighting system 70 also includes a reflector 356 for redirecting at least light emitted by the at least one light emitting element 352. In some embodiments, the reflector 356 includes a metal layer (not shown). In some embodiments, the metal layer includes one or more of silver, gold, aluminum, and titanium. In some embodiments, the reflector 356 includes a multilayer optical film that reflects visible light but transmits infrared light.

[0113] In some embodiments, the display system 350 also includes an infrared sensor 358 disposed proximate to the backlight 200. In some embodiments, the infrared sensor 358 can be configured to obtain an image of an object proximate to the display system 350 (e.g., to detect a fingerprint). A display device (e.g., a mobile phone) that includes the display system 350 can be configured to determine whether the image matches a predetermined image (e.g., an image of a fingerprint of an authorized user).

[0114] In some embodiments, infrared sensor 358 includes one or more of a photodiode array, a charge coupled device (CCD), a charge injection device (CID), a photodiode, an organic photodiode, a complementary metal oxide semiconductor (CMOS), and a thin film transistor (TFT).

[0115] In some embodiments, light guide 354 can use total internal reflection (TIR) ​​to transmit or guide light incident on light guide 354 toward reflector 356. In some cases, light guide 354 can improve the uniformity of light that can be incident on reflector 356. Light guide 354 can be configured to guide light toward reflector 356. At least a portion of the light can be reflected by reflector 356 as reflected light. Specifically, reflector 356 is configured to substantially reflect a portion of light having a wavelength in the visible wavelength range extending from about 420 nm to about 680 nm as reflected light toward emitting surface 71. In addition, reflector 356 is configured to substantially transmit a portion of light having a wavelength in the infrared range extending from about 700 nm to about 1000 nm toward infrared sensor 358.

[0116] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by one skilled in the art utilizing the teachings disclosed herein.

[0117] Although specific embodiments have been illustrated and described herein, it will be appreciated by those skilled in the art that the specific embodiments shown and described may be replaced with a variety of alternative and / or equivalent implementations without departing from the scope of the present disclosure. The present application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, the present 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 illumination system configured to emit light from an emission surface thereof, the emitted light comprising at least red light, the red light comprising a red emission spectrum, the red emission spectrum comprising a first red emission peak at a first red peak wavelength, the red full width at 70% of the maximum value at the first red peak wavelength being FWr1; and An optical film, which is arranged on a red light-emitting element and includes at least one spacer layer arranged between a plurality of first layers and a plurality of second layers, the total number of the first layers and the second layers is at least 10, each of the first layers and the second layers has an average thickness of less than about 500 nanometers (nm), and each of the at least one spacer layer has an average thickness of at least about 5 microns, so that for substantially vertically incident light and for at least a first polarization state, the optical transmittance of the optical film relative to wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600 nm, and the red-infrared full width at 70% of the maximum value at the first red-infrared peak wavelength is FWri1, wherein the red-infrared peak wavelength is at least 10 nm larger than the red peak wavelength, and wherein FWri1 / FWr1≥7.

2. The backlight of claim 1, wherein the light emitted from the emitting surface of the illumination system further comprises: blue light, the blue light having a blue emission spectrum, the blue emission spectrum including a first blue emission peak at a first blue peak wavelength, a blue full width at 70% of the maximum value at the first blue peak wavelength being FWb1; and green light having a green emission spectrum including a first green emission peak at a first green peak wavelength, a green full width at 70% of the maximum value at the first green peak wavelength being FWg1, wherein each of FWb1 and FWg1 is at least 2 times greater than FWr1.

3. The backlight source of claim 1 , wherein when, for a set of the first and second layers having a total of at least 30 layers, including substantially equal numbers of the first and second layers and including the first and second layers that are closest to each other in the optical film, the first layers and the second layers in the set are numbered sequentially from one side of the optical film to the opposite side of the optical film, a scatter plot of layer thicknesses of the first and second layers in the set relative to layer numbers includes a first group of scatter points and a remaining group of scatter points that are spaced at least 5 nm apart along the thickness direction, wherein the scatter points in the first group and the remaining group are located on substantially straight first and second lines, respectively.

4. The backlight of claim 1 , wherein for the substantially normally incident light, for at least the first polarization state, and for a first wavelength range that is at least 10 nm wide and disposed within a range of 420 nm to 680 nm, the optical film, the plurality of the first layers, and the plurality of the second layers have average optical transmittances T, T1, and T2, respectively, 0.7≤T1 / T≤1.3, T1 / T2≤0.

9.

5. The backlight of claim 1 , wherein for the substantially normally incident light, for at least the first polarization state, and for a second wavelength range that is at least 10 nm wide and disposed within a range of 680 nm to 1200 nm, the optical film, the plurality of the first layers, and the plurality of the second layers have average optical transmittances T', T1', and T2', respectively, 0.7≤T2' / T'≤1.3, T1' / T2'≥1.

2.

6. The backlight of claim 1 , wherein for the substantially normally incident light and for at least the first polarization state, the optical transmittance of the optical film at the first red-infrared peak wavelength is Tp, and the average optical transmittance of the optical film over a first wavelength range that is at least 10 nm wide and disposed within a range of 420 nm to 680 nm is T, T <Tp。 7. The backlight source of claim 1 , wherein for the substantially normally incident light, and for at least the first polarization state, the optical transmittance with respect to wavelength of each of the plurality of the first layers and the plurality of the second layers comprises a band edge extending across a transmission range from at least about 35% to at most about 85%, wherein the band edges intersect one another.

8. The backlight of claim 7, wherein the band edges intersect each other at wavelengths no more than 20 nm from the first red-infrared peak wavelength.

9. The backlight of claim 7, wherein the band edges intersect each other at a wavelength that is at least 10 nm greater than the first red peak wavelength.

10. The backlight of claim 7, wherein the band edges intersect each other at wavelengths no more than 40 nm from the first red peak wavelength.

11. The backlight of claim 1 , further comprising a reflective polarizer disposed on the optical film opposite the illumination system and comprising a plurality of polymer layers totaling at least 10, each of the plurality of polymer layers having an average thickness of less than about 500 nm, such that for substantially normal incident light and at least one wavelength in the visible range extending from about 420 nm to about 680 nm, the plurality of polymer layers reflect more than about 60% of incident light having an in-plane first polarization state and transmit more than about 60% of incident light having an orthogonal in-plane second polarization state. 12 . A display system comprising a display panel disposed on the backlight source according to claim 1 and configured to receive illumination from the backlight source and display an image.

13. A backlight source for providing illumination to a display panel configured to display an image, the backlight source comprising: an illumination system configured to emit light from an emission surface thereof, the emitted light comprising at least red light, the red light comprising a red emission spectrum, the red emission spectrum comprising a first red emission peak at a first red peak wavelength, the red full width at 70% of the maximum value at the first red peak wavelength being FWr1; and An optical film, which is arranged on a red light emitting element and includes at least one spacer layer arranged between a plurality of first layers and a plurality of second layers, the total number of the first layers and the second layers is at least 10, each of the first layers and the second layers has an average thickness of less than about 500 nm, and each of the at least one spacer layer has an average thickness of at least about 5 microns, so that for incident light incident on the optical film at an incident angle greater than about 15 degrees, and for at least a first polarization state, the optical transmittance of the optical film with respect to wavelength has a first red-infrared transmittance peak at a first red-infrared peak wavelength greater than about 600 nm, the red-infrared full width at 50% of the maximum value at the first red-infrared peak wavelength is FW'2, wherein the red-infrared full width FW'2 at 50% of the maximum value at the first red-infrared peak wavelength completely covers the red full width FWr1 at 70% of the maximum value at the first red peak wavelength, and FW'2 / FWr1≥2.

14. The backlight of claim 13, wherein the optical transmittance of the optical film at the first red-infrared transmittance peak is less than about 80%.

15. An optical film, comprising at least one spacer layer disposed between a plurality of first layers and a plurality of second layers, the total number of the first layers and the second layers being at least 50, each of the first layers and the second layers having an average thickness of less than about 500 nm, each of the at least one spacer layer having an average thickness of at least about 5 microns, wherein a scatter plot of layer thicknesses of at least 30 sequentially arranged and numbered first layers and second layers of the plurality of first layers and the plurality of second layers relative to layer numbers comprises a first group of scatter points and a remaining group of scatter points spaced along a thickness direction, wherein the scatter points in the first group and the remaining group are located on substantially straight first and second lines, respectively, so that when the optical film is disposed on a substantially Lambertian light source emitting light, the light has corresponding blue emission spectra, green emission spectra, and red emission spectra, the corresponding The blue emission spectrum, the green emission spectrum and the red emission spectrum include corresponding blue peaks, green peaks and red peaks, and the corresponding blue full width, green full width and red full width at 70% of the maximum values ​​at the corresponding blue peaks, green peaks and red peaks are FWb1, FWg1 and FWr1 respectively, wherein FWb1 is at least 2 times of FWr1, and FWg1 is at least 5 times of FWr1, and the optical film transmits the emitted light so that the transmitted light has a color shift relative to the emitted light, and the color shift varies as a function of the transmission angle in a plane substantially perpendicular to the optical film, and has a main color shift peak at a transmission angle of less than about 10 degrees and a color shift platform region that is at least 5 degrees wide and located at a transmission angle greater than about 2 degrees, the main color shift peak has a full width at 80% of the maximum value greater than about 1 degree, and the color shift across the color shift platform region varies with a standard deviation of less than about 0.5.

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