Reflective polarizer and display system

Abstract

A display system includes a display panel including a plurality of light-emitting pixels and a reflective polarizer disposed over the light-emitting pixels. The reflective polarizer may have a reflection band that, for light at substantially normal incidence, has low overlap with an emission spectrum of red light-emitting pixels, but has high overlap with the emission spectrum of red light-emitting pixels for at least one incident angle greater than approximately 40 degrees. The reflective polarizer may have a reflection band that overlaps with an emission spectrum of blue light-emitting pixels for light at substantially normal incidence.

Description

Background Art

[0001] Organic light emitting diode (OLED) displays often include circular polarizers to reduce reflection of ambient light from the display. Summary of the Invention

[0002] This specification relates to reflective polarizers and display systems. The display system may include: a display panel including a plurality of light-emitting pixels; and a reflective polarizer that may be disposed over the light-emitting pixels. The reflective polarizer may increase the light output of the display system by, for example, recycling light that would otherwise be absorbed by the absorptive polarizer. The reflective polarizer may have a reflective spectrum including substantially distinct blue, green, and infrared reflection bands. The reflective polarizer may have a reflective band (e.g., an infrared reflective band) that has low overlap with the emission spectrum of red light-emitting pixels for light at substantially normal incidence, but has high overlap with the emission spectrum of red light-emitting pixels for at least one angle of incidence greater than about 40 degrees. For example, in some embodiments, the reflective polarizer has a reflective band that is at least partially in the near-infrared at normal incidence, and that shifts into the red at higher angles of incidence to increase recycling in the red. The reflective polarizer may have a reflective band that overlaps with the emission spectrum of the blue light-emitting pixels for light at substantially normal incidence. For example, at normal incidence, the reflection band can have a higher reflectivity in the blue than in the green, such that at higher angles of incidence, the shift in the reflection band results in a decrease in reflectivity in the blue, which results in reduced recycling in the blue. According to some embodiments, a reflective polarizer can cause the white point color shift of light emitted from a display system to be lower than the white point color shift of light emitted from a display system incorporating a conventional notch reflective polarizer, while providing less ghosting and / or less ambient light reflection than a display system using a broadband reflective polarizer.

[0003] These and other aspects will become apparent from the detailed description that follows.This brief summary, however, should not be construed in any way as limiting the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 is a schematic cross-sectional view showing the system;

[0005] Figure 2 is a schematic top view of a display panel;

[0006] Figure 3 is a schematic cross-sectional view of light incident on a layer or element;

[0007] Figures 4A to 4B is a schematic graph of the reflection band of a reflective polarizer and the emission spectrum of a pixel;

[0008] Figures 5A to 5C is a schematic graph of the reflection band of a reflective polarizer and the emission spectrum of a pixel;

[0009] Figures 6A to 6B is a graph of the reflective spectrum of the reflective polarizer and the emission spectrum of the luminescent pixel;

[0010] Figure 7 is a schematic graph illustrating the reflectance spectra of a reflective polarizer for light at substantially normal incidence and light at oblique incidence;

[0011] Figure 8 is a graph of the reflectivity of a reflective polarizer for light at substantially normal incidence and light having an angle of incidence of 60 degrees;

[0012] Figure 9 is a schematic graph showing the relationship between the delay and the wavelength;

[0013] Figure 10 is a schematic graph of the transmittance of an absorbing polarizer versus wavelength;

[0014] Figure 11 is a schematic graph of optical gain as a function of polar angle;

[0015] Figure 12 is a graph of the calculated optical gain as a function of polar angle;

[0016] Figure 13A is a schematic graph of the color shift of light leaving a display system on a chromaticity diagram;

[0017] Figure 13B is a schematic graph of the color shift of light leaving a display system as a function of viewing angle;

[0018] Figure 14 is a schematic cross-sectional view of a reflective polarizer;

[0019] Figure 15 is a graph of the thickness distribution of the optical repeating unit;

[0020] Figure 16 is a graph of the reflectivity of the reflective polarizer with respect to the polarization state of the transmitted light;

[0021] Figure 17 is a CIE 1931 xy chromaticity diagram showing white point color shift versus viewing angle for a display without a reflective polarizer;

[0022] Figure 18 is a CIE 1931 xy chromaticity diagram showing white point color shift versus viewing angle for a display with a reflective polarizer;

[0023] Figure 19It is a graph of the chromaticity distance from the color coordinate at normal incidence when the viewing angle changes;

[0024] Figures 20 to 26 is a graph of the percent transmittance versus wavelength for various reflective polarizers;

[0025] Figure 27 is a graph showing the white point color shift as a function of viewing angle on the CIE 1931xy chromaticity diagram for an OLED TV display;

[0026] Figure 28 is a graph showing the white point color shift as a function of viewing angle on the CIE 1976 Uniform Chromaticity Scale u'v' diagram for an OLED TV display;

[0027] Figure 29 is a graph of ambient light reflection from an OLED display;

[0028] Figure 30 is a graph showing white point color shift as a function of viewing angle on a CIE 1931 xy chromaticity diagram for an OLED phone display; and

[0029] Figure 31 is a graph showing the white point color shift as a function of viewing angle on the CIE 1976 Uniform Chromaticity Scale u'v' diagram for an OLED phone display. DETAILED DESCRIPTION

[0030] In the following description, reference is made to the accompanying drawings, which form a part of the present invention and in which various embodiments are shown by way of illustration. The drawings are not necessarily drawn to scale. It should be understood that other embodiments may be envisioned and implemented without departing from the scope or spirit of this description. Therefore, the following detailed description should not be construed in a limiting sense.

[0031] It has been discovered that, according to some embodiments, the reflective polarizers described herein can be used to improve the performance of a display system when configured to receive light output from a display. For example, in some embodiments, a reflective polarizer can be used in a circular polarizer disposed on an organic light emitting diode (OLED) display or other emissive display to increase the brightness of the display and / or the color gamut of the display without causing ghosting or other image degradation. The use of a broadband reflective polarizer in a circular polarizer for an OLED display to increase the brightness of the display due to light recycling is described in U.S. Patent No. 9,773,847 (Epstein et al.). As described in International Patent Application No. CN2018 / 105712 (Xu et al.), it has been discovered that utilizing a notch reflective polarizer having a band edge in the visible spectrum can improve the brightness and / or color gamut of a display while producing substantially less or substantially no ghosting, and / or reduced ambient light reflection, compared to using a broadband reflective polarizer. However, it has been discovered that the use of a notch reflective polarizer can result in increased color shift of ambient reflected light and / or light emitted from the display. According to some embodiments of the present specification, the reflective polarizer has a reflective spectrum selected so that the white light output has a low color shift with changes in viewing angle (e.g., compared to using a conventional notch reflective polarizer; or compared to using a broadband reflective polarizer; or compared to omitting the reflective polarizer). It has been found that this can be achieved, for example, by including a reflective band in the near infrared at normal incidence that shifts into the red at higher angles of incidence, thereby increasing recycling in the red; and / or using a reflective band that has a higher reflectivity in the blue than in the green at normal incidence, such that at higher angles of incidence, the shift in the reflective band results in a decrease in reflectivity in the blue, which reduces recycling in the blue. According to some embodiments, the reflective polarizer can cause the white point color shift of light emitted from the display system to be lower than the white point color shift of light emitted from a display system incorporating a conventional notch reflective polarizer, while providing less ghosting and / or less ambient light reflection than a display system using a broadband reflective polarizer.

[0032] The reflective polarizer may have a reflection band that has a low overlap (e.g., no overlap) with the emission spectrum of the red light-emitting pixel for light at substantially normal incidence, and a high overlap with the emission spectrum of the red light-emitting pixel for at least one angle of incidence greater than about 40 degrees or greater than about 50 degrees. The reflective polarizer may have a reflection band that overlaps with the emission spectrum of the blue light-emitting pixel for light at substantially normal incidence. The reflection band may have a high overlap with the emission spectrum of the blue light-emitting pixel for light at substantially normal incidence, and may have a low overlap with the emission spectrum of the blue light-emitting pixel for at least one angle of incidence greater than about 40 degrees or greater than about 50 degrees. The reflective polarizer may be disposed between the absorptive polarizer and the retarder layer. In some embodiments, the reflective polarizer has at least two or at least three substantially different reflection bands for light at substantially normal incidence in the visible light range (400 nm to 700 nm). In some embodiments, the reflective polarizer has at least one reflection band for light at substantially normal incidence in the visible range and at least one reflection band for light at substantially normal incidence in the near infrared range (700 nm to 2500 nm). In some embodiments, the reflective polarizer substantially reflects light at substantially normal incidence of a first polarization state and substantially transmits light at substantially normal incidence of an orthogonal second polarization state for at least one wavelength in the visible range, or in the wavelength range of 450 nm to 650 nm, or in the wavelength range between the peak emission wavelengths of blue and red pixels. In some such or other embodiments, the reflective polarizer substantially transmits each of the first polarization state and the second polarization state for at least one other wavelength in the visible range, or in the wavelength range of 450 nm to 650 nm, or in the wavelength range between the peak emission wavelengths of blue and red pixels.

[0033] Figure 1is a schematic cross-sectional view of a display system 300 including a display panel 10 and a reflective polarizer 20 disposed on the display panel 10, according to some embodiments. The display system 300 can be suitable for displaying an image (e.g., light 82, 85, 85') to a viewer 333. The display system 300 can also include an absorptive polarizer 50 disposed (e.g., indirectly) on the display panel 10 and a retarder layer 40 disposed between the absorptive polarizer 50 and the display panel 10. In some embodiments, a first adhesive layer 60 bonds the absorptive polarizer 50 to the reflective polarizer 20, and a second adhesive layer 70 bonds the reflective polarizer 20 to the retarder layer 40. The reflective polarizer and the absorptive polarizer (which can be linear absorptive polarizers) can have substantially aligned pass axes (e.g., aligned to within 20 degrees, or within 10 degrees, or within 5 degrees). In some embodiments, an anti-reflective coating 53 is disposed on the absorptive polarizer 50 opposite the first adhesive layer 60. In some embodiments, a glass layer is disposed on the absorbing polarizer 50, and an anti-reflective coating 53 is disposed on the glass layer, with the two being in opposing relationship on the absorbing polarizer 50. For example, an additional layer (such as an adhesive layer) can be disposed between the retarder layer 40 and the display panel 10, or the retarder layer 40 can be disposed directly on the display panel 10. In embodiments where the retarder layer 40 is disposed directly on the display panel 10, Figure 1 It can be described as a schematic partially exploded view, in which the retarder layer 40 is shown as being spaced apart from the display panel 10 for ease of illustration.

[0034] Figure 2 is a schematic top view of the display panel 10. In some embodiments, the display panel 10 includes a plurality of at least first light-emitting pixels. In some embodiments, the display panel 10 includes a plurality of at least blue light-emitting pixels 11b, green light-emitting pixels 11g, and red light-emitting pixels 11r. In some embodiments, the display panel 10 also includes a plurality of white light-emitting pixels 11w. In some embodiments, the display panel 10 can be or include, for example, an organic light-emitting diode (OLED) display panel. In other embodiments, the display panel 10 can be, for example, a micro-LED display panel.

[0035] In some embodiments, various layers or elements of a display system can be characterized by the optical reflectivity, transmittance, and / or absorbance of the layer or element. Figure 3is a schematic cross-sectional view of light 30 incident on layer or element 130. Layer or element 130 may represent, for example, a reflective polarizer 20 or an absorptive polarizer 50. Portion 31 of light 30 may be transmitted, portion 32 of light 30 may be reflected, and portion 33 of light 30 may be absorbed. In some embodiments, for light 30 at substantially normal incidence (e.g., within 20 degrees, or within 10 degrees, or within 5 degrees of normal incidence), reflective polarizer 20 reflects at least about 60% or at least 70% of incident light 30 of at least one wavelength in a first polarization state (e.g., polarized along the x-axis) and transmits at least about 60% or at least about 70% of incident light of at least one wavelength in an orthogonal second polarization state (e.g., polarized along the y-axis). For example, the reflectivity for the first polarization state may have Figure 7 The reflectance spectrum 321 is schematically shown in FIG, and the transmittance for the second polarization state can be as follows Figure 7 In some embodiments, for light 30 incident substantially normally, the absorbing polarizer 50 absorbs at least 60% or at least 70% of the incident light 30 of at least one wavelength in the first polarization state (e.g., x-axis). For example, the absorbance may be as follows: Figure 10 A is schematically shown in FIG.

[0036] In some embodiments, layer or element 130 schematically represents display system 300. In some embodiments, display system 300 has a photopic ambient light reflectance of no more than about 15%, or no more than about 10%, or no more than about 8% for light 30 at substantially normal incidence (e.g., reflective portion 32 can be smaller and absorptive portion 33 can be larger). Figure 1 In some embodiments, the display system 300 has a photopic reflectance of no more than about 15%, or no more than about 10%, or no more than about 8% for light 230 incident on the display system 300 at an angle of incidence α (e.g., as schematically represented by reflected light 232). For example, the angle of incidence α can be about 8 degrees. The photopic reflectance can be measured using a D65 illuminant. For example, the photopic reflectance can be determined using the CIE 1931 photopic brightness function. For example, reducing the bandwidth or intensity of the reflection band can reduce photopic ambient light reflection.

[0037] Figures 4A to 4B is a schematic graph of reflection bands 121, 121' of a reflective polarizer for a first (block) polarization state and an emission spectrum 112 of a pixel. The emission spectrum 112 has an emission peak 113 at a peak wavelength 114 and a full width at half maximum (FWHM) of W1. Figure 4A A reflection band 121 is shown, wherein the reflection band 121 has a full width at half maximum W2, and Figure 4BA reflection band 121' is shown, wherein the reflection band 121' has a full width at half maximum W2'. The reflection band 121 can be for light incident at substantially normal incidence, and the reflection band 121' can be the same reflection band for light incident at a certain tilt angle, which shifts the reflection band to a lower wavelength compared to normal incidence. Alternatively, the reflection band 121' can represent the reflection band of a different embodiment for substantially normal incidence. The FWHM W1 of the emission spectrum 112 overlaps with the FWHM W2 of the reflective polarizer by an overlap range of Ov, and the FWHM W1 of the emission spectrum 112 overlaps with the FWHM W2' of the reflective polarizer by an overlap range of Ov'. In the illustrated embodiment, Ov' <Ov。

[0038] Figures 5A to 5C is a schematic graph of reflection bands 221, 221', 221" of a reflective polarizer for a first (block) polarization state and an emission spectrum 212 of a pixel. The emission spectrum 212 has an emission peak 213 at a peak wavelength 214 and a full width at half maximum (FWHM) of W1. Figure 5A 2. A reflection band 221 is shown for light at substantially normal incidence, wherein the reflection band 221 has a full width at half maximum W2; Figure 5B A reflection band 221′ is shown for light incident at an oblique angle relative to the normal to the reflective polarizer (or it may alternatively represent a reflection band for another embodiment at substantially normal incidence), wherein the reflection band 221′ has a full width at half maximum W2′ and is substantially the same as Figure 5A is shifted to a lower wavelength than Figure 5C Shown with Figure 5B Compared to the reflection band 221 for light incident at a greater oblique angle relative to the normal to the reflective polarizer (or which may alternatively represent the reflection band of another embodiment at substantially normal incidence or at another angle of incidence), wherein the reflection band 221" has a full width at half maximum W2" and is Figure 5B Shifted to a lower wavelength than the FWHM W1 of the emission spectrum 212 and the FWHM W2 of the reflective polarizer do not overlap. The FWHM W1 of the emission spectrum 212 and the FWHM W2' of the reflective polarizer overlap by an amount of Ov'. The FWHM W1 of the emission spectrum 212 and the FWHM W2' of the reflective polarizer overlap by an amount of Ov". In the illustrated embodiment, Ov">Ov'>0.

[0039] In some embodiments, reflection band 121 and emission spectrum 112 may represent, for example, a blue reflection band and an emission spectrum of a blue pixel, and / or may represent, for example, a green reflection band and an emission spectrum of a green pixel. In some embodiments, reflection band 221 and emission spectrum 212 may represent, for example, a red reflection band and an emission spectrum of a red pixel. Unless otherwise indicated, the emission spectrum of a pixel may be understood as the emission spectrum measured perpendicular to the display panel.

[0040] Figures 6A to 6B Graphs of the reflective spectrum 21 of the reflective polarizer and the blue (12b), green (12g), and red (12r) emission spectra of the corresponding blue (11b), green (11g), and red (11r) light-emitting pixels are shown. Also shown in the illustrated embodiment is a white emission spectrum 12w of the white light-emitting pixel 11w. The blue (12b), green (12g), and red (12r) emission spectra have full widths at half maximum (FWHM) for blue (W1b), green (W1g), and red (W1r), respectively. The reflective polarizer includes substantially distinct blue (21b), green (21g), and red (21r) reflection bands having corresponding blue (W2b), green (W2g), and red (W2r) FWHMs at normal incidence, and corresponding blue (W2b'), green (W2g'), and red (W2r') FWHMs at a 40-degree angle of incidence. Figure 6A Reflection bands are shown at normal incidence and at an angle of incidence of 40 degrees. Figure 6B The reflection bands are shown at normal incidence and at angles of incidence of 55 and 60 degrees. The reflection bands can be described as substantially different when they do not overlap or have sufficiently small overlap that the full width at half maximum of the reflection bands do not overlap. Optical modeling shows that compared to a display system using a conventional notched reflective polarizer, Figures 6A to 6B The reflective polarizer causes light emitted from the display system to have a low white point color shift (eg, substantially white light has a low color shift for viewing angles of 0 degrees to 60 degrees on the CIE 1976 Uniform Chromaticity Scale u'v' diagram).

[0041] For light incident substantially normally, the blue, green or red reflection bands reflect visible light primarily within the blue, green or red wavelength range, respectively. The blue wavelength range, the green wavelength range, and the red wavelength range can include a portion of the range from about 400nm to about 500nm, from about 500nm to about 600nm, and from about 600nm to about 700nm, respectively. For example, for light incident substantially normally, the red reflection band can extend into the infrared (e.g., up to about 750nm). For example, for light incident substantially normally, the blue reflection band can extend into the ultraviolet (e.g., as low as about 360nm). The infrared reflection band reflects within the infrared range (e.g., at least a portion of the range from about 700nm to about 1500nm) and can extend into the red (e.g., as low as about 650nm). Reflection bands comprising red and infrared wavelengths (e.g., Figure 6A 21r) in the embodiment can be called a red reflection band, or called an infrared reflection band, or called a red-infrared reflection band.

[0042] In some embodiments, the display system 300 includes a display panel 10 comprising a plurality of at least blue (11b), green (11g) and red (11r) light-emitting pixels having corresponding blue (12b), green (12g) and red (12r) emission spectra including corresponding blue (13b), green (13g) and red (13r) emission peaks having corresponding blue (W1b), green (W1g) and red (W1r) full widths at half maximum (FWHM) at corresponding blue (14b), green (14g) and red (14r) peak wavelengths. The display system 300 may further include a reflective polarizer 20 disposed over a plurality of at least blue, green, and red emitting pixels and including a reflective spectrum 21 including substantially distinct blue (21b), green (21g), and red (21r) reflection bands having respective blue (W2b), green (W2g), and red (W2r) FWHMs such that for light 30 incident substantially normally: for at least one wavelength within each of the FWHMs of the blue, green, and red reflection bands of the first polarization state, the reflective polarizer 20 reflects at least about 60% (e.g., at least about 10% of the incident light) of the first polarization state. Figure 6A , the reflectivity at about 450 nm, about 550 nm, and about 680 nm is greater than 90%); for at least one wavelength within each of the FWHMs of the blue, green, and red reflection bands of an orthogonal second polarization state, the reflective polarizer 20 transmits at least about 60% of the incident light (e.g., the reflectivity in the second polarization (transmittance) state may follow Figure 7curve 191 depicted in , and the transmittance T can be about 1 (or 100%) minus the reflectivity along curve 191); and for each of the first polarization state and the second polarization state, for at least one wavelength between the blue FWHM and the green FWHM (e.g., about 590 nm) and at least one wavelength between the green FWHM and the red FWHM (e.g., about 630 nm), the reflective polarizer transmits at least about 30% of the incident light. In some embodiments, for light 30 at substantially normal incidence, at least about 30%, or at least about 50%, or at least about 70%, or at least about 90% of the FWHM of the blue and green emission spectra overlap with the corresponding blue (ob) and green (og) FWHM of the reflective polarizer. Figure 6A In the embodiment shown, about 100% of the FWHM of the emission spectrum overlaps with the corresponding blue FWHM and green FWHM of the reflective polarizer. In other embodiments, there may be less overlap. For example, the overlap at substantially normal incidence may be as follows: Figure 4B , where Ov' / W1 is greater than about 0.3. In some embodiments, for light 30 at substantially normal incidence, less than about 20%, or less than about 10%, or less than about 5% of the FWHM of the red emission spectrum overlaps with the red FWHM of the reflective polarizer. Figure 6A In the embodiment shown, approximately 0% of the FWHM of the red emission spectrum overlaps with the red FWHM of the reflective polarizer. In some embodiments, for light 30 at substantially normal incidence, there is no overlap between the red FWHM of the reflective polarizer and the FWHM of the red emission spectrum (e.g., the FWHM may be as Figure 5A In other embodiments, there may be some overlap. For example, the overlap at substantially normal incidence may be as shown in FIG. Figure 5B The occurrence is schematically shown in FIG, where Ov' / W1 is less than about 0.2.

[0043] In some embodiments, for example, for wavelengths in the red FWHM: for light 30 at substantially normal incidence, reflective polarizer 20 has an average reflectivity (an unweighted average of the reflectivity over wavelengths in the red FWHM W1r) of less than about 40% for the first polarization state, as Figure 6A In some embodiments, for wavelengths in the red FWHM: for light 30 at substantially normal incidence, the reflective polarizer 20 has an average reflectivity for the second polarization state of less than about 20% (e.g., corresponding to Figure 7191). In some embodiments, for example, for wavelengths in the red FWHM: for light incident at at least one angle of incidence greater than about 50 degrees or in the range of about 50 degrees to about 80 degrees, the reflective polarizer has an average reflectivity greater than about 60% for the first polarization state, as shown in FIG. Figure 6B In some embodiments, for wavelengths in the red FWHM: for light 30 incident at substantially normal incidence, the reflective polarizer 20 has an average reflectivity of less than about 15% for the second polarization state. In some embodiments, for wavelengths in the red FWHM: for light incident at at least one angle of incidence greater than about 50 degrees or in the range of about 50 degrees to about 80 degrees, the reflective polarizer has an average reflectivity of greater than about 70% for the first polarization state.

[0044] The display panel 10 may include pixels having at least three different colors. Alternatively, it may include fewer colors. For example, the display panel may optionally be a monochrome display panel.

[0045] In some embodiments, a display system 300 includes a display panel 10 including a plurality of first light-emitting pixels (e.g., 11r) having a first emission spectrum 12r including a first emission peak 13r having a first full width at half maximum (FWHM) W1r at a first peak wavelength 14r. For example, the first light-emitting pixels can be red light-emitting pixels. The display system 300 can include a reflective polarizer 20 disposed over the plurality of first light-emitting pixels 11r such that, for wavelengths in a first FWHM: for light 30 incident at substantially normal incidence, the reflective polarizer has an average reflectivity of less than about 40% for a first polarization state (e.g., the x-axis) and an average reflectivity of less than about 20% for an orthogonal second polarization state (e.g., the y-axis); and for light incident at at least one angle of incidence greater than about 50 degrees or in a range from about 50 degrees to about 80 degrees, the reflective polarizer has an average reflectivity of greater than about 60% for the first polarization state. In some embodiments, the reflective polarizer has an average reflectivity for the first polarization state of less than about 30% or less than about 25% for wavelengths in the first FWHM and for light 30 at substantially normal incidence. In some embodiments, the reflective polarizer has an average reflectivity for an orthogonal second polarization state of less than about 10% for wavelengths in the first FWHM and for light 30 at substantially normal incidence. In some embodiments, the reflective polarizer has an average reflectivity for the first polarization state of greater than about 70% for wavelengths in the first FWHM and for light incident at at least one angle of incidence greater than about 50 degrees or in a range from about 50 degrees to about 80 degrees.

[0046] In some embodiments, the display system 300 further includes a retarder layer 40 disposed between the reflective polarizer 20 and the display panel 10. In some embodiments, the display system 30 further includes an absorptive polarizer 50, wherein the reflective polarizer 20 is disposed between the absorptive polarizer 50 and the retarder layer 40. In some embodiments, the display panel 10 further includes a plurality of second light-emitting pixels (11g) and a plurality of third light-emitting pixels (11b). In some embodiments, the first light-emitting pixel is a red light-emitting pixel, the second light-emitting pixel is a green light-emitting pixel, and the third light-emitting pixel is a blue light-emitting pixel. In some embodiments, the display panel 10 further includes a plurality of fourth light-emitting pixels (11w), which can be white light-emitting pixels.

[0047] Figure 7 3 is a schematic graph illustrating the reflectance spectra 321 and 321' of a reflective polarizer for light of a first polarization state (e.g., the x-axis) at substantially normal incidence (spectrum 321) and oblique incidence (spectrum 321', whose angle of incidence may be, for example, greater than about 40 degrees or greater than about 50 degrees), as well as the reflectance spectrum 191 for light of a second polarization state (e.g., the y-axis) at substantially normal incidence. In some embodiments, the reflective polarizer has negligible absorbance, such that the transmittance T is approximately 1 (or 100%) minus the reflectance. The blue FWHM, green FWHM, and red FWHM (W1b, W1g, and W1r) are shown, respectively, for some embodiments of the display panel 10. Figure 8 Graphs of calculated reflectance spectra 421, 421' of a reflective polarizer for light of a first polarization state (x-axis) at substantially normal incidence (spectrum 421) and for light at an angle of incidence (normal angle) of 60 degrees (spectrum 421'), with emission spectrum 12 included in the graph.

[0048] In some embodiments, for the first polarization state: for light 30 at substantially normal incidence, the reflective polarizer has a reflectivity at the red emission peak wavelength 14r that is less (e.g., at least 10% less, or at least 20% less, or at least 40% less) than the reflectivity at the green emission peak wavelength 14g (e.g., as in Figure 8 and Figure 7 In some embodiments, for a first polarization state: for at least one incident angle greater than about 40 degrees, or greater than about 50 degrees, or in the range of about 40 degrees to about 80 degrees, the reflective polarizer has a greater reflectivity at the red emission peak wavelength 14r than at the green emission peak wavelength 14g (e.g., as in Figure 8 and Figure 7In some such embodiments or in other embodiments, for light 30 at substantially normal incidence and wavelengths in the blue, green, and red FWHMs (W1b, W1g, and W1r), the reflective polarizer has respective average reflectivities Rb, Rg, and Rr for the first polarization state, where Rb>Rg>Rr (e.g., as in Figures 7 and 8 In some such or other embodiments, for light 30 at substantially normal incidence and wavelengths in the blue, green, and red FWHMs (W1b, W1g, and W1r), the reflective polarizer has an average transmittance of greater than about 60% or greater than about 70% for the wavelengths in each FWHM for the orthogonal second polarization state (e.g., corresponding to Figure 7 ). In some embodiments: Rb-Rg is greater than about 0.2 (or about 20%) or greater than about 0.4 (or about 40%). In some embodiments, Rg-Rr is greater than about 0.1 (or about 10%) or greater than about 0.2 (or about 20%).

[0049] In some embodiments, the display system 300 includes a display panel 10 comprising a plurality of blue (11b), green (11g), and red (11r) light-emitting pixels having respective blue (13g), green (13g), and red (13r) emission peaks; and a reflective polarizer 20 disposed over the plurality of light-emitting pixels and having a reflective spectrum 21 comprising substantially distinct blue (21b), green (21g), and red (21r) reflection bands such that for substantially normally incident light (30) and for at least one wavelength within each of the distinct blue, green, and red reflection bands, the reflective polarizer reflects at least about 70% of the incident light for a first polarization state (x-axis) and transmits at least about 70% of the incident light for an orthogonal second polarization state (y-axis). In some such embodiments, for the first polarization state: for light at substantially normal incidence, the reflectivity of the reflective polarizer at the red emission peak is less than the reflectivity at the green emission peak; and for at least one incident angle greater than about 40 degrees or greater than about 50 degrees or in the range of about 40 degrees to about 80 degrees, the reflectivity of the reflective polarizer at the red emission peak is greater than the reflectivity at the green emission peak.

[0050] In some embodiments, the display system 300 includes an emissive display (e.g., corresponding to the display panel 10) including a plurality of at least blue (11b), green (11g), and red (11r) light-emitting pixels including emission peaks having respective blue (W1b), green (W1g), and red (W1r) full widths at half maximum (FWHM) at respective blue (14b), green (14g), and red (14r) peak wavelengths. The emissive display can be or include, for example, an organic light-emitting display or a micro-LED display. The display system 300 can also include: a reflective polarizer disposed on the emissive display such that, for substantially normally incident light 30 and wavelengths within the blue FWHM, the reflective polarizer: has respective average reflectivities Rb, Rg, and Rr for a first polarization state, Rb>Rg>Rr; and, for an orthogonal second polarization state, has an average transmittance greater than about 60% or greater than about 70% for wavelengths within each FWHM. Rb-Rg and / or Rg-Rr can be within any of the ranges described elsewhere herein.As further described elsewhere herein, the display system 300 can also include a retarder layer 40 disposed on the emissive display.

[0051] The retarder layer 40 may comprise a film, a coating, or a combination of films and coatings. Exemplary films include birefringent polymer film retarders, such as those available from Meadowlark Optics, Frederick, CO. Exemplary coatings for forming the retarder layer include linear photopolymerizable polymer (LPP) materials and liquid crystal polymer (LCP) materials described in U.S. Patent Application Publications 2002 / 0180916 (Schadt et al.), 2003 / 028048 (Cherkaoui et al.), 2005 / 0072959 (Moia et al.), and 2006 / 0197068 (Schadt et al.), and U.S. Patent 6,300,991 (Schadt et al.). Suitable LPP materials include ROP-131EXP 306LPP, and suitable LCP materials include ROF-5185EXP 410LCP, both available from ROLIC Technologies, Allschwil, Switzerland.

[0052] Figure 9is a schematic graph of retardation versus wavelength, illustrating a relationship 56 between wavelength and retardation achieved by an ideal quarter-wave retarder, where wavelength and retardation vary linearly, and an exemplary relationship 54 between wavelength and retardation for some embodiments of the retarder layer 40. It can also be seen that a wavelength-dependent deviation Δ exists between the retarder layer relationship 54 and the ideal quarter-wave relationship 56. In some embodiments, the retarder layer 40 has a smaller deviation Δ from the quarter-wave retarder at the blue peak wavelength 14b than at the red peak wavelength 14r. In some embodiments, the retarder layer 40 has a smaller deviation Δ from the quarter-wave retarder at the blue peak wavelength 14b than at the green peak wavelength 14g. It has been discovered that having the retarder layer 40 have a smaller deviation Δ for blue wavelengths than for red wavelengths can, for example, result in a reduced color shift of ambient light reflected from a display with viewing angle. By appropriately selecting the thickness of the retarder layer, the retarder layer can be selected to have a smaller deviation Δ from the quarter-wave retarder at blue wavelengths. Suitable retarder layers and display systems including retarder layers are further described in U.S. patent application 62 / 906,852, filed on September 27, 2019, entitled “COLOR NEUTRAL EMISSIVE DISPLAY WITH NOTCHED REFLECTIVE POLARIZER.”

[0053] Figure 10is a schematic graph of the transmittance of an absorbing polarizer for light 30 having a first polarization state (e.g., the x-axis) at substantially normal incidence. In some embodiments, Fresnel reflection is negligible, and the absorbance A of the absorbing polarizer is approximately 1 (or 100%) minus the transmittance. In some embodiments, the absorbance A is at least 60% or at least 70% over the entire visible light range (400 nm to 700 nm) or for each of the blue peak wavelength, the green peak wavelength, and the red peak wavelength. In some embodiments, the display system 300 includes an absorbing polarizer 50 disposed on the reflective polarizer 20 opposite the retarder layer 40 such that, for light having a first polarization state at substantially normal incidence, the absorbing polarizer 50 absorbs at least 60% or at least 70% of the incident light for each of the blue peak wavelength, the green peak wavelength, and the red peak wavelength, and has average transmittances Tb, Tg, and Tr for wavelengths within the corresponding blue FWHM, green FWHM, and red FWHM. In some embodiments, Tr>Tb and Tr>Tg (i.e., Tr>Tb and Tr>Tg). In some embodiments, Tr is less than about 30%, or less than about 20%, or less than about 10%. In some embodiments, Tr-Tg is greater than about 5% (or about 0.05). In some embodiments, Tr-Tb is greater than about 5% (or about 0.05) or greater than about 8% (or about 0.08). In some embodiments, for each of the blue peak wavelength, the green peak wavelength, and the red peak wavelength, the transmittance for substantially normally incident light having the second polarization state is at least 60%, or at least 70%, or at least 80%. Suitable absorbing polarizers are commercially available from Sanritz.

[0054] In some embodiments, the reflective polarizer 20 generates optical gain for the optical system by recycling light that would otherwise be absorbed by the absorptive polarizer. The optical gain is the brightness of the optical system with the reflective polarizer (photopic brightness) divided by the brightness of the optical system without the reflective polarizer. The optical gain can be determined based on wavelength and / or can be determined for pixels of different colors. The optical gain can be determined for different propagation directions, which can be determined by the angle of the light propagation direction relative to the display normal outside the display system (e.g., see Figure 1 is defined by the polar angles θ, θ') depicted in .

[0055] Figure 11 is a schematic graph of the optical gain 95r of a first wavelength and the optical gain 95nr of a different second wavelength as a function of the polar angle θ. The first wavelength can be, for example, the peak wavelength of a red pixel. The second wavelength can be, for example, the peak wavelength of a pixel of a different color (e.g., blue, green, or white). Figure 12is a graph of the optical gains 100b, 100g, 100r calculated for the blue, green and red pixels respectively, and the optical gain 100w of the white output produced by all blue, green and red pixels emitting simultaneously.

[0056] In some embodiments, the reflective polarizer 20 is disposed between the absorbing polarizer 50 and the retarder layer 40 such that the display system 300 has an optical gain g0 along a first direction 83 substantially perpendicular to the display and an optical gain g1 along a second direction 86 that makes an angle θ with the first direction that is greater than about 60 degrees or in a range from about 60 degrees to about 80 degrees. In some embodiments, g0 is greater than g1 for the blue peak wavelength 14b and the green peak wavelength 14g; and g0 is less than g1 for the red peak wavelength 14r.

[0057] In some embodiments, the display system 300 includes a display (e.g., corresponding to the display panel 10) comprising a plurality of blue (11b), green (11g), and red (11r) light-emitting pixels; an absorptive polarizer 50 disposed on the display; a retarder layer 40 disposed between the absorptive polarizer 50 and the display; and a reflective polarizer 20 disposed between the absorptive polarizer 50 and the retarder layer 40, such that the display has an optical gain g0 along a first direction 83 substantially perpendicular to the display and an optical gain g1 along a second direction 86 that is at an angle θ greater than about 60 degrees to the first direction. In some embodiments, for wavelengths corresponding to peak emission of the blue (11b) and green (11g) light-emitting pixels, g0 is greater than g1; and for wavelengths corresponding to peak emission of the red light-emitting pixel 11r, g0 is less than g1. In some embodiments, for wavelengths corresponding to peak emission of the red light-emitting pixel, the display has a maximum gain along a direction that is at an angle in the range of 40 to 60 degrees from the first direction (e.g., as in Figure 12 In some embodiments, the display further comprises a plurality of white (11w) emitting pixels. In some embodiments, for the wavelength corresponding to the peak emission of the white (11w) emitting pixels, g0 is greater than g1. The peak emission wavelength of the white emitting pixels can be approximately equal to the peak emission wavelength of the blue emitting pixels (see, e.g., Figure 6A ).

[0058] Figure 13A is a schematic graph of the color shift of light leaving a display system on a chromaticity diagram. As the polar angle (angle relative to the normal of the display panel) changes, the color moves along the illustrated curve. The chromaticity diagram uses two coordinates to represent color, which are labeled as chromaticity coordinate 1 and chromaticity coordinate 2 in the figure. For example, Figure 13AThe CIE (International Commission on Illumination) 1931 xy chromaticity diagram can be schematically represented, where chromaticity coordinate 1 is the CIE x coordinate and chromaticity coordinate 2 is the CIE y coordinate. Figure 13A The CIE 1976 Uniform Chromaticity Scale (UCS) u'v' diagram can be schematically represented, where chromaticity coordinate 1 is the CIE u' coordinate and chromaticity coordinate 2 is the CIE v' coordinate. Figure 13B is a schematic graph of the color shift of light exiting a display system and propagating in a direction having a polar angle θ (angle relative to the normal of the display panel) as a function of the polar angle θ (which may also be referred to as the viewing angle). At least for light propagating substantially perpendicular to the display (θ approximately 0 degrees), the light may be substantially white light. For example, substantially white light may have x and y coordinates on a CIE 1931 xy chromaticity diagram, each within a range of about 0.25 to about 0.35. Substantially white light may be referred to as white light because it will be appreciated that light characterized by a range of chromaticity coordinates may be considered white. The color of light may vary with angle θ. The color shift is the difference in color of light at angle θ relative to the color of light at zero angle. For example, the color shift may be a (Euclidean) distance on a CIE 1931 xy chromaticity diagram (e.g., [(x2 - x1) 2 +(y2-y1) 2 ], where the subscripts indicate the first and second points) or the (Euclidean) distance in u'v' coordinates on the CIE 1976UCS u'v' diagram (e.g. [(u'2 - u'1) 2 +(v'2-v'1) 2 ], where the subscripts represent the first and second points). The color shift can be quantified as a maximum color shift CSmax when the angle θ varies from zero to a certain specified angle (e.g., about 60 degrees, or about 70 degrees, or about 80 degrees), or as a color shift CS1 at a certain specified angle θ1 (e.g., about 60 degrees, or about 70 degrees, or about 80 degrees, or an angle greater than about 60 degrees, or an angle in the range of about 60 degrees to about 80 degrees). In some embodiments, the color shift CSmax and / or CS1 does not exceed that of an otherwise equivalent display system that does not include reflective polarizer 20 (e.g., an otherwise equivalent display system that may appear as Figure 1 The color shift of the display system 300 in which the reflective polarizer 20 is omitted and the absorptive polarizer 50 is attached to the retarder layer 40 is about 0.9 times, or no more than about 0.8 times, or no more than about 0.7 times the corresponding color shift.

[0059] Reference again Figure 1In some embodiments, when the display or display panel 10 emits substantially white light 80, a first portion 81 of the emitted substantially white light exits the display system as first light 82 propagating along a first direction 83 substantially perpendicular to the display or display panel, and a second portion 84 of the emitted substantially white light exits the display system as second light 85 propagating along a second direction 86 at an angle θ to the first direction. For example, the angle θ can be about 60 degrees, or about 70 degrees, or about 80 degrees, or an angle greater than about 60 degrees, or an angle within a range of about 60 degrees to about 80 degrees. In some embodiments, the first light and the second light correspond to respective first and second points on the CIE 1976 uniform chromaticity scale u'v' diagram (e.g., points 90 and 91), and the distance between the first and second points (e.g., CS1 or d) may be less than about 0.03, or less than about 0.025, or less than about 0.023, or less than about 0.02, or less than about 0.015, or less than about 0.01, or even less than about 0.009. In some embodiments, the first light and the second light correspond to respective first and second points on the CIE 1931 xy chromaticity diagram (e.g., points 90 and 91), and the distance between the first and second points (e.g., CS1 or d) may be less than about 0.06.

[0060] The reflective polarizer can have a reflective spectrum selected to cause a lower white point color shift of light emitted from the display system than that of light emitted from a display system incorporating a conventional notch reflective polarizer, while providing less ghosting and / or less ambient light reflection than a display system using a broadband reflective polarizer. The reflective polarizer can have a high transmittance (e.g., at least about 60% or at least about 70%) for each of two orthogonal polarization states for at least one wavelength between the peak emission wavelength 14b of the blue-emitting pixel 11b and the peak emission wavelength 14r of the red-emitting pixel 11r, and can have a high reflectance (e.g., at least about 60% or at least about 70%) for the first polarization state for at least one other wavelength between the peak emission wavelength 14b of the blue-emitting pixel 11b and the peak emission wavelength 14r of the red-emitting pixel 11r.

[0061] In some embodiments, the display system 300 includes a display (e.g., corresponding to the display panel 10) including a plurality of at least blue light-emitting pixels, green light-emitting pixels, and red light-emitting pixels; an absorptive polarizer 50 disposed on the display; a retarder layer 40 disposed between the absorptive polarizer 50 and the display; and a reflective polarizer 20 disposed between the absorptive polarizer and the retarder layer 40, wherein for a wavelength from the peak emission wavelength 14b of the blue light-emitting pixel 11b to the peak emission wavelength 14r of the red light-emitting pixel 11r The reflective polarizer transmits at least about 60% or at least about 70% of light 30 at substantially normal incidence for each of the orthogonal first and second polarization states, such that when the display emits substantially white light 80, a first portion of the emitted substantially white light exits the display system as first light 82 propagating along a first direction 83 substantially perpendicular to the display, and a second portion of the emitted substantially white light exits the display system 300 as second light 85 propagating along a second direction 86 at an angle θ of about 60 degrees to the first direction. The first light 82 and the second light 85 correspond to respective first and second points on a CIE 1976 uniform chromaticity scale u'v' diagram, wherein a distance d between the first and second points is less than about 0.023, or the distance d can be within any range described elsewhere herein. In some embodiments, for light at substantially normal incidence, the reflective polarizer 20 reflects at least about 60% or at least 70% of the incident light of the first polarization state for at least one second wavelength within the range from the peak emission wavelength 14b of the blue-emitting pixel to the peak emission wavelength 14r of the red-emitting pixel. In some embodiments, for light at substantially normal incidence, the reflective polarizer 20 transmits at least about 60% or at least 70% of the incident light of the second polarization state for at least one second wavelength.

[0062] In some implementations, when the display or display panel emits substantially white light 80, a third portion 84' of the emitted substantially white light exits the display system as third light 85' that propagates along a third direction 86' that is at an angle θ' from the first direction 83. In some implementations, the first light corresponds to a first point on the CIE 1976 uniform chromaticity scale u'v' diagram, the third light corresponds to a third point on the CIE 1976 uniform chromaticity scale u'v' diagram, and a maximum distance (e.g., CSmax) between the first point and the third point is less than about 0.025, or less than about 0.023, or less than about 0.02, or less than about 0.016, or less than about 0.015, or less than about 0.014 when the angle θ' varies from about zero degrees to about 70 degrees. In some embodiments, the first light corresponds to a first point on the CIE 1931xy chromaticity diagram, the third light corresponds to a third point on the CIE 1931xy chromaticity diagram, and when the angle θ' changes from about zero degrees to about 70 degrees, the maximum distance between the first point and the third point (e.g., CSmax) is less than about 0.06.

[0063] The reflective polarizer 20 can be a multilayer polymer reflective polarizer. Multilayer polymer reflective polarizers are known in the art and are described in U.S. Patents 5,882,774 (Jonza et al.); 6,179,948 (Merrill et al.); 6,783,349 (Neavin et al.); 6,967,778 (Wheatley et al.); and 9,162,406 (Nakamura et al.). Figure 14 is a schematic cross-sectional view of a reflective polarizer 20 according to some embodiments. The reflective polarizer 20 may include a plurality of alternating polymer first layers (921) and second layers (922). As is known in the art, the thickness distribution of the first and second layers (different thicknesses of different layers) can be selected to provide a desired reflection spectrum band. In some embodiments, the average thickness T of the reflective polarizer 20 (the unweighted average thickness over the entire area of the reflective polarizer) is less than about 30 microns, or less than about 20 microns. In some embodiments, the plurality of alternating polymer first and second layers totals at least 30 (e.g., 50 to 300 layers), and the average thickness t of each of the first and second layers is less than about 500 nm, or less than about 400 nm, or less than about 300 nm. In some embodiments, the reflective polarizer 20 further includes a surface layer 123 at the outermost major surface of the reflective polarizer 20. For example, the surface layer 123 may have a thickness greater than about 1 micron (e.g., 2 microns to 20 microns). In some embodiments, the reflective polarizer 20 can further include a protective boundary layer disposed between the alternating groups of first and second layers.Light 30 is schematically shown at substantially normal incidence and light 34 is incident on the reflective polarizer at an angle of incidence θ.

[0064] In some embodiments, the reflective polarizer 20 has a reflective spectrum (21) including substantially distinct blue (21b), green (21g), and infrared (21r) reflection bands such that for substantially normally incident light (30): the infrared reflection band includes at least one wavelength less than about 750 nm; for a first polarization state (e.g., the x-axis), the reflective polarizer 20 reflects at least about 70% of the incident light 30 for at least one wavelength within each of the blue reflection band, the green reflection band, and the infrared reflection band; for an orthogonal second polarization state (e.g., the y-axis), the reflective polarizer transmits at least about 70% of the incident light for at least one wavelength within each of the blue reflection band, the green reflection band, and the infrared reflection band; and for each of the first polarization state and the second polarization state, the reflective polarizer transmits at least about 50% of the incident light for at least one wavelength between the blue reflection band and the green reflection band and at least one wavelength between the green reflection band and the infrared reflection band. For example, at least one wavelength within each of the blue, green, and infrared reflection bands can include wavelengths 14b, 14g, and 700 nm, respectively. In some embodiments, for light 30 at substantially normal incidence, a red wavelength range (e.g., corresponding to W1) at least about 30 nm wide is disposed between the green and infrared reflection bands, wherein the reflective polarizer has an average transmittance of at least about 50% in the red wavelength range for each of the first and second polarization states (see, e.g., FIG. 1 ). Figure 6A and Figure 7 ). The red wavelength range can be W1, or can be, for example, a wavelength range centered around a peak wavelength I4r and having a width of about 30 nm to about 50 nm. In some embodiments, the reflective polarizer has an average reflectivity of at least about 70% in the red wavelength range for the first polarization state for at least one incident angle θ in the range of about 40 degrees to about 70 degrees (see, e.g., Figure 6B and Figure 7 ).

[0065] In some embodiments, the reflective polarizer 20 has a reflective spectrum (21) including substantially distinct blue (21b), green (21g), and infrared (21r) reflection bands such that for substantially normally incident light (30): for a first polarization state (e.g., the x-axis), the reflective polarizer 20 reflects at least about 70% of the incident light 30 for at least one wavelength within each of the blue, green, and infrared reflection bands; for an orthogonal second polarization state (the y-axis), the reflective polarizer 20 transmits at least about 70% of the incident light 30 for at least one wavelength within each of the blue, green, and infrared reflection bands; and for each of the first and second polarization states, the reflective polarizer transmits at least about 50% of the incident light for at least one wavelength between the blue and green reflection bands. In some embodiments, the infrared reflection band 21r has a FWHM (e.g., W2r) such that for a red wavelength range (e.g., W1r) that is at least about 30 nm wide: for light at substantially normal incidence, there is no overlap between the FWHM and the red wavelength range; and for at least one angle of incidence θ in the range of about 40 degrees to about 70 degrees, substantially the entire red wavelength range overlaps with the FWHM.

[0066] In some embodiments, the infrared reflection band 21r extends from at least about 690 nm to about 720 nm.The infrared reflection band can include a range of red wavelengths as well as infrared wavelengths and in this case may also be referred to as a red reflection band.

[0067] In some embodiments, the reflective polarizer 20 is configured such that for a blue wavelength range (e.g., W1b, or a range centered around 14b or a wavelength in the range of about 430 nm to about 480 nm), a green wavelength range (e.g., W1g, or a range centered around 14g or a wavelength in the range of about 520 nm to about 570 nm), and a red wavelength range (e.g., W1r, or a range centered around 14r or a wavelength in the range of about 600 nm to about 650 nm), the blue wavelength range, the green wavelength range, and the red wavelength range are reflected. Each of the wavelength ranges is at least about 30 nm wide, and for light (30) at substantially normal incidence: the reflective polarizer 20 has an average reflectivity Rb, Rg, and Rr for a first polarization state (e.g., the x-axis) in the corresponding blue, green, and red wavelength ranges, Rb being at least about 70%, Rg being less than Rb, and Rr being less than Rg and less than about 50%; and has an average transmittance greater than about 60% for an orthogonal second polarization state (e.g., the y-axis) in each of the blue, green, and red wavelength ranges. In some embodiments, the reflective polarizer 20 has a reflectivity spectrum including an infrared reflection band 21r such that for at least one incident angle θ in the range of about 40 degrees to about 70 degrees, the reflective polarizer has an average reflectivity of at least about 70% for the first polarization state in the red wavelength range. In some embodiments, the blue wavelength range is about 430 nm to about 480 nm, the green wavelength range is about 520 nm to about 570 nm, and the red wavelength range is about 600 nm to about 650 nm.

[0068] In some embodiments, the optical stack 301 includes a reflective polarizer 20 disposed on a retarder layer 40 (see, e.g., Figure 1 In some embodiments, the retarder layer 40 has a smaller deviation from a quarter-wave retarder for at least one wavelength in the blue wavelength range than for at least one wavelength in the red wavelength range (e.g., see Figure 9 In some embodiments, the optical stack 301 further includes an absorptive polarizer 50 disposed on the reflective polarizer 20 opposite the retarder layer 40 such that, for light 30 having a first polarization state at substantially normal incidence, the absorptive polarizer 50 absorbs at least 60% of the incident light for at least one wavelength in each of the blue, green, and red wavelength ranges and has average transmittances Tb, Tg, and Tr for wavelengths in the respective blue, green, and red wavelength ranges (see, e.g., Figure 10 ). In some embodiments, Tr>Tb and Tr>Tg.

[0069] In some embodiments, the emissive display 10 includes a plurality of at least blue (11b), green (11g), and red (11r) light-emitting pixels having emission peaks with corresponding blue (W1b), green (W1g), and red (W1r) full widths at half maximum (FWHM), wherein a reflective polarizer 20 is disposed on the emissive display, and wherein the blue wavelength range, the green wavelength range, and the red wavelength range are wavelength ranges of the corresponding blue (W1b), green (W1g), and red (W1r) FWHMs.

[0070] Example

[0071] Example 1

[0072] A computational model is used to calculate the reflective and transmissive properties of reflective polarizers. This computational model is driven by a 4×4 matrix solver routine based on the Berriman algorithm, where the reflective and transmissive matrix elements can be calculated for any 1-dimensional stack of layers, where each layer is defined by its physical thickness and a dispersive refractive index tensor, where each principal element of the refractive index tensor is a function of wavelength (λ). Using this computational model, a 1-D stack structure representing an emissive display system is defined, and its reflective and transmissive properties are calculated.

[0073] use Figure 1 A set of Cartesian axes x, y, and z are shown defining the coordinate system of the computational model, where the x-axis is the "block axis" coinciding with the high extinction axis of any absorbing polarizer and the high reflection axis of any reflective polarizer, and the y-axis is the "pass axis" coinciding with the weakly absorbing, highly transmitting axis of the absorbing polarizer and the weakly reflecting axis of any reflective polarizer. is measured from the x-axis, and the polar angle θ is measured from the z-axis.

[0074] The computational stack model simulates the viewer-side reflectance properties of an organic LED (OLED) display using a glass layer stack structure (the outer surface of the display) on top of a circular polarizer covered with a quarter-wave (λ / 4) retarder consisting of a display-quality iodine-based absorbing polarizer with an extraordinary axis located midway between the principal in-plane axes of the absorbing polarizer, with λ selected to be a green wavelength. Furthermore, beneath this retarder layer is a dielectric layer, representing a thin film encapsulant (TFE), which in turn covers the OLED emitting surface, which comprises a spatially organized array of voltage-driven blue, green, and red emitting "pixel" regions, surrounded by metal-like transistor and conductive elements that serve as drivers for the emissive pixels that make up the display.

[0075] Calculations were performed using inputs from the computational stack model to predict the brightness increase in blue, green, and red pixel intensities for light emitted from the OLED emissive surface. These predictions were based on an analysis of the reflectance and transmittance spectra calculated by the stack model, combined with an understanding of the reflectance spectrum of the OLED emissive surface. Analytical expressions were derived to predict the changes in pixel emission color and brightness that result when a reflective polarizer is included in the circular polarizer of the modeled OLED display stack.

[0076] A multilayer optical film reflective polarizer comprising optical repeating units (ORUs) was modeled as consisting of alternating microlayers of 90 / 10 coPEN and low refractive index isotropic microlayers. The isotropic layers were modeled as follows. A blend of polycarbonate and copolyester (PCTg) was prepared as described in U.S. Patent No. 10,185,068 (Johnson et al.) such that the refractive index was approximately 1.57 and such that the layers remained substantially isotropic upon uniaxial orientation of the film. The PC:PCTg molar ratio was approximately 85 mol% PC and 15 mol% PCTg. The PC:PCTg was then blended with PETg in an 85:15 weight ratio ((PC:PCTg):PETg). The high refractive index material, 90 / 10 coPEN, was designated Material A, and the low refractive index material was designated Material B.

[0077] The thickness distribution of microlayer A and B pairs, or ORUs, is mathematically generated. Figure 15 The physical thickness distribution of the ORU is shown in . The ORU thickness distribution is bounded on both sides by a protective boundary layer of low refractive index material with a thickness of 1500 nm.

[0078] Representative values of the refractive index for high-index optical (HIO) layers (birefringent 90 / 10coPEN), denoted as Nx, Ny, Nz along the x, y, and z axes, respectively, and for isotropic low-index optical (LIO) layers (Niso is used to denote the isotropic refractive index), are shown in the following table:

[0079]

[0080] Additionally, the model setup defines a 400 μm glass layer followed by a display absorbing polarizer above the multilayer optical film reflective polarizer. The refractive indices of the glass and dielectric layers directly above the OLED emitting surface are shown in the table below.

[0081]

[0082] The absorbing polarizer is modeled after a Sanritz display polarizer and is assumed to be 10 microns thick. The refractive index (Niso) and losses (Kx, Ky, Kz) of the absorbing polarizer are shown in the table below.

[0083]

[0084] In this model, a quarter-wave retarder layer is positioned beneath the reflective polarizer with its extraordinary axis aligned centered at 45 degrees between the x- and y-axes. The refractive index values for the extraordinary (Ne) and ordinary (No) axes of the retarder are shown in the table below, along with the deviation Δ (in nanometers) from a quarter wavelength at representative wavelengths. These retarder properties can be manipulated in the model by varying the retarder thickness.

[0085]

[0086] The OLED emitting surface is defined in the model as having metal-like phase rotation properties in reflection and has the reflectance values shown in the table below.

[0087] λ Reflection coefficient 450nm 0.3336 530nm 0.4895 630nm 0.5570

[0088] With the exception of the absorbing polarizer, the absorption coefficients of all layers in the OLED model are assumed to be very small.

[0089] Figure 8 Shown are the calculated reflectances (fraction of incident energy reflected) of the multilayer optical film reflective polarizer for polar angles of 0 and 60 degrees for an electric field aligned with the x-axis when the multilayer optical film reflective polarizer is constructed in air. Figure 16 Calculated reflectances of the multilayer optical film reflective polarizer are shown for polar angles of 0 and 60 degrees for an electric field aligned with the y-axis when the multilayer optical film reflective polarizer is constructed in air.

[0090] Calculations are performed using inputs from the computational stack model to predict the degree of brightness increase in the intensity of blue, green, and red pixels emitting light from the OLED emitting surface. These predictions are based on analysis of the reflectance and transmittance spectra calculated by the stack model, combined with an understanding of the reflectance spectrum of the OLED emitting surface based on measurements of the commercial LG V30 OLED smartphone in this embodiment. Analytical expressions are derived to predict the changes in pixel emission color and brightness that result when a reflective polarizer is included in the circular polarizer of the modeled OLED display stack. This computational model is called the Polarization Coherent Recycling Model (PCRM). In this example, for each of the blue emission input, the green emission input, and the red emission input, a calculation is performed with Figure 8 、 Figure 15 and Figure 16 PCRM analysis was performed on an OLED using the described reflective polarizer as part of a circular polarizer. Figure 17Shown are the OLED white point colors on the CIE 1931 xy chromaticity diagram as the polar angle varies from 0 degrees to 72.5 degrees for a display without a reflective polarizer. Figure 18 The corresponding white point CIE 1931 xy color coordinates are shown as the polar angle varies from zero degrees (point 90) to 72.5 degrees (point 91) when a reflective polarizer is included in a circular polarizer stack between an absorbing polarizer and a retarder layer. The distance between points 90 and 91 is denoted as d. Figure 19 is a graph of the distance (d) from the color coordinate at normal incidence (θ=0) on the CIE 1931 xy diagram as a function of viewing angle θ for displays with a reflective polarizer (Example 1) and without a reflective polarizer (No RP).

[0091] In addition to the white state chromaticity coordinates, the increase in photopic brightness of the OLED display incorporating a reflective polarizer relative to the photopic brightness of the OLED display without a reflective polarizer was calculated for each OLED color pixel. Figure 12 The photopic brightness increase is shown for each of the blue, green, and red pixels individually, and for the white output produced by all blue, green, and red pixels emitting simultaneously.

[0092] Examples 2-6 and Comparative Examples C1-C2

[0093] Reflective polarizing films were prepared by coextruding one multilayer optical packet (Examples 3-4 and Comparative Examples C1-C2) or two multilayer optical packets (Example 2 and Examples 5-6). Each packet contained alternating layers of 90 / 10 coPEN (a polymer composed of 90% polyethylene naphthalate (PEN) and 10% polyethylene terephthalate (PET)) and low-refractive-index isotropic layers made from a blend of polycarbonate and copolyester (PC:coPET) to achieve a refractive index of approximately 1.57 and to maintain the isotropic layers substantially isotropic when the film is uniaxially oriented. The PC:coPET molar ratio was approximately 42.5 mol% PC and 57.5 mol% coPET, and had a Tg of 105 degrees Celsius. This isotropic material is selected so that after stretching, its refractive index in both non-stretch directions remains substantially matched to that of the birefringent material in the non-stretch direction, while in the stretch direction, there is a substantial mismatch in refractive index between the birefringent and non-birefringent layers. 90 / 10 PEN and PC:coPET polymers are fed from separate extruders at the target f-ratios (ratio of the optical thickness of the high refractive index layer to the optical thickness of the optical repeat unit) shown in the table below (for two-packet films, the f-ratios for each of the two packs P1 and P2 are given) to a multilayer coextrusion feedblock where these polymers are assembled into one or more packs of alternating optical layers, plus a thicker protective boundary layer of PC:coPET on each side. The multilayer melt is then cast through a film die onto a chill roll in a conventional manner for polyester films where it is quenched. The cast web is then stretched in a parabolic tenter similar to that described in Invited Paper 45.1, "Advanced Polarizer Film for Improved Performance of Liquid Crystal Displays," by Denker et al., presented at the Society for Information Display (SID) International Conference, San Francisco, California, June 4-9, 2006. The number of layers and layer thickness distribution are selected to produce the following: Figures 20 to 26 Desired transmission spectra are shown, showing the percent transmission for the pass and block states at normal incidence (0°) and the transmission for s-polarized light in the block state at 60 degrees of incidence.

[0094] Example Thickness (micrometers) f-ratio Number of layers C1 20.41 0.5 275 C2 23.67 0.24 275 2 58.14 0.5P1,0.30P2 550 3 28.52 0.33 275 4 27.84 0.33 275 5 60.15 0.5P1,0.30P2 550 6 60.68 0.5P1,0.15P2 550

[0095] Figure 27is a graph of the white point color shift as the viewing angle is varied from zero to 80 degrees on the CIE1931 xy coordinates in 10 degree increments for an LG OLED TV without a reflective polarizer (“as is”) and with the reflective polarizer shown in the figure (the reflective polarizer is positioned between the TV’s absorptive polarizer and the retarder layer of the circular polarizer). Figure 28 is a corresponding graph of the shift in white point color defined as a distance on the CIE 1976 uniform chromaticity scale u'v' diagram. Figure 29 is a graph of ambient light reflection from a display for an 8 degree incident angle.

[0096] Figure 30 is a graph of the white point color shift as the viewing angle is varied from zero to 80 degrees in CIE 1931 xy coordinates in 10 degree increments for an LG V30 OLED phone without a reflective polarizer (“as is”) and with the reflective polarizer of Example 2, which is disposed between the phone’s absorptive polarizer and the retarder layer of the circular polarizer. Figure 31 It is a corresponding graph of the shift of the white point color defined as the distance on the CIE 1976 uniform chromaticity scale u'v' diagram.

[0097] Terms such as "about" will be understood by one of ordinary skill in the art in the context of use and description in this specification. If it is not clear to one of ordinary skill in the art in the context of use and description in this specification that "about" should be used to express quantities of feature sizes, quantities, and physical properties, then "about" will be understood to mean an average value within 5% of the specified value. A quantity given as about a specified value may be exactly the specified value. For example, if it is not clear to one of ordinary skill in the art in the context of use and description in this specification, then a quantity having a value of about 1 means that the quantity has a value between 0.95 and 1.05, and the value may be 1.

[0098] All references, patents, and patent applications cited above are hereby incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or conflicts between an incorporated reference portion and this application, the information in the foregoing description shall prevail.

[0099] Unless otherwise indicated, descriptions of elements in the accompanying drawings should be understood to apply equally to corresponding elements in other drawings. Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that a variety of alternative and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any 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 display system, comprising: a display panel, the display panel comprising at least a plurality of blue light-emitting pixels, a plurality of green light-emitting pixels, and a plurality of red light-emitting pixels having corresponding blue emission spectra, green emission spectra, and red emission spectra, the blue emission spectra, the green emission spectra, and the red emission spectra comprising corresponding blue emission peaks, green emission peaks, and red emission peaks having corresponding blue full width at half maximum, green full width at half maximum, and red full width at half maximum at corresponding blue peak wavelengths, green peak wavelengths, and red peak wavelengths; and a reflective polarizer disposed over the plurality of blue, green, and red emitting pixels and comprising a reflective spectrum including a blue, green, and red reflective band, the blue, green, and red reflective bands having respective blue, green, and red full widths at half maximum, such that for light at substantially normal incidence: for a first polarization state, the reflective polarizer reflects at least 60% of the substantially normally incident light for at least one wavelength within each of the full width at half maximum of the blue, green, and red reflection bands; for an orthogonal second polarization state, the reflective polarizer transmits at least 60% of the substantially normally incident light for the at least one wavelength within each of the full width at half maximum of the blue, green, and red reflection bands; for each of the first polarization state and the second polarization state, the reflective polarizer transmits at least 30% of the substantially normally incident light for at least one wavelength between the blue full width at half maximum and the green full width at half maximum and at least one wavelength between the green full width at half maximum and the red full width at half maximum; at least 30% of the full width at half maximum of the blue emission spectrum and the green emission spectrum overlap with the corresponding blue full width at half maximum and green full width at half maximum of the reflective polarizer; and Less than 20% of the full width at half maximum of the red emission spectrum overlaps with the red full width at half maximum of the reflective polarizer. 2 . The display system of claim 1 , wherein the display panel comprises an organic light emitting diode (OLED) display panel.

3. The display system of claim 1 , wherein for the substantially normally incident light, there is no overlap between the red full width at half maximum of the reflective polarizer and the full width at half maximum of the red emission spectrum.

4. A display system, comprising: a display panel comprising a plurality of first light-emitting pixels having a first emission spectrum, the first emission spectrum including a first emission peak having a first full width at half maximum at a first peak wavelength, the plurality of first light-emitting pixels being red light-emitting pixels; and A reflective polarizer is disposed on the plurality of first luminescent pixels such that for wavelengths in the first full width at half maximum: The reflective polarizer has an average reflectivity of less than 40% for a first polarization state and an average reflectivity of less than 20% for an orthogonal second polarization state for light at substantially normal incidence; and The reflective polarizer has an average reflectivity greater than 60% for the first polarization state for light incident at at least one angle of incidence greater than 50 degrees.

5. A display system, comprising: a display comprising a plurality of blue light-emitting pixels, a plurality of green light-emitting pixels, and a plurality of red light-emitting pixels; an absorbing polarizer disposed on the display; a retarder layer disposed between the absorbing polarizer and the display; and a reflective polarizer disposed between the absorbing polarizer and the retarder layer such that the display has an optical gain g0 along a first direction substantially perpendicular to the display and an optical gain g1 along a second direction at an angle θ greater than 60 degrees with the first direction, wherein: For wavelengths corresponding to peak emissions of the blue and green light-emitting pixels, g0 is greater than g1; and For the wavelength corresponding to the peak emission of the red light-emitting pixel, g0 is smaller than g1.

6. The display system of claim 5, wherein for a wavelength corresponding to peak emission of the red emitting pixels, the display has a maximum gain along a direction having an angle in the range of 40 to 60 degrees from the first direction.

7. A display system, comprising: a display panel comprising a plurality of blue light-emitting pixels, a plurality of green light-emitting pixels, and a plurality of red light-emitting pixels having corresponding blue, green, and red emission peaks; and a reflective polarizer disposed over the plurality of light-emitting pixels and comprising a reflectance spectrum including a blue reflection band, a green reflection band, and a red reflection band such that, for substantially normally incident light and for at least one wavelength within each of a different blue reflection band, a green reflection band, and a red reflection band, the reflective polarizer reflects at least 70% of the substantially normally incident light for a first polarization state and transmits at least 70% of the substantially normally incident light for an orthogonal second polarization state; where for the first polarization state: For light at substantially normal incidence, the reflective polarizer has a reflectivity at the red emission peak that is less than a reflectivity at the green emission peak; and For at least one incident angle greater than 40 degrees, the reflective polarizer has a greater reflectivity at the red emission peak than at the green emission peak.

8. The display system of any one of claims 1 to 7, wherein the reflective polarizer has an average thickness of less than 30 microns.

9. A reflective polarizer comprising a plurality of alternating polymeric first and second layers totaling at least 30, each of the first and second layers having an average thickness of less than 500 nm, the reflective polarizer having a reflectance spectrum including a blue reflection band, a green reflection band, and an infrared reflection band such that for light at substantially normal incidence: The infrared reflection band includes at least one wavelength less than 750 nm; for a first polarization state, the reflective polarizer reflects at least 70% of the substantially normally incident light for at least one wavelength within each of the blue reflection band, the green reflection band, and the infrared reflection band; for an orthogonal second polarization state, the reflective polarizer transmits at least 70% of the substantially normally incident light for the at least one wavelength within each of the blue, green, and infrared reflection bands; and For each of the first polarization state and the second polarization state, the reflective polarizer transmits at least 50% of the substantially normally incident light for at least one wavelength between the blue reflection band and the green reflection band and at least one wavelength between the green reflection band and the infrared reflection band.

10. A reflective polarizer comprising a plurality of alternating polymeric first and second layers totaling at least 30, each of the first and second layers having an average thickness of less than 500 nm, the reflective polarizer having a reflectance spectrum including a blue reflection band, a green reflection band, and an infrared reflection band such that for light at substantially normal incidence: for a first polarization state, the reflective polarizer reflects at least 70% of the substantially normally incident light for at least one wavelength within each of the blue reflection band, the green reflection band, and the infrared reflection band; for an orthogonal second polarization state, the reflective polarizer transmits at least 70% of the substantially normally incident light for the at least one wavelength within each of the blue, green, and infrared reflection bands; and For each of the first polarization state and the second polarization state, the reflective polarizer transmits at least 50% of the substantially normally incident light for at least one wavelength between the blue reflection band and the green reflection band, wherein the infrared reflection band has a full width at half maximum such that for a red wavelength range that is at least 30 nm wide: For light at substantially normal incidence, there is no overlap between the full width at half maximum and the red wavelength range; and For at least one incident angle in the range of 40 degrees to 70 degrees, substantially the entire red wavelength range overlaps with the full width at half maximum.

11. A display system, comprising: A display comprising at least a plurality of blue light-emitting pixels, a plurality of green light-emitting pixels, and a plurality of red light-emitting pixels; an absorbing polarizer disposed on the display; a retarder layer disposed between the absorbing polarizer and the display; as well as The reflective polarizer of claim 9 or 10, the reflective polarizer being disposed between the absorptive polarizer and the retarder layer such that, when the display emits substantially white light, a first portion of the emitted substantially white light exits the display system as first light propagating along a first direction substantially perpendicular to the display, and a second portion of the emitted substantially white light exits the display system as second light propagating along a second direction at an angle θ of 60 degrees to the first direction, wherein the first light and the second light correspond to respective first and second points on a CIE 1976 Uniform Chromaticity Scale u'v' diagram, and wherein a distance between the first point and the second point is less than 0.

023.

12. A display system, comprising: A display comprising at least a plurality of blue light-emitting pixels, a plurality of green light-emitting pixels, and a plurality of red light-emitting pixels; an absorbing polarizer disposed on the display; a retarder layer disposed between the absorbing polarizer and the display; and The reflective polarizer of claim 9 or 10, the reflective polarizer being disposed between the absorptive polarizer and the retarder layer, the reflective polarizer transmitting at least 60% of light at substantially normal incidence for each of orthogonal first and second polarization states for at least one first wavelength in a range from a peak emission wavelength of the blue emitting pixel to a peak emission wavelength of the red emitting pixel, such that when the display emits substantially white light, a first portion of the emitted substantially white light exits the display system as first light propagating along a first direction substantially perpendicular to the display, and a second portion of the emitted substantially white light exits the display system as second light propagating along a second direction at an angle θ of 60 degrees to the first direction, wherein the first and second lights correspond to respective first and second points on a CIE 1976 Uniform Chromaticity Scale u'v' diagram, and wherein a distance between the first and second points is less than 0.023.

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